37 resultados para soil critical level
Resumo:
Universities planning the provision of space for their teaching requirements need to do so in a fashion that reduces capital and maintenance costs whilst still providing a high-quality level of service. Space plans should aim to provide sufficient capacity without incurring excessive costs due to over-capacity. A simple measure used to estimate over-provision is utilisation. Essentially, the utilisation is the fraction of seats that are used in practice, or the ratio of demand to supply. However, studies usually find that utilisation is low, often only 20–40%, and this is suggestive of significant over-capacity.
Our previous work has provided methods to improve such space planning. They identify a critical level of utilisation as the highest level that can be achieved whilst still reliably satisfying the demand for places to allocate teaching events. In this paper, we extend this body of work to incorporate the notions of event-types and space-types. Teaching events have multiple ‘event-types’, such as lecture, tutorial, workshop, etc., and there are generally corresponding space-types. Matching the type of an event to a room of a corresponding space-type is generally desirable. However, realistically, allocation happens in a mixed space-type environment where teaching events of a given type are allocated to rooms of another space-type; e.g., tutorials will borrow lecture theatres or workshop rooms.
We propose a model and methodology to quantify the effects of space-type mixing and establish methods to search for better space-type profiles; where the term “space-type profile” refers to the relative numbers of each type of space. We give evidence that these methods have the potential to improve utilisation levels. Hence, the contribution of this paper is twofold. Firstly, we present informative studies of the effects of space-type mixing on utilisation, and critical utilisations. Secondly, we present straightforward though novel methods to determine better space-type profiles, and give an example in which the resulting profiles are indeed significantly improved.
Evaporative Moisture Loss from Heterogeneous Stone: Material- Environment Interactions During Drying
Resumo:
The complexities of evaporation from structurally and mineralogically heterogeneous sandstone (Locharbriggs Sandstone) are investigated through a laboratory-based experiment in which a variety of environmental conditions are simulated. Data reported demonstrate the significance of material-environment interactions on the spatial and temporal variability of evaporative dynamics. Evaporation from porous stone is determined by the interplay between environmental, material and solution properties, which govern the rate and mode by which water is transmitted to, and subsequently removed from, an evaporating surface. Initially evaporation is marked by high rates of moisture loss controlled by external atmospheric conditions; then, when a critical level of surface moisture content is reached, hydraulic continuity between the stone surface and subsurface is disrupted and the drying front recedes
beneath the surface, evaporation rates decrease and are controlled by the ability of the material to transport water vapour to the surface. Pore size distribution and connectivity, as well as other material properties, control the timing of each stage of evaporation and the nature of the transition.
These experimental data highlight the complexity of evaporation, demonstrating that different regions of the same stone can exhibit varying moisture dynamics during drying and that the rate and nature of evaporative loss differs under different environmental conditions. The results identify the importance of material-environment interactions during drying and that stone micro-environmental conditions cannot be inferred from ambient data alone.
These data have significance for understanding the spatial distribution of stone surface weathering-related morphologies in both the natural and built environments where mineralogical and/or structural heterogeneity creates differences in moisture flux and hence variable drying rates. Such differences may provide a clearer explanation for the initiation and subsequent development of complex weathering responses where areas of significant deterioration can be found alongside areas that exhibit little or no evidence surface breakdown.
Resumo:
Data from a series of controlled suction triaxial tests on samples of compacted speswhite kaolin were used in the development of an elasto–plastic critical state framework for unsaturated soil. The framework is defined in terms of four state variables: mean net stress, deviator stress, suction and specific volume. Included within the proposed framework are an isotropic normal compression hyperline, a critical state hyperline and a state boundary hypersurface. For states that lie inside the state boundary hypersurface the soil behaviour is assumed to be elastic, with movement over the state boundary hypersurface corresponding to expansion of a yield surface in stress space. The pattern of swelling and collapse observed during wetting, the elastic–plastic compression behaviour during isotropic loading and the increase of shear strength with suction were all related to the shape of the yield surface and the hardening law defined by the form of the state boundary. By assuming that constant–suction cross–sections of the yield surface were elliptical it was possible to predict test paths for different types of triaxial shear test that showed good agreement with observed behaviour. The development of shear strain was also predicted with reasonable success, by assuming an associated flow rule.
Resumo:
Accelerated soil erosion is an aspect of dryland degradation that is affected by repeated intense drought events and land management activities such as commercial livestock grazing. A soil stability index (SSI) that detects the erosion status and susceptibility of a landscape at the pixel level, i.e., stable, erosional, or depositional pixels, was derived from the spectral properties of an archived time series (from 1972 to 1997) of Landsat satellite data of a commercial ranch in northeastern Utah. The SSI was retrospectively validated with contemporary field measures of soil organic matter and erosion status that was surveyed by US federal land management agencies. Catastrophe theory provided the conceptual framework for retrospective assessment of the impact of commercial grazing and soil water availability on the SSI. The overall SSI trend was from an eroding landscape in the early drier 1970s towards stable conditions in the wetter mid-1980s and late 1990s. The landscape catastrophically shifted towards an extreme eroding state that was coincident with the “The Great North American Drought of 1988”. Periods of landscape stability and trajectories toward stability were coincident with extremely wet El Niño events. Commercial grazing had less correlation with soil stability than drought conditions. However, the landscape became more susceptible to erosion events under multiple droughts and grazing. Land managers now have nearly a year warning of El Niño and La Niña events and can adjust their management decisions according to predicted landscape erosion conditions.
Resumo:
beta1,4-Galactosyltransferase V (beta1,4GalT V; EC 2.4.1.38) is considered to be very important in glioma for expressing transformation-related highly branched N-glycans. Recently, we have characterized beta1,4GalT V as a positive growth regulator in several glioma cell lines. However, the role of beta1,4GalT V in glioma therapy has not been clearly reported. In this study, interfering with the expression of beta1,4GalT V by its antisense cDNA in SHG44 human glioma cells markedly promoted apoptosis induced by etoposide and the activation of caspases as well as processing of Bid and expression of Bax and Bak. Conversely, the ectopic expression of beta1,4GalT V attenuated the apoptotic effect of etoposide on SHG44 cells. In addition, both the beta1,4GalT V transcription and the binding of total or membrane glycoprotein with Ricinus communis agglutinin-I (RCA-I) were partially reduced in etoposide-treated SHG44 cells, correlated well with a decreased level of Sp1 that has been identified as an activator of beta1,4GalT V transcription. Collectively, our results suggest that the down-regulation of beta1,4GalT V expression plays an important role in etoposide-induced apoptosis and could be mediated by a decreasing level of Sp1 in SHG44 cells, indicating that inhibitors of beta1,4GalT V may enhance the therapeutic efficiency of etoposide for malignant glioma.
Resumo:
Samples were taken at each stage of brewing (malt, milling, mashing, wort separation, hop addition, boiling, whirlpool, dilution, fermentation, warm rest, chill-lagering, beer filtration, carbonation and bottling, pasteurization, and storage). The level of antioxidant activity of unfractionated, low-molecular-mass (LMM) and high-molecular-mass (HMM) fractions was measured by the 2,2'-azinobis(3-ethylbenzothiazoline-6-sulfortic acid) radical cation (ABTS(.+)) and ferric-reducing antioxidant power (FRAP) procedures. Polyphenol levels were assessed by HPLC. The LMM fraction ( 0.001) in catechin and ferulic acid levels. Increases in antioxidant activity levels were observed after mashing, boiling, fermentation, chill-lagering, and pasteurization, in line with previous studies on lager. Additionally, increases in the level of antioxidant activity occurred after wort separation and carbonation and bottling and were accompanied by increases in levels of most monitored polyphenols. Data from the ABTS(.-) and FRAP assays indicated that the compounds contributing to the levels of antioxidant activity responded differently in the two procedures. Levels of ferulic, vanillic, and chlorogenic acids and catechin accounted for 45-61% of the variation in antioxidant activity levels.
Resumo:
Solid low-level radioactive waste (LLW) is currently being disposed at a number of facilities in the United Kingdom (UK). The safety of these facilities relies to some extent on the use of engineered barriers, such as a cap, to isolate the waste and protect the environment. Generally, the material used as the barrier layer within such a cap should be of low permeability and it should retain this property over long timescales (beyond a few decades normally required for facilities containing non-radioactive wastes). The objective of this research is to determine the mineralogy of selected geological deposits from the UK and Ireland as part of a larger project to examine their suitability as a capping material, particularly on LLW sites. Mineral transformations, as a result of future climate change, may impact on the long-term performance of the cap and even the disposal facility. X-ray diffraction (XRD) was carried-out on the sand, silt and clay fractions of the London Clay, Belfast Upper Boulder Clay, Irish Glacial Till, Belfast Sleech, and Ampthill Clay geological deposits. Minerals were present that could pose both positive and negative effects on the long-term performance of the cap. Smectite, which has a high shrink swell potential, may produce cracks in London Clay, Belfast Upper Boulder Clay and Ampthill Clay capping material during dry, hotter periods as a possible consequence of future climate change; thus, resulting in higher permeability. Ampthill Clay and Belfast Sleech had elevated amounts of organic matter (OM) at 5.93% and 5.88%, respectively, which may also contribute to cracking. Over time, this OM may decompose and result in increased permeability. Gypsum (CaSO4) in the silt and sand fractions of Ampthill Clay may reduce the impact of erosion during wetter periods if it is incorporated into the upper portion of the cap. There are potential negative effects from the acidity created by the weathering of pyrite (FeS2) present in the silt and sand fractions of Belfast Sleech and Ampthill Clay that could impede the growth of grasses used to stabilize the surface of the capping material if this material is used as part of the vegetative soil layer. Additionally, acidic waters generated from pyrite weathering could negatively impact the lower lying capping layers and the disposal facility in general. However, the calcium carbonate (CaCO3) present in the silt and sand fractions of these deposits, and dolomite (CaMg(CO3)2) in Belfast Sleech, may counter act the acidity.
Resumo:
Iron and Mn redistribute in soil and saprolite during weathering. The geological weathering fronts ofcalcareous sedimentary rock were investigated by examining the bulk density, porosity, and distribution ofCa, Fe, and Mn. Core samples were taken ofsoil, saprolite, and bedrock material from both summit (HHMS-4B) and sideslope (HHMS-5A) positions on an interbedded Nolichucky shale and Maryville limestone landform in Solid Waste Storage Area 6 (SWSA-6). This is a low-level radioactive solids waste disposal site on the Dept. ofEnergy (DOE) Oak Ridge Reservation in Roane County Tennessee. This work was initiated because data about the properties of highly weathered sedimentary rock on this site were limited. The core samples were analyzed for pH, calcium carbonate equivalence (CCE), hydroxylamine-extractable (HA) Mn, and dithionite-citrate (CBD)-extractable Fe and Mn. Low pH values occurred from the soil surface down to the depth of the oxidized and leached saprolite in both cores. The CCE and HA-extractable Mn results were also influenced by the weathering that has occurred in these zones. Extractable Mn oxide was higher at a lower depth in the oxidized and leached saprolite compared with the Fe oxide, which was higher in the overlying soil solum. Amounts of Mn oxides were higher in the sideslope core (HHMS-5A) than in the summit core (HHMS-4B). Iron was more abundant in the deeper weathered summit core, but the highest value, 39.4 g kg-1, was found at 1.8 to 2.4 m in the sideslope core. The zone encompassing the oxidized and partially leached saprolite down to the unoxidized and unleached bedrock had higher densities and larger quantities of CaCO3 than the soil solum and oxidized and leached saprolite. The overlying soil and oxidized and leached saprolite had lower pH and CCE values and were higher in Fe and Mn oxides than the oxidized and unleached saprolite. The distribution of Fe and Mn is important when evaluating soil and saprolite for hazardous waste disposal site assessment.
Resumo:
Survival, growth, above ground biomass accumulation, soil surface elevation dynamics and nitrogen accumulation in accreted sediments were studied in experimental treatments planted with four different densities (6.96, 3.26, 1.93 and 0.95 seedlings m-2) of the mangrove Rhizophora mucronata in Puttalam Lagoon, Sri Lanka. Measurements were taken over a period of 1171 days and were compared with those from unplanted controls. Trees at the lowest density showed significantly reduced survival, whilst measures of individual tree growth did not differ significantly among treatments. Rates of surface sediment accretion (means ± S.E.) were 13.0 (±1.3), 10.5 (±0.9), 8.4 (±0.3), 6.9 (±0.5) and 5.7 (±0.3) mm yr-1 at planting densities of 6.96, 3.26, 1.93, 0.95, and 0 (unplanted control) seedlings m-2, respectively, showing highly significant differences among treatments. Mean (± S.E.) rates of surface elevation change were much lower than rates of accretion at 2.8 (±0.2), 1.6 (±0.1), 1.1 (±0.2), 0.6 (±0.2) and -0.3 (±0.1) mm yr-1 for 6.96, 3.26, 1.93, 0.95, and 0 seedlings m-2, respectively. All planted treatments appeared to accumulate greater nitrogen concentrations in the sediment compared to the unplanted control, and suggests one potential causal mechanism for the facilitatory effects observed; high densities of plants potentially contribute to the accretion of greater amounts of nutrient rich sediment. While this potential process needs further study, this study demonstrated how higher densities of mangroves enhance rates of sediment accretion and surface elevation, processes that may be crucial in mangrove ecosystem adaptation to sea level rise. There was no evidence that increasing plant density evoked a trade-off with growth and survival of the planted trees. Rather facilitatory effects enhanced survival at high densities, suggesting that local land managers may be able to take advantage of plantation densities to help mitigate sea-level rise effects by encouraging positive soil surface elevation increment, and perhaps even greater nutrient retention to promote mangrove growth and ameliorate nearshore eutrophication in tropical island environments.
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The marine oligotrophic ultramicrobacterium Sphingomonas alaskensis RB2256 has a physiology that is distinctly different from that of typical copiotrophic marine bacteria, such as Vibrio angustum S14. This includes a high level of inherent stress resistance and the absence of starvation-induced stress resistance to hydrogen peroxide. In addition to periods of starvation in the ocean, slow nutrient-limited growth is likely to be encountered by oligotrophic bacteria for substantial periods of time. In this study we examined the effects of growth rate on the resistance of S. alaskensis RB2256 to hydrogen peroxide under carbon or nitrogen limitation conditions in nutrient-limited chemostats. Glucose-limited cultures of S. alaskensis RB2256 at a specific growth rate of 0.02 to 0.13 h(-1) exhibited 10,000-fold-greater viability following 60 min of exposure to 25 mM hydrogen peroxide than tells growing at a rate of 0.14 h(-1) or higher. Growth rate control of stress resistance was found to be specific to carbon and energy limitation in this organism. In contrast, V. angustum S14 did not exhibit growth rate-dependent stress resistance. The dramatic switch in stress resistance that was observed under carbon and energy limitation conditions has not been described previously in bacteria and thus may be a characteristic of the oligotrophic ultramicrobacterium, Catalase activity varied marginally and did not correlate with the growth rate, indicating that hydrogen peroxide breakdown was not the primary mechanism of resistance. More than 1,000 spots were resolved on silver-stained protein gels for cultures growing at rates of 0.026, 0.076, and 0.18 h(-1). Twelve protein spots had intensities that varied by more than twofold between growth rates and hence are likely to be important for growth rate-dependent stress resistance. These studies demonstrated the crucial role that nutrient limitation plays in the physiology of S. alaskensis RB2256, especially under oxidative stress conditions.
Resumo:
Science programmes which prepare students to read critically and respond thoughtfully to science-based reports in the media could play an important role in promoting informed participation in the public debate about issues relating to science, technology and society. Evidence based guidance about the practice and pattern of use of science-based media in the classroom is limited. This study sought to identify learning intentions that teachers believe ought to underpin the development of programmes of study designed to achieve this end-result. Teachers views of knowledge, skills and attitudes required to engage critically with science-based news served as a basis for this study. Teachers developed a pedagogical model by selecting appropriate statements of learning intentions, grouping these into coherent and manageable themes and coding them according to perceived level of difficulty. The model is largely compatible with current curricular provision in the UK, highlights opportunities for interdisciplinary collaboration and illustrates the developmental nature of the topic.
Resumo:
Objective To evaluate the feasibility of conducting a definitive study to assess the impact of introducing a rapid PCR-based test for candidemia on antifungal drug prescribing. Method Prospective, single centre, interrupted time series study consisting of three periods of six months' duration. The assay was available during the second period, during which the PCR assay was available for routine use by physicians Monday–Friday with guaranteed 24-h turnaround time. For each period total antifungal drug use, expressed as treatment-days, was recorded and an adjustment was made to exclude estimated use for proven candidemia. Also, during the intervention period, antifungal prescribing decisions for up to 72 h after each PCR result became available were recorded as either concordant or discordant with that result. Results While overall antifungal use remained relatively stable throughout, after adjustment for candidemia, there was a 38% reduction in use following introduction of the PCR test; however, this was nonsignificant at the 95% level. During the intervention period overall concordance between the PCR result and prescribing decisions was 84%. Conclusions The PCR assay for candidemia was requested, prescribing decisions were generally concordant with the results produced and there was an apparent decrease in antifungal prescription, although this was sustained even after withdrawal of the intervention; these findings should be more thoroughly evaluated in a larger trial.
Resumo:
Purpose: Theoretical modelling techniques are often used to simulate the action of ionizing radiations on cells at the nanometre level, Using monoenergetic vacuum-UV (VUV) radiation to irradiate DNA either dry or humidified, the action spectra for the induction of DNA damage by low energy photons and the role of water and can be studied. These data provide inputs for the theoretical models.
Resumo:
The aim of this paper is to identify and classify the numerous managerial issues encountered in the management of personnel in confined site construction. For the purpose of this research, a confined construction site is defined as a site where permanent works fit the site footprint, extending to levels above and/or below ground level, leaving spatial restrictions for other operations (e.g. plant and material movements, materials storage and temporary accommodation etc.) and require effective resource co-ordination beyond normal on-site management input. A literature review and analysis, case studies incorporating interviews and focus groups along with a questionnaire survey were used in order to gain a comprehensive insight into the issues in the management of personnel in a confined construction site environment. The following are the top five leading issues highlighted in the management of personnel in confined site construction; (1) Accidents due to an untidy site, (2) One contractor holding up another because of the lack of space, (3) A risk to personnel because of vehicular traffic on-site, (4) Difficult to facilitate several contractors at one work location, and (5) Numerous personnel working within the one space. In today’s modern environment, spatial restrictions are quickly becoming the norm in the industry. Therefore, the management of personnel on-site becomes progressively more difficult with the decrease in available space on-site. Where such environments exist, acknowledging the numerous issues highlighted above, aids site management in the supervision and co-ordination of personnel on-site, thus reducing accidents, increasing productivity and increase profit margins, in spatially restricted environments. As on-site management professionals successfully identify, acknowledge and counteract the numerous issues illustrated, the successful management of personnel on a confined construction site is achievable. By identifying the numerous issues, on-site management can proactively mitigate such issues through adopting counteractive measures and through successful identification of the traits identified.