星空科学探索频道: 十月 2013

2013年10月31日星期四

A first step in learning by imitation, baby brains respond to another's actions

Now researchers from the University of Washington and Temple University have found the first evidence revealing a key aspect of the brain processing that occurs in babies to allow this learning by observation.

The findings, published online Oct. 30 by PLOS ONE, are the first to show that babies' brains showed specific activation patterns when an adult performed a task with different parts of her body. When 14-month-old babies simply watched an adult use her hand to touch a toy, the hand area of the baby's brain lit up. When another group of infants watched an adult touch the toy using only her foot, the foot area of the baby's brain showed more activity.

"Babies are exquisitely careful people-watchers, and they're primed to learn from others," said Andrew Meltzoff, co-author and co-director of the UW Institute for Learning & Brain Sciences. "And now we see that when babies watch someone else, it activates their own brains. This study is a first step in understanding the neuroscience of how babies learn through imitation."

The study took advantage of how the brain is organized. The sensory and motor area of the cortex, the outer portion of the brain known for its creased appearance, is arranged by body part with each area of the body represented in identifiable neural real estate. Prick your finger, stick out your tongue, or kick a ball and distinct areas of the brain light up according to a somatotopic map.

Other studies show that adults show this somatotopic brain activation while watching someone else use different body parts, suggesting that adults understand the actions of others in relation to their own bodies. The researchers wondered whether the same would be true in babies.

The 70 infants in the study wore electroencephalogram, or EEG, caps with embedded sensors that detected brain activity in the regions of the cortex that respond to movement or touch of the feet and hands. Sitting on a parent's lap, each baby watched as an experimenter touched a toy placed on a low table between the baby and the experimenter.

The toy had a clear plastic dome and was mounted on a sturdy base. When the experimenter pressed the dome with her hand or foot, music played and confetti in the dome spun. The experimenter repeated the action -- taking breaks after every four presses -- until the baby lost interest.

"Our findings show that when babies see others produce actions with a particular body part, their brains are activated in a corresponding way," said Joni Saby, lead author and a psychology graduate student at Temple University in Philadelphia. "This mapping may facilitate imitation and could play a role in the baby's ability to then produce the same actions themselves."

One of the basics for babies to learn is how to copy what they see adults do. In other words, they must first know that it is indeed their hand and not their foot, mouth or other body part that is needed.

The new study shows that babies' brains are organized in a somatotopic way that helps crack the interpersonal code. The connection between doing and seeing actions maps hand to hand, foot to foot, all before they can name those body parts through language.

"The reason this is exciting is that it gives insight into a crucial aspect of imitation," said co-author Peter Marshall, an associate psychology professor at Temple University. "To imitate the action of another person, babies first need to register what body part the other person used. Our findings suggest that babies do this in a particular way by mapping the actions of the other person onto their own body."

Meltzoff added, "The neural system of babies directly connects them to other people, which jump-starts imitation and social-emotional connectedness and bonding. Babies look at you and see themselves."

The National Institutes of Health and the National Science Foundation funded the study.

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Incurable brain cancer gene silenced: Gene regulation technology increases survival rates in mice with glioblastoma

Oct. 30, 2013 — Glioblastoma multiforme (GBM), the brain cancer that killed Sen. Edward Kennedy and kills approximately 13,000 Americans a year, is aggressive and incurable. Now a Northwestern University research team is the first to demonstrate delivery of a drug that turns off a critical gene in this complex cancer, increasing survival rates significantly in animals with the deadly disease.

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The novel therapeutic, which is based on nanotechnology, is small and nimble enough to cross the blood-brain barrier and get to where it is needed -- the brain tumor. Designed to target a specific cancer-causing gene in cells, the drug simply flips the switch of the troublesome oncogene to "off," silencing the gene. This knocks out the proteins that keep cancer cells immortal.

In a study of mice, the nontoxic drug was delivered by intravenous injection. In animals with GBM, the survival rate increased nearly 20 percent, and tumor size was reduced three to four fold, as compared to the control group. The results will be published Oct. 30 in Science Translational Medicine.

"This is a beautiful marriage of a new technology with the genes of a terrible disease," said Chad A. Mirkin, a nanomedicine expert and a senior co-author of the study. "Using highly adaptable spherical nucleic acids, we specifically targeted a gene associated with GBM and turned it off in vivo. This proof-of-concept further establishes a broad platform for treating a wide range of diseases, from lung and colon cancers to rheumatoid arthritis and psoriasis."

Mirkin is the George B. Rathmann Professor of Chemistry in the Weinberg College of Arts and Sciences and professor of medicine, chemical and biological engineering, biomedical engineering and materials science and engineering.

Glioblastoma expert Alexander H. Stegh came to Northwestern University in 2009, attracted by the University's reputation for interdisciplinary research, and within weeks was paired up with Mirkin to tackle the difficult problem of developing better treatments for glioblastoma.

Help is critical for patients with GBM: The median survival rate is 14 to 16 months, and approximately 16,000 new cases are reported in the U.S. every year.

In their research partnership, Mirkin had the perfect tool to tackle the deadly cancer: spherical nucleic acids (SNAs), new globular forms of DNA and RNA, which he had invented at Northwestern in 1996, and which are nontoxic to humans. The nucleic acid sequence is designed to match the target gene.

And Stegh had the gene: In 2007, he and colleagues identified the gene Bcl2Like12 as one that is overexpressed in glioblastoma tumors and related to glioblastoma's resistance to conventional therapies.

"My research group is working to uncover the secrets of cancer and, more importantly, how to stop it," said Stegh, a senior co-author of the study. "Glioblastoma is a very challenging cancer, and most chemo-therapeutic drugs fail in the clinic. The beauty of the gene we silenced in this study is that it plays many different roles in therapy resistance. Taking the gene out of the picture should allow conventional therapies to be more effective."

Stegh is an assistant professor in the Ken and Ruth Davee Department of Neurology at the Northwestern University Feinberg School of Medicine and an investigator in the Northwestern Brain Tumor Institute.

The power of gene regulation technology is that a disease with a genetic basis can be attacked and treated if scientists have the right tools. Thanks to the Human Genome Project and genomics research over the last two decades, there is an enormous number of genetic targets; having the right therapeutic agents and delivery materials has been the challenge.

"The RNA interfering-based SNAs are a completely novel approach in thinking about cancer therapy," Stegh said. "One of the problems is that we have large lists of genes that are somehow disregulated in glioblastoma, but we have absolutely no way of targeting all of them using standard pharmacological approaches. That's where we think nanomaterials can play a fundamental role in allowing us to implement the concept of personalized medicine in cancer therapy."

Stegh and Mirkin's drug for GBM is specially designed to target the Bcl2Like12 gene in cancer cells. Key is the nanostructure's spherical shape and nucleic acid density. Normal (linear) nucleic acids cannot get into cells, but these spherical nucleic acids can. Small interfering RNA (siRNA) surrounds a gold nanoparticle like a shell; the nucleic acids are highly oriented, densely packed and form a tiny sphere. (The gold nanoparticle core is only 13 nanometers in diameter.) The RNA's sequence is programmed to silence the disease-causing gene.

"The problems posed by glioblastoma and many other diseases are simply too big for one research group to handle," said Mirkin, who also is the director of Northwestern's International Institute for Nanotechnology. "This work highlights the power of scientists and engineers from different fields coming together to address a difficult medical issue."

Mirkin first developed the nanostructure platform used in this study in 1996 at Northwestern, and the technology now is the basis of powerful commercialized and FDA-cleared medical diagnostic tools. This new development, however, is the first realization that the nanostructures injected into an animal naturally find their target in the brain and can deliver an effective payload of therapeutics.

The next step for the therapeutic will be to test it in clinical trials.

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Earth-like exoplanet in mass and size: While too hot to support life, Kepler 78b is roughly the size of Earth

Now this same team has found that Kepler 78b shares another characteristic with Earth: its mass. By analyzing the movement of its host star, Kepler 78, the scientists determined that the exoplanet is about 1.7 times as massive as Earth. From the same measurements, they calculated that the planet's density is 5.3 grams per cubic centimeter, closely resembling Earth's density (5.5 grams per cubic centimeter).

The findings make Kepler 78b the smallest exoplanet for which the mass and size are known. These new measurements provide strong evidence that Kepler 78b is composed mostly of rock and iron, similar to Earth.

However, that's where the similarities may end: The exoplanet, due to its extreme proximity to its star, is likely blazing at temperatures too high to support life.

"It's Earth-like in the sense that it's about the same size and mass, but of course it's extremely unlike the Earth in that it's at least 2,000 degrees hotter," says team member Josh Winn, an associate professor of physics at MIT and a member of the Kavli Institute for Astrophysics and Space Research. "It's a step along the way of studying truly Earth-like planets."

Winn and his colleagues, including lead author Andrew Howard, of the University of Hawaii, publish their results this week in the journal Nature. The group's results appear in the same issue as a paper published by a separate group in Geneva, reporting similar results -- scientific agreement that Winn says adds confidence to the mass measurement.

Watching for a wobble

Planets with extremely tight orbits offer scientists a wealth of data: For instance, each week Kepler 78b circles its star about 20 times, giving researchers numerous opportunities to observe its behavior.

The team previously determined Kepler 78b's orbit and size by analyzing the light given off by the star as the planet passes in front of it, or transits. The researchers detected a transit each time the star's light dipped, and measured this dimming to determine the planet's size. (The bigger an exoplanet, the more light it blocks.)

Measuring the planet's mass was a somewhat trickier endeavor. Instead of tracking the planet's motion, the researchers tracked the motion of the star itself. Depending on its mass, a planet can exert a gravitational tug on its star. This stellar motion can be detected as a very slight wobble, known as a Doppler shift.

Winn and his colleagues looked to measure Kepler 78's Doppler shift by analyzing observations from the Keck Observatory in Hawaii -- one of the largest telescopes in the world. The team analyzed starlight data taken over a period of eight days. Despite the telescope's strength, the signal from the star was incredibly faint, making a daunting task for the scientists.

"Each of the eight nights along the way, we were agonizing over it, whether it was worth continuing or not," Winn recalls.

Out, damn starspot

In addition to the challenge of picking out such tiny signals, the researchers had to contend with an effect that initially muddled the data: starspots, dark patches on the surface of stars. Graduate student Roberto Sanchis-Ojeda, who has studied the effect of starspots on exoplanet detection, says the troublesome patches can make a star's Doppler shift appear larger, dramatically complicating scientists' calculations of a planet's mass.

Sanchis-Ojeda was able to solve this puzzle by taking into account Kepler 78's rotational period. By tracking the frequency at which certain starspots reappeared, Sanchis-Ojeda determined that the star completes a full rotation every 12.5 days -- considerably longer than the planet's orbital period of 8.5 hours. From these measurements, Sanchis-Ojeda was able to calculate the star's true Doppler shift.

From his calculations, Sanchis-Ojeda found that the star rotates relatively slowly, at 1.5 meters per second -- about the speed of a jog, or a brisk walk.

"The star is moving at the same speed as when we walk to school or go grocery shopping," Sanchis-Ojeda notes. "The difference is that this star is 400 light-years away, so imagine how complicated it is to measure such speeds from so far away."

From the star's Doppler shift, the team determined that Kepler 78b's mass is 1.7 times that of Earth -- a measurement that suggests the planet is made mostly of rock and iron. Such a composition, Winn says, is not surprising, given the planet's extremely close proximity to its star. A less massive planet, such as one made entirely of gas, would not be able to hold together in such a tight orbit.

While its similarities to Earth likely end with Kepler 78b's size and mass, Winn says there is still more to learn about the planet, such as its surface and atmospheric composition -- a goal that the group plans to pursue next.

Co-authors on the paper include researchers from the University of Hawaii, the University of California at Berkeley, the Harvard-Smithsonian Center for Astrophysics, the University of California at Santa Cruz, and Yale University.

This research received support from NASA and the Kepler Participating Scientist Program.

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Lava world baffles astronomers: Planet Kepler-78b 'shouldn't exist'

Oct. 30, 2013 — Kepler-78b is a planet that shouldn't exist. This scorching lava world circles its star every eight and a half hours at a distance of less than one million miles -- one of the tightest known orbits. According to current theories of planet formation, it couldn't have formed so close to its star, nor could it have moved there.

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"This planet is a complete mystery," says astronomer David Latham of the Harvard-Smithsonian Center for Astrophysics (CfA). "We don't know how it formed or how it got to where it is today. What we do know is that it's not going to last forever."

"Kepler-78b is going to end up in the star very soon, astronomically speaking," agrees CfA astronomer Dimitar Sasselov.

Not only is Kepler-78b a mystery world, it is the first known Earth-sized planet with an Earth-like density. Kepler-78b is about 20 percent larger than Earth, with a diameter of 9,200 miles, and weighs almost twice as much. As a result it has a density similar to Earth's, which suggests an Earth-like composition of iron and rock.

The tight orbit of Kepler-78b poses a challenge to theorists. When this planetary system was forming, the young star was larger than it is now. As a result, the current orbit of Kepler-78b would have been inside the swollen star.

"It couldn't have formed in place because you can't form a planet inside a star. It couldn't have formed further out and migrated inward, because it would have migrated all the way into the star. This planet is an enigma," explains Sasselov.

According to Latham, Kepler-78b is a member of a new class of planets recently identified in data from NASA's Kepler spacecraft. These newfound worlds all orbit their stars with periods of less than 12 hours. They're also small, about the size of Earth. Kepler-78b is the first planet in the new class to have its mass measured.

"Kepler-78b is the poster child for this new class of planets," notes Latham.

The team studied Kepler-78b using a newly commissioned, high-precision spectrograph known as HARPS-North, at the Roque de los Muchachos Observatory on La Palma. They coordinated their work with a second, independent team using the HIRES spectrograph at the Keck Observatory. The teams' measurements agreed with each other, increasing their confidence in the result.

Kepler-78b is a doomed world. Gravitational tides will draw it even closer to its star. Eventually it will move so close that the star's gravity will rip the world apart. Theorists predict that Kepler-78b will vanish within three billion years.

Interestingly, our solar system could have held a planet like Kepler-78b. If it had, the planet would have been destroyed long ago leaving no signs for astronomers today.

Kepler-78b orbits a Sun-like G-type star located 400 light-years from Earth in the constellation Cygnus.

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How the universe's violent youth seeded cosmos with iron

New evidence that iron is spread evenly between the galaxies in one of the largest galaxy clusters in the universe supports the theory that the universe underwent a turbulent and violent youth more than 10 billion years ago. That explosive period was responsible for seeding the cosmos with iron and other heavy elements that are critical to life itself.

Researchers from the Kavli Institute for Particle Astrophysics and Cosmology (KIPAC), jointly run by Stanford University and the Department of Energy's SLAC National Accelerator Laboratory, shed light on this important era by analyzing 84 sets of X-ray telescope observations from the Japanese-US Suzaku satellite. Their results appear in the Oct. 31 issue of the journal Nature.

In particular, the researchers looked at iron distribution throughout the Perseus cluster, a large grouping of galaxies about 250 million light-years away.

"We saw that iron is spread out between the galaxies remarkably smoothly," said Norbert Werner, an astrophysicist at KIPAC and lead author of the paper. "That means it had to be present in the intergalactic gas before the Perseus cluster formed."

The even distribution of these elements supports the idea that they were created at least 10 billion to 12 billion years ago. According to the paper, during this time of intense star formation, billions of exploding stars created vast quantities of heavy elements in the alchemical furnaces of their own destruction. This was also the epoch when black holes in the hearts of galaxies were at their most energetic.

"The combined energy of these cosmic phenomena must have been strong enough to expel most of the metals from the galaxies at early times and to enrich and mix the intergalactic gas," said co-author and KIPAC graduate student Ondrej Urban.

To settle the question of whether the heavy elements created by supernovae remain mostly in their home galaxies or are spread out through intergalactic space, the researchers looked through the Perseus cluster in eight different directions. They focused on the hot, 10-million-degree gas that fills the spaces between galaxies and found the spectroscopic signature of iron reaching all the way to the cluster's edges.

The researchers estimate that the amount of iron in the cluster is roughly equivalent to the mass of 50 billion suns.

"We think most of the iron came from a single type of supernovae, called Type Ia supernovae," said former KIPAC member and co-author Aurora Simionescu, who is currently with the Japanese Aerospace Exploration Agency as an International Top Young Fellow.

In a Type Ia supernova, a star explodes and releases all its material to the void. The researchers believe that at least 40 billion Type Ia supernovae must have exploded within a relatively short period on cosmological time scales in order to release that much iron and have the force to drive it out of the galaxies.

The results suggest that the Perseus cluster is probably not unique and that iron -- along with other heavy elements -- is evenly spread throughout all massive galaxy clusters, said Steven Allen, a KIPAC associate professor and head of the research team.

"You are older than you think -- or at least, some of the iron in your blood is older, formed in galaxies millions of light years away and billions of years ago," Simionescu said.

The researchers are now looking for iron in other clusters and eagerly awaiting a mission capable of measuring the concentrations of elements in the hot gas with greater accuracy.

"With measurements like these, the Suzaku satellite is having a profound impact on our understanding of how the largest structures in our universe grow," Allen said. "We're really looking forward to what further data can tell us."

The research was supported by the Japanese Aerospace Exploration Agency and by the US Department of Energy.

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The secret math of plants: Biologists uncover rules that govern leaf design

The UCLA team discovered the mathematical relationships using "allometric analysis," which looks at how the proportions of parts of an organism change with differences in total size. This approach has been used by scientists since Galileo but had never before been applied to the interior of leaves.

Reporting in the October issue of the American Journal of Botany, the biologists focused on how leaf anatomy varies across leaves of different sizes. They examined plant species from around the world, all grown on the UCLA campus.

While it is easy to observe major differences in leaf surface area among species, they said, differences in leaf thickness are less obvious but equally important.

"Once you start rubbing leaves between your fingers, you can feel that some leaves are floppy and thin, while others are rigid and thick," said Grace John, a UCLA doctoral student in ecology and evolutionary biology and lead author of the research. "We started with the simplest questions -- but ones that had never been answered clearly -- such as whether leaves that are thicker or larger in area are constructed of different sizes or types of cells."

The researchers embedded pieces of leaf in plastic and cut cross-sections thinner than a single cell to observe each leaf's microscopic layout. This allowed them to test the underlying relationship between cell and tissue dimensions and leaf size across species.

Leaves are made up of three basic tissues, each containing cells with particular functions: the outer layer, or epidermis; the mesophyll, which contains cells that conduct photosynthesis; and the vascular tissue, whose cells are involved in water and sugar transport. The team found that the thicker the leaf, the larger the size of the cells in all of its tissues -- except in the vascular tissue.

These relationships also applied to the components of the individual cells. Plant cells, unlike animal cells, are surrounded by carbohydrate-based cell walls, and the scientists discovered that the larger cells of thicker leaves are surrounded by thicker cell walls, in a strict proportionality.

The team was surprised by the "extraordinary" strength of the relationships linking cell size, cell-wall thickness and leaf thickness across diverse and distantly related plant species. These relationships can be described by new, simple mathematical equations, effectively allowing scientists to predict the dimension of cells and cell walls based on the thickness of a leaf. In most cases, the relationships the team found were what is known as "isometric."

"This means that if a leaf has a larger cell in one tissue, it has a larger cell in another tissue, in direct proportion, as if you blew up the leaf and all its cells using Photoshop," said Christine Scoffoni, a doctoral student at UCLA and member of the research team.

By contrast, a leaf's area is unrelated to the sizes of the cells inside. This allows plants to produce leaves with a huge range of surface areas without the need for larger cells, which would be inefficient in function, the researchers said.

The team hypothesized that these strong mathematical relationships arise from leaf development -- the process by which leaves form on the branch, growing from a few cells that divide into many, with cells then expanding until the leaf is fully mature. Because light can penetrate only so many layers of cells, leaves cannot vary much in the number of cells arranged vertically. The expansion of individual cells and their cell walls occurs simultaneously and is reflected in the thickness of the whole leaf. On the other hand, the number of cells arranged horizontally in the leaf continues to increase as leaves expand, regardless of the size of the individual cells.

The new ability to predict the internal anatomy of leaves from their thickness can give clues to the function of the leaf, because leaf thickness affects both the overall photosynthetic rate and the lifespan, said Sack.

"A minor difference in thickness tells us more about the layout inside the leaf than a much more dramatic difference in leaf area," John said.

The design of the leaf provides insights into how larger structures can be constructed without losing function or stability.

"Fundamental discoveries like these highlight the elegant solutions evolved by natural systems," Sack said. "Plant anatomy often has been perceived as boring. Quantitative discoveries like these prove how exciting this science can be. We need to start re-establishing skill sets in this type of fundamental science to extract practical lessons from the mysteries of nature.

"There are so many properties of leaves we cannot yet imitate synthetically," he added. "Leaves are providing us with the blueprints for bigger, better things. We just have to look close enough to read them."

The new allometric equations are an important step toward understanding the design of leaves on a cellular basis, John said. And because leaves are so diverse, she said, there is much to learn. In future research, the group will study species that are very closely related in an effort to uncover any evolutionary relationships between leaf design and function.

"What makes the cross-sections especially exciting is the huge variation from one species to the next," John said. "Some have relatively enormous cells in certain tissues, and cell shapes vary from cylindrical to star-shaped. Each species is beautiful in its distinctiveness. All of this variation needs decoding."

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Business Tabs vs Notebooks; Samsung vs Apple

2013/10/30

IHS PC shipments Although notebook PC shipments reached 47.9 million units in Q3, up 6% from Q2 the market was 5% down on last year’s Q3, says IHS.

Q3 is the fifth consecutive quarter of y-o-y decline starting from Q2 2012 more than one year ago.

The market faces its second consecutive year of decline.

‘Mobile PCs continue to be engaged in a losing battle against tablets,’ says IHS.

Apple shipped 14.25 million iPads in Q3 – both mini and 10 inch – representing 29.7% of unit shipments, but a decrease from Apple’s Q2 shipments of 14.62 million and its market share of 33.5%.

Samsung shipped 10.7 million tablets in Q3 for a 22.2% share.

This time last year, Samsung had 14.1% share while Apple had 42.4% share.

‘The surge in sub-$250 alternatives catapulted Android to the leading operating system in tablets in the third quarter of 2012, but left vendors searching for profit in an increasingly competitive market,’ says IHS.

By contrast, Apple actually increased its revenue per iPad unit in Q3 by $3.

Apple recently passed the 170 million mark in terms of cumulative units sold since the launch of the first iPad.

Samsung, its closest competitor, has shipped 54 million units since it arrived in the tablet market in the fourth quarter of 2010.

Asus grew its Nexus 7 tablet sales 87% in Q3, and Lenovo grew its tablet sales 94.6%.

However, adds IHS: ‘Little-known, regional vendors based in China have blanketed the globe with minimally configured, Android-based, 7.x-inch tablets at price points of $100 or less.’

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Go ahead, dunk your cell phone in salt water

Oct. 30, 2013 — Barrier films, used in everything from food and drug packaging to consumer electronics and solar cells, help prevent your food from spoiling, help to preserve medication, and protect your electronics from damage due to exposure to air or a splash of water. Now a group of researchers in Georgia have developed a new way to produce better films using atomic layer deposition.

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These are not the flimsy films of plastic that may seal a package of cookies. High-end barrier films that safeguard your phone's high-tech organic light-emitting diode (OLED) display from every whiff of oxygen or molecule of water vapor require higher performance transparent materials such as metal oxides.

Existing methods for manufacturing these high-performance barriers aren't perfect. Due to the way they're made, they often have small defects, resulting in tiny holes that let in water or oxygen. That's why Samuel Graham and his colleagues at the Georgia Institute of Technology have been exploring how to use atomic layer deposition to produce better barrier films. At the AVS 60th International Symposium and Exhibition, held in Long Beach, Calif. Oct. 27 -- Nov. 1, Graham will discuss some of the latest developments in this effort.

Graham and his colleagues have created new barrier films that can protect electronics in very harsh environments -- when submerged in salt water for months, for example.

"By creating such barrier films, we are able to extend the lifetime and reliability of electronic devices," Graham said. The new coatings can be used for electronics such as implantable biomedical devices, light-emitting diodes (LED) used in solid-state lighting and displays, solar cells, and organic electrochromic windows, which go from opaque to clear when a voltage is applied. Barrier films will play a large role in the development of many future electronic devices made with organic materials, Graham added.

How Atomic Layer Deposition Works

High-performance barrier films are usually made with techniques such as sputter deposition or plasma-enhanced chemical vapor deposition. In these methods, material is either "sprayed" onto a substrate or grown from a plasma, creating a thin layer that becomes the film. Although efficient and common in industry, these techniques often result in defects, requiring multiple coatings to create good barrier films.

With atomic layer deposition, the researchers have precise control down to the molecular level, allowing them to make thin, even films that have minimal defects. In this process, the researchers surround a substrate with a gas containing a particular metal atom like aluminum. The molecules of the gas attach themselves onto the substrate, forming a single layer of atoms. Next, excess gas is removed from the chamber and another gas is introduced that then oxidizes the metal, creating a metal oxide that's impervious to air or water. The process is repeated to reach the desired thickness, which is only about 10 nanometers. In contrast, films made with more conventional techniques are tens to hundreds of times thicker.

Companies are already developing and selling atomic layer deposition technology, Graham says. But for wide-scale commercial use, more work needs to be done to improve the technology, how fast the materials are deposited, and the chemical stability and mechanical reliability of the films.

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2013年10月30日星期三

Power Supplies XP Power launches 200W green power supplies

2013/10/29

XPE0174-CCB200 XP Power has introduced 200W AC-DC power supplies for medical and industrial use called CCB200 series.

Suiting convection cooled applications that require a very high efficiency in an open frame design, the series has a typical efficiency of 94% and a maximum of 95%, with a flat efficiency curve across the entire operating load range above 20%. Compared to typical 200 Watt supplies, the CCB200, when delivering full power, generates 50% less dissipated heat, resulting in significantly lower component temperatures and therefore an increased product lifetime.

The high efficiency has enabled the convection-cooled units to be packaged in an industry standard 76.2 x 127.0 x 36.32 mm (3.0 x 5.0 x 1.43 inches), usually used for forced-cooled power supplies of this rating. No load power consumption is less than 0.5 W.

The series conforms to the ANSI/AAMI ES60601-1 medical 3^rd edition safety standard and has approval for use in body floating (BF) applications where a patient applied part is used without the need for a further isolation stage. The CCB200 also complies with the internationally recognized UL/EN609501-1 safety standard for IT equipment.

Due to the high efficiency the CCB200 can deliver the full 200 Watt continuous output power over an extended temperature range from – 20 to +70 degrees C without any derating, and up to +85 degrees C with derating. The industry norm is typically + 50 degrees C before derating applies.

The technology employed in the CCB200 ensures the ultra high efficiency rating is achieved from 90 VAC input, unlike current products in the market that have lower efficiencies at low line and therefore have to specify derating. The full operating range of the CCB200 series is 80 – 300 VAC, with full power available from 90 – 264 VAC.

A total of 5 models are available providing the popular nominal outputs from + 12 to +48 VDC. A user trim function provides output voltage adjustment of -4 to + 5% of stated nominal in order to accommodate load losses.

Protection features and control signals include power fail signal, remote sense and remote on/off.

The CCB200 is available from approved regional distributors, or direct from XP Power and come with a 3 year warranty

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ST Transistors ON Diodes YAGEO Resistors Vishay resistors Resistors LED part Fast Recovery Diodes Schottky Diodes NEC Transistors Kingbrigt LED Resistor Arrays NXP Diodes HARRIS IC MOTOROLA IC ST Diodes MAXIM IC TOSHIBA Transistors VISHAY IC Other Parts Renesas parts IC ELPIDA IC LED BB IC IC(Integrated Circuits) chip Filter saws Thick Film Resistors NXP Transistors Texas Instruments(TI) IC AVX Resistors Connectors Switching Diodes TDK IC Thin Film Resistors LITTELFUSE Diodes components Bipolar Transistors Switches MURATA IC IR transistor Discrete Semiconductor Transistors
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Analogue / Linear / Mixed Signal ICs ON Semi voltage controllers are AEC-qualified

2013/10/29

ONSPR2688_NCV8876_LRES ON Semiconductor has introduced two AEC-qualified ICs with wide input voltage operational temperature ranges for use in automotive powertrain and in-cabin systems.

Running off a 2V to 44V input voltage, the NCV8876 non-synchronous boost controller with automatic wake up and shutdown functions is designed to supply a minimum output voltage during start-stop conditions in order to counteract any sag in the vehicle’s battery voltage.

The NCV8876 is enabled when the supply voltage drops below 7.2V, then boost operation is initiated once this voltage goes under 6.8V, with the IC driving an external N-channel MOSFET.

A quiescent current of just 11µA is drawn when the device is in sleep mode so that power consumption is minimised.

The NCV896530 2.1MHz switching frequency dual channel step-down DC-DC converter is targeted at the sophisticated driver assistance systems now being incorporated into modern vehicles.

Both of its channels are externally adjustable (covering 0.9V to 3.3V) and can source currents up to 1600mA.

The NCV8876 and NCV896530 both support a junction temperature range of−40 °C to 150 °C.

The NCV8876 is offered in an SOIC-8 package and the NCV896530 is enclosed in a DFN-10 package.

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