Geologists have known about turbidity currents since at least 1929, when a large earthquake triggered a violent current that traveled several hundred kilometers and damaged 12 trans-Atlantic communications cables. Turbidity currents are still a threat today, as people place more and more cables, pipelines, and other structures on the seafloor. Turbidity currents are also important to petroleum geologists because they leave behind layers of sediment that comprise some of the world’s largest oil reserves.

Despite almost a century of research, geologists have struggled to come up with a conceptual model that describes in detail how turbidity currents form and evolve. The Coordinated Canyon Experiment was designed, in part, to resolve this debate. During this 18-month-long study, researchers from the Monterey Bay Aquarium Research Institute (MBARI), the U.S. Geological Survey, the University of Hull, the National Oceanography Centre, the University of Southampton, the University of Durham, and the Ocean University of China combined their expertise and equipment to monitor a 50-kilometer-long (31-mile) stretch of Monterey Canyon in unprecedented detail.

During the experiment, researchers placed over 50 different instruments at seven different locations in the canyon and made detailed measurements during 15 different turbidity flows. Almost all of the flows began near the head of the canyon in water less than about 300 meters (1,000 feet) deep. Once initiated, the flows traveled at least several kilometers down the canyon. The three largest flows traveled over 50 kilometers, sweeping past the deepest monitoring station in the canyon at a depth of 1,850 meters (6,000 feet).

This extensive research program showed that turbidity currents in Monterey Canyon involve both movements of water-saturated sediment and of sediment-laden water. As described in the recent Nature Communications paper, the most important part of the process is a dense layer of water-saturated sediment that moves rapidly over the bottom and remobilizes the upper few meters of the preexisting seafloor.

This is very different from previous conceptual models of turbidity currents, which focused on flows of turbid, sediment-laden water traveling above the seafloor. The authors of the recent paper did observe plumes of sediment-laden water during turbidity events, but they suggest that these are secondary features that form when the pulse of saturated sediment mixes into the overlying seawater.

“This whole experiment was an attempt to learn what was going on at the bottom of the canyon,” said Charlie Paull, MBARI marine geologist and first author of the recent paper. “For years we have seen instruments on the bottom move in unexpected ways, and we suspected that the seafloor might be moving. Now we have real data that show when, where, and how this happens.” Among the instruments used in the experiment were current meters mounted on seven moorings distributed along the canyon floor. Analyzing the data from these instruments and measuring the time it took for the flows to travel between the moorings, the researchers were surprised to find that the flows appeared to travel down the canyon at speeds greater than the actual measured water currents.

Although tilting and other movements of the current meters could explain some of these observations, the scientists eventually concluded that their instruments were not simply being moved by currents of turbid water flowing above the seafloor.

The researchers also placed beach-ball-sized sensors called benthic event detectors (BEDs) in the seafloor. The BEDs were designed to be transported by turbidity flows while carrying instruments that recorded their depth, horizontal and vertical movement, and rotation. Other motion sensors were mounted on large, steel frames weighing up to 800 kilograms (1,760 pounds). These were designed to remain stationary while the flows passed around them.

However, both the BEDs and the heavy frames were carried far down the canyon during strong turbidity events. In fact, the heavy, awkwardly-shaped instrument frames often traveled just as fast as the relatively light, streamlined BEDs.

The researchers also noticed large sand waves, up to two meters (6.5 feet) tall, on the floor of the canyon. Repeated bottom surveys showed that these sand waves shifted dramatically during turbidity events, remolding the upper two to three meters of the seafloor. But the researchers still weren’t sure exactly how this remolding occurred.

Data from the BEDs provided an important clue. During many events, the BEDs did not just move down the canyon into deeper water, but traveled as fast or faster than the overlying water. They also moved up and down within the flow as much as three meters at regular intervals.

The researchers concluded that, rather than being “dragged” along the bottom by a strong current, their instruments were being “rafted” by a dense, bottom-hugging layer of water-saturated sediment. They hypothesized that the up-and-down motions of the BEDs occurred as the instruments traveled over individual sand waves. As Paull noted, “The BEDs provided an essential kernel of new data that allowed us to understand the movement of the seafloor for the first time.”

“Textbooks and modelling efforts have traditionally focused on dilute flows of sediment-laden water over the bottom,” Paull added. “But we now know that dilute flows are just part of the equation. It turns out that they are the tail end of the process, which really begins at the seafloor. “

The team of U of T chemists, led by Nobel Prize-winning researcher John Polanyi, have found a means to select the impact parameter or miss-distance by which a reagent molecule misses a target molecule, thereby altering the products of chemical reaction. The findings are published today in Science Advances.

“Chemists toss molecules at other molecules all the time in hopes of making something new,” says Polanyi, University Professor in the Department of Chemistry at U of T. “In this study we have found a way to control the outcome by aiming a projectile molecule at a target molecule, with an accuracy of a small fraction of the diameter of the target molecule.”

Molecular dynamics in chemistry is a lot like a game of billiards. Just as a billiard player sends the incoming ball towards the target ball, chemists launch one molecule towards another to produce a chemical reaction. However, this can be done, it is now clear, either by chance as has been the norm, or by design as the new work shows to be possible.

Previously the inherent randomness in molecular motions has prevented chemists from aiming their projectile molecules at the chemical targets, as billiards players do. Instead, they have been obliged to play their game of billiards blindfold.

“Over the years chemists have become very good at playing billiards blindfold, using sticky balls and throwing them strongly or weakly,” Polanyi says. “But we have found a way to take off the blindfold, and aim each shot.”

The researchers achieved this by depositing molecules on a metal crystal, then applying a small current from an atomically sharp metal tip to one of the molecules. This addition of energy caused a ‘projectile’ molecule to shoot across the surface in a straight line, along one of the rail-like ridges on the metal crystal toward a nearby ‘target’ molecule present on the crystal, missing it by a controlled amount.

Different miss-distances, called ‘impact parameters’, were shown reproducibly to give different outcomes, that is to say different patterns of reaction.

“The underlying crystalline surface is our billiard table,” said Kelvin Anggara, a postdoctoral fellow in Polanyi’s research group and a lead author of the study. “By taking advantage of the grooves that nature has conveniently scored across the surface of crystals, we found we could guide the travelling molecular projectile so that it hit the target either head-on or in a glancing collision that missed the target by a desired amount. That way, just as in billiards, we can control the outcome of the molecular collision.”

Selecting the miss-distance or impact parameter in collisions between reagent molecules has till now been termed the “forbidden fruit of reaction dynamics” by Harvard University professor Dudley R. Herschbach, with whom Polanyi shared the 1986 Nobel Prize in Chemistry along with Yuan T. Lee. While the discoveries made by the trio enabled chemists to infer many of the forces at play in a chemical reaction, the impact parameter has defied direct control.

This is true even in the famously well-controlled conditions of “crossed molecular beams.” It is frequently overlooked that though the beams in this elegant method are aimed at one another, the molecules are not. Now the individual molecules can be aimed at one another, quite precisely.

“We believe that this is a major step forward in the control of chemical reactions,” said Anggara, who performed the study along with Polanyi, senior research associate Lydie Leung and graduate student Matthew Timm.

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Materials provided by University of Toronto. Original written by Sean Bettam. Note: Content may be edited for style and length.

Micron-sized spheres created in the lab of Rice environmental engineer Pedro Alvarez are built to catch and destroy bisphenol A (BPA), a synthetic chemical used to make plastics.

The research is detailed in the American Chemical Society journal Environmental Science & Technology.

BPA is commonly used to coat the insides of food cans, bottle tops and water supply lines, and was once a component of baby bottles. While BPA that seeps into food and drink is considered safe in low doses, prolonged exposure is suspected of affecting the health of children and contributing to high blood pressure.

The good news is that reactive oxygen species (ROS) — in this case, hydroxyl radicals — are bad news for BPA. Inexpensive titanium dioxide releases ROS when triggered by ultraviolet light. But because oxidating molecules fade quickly, BPA has to be close enough to attack.

That’s where the trap comes in.

Close up, the spheres reveal themselves as flower-like collections of titanium dioxide petals. The supple petals provide plenty of surface area for the Rice researchers to anchor cyclodextrin molecules.

Cyclodextrin is a benign sugar-based molecule often used in food and drugs. It has a two-faced structure, with a hydrophobic (water-avoiding) cavity and a hydrophilic (water-attracting) outer surface. BPA is also hydrophobic and naturally attracted to the cavity. Once trapped, ROS produced by the spheres degrades BPA into harmless chemicals.

In the lab, the researchers determined that 200 milligrams of the spheres per liter of contaminated water degraded 90 percent of BPA in an hour, a process that would take more than twice as long with unenhanced titanium dioxide.

The work fits into technologies developed by the Rice-based and National Science Foundation-supported Center for Nanotechnology-Enabled Water Treatment because the spheres self-assemble from titanium dioxide nanosheets.

“Most of the processes reported in the literature involve nanoparticles,” said Rice graduate student and lead author Danning Zhang. “The size of the particles is less than 100 nanometers. Because of their very small size, they’re very difficult to recover from suspension in water.”

The Rice particles are much larger. Where a 100-nanometer particle is 1,000 times smaller than a human hair, the enhanced titanium dioxide is between 3 and 5 microns, only about 20 times smaller than the same hair. “That means we can use low-pressure microfiltration with a membrane to get these particles back for reuse,” Zhang said. “It saves a lot of energy.”

Because ROS also wears down cyclodextrin, the spheres begin to lose their trapping ability after about 400 hours of continued ultraviolet exposure, Zhang said. But once recovered, they can be easily recharged.

“This new material helps overcome two significant technological barriers for photocatalytic water treatment,” Alvarez said. “First, it enhances treatment efficiency by minimizing scavenging of ROS by non-target constituents in water. Here, the ROS are mainly used to destroy BPA.

“Second, it enables low-cost separation and reuse of the catalyst, contributing to lower treatment cost,” he said. “This is an example of how advanced materials can help convert academic hypes into feasible processes that enhance water security.”

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Materials provided by Rice University. Original written by Mike Williams. Note: Content may be edited for style and length.

An interdisciplinary team of researchers at Arizona State University has discovered that the answers to these questions may lie in the ability of life to find a middle ground, balancing between robustness and adaptability. The results of their study have been recently published in Physical Review Letters.

The importance of stability

The research team, led by Bryan Daniels of the Center for Biosocial Complex Systems with direction from faculty member Sara Walker of the School of Earth and Space Exploration, sifted through data to better understand the root connections among 67 biological networks that describe how components of these systems interact with one another. The biological networks are sets of individual components (like proteins and genes) that interact with one another to perform important tasks like transmitting signals or deciding a cell’s fate. They measured a number of mathematical features, simulating the networks’ behavior and looking for patterns to provide clues on what made them so special.

To perform their study, they examined data from the Cell Collective database. This rich resource represents biological processes across life — encapsulating a wide range of biological processes from humans to animals, plants, bacteria and viruses. The number of components in these networks ranged from five nodes to 321 nodes, encompassing 6500 different biological interactions.

And these nodes include many of life’s key building blocks — genes and proteins that act as master switches controlling cell division, growth and death, and communication.

Using a wealth of molecular data, scientists can now study the interactions among the building blocks, with an ultimate goal of understanding the key to how life emerges.

“We wanted to know whether the biological networks were special compared to random networks, and if so, how,” says Daniels.

They focused on trying to find a threshold point at which an entire system may change in response to just a small change. Such a change could profoundly upset the balance of life, creating a teeter-totter of fate deciding whether an organism would die or thrive.

“In a stable system, organisms will always come back to their original state,” explains Daniels. “In an unstable system, the effect of a small change will grow and cause the whole system to behave differently.”

Through rigorous testing of the 67 networks, the team found that all of the networks shared a special property: They existed in between two extremes, neither too stable nor unstable.

As such, the team found that sensitivity, which is a measure of stability, was near a special point that biologists call “criticality,” suggesting that the networks may be evolutionarily adapted to an optimal tradeoff between stability and instability.

Life in the balance

Previous studies have shown that a handful of biological systems, from neurons to ant colonies, lie in this middle ground of criticality and this new research expands the list of living systems in this state.

This can be of particular interest to astrobiologists, like co-author Walker who is searching for life on other planets. Understanding how life can take various forms, and why it does so, may help identify life on other planets and determine how it might look different from life on Earth. It can also help inform our search for the origins of life in the lab.

“We still don’t really understand what life is,” says Walker, “and determining what quantitative properties, such as criticality, best distinguish life from non-life is an important step toward building that understanding at a fundamental level so that we may recognize life on other worlds or in our experiments on Earth, even if it looks very different than us.”

The findings also advance the field of quantitative biology by showing that, from the basic building blocks of life, scientists can identify a critical sensitivity that is common across a large swath of biology. And it promises to advance synthetic biology by allowing scientists to use life’s building blocks to more accurately construct biochemical networks that are similar to living systems.

“Each biological system has distinctive features, from its components and its size to its function and its interactions with the surrounding environment,” explains co-author Hyunju Kim of the School of Earth and Space Exploration and the Beyond Center. “In this research, for the first time, we are able to make connections between the theoretical hypothesis on biological systems’ universal tendency to retain the balance at the medium degree of stability and 67 biological models with various characteristics built on actual experiment data.”

In addition to Daniels, Walker, and Kim, the interdisciplinary research team on this study includes co-authors Douglas Moore of the Beyond Center, Siyu Zhou of the Department of Physics, Bradley Karas and Harrison Smith of the School of Earth and Space Exploration, and Stuart Kauffman of the Institute for Systems Biology in Seattle, Washington.

This research emerged from a course led by Walker and Kim on complex systems approaches to understanding life, offered at the School of Earth and Space Exploration. Co-authors Karas, Zhou, and Smith were originally students in the class when the project began.

“In our class project, the analytic tools and codes to study general dynamical systems were provided, and we gave the option for students to choose any dynamical systems they were interested in,” says Kim. “Students were asked to modify the analysis and codes to study various features of each selected system. As a result, we ended up dealing with many different biological networks, investigating more diverse aspects of those systems, and developed more codes and analysis tools, even after the completion of the class.”

The invention also opens the door to a new generation of high-performance electronic devices made with organic materials that will be biodegradable or that can be easily recycled, promising to help substantially reduce e-waste.

The huge volumes of e-waste generated by discarded electronic devices around the world is causing irreversible damage to the environment. Australia produces 200,000 tonnes of e-waste every year — only four per cent of this waste is recycled.

The organic component has the thickness of just one atom — made from just carbon and hydrogen — and forms part of the semiconductor that the ANU team developed. The inorganic component has the thickness of around two atoms. The hybrid structure can convert electricity into light efficiently for displays on mobile phones, televisions and other electronic devices.

Lead senior researcher Associate Professor Larry Lu said the invention was a major breakthrough in the field.

“For the first time, we have developed an ultra-thin electronics component with excellent semiconducting properties that is an organic-inorganic hybrid structure and thin and flexible enough for future technologies, such as bendable mobile phones and display screens,” said Associate Professor Lu from the ANU Research School of Engineering.

PhD researcher Ankur Sharma, who recently won the ANU 3-Minute Thesis competition, said experiments demonstrated the performance of their semiconductor would be much more efficient than conventional semiconductors made with inorganic materials such as silicon.

“We have the potential with this semiconductor to make mobile phones as powerful as today’s supercomputers,” said Mr Sharma from the ANU Research School of Engineering.

“The light emission from our semiconducting structure is very sharp, so it can be used for high-resolution displays and, since the materials are ultra-thin, they have the flexibility to be made into bendable screens and mobile phones in the near future.”

The team grew the organic semiconductor component molecule by molecule, in a similar way to 3D printing. The process is called chemical vapour deposition.

“We characterised the opto-electronic and electrical properties of our invention to confirm the tremendous potential of it to be used as a future semiconductor component,” Associate Professor Lu said.

“We are working on growing our semiconductor component on a large scale, so it can be commercialised in collaboration with prospective industry partners.”

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A capsid is a protein shell that encloses a virus’s genetic blueprint.

The study, led by Cornell University scientists, was published Aug. 1 in the journal Nature and focused on the role of a naturally occurring, small molecule called IP6. The researchers found that IP6 plays an important part in both the immature and mature phases of the HIV life cycle as the virus assembles its structure.

“This small molecule acts in two different assembly steps in the pathway,” said Robert Dick, a postdoctoral researcher at Cornell and the first author of the paper. “A cell can make millions of virus particles, but if they don’t go through the maturation process, they are not infectious.”

The discovery of the key role played by IP6 “opens a door for development of new treatments” that would target that molecule, said Juan R. Perilla, assistant professor of chemistry and biochemistry at the UD.

Perilla and UD doctoral student Chaoyi Xu, who are co-authors of the paper, conducted computational and analytical work for the research project, using supercomputers to model the capsid of the HIV virus and the role of IP6 in its assembly.

“Many experimental techniques are just a snapshot,” Perilla said. “With the computational microscope [the use of laboratory data in combination with supercomputers], you can actually see how things move.”

Perilla and Xu ran their simulations through the Extreme Science and Engineering Environment (XSEDE) project funded by the National Science Foundation, which allocates supercomputer resources to specific research problems. The computers they used were housed at the Pittsburgh Supercomputing Center and the Texas Advanced Computing Center.

Perilla’s research team at UD has done similar types of simulations and analysis on other aspects of HIV and on the hepatitis B virus. The researchers have also investigated other retroviruses, in addition to HIV, including equine and poultry viruses.

“Just as we found that HIV uses IP6 to develop and become infectious, we want to learn how retroviruses in general ‘learned’ to use these kinds of molecules,” Perilla said. “Viruses always evolve, but this particular mechanism is especially important.

“When did it evolve? It’s a question we haven’t answered yet.”

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Until the 1980s, military radar systems were often inadequately shielded against spurious radiation emitted by radar amplifier tubes. Such rays can cause radiation damage to service and maintenance personnel. The persons involved have joined forces in the ‘Association for the support of persons harmed by radar beams’. In 2003, a commission of experts made recommendations on compensatory payments. Since some children of former radar soldiers suffer from physical disabilities attributed to the radiation exposure of their fathers, their offspring are now in the spotlight. Whether radiation led to genotype damage in these children is debated.

A research team from Charité-Universitätsmedizin Berlin, the Berlin Institute of Health (BIH), the Max Delbrück Center for Molecular Medicine, Radboud University Nijmegen (Netherlands) and the University Hospital Bonn have now investigated this question in a pilot study. ‘Through the latest methods of high-throughput sequencing, the complete genomes of parents and their children can now be studied within a short time. This allows us to determine the mutation rates after radiation exposure much more accurately than before’ says first author Dr. med. Manuel Holtgrewe of the Core Unit Bioinformatics (CUBI) of the Berlin Institute of Health (BIH) and Charité-Universitätsmedizin Berlin.

Researchers studied the genomes of twelve families

The scientists studied the genomes of twelve families of radar soldiers. The entire genomes of 18 offspring and their parents were sequenced. The exact radiation exposure of the soldiers cannot be determined retroactively. Researchers estimate, however, that a ‘high dose’ of radiation emanated from the radar systems, especially because radar soldiers very frequently became ill, many from cancer. Scientists compared the mutation rates in the genomes of radar soldier families with that of 28 offspring of parents who were not exposed to radiation.

The focus was on so-called ‘multisite de novo mutations’ (MSDN), which have already been demonstrated in mice because of radiation. An MSDN is present when two or more defects in DNA strands occur adjacently to each other in a line of 20 base pairs. While in the families without radiation exposure, only every fifth offspring had an MSDN, in the radar soldier families this was two out of three offspring. Twelve MSDNs were found in the 18 offspring of radar soldiers, in one family indeed six MSDNs in three offspring. In addition, in two offspring, chromosomal alterations were also detected that had serious clinical consequences. The origin of these mutations could also be traced back to the paternal germ line and only rarely occurs by chance.

‘The results of our pilot study suggest that an accumulation of certain genotype damage by radiation can basically be demonstrated in the next generation,’ says Prof. Dr. med. Peter Krawitz from the Institute for Genomic Statistics and Bioinformatics at the University Hospital Bonn. How pronounced the accumulation of genotype damage by radiation is must be demonstrated by even larger studies, the results of which rely on a much broader database. A team involving Krawitz is currently planning such a follow-up study together with the Institute of Human Genetics of the University Hospital Bonn, the Charité-Universitätsmedizin Berlin and the Berlin Institute of Health (BIH), who are funding it.

The researchers thank the Government Organisation in Support of Radar Victims (BzUR) and its members for supporting the current study. The investigation was facilitated by a private donation of 50,000 euros by Dr. Gisela Sperling.

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In a new study published today, researchers used a job search theoretical model to better understand hunters’ decision-making in order to develop conservation tools to address overhunting in the tropics, where more than three-quarters of all plant and animal species live.

Just as a job applicant goes through a series of decisions each time a potential job is on the table, so too a hunter faces a series of decisions: shoot and gain a reward or delay and wait for another potential prey. What is the optimal stopping point?

Optimal decisions have been used in ecology to address questions about mate or food choice. In this case, an ecologist from the National Institute for Mathematical and Biological Synthesis and a mathematician from Princeton University used it to study hunter diet to determine the optimal stopping point.

Mathematically, the decision to shoot yields what the researchers called a “dietary trait threshold” — the point at which a desired trait such as large body mass or antler size is reached and leads the hunter to take a shot.

Globally, body size is an important determinant of prey value, the researchers wrote, and so it can help predict which species are threatened by overexploitation.

Tropical hunting tends to harvest a wide range of species, across mammals, birds and reptiles. The model is able to identify which ones are subject to hunting pressure. The opportunity cost of each hunting trip is factored in as well.

“Being able to evaluate hunter prey selection is critical to prioritizing limited resources for conservation management,” said lead author and NIMBioS postdoctoral fellow Charlotte Chang.

Chang and co-author Sarah Drohan, a doctoral student in applied mathematics at Princeton University, tested the model using data from the tropical rainforests of Southwest China, a biodiversity hotspot where several species, such as the Gaur and the Green peafowl, are under threat from overhunting.

The model could be used to infer whether there had been changes to harvested prey communities and to evaluate the efficacy of hunting regulations.

“The model was particularly informative and has the potential to simplify monitoring and management of overharvested areas,” Chang said.

Since the Moon is tidally locked to the Earth — it always has the same side facing the Earth — the Earth will never appear to rise above the surface to someone standing on the lunar farside. Orbiting around the Moon, however, gave the Apollo 8 astronauts, Frank Borman, James Lovell, and William Anders this stunning view, before they safely returned home to Earth.

The Apollo 8 mission took place from 21 to 27 December 1968. After completing 10 orbits around the Moon on Christmas Eve, broadcasting images back to Earth and giving live television transmissions, the crew returned to Earth and landed in the Pacific Ocean.

The Working Group for Planetary System Nomenclature (WGPSN) of the International Astronomical Union, who named the craters, is the authority responsible for the naming of planetary features in our Solar System. The two named craters were previously designated by letters.

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