洛阳回流生实力联系电话(渭南新高一靠谱的效果好) (今日更新中)

WASHINGTON, June 16 (Xinhua) -- Cells in the human body are constantly being exposed to stress from environmental chemicals or errors in routine cellular processes. While stress can cause damage, it can also provide the stimulus for undoing the damage. New research by a team of scientists at the University of Rochester has unveiled an important new mechanism that allows cells to recognize when they are under stress and prime the DNA repair machinery to respond to the threat of damage.Their findings will be published Friday in journal Science. Cells in the human body are constantly being exposed to stress from environmental chemicals or errors in routine cellular processes. While stress can cause damage, it can also provide the stimulus for undoing the damage.The scientists, led by biologists Vera Gorbunova and Andrei Seluanov, focused on the most dangerous type of DNA damage -- double strand breaks. Unrepaired, this type of damage can lead to premature aging and cancer. They studied how oxidative stress affects efficiency of DNA repair. Oxidative stress occurs when the body is unable to neutralize the highly-reactive molecules, which are typically produced during routine cellular activities.The research team found that human cells undergoing oxidative stress synthesized more of a protein called SIRT6. By increasing SIRT6 levels, cells were able to stimulate their ability to repair double strand breaks. When the cells were treated with a drug that inactivated SIRT6, DNA repair came to a halt, thus confirming the role of SIRT6 in DNA repair. Gorbunova notes that the SIRT6 protein is structurally related to another protein, SIR2, which has been shown to extend lifespan in multiple model organisms."SIRT6 also affects DNA repair when there is no oxidative stress," explains Gorbunova. "It's just that the effect is magnified when the cells are challenged with even small amounts of oxidative stress."SIRT6 allows the cells to be economical with their resources, priming the repair enzymes only when there is damage that needs to be repaired. Thus SIRT6 may be a master regulator that coordinates stress and DNA repair activities, according to Gorbunova.

New York, Sept. 23 (Xinhua) -- A Chinese scientist was presented a prestigious U.S. award on Friday for the discovery of artemisinin, a drug therapy for malaria that has saved millions of lives across the globe, especially in the developing world.Pharmacologist Tu Youyou, 81, became the first scientist on the Chinese mainland to win Lasker Award, known as "America's Nobels" for their knack of gaining future recognition by the Nobel committee.Tu, a scientist at the China Academy of Chinese Medical Sciences in Beijing, pioneered a new approach to malaria treatment that has benefited hundreds of millions of people and promises to benefit many times more. By applying modern techniques and rigor to a heritage provided by 5000 years of Chinese traditional practitioners, she has delivered its riches into the 21st century."Not often in the history of clinical medicine can we celebrate a discovery that has eased the pain and distress of hundreds of millions of people and saved the lives of countless numbers of people, particularly children, in over 100 countries," Lucy Shapiro, a member of the award jury and professor of Stanford University, said while describing Tu' s discovery.Shapiro said the discovery, chemical identification, and validation of artemisinin, a highly effective anti-malarial drug, is largely due to the "scientific insight, vision and dogged determination" of Professor Tu and her team. She thought Professor Tu's work has provided the world with arguably the most important pharmaceutical intervention in the last half century."The discovery of artemisinin is a gift to mankind from traditional Chinese medicine," Tu said while receiving the award. "Continuous exploration and development of traditional medicine will, without doubt, bring more medicines to the world."

CANBERRA, Sept. 23 (Xinhua) -- A genetic study on Friday found Aboriginal Australians are descended from the first people to leave Africa up to 75,000 years ago.Researchers from the University of Western Australia, Murdoch University and an international team analyzed genetic material of a 100-year-old West Australian Aboriginal man's hair, and found he was directly descended from a migration out of Africa into Asia.The study revealed that Australian Aboriginal ancestors split from the first modern human populations to leave Africa, between 64,000 and 75,000 years ago, at least 24,000 years before other human migrations.According to Dr. Joe Dortch, an archaeologist at the University of Western Australia, the discovery rewrites the history of the human species by confirming humans moved out of Africa in waves of migrations rather than in one single out-of-Africa diaspora.It also rewrites the story about how Aborigines arrived in Australia some 50,000 years ago."So far there are no [archaeological] sites that are over 50, 000 years old so it puts a time limit on that and focuses our future efforts," he said in a statement released on Friday.Dr. Dortch believes the finding will foster a sense of pride in modern Australian Aborigines."No-one else in the world can say 'I am descended from people who have been here 75,000 years'."Associate Professor Darren Curnoe, leader of the Human Evolutionary Biology Lab in the School of Biological, Earth & Environmental Sciences at the University of New South Wales, said the study powerfully confirms that Aboriginal Australians are one of the oldest living populations in the world, certainly the oldest outside of Africa."Australians are truly one of the world's great human populations and a very ancient one at that, with deep connections to the Australian continent and broader Asian region. About this now there can be no dispute," he told Xinhua in an email note.Meanwhile, Professor Alan Cooper, Director of the Australian Centre for Ancient DNA (ACAD) at the University of Adelaide, said while this is a major step forward, the key unresolved question remains the unique story of Aboriginal history within Australia, such as what has happened in those 50,000 years of life in the harsh Australian environment."Unfortunately, the information from a single individual tells us very little about this fascinating, and critically important part of human history. Aborigines are one of the oldest continuous human populations outside Africa, as they note in the paper, and due to the geographic isolation and limited archaeological records remain one of the most mysterious chapters in human history," he told Xinhua on Friday.The study is published on Friday in the journal Science.Indigenous Australians are the original inhabitants of the Australian continent and nearby islands. They together make up more than 2.5 percent of Australia's population.

SAN FRANCISCO, Aug. 15 (Xinhua) --- Google Inc. on Monday announced that it has agreed to buy Motorola Mobility Holdings Inc. for about 12. 5 billion U.S. dollars, the largest purchase for the Internet search giant that will allow it to compete more directly with other mobile phone makers.Google said that it will acquire Motorola Mobility for 40 dollars per share in cash, or a total of about 12.5 billion dollars, a premium of 63 percent to the closing price of Motorola Mobility shares last Friday.The transaction was unanimously approved by the boards of directors of both companies and is expected to close by the end of 2011 or early 2012, subject to regulatory approvals and other closing conditions.Google noted that the acquisition of Motorola Mobility, a dedicated partner of its Android mobile operating system, will enhance competition in mobile computing.Motorola Mobility will remain a licensee of Android and Android will remain open, Google said, adding that it will run Motorola Mobility as a separate business."Motorola Mobility's total commitment to Android has created a natural fit for our two companies. Together, we will create amazing user experiences that supercharge the entire Android ecosystem for the benefit of consumers, partners and developers," Larry Page, Google's chief executive officer (CEO), said in a statement."We have shared a productive partnership with Google to advance the Android platform, and now through this combination we will be able to do even more to innovate and deliver outstanding mobility solutions across our mobile devices and home businesses," said Sanjay Jha, CEO of Motorola Mobility.

MOSCOW, June 27 (Xinhua) -- Russia successfully launched a Cosmos class military satellite on Monday, said spokesman of the Russian Space Forces Alexei Zolotukhin.A Soyuz-U carrier rocket carrying the military satellite blasted off from the Plesetsk Plesetsk space center in northern Russia at 20:00 Moscow time (1600 GMT), Zolotukhin said."The rocket put the Cosmos series military satellite into the designated orbit at 20:08 Moscow time (1608 GMT)," he added.The spokesman also said the launch of the Soyuz-U carrier rocket "was the first time for this type of rockets" in this year.The launch carried out by a team from the Russian Space Forces was supervised by Space Forces Commander Oleg Ostapenko.The satellite, Cosmos-2472, is a new member to a Russian network of about 60-70 military reconnaissance satellites.

来源：资阳报