Influence of acid–base properties of cobalt–molybdenum catalysts supported on magnesium orthophosphates in isomerization of 3,3-dimethylbut-1-ene

AbstractSynthesis and physico-chemical characterization of a pure magnesium phosphate (MgP) prepared by coprecipitation, and MgP modified by introduction of cobalt–molybdenum (4–12wt.% of MoO3 with the Co/Mo ratio fixed at 0.5) have been carried out. The structural properties of these catalysts were characterized by X-ray diffraction, their textural properties were determined by N2 adsorption–desorption isotherms and the dispersion of cobalt–molybdenum was studied by XPS spectroscopy. Their acid properties have been investigated by in situ FT-IR spectroscopy of adsorbed molecules, often, 2,6-dimethylpyridine (pKa=6.7), pyridine (pKa=5.3). Co–Mo incorporation leads to a modification in the MgP acid–base properties, especially on the acid sites type and number. Thus, lower loading of cobalt–molybdenum species decreased the number of strong Lewis acid sites whereas higher loading increased it. It was found that Lewis acid sites on magnesium phosphates play an important role in the isomerization of 3,3-dimethylbut-1-ene.The 3,3-dimethylbut-1-ene (33DMB1) conversion increases with the reaction temperature from 493 to 653K for MgP, but decreases after 573K for MgP supported by Co–Mo. A linear relationship between both types of acid sites and conversion values was found. The deactivation of the catalysts appears at high reaction temperature (>573K)

Micro-Hotspots of Risk in Urban Cholera Epidemics.

Targeted interventions have been delivered to neighbors of cholera cases in major epidemic responses globally despite limited evidence for the impact of such targeting. Using data from urban epidemics in Chad and Democratic Republic of the Congo, we estimate the extent of spatiotemporal zones of increased cholera risk around cases. In both cities, we found zones of increased risk of at least 200 meters during the 5 days immediately after case presentation to a clinic. Risk was highest for those living closest to cases and diminished in time and space similarly across settings. These results provide a rational basis for rapidly delivering targeting interventions

A self-renewal assay for cancer stem cells

Cancers of epithelial origin are responsible for the majority of cancer-related deaths in the USA. Unfortunately, although chemotherapy and/or radiation therapy can sometimes shrink tumors, metastatic cancers of epithelial origin are essentially incurable. It is clear that new approaches are needed to treat these diseases. Although cancer cell lines provide invaluable information, their biological properties often differ in crucial ways from de novo cancer cells. Our laboratory has developed a novel mouse model that reliably permits individual cancer cells isolated directly from patients’ tumors to be assayed. This will allow the characterization of crucial signaling pathways involved in processes such as self-renewal that are critical for tumor formation by the cancer cells within de novo tumors. These tools should lead to new insights into the cellular and molecular mechanisms that drive human breast cancer growth and invasion.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/46932/1/280_2005_Article_97.pd

La estrategia de canasta de bienes territoriales y su repercusión local en empleo e ingresos. El caso de Xicotepec de Juárez, Puebla

Developing a basket of land goods means a systemic strategy for small farmers because it allows reaching multiple objectives in order to promote territorial competitiveness to access market niches with varied rural goods, strengthen social capital and generate better local levels in employment and income, together with increasing and preserving the environment. This analysis implied the application of a system dynamics model which produced possible future scenarios (through Vensim® DSS 5.8) about employment and income obtained by smallholder coffee farmers from Xicotepec de Juárez municipality in Puebla, regarding the setting of the above mentioned strategy for rural development. Results showed that this strategy was implemented successfully and also revealed opportunities for: a) improving the development capacity of small farmers; b) making the institutional context favorable; c) The reinforcement of social capital essential to implement this land strategy.La formación de una canasta de bienes territoriales representa una estrategia de índole sistémica para los pequeños agricultores, al permitir alcanzar múltiples objetivos que den resultados en materia de elevar la competitividad territorial, por medio de acceder a nichos de mercado de bienes rurales diferenciados, fortalecer el capital social y generar mejores niveles locales de empleo e ingresos, así como también mejorar y conservar el entorno ambiental. El análisis consistió en la aplicación de un modelo de dinámica de sistemas que generó posibles escenarios futuros (con el software Vensim® DSS 5.8) en torno a empleos e ingresos de campesinos cafetaleros minifundistas del municipio de Xicotepec de Juárez, Puebla, en relación a la adopción de dicha estrategia de desarrollo territorial rural. Los resultados fueron favorables para la implementación de dicha estrategia e indica las oportunidades para: a) mejorar el desarrollo de capacidades de los pequeños agricultores; b) hacer favorable el contexto institucional; c) fortalecer el capital social indispensable para dicha estrategia territorial

Catalyseurs sulfures à base de cobalt et d'hydroxyapatite

Nous avons préparé par coprécipitation en milieu basique des solides associant du cobalt à une hydroxyapatite déficitaire en calcium. Le cobalt se substitue en partie au calcium dans le réseau de l'apatite. La dispersion du cobalt est meilleure que dans des solides préparés par imprégnation. Les catalyseurs sulfurés sont capables de désulfurer complètement le diméthyldisulfure à 360 ○C et de l'hydrogénolyser en CH3SH à 200 ○C. Le cobalt est extrait à la surface lors de la sulfuration limitant l'agglomération en grosses particules de sulfure peu actif. Les catalyseurs coprécipités sont plus actifs que les catalyseurs imprégnés. L'activité intrinsèque des catalyseurs apatitiques est identique à celle des catalyseurs supportés sur alumine

Bacterial formation of omega-muricholic acid in rats.

In the feces of conventional rats, the amount of omega-muricholic and hyodeoxycholic acids vary according to the diet. To understand this phenomenon, we investigated the bacterial formation of these bile acids. The present paper reports the first isolation, from conventional rat feces, of a strain of Clostridium group III which transforms beta-muricholic acid, the main bile acid in germfree rats, into omega-muricholic acid

Catalyst made of NiMo sulfide supported on hydroxyapatite: Influence of Al addition on support properties and on the catalytic conversion of thiophene

A hydroxyapatite and two apatites enriched with alumina have been synthesized to support NiMo sulfide. Hydroxyapatites are efficient supports of NiMo sulfide catalyst for desulfurization of thiophene. Addition of Al ions during the preparation results in an intimate mixture of crystalline apatite and amorphous AlPO$_{4}$. This leads to an important increase in surface area and porous volume that is beneficial to the catalytic activity. The highest activity is obtained with calcium-deficient apatite because the presence of apatitic HPO$_{4}{}^{2-}$ groups or related surface defects is required to improve the dispersion of the Mo ions in the oxidic precursor. The apatitic catalysts are superior to commercial NiMoP/Al$_{2}$O$_{3}$ catalysts, which makes NiMo/apatite a good candidate for hydrotreating

New Measurements of Methyl Ethyl Ketone (MEK) Photolysis Rates and Their Relevance to Global Oxidative Capacity

International audienceMethyl ethyl ketone (MEK) is one of the most abundant ketones in the atmosphere. MEK can be emitted directly into the atmosphere from both anthropogenic and natural sources, and it is also formed during the gas-phase oxidation of volatile organic compounds (VOCs). MEK is lost via reaction with OH, photolysis and deposition to the surface. Similar to the other atmospheric ketones, the photolysis of MEK may represent a source of HOx (OH + HO2) radicals in the upper troposphere. The degradation of MEK also leads to the atmospheric formation of acetaldehyde and formaldehyde. This work presents a new analysis of the temperature dependence of MEK photolysis cross-sections and a quantification of MEK photolysis rates under surface pressures using the CNRS HELIOS outdoor atmospheric chamber (Chambre de simulation atmosphérique à irradiation naturelle d'Orléans; http://www.era-orleans.org/ERA-TOOLS/helios-project.html). Additionally, we use the GEOS-Chem 3-D CTM (version 10-01, www.geos-chem.org) to investigate the impact of these newly measured rates and cross-sections on the global distribution and seasonality of MEK, as well as its importance to the tropospheric oxidative capacity