Improving the sensitivity for DNA sensing based on double-anchored DNA modified gold nanoparticles

DNA modified nanoparticles (AuNPs) are an established and widely used type of nucleotide sensor. We sought to improve the design by applying short rigid DNA duplexes near the surface of the AuNPs forming a so called double-anchored AuNP sensor, and compared it with other conventional DNA modified AuNPs. The improved design exhibited higher assembly efficiency, and consequently increased its sensitivity to target DNA.     

Nitric oxide sensor based on carbon fiber covered with nickel porphyrin layer deposited using optimized electropolymerization procedure

Electropolymerization regime of meso-tetrakis(3-methoxy-4-hydroxyphenyl) porphyrin is optimized to yield films possessing both electrocatalytical and permselective properties towards nitric oxide oxidation. The sensor composed of electrochemically oxidized carbon fiber, covered solely with nickel porphyrin derivative layer electropolymerized using our method, is characterized by high selectivity towards nitrite (1:600), ascorbate (1:8000) and dopamine (>1:80), determined by constant potential amperometry at 830 mV (vs. Ag/AgCl). Selectivity for ascorbate and dopamine as well as detection limit for NO (1.5 nM at S/N=3) is 5-10 times better than parameters usually reported for Nafion coated porphyrinic sensors. Nafion coating can further enhance selectivity properties as well as aids to the stability of the sensors' responses.     

Use of E corr vs time plots for the qualitative analysis of metallic elements from scientific and technical objects: the SPAMT Test Project

A new analytical tool for copper alloys based on the monitoring of E _corr vs time is presented. This tool is particularly adapted to condition surveys carried out on-site by conservators on historic objects and was optimised so to respond to the needs of the conservation field such as the minimal impact on the artefacts, the portability of the instruments and its ease to use. A database constituted of 66 reference alloys representative of the materials found on technical artefacts with their electrochemical behaviour in three different solutions (Henniez mineral water, KNO₃ and sodium sesquicarbonate) was realised. The validation of the tool and the relevance of the database were assessed on two Swiss collections of technical, scientific and horology artefacts.     

Synthesis and characterization of bis[dicarboxylatotetraorganodistannoxane] units involving 5-[(E)-2-(aryl)-1-diazenyl]-2-hydroxybenzoic acids: An investigation of structures by X-ray diffraction, NMR, electrospray ionisation MS and assessment of in vitro cytotoxicity

Reactions of 5-[(E)-2-(aryl)-1-diazenyl]-2-hydroxybenzoic acids (LHH′, where the aryl group is an R-substituted phenyl ring such that for L¹HH′: R = H; L²HH′: R = 2′-CH₃; L³HH′: R = 3′-CH₃; L⁴HH′: R = 4′-CH₃; L⁵HH′: R = 4′-Cl; L⁶HH′: R = 4′-Br) with ⁿBu₂SnO in a 1:1 molar ratio yielded complexes of composition {[ⁿBu₂Sn(LH)]₂O}₂. The complexes have been characterized by ¹H, ¹³C, ¹¹⁹Sn NMR, ESI-MS, IR and ^119mSn Mössbauer spectroscopic techniques in combination with elemental analyses. The crystal structures of {[ⁿBu₂Sn(L¹H)]₂O}₂ (1), {[ⁿBu₂Sn(L⁴H)]₂O}₂ (4), {[ⁿBu₂Sn(L⁵H)]₂O}₂ (5) and {[ⁿBu₂Sn(L⁶H)]₂O}₂ (6) were determined. The compounds are centrosymmetric tetranuclear bis(dicarboxylatotetrabutyldistannoxane) complexes containing a planar Sn₄O₂ core in which two μ₃-oxo O-atoms connect an Sn₂O₂ ring to two exocyclic Sn-atoms. The four carboxylate ligands display two different modes of coordination where both modes involve bridging of two structurally distinct Sn-atoms. The solution structures were confirmed by ¹¹⁹Sn NMR spectroscopy by observing two tin resonances in compounds 1, and 4-6. The observed difference between the two tin resonances was about 3 ppm while the differences in ¹³C resonances were even smaller. Compounds {[ⁿBu₂Sn(L²H)]₂O}₂ (2) and {[ⁿBu₂Sn(L³H)]₂O}₂ (3) undergo a very complex exchange processes in deuteriochloroform solution. The in vitro cytotoxic activity of compounds 1 and 4 against WIDR, M19 MEL, A498, IGROV, H226, MCF7 and EVSA-T human tumour cell lines is reported.     

Crystalline Mean Curvature Flow of Convex Sets

We prove a local existence and uniqueness result of crystalline mean curvature flow starting from a compact convex admissible set in . This theorem can handle the facet breaking/bending phenomena, and can be generalized to any anisotropic mean curvature flow. The method provides also a generalized geometric evolution starting from any compact convex set, existing up to the extinction time, satisfying a comparison principle, and defining a continuous semigroup in time. We prove that, when the initial set is convex, our evolution coincides with the flat φ-curvature flow in the sense of Almgren-Taylor-Wang. As a by-product, it turns out that the flat φ-curvature flow starting from a compact convex set is unique.     

Anisotropic curvature-driven flow of convex sets

We study in this paper the mean curvature evolution, and in particular the anisotropic mean curvature evolution, of convex sets in R^N${\mathbb{R}}^N$ (without driving forces). If the anisotropy is smooth, we show that the evolution remains convex. If the anisotropy is crystalline, we build a convex evolution which satisfies an equation which is a weak form of the crystalline curvature motion equation.     

Biotinylation of quantum dots for application in fluoroimmunoassays with biotin-avidin amplification

A competitive microplate fluoroimmunoassay was developed for the determination of human serum albumin in urine. It is based on the use of biotinylated CdTe quantum dots (QDs) whose synthesis is optimised in terms of storage stability, purification, and signal-to-noise ratio. The bioconjugated QDs were characterised by gel chromatography and gel electrophoresis. Storage stability and quantum yield were investigated. The excitation/emission wavelengths are 360/620?nm. The immunoassay of human serum albumin in urine has a working range from 1.7 to 10?μg.mL^?1, and the limit of detection is 1.0?μg.mL^?1.

Multiple-step martensitic transformations in Ni-rich NiTi alloys--an in-situ transmission electron microscopy investigation

Multiple-step martensitic transformations in Ni-rich NiTi shape memory alloys have so far been rationalized on the basis of dislocation stress fields, coherency stress fields around Ni 4 Ti 3 precipitates and evolving Ni concentrations between precipitates during ageing. The primary objective of the present paper is to show that such transformations can also occur owing to heterogeneous microstructures that form during ageing of solution annealed defect-free materials. These microstructures are characterized by Ni 4 Ti 3 grain-boundary precipitation and by precipitate-free grain interiors. Two microstructures which give rise to two and three distinct differential scanning calorimetry (DSC) peaks on cooling from the B2 regime are subjected to in-situ cooling and heating cycles in the transmission electron microscope. Martensitic transformations are directly studied and the observations provide a new explanation for multiple-step martensitic transformations in Ni-rich NiTi alloys. Most importantly the results of the present study allow us to understand why DSC chart features on cooling from the B2 regime change during ageing, where they lose their one-step character (after solution annealing at 1123 K for 900 s) and evolve from two-step (after ageing at 773 K for 3.6 ks) to three-step (after ageing at 773 for 36 ks K) transformations.     

Experimental determination and prediction of methane hydrate stability in alcohols and electrolyte solutions

In petroleum exploration and production operations, gas hydrates pose serious flow assurance, economic and safety concerns. Thermodynamic inhibitors are widely used to reduce the risks associated with gas hydrate formation. In this communication, in order to establish the effects of salts and thermodynamic inhibitors on the locus of incipient hydrate–liquid water–vapour (H–L_W–V) curve, we report new experimental dissociation data for various quaternary systems, methane/water/thermodynamic inhibitor/salts for a pressure range of 6.89–29 MPa.     

Piecewise rigidity

In this paper we provide a Liouville type theorem in the framework of fracture mechanics, and more precisely in the theory of SBV deformations for cracked bodies. We prove the following rigidity result: if u∈SBV(Ω,RN) is a deformation of Ω whose associated crack Ju has finite energy in the sense of Griffith's theory (i.e., HN−1(Ju)<∞), and whose approximate gradient ∇u is almost everywhere a rotation, then u is a collection of an at most countable family of rigid motions. In other words, the cracked body does not store elastic energy if and only if all its connected components are deformed through rigid motions. In particular, global rigidity can fail only if the crack disconnects the body.