We give a short proof that if G is a finite group of derived length k and if G admits a fixed-point-free action of the elementary group of order 2n, then G has a normal series of length n all of whose quotients are nilpotent of class bounded in terms of k and n only. 相似文献
An effective analytical method for the screening of mycotoxins, in indoor/outdoor airborne particulate matter, was developed and method performance data are presented. Mycotoxins are natural compounds produced, in particular conditions, as secondary metabolites by filamentous fungi and moulds, and, after their production, they can be transported far from their source. To simulate real samples, an urban dust (reference material 1649a) free from mycotoxins was used as matrix and spiked by the most common mycotoxins, chosen on the basis of studies carried out previously in other real matrices: deoxynivalenol, aflatoxin B1, ochratoxin A, T-2 toxin, zearalenone and sterigmatocystin. The analytical method was optimised and structured in four successive steps: (1) accelerated solvent extraction of the (spiked) analytes from matrix, (2) solid-phase purification (SPE) of the previous extract, (3) pre-concentration of the eluates from SPE and (4) analysis of the concentrated eluates by high performance liquid chromatography tandem mass spectrometry in multiple reaction monitoring mode. After a proper sampling campaign, the method was applied to real indoor and outdoor particulate matter samples, where the clean-up step showed to be very effective and fundamental to avoid misleading analytical results. 相似文献
The [Fe(CO)4{M(NHC)}]– (M = Cu, NHC = IMes, 1; M = Cu, NHC = IPr, 2; M = Ag, NHC = IMes, 3; M = Ag, NHC = IPr, 4; IMes = C3N2H2(C6H2Me3)2; IPr = C3N2H2(C6H3iPr2)2) mono-anions were obtained from the reaction of Na2[Fe(CO)4]·2thf with one equivalent of M(NHC)Cl (M = Cu, Ag; NHC = IMes, IPr) in dmso. Furthermore, the reaction of Na2[Fe(CO)4]·2thf with two equivalents of M(NHC)Cl in thf afforded the neutral compounds Fe(CO)4{M(NHC)}2 (M = Cu, NHC = IMes, 11; M = Cu, NHC = IPr, 12; M = Ag, NHC = IMes, 13; M = Ag, NHC = IPr, 14). 2 and 4 further reacted with one equivalent of M(IPr)Cl (M = Cu, Ag, Au) resulting in the trimetallic clusters Fe(CO)4{Cu(IPr)}{Ag(IPr)} (18), Fe(CO)4{Cu(IPr)}{Au(IPr)} (19), and Fe(CO)4{Ag(IPr)}{Au(IPr)} (20). 1–4, 11–14 and 18–20 have been spectroscopically characterized by IR, 1H and13C{1H} NMR techniques. The molecular structures of 2, 12, 18, 19 and 20 have been determined through single-crystal X-ray diffraction. The structure, bonding and stability of the copper and silver IMes derivatives were compared to the related Fe-Au clusters previously reported on the basis of theoretical calculations. Stability of the Fe–M bonds decreases in the order Au > Cu > Ag, and the same trend was found for what concerns the M-IMes interactions. The decomposition products of 1–4, 11–14 and 18–20 have been studied allowing, among the others, the structural characterization of the new species [Fe2(CO)8{Ag(IPr)}]– (10) and Fe(CO)4(CH2IMes) (21). 相似文献
The hexacarbide clusters [H6–nNi38C6(CO)42]n− (n = 3, 4, 5, or 6) have been directly obtained from the reaction of [Ni6(CO)12]2– with C3Cl6, whereas the related anions, [H6–nNi32C6(CO)36]n− (n = 5 or 6), have been obtained by degradation under carbon monoxide of [Ni38C6(CO)42]6–, or upon thermal treatment at ca. 110 °C of [Ni10C2(CO)16]2– salts. The compound [PPh3Me]6[Ni32C6(CO)36] · 4 MeCN is triclinic, space group P&1macr; (No 2), with a = 15.974(3), b = 17.474(3), c = 18.200(4) Å, α = 61.37(2), β = 69.31(2), γ = 72.35(2)° and Z = 1; final R = 0.033. The structure of [Ni32C6(CO)36]6– has an idealised Oh symmetry and is based on a truncated octahedral Ni32C6 framework, with all edges spanned by bridging carbonyl groups. The six interstitial carbide atoms are lodged in square-antiprismatic cavities. The overall geometry of the Ni32C6 core is very similar to that found previously in [HNi38C6(CO)42]5–, and shows very close interatomic separations. Both [Ni32C6(CO)36]6– and [H6–nNi38C6(CO)42]n− (n = 5 or 6) display electron-sink behaviour. Thus, they have been chemically and electrochemically reduced to their corresponding [Ni32C6(CO)36]n− (n = 7–10), [Ni38C6(CO)42]n− (n = 7–9) and [HNi38C6(CO)42]n− (n = 6–8) derivatives, and several of the involved redox changes show features of electrochemical reversibility. In contrast, both [Ni32C6(CO)36]6– and [H6–nNi38C6(CO)42]n− (n = 5 or 6) support only one partially reversible oxidation step. Their different behaviour upon protonation or oxidation is an indirect, but unambiguous, proof of the hydride nature of [HNi32C6(CO)36]5– and [H6–nNi38C6(CO)42]n− (n = 3, 4, or 5), which could not be validated by 1H-NMR spectroscopy. 相似文献
Segmented poly(ether-ester-amide)s, (PEEA)s, of controlled hydrophilicity degree, based on poly(ε-caprolactone) (PCL), were synthesized according to a facile two-step procedure using α,ω-dihydroxy oligomeric PCL, 4,7,10-trioxa-1,13-tridecanediamine and macromers prepared from poly(ethylene glycol)s and adipoyl chloride. The PEEAs showed Mn values in the range 5–11.5 kDa. A PCL-type crystallinity was found by WAXS. DSC indicated Tm values (49–51 °C) close to that of PCL macromer. Single glass transitions were observed both by DSC and DMTA techniques and the Tg values (−58–−50 °C by DSC) were slightly higher than that of PCL. The water uptake was in the range 4.8–26.0 wt.-% depending on the length of the poly(ethylene glycol) segment.
A chemical investigation of the digestive glands of Mytilus galloprovincialis from North Adriatic Sea led to the isolation of three novel compounds, oxazinin-1 ( 1 ), oxazinin-2 ( 2 ) and oxazinin-3 ( 3 ). Their structures, including the relative stereochemistry, were established by spectroscopic means including extensive 2D NMR and molecular mechanics calculations. The new compounds were analyzed for cytotoxic activity and oxazinin-1 ( 1 ) was shown to inhibit the growth of WEHI 164 and J774 cell lines in vitro. 相似文献
A further chemical investigation of the Caribbean marine sponge Aplysina archeri led to the isolation of a novel bromo compound, archerine ( 1 ). Its structure was established through extensive NMR spectroscopy, including 1H-13C HSQC, 1H-13C HMBC and 1H-15N HMBC experiments, as well as positive FAB MS/MS spectra. The capability of archerine to chelate zinc ions was investigated. Archerine exhibited antihistamine activity on the isolated guinea pig ileum at concentrations as low as 1 μM . 相似文献
Catalytic systems based on unbridged substituted indenyl systems are becoming of interest in the production of elastomeric polypropylene. A full understanding of the structural features necessary to control this kind of behaviour has not yet been achieved, since relatively slight changes in the molecular architecture can lead to polymers with remarkably different properties. We report here our recent findings regarding the study of bicyclic zirconium and titanium complexes as fluxional catalysts in propylene polymerisation. Most of them have been synthesised according to a synthetic procedure that allowed us to prepare a series of complexes in which the ring fused to the cyclopentadienyl moiety is saturated and of different sizes, thus introducing a flexibility parameter that can be finely tuned. The results obtained show that the stereoselectivity induced by this class of catalysts strongly depends both on the structure of the ligand and on the nature of metal atom (Zr vs. Ti). The titanium-based catalysts yield polypropylenes with new and interesting microstructures, in particular when an higher stability is achieved through a careful choice of the substitution pattern of the ligands. 相似文献
