A “Superdove” Takes Flight

Crosspost: I have a new article up on Science Metropolis, a wonderful site run by fellow BU Science Journalism student Joseph Caputo. It’s about pigeons (my article, not the site).  Click here to toss a few breadcrumb-sized hits our way.

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Fake Plastic Trees

A tree is growing at Cornell University. Unlike the English elms, Japanese maple, and swamp oaks lining the Ithaca campus, this specimen is about seven centimeters tall and made of plastic. It is a synthetic tree, the brainchild of two biomolecular engineers, and the first man-made system able to mimic the powerful pumping capability of plants. It could also be the seed of an engineering revolution.

The Telegraph (UK)

Most plants transport water through internal channels called xylem. This system operates upon the principle of negative pressure. Water evaporating from the surface of a leaf creates a tensile force akin to pulling on a rope. This force draws water from the ground, through the roots and up the entire plant. Tobias Wheeler, the leader of the project, explained that the mechanism of water transport in plants was deduced in the 1890s. Efforts to produce a replica of this model, however, have progressed little since then.

The first and greatest hurdle to be overcome was the selection of the material used to construct the tree. Wheeler and his mentor, Abraham Stroock, knew they needed something that would form tiny pores to hold water within the artificial xylem. They eventually hit upon the idea of using a hydrogel, the material used in soft contact lenses. In hydrogels, “the polymer network and the water are… mixed, such that the pores are effectively molecular in scale”, said Stroock.

The finished product is a relatively simple apparatus: two circular regions on the surface of the hydrogel, etched with 80 parallel channels, connected by a central “trunk” groove. Water moved through the synthetic tree at forces of up to 10 atmospheres. The previous record in any liquid pumping system was 0.7 atmospheres.

Wheeler said that scaling up their tiny tree to the size needed for civil engineering projects was “not a trivial matter”. Nevertheless, he and Stroock enthusiastically speculated about a slew of possible applications for their discovery. Biologists could use them to study the finer aspects of plant physiology. Viticulturalists could use them to closely monitor water levels in the vines of wine grapes. Synthetic trees could be used to construct deeper wells and larger heat pipes, cooling homes for a fraction of the cost of air conditioning. The heat transfer systems used today to cool electronics only exist on the centimeter scale.

“We could potentially build the sequoia of heat pipes,” said Stroock.

The original article: Wheeler, Tobias and Stroock, Abraham.  “The transpiration of water at negative pressures in a synthetic tree.” Nature 455:208-212 (11 September 2008)

It Came From the Center of the Galaxy!

University of Chicago

source:University of Chicago

Deep in the heart of the Milky Way lurks an ever-hungry force, consuming planets, stars, and nebulae with voracious appetite. The monster in question is Sagittarius A*, thought to be the location of a massive black hole. Its 25,000 light year distance from Earth and relatively tiny size make SgrA* difficult to observe. A recent study led by MIT astronomer Sheperd Doeleman, published in the Sept. 4 issue of Nature, offers the closest look yet.

Doeleman’s project made use of Very Long Baseline Interferometry, or VLBI. This technique uses multiple telescopes distributed across the planet, which is like using a telescope equal in size to the distance between them. The researchers sought to maximize resolving power by linking telescopes from California, Arizona, and Hawaii, and measuring wavelengths of 1.3mm, the smallest ever attempted. This allowed the scientists to map the size of SgrA* to 37 microarcseconds. To give some idea of the scale, Doeleman said, “it’s like seeing a baseball on the moon with the naked eye.”

But how were the telescopes able to see something from which even light cannot escape? Scientists measured radio, infrared, and x-ray emissions from SgrA*, but these do not originate from the black hole itself. As Alan Marscher, professor of astronomy at Boston University, describes, matter drawn towards the event horizon, the outer limit of the black hole, doesn’t just fall straight in- it spins around like water circling a drain. As it rotates, it loses energy in the form of radiation, which can be picked up by the telescope array.

Mapping SgrA* has bolstered the case for identifying the object at the galactic center as a black hole, given its extremely small size and its extremely large mass of four million solar masses. No other phenomenon is known to have such a high density. There is, Doeleman said, a slight chance that SgrA* could be a more exotic construct known as a Boson star, which is composed of unique particles that exist much closer to each other than in normal stars. The Boson star, however, is only a theoretical possibility, and has yet to be observed.

Furthermore, scientific principles rule out the possibility that SgrA* is an aggregate of matter. According to the laws of physics, “any object that was originally at the center of the galaxy, whether it was a planet, some gravel, or a collection of Hello Kitty dolls, would have collapsed into a black hole after at least 500 years”, said Doeleman.

Future studies will attempt to push the resolving power even further, with telescopes placed even further apart and measuring even smaller wavelengths. Doeleman hopes to eventually make use of the newly constructed ALMA array, a collection of 50 dishes located in Chile. The addition of more telescopes will ultimately allow scientists to construct a real image of a black hole, rather than a mathematical representation.

Still, Marscher mused, there is a point beyond which even the most powerful telescope cannot see. Little is known about the character of what lies beyond the event horizon, he said, and at this point we lack the capability to describe it. “The universe,” he said, “conceals a lot from us.”

Original Article: Doeleman et al.  “Event-horizon-scale structure in the supermassive black hole candidate at the Galactic Centre”.  Nature 455:78-80 (4 September 2008).

Abstract

Sparkwatch is my personal foray into science blogging.  Here I’ll post the various articles and multimedia that I make for class, as well as commentary and links to science news.  To get the ball rolling, though, here is a humorous bit I did for Professor Imbriglio’s science writing class back at Brown:

The Ten Scientific Commandments

I. Thou shalt have no other interests before the pursuit of truth.

II. Thou shalt not take the name of Einstein in vain.

III. Remember to feed the graduate students, occasionally.

IV. Honor the work of those who came before while you improve upon it.

V. Thou shalt not kill, unless compliant with the Animal Welfare Act of 1966 (7 USC, 2131-2159).

VI. Publish or perish.

VII. Thou shalt not plagiarize.

VIII. Thou shalt not bear false witness during peer review.

IX. Thou shalt not covet thy colleague’s endowment.

X. Thou shalt not covet thy colleague’s laboratory, or his postdocs, or his publications, or anything else belonging to thy colleague.