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শুক্রবার, ১ মার্চ, ২০১৩

Turbulence in a crystal

Mar. 1, 2013 ? When a crystal is hit by an intense ultrashort light pulse, its atomic structure is set in motion. A team of scientists from the Max Planck Institute of Quantum Optics (MPQ), the Technischen Universit?t M?nchen (TUM), the Fritz-Haber Institute in Berlin (FHI) and the Universit?t Kassel can now observe how the configuration of electrons and atoms in titanium dioxide, a semiconductor, changes under the impact of an ultraviolet laser pulse, confirming that even subtle changes in the electron distribution caused by the excitation can have a considerable impact on the whole crystal structure.

Knowledge regarding the interaction between light and solid matter on an atomic scale is still comparable to a map with many blank spots. A number of phenomena are still waiting to be observed or understood. A new, up to date unknown aspect of the interplay between light and matter has now been examined by a team of scientists at the Max Planck Institute of Quantum Optics (MPQ), the Technischen Universit?t M?nchen (TUM), the Fritz-Haber Institute in Berlin (FHI) and the Universit?t Kassel using intensive ultraviolet laser pulses with only a few femtoseconds duration (one femtosecond is a millionth of a billionth of a second).

The physicists illuminated a titanium dioxide crystal (consisting of titanium and oxygen atoms) with an intense ultraviolet laser pulse of less than five femtoseconds duration. The laser pulse excites the valence electrons in the crystal and generates a small number of hot electrons with a temperature of several thousand Kelvin. Valence electrons are electrons that are only weakly bound to the atoms in a crystal that interact strongly with each other and therefore form the bond between the atoms in a crystal. The continuous interplay between the positions of the atomic cores and the valence electrons determines the material characteristics such as electric conductivity, optical properties or the crystal lattice structure.

Following the first, intense laser pulse, the changes in the reflectivity of the crystal on the femtosecond timescale were observed by a second, weak light pulse. This measurement provides the scientists with information on the changes in the crystal induced by the first laser pulse: the intense ultraviolet laser pulse did not only heat up the valence electrons but also changed the electron distribution within the lattice. The electron density was reduced around the oxygen atoms and increased around the titanium atoms. This redistribution of the electrons causes a shift of the equilibrium position of the oxygen atoms relative to the titanium atoms, which leads to an oscillatory motion of the oxygen atoms around the new equilibrium position. In an intuitive picture the oxygen atoms in the crystal potential surface can be compared to a ball in a bowl. In the ground state, the ball is at rest at the center of the bowl. The excitation of the electrons corresponds to a sudden shift of the bowl, and the ball oscillates around its new minimum position.

In their experiment, the scientists also observed a suprising effect: after the excitation with the laser pulse, the electrons cool down to room temperature within about 20 femtoseconds, while the crystal is only heated slightly on these timescales. The cooling of the electrons led to an additional significant change in the valence electron distribution. In consequence, the equilibrium position of the lattice was shifted even further from the initial position of the ground state. Such a dependence of the crystal structure on the electron temperature has long been predicted theoretically. Now it could be observed experimentally for the first time. The results show that even subtle changes in the electron distribuition can have a significant impact on the equilibrium state of a crystal. The understanding of such phenomena can be helpful in the design of new materials.

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The above story is reprinted from materials provided by Max Planck Institute of Quantum Optics. The original article was written by Thorsten Naeser.

Note: Materials may be edited for content and length. For further information, please contact the source cited above.

Journal Reference:

Elisabeth M. Bothschafter, Alexander Paarmann, Eeuwe S. Zijlstra, Nicholas Karpowicz, Martin E. Garcia, Reinhard Kienberger, Ralph Ernstorfer. Ultrafast Evolution of the Excited-State Potential Energy Surface of TiO_{2} Single Crystals Induced by Carrier Cooling. Physical Review Letters, 2013; 110 (6) DOI: 10.1103/PhysRevLett.110.067402

Note: If no author is given, the source is cited instead.

Disclaimer: Views expressed in this article do not necessarily reflect those of ScienceDaily or its staff.

Source: http://feeds.sciencedaily.com/~r/sciencedaily/most_popular/~3/FYNvm5HLh0U/130301051617.htm

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My Dad Was Not Ready to Die

Wolfgang Nehring

Courtesy of Cristina Nehring

Life is fragile, use it roughly. Wrest from it all you can. Love in it what you?ve got. For once it begins to end, the greens in your fridge will rot less quickly than you do.

I know because it?s just happened to my dad.

On Jan. 1, my father announced with some pride that he was the only one in our small family who?d made it through the holidays without getting sick. On Jan. 2, he awoke with a fever. On Jan. 3, he was dead.

By the time the coroner sent his body back to the mortuary two weeks later, it was so severely decomposed that the funeral directors beseeched my mother and me not to see it. We were just beginning to sort through vegetables he had bought to make ?my little girl fresh juice that day. Most of them were still good.

Wolfgang Nehring was a scholar and a gentleman, a stoic and a romantic, a handsome devil who kidnapped the woman he loved out of the home of her boyfriend in 1964 and married her immediately thereafter. He was an impassioned lover of German literature; a powerful hiker, swimmer, and prose stylist; an idealistic and demanding university professor; and?surely to his shock?an ?unparalleled grandfather to his exceptional little grandchild, Eurydice.

When Eurydice contracted acute leukemia at age 1, my dad searched high and low for medical advice and visited her in the hospital every day for seven months until she healed. His own hospital experience was less successful: After being wheeled into the emergency room by his general doctor in response to sudden back pain that left him unable to walk, a high fever, vomiting, and a loss of balance, he was sent home without any treatment and died within four hours.

Had this swiftest of exits occurred 20 years down the line, it might, in fact, have been graceful. But my dad stood at the brink of a new life when he was felled by a 20-hour infection and failed by the medical profession. His body was in the best shape it had been in 20 years?100 percent cancer-free, as the coroner intoned to me on the phone: Every organ was apparently healthy. (It is only, ironically, a coroner who can give you so clean a bill of health: No other doctor can conduct as thorough an examination without putting the patient at high risk.) ?Moreover, his horizons were widening, his imagination deepening, and his spirit filling with a fresh kind of love.

Death, it turns out, does not respect our plans for personal improvement. It does not rank us as human beings or decide who?s deserving of its favors and who isn?t.

?Often it repulses those who flirt with it daily and who long?half or whole-heartedly?for its embrace. Often it rapes those who ignore it or spend years engaging its enemy, life. We must get away from the idea that there is justice. We must get away from the idea that the universe is benevolent?either to the good or to the ?healthy.? The only person to whom the universe is benevolent is the person who squeezes all life into a chestnut in his palm and squeezes its juice?the one who grabs quality regardless of quantity.

In the Italian and English Renaissance, this was a clich?: ?Carpe diem,? they called it, ?Seize the day for tomorrow you shall die.? Princes and poets alike used it to get their heartthrobs to sleep with them more quickly: ?The grave?s a fine and private place, but none, I think, do there, embrace,? coaxed the 17th-century lyricist Andrew Marvell. But the transience of our lives is not just an argument for lovemaking. It is an argument for loving. An argument for loving children. Experiences. Tragedies. Destinies we may not have thought intended for us, but which we can make our glory. My dad, when he died, was still director of graduate studies in UCLA?s German Department, but he had begun to plan a new existence in Berlin or Paris, a life of philosophical writing?the Montaigne chapter of his career. His relationship with my mother was the most tender and gentlemanly I recall seeing it. His relationship to my daughter was a thing of resplendent beauty.

Source: http://feeds.slate.com/click.phdo?i=08408d03e6e12e234c6d67038c954a89

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Senate approves Lew as new Treasury chief

Feb 27 (Reuters) - Former world number one Caroline Wozniacki suffered one of her worst career defeats when she bowed out of the Malaysia Open to 186th-ranked Chinese qualifier Qiang Wang on Wednesday. The Dane, top seed at the event in Kuala Lumpur, cruised through the opening set of her first round clash and had a match point in the second before going down 2-6 7-6 6-1. Qualifier Wang, 21, allowed Wozniacki only one point in the second set tiebreak as she levelled the match and rolled through the decider to claim her biggest careeer win. ...

Source: http://news.yahoo.com/senate-panel-backs-lew-treasury-secretary-013852659--sector.html

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Cell sugar concentrations affect hyaluronan production and cancer growth

Thursday, February 28, 2013

According to a recent University of Eastern Finland (UEF) study, elevated cell sugar concentrations increase the production of hyaluronan which, in turn, promotes cancer growth. Regulating the production of hyaluronan may be a way to prevent the spreading of cancer.

Hyaluronan is a long, linear carbohydrate polymer present in the human body. It forms a coating on the surface of many cells and plays a key role in fetal development and in the maintenance of normal tissue balance.

Under normal circumstances, hyaluronan promotes tissue healing; however, it can also maintain inflammation and promote the growth of cancer cells. Due to its high water retention capacity, hyaluronan is widely used in cosmetics and also in the medical sector, for example in the treatment of osteoarthritis symptoms and in eye surgery. Hyaluronan injected into the human body for treatment purposes is not associated with cancer risk.

Cells produce hyaluronan with the help of three cell membrane enzymes (HAS1, HAS2 and HAS3), and the production process also needs glucose derivatives.

Hyaluronan synthase 1, i.e. the HAS1 enzyme, is the least well known of the hyaluronan-producing enzymes, and yet its role in cancer malignity seems to be greater than previously thought. Published in Journal of Biological Chemistry, the UEF study showed that HAS1 requires a higher sugar concentration for the production of hyaluronan than HAS2 and HAS3. This finding may be significant for fighting cancer, as cancer cells are known to thrive on blood glucose. Increased glucose levels can lead to increased production of hyaluronan which, in turn, promotes cancer growth. Increased hyaluronan levels have also been found in diabetics with increased blood sugar levels. Diabetics are known to have a higher risk for breast cancer.

HAS1 also plays a significant role in inflammation, because growth factors associated with inflammation mediation, e.g., interleukins, can increase its activeness. This finding constituted part of the doctoral study of Lic. Med. Hanna Siiskonen, which was recently examined at the University of Eastern Finland.

By regulating hyaluronan levels, it may be possible to prevent the progression of cancer and other pathologies. The first clinical trials involving enzymes which break down hyaluronan have been able to slow down the growth and movement of cancer cells and to enhance the effectiveness of cancer drugs.

At the UEF Institute of Biomedicine, the research group of Professor Raija Tammi and Professor Markku Tammi has been studying hyaluronan for 25 years already, and the group's research is internationally renowned. The group focuses on cell biological mechanisms which regulate hyaluronan production. Together with its partners, the group has established a link between increased hyaluronan levels and a negative cancer prognosis in many cancer types, such as breast, prostate, colon, uterine, lung and ovarian cancer.

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University of Eastern Finland: http://www.uef.fi

Thanks to University of Eastern Finland for this article.

This press release was posted to serve as a topic for discussion. Please comment below. We try our best to only post press releases that are associated with peer reviewed scientific literature. Critical discussions of the research are appreciated. If you need help finding a link to the original article, please contact us on twitter or via e-mail.

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Source: http://www.labspaces.net/127045/Cell_sugar_concentrations_affect_hyaluronan_production_and_cancer_growth

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T-Mobile USA Reports First Customer Growth Since 2009 But ?Challenges Persist Unchanged? As It Waits For Apple Deal To Kick In

Deutsche Telekom, owner of T-Mobile USA, today reported its Q4 and full-year results, and it looks like it is starting to arrest some of the declines in its North American operations: overall subscribers at T-Mobile USA now stand at 33.4 million -- a rise of 0.6% compared to a year ago, and the first time since 2009 that the number has not declined. The company, however, also noted that "challenges persisted unchanged" in the region as revenues declined by 1.4% to to ?3.8 billion ($5 billion) and service revenues specifically were down by nearly 10% to $4.1 billion, as the carrier sits tight and waits for a marketing deal with Apple to kick in this year.

Source: http://feedproxy.google.com/~r/Techcrunch/~3/Dk-CHN7FiOE/

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Pope pledges 'unconditional obedience' to successor in final meeting with cardinals

MADRID, Feb 27 (Reuters) - Lionel Messi has rarely been accused of failing to deliver in big games, having scored in two European Cup finals, but after subdued performances against AC Milan and Real Madrid, questions are being asked. The four-times World Player of the Year and leading scorer in one of the greatest club teams of all time, was a shadow of his usual self at the San Siro in a Champions League last-16 first leg last week, when Barcelona slumped to a 2-0 defeat. ...

Source: http://news.yahoo.com/pope-pledges-unconditional-obedience-successor-final-meeting-cardinals-102556844.html

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