1,057 research outputs found
Hamamlia, a replacement name for the fimbriid bivalve genus Cerkesia Monari non Moiseev
No full textThis note concerns a case of homonymy involving the genus Cerkesia Monari, 2003 (Fimbriidae, Bivalvia), which was instituted based on material from Kimmeridgian shallow-marine limestones in the western Pontides, Turkey (Monari 2003, p. 859). Recently, I discovered that Moiseev (1944, p. 24) had proposed the same name for a stromatoporoidean genus from the Upper Triassic of the
Caucasus, the type species being Cerkesia robinsoni Moiseev, 1944 (p. 25, pl. 3, fig. 1a–c; see also Thomas 1963, p. 22; Edwards and Vevers 1975, p. 60). To remove this homonymy, the name of the fimbriid genus is substituted here by Hamamlia nom. nov., the type species being Hamamlia contiae (Monari 2003) as originally diagnosed (p. 862, pl. 1, figs 1–15, text-figs 2–4). The new name is
after Hamamli, a village near the type locality
The Interplay between Candida albicans, Vaginal Mucosa, Host Immunity and Resident Microbiota in Health and Disease: An Overview and Future Perspectives
No full textVulvovaginal candidiasis (VVC), which is primarily caused by candida albicans, is an infection that affects up to 75% of all reproductive-age women worldwide. recurrent VVC (RVVC) is defined as >3 episodes per year and affects nearly 8% of women globally. At mucosal sites of the vagina, a delicate and complex balance exists between candida spp., host immunity and local microbial communities. In fact, both immune response and microbiota composition play a central role in counteracting overgrowth of the fungus and maintaining homeostasis in the host. If this balance is perturbed, the conditions may favor c. albicans overgrowth and the yeast-to-hyphal transition, predisposing the host to VVC. To date, the factors that affect the equilibrium between candida spp. and the host and drive the transition from C. albicans commensalism to pathogenicity are not yet fully understood. understanding the host- and fungus-related factors that drive VVC pathogenesis is of paramount importance for the development of adequate therapeutic interventions to combat this common genital infection. This review focuses on the latest advances in the pathogenic mechanisms implicated in the onset of VVC and also discusses novel potential strategies, with a special focus on the use of probiotics and vaginal microbiota transplantation in the treatment and/or prevention of recurrent VVC
Regioselectivity in reactions between bis(2-benzothiazolyl)ketone and vinyl grignard reagents: C- versus o-alkylation—Part III
No full textThe reaction between bis(2-benzothiazolyl)ketone and vinyl Grignard reagents bearing different substituents on the vinyl moiety gave the product derived from attack on the carbonylic carbon- and/or oxygen-atom. The regioselectivity of the attack depends on the kind of substituents bound to the vinylic carbon atoms and on their relative position. The reaction between vinylmagnesium bromide and 2-methyl-1-propenylmagnesium bromide was carried out under different experimental conditions and in the presence of radical scavengers. The results indicate a plausible mechanistic pathway involving radical intermediates in the case of O-alkylation, but a polar ones in the case of classic C-alkylation. This agrees with our previous reports indicating a key role played by the delocalization ability of the substituents bound to the carbonyl group in driving the regioselectivity of the vinylmagnesium bromide attack towards O-alkylation. Further support of this was obtained by diffractometric analysis of four distinct bis(heteroaryl)ketones
Monitoring a gas-cooled nuclear reactor core integrity
No full textThis work concerns with the problem of monitoring an Advanced Gas-cooled Nuclear Reactor (AGR) core. In the world wide context of energy production, the advanced gas-cooled reactor (AGR) nuclear power stations are approaching the end of their predicted operational live. Currently, it has been proposed to extend the operational lifetime of the nuclear plants if the distortions of the reactor cores are not as severe as initially predicted, and if it is possible to prove that the reactors are still safe to operate. The purpose of this work is to present a monitoring system based on analytical redundancy and directional residual generation using measurements obtained during the refueling process. In short this problem consists of building an unknown input observer with the role to estimate the friction force produced by the interaction between the wall of the fuel channel and the fuel assembly. This let to estimate the shape of the graphite bricks that comprise the core and, therefore, monitor any distortion of them
Selective formation of one or two C-C bonds promoted by carbanion addition to [Fe2(cp)2(CO)2(μ-CO)(μ-CSMe)]+
No full textThe reactions of [Fe2(cp)2(CO)2(μ-CO)(μ-CSMe)]CF 3SO3 (1; cp = η-C5H5) with a variety of carbon nucleophiles result in C-C bond formation at different sites of the molecule, (allyl)-MgCl (allyl = C3H5) undergoes cp addition to form [Fe2(cp)(η4-C5H5-allyl)(CO) 2(μ-CO)(μ-CSMe)] (2) and the alkylidene complex [Fe2(cp)(η-C5H4-allyl) (CO)2(μ-CO){μ-C(SMe)H}] (3), derived from cp to μ-C hydrogen migration. Li2Cu(CN)R2 adds at the μ-C atom to yield [Fe2(cp)2(CO)2(μ-CO){μ-C(SMe)R}] (R = Ph, 4; R = Me, 8), [FeFe(cp)2(CO)(μ-CO){μ-C(SMe)R}] (R = Ph, 5; R = Me, 9), and [Fe2(cp)2(CO)(μ-CO){μ-C(ηl2-Ph)Ph}] (6) or the vinylidene derivative [Fe2(cp)2(CO)(μ-CO)(μ-C=CH2)] (10) in the case of phenyl or methyl organocuprate reagents, respectively. The latter complexes are the result of C-SMe bond breaking occurring, through different reaction paths, in 4 and 8. Likewise, the formation of [Fe2-(cp)2(CO)(μ-CO){μ-C=C(CN)2}] (11) from 1 and NaCH(CN)2 occurs via a direct addition at the μ-C carbon followed by HSMe elimination. The nucleophilic attack at the terminal CO in 1 is achieved with LiC≡CPh, which forms two new C-C bonds in the alkylidene complex [FeFe(cp)2(CO)(μ-CO){μ-C(SMe)C(O)CCPh}] (12) after C(O)CCPh migration from Fe to the bridging carbene carbon. The analogous [FeFe(cp)2(CO)(μ-CO)(μ-C(SMe)C(O)(2-th)}] (13; 2-th = 2-C4H3S) and [Fe2(cp)(η4-C5H5-(2-th)(CO) 2(μ-CO)(μ-CSMe)] (14) are obtained from 1 and Lith via addition at the CO and cp groups, respectively. The relevance of these reactions is discussed in terms of selective C-C bond formation that, if it occurs at the cp or CO terminal ligands, favors the hydrogen migration (e.g. formation of 3) or the carbyne-carbonyl migratory coupling (e.g. formation of 12 and 13), respectively. The X-ray structures of [Fe2-(cp)2(CO)(μ-CO){μ-C(η2-Ph)Ph}] (6) and [FeFe(cp)2(CO)(μ-CO){μ-C(SMe)C(O)(2-th)}] (13) have revealed the peculiarity of the Ph and SMe group coordination to the iron. Their structural features are discussed in comparison with those of analogous complexes. © 1997 American Chemical Society
Oxazolidin-2-ones-Containing Pseudopeptides that Fold into beta-Bend Ribbon Spirals
No full textThree sets of oligomers containing the 4-carboxy-5-methyl-oxazolidin-2-one (Oxd) moiety have been synthesized with the aim of checking whether these molecules are able to fold in ordered structures: A set [Boc-(L-Ala-L-Oxd)n-OR], B set [Boc-(L-Ala-D-Oxd)n-OR] and C set [Boc-(Aib-L-Oxd)n-OR] preferential conformations have been analyzed with IR absorption, NMR and CD. We have noticed that in these oligomers three stabilizing effects are active: (i) the rigid Oxd –CO-N(C
Unfolding of cytochrome c immobilized on self-assembled monolayers. An electrochemical study.
No full textThe TE process of progressively unfolded bovine cytochrome c (cyt c), immobilized on different self-assembled monolayers, was investigated. Direct electrochemical measurements were performed on cyt c adsorbed on mercaptopyridine (MP) and
mixed 11-mercapto-1-undecanoic acid/11-mercapto-1-undecanol (MUA/MU) at varying temperature,
in the presence of urea as unfolding agent. Under strongly unfolding conditions, a non-native form of
cyt c, in which the Met ligand is replaced by a His, was observed on both MP and
MUA/MU SAMs. The E° of the native form, in which the haem is axially coordinated by Met and
His, slightly shifts to negative values upon increasing urea concentration. However, the non-native bis-His species shows a much lower E° value (by approximately 0.4 V) which is by far enthalpic in origin and largely determined by axial ligand swapping. Analysis of the reduction enthalpies and entropies and of the ET rate constants indicate that the nature of the SAM (hydrophilic or anionic) results in changes in the conformational rearrangement of the cyt c under unfolding conditions
Synthesis and characterization of trigonal-bipyramidal platinum(II) olefin complexes with chalcogenide ligands in axial positions. X-ray molecular structures of [Pt(SMe)(2)(dmphen)(diphenyl fumarate)], its cationic dipositive derivative [Pt(SMe2)(2)(dmphen)(diphenyl fumarate)][BF4](2), and free diphenyl fumarate
No full textThe oxidative addition of RE-ER molecules (E = O, R = H, C(O)Ph, C(O)Me; E = S, Se, Te, R = Me, Ph) to Pt(0) precursors [Pt(N,N-chelate)(olefin)] (1: N,N-chelate = e.g. 2,9-dimethyl-1,10-phenanthroline; olefin = maleic or fumaric ester) has been studied. Symmetrical cleavage of the E-E bonds affords unprecedented trigonal-bipyramidal Pt(II) complexes of the formula [Pt(ER)2(N,N-chelate)(olefin)] (2). Products of type 2, which have been characterized through H-1 and C-13 NMR spectroscopy, contain chalcogenide ligands in the axial positions. The reactivity of the new compounds has also been investigated. Thus, Pt-OH fragments generated by the addition of H2O2 are acetylated by acetic anhydride. Furthermore, S, Se, and Te coordinated to Pt are readily methylated by trimethyloxonium tetrafluoroborate, affording the first examples of dipositive coordinatively saturated platinum(11) cations (3). The structures of the related neutral [Pt(SMe)(2)(2,9-dimethyl-1,10-phenanthroline)(diphenyl fumarate)] and cationic [Pt( Me2)(2)(2,9-dimethyl-1,10-phenanthroline)(diphenyl fumarate)] [BF4](2) compounds have been determined by X-ray diffraction together with that of the free diphenyl fumarate ligand. RI Monari, Magda/B-2648-200
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