Partial least-squares near-infrared determination of hydrocarbons removed from polluted waters by using tanned solid wastes

A new procedure has been developed for the determination of hydrocarbons retained in solid tanned wastes from polluted waters. The method uses near-infrared (NIR) transmission spectra obtained from leachates of the hydrocarbons with CCl₄ using a partial least-squares (PLS) calibration model based on the use of mixtures of n-hexane, isooctane, and toluene diluted with CCl₄. This methodology was applied to the evaluation of the absorption capacity of chrome shavings in water samples polluted with hydrocarbons, resulting in a maximum absorption capacity of 6.30 g hydrocarbons per g solid waste.     

Structural and magnetic properties of nanometric Zn0.5Co0.5Fe2O4 prepared by hydrothermal method

ABSTRACT

The study of the structural, morphology and magnetic properties of Zn_0.5Co_0.5Fe₂O₄ ferrite is the objective of this work. The sample was prepared by hydrothermal method and was characterized by X-ray diffraction (XRD), (SEM) and (TEM) micrographs and magnetization measurements.

The magnetic hysteresis loops, field cooling (FC) and zero field cooling (ZFC) curves, in temperature range (0-400K), were measured using XL-SQUID magnetometer and the values of blocking temperatures (T_B) were determined. The results indicated that Zn_0.5Co_0.5Fe₂O₄ sample were formed in a single spinel phase and gives the value for the lattice parameter (8.3952 Å) and nanosizes of particles (13.8 nm) were compared with these obtained from ZnFe₂O₄ sample prepared also by synthesis method (8.4261 Å and 14 nm). Although, the superparamagnetic behaviour for Co-Zn ferrite has observed at 350K with a blocking temperature (T_B = 300K), that is maximum at the value obtained in the case of Zn-ferrite (T_B = 12K).     

Multilayer transition in a spin 3/2 Blume-Capel model with RKKY interaction

Using Monte Carlo simulation and mean-field theory, we have studied the effect of RKKY interaction on the multi-layer transition and magnetic properties of a spin-3/2 Blume-Capel model of a system formed by two magnetic multi-layer materials, of different thicknesses, separated by a non-magnetic spacer of thickness M. It is found that the multi-layer magnetic order-disorder transition temperature depends strongly on the thicknesses of the magnetic layer and the non-magnetic layer. The transition temperature increases with increasing thickness of the magnetic multi-layers and decreases with increasing thickness of the non-magnetic one. Furthermore, there exists a critical thickness M_L of the non-magnetic spacer beyond which the effect of the RKKY interaction becomes negligible and separate transitions occur in the two magnetic layers. The critical thickness M_L decreases on increasing the magnetic crystal field and/or the Fermi level k_f. Moreover, the multi-layer transition temperature undergoes oscillations as a function of the Fermi level. The susceptibility critical exponents are computed within Monte Carlo simulations.     

TEMPO-oxidation of cellulose: Synthesis and characterisation of polyglucuronans

A series of pseudo amorphous cellulose samples were reacted with catalytic amounts of 2,2,6,6-tetramethyl-1-piperidine oxoammonium salt (TEMPO), sodium hypochlorite and sodium bromide in water. In all samples the primary alcohol groups were selectively oxidised into carboxyl groups, and several water-soluble polyglucuronic acid sodium salts were obtained with different molecular weights. With this reaction system, the degradation of the amorphous cellulose samples may be minimized, provided the oxidation is performed at 4°C and at constant pH 10, with controlled amounts of TEMPO and sodium hypochlorite.     

Gallotannins and Tannic Acid: First Chemical Syntheses and In Vitro Inhibitory Activity on Alzheimer’s Amyloid β‐Peptide Aggregation

The screening of natural products in the search for new lead compounds against Alzheimer’s disease has unveiled several plant polyphenols that are capable of inhibiting the formation of toxic β‐amyloid fibrils. Gallic acid based gallotannins are among these polyphenols, but their antifibrillogenic activity has thus far been examined using “tannic acid”, a commercial mixture of gallotannins and other galloylated glucopyranoses. The first total syntheses of two true gallotannins, a hexagalloylglucopyranose and a decagalloylated compound whose structure is commonly used to depict “tannic acid”, are now described. These depsidic gallotannins and simpler galloylated glucose derivatives all inhibit amyloid β‐peptide (Aβ) aggregation in vitro, and monogalloylated α‐glucogallin and a natural β‐hexagalloylglucose are shown to be the strongest inhibitors.     

Lack of iGb3 and Isoglobo-Series Glycosphingolipids in Pig Organs Used for Xenotransplantation: Implications for Natural Killer T-Cell Biology

α-1,3-Terminated galactose residues on glycoproteins and glycosphingolipids are recognized by natural anti-α-1,3-galactose antibodies in human serum and cause hyperacute rejection in pig-to-human xenotransplantation. Genetic depletion of α-1,3-galactosyl- transferase-1 in pigs abolishes the hyperacute rejection reaction. However, the isoglo- botriosylceramide (iGb3) synthase in pigs may produce additional α-1,3-terminated galactose residues on glycosphingolipids. In both α-1,3-galactosyltranserase-1 knockout mice and pigs, cytotoxic anti-α-1,3-galactose antibodies could be induced; thus, a paradox exists that anti-α-1,3-galactose antibodies are present in animals with functional iGb3 synthases. Furthermore, iGb3 has been found to be an endogenous antigen for natural killer T (NKT) cells, an innate type of lymphocyte that may initiate the adaptive immune responses. It has been reasoned that iGb3 may trigger the activation of NKT cells and cause the rejection of α-1,3-galactosyltransferase-1-deficient organs through the potent stimulatory effects of NKT cells on adaptive immune cells (see ref.^[20]). In this study, we examined the expression of iGb3 and the isoglobo-series glycosphingolipids in pig organs, including the heart, liver, pancreas, and kidney, by ion-trap mass spectrometry, which has a sensitivity of measuring 1% iGb3 among Gb3 isomers, when 5 μg/mL of the total iGb3/Gb3 mixture is present (see ref.^[35]). We did not detect iGb3 or other isoglobo-series glycosphingolipids in any of these organs, although they were readily detected in mouse and human thymus and dendritic cells. The lack of iGb3 and isoglobo-series glycosphingolipids in pig organs indicates that iGb3 is unlikely to be a relevant immune epitope in xenotransplantation.