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581.
Georg Süss-Fink Isabelle Godefroy Matthieu Faure Antonia Neels Helen Stoeckli-Evans 《Journal of Cluster Science》2001,12(1):35-48
The cluster anion [HRu3(CO)11]- (1) reacts with dicyclohexylphosphine in THF solution to give the anionic derivative [HRu3(CO)8(PCy2)2]- (2), protonation of which yields the neutral cluster H2Ru3(CO)8(PCy2)2 (3) and, in the presence of excess phosphine, HRu3(CO)7(PCy2)3 (4). In protic methanol as reaction medium, the reaction of 1 with HPCy2 gives directly the neutral complex H2Ru3(CO)6(PCy2)2(HPCy2)2 (5), together with 4. The single-crystal structure X-ray analysis of 3 shows a closed triangular Ru3 framework. The electron count is in accordance with the EAN rule, but the structure analysis of 5 reveals an open, almost linear Ru3 skeleton, which is electron-deficient with respect to the EAN rule. 相似文献
582.
The concentration fluctuation c of diluted fluorescein dye, a high-Schmidt-number passive scalar (Sc=ν/D ≈ 2000, ν and D are the fluid momentum and dye diffusivities, respectively), is measured in the wake of a circular cylinder using a single-point
laser-induced fluorescence (SPLIF) technique. The streamwise decay rate of the mean and rms values of c is slow in comparison to that of θ, the temperature fluctuation for which the molecular Prandtl number Pr=ν/κ is about 0.7 (κ is the thermal diffusivity). The comparison between mean and rms distributions of c and θ highlights the combined role the Reynolds and Schmidt numbers play in terms of dispersing the scalar. The streamwise
evolution of the probability density functions (pdfs) of c and θ suggest that while p(θ) is approximately Gaussian in the intermediate wake (x/d ≈ 80), p(c) is strongly non-Gaussian, and depends on both x/d and Re. The skewness of c is larger than that of θ along the wake centreline. Arguably, the asymmetry of p(c) reflects the relatively strong organisation of the large-scale motion in the far-wake.
Received: 27 July 2000/Accepted: 22 December 2000 相似文献
583.
Low-order moments of the increments δu andδv where u and v are the axial and radial velocity fluctuations respectively, have been obtained using single and X-hot wires mainly on the
axis of a fully developed pipe flow for different values of the Taylor microscale Reynolds numberR
λ. The mean energy dissipation rate〉ε〈 was inferred from the uspectrum after the latter was corrected for the spatial resolution of the hot-wire probes. The corrected Kolmogorov-normalized
second-order structure functions show a continuous evolution withR
λ. In particular, the scaling exponentζ
v
, corresponding to the v structure function, continues to increase with R
λ in contrast to the nearly unchanged value of ζ
u
. The Kolmogorov constant for δu shows a smaller rate of increase with R
λ than that forδv. The level of agreement with local isotropy is examined in the context of the competing influences ofR
λ and the mean shear. There is close but not perfect agreement between the present results on the pipe axis and those on the
centreline of a fully developed channel flow.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
584.
A new four X-wire vorticity probe has been developed to measure all three components of the vorticity fluctuation vector
simultaneously. The performance of this probe is tested in a turbulent far-wake. The measured Reynolds stresses agree with
those obtained previously from simpler hot wire configurations. The variances of the lateral vorticity components agree within
±15% with those measured with a one-component vorticity probe. The variances of the streamwise vorticity component are also
in reasonable agreement with those inferred from two X-wires. At high wavenumbers, the measured vorticity spectra agree with
those obtained by direct numerical simulation (DNS) in the central region of a turbulent channel flow. The comparison of measured
high-order moments of vorticity on the wake centerline with local isotropy also suggests the probe performs satisfactorily.
Received: 31 December 1997/Accepted: 6 January 1999 相似文献
585.
Lorella Paparo Maria Antonia Maglio Maddalena Cortese Cristina Bruno Mario Capasso Erika Punzo Veronica Ferrucci Vito Alessandro Lasorsa Maurizio Viscardi Giovanna Fusco Pellegrino Cerino Alessia Romano Riccardo Troncone Massimo Zollo 《Molecules (Basel, Switzerland)》2022,27(3)
Butyrate is a major gut microbiome metabolite that regulates several defense mechanisms against infectious diseases. Alterations in the gut microbiome, leading to reduced butyrate production, have been reported in patients with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection. A new butyrate releaser, useful for all the known applications of butyrate, presenting physiochemical characteristics suitable for easy oral administration, (N-(1-carbamoyl-2-phenyl-ethyl) butyramide (FBA), has been recently developed. We investigated the protective action of FBA against SARS-CoV-2 infection in the human small intestine and enterocytes. Relevant aspects of SARS-CoV-2 infection were assessed: infectivity, host functional receptor angiotensin-converting enzyme-2 (ACE2), transmembrane protease serine 2 (TMPRSS2), neuropilin-1 (NRP1), pro-inflammatory cytokines expression, genes involved in the antiviral response and the activation of Nf-kB nuclear factor (erythroid-derived 2-like) 2 (Nfr2) pathways. We found that FBA positively modulates the crucial aspects of the infection in small intestinal biopsies and human enterocytes, reducing the expression of ACE2, TMPRSS2 and NRP1, pro-inflammatory cytokines interleukin (IL)-15, monocyte chemoattractant protein-1 (MCP-1) and TNF-α, and regulating several genes involved in antiviral pathways. FBA was also able to reduce the number of SARS-CoV-2-infected cells, and ACE2, TMPRSS2 and NRP1 expression. Lastly, through the inhibition of Nf-kB and the up-regulation of Nfr2, it was also able to reduce the expression of pro-inflammatory cytokines IL-15, MCP-1 and TNF-α in human enterocytes. The new butyrate releaser, FBA, exerts a preventive action against SARS-CoV-2 infection. It could be considered as an innovative strategy to limit COVID-19. 相似文献
586.
Prof. Dr. Lena Keller Dr. Emilia Oueis Dr. Amninder Kaur Dr. Nasim Safaei Dr. Susanne H. Kirsch Dr. Antonia P. Gunesch Dr. Sibylle Haid Dr. Ulfert Rand Prof. Dr. Luka Čičin-Šain Dr. Chengzhang Fu PD Dr. Joachim Wink Prof. Dr. Thomas Pietschmann Prof. Dr. Rolf Müller 《Angewandte Chemie (International ed. in English)》2023,62(6):e202214595
A new family of highly unusual sesquarterpenoids (persicamidines A–E) exhibiting significant antiviral activity was isolated from a newly discovered actinobacterial strain, Kibdelosporangium persicum sp. nov., collected from a hot desert in Iran. Extensive NMR analysis unraveled a hexacyclic terpenoid molecule with a modified sugar moiety on one side and a highly unusual isourea moiety fused to the terpenoid structure. The structures of the five analogues differed only in the aminoalkyl side chain attached to the isourea moiety. Persicamidines A–E showed potent activity against hCoV-229E and SARS-CoV-2 viruses in the nanomolar range together with very good selectivity indices, making persicamidines promising as starting points for drug development. 相似文献
587.
Martin Linden Silja Hofmann Antonia Herman Nicole Ehler Robin M. Bär Siegfried R. Waldvogel 《Angewandte Chemie (International ed. in English)》2023,62(9):e202214820
Pyrazolines and pyrazoles are common and important motifs of pharmaceutical agents and agrochemicals. Herein, the first electrochemical approach for their direct synthesis from easily accessible hydrazones and dipolarophiles up to decagram scale is presented. The application of a biphasic system (aqueous/organic) even allows for the conversion of highly sensitive alkenes, wherein inexpensive sodium iodide is employed in a dual role as supporting electrolyte and mediator. In addition, mechanistic insight into the reaction is given by the isolation of key step intermediates. The relevance of the presented reaction is underlined by the synthesis of commercial herbicide safener mefenpyr-diethyl in good yields. 相似文献
588.
Giancarlo Ranalli Claudia Belli Giuseppe Lustrato Antonia Meloscia Massimiliano Orsini 《Macromolecular Symposia》2006,238(1):98-104
Due to their growth and metabolism, microorganisms can cause severe damage to Cultural Heritage, through mechanical and chemical processes. In this paper we used molecular approaches to study bacterial communities on samples from the archeological site of Pompei (Italy). In particular four DNA extraction methods without prior cultivation of the microflora were compared. In terms of efficiency, the DNA extraction method based on the Tri-Reagent™ kit gave the best results. All extraction protocols coupled with 16S rDNA fragments PCR amplification were satisfactory; but the best results were obtained by Klentaq DNA LA Polymerase™; this enzyme can be considered an effective tool for amplification of DNA from Cultural Heritage and possibly other environmental samples. 相似文献
589.
Ultrasonic vibrations in the micrometer amplitude range have been proven to be capable to influence frictional contacts with respect to decreasing friction coefficients in experiments on small test set-ups solely loaded by their small weight [1]. In this paper experimental results on applying this effect to large objects are presented. To get large vibration amplitudes and velocities detailed pre-investigation on the excitation of the structures in contact have been performed. These structures are investigated in a roller rig designed for these purposes. (© 2015 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献