Physico-chemical modifications of the interactions between hemp fibres and a lime mineral matrix: impacts on mechanical properties of mortars

International audienceIn order to understand the physico-chemical mechanisms governing interactions between hemp fibres and a lime-based mineral matrix, the consequences of various chemical treatments onto hemp fibres characteristics were measured using scanning electron microscopy, thermal analysis, X-ray diffraction and FTIR spectroscopy. Secondly, effects of these treatments on the mechanical properties of lime mortars incorporating the chemically modified fibres were evaluated using 3 point bending tests. NaOH and EDTA treatments increase the crystallinity index of hemp fibres and increase the experimental rigidity of lime/natural fibres mortars. Treatments with polyethylene imine and a saturated lime solution do not induce any significant changes onto the mechanical properties. These results show that some specific chemical treatments have an impact onto the hemp/lime interfaces quality. The elaborated composite materials exhibit a higher rigidity and an improvement of the matrix /fibre charge transfer. However, the rupture stress is only slightly modified due to a relatively low fibre volumic content (10 %)

Inflammatory biomarkers in Alzheimer's disease plasma.

INTRODUCTION: Plasma biomarkers for Alzheimer's disease (AD) diagnosis/stratification are a "Holy Grail" of AD research and intensively sought; however, there are no well-established plasma markers. METHODS: A hypothesis-led plasma biomarker search was conducted in the context of international multicenter studies. The discovery phase measured 53 inflammatory proteins in elderly control (CTL; 259), mild cognitive impairment (MCI; 199), and AD (262) subjects from AddNeuroMed. RESULTS: Ten analytes showed significant intergroup differences. Logistic regression identified five (FB, FH, sCR1, MCP-1, eotaxin-1) that, age/APOε4 adjusted, optimally differentiated AD and CTL (AUC: 0.79), and three (sCR1, MCP-1, eotaxin-1) that optimally differentiated AD and MCI (AUC: 0.74). These models replicated in an independent cohort (EMIF; AUC 0.81 and 0.67). Two analytes (FB, FH) plus age predicted MCI progression to AD (AUC: 0.71). DISCUSSION: Plasma markers of inflammation and complement dysregulation support diagnosis and outcome prediction in AD and MCI. Further replication is needed before clinical translation

Inflammatory biomarkers in Alzheimer's disease plasma

Introduction:Plasma biomarkers for Alzheimer’s disease (AD) diagnosis/stratification are a“Holy Grail” of AD research and intensively sought; however, there are no well-established plasmamarkers.Methods:A hypothesis-led plasma biomarker search was conducted in the context of internationalmulticenter studies. The discovery phase measured 53 inflammatory proteins in elderly control (CTL;259), mild cognitive impairment (MCI; 199), and AD (262) subjects from AddNeuroMed.Results:Ten analytes showed significant intergroup differences. Logistic regression identified five(FB, FH, sCR1, MCP-1, eotaxin-1) that, age/APOε4 adjusted, optimally differentiated AD andCTL (AUC: 0.79), and three (sCR1, MCP-1, eotaxin-1) that optimally differentiated AD and MCI(AUC: 0.74). These models replicated in an independent cohort (EMIF; AUC 0.81 and 0.67). Twoanalytes (FB, FH) plus age predicted MCI progression to AD (AUC: 0.71).Discussion:Plasma markers of inflammation and complement dysregulation support diagnosis andoutcome prediction in AD and MCI. Further replication is needed before clinical translatio

Interaction of a platinum terpyridine complex with DNA and anion binding to the trinuclear cluster of Rhus laccase

We present a spectroscopic investigation of interactions of Pt(terpy)OH\sp+, where terpy denotes 2,2\sp\prime:6,2\sp{\prime\prime}-terpyridine, with DNA. Absorption spectroscopy and viscometry indicate that, immediately after mixing, Pt(terpy)OH\sp+ intercalates into DNA, preferentially between GC base pairs. The luminescent properties of the complex are greatly affected by the base sequence of the polynucleotide. Intercalation between AT base pairs increases the luminescence, while electron transfer from the guanine residue quenches the luminescence when the complex intercalates between GC base pairs. At room temperature, Pt(terpy)OH\sp+ exhibits absorption maxima in the near-UV and visible regions with extinction coefficients on the order of 1,000 M\sp{-1}. Since these transitions exhibit solvent dependence and occur well below those of the \sp1\pi \to \pi\sp\* transitions of the terpy ligand, we assign them as metal-to-ligand charge transfer (CT) transitions. At room temperature, the complex exhibits a broad, unstructured emission. The uncorrected emission maxima (and lifetimes) are 580 nm (10 ns) in water and 610 nm (117 ns) in acetonitrile. Temperature dependent luminescence in acetonitrile shows that there is a thermally activated quenching route with a barrier height of ca 1,170 cm\sp{-1}. The broad emission signal observed contrasts with the structured high energy emission obtained from metal-perturbed-intraligand states of Pt(terpy)CN\sp+ and Pt(terpy)(xylylCN)\sp{2+}. We also describe electron paramagnetic resonance (EPR) studies of the binding of cyanide to the derivative of laccase in which the type 1 site contains the EPR silent Hg(II) ion (T1Hg laccase). T1Hg laccase forms a dicyanide adduct that exhibits ligand hyperfine structure from two protein nitrogen and two cyanide carbon donors. We also observe a pH-induced transition in the type 2/type 3 cluster occurring at pH 5.5. On the basis of our results and the newly reported crystal structure of the diazide adduct of ascorbate oxidase (Messerschmidt et al., 1993), we conclude that azide and cyanide anions bind at one of the type 3 copper atoms in laccase. These results illustrate the fluctionality of the trinuclear cluster of laccase

Cold ceramics: Low-temperature processing of ceramics for applications in composites

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Heteroaggregation between particles modified by polyelectrolyte multilayers

International audienceThe heteroaggregation of particles is interesting in many fields and particularly in the field of ceramic shaping. In general, heteroaggregation is obtained by mixing powders with opposite surface charges, which may require in some cases surface modifications of the particles. Here we propose to study the behavior of suspensions composed of a mixture of particles with positive and negative charges, created by the adsorption of polyelectrolyte multilayers on their surface. Particular attention is paid to the effect of the number of layers of adsorbed polyelectrolytes and of the ionic strength. This study shows that these surface modifications allow, whatever the number of layers, to have heteroaggregation in the absence of salt. Moreover, depending on the number of adsorbed layers, the addition of salt has a different effect on the suspension behavior. These phenomena can be explained by screening effects already mentioned in the literature for unmixed suspensions of particles modified by polyelectrolyte multilayers. As a consequence, this study highlights that the study of heteroaggregation in these systems is a very simple way to analyze this effect of screening which is difficult to observe on non-mixed suspensions

Selective modification of inorganic surfaces with fluorinated molecules using a Pickering emulsion template

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Synthesis of fluorinated ceramic Janus particles via a Pickering emulsion method

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Caractérisation des interactions physico-chimiques dans un matériau composite à base de phyllosilicates, de chaux et de fibres végétales

Afin de comprendre les mécanismes physico-chimiques régissant les interactions entre des fibres de chanvre et une matrice à base de chaux et d'argiles, les effets de différents traitements chimiques des fibres sur l'état de surface des fibres d'une part et sur les propriétés mécaniques des composites d'autre part ont été évalués. Un traitement basique à l'hydroxyde de sodium (NaOH) permet ainsi d'augmenter les forces d'adhésion entre la fibre et un colloïde de silice et d'accroître les propriétés mécaniques d'un matériau composite dont la matrice est constituée de chaux uniquement ou de chaux et de kaolin. Cette amélioration peut être le résultat d'une augmentation de la rigidité de la fibre et d'une homogénéité en surface qui la rendent plus réactive. Les autres traitements réalisés, avec de l'acide éthylène diamine tétra-acétique (EDTA), du polyéthylène imine (PEI), une solution saturée d'eau de chaux et une solution de chlorure de calcium n'ont pas d'effets sur les propriétés mécaniques.In order to understand the physico-chemical mechanisms governing the interactions between hemp fibres and mineral matrices based on lime and on mixtures of lime and clay minerals, the influence of various chemical treatments of fibres on their surface properties and on macroscopic mechanical properties of mortars were evaluated. treatment with sodium hydroxide (NaOH) removes various organic components from the surface of the fibres, increases the adhesion forces between the fibre and a colloid made of silica and improves the mechanical properties of the resulting composites for lime and lime/kaolin matrices. An explanation for this behaviour could be linked to an increase of the fibre surface roughness and homogeneity. Other chemical treatments, with Ethylene Diamine Tetra-acetic Acid (EDTA), Polythylene imine (PEI), a saturated lime solution and a calcium chloride solution have no impact on the mechanical properties of the composite material.LIMOGES-BU Sciences (870852109) / SudocSudocFranceF

Cohésion à l’interface matrice minérale/fibres cellulosiques : traitements chimiques des fibres et caractérisation

International audienceThe use of cellulosic fibres as reinforcement in a mineral matrix (in our case based on a mixture of phyllosilicates and of a hydraulic lime) presents two major disadvantages which are linked to the absorbent character of fibres as well as to their thermal degradations. To modify the properties of fibres surface, prior to their introduction in composite material, chemical, mechanical and thermal treatments are generally applied. Particularly, chemical treatments using Sodium Hydroxide solutions and the grafting of organic molecules increases the cohesion at fibres/matrix interface and allow ameliorating the mechanical behavior of the final composite. Our study is concentrated on the modification of the hemp fibres surface by chemical treatments (treatment with NaOH, grafting of organosilanes at different chemical compositions and at different concentrations) as well as the characterizations by different functional and structural techniques (DTA/TGA, ATR-FTIR, NMR and SEM)