A preliminary study of metal distribution in three waterhyacinth biotypes

Two waterhyacinth (Eichhornia crassipes (Mart.) Solms) biotypes from Broward County, Florida, were collected and analyzed for chlorophyll content and metal distribution (potassium, calcium, magnesium, cobalt, copper, manganese and iron) in roots, stems and leaves. Two biotypes were distinguished by size (medium or “stunted”, and large or “super”) and by whether they were or were not eaten (“stunted” and ”super”, respectively) by the waterhyacinth weevil, Neochetina eichhorniae Warner. Results are compared with a third biotype (small or “normal”): i.e. plants from the Hillsborough and Peace Rivers where the weevils have not been released. The data indicate abnormal concentration of cobalt and iron in the leaves of the “super” plants relative to the third biotype. Fractions of calcium, magnesium, manganese, iron and copper in roots showed a significant, negative linear correlation coefficient, r, with solubility product constant (log K_sp) for metal carbonates of the small and medium biotypes.     

Lake Sammamish response to wastewater diversion and increasing urban runoff

Lake Sammamish has shown a decrease in its mean annual concentration of phosphorus following diversion of about one third of the external loading in 1968. During 1971–1975 the P concentration averaged 27 μg l⁻¹, in contrast to the prediversion (1964–1966) concentration of 33 μg l⁻¹, and may be equilibrating near the predicted steady state concentration of 22 μg l⁻¹. Neither phytoplankton biomass or Secchi visibility has changed following diversion, however the blue green component of the phytoplankton decreased by nearly 50%. The failure of biomass and visibility to improve is probably a result of similar pre- and postdiversion winter spring epilimnetic P concentrations. The marked reduction in P since diversion occurred during and prior to fall overturn and may have represented a supply of P for later summer early fall blue green algal populations that declined after diversion.Runoff from a rapidly developing westside portion (18%) of the watershed is contributing substantially to P loading of the lake. Development to a density of about ten dwellings ha⁻¹ has increased loading possibly on the order of 14%. Future development of the eastside portion (26% of watershed) may increase loading by 20% and be equivalent to nearly one half of the P previously diverted in 1968.     

The Bacterial Quality of an Upland Stream

Faecal coliform concentrations were determined at stream and water inflow sampling sites within an upland catchment in North Derbyshire containing rough, semiimproved and improved pastures. The results indicated that, during its passage through the catchment, the faecal indicators of the stream increased, and this may constitute a health risk to cavers using a popular recreational cave into which the stream drains. The decline in streamwater quality suggests that a semipermanent store of bacteria existed in catchment soils, and hydrological processes operated to transfer bacteria from the land to the stream channel. Contrary to expectations, intra-catchment differences in the bacterial quality of water at inflow and stream sampling sites could not be related to the intensity of agricultural land use in adjacent areas. This is explained with reference to changes in the nature of hydrological transport pathways associated with the improvement of pastures.     

A Three-Step Approach to Microcomputer Security Controls

Despite their many benefits, microcomputers can dramatically increase the vulnerability of an organization's information system. As these devices are integrated in an organization, computer hardware, software, and data become widely dispersed, enabling more individuals to access information. Widespread use of microcomputers, especially when coupled with their ability to communicate with larger systems, requires early formulation and implementation of security and control procedures that differ substantially from those established in mainframe environments.     

The Role of Organizational Vision in Guiding Idea Generation within SME Contexts

New ideas are required if our organizations are going to survive and grow. Without the ability to think differently, firms can quickly stagnate and decline. A key contributor to the success (or otherwise) of the ideation process is the extent to which organizations provide effective control mechanisms, with existing literature drawing tentative links between this and the subject of organizational vision. The aim of this paper is to explore the control of idea generation in SME contexts, examining the interaction between organizational vision and the guidance of ideation in these settings. Through in‐depth qualitative research with a range of SMEs, this study shows that structure in the form of an outlining framework assists in opening a liminal space for ideation. More importantly, this paper provides empirical evidence, which demonstrates that organizational visions provide this framework by acting as a target, assisting the development of relevant ideas. Ideation, within the SME, is argued to be fundamentally subject to, and contingent upon, the direction of the organization.     

Overview of underground coal gasification operations at Chinchilla,Australia

Underground coal gasification (UCG) is a process which converts deep, un-mineable or difficult to mine coal resources into syngas which can then be converted into valuable end products such as electric power, liquid fuels, synthetic natural gas and chemicals. This paper provides a summary of the UCG operations conducted at the Chinchilla Demonstration Facility in Australia, focusing on gasifiers constructed using directional drilling. A number of the experiences and key lessons learned from operating multiple underground gasifiers over several years at the facility are described. Implications for the implementation in commercial projects using UCG are also discussed. Finally, the potential of UCG as a method for producing syngas from deep coal is discussed and some of the challenges and opportunities are summarized.     

Field D* path-finding on weighted triangulated and tetrahedral meshes

Classic shortest path algorithms operate on graphs, which are suitable for problems that can be represented by weighted nodes or edges. Finding a shortest path through a set of weighted regions is more difficult and only approximate solutions tend to scale well. The Field D* algorithm efficiently calculates an approximate, interpolated shortest path through a set of weighted regions and was designed for navigating robots through terrains with varying characteristics. Field D* operates on unit grid or quad-tree data structures, which require high resolutions to accurately model the boundaries of irregular world structures. In this paper, we extend the Field D* cost functions to 2D triangulations and 3D tetrahedral meshes: structures which model polygonal world structures more accurately. Since robots typically have limited resources available for computation and storage, we pay particular attention to computation and storage overheads when detailing our extensions. We begin by providing analytic solutions to the minimum of each cost function for 2D triangles and 3D tetrahedra. Our triangle implementation provides a 50 % improvement in performance over an existing triangle implementation. While our 3D extension to tetrahedra is the first full analytic extension of Field D* to 3D, previous work only provided an approximate minimization for a single cost function on a 3D cube with unit lengths. Each cost function is expressed in terms of a general function whose characteristics can be exploited to reduce the calculations required to find a minimum. These characteristics can also be exploited to cache the majority of cost functions, producing a speedup of up to 28 % in the 3D tetrahedral case. We demonstrate that, in environments composed of non-grid aligned data, Multi-resolution quad-tree Field D* requires an order of magnitude more faces and between 15 and 20 times more node expansions, to produce a path of similar cost to one produced by a triangle implementation of Field D* on a lower resolution triangulation. We provide examples of 3D pathing through models of complex topology, including pathing through anatomical structures extracted from a medical data set. To summarise, this paper details a robust and efficient extension of Field D* pathing to data sets represented by weighted triangles and tetrahedra, and also provides empirical data which demonstrates the reduction in storage and computation costs that accrue when one chooses such a representation over the more commonly used quad-tree and grid-based alternatives.     

Field Trials of Low-cost Reactive Media for the Passive Treatment of Circum-neutral Metal Mine Drainage in Mid-Wales,UK

This paper addresses the ability of five low-cost reactive materials to remove Zn, Pb, and Cd from Fe-poor, circum-neutral pH metal mine water in Mid-Wales, UK. Compost, fly ash, waste shell material, iron ochre, and a mixture of blast furnace slag (BFS) and basic oxygen furnace slag (BOS) were used in a series of small-scale passive treatment cells to assess metal removal from mine drainage initially containing, on average, 23.5 mg/L Zn, 0.5 mg/L Pb, and 0.05 mg/L Cd. Trial treatment cells contained between 1.5 and 12 kg of reactive media, had a 15 min residence time, and treated a discharge of up to 1 L per minute. Fly ash from a peat-fired power station was found to be the most effective material for metal removal, with concentrations reduced to 0.02 mg/L Zn, 0.0069 mg/L Pb, and 0.0001 mg/L Cd from over 1,000 L of water (between 98.6 and 99.9% removal). The other materials initially achieved high levels of metal removal (between 75 and 99.9% Zn, Pb, and Cd removed); however, all of the materials were saturated with Zn after less than 200 L of water had been treated. Metal sorption ranged from 21.4 mg/g Zn for the peat fly ash to 0.0015 mg/g Cd for the compost and BOS/BFS slag. The results of the pilot-scale field trials can be scaled to demonstrate that a modest-sized fly ash treatment cell (2.6 × 2.6 × 1 m) in size would be sufficient to remove 90% of the total metal load (Pb, Zn, and Cd) from this 10 L/min mine water discharge for a 1 year period. Importantly this research demonstrates that passive treatment for metal mine drainage can comply with water quality directives but cannot be considered a ‘walk-away’ solution; it requires modest (potentially annual) maintenance.     

Confirmation of the Dominant Defect Mechanism in Amorphous In–Zn–O Through the Application of In Situ Brouwer Analysis

The dominant point defect mechanism of amorphous (a‐) indium zinc oxide (IZO) was probed through in situ electrical characterization of sputtered a‐IZO thin films in response to changes in oxygen partial pressure (pO) at 300C. The results yielded a power law dependence of conductivity (σ) versus pO of ～?1/6. This experimental method, known as Brouwer analysis, confirms doubly‐charged oxygen vacancies as the dominant defect species in a‐IZO. The success of this study suggests that Brouwer analysis is a viable method for studying the defect mechanisms of amorphous oxides.