Influência do super-resfriamento nas ligas cu-al-ni com efeito de memória de forma

Nesse trabalho foi avaliada a microestrutura da liga 83%Cu – 13%Al – 4%Ni (porcentagem em peso) em 3 condições experimentais: a) estado bruto de fusão, b) estado bruto de fusão temperada e c) solidificada com fluxo. A liga no estado bruto de fusão apresentou grãos contendo partículas precipitadas no interior dos grãos, sem a presença de martensíta e o contorno desses grãos foi definido pelas partículas segregadas, enquanto a liga no estado bruto de fusão temperada apresentou grãos com a presença de martensíta e contornos sem precipitados. A liga solidificada com fluxo apresentou grãos com a presença de martensíta e sem precipitado

Effects of external irradiation of the neck region on intima media thickness of the common carotid artery

<p>Abstract</p> <p>Background</p> <p>Several studies have shown that common carotid intima-media thickness (IMT) is increased after radiotherapy (RT) to the head and neck. However, further studies are needed to define the exact mechanism of radiation-induced injury in large vessels, investigate the relationship between radiation dose and large vessel injury and evaluate the rate of progress of atherosclerosis in irradiated vessels.</p> <p>Objectives</p> <p>To investigate whether external irradiation to the carotid area has any effect on IMT of the common carotid artery in a group of patients who received RT vs control group matched for age, gender and race.</p> <p>Methods</p> <p>We studied 19 patients (10 male; 47.8 ± 17.4 years) during a 5-month period (January 2009-July 2009); they had completed RT with a mean of 2.9 years before (range: 1 month-6 years) The mean radiation dose to the neck in the irradiated patients was 41.2 ± 15.6 Gy (range: 25-70 Gy). Common carotid IMT was measured with echo-color Doppler. Nineteen healthy adult patients (10 male; 47.8 ± 17.6) were recruited as a control group.</p> <p>Results</p> <p>IMT was not significantly higher in patients when compared to the control group (0.59 ± 0.16 vs 0.56 ± 0.16 mm, p = 0.4). There was no significant difference between the two groups in relation to the absence (p = 0.7) or presence (p = 0.6) of vascular risk factors. Although the difference did not reach statistical significance (p = 0.1), the irradiated young patients (age ≤ 52 years) had IMT measurements higher (0.54 ± 0.08 mm) than the non-irradiated young patients (0.49 ± 0.14 mm). The mean carotid IMT increased with increasing doses of radiation to the neck (p = 0.04).</p> <p>Conclusion</p> <p>This study shows that increased IMT of the common carotid artery after RT is radiation-dose-related. Therefore it is important to monitor IMT, which can be used as an imaging biomarker for early diagnosis of cerebrovascular disease in patients who have had radiotherapy for treatment of cancer of the head and neck and who are at increased risk for accelerated atherosclerosis in carotid arteries.</p

Copyright © 2000, American Society for Microbiology. All Rights Reserved. An Evaluation of Computer-Based Instruction in Microbiology

There has been a tremendous increase in the availability of computer-based instructional (CBI) materials. Some studies have shown an improvement in learning when CBI is used. However, many researchers believe the current studies are inadequate. While CBI software should be thoroughly tested by developers, as educators, we should be concerned about whether or not the CBI materials we use are improving learning in our classrooms with our students. We present an evaluation of a computer-based hypermedia tutorial that was delivered over our General Microbiology website. We found that CBI was at least as effective as text-based material. However, of all students who used CBI, only those who explored most of the site benefited from using the site. Tracking each student’s use of the CBI was critical for understanding who was learning and why. In the past decade, there has been an explosion in the availability and use of computer-based instruction (CBI) in education (see references 9 and 22). CBI comes in many different types, each with its own educational strengths and weaknesses. For example, computers can be used as tutoring systems that present material and then give users an immediate opportunity to evaluate their knowledge (sometimes referre

Influência do super-resfriamento nas ligas cu-al-ni com efeito de memória de forma.

In this work, 83%Cu - 13%Al - 4%Ni (percentage in weight) alloy was evaluated in 3 experimental conditions: a) as-melted, b) as casting quenched and c) flux solidified. Effects of the undercooling phase structures were investigated. Compared with the The as-melted alloy presented grains containing precipitate particles inside of the grains, without martensite morphology and the contour of those grains were defined by the segregated particle. The alloy in the as-melted quenched presented grains with internal martensite morphology and contours without precipitate. The flux solidified alloy presented grains with martensite morphology and without precipitate.Nesse trabalho foi avaliada a microestrutura da liga 83%Cu � 13%Al � 4%Ni (porcentagem em peso) em 3 condições experimentais: a) estado bruto de fusão, b) estado bruto de fusão temperada e c) solidificada com fluxo. A liga no estado bruto de fusão apresentou grãos contendo partículas precipitadas no interior dos grãos, sem a presença de martensíta e o contorno desses grãos foi definido pelas partículas segregadas, enquanto a liga no estado bruto de fusão temperada apresentou grãos com a presença de martensíta e contornos sem precipitados. A liga solidificada com fluxo apresentou grãos com a presença de martensíta e sem precipitado

A Smart Polymer Composite Based on a NiTi Ribbon and a Magnetic Hybrid Material for Actuators with Multiphysic Transduction

A smart composite material constituted of a magnetic hybrid film and a NiTi shape memory alloy (SMA) ribbon was obtained and characterized. The magnetic hybrid film was joined to the NiTi ribbon in order to combine the properties of both materials. This new composite material combines magnetic properties of the hybrid film, (Fe2O3-CMC)/(polyvinyl butyral), and the shape memory properties of the NiTi ribbon, which has a chemical composition of Ti-50.13 at. % Ni. This smart composite material has a mass of 18.3% NiTi ribbon and 81.7% magnetic hybrid film. Results obtained by DSC show that the smart composite material presents a small delay of transformation during warming and cooling because the magnetic hybrid film acts like a thermal insulator. Thermomechanical results indicate that the hybrid material also acts as a mechanical reinforcement, since it is observed that the Stress-Assisted Two-Way Memory Effect (SATWME) of the smart composite is lower than the SATWME of the SMA ribbon. The density current values of phase transformations were clearly identified with a thermomechanical apparatus developed in our laboratory. Finally, displacements of the smart composite material in cantilever configuration are obtained by applying an external magnetic field. All these results demonstrate that the smart composite material can be activated by temperature, electrical current, stress, and/or magnetic field, offering good expectations for actuating applications with multiphysic transduction

Avaliação das propriedades mecânicas de juntas cerâmicas usando fitas amorfas como metal de adição Evaluation of the mechanical properties of ceramic joint using amorphous ribbons as filler metals

Este trabalho teve como objetivo determinar os melhores parâmetros para brasagem de juntas cerâmicas de Al2O3 pré-metalizadas com Ti por processo a plasma utilizando fitas amorfas de ligas Cu49Ag45Cx e como metal de adição. As ligas foram preparadas em forno a arco, e, posteriormente processadas por melt-spinning, variando conteúdo Ce de 4-6. %. A brasagem foi realizada em forno à vácuo e as seguintes variáveis analisadas: tempo de deposição do filme de Ti e temperatura e tempo de brasagem , que foram relacionados com a resistência à flexão em 3 pontos da junta brazada. A equação de regressão linear foi obtida, e verificou-se a interação entre estes fatores. As superfícies cerâmicas metalizadas apresentaram excelente uniformidade e as juntas brasadas muito boa adesão atingindo valores de resistência à flexão de até 176,8 MPa.<br>This work had as objective to establish de best brazing parameter to joint Al2O3 pre-metalized with Ti by plasma process using amorphous ribbons of Cu49g45Ce x alloys as filler metals. The alloys were prepared in arc furnace and processed by melt-spinning process varying the Ce percentiles from 4 to 6. % . The brazing was accomplished in vacuum furnace and the following variables analyzed: deposition time of Ti film, brazing temperature and brazing times which were related to the brazed joint 3-point bending resistance. The interaction between those factors was obtained by linear regression equation. The metalized ceramic surfaces presented an good uniformity and the joint a very good adhesion reaching bending resistance up to 176,8 MPa

Artificial Intelligence Detection of Diabetic Retinopathy

Objective: To compare general ophthalmologists, retina specialists, and the EyeArt Artificial Intelligence (AI) system to the clinical reference standard for detecting more than mild diabetic retinopathy (mtmDR). Design: Prospective, pivotal, multicenter trial conducted from April 2017 to May 2018. Participants: Participants were aged ≥ 18 years who had diabetes mellitus and underwent dilated ophthalmoscopy. A total of 521 of 893 participants met these criteria and completed the study protocol. Testing: Participants underwent 2-field fundus photography (macula centered, disc centered) for the EyeArt system, dilated ophthalmoscopy, and 4-widefield stereoscopic dilated fundus photography for reference standard grading. Main Outcome Measures: For mtmDR detection, sensitivity and specificity of EyeArt gradings of 2-field, fundus photographs and ophthalmoscopy grading versus a rigorous clinical reference standard comprising Reading Center grading of 4-widefield stereoscopic dilated fundus photographs using the ETDRS severity scale. The AI system provided automatic eye-level results regarding mtmDR. Results: Overall, 521 participants (999 eyes) at 10 centers underwent dilated ophthalmoscopy: 406 by nonretina and 115 by retina specialists. Reading Center graded 207 positive and 792 eyes negative for mtmDR. Of these 999 eyes, 26 eyes were ungradable by the EyeArt system, leaving 973 eyes with both EyeArt and Reading Center gradings. Retina specialists correctly identified 22 of 37 eyes as positive (sensitivity 59.5%) and 182 of 184 eyes as negative (specificity 98.9%) for mtmDR versus the EyeArt AI system that identified 36 of 37 as positive (sensitivity 97%) and 162 of 184 eyes as negative (specificity of 88%) for mtmDR. General ophthalmologists correctly identified 35 of 170 eyes as positive (sensitivity 20.6%) and 607 of 608 eyes as negative (specificity 99.8%) for mtmDR compared with the EyeArt AI system that identified 164 of 170 as positive (sensitivity 96.5%) and 525 of 608 eyes as negative (specificity 86%) for mtmDR. Conclusions: The AI system had a higher sensitivity for detecting mtmDR than either general ophthalmologists or retina specialists compared with the clinical reference standard. It can potentially serve as a low-cost point-of-care diabetic retinopathy detection tool and help address the diabetic eye screening burden