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August 28, 2009

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- r HERITAGE FLORIDA JEWISH NEWS, AUGUST 28, 2009 PAGE 17A TEL AVIV It's been a mystery: how can our teeth withstand such an enormous amount of pres- sure. over many years, when tooth enamel is only about as strong as glass? A new study by Professor Herzl Chai of Tel Aviv University's School of Mechanical Engi- neering and his colleagues at the National Institute of Standards and Technology and George Washington University gives the answer. The researchers applied varying degrees of mechani- cal pressure to hundreds of extracted teeth, and studied what occurred on the surface and deep inside them. The study, published in the May 5 issue of the "Proceedings of the Na- Tel Aviv University profes- sor Herzl Chai. tional Academy of Science," shows that it is the highly- sophisticated structure of our teeth that keeps them in one piece and that struc- ture holds promising clues for aerospace engineers as they build the aircraft and space vehicles of the future. "Teeth are made from an extremely sophisticated composite material which reacts in an extraordinary way under pressure," says Chai. "Teeth exhibit graded mechanical properties and a cathedral-like geometry, and over time they develop a network of micro-cracks which help diffuse stress. This, and the tooth's built-in ability to heal the micro- cracks over time, prevents it from fracturing into large pieces when we eat hard food, like nuts." The automotive and avia- tion industries already use sophisticated materials to prevent break-up on impact. For example, airplane bod- ies are made from composite materials layers of glass or carbon fibers held to- gether by a brittle matrix. In teeth, though, fibers aren't arranged in a grid, but are "wavy" in structure. There are hierarchies of fi- bers and matrices arranged in several layers, unlike the single-thickness layers used in aircrafts. Under mechanical pressure, this architecture presents no clear path for the release of stress. Therefore, "tufts"-- built-in micro cracks ab- sorb pressure in unison to prevent splits and major fractures. As Chai puts it. tooth fractures"have a hard time deciding which way to go," making the tooth more resistant to cracking apart. Harnessing this property could lead to a new gen- eration of much stronger composites for planes. Chai. an aerospace en- gineer, suggests that if engineers can incorporate tooth enamel's wavy hi- erarchy, micro-cracking mechanism, and capacity to heal. lighter and stronger aircraft and space vehicles can be developed. Andwhile creating a self-healing air- plane is far in the future, this significant research on the composite structure of teeth can already begin to inspire aerospace engineers--and, of course, dentists. Dental specialists look- ing for new ways to engi- neer that picture-perfect Hollywood smile can use Chai's basic research to help invent stronger crowns. better able to withstand oral wear-and-tear. "They can create smart materials that mimic the properties found in real teeth," he says. In natural teeth, there may notbe anyway to speed up the self-healing ability of tooth enamel, which the Tel Aviv University research found is accomplished by a glue-like substance that fills in micro-cracks over time. But fluoride treat- ments and Keaithy brush- ing habits can help to fill in the tiny cracks and keep teeth strong. what we were going to find," says Dardashti, 61. a New Yorker now living in Tel Aviv who started the Tracing the Tribe blog devoted to Jewish genealogy. "It's the story of Jewish history. Jews went everywhere." But, she says, people who are "Yiddish-speaking Ash- kenazim" are still shocked to find they have Sephardic roots. Harold Rhode. 59, of Po- toma'c, Md.. is one of them. He was surprised to learn that his family roots were not "pure Litvak" or from a Lithuanian shtetl. Rhode's DNA results indi- cated that he shared ances- try with Jews with a known ancestor from Sicily. Now he says, "I'm a pure Litvak of Sicilian origin." When and how Rhode's ancestor migrated to Sicily or from Sicily to Lithuania is unknown, though he says it most likely sometime in the 14th or 15th century. The findings of the Ibe- rian Ashkenaz Project, says Bennett Greenspan, founder and president of Family Tree DNA, indicate "an important discovery within a subset of the-Jewish world of an extended Jewish lineage. And it happens to be a substantial Jewish lineage numerically.'" Still, Dardashti says, more samples and data are needed. She encourages Ashkenazi males with indicators of Sep- hardi ancestry to have their Y DNA tested to determine if they match with known Sephardim or conversos. "Sometimes [your ances- try] is not where you think it is," she says. "You have to be prepared for what you'll find. Be prepared for the unusual." But. Greenspan says, "even though we may label ourselves Mizrahi, Sephardi or Ashkenazi. we all come from the original gene pool that was in the Land of Is- rael. We came from Judea; we're all Judeans." Courtesy Schelly Talalay Dardashti Genealogists Schelly Talalay Dardashh" (1) and Judy Simon launched the Iberian Ashkenaz Project two years ago with the Houston-based firm Family Tree DNA. By Suzanne Kurtz PHILADELPHIA (JTA)-- Despite leaving behind a Yiddish-speaking home in Latvia when he came to , America in 1909, Sam Gold always told his children and grandchildren that they were Sephardic Jews. Many decades later his granddaughter Judy Simon, 60, would finally confirm her grandfather was not meshugge. In 2004, after genetic testing became widely avail- able for genealogists. Simon took a cheek swab from a male cousin and had his Y chromosome DNA tested. "Y-chromosome DNA is passed on uncorrupted from father to son, generation after generation." says Mat- thew Kaplan, project leader at the University of Arizona's Human Origins Genotyping Laboratory. "I can look at a Y chromosome and trace paternal lines all the way back to Africa 100.000 years deep." Markers on the Y DNA can be used to verify a common male ancestor and to ap- proximate a time frame for the shared ancestor between individuals. The results for Simon's cousin came back matchfng man, Ashkenazi males from villages near their grand- father's region in Rezekne, Latvia but also matching two males from Texas and Mexico. With Spanish surnames and a known converso an- cestry, the two men were equally surprised to find they matched with Ash- kenazim. Conversos were Iberian Jews, from Spain Portugal, forced toconvert to Catholicism during the Inquisition of the 14th to 16th centuries. Many fled Iberia for the New World, eventually settling in what is now Mexico and the southwestern region of the United States. "The DNA results con- firmed what my grandfather had been saying all those years: We were Ashkenazi Jews with Sephardic roots." says Simon, a social worker from Stony Brook, N.Y. Most likely, she says. her ances- tors fled Spain in the 15th century for the Ottoman Empire before making there way to Latvia in the late 18th century. After sharing her discov- ery of Sephardic roots with other Jewish genealogists at conferences and online chat rooms. Simon. who also presented her genealogical journey last week to a rapt audience in Philadelphia at the 29th International As- sociation of Jewish Genea- logical Societies Conference on Jewish Genealogy, says "people [of Ashkenazi Jew- ish descent] starting com- ing out of the woodwork" with oral Sephardic histo- ries or Iberian surnames or Sephardic family traditions or even carrying a Mediter- ranean genetic disease. In March 2007, she and fellow Jewish genealogist and writer Schelly Talalay Dardashti decided to launch the Iberian Ashkenaz Proj- ect with Family Tree DNA, a Houston-based commercial genetic genealogy company. The goal of the project was to determine the Y-DNA hap- iogroups and haplotype sig- natures of Ashkenazic males with Iberian surnames or an oral Sephardic history, and to compare them with known Sephardic Jews and converso descendants. The Iberian Ashkenaz Project now has 140 mem- bers. says Simon. Of those, approximately 82 have re- cent Ashkenazi heritage, and 39 percent of them have Y DNA confirmed matches with Sephardim or conver- sos and a Most Recent Com- mon Ancestor. or MRCA. likely to have lived in Iberia during the 14th to 16th centuries. An additional 47 percent matched with Sephardim or conversos, but the MRCAwas more distant, having lived before the 14th century. 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