Time filter

Source Type

Xochimilco, Mexico

Lopez-Cruz I.L.,University of Chapingo | Rojano-Aguilar A.,University of Chapingo | Salazar-Moreno R.,University of Chapingo | Ruiz-Garcia A.,University of Chapingo | Goddard J.,Metropolitan University
Acta Horticulturae

Sensitivity analysis is an important step in developing mathematical modelling of agricultural systems. However, usually for greenhouse crop models, local approaches based on the calculation of derivatives are applied. Unfortunately, the main drawback of local approaches is that derivatives provide information only at the base point where they are computed and do not take into account the rest of the variation range of the model's parameters. In contrast, several so called global sensitivity analysis approaches such as standardized regression coefficients, the elementary effect test, variance-based methods and Monte Carlo Filtering are being developed. In the present work a comparison between a local sensitivity analysis and two global sensitivity methods is carried out. The paper focuses on the methodological issues concerning both local and global sensitivities approaches, where their similarities and differences are discussed. A five-state variables greenhouse lettuce crop model is used in order to show both the strengths and also the weaknesses of the paradigms. In the case of the local method the so-called sensitivity equations are stated and solved. For the global approaches, firstly, probability density functions (PDFs) were assigned to each of the model's parameters. Secondly, five thousands Monte Carlo simulations were conducted in order to calculate the sensitivity indices and measures. The lettuce crop model was implemented in Matlab, and the global sensitivity analysis was programmed using the SimLab (ver. 3.2) software. More reliable results were obtained by the global method based on variance calculation Fourier Amplitude Sensitive Test (FAST) which indentified as the most sensitive parameters for the NICOLET model the coefficients: radiation extinction, photosynthetic efficiency, leaf conductance to CO2, specific growth rate, maintenance respiration and reference temperature. Source

Garbin A.J.I.,Sao Paulo State University | Garbin C.A.S.,Sao Paulo State University | Moimaz S.A.S.,Sao Paulo State University | Baldan R.C.F.,Metropolitan University | Zina L.G.,Sao Paulo State University
Archives of Environmental and Occupational Health

Disorders localized to the musculoskeletal system are a common problem among dental personnel. This study has the aim of surveying epidemiological studies reporting positive associations between dental practice and musculoskeletal disorders (MSKDs). The focus was to evaluate the size of reported risk increase and the extent to what alternative causal explanations were considered. Reports with significant links (p value <.05) were systematically selected from 2 electronic databases. Twenty-five studies were identified. Risk measures were reported in 8 studies, and all of them presented weak associations. The impact of at least 1 competing explanations was analyzed in 32% of studies, but adjustment was considered not adequate in half of them. The evidence on dentistry as a profession with potential risk for development of MSKDs remains questionable. Further research is needed to more carefully elucidate the risk and the impact of MSKDs in this particular occupational group. © 2011 Copyright Taylor and Francis Group, LLC. Source

Cabeza M.,Metropolitan University | Heuze Y.,Metropolitan University | Quintana H.,Metropolitan University | Bratoeff E.,National University of Pharmacy
Asian Journal of Animal and Veterinary Advances

The aim of this study is to compare the effect of Testosterone (T) and finasteride (F)-treatments on the diameter of the pigmented spot of hamster's flank organs as well as on the weight of seminal vesicles and prostate glands in two different animal models: prepuberal and adult hamsters. The treatments administrated to prepuberal hamsters, after 7 days of castration and adults hamsters after 30 days of castration showed similar results in the growth of prostate and seminal vesicles. However, the flank organs response to finasteride from prepuberal hamster was different than that observed for the flank organs from adult hamsters. Daily injections with T plus F in prepuberal castrated hamsters did not decrease the diameter of the flank organs, thus suggesting that the 5α-reductase enzyme is not present in these glands. In conclusion, the flank organs from prepuberal hamsters are a good model for the determination of the androgenic and antiandogenic activity. However, this assay is not suitable for the determination of 5α-reductase inhibitory activity of different steroids in vivo. Furthermore, both adults and prepuber hamsters prostate and seminal vesicles are good models for the determination of the androgenic, antiandrogenic and 5α-reductase inhibitory effects in drugs. © 2010 Academic Journals Inc. Source

News Article
Site: http://news.mit.edu/topic/mitmaterials-science-rss.xml

Undergraduate interns selected for this year’s Summer Scholars program come from Montana to Florida and Puerto Rico and have a diverse set of scientific accomplishments and personal interests. “I’m excited to use this internship as an opportunity to step out of my comfort zone. Interning at MIT will give me a chance to adapt to a new environment, cope with new subject matter, and meet new people,” says Justin Cheng, a Rutgers University junior majoring in materials science and engineering. He’d like to tackle a project related to electronic or photonic materials. “My fun fact is that I received a black belt in karate (Okinawan Shuri-Ryu) when I was in high school,” Florida State University junior Alexandra T. Barth says. She is pursuing a double major in chemistry and physical science and hopes to conduct research in the area of materials chemistry and pursue a doctorate in the field. Cheng and Barth are two of 11 outstanding undergraduates who will conduct graduate level research at MIT in Cambridge, Massachusetts, from June 7 through Aug. 6. The group’s interests range from condensed matter physics and materials science to biotechnology and bioinformatics. “MIT is very fortunate to have this very talented group of students with us, and the faculty all hope that one of them will work with their group,” says Carl V. Thompson, director of the Materials Processing Center and Stavros Salapatas Professor of Materials Science and Engineering at MIT. Center for Materials Science and Engineering Director Michael Rubner adds, "This is an amazingly successful program that will no doubt continue far into the future." Interns will have the opportunity to choose from a multitude of on-campus research opportunities. The scholars will hear faculty, postdocs, and graduate students outline their summer projects in the morning and then tour their labs in the afternoon on Wednesday, June 8, through Friday, June 10. The program is sponsored jointly by the Materials Processing Center and the Center for Materials Science and Engineering at MIT. Suna Njie, a junior at historically black Alabama State University, has lived on three continents and visited seven countries. “Traveling and living in different areas of the world at an early age has opened my eyes to many traditions and lifestyles,” she says. “It is my ultimate dream to become a research professional in the biochemistry field. This will allow me to have an immense impact on the scientific and general community.” “I’m excited to learn more about materials science and engineering and other scientific disciplines through talking with faculty and students alike,” says University of Massachusetts at Amherst junior chemical engineering major Ashley Kaiser. “I hope to research nanostructured materials, especially 2-D materials, and their role in energy and electronics applications.” Kaiser is a gymnast who is challenging herself by learning the still rings, an event that only appears in men’s gymnastics because it requires tremendous upper body strength. “Fascinated with this physical challenge, I worked hard to learn the basics. Today, I still seek advice for this event from my gymnastics coaches and male gymnasts, who always seem surprised to see a girl up on the rings,” she says. Physics major Grant Smith won the Bert Elsbach Honors Scholarship in Physics at Pennsylvania State University last year for exceptional achievement. He has minors in both mathematics and electronic and photonic materials. “I am exposed to coursework dealing with [the] most fundamental natural behaviors punctuated by coursework focused on the application of these concepts to engineering problems,” Smith says. His work under Professor Nitin Samarth at Penn State focuses on topological insulators. He hopes his lab experience at MIT will provide broader experience in the electronic properties of materials. Michael Concepción Santana, a junior at Polytechnic University in San Juan, Puerto Rico, is interested in the pharmaceutical industry, specifically in synthesizing ligands that can deliver drugs to attack disease cells and cure illnesses. He has participated in several research projects including experimental green synthesis and characterization of Podophyllotoxin, a plant-derived organic polymer and potential anti-cancer agent, under Ajay Kumar at Metropolitan University in San Juan. He participated in the Air Force Junior ROTC program during high school and won three military-themed scholarships. “Having that experience during high school developed in me the leadership, character and integrity that is necessary in the field of science and engineering,” Concepción says. Johns Hopkins University junior Michael Porter hopes to pursue research in polymeric biomaterials and drug delivery. “Through this program, I hope to refine and confirm my research interests for graduate school and for a career in research,” he says. Porter, whose father is white and mother is Japanese, recalls difficulty communicating as he grew up in Ohio trying to learn two languages and attending the local Japanese school. “I still find that communication is as fundamental as ever in building and maintaining meaningful relationships,” he says. He previously participated in a summer research internship at UMass Amherst, where he studied the bacterial collection potential of cellulose fiber mats, and how changing their surface charge and topography could impact their effectiveness. As the daughter of a U.S. military employee, Erica Eggleton lived in Germany for six years, attending an American school on base from 7th to 12th grade. “These were my forming years, so I believe that living in Germany helped shape me into the person I grew up to become,” she says. Eggleton, a chemical engineering major at Montana State University, plays mellophone in the university’s Spirit of the West Marching Band as well as French horn in the brass quintet. She is interested in fuel cell research and is a co-author of an International Journal of Hydrogen Energy paper analyzing gas-liquid flow mechanisms in proton exchange membrane fuel cells. “I live in Montana, where the mountains are my backyard and I am surrounded by outdoor activities. Seeing the beauty of our world everyday motivates me to help conserve it for generations to come,” Eggleton says. She hopes her summer internship will offer the opportunity to do work related to renewable energy or sustainable materials. University of Puerto Rico at Mayaguez sophomore Ashley Del Valle Morales is looking forward to exchanging new and exciting concepts about energy and sustainability with diverse scholars, as well taking advantage of the opportunity to acquire and enhance her research skills. “By learning about and implementing new materials, we can minimize pollution, increase the use of recycled and renewable materials and have recycling-friendly designs. My passion lies in creating and generating energy in an efficient, cost-effective and sustainable manner,” she says. Del Valle says she learned to do crochet when she was eight years old, and it has become one of her passions ever since. “All my family says I am a young woman with the soul of a grandmother, because in every free time I get I do crochet,” she says. Vanderbilt University sophomore Victoria Yao also is interested in exploring new ways to affect environmental change and sustainability. She hopes to conduct research from the perspective of her major, chemical engineering. Yao tutors elementary school students in math through the Pencil Projects club and mentors nearby high school Key Clubs through Circle K. “I enjoyed building a relationship with these kids, and I hope to continue this in the future,” she says. Jennifer Coulter, a Rutgers junior physics major, serves as the outreach coordinator for the Society of Physics Students and as a program co-coordinator and frequent mentor for the Douglass Project for Women in STEM. “Through both of these appointments, I feel I have been able to use science education to significantly better the careers of the future researchers of Rutgers,” she says. Coulter hopes to participate in condensed matter physics at MIT during her internship. “I have confidence that this program will allow me to develop my skills in solid state physics and hopefully help me determine my direction as I apply to graduate school,” she says. At Rutgers, Coulter has participated in research under materials science and engineering Professor Dunbar Birnie that led to several publications on solar cell material growth. The Materials Processing Center and Center for Materials Science and Engineering sponsor the nine-week National Science Foundation Research Experience for Undergraduates (NSF REU) internships with support from the National Science Foundation's Materials Research Science and Engineering Centers program (grant number DMR-14-19807).

Nlshimura T.,Metropolitan University | Nlshimura T.,Tokyo Metroplitan University | Seo A.,Metropolitan University | Doi K.,Metropolitan University
Journal of Japan Industrial Management Association

The touch panels have come into widespread use in recent years. For example, touch panels are used in ticket-vending machines at stations and automated teller machines at banks. However, there has been little research regarding touch-panel operability from the standpoint of biomechanics. If an evaluation index that is capable of providing an evaluation based on work posture can be created, that evaluation index can be transformed into a digital human model. Additionally touch-panel operability can be evaluated. The authors therefore applied arm manipulability utilized in the field of robotics to evaluate touch-panel operability and conducted an experiment to evaluate touch-panel usability. Ten healthy male subjects participated in the experiment. They were asked to operate the touch panel under the following conditions: seven touch panel angles (0, 15, 30, 45, 60, 75 and 90 degrees). As the evaluation index, switch operation frequency and subject operation efficiency were utilized to compare arm manipulability results. The results showed that arm manipulability correlates with switch operation frequency and subject operation efficiency. From this study, it was found that it is possible to apply arm manipulability as an evaluation index for touch panels. Source

Discover hidden collaborations