Astronomy
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Opportunity Starts Historic Descent of Tantalizing Martian Gully to
Find Out How Was It Carved
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Huge Endeavour crater spans some 22 kilometers (14 miles) in diameter on the Red Planet. Perseverance Valley slices eastwards at approximately the 8 o’clock position of the circular shaped crater. It sits just north of a rim segment called “Cape Byron.”
Why go and explore the gully at Perseverance Valley?
“Opportunity will traverse to the head of the gully system [at Perseverance] and head downhill into one or more of the gullies to characterize the morphology and search for evidence of deposits,” [Opportunity Deputy Principal Investigator Ray Arvidson of Washington University in St. Louis] elaborated to Universe Today.
“Hopefully test among dry mass movements, debris flow, and fluvial processes for gully formation. The importance is that this will be the first time we will acquire ground truth on a gully system that just might be formed by fluvial processes. Will search for cross bedding, gravel beds, fining or coarsening upward sequences, etc., to test among hypotheses.”
Source of Mars Trojans Might Be Mars Itself
It's one of the major mysteries of the inner solar system: How did Mars — a tiny world only a tenth the mass of Earth — capture its cluster of orbit-sharing Trojan asteroids?
Trojans are asteroids that co-orbit either ahead of a planet, at the L4 Lagrangian point, or behind it at the L5 point. These regions are stable because the gravitational pull of the planet balances that of the Sun. Trojan asteroids have been discovered around Jupiter, Uranus, Neptune, Venus, and Mars. (Only one Trojan (2010 TK7) has been discovered related to the Earth, though the Osiris-REX mission bound for 101955 Bennu is currently on the hunt for more.)
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5261 Eureka is the prototypical Mars Trojan asteroid, and is also known to have an olivine-rich composition. Of the nine Mars Trojans currently known, seven belong to a single cluster, of which Eureka is the largest member, which trails Mars at the L5 point.
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But if the presence of olivine in the Mars Trojans indicates a trip from the Martian surface, it won't have been an easy one. While it's easy enough for an impact to eject some of a planet's surface (similar scenarios explain how Martian meteorites end up on Earth), moving those ejected pieces into a stable orbit alongside the Red Planet would require a significant change in their orbital energy. Polishook's team ran simulations to show that one possible way to make this change would be for the orbit of Mars itself to "jump" before settling into the orbit we see today.
Biology
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Sticky when wet: Strong adhesive for wound healing
When first author Jianyu Li, Ph.D. (former Postdoctoral Fellow at the Wyss Institute and now an Assistant Professor at McGill University) started thinking about how to improve medical adhesives, he found a solution in an unlikely place: a slug. The Dusky Arion (Arion subfuscus), common in Europe and parts of the United States, secretes a special kind of mucus when threatened that glues it in place, making it difficult for a predator to pry it off its surface. This glue was previously determined to be composed of a tough matrix peppered with positively charged proteins, which inspired Li and his colleagues to create a double-layered hydrogel consisting of an alginate-polyacrylamide matrix supporting an adhesive layer that has positively-charged polymers protruding from its surface.
The polymers bond to biological tissues via three mechanisms -- electrostatic attraction to negatively charged cell surfaces, covalent bonds between neighboring atoms, and physical interpenetration -- making the adhesive extremely strong. But the matrix layer is equally important, says Li: "Most prior material designs have focused only on the interface between the tissue and the adhesive. Our adhesive is able to dissipate energy through its matrix layer, which enables it to deform much more before it breaks." The team's design for the matrix layer includes calcium ions that are bound to the alginate hydrogel via ionic bonds. When stress is applied to the adhesive, those "sacrificial" ionic bonds break first, allowing the matrix to absorb a large amount of energy before its structure becomes compromised. In experimental tests, more than three times the energy was needed to disrupt the tough adhesive's bonding compared with other medical-grade adhesives and, when it did break, what failed was the hydrogel itself, not the bond between the adhesive and the tissue, demonstrating an unprecedented level of simultaneous high adhesion strength and matrix toughness.
The researchers tested their adhesive on a variety of both dry and wet pig tissues including skin, cartilage, heart, artery, and liver, and found that it bound to all of them with significantly greater strength than other medical adhesives. The tough adhesive also maintained its stability and bonding when implanted into rats for two weeks, or when used to seal a hole in a pig heart that was mechanically inflated and deflated and then subjected to tens of thousands of cycles of stretching. Additionally, it caused no tissue damage or adhesions to surrounding tissues when applied to a liver hemorrhage in mice -- side effects that were observed with both super glue and a commercial thrombin-based adhesive.
Scientists Enlist Baker’s Yeast to Find New Medicines
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Despite modern technology, drug discovery still largely rests on guesswork. To find a drug that, say, kills cancer cells, scientists sift through libraries containing thousands of chemical compounds, the majority of which will have no effect at all.
“There are many different types of libraries to choose from. A lot of the time you choose a library based on its availability or its cost, not any sort of functional information, and so it becomes a shot in the dark,” says Dr. Jeff Piotrowski, a lead author on the paper who was a postdoctoral fellow in both the Yoshida and Boone labs and now works at the Boston biotechnology company, Yumanity Therapeutics, which uses yeast cells to find drugs for neurodegenerative diseases.
With their chemical genetics platform, Piotrowski and colleagues were able to show which parts of the cell are targeted by thousands of compounds from seven different libraries, six of which have been extensively explored and includes collections from the National Cancer Institute (NCI), the National Institute of Health and the pharmaceutical company Glaxo-Smith-Kline. The seventh and largest collection, from RIKEN in Japan, harbors thousands of virtually unexplored natural products from soil microbes.
Yeasts are currently the only living organism in which scientists have a good handle on the basic cellular processes, such as DNA replication and repair, energy production, and transport of cargo molecules, allowing them to link a drug to a particular bioprocess.
Chemistry
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Lignin
Lignin does what it says on the tin, its name derived from the Latin for wood, lignum. Having said that, although the compound’s role in tree wood is probably most significant, lignin also occurs in plants with the same kind of structure for distributing water and nutrients, the vascular plants, which include ferns and flowering species. Not surprisingly, this means there’s a whole lot of lignin out there, second only as an organic polymer to the ubiquitous cellulose and contributing to about 30 per cent of biomass.
Strictly speaking, lignin is not a compound but a whole family – the exact makeup varies from species to species. Each has a repeating format, with a unit that will typically contain a carbon ring, a short carbon chain, two to four oxygen atoms and sometimes a small number of methyl groups. Unlike many other polymers found in nature, though, lignin doesn’t have a standard structural pattern – there is no equivalent of, say, the elegant helical backbone of DNA. Lignin forms random looking structures in the cell walls of plants. Here, that untidy network makes for added rigidity – hence the importance of lignin in wood. Its function has been likened to the epoxy resin in fibreglass, with cellulose playing the part of the glass fibres. However, this is not the only role that lignin plays.
There’s a reason this compound is found particularly in vascular plants. Cellulose and several other compounds in cell walls are hydrophilic, attracting water and allowing it to pass through. But in the cells that act like a vascular plants’ arteries, water and nutrients must be passed along the tissue efficiently – particularly in trees, where there can be a significant distance between the new growth and the roots. Lignin is hydrophobic, repelling water – so the network of lignin in the cell walls acts to keep the fluids needed for life in place.
There’s a secondary implication of this ability that has proved highly useful to humans. When the compound was first identified by Swiss botanist Augustin Pyramus de Candolle in 1813, he noted that it did not dissolve in water. Once a plant is dead, lignin is far slower to break down than many of the other organic compounds in the plant’s cells. This contributes to our ability to use wood as a versatile structural material, as well as influencing the way that rotting plant matter holds onto a significant amount of nutrients in compost, and enabling the formation of the fossilised carbon fuels such as coal and oil that made the industrial revolution possible. Without lignin’s slow breakdown, far more of the carbon would be quickly distributed through the soil, less likely to be concentrated to form a fossil fuel. What’s more, it’s the presence of significant amounts of lignin in wood that makes it a good fuel, as with a higher carbon and hydrogen to oxygen ratio than other common plant compounds, it produces more energy on burning.
Ecology
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'Missing lead' in Flint water pipes confirms cause of crisis
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The findings—led by researchers at the University of Michigan—support the generally accepted understanding that lead leached into the system because that water wasn't treated to prevent corrosion. While previous studies had pointed to this mechanism, this is the first direct evidence. It contradicts a regulator's claim earlier this year that corrosion control chemicals would not have prevented the water crisis.
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If a lead service line connects to a home with galvanized steel pipes, for example, those pipes can act as lead sponges that can hold and then later release particles containing the toxic metal, said study co-author Brian Ellis, U-M assistant professor of civil and environmental engineering.
In addition to examining pipe samples under a scanning electron microscope, the researchers pulverized the pipe linings to analyze what they're made of. In the Flint pipes, they found a greater ratio of aluminum and magnesium to lead than is typical for lead service lines, when compared with data from 26 other water utilities.
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Water utilities with both corrosive water and lead service lines in their systems add compounds called orthophosphates to prevent that breakdown. When Flint switched from Lake Huron water to the more corrosive Flint River to save money, the utility didn't adjust its treatment process by adding orthophosphates.
‘Omnipresent’ effects of human impact on England’s landscape
revealed by University of Leicester geologists
‘Omnipresent’ signs demonstrating the effects of human impact on England’s landscape have been revealed by researchers from the University of Leicester.
Concrete structures forming a new, human-made rock type; ash particles in the landscape; and plastic debris are just a few of the new materials irreversibly changing England’s landscape and providing evidence of the effects of the Anthropocene, the research suggests.
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Professor Jan Zalasiewicz, from the University of Leicester’s Department of Geology, said: “We are realising that the Anthropocene is a phenomenon on a massive scale – it is the transformation of our planet by human impact, in ways that have no precedent in the 4.54 billion years of Earth history. Our paper explores how these changes appear when seen locally, on a more modest scale, amid the familiar landscapes of England.”
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The research also shows how the chemistry of soils and sediments has been marked by an influx of lead, copper and cadmium pollution – and by plastic debris, pesticide residues and radioactive plutonium.
Physics
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A hybrid material to spot organic contaminants in the atmosphere
The chemist Paula Moriones-Jiménez has obtained a type of hybrid material made up of organic and inorganic components and which is highly porous, a feature of interest for industrial sectors such as the pharmaceutical, automotive and electronic sectors. This material has been applied to detect organic contaminants such as benzene, toluene or xylene in the atmosphere, and also has the potential for use as a water-repellent coating.
The development of hybrid materials is an emerging field in materials science. As the researcher explained, the interest in these materials stems from "the success in combining that stability of inorganic components with the versatility of organic components. Blending them causes the properties of both to be combined and even improved," she said. "Additionally, hybrid materials can be processed in the form of gels, films, fibres, particles or powders. There is virtually no limit to the combinations of organic and inorganic components to produce hybrid materials, which have a huge number of applications in medicine, microelectronics, sensors, optical systems, the automotive industry and decorative surface coatings.
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Nanometric-sized pores
As the researcher confirmed, gel formation time and the properties of the materials obtained are influenced by the conditions for synthesizing these materials and the proportion of the ones that are organic. Thus, for example, the materials can have smaller or larger nanometric pores. "Pore size is crucial in the applications of these materials, because they can, for example, be used for the controlled release of drugs," she said. [...] "Some of the synthesised materials are highly hydrophobic and repel water. This property enables them to be used in the pharmaceutical industry as elements for selectively trapping other materials on their surfaces or retaining them, and in the glass industry as protective coatings," concluded the researcher.