Biological testing tool, Scan-Drop, tests in fraction of time and cost of industry standard

Biological testing tool, Scan-Drop, tests in fraction of time and cost of industry standard

A single instrument that can conduct a wide range of biological scans in a fraction of the time and cost of industry standard equipment has been developed. It uses considerably less material and ultra-sensitive detection methods to do the same thing. Scan Drop, is a portable instrument no bigger than a shoebox that has the capacity to detect a variety of biological specimen. For that reason it will benefit a wide range of users beyond the medical community, including environmental monitoring and basic scientific research.

North-eastern University professor of pharmaceutical sciences, Tania Konry, has developed a single instrument that can conduct a wide range of biological scans in a fraction of the time and cost of industry standard equipment. That's because it uses considerably less material and ultra-sensitive detection methods to do the same thing.

Currently, researchers face enormous time constraints and financial hurdles from having to run these analyses on a regular basis. Hundreds of dollars and 24 hours are what's required to scan biological materials for important bio-markers that signal diseases such as diabetes or cancer. And suppose you wanted to monitor live cancer cells. For that you'd have to use an entirely different method. It takes just as long but requires a whole other set of expensive top-end instrumentation. Want to look at bacteria instead? Be prepared to wait a few days for it to grow before you can get a meaningful result.

Konry's creation, ScanDrop, is a portable instrument no bigger than a shoebox that has the capacity to detect a variety of biological specimen. For that reason it will benefit a wide range of users beyond the medical community, including environmental monitoring and basic scientific research.

The instrument acts as a miniature science lab, of sorts. It contains a tiny chip, made of polymer or glass, that is connected to equally tiny tubes. An extremely small-volume liquid sample-whether it's water or a biological fluid such as serum-flows in one of those tubes, through the lab-on-a-chip device, and out the other side. While inside, the sample is exposed to a slug of microscopic beads fictionalized to react with the lab test's search parameters. For example, one type of bead could be covered with antibodies that selectively bind to e. coli to test water quality. Other types could detect cancer bio-markers or bind to the tetanus virus to test for immunity.

"It can be any biological agent," Konry said. "We take the same approach."

The beads fluoresce when the specific marker or cell in question has been detected; from there, an analysis by Scan-Drop can provide the concentration levels of that marker or cell.

Because the volumes being tested with Scan Drop are so small, the testing time dwindles to just minutes. This means you could get near-real time measures of a changing sample-be it bacteria levels in a flowing body of water or dynamic insulin levels in the bloodstream of a person with diabetes.

Konry noted that not only are other testing mechanisms prohibitively expensive, but they are also fairly useless in the field-particularly in remote areas-because the instruments are large and require long times for analysis. By comparison, Scan Drop's portability makes it much more functional and efficient in the field.

Her team recently joined forces with a group at the University of California at Berkeley, which developed software that can remotely control Scan Drop's activity from anywhere on the planet.

 This functionality could be particularly useful when the instrument is set up in the field to continuously monitor the environment. The achievement, Konry said, adds yet another level of efficiency to the system. 

Preoperative PET cuts unnecessary lung surgeries in half

Preoperative PET cuts unnecessary lung surgeries in half

PET changed patient management in 50 percent of lung cancer cases, a comprehensive statistical analysis reveals. Few studies have been able to pin down exactly what impact preoperative PET has on clinical decision-making and resulting treatment. Preliminary review of the data from this long-term, observational study was inconclusive, but after a more thorough statistical analysis accounting for selection bias and other confounding factors, the researchers were able to conclude that PET imaging eliminated approximately half of unnecessary surgeries.

New quantitative data suggests that 30 percent of the surgeries performed for non-small cell lung cancer patients in a community-wide clinical study were deemed unnecessary. Additionally, positron emission tomography (PET) was found to reduce unnecessary surgeries by 50 percent, according to research published in the March issue of the Journal of Nuclear Medicine.

PET imaging prior to surgery helps stage a patient's disease by providing functional images of tumors throughout the body, especially areas where cancer has spread, otherwise known as metastasis. Few studies have been able to pin down exactly what impact preoperative PET has on clinical decision-making and resulting treatment. Preliminary review of the data from this long-term, observational study of an entire community of veterans was inconclusive about the utility of PET, but after a more thorough statistical analysis accounting for selection bias and other confounding factors, the researchers were able to conclude that PET imaging eliminated approximately half of unnecessary surgeries.

"It has become standard of care for lung cancer patients to receive preoperative PET imaging," said Steven Zeliadt, PhD, lead author of the study conducted at VA Puget Sound Health Care System and associate professor for the University of Washington in Seattle, Wash. "The prevailing evidence reinforces the general understanding within the medical community that PET is very useful for identifying occult metastasis and that it helps get the right people to surgery while avoiding unnecessary surgeries for those who would not benefit."

For this study, researchers reviewed newly diagnosed non-small lung cancer patients who received preoperative PET to assess the real-life effectiveness of PET as a preventative measure against unnecessarily invasive treatment across a community of patients. A total of 2,977 veterans who underwent PET during disease staging from 1997 to 2009 were included in the study. Of these, 976 patients underwent surgery to respect their lung cancer. During surgery or within 12 months of surgery, 30 percent of these patients were found to have advanced-stage metastatic disease, indicating an unnecessary surgery.

Interestingly, the use of PET increased during the study period from 9% to 91%. Conventional multivariate analyses was followed by instrumental variable analyses to account for unobserved anomalies, such as when patients did not undergo PET when it would have been clinically recommended to do so. This new data has the potential to change policy and recommendations regarding the use of oncologic PET for more accurate tumor staging.

"We will likely build more quality measures around this research so that preoperative PET is more strongly recommended to improve the management of care for these patients," added Zeliadt.

Archaeologists discover earliest complete example of a human with cancer, from 3,000 years ago

Archaeologists discover earliest complete example of a human with cancer, from 3,000 years ago

Archaeologists have found the oldest complete example in the world of a human with metastatic cancer in a 3,000 year-old skeleton. The skeleton of the young adult male was found in a tomb in modern Sudan in 2013 and dates back to 1200BC. Analysis has revealed evidence of metastatic carcinoma, cancer which has spread to other parts of the body from where it started, from a malignant soft-tissue tumour spread across large areas of the body, making it the oldest convincing complete example of metastatic cancer in the archaeological record.

Archaeologists have found the oldest complete example in the world of a human with metastatic cancer in a 3,000 year-old skeleton.

The skeleton of the young adult male was found by a Durham University PhD student in a tomb in modern Sudan in 2013 and dates back to 1200BC.

Analysis has revealed evidence of metastatic carcinoma, cancer which has spread to other parts of the body from where it started, from a malignant soft-tissue tumour spread across large areas of the body, making it the oldest convincing complete example of metastatic cancer in the archaeological record.

The researchers from Durham University and the British Museum say the discovery will help to explore underlying causes of cancer in ancient populations and provide insights into the evolution of cancer in the past. Ancient DNA analysis of skeletons and mummies with evidence of cancer can be used to detect mutations in specific genes that are known to be associated with particular types of cancer.

Even though cancer is one of the world's leading causes of death today, it remains almost absent from the archaeological record compared to other pathological conditions, giving rise to the conclusion that the disease is mainly a product of modern living and increased longevity. These findings suggest that cancer is not only a modern disease but was already present in the Nile Valley in ancient times.

Lead author, Michaela Binder, a PhD student in the Department of Archaeology at Durham University, excavated and examined the skeleton. She said: "Very little is known about the antiquity, epidemiology and evolution of cancer in past human populations apart from some textual references and a small number of skeletons with signs of cancer.

"Insights gained from archaeological human remains like these can really help us to understand the evolution and history of modern diseases.

"Our analysis showed that the shape of the small lesions on the bones can only have been caused by a soft tissue cancer even though the exact origin is impossible to determine through the bones alone."

The skeleton is of an adult male estimated to be between 25-35 years old when he died and was found at the archaeological site of Amara West in northern Sudan, situated on the Nile, 750km downstream of the country's modern capital Khartoum. It was buried extended on his back, within a badly deteriorated painted wooden coffin, and provided with a glazed faience amulet as a grave good.

Previously, there has only been one convincing, and two tentative, examples of metastatic cancer predating the 1st millennium BC reported in human remains. However, because the remains derived from early 20th century excavations, only the skulls were retained, thus making a full re-analysis of each skeleton, to generate differential (possible) diagnoses, impossible.

Co-author, Dr Neal Spencer from the Department of Ancient Egypt and Sudan at the British Museum, said: "From footprints left on wet mud floors, to the healed fractures of many ancient inhabitants, Amara West offers a unique insight into what it was like to live there -- and die -- in Egyptian-ruled Upper Nubia 3200 years ago."

The skeleton was examined by experts at Durham University and the British Museum using radiography and a scanning electron microscope (SEM) which resulted in clear imaging of the lesions on the bones. It showed cancer metastases on the collar bones, shoulder blades, upper arms, vertebrae, ribs, pelvis and thigh bones.

The cause of the cancer can only be speculative but the researchers say it could be as a result of environmental carcinogens such as smoke from wood fires, through genetic factors, or from infectious diseases such as schistosomiasis which is caused by parasites.

They say that an underlying schistosomiasis infection seems a plausible explanation for the cancer in this individual as the disease had plagued inhabitants of Egypt and Nubia since at least 1500BC, and is now recognised as a cause of bladder cancer and breast cancer in men.

Michaela Binder added: "Through taking an evolutionary approach to cancer, information from ancient human remains may prove a vital element in finding ways to address one of the world's major health problems."

The tomb, where the skeleton was found, appears to have been used for high-status individuals from the town, but not the ruling elite, based on the tomb architecture and aspects of funerary ritual.

The tomb's architecture is evidence of a hybrid culture blending Pharaonic elements (burial goods, painted coffins) with Nubian culture (a low mound to mark the tomb).

The well preserved pottery recovered from the tomb provides a date within the 20th Dynasty (1187-1064BC), a period when Egypt ruled Upper Nubia, endured conflicts with Libya and while pharaohs such as Ramses III were being buried in the Valley of the Kings.

Astronomers find solar storms behave like supernovae

 

Researchers have studied the behaviour of the Sun's coronal mass ejections, explaining for the first time the details of how these huge eruptions behave as they fall back onto the Sun's surface. In the process, they have discovered that coronal mass ejections have a surprising twin in the depths of space: the tendrils of gas in the Crab Nebula, which lie 6500 light-years away and are millions of times larger.

Researchers at UCL have studied the behaviour of the Sun's coronal mass ejections, explaining for the first time the details of how these huge eruptions behave as they fall back onto the Sun's surface. In the process, they have discovered that coronal mass ejections have a surprising twin in the depths of space: the tendrils of gas in the Crab Nebula, which lie 6500 light-years away and are millions of times larger.

On 7 June 2011, the biggest ejection of material ever observed erupted from the surface of the Sun. Over the days that followed, the plasma belched out by the Sun made its way out into space. But most of the material propelled up from the Sun's surface quickly fell back towards our star's surface.

For the solar physicists at UCL's Mullard Space Science Laboratory, watching these solar fireworks was a unique opportunity to study how solar plasma behaves.

"We've known for a long time that the Sun has a magnetic field, like the Earth does. But in places it's far too weak for us to measure, unless we have something falling through it. The blobs of plasma that rained down from this beautiful explosion were the gift we'd been waiting for," says David Williams, one of the study's authors.

Since 2010, the NASA Solar Dynamics Observatory (SDO) has been constantly photographing the surface of the Sun. To our eyes, our star seems almost unchanging, with occasional fleeting sunspots the only changes that can be seen without special apparatus. But the SDO's instruments can cut through the dazzling brightness, magnify the detail and see wavelengths of light which are blocked by the Earth's atmosphere. This combination of high-quality imaging and constant monitoring means that scientists can now see the detail of how the Sun's dynamic surface changes over time.

The 7 June 2011 eruption was by some margin the biggest recorded since this constant monitoring began, meaning the huge cascade of matter that fell back into the Sun following the eruption was a unique opportunity to study, on an unusually large scale, the fluid dynamics of these phenomena.

"We noticed that the shape of the plume of plasma was quite particular," says Jack Carlyle, lead author of the study. "As it fell into the Sun, it repeatedly split apart like drops of ink falling through water, with fingers of material branching out. It didn't stick together. It's a great example of an effect where light and heavy fluids mix."

Less dense materials typically float on top of denser ones without mixing together, for example oil sitting on water, or layers of different liqueurs in a cocktail. Change the order by putting the denser fluid on top, however, and the denser one will quickly fall through the less-dense one until their positions are reversed.

 The complex pattern formed by the denser fluid as it repeatedly splits and branches into ever-finer 'fingers' of matter, is caused by a phenomenon known as the Rayleigh-Taylor instability.

The team noticed in SDO's high-resolution images that the falling plasma clearly underwent the Rayleigh-Taylor instability as it returned to the Sun's surface. This is as would be expected -- the solar plasma is denser than the solar atmosphere it is falling through. In space, a similar effect has been observed before, albeit on a much larger scale, in the Crab Nebula.

 The Crab Nebula is the remnant of a supernova which exploded in the 10th century. In the millennium that has followed the explosion, denser matter has started to fall back into the centre of the nebula, exhibiting the same finger-like structures as the team observed in the Sun.

A major study of the Crab Nebula in 1996 found that the Rayleigh-Taylor instability in the Crab Nebula was actually slightly modified. The highly magnetised environment in the nebula changes the proportions of the fingers, making them fatter than they would be otherwise.

The UCL team found that the same effect was going on in the 7 June 2011 coronal mass ejection: even in an area where the Sun's magnetic field was weak, it was modifying the Rayleigh-Taylor effect, changing the shape of the plume of plasma as it fell back into the Sun.This is the most spectacular example of the effect ever observed on the Sun.

Kepler finds a very wobbly planet: Rapid and erratic changes in seasons

Kepler finds a very wobbly planet: Rapid and erratic changes in seasons

Imagine living on a planet with seasons so erratic you would hardly know whether to wear Bermuda shorts or a heavy overcoat. That is the situation on a weird, wobbly world found by NASA's planet-hunting Kepler space telescope.

Imagine living on a planet with seasons so erratic you would hardly know whether to wear Bermuda shorts or a heavy overcoat. That is the situation on a weird, wobbly world found by NASA's planet-hunting Kepler space telescope.

The planet, designated Kepler-413b, precesses, or wobbles, wildly on its spin axis, much like a child's top. The tilt of the planet's spin axis can vary by as much as 30 degrees over 11 years, leading to rapid and erratic changes in seasons. In contrast, Earth's rotational precession is 23.5 degrees over 26,000 years. Researchers are amazed that this far-off planet is precessing on a human timescale.

Kepler 413-b is located 2,300 light-years away in the constellation Cygnus. It circles a close pair of orange and red dwarf stars every 66 days. The planet's orbit around the binary stars appears to wobble, too, because the plane of its orbit is tilted 2.5 degrees with respect to the plane of the star pair's orbit. As seen from Earth, the wobbling orbit moves up and down continuously.

Kepler finds planets by noticing the dimming of a star or stars when a planet transits, or travels in front of them. Normally, planets transit like clockwork. Astronomers using Kepler discovered the wobbling when they found an unusual pattern of transiting for Kepler-413b.

"Looking at the Kepler data over the course of 1,500 days, we saw three transits in the first 180 days -- one transit every 66 days -- then we had 800 days with no transits at all. After that, we saw five more transits in a row," said Veselin Kostov, the principal investigator on the observation. Kostov is affiliated with the Space Telescope Science Institute and Johns Hopkins University in Baltimore, Md. The next transit visible from Earth's point of view is not predicted to occur until 2020. This is because the orbit moves up and down, a result of the wobbling, in such a great degree that it sometimes does not transit the stars as viewed from Earth.

Astronomers are still trying to explain why this planet is out of alignment with its stars. There could be other planetary bodies in the system that tilted the orbit. Or, it could be that a third star nearby that is a visual companion may actually be gravitationally bound to the system and exerting an influence.

"Presumably there are planets out there like this one that we're not seeing because we're in the unfavorable period," said Peter McCullough, a team member with the Space Telescope Science Institute and Johns Hopkins University. "And that's one of the things that Veselin is researching: Is there a silent majority of things that we're not seeing?"

Even with its changing seasons, Kepler-413b is too warm for life as we know it. Because it orbits so close to the stars, its temperatures are too high for liquid water to exist, making it inhabitable. It also is a super Neptune -- a giant gas planet with a mass about 65 times that of Earth -- so there is no surface on which to stand.

Ames is responsible for the Kepler mission concept, ground system development, mission operations and science data analysis. NASA's Jet Propulsion Laboratory in Pasadena, Calif., managed Kepler mission development. Ball Aerospace & Technologies Corp. in Boulder, Colo., developed the Kepler flight system and supports mission operations with the Laboratory for Atmospheric and Space Physics at the University of Colorado in Boulder. The Space Telescope Science Institute in Baltimore archives, hosts and distributes Kepler science data. Kepler is NASA's 10th Discovery mission and was funded by the agency's Science Mission Directorate.

Your memory is no video camera: It edits the past with present experiences

Your memory is a wily time traveller, plucking fragments of the present and inserting them into the past, reports a new study. In terms of accuracy, it's no video camera. Rather, memory rewrites the past with current information, updating your recollections with new experiences to aid survival. Love at first sight, for example, is more likely a trick of your memory than a Hollywood-worthy moment.

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Your memory is a wily time traveller, plucking fragments of the present and inserting them into the past, reports a new North western Medicine® study. In terms of accuracy, it's no video camera.

Rather, the memory rewrites the past with current information, updating your recollections with new experiences.

Love at first sight, for example, is more likely a trick of your memory than a Hollywood-worthy moment."When you think back to when you met your current partner, you may recall this feeling of love and euphoria," said lead author Donna Jo Bridge, a post doctoral fellow in medical social sciences at North western University Feinberg School of Medicine. "But you may be projecting your current feelings back to the original encounter with this person."

This the first study to show specifically how memory is faulty, and how it can insert things from the present into memories of the past when those memories are retrieved. The study shows the exact point in time when that incorrectly recalled information gets implanted into an existing memory.

To help us survive, Bridge said, our memories adapt to an ever-changing environment and help us deal with what's important now.

"Our memory is not like a video camera," Bridge said. "Your memory re frames and edits events to create a story to fit your current world. It's built to be current."

All that editing happens in the hippo campus, the new study found. The hippo campus, in this function, is the memory's equivalent of a film editor and special effects team.

For the experiment, 17 men and women studied 168 object locations on a computer screen with varied backgrounds such as an underwater ocean scene or an aerial view of Midwest farmland. Next, researchers asked participants to try to place the object in the original location but on a new background screen. Participants would always place the objects in an incorrect location.

For the final part of the study, participants were shown the object in three locations on the original screen and asked to choose the correct location. Their choices were: the location they originally saw the object, the location they placed it in part 2 or a brand new location.

"People always chose the location they picked in part 2," Bridge said. "This shows their original memory of the location has changed to reflect the location they recalled on the new background screen. Their memory has updated the information by inserting the new information into the old memory."

Participants took the test in an MRI scanner so scientists could observe their brain activity. Scientists also tracked participants' eye movements, which sometimes were more revealing about the content of their memories -- and if there was conflict in their choices -- than the actual location they ended up choosing.

The notion of a perfect memory is a myth, said Joel Voss, senior author of the paper and an assistant professor of medical social sciences and of neurology at Feinberg.

"Everyone likes to think of memory as this thing that lets us vividly remember our childhoods or what we did last week," Voss said. "But memory is designed to help us make good decisions in the moment and, therefore, memory has to stay up-to-date. The information that is relevant right now can overwrite what was there to begin with."

Bridge noted the study's implications for eyewitness court testimony. "Our memory is built to change, not regurgitate facts, so we are not very reliable witnesses," she said.

A caveat of the research is that it was done in a controlled experimental setting and shows how memories changed within the experiment. "Although this occurred in a laboratory setting, it's reasonable to think the memory behaves like this in the real world," Bridge said.

Nature can, selectively, buffer human-caused global warming, say scientists

Nature can, selectively, buffer human-caused global warming, say scientists

Can naturally occurring processes selectively buffer the full brunt of global warming caused by greenhouse gas emissions resulting from human activities? Yes, says a group of researchers in a new study.

Can naturally occurring processes selectively buffer the full brunt of global warming caused by greenhouse gas emissions resulting from human activities?

Yes, find researchers from the Hebrew University of Jerusalem, Johns Hopkins University in the US and NASA's Goddard Space Flight Centre.

As the globe warms, ocean temperatures rise, leading to increased water vapour escaping into the atmosphere. Water vapour is the most important greenhouse gas, and its impact on climate is amplified in the stratosphere.

In a detailed study, the researchers from the three institutions examined the causes of changes in the temperatures and water vapour in the tropical troposphere layer (TTL). The TTL is a critical region of our atmosphere with characteristics of both the troposphere below and the stratosphere above.

The TTL can have significant influences on both atmospheric chemistry and climate, as its temperature determines how much water vapour can enter the stratosphere. Therefore, understanding any changes in the temperature of the TTL and what might be causing them is an important scientific question of significant societal relevance, say the researchers.

The Israeli and US scientists used measurements from satellite observations and output from chemistry-climate models to understand recent temperature trends in the TTL. Temperature measurements show where significant changes have taken place since 1979.

The satellite observations have shown that warming of the tropical Indian Ocean and tropical Western Pacific Ocean -- with resulting increased precipitation and water vapour there -- causes the opposite effect of cooling in the TTL region above the warming sea surface. Once the TTL cools, less water vapor is present in the TTL and also above in the stratosphere.

Since water vapor is a very strong greenhouse gas, this effect leads to a negative feedback on climate change. That is, the increase in water vapour due to enhanced evaporation from the warming oceans is confined to the near- surface area, while the stratosphere becomes drier. Hence, this effect may actually slightly weaken the more dire forecaster aspects of an increasing warming of our climate, the scientists say.

The researchers are Dr. Chaim Garfinkel of the Fredy and Nadine Herrmann Institute of Earth Sciences at the Hebrew University and formerly of Johns Hopkins University, Dr. D. W. Waugh and Dr. L. Wang of Johns Hopkins, and Dr. L. D. Oman and Dr. M. M. Hurwitz of the Goddard Space Flight Centre. Their findings have been published in the Journal of Geophysical Research: Atmosphere, and the research was also highlighted in Nature Climate Change.

Making color: When two red photons make a blue photon

Making color: When two red photons make a blue photon

Can scientists generate any color of light? The answer is not really, but the invention of the laser in 1960 opened new doors for this endeavor. Scientists have now demonstrated a new semiconductor microstructure that performs frequency conversion. This design is a factor of 1000 smaller than previous devices.

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Color is strange, mainly due to perception. Setting aside complex brain processes, what we see is the result of light absorption, emission, and reflection. Trees appear green because atoms inside the leaves are emitting and/or reflecting green photons. Semiconductor LED brake lights emit single color light when electrical current passes through the devices.

Here's a question: Can scientists generate any color of light? The answer is not really, but the invention of the laser in 1960 opened new doors for this endeavor. An early experiment injected high-power laser light through quartz and out popped a different color. This sparked the field of nonlinear optics and with it, a new method of color generation became possible: frequency conversion.

Not all crystals can perform this trick and only through careful fabrication of certain materials is frequency conversion possible. In a result published in Nature Communications, scientists demonstrate a new microstructure that does what's called second harmonic generation (SHG), where the output light has twice the frequency as the input. This new device is a factor of 1000 smaller than previous frequency converters.

You can't really get something from nothing here. Physics demands that both energy and momentum are conserved in the frequency-doubling process. The energy of light is directly related to its frequency through a fundamental constant, thus this conservation law is automatically satisfied. Two photons of fixed energy pass into the conversion crystal and the output photon has a frequency, thus energy, equal to their sum.

The challenging part is momentum conservation and achieving it takes careful engineering. This difficulty arises because light has an associated direction of travel. Materials bend and delay light, and how it occurs is very material dependent. Even more, different frequencies (colors) are bent and delayed differently by a given material. This is called dispersion and is perhaps most familiar as a rainbow, where the constituent colors of sunlight are separated.

Even with dispersion, some materials have naturally occurring refractive properties that allow momentum-matching, and thus frequency conversion. Until about 20 years ago, these materials were the only option for frequency conversion. In the 1990s, scientists began to tackle the momentum conservation issue using a technique called quasi-phase matching (QPM).

When a light wave enters and moves through a crystal its properties such as velocity are altered depending on its color. In the case of second-harmonic generation, the injection light strongly interacts with the medium and a second color, having twice the frequency, is generated. Due to dispersion, the second light wave will be delayed. In QPM, scientists vary the spacing and orientation between the internal crystal layers to compensate for the delay, such that momentum conservation between the injection and output light is conserved. This method of QPM is successful but can be difficult from a fabrication point-of-view. Moreover, miniaturizing their overall size for integration onto chips is limited. This is because the frequency conversion process depends on the physical length of the interaction medium, thus scaling down these types of crystals will lead to an inherent reduction in efficiency.

Now this team has demonstrated a new, arguably simpler way, to achieve QPM and thus frequency conversion. In the new design, gallium arsenide (GaAs) is fabricated into a micrometer-sized disk 'whispering gallery' cavity. Notably, GaAs has one of the largest second-harmonic frequency conversion constants measured. Previously, scientists have harnessed its extremely nonlinear properties through the layer-varying QPM method, leading to device sizes in the centimeter range. This new device is 1000 times smaller.

In the experiment, light from a tapered optical fiber is injected into the cavity. When light travels in a loop with the proper orientation, as opposed to a linear geometry, QPM, and therefore color conversion is achieved. This team skirts around the miniaturization problem because the light can interact many times with the medium by circulating around the disk, yet the overall size can remain small. Using a cavity also means that since the power builds up in the microdisk, less injection power can be used. Think of the architectural example of a whispering gallery -- wherein sound waves add together such that small input signals (whispers) can be heard. This resonant enhancement also happens for light trapped inside microdisk cavities.

NIST scientist and author Glenn Solomon continues, "Through a combination of microcavity engineering and nonlinear optics, we can create a very small frequency conversion device that could be more easily integrated onto optical chips."

Lead author Paulina Kuo, who is currently doing research at NIST in the Information Technology Laboratory,adds, "I am excited because this method for phase-matching is brand new. It is amazing that the crystal itself can provide the phase-matching to ensure momentum conservation, and it's promising to see efficient optical frequency conversion in a really tiny volume."

In terms of future quantum information applications, the simple harmonic generation process can be considered as parametric down conversion (PDC) in reverse. PDC is a method for generating entangled photon pairs and so this device could provide a new technique for accomplishing this.

Gallium arsenide (GaAs) is a common semiconductor and has added benefits such as transmitting and emitting in the infrared (IR) and near IR light, respectively. IR-colored light has applications that include telecommunications and chemical sensing. Kuo adds, "The presence of an absorbing species affects the cavity resonance conditions and, in turn, the amount of frequency conversion in the microdisk. Thus, this device could be used in novel sensing applications."

Bones of a Previously Unknown Species Prove to be One of the Oldest Seabirds

Bones of a Previously Unknown Species Prove to be One of the Oldest Seabirds

Fossils discovered in Canterbury, New Zealand reveal the nature of one of the world's oldest flying seabirds. Thought to have lived between 60.5 and 61.6 million years ago, the fossil is suggested to have formed shortly after the extinction of dinosaurs and many marine organisms.

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Fossils discovered in Canterbury, New Zealand reveal the nature of one of the world's oldest flying seabirds. Thought to have lived between 60.5 and 61.6 million years ago, the fossil is suggested to have formed shortly after the extinction of dinosaurs and many marine organisms.

Bones of the bird were discovered in 2009 by Leigh Love, an amateur fossil collector. The new species, Australornis lovei has been named as such in honour of Love's discovery.

The bird lacks key morphological features of penguins, though it was found near the fossils of the Waimanu manneringi, the oldest penguin, of which it is also estimated to be the same age.

The research is published in Journal of the Royal Society of New Zealand by Dr Gerald Mayr and Dr Paul Scofield. The authors claim the discovery 'represents one of the most significant records of a marine Paleocene bird from the Southern Hemisphere' and supports the 'emerging view that most modern birds were already diversified in the earliest Paleogene'.

Despite the distinctness of this new species, its derived features are not limited to a single bird group. It does resemble an extinct species from Antarctica, however, highlighting the links between Antarctica and New Zealand in the late Cretaceous period.

Timing Is Everything: How the Brain Links Memories of Sequential Events

Timing Is Everything: How the Brain Links Memories of Sequential Events

Suppose you heard the sound of skidding tires, followed by a car crash. The next time you heard such a skid, you might cringe in fear, expecting a crash to follow -- suggesting that somehow, your brain had linked those two memories so that a fairly innocuous sound provokes dread.

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MIT neuroscientists have now discovered how two neural circuits in the brain work together to control the formation of such time-linked memories. This is a critical ability that helps the brain to determine when it needs to take action to defend against a potential threat, says Susumu Tonegawa, the Picower Professor of Biology and Neuroscience and senior author of a paper describing the findings in the Jan. 23 issue of Science.

"It's important for us to be able to associate things that happen with some temporal gap," says Tonegawa, who is a member of MIT's Picower Institute for Learning and Memory. "For animals it is very useful to know what events they should associate, and what not to associate."

The interaction of these two circuits allows the brain to maintain a balance between becoming too easily paralyzed with fear and being too careless, which could result in being caught off guard by a predator or other threat.

The paper's lead authors are Picower Institute postdocs Takashi Kitamura and Michele Pignatelli.

Linking memories

Memories of events, known as episodic memories, always contain three elements -- what, where, and when. Those memories are created in a brain structure called the hippocampus, which must coordinate each of these three elements.

To form episodic memories, the hippocampus also communicates with the region of the cerebral cortex just outside the hippocampus, known as the entorhinal cortex. The entorhinal cortex, which has several layers, receives sensory information, such as sights and sounds, from sensory processing areas of the brain and sends the information on to the hippocampus.

Previous research has revealed a great deal about how the brain links the place and object components of memory. Certain neurons in the hippocampus, known as place cells, are specialized to fire when an animal is in a specific location, and also when the animal is remembering that location. However, when it comes to associating objects and time, "our understanding has fallen behind," Tonegawa says. "Something is known, but relatively little compared to the object-place mechanism."

The new Science paper builds on a 2011 study from Tonegawa's lab in which he identified a brain circuit necessary for mice to link memories of two events -- a tone and a mild electric shock -- that occur up to 20 seconds apart. This circuit connects layer 3 of the entorhinal cortex to the CA1 region of the hippocampus. When that circuit, known as the monosynaptic circuit, was disrupted, the animals did not learn to fear the tone.

In the new paper, the researchers report the discovery of a previously unknown circuit that suppresses the monosynaptic circuit. This signal originates in a type of excitatory neurons discovered in Tonegawa's lab, dubbed "island cells" because they form circular clusters within layer 2. Those cells stimulate inhibitory neurons in CA1 that suppress the set of excitatory CA1 neurons that are activated by the monosynaptic circuit.

This circuit creates a counterbalance that limits the window of opportunity for two events to become linked. "This pathway might provide a mechanism for preventing constant learning of unimportant temporal associations," says Michael Hasselmo, a professor of psychology at Boston University who was not part of the research team.

The findings are "an important demonstration of the functional role of different populations of neurons in entorhinal cortex that provide input to the hippocampus," Hasselmo adds.

Deciphering circuits

The researchers used optogenetics, a technology that allows specific populations of neurons to be turned on or off with light, to demonstrate the interplay of these two circuits.

In normal mice, the maximum time gap between events that can be linked is about 20 seconds, but the researchers could lengthen that period by either boosting activity of layer 3 cells or suppressing layer 2 island cells. Conversely, they could shorten the window of opportunity by inhibiting layer 3 cells or stimulating input from layer 2 island cells, which both result in turning down CA1 activity.

The researchers hypothesize that prolonged CA1 activity keeps the memory of the tone alive long enough so that it is still present when the shock takes place, allowing the two memories to be linked. They are now investigating whether CA1 neurons remain active throughout the entire gap between events.

The research was funded by the RIKEN Brain Science Institute, the Howard Hughes Medical Institute, and the JPB Foundation.