The Science Times section (Tuesday, July 7) of the NY Times has a very interesting article on how material chemists and engineers are studying and altering the molecular structure of the various types of glass to use them in new and unique ways. Students in the Forensic Science course at Bronxville High School examine many of the different types of glass discussed in this article and learn how to distinguish them (using density and refractive index) when found at a possible crime scene. Our students examine samples of soda glass, lead crystal glass, borosilicate glass, tempered glass and laminated glass.
Today's article describes the difference between tempered glass and laminated glass in simple terms and explains glass as an amorphous solid that is strengthened (tempered) by compressing the outer atoms using heat or chemical means. The advantage of tempering a piece of glass is that more tensile force is needed for cracks to appear/grow. Also this additional force and the imbalance created between the outer compressional forces and the inner tensile forces of tempered glasses make it break into many smaller pieces which are less likely to cause injury. This is why tempered glass is used to form the side and rear windows of automobiles. The article talks about Prince Rupert's drop as an illustration of this process. Laminating glass adds additional strength by using adhesives and polymer sheets to join glass layers together. Laminated glass is used to form the windshields of automobiles.
The article introduces the reader to ways in which engineers and scientists re-examine and test the structure of glass to make this ancient material stronger and less expensive to produce.
Links: Science Times Article NY Times Slide Show of Structural Uses of Glass You Tube Video of Prince Rupert's Drop You Tube Video of Annealing Glass (Explains how stress in glass is relieved)
Tuesday, July 7, 2009
Friday, July 3, 2009
Domestic Cattle Genome Sequencing Studies
Articles in the journals Science and Genome Biology, by a Michigan State University researcher and a participant in a 6 year global project with 300 scientists to complete, annotate, and analyze the 22,000 genes of the species Bos taurus, Theresa Casey reports that such studies may open new areas for human health research.
Casey, whose specialty is the study of lactation and mammary gland biology discusses how the study of the bovine genome will lead to a better understanding of the evolution of mammalian milk. She believes that due to the antimicrobial properties of cow's milk, that mammalian milk evolved primarily with an immune function to increase the survival chances of newborn mammals. She feels that the research vistas opened in the field can lead to a better understanding of how to ensure better human health and help to better feed the world's population.
Michigan State News Item
Casey, whose specialty is the study of lactation and mammary gland biology discusses how the study of the bovine genome will lead to a better understanding of the evolution of mammalian milk. She believes that due to the antimicrobial properties of cow's milk, that mammalian milk evolved primarily with an immune function to increase the survival chances of newborn mammals. She feels that the research vistas opened in the field can lead to a better understanding of how to ensure better human health and help to better feed the world's population.
Michigan State News Item
Conception Time and Birth Defects in USA Correlate with Pesticides in Surface Water
A study carried out at Indiana University and reported in the medical journal Acta Paediatrica found that birth defect rates in the US were highest in women who conceived their children in the spring and summer. This time period is also when there is an increased level of pesticides in the surface water. The researchers found a strong association/correlation between the birth defects in women conceiving/having their last menstrual period in the months of April, May, June or July and elevated levels of nitrates, atrazine, and other pesticides in surface water during the same months. Many of these chemicals use is banned in Europe, as they are suspected to be harmful to developing embryos, but their use is permitted in the US. The study relied on findings by the US Geological Survey, the EPA, and other agencies on the seasonal variations of the chemicals in surface water.
Paul Winchester professor of clinical pediatrics at the Indiana University School of Medicine, the first author of the study says, "Elevated concentrations of pesticides and other agrochemicals in surface water during April through July coincided with a significantly higher risk of birth defects in live births conceived by women whose last menstrual period began in the same months."
Indiana University News Release
Paul Winchester professor of clinical pediatrics at the Indiana University School of Medicine, the first author of the study says, "Elevated concentrations of pesticides and other agrochemicals in surface water during April through July coincided with a significantly higher risk of birth defects in live births conceived by women whose last menstrual period began in the same months."
Indiana University News Release
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