Nano-structured polymer-glass hybrid coatings

The increased attention received by polymer nanocomposites in recent years, has opened the way to research on nanostructured glass polymer hybrids for coating applications. Using polyamide 11 and adding fillers (in this case glass) at the nanometre length scale can lead to innovative modifications to the polymer matrix, giving rise to new structures and properties. This could develop new materials with enhanced properties and may enlarge the coating market to other application areas. Some of the main obstacles to overcome are the control of glass particle size to obtain suitable dispersions on the nanoscale with interaction between components. Nanoscale structures require the development of optimal hybrid precursors. Finding a way to develop the hybrids using melt compounding methods like extrusion, particle size processes and coating techniques have been investigated in this research. The nanostructured hybrids are made using macroscopic fillers, which avoids problems with current regulations on ultra-fine particles. Fourier-transform infrared spectroscopy (FTIR) and Raman spectroscopy indicate the glass structure during synthesis of tin fluoride phosphate glass was pyrophosphate, mainly built up from phosphate tetrahedral units with one bridging oxygens present within a particular phosphate tetrahedron Qଵ end groups with a low concentration of phosphate tetrahedral units with two bridging oxygens Qଶ polymeric chains. However, sub-optimal melting produced significantly higher concentrations of phosphate tetrahedral units with no bridging oxygens present within a particular phosphate tetrahedron Q଴ orthophosphate structural units. The variations in NH and P − OH vibrations in the spectra revealed that a critical time and temperature of melting were necessary for the conversion of NHସHଶPOସ to produce sufficient PଶOହ for glass forming. During melting, PଶOହ and SnFଶ formed a low-temperature melt, which facilitated melting of the SnO and promoted the formation of a more stable glass structure. The fluorine breaks the P − O − P bonds and induces depolymerisation. The density of the glass reached a maximum at 450 °C for 25 min driven by the need for conversion of NHସHଶPOସ to PଶOହ and miscibility of SnO in the melt. Inadequate melting times and temperatures gave low glass transition temperature (Tg) values because of weak F − Sn and F − P linkages. Glass stability improved with melting due to increased PଶOହ and SnO miscibility enabling stronger Sn − O − P linkages. The results show that melting conditions during synthesis strongly influence critical glass properties and also provide an understanding of optimum processing necessary for future industrial scale-up. Novel hybrids of tin fluoride phosphate (TFP) glass (composition of 50% SnFଶ + 20% SnO + 30% PଶOହ) were synthesized with polyamide 11 and their morphology and mechanical properties investigated. Hybridization was achieved by melt blending up to 25 vol% of glass using different compounding conditions (temperature, screw speed and residence time). Scanning electron microscopy (SEM) showed that the morphology was greatly influenced by the extrusion processing temperature and the glass content. Transmission electron microscopy (TEM) studies revealed nanoparticles of 40 nm in size and suggested good compatibility. In order to determine the existence of miscibility between hybrid components, measurement of the loss tangent using a Dynamic Mechanical Analysis (DMA), was carried out. The presence of two transition peaks in the hybrid containing 34 vol% tin fluoride phosphate glass implied an immiscible system showing heterogeneously distributed regions of very different molecular mobilities. Contrary to the plasticizer effect reported in the literature for some polyamide 6 - TFP glass hybrids, the measurements of mechanical properties by DMA showed a reinforcement effect of glass in the polymer. This was reflected by the increase of storage modulus (Εᇱ) at low and high temperatures in hybrids containing 13, 18 and 25 vol% tin fluoride phosphate glasses, achieving the highest modulus at 25 vol%. Tensile testing revealed a pronounced reduction in ductility for high glass contents. Finally, the first TFP- PA11 hybrid coating was developed with enhanced fire resistance and adhesion to the metal. Hardness and abrasion tests using different glass Tgs showed an influence of the glass Tg on the final coating application

Engineering the microstructure and magnetism of La2_2CoMnO6_6 thin films by tailoring oxygen stoichiometry

We report on the magnetic and structural properties of ferromagnetic-insulating La$_2$CoMnO$_6$ thin films grown on top of (001) STO substrates by means of RF sputtering technique. Careful structural analysis, by using synchrotron X-ray diffraction, allows identifying two different crystallographic orientations that are closely related to oxygen stoichiometry and to the features (coercive fields and remanence) of the hysteresis loops. Both Curie temperature and magnetic hysteresis turn out to be dependent on the oxygen stoichiometry. In situ annealing conditions allow tailoring the oxygen content of the films, therefore controlling their microstructure and magnetic properties

Comparative proteomics of soluble factors secreted by human breast adipose tissue from tumor and normal breast

Tumor progression depends on the tumor-stroma interaction. In the breast, adipose tissue is the predominant stromal type. We have previously demonstrated that conditioned media (CMs) from explants of human adipose tissue of tumor breasts (hATT) increase proliferation and migration of breast cancer epithelial cells when compared to human adipose tissue from normal breasts (hATN). In this work, we aim to identify specific proteins and molecular/biological pathways associated with the secretion profile of hATT and hATN explants. hATT-CMs and hATN-CMs were separated by SDS-PAGE and analyzed by means of two-dimensional nano-liquid chromatography-mass spectrometry. The data was analyzed using ProteoIQ and FunRich software. In addition, 42 cytokines from hATTCMs and hATN-CMs were assayed by a protein antibody assay. Compared to hATNCMs, hATT-CMs showed greater protein diversity. We found that hATT-CMs presented a greater amount of proteins related to complement system activity, metabolism and immune system, as well as proteins involved in a variety of biological processes such as signal transduction and cell communication. Specifically, apolipoprotein AI and AII, complement component 3, and vimentin and desmin were significantly increased in hATT-CMs versus hATN-CMs. Moreover, a multivariate discriminant analysis of the cytokines detected by the array showed that IL-6, MCP-2 and GRO cytokines were sufficient and necessary to differentiate hATT-CMs from hATN-CMs. This analysis also showed that the levels of these three cytokines, taken together, correlated with stage and histological grade of the tumor in the hATT-CMs group, and with body mass index in the hATN-CMs group.Fil: Fletcher, Sabrina Johanna. Consejo Nacional de Investigaciones Científicas y Técnicas. Instituto de Biología y Medicina Experimental. Fundación de Instituto de Biología y Medicina Experimental. Instituto de Biología y Medicina Experimental; ArgentinaFil: Hapon, María Belén. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mendoza. Instituto de Medicina y Biología Experimental de Cuyo; ArgentinaFil: Callegari, E.. University Of South Dakota; Estados UnidosFil: Crosbie, M. L.. Complejo Médico Policial "Churruca Visca"; ArgentinaFil: Santiso, N.. Complejo Médico Policial "Churruca Visca"; ArgentinaFil: Ursino, A.. Complejo Médico Policial "Churruca Visca"; ArgentinaFil: Amato, A. R.. Complejo Médico Policial "Churruca Visca"; ArgentinaFil: Gutiérrez, A.. Complejo Médico Policial "Churruca Visca"; ArgentinaFil: Sacca, Paula Alejandra. Consejo Nacional de Investigaciones Científicas y Técnicas. Instituto de Biología y Medicina Experimental. Fundación de Instituto de Biología y Medicina Experimental. Instituto de Biología y Medicina Experimental; ArgentinaFil: Dreszman, R.. Consejo Nacional de Investigaciones Científicas y Técnicas. Instituto de Biología y Medicina Experimental. Fundación de Instituto de Biología y Medicina Experimental. Instituto de Biología y Medicina Experimental; ArgentinaFil: Pérez, A.. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Departamento de Matemática; ArgentinaFil: Caron, Ruben Walter. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mendoza. Instituto de Medicina y Biología Experimental de Cuyo; ArgentinaFil: Calvo, Juan Carlos. Consejo Nacional de Investigaciones Científicas y Técnicas. Instituto de Biología y Medicina Experimental. Fundación de Instituto de Biología y Medicina Experimental. Instituto de Biología y Medicina Experimental; ArgentinaFil: Pistone Creydt, Virginia. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mendoza. Instituto de Medicina y Biología Experimental de Cuyo; Argentin

Gate current analysis of AlGaN/GaN on silicon heterojunction transistors at the nanoscale

The gate leakage current of AlGaN/GaN (on silicon)high electron mobility transistor(HEMT) is investigated at the micro and nanoscale. The gate current dependence (25-310 °C) on the temperature is used to identify the potential conduction mechanisms, as trap assisted tunneling or field emission. The conductive atomic force microscopy investigation of the HEMT surface has revealed some correlation between the topography and the leakage current, which is analyzed in detail. The effect of introducing a thin dielectric in the gate is also discussed in the micro and the nanoscale

The economic case for prioritizing governance over financial incentives in REDD+

This article contributes to the ongoing debate on the role of public policies and financial incentives in Reducing Emissions from Deforestation and forest Degradation (REDD+). It argues that the subordination of policies to results-based payments for emission reductions causes severe economic inefficiencies affecting the opportunity cost, transaction cost and economic rent of the programme. Such problems can be addressed by establishing sound procedural, land and financial governance at the national level, before REDD+ economic incentives are delivered at scale. Consideration is given to each governance dimension, the entry points for policy intervention and the impact on costs. International support must consider the financial and political cost of governance reforms, and use a pay-for-results ethos based on output and outcome indicators. This can be done in the readiness process but only if the latter’s legal force, scope, magnitude and time horizon are adequately reconsidered. In sum, the paper provides ammunition for the institutionalist argument that UNFCCC Parties must prioritise governance reform between now and the entry into force of the new climate agreement in 2020, and specific recommendations about how this can be done: only by doing so will they create the basis for the programme’s financial sustainability

Induction of CD4+CD25+FOXP3+ Regulatory T Cells during Human Hookworm Infection Modulates Antigen-Mediated Lymphocyte Proliferation

Hookworm infection is considered one of the most important poverty-promoting neglected tropical diseases, infecting 576 to 740 million people worldwide, especially in the tropics and subtropics. These blood-feeding nematodes have a remarkable ability to downmodulate the host immune response, protecting themselves from elimination and minimizing severe host pathology. While several mechanisms may be involved in the immunomodulation by parasitic infection, experimental evidences have pointed toward the possible involvement of regulatory T cells (Tregs) in downregulating effector T-cell responses upon chronic infection. However, the role of Tregs cells in human hookworm infection is still poorly understood and has not been addressed yet. In the current study we observed an augmentation of circulating CD4+CD25+FOXP3+ regulatory T cells in hookworm-infected individuals compared with healthy non-infected donors. We have also demonstrated that infected individuals present higher levels of circulating Treg cells expressing CTLA-4, GITR, IL-10, TGF-β and IL-17. Moreover, we showed that hookworm crude antigen stimulation reduces the number of CD4+CD25+FOXP3+ T regulatory cells co-expressing IL-17 in infected individuals. Finally, PBMCs from infected individuals pulsed with excreted/secreted products or hookworm crude antigens presented an impaired cellular proliferation, which was partially augmented by the depletion of Treg cells. Our results suggest that Treg cells may play an important role in hookworm-induced immunosuppression, contributing to the longevity of hookworm survival in infected people

Model for random packing of polydisperse frictionless spheres

International audienceWe propose a statistical model for the random packing of frictionless polydisperse spheres in which the complexity of the global packing is distilled into a local stochastic process. We simplify the problem by considering the "granocentric" point of view of a single particle in the bulk, thereby reducing random packing to the assembly of nearest neighbours, followed by a random choice of contacts among them. The model is based on only two parameters, the available solid angle around each particle and the ratio of contacts to neighbors, which are both directly obtainable from experiments or simulations. As a result, the model analytically predicts the microscopic distributions of nearest neighbours and contacts, the local density fluctuations as well as the global density of the packing. We find that this granocentric view captures the essential properties of the polydisperse emulsion packing. This model suggests a general principle of organization for random packing and provides a statistical tool for quantifying the effect of the particle size distribution on the geometry of random packing in a variety of contexts of industrial relevance