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no / In this study, we have shown how particles in carbon black tattoo ink accumulate in the human skin dermis using fine-resolution atomic force microscopy, with which a single ink particle in the collagenous network can be imaged. This information further demonstrates that tattoo inks are nano-particles. Further, we have deposited a commercially available tattoo ink on a glass slide and calculated a range of volumes for single ink particles.

Many non-human animal species use colour to signal dominance, condition or reproductive status. These signals have not previously been noted in humans. This thesis investigates the effects of skin colouration and pigmentation on the apparent health of human faces. Section 2 showed that individuals with increased fruit and vegetable and carotenoid consumption have yellower skin (Study 1) due to increased carotenoid pigmentation in the skin (Study 2). In Section 3, participants enhanced the redness, yellowness and lightness of the skin portions of colour-calibrated facial photographs to optimise healthy appearance. This suggests roles for blood (red) and carotenoid/melanin (yellow) colouration in providing perceptible cues to health. The contrast between lips and facial skin colour was not found to affect the apparent health of the faces, except in the b* (yellowness) axis, where enhanced facial yellowness caused an apparent blue tint to the lips. In Section 4 participants enhanced empirically-derived oxygenated blood colour more than deoxygenated blood colour to optimise healthy appearance. In two-dimensional trials, when both blood colour axes could be manipulated simultaneously, deoxygenated blood colour was removed and replaced with oxygenated blood colour. Oxygenated blood colouration appears to drive the preference for redness in faces. In Section 5 participants increased carotenoid colour significantly more than they increased melanin colour in both single-axis and two-dimensional trials. Carotenoid colour appears to drive the preference for yellowness in faces. In a cross-cultural study (Section 6), preferences for red and yellow in faces were unaffected by face or participant ethnicity, while African participants lightened faces more than UK participants. A preference for more redness in East Asian faces was explained by this group’s lower initial redness. The thesis concludes that pigments that provide sexually-selected signals of quality in many non-human animal species – carotenoids and oxygenated blood - also provide perceptible cues to health in human faces.

Les cellules T spécifiques d'antigène dans la peau participent au contrôle des infections cutanées. Toutefois, leurs mécanismes d'induction après infection ou vaccination ainsi que leur rôle dans la protection et leur maintenance restent à étudier. Nous avons émis l'hypothèse que l'infection cutanée ou la vaccination cutanée pouvaient programmer une réponse cellulaire T spécifique d'antigène cutanée. Notre premier objectif était le développement de modèle d'étude de la peau humaine, des cellules T cutanées et de la vaccination par la peau. Un modèle de greffes de peau humaine à des souris immunodéficientes, a permis de montrer un maintien et la fonctionnalité des cellules présentatrices d'antigènes et cellules T cutanées plusieurs semaines après greffe. J'ai ainsi mis en place un modèle d'étude in vivo des cellules humaines cutanées.Dans un deuxième temps, un essai clinique randomisé chez le volontaire sain, a étudié l'impact de la voie d'administration - intradermique, transcutanée ou intramusculaire - du vaccin antigrippal sur les réponses immunitaires. Cette étude de longue durée et multiparamétrique n'étant pas terminée, nous aborderons les résultats de l'impact de l'inflammation, en particulier CXCL-10, dans l'induction des réponses adaptatives.Enfin, le rôle des lymphocytes T cutanés dans la protection contre les herpesvirus - VZV, HSV-1, HSV-2 - restant méconnus et notamment la potentielle réactivité croisée des cellules T cutanées contre ces 3 virus, j'ai mis en place un modèle murin préclinique permettant d'étudier les réponses T spécifiques cutanées et systémiques à la varicelle après vaccination. Une étude clinique est maintenant en cours de montage. En conclusion, au cours de mon doctorat, j’ai pu mettre en évidence l’importance des LT cutanés notamment mémoires dans la mise en place de la réponse immunitaire après vaccination et/ou infection. Ces données sont importantes pour l’amélioration des stratégies vaccinales. / Antigen -specific T cells in the skin represents a considerable advantage. It has been proposed that these cells may participate in the control of skin infections. However, further investigation is needed to understand their mechanism of induction after infection or vaccination, their maintenance in the skin tissue and their role in the protection upon re-infection. We hypothesized that the skin vaccination or infection can program a cutaneous population of antigen-specific T cell response. In order to study T cell populations in the skin, we set up different in vivo and clinical models of study of human skin T cells. A model of human skin grafts in immunodeficient mice, allowed us to show the persistance of antigen-presenting cells as well as antigen-specific effector T skin cells in human skin engrafted explants. We have demonstrated their functionality several weeks after skin transplantation. This study provides an in vivo model for studying in vivo human skin T cells upon infection or vaccination. In a second part, we performed a randomized clinical trial of healthy volunteers, to study the impact of routes of immunization using trivalent-influenza vaccine (TIV) by intradermal, transcutaneous (hair follicular targeting) or intramuscular routes on immune responses. This long-term study is not completed yet. However, we will discuss the first results of the impact of inflammation including cytokine, CXCL10 on vaccination local side effects and in the induction of adaptive responses. In a third part, we asked the role of T lymphocytes in human skin infections or mucous membranes against herpèsviruses (VZV, HSV-1, and HSV-2). We hypothesized cross-reactive T cell skin against these three viruses. A preclinical mouse model for studying cutaneous and systemic T cell specific responses to varicella after vaccination has been developed. A clinical study is in progress.

A segmentação de pele humana, em imagens coloridas, tem sido largamente estudada nos últimos anos servindo de fundamento para muitos outros estudos como, por exemplo, a detecção de faces. Dentre as inúmeras aplicações de trabalhos relativos à segmentação de pele humana está a de se localizar uma determinada pessoa em locais de grande concentração humana tais como: avenidas, terminais de ônibus, aeroportos, shopping centers e estádios. Desta forma, a necessidade de se obter um sistema que classifique de forma adequada a pele humana tornou-se a principal motivação para o desenvolvimento deste trabalho. Desta forma, propõe-se uma metodologia para melhorar a segmentação de pele humana em imagens coloridas através de um algoritmo mais eficiente. O algoritmo é baseado na média de vizinhanças cujos valores limites, para definição do intervalo de cor equivalente à pele humana, são obtidos através de uma imagem padrão, gerada a priori, com amostras de pele humana. Esta imagem é chamada de \"colcha de retalhos\". A metodologia tem como base de comparação trabalhos anteriores similares, principalmente o desenvolvido por Kovac et al. (2003). Os resultados mostram um desempenho superior da metodologia proposta. / The segmentation of human skin, in colored images, has been studied broadly for the last years serving as foundation for many other studies as, for instance, the detection of faces. Among the countless applications of works related to the segmentation of human skin it is the one of localizing a certain person in places of great human concentration such as: avenues, bus terminals, airports, shopping centers and stadiums. Therefore, the need to obtain a system that classifies in an appropriate way the human skin became the main motivation for the development of this work. This way, a methodology to improve the segmentation of human skin in colored images through a more efficient algorithm is proposed. The algorithm is based on the average of neighborhoods whose limit values, for definition of the interval of equivalent color to the human skins, are obtained through an image pattern, generated in priori, with samples of human skin. This image is called \"bedspread of remnants\". The methodology has as base of comparison similar previous works, mainly the one developed by Kovac et al. (2003). The results show a superior performance of the proposed methodology.

A segmentação de pele humana, em imagens coloridas, tem sido largamente estudada nos últimos anos servindo de fundamento para muitos outros estudos como, por exemplo, a detecção de faces. Dentre as inúmeras aplicações de trabalhos relativos à segmentação de pele humana está a de se localizar uma determinada pessoa em locais de grande concentração humana tais como: avenidas, terminais de ônibus, aeroportos, shopping centers e estádios. Desta forma, a necessidade de se obter um sistema que classifique de forma adequada a pele humana tornou-se a principal motivação para o desenvolvimento deste trabalho. Desta forma, propõe-se uma metodologia para melhorar a segmentação de pele humana em imagens coloridas através de um algoritmo mais eficiente. O algoritmo é baseado na média de vizinhanças cujos valores limites, para definição do intervalo de cor equivalente à pele humana, são obtidos através de uma imagem padrão, gerada a priori, com amostras de pele humana. Esta imagem é chamada de \"colcha de retalhos\". A metodologia tem como base de comparação trabalhos anteriores similares, principalmente o desenvolvido por Kovac et al. (2003). Os resultados mostram um desempenho superior da metodologia proposta. / The segmentation of human skin, in colored images, has been studied broadly for the last years serving as foundation for many other studies as, for instance, the detection of faces. Among the countless applications of works related to the segmentation of human skin it is the one of localizing a certain person in places of great human concentration such as: avenues, bus terminals, airports, shopping centers and stadiums. Therefore, the need to obtain a system that classifies in an appropriate way the human skin became the main motivation for the development of this work. This way, a methodology to improve the segmentation of human skin in colored images through a more efficient algorithm is proposed. The algorithm is based on the average of neighborhoods whose limit values, for definition of the interval of equivalent color to the human skins, are obtained through an image pattern, generated in priori, with samples of human skin. This image is called \"bedspread of remnants\". The methodology has as base of comparison similar previous works, mainly the one developed by Kovac et al. (2003). The results show a superior performance of the proposed methodology.

黑色素生成是為了保護皮膚細胞免受紫外光傷害的一個生化過程。在這過程中，黑色素在人類表皮底層的黑色素細胞的黑色素體內產生。該過程可以被基因，荷爾蒙或環境因素所影響。黑色素的製造量是依賴速度限制酶酪氨酸酶的活性，黑色素體的數量和大小，黑色素體通過黑色素細胞的偽足傳送致角質細胞的速度及黑色素體在角質細胞內的分佈。這些細胞過程會受皮膚顏色或紫外光曝光量的變化而影響。當黑色素的產生超過黑色素的降解，黑色素沉著毛病便出現。根據不同的皮膚類型，年齡組別及累積紫外光曝光程度而引發雀斑或黃褐斑的形成。很多治療方法市面上能夠提供，它們包括人工合成化粧品，激光，整容手術等。這些治療方法通常會產生副作用及蘊藏高風險。因此從天然物質裏尋找治療藥物便成了美容學的一個新的研究方向。在這研究裏，十種草本植物就從自古以來用作治療黑色素沉著毛病的傅統中藥中被挑選出來。那些草本植物被四種擁有不同極性的溶劑提取。小鼠黑色素細胞被用以篩選提取物的降黑色素能力。結果發現當歸的正己烷及二氯甲烷的提取物有正面效用。當歸的化學成份4-乙基間苯二酚、4-乙基苯酚及1-十四烷醇也能降低小鼠黑色素細胞的黑色素量。數種生化技術繼而被應用作研究有效化學物的藥理。他們包括西方墨點法、環磷酸腺苷測試、蛋白激酶A活性測試及酪氨酸酶活性測試。 / Melanogenesis is a biochemical process designated for protecting skin cells from ultraviolet (UV)-induced damage. During the process, melanin is produced in the melanosomes of the melanocytes located at the basal epidermis of human. The process could be affected by genetic, hormonal or environmental factors. Amount of melanin synthesized depending on the activity of the rate-limiting enzyme tyrosinase, number and size of melanosomes, the transfer rate of melanosomes to keratinocytes through the melanocyte dendritic projections and the distribution pattern of melanosomes within keratinocytes. These cellular processes are influenced by variations in skin color or UV exposure amount. When melanin synthesis exceeds melanin degradation, hyperpigmentation disorder arises. This lead to the formation of freckles or chloasma according to different skin types, age groups and degree of cumulative UV exposure. A number of treatments are commercially available, they include applying synthetic cosmetics, laser, plastic surgery, etc. These treatments usually produce side-effects and possess high risk. Therefore, searching for therapeutic agents from natural compounds has become a new research direction in cosmetology. In this study, ten herbs were chosen from traditional Chinese medicine (TCM) which had been applied for treating hyperpigmentation. The herbs were extracted by four solvents with different polarity. The extracts were screened for their hypopigmentary ability by using melan-a cells. It was found that the hexane and dichloromethane extracts of Angelica sinensis possessed positive effects. 4-ethylresorcinol, 4-ethylphenol and 1-tetradecanol, the chemical constituents of A. sinensis, also attenuated melanin amount in melan-a cells. Moreover, several biochemical techniques were utilized to study the pharmaceutical mechanisms of the potent compounds. They include Western blot, cyclic adenosine monophosphate (cAMP) assay, protein kinase A (PKA) activity assay and tyrosinase activity assay. / Detailed summary in vernacular field only. / Lam, Rosanna Yen Yen. / Thesis (Ph.D.)--Chinese University of Hong Kong, 2012. / Includes bibliographical references (leaves 127-146). / Electronic reproduction. Hong Kong : Chinese University of Hong Kong, [2012] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Abstract also in Chinese. / Abstract --- p.i / Chinese Abstract --- p.iii / Acknowledgements --- p.iv / List of Publications --- p.v / Table of Contents --- p.vi / List of Abbreviations --- p.xii / List of Figures --- p.xv / List of Tables --- p.xviii / Chapter Chapter 1 --- Introduction --- p.1 / Chapter 1.1 --- Demand of cosmetics --- p.1 / Chapter 1.2 --- Skin structures and functions --- p.1 / Chapter 1.2.1 --- Epidermis --- p.3 / Chapter 1.2.1.1 --- Stratum corneum --- p.4 / Chapter 1.2.1.2 --- Stratum granulosum --- p.4 / Chapter 1.2.1.3 --- Stratum spinosum --- p.4 / Chapter 1.2.1.4 --- Stratum basale --- p.4 / Chapter 1.2.2 --- Dermis --- p.5 / Chapter 1.2.3 --- Hypodermis --- p.5 / Chapter 1.3 --- Sun irradiation --- p.5 / Chapter 1.4 --- Variety of skin types --- p.6 / Chapter 1.5 --- Biochemical reactions within melanocyte --- p.7 / Chapter 1.6 --- Pigmentation disorder --- p.14 / Chapter 1.7 --- From the view of traditional Chinese medicine --- p.16 / Chapter 1.8 --- Treatments available for hyperpigmentation --- p.18 / Chapter 1.9 --- Aims of study and application of strategies --- p.19 / Chapter Chapter 2 --- Investigation of the inhibitory effect of herbal extracts and their constituent compounds on melanin synthesis --- p.20 / Chapter 2.1 --- Introduction --- p.20 / Chapter 2.2 --- Materials and methods --- p.21 / Chapter 2.2.1 --- Materials --- p.21 / Chapter 2.2.2 --- Herbal extraction --- p.23 / Chapter 2.2.3 --- Cell culture --- p.25 / Chapter 2.2.4 --- Growth curve and melanin production curve --- p.25 / Chapter 2.2.5 --- SRB assay --- p.26 / Chapter 2.2.6 --- Calibration curve for SRB assay --- p.27 / Chapter 2.2.7 --- Measurement of melanin production --- p.27 / Chapter 2.2.8 --- Calibration curve for melanin production assay --- p.28 / Chapter 2.2.9 --- Statistical analysis --- p.28 / Chapter 2.3 --- Results --- p.29 / Chapter 2.3.1 --- Growth curve and melanin production curve for assay development --- p.29 / Chapter 2.3.2 --- Calibration curves of SRB assay and melanin production assay --- p.32 / Chapter 2.3.3 --- Hypopigmentary effect of 40 herbal extracts --- p.35 / Chapter 2.3.4 --- Hypopigmentary effects of chemical components of A. sinensis --- p.41 / Chapter 2.4 --- Discussion --- p.49 / Chapter Chapter 3 --- Study of the effect of potential compounds on melanogenic protein expression by Western blot --- p.54 / Chapter 3.1 --- Introduction --- p.54 / Chapter 3.2 --- Materials and methods --- p.56 / Chapter 3.2.1 --- Materials --- p.56 / Chapter 3.2.2 --- Cell culture --- p.56 / Chapter 3.2.3 --- Preparation of cell lysates --- p.57 / Chapter 3.2.4 --- Protein assay --- p.57 / Chapter 3.2.5 --- SDS-PAGE and membrane transfer --- p.58 / Chapter 3.2.6 --- Washing of blotted antibodies and film exposure --- p.59 / Chapter 3.3 --- Results --- p.61 / Chapter 3.4 --- Discussion --- p.70 / Chapter Chapter 4 --- Study of the effect of potential compounds on melanogenic gene expression by RT-PCR --- p.76 / Chapter 4.1 --- Introduction --- p.76 / Chapter 4.2 --- Materials and methods --- p.76 / Chapter 4.2.1 --- Materials --- p.77 / Chapter 4.2.2 --- Cell culture --- p.77 / Chapter 4.2.3 --- RNA extraction --- p.78 / Chapter 4.2.4 --- cDNA synthesis --- p.78 / Chapter 4.2.5 --- PCR --- p.80 / Chapter 4.3 --- Results --- p.83 / Chapter 4.4 --- Discussion --- p.85 / Chapter Chapter 5 --- Study of the effect of potential compounds on cAMP level by EIA --- p.85 / Chapter 5.1 --- Introduction --- p.86 / Chapter 5.2 --- Materials and methods --- p.86 / Chapter 5.2.1 --- Materials --- p.86 / Chapter 5.2.2 --- Cell culture --- p.86 / Chapter 5.2.3 --- Preparation of cell lysates --- p.86 / Chapter 5.2.4 --- Protein assay --- p.87 / Chapter 5.2.5 --- The cAMP assay --- p.88 / Chapter 5.2.6 --- Preparation of cAMP calibration curve --- p.88 / Chapter 5.2.7 --- Calculation --- p.89 / Chapter 5.2.8 --- Statistical analysis --- p.89 / Chapter 5.3 --- Results --- p.90 / Chapter 5.4 --- Discussion --- p.94 / Chapter Chapter 6 --- Study of the effect of potential compounds on PKA activity by PKA activity assay --- p.96 / Chapter 6.1 --- Introduction --- p.96 / Chapter 6.2 --- Materials and methods --- p.96 / Chapter 6.2.1 --- Materials --- p.97 / Chapter 6.2.2 --- Cell culture --- p.97 / Chapter 6.2.3 --- Preparation of cell lysates --- p.98 / Chapter 6.2.4 --- Protein assay --- p.98 / Chapter 6.2.5 --- The PKA kinase activity assay --- p.100 / Chapter 6.2.6 --- Calculation --- p.100 / Chapter 6.2.7 --- Statistical analysis --- p.100 / Chapter 6.3 --- Results --- p.101 / Chapter 6.4 --- Discussion --- p.104 / Chapter Chapter 7 --- Study of the effect of potential compounds on tyrosinase activity by enzyme inhibition assay --- p.107 / Chapter 7.1 --- Introduction --- p.107 / Chapter 7.2 --- Materials and methods --- p.108 / Chapter 7.2.1 --- Materials --- p.108 / Chapter 7.2.2 --- Assay development for mushroom tyrosinase --- p.109 / Chapter 7.2.3 --- Mushroom tyrosinase inhibition assay --- p.109 / Chapter 7.2.4 --- Cell culture --- p.110 / Chapter 7.2.5 --- Preparation of cellular tyrosinase --- p.110 / Chapter 7.2.6 --- Protein assay --- p.111 / Chapter 7.2.7 --- Cellular tyrosinase inhibition assay --- p.111 / Chapter 7.2.8 --- Calculation --- p.112 / Chapter 7.2.9 --- Statistical analysis --- p.112 / Chapter 7.3 --- Results --- p.113 / Chapter 7.4 --- Discussion --- p.120 / Chapter Chapter 8 --- General discussion --- p.123 / References --- p.127

TGF-β isoforms are important signalling molecules in wound repair in the skin. Transforming growth factor β3 (TGF-β3) has been implicated in scarless healing. In both animal and human models the application of exogenous TGF-β3 causes a reduction in the inflammatory response and improves the architecture of the neodermis. Research into the influence of TGF-β on scarring has tended to focus on fibroblasts. However, keratinocytes play a major role in scarring both indirectly, as a result of their influence over the behaviour of fibroblasts and also by directly influencing wound contraction. Thus, experiments were carried out to investigate the influence of TGF-β3 on the behaviours of a keratinocyte cell line (HaCaT). Incubation with TGF-β3 increased cell spreading and appeared to reduce cell-surface contacts indicated by both SPR imaging and a detachment assay. TGF-β3 also caused a decreased cell alignment response to microcontact printed protein patterns, in part due to the deposition of laminin which is associated with the TGF-β induced cell migration. There is evidence that TGF-β isoforms differentially influence the outcome of wound healing. Similar to the results produce following addition of exogenous TGF-β3, the neutralisation of TGF-β1 and 2 has been shown to reduce scar formation in the adult wounds. During reepithelialisation keratinocytes experience a dynamic environment. Both extracellular matrix proteins and growth factors influence the progression of wound repair which includes both cell migration and proliferation. Few studies have examined collective cell behaviour in response to TGF-β isoforms and ECM coated substrates. Thus both wound closure and cell proliferation assays were conducted for different ECM proteins fibronectin, laminin and collagen type I and for TGF-β1, 2 and 3. Rates of wound closure were significantly reduced on laminin coated substrates while cell proliferation rates were increased. TGF-β2 and 3 induced significant increases in wound closure rates. This appeared to correspond with an increase in the number of cells independently migrating out from the wound margins. Only TGF-β3 caused a significant decrease in cell proliferation over a 4 day period. Laminin332 deposition is central to the reepithelialisation process and is known to be induced in response to TGF-β. Thus experiments were carried out to investigate HaCaT cell laminin332 deposition in response to TGF-β1, 2 and 3. Both an immunofluorescence staining technique and an ELISA based semi-quantification method was used. Following 4 day incubation all TGF-β isoforms significantly increased laminin332 deposition; however TGF-β2 and 3 caused the most significant increases. Integrin receptors enable cell-matrix interactions during wound repair. TGF-β is known to influence the expression of integrin subunits. Thus, experiments were carried out to compare the influence of each TGF-β isoform on the expression of subunits β3, β2, β5, β1 and β4. All TGF-β isoforms significantly increased all subunit expression. TGF-β3 caused the most significant increase in β4 and both TGF-β2 and 3 caused the most significant increase in β2. While there were differences in cell responses to each isoforms, TGF-β3 did not stand out from the other two isoforms. Interestingly, TGF-β2 shared more similarities with TGF-β3 than it did with TGF-β1, in its role in enhancing wound closure and LN332 deposition. These comparative studies have shown that differences exist in the way TGF-β isoforms influence HaCaT cell behaviour, namely migration, laminin deposition and integrin expression.

A detecção de gestos é uma etapa importante em aplicações de interação humanocomputador. Se a mão do usuário é detectada com precisão, tanto a análise quanto o reconhecimento do gesto de mão se tornam mais simples e confiáveis. Neste trabalho, descrevemos um novo método para detecção de pele humana, destinada a ser empregada como uma etapa de pré-processamento para segmentação de gestos de mão em sistemas que visam o seu reconhecimento. Primeiramente, treinamos os modelos de cor e textura de pele (material a ser identificado) a partir de um conjunto de treinamento formado por imagens de pele. Nessa etapa, construímos um modelo de mistura de Gaussianas (GMM), para determinar os tons de cor da pele e um dicionário de textons, para textura de pele. Em seguida, introduzimos um estratégia de fusão estocástica de regiões de texturas, para determinar todos os segmentos de diferentes materiais presentes na imagem (cada um associado a uma textura). Tendo obtido todas as regiões, cada segmento encontrado é classificado com base nos modelos de cor de pele (GMM) e textura de pele (dicionário de textons). Para testar o desempenho do algoritmo desenvolvido realizamos experimentos com o conjunto de imagens SDC, projetado especialmente para esse tipo de avaliação (detecção de pele humana). Comparado com outras técnicas do estado-daarte em segmentação de pele humana disponíveis na literatura, os resultados obtidos em nossos experimentos mostram que a abordagem aqui proposta é resistente às variações de cor e iluminação decorrentes de diferentes tons de pele (etnia do usuário), assim como de mudanças de pose da mão, mantendo sua capacidade de discriminar pele humana de outros materiais altamente texturizados presentes na imagem. / Gesture detection is an important task in human-computer interaction applications. If the hand of the user is precisely detected, both analysis and recognition of hand gesture become more simple and reliable. This work describes a new method for human skin detection, used as a pre-processing stage for hand gesture segmentation in recognition systems. First, we obtain the models of color and texture of human skin (material to be identified) from a training set consisting of skin images. At this stage, we build a Gaussian mixture model (GMM) for identifying skin color tones and a dictionary of textons for skin texture. Then, we introduce a stochastic region merging strategy, to determine all segments of different materials present in the image (each associated with a texture). Once the texture regions are obtained, each segment is classified based on skin color (GMM) and skin texture (dictionary of textons) model. To verify the performance of the developed algorithm, we perform experiments on the SDC database, specially designed for this kind of evaluation (human skin detection). Also, compared with other state-ofthe- art skin segmentation techniques, the results obtained in our experiments show that the proposed approach is robust to color and illumination variations arising from different skin tones (ethnicity of the user) as well as changes of pose, while keeping its ability for discriminating human skin from other highly textured background materials.

A detecção de gestos é uma etapa importante em aplicações de interação humanocomputador. Se a mão do usuário é detectada com precisão, tanto a análise quanto o reconhecimento do gesto de mão se tornam mais simples e confiáveis. Neste trabalho, descrevemos um novo método para detecção de pele humana, destinada a ser empregada como uma etapa de pré-processamento para segmentação de gestos de mão em sistemas que visam o seu reconhecimento. Primeiramente, treinamos os modelos de cor e textura de pele (material a ser identificado) a partir de um conjunto de treinamento formado por imagens de pele. Nessa etapa, construímos um modelo de mistura de Gaussianas (GMM), para determinar os tons de cor da pele e um dicionário de textons, para textura de pele. Em seguida, introduzimos um estratégia de fusão estocástica de regiões de texturas, para determinar todos os segmentos de diferentes materiais presentes na imagem (cada um associado a uma textura). Tendo obtido todas as regiões, cada segmento encontrado é classificado com base nos modelos de cor de pele (GMM) e textura de pele (dicionário de textons). Para testar o desempenho do algoritmo desenvolvido realizamos experimentos com o conjunto de imagens SDC, projetado especialmente para esse tipo de avaliação (detecção de pele humana). Comparado com outras técnicas do estado-daarte em segmentação de pele humana disponíveis na literatura, os resultados obtidos em nossos experimentos mostram que a abordagem aqui proposta é resistente às variações de cor e iluminação decorrentes de diferentes tons de pele (etnia do usuário), assim como de mudanças de pose da mão, mantendo sua capacidade de discriminar pele humana de outros materiais altamente texturizados presentes na imagem. / Gesture detection is an important task in human-computer interaction applications. If the hand of the user is precisely detected, both analysis and recognition of hand gesture become more simple and reliable. This work describes a new method for human skin detection, used as a pre-processing stage for hand gesture segmentation in recognition systems. First, we obtain the models of color and texture of human skin (material to be identified) from a training set consisting of skin images. At this stage, we build a Gaussian mixture model (GMM) for identifying skin color tones and a dictionary of textons for skin texture. Then, we introduce a stochastic region merging strategy, to determine all segments of different materials present in the image (each associated with a texture). Once the texture regions are obtained, each segment is classified based on skin color (GMM) and skin texture (dictionary of textons) model. To verify the performance of the developed algorithm, we perform experiments on the SDC database, specially designed for this kind of evaluation (human skin detection). Also, compared with other state-ofthe- art skin segmentation techniques, the results obtained in our experiments show that the proposed approach is robust to color and illumination variations arising from different skin tones (ethnicity of the user) as well as changes of pose, while keeping its ability for discriminating human skin from other highly textured background materials.