Rolf Hesterberg  Michel Bonin  Martin Sommer  Matthias Burgener  Bernhard Trusch  Dragan Damjanovic  Jürg Hulliger 《Journal of Applied Crystallography》2019,52(3):564-570

The growth speed of (hkl) faces in the vapour phase, the absolute structure obtained by X‐ray crystallography, and the value and the sign of the pyroelectric coefficient of meta‐nitroaniline (mNA) were analysed in detail. The in situ observation of morphologically well developed faces of several mNA crystals growing in evacuated ampoules reveals no pronounced growth speed anisotropy for polar faces defining the unique axis 2 of the mm2 group. Scanning pyroelectric microscopy confirms mono‐domain mNA crystals. X‐ray measurements in the space group Pca2₁ show that the molecular planes coincide with the {} and {} faces, and the nitro groups cover the {201} face in the opposite direction to the crystal tip, characterizing the polar habitus studied here. At room temperature, the sign of the pyroelectric coefficient is positive for a measured effective value of 6.3 µC m⁻² K⁻¹, in good agreement with values reported by other authors. From previous elastic and piezoelectric published data, the secondary pyroelectric effect was calculated to be positive and far greater than the effective one, yielding a negative value for the primary pyroelectric coefficient.  相似文献   

    

Quanqing Li  Kaimin Teng  Xian Wu  Wenbo Wang 《Mathematical Methods in the Applied Sciences》2019,42(5):1480-1487

In this paper, we study the following fractional Schrödinger equation with critical or supercritical growth where 0 < s < 1, N > 2s, λ > 0, , , ( ? Δ)^s denotes the fractional Laplacian of order s and f is a continuous superlinear but subcritical function. Under some suitable conditions, we prove that the equation has a nontrivial solution for small λ > 0 by variational methods. Our main contribution is related to the fact that we are able to deal with the case .  相似文献   

    

Insung Han  Xianghui Xiao  Haiping Sun  Ashwin J. Shahani 《Acta Crystallographica. Section A, Foundations and Advances》2019,75(2):281-296

Quasicrystals and their approximants have triggered widespread interest due to the challenge of solving their complex crystal structures as well as their possibly exceptional properties. The structural motifs of approximants are similar to those of the corresponding quasicrystals, but to what extent are their crystallization pathways the same? Unfortunately, there have been very few in situ experimental investigations to answer this question. Here, by leveraging the high penetrating power of hard X‐rays, synchrotron‐based X‐ray tomography was conducted in order to capture the nucleation and growth of a decagonal quasicrystal and its related approximant. The combination of data‐driven computational analysis with new thermodynamic databases allowed the characterization, with high precision, of the constitutional and kinetic driving forces for crystallization. The experimental results prove that the growth of both crystals from a liquid is dominated by first‐order kinetics. Nevertheless, and somewhat surprisingly, significant differences were observed in their rates of nucleation and growth. The reasons for such divergent behaviours are discussed in light of contemporary theories of intermetallic crystallization.  相似文献   

    

Carmen Stelian  Jessica Muzy  Serge Labor  Marc Fivel  Hugues Cabane  Thierry Duffar 《Crystal Research and Technology》2019,54(1)

Crystal growth of oxides is generally difficult since large curvatures of the growth interface in these systems generate high thermal stress, dislocations and crystal cracking. Three‐dimensional numerical modeling is applied to investigate thermal stress distribution in sapphire and langatate La3Ta0.5Ga5.5O14 (LGT) semi‐transparent crystals grown by Czochralski (Cz) and Edge‐defined Film‐fed Growth (EFG) techniques. The analysis of thermal stress distribution in a sapphire ingot grown in a Czochralski furnace shows high von Mises stresses distributed almost symmetrically on large areas in the crystal. Thermal stress computations for piezoelectric langatate crystals grown in a Czochralski configuration show non‐symmetrical von Mises distribution with higher stress on one side of the ingot. These numerical results are in agreement with experimental results showing non‐symmetrical cracking at the outer surface of the crystal. 3D modeling of multi‐die EFG growth of white sapphire ribbons shows that the von Mises stress is almost constant when the number of ribbons is increased from two to ten. Two models are applied to simulate the internal radiative heat transfer in the sapphire crystals: P1 approximation and the Rosseland radiation model. Numerical results show that applying Rosseland formula introduces significant errors in temperature field calculations especially in the case of the EFG configuration.  相似文献   

    

《Applied Mathematics Letters》2019

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Krishnendu Sarkar  Pallab Banerji 《physica status solidi b》2019,256(10)

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《Physics letters. A》2019,383(17):2028-2032

We find that the simple coupling of network growth to the position of a random walker on the network generates a traveling wave in the probability distribution of nodes visited by the walker. We argue that the entropy of this probability distribution is bounded as the network size tends to infinity. This means that the growth of a space coupled to a random walker situated in it constrains its dynamics to a set of typical random walker trajectories, and walker trajectories inside the growing space are compressible.  相似文献   

    

《Computational Biology and Chemistry》2019

BackgroundThe recombinant human truncated Keratinocyte growth factor (Palifermin) is the only FDA approved medicine for the treatment of oral mucositis. The Keratinocyte growth factor is a fairly unstable protein due to its high aggregation propensity and therefore its expression as a secretory protein may results in the production of a protein with more stability, higher solubility, better folding, enhanced biological activity, N-terminal authenticity and simplified downstream processing.ObjectiveThe aim of this study was in silico evaluation of 31 different secretory signal peptides to determine the best theoretical candidates for the secretory production of recombinant truncated human KGF in E. coli.MethodsThirty different prokaryotic signal peptides experimentally shown to be capable of recombinant protein secretion in E.coli, along with the native KGF signal peptide were selected for further investigations. The signal peptide sequences were retrieved from the UniProt database. The ability of SPs to act as a secretory leader peptide for rhKGF and the location of cleavage sites were predicted by SignalP 4.1. Physicochemical properties of the signal peptides, which may influence protein secretion, were analyzed by ProtParam and PROSOII. Furthermore, the mRNA secondary structure and Gibbs free energy profile of the selected SPs were analyzed in the fusion state with the rhKGF using Visual Gene Developer package.Results and ConclusionComputational analysis of the physicochemical properties affecting protein secretion identified Sec-B dependent OmpC, Bla, and StaI and SRP dependent TolB signal peptides as the best theoretical candidates for the secretory production of recombinant truncated human KGF in E.coli.  相似文献   

    

Katsuya Hyodo  Yoshinori Arisaka  Satoshi Yamaguchi  Tetsuya Yoda  Nobuhiko Yui 《Macromolecular bioscience》2019,19(4)

Modulation of material properties and growth factor application are critical in constructing suitable cell culture environments to induce desired cellular functions. Sulfonated polyrotaxane (PRX) surfaces with immobilized vascular endothelial growth factors (VEGFs) are prepared to improve network formation in vascular endothelial cells. Sulfonated PRXs, whereby sulfonated α‐cyclodextrins (α‐CDs) are threaded onto a linear poly(ethylene glycol) chain capped with bulky groups at both terminals, are coated onto surfaces. The molecular mobility of sulfonated PRX surfaces is modulated by tuning the number of threading α‐CDs. VEGF is immobilized onto surfaces with varying mobility. Low mobility and VEGF‐immobilization reinforce cell proliferation, yes‐associated protein activity, and rhoA, pdgf, ang‐1, and pecam‐1 gene expression. Highly mobile surfaces and soluble VEGF weakly affect these cell responses. Network formation is strongly stimulated in vascular endothelial cells only on low‐mobility VEGF‐immobilized surfaces, suggesting that molecular mobility and VEGF immobilization synergistically control cell function.  相似文献   

    

Tieyan Si  Xian Zou  Zhiguang Wu  Tianlong Li  Xin Wang  Krasnyuk Ivan Ivanovich  Qiang He 《化学:亚洲杂志》2019,14(14):2460-2464

We report the bubble dragged microrocket consisting of functionalized multilayer polymer covered asymmetrically by platinum nanoparticles. The microrocket is pushed back during bubble growth over a small step and dragged forward over a big step during bubble explosion. Each bubble explosion induced a shock wave of gas which propagates in water at ultrafast speed. The bubble dragged microrocket can move along an approximate straight line instead of a fluctuating circle which is the trajectory of a bubble‐pushed microrocket in most cases, which makes it a promising candidate for drug delivery and simulating rod‐shaped bacteria.  相似文献