The crafty chemist

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Posts tagged with "physics"

thekidshouldseethis:

This Rube Goldberg machine is “powered” by a single beam of light, using mirrors, magnifying glasses, and reflective surfaces to burn through strings, melt ice, pop balloons, and more… 
Watch the video.

thekidshouldseethis:

This Rube Goldberg machine is “powered” by a single beam of light, using mirrors, magnifying glasses, and reflective surfaces to burn through strings, melt ice, pop balloons, and more… 

Watch the video.

Sep 9

The Weissenburg effect

In the above gif (clear liquid) a dilute (0.025 wt%) solution of a high molecular weight (2×106 g/mol) polystyrene polymer (Polysciences Inc) is dissolved in a low molecular weight (~100 g/mol) newtonian viscous (~30 Pa.s) solvent (Piccolastic, Hercules Inc).

In the experiment a rod is rotated with its end immersed in the fluid outlined above.  In the Newtonian case inertia would dominate and the fluid would move to the edges of the container,away from the rod. 

Here however the elastic forces generated by the rotation of the rod (and the consequent stretching of the polymer chainsin solution) result in a positive normal force - the fluid rises up the rod.  The bulbous shape remaining at the end of the video is the onset of instability as the mass that has been forced up the rod a) relaxes and b) overcomes the force pushing from below.

Source

Video source, GIF source

Sep 8
invaderxan:

A cardboard cut-out of a cat imaged by photons that never went through the cut-out itself. Physicists have devised a way to take pictures using light that has not interacted with the object being photographed.
[x]

This is just so weird:

The researchers imaged a cut-out of a cat, a few millimetres wide, as well as other shapes etched into silicon. The team probed the cat cut-out using a wavelength of light which they knew could not be detected by their camera. “That’s important, it’s the proof that it’s working,” says Zeilinger.

but that’s because:

One advantage of the technique is that the two photons need not be of the same energy, Zeilinger says, meaning that the light that touches the object can be of a different colour than the light that is detected. For example, a quantum imager could probe delicate biological samples by sending low-energy photons through them while building up the image using visible-range photons and a conventional camera. (The work is published in the 28 August issue of Nature1.)
Zeilinger and his colleagues based the technique on an idea first outlined in 1991, in which there are two paths down which a photon can travel. Each contains a crystal that turns the particle into a pair of entangled photons2, 3. But only one path contains the object to be imaged.
According to the laws of quantum physics, if no one detects which path a photon took, the particle effectively has taken both routes, and a photon pair is created in each path at once, says Gabriela Barreto Lemos, a physicist at Austrian Academy of Sciences and a co-author on the latest paper.
In the first path, one photon in the pair passes through the object to be imaged, and the other does not. The photon that passed through the object is then recombined with its other ‘possible self’ — which travelled down the second path and not through the object — and is thrown away. The remaining photon from the second path is also reunited with itself from the first path and directed towards a camera, where it is used to build the image, despite having never interacted with the object.

This is the strangest thing I’ve read all week.

invaderxan:

A cardboard cut-out of a cat imaged by photons that never went through the cut-out itself. Physicists have devised a way to take pictures using light that has not interacted with the object being photographed.

[x]

This is just so weird:

The researchers imaged a cut-out of a cat, a few millimetres wide, as well as other shapes etched into silicon. The team probed the cat cut-out using a wavelength of light which they knew could not be detected by their camera. “That’s important, it’s the proof that it’s working,” says Zeilinger.

but that’s because:

One advantage of the technique is that the two photons need not be of the same energy, Zeilinger says, meaning that the light that touches the object can be of a different colour than the light that is detected. For example, a quantum imager could probe delicate biological samples by sending low-energy photons through them while building up the image using visible-range photons and a conventional camera. (The work is published in the 28 August issue of Nature1.)

Zeilinger and his colleagues based the technique on an idea first outlined in 1991, in which there are two paths down which a photon can travel. Each contains a crystal that turns the particle into a pair of entangled photons2, 3. But only one path contains the object to be imaged.

According to the laws of quantum physics, if no one detects which path a photon took, the particle effectively has taken both routes, and a photon pair is created in each path at once, says Gabriela Barreto Lemos, a physicist at Austrian Academy of Sciences and a co-author on the latest paper.

In the first path, one photon in the pair passes through the object to be imaged, and the other does not. The photon that passed through the object is then recombined with its other ‘possible self’ — which travelled down the second path and not through the object — and is thrown away. The remaining photon from the second path is also reunited with itself from the first path and directed towards a camera, where it is used to build the image, despite having never interacted with the object.

This is the strangest thing I’ve read all week.

Sep 6

The Coanda effect

"So, one would expect the air to flow out of the fan horizontally in all directions, but due to the Coanda effect; the air bends down, to almost 90 degrees.

The airflow is being pushed down by the air above, because the pressure of the air in between the flow and the curved surface, is reduced by the suction of the airflow.

Air is being accelerated down, and part of the upper surface is in touch with reduced air pressure. This action gives the object a force up, thrust, that can lift the object.
Henri Coanda realized this, and then designed a flying disc based on this effect, in 1932!”

The Coanda effect, named after Romanian aerospace pioneer Henri Coanda is the basis of an experimental flying saucer which went into production in 1958. Albeit it couldn’t fly more than a couple of feet off the ground, but theoretically if it were lighter it should have been able to overcome the ground effect and fly. It was called the Avrocar; it wasn’t very practical however due to it’s instability, noise, and overheating problems - only two were ever produced before the program was disbanded by the US military. The design was thought to be the inspiration for the first hover craft.

Video source, Avrocar image source, Avrocar video

8bitfuture:

Worlds fastest camera shoots 4.4 trillion frames per second.
A Japanese team has created a recording device able to acquire 4.4 trillion images per second, at a 450 x 450 pixel resolution. The technique could be used to further research into heat conduction and chemical reactions, according to its creators.
If the resolution can be improved, it could also prove useful for manufacturing, where it could keep track of laser cuttings in real time.

The technique, known as a Sequentially Timed All-optical Mapping Photography, or STAMP for short, shuns the conventional methods employed by other superspeed cameras to achieve results up to 1,000 times faster than has been previously available. The current leading brand of high-speed real-time recording is a method unfortunately known as the pump-probe process, where light is “pumped” at the subject and then “probed” for absorption. STAMP differs from this by skipping the need to constantly probe, or measure, the scene to construct an image, instead it uses single-shot bursts to acquire images and maps the spatial profile of the subject to the temporal profile at a 450x450-pixel resolution.


Just to clarifying the below gif is imaging at 1 trillion frames per second. You can actually see light is slowed down enough to perceive it’s movement using one of these cameras.

8bitfuture:

Worlds fastest camera shoots 4.4 trillion frames per second.

A Japanese team has created a recording device able to acquire 4.4 trillion images per second, at a 450 x 450 pixel resolution. The technique could be used to further research into heat conduction and chemical reactions, according to its creators.

If the resolution can be improved, it could also prove useful for manufacturing, where it could keep track of laser cuttings in real time.

The technique, known as a Sequentially Timed All-optical Mapping Photography, or STAMP for short, shuns the conventional methods employed by other superspeed cameras to achieve results up to 1,000 times faster than has been previously available. The current leading brand of high-speed real-time recording is a method unfortunately known as the pump-probe process, where light is “pumped” at the subject and then “probed” for absorption. STAMP differs from this by skipping the need to constantly probe, or measure, the scene to construct an image, instead it uses single-shot bursts to acquire images and maps the spatial profile of the subject to the temporal profile at a 450x450-pixel resolution.

Just to clarifying the below gif is imaging at 1 trillion frames per second. You can actually see light is slowed down enough to perceive it’s movement using one of these cameras.

starstuffblog:

Researchers map quantum vortices inside superfluid helium nanodroplets
First ever snapshots of spinning nanodroplets reveal surprising features Scientists have, for the first time, characterized so-called quantum vortices that swirl within tiny droplets of liquid helium. The research, led by scientists at the U.S. Department of Energy’s Lawrence Berkeley National Laboratory (Berkeley Lab), the University of Southern California, and SLAC National Accelerator Laboratory, confirms that helium nanodroplets are in fact the smallest possible superfluidic objects and opens new avenues to study quantum rotation.
"The observation of quantum vortices is one of the most clear and unique demonstrations of the quantum properties of these microscopic objects," says Oliver Gessner, senior scientist in the Chemical Sciences Division at Berkeley Lab. Gessner and colleagues, Andrey Vilesov of the University of Southern California and Christoph Bostedt of SLAC National Accelerator Laboratory at Stanford, led the multi-facility and multi-university team that published the work this week in Science.
The finding could have implications for other liquid or gas systems that contain vortices, says USC’s Vilesov. “The quest for quantum vortices in superfluid droplets has stretched for decades,” he says. “But this is the first time they have been seen in superfluid droplets.” Superfluid helium has long captured scientist’s imagination since its discovery in the 1930s. Unlike normal fluids, superfluids have no viscosity, a feature that leads to strange and sometimes unexpected properties such as crawling up the walls of containers or dripping through barriers that contained the liquid before it transitioned to a superfluid.
Helium superfluidity can be achieved when helium is cooled to near absolute zero (zero kelvin or about -460 degrees F). At this temperature, the atoms within the liquid no longer vibrate with heat energy and instead settle into a calm state in which all atoms act together in unison, as if they were a single particle.
For decades, researchers have known that when superfluid helium is rotated—in a little spinning bucket, say—the rotation produces quantum vortices, swirls that are regularly spaced throughout the liquid. But the question remained whether anyone could see this behavior in an isolated, nanoscale droplet. If the swirls were there, it would confirm that helium nanodroplets, which can range in size from tens of nanometers to microns, are indeed superfluid throughout and that the motion of the entire liquid drop is that of a single quantum object rather than a mixture of independent particles.
But measuring liquid flow in helium nanodroplets has proven to be a serious challenge. “The way these droplets are made is by passing helium through a tiny nozzle that is cryogenically cooled down to below 10 Kelvin,” says Gessner. “Then, the nanoscale droplets shoot through a vacuum chamber at almost 200 meters-per-second. They live once for a few milliseconds while traversing the experimental chamber and then they’re gone. How do you show that these objects, which are all different from one another, have quantum vortices inside?”
The researchers turned to a facility at SLAC called the Linac Coherent Light Source (LCLS), a DOE Office of Science user facility that is the world’s first x-ray free-electron laser. This laser produces very short light pulses, lasting just a ten-trillionth of a second, which contain a huge number of high-energy photons. These intense x-ray pulses can effectively take snapshots of single, ultra-fast, ultra-small objects and phenomena.
"With the new x-ray free electron laser, we can now image phenomenon and look at processes far beyond what we could imagine just a decade ago," says Bostedt of SLAC. "Looking at the droplets gave us a beautiful glimpse into the quantum world. It really opens the door to fascinating sciences."
In the experiment, the researchers blasted a stream of helium nanodroplets across the x-ray laser beam inside a vacuum chamber; a detector caught the pattern that formed when the x-ray light diffracted off the drops.
The diffraction patterns immediately revealed that the shape of many droplets were not spheres, as was previously assumed. Instead, they were oblate. Just as the Earth’s rotation causes it to bulge at the equator, so too do rotating nanodroplets expand around the middle and flatten at the top and bottom.
But the vortices themselves are invisible to x-ray diffraction, so the researchers used a trick of adding xenon atoms to the droplets. The xenon atoms get pulled into the vortices and cluster together.
"It’s similar to pulling the plug in a bathtub and watching the kids’ toys gather in the vortex," says Gessner. The xenon atoms diffract x-ray light much stronger than the surrounding helium, making the regular arrays of vortices inside the droplet visible. In this way, the researchers confirmed that vortices in nanodroplets behave as those found in larger amounts of rotating superfluid helium.
Armed with this new information, the researchers were able to determine the rotational speed of the nanodroplets. They were surprised to find that the nanodroplets spin up to 100,000 times faster than any other superfluid helium sample ever studied in a laboratory.
Moreover, while normal liquid drops will change shape as they spin faster and faster—to resemble a peanut or multi-lobed globule, for instance—the researchers saw no evidence of such shapeshifting in the helium nanodroplets. “Essentially, we’re exploring a new regime of quantum rotation with this matter,” Gessner says.
"It’s a new kind of matter in a sense because it is a self-contained isolated superfluid," he adds. "It’s just all by itself, held together by its own surface tension. It’s pretty perfect to study these system
 IMAGE…This is an illustration of analysis of superfluid helium nanodroplets. Droplets are emitted via a cooled nozzle (upper right) and probed with x-ray from the free-electron laser. The multicolored pattern (upper left) represents a diffraction pattern that reveals the shape of a droplet and the presence of quantum vortices such as those represented in the turquoise circle with swirls (bottom center).
Credit: Felix P. Sturm and Daniel S. Slaughter, Berkeley Lab.

starstuffblog:

Researchers map quantum vortices inside superfluid helium nanodroplets

First ever snapshots of spinning nanodroplets reveal surprising features

Scientists have, for the first time, characterized so-called quantum vortices that swirl within tiny droplets of liquid helium. The research, led by scientists at the U.S. Department of Energy’s Lawrence Berkeley National Laboratory (Berkeley Lab), the University of Southern California, and SLAC National Accelerator Laboratory, confirms that helium nanodroplets are in fact the smallest possible superfluidic objects and opens new avenues to study quantum rotation.

"The observation of quantum vortices is one of the most clear and unique demonstrations of the quantum properties of these microscopic objects," says Oliver Gessner, senior scientist in the Chemical Sciences Division at Berkeley Lab. Gessner and colleagues, Andrey Vilesov of the University of Southern California and Christoph Bostedt of SLAC National Accelerator Laboratory at Stanford, led the multi-facility and multi-university team that published the work this week in Science.

The finding could have implications for other liquid or gas systems that contain vortices, says USC’s Vilesov. “The quest for quantum vortices in superfluid droplets has stretched for decades,” he says. “But this is the first time they have been seen in superfluid droplets.”

Superfluid helium has long captured scientist’s imagination since its discovery in the 1930s. Unlike normal fluids, superfluids have no viscosity, a feature that leads to strange and sometimes unexpected properties such as crawling up the walls of containers or dripping through barriers that contained the liquid before it transitioned to a superfluid.

Helium superfluidity can be achieved when helium is cooled to near absolute zero (zero kelvin or about -460 degrees F). At this temperature, the atoms within the liquid no longer vibrate with heat energy and instead settle into a calm state in which all atoms act together in unison, as if they were a single particle.

For decades, researchers have known that when superfluid helium is rotated—in a little spinning bucket, say—the rotation produces quantum vortices, swirls that are regularly spaced throughout the liquid. But the question remained whether anyone could see this behavior in an isolated, nanoscale droplet. If the swirls were there, it would confirm that helium nanodroplets, which can range in size from tens of nanometers to microns, are indeed superfluid throughout and that the motion of the entire liquid drop is that of a single quantum object rather than a mixture of independent particles.

But measuring liquid flow in helium nanodroplets has proven to be a serious challenge. “The way these droplets are made is by passing helium through a tiny nozzle that is cryogenically cooled down to below 10 Kelvin,” says Gessner. “Then, the nanoscale droplets shoot through a vacuum chamber at almost 200 meters-per-second. They live once for a few milliseconds while traversing the experimental chamber and then they’re gone. How do you show that these objects, which are all different from one another, have quantum vortices inside?”

The researchers turned to a facility at SLAC called the Linac Coherent Light Source (LCLS), a DOE Office of Science user facility that is the world’s first x-ray free-electron laser. This laser produces very short light pulses, lasting just a ten-trillionth of a second, which contain a huge number of high-energy photons. These intense x-ray pulses can effectively take snapshots of single, ultra-fast, ultra-small objects and phenomena.

"With the new x-ray free electron laser, we can now image phenomenon and look at processes far beyond what we could imagine just a decade ago," says Bostedt of SLAC. "Looking at the droplets gave us a beautiful glimpse into the quantum world. It really opens the door to fascinating sciences."

In the experiment, the researchers blasted a stream of helium nanodroplets across the x-ray laser beam inside a vacuum chamber; a detector caught the pattern that formed when the x-ray light diffracted off the drops.

The diffraction patterns immediately revealed that the shape of many droplets were not spheres, as was previously assumed. Instead, they were oblate. Just as the Earth’s rotation causes it to bulge at the equator, so too do rotating nanodroplets expand around the middle and flatten at the top and bottom.

But the vortices themselves are invisible to x-ray diffraction, so the researchers used a trick of adding xenon atoms to the droplets. The xenon atoms get pulled into the vortices and cluster together.

"It’s similar to pulling the plug in a bathtub and watching the kids’ toys gather in the vortex," says Gessner. The xenon atoms diffract x-ray light much stronger than the surrounding helium, making the regular arrays of vortices inside the droplet visible. In this way, the researchers confirmed that vortices in nanodroplets behave as those found in larger amounts of rotating superfluid helium.

Armed with this new information, the researchers were able to determine the rotational speed of the nanodroplets. They were surprised to find that the nanodroplets spin up to 100,000 times faster than any other superfluid helium sample ever studied in a laboratory.

Moreover, while normal liquid drops will change shape as they spin faster and faster—to resemble a peanut or multi-lobed globule, for instance—the researchers saw no evidence of such shapeshifting in the helium nanodroplets. “Essentially, we’re exploring a new regime of quantum rotation with this matter,” Gessner says.

"It’s a new kind of matter in a sense because it is a self-contained isolated superfluid," he adds. "It’s just all by itself, held together by its own surface tension. It’s pretty perfect to study these system


IMAGE…This is an illustration of analysis of superfluid helium nanodroplets. Droplets are emitted via a cooled nozzle (upper right) and probed with x-ray from the free-electron laser. The multicolored pattern (upper left) represents a diffraction pattern that reveals the shape of a droplet and the presence of quantum vortices such as those represented in the turquoise circle with swirls (bottom center).

Credit: Felix P. Sturm and Daniel S. Slaughter, Berkeley Lab.

astrodidact:

http://pda.sciencealert.com.au/news/20141305-25508.html

hmmm…

Researchers have proved that the amount of heat graphene conducts changes depending on the length of the sample.
This contradicts Fourier’s law, which states thermal conductivity is an intrinsic material property that’s independent of size or shape.

astrodidact:

http://pda.sciencealert.com.au/news/20141305-25508.html

hmmm…

Researchers have proved that the amount of heat graphene conducts changes depending on the length of the sample.

This contradicts Fourier’s law, which states thermal conductivity is an intrinsic material property that’s independent of size or shape.

Hello! :) I was wondering why the electromagnetic spectrum stops at gamma rays. Why is there no kind of radiation with even more energy? Does it have to do with a "limit" on such small wavelengths (meaning, it's not possible to have a smaller wavelength)? Or is it because there is nothing in the universe capable of actually producing radiation with a higher energy than gamma rays? I was reading about GRB's and began wondering. :) Thanks a lot!

nanodash:

nanodash:

Hello!

Right…time to go research. NASA is probably a good place to start, hang on…

Well that didn’t help. Anyways.

The definition of gamma rays is a quare little duck. These days it’s that (with the exception of astronomical sources, which are crazy energetic anyway) X-Rays come from electrons and gamma rays come from nuclei (Like in radioactive decay). But this isn’t a strict definition, people mix them all the time. And yeah, the reason there’s nothing above them for now is the most energetic sources in the galaxy still just make gamma rays. The properties of the photon would have to change to call it something else. But…and here’s where it gets (more) interesting.

How big could a photon’s energy be? Well…The bigger the energy, the smaller the wavelength. The smallest length possible is theorised to be the Planck length. The Planck length is the smallest theoretical length that could ever be measured. Beyond that notions of space kind of break down. A photon that had a wavelength equal to the Planck length would have about 10 billion joules (10 Gigajoules) of energy). That’s about the same as 25 lightning bolts. In a single photon.

If you made a 5mW laser (a laser pointer) using these photons, to keep up that power it would need to release a single photon every 76000 years.

Which is awesome.

In case you missed it

mindblowingscience:

Getting a charge out of water droplets

Last year, MIT researchers discovered that when water droplets spontaneously jump away from superhydrophobic surfaces during condensation, they can gain electric charge in the process. Now, the same team has demonstrated that this process can generate small amounts of electricity that might be used to power electronic devices.
The new findings, by postdoc Nenad Miljkovic, associate professor of mechanical engineering Evelyn Wang, and two others, are published in the journalApplied Physics Letters.
This approach could lead to devices to charge cellphones or other electronics using just the humidity in the air. As a side benefit, the system could also produce clean water.
The device itself could be simple, Miljkovic says, consisting of a series of interleaved flat metal plates. Although his initial tests involved copper plates, he says any conductive metal would do, including cheaper aluminum.

Continue Reading.

mindblowingscience:

Getting a charge out of water droplets

Last year, MIT researchers discovered that when water droplets spontaneously jump away from superhydrophobic surfaces during condensation, they can gain electric charge in the process. Now, the same team has demonstrated that this process can generate small amounts of electricity that might be used to power electronic devices.

The new findings, by postdoc Nenad Miljkovic, associate professor of mechanical engineering Evelyn Wang, and two others, are published in the journalApplied Physics Letters.

This approach could lead to devices to charge cellphones or other electronics using just the humidity in the air. As a side benefit, the system could also produce clean water.

The device itself could be simple, Miljkovic says, consisting of a series of interleaved flat metal plates. Although his initial tests involved copper plates, he says any conductive metal would do, including cheaper aluminum.

Continue Reading.

txchnologist:

Electric Fields Made Visible

Physics educator James Lincoln helps people understand the natural world. The gifs above are from a Youtube video he made on how to “see” an electric field, the region around a charged object where electric force is experienced. When the object is positively charged, electric field lines extend radially outward from the object. When the object is negatively charged, the lines extend radially inward.  

Click the gifs for more info or see the full video below.

Read More