Preparation and characterisation of palladium, platinum and manganese di(organo)carbene complexes from quinolinone and quinolinium precursors

A series of palladium, platinum and manganese di(organo) carbene complexes have been prepared from 4-chloro-N-methylquinolinone by processes that involve alkylation before or after attachment to the metal unit; the nucleophilic heteroatoms necessary for eventual carbene formation and stabilisation are separated from the C-donor atom by three bonds.

New modular structure DC-DC converter without electrolytic capacitors for renewable energy applications

A Microscopic Study of Iron and Manganese Oxide Distribution in Soils from East Tennessee (U.S.A.)

Soils and saprolites developed from interbedded shales and limestones of the Conasauga Group are widespread in the Valley and Ridge Province of East Tennessee. Thin sections from four soil profiles were examined by petrographic and scanning electron microscopy including backscatter electron and energy-dispersive X-ray analyses. Iron and manganese released by weathering had migrated differentially downward and precipitated as crystalline and noncrystalline oxides. Oxides were observed as nodules, granular particulates, pore fillings, and coatings on other minerals, packing voids, vesicles, channels, and chambers. Iron oxides formed predominantly as coatings on packing-void walls and on laminated clays in vesicles and channels. Manganese oxides occurred as an early replacement phase of packing voids and of fracture-filling carbonate minerals. Iron oxides were dominant in moderately well-drained and oxidized horizons of the soil solum, whereas manganese oxides were abundant in the oxidized and moderately leached saprolite zone where the water table fluctuates seasonally. Therefore, a manganese enrichment zone, on a bulk soil basis, occurred generally below the iron oxide zone in the soil profile. Such differential migration and accumulation of iron and manganese have been controlled by localized soil microenvironments. Micromorphologic features observed in this study are important in land-use evaluation for hazardous waste disposal. © 1990.

Microstructure, mechanical properties and fractography of heat-treated manganese steel

A Fe-8.46%Mn-0.24%Nb-0.038%C (wt.%) manganese steel was investigated. The steel has a 100% bcc structure after heat treatment at 850°C for 1.5 h, water quenching or air cooling. Martensite interlocked microstructure consisting of fine martensite plates/needles with different spatial orientations was found. Austenite forms, in small amounts, after a 600°C reheating treatment. Scanning electron microscopy images and energy dispersive spectrometry of the fracture surfaces revealed both ductile and brittle types of failure and precipitates. Deep quenching after the heat treatments does not change the phase composition or the hardness. NbC is formed in the steel, in high number densities. It plays a role in the impact fracture process, by acting as void nucleation sites, facilitating ductile fracture with dimples appearing on the fracture surface.

Manganese Superoxide Dismutase Is a Promising Target for Enhancing Chemosensitivity of Basal-Like Breast Carcinoma

AIMS: Although earlier reports highlighted a tumor suppressor role for manganese superoxide dismutase (MnSOD), recent evidence indicates increased expression in a variety of human cancers including aggressive breast carcinoma. In the present article, we hypothesized that MnSOD expression is significantly amplified in the aggressive breast carcinoma basal subtype, and targeting MnSOD could be an attractive strategy for enhancing chemosensitivity of this highly aggressive breast cancer subtype.

RESULTS: Using MDA-MB-231 and BT549 as a model of basal breast cancer cell lines, we show that knockdown of MnSOD decreased the colony-forming ability and sensitized the cells to drug-induced cell death, while drug resistance was associated with increased MnSOD expression. In an attempt to develop a clinically relevant approach to down-regulate MnSOD expression in patients with basal breast carcinoma, we employed activation of the peroxisome proliferator-activated receptor gamma (PPARγ) to repress MnSOD expression; PPARγ activation significantly reduced MnSOD expression, increased chemosensitivity, and inhibited tumor growth. Moreover, as a proof of concept for the clinical use of PPARγ agonists to decrease MnSOD expression, biopsies derived from breast cancer patients who had received synthetic PPARγ ligands as anti-diabetic therapy had significantly reduced MnSOD expression. Finally, we provide evidence to implicate peroxynitrite as the mechanism involved in the increased sensitivity to chemotherapy induced by MnSOD repression.

INNOVATION AND CONCLUSION: These data provide evidence to link increased MnSOD expression with the aggressive basal breast cancer, and underscore the judicious use of PPARγ ligands for specifically down-regulating MnSOD to increase the chemosensitivity of this subtype of breast carcinoma.

Conserved histidine of metal transporter AtNRAMP1 is crucial for optimal plant growth under manganese deficiency at chilling temperatures

Manganese (Mn) is an essential nutrient required for plant growth, in particular in the process of photosynthesis. Plant performance is influenced by various environmental stresses including contrasting temperatures, light or nutrient deficiencies. The molecular responses of plants exposed to such stress factors in combination are largely unknown. 

Screening of 108 Arabidopsis thaliana (Arabidopsis) accessions for reduced photosynthetic performance at chilling temperatures was performed and one accession (Hog) was isolated. Using genetic and molecular approaches, the molecular basis of this particular response to temperature (GxE interaction) was identified. 

Hog showed an induction of a severe leaf chlorosis and impaired growth after transfer to lower temperatures. We demonstrated that this response was dependent on the nutrient content of the soil. Genetic mapping and complementation identified NRAMP1 as the causal gene. Chlorotic phenotype was associated with a histidine to tyrosine (H239Y) substitution in the allele of Hog NRAMP1. This led to lethality when Hog seedlings were directly grown at 4 degrees C. 

Chemical complementation and hydroponic culture experiments showed that Mn deficiency was the major cause of this GxE interaction. For the first time, the NRAMP-specific highly conserved histidine was shown to be crucial for plant performance.

Selective Hydrogenation of Halogenated Arenes using porous Manganese Oxide (OMS-2) and Platinum supported OMS-2 Catalysts

Porous manganese oxide (OMS-2) and platinum supported on OMS-2 catalysts have been shown to facilitate the hydrogenation of the nitro group on chloronitrobenzene to give chloroaniline with no dehalogenation. Complete conversion was obtained within 2 h at 25 [degree]C and, although the rate of reaction increased with increasing temperature up to 100 [degree]C, the selectivity to chloroaniline remained at 99.0%. Use of Pd/OMS-2 or Pt/Al2O3 resulted in significant dechlorination even at 25 [degree]C and 2 bar hydrogen pressure giving selectivity to chloroaniline of 34.5% and 77.8%, respectively, at complete conversion. This demonstrates the potential of using platinum group metal free catalysts for the selective hydrogenation of halogenated aromatics. Two pathways were observed for the analogous nitrobenzene hydrogenation depending on the catalyst used. The hydrogenation of nitrobenzene was found to follow a direct pathway to aniline and nitrosobenzene over Pd/OMS-2 in contrast to the OMS and Pt/OMS-2 catalysts which resulted in formation of nitrosobenzene, azoxybenzene and azobenzene/hydrazobenzene intermediates before complete conversion to aniline. These results indicate that for the Pt/OMS-2 the hydrogenation proceeds predominantly over the support with the metal acting to dissociate the hydrogen. In the case of the Pd/OMS-2 both the hydrogenation and the hydrogen adsorption occur on the metal sites.