A New Method for Characterization of Natural Zeolites and Organic Nanostructure using Atomic Force Microscopy

In order to study and develop an economic solution to environmental pollution in water, a wide variety of materials were investigated. Natural zeolites emerge from that research as the best in class of this category. Zeolites are natural materials relatively abundant and non biodegradable, economic and good to perform processes of environmental remediation. This paper contains a full description of a new method to characterize superficial properties of natural zeolites of exotic provenience (Caribbean Islets) with atomic force microscopy (AFM). AFM works with the optical microscope simplicity and the high resolution typical of a transmission electron microscope (TEM). Structural information of mesoporous material is obtained using scanning and transmission electron microscopy (SEM and TEM), only if the sample is conductive, otherwise the sample has to be processed through the grafitation technique, but this procedure induces errors of topography. Therefore, the existing AFM method, to observe zeolite powders, is made in a liquid cell-head scanner, but this work puts in evidence and confirms that it is possible to use an ambient air-head scanner to obtain a new kind of microtopography. Once optimized, this new method allows investigating of organic micelles, very soft nanostructure, of cetyltriammonium bromide (CTAB) upon an inorganic surface such as natural zeolites. It is shown some correlation between SEM microphotographies and AFM 3D images

Insulin-like growth factor-1 is a negative modulator of glucagon secretion

Glucagon secretion involves a combination of paracrine, autocrine, hormonal, and autonomic neural mechanisms. Type 2 diabetes often presents impaired glucagon suppression by insulin and glucose. Insulin-like growth factor-I (IGF-1) has elevated homology with insulin, and regulates pancreatic β-cells insulin secretion. Insulin and IGF-1 receptors share considerable structure homology and function. We hypothesized the existence of a mechanism linking the inhibition of α-cells glucagon secretion to IGF-1. Herein, we evaluated the association between plasma IGF-1 and glucagon levels in 116 nondiabetic adults. After adjusting for age gender and BMI, fasting glucagon levels were positively correlated with 2-h post-load glycaemia, HOMA index and fasting insulin, and were negatively correlated with IGF-1 levels. In a multivariable regression, the variables independently associated to fasting glucagon were circulating IGF-1 levels, HOMA index and BMI, explaining 20.7% variation. To unravel the molecular mechanisms beneath IGF-1 and glucagon association, we investigated whether IGF-1 directly modulates glucagon expression and secretion in an in vitro model of α-cells. Our data showed that IGF-1 inhibits the ability of low glucose concentration to stimulate glucagon expression and secretion via activation of the phosphatidylinositol-3-kinase/Akt/FoxO1 pathway. Collectively, our results suggest a new regulatory role of IGF-1 on α-cells biological function

Adaptive multibeam phased array design for a Spacelab experiment

The parametric tradeoff analyses and design for an Adaptive Multibeam Phased Array (AMPA) for a Spacelab experiment are described. This AMPA Experiment System was designed with particular emphasis to maximize channel capacity and minimize implementation and cost impacts for future austere maritime and aeronautical users, operating with a low gain hemispherical coverage antenna element, low effective radiated power, and low antenna gain-to-system noise temperature ratio

Correlation between macroscopic sugar transfer and nanoscale interactions in cation exchange membranes

Previous experimental work has shown that the transfer of organic solutes through ion-exchange membranes depends on the membrane counter-ion and that this dependence is probably linked to the interactions taking place at the nanoscale inside the membrane matrix. In this paper, a computational approach is carried out, combining quantum mechanics and molecular mechanics to determine the interactions occurring at the nanoscale, taking a cation exchange membrane as example. Building blocks are first accurately studied at high level of quantum theory, before being merged in macromolecular models. The computed interactions are then compared to the experimental values of the solute flux in order to point out the nanoscale mechanisms governing the solute transfer. The computed glucose-polymer fragment interactions, related to the sugar solubility inside the membrane, are found to be almost independent from the membrane counter ion. On the contrary, significant variations of the chain-chain interaction, i.e. the interaction energies per trapped water molecule or hydrogen bonding wire connecting the polymer fragments, were observed according to the cation. Moreover, a correlation was pointed out with the experimental sugar fluxes obtained with 3 different sugars. Increasing chain-chain interactions inside the membrane was found to give decreasing sugar flux. Then this work shows that the cohesion energy between the polymer fragments fixes the dependence of the sugar flux versus the membrane counter-ion. The crucial role of the water molecules coordinating the cations is also highlighted

Structural properties of cation exchange membranes: characterization,electrolyte effect and solute transfer

Experimental investigations have shown that the presence of electrolytes has a strong influence on the transfer of neutral organic solutes through ion exchange membranes used in electrodialysis. It was further demonstrated that this influence is due to the impact of the membrane counter-ions on the noncovalent interactions existing between the hydrated and charged polymer chains in the membrane. The aim of this work is to investigate the structural properties of hydrated CMX membranes equilibrated with different counter-ions. Different methods, such as Infrared spectra (IR), contact angle and Differential Scanning Calorimetry (DSC) measurements, were used to characterize the membrane samples soaked in different electrolytes. In addition, IR spectra were calculated using a quantum mechanics approach and compared with the experimental ones. Shifts of characteristic IR peaks as function of membrane ionic form were observed in both experimental and computed spectra. Both spectra present shifts to lower wavenumber in presence of cations with higher hydration number. The contact angle of CMX membranes also increases in presence of more hydrated ions revealing a decrease of the hydrophilicity of the membrane. Concerning DSC, the freezing temperature of the water entrapped in the membrane polymeric network soaked with different electrolytes was measured. A shift at lower temperature was found for more hydrated trapped ions. The computational and experimental membrane structural properties were correlated with the corresponding transfer properties (sugar fluxes) and a good agreement was obtained

The Prejudicial Effects of Cameras in the Courtroom

The Supreme Court recently held in Chandler v. Florida, that absent a showing of actual prejudice, it is not per se unconstitutional to televise trials over the objection of the defendant. This decision has a direct bearing on state court procedures, as over one-half of the states currently permit television coverage of trials in one form or another. However, sheer numbers supporting a proposition do not make that proposition right , nor does a Supreme Court decision upholding its constitutionality imply an unqualified stamp of approval. In fact, previous Supreme Court decisions have overturned convictions because the defendant\u27s right to a fair trial had been violated as a result of media coverage of his case