Fluorocarbon evaporative cooling developments for the ATLAS pixel and semiconductor tracking detectors

Heat transfer coefficients 2-5.103 Wm-2K-1 have been measured in a 3.6 mm I.D. heated tube dissipating 100 Watts - close to the full equivalent power (~110 W) of a barrel SCT detector "stave" - over a range of power dissipations and mass flows in the above fluids. Aspects of full-scale evaporative cooling circulator design for the ATLAS experiment are discussed, together with plans for future development

Spearfishing Regulation Benefits Artisanal Fisheries: The ReGS Indicator and Its Application to a Multiple-Use Mediterranean Marine Protected Area

The development of fishing efficiency coupled with an increase of fishing effort led to the overexploitation of numerous natural marine resources. In addition to this commercial pressure, the impact of recreational activities on fish assemblages remains barely known. Here we examined the impact of spearfishing limitation on resources in a marine protected area (MPA) and the benefit it provides for the local artisanal fishery through the use of a novel indicator. We analysed trends in the fish assemblage composition using artisanal fisheries data collected in the Bonifacio Strait Natural Reserve (BSNR), a Mediterranean MPA where the spearfishing activity has been forbidden over 15% of its area. Fish species were pooled into three response groups according to their target level by spearfishing. We developed the new flexible ReGS indicator reflecting shifts in species assemblages according to the relative abundance of each response group facing external pressure. The catch per unit effort (CPUE) increased by ca. 60% in the BSNR between 2000 and 2007, while the MPA was established in 1999. The gain of CPUE strongly depended on the considered response group: for the highly targeted group, the CPUE doubled while the CPUE of the untargeted group increased by only 15.5%. The ReGS value significantly increased from 0.31 to 0.45 (on a scale between 0 and 1) in the general perimeter of this MPA while it has reached a threshold of 0.43, considered as a reference point, in the area protected from spearfishing since 1982. Our results demonstrated that limiting recreational fishing by appropriate zoning in multiple-use MPAs represents a real benefit for artisanal fisheries. More generally we showed how our new indicator may reveal a wide range of impacts on coastal ecosystems such as global change or habitat degradation

Ambiguity on assignment of NIR vibrational bands for polymerization monitoring of DGEBA/MCDEA system

International audienceThe curing process of epoxy affects the chemical structure of the final network so mechanical and physical properties of the polymeric matrix for a composite may be modified according to the polymerisation conditions. This paper describes the ambiguity in assignment of reference bands to follow the cure of poly-epoxy reactive systems using a laboratory-made system which allows the coupling of dielectric analysis and Fourier Transform Near Infrared Spectroscopy (FTNIR). The dielectric measurements were obtained using interdigitated electrode. In situ monitoring of extent of reaction was carried out from room temperature up to 160 °C using fibre-optic FTNIR spectroscopy. For the DGEBA/MCDEA system the epoxy band at 6060 cm-1 was chosen in preference to the band at 4530 cm-1 as representative of the epoxy function evolution during polymerisation because a small unknown peak probably due to the hardener appears in the 4530 cm-1 region. The bands at 4620 and 4680 cm-1 assigned to aromatic combination bands and widely used as reference bands are not unique for this formulation hence the band at 5980 cm-1 is used as reference. The Principal Components Analysis (PCA) shows clearly also that the bands at 4620 and 4680 cm-1 vary during the polymerisation. Surprisingly, the band at 4530 cm-1 is equivalent to the one at 6060 cm-1 to calculate the conversion rate. It is probably due to the fact that the hardener band near 4530 cm-1 follows the same behaviour as the epoxy band at 4530 cm-1

Semi-interpenetrating polymer networks based on polyurethane and poly(2-hydroxyethyl methacrylate): Dielectric study of relaxation behavior

International audienceThe study of molecular dynamics by broadband dielectric spectroscopy (BDS) is presented for polyurethane (PU), poly(2-hydroxyethyl methacrylate) (PHEMA) and for semi-IPNs based on PU and PHEMA synthesized by photopolymerization. The dielectric properties were performed in wide range of frequencies and temperatures with the goal to establish the relation between the relaxations and the structure. Five relaxation phenomena were finally detected for PHEMA : gamma-, beta sw-, beta-relaxations at low temperatures and a-relaxation at 150 degrees C at high frequencies plus ionic conductivity relaxation which starts at 0 degrees C. For semi-IPNs the overlapping of gamma- and beta sw-relaxations of PHEMA (-125/-75 degrees C) then with increasing the temperature alpha-relaxation in PU (-75/0 degrees C), next ionic conductivity relaxation which starts at 0 degrees C, and finally the alpha-relaxation of PHEMA (+125/+170 degrees C) were detected. The alpha-relaxation of PHEMA in semi-IPNs shifts to lower temperatures and became broader with increasing amount of PU due to incomplete phase separation in the system and formation of interphases. The dielectric relaxation phenomena were fitted with Havriliak-Negami equation. Activation energy, tau(o) and alpha parameters were calculated. For alpha-relaxations corresponding dielectric characteristics have been determined from Vogel-Fulcher-Tammann equation. The relaxation map for investigated PU, PHEMA and semi-IPNs was built

Can environmental contamination be explained by particular traits associated with patients?

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Phase separation in the polyurethane/poly(2-hydroxyethylmethacrylate) semi-interpenetrating polymer networks synthesized by different ways

International audienceThe thermal, dynamic mechanical analysis, morphology and mechanical properties of semi-interpenetrating polymer networks based on crosslinked polyurethane (PU) and poly(2-hydroxyethyl methacrylate) (PHEMA) synthesized by photopolymerization and by thermopolymerization have been investigated. The thermal analysis has evidenced the two glass temperature transitions in the semi-ΙPNs and this is confirmed by the thermodynamic miscibility investigation of the systems. The Dynamic Mechanical Analysis spectra have shown that the phase separation is more significant in the thermopolymerized semi-ΙPNs: the tan δ peaks of constituent polymers are more distinct and the minimum between the two peaks is deeper. The calculated segregation degree values of semi-IPN's components are significantly higher for thermopolymerized semi-IPNs, thereby the process of phase separation in the thermopolymerized semi-IPNs is more developed. The structures of two series of samples investigated by SEM are completely different. The mechanical properties reflect these changes in structure of semi-IPNs with increasing amount of PHEMA and with the changing of the method of synthesis. The results suggest that the studied semi-IPNs are two-phase systems with incomplete phase separation. The semi-IPN samples with early stage of phase separation demonstrate higher mechanical characteristics