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Reports on the preparation of small particles of Fe[sub3]O[sub4] embedded in copper (Cu) matrix by direct milling of a mixture of Cu and Fe[sub3]O[sub4] and by reaction milling of CuO and iron. Information on the use of ball milling; Instrument used to perform x-ray powder diffraction measurements; Reduction in the size of the CuO particles during the first 20 minutes of milling.

The Modern-Era Retrospective Analysis for Research and Applications-2 (MERRA2) version of the Goddard Earth Observing System-5 (GEOS-5) atmospheric general circulation model (AGCM) is currently in use in the NASA Global Modeling and Assimilation Office (GMAO) at a wide range of resolutions for a variety of applications. Details of the changes in parameterizations subsequent to the version in the original MERRA reanalysis are presented here. Results of a series of atmosphere-only sensitivity studies are shown to demonstrate changes in simulated climate associated with specific changes in physical parameterizations, and the impact of the newly implemented resolution-aware behavior on simulations at different resolutions is demonstrated. The GEOS-5 AGCM presented here is the model used as part of the GMAO MERRA2 reanalysis, global mesoscale simulations at 10 km resolution through 1.5 km resolution, the real-time numerical weather prediction system, and for atmosphere-only, coupled ocean-atmosphere and coupled atmosphere-chemistry simulations. The seasonal mean climate of the MERRA2 version of the GEOS-5 AGCM represents a substantial improvement over the simulated climate of the MERRA version at all resolutions and for all applications. Fundamental improvements in simulated climate are associated with the increased reevaporation of frozen precipitation and cloud condensate, resulting in a wetter atmosphere. Improvements in simulated climate are also shown to be attributable to changes in the background gravity wave drag, and to upgrades in the relationship between the ocean surface stress and the ocean roughness. The series of resolution-aware parameters related to the moist physics was shown to result in improvements at higher resolutions and result in AGCM simulations that exhibit seamless behavior across different resolutions and applications. [ABSTRACT FROM AUTHOR]

The Modern-Era Retrospective Analysis for Research and Applications-2 (MERRA2) version of the Goddard Earth Observing System-5 (GEOS-5) atmospheric general circulation model (AGCM) is currently in use in the NASA Global Modeling and Assimilation Office (GMAO) at a wide range of resolutions for a variety of applications. Details of the changes in parameterizations subsequent to the version in the original MERRA reanalysis are presented here. Results of a series of atmosphere-only sensitivity studies are shown to demonstrate changes in simulated climate associated with specific changes in physical parameterizations, and the impact of the newly implemented resolution-aware behavior on simulations at different resolutions is demonstrated. The GEOS-5 AGCM presented here is the model used as part of the GMAO MERRA2 reanalysis, global mesoscale simulations at 10 km resolution through 1.5 km resolution, the real-time numerical weather prediction system, and for atmosphere-only, coupled ocean-atmosphere and coupled atmosphere-chemistry simulations. The seasonal mean climate of the MERRA2 version of the GEOS-5 AGCM represents a substantial improvement over the simulated climate of the MERRA version at all resolutions and for all applications. Fundamental improvements in simulated climate are associated with the increased reevaporation of frozen precipitation and cloud condensate, resulting in a wetter atmosphere. Improvements in simulated climate are also shown to be attributable to changes in the background gravity wave drag, and to upgrades in the relationship between the ocean surface stress and the ocean roughness. The series of resolution-aware parameters related to the moist physics was shown to result in improvements at higher resolutions and result in AGCM simulations that exhibit seamless behavior across different resolutions and applications. [ABSTRACT FROM AUTHOR]

Mechanochemical reactions can provide compounds, phases, and microstructures that are essentially different from the products of ordinary reactions. In this paper, the origin of this uniqueness is discussed in light of the recent advances of the field. It is claimed that the local availability of large batches of energy, well above kT, is the key feature of mechanochemical reactions. As a consequence, reactions that cannot occur thermally become possible, similarly to the reactions induced by the energy of photons in photochemistry. However, the situation is more complex, as macroscopic deformation affects many defect sites simultaneously. The direction of the mechanical load relative to the orientation of a molecule or the crystallographic axes of a solid can be important. Many mechanochemical reactions of organic compounds take place at low milling energy that is not sufficient to break primary bonds, but the gentle mechanical grinding can influence the relative position of macromolecules, leading to the formation of unique cocrystals and compounds. In inorganic systems, unusual products form due to forced mixing and the high defect density generated by intense milling. [ABSTRACT FROM AUTHOR]

Ball milling induces self-sustaining reaction in binary Sn-Se and Zn-Se powder mixtures. But if such mixtures are blended, the ignition time increases at either end of the concentration scale and the suppression of ignition can take place in an intermediate concentration interval. This phenomenon was investigated in (1 - x)(Sn+Se)+x(Zn+Se) and (1 - x)(Sn+2Se)+x(Zn+Se) mixtures, by measuring the ignition time as a function of both composition and milling conditions and investigating activated and reacted mixtures using X-ray diffraction and scanning electron microscopy. At the Sn-rich compositions of the first system, ignition happened as soon as the mill was started, in spite of the rather low adiabatic temperature of the reaction. Simultaneous local melting of Sn and Se is suggested as a possible explanation for immediate ignition. It can also explain the asymmetry of the properties of the binary reactions, namely that Sn+Se is less exothermic but easy to ignite, while Zn-Se is more exothermic but difficult to ignite. Similar asymmetry is considered as the reason for the increase of the ignition time and the loss of ignition in other mixed metal-chalcogen systems. [ABSTRACT FROM AUTHOR]

A large variety of synthesis strategies and processing techniques are currently being used to obtain new multicomponent oxides and/or modify existing ones. Among them, mechanochemical processing has become very popular because it is simple to implement, solvent free, and capable of providing enough volume of the target material in an economically viable manner. The preparation of complex oxides can benefit from mechanochemical methods for two important reasons: First, it is not a diffusion-controlled process and thus, high-rate solid state reactions can be promoted between oxides with different physical and chemical properties without using high temperatures; secondly, because reactants are processed under non-equilibrium conditions, uncommon metastable phases are frequently obtained featuring flexible crystal structures, small particle size, high concentration of defects, and off-stoichiometry. Furthermore, conversion to the 'true' equilibrium phases induced by additional processing (e.g., firing) offers the possibility of isolating fairly stable intermediate states with unusual and desirable properties that are inaccessible for more conventional processing techniques. As oxide particles are hard and brittle, the number of oxide systems prepared by means of mechanochemical methods grew rapidly only in recent years when more powerful milling devices and abrasion-resistant milling tools became available. This article summarizes recent work carried out in the field; only dry milling of oxides (and occasionally carbonates) in the absence of additives is considered. Some of the main challenges of mechanochemical processing are also highlighted and discussed. [ABSTRACT FROM AUTHOR]

It is argued that mechanical action can induce a unique chemical reaction, if enough mechanical energy is concentrated in the bonds involved in the process to bypass the activation energy. This can happen at crack tips, at the core of dislocations, or at the asperities of colliding or sliding surfaces. A mechanical reaction is always complex, as the macroscopic work is distributed among many possible reaction sites. In comparison, an elementary photochemical reaction is induced by a single photon, while thermochemical reactions rely on the accidental concentration of energy by thermal fluctuations. The paper also compares mechanochemical synthesis in a ball mill with reactions under well-defined loading conditions and mechanochemical experiments carried out on the molecular scale. Closer interaction among those branches of mechanochemistry is urged. [ABSTRACT FROM AUTHOR]

Abstract: Cu plates were coated mechanically with a mixture of Ti and Zr powders. The targets were Cu discs that replaced the end-plate of the milling vial of a SPEX 8000 shaker mill, while a small amount of Ti–Zr mixture was milled as usual. It is shown that the coatings build up via a combination of deposition, wear, deformation and defect-enhanced diffusion processes. Tests carried out using conventional and synchrotron X-ray diffraction and scanning electron microscopy revealed that the top layer of the coatings is uniform and amorphous, while the morphology of regions close to the target-coating interface is coarser. [Copyright &y& Elsevier]

Faraday induced the mechanochemical reduction of AgCl with Zn, Sn, Fe and Cu in 1820, using trituration in a mortar. This experiment is revisited, employing a mortar-and-pestle and a ball mill as mechanochemical reactors. The reaction kinetics depends both on the thermochemical properties and the hardness of the reactants. When using Zn as the reducing agent, Faraday likely observed a mechanically induced self-sustaining process (MSR), or at least he came very close to doing so. [ABSTRACT FROM AUTHOR]

Abstract: Discs of Al 6061 and Al 2024 alloys were coated with Ni powder by surface mechanical attrition treatment. The microstructure of the cross-section of the specimens was investigated by scanning electron microscopy and X-ray diffraction. Mechanical properties were studied by dynamic hardness tests. [Copyright &y& Elsevier]

The ball milling-induced reduction of MoS2 by Al has been investigated. Although this is a highly exothermic reaction that, based on its thermodynamic properties, should progress as a self-sustaining process, ignition could not be achieved by ball milling. In order to identify the reason, XRD, particle size distribution, SEM, and DTA measurements were carried out on a series of samples milled for different durations. It was found that the largest composite agglomerates broke up due to the presence of a fine dispersion of MoS2 particles. SEM also revealed that the grains are packed rather loosely within the agglomerates. These results indicate that a self-sustaining process can take place only if large and well-compacted composite particles are present. [ABSTRACT FROM AUTHOR]

The temperature increase of the milling balls in two laboratory mills, frequently used for mechanical alloying and mechanochemical experiments, was studied using direct calorimetric measurements. The ball temperature remains below 100 °C in a SPEX 8000 shaker mill and it is cooler when flat-ended rather than round-ended vial is used, although the milling intensity, as measured by the mechanical dose rate, follows the opposite trend. Temperatures over 200 °C are typical in planetary mills operating at similar milling intensities. It is suggested that the higher ball temperatures result from more oblique collisions and friction, while the lower temperature but higher intensity of the shaker mill with flat-ended vial is due to the larger proportion of frontal impacts. [ABSTRACT FROM AUTHOR]

The experiments of M. Carey Lea (1823–1897) are usually considered the first systematic investigations on the chemical effects of mechanical action. This paper collects the most important facts about Lea's life and discusses his research from the point of view of mechanochemistry. Lea was born into a family of considerable privilege and exceptional achievements. He suffered from weak health throughout his life. Consequently, he was educated at home by a tutor and later worked in the private laboratory of his home in Philadelphia. Lea was primarily a photochemist, his first mechanochemical observation in 1866 concerned the pressure sensitivity of photographic plates. Later in his life, he investigated the effect of various kinds of energy—heat, light, mechanical action—on allotropic (colloidal) silver and silver halides. The “parallelism” of the results motivated Lea to study the mechanochemical decomposition of dozens of stable compounds between 1892 and 1894. He observed the decomposition of silver and mercuric chlorides by trituration in a mortar, although the same compounds are known to melt or sublime undecomposed when heated. Lea was elected member of the National Academy of Sciences in 1892. [ABSTRACT FROM AUTHOR]

A new geometry is proposed and explored for the investigation of mechanochemical reactions. Typical displacement reactions between an oxide (PbO, CuO, and WO3) and Al as the reducing metal are studied, but instead of starting with a mixture of two powder reactants, Al is introduced in the form of a plate attached to the inside wall of the milling vial and only the oxide is milled in powder form. Consequently, the reaction takes place at the surface of the aluminium plate, where the microstructure can be investigated easily using SEM. The phase composition is followed by XRD. Of the three oxide components, the reaction is the fastest with PbO due to the intense ductile mixing at the interface. The current configuration can be utilized for the investigation of any mechanochemical or mechanical alloying process where at least one of the components can be prepared in the form of a ductile plate that is capable of withstanding the multiple impacts from the milling balls. [ABSTRACT FROM AUTHOR]

Mechanochemical transformations of copper sulphides were induced by processing in a Fritsch Pulverisette 6 planetary mill. The main changes during high-energy milling are the phase transformations of the djurleite Cu1.94S which is the main phase in a starting material. Digenite, which is in fact a group of copper sulphides (Cu1.80S, Cu1.765S and Cu9−xS5, respectively) together with chalcocite (Cu1.96S and Cu2S, respectively) are the main phases among the mechanochemical products. The reactivity of the products is compared to their physico-chemical transformations during high energy milling. [Copyright &y& Elsevier]

The paper deals with the properties of a new 4H-SnS2 phase (N-phase) synthesized together with berndtite 4H-SnS2 by a mechanochemical route from elemental tin and sulphur. The surface and bulk properties of SnS2 phases were verified by surface area measurements, particle size analysis, electron microscopy, XRD, Mo¨ssbauer spectroscopy and chemical dissolution methods. The particles of synthesized product are 12–18 nm in size and during milling, secondary particles (aggregates) are formed that are 20–60 μm in size. The particle size and a high developed surface area (7–21 m2 g−1) greatly influence the solid–liquid reaction and solid transformations of mechanosynthesized tin sulphide products. [Copyright &y& Elsevier]

Recently. species specific monoclonal antibodies, directed against the interleukin-2 (IL-2) receptor of murine, rat and human origin, have been produced. In this study we demonstrate with immunohistological methods that cells reacting with these antibodies are present in normal primary and secondary lymphatic organs. The cells are exclusively localized in T cell-dependent areas, and their number increased as a result of immunization. [ABSTRACT FROM AUTHOR]

The proportion and anatomical localization in murine thymus of T cell subpopulations, including those which are defined by the monoclonal anti-interleukin 2 (anti-IL-2) receptor antibody AMT-13, were studied by flow cytofluometry and by immunohistochemical methods, both in irradiated and in normal mice. As a consequence of irradiation the proportion of AMT-13 positive cells and that of Lyt-1 positive cells were markedly enhanced, while the proportion of Lyt-2 positive cells was reduced. The vast majority of the AMT-13 positive cells both in normal and in irradiated thymi were located in the subcapsular area of the thymic cortex, whereas the irradiation resistant Lyt-1 positive cells were located in the medulla. These findings arc compatible with the view that, similar to the developing thymus in the mouse embryo, in the regenerating adult thymus. AMT-13+ cells include the activated pro-thymocytes that repopulate the irradiated thymus. [ABSTRACT FROM AUTHOR]

Evaluates the dynamics of the square wheel. Kinematic relationships of the square wheel; Derivation of conditions for rolling without slipping; Emphasis on the fact that the instantaneous axis of rotation is accelerating.

Abstract: The preparation of nanosized antimony (grain size 19nm) by high-energy milling of antimony sulphide Sb2S3 with elemental Fe as reducing element is reported. The mechanochemical reduction was performed in a planetary ball mill for 10–180min. The process is rather straightforward with elemental antimony and iron sulphide (pyrrhotite-4H) being the only solid-state products. The process kinetics as described by X-ray diffraction (XRD) and vibrating sample magnetometer (VSM) magnetometry shows that most of the reduction is complete after 60min of milling. [Copyright &y& Elsevier]

A simple method is proposed for the comparison of the mechanical dose rates of different mills, based on measuring the ignition time of a mechanically-induced self-propagating reaction (MSR). Specifically, a SPEX 8000 Mixer Mill with round-ended and flat-ended milling vials and a Fritsch Pulverisette-6 planetary mill are compared, using the ignition of MSR between Zn and S powders as the test reaction. The method facilitates the comparison of reaction kinetics data obtained by using different milling equipment. [ABSTRACT FROM AUTHOR]

An unusual multiple combustion effect has been observed during the mechanochemical reaction of zirconium and sulphur powders. Ball milling induces combustion in this highly exothermic system, but the combustion is quenched repeatedly, after consuming only a fraction of the reactants. The process concludes with a final, more energetic combustion, releasing about 70% of the reaction heat. The evaporation of sulfur at the reaction site may explain this behavior. © 1996 American Institute of Physics. [ABSTRACT FROM AUTHOR]

Review: 117 refs. [ABSTRACT FROM AUTHOR]

Abstract: The mechanochemical treatment of the sulphidic minerals galena PbS, chalcopyrite CuFeS2 and chalcosine Cu2S with elemental Fe have been studied. Metallic Pb and Cu are produced as a result of the reducing power of iron. The kinetics of the chalcosine reduction has been followed by X-ray examination of the reaction products. The reduction processes are very fast and the ambient temperature and atmospheric pressure are sufficient for their propagation. [Copyright &y& Elsevier]

Monoclonal antibodies anti-Ly 1. anti-Ly 2 and GK1.5 were applied to determine phenotypes of T cells within granulomas formed as a result of infection of mice with the facultative intraccllular bacterium Listeria monocytogenes. Early in granuloma formation, equal numbers of Ly 1+ , Ly 2+ and L3T4+ cells were found, T cells of different phenotypes being evenly distributed over the lesions. In mature granulomas, numbers of Ly 1+ and L3T4+ cells about doubled as compared to incipient granulomas, Ly 2+ cells, however, remained constant. Whereas Ly 1+ and L3T4+ cells within mature granulomas still were evenly distributed, Ly 2+ cells were predominantly Iocalized in the periphery of the lesions. The data indicate that both, specific Ly 2+ and L3T4+ T cells, display characteristic dynamics within granulomas: Ly 2+ T cells which most likely mature from Ly 1+2+ T cells over time locate to the periphery. Concomitantly. L3T4+ T cells are enriched maintaining their distribution all over the lesions. [ABSTRACT FROM AUTHOR]

Several letters to the editor are presented in response to the article "Oral Sucrose as an Analgesic Drug for Procedural Pain in Newborn Infants: A Randomised Controlled Trial," by R. Slater and colleagues in a 2010 issue, along with the authors' reply.

Examines the realism of extratropical cyclones, fronts, jet streams and the tropopause in the Goddard Earth Observing System (GEOS) general circulation model. Use of GEOS-1 reanalysis climatology; Derivation of the latitude-longitude grid spacing; Characteristics of frontal systems.

The article reflects on why simulating the Intertropical Convergence Zone (ITCZ) in global climate models (GCMs) is highly sensitive to model physics. The section examines how the high sensitivity of the ITCZ to the model physics arises and how it is related to the types of systematic ITCZ errors forecasted, including the false double ITCZ. The research includes a discussion of how to change the model physics to remove ITCZ systematic error. It presents the components of the model physics under consideration for the purpose of rain reevaporation, cumulus friction, and convection onset criterion.