Local smoothing effects for the water-wave problem with surface tension

The water-wave problem with a one-dimensional free surface of infinite depth is considered, based on the formulation as a second-order nonlinear dispersive equation. The local smoothing effects are established under the influence of surface tension, stating that on average in time solutions acquire locally 1/4 derivative of smoothness as compared to the initial state. The analysis combines energy methods with techniques of Fourier integral operators. To cite this article: H. Christianson et al., C. R. Acad. Sci. Paris, Ser. I 347 (2009).     

Novel amphiphilic homopolymers containing meta‐ and para‐pyridine moieties with living characteristics and their self‐assembly

Amphiphilic monomers containing the isomeric pyridine moieties 3‐(4‐vinylphenyl)pyridine (3VPPy) and 4‐(4‐vinylphenyl)pyridine (4VPPy) were synthesized using the Suzuki coupling reaction. A living anionic polymerization of 3VPPy and 4VPPy was successfully performed under various conditions to overcome the limitations of anionic polymerization and to compare their properties with those of poly(2‐(4‐vinylphenyl)pyridine) as reported previously. Several characteristics of the resulting isomeric P3VPPy and P4VPPy were studied, such as thermal stability, solubility, and the living nature. The block copolymerization of 4VPPy with 2‐vinylpyridine and MMA was carried out without additive to estimate the nucleophilicity of P4VPPy and to confirm its living nature. Additionally, each amphiphilic homopolymer of P3VPPy and P4VPPy containing both a hydrophilic pyridine unit and a hydrophobic styrene unit was tested for self‐assembly behavior in a mixed solvent (THF/water) and monitored with TEM and SEM. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2013 , 51, 3458–3469     

Functional characterization of human oncoprotein gankyrin in Zebrafish

Gankyrin is an oncoprotein containing seven ankyrin repeats that is overexpressed in hepatocellular carcinoma (HCC). Gankyrin binds to Mdm2, which results in accelerated ubiquitylation via degradation of p53, and it also plays an important role in cell proliferation. However, little is known about the relationships between p53 levels, cell proliferation, and gankyrin over-expression. In order to investigate the influence of gankyrin protein on p53 and Mdm2 in a zebrafish model, we injected human gankyrin (hgankyrin) containing expression vectors (pCS2-hgankyrin, pCS2-hgankyrin-EGFP) into zebrafish embryos. To measure p53 and Mdm2 expression in hgankyrin-injected embryos, RT-PCR, Northern blot and in-situ hybridization and BrdU immunostaining were used. In addition, to know the effect of hgankyrin on cell proliferation in vitro, cell viability assays such as MTT, trypan blue staining and RT-PCR following transfection of hgankyrin-containing vector into HEK 293 cell line were performed. In vivo results indicated that p53 mRNA levels decreased but those of Mdm2 were not decreased in the presence of hgankyrin. These results suggest that gankyrin downregulates p53 expression and not Mdm2 expression. In the study of cell proliferation, BrdU-positive cells were predominantly increased in the head and tail regions in hgankyrin-injected zebrafish. Additional in vitro studies using trypan blue staining and MTT assay showed that gankyrin-expressing HEK 293 cells proliferated at a faster rate, indicating that gankyrin promotes cell proliferation. Our results demonstrate that hgankyrin overexpression downregulates p53 expression and promotes cell proliferation in zebrafish. Gankyrin may play an important role in tumorigenesis via its effects on p53 and cell proliferation.     

Reduction of U<Subscript>3</Subscript>O<Subscript>8</Subscript> to U by a metallic reductant,Li

Reduction of U₃O₈ was investigated for the recycling of spent oxide fuel from a commercial nuclear power plant. The possible reduction methods were proposed and compared. Based on the thermodynamic analysis, Li metal was selected as a reductant. The optimum reaction temperature for the reduction of U₃O₈ was investigated at the wider reaction temperature range. The adverse oxidation of U metal by Li₂O at 1,000 °C was experimentally verified. Ellingham diagram was constructed to investigate the extent of the uranium oxides reduction when the reaction was carried out above melting point of U metal.     

Ferrofluid mediated nanocytometry

We present a low-cost, flow-through nanocytometer that utilizes a colloidal suspension of non-functionalized magnetic nanoparticles for label-free manipulation and separation of microparticles. Our size-based separation is mediated by angular momentum transfer from magnetically excited ferrofluid particles to microparticles. The nanocytometer is capable of rapidly sorting and focusing two or more species, with up to 99% separation efficiency and a throughput of 3 × 10(4) particles/s per mm(2) of channel cross-section. The device is readily scalable and applicable to live cell sorting with biocompatible ferrofluids, offering competitive cytometer performance in a simple and inexpensive package.     

Detecting quantum critical points using bipartite fluctuations

We show that the concept of bipartite fluctuations F provides a very efficient tool to detect quantum phase transitions in strongly correlated systems. Using state-of-the-art numerical techniques complemented with analytical arguments, we investigate paradigmatic examples for both quantum spins and bosons. As compared to the von Neumann entanglement entropy, we observe that F allows us to find quantum critical points with much better accuracy in one dimension. We further demonstrate that F can be successfully applied to the detection of quantum criticality in higher dimensions with no prior knowledge of the universality class of the transition. Promising approaches to experimentally access fluctuations are discussed for quantum antiferromagnets and cold gases.     

尺寸效应对Al纳米线凝固行为的影响

结合EAM镶嵌原子作用势, 通过经典的分子动力学模拟研究了不同截面尺寸Al纳米线在两种冷却速率下的凝固行为, 并采用键对分析技术探讨了相变过程中原子团簇的演化情况. 结果表明:Al纳米线的最终结构不仅与冷却速率有关, 还呈现出明显的尺寸效应. 在较快的冷却速率下, 五种截面尺寸的Al纳米线均得到了多壳螺旋结构; 而当冷却速率降低以后, 除了N₃纳米线发生了断裂以外, 其余纳米线的结构随着截面尺寸的增加, 逐渐从多壳螺旋结构经由类-六边形多壳结构最终过渡到稳定的晶态结构.     

Pumpless, selective docking of yeast cells inside a microfluidic channel induced by receding meniscus

We present a simple cell docking method induced by receding meniscus to capture non-adherent yeast cells onto microwells inside a microfluidic channel. Microwells were fabricated either by capillary moulding of UV curable polyurethane acrylate (PUA) onto glass substrate or direct replica moulding of poly(dimethyl siloxane) (PDMS). A cell suspension of the budding yeast, Saccharomyces cerevisiae, was introduced into the microfluidic channel by surface tension driven capillary flow and a receding meniscus was subsequently generated by evaporation. As the meniscus progressed, one to multiple yeast cells were spontaneously captured onto microwells by lateral capillary force created at the bottom of the meniscus. Using this cell-based platform, we observed the response of yeast cells upon stimulation by a mating pheromone (alpha-factor) by monitoring the expression of green fluorescent protein (GFP) with time. It was observed that alpha-factor triggered the expression of GFP at 60 min after stimulation and the fluorescence intensity was sustained for an additional 60 min without changes.