Gravity Lenses: When Galaxies Eat Galaxies

Gravity Lenses: When Galaxies Eat Galaxies

  9:44:00 AM    Science Lover

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Using gravitational "lenses" in space, University of Utah astronomers discovered that the centers of the biggest galaxies are growing denser -- evidence of repeated collisions and mergers by massive galaxies with 100 billion stars.

This image, taken by the Hubble Space Telescope, shows 
a ring of light from a distant galaxy created when a closer 
galaxy in the  foreground – not shown in this processed 
image – acts as a “gravitational lens” to bend the light 
from the more distant galaxy into the ring of light, 
known as an Einstein ring. In a new study, University of 
Utah astronomer Adam Bolton and colleagues measured 
these Einstein rings to determine the mass of 79 lens 
galaxies that are massive elliptical galaxies, the largest 
kind of galaxy with 100 billion stars. The study found 
the centers of these big galaxies are getting denser over 
time, evidence of repeated collisions between massive 
galaxies. (Credit: Joel Brownstein, University of Utah, 
for NASA/ESA and the Sloan Digital Sky Survey)

"We found that during the last 6 billion years, the matter that makes up massive elliptical galaxies is getting more concentrated toward the centers of those galaxies. This is evidence that big galaxies are crashing into other big galaxies to make even bigger galaxies," says astronomer Adam Bolton, principal author of the new study.

"Most recent studies have indicated that these massive galaxies primarily grow by eating lots of smaller galaxies," he adds. "We're suggesting that major collisions between massive galaxies are just as important as those many small snacks."

The new study -- published recently in The Astrophysical Journal -- was conducted by Bolton's team from the Sloan Digital Sky Survey-III using the survey's 2.5-meter optical telescope at Apache Point, N.M., and the Earth-orbiting Hubble Space Telescope.

The telescopes were used to observe and analyze 79 "gravitational lenses," which are galaxies between Earth and more distant galaxies. A lens galaxy's gravity bends light from a more distant galaxy, creating a ring or partial ring of light around the lens galaxy.

The size of the ring was used to determine the mass of each lens galaxy, and the speed of stars was used to calculate the concentration of mass in each lens galaxy.

Bolton conducted the study with three other University of Utah astronomers -- postdoctoral researcher Joel Brownstein, graduate student Yiping Shu and undergraduate Ryan Arneson -- and with these members of the Sloan Digital Sky Survey: Christopher Kochanek, Ohio State University; David Schlegel, Lawrence Berkeley National Laboratory; Daniel Eisenstein, Harvard-Smithsonian Center for Astrophysics; David Wake, Yale University; Natalia Connolly, Hamilton College, Clinton, N.Y.; Claudia Maraston, University of Portsmouth, U.K.; and Benjamin Weaver, New York University.

Big Meals and Snacks for Massive Elliptical Galaxies

The new study deals with the biggest, most massive kind of galaxies, known as massive elliptical galaxies, which each contain about 100 billion stars. Counting unseen "dark matter," they contain the mass of 1 trillion stars like our sun.

"They are the end products of all the collisions and mergers of previous generations of galaxies," perhaps hundreds of collisions," Bolton says.

Despite recent evidence from other studies that massive elliptical galaxies grow by eating much smaller galaxies, Bolton's previous computer simulations showed that collisions between large galaxies are the only galaxy mergers that lead, over time, to increased mass density on the center of massive elliptical galaxies.

When a small galaxy merges with a larger one, the pattern is different. The smaller galaxy is ripped apart by gravity from the larger galaxy. Stars from the smaller galaxy remain near the outskirts -- not the center -- of the larger galaxy.

"But if you have two roughly comparable galaxies and they are on a collision course, each one penetrates more toward the center of the other, so more mass ends up in the center," Bolton says.

Other recent studies indicate stars are spread more widely within galaxies over time, supporting the idea that massive galaxies snack on much smaller ones.

"We're finding galaxies are getting more concentrated in their mass over time even though they are getting less concentrated in the light they emit," Bolton says.

He believes large galaxy collisions explain the growing mass concentration, while galaxies gobbling smaller galaxies explain more starlight away from galactic centers.

"Both processes are important to explain the overall picture," Bolton says. "The way the starlight evolves cannot be explained by the big collisions, so we really need both kinds of collisions, major and minor -- a few big ones and a lot of small ones."

The new study also suggests the collisions between large galaxies are "dry collisions" -- meaning the colliding galaxies lack large amounts of gas because most of the gas already has congealed to form stars -- and that the colliding galaxies hit each other "off axis" or with what Bolton calls "glancing blows" rather than head-on.

Sloan Meets Hubble: How the Study Was Conducted

The University of Utah joined the third phase of the Sloan Digital Sky Survey, known as SDSS-III, in 2008. It involves about 20 research institutions around the world. The project, which continues until 2014, is a major international effort to map the heavens as a way to search for giant planets in other solar systems, study the origin of galaxies and expansion of the universe, and probe the mysterious dark matter and dark energy that make up most of the universe.

Bolton says his new study was "almost gravy" that accompanied an SDSS-III project named BOSS, for Baryon Oscillation Spectrographic Survey. BOSS is measuring the history of the universe's expansion with unprecedented precision. That allows scientists to study the dark energy that accelerates expansion of the universe. The universe is believed to be made of only 4 percent regular matter, 24 percent unseen "dark matter" and 72 percent yet-unexplained dark energy.

During BOSS' study of galaxies, computer analysis of light spectra emitted by galaxies revealed dozens of gravitational lenses, which were discovered because the signatures of two different galaxies are lined up.

Bolton's new study involved 79 gravitational lenses observed by two surveys:

- The Sloan Survey and the Hubble Space Telescope collected images and emitted-light color spectra from relatively nearby, older galaxies -- including 57 gravitational lenses -- 1 billion to 3 billion years back into the cosmic past.

- Another survey identified 22 lenses among more distant, younger galaxies from 4 billion to 6 billion years in the past.

The rings of light around gravitational-lens galaxies are named "Einstein rings" because Albert Einstein predicted the effect, although he wasn't the first to do so.

"The more distant galaxy sends out diverging light rays, but those that pass near the closer galaxy get bent into converging light rays that appear to us as of a ring of light around the closer galaxy," says Bolton.

The greater the amount of matter in a lens galaxy, the bigger the ring. That seems counterintuitive, but the larger mass pulls with enough gravity to make the distant star's light bend so much that lines of light cross as seen by the observer, creating a bigger ring.

If there is more matter concentrated near the center of a galaxy, the faster stars will be seen moving toward or being slung away from the galactic center, Bolton says.

Alternative Theories

Bolton and colleagues acknowledge their observations might be explained by theories other than the idea that galaxies are getting denser in their centers over time:

- Gas that is collapsing to form stars can increase the concentration of mass in a galaxy. Bolton argues the stars in these galaxies are too old for that explanation to work.

- Gravity from the largest massive galaxies strips neighboring "satellite" galaxies of their outskirts, leaving more mass concentrated in the centers of the satellite galaxies. Bolton contends that process is not likely to produce the concentration of mass observed in the new study and explain how the extent of that central mass increases over time.

- The researchers merely detected the boundary in each galaxy between the star-dominated inner regions and the outer regions, which are dominated by unseen dark matter. Under this hypothesis, the appearance of growing galaxy mass concentration over time is due to a coincidence in researchers' measurement method, namely that they are measuring younger galaxies farther from their centers and measuring older galaxies closer to their centers, giving an illusion of growing mass concentration in galactic centers over time. Bolton says this measurement difference is too minor to explain the observed pattern of matter density within the lens galaxies.

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Turning Thoughts into Words A new approach allows more information to be extracted from the brain.

Turning Thoughts into Words A new approach allows more information to be extracted from the brain.

  2:23:00 AM    Science Lover

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Brain-computer interfaces could someday provide a lifeline to "locked-in" patients, who are unable to talk or move but are aware and awake. Many of these patients can communicate by blinking their eyes, but turning blinks into words is time-consuming and exhausting.

Scientists in Utah have now demonstrated a way to determine which of 10 distinct words a person is thinking by recording the electrical activity from the surface of the brain.

Brian interface: The micro electrodes
shown here were used to record brain
signals in order to decode ten words
from a patient’s thoughts.
Credit: Spencer Kellis, University of Utah

The new technique involves training algorithms to recognize specific brain signals picked up by an array of nonpenetrating electrodes placed over the language centers of the brain, says Spencer Kellis, one of the bioengineers who carried out the work at the University of Utah, in Salt Lake City. The approach used is known as electrocorticography (ECoG). The group was able to identify the words "yes," "no," "hot, "cold," "thirsty," "hungry," "hello," "goodbye," "more," and "less" with an accuracy of 48 percent.

"The accuracy definitely needs to be improved," says Kellis. "But we have shown the information is there."

Individual words have been decoded from brain signals in the past using functional magnetic resonance imaging (fMRI), says Eric Leuthardt, director of the Center for Innovation in Neuroscience and Technology at Washington University School of Medicine in St. Louis, Missouri. This is the first time that the feat has been performed using ECoG, a far more practical and portable approach than fMRI, he says.

Working with colleagues Bradley Greger and Paul House, Kellis placed 16 electrodes on the surface of the brain of a patient being treated for epilepsy. The electrodes recorded signals from the facial motor cortex--an area of the brain that controls face muscles during speech--and over the Wernicke's area, part of the cerebral cortex that is linked with language. To train the algorithm, signals were analyzed as the patient was asked to repeatedly utter the 10 words.

ECoG has long been used to locate the source of epileptic seizures in the brain. But electrodes used are typically several hundred microns in size and are positioned centimeters apart, says Kellis. "The brain is doing processing at a much finer spatial scale than is really detectable by these standard clinical electrodes," he says. The Utah team used a new type of microelectrode array developed by PMT Neurosurgical. The electrodes are much smaller--40 microns in size--and are separated by a couple of millimeters.

It's possible to use less invasive techniques, such as electroencephalography (EEG), which places electrodes on the scalp, to enable brain-to-computer communications. Adrian Owen, a senior scientist in the Cognition and Brain Sciences Unit at the University of Cambridge, UK, has shown that EEG signals can be used to allow people in a persistent vegetative state to communicate "yes" and "no."

But with EEG, many of the signals are filtered out by the skull, says Leuthardt. "What's really nice about ECoG is its potential to give us a lot more information," he says.

Decoding 10 words is "very cool," says Owen, but the accuracy will need to improve dramatically, given the patients the technology is aimed at. "I don't think even 60 percent or 70 percent accuracy is going to work for patients who cannot communicate in any other way and where there is no other margin for verification," he says.

Ultimately, the hope is that ECoG will enable much more sophisticated communication. Last year Leuthardt showed that ECoG could be used to decode vowel and consonant sounds--an approach that might eventually be used to reconstruct a much larger number of complete words.

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First Evidence Of Virus In Malignant Prostate Cells: XMRV Retrovirus Linked To More Aggressive Tumors

First Evidence Of Virus In Malignant Prostate Cells: XMRV Retrovirus Linked To More Aggressive Tumors

  9:53:00 PM    Science Lover

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In a finding with potentially major implications for identifying a viral cause of prostate cancer, researchers at the University of Utah and Columbia University medical schools have reported that a type of virus known to cause leukemia and sarcomas in animals has been found for the first time in malignant human prostate cancer cells.

Histopathology of adenocarcinoma of the prostate. (Credit: CDC/Dr. Edwin P. Ewing, Jr.)

If further investigation proves the virus, XMRV (Xenotropic murine leukemia virus-related virus), causes prostate cancer in people, it would open opportunities for developing diagnostic tests, vaccines, and therapies for treating the cancer, according to the study published Sept. 7 online in the Proceedings of the National Academy of Sciences. Prostate cancer is expected to strike nearly 200,000 U.S. males this year, making it the second most common form of cancer, outside of skin cancers, among men.


"We found that XMRV was present in 27 percent of prostate cancers we examined and that it was associated with more aggressive tumors," said Ila R. Singh, M.D., Ph.D., associate professor of pathology at University of Utah and the study's senior author. "We still don't know that this virus causes cancer in people, but that is an important question we're going to investigate."


Singh, also a member of the U of U's Huntsman Cancer Institute and associate medical director at ARUP Laboratories, moved to Utah from Columbia University Medical Center in 2008, where she began this research. She remains an adjunct faculty member at Columbia.


Along with providing the first proof that XMRV is present in malignant cells, the study also confirmed that XMRV is a gammaretrovirus, a simple retrovirus first isolated from prostate cancers in 2006 by researchers at the University of California, San Francisco (UCSF), and the Cleveland Clinic. Gammaretroviruses are known to cause cancer in animals, but have not been shown to do so in humans. The UCSF study did not examine benign (non-malignant) prostate tissues, so could not link XMRV to prostate cancer. They also did not find the virus in malignant cells.


Singh and her fellow researchers examined more than 200 human prostate cancers, and compared them to more than 100 non-cancerous prostate tissues. They found 27 percent of the cancers contained XMRV, compared to only 6 percent of the benign tissues. The viral proteins were found almost exclusively in malignant prostatic cells, suggesting that XMRV infection may be directly linked to the formation of tumors.


Retroviruses insert a DNA copy of their genome into the chromosomes of the cells they infect. Such an insertion sometimes occurs adjacent to a gene that regulates cell growth, disrupting normal cell growth, resulting in more rapid proliferation of such a cell, which eventually develops into a cancer. This mechanism of carcinogenesis is followed by gammaretroviruses in general. Singh is currently examining if a similar mechanism might be involved with XMRV and prostate cancer.


In another important finding of the study, Singh and her colleagues also showed that susceptibility to XMRV infection is not enhanced by a genetic mutation, as was previously reported. If XMRV were caused by the mutation, only the 10 percent of the population who carry the mutated gene would be at risk for infection with virus. But Singh found no connection between XMRV and the mutation, meaning the risk for infection may extend to the population at large.


While the study answers important questions about XMRV, it also raises a number of other questions, such as whether the virus infects women, is sexually transmitted, how prevalent it is in the general population, and whether it causes cancers in tissues other than the prostate.


"We have many questions right now," Singh said, "and we believe this merits further investigation."


Viruses have been shown to cause cancer of the cervix, connective tissues (sarcomas), immune system (lymphoma), and other organs. If the retrovirus is shown to cause prostate cancer, this could have important implications for preventing viral transmission and for developing vaccines to prevent XMRV infection in people.


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Radio Waves 'See' Through Walls

Radio Waves 'See' Through Walls

  1:26:00 PM    Science Lover

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University of Utah engineers showed that a wireless network of radio transmitters can track people moving behind solid walls. The system could help police, firefighters and others nab intruders, and rescue hostages, fire victims and elderly people who fall in their homes. It also might help retail marketing and border control.

On the left, a person walks around inside a square of 28 radio transceivers (mounted on plastic pipes) in the Warnock Engineering Building's atrium at the University of Utah. The person creates "shadows" in the radio waves, resulting in the image displayed on right, in which the person appears as a reddish-orange-yellow blob. University of Utah engineers also showed this method can "see" through walls to make blurry images of people moving behind the walls. They hope the technique will help police, firefighters and other emergency responders apprehend burglars and rescue hostages, fire victims and others. (Credit: Sarang Joshi and Joey Wilson, University of Utah)

"By showing the locations of people within a building during hostage situations, fires or other emergencies, radio tomography can help law enforcement and emergency responders to know where they should focus their attention," Joey Wilson and Neal Patwari wrote in one of two new studies of the method.

Both researchers are in the university's Department of Electrical and Computer Engineering – Patwari as an assistant professor and Wilson as a doctoral student.

Their method uses radio tomographic imaging (RTI), which can "see," locate and track moving people or objects in an area surrounded by inexpensive radio transceivers that send and receive signals. People don't need to wear radio-transmitting ID tags.

One of the studies – which outlines the method and tests it in an indoor atrium and a grassy area with trees – is awaiting publication soon in IEEE Transactions on Mobile Computing, a journal of the Institute of Electrical and Electronics Engineers.

The study involved placing a wireless network of 28 inexpensive radio transceivers – called nodes – around a square-shaped portion of the atrium and a similar part of the lawn. In the atrium, each side of the square was almost 14 feet long and had eight nodes spaced 2 feet apart. On the lawn, the square was about 21 feet on each side and nodes were 3 feet apart. The transceivers were placed on 4-foot-tall stands made of plastic pipe so they would make measurements at human torso level.

Radio signal strengths between all nodes were measured as a person walked in each area. Processed radio signal strength data were displayed on a computer screen, producing a bird's-eye-view, blob-like image of the person.

A second study detailed a test of an improved method that allows "tracking through walls." That study has been placed on arXiv.org, an online archive for preprints of scientific papers. The study details how variations in radio signal strength within a wireless network of 34 nodes allowed tracking of moving people behind a brick wall.

The method was tested around an addition to Patwari's Salt Lake City home. Variations in radio waves were measured as Wilson walked around inside. The system successfully tracked Wilson's location to within 3 feet.

The wireless system used in the experiments was not a Wi-Fi network like those that link home computers, printers and other devices. Patwari says the system is known as a Zigbee network – the kind of network often used by wireless home thermostats and other home or factory automation.

Wilson demonstrated radio tomographic imaging during a mobile communication conference last year, and won the MobiCom 2008 Student Research Demo Competition. The researchers now have a patent pending on the method.

"I have aspirations to commercialize this," says Wilson, who has founded a spinoff company named Xandem Technology LLC in Salt Lake City.

The research was funded by the National Science Foundation.

How It Works

Radio tomographic imaging (RTI) is different and much less expensive than radar, in which radar or radio signals are bounced off targets and the returning echoes or reflections provide the target's location and speed. RTI instead measures "shadows" in radio waves created when they pass through a moving person or object.

RTI measures radio signal strengths on numerous paths as the radio waves pass through a person or other target. In that sense, it is quite similar to medical CT (computerized tomographic) scanning, which uses X-rays to make pictures of the human body, and seismic imaging, in which waves from earthquakes or explosions are used to look for oil, minerals and rock structures underground. In each method, measurements of the radio waves, X-rays or seismic waves are made along many different paths through the target, and those measurements are used to construct a computer image.

In their indoor, outdoor and through-the-wall experiments, Wilson and Patwari obtained radio signal strength measurements from all the transceivers – first when the rectangle was empty and then when a person walked through it. They developed math formulas and used them in a computer program to convert weaker or "attenuated" signals – which occur when someone creates "shadows" by walking through the radio signals – into a blob-like, bird's-eye-view image of that person walking.

RTI has advantages. "RF [radio frequency] signals can travel through obstructions such as walls, trees and smoke, while optical and infrared imaging systems cannot," the engineers wrote. "RF imaging will also work in the dark, where video cameras will fail."

Even "where video cameras could work, privacy concerns may prevent their deployment," Wilson and Patwari wrote. "An RTI system provides current images of the location of people and their movements, but cannot be used to identify a person."

Would bombardment by radio waves pose a hazard? Wilson says the devices "transmit radio waves at powers 500 times less than a typical cell phone."

"And you don't hold it against your head," Patwari adds.

Radio 'Eyes' to the Rescue

Patwari says the system still needs improvements, "but the plan is that when there is a hostage situation, for example, or some kind of event that makes it dangerous for police or firefighters to enter a building, then instead of entering the building first, they would throw dozens of these radios around the building and immediately they would be able to see a computer image showing where people are moving inside the building."

"They are reusable and you can pick them up afterwards," he says.

The technique cannot distinguish good guys from bad guys, but at least will tell emergency personnel where people are located, he adds.

Patwari says radio tomography probably can be improved to detect people in a burning building, but also would "see" moving flames. "You may be able to look at the image and say this is a spreading fire and these are people," says Patwari.

Wilson believes radio imaging also could be used in "a smarter alarm system. … What if you put radios in your home [built into walls or plugged into outlets] and used tomography to locate people in your home. Not only would your security system be triggered by an intrusion, but you could track the intruder online or over your phone."

Radio tomography even might be used to study where people spend time in stores.

"Does a certain marketing display get people to stop or does it not?" Wilson asks. "I'm thinking of retail stores or grocery stores. They spend a lot of money to determine, 'Where should we put the cereal, where should we put the milk, where should we put the bread?' If I can offer that information using radio tomographic imaging, it's a big deal."

Radio image tracking might help some elderly people live at home. "The elderly want to stay in their homes but don't want a camera in their face all day," Wilson says. "With radio tomographic imaging, you could track where they are in their home, did they get up at the right time, did they go to the medicine cabinet, have they not moved today?"

Wilson says a computer monitoring the radio images might detect an elderly person falling down the stairs based on the unusually fast movement.

He says radio tracking also might be a relatively inexpensive method of border security, and would work in dark and fog unlike cameras.

Another possible use: automatic control of lighting, heating and air conditioning in buildings, says Wilson. Radio tracking might even control sound systems so that the best sound is aimed where people are located, as well as noise cancellation systems which could be aimed automatically at noise sources, Patwari says.
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