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Changing human activities coupled with a dynamic environment over the past few centuries have caused fluctuating periods of decline and recovery of corals reefs in the Hawaiian Islands, according to a study sponsored in part by the Institute for Ocean Conservation Science at Stony Brook University. Using the reefs and island societies as a model social-ecological system, a team of scientists reconstructed 700 years of human-environment interactions in two different regions of the Hawaiian archipelago to identify the key factors that contributed to degradation or recovery of coral reefs.

When the Earth's carbon dioxide level increased at a rapid rate during the Triassic-Jurassic period 200 million years ago, nearly half the ocean's marine life became extinct. USC Dornsife geologists contributed to a recent paper that examines materials embedded in ancient rocks to provide clues about the possibility of similar future global events.

The composition of the Earth's core remains a mystery. Scientists know that the liquid outer core consists mainly of iron, but it is believed that small amounts of some other elements are present as well. Oxygen is the most abundant element in the planet, so it is not unreasonable to expect oxygen might be one of the dominant "light elements" in the core. However, new research from a team including Carnegie's Yingwei Fei shows that oxygen does not have a major presence in the outer core. This has major implications for our understanding of the period when the Earth formed through the accretion of dust and clumps of matter. Their work is published Nov. 24 in Nature.

Over the past few years I've had an uncomfortable sense that someone, or something, has been tinkering with my brain, remapping the neural circuitry, reprogramming the memory. My mind isn't going-so far as I can tell-but it's changing. I'm not thinking the way I used to think. I can feel it most strongly when I'm reading. Immersing myself in a book or a lengthy article used to be easy. My mind would get caught up in the narrative or the turns of the argument, and I'd spend hours strolling through long stretches of prose. That's rarely the case anymore. Now my concentration often starts to drift after two or three pages. I get fidgety, lose the thread, begin looking for something else to do. I feel as if I'm always dragging my wayward brain back to the text. The deep reading that used to come naturally has become a struggle. I think I know what's going on. For more than a decade now, I've been spending a lot of time online, searching and surfing and sometimes adding to the great databases of the Internet. The Web has been a godsend to me as a writer. Research that once required days in the stacks or periodical rooms of libraries can now be done in minutes. A few Google searches, some quick clicks on hyperlinks, and I've got the telltale fact or pithy quote I was after. Even when I'm not working, I'm as likely as not to be foraging in the Web's info-thickets'reading and writing e-mails, scanning headlines and blog posts, watching videos and listening to podcasts, or just tripping from link to link to link. (Unlike footnotes, to which they're sometimes likened, hyperlinks don't merely point to related works; they propel you toward them.)

By taking advantage of the properties of periodic systems, physicists have described how to efficiently time-reverse ultrashort electromagnetic pulses. Since a time-reversed pulse evolves as if time runs backwards, time reversal eliminates any distortions or scattering that occurred at earlier times, regardless of the medium the pulse has propagated through.

In the first study of its kind, researchers have linked a natural global climate cycle to periodic increases in warfare. The arrival of El Niño, which every three to seven years boosts temperatures and cuts rainfall, doubles the risk of civil wars across 90 affected tropical countries, and may help account for a fifth of worldwide conflicts during the past half-century, say the authors. The paper, written by an interdisciplinary team at Columbia University's Earth Institute, appears in the current issue of the leading scientific journal Nature.

A NASA-led study has documented an unprecedented depletion of Earth's protective ozone layer above the Arctic last winter and spring caused by an unusually prolonged period of extremely low temperatures in the stratosphere.

The immune system recognizes and neutralizes or destroys toxins and foreign pathogens that have gained access to the body. Autoimmune diseases result when the system attacks the body's own tissues instead. One of the most common examples is multiple sclerosis (MS). MS is a serious condition in which nerve-cell projections, or axons, in the brain and the spinal cord are destroyed as a result of misdirected inflammatory reactions. It is often characterized by an unpredictable course, with periods of remission being interrupted by episodes of relapse.

When atoms combine to form compounds, they must follow certain bonding and valence rules. For this reason, many compounds simply cannot exist. But there are some compounds that, although they follow the bonding and valence rules, still are thought to not exist because they have unstable structures. Scientists call these compounds "impossible compounds." Nevertheless, some of these impossible compounds have actually been fabricated (for example, single sheets of graphene were once considered impossible compounds). In a new study, scientists have synthesized another one of these impossible compounds -- periodic mesoporous hydridosilica -- which can transform into a photoluminescent material at high temperatures.