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First Chilling Laser Developed for Bio Research (Not Supervillainy)

 

Since the first laser was invented in 1960, they’ve almost always given off heat—either as a useful tool, a byproduct, or a fictional way to vanquish intergalactic enemies. Until now, however, those concentrated beams of light have never been able to cool liquids. University of Washington researchers are the first to solve a decades-old puzzle—figuring out how to make a laser refrigerate water and other liquids under real-world conditions.

In a study published in the Proceedings of the National Academy of Sciences, the team used an infrared laser to cool water by about 36°F—a major breakthrough in the field.

“Typically, when you go to the movies and see Star Wars laser blasters, they heat things up. This is the first example of a laser beam that will refrigerate liquids like water under everyday conditions,” said senior author Peter Pauzauskie, UW aLaser-cooled nanocrystals emit a reddish-green glow that can be seen by the naked eye.ssistant professor of materials science and engineering. “It was really an open question as to whether this could be done because normally water warms when illuminated.”

The discovery could help industrial users “point cool” tiny areas with a focused point of light. Microprocessors, for instance, might someday use a laser beam to cool specific components in computer chips to prevent overheating and enable more efficient information processing.

Scientists could also use a laser beam to precisely cool a portion of a cell as it divides or repairs itself, essentially slowing these rapid processes down and giving researchers the opportunity to see how they work. Or they could cool a single neuron in a network—essentially silencing without damaging it—to see how its neighbors bypass it and rewire themselves.

“There’s a lot of interest in how cells divide and how molecules and enzymes function, and it’s never been possible before to refrigerate them to study their properties,” said Pauzauskie, who is also a scientist at the US DoE’s Pacific Northwest National Laboratory in Richland, WA. “Using laser cooling, it may be possible to prepare slow-motion movies of life in action. And the advantage is that you don’t have to cool the entire cell, which could kill it or change its behavior.”

The UW team chose infrared light for its cooling laser with biological applications in mind, as visible light could burn cells. They demonstrated that the laser could refrigerate saline solution and cell culture media that are commonly used in genetic and molecular research.

To achieve the breakthrough, the UW team used a material commonly found in commercial lasers but essentially ran the laser phenomenon in reverse. They illuminated a single microscopic crystal suspended in water with infrared laser light to excite a unique kind of glow that has slightly more energy than that amount of light absorbed.

This higher-energy glow carries heat away from both the crystal and the water surrounding it. The laser refrigeration process was first demonstrated in vacuum conditions at Los Alamos National Laboratory in 1995, but it has taken nearly 20 years to demonstrate this process in liquids.


NASA Robots Off to School

NASA has announced that it hopes to eventually send its mighty R5 Valkyrie robots to Mars—but that first they need to go to college.

NASA is interested in humanoid robots because they can help or even take the place of astronauts working in extreme space environments. Robots, like the R5, could be used in future NASA missions either as precursor robots performing mission tasks before humans arrive or as human-assistive robots actively collaborating with the human crew.

The 1.8-m, 131-kg and immensely strong R5 Valkyrie model was originally designed to complete disaster-relief maneuvers, so to get it ready for the tougher conditions of deep space, two prototypes are being sent to two universities—one each to Massachusetts Institute of Technology (MIT; Cambridge, MA) and Northeastern University (Boston, MA). Each school will receive up to $250,000 per year for two years to fund research, along with technical support from NASA.

No, the robots won’t be matriculating and won’t have to stay iNASA R5 Valkyrie robot: Before it goes to Mars, it’s going to college.n the freshman dorms—although it’s fun to imagine them at freshman mixers or in line at the cafeteria. Instead, they’ll be the subjects of research programs. The schools were chosen through a competitive selection process from groups entered in the Defense Advanced Research Projects Agency (DARPA) Robotics Challenge. MIT’s proposal, “Robust Autonomy for Extreme Space Environments” was made by an MIT Computer Science and Artificial Intelligence Laboratory (CSAIL) team led by principal investigator Russ Tedrake. The other winning proposal, “Accessible Testing on Humanoid-Robot-R5 and Evaluation of NASA Administered (ATHENA) Space Robotics Challenge,” was from a Northeastern University team led by principal investigator Taskin Padir.

“Advances in robotics, including human-robotic collaboration, are critical to developing the capabilities required for our journey to Mars,” said Steve Jurczyk, associate administrator for the Space Technology Mission Directorate (STMD) at NASA Headquarters in Washington. “We are excited to engage these university research groups to help NASA with this next big step in robotics technology development.”

According to an MIT news release, Tedrake serves as head of CSAIL’s Robot Locomotion Group and is no stranger to “educating” autonomous robots. “Over the past three years he led a team of more than 20 researchers to develop algorithms for a government competition to get another 6-foot-tall humanoid robot named Atlas to open doors, turn valves, drill holes, climb stairs, scramble over cinder blocks, and drive a car—all in the space of one hour.”

After the two-year programs are completed, the robots are expected to return to NASA—though without diplomas: it takes more than strength and dexterity to earn those.


Assessing Laser Weld Quality: The Shadow Knows

Without physically testing a laser weld one usually resorts to assessing its quality by assessing its appearance. The morphology of the molten pools created by laser welding is the final outward manifestation of combined variables such as the metal vapor pressure, surface tension, gravity, and the pressure of the shielding gas, and it plays an important role in determining the weld appearance. An experienced laser welder will be able to look at a weld and have a good idea if it is of qood quality.

The challenge is to enable that assesment to happen quickly enough that it can keep pace with the high welding speeds made possible by modern laser welding equipment. Can the inspection be simplified enough to be automated?
Laser weld shadow analysis: experimental setup.
Yanxi Zhang and Xiangdong Gao of Guangdong University of Technology (Guangzhou, China) and Seiji Katayama of Osaka University’s Joining and Welding Research Institute (Osaka, Japan) joined together to throw some light on the subject. They made a high-speed visual sensing system that used an auxiliary diode laser light to illuminate molten pools and cast their shadow. A high-speed (5000 frames/sec) camera captures visual morphology information, recording the area of a casted shadow, maximal distance between points in the shadow and the keyhole position, the maximal width and the tilt of the shadow.

In “Weld Appearance Prediction with BP Neural Network Improved by Genetic Algorithm during Disk Laser Welding,” published in SME’s Journal of Manufacturing Processes, the scientists describe how they applied principal components analysis (PCA) ito analyze the characteristics of the molten pools’ shadow in order to reduce their redundancy. Then BP neural network improved by genetic algorithm (GABP) was used to model the relation between welding appearance and the characteristics of the molten-pool-shadows. The effectiveness of this model was verified through two different welding speed experiments.

This work provides an effective way to assess laser weld quality in real-time. Read the entire paper at http://tinyurl.com/JMS-weldshadow.

Tech Front is edited by Senior Editor Michael C. Anderson

 

 

This article was first published in the January 2016 edition of Manufacturing Engineering magazine. Click here for PDF.


Published Date : 1/1/2016

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