Descripción: Two copper complex solvatomorphs, namely (3,10-C-meso-3,5,7,7,10,12,14,14- octamethyl-1,4,8,11-tetraazacyclotetradecane)bis(perchlorato-κO)copper(II) 1.2-hydrate, [Cu(ClO4)2(C18H 40N4)]·1.2H2O, (I), and (3,10-C-meso-3,5,7,7,10,12,14,14-octamethyl-1,4,8,11-tetraazacyclotetradecane) bis(perchlorato-κO)copper(II), [Cu(ClO4)2(C 18H40N4)], (II), are described and compared with each other and with a third, already reported, anhydrous diastereomer, denoted (III). Both compounds present very similar centrosymmetic coordination environments, with the CuII cation lying on an inversion centre in a distorted 4+2 octahedral environment, defined by the macrocyclic N4 group in the equatorial sites and two perchlorate groups in trans-axial positions [one of the perchlorate ligands in (I) is partially disordered]. The most significant difference in molecular shape is seen in the orientation of the perchlorate anions, and the influence of this on the intramolecular hydrogen bonding is discussed. The (partially) hydrated state of (I) favours the formation of chains along [011], while the anhydrous character of (II) and (III) promotes loosely bound structures with low packing indices. © 2013 International Union of Crystallography.

Descripción: The effect of pore size to H2O2 detection by macroporous and mesoporous Prussian blue type electrocatalysts is reported in the present paper. The macroporous electrocatalysts were prepared employing spherical colloidal particles of different sizes (300, 460, 600 and 800 nm) as sacrificial templates to synthesize a copper hexacyanoferrate/polypyrrole (CuHCNFe/Ppy) hybrid material. Surprisingly, macroporous and non-porous CuHCNFe/Ppy displayed very similar results, which led to a discussion that application of macroporous platforms in sensors must consider the material wettability and the influence of electrochemical kinetics on analyte detection. In order to evaluate the effect of smaller pores, the performance of the macroporous H2O2 sensors was also compared to electrocatalysts synthesised through the immobilization of Prussian blue and CuHCNFe layers inside the cavities of mesoporous TiO2 films with diameters of 13, 20 and 40 nm. In this scale, the results were superior than those achieved with the non-porous sensors, demonstrating the possibility of controlling the performance of H2O2 sensors according to the pore diameter and the amount of immobilized material. Among the tested porous materials, the H2O2 sensor with better performance was achieved using the 20-nm diameter TiO2 platform functionalized with Prussian blue, which presented a sensitivity of (930 ± 50) μA cm-2 mmol-1 L, detection limit of (0.49 ± 0.08) μmol L-1, response time of (6 ± 2) seconds and linear range up to (1.3 ± 0.1) mmol L-1. This performance was extremely satisfactory considering sensors operating by chronoamperometry. © 2013 Elsevier Ltd. All rights reserved.

Descripción: The three transition-metal complexes, (meso-5,7,7,12,14,14-hexa methyl-1,4,8,11-tetra azacyclo tetra decane-κ4 N)bis (perchlorato-κO)copper(II), [Cu(ClO4)2(C18H40N4)], (I), (meso-5,7,7,12,14,14-hexa methyl-1,4,8,11-tetra azacyclo tetra decane-κ4 N)bis (nitrato-κO)zinc(II), [Zn(NO3)2(C18H40N4)], (II), and aqua chlorido (meso-5,7,7,12,14,14-hexa methyl-1,4,8,11-tetraazacyclo tetra decane-κ4 N)copper(II) chloride, [CuCl(C18H40N4)(H2O)]Cl, (III), are described. The mol ecules display a very similarly distorted 4+2 octa hedral environment for the cation [located at an inversion centre in (I) and (II)], defined by the macrocycle N4 group in the equatorial sites and two further ligands in trans-axial positions [two O-ClO3 ligands in (I), two O-NO2 ligands in (II) and one chloride and one aqua ligand in (III)]. The most significant difference in mol ecular shape resides in these axial ligands, the effect of which on the intra- and inter molecular hydrogen bonding is discussed. In the case of (I), all strong hydrogen-bond donors are saturated in intra molecular inter actions, while weak inter molecular C - H⋯O contacts result in a three-dimensional network. In (II) and (III), instead, there are N - H and O - H donors left over for inter molecular inter actions, giving rise to the formation of strongly linked but weakly inter acting chains. © 2013 International Union of Crystallography.

Descripción: Measurements on the ion flux transmission in a magnetically filtered d-c vacuum arc are presented. The device includes a metallic plasma-generating chamber with water-cooled electrodes coupled to a substrate chamber through a quarter-torus magnetic filter. It is employed a Copper cathode (6 cm in diameter) with a Copper annular anode. The filter consists in a steel cylinder 500 mm length and 100 mm inner diameter with 90° of bending angle and corrugated lateral walls, surrounded by a magnetic field generating coil. The arc is operated at a current level of 100 A, and the intensity of the filtering magnetic field was in the range 0-200 G (measured at the knee of the filter). This magnetic field is enough high so as to magnetize the electrons but not the ions. The discharge is ignited by bringing (and later removing) a tungsten striker into contact with the cathode. The arc voltage drop, the floating potentials of the filter and the plasma, and the ion current collected by probes located at different positions as functions of the magnetic field intensity are reported and compared with measurements presented in the literature with other similar devices.

Descripción: The Arroyo La Chilca-Zanjón del Buitre alteration zone, San Rafael Massif, Mendoza. The Arroyo La Chilca-Zanjón del Buitre alteration zone is located in the San Rafael Massif (35°24'8" S; 68°19'25,8" W), Mendoza. Previous works defined preliminary this deposit as a porphyry copper system genetically linked to the gondwanan magmatism. This alteration zone is hosted by a sequence composed of ignimbritic breccias and ignimbrites of trachyandesitic composition with interbedded tuffaceous sandstones and andesitic lavas flows intruded by trachyandesitic-dacitic and andesitic hypabyssal bodies. The lithology and geochemistry of the volcanic sequence confirm the link with the Choiyoi Magmatic Cycle lower section (Lower Permian). The alteration zone consists of a potassic halo with a parageneses of K-feldspar-quartzmagnetite overprinted by phyllic alteration with an assemblage of quartz-muscovite-pyrite-(rutile) and quartz -pyrite veins. A late carbonatization process overprints both the potassic and phyllic alteration. Outside the alteration zone pyrite-chalcopyrite- galena-sphalerite veins with quartz gangue crop out. Metals geochemistry shows moderate Ag and Au anomalies and little Cu, Mo, Pb and Zn anomalies. Statistical analyses allow defining one Cu-Mo mineralizing stage and another Mo mineralizing stage only recognized in Zanjón del Buitre. Moreover, two Zn mineralizing stages, one of them probably genetically related to the Cu stage, were also recognized.

Descripción: Drill samples from the Carrizal uranium ore deposit located in Western Precordillera, Province of San Juan, Argentina, were studied by petrography, ore microscopy, X-ray diffraction, energy dispersive electron microscope and microprobe methods. A mesothermal ore paragenesis composed of arsenic-nickel-cobalt-uranium-bismuth minerals was identified. The established paragenetic sequence is pyrite-bismuthinite; nickeline-gersdorffite-rammelsbergite-pechblende, in an assemblage hosted by lithic breccia. A second mineralization stage produced a porphyry copper deposit, spatially but not genetically associated with the above described assemblage. © 1997 Asociación Geológica Argentina.

Descripción: El Infiernillo Mining District is located in the San Rafael Block (34°38'20";68°47'37"), province of Mendoza, Argentina. It is a porphyry Cu (Mo) type deposit which is hosted by a volcaniclastic sequence. It develops an alteration halo with a concentric pattern consisting of a central quartz neck surrounded by a potassic alteration zone and outwards a phyllic halo and small polymetallic veins. The potassic halo has a paragenesis of K-feldspar-quartz-(biotite). Three silicification phases are related to this alteration stage, one of them (with temperature between 550° and 390°C and salinity between 35 and 47 %) genetically linked to the copper mineralization. The phyllic alteration consists of quartz-illite-(rutile) with minor albite. The albitization process points out to an early phase of this phyllic stage. The fluid inclusions together with the textures of the quartz neck suggest the shallowing of the active hydrothermal system. The disseminated ore paragenesis consists of bornite, chalcopyrite-molibdenite, pyrite, (galena-sphalerite). The presence of molibdenite-quartz veins indicate the transition from the potassic to the phyllic stage while the pyrite-quartz ones point out to a transition to a fragile deformation regime during which the polymetallic veins, with a paragenesis of chalcopyrite- sphalerite, pyrite, (Ag) tetrahedrite, galena were formed. The petrologic characteristics of the volcaniclastic host rocks reveal that they correspond to the lower section of Choiyoi magmatic cycle. The magmatic and structural controls constrain the age of this ore deposit to the Early-Middle to Late Permian.

Descripción: 1. 1. The effect of several metals and reagents on the decarboxylation rate of uroporphyrinogen I by using a 16-fold purified preparation of Uroporphyrinogen Decarboxylase from Rhodopseudomonas palustris, was studied. 2. 2. 1 mM Hg2+ and Cu2+ were strong inhibitors, 1 mM Zn2+ and Fe2+ under certain conditions and 1 mM Fe3+ and Cr3+ also inactivated the enzyme, but Pb2+, Cd2+, and Al3+ did not. Metals inhibition was reversed by 1 mM GSH or CvSH. 3. 3. 0.1 mM DTNB and PCMB, 1 mM pyridoxal phosphate and 100 mM chloral hydrate, as well as 1 mM 2-methoxy-5-nitrotropone and 0.2 mM diethylpyrocarbonate inhibited Uroporphyrinogen Decarboxylase; while GSH, CySH, N-ethylmaleimide, sodium thioglycolate, 1,4-dithioerythritol, EDTA and O-phenantroline did not modify activity. 4. 4. Data obtained would indicate that one cysteine, one or two histidine residues and probably a lysine group are required for enzyme activity. © 1987.

Descripción: An experimental study of the plasma jet generated in a pulsed copper vacuum arc with an annular anode and operated with a linear magnetic filter is presented. Two types of filters were employed, one consisting of an insulating duct and the other of a conducting duct, both of them surrounded by an external coil, which generates the axial magnetic field. To improve the ion flux at the filter entrance another auxiliary magnetic field in the cathode region was applied (focusing field). Also, the cathode shape was modified to confine the cathode spot onto the front cathode surface. Operating the arc under vacuum conditions, probe measurements of the ion saturation current and the plasma potential at different axial positions along the ducts and for different filtering magnetic field values are reported. A comparison between both kinds of filters is also presented. © 2006 American Institute of Physics.

Descripción: An atomistic model for Cu electrodeposition under nonequilibrium conditions is presented. Cu electrodeposition takes place with a height-dependent deposition rate that accounts for fluctuations in the local [formula presented] ions concentration at the interface, followed by surface diffusion. This model leads to an unstable interface with the development of protrusions and grooves. Subsequently the model is extended to account for the presence of organic additives, which compete with [formula presented] for adsorption at protrusions, leading to a stable interface with scaling exponents consistent with those of the Edwards-Wilkinson equation. The model reproduces the interface evolution experimentally observed for Cu electrodeposition in the absence and in the presence of organic additives. © 2002 The American Physical Society.

Descripción: These concretions form discrete spherical bodies 2 to 20 cm in sizes, within medium grained massive sandstone (arkosic arenite). Three concentric zones are recognized: a) dark green to black core composed of quartz and feldespar cemented by illite and roscoellite, b) an intermediate pale red zone of hematite-coated quartz, and c) a white, iron-leached outer zone. Edax and ICP analyses reveal high concentrations of vanadium mainly in zones a) and b) (60340 and 2582 ppm respectivily), uranium (237 and 163 ppm), rubidium (252ppm) and copper (178ppm). The concretions are interpreted as formed under eodiagenetic conditions before the development of haematite cement which gave the red colour to the host rock.

Descripción: An experimental study of the metallic ion flux in a pulsed copper vacuum arc with an annular anode and operated with an axial magnetic field is presented. It is employed an insulating drift duct surrounded by an external coil which generates an axial magnetic field. Operating the arc under vacuum condition, measurements of the ion flux and the plasma potential at different axial positions along the duct and different magnetic field values are presented. The arc voltage and the total discharge current as functions of the magnetic field intensity are also reported. We find that the decay of the ion flux through the duct walls is not exponential. A simplified model for the ion emission is used in order to obtain an interpretation of the measured ion current for different axial positions and magnetic field strength, and a good agreement with the experimental points is found.

Descripción: The possible involvement of apoplastic reactive oxygen species produced by the oxidation of free polyamines in the leaf growth of salinized maize has been studied here. Salt treatment increased the apoplastic spermine and spermidine levels, mainly in the leaf blade elongation zone. The total activity of polyamine oxidase was up to 20-fold higher than that of the copper-containing amine oxidase. Measurements of H2O2, ·O2-, and HO· production in the presence or absence of the polyamine oxidase inhibitors 1,19-bis- (ethylamine)-5,10,15 triazanonadecane and 1,8-diamino-octane suggest that, in salinized plants, the oxidation of free apoplastic polyamines by polyamine oxidase by would be the main source of reactive oxygen species in the elongation zone of maize leaf blades. This effect is probably due to increased substrate availability. Incubation with 200 μM spermine doubled segment elongation, whereas the addition of 1,19-bis-(ethylamine)-5,10,15 triazanonadecane and 1,8-diamino-octane to 200 μM spermine attenuated and reversed the last effect, respectively. Similarly, the addition of MnCl2 (an ·O2- dismutating agent) or the HO· scavenger sodium benzoate along with spermine, annulled the elongating effect of the polyamine on the salinized segments. As a whole, the results obtained here demonstrated that, under salinity, polyamine oxidase activity provides a significant production of reactive oxygen species in the apoplast which contributes to 25-30% of the maize leaf blade elongation.

Descripción: Oxidative stress plays a critical role in the pathogenesis of diabetes, hypertension and atherosclerosis. Some authors reported that fat accumulation correlates to systemic oxidative stress in humans and mice, but the relationship of lipid production and oxidative metabolism is still unclear. In our laboratory we used 3T3-L1 preadipocytes, which are able to differentiate into mature adipocytes and accumulate lipids, as obesity model. We showed that intracellular reactive oxygen species (ROS) and antioxidant enzymes superoxide dismutase (SOD) and glutathione peroxidase (GPx) activities increased in parallel with fat accumulation. Meanwhile N-acetylcysteine (NAC), a well known antioxidant and Glutathione (GSH) precursor, inhibited ROS levels as well as fat accumulation in a concentration-dependent manner. NAC also inhibited both adipogenic transcription factors CCAAT/enhancer binding protein beta (C/EBP) and peroxisomal proliferator activated receptor gamma (PPAR β) expression; we suggested that intracellular GSH content could be responsible for these effects. © 2011 by the authors; licensee MDPI, Basel, Switzerland.