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1.
Prof. Henning Hopf Prof. Stephen A. Matlin Prof. Goverdhan Mehta Prof. Alain Krief 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2020,132(6):2170-2174
In chemistry and other sciences, hype has become commonplace, compounded by the hypocrisy of those who tolerate or encourage it while disapproving of the consequences. This reduces the credibility and trust upon which all science depends for support. Hype and hypocrisy are but first steps down a slippery slope towards falsification of results and dissemination of fake science. Systemic drivers in the contemporary structure of the science establishment encourage exaggeration and may lure the individual into further steps along the hype-hypocrisy-falsification-fakery continuum. Collective, concerted intervention is required to effectively discourage entry to this dangerous pathway and to restore and protect the probity and reputation of the science system. Chemists must play and active role in this effort. 相似文献
2.
Dr. Showkat Rashid Dr. Bilal A. Bhat Prof. Goverdhan Mehta 《Chemistry (Weinheim an der Bergstrasse, Germany)》2020,26(71):17005-17010
Previously unknown entities in the form of 1,2,3,4,5,6,7,8,9,10-decahydroxydecalins (DHDs) have been conceptualized and the first member of this class, an inosito-inositol, has been synthesized from aromatic hydrocarbon naphthalene following a flexible strategy that is amenable to diversity creation. The DHD accessed here has been subjected to preliminary in silico evaluation with Aβ and may hold some promise in Alzheimer's disease therapeutics. 相似文献
3.
Recently developed strategies for late stage modification of peptides through CH activation, an arena of contemporary interest in chemical biology and drug discovery, are discussed. Through this tactic, non-polar amino acids in peptides have been selectively functionalized and CH activation enabled new CC and CX bond formations (arylation, alkynylation, fluorination, hydroxylation, azidation, etc.) are documented. Significant advances have been made in Pd or Au-catalyzed, racemization-free, tryptophan specific modifications of large peptides via CH arylation and alkynylation reactions without any protecting group requirement. Development of a new biaryl stapling technique for complex peptides, 18F radiofluorine introduction and diversity oriented post synthetic applications on bio-active cyclopeptides like valinomycin and aureobasidin are additional highlights which underscores the vast potential of late stage CH activation reactions in peptide based therapeutics research. 相似文献
4.
5.
Summary The unsteady, compressible Navier-Stokes equations in Reynolds-averaged variables are solved for a shock wave turbulent boundary layer interaction. For the free stream Mach number 3.7 and Reynolds number 8.202×106 computation is performed using MacCormack's explicit-implicit finite difference scheme with 42×42 grid points. It is found that the peak heating amplification correlation agrees well with computational results.
Numerische Untersuchung des Auftreffens einer schiefen Stoßwelle auf eine ebene Platte
Zusammenfassung Die Navier-Stokes-Gleichungen in instationärer, kompressibler Form mit Reynolds-gemittelten Variablen werden für die gegenseitige Beeinflussing einer Stoßwelle mit einer turbulenten Grenzschicht gelöst. Die Berechnung wird anhand des MacCormack's explizit-impliziten Finite-Differenzen-Verfahrens mit 42×42 Gitterpunkten für eine Freistrahl-Machzahl von 3,7 und einer Reynoldszahl von 8,202·106 durchgeführt. Die Rechenergebnisse stimmen mit den Experimenten gut überein.相似文献
6.
Conclusions An experimental study which shows the effects of relatively small changes in the initial conditions on the development of the three-dimensional structure of a plane mixing layer originating from laminar boundary layers has been completed. It was shown that while the exact shapes and positions of the streamwise vortex structures are not the same for the two initial conditions, their overall distribution, reorganization and decay are very similar. The present results imply that while some of the specific details of the streamwise vortex structure may be facility dependent, a relatively strong structure, which produces significant three-dimensionality, should form in all mixing layers originating from laminar boundary layers. After some initial readjustments, the structure will appear in the form of counter-rotating pairs of streamwise vortices which, in the mean, grow with the mixing layer and decay in strength.The present results also serve as a warning that small changes in initial conditions may significantly affect the Reynolds stress distributions in the near-field. The most likely mechanism for this is through the effects of very small changes in initial boundary layer properties on the details (strength and location) of the spanwise vortex roll-up. Despite these relatively large differences in the near-field, both mixing layers attain comparable turbulence structure and growth rates in the far-field. In addition, the behavior of the streamwise vortex structure does not appear to be affected by the differences in the near-field Reynolds stress distributions. 相似文献
7.
R.C. Mehta 《Shock Waves》2002,11(6):431-440
The pressure oscillations over a forward facing spike attached to an axisymmetric blunt body are simulated by solving time-dependent
compressible Navier–Stokes equations. The governing fluid flow equations are discretized in spatial coordinates employing
a finite volume approach which reduces the equations to semidiscretized ordinary differential equations. Temporal integration
is performed using the two-stage Runge–Kutta time stepping scheme. A global time step is used to obtain a time-accurate numerical
solution. The numerical computation is carried out for a freestream Mach number of 6.80 and for spike length to hemispherical
diameter ratios of 0.5, 1.0 and 2.0. The flow features around the spiked blunt body are characterized by a conical shock wave
emanating from the spike tip, a region of separated flow in front of the hemispherical cap, and the resulting reattachment
shock wave. Comparisons of the numerical results are made with the available experimental results, such as schlieren pictures
and the surface pressure distribution along the spiked blunt body. They are found to be in good agreement. Spectral analysis
of the computed pressure oscillations are performed employing fast Fourier transforms. The surface pressure oscillations over
the spike and phase plots exhibit a behaviour analogous to that of the Van der Pol equation for a self-sustained oscillatory
flow.
Received 28 February 2001 / Accepted 17 January 2002 相似文献
8.
R. D. Mehta 《Experiments in fluids》1990,8(6):354-356
An experimental comparison method is proposed for the verification of mean flow and turbulence measurements obtained with a three-dimensional laser Doppler velocimeter system. Such measurements can include large errors caused by problems unique to three-dimensional systems. Direct comparisons of laser and hot cross-wire measurements obtained in two-dimensional flows, as is the common practice, will not bear out all the errors associated with three-dimensional laser systems. It is proposed here that the errors may be adequately quantified by making the direct comparisons in a weakly three-dimensional turbulent shear flow. The weak three-dimensional flow ensures high accuracy of the cross-wire data while still generating sufficiently strong secondary mean flow and Reynolds shear stresses so that all the laser measurements may be fully verified. This type of shear flow is easily generated by introducing a weak streamwise vortex into a nominally two-dimensional turbulent shear layer. 相似文献
9.
In order to initiate a comprehensive study of graft copolymerization of vinyl monomers onto soluble protein-gelatin, we have studied grafting of ethyl acrylate (EA) and methyl methacrylate (MMA) onto gelatin using eerie ammonium nitrate (CAN) and eerie ammonium sulfate (CAS) as the redox initiator in an aqueous medium. A small amount of mineral acid (HNO3 with CAN and H2SO4 with CAS) was found to catalyze the graft copolymerization. Graft copolymerization reactions were carried out at different temperatures. Maximum grafting occurred at 65°C both with EA and MMA. Percentage grafting has been determined as function of 1) concentration of monomer (EA and MMA), 2) concentration of initiator (CAN and CAS), 3) concentration of acid (HNO3 and H2SO4), 4) time, and 5) temperature. 相似文献
10.
The ring opening polymerization of L-lactide was studied in bulk using stannous octoate as initiator. In some experiments, triphenylphosphine, a Lewis base was also used as co-initiator. The polymerization was carried out at 130°C up to 29 h. The monomer was used after recrystallizing three times with dry toluene. Experiments were carried out using a wide range of monomer to initiator ratio. The averages and distributions of molar masses of resulting PLA have been determined by means of size exclusion chromatography, SEC. It is shown that the (mode, process) procedure of dispersion of the catalyst in polymerization system affects the molar mass distribution of the product as is evidenced by the bimodality or even trimodality observed in the SEC chromatograms. 相似文献