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991.
Laachachi A Ball V Apaydin K Toniazzo V Ruch D 《Langmuir : the ACS journal of surfaces and colloids》2011,27(22):13879-13887
The present paper relies on the original idea to design multifunctional coatings, and in particular highly efficient intumescent flame retardant coatings, based on the diffusion of polyphosphates (PSPs) in exponentially growing "layer-by-layer" films made from montmorillonite (MMT) and poly(allylamine) (PAH). Here, we used polyphosphates as an acid source, polyallylamine as both a carbon source and a swelling agent, and finally clays to reinforce the intumescent char strength and also for their oxygen barrier property. The coatings made from the alternated deposition of n = 60 layer pairs of PAH and MMT reach a considerable thickness of ~18 μm with well-defined ordering of the MMT in the direction parallel to the substrate. Structural, morphological, mechanical, gas barrier, and fire resistance properties of these films have been studied. Excellent oxygen barrier properties and extraordinary fire resistance properties are demonstrated based on the basis of a strong increase of the time to ignition and on a decrease of the heat release rate of polylactide substrates during mass loss calorimeter tests. This new and innovative intumescent flame retardant system based on (PAH-MMT)(n)-PSP coatings is a promising universal treatment for current polymeric materials. 相似文献
992.
993.
Given a smooth complex threefold X, we define the virtual motive $[\operatorname{Hilb}^{n}(X)]_{\operatorname {vir}}$ of the Hilbert scheme of n points on X. In the case when X is Calabi–Yau, $[\operatorname{Hilb}^{n}(X)]_{\operatorname{vir}}$ gives a motivic refinement of the n-point degree zero Donaldson–Thomas invariant of X. The key example is X=?3, where the Hilbert scheme can be expressed as the critical locus of a regular function on a smooth variety, and its virtual motive is defined in terms of the Denef–Loeser motivic nearby fiber. A crucial technical result asserts that if a function is equivariant with respect to a suitable torus action, its motivic nearby fiber is simply given by the motivic class of a general fiber. This allows us to compute the generating function of the virtual motives $[\operatorname{Hilb}^{n} (\mathbb{C}^{3})]_{\operatorname{vir}}$ via a direct computation involving the motivic class of the commuting variety. We then give a formula for the generating function for arbitrary X as a motivic exponential, generalizing known results in lower dimensions. The weight polynomial specialization leads to a product formula in terms of deformed MacMahon functions, analogous to Göttsche’s formula for the Poincaré polynomials of the Hilbert schemes of points on surfaces. 相似文献
994.
ABSTRACT Energy losses in solar cells caused by the spectral mismatch can be reduced by adapting the solar spectrum using a downconversion material where one higher energy visible photon is ‘cut' into two lower energy near-infrared photons that both can be absorbed by the solar cell. Downconversion with the (Pr3+, Yb3+) couple in YF3 is investigated. Based on analysis of luminescence and diffuse reflectance spectra it is evident that two-step energy transfer takes place from the 3P0 level of Pr3+ (around 490 nm) exciting two Yb3+ to the 2F5/2 level giving emission around 980 nm. The transfer efficiency increases with Yb3+ concentration and is 86% for YF3 doped with 0.5% Pr3+ and 30% Yb3+. Due to concentration quenching the intensity of emission from Yb3+ is strongly reduced and the 2F5/2 emission intensity reaches a maximum for the sample with 0.5% Pr3+ and 2–5% Yb3+ at 300 K. Temperature dependent measurements reveal the role of the Pr3+ 1G4 level in the energy transfer between Pr3+ and Yb3+. Back-transfer of excitation energy from the Yb3+ 2F5/2 level to the 1G4 level of Pr3+ occurs and quenches the Yb3+ emission. The quenching is shown to become more efficient between 4 and 50 K due to faster phonon-assisted energy transfer between the Yb3+ donors. Upon raising the temperature from 50 to 300 K, the luminescence life time of the Yb3+ emission increases again because the small energy difference between the Pr3+ (1G4) level and the Yb3+ (2F5/2) level (~300 cm?1) which makes the 1G4 less efficient as a trap for the excitation energy. The present results give insight into factors involved in the concentration quenching in downconversion materials based on the (Pr3+, Yb3+) couple. 相似文献
995.
The distance d(i,j) between any two vertices i and j in a graph is the number of edges in a shortest path between i and j. If there is no path connecting i and j, then d(i,j)=∞. In 2001, Latora and Marchiori introduced the measure of efficiency between vertices in a graph (Latora and Marchiori, 2001) [1]. The efficiency between two vertices i and j is defined to be ∈i,j=j. In this paper, we investigate the efficiency of star-like networks, and show that networks of this type have a high level of efficiency. We apply these ideas to an analysis of the Metropolitan Atlanta Rapid Transit Authority (MARTA) Subway system, and show this network is 82% as efficient as a network where there is a direct line between every pair of stations. 相似文献
996.
Jun Zhou Xiaosheng Gao James C. Sobotka Bryan A. Webler Brian V. Cockeram 《International Journal of Solids and Structures》2014
One of the major drawbacks of the Gurson-type of porous plasticity models is the inability of these models to predict material failure under low stress triaxiality, shear dominated conditions. This study addresses this issue by combining the damage mechanics concept with the porous plasticity model that accounts for void nucleation, growth and coalescence. In particular, the widely adopted Gurson–Tvergaard–Needleman (GTN) model is extended by coupling two damage parameters, representing the volumetric damage (void volume fraction) and the shear damage, respectively, into the yield function and flow potential. The effectiveness of the new model is illustrated through a series of numerical tests comparing its performance with existing models. The current model not only is capable of predicting damage and fracture under low (even negative) triaxiality conditions but also suppresses spurious damage that has been shown to develop in earlier modifications of the GTN model for moderate to high triaxiality regimes. Finally the modified GTN model is applied to predict the ductile fracture behavior of a beta-treated Zircaloy-4 by coupling the proposed damage modeling framework with a recently developed J2–J3 plasticity model for the matrix material. Model parameters are calibrated using experimental data, and the calibrated model predicts failure initiation and propagation in various specimens experiencing a wide range of triaxiality and Lode parameter combinations. 相似文献
997.
The lowest singlet and triplet excited states of the two paired electrons in a chemical bond are treated by the time-dependent Hartree-Fock (H.F.) method, with the π electrons of the double bond in ethylene as an example. The results depend on a dimensionless parameter g which describes the strength of the electron correlation effects, and they are compared with a simple configuration interaction calculation. When g is small the frequencies and amplitudes of the Hartree-Fock oscillations give an accurate estimate of the energies and intensities of the two lowest transitions, the correlation energy and the pair distribution function of the gound state. The correlation energy is related to the zero-point energy of the oscillations. As g increases the H.F. method overestimates the correlation corrections and breaks down completely if g = 1. At this point the triplet oscillation becomes unstable, because the molecular orbital wave-function with two paired electrons ceases to be the state of lowest energy. When g is large the H.F. results violate spin conservation and the exclusion principle. 相似文献
998.
Seth Madren Will McElroy Kristin Schultz-Kuszak Boris Boumajny Yao Shu Sabine Sautter Helen C. Zhao Abby Schadock-Hewitt Chris Chumsae Nancy Ball Xiaoying Zhang Kimberly Rish Shukui Zhang Christine Wurm Sumin Cai Scott P. Bauer Cinzia Stella Laura Zheng Brian Roper David A. Michels Gang Wu Bostjan Kocjan Matej Birk Simon Erik Erdmann Xiaoping He Brad Whittaker Yvonne Song Hannah Barrett Kevin Strozyk Ye Jing Long Huang Vishal Mhatre Paul McLean Tiantian Yu Huijuan Yang Minna Mattila 《Electrophoresis》2022,43(9-10):1050-1058
An international team spanning 19 sites across 18 biopharmaceutical and in vitro diagnostics companies in the United States, Europe, and China, along with one regulatory agency, was formed to compare the precision and robustness of imaged CIEF (ICIEF) for the charge heterogeneity analysis of the National Institute of Standards and Technology (NIST) mAb and a rhPD-L1-Fc fusion protein on the iCE3 and the Maurice instruments. This information has been requested to help companies better understand how these instruments compare and how to transition ICIEF methods from iCE3 to the Maurice instrument. The different laboratories performed ICIEF on the NIST mAb and rhPD-L1-Fc with both the iCE3 and Maurice using analytical methods specifically developed for each of the molecules. After processing the electropherograms, statistical evaluation of the data was performed to determine consistencies within and between laboratory and outlying information. The apparent isoelectric point (pI) data generated, based on two-point calibration, for the main isoform of the NIST mAb showed high precision between laboratories, with RSD values of less than 0.3% on both instruments. The SDs for the NIST mAb and the rhPD-L1-Fc charged variants percent peak area values for both instruments are less than 1.02% across different laboratories. These results validate the appropriate use of both the iCE3 and Maurice for ICIEF in the biopharmaceutical industry in support of process development and regulatory submissions of biotherapeutic molecules. Further, the data comparability between the iCE3 and Maurice illustrates that the Maurice platform is a next-generation replacement for the iCE3 that provides comparable data. 相似文献
999.
Rhodium(II) Metallopeptide Catalyst Design Enables Fine Control in Selective Functionalization of Natural SH3 Domains
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Farrukh Vohidov Dr. Jane M. Coughlin Dr. Zachary T. Ball 《Angewandte Chemie (International ed. in English)》2015,54(15):4587-4591
Chemically modified proteins are increasingly important for use in fundamental biophysical studies, chemical biology, therapeutic protein development, and biomaterials. However, chemical methods typically produce heterogeneous labeling and cannot approach the exquisite selectivity of enzymatic reactions. While bioengineered methods are sometimes an option, selective reactions of natural proteins remain an unsolved problem. Here we show that rhodium(II) metallopeptides combine molecular recognition with promiscuous catalytic activity to allow covalent decoration of natural SH3 domains, depending on choice of catalyst but independent of the specific residue present. A metallopeptide catalyst succeeds in modifying a single SH3‐containing kinase at endogenous concentrations in prostate cancer (PC‐3) cell lysate. 相似文献
1000.
Synthesis, crystal structure, thermal stability, and electronic band structure of four new metal antimonides AMSb (A = Rb, Cs; M = Zn, Cd) are reported. CsZnSb and RbZnSb crystallize in the hexagonal ZrBeSi structure type, in a P63/mmc space group (no. 194, Z = 2) and unit cell dimensions of a = 4.5588(2)/4.5466(4) Å and c = 11.9246(6)/11.0999(10) Å. CsCdSb and RbCdSb crystallize in the tetragonal PbFCl structure type in a P4/nmm space group (no. 129; Z = 2) and unit cell parameters of a = 4.8884(5)/4.8227(3) Å and c = 8.8897(9)/8.5492(7) Å. All four compounds are air- and water-sensitive and are shown through DSC measurements to decompose between 975 K and 1060 K. Analysis of the calculated electronic band structure shows that the Zn-containing antimonides are topologically trivial narrow bandgap semiconductors, whereas Cd-containing compounds exhibit a band inversion along Γ-Z direction. 相似文献