Dissertations / Theses on the topic 'Extended exposure'

The purpose of this research was to determine the influence of extended dosing of zinc on the carbon cycling and biomass characteristics of freshwater epilithon. Experiments were conducted in artificial streams continuously dosed with 0.00, 0.05, or 1.00 mg Zn liter⁻¹ for 20 to 30 days during summer and fall, 1984 and 1985. Repeated measurement of epilithon structure and function included estimates of ¹⁴C-glucose respiration, ¹⁴C-glutamate respiration, O₂ and CO₂ flux rates, ash-free dry weight (AFDW), protein, carbohydrate, and algal pigment concentrations, and total and zinc-tolerant colony forming units. An increase in epilithic glucose respiration per unit biomass consistently occurred 5 to 10 days after dosing with 1.0 mg Zn liter⁻¹ was started. At the same time significantly lower epilithon biomass occurred in the high dosed streams relative to controls in 3 out of 4 studies. Although algal pigment concentrations were lowest in the high dose streams at the midpoint of the studies, the chlorophyll a-to-pheophytin a ratio remained high, indicating that the minimal algal population was not senescing in situ. After 30 days, the epilithon dosed with 1.0 mg Zn liter⁻¹ had higher AFDW, protein, and carbohydrate concentrations than the other treatments. By 20 days, the high zinc treatment showed evidence of more total and zinc-tolerant colony forming units and lower rates of O₂ and CO₂ flux than epilithon from control streams. The high rates of glucose respiration were characteristic of epilithic communities stressed by 1.0 mg Zn liter⁻¹, and this response was not apparently due to in situ senescence of zinc-sensitive cells; the results suggested that epilithic biomass was washed out of the systems, not being degraded in situ. The development of unique epilithon communities that are acclimated to prolonged zinc exposure is evident in the eventual recolonization of the artificial surfaces, glucose respiration rates that are comparable to controls, and presence of zinc-tolerant heterotrophs.
Ph. D.

It is well-established that the attention of alcoholics (as compared to non-alcoholics, or social drinkers) is captured more by alcohol-related than by neutral stimuli. This phenomenon is called an alcohol-related attentional bias (AAB). The traditional paradigms for measuring AAB have been the modified Stroop and visual dot-probe paradigms. I have adapted the flicker paradigm for induced change blindness paradigm (flicker ICB paradigm) from visual cognition. In the traditional use of the flicker ICB paradigm a singe change is implemented in a visual scene and then removed. If the change process is masked and the implementation/removal of the change is cycled, the change takes a surprisingly long time to spot. The theoretical underpinning of this phenomenon implies that the change is not detected unless attention is directed to the object carrying the change. In my own modification of this paradigm, two (not one) changes are simultaneously made and instructions to detect “the change” are given. In this way an alcohol-related and a neutral change are made to compete for attention. Using this paradigm the AAB hypothesis is that those detecting the alcohol-related change will have higher usual consumption that those detecting the neutral change. In a series of 12 studies, I have shown that social drinkers detecting the alcohol-related change have consumption levels above those detecting the neutral change: a differential AAB within social drinkers. Further, when the object carrying the alcohol-related change is embedded in the neutral group and the neutral object carrying the change is embedded in the alcohol group, the direction of the AAB is reversed. This suggests that the group of objects in which the changing object is embedded drives the change detection rather than the changing object, itself. A similar conclusion is reached when both changing objects are identically-alcohol or identically-neutral. Finally, the role of the context or group in driving change detection was confirmed by embedding the alcohol-changing and neutral-changing objects in groups that did not provide differential alcohol-related and neutral information. Under these latter conditions of test, the AAB disappeared. In the penultimate experiment reported in this thesis continuous eye-movement monitoring over 30 seconds to the same stimuli as described above (but not incorporating changes or masks) was used to measure attention towards alcohol-related objects even more directly. Using this method a differential AAB within social drinkers was shown. In a final experiment the more traditional version of the flicker ICB paradigm (containing a single change) was used to explore AAB in drinkers in treatment in which for the first time it was shown that AAB increased with alcohol problem severity.

Background & Aims: There is on-going and growing concern regarding acute and chronic human health effects associated with exposure to combustion-related air pollutants. This thesis describes the development and evaluation of novel methods for assessing exposure to combustion-related air pollutants [particulate matter (PM),black carbon (BC) and nitrogen dioxide (NO₂)] in indoor and outdoor environments. Methods: The methods that were developed and evaluated included: mass and darkness/colour analysis of airborne particle samples; passive samplers; portable real time monitors; and GC-MS analysis of particulate-bound polycyclic aromatic hydrocarbons (pPAHs). These methods were used to measure PM, BC and NO₂ in indoor offices and outdoor streets in Glasgow city centre, and an industrial hydraulic fracturing test site in Poland. Results: Detailed evaluation and calibration of novel methods for darkness measurement of low mass particulate material specimens collected on filters were completed to allow subsequent application in BC exposure estimation. Similarly,detailed evaluation allowed the refinement of procedures for field calibration of portable real-time monitors for BC, NO₂ and O₃. Indoor concentrations of PM, BC and NO₂ measured using the calibrated monitoring instruments were influenced by outdoor sources through natural ventilation and the proximity of buildings to urban roadsides. Outdoor measurements at 2 heights indicated that children are likely to experience higher exposures to combustion-related air pollutants from vehicle emissions. Marked elevations of BC and NO₂ concentrations were observed in downwind proximity to industrial fracking equipment sources, where average BC and NO₂ concentrations (11.2 & 111.3 μg/m³) were 2 to 3 times higher than average BC and NO₂ exposures experienced while walking in Glasgow city centre (3.7 & 42.3 μg/m³).Conclusions: Novel exposure science and environmental engineering approaches were developed to allow improved characterisation of short-term to medium-term personal and environmental exposures to combustion-related air pollutants in a wide range of occupational and environmental settings.

The effect of a single exposure of He-Ne laser on collagen content was studied in vivo using laboratory animals. A standardized 1.5 cm full thickness skin incision was made on the dorsum of 24 Sprague-Dawley rats. The rats were divided into six equal size groups, three groups functioning as controls and three groups functioning as experimental. The experimental animals were irradiated with He-Ne laser four days post-incision for 16 minutes to deliver a total dose of 5.99 J/cm$ sp2$. On days 6, 10 and 14 post-incision, control and experimental animals had the healing wounds excised for analysis of collagen content by assaying spectrophotometrically the hydroxyproline content within the tissue samples.
The results of the hydroxyproline content were analyzed using independent-groups t-test and analysis of variance. It was demonstrated that even though the mean values of hydroxyproline within the experimental groups were higher than the respective control groups, no statistical significance could be attributed to this observation.

Proučavane su koroziona postojanost i tendencija lepljenja različitihmaterijala u kontaktu sa tečnom Al–Si–Cu legurom. Ispitivanjem suobuhvaćeni čelik za rad na toplo, plazma nitrirani čelik i dupleksslojevi sa CrN, TiAlN, TiAlSiN i CrAlN prevlakama, različitog nivoapovršinske hrapavosti. Za ispitivanja pomenutih fenomenaprimenjena je metoda izvlačenja, koja je unapređena kako bi se povećalenjena tačnost i verodostojnost simulacije procesa livenja. Korozioniefekti su pojačani tako što su uzorci osim kratkog kontakta sa odlivkomzadržavani i u dužim periodima u kontaktu sa tečnom legurom (5 i 20min). Uprkos opštim stavovima, za ispitivane materijale jeustanovljeno da su sile izvlačenja uzoraka iz Al–Si–Cu odlivakanezavisne od njihovog hemijskog sastava. Uticaj hrapavosti je izraženkod uzoraka sa prevlakama kod kojih pri smanjenju hrapavosti dolazi dopovećanja sile izvlačenja. Sve ispitane prevlake su sklone mehaničkomlepljenju Al–Si–Cu legure za svoje površine, ali sa aspekta korozije utečnom metalu značajno prevazilaze performanse čelika i plazmanitriranog sloja. Duži kontakt livene legure sa površinama prevlakauzrokovao je niže vrednosti sila izvlačenja, što je posledicaoksidacije površina prevlaka. Ustanovljeno je da su ispitivaneprevlake inertne ka tečnoj leguri aluminijuma. Međutim, dolazi dooksidacije i korozije materijala podloge kroz greške rasta koje suprisutne u prevlakama. Stečena znanja o identifikovanimmehanizmima habanja i propadanja zaštitnih slojeva prevlakaposlužiće daljem razvoju dupleks slojeva namenjenih za zaštitu alataza livenje pod pritiskom.
Corrosion resistance and soldering tendency of different materials in moltenAl–Si–Cu alloy were studied. Hot-working tool steel, plasma nitrided steel andduplex layers with CrN, TiAlN, TiAlSiN and CrAlN top coatings, which wereproduced to various degree of surface roughness, were covered by the study.An ejection test was employed for investigation of the concerned phenomena.The ejection test was improved in order to increase its accuracy and thereliability of process simulation. Samples were examined in both short andextended periods of contact (5 and 20 min) with liquid casting. Castingsolidification was extended in order to intensify the corrosion effects. Contraryto common findings, it was found that the ejection force of the investigatedmaterials does not depend on their chemical composition. For the coatedsamples, a pronounced dependence of the ejection force on the surfaceroughness was found. The ejection force increases with decrease in surfaceroughness. All investigated coatings are prone to mechanical soldering by Al–Si–Cu alloy. Still, their corrosion resistance substantially exceeds the corrosionresistance of steel and plasma nitrided layer. Longer exposure of coatedsamples to cast alloy induced lower ejection forces, which is a consequenceof coatings oxidation. It was found that the investigated coatings are inert toliquid aluminium. However, the underlying material undergoes oxidation andcorrosion through coating growth defects. The findings concerning the wearmechanisms of protective layers support further development of duplex layersintended for die casting tools protection.

abstract: Air pollution has been linked to various health problems but how different air pollutants and exposure levels contribute to those diseases remain largely unknown. Researchers have mainly relied on data from government air monitoring stations to study the health effects of air pollution exposure. The limited information provided by sparse stations has low spatial and temporal resolution, which is not able to represent the actual exposure of individuals. A tool that can accurately monitor personal exposure provides valuable data for epidemiologists to understand the relationship between air pollution and certain diseases. It also allows individuals to be aware of any ambient air quality issues and prevent air pollution exposure. To build such a tool, sensors with features of fast response, small size, long lifetime, high sensitivity, high selectivity, and multi-analyte sensing are of great importance. In order to meet these requirements, three generations of novel colorimetric sensors have been developed. The first generation is mosaic colorimetric sensors based on tiny sensor blocks and by detecting absorbance change after each air sample injection, the target analyte concentration can be measured. The second generation is a gradient-based colorimetric sensor. Lateral transport of analytes across the colorimetric sensor surface creates a color gradient that shifts along the transport direction over time, and the sensor tracks the gradient shift and converts it into analyte concentration in real-time. The third generation is gradient-based colorimetric arrays fabricated by inkjet-printing method that integrates multiple sensors on a miniaturized sensor chip. Unlike traditional colorimetric sensors, such as detection tubes and optoelectronic nose, that are typically for one-time use, the presented three generations of colorimetric sensors aim to continuously monitor multiple air pollutants and the sensor lifetime and fabrication methods have been improved over each generation. Ozone, nitrogen dioxide, formaldehyde and carbon monoxide are chosen as analytes of interest. The performance of sensors has been validated in the lab and field tests, proving the capability of the sensors to be used for personal exposure monitoring.
Dissertation/Thesis
Doctoral Dissertation Chemistry 2019

碩士
國立中央大學
通訊工程研究所碩士在職專班
97
The photo captured by the camera is often different from what we see due to the limited dynamic range of the camera sensors. To produce an image with true luminance, the high dynamic range (HDR) image capturing technique is a good solution. It provides a wider dynamic range than the traditional techniques, and is able to re-produce the luminance with high fidelity. This work proposes an adaptive high dynamic range image fusion algorithm. By utilizing the exposure curve characteristics of image sensors and the exposure parameters of each image, it can convert the actual luminous intensity into image data with high accuracy. This method can extend the linear range of the luminous intensity by effectively fusing images with different exposures. The luminance processing is based on the principle of preserving the image information so as to re-produce the true luminous distribution of the image. In addition, the edge information is also kept with the propose method. The simulation results show that the proposed algorithm is able to reach wide system dynamic range. Both objective and subjective measures show superior performance compared with existing methods. With different capturing environments, it generally produces high dynamic range images with better performance of details and contrast in both bright and dark areas.

The potent neurotoxin saxitoxin (STX) belongs to a group of structurally related analogues, collectively known as the paralytic shellfish toxins, produced by both marine and freshwater phytoplankton. This group of toxins act by blocking the voltage-gated sodium channels, halting the inflow of sodium ions and the subsequent generation of action potentials. While acute exposure has been well researched, with safety guidelines applied, chronic low dose exposure from neither marine or freshwater sources has been investigated. Given the role of cellular electrical activity in neurodevelopment this latter pattern of exposure may be of significant public health concern. This background has been addressed in chapter 1; “Low dose extended exposure to saxitoxin and its potential neurodevelopmental effects: a review”, and the published manuscript can be found in Appendix 1. Given this lack of investigation we aimed to determine if STX had an adverse effect on neurodevelopment following low dose extended exposure using two models of neuronal development. Further, we aimed to establish an assay which could be used to determine if any adverse neurodevelopmental effects recorded were due to direct STX toxicity. Firstly, using model neuronal cell lines it was shown that STX at or below the current drinking water guideline (0.25-3μg/L) caused a significant concentration dependent decrease in the development of neuronal morphology following an extended exposure period. This research is presented in chapter 2; “Extended low-dose exposure to saxitoxin inhibits neurite outgrowth in model neuronal cells” and the published manuscript can be found in Appendix 2. In addition to investigating the neurodevelopmental effects of STX, an assay measuring viability indirectly through cellular metabolism was established to be used with STX. The assay was used to eliminate the possibility of nonspecific cell toxicity as a cause of the effects on neurodevelopment. The assay was successfully optimised in two cell lines and tested with STX (0.25- 10μg/L) and ZnSO4 (10-4-10-1M), a known cytotoxic compound. The assay showed that STX is not toxic in our cell line under the conditions used for chapter 2. These results are reported in Chapter 3; “Optimisation of a real time resazurin based assay for use in OVCAR-3 and SH-SY5Y cells”. Moving to a model which more accurately models mammalian neuronal differentiation, the effect of STX at the drinking water guideline (3μg/L) and a predicted algal bloom concentration (10μg/L) was investigated using embryonic stem cells. Cells were differentiated using a previously described method of neuronal differentiation and assessed by examination of morphological development of neuronal features and expression of gene markers. A concentration dependent decrease in morphological neuronal index scores was recorded, confirming the results of chapter 1, in addition the expression of neuronal markers nestin and MAP2 were increased following exposure to STX (3μg/L) while ßIII-Tubulin was delayed by 3 days in both STX treatment groups. This research is presented in chapter 4; “Low dose exposure to saxitoxin affects neuronal differentiation of D3 embryonic stem cells”. These results suggest that STX, and potentially its analogues, interfere with proper neuronal development at environmentally relevant concentrations. Whilst further work is required to investigate the mechanisms causing the adverse effects seen, the work presented here raises awareness that this pattern of exposure could be of significant public health concern and deserves further investigation.
Thesis (Ph.D.) (Research by Publication) -- University of Adelaide, Adelaide Medical School, 2017.

Dissertação de Mestrado em Bioquímica apresentada à Faculdade de Ciências e Tecnologia
A linha celular contínua BEAS-2B, derivada de células epiteliais brônquicas humanas normais, foi estabelecida em 1988, pelo grupo de Curtis C. Harris, como um modelo in vitro do epitélio brônquico normal, para o estudo da carcinogénese pulmonar.De igual maneira às células de outras linhas celulares contínuas, as células BEAS-2B sofrem variações genéticas e fenotípicas quando cultivadas in vitro por longos períodos de tempo, nomeadamente ao nível da expressão genética e morfologia. Estas variações podem explicar, pelo menos em parte, as inconsistências encontradas na literatura em estudos que utilizaram esta linha celular. Mais importante, a linha celular alterada pode deixar de ser um modelo confiável do material original.O primeiro objetivo de presente estudo foi caracterizar ainda mais os efeitos das passagens sucessivas no fenótipo da linha celular BEAS-2B, nomeadamente no conteúdo proteico, taxa de produção de lactato, capacidade migratória, resposta ao stress e resistência a concentrações levemente citotóxicas de dicromato de potássio, um agente carcinogénico pulmonar. Observámos que duas destas características (resposta ao stress e taxa de produção de lactato) variaram significativamente ao longo do tempo em cultura. Em conjunto, as nossas observações e as de outros sugerem que o grau de transformação desta linha celular muda com as passagens extensivas.O segundo objetivo do presente trabalho foi avaliar o impacto da exposição prolongada a uma leve concentração citotóxica de Cr(VI) em várias características da linha celular BEAS-2B, nomeadamente na morfologia e padrão de crescimento, taxa de crescimento, potencial clonogénico e resistência a Cr(VI). Concluímos que a exposição ao Cr(VI) por vários meses afetou a morfologia e o padrão de crescimento da linha celular BEAS-2B e diminuiu as suas taxas de crescimento. Por outro lado, não foram observadas diferenças significativas no potencial clonogénico e na resistência ao Cr(VI).
The BEAS-2B continuous cell line, derived from normal human bronchial epithelial (NHBE) cells, has been established in 1988, by the group of Curtis C. Harris, as an in vitro model of normal bronchial epithelium, for the study of lung carcinogenesis.Similar to cells from other continuous cell lines, the BEAS-2B cells are known to undergo genetic and phenotypic variations when grown in vitro over extended periods of time, namely at the level of gene expression and morphology. These variations might explain, at least partly, inconsistencies found in the literature in studies conducted using this cell line. Importantly, the altered cell line may no longer be a trustworthy model of the original material.The first aim of the present study was to further characterize the effects of extended passaging on the phenotype of the BEAS-2B cell line, namely in terms of protein content, rate of lactate production, migratory capacity, stress response and resistance to mildly cytotoxic concentrations of potassium dichromate, a lung carcinogen. We found that two of these traits (stress response and rate of lactate production) changed significantly over time in culture. Altogether, our observations and those of others suggest that the degree of transformation of this cell line changes upon extensive passaging.The second aim of the present study was to assess the impact of a prolonged exposure to mildly cytotoxic concentration Cr(VI) on several traits of the BEAS-2B cell line, namely their morphology and pattern of growth, growth rate, clonogenic potential and resistance to Cr(VI). We found that exposure to Cr(VI) for several months changed the morphology and the growth pattern of the BEAS-2B cell line and decreased its growth rates. On the other hand, no significant changes were observed in terms of clonogenic potential and resistance to Cr(VI).
Outro - 16/12
Outro - PTDC/BTM-SAL/29297/2017;POCI-01-0145-FEDER-029297
Outro - UIDB/00070/2020
Outro - UIDB/04539/2020

碩士
中國文化大學
國際企業管理研究所
90
Facing the variety of consumer’s demand nowadays, firms develop market in different segments. Firms operate market by using different ways as well as different types of information exposure. However, what are consumers’ response to the exposure of information? Do the perceived values of consumers be influenced by the extends of different information exposure? These topics are really worth study. This study, which is the first try, integrate 3 constructs of information exposure, the information exposure content, the information exposure volume and the information exposure frequency in consist of the extend of information exposure. Try to measure and to explicit the relationship between the extend of information exposure and consumers perceived values by adopting varies of products categories and products involvements as moderators. Random samples are selected from individual consumers, located at Taipei city and Taipei county, and reached a total of 1205 valid questionnaires. The results of this study support the hypothesis that the degree of exposure content is related positively to the degree of influence in consumers perceived values. Whereas, the degree of exposure frequency and exposure volume are unrelated to consumers perceived values. However, the products categories have significant difference between information exposure and consumers perceived value. In addition, the results indicate a significant positive association between the information exposure and consumers perceived value in consumers incomes.. On the contrary, it also indicates that a significant negative association between the information exposure and consumers perceived values in consumers educational backgrounds. Therefore we suggest that a firm should persuade consumers of different levels into objective products in different ways besides a firm should fully disclose the information if the objective product is superior on that attribute.