Design and Stereoselective Synthesis of ProM‐2: A Spirocyclic Diproline Mimetic with Polyproline Type II (PPII) Helix Conformation

With the aim of developing polyproline type II helix (PPII) secondary‐structure mimetics for the modulation of prolin‐rich‐mediated protein–protein interactions, the novel diproline mimetic ProM‐2 was designed by bridging the two pyrrolidine rings of a diproline (Pro–Pro) unit through a Z‐vinylidene moiety. This scaffold, which closely resembles a section of a PPII helix, was then stereoselectively synthesized by exploiting a ruthenium‐catalyzed ring‐closing metathesis (RCM) as a late key step. The required vinylproline building blocks, that is, (R)‐N‐Boc‐2‐vinylproline (Boc=tert‐butyloxycarbonyl) and (S,S)‐5‐vinylproline‐tert‐butyl ester, were prepared on a gram scale as pure stereoisomers. The difficult peptide coupling of the sterically demanding building blocks was achieved in good yield and without epimerization by using 2‐(1H‐7‐azabenzotriazol‐1‐yl)‐1,1,3,3‐tetramethyluronium hexafluorophosphate (HATU)/N,N‐diisopropylethylamine (DIPEA). The RCM proceeded smoothly in the presence of the Grubbs II catalyst. Stereostructural assignments for several intermediates were secured by X‐ray crystallography. As a proof of concept, it was shown that certain peptides containing ProM‐2 exhibited improved (canonical) binding towards the Ena/VASP homology 1 (EVH1) domain as a relevant protein interaction target.     

Copolymer-controlled homogeneous precipitation for the synthesis of porous microfibers of alumina

Mesoporous aluminas with a uniform fibrous morphology were synthesized using a copolymer-controlled homogeneous precipitation method under hydrothermal conditions. Scanning electron microscopy, X-ray diffraction, solid-state magic-angle spinning nuclear magnetic resonance, transmission electron microscopy, thermogravimetric analysis, nitrogen adsorption, Fourier transform infrared spectrometry, and elemental analysis techniques were used to characterize the samples. The effect of various synthesis conditions on the morphology and mesoporous structure of the alumina fibers was investigated. Such porous alumina microfibers may find applications in nanotechnology and catalysis. They can also be used as advanced high-temperature composite materials and templates for fabrication of fibrous materials of various compositions, such as carbon, transition-metal oxides, and polymers.     

Ni/Al2O3 catalysts for CO methanation: Effect of Al2O3 supports calcined at different temperatures

The correlation between phase structures and surface acidity of Al₂O₃ supports calcined at different temperatures and the catalytic performance of Ni/Al₂O₃ catalysts in the production of synthetic natural gas (SNG) via CO methanation was systematically investigated. A series of 10 wt% NiO/Al₂O₃ catalysts were prepared by the conventional impregnation method, and the phase structures and surface acidity of Al₂O₃ supports were adjusted by calcining the commercial γ-Al₂O₃ at different temperatures (600–1200 °C). CO methanation reaction was carried out in the temperature range of 300–600 °C at different weight hourly space velocities (WHSV = 30000 and 120000 mL·g^?1·h^?1) and pressures (0.1 and 3.0 MPa). It was found that high calcination temperature not only led to the growth in Ni particle size, but also weakened the interaction between Ni nanoparticles and Al₂O₃ supports due to the rapid decrease of the specific surface area and acidity of Al₂O₃ supports. Interestingly, Ni catalysts supported on Al₂O₃ calcined at 1200 °C (Ni/Al₂O₃-1200) exhibited the best catalytic activity for CO methanation under different reaction conditions. Lifetime reaction tests also indicated that Ni/Al₂O₃-1200 was the most active and stable catalyst compared with the other three catalysts, whose supports were calcined at lower temperatures (600, 800 and 1000 °C). These findings would therefore be helpful to develop Ni/Al₂O₃ methanation catalyst for SNG production.     

Finite-Time Blowup for the Inviscid Primitive Equations of Oceanic and Atmospheric Dynamics

In an earlier work we have shown the global (for all initial data and all time) well-posedness of strong solutions to the three-dimensional viscous primitive equations of large scale oceanic and atmospheric dynamics. In this paper we show that for certain class of initial data the corresponding smooth solutions of the inviscid (non-viscous) primitive equations, if they exist, they blow up in finite time. Specifically, we consider the three-dimensional inviscid primitive equations in a three-dimensional infinite horizontal channel, subject to periodic boundary conditions in the horizontal directions, and with no-normal flow boundary conditions on the solid, top and bottom boundaries. For certain class of initial data we reduce this system into the two-dimensional system of primitive equations in an infinite horizontal strip with the same type of boundary conditions; and then we show that for specific sub-class of initial data the corresponding smooth solutions of the reduced inviscid two-dimensional system develop singularities in finite time.     

Comparison of stochastic resonance in static and dynamical nonlinearities

We compare the stochastic resonance (SR) effects in parallel arrays of static and dynamical nonlinearities via the measure of output signal-to-noise ratio (SNR). For a received noisy periodic signal, parallel arrays of both static and dynamical nonlinearities can enhance the output SNR by optimizing the internal noise level. The static nonlinearity is easily implementable, while the dynamical nonlinearity has more parameters to be tuned, at the risk of not exploiting the beneficial role of internal noise components. It is of interest to note that, for an input signal buried in the external Laplacian noise, we show that the dynamical nonlinearity is superior to the static nonlinearity in obtaining a better output SNR. This characteristic is assumed to be closely associated with the kurtosis of noise distribution.     

Pointwise inequalities of logarithmic type in Hardy-Hölder spaces

We prove some optimal logarithmic estimates in the Hardy space H ^∞(G) with Hölder regularity, where G is the open unit disk or an annular domain of ?. These estimates extend the results established by S.Chaabane and I.Feki in the Hardy-Sobolev space H ^k,∞ of the unit disk and those of I. Feki in the case of an annular domain. The proofs are based on a variant of Hardy-Landau-Littlewood inequality for Hölder functions. As an application of these estimates, we study the stability of both the Cauchy problem for the Laplace operator and the Robin inverse problem.     

卫星系统中的混沌控制

对于非线性扰动系统对指令信号的跟踪问题,提出解析条件和实现方法.对在反馈中包含线性动力和非线性两部份的非线性扰动设备进行了研究,设备的非线性部份和扰动是未知的但是有界的.提出控制卫星天平动角的算法,用图示对该算法作了说明.     

On the buckling of elastic plates

The Föppl-von Kármán equations are used toexplore the onset of linear instability and the subsequent nonlineardevelopment of buckling patterns in a flat elastic plate dueto an imposed shear or body force such as gravity. Experimentalresults are also presented for a clamped and sheared sheet ofNeoprene rubber and these compare favourably with theory.     

Random Polyesteramides Based on Glycolic Acid and β-Alanine

A series of random polyesteramides (PEAs) within a range of molar composition from 90/10 to 10/90 were synthesized by a direct melt polycondensation of glycolic acid and β-alanine. Their structures were fully characterized by NMR spectroscopy. The resulting copolymers are amorphous and present increasing glass transition temperatures at increasing β-alanine contents. The copolymers were also characterized by, FTIR, TGA and viscosimetry measurements.