Synthesis, characterization of a new carbonylated zirconium metallocene using a dichloro-zirconocene derived from partially alkylated s-indacene

Indexación: ScieloThis work describes the synthesis and characterization of new organometallic species, an unprecedented mononuclear zirconium complex bearing a tetraalkylated s-indacene ligand, and secondly, its respective dicarbonyl complex obtained by reduction with Mg/HgCl2. Theoretical calculations of these two compounds were carried out to gain further understanding of these novel molecular systems.http://www.scielo.cl/scielo.php?script=sci_arttext&pid=S0717-97072009000300014&lng=es&nrm=is

ADSORPTION ESSAYS OF PALLADIUM IN MODIFIED SILICA GEL WITH THIOURONIUM GROUPS: EXPERIMENTAL AND THEORICAL STUDIES

Indexación: Web of Science; ScieloThe silylant 3-cloropropyltriethoxysilyl was anchored over silica gel in anhydrous conditions in order to react with thiourea to obtain modified silica gel with thiouronium. The aim to obtain an inorganic support that is able to hijack metals from the VIII group such as palladium. The product was characterized by Sbet and FTIR infrared spectroscopy. For the determination of the structure in the modified silica gel NMR spectra of silicon and carbon were preformed in solid state. The coordination form of the modified silica gel to the metal was studied computationally in the context of the DFT theory, using the ADF code. This was a collaborative work with "Fundación Chile" for the recuperation of precious metals from the mining industry.http://ref.scielo.org/gk7rm

Hyphomycetes Acuáticos en Chile: estudio en el Estero de Limache; un afluente del Río Aconcagua

Mediante toma de muestras seriadas efectuadas en el transcurso de un año, se estudia la presencia de Hyphomycetes acuáticos aplicando la técnica de filtrado de las aguas según el método de lqbal y Webster (1973).Se contabilizaron los conidios de hongos acuáticos y algunos terrestres, junto a las diatomeas retenidas en los filtros, analizando cualitativa y cuantitativamente los resultados con algunas variables del medio ambiente tales como: Oxígeno disuelto, Nitratos, Amonios, Temperatura, Pluviosidad y efectos estacionales.Se detectaron formas conidiales correspondientes a 13 géneros y 20 especies de Hyphomycetes acuáticos. Las especies dominantes fueron: Alatospora acuminata lngold, Flagellospora penicillioides lngold, Tetracladium marchalianum de Wild, Trisc       ophorus monosporus lngold y Triscelophorus sp. C

Effects of UV radiation on the RNA/DNA ratio of Copepods from Antarctica and Chile

The effect of ultraviolet (UV) radiation on marine organisms has been an important focus of recent research, with depletion of the ozone layer resulting in increased UV radiation at high latitudes. Several studies have identified negative impacts of UV radiation on the biology of zooplanktonic organisms. This study used the RNA/DNA ratio as a measure of stress in copepod assemblages from Fíldes Bay in Antarctica and Quintay Bay on the central coast of Chile, two areas with high UV radiation but different photobiologic histories. Controlled time-light experiments were performed with copepods from the two locations, exposing them to white light, UV light, or darkness. The results showed different responses to UV radiation. Copepods from Fíldes Bay showed a slow metabolic response to UV radiation after 4 and 8 h of exposure. Copepods from Quintay Bay showed a fast metabolic response after 4 h of exposure (4 orders of magnitude higher than that for Fíldes Bay copepods) followed by a rapid return toward baseline after 8 h of exposure. These different responses probably reflect the time the copepod assemblages have been exposed to increased UV radiation and the extent of adaptive stress responses to cope with that increased UV radiation. The results of this study show that the RNA/DNA ratio is a useful indicator of the physiologic status of marine organisms and is a useful tool to measure the effects of changing environmental conditions on marine ecosystems, such as those associated with global climate change

Triple-Decker Pentalene Complex of Iron and Cobalt

In [1(1,2,3,3a,6a-ƞ)-1,4-dihydropentalenyl][µ-1](1,2,3,3a,-6a-ƞ):2(3a,4,5,6,6a-ƞ)-pentalene][2(ƞ5)-pentamethylcyclopentadienyl]cobaltiron, [CoFe(C8H7)Cp*(C8H6)] (Cp*=C10H15), the Cp*-Co and (C8H7)-Fe moieties reside on opposite sides of the fused bridging pentalene ring system

Triple-Decker [Cp*Fe(C8H6)Fe(C8H7)]

The title compound [2(1,2,3,3a,6a-ƞ)pentalene]-[l(ƞ5)-pentamethylcyclopentadienyl]diiron, [Fe2(C8H7)-(C10H15)(C8H6)], has a metallocenic structure with the two pentalene ligands adopting an eclipsed conformation. In the central pentalene ligand, all the peripheral bonds are of similar length whereas the bridge bond is longer; there are two significantly different Fe-C distances, i.e. a mean value of 2.121(3)A for the Fe-Cbridge distances and a mean value of 2.028(3)A for the distances from the Fe atoms to all other Catoms. In the terminal pentalene ligand, the C-C and C-Fe distances in the ring bonded to the Fe atom are all similar

Climacteric fruit ripening: Ethylene-dependent and independent regulation of ripening pathways in melon fruit

Cantaloupe melons have a typical climacteric behaviour with ethylene playing a major role in the regulation of the ripening process and affecting the ripening rate. Crossing of Cantaloupe Charentais melon with a non-climacteric melon indicated that the climacteric character is genetically dominant and conferred by two duplicated loci only. However, other experiments made by crossing two non-climacteric melons have generated climacteric fruit, indicating that different and complex genetic regulation exists for the climacteric character. Suppression of ethylene production by antisense ACC oxidase RNA in Charentais melon has shown that, while many ripening pathways were regulated by ethylene (synthesis of aroma volatiles, respiratory climacteric and degreening of the rind), some were ethylene-independent (initiation of climacteric, sugar accumulation, loss of acidity and coloration of the pulp). Softening of the flesh comprised both ethylene-dependent and independent components that were correlated with differential regulation of cell wall degrading genes. These results indicate that climacteric (ethylene-dependent) and non-climacteric (ethylene-independent) regulation coexist during climacteric fruit ripening. In addition, ethylenesuppressed melons allowed demonstrating that the various ethylene-dependent events exhibited differential sensitivity to ethylene and that ethylene was promoting sensitivity to chilling injury. Throughout this review, the data generated with melon are compared with those obtained with tomato and other fruit

Prevalence, risk factors, and identification of Salmonella spp. in stray dogs of northwest Mexico

Salmonellosis has a worldwide relevance in aspects associated with public health, as only in 2009 were reported 93.8 million cases in humans. The objective of the study was to establish the prevalence, risk factors and bacteriological and molecular identification of Salmonella spp in stray dogs in urban, rural and coastal areas of Mexicali, a city in northwest Mexico. From May 2014 to February 2015, 385 dogs were tested. Sampling was performed by rectal swab and conventional bacteriological techniques were applied, for later implementation of the API 20E system and molecular identification by polymerase chain reaction (PCR). The data were analysed statistically by means of descriptive statistics and multiple logistic regression modelling. A prevalence of 6.27% was obtained in the dogs examined, the samples obtained were characterised to subspecies (Salmonella enterica subspecies enterica and Salmonella enterica subspecie arizonae). The geographical region with the highest prevalence in the study was the coast (10%), followed by the rural area (8.57%) and the urban area (5.8%), however, no significant statistical differences were detected. There was significant difference in the prevalence by age of dogs under one year (P<0.05). The identification of Salmonella in dogs from northwest Mexico could correspond to serovars of zoonotic importance indicating a potential risk for the population