Mineral and geochemical characterization of a leptic aluandic soil and a thapto aluandic-ferralsol developed on trachytes in Mount Bambouto (Cameroon volcanic line)

Mineral and geochemical investigations were carried out on soil samples and fresh rock (trachytes) from two selected soil profiles (TM profile on leptic aluandic soils and TL profile on thapto aluandic-ferralsols) from Mount Bambouto to better understand geochemical processes and mineral paragenesis involved in the development of soils in this environment. In TM profile, the hydrated halloysites and goethite occur in the weathered saprolite boulders of BC horizon while dehydrated halloysite, gibbsite and goethite dominate the soils matrices of BC and A horizons. In TL profile, the dehydrated halloysites and goethite are the most abundant secondary minerals in the weathered saprolites of C and BC horizons while gibbsite, hematite and kaolinite occur in the soil matrices of BC, B and A horizons. The highest gibbsite content is in the platy nodules of B horizon. In both soil profiles, organo-metal complexes (most likely of AI and Fe) are present in the surface A horizon. Geochemically, between the fresh rock and the weathered saprolites in both soils, SiO2, K2O, CaO, Na2O and MgO contents decrease strongly while Fe2O3 and Al2O3 tend to accumulate. The molar ratio of SiO2/Al2O3 (Ki) and the sum of Ca, Mg, K and Na ions (TRB) also decreases abruptly between fresh rocks and the weathered saprolites, but increases significantly at the soil surface. The TM profile shows intense Al enrichment whereas the TL profile highlights enrichment in both AI and Fe as the weathering progresses upwards. Both soil profiles are enriched in Ni, Cu, Ba and Co and depleted in U, Th, Ta, Hf, Y, Sr, Pb, Zr and Zn relative to fresh rock. They also show a relatively low fractionation of the rare earth elements (REE: La, Nd, Sm, Eu, Tb, Yb and Lu), except for Ce which tends to be enriched in soils compared to CI chondrite. All these results give evidence of intense hydrolysis at soil deep in Mount Bambouto resulting in the formation of halloysite which progressively transforms into gibbsite and/or dehydrated halloysite. At the soil surface, the prominent pedogenetic process refers to andosolization with formation of organo-metal complexes. In TL profile, the presence of kaolinite in soil matrices BC and B horizons is consistent with ferralitization at soil deep. In conclusion, soil forming processes in Mount Bambouto are strongly influenced by local climate: (i) in the upper mountain (>2000 m), the fresh, misty and humid climate favors andosolization; whereas (ii) in the middle lands (1700-2000 m) with a relatively dry climate, both andosolization at the soil surface and ferralitization at soil deep act together. (C) 2009 Elsevier B.V. All rights reserved.

Re-evaluating base-metal artefacts: an inscribed lead strap-end from Crewkerne, Somerset

Strap-ends represent the most common class of dress accessory known from late Anglo-Saxon England. At this period, new materials, notably lead and its alloys, were being deployed in the manufacture of personal possessions and jewellery. This newly found strap-end adds to the growing number of tongue-shaped examples fashioned from lead dating from this period. It is, however, distinctive in being inscribed with a personal name. The present article provides an account of the object and its text, and assesses its general significance in the context of a more nuanced interpretation of the social status of lead artefacts in late Anglo-Saxon England.

Electric field alignment in thin films of cylinder-forming diblock copolymer

We investigate thin films of cylinder-forming diblock copolymer confined between electrically charged parallel plates, using self-consistent-field theory ( SCFT) combined with an exact treatment for linear dielectric materials. Our study focuses on the competition between the surface interactions, which tend to orient cylinder domains parallel to the plates, and the electric field, which favors a perpendicular orientation. The effect of the electric field on the relative stability of the competing morphologies is demonstrated with equilibrium phase diagrams, calculated with the aid of a weak-field approximation. As hoped, modest electric fields are shown to have a significant stabilizing effect on perpendicular cylinders, particularly for thicker films. Our improved SCFT-based treatment removes most of the approximations implemented by previous approaches, thereby managing to resolve outstanding qualitative inconsistencies among different approximation schemes.

Model catalyst studies of the strong metal-support interaction: Surface structure identified by STM on Pd nanoparticles on TiO2(110)

Model catalysts of Pd nanoparticles and films on TiO2 (I 10) were fabricated by metal vapour deposition (MVD). Molecular beam measurements show that the particles are active for CO adsorption, with a global sticking probability of 0.25, but that they are deactivated by annealing above 600 K, an effect indicative of SMSI. The Pd nanoparticles are single crystals oriented with their (I 11) plane parallel to the surface plane of the titania. Analysis of the surface by atomic resolution STM shows that new structures have formed at the surface of the Pd nanoparticles and films after annealing above 800 K. There are only two structures, a zigzag arrangement and a much more complex "pinwheel" structure. The former has a unit cell containing 7 atoms, and the latter is a bigger unit cell containing 25 atoms. These new structures are due to an overlayer of titania that has appeared on the surface of the Pd nanoparticles after annealing, and it is proposed that the surface layer that causes the SMSI effect is a mixed alloy of Pd and Ti, with only two discrete ratios of atoms: Pd/Ti of 1: 1 (pinwheel) and 1:2 (zigzag). We propose that it is these structures that cause the SMSI effect. (c) 2005 Elsevier Inc. All rights reserved.

Metal bioaccumulation and cellular fractionation in an epigeic earthworm (Lumbricus rubellus): the interactive influences of population exposure histories, site-specific geochemistry and mitochondrial genotype

Subcellular fractionation techniques were used to describe temporal changes (at intervals from T0 to T70 days) in the Pb, Zn and P partitioning profiles of Lumbricus rubellus populations from one calcareous (MDH) and one acidic (MCS) geographically isolated Pb/Zn-mine sites and one reference site (CPF). MDH and MCS individuals were laboratory maintained on their native field soils; CPF worms were exposed to both MDH and MCS soils. Site-specific differences in metal partitioning were found: notably, the putatively metal-adapted populations, MDH and MCS, preferentially partitioned higher proportions of their accumulated tissue metal burdens into insoluble CaPO4-rich organelles compared with naive counterparts, CPF. Thus, it is plausible that efficient metal immobilization is a phenotypic trait characterising metal tolerant ecotypes. Mitochondrial cytochrome oxidase II (COII) genotyping revealed that the populations indigenous to mine and reference soils belong to distinct genetic lineages, differentiated by 13%, with 7 haplotypes within the reference site lineage but fewer (3 and 4, respectively) in the lineage common to the two mine sites. Collectively, these observations raise the possibility that site-related genotype differences could influence the toxico-availability of metals and, thus, represent a potential confounding variable in field-based eco-toxicological assessments.

The assessment of benchmarks executed on bare-metal and using para-virtualization

A full assessment of para-­virtualization is important, because without knowledge about the various overheads, users can not understand whether using virtualization is a good idea or not. In this paper we are very interested in assessing the overheads of running various benchmarks on bare-­‐metal, as well as on para-­‐virtualization. The idea is to see what the overheads of para-­‐ virtualization are, as well as looking at the overheads of turning on monitoring and logging. The knowledge from assessing various benchmarks on these different systems will help a range of users understand the use of virtualization systems. In this paper we assess the overheads of using Xen, VMware, KVM and Citrix, see Table 1. These different virtualization systems are used extensively by cloud-­‐users. We are using various Netlib1 benchmarks, which have been developed by the University of Tennessee at Knoxville (UTK), and Oak Ridge National Laboratory (ORNL). In order to assess these virtualization systems, we run the benchmarks on bare-­‐metal, then on the para-­‐virtualization, and finally we turn on monitoring and logging. The later is important as users are interested in Service Level Agreements (SLAs) used by the Cloud providers, and the use of logging is a means of assessing the services bought and used from commercial providers. In this paper we assess the virtualization systems on three different systems. We use the Thamesblue supercomputer, the Hactar cluster and IBM JS20 blade server (see Table 2), which are all servers available at the University of Reading. A functional virtualization system is multi-­‐layered and is driven by the privileged components. Virtualization systems can host multiple guest operating systems, which run on its own domain, and the system schedules virtual CPUs and memory within each Virtual Machines (VM) to make the best use of the available resources. The guest-­‐operating system schedules each application accordingly. You can deploy virtualization as full virtualization or para-­‐virtualization. Full virtualization provides a total abstraction of the underlying physical system and creates a new virtual system, where the guest operating systems can run. No modifications are needed in the guest OS or application, e.g. the guest OS or application is not aware of the virtualized environment and runs normally. Para-­‐virualization requires user modification of the guest operating systems, which runs on the virtual machines, e.g. these guest operating systems are aware that they are running on a virtual machine, and provide near-­‐native performance. You can deploy both para-­‐virtualization and full virtualization across various virtualized systems. Para-­‐virtualization is an OS-­‐assisted virtualization; where some modifications are made in the guest operating system to enable better performance. In this kind of virtualization, the guest operating system is aware of the fact that it is running on the virtualized hardware and not on the bare hardware. In para-­‐virtualization, the device drivers in the guest operating system coordinate the device drivers of host operating system and reduce the performance overheads. The use of para-­‐virtualization [0] is intended to avoid the bottleneck associated with slow hardware interrupts that exist when full virtualization is employed. It has revealed [0] that para-­‐ virtualization does not impose significant performance overhead in high performance computing, and this in turn this has implications for the use of cloud computing for hosting HPC applications. The “apparent” improvement in virtualization has led us to formulate the hypothesis that certain classes of HPC applications should be able to execute in a cloud environment, with minimal performance degradation. In order to support this hypothesis, first it is necessary to define exactly what is meant by a “class” of application, and secondly it will be necessary to observe application performance, both within a virtual machine and when executing on bare hardware. A further potential complication is associated with the need for Cloud service providers to support Service Level Agreements (SLA), so that system utilisation can be audited.

A comparative study of the effects of metal contamination on collembola in the field and in the laboratory

We examined the species diversity and abundance of Collembola at 32 sampling points along a gradient of metal contamination in a rough grassland site ( Wolverhampton, England), formerly used for the disposal of metal-rich smelting waste. Differences in the concentrations of Cd, Cu, Pb and Zn between the least and most contaminated part of the 35 metre transect were more than one order of magnitude. A gradient of Zn concentrations from 597 to 9080 mug g(-1) dry soil was found. A comparison between field concentrations of the four metals and previous studies on their relative toxicities to Collembola, suggested that Zn is likely to be responsible for any ecotoxicological effects on springtails at this site. Euedaphic ( soil dwelling) Collembola were extracted by placing soil cores into Tullgren funnels and epedaphic ( surface dwelling) species were sampled using pitfall traps. There was no obvious relationship between the total abundance, or a range of commonly used diversity indices, and Zn levels in soils. However, individual species showed considerable differences in abundance. Metal "tolerant'' (e.g., Ceratophysella denticulata) and metal "sensitive'' (e.g., Cryptopygus thermophilus) species could be identified. Epedaphic species appeared to be influenced less by metal contamination than euedaphic species. This difference is probably due to the higher mobility and lower contact with the soil pore water of epedaphic springtails in comparison to euedaphic Collembola. In an experiment exposing the standard test springtail, Folsomia candida, to soils from all 32 sampling points, adult survival and reproduction showed small but significant negative relationships with total Zn concentrations. Nevertheless, juveniles were still produced from eggs laid by females in the most contaminated soils with 9080 mug g(-1) Zn. Folsomia candida is much more sensitive to equivalent concentrations of Zn in the standard OECD soil. Thus, care should be taken in extrapolating the results of laboratory toxicity tests on metals in OECD soil to field soils, in which, the biological availability of contaminants is likely to be lower. Our studies have shown the importance of ecotoxicological effects at the species level. Although there may be no differences in overall abundance, sensitive species that are numerous in contaminated sites, and which may play important roles in decomposition("keystone species'') can be greatly reduced in numbers by pollution.

The influence of commercial film-forming polymers on reducing salt spray injury in evergreen oak (Quercus ilex L.) and laurel (Prunus laurocerasus L.)

A field trial was undertaken to determine the influence of four commercially available film-forming polymers (Bond [alkyl phenyl hydroxyl polyoxyethylene], Newman Crop Spray 11E™ [paraffinic oil], Nu-Film P [poly-1-p menthene], and Spray Gard [di-1-p menthene]) on reducing salt spray injury on two woody species, evergreen oak (Quercus ilex L.) and laurel (Prunus laurocerasus L.). Irrespective of species, the film-forming polymers Nu-Film-P and Spay Gard did not provide any significant degree of protection against salt spray damage irrespective of concentration (1% or 2%) applied as measured by leaf chlorophyll concentrations, photosynthetic efficiency, visual leaf necrosis, foliar sodium and chloride content, and growth (height, leaf area). The film-forming polymer Newman Crop Spray 11E™ provided only 1-week protection against salt spray injury. The film-forming polymer Bond provided a significant (P < 0.05) degree of protection against salt spray injury 3 months after application as manifest by higher leaf chlorophyll content, photosynthetic efficiency, height and leaf area, and lower visual leaf necrosis and foliar Na and Cl content compared with nontreated controls. In conclusion, results indicate that application of a suitable film-forming polymer can provide a significant degree of protection of up to 3 months against salt spray injury in evergreen oak and laurel. Results also indicate that when applied at 1% or 2% solutions, no problems associated with phytotoxicity and rapid degradation on the leaf surface exist.