Microwave Absorbing properties of metal functionalized-CNT-polymer composite for stealth applications.

In this study, we report on the electrical properties of multi-wall carbon nanotubes (MWCNT) composites functionalized with metal or metal alloy oxides and embedded in a polyurethane matrix to develop a lightweight material for microwave absorption and shielding. The CNT nanoparticles are functionalized with metallic oxides such as Cobalt oxide, Iron oxide, and Cobalt Iron oxide, at three different concentrations. Metallic oxides are used at 5%, 10%, and 20% concentration of the total CNT percentage weight. The resulting functionalized CNT is mixed with polyurethane polymer at 5% wt of the total composite weight. Three sets of cylindrical samples are developed, and each set contains three different metal oxide concentrations. The dielectric properties of the nine developed samples are obtained by measuring their permittivity spectra using an open-ended coaxial probe technique in the spectral range 5-50 GHz. The absorption efficiency of the composites is then obtained by calculating the reflection loss at normal incidence. The results show that the spectral range of absorption can be tuned by changing the CNT concentration, and the material thickness. Functionalized CNT with different alloyed metal oxides enhanced the absorption efficiency of the polyurethane/CNT composites. Such functionalized composites can be used to replace the common heavyweight materials used for microwave applications.

[Relevance of the health insurance databases to study spatial disparities in asthma prevalence: A study in southeastern France]. / Intérêt des données de remboursement de l'assurance-maladie pour l'étude des disparités territoriales de la prévalence de l'asthme : une étude en Provence-Alpes-Côte d'Azur.

BACKGROUND: Data on asthma prevalence at a small-area level would be useful to set up and monitor French local public health policies. This study, based on drug reimbursement databases in southeastern France, aimed to (1) compare asthma-like disorders prevalence estimated by using three different indicators; (2) study sociodemographic characteristics associated with these indicators; (3) verify whether these indicators are equivalent to study geographical disparities of the asthma-like disorders prevalence at a small-area level. METHODS: The study was conducted among the beneficiaries of the National Health Insurance Fund aged 18-44 years residing in southeastern France in 2010 (n=1,371,816). Using data on asthma drugs reimbursements (therapeutic class R03), we built three indicators to assess asthma-like disorders prevalence: at least 1, 2 or 3 purchase(s) in 2010. We analyzed sociodemographic characteristics associated with these indicators, and their geographical disparities at a small-area level using multilevel logistic regression models. RESULTS: The crude asthma-like disorders prevalence varied between 2.6 % and 8.4 % depending on the indicator. It increased with age, was higher for women than for men, and among low-income people for all three indicators. We measured significant geographical disparities. Areas with high prevalence rates were the same regardless of the indicator. CONCLUSION: The indicators built in this study can be useful to identify high prevalence areas. They could contribute to launch discussion on environmental health issues at the local level.

The role of aggregation of ferrite nanoparticles on their magnetic properties.

We have studied the magnetic properties of aggregates of Mn0.5Zn0.5Gd(x)Fe(2-x)O4 ferrite nanoparticles, with x = 0.01, 0.02, 0.03, 0.04, 0.05, 0.06, 0.07, 0.08, 0.09, 0.10, 0.11, 0.12, 0.13, 0.14, 0.15, 0.16, 0.18, 0.20. The scanning electron microscopy micrographs show significant aggregation of the nanoparticles in all samples. Zero field cooled and field cooled magnetization measurements were conducted on all samples from 400 K down to 5 K. Most zero field cooled curves were found to exhibit the usual behavior but with wide peaked regions. For some x values, the field cooled magnetization was found to increase slowly with decreasing temperature, and becomes nearly constant at low temperatures. The measurements of magnetization versus applied magnetic field were conducted on all samples at 5 K and 305 K in the field range from -15000 to 15000 Oe. At 305 K the magnetization for all samples was observed to saturate, while at 5 K the magnetization did not reach saturation for some values of x. The saturation magnetization values were suggested to be proportional to the size of particles. These results were discussed and suggested to be due to the inter-particle dipolar and exchange interactions between the particles in the aggregates, the large particle size distribution and the surface magnetization effects.

Stabilization of halophilic malate dehydrogenase.

Malate dehydrogenase from the extreme halophile, Halobacterium marismortui, is stable only in highly concentrated solutions of certain salts. Previous work has established that its physiological environment is saturated in KCl; it remains soluble is saturated NaCl or KCl solutions; also it unfolds in solutions containing less than 2.5 M-NaCl or -KCl, salt concentrations which are still relatively high. New data show that the structure of this enzyme can be stabilized in a range of high concentrations of Mg2+ or other "salting-in" ions, also with exceptional protein-solvent interactions. "Salting-in" ions, contrary to stabilizing protein structure, usually favour unfolding. These, and most other results concerning the structure, stability and solvent interactions of the protein cannot be understood in terms of the usual effects of salts on protein structure. In this paper, a novel stabilization model is proposed for halophilic malate dehydrogenase that can account for all observations so far. The model results from experiments on the protein in salt solutions chosen for their different effects on protein stability (potassium phosphate, a strongly "salting-out" agent, and MgCl2, which is "salting-in"), and previously published data from NaCl and KCl solutions (mildly "salting-out"). Enzymic activity and stability measurements were combined with neutron scattering, ultracentrifugation and quasi-elastic light-scattering experiments. The analysis showed that the structure of the protein in solution as well as the dominant stabilization mechanisms were different in different salt solutions in which this enzyme is active. Thus, in molar concentrations of phosphate ions, stabilization and hydration are similar to those of non-halophilic soluble proteins, in which the hydrophobic effect dominates. In high concentrations of KCl, NaCl or MgCl2, on the other hand, solution particles are formed in which the protein dimer interacts with large numbers of salt and water molecules (the mass of solvent molecules involved depends on the nature of the salt but it is approximately equivalent to the protein mass). It is proposed that, under these conditions, the hydrophobicity of the protein core is too weak to stabilize the folded structure and the main stabilization mechanism is the formation of co-operative hydrate bonds between the protein and hydrated salt ions. Model predictions are in agreement with all experimental results, such as the different numbers of solvent molecules found in the solution particles formed with different salts, the loss of the exceptional solvent interactions concomitant with unfolding at non-physiological salt concentrations, and the different temperature denaturation curves observed for different salt solutions.(ABSTRACT TRUNCATED AT 400 WORDS)

Bovine serum albumin and aqueous guanidine hydrochloride solutions. Preferential and absolute interactions and comparison with other systems.

The partial specific volume, upsilon20, of bovine serum albumin at 25 degrees C was found to be 0.728 +/- 0.001 ml/g in solutions of guanidine hydrochloride (GuHC1), 0.01 M dithioerythritol (DTE), independent of GuHC1 concentration (3-6 M). The volume decrease upon denaturation is about 400 ml/mol (upsilon20 in water at the same temperature was found to be 0.734). From the reduced density increments at constant chemical potential of diffusible solutes, The apparent volumes, phi, were found to increase from 0.693 ml/g at 3 M GuHC1 to about 0.725 ml/g at 7 M GuHC1. The phenomenological interaction parameter, xi3 (grams of GuHC1 "bound" per gram of protein), was found to decrease from about 0.2 at 3 M GuHC1 to about 0.07 at 6.4 M GuHC1. The phenomenological interaction parameter, xi1 (grams of water "bound" per gram of protein), is negative and become less negative with increase in GuHC1 concentration. The relation between xi3 and xi1 and physical binding and exclusion of low-molecular-weight components are discussed in terms of simple model consideration. It is concluded that over the range of GuHC1 concentrations studied about 0.2 g of water as well as 0.28 g of GuHC1 are bound per gram of protein. This corresponds on the average to 1.3 molecules of water and 0.35 molecule of GuHC1 per amino acid residue. Similar results were found by recalculating some previous results for aldolase. These results on proteins in GuHC1 solution are in marked contrast to the behavior of DNA at high concentrations of NaCl and CsCl, which is analyzed on the basis of earlier work.