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Saha RK Franceschini E Cloutier G 《The Journal of the Acoustical Society of America》2011,129(4):2269-2277
A computer simulation study to produce ultrasonic backscatter coefficients (BSCs) from red blood cell (RBC) clusters is discussed. The simulation algorithm is suitable for generating non-overlapping, isotropic, and fairly identical RBC clusters. RBCs were stacked following the hexagonal close packing (HCP) structure to form a compact spherical aggregate. Such an aggregate was repeated and placed randomly under non-overlapping condition in the three-dimensional space to mimic an aggregated blood sample. BSCs were computed between 750 KHz and 200 MHz for samples of various cluster sizes at different hematocrits. Magnitudes of BSCs increased with mean aggregate sizes at low frequencies (<20 MHz). The accuracy of the structure-factor-size-estimator (SFSE) method in determining mean aggregate size and packing factor was also examined. A good correlation (R(2) ≥ 0.94) between the mean size of aggregates predicted by the SFSE and true size was found for each hematocrit. This study shows that for spherical aggregates there exists a region for each hematocrit where SFSE works most accurately. Typically, error of SFSE in estimating mean cluster size was <20% for dimensions between 14 and 17 μm at 40% hematocrit. This study suggests that the theoretical framework of SFSE is valid under the assumption of isotropic aggregates. 相似文献
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Emilie Dufresne 《代数通讯》2013,41(11):3987-3992
This article gives the first explicit example of a finite separating set in an invariant ring which is not finitely generated, namely, for Daigle and Freudenburg's 5-dimensional counterexample to Hilbert's Fourteenth Problem. 相似文献
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Jimmy Mergy Audrey Fournier Emilie Hachet Rachel Auzély‐Velty 《Journal of polymer science. Part A, Polymer chemistry》2012,50(19):4019-4028
We present herein a mild and rapid method for the modular functionalization of polysaccharides. Several ene‐functional charged and neutral polysaccharides, that is, hyaluronic acid and dextran, were prepared by esterification of the hydroxyl groups with pentenoic anhydride. The modified polysaccharides were then reacted with six model mercaptans under UV light, leading to linear polymers modified with hydrophobic groups, peptides, or oligosaccharides as well as chemical hydrogels. The thiol‐ene coupling reactions were found to proceed with high efficiency in short reaction times and with nearly no degradation of the polysaccharide backbone. Moreover, they were carried out in aqueous media, without the use of any metal catalysts, enhancing the attractive nature of this process. Notably, we investigated whether it is feasible to prepare cell‐responsive hydrogels by sequential bioconjugation and cross‐linking of the polysaccharide backbone with a bioactive peptide and poly(ethylene glycol)‐dithiol, respectively. All together, these results highlight the potential of this coupling strategy for the modular functionalization of polysaccharides under click chemistry‐like conditions. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012 相似文献
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Zhen Cao Dr. Antoine Scalabre Dr. Sylvain Nlate Sonia Buffière Dr. Reiko Oda Dr. Emilie Pouget Dr. Brigitte Bibal 《Chemistry (Weinheim an der Bergstrasse, Germany)》2021,27(1):427-433
The combination of metal catalyst and inorganic silica frameworks provides a greener approach to recyclable catalysis. In this study, three phosphine–gold chloride complexes have been successfully covalently grafted onto chiral silica nanohelices. The resulting 3D ensembles showed chiroptical properties that allowed the monitoring of the supported ligands. The heterogeneous gold chloride catalysts in cooperation with silver triflate exhibited high reactivity in various reactions, especially in the spirocyclization of aryl alkynoate esters, for which a catalytic loading of 0.05 mol % could be employed. The heterogeneous catalysts could be easily recovered and recycled seven or eight times without any loss of efficiency. By adding more silver triflate, 25 cycles with full conversion were achieved owing to a complex catalytic system based on silica and metallic species. 相似文献
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Dr. Emilie Mathieu Audrey E. Tolbert Dr. Karl J. Koebke Prof. Cédric Tard Dr. Olga Iranzo Prof. James E. Penner-Hahn Prof. Clotilde Policar Prof. Vincent Pecoraro 《Chemistry (Weinheim an der Bergstrasse, Germany)》2020,26(1):249-258
Superoxide dismutases (SODs) are highly efficient enzymes for superoxide dismutation and the first line of defense against oxidative stress. These metalloproteins contain a redox-active metal ion in their active site (Mn, Cu, Fe, Ni) with a tightly controlled reduction potential found in a close range around the optimal value of 0.36 V versus the normal hydrogen electrode (NHE). Rationally designed proteins with well-defined three-dimensional structures offer new opportunities for obtaining functional SOD mimics. Here, we explore four different copper-binding scaffolds: H3 (His3), H4 (His4), H2DH (His3Asp with two His and one Asp in the same plane) and H3D (His3Asp with three His in the same plane) by using the scaffold of the de novo protein GRα3D. EPR and XAS analysis of the resulting copper complexes demonstrates that they are good CuII-bound structural mimics of Cu-only SODs. Furthermore, all the complexes exhibit SOD activity, though three orders of magnitude slower than the native enzyme, making them the first de novo copper SOD mimics. 相似文献