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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
251

De-icing salt and the roadside environment : Air-borne exposure, damage to Norway spruce and system monitoring

Blomqvist, Göran January 2001 (has links)
After decades of investigation, we still have to deal withthe problem of environmental effects of the use of de-icingsalt on roads. Lacking useful indicators of the system, westill do not know the environmental utility of ameliorativemeasures taken. The thesis aims at i) describing the system of de-icing practices and theirenvironmental effects with special reference to the exposure ofthe roadside environment to air-borne salt and damage to Norwayspruce seedlings and ii) at proposing indicators for afollow-up system. By collecting bulk deposition and relatingthe deposition pattern to factors concerning wind androad-maintenance characteristics, the influence of thesefactors on air-borne exposure is investigated. By exposingNorway spruce (Picea abies(L.) Karst.) seedlings to roadsideconditions the influence ofsalt exposure on the degree ofdamage is investigated. Based on a comparison of severalsystems of monitoring, improvements are suggested by proposingnew indicators for salt use and its environmental effects. A large part of the salt that is applied on the road surfacewill be transported by air and deposited on the ground in theroadside. While the vast majority of the salt will be depositedwithin some tens of metres of the road, some may still be windtransported several hundred metres away. The wind directionplays an important role for the deposition already at adistance of some ten metres from the road. Wind speedinfluences the distance to which the salt is transported.Chloride concentration in unwashed needles collected after thesalting season is positively related to the bulk deposition ofCl during the exposure. The degree of damage can be describedby a sigmoid curve of response to the Cl concentration inneedles. Improvements to the follow-up system are suggested byproposing indicators of the driving forces, pressures, states,impacts and possible responses as regards the undesired impactson water resources, vegetation and the roadside scenery as asocietal asset. <b>Keywords:</b>road, de-icing salt, air-borne, environmentalimpact, vegetation damage, Norway spruce, seedling, follow-up,monitoring, indicator
252

Ekologiska fotavtryck för koldioxidutsläpp för Stockholms län, Norrbottens län och Stockholms läns landsting : En kritisk metodgranskning baserad på kvantitativa data

Johansson, Bodil January 2007 (has links)
Human existence and welfare depend on functional ecosystems. Ecosystems are critical to sustain life-support services for human well-being. One method that visualizes that humanity requires ecosystem services for resource consumption and assimilation of produced waste is ecological footprints. This study focuses on the ecosystem service carbon sequestering. A quantification of this ecosystem service showed the potential for accumulation of carbon in different ecosystems in Stockholm and Norrbotten County for the years of 1995 and 2004. This study also provides an estimate of the ecosystem area that is appropriated to accumulate all carbon from total carbon dioxide emissions in Stockholm and Norrbotten County respectively. The appropriated ecosystem area represents the ecological footprint. The ecological footprint is also calculated for Stockholms läns landsting`s total carbon dioxide emissions in 2004. The total potential for accumulation of carbon is lower in the ecosystems in Stockholm County in 2004 than in 1995 and the corresponding figure for Norrbotten County has increased. The results indicate that the total potential for carbon accumulation in Stockholm County was approximately 427 kton C year-1 in 1995 and 352 kton C year -1 in 2004. In 1995 the ecosystems in Stockholm County could assimilate 26% of the county’s total emissions whereas the figure for 2004 was 21%. In Norrbotten County, the total potential for accumulation was approximately 2 824 kton C year -1 in 1995 and 2 983 kton C year -1 in 2004. The ecosystem area that is appropriated to assimilate total emissions of carbon dioxide was smaller in 2004 than in 1995 in Stockholm County and larger in Norrbotten County. The ecological footprint for total carbon dioxide emissions in Stockholm County was 12 696 km2 in 1995 and 12 506 km2 in 2004. The corresponding estimate for Norrbotten County indicate that the ecological footprint for total carbon sequestering was 14 457 km2 in 1995 and 32 146 km2 in 2004. The result shows that both regions require large areas of ecosystem to absorb total emissions of carbon dioxide. Stockholms läns landsting´s ecological footprint was 409 km2, which corresponds to 3.3 % of the County’s total ecological footprint. Stockholm County depends on ecosystem areas outside the region for assimilation of the region’s total emissions of carbon dioxide. According to the results Norrbotten County is self-sufficient with regard to the ecosystem service carbon accumulation. This study also includes a discussion of the advantages and limitations of the ecological footprint as a methodology. The received results serve as the starting point for this discussion. Ecological footprints are pedagogic and communicative indicators and can therefore reach out to a broad audience which is a great advantage with the method. It is a static measure and is therefore incapable of giving any presages. Ecological footprints do not take the dynamics and complexity of ecosystems into account and can therefore not provide any information about the possibilities for ecosystems to deliver ecosystem services at the same quality and quantity in the future. The method does not take socio-economic factors into consideration. For these reasons, ecological footprint should not be used as an indicator for sustainability. On the other hand, ecological footprint can illustrate why an ecologically sustainable development is necessary by visualizing that human welfare and existence rely on functional ecosystems.
253

Microbial Risk Perspective on the Temporal and Spatial Variability of Indicator Bacteria in Texas Urban and Rural Watersheds

Srinivasan Ravichandran, Sriambharrish 2011 May 1900 (has links)
The high incidence of pathogens is one of the main causes for impaired surface water quality designations in the United States. Pathogen presence in fresh water is monitored through the detection of indicator bacteria. Indicator bacteria concentrations, spatial and temporal variability, and microbial risks were evaluated in two rural watersheds, the Bosque and Leon Rivers, and one predominantly urban watershed, the San Jacinto River, all in Texas. Human health risk was predicted from contaminated waters as indicated by ingestion of Escherichia coli found in surface water for contact recreation scenarios. The watersheds were chosen because many segments were previously placed on the 303 (d) list (published by the TCEQ) for failing the indicator bacteria standards. Predominantly urban areas of the San Jacinto River and rural portions of the Bosque and Leon Rivers, where Concentrated Animal Feeding Operations (CAFOs) are numerous, were compared to relatively pristine rural watersheds. Spatial analysis of the watersheds with E.coli concentrations exceeding the single sample (394 MPN/100mL) and the geometric mean standards (126 MPN/100mL) indicated that land use is a significant factor influencing the incidence of bacterial concentrations. Non-agricultural rural areas of the watersheds, such as forests and rangelands, had significantly lower E.coli concentrations compared to the agricultural areas and urban land uses. Human health risk due to ingestion of E.coli as an indicator organism indicated a similar pattern to that of their concentrations in that urban and agricultural areas had a greater risk compared to the other rural areas of the watersheds. The risk estimate for urban and agricultural areas exceeded the acceptable limit of one in ten thousand (10^-4), indicating a potential for adverse health effects to humans. Temporal variability in the watersheds as a function of streamflow, rainfall, and temperature indicated a positive correlation between bacterial concentration and high streamflow, rainfall and temperature. The positive correlation for these effects was greater in the rural areas compared to urban areas, indicating the presence of multiple factors responsible for E.coli concentrations in urban areas. Thus, land use was confirmed to be a major factor contributing to the presence of indicator bacteria in surface waters.
254

Evaluation of the Compartment Bag Test for the Detection of Escherichia coli in Drinking Water

Miller, Candace D 17 May 2013 (has links)
INTRODUCTION: More than 1.8 million diarrheal disease deaths can be attributed to the lack of access to water, sanitation and hygiene. These deaths occur mostly in developing countries where water quality testing resources are limited. Several tests are currently used to detect and quantify E. coli and other fecal coliforms in drinking water, however they can be expensive, complex, and technically demanding. There is a need for a simple, reliable, low-cost water quality test that can be used in resource limited settings. Therefore, the purpose of this research was to perform a rigorous evaluation of the recently developed compartment bag test for detection and quantification of E. coli against the standard method, membrane filtration. METHODS AND RESULTS: A total of 270 water samples were collected from forty-five various naturally contaminated water sources around metro-Atlanta from August 2011 through April 2012 and processed using the compartment bag test and membrane filtration with mI agar. Concentrations of E. coli were significantly correlated with a correlation coefficient of 0.904 (95% CI 0.859 – 0.950). Sensitivity and specificity were 94.9% and 96.6%, respectively. CONCLUSION: These results suggest that the compartment bag test produces results consistent with those produced by membrane filtration on mI agar. Based upon its performance, the compartment bag test has the potential to be used as a reliable, low-cost drinking water quality test globally where water quality testing resources are not readily available, and can be implemented in monitoring activities for microbial water quality.
255

Distributional patterns of diatom communities in Mediterranean rivers

Tornés Bes, Elisabet 03 April 2009 (has links)
Aquesta tesi tracta la jerarquia i l'heterogeneïtat dels sistemes fluvials que afecten l'estructura de les comunitats bentòniques de diatomees. A nivell regional, es van buscar diferents grups de punts i les seves espècies indicadores, es va estudiar la resposta de les comunitats de diatomees als gradients ambientals, es va avaluar la utilitat de diferents índexs de diatomees i es va buscar el millor sistema de classificació per a condicions de referència. A nivell de conca, es volien definir els factors que determinen la distribució longitudinal de la diversitat de les comunitats de diatomees. Finalment, a nivell d'hàbitat es van determinar quins factors afecten les algues i els cianobacteris a aquesta escala i es va examinar la contribució relativa de l'ambient i l'espai en la distribució de la biomassa i composició d'algues i cianobacteris. Per tant, els diferents capítols d'aquesta tesi han estat desenvolupats seguint aquest esquema. / This thesis deals with the hierarchy and heterogeneity of stream systems affecting the structure of benthic diatom communities. At a regional level, I search for different groups of sites and their indicator taxa, I studied the responses of the diatom communities to the gradients of environmental variables, I tested the usefulness of diatom indices and I searched for the best classification system for reference conditions. At a watershed level my interest was to define the factors that determined the longitudinal distribution of diversity of diatom communities. Finally, at a habitat level it was interesting to determine the factors affecting algae and cyanobacteria at this scale and examine the relative effects of environmental factors and space on the distribution of biomass and composition of benthic algae and cyanobacteria. Thus, the different chapters of the thesis had been approached following this scheme.
256

Sources of human pathogens in urban waters

Younis Hussein, Mariam January 2009 (has links)
The presence of human pathogens in water indicates the sanitary risk associated with different types of water utilization. This study surveyed the sources of human pathogens in urban waters. In order to evaluate the microbiological water quality of urban water, the enumeration of various indicator bacteria (total coliform, fecal coliform, E.coli and enterococci) is usually used. The abundance of indicator bacteria in urban water indicates the level of fecal contamination and the presence of other human pathogens such as protozoan pathogens (Giardia lamblia & Cryptosporidium parvum). Fecal pollution of urban waters can be from human and animal origin. Point sources of fecal contamination in an urbanized area are the effluents of urban wastewater treatment plants. While non-point sources are usually originated from diffuse sources such as (runoff from roads, parking lots, pets, leaks, failing septic systems and illegal sewer connections to storm drains). urban stormwater is considered as a major carrier for delivering human pathogens from diffuse sources to receiving waters. Increases in urban stormwater volumes have resulted from increasing urbanization and growth of impervious surfaces. In order to reduce high amounts of human pathogens in urban waters, different methods are used nowadays to develop urban wastewater treatment plants technologies and urban stormwater management practices.
257

Didaktiska arter

Hylin, Anna January 2012 (has links)
The study intends to find easily recognizable indicator species for water quality in the constructed wetland of Flemingsbergsviken. The study is relevant since indicator species can be difficult to determine for common people. Easily recognizable indicator species could improve dialogue between the scientific community, administrative authorities and the general public. Such species could be used in education systems, associations or in information campaigns. Therefore, I have chosen to refer to these species as didactical species. Water quality was examined by measuring conductivity, pH and oxygen content in relation to distance from the wetland inlet. The results demonstrate a significant correlation between conductivity and distance. Species occupy different ecological niches and distribution patterns of species in the wetland can be expected to follow changes in abiotic factors, such as water quality. Potential indicator species were investigated by inventorying twelve species of plants and animals. The results show significant linear or curvilinear correlations between one or several water quality factors and the species reedmace, common reed, yellow iris, freshwater woodlouse, twisted ramshorn, damsel- and dragonfly larvae. By carrying out a questionnaire aimed at a group of adults and by talking to a group of children, conclusions could be made regarding indicator species that were easy to recognize and associate to. The results demonstrate that adults found common reed and reedmace most easy to recognize while children found the freshwater woodlouse most interesting. Thus, these indicator species for water quality can be included in the concept didactical species. / Studien syftar till att finna indikatorarter för vattenkvalitet i Flemingsbergsvikens våtmarksanläggning som är lätta att känna igen och associera till. Studien är relevant då indikatorarter kan vara svårbestämda för gemene man. Arter som är lättigenkännbara skulle kunna förbättra dialog mellan forskarsamhället, allmänheten och myndigheter och kan användas i utbildningssyfte inom skolor, föreningar eller i informationskampanjer. Jag har därför valt att kalla arterna för didaktiska arter. Vattenkvalitet undersöktes genom att mäta konduktivitet, pH och syrgashalt i förhållande till avstånd från inlopp. Resultaten visade att det finns ett signifikant samband mellan konduktivitet och avstånd. Eftersom arter upptar olika ekologiska nischer kan artutbredningsmönstret i våtmarken förväntas följa förändringar i abiotiska faktorer, såsom vattenkvalitet. Potentiella indikatorarter undersöktes genom att inventera tolv växt- och djurarter i anläggningen. Resultaten visar signifikanta linjära eller kurvlinjära samband med en eller flera utav vattenkvalitetsfaktorerna och arterna bredkaveldun, vass, gul svärdslilja, sötvattengråsugga, remskivsnäcka samt trollsländelarver. Genom en enkätundersökning för en grupp vuxna samt samtal med en grupp förskolebarn kunde det dras slutsatser om vilka av indikatorarterna för vattenkvalitet som var lättast att känna igen och associera till. Resultaten visar att de vuxna upplevde vass och bredkaveldun som lättast att känna igen medan barnen upplevde att sötvattengråsugga var mest intressant. Dessa indikatorarter för vattenkvalitet kan således inkluderas i begreppet didaktiska arter.
258

Patterns and Behavioural Outcomes of Antipsychotic Use among Nursing Home Residents: a Canadian and Swiss Comparison

Arditi, Chantal January 2006 (has links)
<b>Background. </b> Although antipsychotic medications are primarily intended to treat schizophrenia and psychotic symptoms in adults, they are commonly administered to nursing home residents as pharmacotherapy for "off-label" indications such as disruptive behaviour. However, clinical trials have demonstrated limited efficacy and serious side-effects of antipsychotics among the elderly. As previous studies have reported inappropriate use in several countries, their use in nursing home residents ought to be monitored to detect and reduce inappropriate administration. <br /><br /> <b>Objectives. </b> The aim of this study was a) to determine and compare prevalence rates of antipsychotic use in Ontario and Swiss nursing homes, b) to identify determinants of antipsychotics use in these two countries, by means of a cross-sectional design, and c) to investigate the impact of antipsychotic use on behaviours over time in Ontario and Swiss residents, by means of a longitudinal design. <br /><br /> <b>Methods. </b> This study involved secondary data analysis of 1932 residents from 24 nursing homes in the province of Ontario in Canada and 1536 residents from 4 nursing homes in a German-speaking canton in Switzerland. Residents were assessed with the Minimum Data Set (MDS) tool. Resident characteristics and prevalence rates were compared internationally with the chi-square test. Demographic and clinical determinants of antipsychotic use, as well as behavioural change associated with antipsychotics, were analyzed using logistic regression. <br /><br /> <b>Results. </b> Although Ontario nursing home residents had an overall heavier-care profile than Swiss residents, antipsychotics were administered to 25% of the Ontario residents compared to 29. 5% of the Swiss residents. The adjusted rate among residents without appropriate conditions was also lower in Ontario (14%) than in Switzerland (24. 5%). Apart from schizophrenia, bipolar disorder and cognitive impairment, antipsychotic use was determined by a different range of characteristics in these two countries. Antipsychotic use was not predictive of behavioural improvement. <br /><br /> <b>Conclusion. </b> The high adjusted rates of antipsychotic use in Ontario and Swiss nursing home residents, as well as the presence of "inappropriate indications" and "facility" as determinants of their use, raise concerns about the appropriateness of their administration in both countries. Their lack of effectiveness to improve behaviours also questions their use as long-term treatment for behaviour disturbances. Changes in practice patterns and implementation of policies are warranted to reduce inappropriate prescribing practices to enhance the quality of care provided to residents in nursing homes.
259

Naturvärdesbedömning av naturreservatet Blänkabacken, i Örebro kommun : Inventering av signalarter med fokus på mossor och lavar som indikerar höga naturvärden i skogsmiljöer. / Assessment of biodiversity values in the nature reserve Blänkabacken, Örebro Municipality : Inventory of indicator species with focus on bryophytes and lichens that indicate high nature value in forest enviroments.

Pettersson, Kristin January 2011 (has links)
No description available.
260

Improving WiFi positioning through the use of successive in-sequence signal strength samples

Hallström, Per, Dellrup, Per January 2006 (has links)
As portable computers and wireless networks are becoming ubiquitous, it is natural to consider the user’s position as yet another aspect to take into account when providing services that are tailored to meet the needs of the consumers. Location aware systems could guide persons through buildings, to a particular bookshelf in a library or assist in a vast variety of other applications that can benefit from knowing the user’s position. In indoor positioning systems, the most commonly used method for determining the location is to collect samples of the strength of the received signal from each base station that is audible at the client’s position and then pass the signal strength data on to a positioning server that has been previously fed with example signal strength data from a set of reference points where the position is known. From this set of reference points, the positioning server can interpolate the client’s current location by comparing the signal strength data it has collected with the signal strength data associated with every reference point. Our work proposes the use of multiple successive received signal strength samples in order to capture periodic signal strength variations that are the result of effects such as multi-path propagation, reflections and other types of radio interference. We believe that, by capturing these variations, it is possible to more easily identify a particular point; this is due to the fact that the signal strength fluctuations should be rather constant at every position, since they are the result of for example reflections on the fixed surfaces of the building’s interior. For the purpose of investigating our assumptions, we conducted measurements at a site at Växjö university, where we collected signal strength samples at known points. With the data collected, we performed two different experiments: one with a neural network and one where the k-nearest-neighbor method was used for position approximation. For each of the methods, we performed the same set of tests with single signal strength samples and with multiple successive signal strength samples, to evaluate their respective performances. We concluded that the k-nearest-neighbor method does not seem to benefit from multiple successive signal strength samples, at least not in our setup, compared to when using single signal strength samples. However, the neural network performed about 17% better when multiple successive signal strength samples were used.

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