A Molecular Motor with an Atomic Bearing

Researchers have managed to make a molecular motor that resembles a conventional ball bearing with a specialized molecule that spins around a ruthenium atom like a windmill, which acts as the bearing.

Perera et. al., Nature Nanotechnology

Write the authors in the study's abstract: "Previously, rotary molecular motors³ powered by light^{4, 5, 6} and chemical^{7, 8, 9, 10, 11} energy have been developed. In electrically driven motors, tunnelling electrons from the tip of a scanning tunnelling microscope have been used to drive the rotation of a simple rotor¹² in a single direction and to move a four-wheeled molecule across a surface¹³. Here, we show that a stand-alone molecular motor adsorbed^{[editor's link]} on a gold surface can be made to rotate in a clockwise or anticlockwise direction by selective inelastic electron tunnelling through different subunits of the motor. Our motor is composed of a tripodal stator for vertical positioning, a five-arm rotor for controlled rotations, and a ruthenium atomic ball bearing connecting the static and rotational parts. The directional rotation arises from sawtooth-like rotational potentials, which are solely determined by the internal molecular structure and are independent of the surface adsorption site."

Writes John Timmer for Ars Technica:

The base of the system involves a boron atom that coordinates three ringed structures that are chemically similar to the bases of DNA. Nitrogens at a corner of these ringed structures coordinate the ruthenium atom, placing it at the peak of a three-sided pyramid. (This compound has the succinct name [n⁵-1-(4- tolyl )-2,3,4,5-tetra(4-ferrocenylphenyl) cyclopentadienyl hydrotris [6-((ethylsulphanyl)methyl)indazol-1-yl] borate ruthenium(II)], which should provide some sense of its complexity.)

The authors cleaned off a gold surface, and then dropped the pyramids onto it. With those in place, they layered on something that looks a bit like a five-armed windmill. A five-atom ring sits at the center, with further rings extending out at each corner to form the blades of the windmill. For four of the five arms, the authors placed a complex of rings surrounding an iron atom. The fifth arm was left blank so that they could actually tell when something shifted. (If all arms were identical, it would be impossible to tell different configurations apart.)

It was possible to arrange this molecule so that the central five-carbon ring sat directly on top of the ruthenium atom. That let the ruthenium act like a ball bearing, allowing the molecule sitting atop it to rotate, spinning like a windmill tilted on to its back, with its blades oriented horizontally.

To actually get it to rotate, a scanning-tunneling microscope was again used to inject electrons into the system. The added charges allowed the rings to overcome interactions with the base, and click one position forward (with five positions, corresponding to the five arms, providing a complete rotation). But the authors could also control the direction of rotation. Pump the electrons into one of the iron-containing arms, and the motor would turn in one direction; put them into the single truncated arm, and it would turn in the opposite one.

These little things take a lot to power, though. It takes a scanning-electron microscope to accurately inject the electrons into the system; without them, these systems aren't going to find practical use, but it's a remarkable demonstration of molecular engineering, and adds to our knowledge of what kinds of molecular mechanics are even possible.

The study was published on 23 December 2012 and was conducted by U. G. E. Perera, H. Kersell, Y. Zhang & S-W. Hla (the Nanoscale and Quantum Phenomena Institute, Ohio University, Athens, Ohio), G. Vives, J. Echeverria, M. Grisolia,  C. Joachim (GNS & MANA Satellite, CEMES, CNRS, Toulouse Cedex, France), G. Rapenne (Université de Toulouse, Toulouse, France), F. Ample and C. Joachim (IMRE, A*STAR [Agency for Science, Technology and Research]), 3 Research Link, Singapore).

Memristor-Using Circuit with Neuron-like Behavior

The memristor is a type of electrical circuit that can change its resistance level to electrical conduction based on the amount of current flowing through it and remember the last resistance level it was at when current is stopped, hence the name. Pretty nifty.

These have been known about in theory since 1971, but haven't found any truly practical application until research published on 19 December 2009 in the Proceedings of the National Academy of Sciences from Hewlett-Packard's laboratories in Palo Alto, California led to a dynamic, self-reprogramming Boolean (named after computer scientist George Boole) sum-of-product circuit.

Published 16 December 2012 in the journal Nature, researchers R. Stanley Williams -- who was on the team that published the 2009 memristor article -- Matthew D. Pickett, and Gilberto Medeiros-Ribeiro have shown that memristors can be used with what are called Mott insulators to build and release a charge using heat. They do this by using material that is not very electrically conductive at lower temperatures due to interactions among the electrons that prevent them from conducting, or flowing out in the same direction. At higher temperatures, as the current increases, these interactions decrease, the electrons begin to agree, and the memristor turns into a conductor, allowing a charge to be released.

Using these "Mott memristors", the team has created what they dub the neuristor using the material niobium dioxide. A bit of background on neurons, the analogous biological brain cells that the team is attempting to emulate: Unlike binary computer systems that communicate information via states that are simply either on or off (1 or 0; high voltage/low voltage), neurons communicate information by spiking from less excited states with electrical activity to various degrees on gradients, and networking with other neurons that are spiking at the same frequencies to produce spiking patterns that represent perceptions.

The neuristor is a memristor-capacitor circuit that is capable of networking capacitor-checked memristors so that their outputs spike at certain frequencies, much like neurons. They are much more regular than neuronal spiking, but as John Timmer writes for Ars Technica, "it might be possible to create versions that are a bit more variable than this one. And, more significantly, it should be possible to fabricate them in large numbers, possibly right on a silicon chip."

Continues Timmer:

To get the sort of spiking behavior seen in a neuron, the authors turned to a simplified model of neurons based on the proteins that allow them to transmit electrical signals. When a neuron fires, sodium channels open, allowing ions to rush into a nerve cell, and changing the relative charges inside and outside its membrane. In response to these changes, potassium channels then open, allowing different ions out, and restoring the charge balance. That shuts the whole thing down, and allows various pumps to start restoring the initial ion balance.

In the authors' circuit, there were two units, one representing the sodium channels, the other the potassium channels. Each unit consisted of a capacitor (to allow it to build up charge) in parallel to a memristor (which allowed the charge to be released suddenly. In the proper arrangement, the combination produces spikes of activity as soon as a given voltage threshold is exceeded. The authors have termed this device a "neuristor."

As it currently stands, the NbO₂ neuristor uses too much power to put in large numbers on a chip. But there are other types of Mott resistors known, and the authors think that it should be possible to find one that's both low power and compatible with current chip-making techniques.

Quantum computing still has quite a way to go, and artificial intelligence as we oft dream of it would probably rely on the kinds of raw computing power quantum computing can offer, but these new neuristors appear promising for modeling neuronal behavior in silicon circuitry.

Boson Sampling Technique Holds Promise for Quantum Computing

Quantum computing is the realm of computer science devoted to the notion that inter-atomic quantum properties can ultimately be utilized as functional logic gates and networked to perform computational algorithms as an alternative to much larger, more cumbersome and slower silicon circuitry.

John Timmer writes for Ars Technica: "A quantum computer isn't like our existing computers, where electrons flow through a series of switches. Instead, a carefully prepared quantum system is allowed to evolve, and it is then measured. The system only provides us with an answer because we can map different answers to all the possible states that the system can end up in. Because quantum systems evolve very quickly, it should be possible for these systems to arrive at an answer much faster than a typical computer."

Researchers from Australia have created a simple circuit using a technique called boson sampling, which samples bosons scattered by photons in controllable probability distributions.

"There is extremely strong evidence to support that Boson Sampling cannot be simulated efficiently on a classical computer, so demonstrating the Boson Sampling algorithm in the lab with a real quantum computer is strong evidence to show that one can indeed harness a computational advantage with quantum physics," [Matthew Broome, from Australia's University of Queensland told Ars].

Boson sampling is, as noted in the abstract, "sampling the output distributions of n [amount of] bosons scattered by some linear-optical unitary process. Here, we test the central premise of boson sampling, experimentally verifying that 3-photon scattering amplitudes are given by the permanents of submatrices generated from a unitary describing a 6-mode integrated optical circuit. We find the protocol to be robust, working even with the unavoidable effects of photon loss, non-ideal sources, and imperfect detection. Scaling this to large numbers of photons will be a much simpler task than building a universal quantum computer."

The Relation of Axial and Orbital Precessions to Volcanic Activity

Precession on a gyroscope.

The Earth undergoes large climate cycles that correspond with cycles in its axial and orbital precessions that affect the Earth's tilt toward the Sun, which in turn effects the possible severities of the planet's seasons. The combined effect of these precessions creates climactic cycles that manifest as growing or shrinking ice sheets. Growing ice sheets, especially as seen in ice ages, push down on the Earth's crust, trapping pressure that is released when the ice lets up and the crust is allowed to swell again. This swelling has been found to correlate strongly with volcanic activity in volcanically-prone areas of the Earth's crust.

As Scott K. Johnson writes for Ars Technica on 11 December 2012, "If the pressure pushing down on a magma chamber decreases as the crust rebounds upwards, it becomes easier for the magma to work its way to the surface, leading to an eruption. In this way, large climate changes could act to loosen the corks keeping eruptions bottled in, so to speak."

Evidence for this geological phenomenon has been found in a study published by Steffen Kutterolf, Marion Jegen, Jerry X. Mitrovica, Tom Kwasnitschka, Armin Freundt and Peter J. Huybers of the Geological Society of America on 4 September 2012.

Peruvian Spider Builds Spider-like Decoys

A potentially new species of spider that builds spider-resembling assemblages of debris onto its web has been discovered in the Peruvian Amazon Rainforest by a research expedition led by Phil Torres of the Peru Nature blog. One should be cautioned from thinking that this is the sudden realization of a particularly cognizant spider, however -- the genus, Cyclosa, is known to be fond of clumping trash to their webs. Years of generations of spiders doing this in slightly different ways would be able to stumble, through trial and error, upon a symmetrical pattern of debris that resembles the shape of itself. And as a by-product of this experimental behavior, spiders with trash clumps that look more spider-like are that much less likely to be attacked by predators that are conditioned to recognize the distinctive pattern of a spider and instead attack the decoy.

Phil Torres

The spiders left over from the successful survival rate increase that the spider-shaped decoy affords them from predators continue to pass on this behavior to their offspring while non-spider-shaped-decoy-using spiders are more likely to be killed before reproducing.

Writes Torres:

From afar, it appears to be a medium sized spider about an inch across, possibly dead and dried out, hanging in the center of a spider web along the side of the trail. Nothing too out of the ordinary for the Amazon. As you approach, the spider starts to wobble quickly forward and back, letting you know this spider is, in fact, alive. 

Step in even closer and things start to get weird- that spider form you were looking at is actually made up of tiny bits of leaf, debris, and dead insects. The confusion sets in. How can something be constructed to look like a spider, how is it moving, and what kind of creature made this!?

It turns out the master designer behind this somewhat creepy form is in fact a tiny spider, only about 5mm in body length, that is hiding behind or above that false, bigger spider made up of debris. After discussing with several spider experts, we've determined it is quite probable that this spider is a never-before-seen species in the genus Cyclosa. This genus is known for having spiders that put debris in their webs to either attract prey or, as in this case, confuse anything trying to eat them. 

You could call it a spider decoy, in a sense. The spiders arrange debris along specialized silk strands called stabilimenta in a symmetrical form that makes it look almost exactly like a larger spider hanging in the web. Studies have found that some Cyclosa species have a higher survival rate against potential predators like paper wasps because the wasps end up attacking the debris in the web rather than the spider itself. As seen here, Cyclosa can make debris look a bit like a spider, but not nearly as detailed as the spiders found at the Tambopata Research Center which have a complex form that actually looks like a bigger version of themselves, complete with legs and all.

The potential species is not yet named. "It takes a lot of time and effort to go from finding [a potential species] in the field to actually describing it. Specimens will have to be collected to compare to known species, dissections done on identifying features like the genitalia, and descriptions will have to be written to show why this species is different from others,  a type specimen will have to be selected, and the eventual publication of all of that information in a journal. Only then can it be considered a named new species to science," Torres writes.

Protein's Role in Chromosomal Divide Also Found to Have Role in Slowing Aging

From WIRED on 12 December 2012: [T]here’s hope that [Jan van Deursen at the Mayo Clinic in Rochester, Minnesota] may have identified a new drug target to slow aging. “There [are] no negative consequences that he identified” to having more BubR1^{[editor's link]}, says Paul Hasty, who studies aging and DNA repair at the University of Texas Health Science Center in San Antonio. “You need to figure out exactly what BubR1 is doing to achieve this desired effect,” he adds, but this could be the first step on a long path toward new treatments that delay aging—and possibly prevent cancer.

Baker et al./Nature Cell Biology

6144 Insect Species Found in 1.18 Acres of Rainforest

A massive study published in the journal Science on 14 December 2012 cataloged the arthropod diversity of a 0.48 hectare area in the San Lorenzo Rainforest in Costa Rica. Researchers collected 6144 species and "extrapolated total species richness to larger areas on the basis of competing models." It was led by Yves Basset of the Smithsonian Tropical Research Institute, the Universidad de Panamá in Panama City, Panama and the University of South Bohemia in the Czech Republic.

"The whole 6000-hectare forest reserve most likely sustains 25,000 arthropod species. Notably, just 1 hectare of rainforest yields >60% of the arthropod biodiversity held in the wider landscape," the study's abstract continues.

"Terry Erwin, an entomologist at the Smithsonian Institution’s National Museum of Natural History in Washington, D.C., who was not involved in the study, cautions against putting too much weight on the estimated number of species," writes Sarah C.P. Williams for WIRED.

"This study is exciting because they’ve taken a large team of people and used every technique available,” Erwin told WIRED; “but to take a little sample from one place and scale up, it’s been critiqued and critiqued and it just doesn’t work."

"Erwin adds that further surveys of the tree diversity across the entire San Lorenzo rainforest could help make better predictions of the total number of arthropod species there," writes Williams.

"For now, the results can help scientists determine additional factors that influence biodiversity and develop models of the impact of habitat loss on arthropod diversity and abundance," Basset tells WIRED.

"With this baseline count, and the calculated ratios between types of organisms, researchers can begin to assess how adding or removing one particular area or type of tree or animal affects this balance and can then begin to set conservation priorities," continues Williams.

“If we want to understand and conserve life on Earth, we had better start understanding and conserving the arthropods of tropical forests," concludes Basset. 

"Insects perform a vast number of important functions in our ecosystem," writes Zora Warren of the Harvard Graduate School in Education. "They aerate the soil, pollinate blossoms, and control insect and plant pests; they also decompose dead materials, thereby reintroducing nutrients into the soil. Burrowing bugs such as ants and beetles dig tunnels that provide channels for water, benefiting plants. Bees play a major role in pollinating fruit trees and flower blossoms. Gardeners love the big-eyed bug and praying mantis because they control the size of certain insect populations, such as aphids and caterpillars, which feed on new plant growth. Finally, all insects fertilize the soil with the nutrients from their droppings."

The greater the degree of biodiversity in an area, the greater the chances for ecological niche emergence to occur. Insects are significant to the ecological health of most ecosystems. In addition to what Warren described, they are also a source of food for many predators, and are part of many complex food chains.

Insects can be found in almost every kind of environment on the planet. Gynaephora groenlandica, or the Arctic Wooly Moth, is a hardy example of insect durability -- they can be found in the Arctic Circle, Northern Canada and Greenland specifically. Besides that less common example, though, most insects prefer warm, moist environments, hence rainforests as a popular target for tracking their diversity and how their diversity impacts the greater ecology of an area.