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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.

Effect of ionic end groups on diffusion and film formation in polystyrene latexes /

Kim, Sung Dug, January 1999 (has links)
Thesis (Ph. D.)--Lehigh University, 2000. / Includes vita. Includes bibliographical references (leaves 170-171).

Influencia da variação dos agentes emulsionantes na heterogeneidade de filmes de latices

Keslarek, Amauri Jose 02 August 2018 (has links)
Orientador : Fernando Galembeck / Tese (doutorado) - Universidade Estadual de Campinas, Instituto de Quimica / Made available in DSpace on 2018-08-02T21:36:24Z (GMT). No. of bitstreams: 1 Keslarek_AmauriJose_D.pdf: 13799727 bytes, checksum: d5d9debd26dce212e8b8c8896cb15e6d (MD5) Previous issue date: 2002 / Doutorado

The ultraviolet absorption of stretched and unstretched GR-S latex films

Mayo, Eleanor Grace January 1947 (has links)
This work on the ultraviolet absorption of stretched and unstretched Type 3 GR-S latex films, was undertaken on the suggestion of Dr. H. D. Smith and Dr. E. Guth, with the expectation that the ultraviolet absorption could give information on the arrangement of the molecules in the stretched state as compared with the unstretched latex. Previous investigators have found that styrene has an absorption band with maximum absorption at 2850 angstroms. Since styrene is one of the constituents of GR-S latex, it was supposed that this absorption band would also appear in any spectral analysis of the latex. To find the nature of this band and its behaviour upon stretching the sample was one of the objectives of this research. The type of spectrograph used for this work was a Hilger E496.303 with a wavelength scale, and Spekker photometer attachment. Eastman Type II-F spectroscopic plates were used for all readings. A tungsten steel spark with about 25,000 volts across the electrodes was used as a source for all plates. The unstretched films were prepared by coating a pane of glass with a ten percent solution of zinc chloride, and when dry, the glass was coated with the latex. After drying, a very thin film of rubber was deposited on the glass which could be peeled off as needed. By this method ultraviolet transparent films of initial thickness 0.020 cm. were obtained. These films were stretched into the shape of a spherical bubble by means of nitrogen gas. By calculating the surface areas of the stretched samples and assuming Poisson's Ratio to be 1/2 for rubber, the thicknesses of the stretched samples could be calculated. A narrow absorption band was found for latex of thickness 0.00260 cm. in the region of 2850 angstroms which did not appear to shift with further stretch. A slight broadening effect upon stretching might have been present but it would not amount to more than 5 or 10 angstroms in either direction. From this it was concluded that the absorption centres of the styrene molecules remained unaffected during stretching. Absorption coefficients were also calculated by Lambert's Law on the assumption that the total loss of radiation was due to absorption. It was found that a decrease in thickness was followed by an increase in the absorption coefficient for a constant wavelength. To obtain the true absorption coefficients, the coefficients computed, by Lambert's Law must, be corrected for surface reflection and body scattering. This may affect the values of the coefficients but not the position of the band. The Increase in scattering with a decrease in thickness is suggested to be due to the existence of microcrystals when the latex is under stress. / Science, Faculty of / Physics and Astronomy, Department of / Graduate

Exposição ocupacional e hipersensibildade ao latex nos trabalhadores das equipes de enfermagem e medica da UTI neonatal de um hospital universitario

Lopes, Rosimeire Aparecida Mendes 08 May 2002 (has links)
Orientadore: Maria Cecilia Cardoso Benatti, Ricardo de Lima Zollner / Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Ciências Médicas / Made available in DSpace on 2018-08-03T15:28:52Z (GMT). No. of bitstreams: 1 Lopes_RosimeireAparecidaMendes_M.pdf: 239011 bytes, checksum: 1a858728c79cdda151cb2df1d2e4b775 (MD5) Previous issue date: 2002 / Resumo: OBJETIVOS: Identificar a prevalência de hipersensibilidade do tipo I ao látex nos trabalhadores das equipes de enfermagem e médica da Unidade de Terapia Intensiva Neonatal, verificar a associação dos fatores de risco e história de manifestações clínicas. SUJEITOS E MÉTODOS: Tratou-se de estudo descritivo de corte transversal, com 96 trabalhadores da Unidade de Terapia Intensiva Neonatal do Centro de Atenção Integral à Saúde da Mulher da Universidade Estadual de Campinas, sendo 26 enfermeiros, 23 técnicos de enfermagem, 26 auxiliares de enfermagem, dois atendentes de enfermagem, 4 médicos docentes e assistentes e cinco médicos residentes. A coleta dos dados ocorreu de julho a novembro de 2001 e constou da aplicação individual de questionário, coleta de amostra de sangue para o teste sorológico empregandose o método ELISA e testes cutâneos de punctura com antígenos extraídos de luvas de látex. Para análise estatística dos dados foi utilizada análise descritiva. Para verificar associação ou comparar proporções foi utilizado o teste exato de Fisher e na comparação de variáveis contínuas entre dois grupos, o teste de Mann-Whitney. RESULTADOS: A prevalência obtida foi de 8%, sendo dois enfermeiros, três técnicos de enfermagem, um auxiliar de enfermagem, um médico e um residente. Os oito casos tiveram teste cutâneo por punctura positivo e apenas um caso apresentou concordância entre teste sorológico e cutâneo. A média geral da idade foi de 35 anos, com população predominantemente feminina (93%) e onde se encontraram os casos positivos. A equipe de enfermagem representou 75% dos casos positivos, as equipes médica e residente representaram 12,5% cada. Não foram observadas evidências de associações entre o teste cutâneo por punctura e as características sociodemográficas estudadas, a função, o tempo de uso de luvas em anos, a dermatite de contato - prurido (n=36), fissura (n=24) e descamação (n=21) - e urticária. No grupo geral, houve evidência de associação entre o teste cutâneo por punctura e o tempo de uso diário de luvas durante o plantão, onde os casos com teste cutâneo negativo utilizavam luvas por mais tempo durante o plantão, em média 111 minutos, e os positivos utilizavam em média 56 minutos. Houve também evidência de associação para relato de atopia, sendo sete trabalhadores atópicos e um não atópico positivos ao teste cutâneo. A evidência de associação também ocorreu para o relato de eczema, onde quatro de nove sujeitos foram positivos ao teste e para a alergia alimentar, sendo que das frutas relatadas a evidência de associação ocorreu somente para alergia ao abacaxi. Para sintomas provocados pela exposição ambiental aos antígenos, a evidência de associação ocorreu para ataques de espirros, respiração difícil e angioedema e houve evidência de associação entre história sugestiva de alergia durante a realização de exames e teste cutâneo / Abstract: Objective: to identify the prevalence of type 1 hypersensitivity to latex among hospital nursing staff and doctors in a neonatal intensive care unit, verifying the association between the risk factors and the history of clinical manifestation with the test used. Subjects and methods: a cross-section descriptive survey was carried out focusing on ninety-six hospital staff from the neonatal intensive care unit of the Center of Integral Attention to Women¿s Health at the State University of Campinas. We surveyed twenty- three registered nurses, twenty-three nursing technicians, twenty-six nurses¿ aides, 2 nursing attendants, fourteen doctors, and 5 resident doctors. The collection of data occurred from July to November 2001 and all subjects were interviewed, asked to donate blood samples for the ELISA serological test, and to undergo skin prick test with an antigen extracted from latex gloves. A descriptive analysis of the statistical data was done. In order to verify association or to compare proportions, the precise test of Fisher was used and the Mann-Whitney test was used to compare continuous variables between two groups. Results: The prevalence obtained was of 8%; two registered nurses, three nursing technicians, one nurse¿s aide, one resident doctor and one doctor. The eight cases of the skin prick tests were positive, and only one serological test was in agreement with the skin test. The positive cases (93%) consisted predominantly of females with an average age of 35. The nursing staff made up 75% of the positive cases, while resident doctors and doctors made up 12,5% of the cases each. There was no evidence of associations between the skin prick test and the sociodemographic characteristics studied; the function; exposure to latex in number of years; contact dermatitis ¿ itching (n=36), cracking (n=24) and peeling (n=21) ¿ and urticaria. In the group as a whole, there was evidence of an association between the skin prick test and the daily exposure time to latex gloves while on duty, where individuals who had used latex gloves for a long period of time (111 minutes) had negative skin prick test, whereas individuals who had used the gloves for 56 minutes on average had positive skin prick test. Also, there was evidence of association between the reported atopy and the skin prick test, where eight health care workers¿ skin prick tests were positive, seven workers were atopic and one was not. Evidence of association also occurred for the reported eczema cases, where four out of nine individuals¿ tests were positive. And for the reported food allergy cases, pineapple showed evidence of association with the skin prick test. For symptoms provoked by environmental exposure to antigens, evidence of association occurred for sneezing attacks, respiration difficulty and angiodema. Also, there was evidence of association between a history suggestive of allergies in exam procedure and skin prick test / Mestrado / Enfermagem e Trabalho / Mestre em Enfermagem

Rheo- and electro-optical studies of ordered latices

Tomita, M. (Minoru) January 1984 (has links)
No description available.

The preparation and characterization of synthetic latexes

Labib, Mohamed E. January 1979 (has links)

Efeito da membrana de látex natural sobre o reparo de áreas doadoras do palato para enxerto gengival livre : estudo clínico, controlado e randomizado /

Spin, José Rodolfo January 2018 (has links)
Orientador: Rosemary Adriana Chiérici Marcantonio / Resumo: O objetivo desse estudo foi avaliar o efeito de uma membrana de látex natural sobre a cicatrização de feridas no palato duro provenientes da remoção de enxerto gengival livre. Vinte e quatro pacientes participaram desse estudo e foram divididos aleatoriamente em 2 grupos de acordo com o tratamento utilizado para proteger o leito doador: Grupo controle (GC): A ferida foi recoberta com placa acrílica associada ao cimento cirúrgico (n=14); Grupo Látex (GL): A ferida foi recoberta com placa acrílica associada a membrana de látex natural (n=10). Foram realizadas tomadas fotográficas padronizadas das regiões das feridas nos períodos de baseline, 3, 7, 15 e 30 dias após o procedimento cirúrgico. Um examinador cego e calibrado realizou avaliação clínica, levando se em consideração os parâmetros: 1) fechamento de ferida; 2) área de superfície epitelizada por meio da utilização da água oxigenada aplicada na região; 3) Avaliação do auto relato de sensação dolorosa por meio da aplicação da escala de dor VAS. Os resultados obtidos mostraram que em ambos os grupos, houve diminuição gradativa da área da ferida cirúrgica, sendo que a partir dos 15 dias essa era inexistente para todos os pacientes avaliados e em relação à dor houve uma redução significativa da sensibilidade dolorosa relatada pelos pacientes do grupo látex em relação ao grupo controle. O uso da membrana de látex não promoveu efeito adicional a cicatrização, apresentando os mesmos resultados clínicos que a utilização de cimento... (Resumo completo, clicar acesso eletrônico abaixo) / Abstract: The aim of this project was to evaluate the effect of a natural latex membrane in wound healing on donor sites of free gingival grafts. Twenty-four patients were used in this study and were randomly divided in 2 groups according with the treatment used to protect the donor site: Control group (CG) – Donor site was covered with an acrylic plate associated with surgical cement (n=14); Látex group (LG) – Donor site was covered with acrylic plate associated with a natural latex membrane and surgical cement (n=10). At baseline, 3, 7, 15 and 30 days after surgery, standardized photos of the wound were taken. A blind and calibrated examiner made the clinical evaluation by considering the parameters: 1) total wound area; 2) epithelized surface area through the use of hydrogen peroxide applied in the region; 3) Evaluation of self-report of pain sensation through the application of the VAS pain scale. The achieve results showed that both groups had a gradual decrease in the area of the surgical wound, and from 15 days this was non-existent for all patients evaluated and on the pain avaliation we found that the patients in latex group had significant reduction in reported pain when compared to the control group. The use of natural latex membrane didn’t promote any additional effect for wound healing, showing the same clinical results as the use of surgical cement with the addition of a lower pain report by the patients. / Mestre

Immunomodulatory roles of endotoxin and glutaraldehyde in the development of latex allergy

Howell, Michael D. January 1900 (has links)
Thesis (Ph. D.)--West Virginia University, 2002. / Title from document title page. Document formatted into pages; contains xvii, 194 p. : ill. (some col.). Vita. Includes abstract. Includes bibliographical references (p. 163-181).

Avaliação in vitro e in vivo da capacidade antioxidante e antitumoral da fração C do látex de Hevea brasiliensis RRIM 600 /

Kerche-Silva, Leandra Ernst. January 2017 (has links)
Orientador: Aldo Eloizo Job / Banca: Eduardo Rene Perez Gonzalez / Banca: Edgardo Alfonso Gomes Pineda / Banca: Antonio Hernandes Chaves Neto / Banca: Aneli de Melo Barbosa / Resumo: Biomateriais podem ser definidos como dispositivos que entram em contato com sistemas biológicos tanto na forma de sólidos quanto de líquidos e géis. Para um novo biomaterial, são necessários testes toxicológicos e de interação in vitro e in vivo. O látex é uma substância branca e leitosa que exsuda da casca da Hevea brasiliensis quando a mesma é perfurada e que tem sido apontado como um biomaterial promissor. O látex quando centrifugado em alta velocidade é separado em três frações: a fração com partículas de borracha, uma fração aquosa chamada fração C e uma fração de fundo chamada fração B. A fração C é a fração metabolicamente ativa do látex. Assim, o presente estudo investigou os potenciais efeitos antioxidantes, citotóxicos, genotóxicos e antitumorais da fração C do látex da Hevea brasiliensis. Para isso, foram utilizados os testes de sequestro de radicais livres e capacidade antioxidante total em meio in vitro sem células; o teste do MTT, o ensaio do cometa, avaliação de morte celular com coloração com Hoechst 33342 e Iodeto de Propídio (PI) e avaliação de parâmetros bioquímicos de estresse oxidativo em meio in vitro com duas linhagens celulares, a CHO-k1, linhagem de células normais de epitélio de ovário de hamster, e a B16F10, linhagem de células de melanoma murino; e a ação da fração C na indução de carcinoma de células escamosas (SCC) em camundongos SKH-1 por exposição crônica à radiação UVB. Nossos resultados mostraram que a fração C é antioxidante, com capacidade... (Resumo completo, clicar acesso eletrônico abaixo) / Abstract: Biomaterials can be defined as devices that come in contact with biological systems in the form of solids, liquids and gels. In vitro and in vivo toxicological tests are needed for a new biomaterial to come out. Latex is a while and milky solution that exsudes from Hevea Brasiliensis bark when perforated, and it has been appointed as a new promising biomaterial. When centrifuged in high speed, latex can be separated in three parts: rubber particle fraction, aqueous C-serum fraction and a bottom fraction called B-serum. C-serum is the part that is metabolically active. In this way, the aim of this work was to investigate potential antioxidant, cytotoxic, genotoxic and antitumor effect of latex C-serum from Hevea brasiliensis. For this purpose, we used in vitro free-radical scavenger and total antioxidant capacity tests; MIT test, comet assay, staining with Hoechst 33342 and Propidium Iodide (PI) to evaluate cell death, and evaluation of biochemical parameters of oxidative stress in Chinese hamster ovary epithelium normal cell line, CHO-K1, and murine melanoma cell line, B16F10; and C-serum effects in the inductino of squamous cell carcinoma (SCC) in KKH-1 mice by chronic UVB exposure. Our results show that latex C-serum is an antioxidant compound that was able to scavenge HO and NO radicals and H2O2. C-serum did not after the cell viability in CHO-k1 cells and it did not promote DNA damage in these cells, it did not after the levels of apoptotic and necrotic cells for this cell lineage and did not alter total thiol and MDA levels in these cells. However, for B16F10 cells, latex C-serum presented antitumor effect, reducing cell viability, inducing DNA damage and cell death, and altering total thiol and MDA levels in these cells. In the animals chronically exposed to UVA radiation, latex C-serum proteted the erythrocytes and skin cells from oxidative stress promote by the irradiation, and... (Complete abstract electronic access below) / Doutor

A study of the internal particle morphology of composite polymer latices

Lye, J. E. January 1987 (has links)
No description available.

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