Dissertations / Theses on the topic 'Ultraviolet light (UVB)'

Mast cells (MCs) play a central role in inflammation by releasing mediators following activation. S100A8 and S100A9 are abundantly expressed in inflammatory sites such as asthmatic lung, sunburnt skin and atherosclerosis where MCs are involved in pathogenesis; roles of S100A8 in MC function are undetermined. The aims of this thesis were to determine effects of S100A8 on MC activation, particularly provoked by IgE and UVB. Initially, effects of UVB on MC activation were investigated as detailed functions were unclear. Cord blood-derived human mast cells (CBMCs) were treated in vitro with varying doses of UVB and production of multiple cytokines and viability investigated. UVB exposure selectively increased levels of IL-8 (CXCL8), and to a less extent IL-1β, but not eight other cytokines tested. New protein synthesis partially contributed and IL-8 production was p38 MAPK-dependent. UVB dose-dependently induced MC apoptosis indicating a potential regulatory mechanism of MC function. The ability of recombinant S100A8, S100A9 or S100A8/9 heterodimer to modulate IgE/antigen (DNP/anti-DNP)-mediated activation of a murine MC line, and of bone marrow-derived (mBM) MC activation was determined. The S100s did not directly induce degranulation or induce IL-6. S100A8 significantly inhibited DNP/anti-DNP-provoked degranulation, and IL-6 and TNF mRNA and protein induction. S100A8 did not alter FcεRIα expression. S100A9 was less effective; and the S100A8/9 complex was also suppressive. S100A8 only weakly suppressed non-specific MC degranulation. Mutation of Cys41 in S100A8 negated its suppressive activity. Because S100A8 scavenges oxidants via this reactive Cys residue, we propose that this may mediate its ability to downmodulate IgE-dependent MC responses. Similar to the thiol scavenger N-acetyl-L-cysteine, S100A8 but not the Ala41 mutant, attenuated DNP/anti-DNP-provoked LAT phosphorylation. However, the disulfide-bonded S100A8 dimer and S100A8 containing a sulfinamide bond between Cys41 and Lys34/35 also reduced MC activation, indicating an additional pathway(s). S100A8 did not suppress antigen/IgE-induced responses of CBMC possibly because these may not truly reflect fullymature human tissue MCs. S100A8 did not alter UVB-induced IL-8 release by CBMCs, or affect apoptosis. Murine S100A8 may have anti-inflammatory properties by regulating MC activation in an activator-specific manner, at least partially by scavenging ROS to suppress intracellular signalling.

Aluminum Gallium Nitride (AlGaN) / Gallium Nitride (GaN) based deep ultraviolet (DUV) light emitting didoes (LEDs) with emission wavelengths between 200-280 nm enable key emerging technologies such as water/air purification and sterilization, covert communications and portable bio-agent detection/identification systems for homeland security, and surface and medical device sterilization. These devices produce a large amount of undesired heat due to low quantum efficiencies in converting electrical input to optical output. These low efficiencies are attributed to difficulties in the growth&doping of AlₓGa₁₋ₓN materials and UV absorbing substrates leading to excessive joule heating, which leads to device degradation and a spectral shift in the emission wavelength. With this regard, effective thermal management in these devices depends on the removal of this heat and reduction of the junction temperature. This is achieved by decreasing the package thermal resistance from junction-to-air with cost-effective solutions. The use of heat sinks, thermal interface materials, and high conductivity heat spreaders is instrumental in the reduction of the overall junction-to-air thermal resistance. This thesis work focuses on thermal modeling of flip-chip packaged deep UV LEDs to gain a better understanding of the heat propagation through these devices as well as the package parameters that have the biggest contributions to reducing the overall thermal resistance. A parametric study focusing on components of a lead frame package is presented to ascertain the thermal impacts of various package layers including contact metallizations, thermal spreading sub-mounts, and thermal interface materials. In addition the use of alternative thermal interface materials such as phase change materials and liquid metals is investigated experimentally.

Orientadores Sylvio Luis Honório, Claudio Luiz Messias
Tese (doutorado) - Universidade Estadual de Campinas, Faculdade de Engenharia Agrícola
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Resumo: O cultivo da batateira (Solanum tuberosum L.) apresenta problemas fitossanitários decorrentes do ataque de pragas e doenças, o que acarreta altos cultos de produção. As principais doenças pós-colheita em batata-semente são: podridão seca (agente causal: Fusarium solani), rhizoctoniose (agente causal: Rhizoctonia solani) e podridão mole (agente causal: Pectobacterium carotovorum subsp. carotovorum). Os principais glicoalcaloides presentes na batata são a ?-chaconina e ?-solanina, os quais possuem propriedades antimicrobianas e podem ser estimulados por diversos fatores, com destaque para a luz. O objetivo desta pesquisa foi investigar a aplicação da radiação ultravioleta UV-C e da luz fluorescente no controle dos patógenos Fusarium solani, Rhizoctonia solani e Pectobacterium carotovorum subsp. carotovorum nas cultivares Ágata, Atlantic e Monalisa de batata-semente após a colheita. A pesquisa foi realizada em duas etapas: (I) avaliou-se in vitro o efeito da radiação UV-C no desenvolvimento das colônias de F. solani e de R. solani e na germinação dos conídios de F. solani. In vivo avaliou-se o efeito da radiação UV-C e da luz fluorescente na severidade e na incidência de podridão seca e de rhizoctoniose na brotação, na perda de massa e no teor de sólidos solúveis em batata-semente 'Agata' e 'Atlantic'; (II): avaliou-se in vitro o efeito da radiação UV-C no desenvolvimento das colônias de P. carotovorum subsp. carotovorum. In vivo avaliou-se o efeito da radiação UV-C e da luz fluorescente na severidade e na incidência da podridão mole, na concentração de ?-chaconina e de ?-solanina, na brotação, na perda de massa e no teor de sólidos solúveis em batata-semente 'Agata' e 'Monalisa'. A exposição de F. solani e R. solani a uma densidade de energia de 105,6 kJ.m-2 de radiação UV-C diminui o desenvolvimento das colônias desses fungos para estudos in vitro. Para a germinação de conídios de F. solani foi exposta a uma densidade de energia de 52,8 kJ.m-2 de radiação UV-C. Além disso, a luz fluorescente foi mais eficaz do que a radiação UV-C para o controle da podridão seca e da rhizoctoniose, sem afetar a brotação. A exposição de P. carotovorum subsp. carotovorum na densidade de energia de 34,5 kJ.m-2 de radiação UV-C inibiu o desenvolvimento das colônias para estudos in vitro. A luz fluorescente foi mais eficaz do que a radiação UV-C para controle da podridão mole em tubérculos de batata, assim como, estimulou a síntese de glicoalcaloides. O controle da podridão mole em tubérculos de batata está relacionado a maior concentração de ?-chaconina e ?-solanina, especialmente na periderme. Os teores de ?-chaconina (11,6 a 26,0 mg.kg-1P.F.) e ?-solanina (11,4 a 25,1 mg.kg-1P.F.) mostraram-se eficazes para o controle da podridão mole. Além disso, a brotação não foi afetada de forma adversa
Abstract: The cultivation of potato (Solanum tuberosum L.) in the tropics suffers the attack of pests and diseases, burdening the cost of production. The main postharvest diseases in potato seeds are the dry rot (pathogen: Fusarium solani), black scab (pathogen: Rhizoctonia solani) and wet rot (pathogen: Pectobacterium carotovorum subsp. carotovorum. The efficiency of UV-C against a wide variety of microorganisms has been reported and there is interest in applying for seed disinfection. Potato plants contain glycoalkaloids being ?-chaconine and ?-solanine the main ones. The accumulation of these glycoalkaloids can be stimulated by several factors, especially light, having them important antimicrobial properties. The aim of this research was to evaluate the the postharvest application of ultraviolet (UV-C) radiation and the fluorescent light to control the pathogens: F. solani, R. solani, and P. carotovorum subsp. carotovorum on 'Agata', 'Atlantic', and 'Monalisa' potato seeds. The research was conducted in two stages: (I) the evaluation in vitro of the effect of UV-C radiation on the growth of F. solani and R. solani colonies and F. solani conidias germination and the in vivo effect of UV-C radiation and fluorescent light on dry rot and black scab severity and incidence, mass loss and soluble solids content on 'Agata' and 'Atlantic' and (II) the evaluation in vitro of the effect of UV-C radiation on P. carotovorum subsp. carotovorum colonies and was reported in vivo the effect of UV-C radiation and the fluorescent light on the severity and incidence of wet rot, ?-chaconine and ?-solanine, concentration, tuber sprouting, weight loss and soluble solids on 'Agata' and 'Monalisa'. Exposure of R. solani and F. solani at an energy density of 105,6 kJ.m-2 of UV-C radiation decreases the development of fungi colonies in vitro. Energy density of 52,8 kJ.m-2 inhibited the F. solani conidias germination. Moreover the fluorescent light was more effective than UV-C radiation to control dry root and black scab, without affecting the sprouting. The in vivo experiments showed that treated and untreated. UV-C tubers stored under fluorescent light were more effective to control soft rot than the UV-C treated tubers and stored under darkness. Control tubers under fluorescent light, UV-C treated under darkness, and UV-C treated under fluorescent light showed an increased concentration of ?-chaconine (11,6 to 26,0 mg.kg-1F.W.) and ?-solanine (11,4 a 25,1 mg.kg-1F.W.) for both cultivars
Doutorado
Tecnologia Pós-Colheita
Doutor em Engenharia Agrícola

UV-C LEDs in the range of 265–280 nm are needed to develop new disinfection and biotechnology applications. The market share for UV-C LED, versus UV-C lamps (Hg discharge and Xe), increased from 8% in 2008 ($240M) to 25% in 2018 ($810M). However, while low-pressure mercury lamps are ~30% energy efficient, the best commercial UV-C LEDs in the 265–280 nm range are ~2% energy efficient; InGaN blue LEDs are 80% energy efficient. Research on AlGaN LEDs has made significant progress into AlGaN material quality (including threading dislocation density and n-AlGaN electrical conductivity) but has lagged regarding light extraction efficiency. Light extraction from UV LEDs is limited by p-GaN absorption because of the lack of p-contact to p-AlGaN with AlN fraction (AlN content > 50%). Furthermore, AlGaN emitters at the 265–280 nm range emit 40–50% of their emissions as transverse magnetic (TM) waves, which are harder to extract than transverse electric (TE) waves.

SiC is an absorbing substrate that has been largely overlooked in developing UV-C LEDs, even though it has a small lattice mismatch with AlN (~1%) and a similar Wurtzite crystal structure and is more chemically stable. We demonstrate the first lateral thin-film flip-chip (TFFC) ultraviolet (UV) light-emitting diodes grown on SiC. UV LEDs were made at 310 nm, 298 nm, 278 nm, and 265 nm.

In this dissertation, we discuss the design, epi development, and fabrication of TFFC AlGaN LEDs with reflective p-contacts. The AlGaN:Mg growth temperature and the Mg doping profile in AlGaN:Mg were found to significantly impact the electroluminescence (EL) efficiency of the AlGaN MQWs. KOH roughening enhanced the light-extraction efficiency (LEE) by 100% and by ~180–200% for UV LEDs with 10 nm p-GaN and 5 nm p-GaN, respectively, without affecting the devices’ IV characteristics. The thin-film architecture led to a high LEE of about ~28–30% without LED encapsulation when used with LEDs with 5 nm p-GaN. The best light extraction efficiency in the literature is ~24% (without LED encapsulation) for a 275 nm flip-chip LED grown on PSS sapphire substrate. KOH roughening of AlN is discussed and is compared to KOH roughening of N-Face GaN. To advance LEE further, we attempted to develop LEDs with transparent current n-AlGaN spreading layers as well as highly doped n⁺-AlGaN tunnel junctions on top of UV-C LEDs. Reflective and ohmic n-contacts with low resistivities were developed for the n-Al_.58Ga_.42N regrown by MBE. Furthermore, a highly reflective MgF₂/Al omnidirectional mirror was developed, which can be used with n-contact microgrid to further enhance the LEE in UV-C LEDs with a transparent tunnel junction.

Thesis (Ph.D.)--University of Wollongong, 2005.
Typescript. EMBARGOED - This thesis is subject to a 12 month embargo (07/03/06 to 07/03/07) and may only be viewed and copied with the permission of the author. For further information please Contact the Archivist. Includes bibliographical references: leaf 236-266.

Las enfermedades complejas se encuentran entre las más comunes y son causadas por una combinación de factores genéticos y ambientales (contaminación ambiental, estilo de vida, etc). Entre las enfermedades complejas que se pueden destacar se encuentran la obesidad, el asma, la hipertensión o la diabetes. Diversos estudios científicos sugieren que el hecho de padecer enfermedades complejas está condicionado a la aparición o acumulación de determinados factores ambientales. Asimismo, se ha descrito que los factores ambientales son unos de los principales contribuyentes a la carga mundial de morbilidad. Todo esto nos lleva a definir el término exposoma como el conjunto de factores ambientales a los que un individuo se ve expuesto desde la concepción hasta la muerte. El estudio de la mecánica subyacente que vincula el exposoma con la salud es un campo de investigación emergente con un fuerte potencial para proporcionar nuevos conocimientos sobre la etiología de las enfermedades. La primera parte de esta tesis se centra en la exposición a la radiación ultravioleta. La exposición a la radiación ultravioleta proviene de fuentes tanto naturales como artificiales. La radiación ultravioleta incluye tres subtipos de radiación según su longitud de onda (UVA 315-400 nm, UVB 315-295 nm y UVC 295-200 nm). Si bien la principal fuente natural de radiación ultravioleta es el Sol, la UVC no llega a la superficie de la Tierra debido a su absorción por la capa estratosférica de ozono. En consecuencia, la exposición a radiación ultravioleta a la que estamos usualmente sometidos consisten en una mezcla de UVA (95 %) y UVB (5 %). Los efectos de la radiación ultravioleta en humanos pueden ser beneficiosos o perjudiciales dependiendo de su cantidad y forma. Los efectos perjudiciales y agudos de la radiación ultravioleta incluyen eritema, oscurecimiento del pigmento, retraso en el bronceado y engrosamiento de la epidermis. Repetidas lesiones en la piel producidas por radiación ultravioleta pueden predisponer, en última instancia, a efectos crónicos de fotoenvejecimiento, inmunosupresión y fotocarcinogénesis. El mayor efecto beneficioso de la radiación ultravioleta es la síntesis cutánea de la vitamina D. La vitamina D es necesaria para mantener el calcio fisiológico y del fósforo para la mineralización ósea y para prevenir el raquitismo, la osteomalacia y la osteoporosis. El paradigma del exposoma es trabajar con múltiples exposiciones a la vez en vez centrarse en una sola exposición. Este enfoque permite tener una visión más parecida a la realidad que vivimos. Luego, la segunda parte se centra en las herramientas para explorar cómo caracterizar y analizar el exposoma y cómo probar sus efectos en múltiples capas biológicas intermedias para proporcionar información sobre los mecanismos moleculares subyacentes que vinculan las exposiciones ambientales a los resultados de salud.
Most common diseases are caused by a combination of genetic, environmental and lifestyle factors. These diseases are referred to as complex diseases. Examples of this type of diseases are obesity, asthma, hypertension or diabetes. Several empirical evidence suggest that exposures are necessary determinants of complex disease operating in a causal background of genetic diversity. Moreover, environmental factors have long been implicated as major contributors to the global disease burden. This leads to the formulation of the exposome, that contains any exposure to which an individual is subjected from conception to death. The study of the underlying mechanics that links the exposome with human health is an emerging research field with a strong potential to provide new insights into disease etiology. The first part of this thesis is focused on ultraviolet radiation (UVR) exposure. UVR exposure occurs from both natural and artificial sources. UVR includes three subtypes of radiation according to its wavelength (UVA 315-400 nm, UVB 315-295 nm, and UVC 295-200 nm). While the main natural source of UVR is the Sun, UVC radiation does not reach Earth's surface because of its absorption by the stratospheric ozone layer. Then, exposures to UVR typically consist of a mixture of UVA (95%) and UVB (5%). Effects of UVR on human can be both beneficial and detrimental, depending on the amount and form of UVR. Detrimental and acute effects of UVR include erythema, pigment darkening, delayed tanning and thickening of the epidermis. Repeated UVR-induced injury to the skin, may ultimately predispose one to the chronic effects photoaging, immunosuppression, and photocarcinogenesis. The beneficial effect of UVR is the cutaneous synthesis of vitamin D. Vitamin D is necessary to maintain physiologic calcium and phosphorous for normal bone mineralization and to prevent rickets, osteomalacia, and osteoporosis. But the exposome paradigm is to work with multiple exposures at a time and with one or more health outcomes rather focus in a single exposures analysis. This approach tends to be a more accurate snapshot of the reality that we live in complex environments. Then, the second part is focused on the tools to explore how to characterize and analyze the exposome and how to test its effects in multiple intermediate biological layers to provide insights into the underlying molecular mechanisms linking environmental exposures to health outcomes.

Harmful algae blooms (HABs) have caused millions dollars in annual losses to the aquaculture industry, inhibited beach recreation, and have threatened marine and human health. HABs and red tides can develop suddenly and their frequency, geographic range, and intensity have increased over the past decade. A possible source for spreading and seeding new areas expanding the geographic range of HABs is ballast water. The process of ballast water discharge has been identified as a primary vector for the translocation of non-indigenous species (NIS) and invasive species. National and international efforts are currently underway to address the impact of NIS and invasive species. Policy is being developed detailing stringent rules to kill, remove, or otherwise inactive organisms in ballast water prior to or upon discharge. Currently, vendors are developing technologies to treat ballast water and U.S. and international facilities are testing these technologies to verify their efficacy. Ultraviolet (UV) radiation is commonly employed in ballast water treatment technologies. Previous studies have shown that UV light is effective for disinfecting drinking water, but the response of non-pathogenic and marine organisms is largely unknown. The purpose of this research was to measure the viability of the durable red-tide forming dinoflagellate, Lingulodinium polyedra following UV treatment. Two methods were used to measure the viability signal; manual epifluorescence microscopy with correlated viability stains and Pulse Amplitude Modulated (PAM) fluorometry to measure the physiological state of the organism following UV treatment. The number of cysts was also enumerated. The results showed that there was a significant decrease in the number of living L. polyedra cells following a UV treatment of more than 100 mWs cm-2. The results also have showed a significant increase in the number of L. polyedra cysts following UV treatment as low as 50 mWs cm-2.

Ultraviolet radiation reaching the Earth’s surface (UVR, 280-400 nm) may penetrate deep into the clear oligotrophic waters influencing a large part of the euphotic layer. Marine heterotrophic bacteria at the surface of the oceans are especially sensitive to the damaging solar radiation due to their haploid genome with little or no functional redundancy and lack of protective pigmentation. In a context of climate change and ozone depletion, it is clearly important to understand the physiology and underlying molecular UVR responses of abundant marine bacteria species. We chose the marine ultramicrobacterium Sphingopyxis alaskensis as a reference species to study the impact of solar radiation due to its numerical abundance in oligotrophic waters and its photoresistance, previously reported. For this purpose, we focused on the formation of the two major UVB-induced DNA photoproducts (CPDs and 6-4PPs) as well as the differential protein expression under solar radiation. We first demonstrated that the GC content of prokaryotic genome had a major effect on the formation of UVB-induced photoproducts, quantified by HPLC-MS/MS. Due to its high GC content, S. alaskensis presented a favoured formation of highly mutagenic cytosine-containing photoproducts and therefore would be more susceptible to UVinduced mutagenesis. By comparing S. alaskensis to another marine bacterium Photobacterium angustum, we observed for the latter strain a remarkable resistance to high UVB doses associated with a decrease in the rate of formation of CPDs explained by a non-conventional activity of photolyase. We also demonstrated that DNA damage in S. alaskensis was markedly modulated by growth temperature and time spent in stationary phase. In order to assess the effects that environmental UV-R had on regulatory networks and pathways of S. alaskensis, and determine how the cell’s physiology was affected, a quantitative proteomics investigation was performed. Changes in proteome were analyzed, with the recent and powerful mass spectrometry based approach using iTRAQ methodology. Approximately, one third of the proteome of S. alaskensis was identified, with 119 statistically and significantly differentially abundant proteins. Cellular processes, pathways and interaction networks were determined and gave us unique insight into the biology of UV response and adaptation of S. alaskensis.

The use of smartphone for the detection of biological constituents is becoming a useful tool as a point-of-care (POC) device and diagnostics. When combined with microfluidic paper analytic devices (μPAD) and particle immunoassays, we have the ability to detect bacterial pathogens with sensitivity and specificity. Environmental conditions as well as variability in smartphone imaging and the cellulose in paper microfluidics however can sometimes easily interfere with the detection of small signal changes. Combining this issue with the detection of pathogens in blood (our model biological sample of interest) becomes difficult with such a platform because of the complexity of the sample matrix. However, in this research we take a novel approach at utilizing polystyrene’s auto-fluorescence and the high energy of UV LEDs in a particle immunoassay in order to increase our signal change. We first characterized how the smartphone actually responds to UV light (275-385 nm) with respect to the RGB components in its images. We were then able to determine a favorable response using the 385 nm UV LED. The detection of green fluorescence by polystyrene particles was possible by analyzing the smartphone’s image in the green channel. There was a significant difference in signal change with blood samples including polystyrene versus just blood samples with a normalized signal intensity change of 2.5 (150%). The detection of polystyrene fluorescence was translated into a field deployable prototype, where preliminary trials showed promising results in detecting Escherichia coli in blood with a current limit of detection of 50 CFU/ml. With further experimentation and optimization the limit of detection could be improved to 10 CFU/mL, making it a very useful tool in the detection of blood borne pathogens to prevent complications with onset bacteremia and the more serious cases of sepsis. This assay platform could provide an easy to use solution with detection in a short time (assay time of 1 min) compared to the lengthy blood culture monitoring or biomarker detection.

Patients of Hutchinson-Gilford Progeria Syndrome (HGPS) display a rate of aging up to ten times that of normal human populations. It might be expected that HGPS cells would have a decreased ability to repair DNA damage through the cell cycle as compared to normal cells such as those of the BJ cell line since DNA damage accumulation is a hallmark phenotype of aging. On earth, we are exposed to far more ultraviolet-B (UV-B, 280-315 nm) and UV-A (315-400 nm) than UV-C (100-280 nm) radiation, since the latter is filtered-out by the atmospheric ozone layer. The relative sensitivity of prematurely aging HGPS cells to UV-B irradiation is unknown. It was hypothesized that the normal fibroblast cell line (BJ) would exhibit a higher rate of DNA repair and a higher level of cell viability after exposure to ultraviolet radiation than would be observed with the HGPS cells, and that these differences would be greater as the HGPS cells age in culture. A Cell-Titer Blue Viability Assay (Promega) was used to determine the effect of UV-B and UV-C on metabolic activity, an indicator for cell viability, in HGPS, BJ, and A549 (a human lung carcinoma) cells. A translesion DNA synthesis protein, pol-η, and several other DNA transcription and repair-related proteins also were hypothesized to be altered in the HGPS cell line, both before and after UV-induced DNA damage, as compared to the BJ cell line. Western blotting was used to monitor these proteins in BJ and HGPS cells following UV-C exposure. No differences in short-term viability were observed between BJ and HGPS cells, reflecting similarities in their repair abilities on the cellular level; however, there were significant differences in long-term viability. Enzyme Linked Immunosorbant Assays (ELISA) revealed a significant difference in DNA repair at the molecular level. Moreover, Western blotting revealed differences in the amounts of several repair-related proteins following UV exposure, including pol-η, an important trans-lesion synthesis protein. Although the difference in DNA repair did not appear at the cellular level, it is apparent that HGPS cells show a greater sensitivity to both UV-B and UV-C irradiation as compared to normal BJ fibroblasts and A549 carcinoma cells.

This study presents the first attempt to combine the fields of ultraviolet (UV) photobiology, plant cell wall biochemistry, aerobic methane production and reactive oxygen species (ROS) mechanisms to investigate the effect of UV radiation on vegetation foliage. Following reports of a 17% increase in decomposition rates in oak (Quercus robur) due to increased UV, which were later ascribed to changes in cell wall carbohydrate extractability, this study investigated the effects of decreased UV levels on ash (Fraxinus excelsior), a fast-growing deciduous tree species. A field experiment was set up in Surrey, UK, with ash seedlings growing under polytunnels made of plastics chosen for the selective transmission of either all UV wavelengths, UV-A only, or no UV. In a subsequent field decomposition experiment on end-of-season leaves, a significant increase of 10% in decomposition rate was found after one year due to removal of UV-B. However, no significant changes in cell wall composition were found, and a sequential extraction of carbohydrate with different extractants suggested no effects of the UV treatments on cell wall structure. Meanwhile, the first observations of aerobic production of methane from vegetation were reported. Pectin, a key cell wall polysaccharide, was identified as a putative source of methane, but no mechanism was suggested for this production. This study therefore tested the effect of UV irradiation on methane emissions from pectin. A linear response of methane emissions against UV irradiation was found. UV-irradiation of de-esterified pectin produced no methane, demonstrating esters (probably methyl esters) to be the source of the observed methane. Addition of ROS-scavengers significantly decreased emissions from pectin, while addition of ROS without UV produced large quantities of methane. Therefore, this study proposes that UV light is generating ROS which are then attacking methyl esters to create methane. The study also demonstrates that this mechanism has the potential to generate several types of methyl halides. These findings may have implications for the global methane budget. In an attempt to demonstrate ROS generation in vivo by UV irradiation, radio-labelling techniques were developed to detect the presence of oxo groups, a product of carbohydrate attack by ROS. Using NaB3H4, the polysaccharides of ash leaflets from the field experiment were radio-labelled, but did not show any significant decrease in oxo groups due to UV treatments. However, UV-irradiation of lettuce leaves showed a significant increase in radio-labelling, suggesting increased UV irradiation caused an increase in the production of ROS. The study shows that the use of this radio-labelling technique has the potential to detect changes in ROS production due to changes in UV levels and could be used to demonstrate a link between ROS levels and methane emissions.

En aquest treball es va estudiar l’efecte dels tractaments UVC (llum ultravioleta C) en continu, utilitzant un reactor UVC amb unes característiques intrínseques específiques (Patent nº 2.965.766 B2), a la supervivència de Bacillus subtilis i altres microorganismes inoculats en diferents matrius alimentàries líquides de pH neutre amb diferent coeficient d’absorció (254 nm). A més, es van combinar els tractaments de UVC amb tractaments d’UHPH (Ultra Alta Homogeneïtzació per Pressió) a diferents pressions (100 i/o 200 MPa) i temperatures (20 i/o 60 ºC) per poder avaluar el possible efecte sinèrgic, additiu o complementari de les dues tecnologies (UHPH-UVC). Es van aplicar tres tractaments UVC (T1, T2 i T3) que diferien en el nombre d’entrades al reactor (valor NET), tot i que les dosis UVC aplicades van ser les mateixes (entre 10 i 160 J/ml). A les espores de B. subtilis inoculades en llet sencera, llet desnatada, liquat de soja i te verd els millors resultats es van obtenir en el tractament amb major valor NET (T3) i a la major dosi (160 J/mL), amb una letalitat en tots els casos igual o superior de 5 log. No obstant, la major eficàcia (p <0,05) es va obtenir en la matriu de menor coeficient el te verd, on no es van apreciar diferències en la letalitat en funció de la temperatura del reactor (4, 20 i 55 ºC). En el te verd i el liquat de soja, a més de B. subtilis, es varen inocular conidiospores d’Aspergillus niger, Escherichia coli i Listeria monocytogenes. El microorganisme més resistent als tractaments UVC va ser A. niger, la letalitat fins i tot amb el tractament T3 i a la màxima dosi (160 J/mL) no es va arribar a reduir 5 log. Les formes vegetatives d’E. coli i especialment L. monocytogenes van mostrar una major sensibilitat. Al liquat de soja, es va aconseguir una reducció de 5 log en el tractament T3 i a dosis de 120 i 80 J/mL, respectivament. Mentre que en el te verd, la dosi necessària amb el tractament T3 va ser de només de 10 J/mL en els tractaments T1 i T2 de 80 J/mL sobre E. coli. En el cas de L. monocytogenes, el te va mostrar per se mostrar activitat antilisteria. En els tractaments UHPH de 100 i/o 200 MPa a 20 i/o 60 ºC la letalitat obtinguda en la espores de B. subtilis inoculades en llet sencera i desnatada i liquat de soja va ser molt reduïda, però, en el cas de les conidiospores de A. niger en liquat de soja tractat a 200 MPa a 20 ºC i a 60 ºC es va aconseguir una reducció completa. Considerant l’efecte de la UVC en B. subtilis i de la UHPH en A. niger, es van aplicar de forma combinada tractaments UHPH i UVC. Tant per a les conidiospores d’A niger inoculades en liquat de soja com les espores de B. subtilis inoculades en liquat de soja, llet sencera i llet desnatada no es va observar efecte sinèrgic o additiu, sent la letalitat obtinguda similar als tractaments UVC en el cas del liquat de soja i llet sencera. En el cas de la llet desnatada va ser inferior. Només es va obtenir una letalitat més gran en la combinació UHPH i UVC en els tractaments T1 de la llet sencera, però la letalitat obtingudes va ser inferior a 2 log. En les matrius amb elevat coeficient d’absorció és difícil aconseguir una esterilització comercial ja que la dosi UVC estimades en els models van ser molt elevades, tot i que sí que seria factible en el te verd, especialment si es combinés amb UHPH.
En este trabajo se estudió el efecto de los tratamientos UVC (Ultravioleta C) en continuo, utilizando un reactor UVC con unas características intrínsecas específicas (Patente nº 2 965 766 B2), en la supervivencia de Bacillus subtilis y otros microorganismos inoculados en distintas matrices alimentarias líquidas de pH neutro con diferente coeficiente de absorción (254 nm). Además, se combinaron los tratamientos de UVC con tratamientos de UHPH (Ultra Alta Homogeneización por Presión) a diferentes presiones (100 y/o 200 MPa) y temperaturas (20 y/o 60 ºC) para poder evaluar el posible efecto sinérgico, aditivo o complementario de ambas tecnologías (UHPH-UVC). Se aplicaron tres tratamientos UVC (T1, T2 y T3) que diferían en el número de entradas en el reactor (valor NET), aunque las dosis UVC aplicadas fueron las mismas (entre 10 y 160 J/mL). En las esporas de B. subtilis inoculadas en leche entera, leche desnatada, licuado de soja y té verde los mejores resultados se obtuvieron en el tratamiento con mayor valor NET (T3) y a la mayor dosis (160 J/mL), con una letalidad en todos los casos igual o superior de 5 log. Sin embargo, la mayor eficacia (p < 0,05) se obtuvo en la matriz de menor coeficiente el té verde, no apreciándose diferencias en la letalidad en función de la temperatura del reactor (4, 20 y 55 ºC) . En el té verde y el licuado de soja inoculadas además de B. subtilis, con conidiosporas de Aspergillus niger, Escherichia coli y Listeria monocytogenes el microorganismo más resistente a los tratamientos UVC fue A. niger, cuya letalidad incluso con el tratamiento T3 y a la máxima dosis (160 J/mL) no se llegó a reducir 5 log. Las formas vegetativas de E. coli y especialmente L. monocytogenes mostraron una mayor sensibilidad. En el licuado de soja, se alcanzó una reducción de 5 log en el tratamiento T3 ya dosis de 120 y 80 J/mL, respectivamente. Mientras que en el té verde, la dosis necesaria con el tratamiento T3 fue de sólo10 J/mL y en los tratamientos T1 y T2 de 80 J/mL sobre E. coli. En el caso de L. monocytogenes el té mostró per se mostró actividad antilisteria. En los tratamientos UHPH de 100 y/o 200 MPa a 20 y/o 60 ºC la letalidad obtenida en la esporas de B. subtilis inoculadas en leche entera y desnatada y licuado de soja fue muy reducida, sin embargo, en el caso de las conidiosporas de A. niger en licuado de soja tratado a 200 MPa a 20 ºC y a 60 ºC se consiguió una reducción completa. Considerando el efecto de la UVC en B. subtilis y de la UHPH en A. niger, se aplicaron de forma combinada tratamientos UHPH y UVC. Tanto para las conidiosporas de A. niger inoculadas en licuado de soja como las esporas de B. subtilis inoculadas en licuado de soja, leche entera y leche desnatada no se observó efecto sinérgico o aditivo, siendo la letalidad obtenida similar a los tratamientos UVC en el caso del licuado de soja y leche entera y en el caso de la leche desnatada fue inferior. Solo se obtuvo una letalidad mayor en la combinación UHPH y UVC en los tratamientos T1 de la leche entera, sin embargo la letalidad obtenidas fue inferior a 2 log. En las matrices con elevado coeficiente de absorción es difícil conseguir una esterilización comercial ya que la dosis UVC estimadas en los modelos fueron muy elevadas, aunque sí que sería factible en el té verde, especialmente si se combinara con UHPH.
In this work we studied the effect of UVC (Ultraviolet C) treatments in continuous, using a UVC reactor with specific intrinsic characteristics (Patent No. 2 965 766 B2), on the survival of Bacillus subtilis and other microorganisms inoculated in different food matrices with pH neutral liquids over different absorption coefficient (254 nm). In addition, UVC treatments were combined with UHPH (Ultra High Pressure Homogenization) treatments at different pressures (100 and / or 200 MPa) and temperatures (20 and / or 60 ° C) in order to evaluate the possible synergistic, additive or complementary effect of both technologies (UHPH-UVC). Three UVC treatments (T1, T2 and T3) were applied that differed in the number of entries in the reactor (NET value), although the UVC doses applied were the same (between 10 and 160 J / mL). In B. subtilis spores inoculated in whole milk, skim milk, soy smoothie and green tea the best results were obtained in the treatment with the highest NET value (T3) and at the highest dose (160 J / mL), with lethality in all cases equal to or greater than 5 log. However, the highest efficacy (p <0.05) was obtained in the lowest coefficient matrix of green tea, with no differences in lethality depending on the reactor temperature (4, 20 and 55 ° C). In green tea and soy smoothie inoculated in addition to B. subtilis, with conidiospores of Aspergillus niger, Escherichia coli and Listeria monocytogenes the microorganism most resistant to UVC treatments was A. niger, whose lethality even with T3 treatment and maximum dose (160 J / mL) 5 log was not reduced. Vegetative forms of E. coli and especially L. monocytogenes showed greater sensitivity. In the soy smoothie, a reduction of 5 log was achieved in the T3 treatment and at doses of 120 and 80 J / mL, respectively. While in green tea, the necessary dose with the T3 treatment was only 10 J / mL and in the T1 and T2 treatments 80 J / mL on E. coli. In the case of L. monocytogenes, tea showed per se antilisteria activity. In the UHPH treatments of 100 and / or 200 MPa at 20 and / or 60 ° C the lethality obtained in the B. subtilis spores inoculated in whole and skimmed milk and soy liquefied was very reduced, however, in the case of A. niger conidiospores in soybean smoothie treated at 200 MPa at 20 ° C and at 60 ° C a complete reduction was achieved. Considering the effect of UVC in B. subtilis and UHPH in A. niger, UHPH and UVC treatments were applied in combination. For both A. niger conidiospores inoculated in soybean smoothie and B. subtilis spores inoculated in soybean smoothie, whole milk and skim milk no synergistic or additive effect was observed. The lethality obtained was similar to UVC treatments in the case of soy and whole milk smoothie and in the case of skim milk it was lower. Only a higher lethality was obtained in the UHPH and UVC combination in the T1 treatments of whole milk, however the lethality obtained was less than 2 log. In matrices with high absorption coefficient it is difficult to achieve commercial sterilization since the UVC doses estimated in the models were very high, although it would be feasible in green tea, especially if combined with UHPH.

El plasma dessecat per atomització (SDP) és una font de proteïnes funcionals obtinguda a partir de sang d’animals sans, aprovats per les autoritats veterinàries per al consum humà. La sang es recull a l'escorxador, es tracta amb anticoagulant, es refreda i es transporta a instal·lacions industrials on es centrifuga per separar els glòbuls vermells de la fracció plasmàtica. Després, el plasma es concentra i s'asseca a altes temperatures (80ºC) per convertir-lo en pols. Aquest mètode conserva l’activitat biològica de les proteïnes. El SDP s’utilitza principalment en dietes de porcí per millorar significativament el guany diari, la ingesta, l’eficiència productiva i per reduir el retard causat per l’aparició de diarrea després del deslletament. Tot i que el SDP es considera un producte segur i el seu procés de fabricació consta diverses etapes de bioseguretat, la seva seguretat sovint es qüestiona donada la seva naturalesa de subproducte hemoderivat, especialment quan apareixen patògens emergents o reemergents. Aquesta tesi doctoral es va centrar en l'avaluació i la validació d'una nova etapa redundant d'inactivació de patògens per a implementar en el procés de producció de SDP, la irradiació UV-C. El treball ha consistit en avaluar l’efectivitat del tractament per irradiació UV-C mitjançant un dispositiu de flux turbulent, SurePure TurbulatorTM, a l’irradiar un plasma natiu inoculat artificialment amb diferents patògens d’interès per a la indústria porcina. Als estudis 1 i 2 es va avaluar l’efecte UV-C sobre la supervivència de Salmonella typhimurium, S. choleraesuis, Enterococcus faecium i Escherichia coli K88 i K99 sotmesos a diferents dosis UV-C. Es van trobar cinètiques d'inactivació no lineal amb un valor de reducció de 4 log10 (4D), proper a 3000 J/L en tots els casos. A l’estudi 3 es va analitzar l’efecte de l’UV-C sobre diferents virus d’interès en la indústria del porcí. La selecció de virus amb envolta va incloure el Virus de la pseudoràbia (PRV), el Virus de la síndrome respiratòria i reproductiva porcina (PRRSV), el Virus de la diarrea epidèmica porcina (PEDV), el Virus de la diarrea viral bovina, el Virus de la grip porcina (SIV) i el Virus de la pesta porcina clàssica (CSFV); i, com a virus sense envolta, el Parvovirus porcí (PPV), Virus de la malaltia vesicular de porc (SVDV), Circovirus porcí 2 (PCV-2) i Senecavirus A (SVA). Tots aquests virus van ser sotmesos a diferents dosis UV-C i, mitjançant la titulació de les mostres, es va construir la seva corba d'inactivació. En termes generals, els resultats van mostrar que els virus amb envolta tenen una sensibilitat superior a l’UV-C, amb valors 4D inferiors a 2000 J/L, que els que no presenten envolta, presentant valors propers a 3000 J/L o més. A l’estudi 4 es va dur a terme un bioassaig utilitzant diferents grups de garrins, inoculats intraperitonealment amb plasma irradiat per UV-C a 0 J/L (plasma no tractat), 3000 i 9000 J/L. Els resultats van mostrar que cap dels porcs dels grups que rebien el plasma irradiat per UV-C es va infectar ni va seroconvertir en front als virus detectats al plasma inicial (PCV-2, PRRSV (soques europees), SIV, PPV, Virus de l’hepatitis E i Rotavirus A), confirmant així l’eficàcia de l’UV-C. Alhora, es varen dissenyar mètodes convencionals de PCR per amplificar amplicons llargs dels genomes de PCV-2 i PEDV. Mitjançant la comparació dels resultats amb els de PCRs quantitatives, es va demostrar que l’UV-C va ser capaç de danyar el genoma viral. Els resultats globals de la present tesi doctoral mostren que l’aparell d’UV-C SurePure TurbulatorTM és eficaç inactivant un ampli ventall de bacteris i virus presents de forma natural en plasma animal líquid recollit d’escorxadors comercials.
El plasma secado por atomización (SDP) es una fuente de proteína funcional obtenida de la sangre de animales sanos, aprobada por las autoridades veterinarias para el consumo humano. La sangre se recoge en el matadero, se trata con anticoagulante, se enfría y se transporta a instalaciones industriales en las que se centrifuga para separar los glóbulos rojos de la fracción plasmática. Luego, el plasma se concentra y se seca por atomización a altas temperaturas (80°C) para convertirlo en polvo. Dicho método conserva la actividad biológica de sus proteínas. El SDP se usa principalmente en dietas porcinas para mejorar significativamente la ganancia diaria, la ingesta, la eficiencia de producción y para reducir el retraso causado por la aparición de diarrea posterior al destete. Aunque el SDP se considera un producto seguro y su proceso de fabricación consta de varias etapas de bioseguridad, su seguridad a menudo se cuestiona debido a su naturaleza de subproducto hemoderivado, especialmente cuando aparecen patógenos emergentes o reemergentes en las poblaciones animales. Esta tesis doctoral se centró en la evaluación y validación de una nueva etapa redundante de inactivación de patógenos a implementar en el proceso de fabricación de SDP, la radiación UV-C. El trabajo ha consistido en evaluar la efectividad del tratamiento de irradiación con UV-C utilizando un dispositivo de flujo turbulento, SurePure TurbulatorTM, al irradiar plasma inoculado artificialmente con diferentes patógenos de interés para la industria porcina. En los estudios 1 y 2, el efecto UV-C sobre la supervivencia bacteriana se evaluó sobre Salmonella typhimurium, S. choleraesuis, Enterococcus faecium y Escherichia coli K88 y K99, sometidas a diferentes dosis de UV-C. Todas las bacterias analizadas mostraron una cinética de inactivación no lineal con un valor de reducción de 4 log10 (4D) cercano a 3000 J/L en todos los casos. En el estudio 3, se analizó el efecto de UV-C en diferentes virus de interés. La selección de virus con envuelta incluyó el Virus de la pseudorabia (PRV), Virus del síndrome respiratorio y reproductivo porcino (PRRSV), Virus de la diarrea epidémica porcina (PEDV), Virus de la diarrea viral bovina (BVDV), Virus de la influenza porcina A (SIV) y el virus de la peste porcina clásica (CSFV). El Parvovirus porcino (PPV), Virus de la enfermedad vesicular porcina, Circovirus porcino 2 (PCV-2) y Senecavirus A (SVA) fueron elegidos como virus sin envuelta. Los virus se sometieron a diferentes dosis de UV-C y, mediante la titulación de las muestras, se construyó su curva de inactivación. Los resultados mostraron que los virus envueltos tienen una mayor sensibilidad al l UV-C, con valores 4D inferiores a 2000 J/L, que los no envueltos, con valores 4D alrededor de 3000 J/L o superiores. En el estudio 4 se realizó un bioensayo utilizando diferentes grupos de lechones inoculados por vía intraperitoneal con plasma irradiado por UV-C a 0 (plasma no tratado), 3000 y 9000J/L. Ninguno de los cerdos en los grupos que recibieron el plasma irradiado por UV-C presentó infección o seroconversión frente a los virus cuyo genoma se detectó en el plasma inicial (PCV-2, PRRSV (cepas europeas), SIV, PPV, Virus de la hepatitis E y Rotavirus A), lo que confirma la eficacia de UV-C. Además, se diseñaron PCR convencionales para amplificar amplicones largos de los genomas de PCV-2 y PEDV. Al comparar los resultados con los obtenidos por PCR cuantitativa en tiempo real, se demostró que la UV-C podía dañar el genoma viral. Los resultados generales de la presente tesis doctoral demuestran que el diseño del turbulador SurePure UV-C fue eficaz para inactivar una amplia gama de bacterias y virus presentes de forma natural en el plasma animal líquido comercial.
Spray dried plasma (SDP) is a functional protein source obtained from blood of healthy animals, approved by the veterinary authorities to be fit for slaughter for human consumption. Blood is collected at the slaughterhouse, treated with an anticoagulant, chilled and transported to industrial facilities in which blood is centrifuged to separate the red blood cells from the plasma fraction. Plasma is then concentrated and spray dried at high temperatures (80ºC throughout its substance) to convert it in a powder. Such method preserves the biological activity of its proteins. SDP is mainly used in pig feed diets to significantly improve daily gain, feed intake, production efficiency, and to reduce post-weaning lag caused by the appearance of post-weaning diarrhea. Although SDP is considered a safe product and its manufacturing process consists of several biosafety steps, the security of the SDP is often questioned due to its nature as raw blood by-product, especially when emergent or re-emergent pathogens appear in animal populations. This PhD Thesis focused on the evaluation and validation of a new redundant pathogen inactivation step that may be implemented in the manufacturing process of SDP, the UV-C irradiation. The work has consisted in evaluating the effectiveness of the UV-C irradiation treatment using a turbulent flow device, SurePure TurbulatorTM, when irradiating raw plasma artificially inoculated with different pathogens of interest for the swine industry. In studies 1 and 2 the UV-C effect on bacterial survival was assessed on Salmonella typhimurium, S. choleraesuis, Enterococcus faecium, and Escherichia coli K88 and K99 strains subjected to different UV-C doses. All tested bacteria showed non-linear inactivation kinetics with 4 log10 (4D) reduction value in all cases close to 3000 J/L. In study 3, the effect of UV-C on different viruses of interest in the swine industry was analyzed. The selection of enveloped viruses included Pseudorabies virus, Porcine reproductive and respiratory syndrome virus (PRRSV), Porcine epidemic diarrhea virus (PEDV), Bovine viral diarrhea virus, Swine inflenza A virus (SIV) and Classical swine fever virus. On the other hand, Porcine parvovirus (PPV), Swine vesicular disease virus, Porcine circovirus 2 (PCV-2) and Senecavirus A (SVA) were chosen as non-enveloped viruses. All these viruses were subjected to different UV-C doses and, by titration of the samples at each UV-C dose, the inactivation curve for each virus was constructed. In general terms, results showed that enveloped viruses have a higher sensitivity to UV-C than non-enveloped ones, being the 4D values less than 2000 J/L for enveloped viruses and around 3000 J/L or higher for non-enveloped ones. To validate the effectiveness of the plasma UV-C irradiation measured in previous studies, a bioassay was carried out in the study 4 using different groups of piglets inoculated intraperitoneally with UV-C irradiated plasma at 0 (untreated plasma), 3000, and 9000J/L. The results showed that none of the pigs in the groups that received the plasma irradiated by UV-C were infected or seroconverted against the viruses which genome was detected in the initial plasma (PCV-2, PRRSV (European strains), SIV, PPV, Hepatitis E virus and Rotavirus A), thus confirming the efficacy of UV-C. Furthermore, in the study 4, conventional PCR methods able to generate long amplicons were designed to amplify fragments of approximately 1.7 kb of PCV-2 and PEDV genomes. By comparison of the results with those of real time quantitative PCRs to detect the same viruses (using short amplicons), it was demonstrated that UV-C was able to damage the viral genome. Overall results of the present PhD Thesis showed that the SurePure UV-C Turbulator design was effective in inactivating a wide range of bacteria and viruses spiked and naturally present in commercially collected liquid animal plasma.

Orientador: Peterson Bueno de Moraes
Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Tecnologia
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Resumo: A indústria têxtil gera elevados volumes de efluentes com alta carga orgânica e compostos recalcitrantes, os quais são tratados por sistemas baseados em processos físicos, químicos e biológicos convencionais. Entretanto, o caráter não destrutivo dos tratamentos convencionais representa um sério problema no setor. Nos últimos 20 anos, os Processos Oxidativos Avançados (POA) têm estado em evidência devido à sua capacidade em degradar inúmeros compostos orgânicos contidos em águas e efluentes. Uma grande quantidade de trabalhos utilizando luz UV a partir de lâmpadas de vapor de mercúrio tem resultado em elevada eficiência de degradação de substratos recalcitrantes incluindo efluentes têxteis; entretanto, demandam elevado consumo de energia elétrica, encarecendo o tratamento. Em contrapartida, o surgimento de Diodos Emissores de Luz Ultravioleta (LED UV) abre novas fronteiras de aplicação no campo de tratamento de águas residuárias, quanto a custo, operacionalidade e tamanho dos sistemas. Nesse trabalho estudou-se a degradação de um efluente têxtil simulado contendo o corante Remazol Azul Brilhante (C.I. Reactive Blue 19) através de processos eletroquímicos e fotoeletroquímicos que utilizam LED UV, utilizando-se dois reatores: um operando em batelada contendo o fotocatalisador TiO2 e o outro, em fluxo, contendo um cátodo (tela cilíndrica de aço-inoxidável), um tubo de quartzo contendo os LED UV e o Anodo Dimensionalmente Estável (ADE 70%TiO2/30%RuO2). Os resultados demonstraram que, no reator de bancada, a eficiência de remoção de cor foi de 100% para concentração inicial de 50 mg L-1 do corante, em 24 horas de tratamento. No reator em fluxo, utilizando Na2SO4 como eletrólito, o processo eletrolítico resultou em eficiência de 65%; o fotoeletrocatalítico, em 68%, operando a 750 L h-1 e em 57,3 mA cm-2. Quando foi utilizado o eletrólito NaCl, obteve-se remoção de 100% da cor em 5 minutos de tratamento a 750 L h-1, independente da concentração inicial do corante utilizada (50 mg L-1 ou 100 mg L-1), da concentração do eletrólito (0,05 M ou 0,1 M), da densidade de corrente (14,3 mA cm-2 , 28,7 mA cm-2 ou 57,3 mA cm-2) e do processo utilizado
Abstract: The textile industry generates large amount of wastewater containing significant organic load and recalcitrant compounds, which in most cases are treated by conventional systems involving physical, chemical and biological processes, the latter represented mainly by activated-sludge treatment. However, the non-destructive profile of conventional treatments is a serious problem for textile-based industry. Over the past 20 years, the study of Advanced Oxidation Processes (AOP) has been carried out due to its high capacity degradation of numerous organic pollutants contained in waters and wastewaters. Research using UV light from mercury vapor lamps usually has resulted in high efficiency degradation of recalcitrant substrates including textile effluents but requires high electrical power consumption besides other drawbacks. In contrast, the emergence of Ultraviolet Light Emitting Diodes (UV LED) opens new perspectives for application on wastewater treatment, concerning efficiency, footprint and costs of the systems. In this work we studied the degradation of a simulated wastewater containing a textile dye, Remazol Brilliant Blue (C.I. Reactive Blue 19) through electrochemical and photoelectrochemical processes using UV LED as ultraviolet radiation source. The experimental apparatus consisted of two systems: the first, a bench-scale reactor containing TiO2 photocatalyst (P25 DEGUSSA) in solution, and another pilot-scale system operated in batch recirculation mode composed of an tubular stainless-steel screen cathode, a quartz tube containing the UV LED and a oxide-coated titanium anode (DSA©30%TiO2/70%RuO2). The results showed total decolorization of a solution containing 50 mg L-1 of RB in 24-hour treatment in the bench-scale reactor. Tests on flow reactor using Na2SO4 as supporting electrolyte resulted in 65% of color removal using electrolytic process and 68% for photoelectrocatalytic process operating at 750 L h-1 and 57.3 mA cm-2. In experiments using the electrolyte NaCl it was obtained 100% in the color degradation within 5 minutes of treatment at 750 L h-1, regardless of the: initial concentration of dye used (50 mg L-1; 100 mg L-1), concentration of the electrolyte (0.05 M; 0.1 M) and current density value (14.3; 28.7; 57.3 mA cm-2)
Mestrado
Tecnologia e Inovação
Mestra em Tecnologia

Understanding the composition of camel milk coupled with studying the effects of thermal and non-thermal treatments on its components and bacterial inactivation were the general objectives of this dissertation. In the first study (Chapter 2), the gross composition of camel milk including milk protein, fat, casein, total solids, lactose, ash, and mineral content were analyzed. In addition, fatty acid profile, amino acid profile, protein fractions, and volatile compounds were evaluated as well. Our results revealed that camel milk has its unique nutrients profile. These findings make it easier for the researchers and consumers to understand some of the nutritional attributes of camel milk.The impact of non-thermal ultrasound treatment (900 W, 20 kHz, 100% power level) on some milk-borne microorganisms and the components of camel milk was studied in Chapter3. We reported that continuous ultrasound processing was efficient in inactivating Escherichia coli (E.coli) O157: H7 and Salmonella Typhimurium (S. Typhimurium) in camel milk without detrimental effects on milk fatty acids profile, lipid peroxides, and protein fractions except for some changes in milk volatile compounds (VC). In Chapter 4, another non-thermal technique, ultraviolet-C (UV-C) light, was applied to camel milk to study the effects of different UV-C light doses on the viability of E. coli O157:H7 and S. Typhimurium and the chemical changes to milk components. The main findings of this study were: (i) UV-C treatment at a dose of 12.45 mJ/cm2 resulted in only 3.9-log10 for both bacterial strains which did not meet the Food and Drug Administration (FDA) requirements for the 5-log pathogen reduction; (ii) the UV-C treatment at the above dose, had limited effects on camel milk components. Thermal pasteurization of milk was first introduced to prevent milk-borne infectious diseases, however, its effects on camel milk components and quality are still unknown. Therefore, in Chapter 5, we investigated the efficacy of three previously reported thermal methods: PAST-1 (65ºC/30 min), PAST-2 (72ºC/5 min), and PAST-3 (80ºC/5 min) on bacterial inactivation and some camel milk components such as the fatty acid profile, lipid peroxidation, VC, and milk protein fractions. Complete elimination (6 log10 CFU/ml reduction) of E. coli O157: H7 was achieved using all pasteurization methods, however, only 3.4 log10 CFU/ml reduction of the total viable counts was reported using PAST-1 and PAST-3 methods. We also reported that the PAST-1 and PAST-3 methods did not affect the chemical composition of camel milk. In conclusion, we assessed the main components of camel milk along with the amino fatty acid profile, acid profile, volatile compounds, and protein fractions. Thermal methods were more effective than the non-thermal methods in terms of microbial inactivation and most camel milk components were not significantly influenced by thermal and non-thermal methods.

La décontamination microbienne est sujet majeur de préoccupation du secteur agroalimentaire. Des nouvelles technologies physiques de décontamination, dites athermiques, sont d’un emploi croissant. La Lumière Pulsée, utilisée pour décontaminer les surfaces et les liquides clairs, en fait partie. Elle utilise des flashes de lumière blanche riches en UV, et délivrés en moins d'une milliseconde. La plupart des traitements par lumière pulsée sont définis dans la littérature par des paramètres spécifiques à l'équipement utilisé. Le but de cette étude a été dans un premier temps de caractériser le traitement par lumière pulsée par les grandeurs physiques appropriées (fluence, tension aux bornes de la lampe, etc…), en reliant une dose de lumière à niveau de décontamination microbienne. L'équipement pilote de la société CLARANOR a révélé des réduction logarithmiques allant jusqu'à plus de 5 unités sur des spores de B. subtilis, et de plusieurs autres espèces de bactéries sporulées, avec des fluences inférieures à 1,5 J/cm², appliquée en un seul flash La mise au point d'une méthode d'inoculation par spray à permis d'évaluer l'efficacité décontaminante de la lumière sur différentes surfaces, y compris des hydrophobes, par pulvérisation des microorganismes en couches formées d’une seule épaisseur de cellules. L'application de la technologie sur des surfaces inertes comme le polystyrène a montré une décontamination notamment sur des spores de B. subtilis, et d'A. niger, supérieures à 4 cycles logarithmiques en utilisant des fluences inférieures à 1 J/cm². L'influence des facteurs liés au système d'éclairage a montré une importance capitale des longueurs d'onde UV, mais ne permettent pas de réduire l'efficacité à la seule action de la dose UV-C. L'efficacité de la technologie a permis de réaliser une étude concernant la décontamination de sirop de sucre dans une optique d'application industrielle. Une réduction supérieure à 3 cycles logarithmiques de spores d'A. acidoterrestris dans du sirop de saccharose a été obtenue en flux continu, sur une épaisseur de 10 mm de liquide
Microbial decontamination is a major concern in the food industry. Non-thermal physical technologies are increasingly used. Pulsed Light used to decontaminate surfaces and clear liquids is one of these new technologies. Pulsed Light uses intense flashes of white light rich in UV, delivered in less than one millisecond. Most of treatments are characterised in the literature using parameters which are specific to the equipment. The aim of this study was firstly to characterise the PL treatment in expressing a log reduction as a function of the dose received by the microorganism. The pulsed light pilot of the CLARANOR company allowed a high decontamination of B. subtilis spores and other sporulating bacterial species, with more than 5 log reductions at fluences lower than 1.5 J/cm², obtained in only one flash. The development of a spray inoculation method was made to evaluate the decontamination efficiency on different surfaces, including hydrophobic surfaces, with a monolayer inoculation. The Pulsed light efficiency on inert surfaces such as polystyrene lead to high decontaminations including B. subtilis and A. niger spores, with more than 4 log reductions using fluences lower than 1 J/cm² in both cases. The influence of the physical factors of the light showed that UV wavelengths are essential for the decontamination, but the efficiency is not totally explained by the action of the UV-C dose. The efficiency of pulsed light allowed to study sugar syrup decontamination, in view of industrial application. Three log reductions of A. acidoterrestris spores were obtained in 10 mm thickness sugar syrup, using a flow-through system

L’utilisation de réseaux optiques dans la géométrie de diffraction conique a connu ces dernières décennies un essor remarquable dans les domaines UV et X grâce à ses propriétés particulières: absence de l’écrantage derrière les traits du réseau aux incidences rasantes, faible dispersion angulaire limitant l’étirement temporel, efficacité de diffraction élevée. Son usage s’est imposé pour la monochromatisation d’impulsions ultra-brèves. C’est aussi l’une des deux options retenues par la Nasa pour le spectrographe à réseau de l’Observatoire à rayon X de la future mission Lynx. Ce travail de thèse contribue au développement de méthodes numériques pour modéliser les effets de diffraction par des réseaux dans une géométrie encore peu étudiée sous cet aspect. La complexité de cette étude réside dans le couplage inhérent entre les deux états fondamentaux de polarisation. Du point de vue numérique, il impose un calcul ‘’vectoriel’’, là où, en géométrie classique des calculs scalaires suffisent. Notre travail s’est appuyé sur les méthodes numériques de calcul de diffraction par des structures périodiques déjà développées dans le cadre de la géométrie classique. Ces méthodes sont basées sur la théorie différentielle, qui consiste à propager une série d’ondes planes au travers de la zone modulée. La méthode différentielle employée est complétée par l’usage de l’algorithme de propagation de la matrice réflectivité. On contourne ainsi certains problèmes de convergence. Dans la partie théorique de ce travail, ces algorithmes sont étendus pour s’adapter aux cas de géométrie oblique. Sur cette base théorique, nous avons pu développer un code de calcul, nommé COROX, fonctionnant dans toutes les géométries d’utilisation. Un certain nombre de réseau types ont été étudiés, tant en géométrie oblique que classique, pour mettre en évidence, non seulement les efficacités de diffraction mais encore les effets de polarisation, (paramètres de Stokes et matrice de Müller) ainsi que les phases spectrales. Des propriétés intéressantes ont été remarquées, comme l’existence d’une composante circulaire non négligeable diffractée par réseau lamellaire quand l’onde incidente polarisée à 45° par rapport au plan du réseau. Le comportement de la phase spectrale est également une donnée significative pour une future gestion d’impulsions ultra-brèves. Des mesures de diffraction ont été effectuées sur la ligne Métrologie du Synchrotron SOLEIL, sur un réseau blazé de 150 traits/mm. Un accord raisonnable entre efficacités mesurées et calculées est constaté si l’on tient compte de la forte rugosité du réseau étudié
The conical geometry of optical grating diffraction has been suggested and studied, in the last 10 years, for cutting edge applications in the VUV and X-ray domains, due to its specific properties such as: absence of screen inside the grating grooves at grazing incidence, low angular dispersion which limits the temporal spread of short pulses, very high diffraction efficiencies. It has been accepted as the first choice technology for VUV short pulses monochromatization. It is also one of the two options selected by NASA, for the grating spectrograph of the future X-ray Observatory of the Lynx mission. This thesis reports our contribution to the development of numerical methods in order to model the effects of diffraction by optical gratings in this still little studied geometry. This study is made more complex by an inherent coupling between the two fundamental polarization modes. From the numerical aspect, it requires performing “vectorial” computations, whereas, in a classical diffraction geometry, scalar computations are sufficient. Our work is based on numerical methods already developed for modeling optical diffraction by periodic structures in the framework of classical geometry. These methods are using on the differential theory, whose main concept is propagating a set of plane waves throughout the modulated area. We use the differential method together with an algorithm of reflectivity matrix propagation. It overcomes some of the convergence issues. In the theoretical part of this work, reflectivity matrix algorithms are extended to the case of oblique geometry. On these theoretical grounds, we developed a computation code, named COROX, which can be applied in any geometry. A number of typical grating cases have been studied, both in the conical and of le classical one. The output is not only the diffraction efficiencies, but also the polarization properties (Stokes parameters, Müller matrix), as well as the spectral phases. Interesting properties have been noticed, such as the presence of a non-negligible circularly polarized component diffracted from a lamellar grating when the incident wave is linearly polarized at 45° from the grating plane. The spectral phase behavior is also a significant data for an eventual shape tayloring of ultrashort pulses. Diffraction efficiency measurements have been performed on the Metrology beamline of Synchrotron SOLEIL, using a 150 lines/mm blazed grating as a test object. A reasonable agreement between measured and computed efficiencies has been obtained, provided that the rather high roughness of this grating is taken into account

D.Phil. Faculty of Health Sciences, University of the Witwatersrand, 2009
In this thesis I describe the development of an animal model of sustained hyperalgesia induced by exposure to ultraviolet (UV) A light to the rat’s tail, and the role of the Cfibre barrage and peripheral afferent fibre sensitization in this model of hyperalgesia. Exposure of rats’ tails to UVA-light caused hyperalgesia to a noxious thermal challenge, immersion of the rats’ tails into 49°C water, and a noxious mechanical challenge, application of a static force of 3.9N by a bar algometer onto the rats’ tails. The hyperalgesia to the thermal challenge lasted eight days and hyperalgesia to the mechanical challenge continued for up to 16 days. Despite the sustained hyperalgesia, rats exposed to UVA-light showed no overt signs of morbidity as they gained weight normally and were mobile throughout the study. Histological examination of rat tail tissue showed mild, chronic inflammation in rats exposed to UVA-light and in rats that had their tails covered with a protective layer of aluminium foil during UVA-light exposure. This inflammation was therefore not responsible for the behavioural hyperalgesia. To investigate the role of C-fibre barrage in the development of hyperalgesia after UVA-light exposure, I pre-emptively blocked C-fibre activation during UVA-light exposure with the local anaesthetic bupivacaine. Injection of bupivacaine (1ml of 0.5%), into the base of the tail prevented the development of thermal hyperalgesia to tail immersion in 49°C water. However, it did not prevent the development of hyperalgesia to a noxious punctate challenge. Thus the sustained mechanical hyperalgesia did not depend on the activation of the C-fibre barrage, but thermal hyperalgesia did depend on the activation of a C-fibre barrage during the conditioning event of UVA-light exposure. Lastly, in rats anaesthetised with enflurane, I examined the responses of coccygeal primary afferent fibres to noxious thermal and mechanical stimulation after UVA-light exposure of their receptive fields on the tail. I investigated only pure nociceptive afferents and ignored those afferents that responded to challenges in the noxious and non-noxious ranges. The peak firing rates and areas under the curve of post-challenge histograms, a measure of neuronal firing over time, of Ad- and C-fibres were increased when noxious blunt and punctate challenges were applied to the rats’ tails after UVA-light exposure, showing that Ad- and C-fibres that encode for noxious mechanical challenges were sensitized. The peak firing rate of C-fibres that were responsive to noxious thermal challenges were not increased after UVA-light exposure. Therefore, thermal hyperalgesia was probably mediated by sensitization of central nervous system neurones. In summary, I developed a model of sustained mechanical and thermal hyperalgesia caused by UVA-light exposure of the rat tail. The thermal hyperalgesia was initiated by the C-fibre barrage, while mechanical hyperalgesia did not depend on the C-fibre barrage and peripheral afferent sensitization of Ad- and C-fibres could account for the mechanical hyperalgesia.

The lethal effect of ultraviolet (UV) light on microorganisms is well known and many studies have been undertaken into the effects of UV induced damage. Most of this work has been experimental; by comparison relatively little theoretical work has been undertaken to analyse the kinetics of the UV inactivation process, or to develop quantitative methodologies to support the experimental work. This paper presents a new and simple model for quantifying the photolysis rate. A theoretical study is also presented in this paper which quantifies photolysis rates for E. coli O26 and E. coli O157:H7. This study uses experimental data collected by Tosa and Hirata, and reveals the photolysis rate for E. coil O26 during the UV irradiation process to be 4.69 x 10(-3) m2 J(-1). By comparison, E. coli O157:H7 is much more susceptible to UV induced damage than E. coli O26, having a photolysis constant of only 2.09 x 10(-3) m2 J(-1).

碩士
國防醫學院
生物化學研究所
102
In this study we found that ultraviolet B exposure can decrease adhesion cell number, increase intracellular ROS and induce cell death . In addition, UVB can decrease fibronectin protein expression. All of these effect induce by UVB can be blocked by Sulforaphane. UVB radiation decrease Nrf2 protein expression and sulforaphane can reverse it and inhibit Nrf2 downstream targeting genes expression such as HO-1 and NQO1. By increasing antioxidant gene expression sulforaphane can decrease intracellular ROS and protect cells. Similarly N-acetylcysteine can decrease intracellular ROS and protect cells from UVB. Taken together, we demonstrate that sulforaphane protect cell from UVB induced damage by activating Nrf2.

In diploid yeast cells, mitotic recombination is very important for repairing double-strand breaks (DSB). When repair of a DSB results in crossovers, it may cause loss of heterozygosity (LOH) of markers centromere-distal to the DSB in both daughter cells. Gene conversion events unassociated with crossovers cause LOH for an interstitial section of a chromosome. Alternatively, DSBs can initiate break-induced replication (BIR), causing LOH in only one of the daughter cells. Mapping mitotic LOH contributes to understanding of mechanisms for repairing DSBs and distribution of these recombinogenic lesions. Methods for selecting mitotic crossovers and mapping the positions of crossovers have recently been developed in our lab. Our current approach uses a diploid yeast strain that is heterozygous for about 55,000 SNPs, and employs SNP-Microarrays to map LOH events throughout the genome. These methods allow us to examine selected crossovers on chromosome V and unselected mitotic recombination events (crossovers, gene conversion events unassociated with crossovers, and BIR events) at about 1 kb resolution across the genome.

Mitotic recombination can be greatly induced by UV radiation. However, prior to my research, the nature of the recombinogenic lesions and the distribution of UV-induced recombination events were relatively uncharacterized. Using SNP microarrays, we constructed maps of UV-induced LOH events in G1-synchronized cells. Mitotic crossovers were stimulated 1500-fold and 8500-fold by UV doses of 1 J/m2 and 15 J/m2, respectively, compared to spontaneous events. Additionally, cells treated with 15 J/m2 have about eight unselected LOH events per pair of sectors, including gene conversions associated and unassociated with crossovers as well as BIR events. These unselected LOH events are distributed randomly throughout the genome with no particular hotspots; however, the rDNA cluster was under-represented for the initiation of crossover and BIR events. Interestingly, we found that a high fraction of recombination events in cells treated with 15 J/m2 reflected repair of two sister chromatids broken at roughly the same position. In cells treated with 1 J/m2, most events reflect repair of a single broken sister chromatid (Chapter 2).

The primary pathway to remove pyrimidine dimers introduced by UV is the nucleotide excision repair (NER) pathway. In NER, the dimer is excised to generate a 30-nucleotide gap that can be replicated to form DSBs if not filled in before DNA replication. The NER gap can also be expanded by Exo1p to form single stranded gaps greater than one kilobase. Alternatively, in the absence of NER, unexcised dimers could result in blocks of DNA replication forks. Resolving the stalled replication fork could lead to recombinogenic breaks. In Chapter 3 and Chapter 4, we analyzed recombination events in strains defective in various steps of processing of UV-induced DNA damage, including exo1 and rad14 mutants.

In Chapter 3, I show that Exo1p-expanded NER gaps contribute to UV-induced recombination events. Interestingly, I also found that Exo1p is also required for the hotspot activity of a spontaneous crossover hotspot involving a pair of inverted Ty repeats. In addition to its role of expanding a nick to a long single-stranded gap, Exo1p is also a major player in DSB end resection. Therefore, I examined the gene conversion tract lengths in strains deleted for EXO1. I found that, although crossover-associated gene conversion tracts become shorter in the exo1 mutant as expected, noncrossover tract lengths remained unaffected. As a result, noncrossover tracts are longer than crossover tracts in the exo1 mutant while the opposite result was observed in the wild-type strains. I proposed models to rationalize this observation.

In Chapter 4, to investigate whether the substantial recombinogenic effect in UV in G1-synchronized cells requires NER, we mapped UV-induced LOH events in NER-deficient rad14 diploids treated with 1 J/m2. Mitotic recombination between homologs was greatly stimulated, which suggests that dimers themselves can also cause recombination without processing by NER. We further show that UV-induced inter-homolog recombination events (noncrossover, crossover and BIR) depend on the resolvase Mus81p, and are suppressed by Mms2p-mediated error-free post-replication repair pathway.

The research described in Chapters, 2, 3, and 4 are in the publications Yin and Petes (2013), Yin and Petes (2014), and Yin and Petes (2015), respectively.

Dissertation

The main objective of this study was to determine the applicability of advanced water treatment processes namely granular activated carbon (GAC) adsorption, ultraviolet (UV) light disinfectant and ozone in the management of deteriorating water quality in the Mid-Vaal River system for drinking purposes. Both the scarcity and the deteriorating quality of water in South Africa can be addressed by investigating advanced water treatment processes such as GAC adsorption, UV light disinfectant and ozone. Previously disregarded water resources have the potential to be purified and advanced treatments can improve water quality where conventional water treatments have failed. In addition, advanced treatment processes can be applied to treat used water. The two sampling sites selected for the study, Rand Water Barrage (RWB) and Midvaal Water Company (MWC), are both located in the Middle Vaal Water Management Area with RWB upstream of MWC. RWB uses GAC adsorption and UV light disinfection and MWC uses ozone as pre- and intermediate treatment process steps for water purification. The quality of the source water at both sampling sites was determined by analysing the physical and chemical characteristics as well as the algal and invertebrate compositions of the source water. The physical and chemical water quality variables measured included pH, conductivity, turbidity, dissolved organic carbon (DOC), total organic carbon (TOC), total photosynthetic pigments (TPP), microcystin and geosmin. The source water of both sites was characterised as hypertrophic on account of high chlorophyll concentrations. The water quality of the two sites was distinctly different and a downstream change was observed. The source water of RWB was characterised by high microcystin, geosmin, DOC, TOC and conductivity measurements and dominated by Bacillariophyceae (diatoms) and Cyanophyceae (blue-green bacteria). Problematic species that were present in the source water of RWB included Aulacoseira sp., other unidentified centric diatoms, Pandorina sp., Anabaena sp., Microcystis sp., Oscillatoria sp., Cryptomonas sp., Ceratium sp. and Trachelomonas sp. The source water of MWC was characterised by high pH, turbidity and TPP measurements and was dominated by Chlorophyceae (green algae) and Bacillariophyceae (diatom) species. Problematic algal species that were present in the source water of MWC included Cyclotella sp., Coelastrum sp., Pediastrum sp. and Scenedesmus sp. The source water of MWC was deemed to be of a better quality due to the lower Cyanophyceae concentrations and lower microcystin levels. The invertebrate composition of both sites was similar with Rotatoria as the dominant invertebrate group. The efficacy of GAC adsorption/UV light disinfection/ozonation on restoring the physical and chemical characteristics of the source water at both sampling sites as well as the algal and invertebrate compositions was determined by ascertaining the nature of the change in or the percentage removal of a water quality variable. The potable water of both sites complied with the standards of water intended for domestic use except for the conductivity at RWB that was slightly elevated. The phytoplankton was removed effectively from the source water of both sites but the removal of invertebrates was unsatisfactory. GAC adsorption and filtration proved to be more effective in the removal of TPP, turbidity, DOC, microcystin and geosmin than ozone. Ozone effected an increase in DOC. UV light disinfection had no or little effect on restoring the water quality variables investigated in this study.
M (Environmental Sciences), North-West University, Potchefstroom Campus, 2015

Dissertação de mestrado integrado em Engenharia Biológica (área de especialização em Tecnologia Química e Alimentar)
A madeira é um material natural, sustentável e ecológico largamente usado como um material de construção. No entanto, é muito mais facilmente degradado por fatores ambientais, dos quais são exemplo os microrganismos, a água e a radiação solar, do que qualquer outro material. Os revestimentos para a madeira, incluindo os produtos de acabamentos como os esmaltes, servem e têm os principais objetivos de decorar, dando a aparência desejada, e proteger a sua superfície. Ao selecionar-se um acabamento, deve considerar-se a aparência, a proteção e a facilidade de limpeza, assim como as propriedades da superfície da madeira que podem afetar a aplicação e desempenho do acabamento, isto é, a sua vida útil. Para que esta seja o mais longa possível é fundamental que as condições ambientais, no caso da madeira exterior, juntamente com a própria estrutura deste substrato e os demais fatores a ela extrínsecos sejam tidas em conta, para que a performance dos revestimentos seja resistente a estes parâmetros e possa desempenhar as funções para as quais o produto é desenvolvido. Desta forma, o presente projeto teve como intuito estudar e analisar diversos ligantes existentes no mercado indicados para a formulação deste tipo de produto, de modo a selecionar aqueles que apresentem a máxima resistência à radiação ultravioleta, em particular, possível. Estudaram-se dois diferentes tipos de ligantes, acrílicos e alquídicos, de onde se concluiu que os que apresentaram melhor comportamento face ao envelhecimento acelerado, que envolveu a exposição à radiação ultravioleta, foram os ligantes acrílicos. Também a tendência para o amarelecimento dos produtos formulados com estes ligantes foi melhor do que a constatada com os ligantes alquídicos. Nos esmaltes desenvolvidos com ligantes acrílicos, dois, em particular, evidenciaramse pela boa performance geral que apresentaram relativamente aos diversos parâmetros estudados e avaliados no estudo. Por este ser bastante preliminar e breve para o tipo de trabalho exigido, deve ser salientado que as formulações usadas para o desenvolvimento de todos os esmaltes devem sofrer alterações, para ser otimizado, por exemplo, o tempo aberto dos mesmos, entre outros aspetos.
Wood is a natural, sustainable and eco-friendly type of material, widely used as a construction material. However, it’s much more easily degraded by environmental aspects, such as microorganisms, water and sunlight, than any other type of construction material. Wood coatings, including enamels, have the purpose to decorate, giving the desired appearance, and protect wood. By selecting a coating, it must be considered its protection functions as well as the main factors that affect coatings performance on wood, which means, it’s useable life. To make this as long as possible, it is essential that weathering conditions, together with the type of wood and other variables, are taken into account, to allow the best performance and resistance for the developed product. Therefore, this project aims to study different types of binders in the market, specific for the type of product wanted, and select those who present the best resistance to artificial weathering conditions, especially to UV-light. Acrylic and alkyd binders were studied, revealing that acrylic ones exhibited the best resistance and behavior on artificial weathering. The yellowing tendency of products formulated with this type of binders were better than alkyd ones. Two acrylic binders reported a good overall performance giving the analyzed characteristics. Giving the fact that this project was very short and of preliminary assessment, it must be emphasized, however, that the formulations used should be modified, in order to achieve better values in, for instance, open time, among others.