This dissertation establishes a precipitation climatology for common storm types and structures in southeast Texas, investigating diurnal, seasonal, and interannual rainfall variations in addition to climatological differences in raindrop size distributions and storm divergence profiles. Divergence profiles observed by an S-band, Doppler radar are compared to ensemble simulations of ten precipitating systems occurring in warm season, weakly baroclinic, and strongly baroclinic environments. Eight triply-nested mesoscale model simulations are conducted for each case using single- and double- moment microphysics with four convective treatments (i.e., two convective parameterizations and explicit vs. parameterized convection at 9 km). Observed and simulated radar reflectivities are objectively separated into convective, stratiform, and non-precipitating anvil columns and comparisons are made between ensemble mean echo coverages and levels of non-divergence (LNDs). In both the model and observations, storms occurring in less baroclinic environments have more convective rain area, less stratiform rain area, and more elevated divergence profiles. The model and observations agree best for well-organized, leading-line trailing stratiform systems. Excessive convective rain area and elevated LNDs are simulated for several less organized cases. Simulations parameterizing convection on the intermediate grid produced less elevated divergence profiles with smaller magnitudes compared to their explicit counterparts. In one warm season case, double-moment microphysics generated lower LNDs associated with variations in convective intensity and depth, detraining less ice to anvil and stratiform regions at midlevels relative to a single-moment scheme. Similarly, mesoscale convective vortex simulations employing an ensemble-based versus a single-closure convective parameterization produced the least elevated heating structures (closer to observed) resulting in the weakest midlevel vortices. Finally, this dissertation is unique in that some of the data collection and a portion of the analysis involved 95 undergraduates in a five-year research and education program, the Student Operational ADRAD Project (SOAP). In addition to documenting the program's structure and implementation, student-reported experiences, confidence, and interest in performing SOAP tasks are also analyzed. Students participating in SOAP for multiple years were significantly more confident in performing SOAP tasks, more likely to obtain science or meteorology-related employment upon graduation, and more likely to matriculate to graduate programs, suggesting programs like SOAP have a strong influence on students' career outcomes and self-efficacy.

OBJECTIVES: 1) To measure the prevalence of precipitating events in pediatric chronic pain patients and 2) to compare pain and functional disability outcomes at evaluation and 4-month follow-up by presence and type of precipitating event. METHODS: Precipitating events (e.g., injury) were coded from the medical record for 401 youth (6-19) who presented to a tertiary care chronic pain clinic. Four-month follow-up disability and pain were collected for 187 patients. In addition to frequency of events, we examined differences in pain and disability measures by event type at evaluation and follow-up using multiple statistical analysis strategies. RESULTS: Two-thirds of patients had a precipitating event prior to pain onset. Injury was the most common (55%), followed by chronic disease (23%), infection/illness (12.8%), and surgery (7.5%). Patients whose pain was triggered by injury reported the highest average pain levels, F(3, 340)=2.67, p<.05 and functional disability, F(3, 295)=3.54, p<.05. There were multiple cases of event groups that had significantly different baseline and follow-up psychological measures when compared to the rest of the patient population. Trajectories of pain and disability did not differ between patients with and without a precipitating event. Patients with injuries reported greater improvement in functional disability at follow-up (time x injury) F(1, 183)=4.88, p<.05 whereas patients with chronic disease reported less improvement in disability (time x chronic disease), F(1, 183)=5.49, p<.05. No other interactions were significant for disability or pain. CONCLUSIONS: A majority of patients had experienced some form of precipitating event prior to their pain onset, and the presence of a precipitating event had varied effects on the treatment outcomes of patients at four-month follow-up. Although patients with injuries presented with greater disability and pain, they had significantly more improvement, while chronic disease patients were less likely to improve in terms of functional disability. Type of precipitating event appears to be associated with treatment response and can inform clinical prognoses.

No / The effect of a self-induced electric field is investigated analytically and numerically on differential and mean electron spectra produced by beam electrons during their precipitation into a flaring atmosphere as well as on the emitted hard X-ray (HXR) photon spectra. The induced electric field is found to be a constant in upper atmospheric layers and to fall sharply in the deeper atmosphere from some "turning point" occurring either in the corona (for intense and softer beams) or in the chromosphere (for weaker and harder beams). The stronger and softer the beam, the higher the electric field before the turning point and the steeper its decrease after it. Analytical solutions are presented for the electric fields, which are constant or decreasing with depth, and the characteristic "electric" stopping depths are compared with the "collisional" ones. A constant electric field is found to decelerate precipitating electrons and to significantly reduce their number in the upper atmospheric depth, resulting in their differential spectra flattening at lower energies (<100 keV). While a decreasing electric field slows down the electron deceleration, allowing them to precipitate into deeper atmospheric layers than for a constant electric field, the joint effect of electric and collisional energy losses increases the energy losses by lower energy electrons compared to pure collisions and results in maxima at energies of 40-80 keV in the differential electron spectra. This, in turn, leads to the maxima in the mean source electron spectra and to the "double power law" HXR photon spectra (with flattening at lower energies) similar to those reported from the RHESSI observations. The more intense and soft the beams are, the stronger is the lower energy flattening and the higher is the "break" energy where the flattening occurs.

Submitted by Ana Hilda Fonseca (anahilda@ufba.br) on 2014-09-09T17:09:12Z No. of bitstreams: 1 DISSERTAÇÃO - CLÁUDIO TARANTO.pdf: 18450159 bytes, checksum: 76f9d1c02e4cdba72b38d11a61fcc786 (MD5) / Approved for entry into archive by Fatima Cleômenis Botelho Maria (botelho@ufba.br) on 2014-09-09T17:15:00Z (GMT) No. of bitstreams: 1 DISSERTAÇÃO - CLÁUDIO TARANTO.pdf: 18450159 bytes, checksum: 76f9d1c02e4cdba72b38d11a61fcc786 (MD5) / Made available in DSpace on 2014-09-09T17:15:00Z (GMT). No. of bitstreams: 1 DISSERTAÇÃO - CLÁUDIO TARANTO.pdf: 18450159 bytes, checksum: 76f9d1c02e4cdba72b38d11a61fcc786 (MD5) / Considerando a busca por tecnologias mais limpas e sustentáveis, o hidrogênio surge como uma das fontes de energia mais práticas e sustentáveis do futuro. Esse combustível é obtido comercialmente pela reforma de gás natural, seguido de uma etapa de purificação, conhecida como conversão de monóxido a dióxido de carbono com vapor d’água (reação de HTS, High Temperature Shift). Os catalisadores comerciais empregados nessa reação são constituídos por hematita (-Fe2O3) contendo cromo hexavalente, um íon tóxico aos seres humanos e ao meio ambiente. Por essa razão, diversas pesquisas têm sido desenvolvidas visando a substituir o cromo nesses sólidos. Com o objetivo de otimizar as propriedades de catalisadores baseados em hematita contendo alumínio (Fe/Al=10) e cobre (Fe/Cu=10) para a reação de HTS, neste trabalho, estudou-se o efeito do agente precipitante sobre as propriedades desses sólidos. As amostras foram preparadas através do processo sol-gel, misturando-se soluções de nitrato férrico e nitrato de alumínio e usando diferentes agentes precipitantes (hidróxido de sódio e hidróxido de amônio), seguida de impregnação com solução alcoólica de cobre. Os sólidos foram caracterizados por termogravimetria, espectroscopia no infravermelho com transformada de Fourier, difração de raios X, medida de área superficial específica e de porosidade, redução à temperatura programada e espectroscopia Mössbauer. Os catalisadores foram avaliados na reação de HTS a 1 atm e 400 °C. Observou-se a formação da hematita e magnetita nos catalisadores antes e após a reação, respectivamente, não se detectando nenhuma outra fase. Os dopantes foram inseridos na rede do óxido de ferro, o que pode ser explicado pela similaridade dos raios iônicos das espécies Cu+2, Al+3 e Fe+3; esse processo foi facilitado pelo hidróxido de amônio. Quando presentes isoladamente, o alumínio e o cobre aumentaram a área superficial específica dos sólidos obtidos com hidróxido de amônio mas o hidróxido de sódio inibiu a ação textural do cobre e alumínio, juntos ou isoladamente. O hidróxido de amônio favoreceu o desenvolvimento de mesoporos interparticulares nos sólidos macroporosos obtidos. A redutibilidade da hematita foi alterada pela presença dos dopantes e pela natureza do agente precipitante; o alumínio dificultou a formação da magnetita (Fe3O4) e do ferro metálico enquanto o cobre e o hidróxido de amônio facilitaram esses processos. Dessa forma, a presença simultânea dos dopantes favoreceu a formação da fase ativa (magnetita) e a estabilidade do catalisador, retardando sua desativação pela formação de ferro metálico. Todos os catalisadores foram ativos na reação de HTS, mas aqueles contendo cobre, e obtidos com hidróxido de sódio, foram os mais ativos, devido a um aumento na atividade dos sítios ativos e à maior facilidade de formação da fase ativa (magnetita). O papel do alumínio foi relacionado ao aumento da resistência dos catalisadores à redução da fase ativa. O catalisador mais promissor foi aquele preparado com hidróxido de sódio, que apresentou elevada atividade (10,68 x 10-7 mol.s-1.g-1) e alta resistência à redução da fase ativa (magnetita), com a vantagem de não ser tóxico, podendo ser manuseado e descartado sem risco à saúde humana e ao meio ambiente. / Considering the search for cleaner and more sustainable technologies, hydrogen emerges as one of the most practical and sustainable energy source in the future. This fuel is commercially obtained by natural gas reforming, followed by a purification step known as the water gas shift reaction at high temperatures (HTS, High Temperature Shift). The commercial catalysts for this reaction are composed of hematite (-Fe2O3) containing hexavalent chromium, a toxic ion to humans and the environment. For this reason, many studies have been carried out aiming to replace chromium in these solids. In order to optimize the properties of catalysts based on hematite containing aluminum (Fe/Al= 10) and copper (Fe/Cu= 10) for the HTS reaction, the effect of precipitating agent on the properties of these solids was studied in this work. Samples were prepared by sol-gel process by mixing solutions of iron nitrate and aluminum nitrate and using different precipitating agents (sodium hydroxide and ammonium hydroxide) and impregnated with an alcoholic solution of copper. The solids were characterized by thermogravimetry, Fourier transform infrared spectroscopy, X-ray diffraction, specific surface area and porosity measurement, temperature programmed reduction and Mössbauer spectroscopy. The catalysts were evaluated in the HTS reaction at 1 atm and 400 °C. It was found hematite and magnetite in the catalysts before and after reaction, respectively and no other phase was detected. The dopants were found to be into the iron oxide lattice, a fact that was explained by the similarity of the ionic radii of Cu+2, Al+3 and Fe+3 species, this process being facilitated by ammonium hydroxide. Aluminum and copper alone increased the specific surface area of the solids obtained with ammonium hydroxide but sodium hydroxide inhibited the textural action of copper and aluminum, together or separately. Ammonium hydroxide favored the development of nterparticlemesopores in the macroporous solids obtained. The reducibility of hematite was changed by the dopants and by the kind of the precipitating agent, aluminum hindering the formation of magnetite (Fe3O4) and metallic iron while copper and ammonium hydroxide facilitated this process. Therefore, the dopants favored the formation of active phase (magnetite) and the catalyst stability, delaying its deactivation through the formation of metallic iron. All catalysts were active in HTS reaction, those containing copper and obtained with sodium hydroxide being the most active ones, due to increase in the activity of the active sites and the ease of formation of active phase (magnetite). The role of aluminum was related to increased resistance to reduction of the active phase. The most promising catalyst was the one prepared with sodium hydroxide, which showed high activity (10.68 x 10- 7 mol.s-1.g-1) and high resistance against the reduction of the active phase (magnetite), with the advantage of being non-toxic and can be handled and disposed without risk to human health and the environment.

Les données satellitaires représentent aujourd'hui la vaste majorité des observations assimilées dans les modèles de prévision numérique du temps. Leur exploitation reste cependant sous-optimale, seulement 10% du volume total est assimilé en opérationnel. Environ 80% des données infrarouges étant affectées par les nuages, il est primordial de développer l'assimilation des observations satellitaires dans les zones nuageuses. L'exploitation du sondeur hyperspectral infrarouge IASI a déjà permis une amélioration des prévisions météorologiques grâce à sa précision et son contenu en information jamais inégalés. Son utilisation dans les zones nuageuses reste cependant très complexe à cause de la forte non-linéarité des processus nuageux dans l'infrarouge. Cette thèse propose donc une méthode permettant d'exploiter au mieux les observations nuageuses du sondeur IASI. Un modèle de transfert radiatif avancé utilisant les propriétés microphysiques du nuage a été évalué. Cette méthode présente l'avantage majeur d'utiliser les profils de condensats nuageux produits par les modèles de prévision. Grâce à ce nouveau schéma, les profils de contenus en eau nuageuse ont pu être inversés avec succès à partir des observations IASI et d'un schéma d'assimilation variationnelle uni-dimensionnel (1D-Var). L'impact de ces observations en termes d'analyse et d'évolution des variables nuageuses dans le modèle de prévision a aussi été évalué. Cette étude est une première évaluation du choix des variables de contrôle utilisées lors des inversions. Un modèle simplifié uni-colonne du modèle de prévision AROME a permis de faire évoluer les profils analysés par le 1D-Var sur une période de trois heures. Des résultats prometteurs ont montré la bonne conservation de l'incrément d'analyse pendant plus d'une heure et demie de prévision. La formation des systèmes fortement précipitants étant fortement liée aux contenus en eau nuageuse, ces résultats encourageants laissent entrevoir des retombées majeures pour la prévision des évènements de pluie intense et les applications de prévision numérique à très courte échéance. / Nowadays, most data assimilated in numerical weather prediction come from satellite observations. However, the exploitation of satellite data is still sub-optimal with only 10 to 15% of these data assimilated operationally. Keeping in mind that about 80% of infrared data are affected by clouds, it is a priority to develop the assimilation of cloud-affected satellite data. The hyperspectral infrared sounder IASI has already contributed to the improvement of weather forecasts thanks to its far better spectral resolution and information content compared to previous instruments. The use of cloud-affected IASI radiances is still very complicated due to the high non-linearity of clouds in the infrared. This PhD work suggests an innovative way to take advantage of cloud-affected radiances observed by IASI. An advanced radiative transfer model using cloud microphysical properties has been evaluated. This method has the advantage of using cloud water content profiles directly produced by numerical weather prediction models. Thanks to this new scheme, profiles of cloud water contents have been successfully retrieved from IASI cloud-affected radiances with a one dimensional variational assimilation scheme (1D-Var). The impact of these data in terms of analysis and evolution of cloud variables has been evaluated in a numerical weather prediction model. This study is the first step in evaluating the choice that has been made for the control variables used during the retrievals. A simplified one-dimensional version of the AROME model was used to run three-hour forecasts from the 1D-Var analysed profiles. Promising results have shown a good maintenance of the analysis increment during more than one hour and a half of forecast. In regard to these encouraging results, a positive impact on nearcasting applications and forecasts of heavy rainfall events, which are highly coupled to cloud variables, can be expected in the future.

A porfiria cutânea tardia é causada pela deficiência parcial, herdada ou adquirida, da atividade enzimática da uroporfirinogênio decarboxilase, resultando no acúmulo de uroporfirina e hepta-carboxil porfirinogênio no fígado. Os objetivos deste trabalho foram o estudo das características clínicas e laboratoriais: bioquímica, imunofluorescência e microscopia óptica de 28 doentes com porfiria cutânea tardia, antes e após o tratamento com cloroquina. A microscopia óptica e imunofluorescência direta foram feitas em 23 doentes com porfiria ativa antes do tratamento, em sete doentes com apenas remissão clínica, e em oito doentes com remissão clínica e bioquímica, isto é, porfiria inativa. Sete doentes foram do sexo feminino (25%) e 21 doentes do sexo masculino (75%). A ingestão de álcool foi o fator desencadeante predominante nos homens, e a terapia com estrógeno nas mulheres (anticoncepção e reposição hormonal). A hepatite C esteve associada em 57,1% do total dos doentes (71,4% dos homens e 14,3% das mulheres). Na microscopia óptica de 23 doentes, 86,9% apresentavam bolhas subepidérmicas, e 95,6% exibiam vasos da derme superior com paredes espessadas por depósito de material ácido periódico-Schiff positivo e diastase-resistente. O espessamento dos vasos persistiu em quatro de cinco doentes com remissão bioquímica, porém se apresentava de forma menos intensa. Quanto à imunofluorescência direta dos 23 doentes com porfiria ativa, quatro apresentavam imunofluorescência negativa e 19 apresentavam depósitos de IgG e de complemento (C3) de forma característica no interior e em torno dos vasos e na junção dermo-epidérmica. A IgG estava presente nos vasos de 65,2% e na junção dermo-epidérmica de 47,8%, e C3 estava presente nos vasos de 52,2% e na junção dermo-epidérmica de 39,1%. A fluorescência na parede dos vasos era homogênea, com intensidade moderada ou intensa, e com a sua presença e intensidade tão notável quanto à da junção dermo-epidérmica em 57,9% dos casos. Na remissão clínica durante o tratamento e na remissão bioquímica, o depósito de IgG estava presente na parede dos vasos de 85,7% e 87,5%, respectivamente, e o depósito de C3 nos vasos estava presente em 14,3% e 37,5%, respectivamente. Comparando os doentes antes do tratamento com os doentes em remissão clínica e os que estão em remissão bioquímica, o número de casos com depósito de complemento (C3) nos vasos diminuiu (de 52,2% antes do tratamento, para 14,3% e 37,5%, respectivamente). Na remissão bioquímica a fluorescência predominava mais na parede dos vasos do que na junção dermo-epidérmica em 71,4% dos doentes. O imunomapeamento antigênico da bolha, para determinar o nível da clivagem na junção dermo-epidérmica, foi realizado em sete doentes sem tratamento prévio. Em três casos todos os antígenos, a saber: BP 180 (antígeno do penfigóide bolhoso), laminina, colágeno tipo IV e colágeno tipo VII, estavam localizados em ambos os lados da bolha (sem padrão de clivagem); em dois casos todos os antígenos foram encontrados na base da bolha (clivagem intraepidérmica); em um caso o colágeno tipo IV foi encontrado no teto e o colágeno tipo VII em ambos os lados da bolha (clivagem na sublâmina densa); e em um caso todos antígenos foram encontrados no teto da bolha (clivagem abaixo da sublâmina densa). Portanto, não houve um padrão característico do nível de clivagem no imunomapeamento. Provavelmente o mecanismo que define o nível de clivagem é a lesão fotodinâmica dos lisossomos ao nível dos queratinócitos basais e/ou das células dérmicas. / Porphyria cutanea tarda is caused by the inherited or acquired partial deficiency of the uroporphyrinogen decarboxylase enzyme activity, resulting in the accumulation of uroporphyrin and hepta-carboxyl porphyrinogen in the liver. The purpose of this study was to investigate the clinical and laboratory features: biochemistry and the alterations on skin morphology, on light microscopy and immunofluorescence of 28 patients with the diagnosis of porphyria cutanea tarda, before and after treatment with chloroquine. We report the results of light microscopy and direct immunofluorescence on 23 patients with active porphyria cutanea tarda before treatment, seven patients with clinical remission, and eight patients with clinical and biochemical remission, i.e. inactive porphyria. Seven patients were females (25%) and 21 were males (75%). Alcohol intake was the predominant etiological factor in male patients and estrogen therapy in female patients (contraceptive agents or postmenopausal hormone replacement therapy). Hepatitis C was present in 57,1% of the patients (71,4% of the males and 14,3% of the females). In light microscopy of 23 patients, 86,9% had subepidermal bullae and 95,6% had deposits of PAS-positive diastase-resistant material thickening the vessel wall of the superficial dermis. This thickening of the vessel persisted after biochemical remission in four of five patients but it was less intense. Of the 23 patients with active porphyria, the direct immunofluorescence of four patients was negative and 19 patients revealed IgG and complement (C3) bound in a rather characteristic pattern in and around vessel walls and on the dermal-epidermal junction. IgG was present on the vessels of 65,2% and on the dermal-epidermal junction of 47,8%. C3 was present on the vessels of 52,2% and on the dermal-epidermal junction of 39,1%. The fluorescence on the vessel walls was homogeneous, moderate or very intense and its presence and intensity was as noticeable as on the dermal-epidermal junction in 57,9% of the patients. Patients with clinical remission or biochemical remission had deposit of IgG on the vessel wall in 85,7% and 87,5%, respectively, and deposit of C3 on the vessel wall in 14,3% and 37,5%, respectively. Comparing the patients before treatment to those with clinical remission or with biochemical remission, the number of cases with deposit of C3 on the vessel lessoned (from 52,2% before treatment to 14,3% and 37,5%, respectively). Patients with biochemical remission had the fluorescence predominating on the vessel walls rather than on the dermal-epidermal junction (71,4%). Immunofluorescence mapping of the dermal-epidermal junction, in order to determine the level of the subepidermal split, was possible in seven patients with active porphyria without previous treatment. In three cases all the antigens, i.e. BP180 (bullous pemphigoid antigen), laminin, type IV collagen and type VII collagen, were found on both sides of the bulla (no split level); in two cases all the antigens were found on the floor of the bulla (intra-epidermal split); in one case type IV collagen was found on the roof and type VII collagen on both sides of the bulla (split occurred on the sublamina densa); and in one additional case all the antigens were found on the roof of the bulla (split occurred below sublamina densa). Therefore no standard split level occurs on the dermal-epidermal junction. Probably what defines the split level is the photodynamically induced lysosomal damage affecting keratinocytes of the basal layer and/or dermal cells.

A porfiria cutânea tardia é causada pela deficiência parcial, herdada ou adquirida, da atividade enzimática da uroporfirinogênio decarboxilase, resultando no acúmulo de uroporfirina e hepta-carboxil porfirinogênio no fígado. Os objetivos deste trabalho foram o estudo das características clínicas e laboratoriais: bioquímica, imunofluorescência e microscopia óptica de 28 doentes com porfiria cutânea tardia, antes e após o tratamento com cloroquina. A microscopia óptica e imunofluorescência direta foram feitas em 23 doentes com porfiria ativa antes do tratamento, em sete doentes com apenas remissão clínica, e em oito doentes com remissão clínica e bioquímica, isto é, porfiria inativa. Sete doentes foram do sexo feminino (25%) e 21 doentes do sexo masculino (75%). A ingestão de álcool foi o fator desencadeante predominante nos homens, e a terapia com estrógeno nas mulheres (anticoncepção e reposição hormonal). A hepatite C esteve associada em 57,1% do total dos doentes (71,4% dos homens e 14,3% das mulheres). Na microscopia óptica de 23 doentes, 86,9% apresentavam bolhas subepidérmicas, e 95,6% exibiam vasos da derme superior com paredes espessadas por depósito de material ácido periódico-Schiff positivo e diastase-resistente. O espessamento dos vasos persistiu em quatro de cinco doentes com remissão bioquímica, porém se apresentava de forma menos intensa. Quanto à imunofluorescência direta dos 23 doentes com porfiria ativa, quatro apresentavam imunofluorescência negativa e 19 apresentavam depósitos de IgG e de complemento (C3) de forma característica no interior e em torno dos vasos e na junção dermo-epidérmica. A IgG estava presente nos vasos de 65,2% e na junção dermo-epidérmica de 47,8%, e C3 estava presente nos vasos de 52,2% e na junção dermo-epidérmica de 39,1%. A fluorescência na parede dos vasos era homogênea, com intensidade moderada ou intensa, e com a sua presença e intensidade tão notável quanto à da junção dermo-epidérmica em 57,9% dos casos. Na remissão clínica durante o tratamento e na remissão bioquímica, o depósito de IgG estava presente na parede dos vasos de 85,7% e 87,5%, respectivamente, e o depósito de C3 nos vasos estava presente em 14,3% e 37,5%, respectivamente. Comparando os doentes antes do tratamento com os doentes em remissão clínica e os que estão em remissão bioquímica, o número de casos com depósito de complemento (C3) nos vasos diminuiu (de 52,2% antes do tratamento, para 14,3% e 37,5%, respectivamente). Na remissão bioquímica a fluorescência predominava mais na parede dos vasos do que na junção dermo-epidérmica em 71,4% dos doentes. O imunomapeamento antigênico da bolha, para determinar o nível da clivagem na junção dermo-epidérmica, foi realizado em sete doentes sem tratamento prévio. Em três casos todos os antígenos, a saber: BP 180 (antígeno do penfigóide bolhoso), laminina, colágeno tipo IV e colágeno tipo VII, estavam localizados em ambos os lados da bolha (sem padrão de clivagem); em dois casos todos os antígenos foram encontrados na base da bolha (clivagem intraepidérmica); em um caso o colágeno tipo IV foi encontrado no teto e o colágeno tipo VII em ambos os lados da bolha (clivagem na sublâmina densa); e em um caso todos antígenos foram encontrados no teto da bolha (clivagem abaixo da sublâmina densa). Portanto, não houve um padrão característico do nível de clivagem no imunomapeamento. Provavelmente o mecanismo que define o nível de clivagem é a lesão fotodinâmica dos lisossomos ao nível dos queratinócitos basais e/ou das células dérmicas. / Porphyria cutanea tarda is caused by the inherited or acquired partial deficiency of the uroporphyrinogen decarboxylase enzyme activity, resulting in the accumulation of uroporphyrin and hepta-carboxyl porphyrinogen in the liver. The purpose of this study was to investigate the clinical and laboratory features: biochemistry and the alterations on skin morphology, on light microscopy and immunofluorescence of 28 patients with the diagnosis of porphyria cutanea tarda, before and after treatment with chloroquine. We report the results of light microscopy and direct immunofluorescence on 23 patients with active porphyria cutanea tarda before treatment, seven patients with clinical remission, and eight patients with clinical and biochemical remission, i.e. inactive porphyria. Seven patients were females (25%) and 21 were males (75%). Alcohol intake was the predominant etiological factor in male patients and estrogen therapy in female patients (contraceptive agents or postmenopausal hormone replacement therapy). Hepatitis C was present in 57,1% of the patients (71,4% of the males and 14,3% of the females). In light microscopy of 23 patients, 86,9% had subepidermal bullae and 95,6% had deposits of PAS-positive diastase-resistant material thickening the vessel wall of the superficial dermis. This thickening of the vessel persisted after biochemical remission in four of five patients but it was less intense. Of the 23 patients with active porphyria, the direct immunofluorescence of four patients was negative and 19 patients revealed IgG and complement (C3) bound in a rather characteristic pattern in and around vessel walls and on the dermal-epidermal junction. IgG was present on the vessels of 65,2% and on the dermal-epidermal junction of 47,8%. C3 was present on the vessels of 52,2% and on the dermal-epidermal junction of 39,1%. The fluorescence on the vessel walls was homogeneous, moderate or very intense and its presence and intensity was as noticeable as on the dermal-epidermal junction in 57,9% of the patients. Patients with clinical remission or biochemical remission had deposit of IgG on the vessel wall in 85,7% and 87,5%, respectively, and deposit of C3 on the vessel wall in 14,3% and 37,5%, respectively. Comparing the patients before treatment to those with clinical remission or with biochemical remission, the number of cases with deposit of C3 on the vessel lessoned (from 52,2% before treatment to 14,3% and 37,5%, respectively). Patients with biochemical remission had the fluorescence predominating on the vessel walls rather than on the dermal-epidermal junction (71,4%). Immunofluorescence mapping of the dermal-epidermal junction, in order to determine the level of the subepidermal split, was possible in seven patients with active porphyria without previous treatment. In three cases all the antigens, i.e. BP180 (bullous pemphigoid antigen), laminin, type IV collagen and type VII collagen, were found on both sides of the bulla (no split level); in two cases all the antigens were found on the floor of the bulla (intra-epidermal split); in one case type IV collagen was found on the roof and type VII collagen on both sides of the bulla (split occurred on the sublamina densa); and in one additional case all the antigens were found on the roof of the bulla (split occurred below sublamina densa). Therefore no standard split level occurs on the dermal-epidermal junction. Probably what defines the split level is the photodynamically induced lysosomal damage affecting keratinocytes of the basal layer and/or dermal cells.