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Beautiful video on The Flight of the AirJelly:


In this video, watch as FESTO‘s artificial jellyfish floats through the air, directed by peristaltic propulsion. Eight tentacles powered by an electric drive propel the helium-filled body of the giant jelly. In a pdf describing the project, the designers explained the thought process that led to the creation of the AirJelly:

Can the jellyfish’s motion through water serve as a propulsion principle for an airborne object? In other words, is it possible to glide through the air as a jellyfish swims through water?…Seeking recourse to jellyfish as a source of inspiration for powering gas-filled balloons is an obvious thought; after all, a jellyfish consists of water to 99%. Its weight-to-volume ratio is approximately 1, and the figure is similar for a gas-filled balloon.

The design of the AirJelly’s tentacles was derived from the functional anatomy of a fish’s fin. Each tentacle’s geometric structure bends in the direction of the applied force to produce peristaltic motion — a wave of contraction preceded by a wave of relaxation propagates in a wave down the tentacle, propelling the AirJelly forward.

The AirJelly’s motion in 3-D space is controlled by a 55 cm long pendulum positioned at the top of the jellyfish. By setting the pendulum in motion in the X and/or Y directions, the center of mass of the jellyfish is displaced and AirJelly floats in the same direction.

CURIO: 115-Year-Old Medical X-Ray Machine Comes Back to Life

A team of physicists, engineers and radiologists recently revived a first-generation X-ray device that had been collecting dust in a Dutch warehouse. The antique machine still sparked and glowed like a prop in an old science fiction movie, and used thousands of times more radiation than its modern counterparts to make an image.

The old machine was originally built in 1896 by two scientists in Maastricht, the Netherlands, just weeks after German physicist Wilhelm Conrad Röntgen reported his discovery of X-rays — an achievement that won him the first-ever Nobel Prize in physics and sparked a rash of copycat experiments.

H.J. Hoffmans, a physicist and high school director in Maastricht, and L. Th. van Kleef, director of a local hospital, assembled the system from equipment already on hand at Hoffmans’ high school and used it to take some of the first photographs of human bones through the skin, including in van Kleef’s 21-year-old daughter’s hand.

Since then, X-rays, which are the right wavelength to tunnel through muscle but are slowed by denser bones, have become almost synonymous with medical imaging. But most of those first X-ray systems were lost to history. Because the techniques and technology to measure radiation doses weren’t invented until decades after the first X-ray machines came about, no one knows exactly how powerful those systems were.

An 1896 Crookes tube emitting X-rays.

“There’s a gap in knowledge with respect to these old machines,” said medical physicist Gerrit Kemerink of the Maastricht University Medical Center. “By the time they could measure the properties, these machines were long gone.”

About a year ago, when Kemerink’s colleague at the hospital dug Hoffmans and van Kleef’s aging machine out of storage to use in a local TV program on the history of health care in the region, Kemerink grew curious about what the gadget could do. In a paper published online in Radiology, Kemerink reports the first-ever diagnostics on a first generation X-ray device.

“I decided to try to do some measurements on this equipment, because nobody ever did,” he said.

Aside from a modern car battery and some wires, the researchers used only the original equipment, including an iron cylinder wrapped in wire to transfer electrical energy from one circuit to another and a glass bulb with metal electrodes at each end.

The glass bulb, technically called a Crookes tube, contained a tiny bit of air, about a millionth of normal air pressure. When the researchers placed a high voltage over the tube, the electrons in the gas were ripped from their atoms and zipped across the tube from one electrode to the other.

Electrons naturally emit X-rays when they speed up, slow down or change direction. When the electrons hit the glass walls of the Crookes tube, they came to a screeching halt, giving off a ghostly green glow and invisible X-rays.

The machine took some coaxing before it would glow, Kemerink said. The team fiddled with it for a solid half hour with no success.

“At the time we were thinking that it would be possible that we would not succeed with our plans,” he said. “But then suddenly something happened, and we were in business.”

Kemerink now thinks that the gas pressure inside the bulb was too high for the electrons to travel through the tube. But then a bit of aluminum on one of the electrodes melted, sucking gases from inside the bulb.

“It’s a technique used today to improve your vacuum: Evaporate metal and trap some gases,” he said. “That is what happened, although we did not do it on purpose.”

Images of a hand specimen from an 86-year-old woman taken with the old X-ray machine (left) and a modern one (right). The exposure for the 1896 system took 21 minutes.

The researchers used standard hospital radiation-detecting devices to measure the amount of X-rays needed to take an image of the bones in a human hand (this time, a specimen borrowed from the anatomy department, not from a living person). The old machine took surprisingly clear pictures, but gave the skin a dose of radiation 1,500 times greater than the same image would require today. An exposure that takes 21 milliseconds (thousandths of a second) on a modern machine took up to 90 minutes on the antique system.

“It was interesting that the image quality was actually that good,” said radiologist Tom Beck of Quantum Medical Metrics, a company that researches ways to get structural information from bones using medical imaging. “That was surprising.”

This first-generation system did not produce enough radiation to cause health problems, although Kemerink and colleagues all stood behind a transparent lead shield whenever the machine was on, just in case. But X-ray devices got steadily more powerful shortly after Hoffmans and van Kleef built their machine, and technicians didn’t always take precautions against harmful radiation.

“Within weeks, people reported skin burns, a little bit later even much worse things,” like blisters and sores that wouldn’t heal, Kemerink said. Some workers had to have fingers or even a whole arm amputated. “Many of these early X-ray workers developed cancer, and many of them died untimely, very young.”

The difference in danger highlights how far X-rays have come, he said. In another study published online Feb. 15 in Insights into Imaging, Kemerink and colleagues showed that, with all the shielding used today, modern X-ray workers feel less radiation in the hospital than they do at home.

“There’s so much to say about how far we’ve come,” Kemerink said. “These machines when they started they were extremely dangerous. Now in all those years, they improved technology so far that you can really neglect what you are receiving when you do normal X-ray scans.”

Working with the machine was “very special, I must say,” Kemerink added. The air smelled of ozone, the interruptor buzzed, lightning crackled in the spark gap, and the insides of the human body showed themselves.

“Our experience with this machine,” the researchers wrote, “was, even today, little less than magical.”


Natalie Angier in The Smithsonian:

Bacteria-Bonnie-Bassler-631Bassler, 48, has been fabulously successful in her career, winning laurels like a MacArthur Foundation “genius” award, membership in the National Academy of Sciences, a coveted position with the Howard Hughes Medical Institute and the presidency of the American Society for Microbiology. And all that can be traced to her deep appreciation for the power of communication. Messaging is the medium in which Bassler shines. Bassler is at the forefront of the fast-growing field of “quorum sensing,” the study of how microbes communicate with each other as they go about building the vast interlocking infrastructure of life on which we macrobes depend.

In recent years she and other microbiologists have discovered that bacteria are not the dull solipsists of long-standing reputation, content to merely suck in food, double in size, divide down the middle and repeat ad infinitum, attending to nothing but their obtuse, unicellular selves. Instead, bacteria turn out to be the original newshounds, glued to their cellphones and Internet chat lines. They converse in a complex chemical language, using molecules to alert one another to who’s out there, in what numbers and how best to behave given the present company. Bacteria survey their ranks, they count heads, and if the throng is sufficiently large and like-minded—if there is a quorum—they act. Through chemical signaling, tiny bacterial cells can band together and perform the work of giants. They can compost an elephant, fertilize an oak forest or light up the oceans in the eerie teal glow of bioluminescence. Some bacterial collusions are far less charming and do real harm. Molecular communication allows 600 different species of bacteria to organize themselves into the slimy dental plaque that leads to tooth decay, for example, and it likely enables the nasty pathogens that cause streptococcal pneumonia or bubonic plague to time the release of their toxins for maximum impact on their human hosts.

More here.
Faces of our Ancestors. A great slide show from It features reconstructions of what the faces of our ancestors may have looked like, based on the skull bones.
From 3Quarks


From PhysOrg:

NerveGraduate students at the University of Wisconsin, Madison, led by Minrui Yu, have published an ACS Nano paper, "Semiconductor Nanomembrane Tubes: Three-Dimensional Confinement for Controlled Neurite Outgrowth," in which they show that they have been able to successfully coax nerve cell tendrils to grow through tiny tubes made of the semi-conductor materials silicon and germanium. While this ground-breaking research may not portend cyborgs or even human brains enmeshed with computer parts, it does open the door to the possibility of regenerating nerve cells damaged due to disease or injury.

Yu and his team, led by Justin Williams, a biomedical engineer, created tubes of varying sizes and shapes, small enough for a nerve cell to glam on to, but not so big that it could fit all the way inside. The tubes were then coated with  from mice and then watched to see how they would react. Instead of sitting idly, the nerve cells began to send tendrils through the tunnels, as if searching for a path to something or somewhere else. In some instances they actually followed the contours of the tubes, which means, in theory, that the nerves could be grown into structures. Scientists have known for a while that nerve cells have a seek feature, but aren’t yet sure what it is they are seeking or if it’s just a random thing they do. By setting up nerve cells to follow pre-planned paths through tiny tubes, the research team hopes to find the answer to that by installing listening devices to record electrical emissions from nerves, which could in theory lead to recorded conversations between nerve cells. The hope of course, in this type of research, is that a way can be found to connect a computer of some sort to a group of nerve cells to reestablish communication that has been disrupted.

More here.

Norwegian landscape photographer Terje Sorgjerd spent one week around Kirkenes and the Norway-Russia border, in -25 Celsius temperature, to make this magnificent time-lapse video of the Aurora Borealis.

The Aurora from Terje Sorgjerd on Vimeo.

Credit: Illustrations by Juan Cisneros

Saber-toothed predators are rare, but vegetarians sporting such fangs are members of an even more exclusive club. Scientists have now described one such creature, a short-snouted, tapir-sized animal known asTiarajudens eccentricus. The so-called therapsid, a close relative of the creatures that eventually gave rise to mammals, lived about 260 million years ago in an arid region of what is now Brazil. It had molarlike teeth suitable for grinding a fibrous diet of ferns, leaves, and stems. But unlike most of its vegetarian kin, Tiarajudens also sported sturdy saber-like teeth that measured at least 12 centimeters long (part of the species’ name translates as “unusual tooth.”) Those fangs didn’t have serrations along their edges and likely weren’t used for chewing, say the paleontologists who describe Tiarajudens fossils online today in Science. Instead, they suggest, the distinctive teeth could have been used to deter predators, to spar with rivals, or as a way for individuals of the species to easily recognize their cohorts. 

See more ScienceShots.


Why is there a short-term increase in global precipitation in response to diminished CO2 forcing?

Long Cao

Department of Global Ecology, Carnegie Institution, Stanford, California, USA

Govindasamy Bala

Center for Atmospheric and Oceanic Sciences, Indian Institute of Science, Bangalore, India

Divecha Center for Climate Change, Indian Institute of Science, Bangalore, India

Ken Caldeira

Department of Global Ecology, Carnegie Institution, Stanford, California, USA

Recently, it was found that a reduction in atmospheric CO2 concentration leads to a temporary increase in global precipitation. We use the Hadley Center coupled atmosphere-ocean model, HadCM3L, to demonstrate that this precipitation increase is a consequence of precipitation sensitivity to changes in atmospheric CO2 concentrations through fast tropospheric adjustment processes. Slow ocean cooling explains the longer-term decrease in precipitation. Increased CO2 tends to suppress evaporation/precipitation whereas increased temperatures tend to increase evaporation/precipitation. When the enhanced CO2 forcing is removed, global precipitation increases temporarily, but this increase is not observed when a similar negative radiative forcing is applied as a reduction of solar intensity. Therefore, transient precipitation increase following a reduction in CO2-radiative forcing is a consequence of the specific character of CO2 forcing and is not a general feature associated with decreases in radiative forcing.

Received 10 January 2011; accepted 28 February 2011; published 24 March 2011.

Citation: Cao, L., G. Bala, and K. Caldeira (2011), Why is there a short-term increase in global precipitation in response to diminished CO2 forcing?Geophys. Res. Lett.38, L06703, doi:10.1029/2011GL046713.

March 23, 2011

Annual maximum ice extent reached

Arctic sea ice extent appeared to reach its maximum extent for the year on March 7, marking the beginning of the melt season. This year's maximum tied for the lowest in the satellite record. NSIDC will release a detailed analysis of the 2010 to 2011 winter sea ice conditions during the second week of April.

map from space showing sea ice extent, continentsFigure 1. Arctic sea ice extent on March 7 was  14.64 million square kilometers (5.65 million square miles). The orange line shows the 1979 to 2000 median extent for that day. The black cross indicates the geographic North Pole. Sea Ice Index dataAbout the data
—Credit: National Snow and Ice Data Center

High-resolution image

Overview of conditions

On March 7, 2011, Arctic sea ice likely reached its maximum extent for the year, at 14.64 million square kilometers (5.65 million square miles). The maximum extent was 1.2 million square kilometers (463,000 square miles) below the 1979 to 2000 average of 15.86 million square kilometers (6.12 million square miles), and equal (within 0.1%) to 2006 for the lowest maximum extent in the satellite record.

graph with months on x axis and extent on y axisFigure 2. The graph above shows daily Arctic sea ice extent as of March 22, 2011, along with daily ice extents for 2006, which had the previous lowest maximum extent, and 2007, the year with the lowest minimum extent in September. Light blue indicates 2011, green shows 2007, light green shows 2006, and dark gray shows the 1979 to 2000 average. The gray area around the average line shows the two standard deviation range of the data. Sea Ice Index data.
—Credit: National Snow and Ice Data Center

High-resolution image

Conditions in context

As of March 22, ice extent has declined for five straight days. However there is still a chance that the ice extent could expand again. Sea ice extent in February and March tends to be quite variable, because ice near the edge is thin and often quite dispersed. The thin ice is highly sensitive to weather, moving or melting quickly in response to changing winds and temperatures, and it often oscillates near the maximum extent for several days or weeks, as it has done this year.

Since the start of the satellite record in 1979, the maximum Arctic sea ice extent has occurred as early as February 18 and as late as March 31, with an average date of March 6.

Final analysis pending

In the beginning of April, NSIDC will issue a formal announcement with a full analysis of the 2010 to 2011 winter season, and graphics comparing this year to the long-term record. We will also announce the monthly average March sea ice extent, the measure scientists rely on for accurate analysis and comparison over the long term.

For previous analyses, please see the drop-down menu under Archives in the right navigation at the top of this page.

Fossil flower fills evolutionary knowledge gap - March 30, 2011

fossil flower.pngAn early example of the most diverse group of flowering plants has been unearthed in the remarkably rich Yixian Formation in China.

The beautifully preserved stem suggests that early examples of eudicot plants were flourishing between 123 and 126 million years ago, Ge Sun and David Dilcher, of the Shenyang Normal University, and their colleagues report in Nature.

Eudicots are one of five currently recognised lineages of the angiosperms – the flowering plants.

Fossil pollen has already placed eudicots as present 127 to 125 million years ago. Now the new fossil (Leefructus gen. nov.) suggests they were “already present and diverse” around that time, in the early Cretaceous period. It also suggests that angiosperms may have evolved before the Cretaceous, write Sun and Dilcher.

New Dinosaur, Crocodile Cousin Found in Brazil


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