Stakeholders’ perceptions of the impacts of invasive exotic plant species in the Mediterranean region

Invasive species pose an increasing environmental problem across the globe, but to date socio-economic perspectives on this problem have been limited. In this study stakeholder perceptions of the impacts of invasive exotic plant species on the islands of Mallorca, Sardinia and Crete are examined through the use of semi-structured interviews, Likert scales and Contingent Valuation. Results showed substantial concerns about the impact of invasive exotic plant species on the islands, particularly on Mallorca where awareness of the issue has increased in recent times due to campaigns to eradicate terrestrial and aquatic invasive plants. Not all perceptions are negative and several respondents suggest that a turnover in local species is an inherent part of the sense of the place in the region. If the management of invasive exotic plant species in the Mediterranean region is to improve then there is a need to raise awareness of the impact of invasive species amongst both the general public and professional stakeholders.     

In vitro enzymatic reduction kinetics of mineral oxides by membrane fractions from Shewanella oneidensis MR-1

This study documents the first example of in vitro solid-phase mineral oxide reduction by enzyme-containing membrane fractions. Previous in vitro studies have only reported the reduction of aqueous ions. Total membrane (TM) fractions from iron-grown cultures of Shewanella oneidensis MR-1 were isolated and shown to catalyze the reduction of goethite, hematite, birnessite, and ramsdellite/pyrolusite using formate. In contrast, nicotinamide adenine dinucleotide (NADH) and succinate cannot function as electron donors. The significant implications of observations related to this cell-free system are: (i) both iron and manganese mineral oxides are reduced by the TM fraction, but aqueous U(VI) is not; (ii) TM fractions from anaerobically grown, but not aerobically grown, cells can reduce the mineral oxides; (iii) electron shuttles and iron chelators are not needed for this in vitro reduction, documenting conclusively that reduction can occur by direct contact with the mineral oxide; (iv) electron shuttles and EDTA stimulate the in vitro Fe(III) reduction, documenting that exogenous molecules can enhance rates of enzymatic mineral reduction; and (v) multiple membrane components are involved in solid-phase oxide reduction. The membrane fractions, consisting of liposomes of cytoplasmic and outer membrane segments, contain at least 100 proteins including the enzyme that oxidizes formate, formate dehydrogenase. Mineral oxide reduction was inhibited by the addition of detergent Triton X-100, which solubilizes membranes and their associated proteins, consistent with the involvement of multiple electron carriers that are disrupted by detergent addition. In contrast, formate dehydrogenase activity was not inhibited by Triton X-100. The addition of anthraquinone-2,6-disulfonate (AQDS) and menaquinone-4 was unable to restore activity; however, menadione (MD) restored 33% of the activity. The addition of AQDS and MD to reactions without added detergent increased the rate of goethite reduction. The Michaelis-Menten K_m values of 71 ± 22 m²/L for hematite and 50 ± 16 m²/L for goethite were calculated as a function of surface area of the two insoluble minerals. V_max was determined to be 123 ± 14 and 156 ± 13 nmol Fe(II)/min/mg of TM protein for hematite and goethite, respectively. These values are consistent with in vivo rates of reduction reported in the literature. These observations are consistent with our conclusion that the enzymatic reduction of mineral oxides is an effective probe that will allow elucidation of molecular chemistry of the membrane-mineral interface where electron transfer occurs.     

Parallel 3-D Simulation of a Fault Gouge Using the Lattice Solid Model

Despite the insight gained from 2-D particle models, and given that the dynamics of crustal faults occur in 3-D space, the question remains, how do the 3-D fault gouge dynamics differ from those in 2-D? Traditionally, 2-D modeling has been preferred over 3-D simulations because of the computational cost of solving 3-D problems. However, modern high performance computing architectures, combined with a parallel implementation of the Lattice Solid Model (LSM), provide the opportunity to explore 3-D fault micro-mechanics and to advance understanding of effective constitutive relations of fault gouge layers. In this paper, macroscopic friction values from 2-D and 3-D LSM simulations, performed on an SGI Altix 3700 super-cluster, are compared. Two rectangular elastic blocks of bonded particles, with a rough fault plane and separated by a region of randomly sized non-bonded gouge particles, are sheared in opposite directions by normally-loaded driving plates. The results demonstrate that the gouge particles in the 3-D models undergo significant out-of-plane motion during shear. The 3-D models also exhibit a higher mean macroscopic friction than the 2-D models for varying values of interparticle friction. 2-D LSM gouge models have previously been shown to exhibit accelerating energy release in simulated earthquake cycles, supporting the Critical Point hypothesis. The 3-D models are shown to also display accelerating energy release, and good fits of power law time-to-failure functions to the cumulative energy release are obtained.     

On the effects of petrographic composition on coalbed methane sorption

The effect of petrographic composition on the methane sorption capacity has been determined for a suite of coals and organic-rich shales. Subbituminous and bituminous coals were separated into bright and dull lithotypes by hand-picking. The methane sorption capacities range between 0.5 and 23.9 cm³/g at a pressure of 6 MPa. The low volatile bituminous Canmore coal and the anthracite sample have the highest capacities with the “natural coke” having the lowest. For low-rank coals there is no significant difference between bright and dull samples except for one coal with the dull sample having a greater sorption capacity than its bright equivalent. For higher-rank coals, the bright samples have a greater methane capacity than the dull samples and the difference between sample pairs increases with rank. The boghead coal samples have the highest sorption capacities in the liptinite-rich coals suite and are higher than subbituminous to medium volatile bituminous samples. Pore size distribution indicates that methane is held as solution gas in liptinite-rich coals and by physical sorption in micropores in liptinite-poor coals. These contrasting processes illustrate that liptinite-rich samples need to be independently assessed. The positive relationship between reactive inertinite content and methane sorption capacity occurs within the subbituminous to medium volatile bituminous coals because the reactive inertinite is structurally similar to vitrinite and have a higher microporosity than non-reactive inertinite. Reactivity of inertinite should be assessed in CBM studies of dull coals to provide a better understanding of petrographic composition effects on methane capacity.     

Trends in landslide occurrence in Nepal

Nepal is a mountainous, less developed kingdom that straddles the boundary between the Indian and Himalayan tectonic plates. In Nepal, landslides represent a major constraint on development, causing high levels of economic loss and substantial numbers of fatalities each year. There is a general consensus that the impacts of landslides in countries such as Nepal are increasing with time, but until now there has been little or no quantitative data to support this view, or to explain the causes of the increases. In this paper, a database of landslide fatalities in Nepal has been compiled and analysed for the period 1978–2005. The database suggests that there is a high level of variability in the occurrence of landslides from year to year, but that the overall trend is upward. Analyses of the trends in the data suggest that there is a cyclicity in the occurrence of landslide fatalities that strongly mirrors the cyclicity observed in the SW (summer) monsoon in South Asia. Perhaps surprisingly the relationship is inverse, but this is explained through an inverse relationship between monsoon strength and the amount of precipitation in the Hill District areas of Nepal. It is also clear that in recent years the number of fatalities has increased dramatically over and above the effects of the monsoon cycle. Three explanations are explored for this: land-use change, the effects of the ongoing civil war in Nepal, and road building. It is concluded that a major component of the generally upward trend in landslide impact probably results from the rural road-building programme, and its attendant changes to physical and natural systems.     

Fault slip in the 1997 Manyi, Tibet earthquake from linear elastic modelling of InSAR displacements

The M _w 7.6 1997 Manyi earthquake occurred in an area of central northern Tibet where sparse vegetation coverage and a lack of human habitation provide excellent conditions for Interferometric Synthetic Aperture Radar (InSAR) studies. We use coseismic pairs of radar images acquired by the ESA ERS-2 satellite to construct interferograms of the surface displacement field due to the earthquake. The location and extent of the coseismic fault rupture are mapped using a combination of optical satellite imagery, high-resolution digital topography, interferometric correlation and azimuth offset measurements; in so doing, we are able to relate prominent geomorphic features in the fault zone to bends in the fault.
Using elastic dislocation models consistent with this mapped fault trace, we then test a range of fault geometries and slip conditions to find the combination which best explains the InSAR displacements. Our favoured model contains a reversal in fault dip, approximately halfway along its length, occurring at the location of a restraining bend. Slip on this model fault is heterogeneous, with two areas of peak slip of 7 m or greater, and components of dip-slip displacement which vary significantly along-strike. The success of this model in fitting the data implies that an observed asymmetry in the coseismic interferograms can be explained in terms of the local fault geometry, rather than by using non-linear elastic rheologies as suggested by earlier authors.     

鼓丘和巨型冰川线理的冰川摩擦学:剥蚀和沉积的争论之谜得到解决?

冰流是指冰盖中快速流动(高达10 km/a)的区域.冰流通常长达1000 km,宽200 km,嵌入在冰盖中.沿其流动方向形成了低幅度波纹状基岩床.这些波纹状基岩床由一些高度拉伸的沿着流向呈平行状分布的脊和沟槽(巨型冰川线理)组成.这些巨型冰川线理在空间上继承自体积大、拉伸程度低的鼓丘.由于鼓丘核部的地质条件复杂多变且不存在特征性的岩相,同时很难直接观察到现代冰盖下鼓丘的形成,因而鼓丘的起源在世界上仍然是未解之谜.基于新的高分辨率(0.5 m)LiDAR数据绘制的地形图和对更新世古冰流岩床进行野外地质考察表明,鼓丘和巨型冰川线理是底形连续体(后者由前者演化而来).它们由基岩或部分岩石和早期较老的沉积物组成,基于此部分学者提出了鼓丘的侵蚀起源说.本文重点介绍了类似鼓丘和巨型冰川线理的椭圆-流线型和带有沟槽的表面,这些表面广泛形成于多种非冰川的地质环境中(无论是在地球上还是在火星上),它们是由于受限剪切作用下颗粒状碎屑对基底面的磨损所产生的.变质核杂岩中的大型滑脱断层和俯冲带巨型逆冲断层的表面显示出槽状表面,其形状和规模能够与巨型冰川线理相类比.多尺度的断层面上都表现出了逐渐消除的类似鼓丘状的"椭圆形凸起",形成带凹槽的岩石光滑面,从而减少了阻力并允许继续滑动.现代冰流岩床记录的冰下地震的独特"纹理"与凹槽内基底面遭受的局部侵蚀和剪切一致,冰下地貌特征加强了与断层运动学的联系.火山碎屑流、陨石撞击坑周围的溅射毯以及滑坡和块体搬运沉积体系的滑动,它们的下垫面都会形成类似巨型冰川线理的沟槽.在人造和生物材料的摩擦接触表面上,也可以重现这些由粒状"磨损碎屑"(被定义为"第三层")切割形成的类似鼓丘的椭圆形凸起和类似巨型冰川线理的沟槽表面.因此,我们提议将鼓丘和巨型冰川线理作为冰川动力学研究的相关组成部分,可以称之为"磨损痕迹"或者"流向剪切痕".它们是由于不同的冰流速度拖曳粗颗粒的变形冰碛物切割底面(沉积物或者岩石(或其他岩相组合))形成的.地学界颇具争议的鼓丘-冰川线理成因谜团已逐渐清晰.     

Geology and resource development of the Kelvin kimberlite pipe,Northwest Territories,Canada

The early Cambrian to late Neoproterozoic Kelvin kimberlite pipe is located in the southeast of the Archean Slave Craton in northern Canada, eight km northeast of the Gahcho Kué diamond mine. Kelvin was first discovered in 2000 by De Beers Canada. Subsequent exploration undertaken by Kennady Diamonds Inc. between 2012 and 2016 resulted in the discovery of significant thicknesses of volcaniclastic kimberlite that had not previously been observed. Through extensive delineation drilling Kelvin has been shown to present an atypical, steep-sided inclined L-shaped pipe-like morphology with an overall dip of 15 to 20°. With a surface expression of only 0.08 ha Kelvin dips towards the northwest before turning north. The body (which remains open at depth) has been constrained to a current overall strike length of 700 m with varying vertical thickness (70 to 200 m) and width (30 to 70 m). Detailed core logging, petrography and microdiamond analysis have shown that the pipe infill comprises several phases of sub-horizontally oriented kimberlite (KIMB1, KIMB2, KIMB3, KIMB4, KIMB7 and KIMB8) resulting from multiple emplacement events. The pipe infill is dominated by Kimberley-type pyroclastic kimberlite or “KPK”, historically referred to as tuffisitic kimberlite breccia or “TKB”, with less common hypabyssal kimberlite (HK) and minor units with textures transitional between these end-members. An extensive HK sheet complex surrounds the pipe. The emplacement of Kelvin is believed to have been initiated by intrusion of this early sheet system. The main pipe-forming event and formation of the dominant KPK pipe infill, KIMB3, was followed by late stage emplacement of additional minor KPK and a hypabyssal to transitional-textured phase along the upper contact of the pipe, cross-cutting the underlying KIMB3. Rb-Sr age dating of phlogopite from a late stage phase has established model ages of 531 ± 8 Ma and 546 ± 8 Ma. Texturally and mineralogically, the Kelvin kimberlite is similar to other KPK systems such as the Gahcho Kué kimberlites and many southern African kimberlites; however, the external morphology, specifically the sub-horizontal inclination of the pipe, is unique. The morphology of Kelvin and the other kimberlites in the Kelvin-Faraday cluster defines a new type of exploration target, one that is likely not unique to the Kennady North Project area. Extensive evaluation work by Kennady Diamonds Inc. has resulted in definition of a maiden Indicated Mineral Resource for Kelvin of 8.5 million tonnes (Mt) of kimberlite at an average grade of 1.6 carats per tonne (cpt) with an average diamond value of US$ 63 per carat (ct).