Thermal,morphostructural and spectrometric characterization of an antibacterial kaolinite-based filter modified with silver for water treatment

Journal of Thermal Analysis and Calorimetry - The aim of this work is to synthesize and characterize a new structured silver–clay dried, calcined or sintered at different temperatures...     

13C NMR investigations of molecular order of rod-like,bent-core,and thiophene mesogens

In this review, methods to obtain the orientational order of topologically variant molecular mesogens using by one- and two-dimensional (2D) solid-state ¹³C nuclear magnetic resonance (NMR) spectroscopy are described. Besides ¹³C chemical shifts, the ¹³C─¹H dipolar couplings measured from 2D-separated local field (SLF) technique are used for computing the order parameters of a variety of mesogens. The investigated molecules are composed of a variable number of rings in the core, that is, core ranging from simply one ring to five rings. Among the mesogens investigated, a special focus has been placed on mesogens with thiophene rings, which are gaining popularity as liquid crystalline organic semiconductors. The replacement of a phenyl ring by thiophene in the core has a dramatic influence on molecular topology, as observed from the measured order parameters. The review highlights the advantages of the 2D SLF method for understanding the local dynamics and for mapping the topology of mesogens through the measured order parameters. SLF NMR studies of as many as 24 molecular mesogens that vary in terms of the molecular structure as well as topology are covered in the review. Order parameters of the rings have been estimated from the ¹³C─¹H dipolar couplings in the nematic, smectic A, smectic C, and tilted hexatic phases as well as in B₁ and B₂ mesophases of various mesogens. It is anticipated that, in the years to come, the 2D SLF method would provide advanced molecular information on structurally complex mesogens that are emerging in liquid crystal science through the incessant efforts of synthetic chemists. The mini review covers the orientational order of topologically variant molecular mesogens determined by 1D and 2D solid-state ¹³C NMR spectroscopy. Accordingly, rod-like, bent-core, and thiophene mesogens were subjected to 2D SLF measurements to get the order parameters from which the topology was established. The replacement of phenyl ring by thiophene and its influence on order parameters as well as on molecular topology is also discussed.     

Global variations in peak bone mass as studied by dual-energy X-ray absorptiometry

In 1994, the International Atomic Energy Agency (IAEA) initiated a 5-year Co-ordinated Research Project (CRP) to determine geographical and racial differences in peak bone mineral density (BMD) in men and women aged 15-49 years. The study demonstrates that there are distinct global differences in BMD at the hip and spine in both men and women approximating to one population standard deviation between populations with the highest and lowest BMD. These differences persist following adjustments for age, sex and body size. Such information is valuable in understanding the reasons for global differences in fracture rate and predicting future trends in fracture incidence. This revised version was published online in August 2006 with corrections to the Cover Date.     

Compositions for health products obtained by treatment of tomato with beta-cyclodextrin

The aim of this work was to produce lycopene-containing powders from tomato products by a solvent-free method making use of β-cyclodextrin (βCD). Powders were prepared by spray-drying a tomato concentrate (TC), one of the most bioavailable form of lycopene, after mechanical treatment with βCD in different weight ratios. The obtained product was centrifuged to eliminate partly food matrix and characterized for the amount of lycopene hydrodispersed/hydrosolubilized in the aqueous fraction. The chemical antioxidant activity of sera was evaluated too. Powders obtained by spray-drying sera exhibited good flow properties, a lycopene content between 0.4 and 1.09 mg/g and excellent water dispersability. The process developed, which makes use of βCD for the treatment of tomato products, turns to be of great interest to obtain a bulk material for nutraceuticals displaying superior biovailability of lycopene.     

New aspects on the transuranics transfer in the Palomares marine environment

The environmental contamination of transuranics following the Palomares accident in 1966 (Southern Spain) has been continuous monitored on land and scientific programs are still running. The study of the land to sea transfer of the contamination started in 1986, focussed on the depositional history recorded in marine sediments. At the continental shelf, south of the mouth of the Almanzora river, enhanced levels of plutonium and americium were found which could be related to the accident. Additional analysis of marine sediments, collected far from the impact point, showed the presence of a hot particle. The study of the chronology of this sediment core and the isotopic ratios are given in this paper to assess the origin and pathway of the particle. The route of this particle was found to be the aerial transfer at the time of the accident.     

Transport properties of alkyltrimethylammonium bromide surfactants in aqueous solutions

Differential mutual diffusion coefficients of n-alkyltrimethylammonium bromides [CH₃(CH₂)_n–1N(CH₃)₃Br, C_nTAB] (n=10, 12, 14, 16) have been measured in aqueous solutions at 298.15 K using a conductimetric cell and an automatic apparatus to follow diffusion. The cell is based on an open-ended capillary, and the technique follows the diffusion process by measuring the resistance of a solution inside the capillaries at various times. The electrical conductances of those solutions have also been measured to calculate the critical micellar concentration (cmc). Thermodynamic analysis of the data suggests that the free ion concentration decreases at concentrations above the cmc, in agreement with theoretical predictions. The obtained values of the micellization parameters were used to model the mutual diffusion coefficients of C_nTAB aqueous solutions.     

Transparent conducting oxides: texture and microstructure effects on charge carrier mobility in MOCVD-derived CdO thin films grown with a thermally stable, low-melting precursor

A series of low-melting, thermally stable cadmium metal-organic chemical vapor deposition (MOCVD) precursors have been synthesized, structurally and spectroscopically characterized, and implemented in growth of highly conductive and transparent CdO thin films. One member of the series, bis(1,1,1,5,5,5-hexafluoro-2,4-pentanedionato)(N,N-diethyl-N',N'-dimethyl-ethylenediamine)cadmium(II), Cd(hfa)(2)()(N,N-DE-N',N'-DMEDA), represents a particularly significant improvement over previously available Cd precursors, owing to the low melting point and robust thermal stability. High-quality CdO films were grown by MOCVD on glass and single-crystal MgO(100) between 300 and 412 degrees C. Film growth parameters and substrate surface have large effects on microstructure and electron carrier transport properties. Enhanced mobilities observed for highly biaxially textured films grown on MgO(100) vs glass are attributed, on the basis of DC charge transport and microstructure analysis, to a reduction in neutral impurity scattering and/or to a more densely packed grain microstructure. Although single-grained films grown on MgO(100) exhibit greater mobilities than analogues with discrete approximately 100 nm grains and similar texture, this effect is attributed, on the basis of charge transport and Hall effect measurements as well as optical reflectivity analysis, to differences in carrier concentration rather than to reduced grain boundary scattering. Unprecedented conductivities and mobilities as high as 11,000 S/cm and 307 cm(2)/V.s, respectively, are obtained for epitaxial single-grained films (X-ray diffraction parameters: fwhm(omega) = 0.30 degrees, fwhm(phi) = 0.27 degrees ) grown in situ on MgO(100) at a relatively low temperature (400 degrees C).     

Evolution of self-assembled silica-tetrapropylammonium nanoparticles at elevated temperatures

The time evolution of silica nanoparticles in solutions of tetrapropylammonium (TPA) has been studied using a combination of small-angle scattering, conductivity, and pH measurements to provide the first comprehensive analysis of nanoparticle structural and compositional changes at elevated temperatures. We have found that silica-TPA nanoparticles subjected to hydrothermal treatment (70-90 degrees C) grow via an Ostwald ripening mechanism with growth rates that depend on both pH and temperature. Small-angle X-ray (SAXS) and neutron (SANS) scattering confirm that the core-shell structure of the particles, initially present at room temperature, is maintained during heating, but an evolution toward sphericity is evidenced especially at high values of pH. SAXS absolute intensity calculations were utilized to calculate the changes in nanoparticle composition and concentration over time. These changes along with the conductivity and pH measurements and SANS contrast matching studies indicate that, upon heating, TPA becomes embedded in the core of nanoparticles giving rise to more zeolitic-looking nanomaterials.     

Utilisation of 1,3-dialkylimidazolium-2-carboxylates as CO2-carriers in the presence of Na and K: application in the synthesis of carboxylates, monomethylcarbonate anions and halogen-free ionic liquids

1,3-Dialkylimidazolium-2-carboxylate compounds have recently been fully characterised. Here we describe the utilisation of 1,3-dimethyl (1a) and 1-butyl-3-methyl-imidazolium-2-carboxylate (1b) in a carboxylation reaction with transfer of the CO₂ moiety to benzoylacetone and methanol for the synthesis, in high yield, of benzoylacetate and monoalkylcarbonate anions, respectively. Conversely, when compounds 1a and b are reacted with carbonylic substrates lacking C-H active bonds, a product resulting from nucleophilic attack of the 1,3-dialkylimidazol-2-ylidene species on the carbonyl moiety is obtained. The reported reactions can find applications in organic synthesis and in the synthesis of halogen-free ionic liquids.     

Electrocatalytic Properties of a Novel Poly‐1‐Naphthylamine‐Modified Electrode Using Ascorbic Acid as Molecule Probe

A glassy carbon electrode was modified with an electropolymerized film of 1‐naphthylamine in aqueous solution. The electrocatalytic properties of this modified electrode (ME) were investigated using ascorbic acid (AA) as probe molecule. The electrochemical behavior of AA in buffer solution was examined by voltammetry and amperometry. The results showed that the ME exhibited good electrocatalytic activity towards the oxidation of AA, as a consequence, it can be used as amperometric sensor of this analyte in a flow injection system with good sensitivity. Calibration curves were linear over the concentration range 0.05–1.50 mM with a phosphate buffer solution pH 3 as the carrier, the detection limit was 1 ppm (S/N=3). The methods were applied to the determination of AA in beverages and pharmaceutical products. A good correlation with a reference method was attained.