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感觉一周过得好快~~~
大学四年都过得好快啊~~ 上周毕业了，忧桑~~
一周没有学习，这周要疯狂的补作业了！
周一的科技来了 一共五篇文章 Time1，Time2，Time3各为一篇，Time4,Time5为一篇，obstacle为一篇，是关于基因的~~
上周很多人都觉得内容有点多了~~ 这次减少了一些
大家有什么意见都要提出来啊·~~
Ready Go ！！！新的一个月，新的一星期 大家加油！
Part I：Speed
【Time 1】
[Title]No link found between vaccines and nerve-damaging condition Recently immunized people are not more apt to develop Guillain-Barre syndrome
Shortly after getting a vaccination, people are no more likely to develop a dangerous nerve-damaging condition called Guillain-Barré syndrome, or GBS, than they are at other times, a new analysis finds.
Roger Baxter of Kaiser Permanente Northern California in Oakland, and his colleagues reviewed medical records from 1994 to 2006 of more than 3 million Kaiser members and found 415 diagnoses of GBS. Only 25 of these people had received any vaccine in the six weeks prior to being diagnosed with the condition. None were children. Analyses showed that people were no more likely to develop GBS during those six weeks than they were 1.5 to 9 months following a vaccination, the researchers report in the July 15 Clinical Infectious Diseases.
An earlier study had found an association between receiving the 1976 swine flu vaccine and increased GBS risk, but nearly all studies since then have failed to find a GBS link to flu shots or other vaccinations.
Nearly 7 million flu shots were dispensed to the Kaiser members during the study period. GBS showed up in 18 of these people in the six weeks after getting a flu shot. But 13 of them had a respiratory or gastrointestinal illness at the time, a known risk factor for GBS. (209) http://www.sciencenews.org/view/generic/id/351252/description/News_in_Brief_No_link_found_between_vaccines_and_nerve-damaging_condition
【Time 2】 [Title]Mystery Meteorite ——The case for (and against) a rock from Mercury
There are rocks from the moon, rocks from Mars — and now, just maybe, a rock from Mercury. In early 2012, a nomad in the western Sahara spotted some green stones scattered on the sand. Knowing that the empty desert was a good place to find rocks from space, and that meteorite dealers would pay good money for them, he picked up about three dozen that looked related. By spring all 345 grams of them were for sale in Erfoud, Morocco. Stefan Ralew, a meteorite dealer from Germany who was cruising the markets, spotted the stones and asked about them. The seller said he thought they were from a Martian meteorite. But Ralew argued that they couldn’t be from a meteorite of any type because of their bizarre, lustrous, emerald color.
Thus began a scientific detective story to unravel the mystery of NWA (for North West Africa) 7325. And while the story isn’t finished yet, one thing is clear: The main character is a very interesting something. It may be the first meteorite ever to hail from the planet closest to the sun. To have any meteorite formally classified, a dealer must donate 20 grams or 20 percent of the sample to a scientific institution. Ralew had worked before with Anthony Irving, a meteorite expert at the University of Washington in Seattle. So Ralew shipped some stones to Irving, who got to work studying their mineralogy and sharing samples with scientists for other tests.
NWA 7325 has several curious characteristics. It contains lots of magnesium, which most meteorites don’t have, and almost no iron, which most meteorites do. Its pale hue — different from the dark gray or black of many meteorites — suggests it came from the outer portion of a celestial body that separated into layers the way planets do, with a dense, hot core surrounded by a much lighter crust.
Likely candidates would be rocky planets Mercury, Venus or Mars. Scientists rule Venus out because its thick atmosphere burns up any incoming (or outgoing) rocks. Mars is also out of the running. Researchers know of 67 meteorites from Mars, but NWA 7325’s ratio of oxygen isotopes, each with varying numbers of neutrons in its atomic nucleus, is nothing like the oxygen ratios from known Martian meteorites. “We’re dealing with a place that we didn’t know about before,” says Irving. “It’s not any of the usual suspects.” (396) http://www.sciencenews.org/view/feature/id/350972/description/Mystery_Meteorite
【Time 3】 [Title]Cancer Is a Result of a Default Cellular 'Safe Mode,' Physicist Proposes
With death rates from cancer have remained largely unchanged over the past 60 years, a physicist is trying to shed more light on the disease with a very different theory of its origin that traces cancer back to the dawn of multicellularity more than a billion years ago.
In this month's special issue of Physics World devoted to the "physics of cancer," Paul Davies explains his radical new theory. Davies was brought in to lead the centre in 2009 having almost no experience in cancer research whatsoever. With a background in theoretical physics and cosmology, he was employed to bring fresh, unbiased eyes to the underlying principles of the disease.
He has since raised questions that are rarely asked by oncologists: thinking about why cancer exists at all and what place it holds in the grand story of life on Earth.
His new theory, drawn together with Charles Lineweaver of the Australian National University, suggests that cancer is a throwback to an ancient genetic "sub-routine" where the mechanisms that usually instruct cells when to multiply and die malfunctions, thus forcing the cells to revert back to a default option that was programmed into their ancestors long ago.
"To use a computer analogy, cancer is like Windows defaulting to 'safe mode' after suffering an insult of some sort," Davies writes. The result of this malfunction is the start of a cascade of events that we identify as cancer -- a runaway proliferation of cells that form a tumour, which eventually becomes mobile itself, spreading to other parts of the body and invading and colonizing.
Orthodox explanations suppose that cancer results from an accumulation of random genetic mutations, with the cancer starting from scratch each time it manifests; however, Davies and Lineweaver believe it is caused by a set of genes that have been passed on from our very early ancestors and are "switched on" in the very early stages of an organism's life as cells differentiate into specialist forms.
The pair suggests that the genes that are involved in the early development of the embryo -- and that are silenced, or switched off, thereafter -- become inappropriately reactivated in the adult as a result of some sort of trigger or damage, such as chemicals, radiation or inflammation. "Very roughly, the earlier the embryonic stage, the more basic and ancient will be the genes guiding development, and the more carefully conserved and widely distributed they will be among species," Davies writes.
Several research teams around the world are currently providing experimental evidence that shows the similarities between the expression of genes in a tumour and an embryo, adding weight to Davies and Lineweaver's theory.
Davies makes it clear that radical new thinking is needed; however, just like ageing, he states that cancer cannot generally be cured but can be mitigated, which we can only do when we better understand the disease, and its place in the "great sweep of evolutionary history." (441) http://www.sciencedaily.com/releases/2013/06/130630225413.htm
【Time 4】 [Title]The Arctic was once warmer, covered by trees
Pliocene epoch featured greenhouse gas levels similar to today's but with higher average temperatures The Arctic wasn’t always frozen tundra. About 3.6 million years ago, the far north was blanketed in boreal forests, and summers were 8 degrees Celsius warmer than they are today, geologists report May 9 in Science.
Researchers pieced together that picture from sediments buried beneath Lake El’gygytgyn, about 100 kilometers north of the Arctic Circle in northeastern Russia. The sediments preserve the most complete history of Arctic climate on land over the last 3.6 million years.
“It’s an unprecedented record,” says study coauthor Julie Brigham-Grette, a geologist at the University of Massachusetts Amherst. “It gives us a way of envisioning what the future may hold.”
The sediments preserve the end of the Pliocene epoch, which lasted from 5.3 million to 2.6 million years ago. The Pliocene was the last time the atmospheric carbon dioxide concentration was roughly 400 parts per million — a benchmark that Earth may soon reach. Because the continents were in about the same locations as they are today, events during the Pliocene may be the best analog for what could happen in the future, says geologist Gifford Miller of the University of Colorado Boulder.
Previous geologic evidence had indicated the Pliocene Arctic was warm, but these terrestrial records are spotty, providing only isolated snapshots of time, Brigham-Grette says. Lake El’gygytgyn, by contrast, provides exceptionally well-preserved sediments over a long time frame because the region is too dry for large glaciers to grow and then erode away the record, she says. The lake formed after a meteorite struck about 3.6 million years ago, creating an impact crater.
To get a more comprehensive look at Arctic climate, Brigham-Grette and colleagues drilled a 318-meter-long core from the lake’s bottom. From 3.6 million to 3.4 million years ago, average summer temperatures were about 15°, the team determined through analyses of the sediments’ chemistry and trapped pollen. The region also received 600 millimeters of precipitation each year, making it three times as wet as today. (323)
【Time 5】 From 3.26 million to 2.2 million years ago, temperatures gradually cooled in a series of steps that coincided with the beginnings of a glacial period. Forests gave way to shrubby environments, and the Arctic became more arid. Despite the cooling, Arctic summers generally stayed 3 to 6 degrees warmer than they are today, until about 2.2 million years ago. Even during periods when changes in Earth’s orbit should have made the Arctic cold, warm summers persisted. “We didn’t expect it to be so consistently warm,” Brigham-Grette says.
These findings hint that the switch to a glacial period may be more complicated than scientists realized. Comparisons with other climate records from the oceans and the tropics may help researchers identify the mechanisms that drove the Earth’s stepped transition from warm to cool, Brigham-Grette says.
The past’s high temperatures also highlight another quandary, says Ashley Ballantyne, a climate scientist at the University of Montana in Missoula. Climate simulations have a hard time replicating the Arctic’s warm Pliocene temperatures. The missing puzzle piece may be sea ice, he says.
Lacking a complete record of sea ice, researchers have assumed that the Pliocene Arctic had no summer sea ice and small amounts of sea ice in winter. In a study accepted for publication in Palaeogeography, Palaeoclimatology, Palaeoecology, Ballantyne, Miller and others demonstrate that without winter sea ice — which normally prevents heat in the ocean from escaping to the atmosphere — simulations can achieve the extremely warm Arctic temperatures.
That sea ice might have been completely absent from the Arctic in the Pliocene is “a bit alarming,” Ballantyne says. If that were to happen in the future, he says, “it doesn’t bode well for animals that coevolved with sea ice.” (284) http://www.sciencenews.org/view/generic/id/350292/description/The_Arctic_was_once_warmer_covered_by_trees
Part II： Obstacle
【Time 6】
[Title]Gene Deletion Affects Early Language and Brain White Matter
chromosomal deletion is associated with changes in the brain's white matter and delayed language acquisition in youngsters from Southeast Asia or with ancestral connections to the region, said an international consortium led by researchers at Baylor College of Medicine. However, many such children who can be described as late-talkers may overcome early speech and language difficulties as they grow.
The finding involved both cutting edge technology and two physicians with an eye for unusual clinical findings. Dr. Seema R. Lalani, a physician-scientist at BCM and Dr. Jill V. Hunter, professor of radiology at BCM and Texas Children's Hospital, worked together to identify this genetic change responsible for expressive language delay and brain changes in children, predominantly from Southeast Asia.
Laani, assistant professor of molecular and human genetics at BCM, is a clinical geneticist and also signs out diagnostic studies called chromosomal microarray analysis, a gene chip that helps identify abnormalities in specific genes and chromosomes, as part of her work at BCM's Medical Genetics Laboratory.
"I got intrigued when I kept seeing this small (genomic) change in children from a large sample of more than 15,000 children referred for chromosomal microarray analysis at Baylor College of Medicine. These children were predominantly Burmese refugees or of Vietnamese ancestry living in the United States. It started with two children whom I evaluated at Texas Children's Hospital and soon realized that there was a pattern of early language delay and brain imaging abnormalities in these individuals carrying this deletion from this part of the world. Within a period of two to three years, we found 13 more families with similar problems, having the same genetic change. There were some children who obviously were more affected than the others and had cognitive and neurological problems, but many of them were identified as late-talkers who had better non-verbal skills compared to verbal performance," said Lalani. Hunter, helped in determining the specific pattern of white matter abnormalities in the MRI (magnetic resonance imaging) scans in children and their parents carrying this deletion. Most of the children either came from Southeast Asia or were the offspring of people from that area. (White matter is the paler material in the brain that consists of nerve fibers covered with myelin sheaths.)
Now, in a report that appears online in the American Journal of Human Genetics, Lalani, Hunter and an international group of collaborators identify a genomic deletion on chromosome 2 that is associated with bright white spots that show up in an MRI in the white matter of the brain . The chromosomal deletion removes a portion of a gene known as TM4SF20 that encodes a protein that spans the cellular membrane. They do not know yet what the function of the protein is. They found this genetic change in children from 15 unrelated families mainly from Southeast Asia. "This deletion could be responsible for early childhood language delay in a large number of children from this part of the world," says Lalani.
She credits Dr. Wojciech Wiszniewski, an assistant professor of molecular and human genetics at BCM with doing much of the work. Wiszniewski has an interest in genomic disorders and is working under the mentorship of Dr. James R. Lupski, vice chair of the department of molecular and human genetics.
Lupski said, "Professor Lalani has made a stunning discovery in that she provides evidence that population-specific intragenic CNV (copy number variation -- a deletion or duplication of the chromosome) can contribute to genetic susceptibility of even common complex disease such as speech delay in children."
"In a way, this is a good news story," said Hunter. There is evidence from family studies that some of these children may do quite well in the future, said Lalani.
Lalani elaborates. "This is a genetic change that is present in 2 percent of Vietnamese Kinh population (an ethnic group that makes up 90 percent of the population in that country)," she said. "In the 15 families we have identified, all children have early language delay. Some are diagnosed with autism spectrum disorder, and if you do a brain MRI study, you find white matter changes in about 70 percent of them. We have found this change in children who are Vietnamese, Burmese, Thai, Indonesian, Filipino and and Micronesian. It is very likely that children from other Southeast Asian countries within this geographical distribution also carry this genetic change."
Because these are all within a geographic location, she suspects that there is an ancient founder effect, meaning that at some point in the distant past, the gene deletion occurred spontaneously in an individual, who then passed it on to his or her children and to succeeding generations.
"It is important to follow these children longitudinally to see how these late-talkers develop as they grow," said Lalani. "We have also seen this deletion in children whose parents clearly were late-talkers themselves, but overcame the earlier problems to become doctors and professionals. The variability within the deletion carriers is fascinating and brings into question genetic and environmental modifiers that contribute to the extent of disease in these children.
Language delays mean that they may speak only two or three words at age 2, in comparison to other children who would generally have between 75-100 word vocabulary by this age. While there is evidence that children with this deletion may catch up, it is unclear if they continue to have better non-verbal skills than verbal skills. It is also unclear how the specific brain changes correlate with communication disorders in these children.
In fact, when doctors check the parents of these children, they often find similar white matter changes in the parent carrying the deletion. "Young parents in their 30s should not have age-related white matter changes in the brain and these changes should definitely not be present in healthy children," said Lalani. Hunter said they are not sure how the gene variation relates to the changes in brain white matter and how all of these result in delay in language. (998) http://www.sciencedaily.com/releases/2013/06/130627125158.htm
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