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A preparação de materiais vítreos e cerâmicos pelo processo sol-gel vem ganhando um desenvolvimento muito grande nos últimos anos, superando em muitos casos as tecnologias convencionais. Este trabalho apresenta um processo sol-gel original de modo a obter sílica densa, amorfa e monolítica cuja estrutura gel é reforçada mecanicamente pela adição ao sol inicial de microesferas de sílica preparadas pelo método de Stöber ou pó de sílica comercial (Cab-O-Sil M5), evitando o problema de quebras. Análises feitas com microscopia eletrônica de transmissão (TEM), área superficial BET, tempo de gelificação, difratometria de raio-x, densidade, microdureza Vickers, espectroscopia de absorção óptica do ultravioleta ao infravermelho caracterizam cada uma das etapas das transições sol-gel úmido-gel seco-vidro. Os materiais vítreos preparados apresentam qualidade óptica comparável à da sílica comercialThe preparation of glasses and ceramics by the sol-gel process received notable development in the last few years, showing in many cases great advantages on conventional technologies. This work presents an original sol-gel process in order to obtain dense, amorphous and monolithic-silica whose gel structure is reinforced mechanically by addition to the initial sol of either silica microspheres prepared by the Stöber method or fumed silica powder (Cab-O-Sil M5 Cabot), avoiding the cracks problem. Analysis of transmission electron microscopy (TEM), BET surface area, gelation time, x-ray difratometry, density, Vickers microhardness, optical spectroscopy absorption from UV to IR were used to characterize each step of the process sol-wet, gel-dry gel-glass. SiO2 glasses materials prepared in this way present optical quality similar to that obtain commerciall

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A preparação de materiais vítreos e cerâmicos pelo processo sol-gel vem ganhando um desenvolvimento muito grande nos últimos anos, superando em muitos casos as tecnologias convencionais. Este trabalho apresenta um processo sol-gel original de modo a obter sílica densa, amorfa e monolítica cuja estrutura gel é reforçada mecanicamente pela adição ao sol inicial de microesferas de sílica preparadas pelo método de Stöber ou pó de sílica comercial (Cab-O-Sil M5), evitando o problema de quebras. Análises feitas com microscopia eletrônica de transmissão (TEM), área superficial BET, tempo de gelificação, difratometria de raio-x, densidade, microdureza Vickers, espectroscopia de absorção óptica do ultravioleta ao infravermelho caracterizam cada uma das etapas das transições sol-gel úmido-gel seco-vidro. Os materiais vítreos preparados apresentam qualidade óptica comparável à da sílica comercialThe preparation of glasses and ceramics by the sol-gel process received notable development in the last few years, showing in many cases great advantages on conventional technologies. This work presents an original sol-gel process in order to obtain dense, amorphous and monolithic-silica whose gel structure is reinforced mechanically by addition to the initial sol of either silica microspheres prepared by the Stöber method or fumed silica powder (Cab-O-Sil M5 Cabot), avoiding the cracks problem. Analysis of transmission electron microscopy (TEM), BET surface area, gelation time, x-ray difratometry, density, Vickers microhardness, optical spectroscopy absorption from UV to IR were used to characterize each step of the process sol-wet, gel-dry gel-glass. SiO2 glasses materials prepared in this way present optical quality similar to that obtain commerciall

Impact of visible light on skin health: The role of antioxidants and free radical quenchers in skin protection

Until recently, the primary focus of photobiology has centered on the impact of UV radiation on skin health, including DNA damage and oncogenesis; however, the significant effects of visible light (VL) on skin remain grossly underreported. VL has been reported to cause erythema in individuals with light skin (Fitzpatrick skin types [FSTs] I-III) and pigmentary changes in individuals with dark skin types (FSTs IV-VI). These effects have importance in dermatologic diseases and potentially play a role in conditions aggravated by sun exposure, including phototoxicity in patients with FSTs I to III and post-inflammatory hyperpigmentation and melasma in patients with FSTs IV to VI. The induction of free radicals, leading to the generation of reactive species, is one driving mechanism of VL-induced skin pathologies, leading to the induction of melanogenesis and hyperpigmentation. Initial clinical studies have demonstrated the effectiveness of topical sunscreen with antioxidant combinations in inhibiting VL + UV-A1-induced erythema in FSTs I to III and reducing pigmentation in FSTs IV to VI. Antioxidants may help prevent the worsening of pigmentary disorders and can be incorporated into photoprotective strategies. It is essential that dermatologists and the public are aware of the impact of VL on skin, especially in patients with skin of color, and understand the available options for VL protection

Impact of visible light on skin health: The role of antioxidants and free radical quenchers in skin protection

Until recently, the primary focus of photobiology has centered on the impact of UV radiation on skin health, including DNA damage and oncogenesis; however, the significant effects of visible light (VL) on skin remain grossly underreported. VL has been reported to cause erythema in individuals with light skin (Fitzpatrick skin types [FSTs] I-III) and pigmentary changes in individuals with dark skin types (FSTs IV-VI). These effects have importance in dermatologic diseases and potentially play a role in conditions aggravated by sun exposure, including phototoxicity in patients with FSTs I to III and post-inflammatory hyperpigmentation and melasma in patients with FSTs IV to VI. The induction of free radicals, leading to the generation of reactive species, is one driving mechanism of VL-induced skin pathologies, leading to the induction of melanogenesis and hyperpigmentation. Initial clinical studies have demonstrated the effectiveness of topical sunscreen with antioxidant combinations in inhibiting VL + UV-A1-induced erythema in FSTs I to III and reducing pigmentation in FSTs IV to VI. Antioxidants may help prevent the worsening of pigmentary disorders and can be incorporated into photoprotective strategies. It is essential that dermatologists and the public are aware of the impact of VL on skin, especially in patients with skin of color, and understand the available options for VL protection

Nanocompósitos de blendas HDPE/LLDPE e OMMT - parte I: avaliação das propriedades termo-mecânicas e da resistência ao intemperismo

Nanocompósitos de blendas de polietileno de alta densidade (HDPE) com polietileno linear de baixa densidade (LLDPE) e OMMT (montmorilonita organofílica) foram preparados sob fusão em extrusora de dupla-rosca, utilizando HDPE-g-MA como agente compatibilizante. A caracterização estrutural foi realizada por análises de difração de raios X em alto ângulo (WAXD), microscopia eletrônica de transmissão (MET). Os resultados indicam que a adição do agente compatibilizante favoreceu a formação da microestrutura predominantemente intercalada. Estudos dinâmico-mecânicos mostraram que a adição do agente compatibilizante aumentou as interações entre a carga e a matriz poliolefínica. As diferentes condições de intemperismo as quais os materiais foram submetidos influenciaram no comportamento mecânico dos nanocompósitos de blenda HDPE/LLDPE. Os tratamentos realizados em estufa com circulação forçada de ar e em água proporcionaram o alívio de tensões residuais presentes no sistema, enquanto que o tratamento realizado em câmara de envelhecimento acelerado levou à formação de grupos carbonílicos, de pequena massa molar, que diminuíram o grau de cristalinidade e o módulo elástico dos nanocompósitos

Evaluation of efficacy of antioxidant-enriched sunscreen prodcuts against long wavelength ultraviolet A1 and visible light

ObjectiveThe synergistic effects of VL and long wavelength UVA1 (VL + UVA1, 370–700 nm) on inducing pigmentation and erythema in skin have been demonstrated and linked to exacerbation of dermatologic conditions including melasma and post-inflammatory hyperpigmentation. This study aimed to compare the photoprotection of organic sunscreens enriched with antioxidant (AO) combinations against VL + UVA1 induced biologic effects. The efficacy was compared with that offered by a commercially available tinted sunscreen.MethodsTen healthy adult subjects with Fitzpatrick skin phototypes IV–VI were enrolled (nine completed). VL + UVA1 dose of 380 J/cm2 was utilized. Assessment methods were polarized photography, investigator global scoring and diffuse reflectance spectroscopy (DRS). Measurements were obtained at baseline and immediately, 24 h and 7 days after irradiation.ResultsSites treated with tinted sunscreen product had significantly less pigmentation compared with untreated but irradiated skin at all time points. However, DRS results demonstrated that the 5-AO sunscreen performed comparably or better than all sunscreens tested with relatively lower dyschromia, delayed erythema and pigmentation.ConclusionThese results highlight the potential of AO-enriched sunscreens to be photoprotective against VL + UVA1. The combination of efficacy and the cosmetic appearance of this product may provide wider acceptability which is crucial considering the limited available means of protection against this waveband.RésuméObjectifles effets synergiques de la lumière visible (LV) et des rayons ultraviolets long (UVA1) (LV + UVA1, 370 à 700 nm) sur l’induction de la pigmentation et de l’érythème cutané ont été démontrés et liés à l’exacerbation des affections dermatologiques, notamment le mélasma et l’hyperpigmentation post-inflammatoire. Cette étude visait à comparer la photoprotection des écrans solaires organiques enrichis en associations antioxydantes (AO) contre les effets biologiques induits par LV+UVA1. L’efficacité a été comparée à celle offerte par un écran solaire teinté disponible dans le commerce.Méthodesdix sujets adultes en bonne santé présentant des phototypes cutanés de Fitzpatrick IV à VI ont été inclus (neuf ont terminé l’étude). On a utilisé une dose LV+UVA1 de 380 J/cm2. Les méthodes d’évaluation étaient la photographie polarisée, le score global de l’investigateur et la spectroscopie de réflectance diffuse (DRS). Les mesures ont été obtenues immédiatement à l’entrée dans l’étude et, 24 h et 7 jours après l’irradiation.Résultatsles sites traités avec un produit de protection solaire teinté présentaient une pigmentation significativement inférieure à celle de la peau non traitée mais irradiée, à toutes les heures de mesure. Cependant, les résultats de la DRS ont démontré que l’écran solaire 5-AO fonctionnait de manière comparable ou mieux que tous les écrans solaires testés avec une dyschromie, un érythème retardé et une pigmentation relativement plus faible.Conclusionces résultats mettent en évidence le potentiel des écrans solaires enrichis en AO comme facteur de photoprotection contre LV+UVA1. La combinaison de l’efficacité et de l’aspect esthétique de ce produit peut permettre une plus grande acceptabilité, ce qui est essentiel compte tenu de la disponibilité limitée des moyens de protection contre cette gamme d’ondes.The synergistic effects of VL and long wavelength UVA1 (VL + UVA1, 370–700 nm) on inducing pigmentation and erythema in skin have been demonstrated and linked to exacerbation of dermatologic conditions including melasma and post-inflammatory hyperpigmentation. This study aims to compare the photoprotection of organic sunscreens enriched with antioxidant (AO) combinations against VL + UVA1 induced biologic effects. The efficacy was compared to that offered by a commercially available tinted sunscreen.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/173006/1/ics12785.pdfhttp://deepblue.lib.umich.edu/bitstream/2027.42/173006/2/ics12785_am.pd

Evaluation of efficacy of antioxidant-enriched sunscreen prodcuts against long wavelength ultraviolet A1 and visible light

OBJECTIVE: The synergistic effects of VL and long wavelength UVA1 (VL+UVA1, 370-700 nm) on inducing pigmentation and erythema in skin have been demonstrated and linked to exacerbation of dermatologic conditions including melasma and post-inflammatory hyperpigmentation. This study aims to compare the photoprotection of organic sunscreens enriched with antioxidant (AO) combinations against VL+UVA1 induced biologic effects. The efficacy was compared to that offered by a commercially available tinted sunscreen. METHODS: Ten healthy adult subjects with Fitzpatrick skin phototypes IV-VI were enrolled (nine completed). VL+UVA1 dose of 380 J/cm(2) was utilized. Assessment methods were polarized photography, investigator global scoring, and diffuse reflectance spectroscopy (DRS). Measurements were obtained at baseline and immediately, 24 hours, and 7 days after irradiation. RESULTS: Sites treated with tinted sunscreen product had significantly less pigmentation compared with untreated but irradiated skin at all time points. However, DRS results demonstrated that the 5-AO sunscreen performed comparably or better than all sunscreens tested with relatively lower dyschromia, delayed erythema and pigmentation. CONCLUSION: These results highlight the potential of AO enriched sunscreens to be photoprotective against VL+UVA1. The combination of efficacy and the cosmetic appearance of this product may provide wider acceptability which is crucial considering the limited available means of protection against this waveband

Nanocompósitos de blendas HDPE/LLDPE e OMMT - Parte II: avaliação das propriedades térmica, óticas e de transporte a gases

Nanocompósitos de blendas de polietileno de alta densidade (HDPE) com polietileno linear de baixa densidade (LLDPE) e OMMT (montmorilonita organofílica) foram preparados sob fusão em extrusora de dupla-rosca, utilizando HDPE-g-MA como agente compatibilizante. Os nanocompósitos foram caracterizados através das propriedades térmicas, óticas e de transporte de gases. A blenda HDPE/LLDPE e os nanocompósitos das blendas HDPE/LLDPE como esperado comportam-se como barreira ao vapor de água e são permeáveis ao CO2 e O2. A adição de nanoargila modificou o grau de cristalinidade da matriz polimérica dos nanocompósitos e a diminuição do coeficiente de permeabilidade foi atribuída ao aumento do grau de cristalinidade e do aumento ao caminho difusional para as moléculas do gás passarem pelo filme polimérico. O caminho difusional mais longo devido ao aumento da tortuosidade está relacionado a uma boa dispersão da carga inorgânica, boa molhabilidade desta pela matriz e forte interações na interface. Modelos teóricos de permeabilidade propostos por Nielsen e Bharadwaj foram utilizados para estimar a razão de aspecto da nanoargila nos nanocompósitos e forneceram resultados que se correlacionam bem com as morfologias observadas por microscopia eletrônica de transmissão