Synthesis and hydrogen adsorption properties of a new iron based porous metal-organic framework

A new metal-organic framework [Fe₃O(OOC-C₆H₄-COO)₃(H₂O)₃]Cl·(H₂O)_x was synthesized with a specific surface area of 2823 m²/g and a lattice parameter of 88.61 Å. Isostructural with MIL-101, this compound exhibits similar hydrogen adsorption properties, with maximum adsorption capacity of 5.1wt.% H at 77 K. The adsorption enthalpy of hydrogen for MIL-101 and ITIM-1 (MIL-101Fe) at zero coverage was calculated for a wide temperature range of 77 K ÷ 324 K, considering corrections for the variation of hydrogen gas entropy with the temperature. The resulted adsorption enthalpy is 9.4 kJ/mol for MIL-101, in excellent agreement with the value reported in literature from microcalorimetric measurements, and a value of 10.4 kJ/mol at zero coverage was obtained for ITIM-1 (MIL-101Fe).     

Magnesia supported Au and Ag catalysts for the preparation of few-layer graphene–metal nanocomposites: relationship between catalyst structure and the properties of graphene composites

Magnesia supported Au, Ag, and Au–Ag nanostructured catalysts were prepared, characterized, and used to synthesize few-layer graphene–metal nanoparticle (Gr–MeNP) composites. The catalysts have a mezoporous structure and a mixture of MgO and MgO·H₂O as support. The gold nanoparticles (AuNPs) are uniformly dispersed on the surface of the Au/MgO catalysts, and have a uniform round shape with a medium size of ~8 nm. On the other hand, the silver nanoparticles (AgNPs) present on the Ag/MgO catalyst have an irregular shape, larger diameters, and less uniform dispersion. The Au–Ag/MgO catalyst contains large Au–Ag bimetallic particles of ~20–30 nm surrounded by small (5 nm) AuNPs. Following the RF-CCVD process and the dissolution of the magnesia support, relative large, few-layer, wrinkled graphene sheets decorated with metal nanoparticles (MeNPs) are observed. Graphene–gold (Gr–Au) and graphene–silver (Gr–Ag) composites had 4–7 graphitic layers with a relatively large area and similar crystallinity for samples prepared in similar experimental conditions. Graphene–gold–silver composites (Gr–Au–Ag) presented graphitic rectangles with round, bent edges, higher crystallinity, and a higher number of layers (8–14). The MeNPs are encased in the graphitic layers of all the different samples. Their size, shape, and distribution depend on the nature of the catalyst. The AuNPs were uniformly distributed, had a size of about 15 nm, and a round shape similar to those from Au/MgO catalyst. In Gr–Ag, the AgNPs have a round shape, very different from that of the Ag/MgO catalyst, large size distribution and are not uniformly distributed on the surface. Agglomerations of AgNPs together with large areas of pristine few-layer graphene were observed. In Gr–Au–Ag composites, almost exclusively large bimetallic particles of about 25–30 nm, situated at the edge of graphene rectangles have been found.     

Amorphous alumina coatings: processing, structure and remarkable barrier properties

Amorphous aluminium oxide coatings were processed by metalorganic chemical vapour deposition (MOCVD); their structural characteristics were determined as a function of the processing conditions, the process was modelled considering appropriate chemical kinetic schemes, and the properties of the obtained material were investigated and were correlated with the nanostructure of the coatings. With increasing processing temperature in the range 350 degrees C-700 degrees C, subatmospheric MOCVD of alumina from aluminium tri-isopropoxide (ATI) sequentially yields partially hydroxylated amorphous aluminium oxides, amorphous Al2O3 (415 degrees C-650 degrees C) and nanostructured gamma-Al2O3 films. A numerical model for the process allowed reproducing the non uniformity of deposition rate along the substrate zone due to the depletion of ATI. The hardness of the coatings prepared at 350 degrees C, 480 degrees C and 700 degrees C is 6 GPa, 11 GPa and 1 GPa, respectively. Scratch tests on films grown on TA6V titanium alloy reveal adhesive and cohesive failures for the amorphous and nanocrystalline ones, respectively. Alumina coating processed at 480 degrees C on TA6V yielded zero weight gain after oxidation at 600 degrees C in lab air. The surface of such low temperature processed amorphous films is hydrophobic (water contact angle 106 degrees), while the high temperature processed nanocrystalline films are hydrophilic (48 degrees at a deposition temperature of 700 degrees C). It is concluded that amorphous Al2O3 coatings can be used as oxidation and corrosion barriers at ambient or moderate temperature. Nanostructured with Pt or Ag nanoparticles, they can also provide anti-fouling or catalytic surfaces.     

Bacterial Mining

Abstract

Bacterial mining (biomining) represents the use of microorganisms to leach out metals from ores or mine tailings (wastes), followed by the subsequent recovery of metals of interest from the leaching solution. This leaching of metals from ores is a natural process, which can be considerably accelerated by inducing and/or supporting the microbial activity of certain species with the ability to solubilize metals. This process is usually known as biosolubilization and constitutes the basis of many remedial technologies for environments polluted with metals, and also providing the additional potential for recovery of any particular metal of interest. Bacterial mining is part of a vast research field that emerged relatively recently as a border science called biohydrometallurgy. This research field became very important in the context of raw material crises on which technological crises is grafted. In other words, the conventional technologies operating for metal extraction, mainly in the case of lower grade ores, are generally disruptive and less cost-efficient when compared to biomining. Thus, during the last 10–15 years, the interest in biohydrometallurgy, and subsequently in bacterial mining, has increased. The focus has been on two main topics—mineral bioprocessing and biorecovery.     

The influence of sulphur on the processing of zirconia based ceramics

Yttria stabilized zirconia powders were synthesized by the coprecipitation route. Zirconium oxychloride containing sulphur as contamination and analytical grade yttrium chloride were used as raw materials. Powders were calcined at temperatures between 600 and 1100 °C and ground by ball and attrition milling. The ceramic bodies were sintered at 1350 and 1550 °C for 1 h and the apparent density was measured. In the present work it is shown that the most deleterious effect of sulphur was observed in 3 mol% yttria stabilized zirconia, especially when the pellets were obtained at high pressures and sintered at 1500 °C. The elimination of sulphur at higher calcination temperatures minimizes the effects caused by this contamination, despite the reduction of powder surface area. The best processing condition to obtain high density zirconia ceramics from powders contaminated with sulphur was established.     

Residual service life test for a machine with friction

A test and heat friction based method for evaluation of the technical condition and residual service life of machinery is presented. It is applicable for mechanisms in which friction of the moving parts leads to wear and to increased heat release. The diagnostic parameter adopted is the peak point of the temperature change rate, observed on the machine casing during the starting stage. The method was tested on the SAWA power reduction gears of KOCKS heavy portal transtainer cranes. Copyright © 2006 John Wiley & Sons, Ltd.     

Prostaglandins promote and block adipogenesis through opposing effects on peroxisome proliferator-activated receptor gamma

Fat cell differentiation is a critical aspect of obesity and diabetes. Dietary fatty acids are converted to arachidonic acid, which serves as precursor of prostaglandins (PGs). PGJ2 derivatives function as activating ligands for peroxisome proliferator-activated receptor gamma (PPAR gamma), a nuclear hormone receptor that is central to adipogenic determination. We report here that PGF2 alpha blocks adipogenesis through activation of mitogen-activated protein kinase, resulting in inhibitory phosphorylation of PPAR gamma. Both mitogen-activated protein kinase activation and PPAR gamma phosphorylation are required for the anti-adipogenic effects of PGF2 alpha. Thus, PG signals generated at a cell surface receptor regulate the program of gene expression required for adipogenesis by modulating the activity of a nuclear hormone receptor that is directly activated by other PG signals. The balance between PGF2 alpha and PGJ2 signaling may thus be central to the development of obesity and diabetes.     

Architecting noncooperative networks

In noncooperative networks users make control decisions that optimize their individual performance measure. Focusing on routing, two methodologies for architecting noncooperative networks are devised, that improve the overall network performance. These methodologies are motivated by problem settings arising in the provisioning and the run time phases of the network. For either phase, Nash equilibria characterize the operating point of the network. The goal in the provisioning phase is to allocate link capacities that lead to systemwide efficient Nash equilibria. The solution of such design problems is, in general, counterintuitive, since adding link capacity might lead to degradation of user performance. For systems of parallel links, it is shown that such paradoxes cannot occur and that the optimal solution coincides with the solution in the single-user case. Extensions to general network topologies are derived. During the run time phase, a manager controls the routing of part of the network flow. The manager is aware of the noncooperative behavior of the users and makes its routing decisions based on this information while aiming at improving the overall system performance. We obtain necessary and sufficient conditions for enforcing an equilibrium that coincides with the global network optimum, and indicate that these conditions are met in many cases of interest     

Building open programmable multimedia networks

Recent advances in distributed systems and transportable software and increasing demand for better quality of service (QoS) control in multiservice networks are driving a reexamination of network software architectures. We established the Comet (Control, Management, and Telemedia) Group at Columbia University's Center for Telecommunications Research to provide comprehensive understanding of network software architecture for the 1990s and beyond. This research focuses on developing new network architectures that support service creation, QoS control, and the joint allocation of computing and communications resources. This provides an opportunity to reconcile the perspectives of the computing and communication communities. Future multiservice (multimedia) networks will carry traffic such as video, audio, and computer data with diverse QoS requirements. Such networks will thus require that we develop ways to manage many physical and logical entities, services, and users