Noteworthy Research |

23May 2013

Researchers Turn a Smartphone into a Biosensor

University of Illinois researchers developed a cradle and app for the iPhone to make a handheld biosensor that uses the phone’s own camera and processing power to detect any kind of biological molecules or cells. | Photo by Brian T. Cunningham

University of Illinois at Urbana-Champaign researchers have developed a cradle and app for the iPhone that uses the phone’s built-in camera and processing power as a biosensor to detect toxins, proteins, bacteria, viruses and other molecules.

Having such sensitive biosensing capabilities in the field could enable on-the-spot tracking of groundwater contamination, combine the phone’s GPS data with biosensing data to map the spread of pathogens, or provide immediate and inexpensive medical diagnostic tests in field clinics or contaminant checks in the food processing and distribution chain.

“We’re interested in biodetection that needs to be performed outside of the laboratory,” said team leader Brian Cunningham, a professor of electrical and computer engineering and of bioengineering at the U. of I. “Smartphones are making a big impact on our society – the way we get our information, the way we communicate. And they have really powerful computing capability and imaging. A lot of medical conditions might be monitored very inexpensively and non-invasively using mobile platforms like phones. They can detect molecular things, like pathogens, disease biomarkers or DNA, things that are currently only done in big diagnostic labs with lots of expense and large volumes of blood.”

The wedge-shaped cradle contains a series of optical components – lenses and filters – found in much larger and more expensive laboratory devices. The cradle holds the phone’s camera in alignment with the optical components.

At the heart of the biosensor is a photonic crystal. A photonic crystal is like a mirror that only reflects one wavelength of light while the rest of the spectrum passes through. When anything biological attaches to the photonic crystal – such as protein, cells, pathogens or DNA – the reflected color will shift from a shorter wavelength to a longer wavelength.

For the handheld iPhone biosensor, a normal microscope slide is coated with the photonic material. The slide is primed to react to a specific target molecule. The photonic crystal slide is inserted into a slot on the cradle and the spectrum measured. Its reflecting wavelength shows up as a black gap in the spectrum. After exposure to the test sample, the spectrum is re-measured. The degree of shift in the reflected wavelength tells the app how much of the target molecule is in the sample.

Video of the App in Action:

The entire test takes only a few minutes; the app walks the user through the process step by step. Although the cradle holds only about $200 of optical components, it performs as accurately as a large $50,000 spectrophotometer in the laboratory. So now, the device is not only portable, but also affordable for fieldwork in developing nations.

In a paper published in the journal Lab on a Chip (citation below), the team demonstrated sensing of an immune system protein, but the slide could be primed for any type of biological molecule or cell type. The researchers are working to improve the manufacturing process for the iPhone cradle and are working on a cradle for Android phones as well. They hope to begin making the cradles available next year.

Cunningham’s group is now collaborating with other groups across campus at the U. of I. to explore applications for the iPhone biosensor. The group recently received a grant from the National Science Foundation to expand the range of biological experiments that can be performed with the phone, in collaboration with Steven Lumetta, a professor of electrical and computer engineering and of computer science at the U. of I. They are also are also working with food science and human nutrition professor Juan Andrade to develop a fast biosensor test for iron deficiency and vitamin A deficiency in expectant mothers and children.

In addition, Cunningham’s team is working on biosensing tests that could be performed in the field to detect toxins in harvested corn and soybeans, and to detect pathogens in food and water.

“It’s our goal to expand the range of biological experiments that can be performed with a phone and its camera being used as a spectrometer,” Cunningham said. “In our first paper, we showed the ability to use a photonic crystal biosensor, but in our NSF grant, we’re creating a multi-mode biosensor. We’ll use the phone and one cradle to perform four of the most widely used biosensing assays that are available.”

Source: University of Illinois at Urbana-Champaign

Reference:

Gallegos, D., Long, K., Yu, H., Clark, P., Lin, Y., George, S., Nath, P., & Cunningham, B. (2013). Label-free biodetection using a smartphone Lab on a Chip, 13 (11) DOI: 10.1039/C3LC40991K

09May 2013

Study Finds Brain System for Emotional Self-Control

Jason Carr ⋅ 3 Comments

Different brain areas are activated when we choose to suppress an emotion, compared to when we are instructed to inhibit an emotion, according a new study from the UCL Institute of Cognitive Neuroscience and Ghent University.

In this study, published in Brain Structure and Function (citation below), the researchers scanned the brains of healthy participants and found that key brain systems were activated when choosing for oneself to suppress an emotion. They had previously linked this brain area to deciding to inhibit movement.

“This result shows that emotional self-control involves a quite different brain system from simply being told how to respond emotionally,” said lead author Dr. Simone Kuhn (Ghent University).

In most previous studies, participants were instructed to feel or inhibit an emotional response. However, in everyday life we are rarely told to suppress our emotions, and usually have to decide ourselves whether to feel or control our emotions.

In this new study the researchers showed fifteen healthy women unpleasant or frightening pictures. The participants were given a choice to feel the emotion elicited by the image, or alternatively to inhibit the emotion, by distancing themselves through an act of self-control.

The researchers used functional magnetic resonance imaging (fMRI) to scan the brains of the participants. They compared this brain activity to another experiment where the participants were instructed to feel or inhibit their emotions, rather than choose for themselves.

Different parts of the brain were activated in the two situations. When participants decided for themselves to inhibit negative emotions, the scientists found activation in the dorso-medial prefrontal area of the brain. They had previously linked this brain area to deciding to inhibit movement.

In contrast, when participants were instructed by the experimenter to inhibit the emotion, a second, more lateral area was activated.

“We think controlling one’s emotions and controlling one’s behaviour involve overlapping mechanisms,” said Dr. Kuhn.

“We should distinguish between voluntary and instructed control of emotions, in the same way as we can distinguish between making up our own mind about what do, versus following instructions.”

Regulating emotions is part of our daily life, and is important for our mental health. For example, many people have to conquer fear of speaking in public, while some professionals such as health-care workers and firemen have to maintain an emotional distance from unpleasant or distressing scenes that occur in their jobs.

Professor Patrick Haggard (UCL Institute of Cognitive Neuroscience) co-author of the paper said the brain mechanism identified in this study could be a potential target for therapies.

“The ability to manage one’s own emotions is affected in many mental health conditions, so identifying this mechanism opens interesting possibilities for future research.

“Most studies of emotion processing in the brain simply assume that people passively receive emotional stimuli, and automatically feel the corresponding emotion. In contrast, the area we have identified may contribute to some individuals’ ability to rise above particular emotional situations.

“This kind of self-control mechanism may have positive aspects, for example making people less vulnerable to excessive emotion. But altered function of this brain area could also potentially lead to difficulties in responding appropriately to emotional situations.”

Source: University College London

Reference:

Kühn, S., Haggard, P., & Brass, M. (2013). Differences between endogenous and exogenous emotion inhibition in the human brain Brain Structure and Function DOI: 10.1007/s00429-013-0556-0

01May 2013

Human Brain vs. Supercomputer

Jason Carr ⋅ 3 Comments

The Blue Gene/Q Sequoia. (Image via IBM)

Last November, IBM revealed that its lightning speed, Blue Gene/Q Sequoia supercomputer achieved a record simulation of more than 530 billion neurons. The Blue Gene/ Q Sequoia can perform over 16 quadrillion calculations per second, ranking as the second-fastest supercomputer in the world. (The number one spot is held by Cray’s Titan, built by the Oak Ridge Laboratory in Tennessee.)

So the question arises…

Is the human brain, in fact, smarter than a supercomputer with these capabilities? Kwabena Boahen, Ph.D. professor at Stanford University and director of the Brains in Silicon Research Laboratory says it is.

“The brain is actually able to do more calculations per second than even the fastest supercomputer,” said Boahen.

Of course, the brain makes a single calculation much slower than a supercomputer, but the brain can actually execute more calculations per second because it is “massively parallel.” What this means is that networks of neurons actually work together to simultaneously solve many problems at once. However, in computing platforms, each step must be completed before the next step begins.

Creating the brain simulator

Boahen and researchers at his laboratory have worked to create a replica of the brain’s computing abilities using original hardware and software applications. So far what they’ve developed is a computing platform that mimics the activity of one million neurons. (Not quite the amount that are in the human brain.)

Two graduate students from Stanford University worked with Boahen to develop the Neurogrid. (Image credit: Samir Menon/ Stanford University)

What separates their platform, which they’ve named “Neurogrid,” from a supercomputer, is that it’s the first simulation platform that can model one million neurons in real time, and therefore offers researchers a compelling tool for studying the human brain.

Neurogrid contains 16 chips, each containing over 65,000 silicon “neurons.” The neurons’ activity can be programmed according to about 80 factors, which grants researchers the ability to mimic the unique characteristics of different kinds of neurons. The soft-wired “synapses” intersect across the board and shut signals between the simulated neurons and the thousands of neurons they are connected with. This set up creates an accurate representation of what kind of communication actually takes place in the brain.

Why is the Neurogrid more effective than a supercomputer?

So far, findings show that the Blue Gene/ Q Sequoia supercomputer’s simulation took 1,500 times longer than it would take the brain to do the same activity. Even more affordable brain simulators that use computing powers such as central and graphical processing units are slower than the brain.
“Neurogrid doesn’t take an hour to simulate a second of brain activity. It takes a second to simulate a second of brain activity,” said Boahen.

The Neurogrid is also more energy efficient than a supercomputer, using a fraction of the energy. The Blue Gene/ Q Sequoia uses 8 megawatts of electricity (that’s enough to power 160,000 homes) while the Neurogrid uses just 5 watts (enough to power just one cellphone charger).

Future impact

Neurogrid will not only be able to help researchers discover more about the inner workings of the brain, but also has the potential to reveal more about diseases such as autism and schizophrenia. Neurogrid can also be used to create new systems for advancements in neural prosthetics and robotic controllers.

Source: Hearst Electronics Products Magazine.

25Apr 2013

Newborn Stars and their Effect on the Universe

Jason Carr ⋅ 3 Comments

When galaxies form new stars, they sometimes do so in frantic episodes of activity known as starbursts. These events were commonplace in the early Universe, but are rarer in nearby galaxies.

During these bursts, hundreds of millions of stars are born, and their combined effect can drive a powerful wind that travels out of the galaxy. These winds were known to affect their host galaxy — but this new research [Paper here - PDF] now shows that they have a significantly greater effect than previously thought.

An international team of astronomers observed 20 nearby galaxies, some of which were known to be undergoing a starburst. They found that the winds accompanying these star formation processes were capable of ionizing [1] gas up to 650 000 light-years from the galactic center — around twenty times further out than the visible size of the galaxy. This is the first direct observational evidence of local starbursts impacting the bulk of the gas around their host galaxy, and has important consequences for how that galaxy continues to evolve and form stars.

“The extended material around galaxies is hard to study, as it’s so faint,” says team member Vivienne Wild of the University of St. Andrews. “But it’s important — these envelopes of cool gas hold vital clues about how galaxies grow, process mass and energy, and finally die. We’re exploring a new frontier in galaxy evolution!”

The team used the Cosmic Origins Spectrograph (COS) instrument [2] on the NASA/ESA Hubble Space Telescope to analyze light from a mixed sample of starburst and control galaxies. They were able to probe these faint envelopes by exploiting even more distant objects — quasars, the intensely luminous centers of distant galaxies powered by huge black holes. By analyzing the light from these quasars after it passed through the foreground galaxies, the team could probe the galaxies themselves.

“Hubble is the only observatory that can carry out the observations necessary for a study like this,” says lead author Sanchayeeta Borthakur, of Johns Hopkins University. “We needed a space-based telescope to probe the hot gas, and the only instrument capable of measuring the extended envelopes of galaxies is COS.”

The starburst galaxies within the sample were seen to have large amounts of highly ionized gas in their halos — but the galaxies that were not undergoing a starburst did not. The team found that this ionization was caused by the energetic winds created alongside newly forming stars.

This has consequences for the future of the galaxies hosting the starbursts. Galaxies grow by accreting gas from the space surrounding them, and converting this gas into stars. As these winds ionize the future fuel reservoir of gas in the galaxy’s envelope, the availability of cool gas falls — regulating any future star formation.

“Starbursts are important phenomena — they not only dictate the future evolution of a single galaxy, but also influence the cycle of matter and energy in the Universe as a whole,” says team member Timothy Heckman, of Johns Hopkins University. “The envelopes of galaxies are the interface between galaxies and the rest of the Universe — and we’re just beginning to fully explore the processes at work within them.”

Source: ESA/Hubble Information Centre

Notes

[1] A gas is said to be ionised when its atoms have lost one or more electrons — in this case by energetic winds exciting galactic gas and knocking electrons out of the atoms within.

[2] Spectrographs are instruments that break light into its constituent colours and measure the intensity of each colour, revealing information about the object emitting the light — such as its chemical composition, temperature, density, or velocity.

Reference:

Sanchayeeta Borthakur, Timothy Heckman, David Strickland, Vivienne Wild, & David Schiminovich (2013). The Impact of Starbursts on the Circumgalactic Medium The Astrophysical Journal arXiv: 1303.1183v2

06Mar 2013

Dead Sparrow Turned into Robot to Study Bird Behavior

Jason Carr ⋅ 3 Comments

Researchers at Duke University recently took a major step toward better understanding how swamp sparrows use a combination of song and visual displays to communicate with one another. How they came about making this discovery, though, is what makes this story particularly newsworthy — they stuffed a deceased swamp sparrow with a miniature computer and some robotics to give it the ability to flap its wings as if it were alive.

Duke biologist Rindy Anderson led a team of biologists on the study, receiving technical assistance from engineering undergraduate student David Perch. The team brought “Robosparrow,” as it is aptly referred to, to a swamp sparrow breeding ground and placed it in the territories of live males.

Once all systems were go, the robotic bird “sang” swamp sparrow songs vis-à-vis a nearby sound system that let the birds know it was intruding on their ground. Anderson observed from a distance, sitting amid the tall swampy grasses, and changed the bird’s behavior to study various responses. They had it sing in a stationary position, shift side to side, and as mentioned before, flap its wings.

What they found was a song combined with wing waves is more potent than song alone, and that wing waves by themselves evoked the most aggressive response from live male birds.

“What I didn’t expect to see was that the birds would give strikingly similar aggressive wing-wave signals to the three types of invaders,” Anderson said. That is to say, she thought the defending birds would simply match the signals of the intruding robosparrow. What they instead discovered was that the males are more individualistic and consistent in the level of aggressiveness that they want to signal.

“That response makes sense, in retrospect, since attacks can be devastating,” she said. What Anderson means by this is that male swamp sparrows only want to signal a certain level of aggression to see if they can scare off an intruder without provoking any sort of physical conflict that could result in severe injury or death. Some sparrows were intimidated by robosparrow’s flapping, while others responded with a more aggressive flapping pattern.

Also worth noting from this study is that whether the robosparrow waved its wings or not, some live male sparrows still came in and attacked it. “It’s high stakes for these little birds. They only live a couple of years, and most only breed once a year, so owning a territory and having a female is high currency,” Anderson said.

Looking ahead, Anderson and her team plan to further test how the sparrows use wing waves combined with a characteristic twitter called “soft-song” to show aggression and fend off competition. Unfortunately, it’s going to take some time before the bot gets back in the field, as robosparrow’s motor is burned out from its last run, and the bird’s head was ripped off during one of the attacks.

Source: duke.edu, electronicproducts.com

Reference:

Anderson, R., DuBois, A., Piech, D., Searcy, W., & Nowicki, S. (2013). Male response to an aggressive visual signal, the wing wave display, in swamp sparrows Behavioral Ecology and Sociobiology DOI: 10.1007/s00265-013-1478-9

11Feb 2013

Cell Circuits Remember Their History

Jason Carr ⋅ 1 Comment

Engineers at MIT have developed genetic circuits in bacterial cells that not only perform logic functions, but also remember the results. (Credit: Liang Zong and Yan Liang)

MIT engineers have created genetic circuits in bacterial cells that not only perform logic functions, but also remember the results, which are encoded in the cell’s DNA and passed on for dozens of generations.

The circuits, described in the Feb. 10 online edition of Nature Biotechnology (citation below), could be used as long-term environmental sensors, efficient controls for biomanufacturing, or to program stem cells to differentiate into other cell types.

“Almost all of the previous work in synthetic biology that we’re aware of has either focused on logic components or on memory modules that just encode memory. We think complex computation will involve combining both logic and memory, and that’s why we built this particular framework to do so,” says Timothy Lu, an MIT assistant professor of electrical engineering and computer science and biological engineering and senior author of the Nature Biotechnologypaper.

Lead author of the paper is MIT postdoc Piro Siuti. Undergraduate John Yazbek is also an author.

More than logic

Synthetic biologists use interchangeable genetic parts to design circuits that perform a specific function, such as detecting a chemical in the environment. In that type of circuit, the target chemical would generate a specific response, such as production of green fluorescent protein (GFP).

Circuits can also be designed for any type of Boolean logic function, such as AND gates and OR gates. Using those kinds of gates, circuits can detect multiple inputs. In most of the previously engineered cellular logic circuits, the end product is generated only as long as the original stimuli are present: Once they disappear, the circuit shuts off until another stimulus comes along.

Lu and his colleagues set out to design a circuit that would be irreversibly altered by the original stimulus, creating a permanent memory of the event. To do this, they drew on memory circuits that Lu and colleagues designed in 2009. Those circuits depend on enzymes known as recombinases, which can cut out stretches of DNA, flip them, or insert them. Sequential activation of those enzymes allows the circuits to count events happening inside a cell.

Lu designed the new circuits so that the memory function is built into the logic gate itself. With a typical cellular AND gate, the two necessary inputs activate proteins that together turn on expression of an output gene. However, in the new circuits, the inputs stably alter regions of DNA that control GFP production. These regions, known as promoters, recruit the cellular proteins responsible for transcribing the GFP gene into messenger RNA, which then directs protein assembly.

For example, in one circuit described in the paper, two DNA sequences called terminators are interposed between the promoter and the output gene (GFP, in this case). Each of these terminators inhibits the transcription of the output gene and can be flipped by a different recombinase enzyme, making the terminator inactive.

Each of the circuit’s two inputs turns on production of one of the recombinase enzymes needed to flip a terminator. In the absence of either input, GFP production is blocked. If both are present, both terminators are flipped, resulting in their inactivation and subsequent production of GFP.

Once the DNA terminator sequences are flipped, they can’t return to their original state — the memory of the logic gate activation is permanently stored in the DNA sequence. The sequence also gets passed on for at least 90 generations. Scientists wanting to read the cell’s history can either measure its GFP output, which will stay on continuously, or if the cell has died, they can retrieve the memory by sequencing its DNA.

Using this design strategy, the researchers can create all two-input logic gates and implement sequential logic systems. “It’s really easy to swap things in and out,” says Lu, who is also a member of MIT’s Synthetic Biology Center. “If you start off with a standard parts library, you can use a one-step reaction to assemble any kind of function that you want.”

Long-term memory

Such circuits could also be used to create a type of circuit known as a digital-to-analog converter. This kind of circuit takes digital inputs — for example, the presence or absence of single chemicals — and converts them to an analog output, which can be a range of values, such as continuous levels of gene expression.

For example, if the cell has two circuits, each of which expresses GFP at different levels when they are activated by their specific input, those inputs can produce four different analog output levels. Moreover, by measuring how much GFP is produced, the researchers can figure out which of the inputs were present.

That type of circuit could offer better control over the production of cells that generate biofuels, drugs or other useful compounds. Instead of creating circuits that are always on, or using promoters that need continuous inputs to control their output levels, scientists could transiently program the circuit to produce at a certain level. The cells and their progeny would always remember that level, without needing any more information.

Used as environmental sensors, such circuits could also provide very precise long-term memory. “You could have different digital signals you wanted to sense, and just have one analog output that summarizes everything that was happening inside,” Lu says.

This platform could also allow scientists to more accurately control the fate of stem cells as they develop into other cell types. Lu is now working on engineering cells to follow sequential development steps, depending on what kinds of inputs they receive from the environment.

Source: Massachusetts Institute of Technology

Reference:

Siuti, P., Yazbek, J., & Lu, T. (2013). Synthetic circuits integrating logic and memory in living cells Nature Biotechnology DOI: 10.1038/nbt.2510

17Jan 2013

Soft Lego Built in the Computer

Jason Carr ⋅ 3 Comments

Simulation snapshot of a cubic crystal built of soft patchy diblock star polymers. (Copyright: American Physical Society)

Barbara Capone of the Computational Physics Group of the University of Vienna has developed a new method for the construction of building blocks at the nanoscale. The researcher in Soft Matter Physics, who works at the group of Christos Likos, Professor for Multiscale Computational Physics, is specialized on topics of self-assembly of materials at the nanoscale and she has published, together with her colleagues, a paper at the prestigious Journal “Physical Review Letters” on “soft Lego” (cited below).

In developing these novel self-assembling materials, postdoc Barbara Capone has focused on the design of organic and inorganic building blocks, which are robust and can be produced at large scale. Capone has put forward, together with her colleagues at the Universities of Vienna and Mainz, a completely new pathway for the construction of building blocks at the nanoscale.

“Soft Lego” orders in crystal structures
The team of researchers has shown that so-called block copolymer stars – that means polymers that consist of two different blocks and they are chemically anchored on a common point – have a robust and flexible architecture and they possess the ability to self-assemble at different levels. At the single-molecule level, they first order as soft patchy colloids which serve then as “soft Lego” for the emergence of larger structures. At the next level of self-assembly, the colloids form complex crystal structures, such as diamond or cubic phases.

Simulation snapshot of a diamond crystal built of soft patchy diblock star polymers (Copyright: American Physical Society)

The spatial ordering in the crystals can be steered through the architecture of the “soft Lego” and opens up the possibility for the construction of new materials at the macroscopic scale with desired structure. In this way, crystals can be built that have applications in, e.g., photonics, acting as filters for light of certain frequencies or as light guides.

Source: University of Vienna

Reference:

Capone, B., Coluzza, I., LoVerso, F., Likos, C., & Blaak, R. (2012). Telechelic Star Polymers as Self-Assembling Units from the Molecular to the Macroscopic Scale Physical Review Letters, 109 (23) DOI: 10.1103/PhysRevLett.109.238301

07Jan 2013

New Path to More Efficient Organic Solar Cells

Jason Carr ⋅ 2 Comments

Image Credit: Harald Ade, NC State University

Why are efficient and affordable solar cells so highly coveted? Volume. The amount of solar energy lighting up Earth’s land mass every year is nearly 3,000 times the total amount of annual human energy use. But to compete with energy from fossil fuels, photovoltaic devices must convert sunlight to electricity with a certain measure of efficiency. For polymer-based organic photovoltaic cells, which are far less expensive to manufacture than silicon-based solar cells, scientists have long believed that the key to high efficiencies rests in the purity of the polymer/organic cell’s two domains – acceptor and donor. Now, however, an alternate and possibly easier route forward has been shown.

Working at Berkeley Lab‘s Advanced Light Source (ALS), a premier source of X-ray and ultraviolet light beams for research, an international team of scientists found that for highly efficient polymer/organic photovoltaic cells, size matters.

“We’ve shown that impure domains if made sufficiently small can also lead to improved performances in polymer-based organic photovoltaic cells,” says Harald Ade, a physicist at North Carolina State University, who led this research. “There seems to be a happy medium, a sweet-spot of sorts, between purity and domain size that should be much easier to achieve than ultra-high purity.”

Ade, a longtime user of the ALS, is the corresponding author of a paper describing this work in Advanced Energy Materials titled “Absolute Measurement of Domain Composition and Nanoscale Size Distribution Explains Performance in PTB7:PC71 BM Solar Cells.” Co-authors are Brian Collins, Zhe Li, John Tumbleston, Eliot Gann and Christopher McNeill [Citation below].

Solar cell conversion efficiency in polymer/organic photovoltaic cells hinges on excitons – electron/hole pairs energized by sunlight – getting to the interfaces of the donor and acceptor domains quickly so as to minimize energy lost as heat. Conventional wisdom held that the greater the purity of the domains, the fewer the impedances and the faster the exciton journey.

Ade and his co-authors became the first to simultaneously measure the domain size, composition and crystallinity of an organic solar cell. This feat was made possible by ALS beamlines 11.0.1.2, a Resonant Soft X-ray Scattering (R-SoXS) facility; 7.3.3, a Small- and Wide-Angle X-Ray Scattering (SAXS/WAXS/) end-station; and 5.3.2, an end-station for Scanning Transmission X-Ray Microscopy (STXM).

Says Collins, the first author on the Advanced Energy Materials paper, “The combination of these three ALS beamlines enabled us to obtain comprehensive pictures of polymer-based organic photovoltaic film morphology from the nano- to the meso-scales. Until now, this information has been unattainable.”

The international team used the trifecta of ALS beams to study the polymer/fullerence blend PTB7:PC71BM in thin films made from chlorobenzene solution with and without the addition (three-percent by volume) of the solvent diiodooctane. The films were composed of droplet-like dispersions in which the dominant acceptor domain size without the additive was about 177 nanometers. The addition of the solvent shrank the acceptor domain size down to about 34 nanometers while preserving the film’s composition and crystallinity. This resulted in an efficiency gain of 42-percent.

“In showing for the first time just how pure and how large the acceptor domains in organic solar devices actually are, as well as what the interface with the donor domain looks like, we’ve demonstrated that the impact of solvents and additives on device performance can be dramatic and can be systematically studied,” Ade says. “In the future, our technique should help advance the rational design of polymer-based organic photovoltaic films.”

Source: DOE/Lawrence Berkeley National Laboratory

Reference:

Collins, B., Li, Z., Tumbleston, J., Gann, E., McNeill, C., & Ade, H. (2012). Absolute Measurement of Domain Composition and Nanoscale Size Distribution Explains Performance in PTB7:PC BM Solar CellsAdvanced Energy Materials DOI: 10.1002/aenm.201200377

04Dec 2012

Herschel and Keck take Census of the Invisible Universe

Jason Carr ⋅ 2 Comments

Image Credits: ESA–C. Carreau/C. Casey (University of Hawai’i); COSMOS field: ESA/Herschel/SPIRE/HerMES Key Programme; Hubble images: NASA, ESA

By combining the observing powers of ESA’s Herschel space observatory and the ground-based Keck telescopes, astronomers have characterised hundreds of previously unseen starburst galaxies, revealing extraordinary high star-formation rates across the history of the Universe.

Starburst galaxies give birth to hundreds of solar masses’ worth of stars each year in short-lived but intense events. By comparison, our own Milky Way Galaxy on average produces the equivalent of only one Sun-like star per year.

Starburst galaxies generate so much starlight that they should outshine our Galaxy hundreds to thousands of times over, but the enormous quantities of gas fuelling them also contain vast amounts of dust as a result of the frantic star formation. The dust absorbs much of the visible light, meaning that many of them look quite insignificant in that part of the spectrum. However, the dust is warmed by the surrounding hot stars and re-emits the energy at far-infrared wavelengths.

Using ESA’s infrared Herschel space observatory, astronomers measured the temperature and brightness of thousands of dusty galaxies. From these, their star-formation rate could be then calculated.

“Starburst galaxies are the brightest galaxies in the Universe and contribute significantly to cosmic star formation, so it’s important to study them in detail and understand their properties,” says Dr Caitlin Casey of the University of Hawai‘i, lead author of the papers discussing the results in the Astrophysical Journal.

“Some of the galaxies found in this new survey have star-formation rates equivalent to the birth of several thousand solar-mass stars per year, constituting some of the brightest infrared galaxies yet discovered.”

To provide context to the observations and understand how star formation has changed over the Universe’s 13.7 billion year history, the distances to the galaxies were also needed.

With Herschel signposting the way, Dr Casey’s team used spectrometers on the twin 10-metre W.M. Keck telescopes on Mauna Kea, Hawai‘i, and obtained the redshifts of 767 of the starburst galaxies. Redshifts provide astronomers with a measure of how long the light from each galaxy has travelled across the Universe, which, in turn, indicates when in cosmic history the light from each galaxy was emitted. For most of the galaxies it was found that the light has been travelling towards us for 10 billion years or less. About 5% of the galaxies are at even greater redshifts: their light was emitted when the Universe was only 1–3 billion years old.

“The Herschel data tell us how fiercely and prolifically these galaxies are producing stars,” says Seb Oliver from University of Sussex, UK, and Principal Investigator for the HerMES Key Programme, within which the data have been collected.

“Combining this information with the distances provided by the Keck data, we can uncover the contribution of the starburst galaxies to the total amount of stars produced across the history of the Universe.”

How such large numbers of starburst galaxies formed during the first few billions of years of the Universe’s existence poses a vital problem for galaxy formation and evolution studies. One leading theory proposes that a collision between two young galaxies could have sparked an intense short-lived phase of star formation. Another theory speculates that, when the Universe was young, individual galaxies had much more gas available to them to feed from, enabling higher rates of star formation without the need of collisions.

“It’s a hotly debated topic that requires details on the shape and rotation of the galaxies before it can be resolved,” adds Dr Casey.

“Before Herschel, the largest similar survey of distant starbursts involved only 73 galaxies – we’ve improved on that by over a factor of ten in this combined survey with Keck to determine the characteristics of this important galaxy population,” adds Göran Pilbratt, ESA’s Herschel project scientist.

Source: ESA

08Oct 2012

Solving Environmental Problems Through Metabolic Engineering

Jason Carr ⋅ 3 Comments

Environmental problems, such as depleting natural resources, highlight the need to establish a renewable chemical industry. Metabolic engineering enhances the production of chemicals made by microbes in so-called “cell factories”. Next Monday, scientist Professor Sang Yup Lee of KAIST (Korea Advanced Institute of Science and Technology) will explain how metabolic engineering could lead to the development of solutions to these environmental problems. Professor Lee’s work is cited below for reference.

Transmission of an electron micrograph of metabolically engineered Escherichia coli cells accumulating poly(lactate-co-3hydroxybutyrate) copolymers.

For example, the polyester polylactic acid (PLA) is a biodegradable material with a wide range of uses, from medical implants, to cups, bags, food packaging and disposable tableware. It and its co-polymer can be produced by direct fermentation of renewable resources using metabolically engineered Escherichia coli.

Microorganisms isolated from nature use their own metabolism to produce certain chemicals. But they are often inefficient, so metabolic engineering is used to improve microbial performance. Beginning in the 1990s, metabolic engineering involves the modification of microbial cells to enhance the production of what’s known as a bioproduct. This bioproduct can be something that the cell produces naturally, like ethanol or butanol. It can also be something that the cells mechanisms can produce if their natural metabolic pathways are altered in some way. The range of uses of this bioproduct can be broadened through metabolic engineering, which can also optimize the overall process of bioproduct synthesis.

Recently, metabolic engineering has become more powerful, through the integration of itself with systems and synthetic biology. Systems biology is a relatively new approach to biological research which looks at the complex interactions within whole cell systems. It allows cell-wide understanding of metabolic reactions and the way these are regulated by the cell’s genes.

Synthetic biology is another new approach that designs and constructs new biological functions and systems that aren’t found in nature. It allows the design of new genes, modules and circuits that can be used to modulate the cells metabolism to make more of the desired bioproduct. So systems metabolic engineering can now develop superior microorganisms much more efficiently through the integration of itself with systems biology and synthetic biology.

Professor Lee will introduce general strategies for systems metabolic engineering which will be accompanied by many successful examples, including the production of chemicals, fuels and materials such as propanol, butanol, 1,4-diaminobutane, 1,5-diaminopentane, succinic acid, polyhydroxyalkanoates, and polylactic acid.

Professor Sang Yup Lee said: “Bio-based production of chemicals and materials will play an increasingly important role in establishing a sustainable world. To make the bioprocess efficient and economically competitive, it is essential to improve the performance of microorganisms through systems metabolic engineering. From industrial solvents to plastics, an increasing number of products of everyday use will be produced through bioprocesses.”

Professor Lee will present the 5th Environmental Microbiology Lecture on 8 October 2012 at the Royal Society of Medicine. Registration begins at 17.30 and the lecture will start 18.30.

Source: The Korea Advanced Institute of Science and Technology (KAIST)

Reference:

Yu Kyung Jung, Tae Yong Kim, Si Jae Park, & Sang Yup Lee (2010). Metabolic engineering of Escherichia coli for the production of polylactic acid and its copolymers. Biotechnology and Bioengineering, 105 (1), 161-171 : 10.1002/bit.22548