Integridade estrutural de compósitos laminados em fibra de carbono sujeitos a diferentes taxas de desgaste e absorção de água : protótipo de máquina de testes

Trabalho final de mestrado para obtenção do grau de Mestre em Engenharia MecânicaDesde sempre no panorama do ciclismo de alta competição se fizeram todos os esforços para melhorar os resultados dos atletas. Grande parte destes trabalhos está no desenvolvimento das bicicletas e seus componentes. A empresa Morphis Composites que está em fase de desenvolvimento de carretos de desviador em fibra de carbono. Estando estes componentes em material compósito laminado expostos à atmosfera, poderá estar em causa a sua integridade estrutural pois sabe-se que irão absorver água por difusão e se vão desgastar de forma diferente de carretos de outros materiais. Tudo isto poderá levar ao aumento do seu atrito na transmissão, sendo que é necessária a criação de meios para a avaliação desta temática. No presente trabalho faz-se o projecto e construção de um protótipo para medição de atrito em transmissões de bicicleta. Inclui-se uma breve pesquisa bibliográfica sobre correntes de rolos industriais e de ciclismo, o seu funcionamento e mecanismos de atrito. Além disto fez-se também uma breve pesquisa sobre os efeitos da absorção de água na fibra de carbono. Para o dimensionamento do sistema de medição procuraram-se resultados de trabalhos similares de forma a aferir as grandezas a medir e a sensibilidade necessária. O protótipo deve medir a potência conduzida à transmissão para esta rodar em vazio a uma velocidade constante que foi fixada neste caso em 60 rpm, sendo que quanto mais baixa a potencia medida menor o atrito da transmissão. O sensor usado é uma roseta colada a +45 e -45 graus no veio que fornece movimento ao sistema. O sinal é retirado do veio em rotação através de um sistema de anéis deslizantes em bronze onde se usaram escovas de grafite e de filamentos de cobre. Após a construção do protótipo fez-se a calibração estática dos sistemas de medição com bons resultados de sensibilidade e repetibilidade. Estes resultados empíricos também foram comparados com os resultados teóricos não tendo havido discrepâncias relevantes, provando a qualidade das medições de binário obtidas pelos extensómetros. No entanto, devido ao ruído introduzido no sinal pelas escovas em movimento, não foi possível obter resultados de qualidade nos ensaios dinâmicos para a potência e atrito na transmissão em rotação com o presente protótipo. No final apresentam-se sugestões para melhoria em trabalhos futuros.Ever since the beginning of high competition in cycling, that every erffort has been made to improve the results of the athletes. Much of this work is in the development of bicycles and their components. The company Morphis Composites is in the development stage of carbon fiber rear derailleur sprockets. These components made of laminated composite material are exposed to the atmosphere, thus their structural integrity may be affected because it is known that they will absorb water by diffusion and will wear differently from sprockets made of other materials, such as metals. All this can lead to the increase of its friction in the transmission, and it is necessary to create means for the evaluation of this situation. In the present work, the design and construction of a prototype for measuring friction in bicycle transmissions is done. A brief literature review on industrial roller and cycling chains, their operation and friction mechanisms is included. In addition, a brief research was also made on the effects of water absorption on carbon fiber. For the sizing of the measurement system, results of similar work were sought in order to understand the quantities to be measured and the required sensitivity. The prototype shall measure the power delivered to the transmission to idle at a constant speed which has been set at 60 rpm in this case, the lower the measured power the lower the transmission friction. The sensor used is a rosette glued to +45 and -45 degrees in a section of the main shaft before the main sprocket. The signal is drawn from the rotating shaft through a bronze slip ring system where graphite brushes and copper filaments were used. Upon prototype building the static calibration of the measurement systems was made with good results of sensitivity and repeatability. These empirical results were also compared with what would theoretically be expected and there were no relevant discrepancies, proving the quality of the torque measurements obtained by the extensometers. However, due to the noise introduced into the signal by the moving brushes, it was not possible to obtain quality results in the dynamic tests for power and friction in the rotational transmission with the present prototype. At the end, suggestions are presented for improvement in future work.N/

Tight-binding parameters for charge transfer along DNA

We systematically examine all the tight-binding parameters pertinent to charge transfer along DNA. The $\pi$ molecular structure of the four DNA bases (adenine, thymine, cytosine, and guanine) is investigated by using the linear combination of atomic orbitals method with a recently introduced parametrization. The HOMO and LUMO wavefunctions and energies of DNA bases are discussed and then used for calculating the corresponding wavefunctions of the two B-DNA base-pairs (adenine-thymine and guanine-cytosine). The obtained HOMO and LUMO energies of the bases are in good agreement with available experimental values. Our results are then used for estimating the complete set of charge transfer parameters between neighboring bases and also between successive base-pairs, considering all possible combinations between them, for both electrons and holes. The calculated microscopic quantities can be used in mesoscopic theoretical models of electron or hole transfer along the DNA double helix, as they provide the necessary parameters for a tight-binding phenomenological description based on the $\pi$ molecular overlap. We find that usually the hopping parameters for holes are higher in magnitude compared to the ones for electrons, which probably indicates that hole transport along DNA is more favorable than electron transport. Our findings are also compared with existing calculations from first principles.Comment: 15 pages, 3 figures, 7 table

Multi-ancestry transcriptome-wide association analyses yield insights into tobacco use biology and drug repurposing

Most transcriptome-wide association studies (TWASs) so far focus on European ancestry and lack diversity. To overcome this limitation, we aggregated genome-wide association study (GWAS) summary statistics, whole-genome sequences and expression quantitative trait locus (eQTL) data from diverse ancestries. We developed a new approach, TESLA (multi-ancestry integrative study using an optimal linear combination of association statistics), to integrate an eQTL dataset with a multi-ancestry GWAS. By exploiting shared phenotypic effects between ancestries and accommodating potential effect heterogeneities, TESLA improves power over other TWAS methods. When applied to tobacco use phenotypes, TESLA identified 273 new genes, up to 55% more compared with alternative TWAS methods. These hits and subsequent fine mapping using TESLA point to target genes with biological relevance. In silico drug-repurposing analyses highlight several drugs with known efficacy, including dextromethorphan and galantamine, and new drugs such as muscle relaxants that may be repurposed for treating nicotine addiction

International nosocomial infection control consortium (INICC) report, data summary of 36 countries, for 2004-2009

The results of a surveillance study conducted by the International Nosocomial Infection Control Consortium (INICC) from January 2004 through December 2009 in 422 intensive care units (ICUs) of 36 countries in Latin America, Asia, Africa, and Europe are reported. During the 6-year study period, using Centers for Disease Control and Prevention (CDC) National Healthcare Safety Network (NHSN; formerly the National Nosocomial Infection Surveillance system [NNIS]) definitions for device-associated health care-associated infections, we gathered prospective data from 313,008 patients hospitalized in the consortium's ICUs for an aggregate of 2,194,897 ICU bed-days. Despite the fact that the use of devices in the developing countries' ICUs was remarkably similar to that reported in US ICUs in the CDC's NHSN, rates of device-associated nosocomial infection were significantly higher in the ICUs of the INICC hospitals; the pooled rate of central line-associated bloodstream infection in the INICC ICUs of 6.8 per 1,000 central line-days was more than 3-fold higher than the 2.0 per 1,000 central line-days reported in comparable US ICUs. The overall rate of ventilator-associated pneumonia also was far higher (15.8 vs 3.3 per 1,000 ventilator-days), as was the rate of catheter-associated urinary tract infection (6.3 vs. 3.3 per 1,000 catheter-days). Notably, the frequencies of resistance of Pseudomonas aeruginosa isolates to imipenem (47.2% vs 23.0%), Klebsiella pneumoniae isolates to ceftazidime (76.3% vs 27.1%), Escherichia coli isolates to ceftazidime (66.7% vs 8.1%), Staphylococcus aureus isolates to methicillin (84.4% vs 56.8%), were also higher in the consortium's ICUs, and the crude unadjusted excess mortalities of device-related infections ranged from 7.3% (for catheter-associated urinary tract infection) to 15.2% (for ventilator-associated pneumonia). Copyright © 2012 by the Association for Professionals in Infection Control and Epidemiology, Inc. Published by Elsevier Inc. All rights reserved

Global Retinoblastoma Presentation and Analysis by National Income Level

Importance: Early diagnosis of retinoblastoma, the most common intraocular cancer, can save both a child's life and vision. However, anecdotal evidence suggests that many children across the world are diagnosed late. To our knowledge, the clinical presentation of retinoblastoma has never been assessed on a global scale. Objectives: To report the retinoblastoma stage at diagnosis in patients across the world during a single year, to investigate associations between clinical variables and national income level, and to investigate risk factors for advanced disease at diagnosis. Design, Setting, and Participants: A total of 278 retinoblastoma treatment centers were recruited from June 2017 through December 2018 to participate in a cross-sectional analysis of treatment-naive patients with retinoblastoma who were diagnosed in 2017. Main Outcomes and Measures: Age at presentation, proportion of familial history of retinoblastoma, and tumor stage and metastasis. Results: The cohort included 4351 new patients from 153 countries; the median age at diagnosis was 30.5 (interquartile range, 18.3-45.9) months, and 1976 patients (45.4) were female. Most patients (n = 3685 84.7%) were from low-and middle-income countries (LMICs). Globally, the most common indication for referral was leukocoria (n = 2638 62.8%), followed by strabismus (n = 429 10.2%) and proptosis (n = 309 7.4%). Patients from high-income countries (HICs) were diagnosed at a median age of 14.1 months, with 656 of 666 (98.5%) patients having intraocular retinoblastoma and 2 (0.3%) having metastasis. Patients from low-income countries were diagnosed at a median age of 30.5 months, with 256 of 521 (49.1%) having extraocular retinoblastoma and 94 of 498 (18.9%) having metastasis. Lower national income level was associated with older presentation age, higher proportion of locally advanced disease and distant metastasis, and smaller proportion of familial history of retinoblastoma. Advanced disease at diagnosis was more common in LMICs even after adjusting for age (odds ratio for low-income countries vs upper-middle-income countries and HICs, 17.92 95% CI, 12.94-24.80, and for lower-middle-income countries vs upper-middle-income countries and HICs, 5.74 95% CI, 4.30-7.68). Conclusions and Relevance: This study is estimated to have included more than half of all new retinoblastoma cases worldwide in 2017. Children from LMICs, where the main global retinoblastoma burden lies, presented at an older age with more advanced disease and demonstrated a smaller proportion of familial history of retinoblastoma, likely because many do not reach a childbearing age. Given that retinoblastoma is curable, these data are concerning and mandate intervention at national and international levels. Further studies are needed to investigate factors, other than age at presentation, that may be associated with advanced disease in LMICs. © 2020 American Medical Association. All rights reserved