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Thursday, 29 September 2016
Friday, 10 June 2016
In The Life of The ISS
In In The Life of The ISS – Question Time
This post is dedicated to our friend Mihaela from Facebook that recently asked us a question that is partially related to the International Space Station (ISS). The Question was…
How many sunrises can an astronaut see from an orbiting space station, if it orbits the Earth in 90 minutes, and why?
This is a brilliant question and thank you Mihaela for asking us to look into it for you. I will be going through two parts to answering this. The first part is the straight forward answer, we will then go through a little more information about the ISS with some visulisations, that will help see why the aforementioned occurs. I have also used the ISS as an example as this is the most commonly known space station (seriously, isn’t it pretty cool we have space stations just whipping above us as we speak), plus there are some great apps available that allow you to track the ISS.
The Short Answer…
The ISS takes 92 minutes to orbit the earth once. Where as somewhere on Earth takes 24 hours to complete a full rotation and we see one sun rise and one sunset.
As it takes approximately 92 minutes for the ISS to complete and orbit, this means that every 45 minutes or so they will witness a sunrise or a sunset as they effectively pass over the point that Earth would be having a sun rise or a sun set at that particular time.
This means, over the course of 24 hours (Earth’s full rotation) the ISS will observe between 15 and 16 sun rises and sunsets.
Now a little more information on the ISS
The space station is made of many pieces. The pieces were put together in space by astronauts. The space station’s orbit is about 220 miles above Earth. NASA uses the station to learn about living and working in space. These lessons will help NASA explore space.
Questions and Facts
How Old Is the Space Station?
The first piece of the International Space Station was launched in 1998. A Russian rocket launched that piece. After that, more pieces were added. Two years later, the station was ready for people. The first crew arrived on November 2, 2000. People have lived on the space station ever since. Over time more pieces have been added. NASA and its partners around the world finished the space station in 2011.
How Big Is the Space Station?
The space station is as big inside as a house with five bedrooms. It has two bathrooms, a gymnasium and a big bay window. Six people are able to live there. It weighs almost a million pounds. It is big enough to cover a football field including the end zones. It has science labs from the United States, Russia, Japan and Europe.
What Are the Parts of the Space Station?
The space station has many parts. The parts are called modules. The first modules had parts needed to make the space station work. Astronauts also lived in those modules. Modules called “nodes” connect parts of the station to each other. Labs on the space station let astronauts do research.
On the sides of the space station are solar arrays. These arrays collect energy from the sun. They turn sunlight into electricity. Robot arms are attached outside. The robot arms helped to build the space station. They also can move astronauts around outside and control science experiments.
Airlocks on the space station are like doors. Astronauts use them to go outside on spacewalks.
Docking ports are like doors, too. The ports allow visiting spacecraft to connect to the space station. New crews and visitors enter the station through the docking ports. Astronauts fly to the space station on the Russian Soyuz. The crew members use the ports to move supplies onto the station.
Why Is the Space Station Important?
The space station is a home in orbit. People have lived in space every day since the year 2000. The space station’s labs are where crew members do research. This research could not be done on Earth.
Scientists study what happens to people when they live in space. NASA has learned how to keep a spacecraft working for a long time. These lessons will be important in the future.
NASA has a plan to send humans deeper into space than ever before. The space station is one of the first steps. NASA will use lessons from the space station to get astronauts ready for the journey ahead.
Some Quick Facts about the ISS
- 1. It took an astounding 136 space flights on seven different types of launch vehicles to build it.
- 2. It flies at 4.791 miles per second (7.71 km/s). That’s fast enough to go to the Moon and back in about a day.
- 3. It weighs almost 1 million pounds including visiting spacecraft. Picture 120,000 gallons of milk in supermarket cartons in your mind.
- 4. It has 8 miles of wire just to connect the electrical power system. That will be enough to connect a hair dryer in Newark, New Jersey, to a power plug in New York City.
- 5. It has a complete surface area the size of a US football field, which actually makes it almost as large as the Tantive IV, the Corellian Corvette that carried Princess Leia.
- 6. It has more livable space than a 6-bedroom house.
- 7. It has two bathrooms, a gymnasium and a 360-degree bay window.
- 8. It’s been the spaceport for 89 Russian Soyuz spacecraft, 37 Space Shuttle missions, three SpaceX Dragons, four Japanese HTV cargo spacecraft, and four European ATV cargo spacecraft.
- 9. All its research experiments and spacecraft systems are housed in a bit more than one hundred telephone-booth sized racks.
- 10. The US solar array surface area on the is 38,400 sq. feet (.88 acre), which is large enough to cover 8 basketball courts
- 11. According to NASA, “there are 52 computers controlling the ISS.” Just for the US segment, there are “1.5 million lines of flight software code run on 44 computers communicating via 100 data networks transferring 400,000 signals.”
- 12. Its internal pressurized volume is 32,333 cubic feet, which is about the same of a Jumbo Boeing 747.
- 13. The ISS crews have eaten about 25,000 meals since 2000. That’s a staggering “seven tons of supplies per three astronauts for six months.” That’s 32,558 Big Macs.
- 14. 211 people from 15 countries have visited the ISS so far.
- 15. When it reaches the end of its life, some of the most modern Russian modules—like Nauka—will be reused to make a third space station to support interplanetary mission to Mars, the Moon and Saturn, serving as a launching and return point.
Some Questions Answered by the NASA Team
Do you believe in that the design of the ISS will cause a problem in case of a meteor shower? Why?
That’s a really good question. The space environment is a very harsh environment: there’s radiation and micrometeorite strikes, and other things in the environment that cause it to be very hazardous. So, one of the things that we’ve designed the space station for is to protect the astronauts against micrometeorite striking the outer shell of the space station. Now, in doing so, the basic design philosophy of the pressurized modules has been to develop an inner shell, which contains the pressurized interior of the space station, and then a layer of insulation around that inner shell, and then an outer armor plating, if you will, to the exterior. And what that does is protects against small pieces of debris that strike the station and can cause leaks. Now, for larger pieces of debris: they actually track them and have to actually move the space station out of the way of the larger pieces that could cause serious damage to the station.
What kind of contingency plan does the ISS have in case of an emergency? How long do life support systems on board last for the stranded astronauts? Is there such a thing as an emergency launch to the ISS using the current space shuttles?
Well, there are several redundant systems on the space station, which really enable the astronauts to survive for long periods of time without a space shuttle or a Russian re-supply ship coming to bring additional supplies. Now, in the event of an outright emergency, where the lives of the astronauts were threatened, they would have to evacuate the space station using the Soyuz module, but the life support systems themselves are designed to last for months at a time without a re-supply ship.
What would you say to date has been the greatest benefit to mankind from the space station, and what is its predicted benefits?
Well, I think it’s all a matter of judgment, but to me the greatest benefit of the space station is the international cooperation to date that we’ve had with over 16 different countries contributing to the International Space Station; countries that were at one time, enemies of each other, have now come together to do something that will benefit mankind. I think down the road the space station will bring great leaps in science, in medical fields, in the materials manufacturing fields, and it will also teach us a lot about long duration human space flight so that we can expand our civilization beyond Earth.
Why is the center truss section called S-Zero?
That’s actually a really good question, because the trusses are named for whether they’re on the starboard side or the port side; so you have S-Zero, S-One, P-One, S-Three, P-Three, P-Four, S-Four, P-Five, S-Five. Well, S-Zero being in the middle, I guess they couldn’t decide whether to call it S-Zero or P-Zero, and maybe they flipped a coin or whatever else and decided to call it S-Zero, but it’s actually in the center, it’s not on the starboard side or the port side, so it could have just as easily been named P-Zero.
Does the International Space Station have any hardware or machines that were specifically invented for it and cannot be found anywhere else? What are they?
Well, the International Space Station has lots of unique hardware elements that were designed specifically for the International Space Station. They also use off-the-shelf technology when possible; one instance of that is the cameras that they use on the space station for the interior of the space station are actually just off-the-shelf camcorders. But, some, there’s certainly a great amount of technology that was developed specifically for the International Space Station to function specifically in the space environment. I think one of the best examples of that is the Canadian robotic arm. The Canadian robotic arm was developed specifically for the International Space Station and fills the task of actually constructing the International Space Station, and it doesn’t even function in the Earth environment in the one-G conditions that we have here on Earth.
When will the International Space Station be completed?
Well also that’s a very interesting question. The core complete milestone that we are reaching for right now is due in the mid-2004 timeframe. Now, after we finish building what’s essentially the core of the International Space Station then we have a lot of additional options to add elements developed by international partners, and other additional features that we might want to add. The fact that the space station was designed the way it was allows us to once we get to the core complete milestone to expand it to provide lots of additional capabilities.
Which ISS docking port is being used by the Soyuz TM-34 spacecraft? Also, where on the station will Endeavour and Leonardo dock?
Well, the Soyuz module is nominally docked to the end of the Russian service module. Now, there are additional docking ports on the Russian functional cargo block, I’m sorry, on the bottom of the service module, where the Soyuz modules can be docked. And when they bring a second one up onto orbit in order to switch out the first one when they have to replace them, they actually have to move one of the Soyuz modules from the end of the service module to the bottom of the service module, and the second service module goes on to the end. The space shuttle, on the other hand, docks to the American side of the space station, to the Destiny laboratory. And the MPLM, Leonardo, in this case, is docked to Node-1, which was also built by an American company, Boeing.
Is it possible to give the times and locations of when the ISS passes over Central California?
Well, it’s actually possible to find out when the space station will be passing over your head no matter where you live, and there’s a website, it’s http://spaceflight.nasa.gov, and if you go that website, you can follow links and actually no matter what city you are in the country, you can find out when the space station will be traveling overhead.
With respect to the space station, why can’t we just shoot the trash off towards the sun instead of bringing it back to Earth?
Well, that’s actually a question that I used to wonder about when I was growing up, why didn’t we just put all the trash into the sun to save our garbage problems here on Earth. Unfortunately, it would take a lot of rocket power to get anything to the Sun, and so it’s sort of a limiting factor to be able to launch something out the sphere of influence of the Earth. Now, the trash on the International Space Station, not all of it is brought back to Earth. Some of it is placed in the Russian Progress modules, which are sent on a trajectory into the Earth’s atmosphere that burns it back up. So it’s not all brought back to Earth, just some of it in the MPLM modules.
After the completion of the ISS, how much will it contribute to the flight of humans to Mars, and return trips to the Moon?
Well, this kind of goes with the earlier question, about what the benefits of the International Space Station are. If we’re going to go to Mars, or spend long periods of time on the Moon, we have to learn what the effects of long term space flight is going to be on our astronauts. We don’t have a lot of information about what the space environment does to our astronauts, beyond, say six months. There are astronauts, particularly from Russia, who have spend more time than that in space, but very few, so we don’t have a large amount of data, and it’d be very risky to send astronauts to Mars, to spend say, a year and a half outside of the Earth environment, or more, without knowing exactly what the effects of the long term exposure to space would be. So, the International Space Station in addition to us just developing the technology to live in space for large amounts of time, it gives us the information that we need about how long astronauts can safely stay in space.
Is it possible to use a flywheel mechanism to produce power for the space station? Have there been any experiments using this technology to produce power in space?
Well, it’s actually not possible to use flywheels to generate power in the classical sense, but you can use flywheels to store power. So, you would have to use some other source to generate the power, but then to store it you could spin up flywheels and then use the kinetic energy from the flywheels to actually store energy. But because the power requirements of the space station are so large, it’s a lot more practical for us to use batteries to store power on the station. So, the answer to the question is no, we don’t use flywheels to store power.
How many different civilian contracting companies, on average, participate in the building of one of our space station modules?
Well, most of the American space station modules were developed and built by the prime contractor for the space station, which is Boeing. Now, Boeing has dozens, if not hundreds of subcontractors that it uses to build everything from the smallest screw used on the space station to a complex computer, or a solar array. So, there’s one prime contractor, but dozens, if not hundreds of subcontractors.
When the space station needs to make an orbital adjustment, do the occupants of the space station feel the movement of the adjustment?
Well, the reason why I think that’s such a good question is because it really highlights one of the most fundamental laws of physics we have, and there are basically three laws of physics that Isaac Newton postulated hundreds of years ago, and one of those laws it that force equals mass times acceleration. Now, the key thing about these laws is that no matter where you are in the universe, they are true. So whether you’re on Earth or whether you’re in space, these laws are true. Now, this particular law, force equals mass plus acceleration, when you press the gas pedal in your car, your car accelerates, you go from say, 55 miles an hour to 60 miles an hour. That acceleration is what causes you to feel that force. Now, in space, when they fire the thrusters on the space station, the space station also accelerates. But the acceleration is generally very, very small. So sometimes the astronauts might not notice the space station is accelerating. But that also brings in another interesting point, in what they might see, since the astronauts are floating free with respect to the space station, that when the space station fires it thrusters, the space station would move, and the astronauts, not touching one of the surfaces, would not move, so they would see the space station actually moving around them.
During a 24 hour period, how many times does the ISS orbit the Earth?
Well, the space station orbits Earth about every 90 minutes, so that means in a 24 hour day, the space station orbits approximately 16 times.
In operating, maintaining, and troubleshooting problems on the ISS, how involved does the ISS crew get versus the control center team?
Well, that’s a very good question. NASA has an entire army of people supporting the operations of the International Space Station. Of course, the astronauts are often the first line of defense, and especially in emergency situations, they have to make quick, critical decisions that will allow everybody to be safe. Now, the mission control people are a huge part of supporting that and laying out those plans for the emergency situations. But, in the event that something goes wrong on the station, NASA has the ability to go back to the people who actually designed the hardware and ask them what they think about the problem, and if it’s something they might have seen before in ground testing. So it’s a collaborative effort across all of the different countries that make up the hardware that we use on the International Space Station.
On certain days we are able to visualize the space station as it seems to streak across the sky. How fast is the ISS traveling?
Well, in order for the space station to stay in orbit, it has to travel at seven kilometers per second, which the equivalent in miles per hour, is around 15,500 miles per hour. So that’s pretty fast!
I hope you enjoyed this post and Mihaela, I hope this answered your question and then some more 🙂 thank you so so much for the question. If you or anyone else has any more questions please let us know on our Scientia facebook page or use the forums on Scientia to start your own thread.
– Credit and Resource –
NASA
In The Life of The ISS
Saturday, 28 May 2016
Link Between Primordial Black Holes and Dark Matter
Scientist suggests possible link between primordial black holes and dark matter
Left: This image from NASA’s Spitzer Space Telescope shows an infrared view of a sky area in the constellation Ursa Major. Right: After masking out all known stars, galaxies and artifacts and enhancing what’s left, an irregular background glow appears. This is the cosmic infrared background (CIB); lighter colors indicate brighter areas. The CIB glow is more irregular than can be explained by distant unresolved galaxies, and this excess structure is thought to be light emitted when the universe was less than a billion years old. Scientists say it likely originated from the first luminous objects to form in the universe, which includes both the first stars and black holes. Credit: NASA/JPL-Caltech/A. Kashlinsky (Goddard)
Scientia — Dark matter is a mysterious substance composing most of the material universe, now widely thought to be some form of massive exotic particle. An intriguing alternative view is that dark matter is made of black holes formed during the first second of our universe’s existence, known as primordial black holes. Now a scientist at NASA’s Goddard Space Flight Center in Greenbelt, Maryland, suggests that this interpretation aligns with our knowledge of cosmic infrared and X-ray background glows and may explain the unexpectedly high masses of merging black holes detected last year.
“This study is an effort to bring together a broad set of ideas and observations to test how well they fit, and the fit is surprisingly good,” said Alexander Kashlinsky, an astrophysicist at NASA Goddard. “If this is correct, then all galaxies, including our own, are embedded within a vast sphere of black holes each about 30 times the sun’s mass.”
In 2005, Kashlinsky led a team of astronomers using NASA’s Spitzer Space Telescope to explore the background glow of infrared light in one part of the sky. The researchers reported excessive patchiness in the glow and concluded it was likely caused by the aggregate light of the first sources to illuminate the universe more than 13 billion years ago. Follow-up studies confirmed that this cosmic infrared background (CIB) showed similar unexpected structure in other parts of the sky.
In 2013, another study compared how the cosmic X-ray background (CXB) detected by NASA’s Chandra X-ray Observatory compared to the CIB in the same area of the sky. The first stars emitted mainly optical and ultraviolet light, which today is stretched into the infrared by the expansion of space, so they should not contribute significantly to the CXB.
Yet the irregular glow of low-energy X-rays in the CXB matched the patchiness of the CIB quite well. The only object we know of that can be sufficiently luminous across this wide an energy range is a black hole. The research team concluded that primordial black holes must have been abundant among the earliest stars, making up at least about one out of every five of the sources contributing to the CIB.
The nature of dark matter remains one of the most important unresolved issues in astrophysics. Scientists currently favor theoretical models that explain dark matter as an exotic massive particle, but so far searches have failed to turn up evidence these hypothetical particles actually exist. NASA is currently investigating this issue as part of its Alpha Magnetic Spectrometer and Fermi Gamma-ray Space Telescope missions.
“These studies are providing increasingly sensitive results, slowly shrinking the box of parameters where dark matter particles can hide,” Kashlinsky said. “The failure to find them has led to renewed interest in studying how well primordial black holes—black holes formed in the universe’s first fraction of a second—could work as dark matter.”
Physicists have outlined several ways in which the hot, rapidly expanding universe could produce primordial black holes in the first thousandths of a second after the Big Bang. The older the universe is when these mechanisms take hold, the larger the black holes can be. And because the window for creating them lasts only a tiny fraction of the first second, scientists expect primordial black holes would exhibit a narrow range of masses.
Primordial black holes, if they exist, could be similar to the merging black holes detected by the LIGO team in 2014. This computer simulation shows in slow motion what this merger would have looked like up close. The ring around the black holes, called an Einstein ring, arises from all the stars in a small region directly behind the holes whose light is distorted by gravitational lensing. The gravitational waves detected by LIGO are not shown in this video, although their effects can be seen in the Einstein ring. Gravitational waves traveling out behind the black holes disturb stellar images comprising the Einstein ring, causing them to slosh around in the ring even long after the merger is complete. Gravitational waves traveling in other directions cause weaker, shorter-lived sloshing everywhere outside the Einstein ring. If played back in real time, the movie would last about a third of a second. Credit: SXS Lensing
On Sept. 14, gravitational waves produced by a pair of merging black holes 1.3 billion light-years away were captured by the Laser Interferometer Gravitational-Wave Observatory (LIGO) facilities in Hanford, Washington, and Livingston, Louisiana. This event marked the first-ever detection of gravitational waves as well as the first direct detection of black holes. The signal provided LIGO scientists with information about the masses of the individual black holes, which were 29 and 36 times the sun’s mass, plus or minus about four solar masses. These values were both unexpectedly large and surprisingly similar.
“Depending on the mechanism at work, primordial black holes could have properties very similar to what LIGO detected,” Kashlinsky explained. “If we assume this is the case, that LIGO caught a merger of black holes formed in the early universe, we can look at the consequences this has on our understanding of how the cosmos ultimately evolved.”
In his new paper, published May 24 in The Astrophysical Journal Letters, Kashlinsky analyzes what might have happened if dark matter consisted of a population of black holes similar to those detected by LIGO. The black holes distort the distribution of mass in the early universe, adding a small fluctuation that has consequences hundreds of millions of years later, when the first stars begin to form.
For much of the universe’s first 500 million years, normal matter remained too hot to coalesce into the first stars. Dark matter was unaffected by the high temperature because, whatever its nature, it primarily interacts through gravity. Aggregating by mutual attraction, dark matter first collapsed into clumps called minihaloes, which provided a gravitational seed enabling normal matter to accumulate. Hot gas collapsed toward the minihaloes, resulting in pockets of gas dense enough to further collapse on their own into the first stars. Kashlinsky shows that if black holes play the part of dark matter, this process occurs more rapidly and easily produces the lumpiness of the CIB detected in Spitzer data even if only a small fraction of minihaloes manage to produce stars.
As cosmic gas fell into the minihaloes, their constituent black holes would naturally capture some of it too. Matter falling toward a black hole heats up and ultimately produces X-rays. Together, infrared light from the first stars and X-rays from gas falling into dark matter black holes can account for the observed agreement between the patchiness of the CIB and the CXB.
Occasionally, some primordial black holes will pass close enough to be gravitationally captured into binary systems. The black holes in each of these binaries will, over eons, emit gravitational radiation, lose orbital energy and spiral inward, ultimately merging into a larger black hole like the event LIGO observed.
“Future LIGO observing runs will tell us much more about the universe’s population of black holes, and it won’t be long before we’ll know if the scenario I outline is either supported or ruled out,” Kashlinsky said.
Kashlinsky leads science team centered at Goddard that is participating in the European Space Agency’s Euclid mission, which is currently scheduled to launch in 2020. The project, named LIBRAE, will enable the observatory to probe source populations in the CIB with high precision and determine what portion was produced by black holes.
– Credit and Resource –
More information: A. Kashlinsky. LIGO GRAVITATIONAL WAVE DETECTION, PRIMORDIAL BLACK HOLES, AND THE NEAR-IR COSMIC INFRARED BACKGROUND ANISOTROPIES, The Astrophysical Journal (2016). DOI: 10.3847/2041-8205/823/2/L25 , On Arxiv: arxiv.org/abs/1605.04023
Journal reference: Astrophysical Journal Letters, Astrophysical Journal, arXiv
Provided by: NASA
Link Between Primordial Black Holes and Dark Matter
Neuroscientists illuminate role of autism gene
Neuroscientists illuminate role of autism linked gene. Loss of Shank gene prevents neuronal synapses from properly maturing.
Scientia — A new study from MIT neuroscientists reveals that a gene mutation associated with autism plays a critical role in the formation and maturation of synapses — the connections that allow neurons to communicate with each other.
Many genetic variants have been linked to autism, but only a handful are potent enough to induce the disorder on their own. Among these variants, mutations in a gene called Shank3 are among the most common, occurring in about 0.5 percent of people with autism.
Scientists know that Shank3 helps cells respond to input from other neurons, but because there are two other Shank proteins, and all three can fill in for each other in certain ways, it has been difficult to determine exactly what the Shank proteins are doing.
“It’s clearly regulating something in the neuron that’s receiving a synaptic signal, but some people find one role and some people find another,” says Troy Littleton, a professor in the departments of Biology and of Brain and Cognitive Sciences at MIT, a member of MIT’s Picower Institute for Learning and Memory, and the senior author of the study. “There’s a lot of debate over what it really does at synapses.”
Key to the study is that fruit flies, which Littleton’s lab uses to study synapses, have only one version of the Shank gene. By knocking out that gene, the researchers eliminated all Shank protein from the flies.
“This is the first animal where we have completely removed all Shank family proteins,” says Kathryn Harris, a Picower Institute research scientist and lead author of the paper, which appears in the May 25 issue of the Journal of Neuroscience.
Synaptic organization
Scientists already knew that the Shank proteins are scaffold proteins, meaning that they help to organize the hundreds of other proteins found in the synapse of a postsynaptic cell — a cell that receives signals from a presynaptic cell. These proteins help to coordinate the cell’s response to the incoming signal.
“Shank is essentially a hub for signaling,” Harris says. “It brings in a lot of other partners and plays an organizational role at the postsynaptic membrane.”
In fruit flies lacking the Shank protein, the researchers found two dramatic effects. First, the postsynaptic cells had many fewer boutons, which are the sites where neurotransmitter release occurs. Second, many of the boutons that did form were not properly developed; that is, they were not surrounded by all of the postsynaptic proteins normally found there, which are required to respond to synaptic signals.
The researchers are now studying how this reduction in functional synapses affects the brain. Littleton suspects that the development of neural circuits could be impaired, which, if the same holds true in humans, may help explain some of the symptoms seen in autistic people.
“During critical windows of social and language learning, we reshape our connections to drive connectivity patterns that respond to rewards and language and social interactions,” he says. “If Shank is doing similar things in the mammalian brain, one could imagine potentially having those circuits form relatively normally early on, but if they fail to properly mature and form the proper number of connections, that could lead to a variety of behavioral defects.”
Pinpointing an exact link to autism symptoms would be difficult to do in fruit fly studies, however.
“Although the core molecular machines that allow neurons to communicate are highly conserved between fruit flies and humans, the anatomy of the various circuits that are formed during evolution are quite different,” Littleton says. “It’s hard to jump from a synaptic defect in the fly to an autism-like phenotype because the circuits are so different.”
An unexpected link
The researchers also showed, for the first time, that loss of Shank affects a well-known set of proteins that comprise the Wnt (also known as Wingless) signaling pathway. When a Wnt protein binds to a receptor on the cell, it initiates a series of interactions that influence which genes are turned on. This, in turn, contributes to many cell processes including embryonic development, tissue regeneration, and tumor formation.
When Shank is missing from fruit flies, Wnt signaling is disrupted because the receptor that normally binds to Wnt fails to be internalized by the cell. Normally, a small segment of the activated receptor moves to the cell nucleus and influences the transcription of genes that promote maturation of synapses. Without Shank, Wnt signaling is impaired and the synapses do not fully mature.
“The Shank protein and the Wnt protein family are thought to be involved in autism independently, but the fact that this study discovered that Wnt and Shank are interacting brings the story into better focus,” says Bryan Stewart, a professor of cell and systems biology at the University of Toronto at Mississauga, who was not involved in the research. “Now we can look and see if those interactions between Wnt and Shank are potentially responsible for their role in autism.”
The finding raises the possibility of treating autism with drugs that promote Wnt signaling, if the same connection is found in humans.
“Because the link to Wnt signaling is new and hasn’t been picked up in mammalian studies, we really hope that that can inspire people to look for a connection to Wnt signaling in mammalian models, and maybe that can offer another avenue for how loss of Shank could be counteracted,” Harris says.
– Credit and Resource –
The research was funded by the National Institutes of Health and the Simons Center for the Social Brain at MIT.
Anne Trafton | MIT News Office
Neuroscientists illuminate role of autism gene
Automatic bug finder - Analysis Practical Coding
Automatic bug finder. System could make complex analysis practical for programs that import huge swaths of code.
Scientia — Symbolic execution is a powerful software-analysis tool that can be used to automatically locate and even repair programming bugs. Essentially, it traces out every path that a program’s execution might take.
But it tends not to work well with applications written using today’s programming frameworks. An application might consist of only 1,000 lines of new code, but it will generally import functions — such as those that handle virtual buttons — from a programming framework, which includes huge libraries of frequently reused code. The additional burden of evaluating the imported code makes symbolic execution prohibitively time consuming.
Computer scientists address this problem by creating simple models of the imported libraries, which describe their interactions with new programs but don’t require line-by-line evaluation of their code. Building the models, however, is labor-intensive and error prone, and the models require regular updates, as programming frameworks are constantly evolving.
Researchers at MIT’s Computer Science and Artificial Intelligence Laboratory, working with colleagues at the University of Maryland, have taken an important step toward enabling symbolic execution of applications written using programming frameworks, with a system that automatically constructs models of framework libraries.
The researchers compared a model generated by their system with a widely used model of Java’s standard library of graphical-user-interface components, which had been laboriously constructed over a period of years. They found that their new model plugged several holes in the hand-coded one.
They described their results in a paper they presented last week at the International Conference on Software Engineering. Their work was funded by the National Science Foundation’s Expeditions Program.
“Forty years ago, if you wanted to write a program, you went in, you wrote the code, and basically all the code you wrote was the code that executed,” says Armando Solar-Lezama, an associate professor of electrical engineering and computer science at MIT, whose group led the new work. “But today, if you want to write a program, you go and bring in these huge frameworks and these huge pieces of functionality that you then glue together, and you write a little code to get them to interact with each other. If you don’t understand what that big framework is doing, you’re not even going to know where your program is going to start executing.”
Consequently, a program analyzer can’t just dispense with the framework code and concentrate on the newly written code. But symbolic execution works by stepping through every instruction that a program executes for a wide range of input values. That process becomes untenable if the analyzer has to evaluate every instruction involved in adding a virtual button to a window — the positioning of the button on the screen, the movement of the button when the user scrolls down the window, the button’s change of appearance when it’s pressed, and so on.
For purposes of analysis, all that matters is what happens when the button is pressed, so that’s the only aspect of the button’s functionality that a framework model needs to capture. More precisely, the model describes only what happens when code imported from a standard programming framework returns control of a program to newly written code.
“The only thing we care about is what crosses the boundary between the application and the framework,” says Xiaokang Qiu, a postdoc in Solar-Lezama’s lab and a co-author on the new paper. “The framework itself is like a black box that we want to abstract away.”
To generate their model, the researchers ran a suite of tutorials designed to teach novices how to program in Java. Their system automatically tracked the interactions between the tutorial code and the framework code that the tutorials imported.
“The nice thing about tutorials is that they’re designed to help people understand how the framework works, so they’re also a good way to teach the synthesizer how the framework works,” Solar-Lezama says. “The problem is that if I just show you a trace of what my program did, there’s an infinite set of programs that could behave like that trace.”
To winnow down that set of possibilities, the researchers’ system tries to fit the program traces to a set of standard software “design patterns.” First proposed in the late 1970s and popularized in a 1995 book called “Design Patterns,” design patterns are based on the idea that most problems in software engineering fit into just a few categories, and their solutions have just a few general shapes.
Computer scientists have identified roughly 20 design patterns that describe communication between different components of a computer program. Solar-Lezama, Qiu, and their Maryland colleagues — Jinseong Jeon, Jonathan Fetter-Degges, and Jeffrey Foster — built four such patterns into their new system, which they call Pasket, for “pattern sketcher.” For any given group of program traces, Pasket tries to fit it to each of the design patterns, selecting only the one that works best.
Because a given design pattern needs to describe solutions to a huge range of problems that vary in their particulars, in the computer science literature, they’re described in very general terms. Fortunately, Solar-Lezama has spent much of his career developing a system, called Sketch, that takes general descriptions of program functionality and fills in the low-level computational details. Sketch is the basis of most of his group’s original research, and it’s what reconciles design patterns and program traces in Pasket.
“The availability of models for frameworks such as Swing [Java’s library of graphical-user-interface components] and Android is critical for enabling symbolic execution of applications built using these frameworks,” says Rajiv Gupta, a professor of computer science and engineering at the University of California at Riverside. “At present, framework models are developed and maintained manually. This work offers a compelling demonstration of how far synthesis technology has advanced. The scalability of Pasket is impressive — in a few minutes, it synthesized nearly 2,700 lines of code. Moreover, the generated models compare favorably with manually created ones.”
– Credit and Resource –
Larry Hardesty | MIT News Office
Automatic bug finder - Analysis Practical Coding
Juno Spacecraft Crosses Jupiter/Sun Gravity Boundary
NASA’s Juno Spacecraft Crosses Jupiter/Sun Gravitational Boundary
Scientia — Since its launch five years ago, there have been three forces tugging at NASA’s Juno spacecraft as it speeds through the solar system. The sun, Earth and Jupiter have all been influential — a gravitational trifecta of sorts. At times, Earth was close enough to be the frontrunner. More recently, the sun has had the most clout when it comes to Juno’s trajectory. Today, it can be reported that Jupiter is now in the gravitational driver’s seat, and the basketball court-sized spacecraft is not looking back.
This artist’s rendering shows NASA’s Juno spacecraft making one of its close passes over Jupiter.
Credits: NASA/JPL-Caltech
“Today the gravitational influence of Jupiter is neck and neck with that of the sun,” said Rick Nybakken, Juno project manager at NASA’s Jet Propulsion Laboratory in Pasadena, California. “As of tomorrow, and for the rest of the mission, we project Jupiter’s gravity will dominate as the trajectory-perturbing effects by other celestial bodies are reduced to insignificant roles.”
Juno was launched on Aug. 5, 2011. On July 4 of this year, it will perform a Jupiter orbit insertion maneuver — a 35-minute burn of its main engine, which will impart a mean change in velocity of 1,212 mph (542 meters per second) on the spacecraft. Once in orbit, the spacecraft will circle the Jovian world 37 times, skimming to within 3,100 miles (5,000 kilometers) above the planet’s cloud tops. During the flybys, Juno will probe beneath the obscuring cloud cover of Jupiter and study its auroras to learn more about the planet’s origins, structure, atmosphere and magnetosphere.
Juno’s name comes from Greek and Roman mythology. The mythical god Jupiter drew a veil of clouds around himself to hide his mischief, and his wife — the goddess Juno — was able to peer through the clouds and reveal Jupiter’s true nature.
NASA’s Jet Propulsion Laboratory, Pasadena, California, manages the Juno mission for the principal investigator, Scott Bolton, of Southwest Research Institute in San Antonio. Juno is part of NASA’s New Frontiers Program, which is managed at NASA’s Marshall Space Flight Center in Huntsville, Alabama, for NASA’s Science Mission Directorate. Lockheed Martin Space Systems, Denver, built the spacecraft. The California Institute of Technology in Pasadena manages JPL for NASA.
– Credit and Resource –
NASA
Juno Spacecraft Crosses Jupiter/Sun Gravity Boundary
Life on Ceres
Life on Ceres? Mysterious changes in the bright spots still baffle scientists
Scientia –Bright spots on the dwarf planet Ceres continue to puzzle researchers. When recently a team of astronomers led by Paolo Molaro of the Trieste Astronomical Observatory in Italy, conducted observations of these features, they found out something unexpected. The scientists were surprised to detect that the spots brighten during the day and also show other variations. This variability still remains a mystery.
The bright features have been discovered by NASA’s Dawn spacecraft which is orbiting this dwarf planet, constantly delivering substantial information about it. These spots reflect far more light than their much darker surroundings. The composition of these features is discussed as the scientists debate if they are made of water ice, of evaporated salts, or something else.
Molaro and his colleagues studied the spots on Ceres in July and August 2015, using the High Accuracy Radial velocity Planet Searcher (HARPS), as was reported by the European Southern Observatory (ESO) earlier this year. This instrument, mounted on ESO’s 3.6m telescope at La Silla Observatory in Chile, enables measurements of radial velocities with the highest accuracy currently available.
By utilizing HARPS, the researchers found out unexpected changes in the mysterious bright spots. However, at the beginning they thought that it was an instrumental problem. But after double checking, they had to conclude that the radial velocity anomalies were likely real. Then the team noticed that they were connected to periods of time when the bright spots in the Occator crater were visible from the Earth. So the scientists made an association between them.
However, these detected variations still continue to perplex the astronomers as they haven’t found a plausible explanation for their occurrence.
“We know nothing about these changes, really. And this increases the mystery of these spots,” Molaro told Astrowatch.net.
One of the proposed hypotheses is that the observed changes could be triggered by the presence of volatile substances that evaporate due to solar radiation. When the spots are on the side illuminated by the sun they form plumes that reflect sunlight very effectively. The scientists suggest that these plumes then evaporate quickly, lose reflectivity and produce the observed changes.
“It is already well known that a lot of water hides beneath the surface of Ceres, so water ice or clathrates hydrates are the most natural hypotheses. But a proper answer will be hopefully provided by scientists working in the Dawn team in the coming months,” Molaro said.
He noted that the indication of variability needs to be confirmed by direct imaging of Occator’s bright spot at the highest available spatial resolution.
“This kind of measurements are underway. I would say that the detection of a variability improves our ignorance rather than our understanding of this planetary body,” Molaro revealed.
The team is currently applying for further observations by the end of this year to repeat in a more systematical way what they have done in their pilot project. An important aspect of their work is to have shown a new way to study Ceres from ground, which could turn out to be useful even after the end of the Dawn mission. However by now, they are eager to see the results from the Dawn spacecraft in the next months.
If the team’s theory is confirmed, Ceres would seem to be internally active. While this dwarf planet is known to be rich in water, it is unclear whether this is related to the bright spots. It is also still debated if Ceres due to its vast reservoir of water, could be a suitable place to host microbial life.
“Life as we know it on Earth needs liquid water, biogenic elements and a stable source of energy. Is Ceres a good place to have these things simultaneously and for a substantial amount of time, like billions of years? Nobody knows at the moment,” Molaro concluded.
A little about Ceres
- -Discovered: January 1,1801 by Giuseppe Piazzi of Italy (first asteroid/dwarf planet discovered)
- -Size: 975 by 909 kilometers (606 by 565 miles)
- -Shape: Spheroid
- -Rotation: Once every 9 hours, 4.5 minutes
The object is known by astronomers as “1 Ceres” because it was the very first minor planet discovered. As big across as Texas, Ceres’ nearly spherical body has a differentiated interior – meaning that, like Earth, it has denser material at the core and lighter minerals near the surface. Astronomers believe that water ice may be buried under Ceres’ crust because its density is less than that of the Earth’s crust, and because the dust-covered surface bears spectral evidence of water-bearing minerals. Ceres could even boast frost-covered polar caps.
Astronomers estimate that if Ceres were composed of 25 percent water, it may have more water than all the fresh water on Earth. Ceres’ water, unlike Earth’s, is expected to be in the form of water ice located in its mantle.
– Credit and Resource –
NASA
Life on Ceres
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