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1
Reed, Susan, of Western Sydney Hawkesbury University e of Science Technology and Environment College. "Development of method to assess skin contact to chemicals". THESIS_CSTE_XXX_Reed_S.xml, 2001. http://handle.uws.edu.au:8081/1959.7/611.
Testo completoAbstract (sommario):
Chemical exposure of the skin has become a route of entry of some chemicals into the body and has come under major review in recent times. This research aims to develop a method of estimating skin exposure that is both reliable and non-prohibitive in cost. This involved the design and testing of skin patches adaptable for monitoring skin exposure to chemicals using several different types of absorbents which could be easily worn against skin. The final design of the patch used either activated charcoal or tenax as the absorbing medium. The patches were then desorbed with a solvent in order to analyse the chemicals. The results of the study showed that many skin exposures do not have a direct relationship with inhalation exposures, which is important because currently there are no estimates of the levels of skin exposures that may have potential long term health effects. The patch has proved successful for detecting the presence and determining the amount of chemicals that come in contact with the skin. Charcoal patches have the widest application, but are not suitable for all situations and tenax should be used on these occasions.Doctor of Philosophy (PhD)
2
Reed, Susan. "Development of method to assess skin contact to chemicals". Thesis, View thesis View thesis, 2001. http://handle.uws.edu.au:8081/1959.7/611.
Testo completoAbstract (sommario):
Chemical exposure of the skin has become a route of entry of some chemicals into the body and has come under major review in recent times. This research aims to develop a method of estimating skin exposure that is both reliable and non-prohibitive in cost. This involved the design and testing of skin patches adaptable for monitoring skin exposure to chemicals using several different types of absorbents which could be easily worn against skin. The final design of the patch used either activated charcoal or tenax as the absorbing medium. The patches were then desorbed with a solvent in order to analyse the chemicals. The results of the study showed that many skin exposures do not have a direct relationship with inhalation exposures, which is important because currently there are no estimates of the levels of skin exposures that may have potential long term health effects. The patch has proved successful for detecting the presence and determining the amount of chemicals that come in contact with the skin. Charcoal patches have the widest application, but are not suitable for all situations and tenax should be used on these occasions.
3
Ibrahim, Sarah A. "A Structure-Enhancement Relationship and Mechanistic Study of Chemical Enhancers on Human Epidermal Membrane based on Maximum Enhancement Effect (Emax)". University of Cincinnati / OhioLINK, 2010. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1266598335.
Testo completo
4
Robson, Denise Lesley. "Buprenorphine hydrochloride permeation through human skin in vitro; the effect of chemical enhancement and iontophoresis : effect of pH, distribution ratio, penetration enhancers azone and oleyl alcohol, and iontophoresis on the permeation of buprenorphin". Thesis, University of Bradford, 1988. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.329293.
Testo completo
5
Reed, Susan. "Development of method to assess skin contact to chemicals /". View thesis View thesis, 2001. http://library.uws.edu.au/adt-NUWS/public/adt-NUWS20030520.115134/index.html.
Testo completoAbstract (sommario):
Thesis (Ph.D.) -- University of Western Sydney, Hawkesbury, 2001.A thesis presented in fulfilment of the requirement for the degree of Doctor of Philosophy, College of Science, Technology and Environment, University of Western Sydney, Richmond, April 2001. Bibliography : leaves 138-148.
6
Tonge, Robert Patrick. "The cutaneous disposition of the sensitizing chemicals hydroxycitronellal and dinitrochlorobenzene". Thesis, Imperial College London, 1995. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.309531.
Testo completo
7
McHugh, Peter J. "Sunlight-induced DNA damage in relation to sunscreening chemicals". Thesis, University of Oxford, 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.319052.
Testo completo
8
Ashrafi, Parivash. "Predicting the absorption rate of chemicals through mammalian skin using machine learning algorithms". Thesis, University of Hertfordshire, 2016. http://hdl.handle.net/2299/17310.
Testo completoAbstract (sommario):
Machine learning (ML) methods have been applied to the analysis of a range of biological systems. This thesis evaluates the application of these methods to the problem domain of skin permeability. ML methods offer great potential in both predictive ability and their ability to provide mechanistic insight to, in this case, the phenomena of skin permeation. Historically, refining mathematical models used to predict percutaneous drug absorption has been thought of as a key factor in this field. Quantitative Structure-Activity Relationships (QSARs) models are used extensively for this purpose. However, advanced ML methods successfully outperform the traditional linear QSAR models. In this thesis, the application of ML methods to percutaneous absorption are investigated and evaluated. The major approach used in this thesis is Gaussian process (GP) regression method. This research seeks to enhance the prediction performance by using local non-linear models obtained from applying clustering algorithms. In addition, to increase the model's quality, a kernel is generated based on both numerical chemical variables and categorical experimental descriptors. Monte Carlo algorithm is also employed to generate reliable models from variable data which is inevitable in biological experiments. The datasets used for this study are small and it may raise the over-fitting/under-fitting problem. In this research I attempt to find optimal values of skin permeability using GP optimisation algorithms within small datasets. Although these methods are applied here to the field of percutaneous absorption, it may be applied more broadly to any biological system.
9
Bian, Junxing. "Skin permeation enhancement using chemical enhancers and polymeric microneedles for chemicals and peptides". Thesis, University of Sydney, 2020. https://hdl.handle.net/2123/23624.
Testo completoAbstract (sommario):
It is often a challenge to effectively deliver drugs through the skin into the internal environment. Compared with oral administration and other dosage forms, transdermal administration has multiple advantages. Among the various transdermal administration approaches, microneedles emerge as a powerful tool in recent years, owing to its simple concept and proven efficacy. In this project, we aim to develop a hot-embossing method using menthol as the carrier material to fabricate drug-laden microneedle patches. We compared the transdermal delivery of several drugs with different dosage forms and tried to enhance their transdermal absorption by chemical and physical enhancers including this menthol-based microneedle method. It is hypothesized that this approach can be used for chemicals with various properties to enhance their percutaneous absorption. For chemical drugs, we studied the transdermal absorption of cromolyn sodium in propylene glycol (PG) and the transdermal absorption of diclofenac diethylamine gels. For peptides, we studied an anti-pigmentation peptide with strong polarity, which has extremely low skin permeation. We esterified the peptide molecule to increase its lipophilicity for skin permeation. Following esterification, we studied the transdermal absorption of the peptide and its derivative in PG with chemical penetration enhancers. Apart from chemical permeation enhancement, we also used dissolving microneedles (MNs) as the physical method to enhance transdermal delivery of the chemicals and peptides. The transdermal experiments were carried out by using vertical Franz diffusion cells and cadaverous human skin samples. The results showed that in PG solution, the cumulative permeated amount of hydrophilic cromolyn sodium was very limited. In contrast, the lipophilic diclofenac showed much higher skin permeation than cromolyn sodium. For the native peptide in PG with or without permeation enhancers, the skin permeation was not detectable. However, after molecular modification, due to the enhancement of lipophilicity of peptide, its skin absorption was improved. Two penetration enhancers, namely oleic acid and camphor did not enhance the transdermal absorption of the esterified peptide while another chemical enhancer, namely, menthol, increased the skin absorption of the esterified peptide. For the physical enhancement, drug laden MN patches increased the skin permeation of all four permeants.
10
Lee, Su-Gil. "Dermal and ocular exposure during the spray application of selected industrial chemicals /". Title page, abstract and table of contents only Title page, abstract and table of contents only, 2004. http://web4.library.adelaide.edu.au/theses/09PH/09phl4770.pdf.
Testo completo
11
Karsten, Aletta Elizabeth. "The effect of skin phototype on laser propagation through skin". Thesis, University of Pretoria, 2012. http://hdl.handle.net/2263/24272.
Testo completoAbstract (sommario):
The use of lasers for diagnosis and treatment in medical and cosmetic applications is increasing worldwide. Not all of these modalities are superficial and many require laser light to penetrate some distance into the tissue or skin to reach the treatment site. Human skin is highly scattering for light in the visible and near infrared wavelength regions, with a consequent reduction of the fluence rate. Melanin, which occurs in the epidermis of the skin, acts as an absorber in these wavelength regions and further reduces the fluence rate of light that penetrates through the epidermis to a treatment site. In vivo fluence rate measurements are not viable, but validated and calibrated computer models may play a role in predicting the fluence rate reaching the treatment site. A layered planar computer model to predict laser fluence rate at some depth into skin was developed in a commercial raytracing environment (ASAP). The model describes the properties of various skin layers and accounts for both the absorption and scattering taking place in the skin. The model was validated with optical measurements on skin-simulating phantoms in both reflectance and transmission configurations. It was shown that a planar epidermal/dermal interface is adequate for simulation purposes. In the near infrared wavelength region (676 nm), melanin (consisting of eumelanin and pheomelanin) is the major absorber of light in the epidermis. The epidermal absorption coefficient is one of the required input parameters for the computer model. The range of absorption coefficients expected for typical South African skin phototypes (ranging from photo-sensitive light skin, phototype I on the Fitzpatrick scale, to the photo-insensitive darker skin phototype V) was not available. Non-invasive diffuse reflectance spectroscopy measurements were done on 30 volunteers to establish the expected range of absorption coefficients. In the analysis it became apparent that the contributions of the eumelanin and pheomelanin must be accounted for separately, specifically for the Asian volunteers. This is a new concept that was introduced in the diffuse reflectance probe analysis. These absorption coefficient measurements were the first to be done on the expected range of skin phototypes for the South African population. Other authors dealing with diffuse reflectance probe analysis only account for the dominant eumelanin. Both the epidermal absorption coefficient and thickness are important in the prediction of the fluence rate loss. The computer model was used to evaluate the effect of the epidermal absorption coefficient (a parameter dictated by an individual’s skin phototype) and the epidermal thickness on the fluence rate loss through the skin. The epidermal absorption is strongly wavelength dependent with the higher absorption at the shorter wavelengths. In the computer model a longer wavelength of 676 nm (typical for a photodynamic treatment (PDT) of cancer) was used. For the darker skin phototypes (V) only about 30% of the initial laser fluence rate reached a depth of 200 ìm into the skin (just into the dermis). For the PDT application, results from the computer model indicated that treatment times need to be increased by as much as 50% for very dark skin phototypes when compared to that of very light phototypes.Thesis (PhD)--University of Pretoria, 2012.
Physics
unrestricted
12
Horst, Joanna Horst. "Effect of Multiple Skin-to-Skin Experiences on Exclusive Breastfeeding Rates". ScholarWorks, 2017. https://scholarworks.waldenu.edu/dissertations/3612.
Testo completoAbstract (sommario):
Breastmilk feeding at birth demonstrates short- and long-term medical and neurodevelopmental advantages. Infants who are exclusively breastfed demonstrate less nausea, vomiting, and diarrhea, and they experience less upper respiratory and ear infections than do infants who are not breastfed. One strategy that supports breastfeeding initiation is providing skin-to-skin contact (STS) with mothers and newborns immediately upon birth. The purpose of this project was to evaluate the impact of a second session of STS on the postpartum unit on exclusive breastfeeding rates at discharge. A retrospective comparison design using Swanson's caring model was used to guide the evaluation study that examined and compared the rate of exclusive breastfeeding before and after the new model of care was implemented. The historical controls rate included all delivered women in a 3-month period who expressed a desire to exclusively breastfeed and who had one session of STS. In this group, the exclusive breastfeeding rates were 46% at discharge. After the practice change, the 75 women who expressed a desire to exclusively breastfeed and who had the second session of STS demonstrated exclusive breastfeeding rates of 72% at discharge. The increased rate of exclusive breastfeeding and the promotion of newborn health represent a major contribution to positive social change through the introduction of a second session of STS. The extension of the STS practice from only the immediate postdelivery setting to the postpartum setting provides a contribution to nursing practice that can be shared in any birth or similar practice setting.
13
Nanayakkara, Gihan Ravinda. "Some effects of schistosome cercarial secretions and chemical agents on the permeability of human skin". Thesis, King's College London (University of London), 2006. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.428044.
Testo completo
14
Filby, Amy Louisa. "Molecular effect pathways of endocrine disrupting chemicals in fish". Thesis, University of Exeter, 2006. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.439828.
Testo completo
15
BARAI, NAMRATA D. "EFFECT OF HYDRATION ON SKIN PERMEABILITY". University of Cincinnati / OhioLINK, 2002. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1016480955.
Testo completo
16
Zhang, Weicheng. "Prediction of the skin sensitization potential of organic chemicals through in vitro bioassay and chemoassay information". Doctoral thesis, Technische Universitaet Bergakademie Freiberg Universitaetsbibliothek "Georgius Agricola", 2015. http://nbn-resolving.de/urn:nbn:de:bsz:105-qucosa-161710.
Testo completoAbstract (sommario):
Skin sensitization resulting for allergic contact dermatitis (ACD) is an occupational and environmental health issue. The allergic hazard for workers and consumers is a serious problem for individuals, employers and marketing certain products. Consequently, it is necessary to accurately identify chemicals skin sensitization potential. According to the new EU chemical regulation REACH (Registration, Evaluation, Authorization and Restriction of Chemicals), information of skin sensitization of chemicals manufactured or imported at or above 1 ton/year should be available.
Currently, valid approaches assessing skin sensitization rely on animal testing, such as local lymph node assay (LLNA). However, it now ultimately eliminates using animals for this purpose. Based on the fact that a key step in the skin sensitization process is formatting a covalent adduct between allergic sensitizers and proteins and/or peptides in skin, a lot of additional approaches are proposed and developed for replacing or reducing animal used. In this research, three bioassays, 24 h growth inhibition toward Tetrahymena pyriformis, long term (24 h) and short term (30 min) bacterial toxicity (to Vibrio fischeri), and a kinetic glutathione chemoassay are applied for predicting the organic chemicals’ skin sensitization potential. The major results and conclusions obtained are listed as follows:
1. Toxicity enhancement (Te) of 55 chemicals comprising different sensitization potencies were determined and compared with their narcotic toxicity to predict their skin sensitization. Three linear regressions yielded for all allergic sensitizer without nonsensitizers for each bioassay. The linear regressions are improved after classifying sensitizers into five different reaction mechanistic domains. Correspondingly, five different slopes from various reaction mechanisms indicate a decreased sensitivity of toxicity enhancement to skin sensitization potential with order SNAr > SN2 > acylation ≈ Schiff base > aromatic Michael addition. Based on the fact that a key step in the skin sensitization process is forming a covalent adduct between allergic sensitizers and proteins and/or peptides, Te > 10 as a threshold is applied to discriminate these allergic sensitizers, with 100% accuracy for strong (with extreme) and weaker sensitizers, up to 72% accuracy for moderate sensitizers and less than 69% accuracy for nonsensitizers. Compared with these bioassays, a decreasing order of sensitivities is 24 h growth inhibition (Tetrahymena pyriformis) > 24 h growth inhibition (Vibrio fischeri) > 30 min bioluminescence inhibition (Vibrio fischeri). These three bioassays are useful tools for screening sensitization potency of allergic chemicals, and the toxicity enhancement (Te) can be used to discriminate sensitizers from weak or nonsensitizers. However, in this context we should separate aromatic from aliphatic Mas (Michael acceptors). Moreover, metabolic biotransformation should be considered during predicting nonsensitizers’ skin sensitization.
2. Chemical reactivity of selected 55 compounds measuring through kinetic glutathione chemoassay applies to predict their skin sensitization. This chemoassay confirms the fact that the key step of sensitizers eliciting skin sensitization is formatting a covalent adduct between sensitizers and skin proteins or peptides. The chemical reactivity of tested sensitizers strongly relates with their sensitization potential, with strong (extreme) sensitizers presenting the highest reactivity as followed with moderate sensitizers, weak sensitizers as well as nonsensitizers. Moreover, an integrated platform of this chemoassay data and three bioassays data is performed, and this performance shows good sensitivity for monitoring skin sensitization potency, with more rational accuracy for each sensitizing classifications.
3. Thiol reactivity (kGSH) as well as toxicity enhancement (Te) of additional 21 aliphatic α,β-unsaturated compounds are determined for predicting their skin sensitization potential. The linear regressions of skin sensitization versus thiol reactivity and skin sensitization versus toxicity enhancement are significantly improved after classifying these 21 compounds to four chemical subgroups (acrylates, other esters, ketones and aldehydes). Thiol reactivity of these subgroups presented different sensitivity to skin sensitization, with a decreasing order as acrylates (－2.05) > other esters (－1.26) > ketones (－0.43) > aldehydes (－0.21). Moreover, thiol reactivity is confirmed to be a more sensitive tool for predicting skin sensitization, compared with toxicity enhancement. Although the datasets are probably too small to give a definite decision, hydrophobicity reveals contribution to skin sensitization for aliphatic MAs, which is different with literature report. This study suggests that aliphatic MAs should be treated separately into different chemical subgroups for analysis, and their skin sensitization potency can be predicted using kinetic glutathione chemoassay as well as toxicity enhancement bioassay.
17
Arritt, Fletcher Marion. "Efficacy of Selected Chemicals on the Attachment and Survival of Campylobacter jejuni on Chicken Breast Skin". Thesis, Virginia Tech, 2000. http://hdl.handle.net/10919/31083.
Testo completoAbstract (sommario):
Campylobacter is considered to be the leading cause of acute bacterial gastroenteritis in humans in the United States with Campylobacter jejuni being responsible for 80-90% of those infections. Many cases of Campylobacter gastroenteritis have been linked to the consumption of raw or undercooked chicken. The population of bacteria on the breast skin has been reported to be greater than on other edible portions of the chicken carcass making this an important site to control the organism and to study bacterial attachment properties. This research examined the efficacy of trisodium phosphate (TSP)(10%), cetylpyridinium chloride (CPC)(0.1% & 0.5%), acidified sodium chlorite (ASC)(0.1%), Tween 80 (polysorbate 80) (1%) and water (50°C) for reducing the number of viable Campylobacter jejuni on inoculated chicken breast skin. All chemicals were evaluated using contact times of 30 sec., 3 min. or 10 min. Statistically significant (p £ 0.05) differences in the reduction of C. jejuni populations were observed across chemical treatments and contact time. When bacteria were applied before treatment, a reduction of >1.0 log10 CFU/skin was achieved with 0.5% CPC (2.89), 10% TSP (1.63), 0.1% ASC (1.52), and 0.1% CPC (1.42). When bacteria were applied after treatment, a reduction of >1.0 log10 CFU/skin was achieved with 0.5% CPC (4.67) and 10% TSP (1.28). The main effects of contact time were statistically significant (p=0.02) only when bacteria were applied after treatment.Master of Science
18
Tonolli, Paulo Newton. "Photosensitization of Lipofuscin in Skin Keratinocytes: Effect of Visible Light on Human Skin". Universidade de São Paulo, 2018. http://www.teses.usp.br/teses/disponiveis/46/46131/tde-12122018-114252/.
Testo completoAbstract (sommario):
Lipofuscin is an autofluorescent pigment progressively accumulated during cellular aging, in several tissues, such as heart, muscle and retina, especially in the postmitotic period. That phenomenon may result from oxidative stress, when biomolecules and organelles (mainly mitochondria) are damaged, generating non-degradable products inside lysosomes. Lipofuscin can be photosensitized, promoting photoxidative processes in cellular components. Many studies on lipofuscin were made using the human retinal pigment epithelial cells, but very little is known about lipofuscin from human skin. In this work we investigated the photoinduced formation (UVA and visible light) of lipofuscin and the consequence of its photosensitization by visible light. We also established an efficient protocol for the induction of lipofuscinogenesis, through specific damage in mitochondria and lysosomes. Cells that accumulated lipofuscin, after exposure to UVA and blue light, became sensitive to visible light (400-750 nm). We characterized the absorption and fluorescence emission of lipofuscin, as well as its fluorescence lifetime through the time resolved fluorescence microscopy (FLIM). We observed that lipofuscin in keratinocytes has absorption maximum in the blue region of light spectrum (420-450 nm), and maximum emission in the red. When photosensitized at 466 nm, lipofuscinloaded HaCaT cells had reduced cell viability, which was related with singlet oxygen generation, accumulated 8-oxo-dG premutagenic lesions and breaks in the DNA strand. Besides, we investigated the efficiency of different wavelengthsin visible light spectrum (408, 466, 522 and 650 nm) to promote lipofuscin formation due to damages in both mitochondria and lysosomes. Blue (408 and 466 nm) and green light (522 nm), but not red light (650 nm), promoted damage in mitochondria (membrane and DNA integrity) and lysosomes (membrane integrity and autophagic activity), effectively inducing lipofuscinogenesis. Thus, in addition to UVA, visible spectrum itself increases the sensitivity of keratinocytes to the visible light, through the generation of lipofuscin. Finally, we tested the carcinogenic potential of high-energy blue light (408 nm), by chronically irradiating HaCaT cells. For the first time in the literature, the formation of pyrimidine cyclobutane (CPD) dimers in the nuclear DNA of HaCaT cells was observed immediately or after several cycles of irradiation at 408 nm. We identified four major changes involved with the process of malignant transformation: genomic instability, decrease in the expression of tumor suppressor protein p16INK4a, increase in the proliferation rate and resistance to UVA-induced apoptosisA lipofuscina é um pigmento autofluorescente acumulado progressivamente durante o envelhecimento celular em diversos tecidos, como o músculo cardíaco e retina, principalmente no período pós-mitótico. Esse fenômeno pode ocorrer em decorrência do estresse oxidativo, quando biomoléculas e organelas (principalmente mitocôndrias) sofrem danos, gerando produtos não degradáveis no interior dos lisossomos. A lipofuscina pode ser fotossensibilizada promovendo processos fotoxidativos nos componentes celulares. Muitos estudos de lipofuscina foram feitos em células do epitélio pigmentar da retina de olho humano, mas conhece-se muito pouco sobre a lipofuscina de pele humana. Neste trabalho nós investigamos a formação fotoinduzida (UVA e luz visível) de lipofuscina e as consequências da sua fotossensibilização pela luz visível. Nós também estabelecemos protocolos eficazes na indução de lipofuscinogênese, por meio de dano específico em mitocôndrias e lisossomos. Células que acumularam lipofuscina, após exposição à UVA ou luz azul, tornaram-se sensíveis à luz visível (400-750 nm). Caracterizamos as propriedades de absorção e de emissão da lipofuscina e seu tempo de vida de fluorescência, utilizando a microscopia de fluorescência resolvida no tempo (FLIM). Observamos que lipofuscina em queratinócitos tem máximo de absorção na região do azul (420-450 nm), com emissão máxima de fluorescência no vermelho. As células HaCaT carregadas com lipofuscina efotossensibilizadas no visível, tiveram redução da viabilidade celular, que foi relacionada com a geração de oxigênio singlete, bem como acumularam lesões pré-mutagênicas 8-oxo-dG e quebras na fita de DNA. Também, investigamos a eficiência de diferentes comprimentos de onda da luz visível (408, 466, 522 e 650 nm) em promover a formação de lipofuscina em consequência de lesões em mitocôndrias e lisossomos. Tanto a luz azul (408 e 466 nm) quanto a luz verde (522 nm), mas não vermelha (650 nm) promoveram dano em mitocôndrias (integridade de membrana e DNA) e lisossomos (integridade de membrana e atividade autofágica), induzindo eficientemente lipofuscinogênese. Logo, além de UVA, o próprio espectro do visível aumenta a sensibilidade de queratinócitos à luz visível, através da geração de lipofuscina. Por fim, testamos o potencial carcinogênico da luz azul de alta energia (408 nm), irradiando células HaCaT cronicamente. Identificamos quatro mudanças principais envolvidas com o processo de transformação maligna: instabilidade genômica, redução da expressão de proteína supressora de tumor p16INK4a, aumento da taxa de proliferação, e resistência à apoptose. Além disso, a formação de dímeros de pirimidina ciclobutano (CPD) no DNA nuclear de células HaCaT logo após ou depois de vários ciclos de irradiação com 408 nm foi observada pela primeira vez na literatura.
19
Chen, Andrew Chih-Chieh. "Effect of oral nicotinamide on non-melanoma skin cancer and skin barrier function". Thesis, The University of Sydney, 2016. http://hdl.handle.net/2123/15831.
Testo completoAbstract (sommario):
Exposure to ultraviolet radiation and immunosuppression are the principal causes of non-melanoma skin cancer (NMSC). One of the skin’s main functions is to act as a barrier against environmental insults and transepidermal water loss (TEWL) is a marker of skin barrier function. Previous phase 2 studies have shown nicotinamide (NAM) to reduce premalignant actinic keratoses. Topical NAM has been shown to reduce TEWL. The effects of oral NAM were evaluated in two clinical trials. The Oral Nicotinamide To Reduce Actinic Cancer (ONTRAC) study was a multicentre phase 3, double-blind, randomised controlled trial in 386 immune-competent participants with at least 2 NMSCs in the past 5 years. Participants were randomised to receive 500mg of NAM or placebo twice daily for 12 months, with assessment at 3-monthly intervals for 18 months. TEWL measurements were taken 3-monthly for 12 months in 292 participants at a single study site. The primary end point was the number of new histologically-confirmed NMSCs during the 12-month intervention period. A second, phase 2 pilot study was undertaken in 22 immunosuppressed renal transplant recipients who were randomised to receive 500mg of NAM or placebo twice daily for 6 months, with assessments at 2-monthly intervals. The ONTRAC study found a 23% relative rate reduction in new NMSCs in the NAM group compared to the placebo group (p=0.02). The estimated relative reduction in TEWL with NAM at 12 months was 6% on the forehead (p=0.04) and 8% on the limbs (p=0.04). The nicotinamide renal transplant pilot study found new NMSCs to be 35% lower in the NAM group than the placebo group (p=0.4). Oral NAM was well-tolerated and safe. The work described in this thesis provides evidence that NAM is a new chemopreventive agent for NMSC in high-risk immune-competent patients. Phase 3 studies are now warranted in immunosuppressed organ transplant recipients. Nicotinamide is also a potential new systemic agent for improving skin barrier function.
20
Coberly, Samantha W. "The effect of household chemicals on deciduous and permanent tooth class". Thesis, Wichita State University, 2013. http://hdl.handle.net/10057/6807.
Testo completoAbstract (sommario):
Dental anthropology was wide ranging implications for the field of anthropology. Teeth have become important sources of data about the individual as well as possibly being able to identify them. One problem that can arise is the chemical destruction of teeth whether it be diagenesis in an archaeological context or deliberately in a forensic context. In terms of deliberate destruction of the body several household chemicals are cheap and easily assessable. The purpose of this research is to look at how six household chemicals affect both deciduous and permanent tooth classes. The six chemicals include, Vinegar (acetic acid), Bleach (sodium hypochlorite), Biz (Sodium per carbonate), Lye (Sodium Hydroxide) Ammonia and the control (tap water). The teeth were placed in jars containing the chemical for twenty-four hours. Every hour the weight and mesial/distal length were measured. Of the six chemicals, vinegar affected the teeth the most.Thesis (M.A.)--Wichita State University, Fairmount College of Liberal Arts and Sciences, Dept. of Anthropology
21
Turan, Nahid. "The effect of plasticisers and related chemicals on sulphate supply enzymes". Thesis, University of Birmingham, 2006. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.433746.
Testo completo
22
Delacruz, C. Ligia. "The effect of natural toxicants and other chemicals on the kidney". Thesis, University of Surrey, 1988. http://epubs.surrey.ac.uk/847359/.
Testo completoAbstract (sommario):
Repeated administration of ochratoxin A (OTA) caused renal morphological dose-related changes, that were associated with proximal tubular and glomerular damage the latter showing oedema and prominent PAS staining suggestive of glomerular basement membrane thickening. On the other hand, the combined administration of repeated doses of OTA and aflatoxin B[1] (2. 5 mg and 100 ug per kg, respectively), appeared to have a synergistic effect, characterized by severe disruption of proximal tubules and general morphological derrangement of the glomerulus, involving intense and faint staining nuclei (suggestive of cell necrosis) and cytoplasmic vacuolation, which was not seen with either toxin alone. When clinical biochemical parameters were measured after repeated administration of a low dose of OTA, enzymuria, glucosuria, polyuria and proteinuria were observed, with glucose and alkaline phosphatase as the most sensitive parameters. Metabolic studies performed in vitro showed that isolated pig and rat glomeruli incorporate different amino acids linearly for several hours at different rates and perform oxidative metabolism of glucose and fatty acids to CO[2] also linearly. For pig glomeruli the order of amino acid incorporation was LEU >> PRO = HIS > LYS > GLY and for rat glomeruli it was TRP >> PHE > TYR = LEU > PRO > HIS. The same amino acids were incorporated in a similar way in rat tubules, but the incorporation rate is 10-fold lower. When de novo synthesis of protein by pig glomeruli exposed to different chemicals was assessed, using proline (PRO) as the precursor, adriamycin (ADR) and ethacrynic acid (ETA) inhibited protein synthesis more than 2-bromoethanamine (BEA) and streptomycin (STR), and much more than puromycin aminonucleoside (PAN). When isolated rat glomeruli were exposed to low concentrations of OTA, there was a generalized inhibition on de novo synthesis of protein from the six amino acids tested and the aromatic amino acids (TRP, TYR and PHE) were more sensitive to OTA effect than PRO. Low concentrations of OTA (10 - 100 uM) enhanced glomerular and tubular glucose metabolism to CO[2] and only high concentrations of the mycotoxin (1000 uM) caused significant inhibition of glomerular and proximal tubular linolenic acid metabolism.
23
Howard, Samuel Clarence. "The effect of three holding tank chemicals on anaerobic wastewater treatment". Thesis, Virginia Tech, 1988. http://hdl.handle.net/10919/45158.
Testo completoAbstract (sommario):
Sewage-holding tanks aboard recreational boats store human wastes, thereby preventing the direct discharge of wastewater to the aquatic environment. Water-conserving toilets and limited holding tank volumes produce a highly concentrated waste that must be periodically dumped to a wastewater treatment system. Prior to disposal, many boat operators add commercial preparations to control odors produced in their chemical toilets and holding tanks.
The objective of this study was to determine the effects of three holding-tank chemicals on anaerobic wastewater treatment. Specifically, septic-tank performance with respect to effluent total suspended solids (TSS) and chemical oxygen demand (COD) was evaluated. Potential drain-field failure was the concern that led to the selection of TSS and COD. Drain-field failure could result from high solids carry-over or from a high concentration of COD in the effluent which would promote excessive bio-mat growth and clog the system. Laboratory septic tanks were constructed and operated for this evaluation.
Methanol, paraformaldehyde and formaldehyde were each listed as an active ingredient in one of three chemical compounds used by recreational boat owners to deodorize sewage-holding tanks. septic-tank effluent TSS concentrations were not adversely effected by the shockloading with wastewater containing these chemicals. Concentrations expected to be achieved by dilution (20 and 50 percent of the recommended additive dose) resulted in septic-tank effluent COD within an acceptable range, which was determined by operation of a control system. Wastewaters containing these concentrations were not detrimental to the septic-tank treatment system. However, the full manufacturers' recommended dose of the odor control chemicals disrupted the system's ability to degrade COD. At full strength, the para formaldehyde and formaldehyde deodorants were particularly detrimental; no recovery occurred after the two-day shock-dose was completed.Master of Science
24
Huaytia, Fernandez Ricardo. "Skin and proximity effect analysis of traction motor". Thesis, KTH, Elektrisk energiomvandling, 2012. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-96302.
Testo completoAbstract (sommario):
Traction motors are thermally pressed to obtain a high torque per unit volume at the same time as a relatively high frequency is used. Because of the high frequency the phenomenon skin effect and proximity effects appear, this is explored in the thesis. To find a link between the parasitic and thermal effects on the insulation is important. In this thesis, a finite element model of the Flux 2D suitable for skin effect analysis is developed; also a thermal network has been developed to find thermal hotspots in the stator slot. In this thesis, sinusoidal supplies for two operating points are studied and triangular sinusoidal PWM supply is as well studied for the nominal operating point.
25
Said, Dina. "Effect of Hand Hygiene Procedures on Skin Biomarkers". University of Cincinnati / OhioLINK, 2006. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1146608923.
Testo completo
26
Dinsmore, Kristen G., Bethany Campbell, Timothy Archibald, Greg Mosier, Stacy D. Brown e Alexei Gonzalez-Estrada. "Refrigerated Stability of Diluted Cisatracurium, Rocuronium, and Vecuronium for Skin Testing after Perioperative Anaphylaxis". Digital Commons @ East Tennessee State University, 2018. https://dc.etsu.edu/etsu-works/5266.
Testo completoAbstract (sommario):
RATIONALE: The purpose of this study is to investigate the stored stability of dilutions of neuromuscular blocking agents (NMBAs), namely cisatracurium, rocuronium, and vecuronium, for skin prick/intradermal testing.
METHODS: Concentrations of NMBAs were monitored by liquid chromatography-mass spectrometry (LC-MS/MS) for a period of 14 days. Dilutions of NMBAs were prepared in saline by factors of 10x, 100x, 1,000x, and 100,000x as sensitivity of the assay allowed. Diluted drug products were stored in a laboratory refrigerator until sampling. On sampling days, aliquots of each dilution were removed and compared to a freshly prepared set of reference dilutions.
RESULTS: The results are measured as beyond use date (BUD) defined as recovery of drug versus the reference (90-110%). Based on the LC-MS/MS data, the BUD for cisatracurium diluted to 10x and 100x is 96 hours. Higher dilutions (1,000x to 100,000x) should be used immediately following preparation (within less than 24 hours). Vecuronium at 10x and 100x also has a BUD of 96 hours, and the 1,000x dilution is stable for 24 hours. The 10,000x dilution should be used immediately. Rocurium at 10x to 1,000x has a BUD of 48 hours, yet higher dilutions (10,000x and 100,000x) should be used immediately.
CONCLUSIONS: With increasing dilution factors, the stability of these drugs in saline decreases, increasing deviation between samples and references. The most stable dilutions for each of the drugs tested were 10x and 100x. Stability of these drugs is likely compromised by hydrolysis of the ester bonds in the drug molecules.
27
Li, Jing Adela, e 李晶. "Temperature-dependent toxic effects of selected chemicals on marine organisms". Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2014. http://hdl.handle.net/10722/211051.
Testo completoAbstract (sommario):
Anthropogenically driven climate change not only results in rising of sea temperature but also leads to more frequent and longer-lasting cold and heat waves. Meanwhile, coastal marine ecosystems are constantly challenged by increasing threats of chemical pollution. Temperature and chemical stressors can jointly affect the livelihood of marine organisms, but their combined effects are still poorly understood. Therefore, this study aimed to investigate the effects of thermal stress and chemical exposure on the marine medaka Oryzias melastigma, copepod Tigriopus japonicus and rotifer Brachionus koreanus. The four selected chemical contaminants included copper sulphate pentahydrate (Cu), dichlorophenyltrichloroethane (DDT), triphenyltin chloride and copper pyrithione. It was hypothesized that marine organisms are more susceptible to chemical exposure at both cold and warm extremes.
In vivo acute ecotoxicity tests were conducted over a wide temperature range to ascertain the relationship between thermal stress and chemical toxicity. For O. melastigma larvae, the lowest toxicity occurred at an optimum temperature range; the chemical toxicity further increased with temperature increase or decrease from this optimum, and exacerbated at extremely low and high temperatures. For T. japonicus and B. koreanus, the chemical toxicity generally increased with increasing temperature. Such inter-species dissimilarities were possibly due to differences in the uptake route, detoxification mechanism, avoidance behaviour and physiological response between the fish and the copepod or rotifer.
Experiments were conducted to evaluate the temperature-dependent physiological and biochemical responses, and thermal tolerance of O. melastigma larvae. The growth in the fish larvae showed an inverse and negatively skewed V-shape relationship with temperature, with a significant reduction in performance at both low and high thermal extremes. A mismatch between demand and supply of oxygen and energy under extremely cold and warm conditions was probably the primary cause of growth inhibition and metabolic impairment, leading to a temporary adaptation by a shift to anaerobiosis and an induction of heat shock proteins (HSPs).
Temperatures at both cold and warm extremes increased toxicities of DDT and Cu to O. melastigma larvae, resulting in restricted growth and interrupted oxygen consumption rate. The fish larvae modulated their metabolic pathway and produced stress proteins (i.e., HSPs and metallothioneins) for adaptation to the combined stress. However, such responses were disrupted by combinations of thermal extremes, in particular high temperature, and high chemical concentration. Most importantly, both DDT and Cu exposure significantly reduced the thermal tolerance of the fish larvae.
The interacting effect of temperature and Cu was also investigated on T. japonicus. The results showed that their combined effect could significantly reduce the survival, lengthen the developmental time and change the sex ratio of the copepod. Transcriptions of several stress-related genes (i.e., glutathione reductase, glutathione S-transferases and HSPs) in the adult T. japonicus were significantly affected by the joint-effect of temperature and Cu exposure, implying that these genes played essential roles in protecting the cellular integrity against the stresses.
This study advanced the understanding on the temperature-dependent toxicity of chemical contaminants to marine organisms, and provided valuable information and empirical models for deriving water quality criteria of chemical contaminants at various temperatures.published_or_final_version
Biological Sciences
Doctoral
Doctor of Philosophy
28
Williams, Delyth Einir. "Xenobiotic metabolism in skin and the effect of age". Thesis, Cardiff University, 1995. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.395694.
Testo completo
29
Loveday, J. S. "Skin effect measurements of the bulk modulus of potassium". Thesis, University of Bristol, 1987. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.233723.
Testo completo
30
Al-Attwani, Jasim Hussein. "The effect of probiotics on bacterial human skin pathogens". Thesis, University of Plymouth, 2014. http://hdl.handle.net/10026.1/3087.
Testo completoAbstract (sommario):
Probiotic bacteria have been investigated in the prevention and treatment of various diseases and allergies. The current study was undertaken to determine the effect of eight probiotic Lactobacillus species against bacterial human skin pathogens using several techniques. Antimicrobial activity of lactobacilli against Staphylococcus aureus, Staphylococcus epidermidis, Pseudomonas aeruginosa and Propionibacterium acnes was evaluated using lactobacilli broth cultures (BCB) and cell free supernatant (CFS). Antimicrobial activity was significantly greater with BCB compared with CFS especially for Lactobacillus plantarum and Lactobacillus acidophilus. Lactobacilli and pathogen aggregation, biofilm formation and adhesion to keratin were assessed. L. casei and L. plantarum were selected for further study as they showed the greatest co-aggregation (18.02 ± 1.34% with L. casei and 14.92 ± 1.45% with L. plantarum) with the pathogens (16.63 ± 1.65% with S. aureus 3761 and 14.58 ± 1.68% with P. aeruginosa) and prevention of biofilm formation by the pathogens. The antimicrobial activity of human beta defensin-2 (hBD-2) alone or with L. plantarum against pathogens was assessed. The results with hBD-2 showed that hBD-2 (10 μg / ml for 5 h) and L. plantarum together were significantly more inhibitory against S. aureus than hBD-2 alone. The presence of NaCl reduced the effectiveness of hBD-2 alone and with L. plantarum. In the presence of L. plantarum, inactivation of mprF and dlt genes led to increased binding of hBD-2 by the bacterial cell wall, and then inhibition growth of bacterial cell wall. Studies investigated the effect of exposure of methicillin resistant Staphylococcus aureus (MRSA) to the supernatant of L. plantarum the susceptibility of MRSA to β-lactams. MRSA became sensitive to β-lactams when treated with culture supernatant of L. plantarum. Gene expression studies demonstrated that the mecR1-mecI-mecA-PBP2 signalling pathway was impeded by exposure to culture supernatant of L. plantarum and β-lactams. The studies reported here demonstrate a possible alternative approach to dealing with skin pathogens, which may have clinical implications especially with regard to MRSA infections, and continued research is advised.
31
Prater, Mary Renee. "Immunotoxicity of Dermal Permethrin and Cis-Urocanic Acid: Effects of Chemical Mixtures in Environmental Health". Diss., Virginia Tech, 2002. http://hdl.handle.net/10919/11047.
Testo completoAbstract (sommario):
The present study examined adverse effects of sunlight exposure (mimicked by intradermal cis-urocanic acid, cUCA) on local and systemic immune responses, with or without co-exposure to the immunotoxic insecticide permethrin. A single exposure to cUCA caused diminished splenic macrophage phagocytosis that was persistent up to 30 days post-exposure. Five-day exposure to cUCA subtly increased splenocyte proliferation in response to the T cell mitogen Concanavalin A. Four-week exposure to cUCA caused increased splenic lymphocyte cellularity, thymic hypocellularity, and enhanced hydrogen peroxide production by splenic leukocytes. Single exposure to topical permethrin resulted in decreased thymic and splenic weight and cellularity, and inhibited antibody production by splenic B cells. cUCA worsened the negative effect of permethrin on both thymic weight and cellularity, and depressed splenocyte blastogenesis, hydrogen peroxide production, and antibody production. Five-day exposure to either cUCA or permethrin also caused persistent decreased contact hypersensitivity responses, an effect that became more than additive when the chemicals were administered concurrently. Defects in antigen processing and presentation by cutaneous Langerhans cells were evaluated as possible contributing mechanisms to the cutaneous immunosuppression, using mice with deleted genes. Vehicle-exposed IFNg knockout mice displayed approximately a 22.1% depression in the ear swelling response as compared to control C57BL/6N mice, suggesting that this cytokine may be required for mounting a control-level hypersensitivity response. Ear swelling in cUCA-exposed IFNg knockout mice displayed a 21.4% depressed response as compared to cUCA-exposed wild-type C57BL/6N mice, again suggesting that IFNg is an important cytokine in the contact hypersensitivity (CH) response. TNFaR knockout mice exposed to cUCA displayed 33.9% greater ear swelling than cUCA-exposed wild-type C57BL/6N mice, suggesting that increased TNFa may be involved in inhibited CH by cUCA. TNFaR knockout mice exposed to permethrin displayed 33.9% greater ear swelling than permethrin-exposed C57BL/6N mice, suggesting that increased TNFa may also be involved in inhibited CH by permethrin. C57BL/6N mice exposed to cUCA + permethrin displayed severe reduction of the CH response to 8.7% of the control level. IFNg knockout mice exposed to permethrin + cUCA showed essentially identical depression of the CH response as IFNg knockout mice exposed to either permethrin or cUCA alone. These results suggest that IFNg is required for the greater than additive immunotoxic effect that occurred when these two agents were co-administered. TNFaR knockout mice exposed to cUCA + permethrin displayed 8.7 fold greater ear swelling than similarly exposed C57BL/6N mice, again suggesting that increased TNFa is involved in inhibited CH by both cUCA and permethrin.Ph. D.
32
Rabe, Richard L. "Drag and pressure die flow effects on the production and properties of a Rayon-Nylon skin-core type composite fiber". Ohio University / OhioLINK, 1987. http://rave.ohiolink.edu/etdc/view?acc_num=ohiou1183057790.
Testo completo
33
Quinn, Amie L., e University of Lethbridge Faculty of Arts and Science. "The impacts of agricultural chemicals and temperature on the physiological stress response in fish". Thesis, Lethbridge, Alta. : University of Lethbirdge, Faculty of Arts and Science, 2007, 2007. http://hdl.handle.net/10133/676.
Testo completoAbstract (sommario):
Fish are exposed to multiple stressors in their environment. The interactive
effects of pesticide exposure and increased temperature on the physiological stress
response were investigated in a comparative field study with cold-water (whitefish,
Prosopium williamsoni) and cool-water (sucker, Catostomus) fish from the Oldman
River, Alberta, Canada, and in a laboratory study with rainbow trout, Oncorhynchus
mykiss. Physiogical stress indicators were measured, and exposure to pesticides was
estimated using acetylcholinesterase (AChE) inhibition. Species-specific differences in
AChE activities and responses of the physiological stress axis were detected in whitefish
and suckers, suggesting that whitefish are a more sensitive species to temperature and
pesticide stress. In vivo Dimethoate exposure inhibited AChE activity in various tissues
and disrupted the physiogical stress response. Commercial Dimethoate, in vitro, caused a
decrease in viability and cortisol secretion while pure grade Dimethoate did not. The
results from this study can be used in predictions of fish vulnerability to stress.ix, 137 leaves : ill. ; 29 cm.
34
Klíma, Petr. "Skin efekt ve vysokootáčkových elektrických strojích". Master's thesis, Vysoké učení technické v Brně. Fakulta elektrotechniky a komunikačních technologií, 2019. http://www.nusl.cz/ntk/nusl-401967.
Testo completoAbstract (sommario):
This master thesis deals with the suppression of the skin and proximity effects in high-speed machines. The first part summarizes the general knowledge of high-speed machines. The second part is devoted to the principle and possible suppression of consequences caused by skin and proximity effects. The third part shows the simulation results of models of a synchronous machine with permanent magnets. The results of these simulations reveal the consequences of skin and proximity effects. In addition, design measures are proposed to limit these and other undesirable phenomena to achieve the highest possible efficiency.
35
Wang, Qi. "The morphological effect of electron irradiation on the healing of skin wounds and skin grafts in the rat". Thesis, Queen's University Belfast, 1995. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.324846.
Testo completo
36
Ray, Chaudhuri Siladitya. "Mathematical Modeling of Percutaneous Absorption of Volatile Solvents Following Transient Liquid-Phase Exposures". University of Cincinnati / OhioLINK, 2007. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1179468433.
Testo completo
37
Duit, Rebecca Christina. "Novel insights into hair structure and the effects of chemical stressors on hair and skin using label-free advanced light microscopy". Thesis, Durham University, 2017. http://etheses.dur.ac.uk/12101/.
Testo completoAbstract (sommario):
There is a need for a better method to image hair as the current methods involve embedding the hair in resin, which may produce artefacts, or using dyes which are limited in their depth of penetration into the hair. The research performed in this thesis endeavours to characterise the cellular structure of human hair with label-free imaging using autofluorescence and fluorescence lifetime imaging. Wavelengths were shown to selectively excite the hair cuticle, cortex and medulla, and subcellular compartments. Development of an optical transverse imaging method enabled discoveries including different fluorescence lifetimes across the cuticle cell layers and suggests the cuticle layers possess differing chemical environments. A new method was developed to distinguish between eumelanin and pheomelanin using 405nm and 633nm wavelengths. The newly developed methods were additionally used in the characterisation of an unidentified hair and skin disorder, which found poorly differentiated cuticle cells and showed differences in the fluorescence lifetimes of the hair compared to control hairs. The hair care industry needs more efficacious chemical depilatories and information into their action. This was elucidated using the developed methods and a new dynamic imaging method. Potassium thioglycolate was shown to cause drastic expansion of the hair which was amplified by the addition of guanidine carbonate, creating fissures through the cuticle and into the cortex. Other experimental depilatory formulations were tested and were found to have varying effects upon the structure of the hair. New chemical depilatories require development because existing depilatories can cause irritation in the skin. Potassium thioglycolate and guanidine carbonate were tested on HaCaT cells, isolated cornified envelopes, and HEKn cells in a 3D epidermal model. An investigation into the differentiation, proliferation and acute stress response of the cells showed that the treatments had no significant effect on these markers. However, the chemicals negatively affected HaCaT cell viability and damaged the cornified envelopes. Despite this, the viability and structural integrity of the living cells of the epidermal model were maintained through the protection provided by the stratum corneum.
38
Tomic, Tjasa. "Functionalised cellulosic materials for hydrolysis free reactive dyeing and the fixation of effect chemicals". Thesis, University of Manchester, 2009. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.498845.
Testo completo
39
Young, Stephen Robert. "The effect of therapeutic ultrasound on the biological mechanisms involved in dermal repair". Thesis, King's College London (University of London), 1988. https://kclpure.kcl.ac.uk/portal/en/theses/the-effect-of-therapeutic-ultrasound-on-the-biological-mechanisms-involved-in-dermal-repair(6c2b4920-3344-4112-80f3-04fec1bfefdf).html.
Testo completo
40
Black, C. E. "The effect of nicotine on endothelial function in human skin flaps". Thesis, Queen's University Belfast, 2004. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.403236.
Testo completo
41
Godart, Marie-Aude. "Effect of skin fracture on failure of a bilayer polymer plate". Thesis, Imperial College London, 2007. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.444085.
Testo completo
42
Grady, George. "The effect of resveratrol on ultraviolet light-induced skin cell death". Marietta College Honors Theses / OhioLINK, 2013. http://rave.ohiolink.edu/etdc/view?acc_num=marhonors1366909727.
Testo completo
43
Suarez, Pozos Edna. "The effect of skin tension on the formation of keloid scars". Thesis, University of Manchester, 2014. https://www.research.manchester.ac.uk/portal/en/theses/the-effect-of-skin-tension-on-the-formation-of-keloid-scars(6762b081-6818-441b-98e6-6a74ae7b50da).html.
Testo completoAbstract (sommario):
Keloid scars (KS) are a type of abnormal scarring which is unique to humans. They extend beyond the confines of the original wound margins, do not regress over time and invade the surrounding unaffected skin. The mechanisms involved in the formation of KS remain largely unknown. Clinical observation has shown that in areas where increased tension occurs, such as the sternum, there is a greater propensity for developing KS. However, the precise relationship between skin tension and KS development is yet to be identified. In view of this, I hypothesize that skin tension plays a significant role in KS development by affecting tension-related biomarkers that may alter the phenotype of KS. Therefore, the objective of this research was to investigate the effect of skin tension in the formation of KS. To this end, the first aim was to identify possible targets among biomarkers that might contribute to the differentiation between KS and hypertrophic scars in tissue and cells obtained from diverse anatomical locations. The second aim was to investigate the effect of tension-related biomarkers on extracellular matrix (ECM) steady-state synthesis in keloid fibroblasts (KF) extracted from a highly tensioned body region (the sternum). The third aim was to develop a 3D in-vitro model to mimic in-vivo tension and to evaluate KF behaviour and ECM synthesis under tension. To achieve these aims 21 biomarkers were selected from published microarray and in-house microarray studies, the inclusion criteria was based on up-regulation of the genes in KS in relation to fibrosis, apoptosis and tension. For this purpose, samples from normal skin and KS were used to perform qRT-PCR screening in tissue and cells, as well as protein analysis by Western and In-cell Western blot. The siRNA knockdown technique was employed to evaluate the functional role of the tension-related markers in keloid fibroblasts. Finally, a photogrammetry technique was employed to evaluate skin tension in-vivo; the results from this evaluation were used in the development and design of a novel in-vitro 3D-model. The first biomarker screening in tissue showed convincing up-regulation of five tension-related targets (Hsp27, PAI-2 and α2β1-integrin, MMP-19 and CPRP). In addition, the expression of the above-mentioned targets was significantly higher in samples from the sternum compared to samples from other anatomical locations. To further validate these findings, the screening of the 21 biomarkers was assessed in KS and KF taken from the sternum. The results demonstrated over expression of 3 of the 5 tension-related targets (Hsp27, PAI-2 and α2β1-Integrin). It was also demonstrated that Hsp27, PAI-2 and α2β1-Integrin performed a functional role in terms of regulation of extracellular matrix production and deposition in KF when their expression was down-regulated by siRNA knockdown. Using the newly created 3D model, it was shown that mechanical tension significantly induced the expression of Hsp27, PAI-2 and α2β1-Integrin as well as ECM components such as Collagen I. Furthermore, the results showed that the knockdown of the expression of Hsp27, PAI-2 and α2β1-integrin in fibroblast populated collagen lattices subjected to tension influenced not only the ECM synthesis but also adhesion and spreading genes in keloid and normal fibroblasts. In summary, this research convincingly shows that skin tension alters keloid fibroblast behaviour, morphology, mechano-responsive gene expression and extracellular matrix production. The findings from my thesis offer insight into keloid pathobiology and provide options for targeted treatment of specific genes affected in keloids by biomechanical stress.
44
Mirrashed, Fakhereh. "High-resolution magnetic resonance imaging of the skin and the effect of hydration". Thesis, University of Exeter, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.244405.
Testo completo
45
Worsham, Jessica Nicole. "5-HT3 Receptor Ligands and Their Effect on Psychomotor Stimulants". VCU Scholars Compass, 2008. http://scholarscompass.vcu.edu/etd/1054.
Testo completoAbstract (sommario):
Drug abuse and addiction are considered to be a result, at least in part, of the rewarding effects produced by increasing dopamine levels. 5-HT3 serotonin receptors have been shown to indirectly affect dopamine levels. Therefore, the effect of the 5-HT3 receptor partial agonist, MD-354, on the actions of psychomotor stimulants was analyzed in mouse locomotor activity assays to determine whether MD-354 is working through a 5-HT3 receptor agonist or antagonist mode of action. Studies with (+)amphetamine and (+)methamphetamine in combination with MD-354 indicated MD-354 is either devoid of action or is behaving similar to the 5-HT3 receptor antagonist, ondansetron. This effect could be occurring centrally; however peripheral effects can not be discounted. In combination with cocaine, MD-354 behaved similar to the 5-HT3 receptor agonist, SR 57227A, known to act both centrally and peripherally. This difference between central and peripheral effects could account for the different modes of action observed with MD-354. Studies also involved synthesis of potentially brain-penetrant carbamate analogs of MD-354, and QSAR to assist in validating a 5-HT3 receptor agonist pharmacophore.
46
Nongauza, Sinethemba Aubrey. "An investigation of the effect of co-solvents on the hydrothermal liquefaction of microalgae biomass". Thesis, Nelson Mandela Metropolitan University, 2015. http://hdl.handle.net/10948/21667.
Testo completoAbstract (sommario):
The study introduces and demonstrates the viability of the continuous flow reactor (CFR) system for the production of bio-crude oil (BCO) from wet microalgae. Preliminary experiments conducted in the CFR system in hot compressed water (HCW) were successful in converting wet microalgae into liquid BCO. However, the synthesis and aggregation of high boiling point (HBP) components of BCO and the accumulation of char in the tubular piping of CFR system were identified as the limiting factor to the viability of the system. The aggregation of HBP components and the accumulation of char result to system blockage which prevents the continuous flow of the liquefaction product mixture in the CFR system. Inhibiting the reactions leading to the formation of HBP components and char will improve the performance of the CFR system. Therefore, the study seeks to incorporate co-solvents in the liquefaction reaction media in an attempt to inhibit or minimize the prevalence of HBP components of BCO. As such, different co-solvents were screened for their influence on improving the quality of BCO with respect to its boiling point profile (BPP), initial and final boiling point, as well as the amount of char recovered from each experiment. Only one co-solvent was chosen for further exploration in the CFR system. Batch liquefaction reactor’s (BLR) made up of stainless steel were used to carry out the co-solvent screening experiments. These experiments were carried out at a constant temperature (280 °C), pressure (75 bar), and co-solvent concentration (10 wt.%), at varying residence times. Solvent extraction with dichloromethane (DCM) was performed on the liquefaction product mixture to separate the products, viz. BCO, char and water soluble components. The extracted BCO was analysed through simulated distillation (SimDis) to obtain the BPP. The BPP properties of the BCO samples, from different liquefaction media, and the amount of char recovered were highly influenced by the addition of a co-solvent. The final boiling point (FBP) of tetralin, heptane, and n-octanol BCO products were significantly reduced to below 500 °C for all tested residence times except at 20 minutes. The residence time also proved to be influential in the processing of wet microalgae. n-Octanol was selected as the optimal performing co-solvent and was used for the continuous liquefaction of wet microalgae in the CFR system. The CFR system was modified by adding a co-solvent feed line into the continuous system since n-octanol was insoluble in water. The n-octanol pump was set at different flow rates, 0.2, 0.3, and 0.4 g/min, which resulted in a concentration of about 10 wt.% in the reactor feed. The concentration of n-octanol had a significant influence on the BPP of BCO components. The FBP’s were reduced with an increase in n-octanol concentration. The initial boiling point (IBP) of n-octanol BCO was increased to just above 100 °C which was required for the stability of the BCO product. The components of BCO were identified by GCMS. n-Octanol also proved to affect the composition of the BCO with respect to its components. HCW BCO components were significantly different from those identified from n-octanol BCO. A second co-solvent (tetralin) was used to prove whether the difference on the components of BCO was affected by n-octanol. The results proved that indeed the addition of different solvents in liquefaction reaction media favours the formation of different components. The amount of char formed was also reduced when using a co-solvent. A decrease in the oxygen/nitrogen compounds was also observed in the presence of a co-solvent, thus improving BCO properties.
47
Benetti, Monã Hegel. "Efeito skin no dínamo de Ponomarenko". reponame:Repositório Institucional da UFABC, 2017.
Cerca il testo completoAbstract (sommario):
Orientador: Prof. Dr. Francisco Eugenio Mendonça da SilveiraDissertação (mestrado) - Universidade Federal do ABC, Programa de Pós-Graduação em Física, 2017.
Através do estudo da teoria cinética dos dínamos, onde se destaca o dínamo ou processo de Ponomarenko, nos deparamos com uma análise, até agora desenvolvida na literatura, restrita à aproximação em que a superfície que encerra o escoamento responsável pelo efeito dínamo é considerada dielétrica. Este trabalho oferece um tratamento analítico do processo de Ponomarenko onde essa mesma superfície, que confina o movimento do fluido, passa a ser condutora, o que permite o surgimento do efeito skin. Será apresentada, portanto, uma solução geral, da qual é possível deduzir, em certas condições, a relação de dispersão, já conhecida na literatura, para o qual o efeito dínamo é considerado importante e, em outras, a relação de dispersão ainda não conhecida, em que o efeito skin se torna importante. Por fim, apresentamos novamente a solução geral que contém ambos os efeitos, considerando duas aproximações caracterizadas como: dínamo de baixa rotação e dínamo de alta rotação. Que serão úteis para indicarem a tendência do sistema em relação ao efeito dínamo.
Through the study of the kinematic dynamo theory, where the Ponomarenko dynamo stands out, we come across an analysis, until now developed in the literature, restricted to the approximation in which the surface, that contains the flow responsible for the dynamo effect, is considered dielectric. This work offers an analytical treatment of the Ponomarenko process, where the surface that confines the movement of the fluid, becomes conductive, which allows the appearance of the skin effect. A general solution will, therefore, be presented, from which it is possible to derive, under certain conditions, the dispersion relation already known in the literature, for which the dynamo effect is considered important and, others, the new dispersion relation, in which the skin effect becomes important. Finally, we present, again, the general skin effect solution that contains both effects, considering two approaches, characterized as: slowly rotation dynamo and fastly rotation dynamo. They will be useful to indicate the tendency of the system exhibit to the dynamo effect.
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