“We are optimistic for the performance of the industry overall this year. Economic and job growth should continue to drive expansion in exhibitions,” says Allen Shaw, CEIR economist and chief economist for Global Economic Consulting Associates, Inc. The tradeshow industry continued its steady recovery following the market collapse in the late 2000s, according to the Center for Exhibition Industry Research (CEIR). The CEIR Index, a composite figure that accounts for net square footage (NSF), number of exhibitors, attendance and revenue of all major U.S. tradeshows, was up 1.8 percent last year. While the growth is slightly off the projected 2.0-percent return, it marks the fourth-consecutive year of positive gains. The group is forecasting continued improvement over the next three years, as well. Projections show 2.8-percent growth this year, followed by 2.4- and 2.0-percent gains in 2016 and 2017, respectively. Market-by-market performance varied considerably in 2014. Up 5.2 percent, financial, legal and real estate shows were at the top of the industry, followed by building, construction, home and repair (5.1 percent) and food (4.4 percent). Education (-3.0 percent), machinery and finished business outputs (-1.0 percent) were at the opposite end of the spectrum.
WILMINGTON, MA – Wilmington Public Schools is seeking substitute teachers at the elementary school, middle school and high school levels, according to a job listing posted on October 1.Substitute teacher rates in Wilmington are as follows:Day to day: $75/day without a DESE license, $85/day with a DESE license45-59 days in the same assignment: $100/day without a DESE license, $110/day with a DESE license60-90 days in the same assignment: $115/day without a DESE license, $125/day with a DESE license91 or more days in the same assignment: $250.84/day (must have a DESE license)The school system is also seeking substitute educational assistants ($60/day), substitute LPNs ($75/day), and substitute nurses ($125/day).View the job posting, which includes further information about the application process, HERE.Got a question? Contact Andrea Armstrong, Human Resources Director, at 978-694-6000 or firstname.lastname@example.org.Like Wilmington Apple on Facebook. Follow Wilmington Apple on Twitter. Follow Wilmington Apple on Instagram. Subscribe to Wilmington Apple’s daily email newsletter HERE. Got a comment, question, photo, press release, or news tip? Email email@example.com.Share this:TwitterFacebookLike this:Like Loading… RelatedWilmington Public Schools Hiring Substitute Teachers, Educational Assistants & Nurses For Upcoming School YearIn “Education”Wilmington Public Schools Hiring Substitute Teachers, Educational Assistants & NursesIn “Education”Wilmington Public Schools Hiring Substitute Teachers, Educational Assistants & NursesIn “Education”
Citation: Scientists go to great lengths to extend superlow friction (2015, February 13) retrieved 18 August 2019 from https://phys.org/news/2015-02-scientists-great-lengths-superlow-friction.html Researchers investigated the superlow friction of the chain structures above. They found that superlubricity can theoretically hold for tens of cemtimeters and disappears above a critical chain length, which depends on a material’s intrinsic properties. Credit: Ma, et al. ©2015 American Physical Society In the new study published in Physical Review Letters, researchers Ming Ma, et al., have theoretically investigated the maximum length of a chain of particles that exhibits superlubricity. Their model shows that this critical length depends on the experimental parameters and the material’s properties, especially its stiffness. For very stiff materials, such as carbon nanotubes, the scientists found that superlubricity may hold for up to tens of centimeters, after which it abruptly disappears. “These results indicate an avenue for achieving superlow friction at the macroscale, and can potentially aid in the rational design of superlubric materials for nanomechanical applications,” Michael Urbakh, a professor at Tel Aviv University and one of the study’s lead authors, told Phys.org.As the scientists explain, superlow friction relies on a special arrangement of atoms on a material’s surface. In graphite, for instance, the surface atoms have a bumpy hexagonal arrangement like egg cartons/boxes. In certain orientations, two surfaces of graphite can mesh in such a way that the “bumps” can slide past one other effortlessly, and friction drops to almost zero. In contrast, when the same pieces of graphite are slightly rotated with respect to each other, their surface atoms can no longer easily slide, and the materials exhibit the familiar effects of friction. This kind of change in geometrical configuration can explain the abrupt transition between the frictionless and friction regimes in the researchers’ models. A shorter nanotube, or chain, exhibits superlubricity because its particles are mismatched, or incommensurate, with the underlying substrate atoms. Since the atoms avoid interlocking with each other, the chain easily slides on the surface. But for a longer chain, a mechanical instability triggers lattice matching at the chain’s leading edge. As a result, the particles become in registry, or commensurate, with the atoms in the substrate lattice, and friction suddenly increases.The researchers’ simulations also revealed that the critical chain length forms a sharp boundary between two phases based on interparticle distance: the distance between particles is smaller in the shorter chain than in the longer chain. At exactly the critical length, an abrupt jump in this distance occurs, along with the abrupt jump in friction. By better understanding superlubricity and its limits, the researchers hope to extend the effect to as large a scale as possible. Superlubricity could prove very useful for designing nanoscale systems with low wear and tear, and it could be even more useful if it could be extended to larger scales. “The challenge here is to scale up the size of the sliding objects without losing the perfect egg-box geometry necessary for superlubricity,” said coauthor Andrea Vanossi at the CNR-IOM Democritos National Simulation Center and the International School for Advanced Studies (SISSA), both in Trieste, Italy. “Normally, as the size of the objects grows, defects and imperfections comes into play. Only recently, thanks to the impressive advances in the synthesis techniques, has it been possible to produce defect-free, atomically perfect elongated nanostructures such as carbon nanotubes, graphene nanoribbons, and conjugated polymers. Once it is possible to have two large-scale, geometrically perfect surfaces rub against each other without friction, and to apply this material as a coating to ball bearings and moving machine parts, there will be huge savings ahead in the areas of energy, resource consumption, and maintenance.”The researchers are currently working to expand their approach to understand mechanisms limiting superlow friction between 3D materials. © 2015 Phys.org (Phys.org)—When nanosized pieces of graphite slide against each other, there can be virtually no friction between them. For many years, superlow friction, or “superlubricity,” was known to exist only on the nanoscale. Then in 2012, scientists first demonstrated superlubricity beyond the nanoscale when they discovered the phenomenon in micrometer-sized graphite. Building on this and related research, scientists in a new study have now theoretically shown that superlow friction could extend to lengths of tens of centimeters. More information: Ming Ma, et al. “Critical Length Limiting Superlow Friction.” Physical Review Letters. DOI: 10.1103/PhysRevLett.114.055501 Journal information: Physical Review Letters Friction almost vanishes in microscale graphite Explore further This document is subject to copyright. Apart from any fair dealing for the purpose of private study or research, no part may be reproduced without the written permission. The content is provided for information purposes only.
This document is subject to copyright. Apart from any fair dealing for the purpose of private study or research, no part may be reproduced without the written permission. The content is provided for information purposes only. In order for life to have existed on Mars (or if it still does in a place we have not found yet) it would have to have an energy source of some kind. Prior research has suggested such a source might be nitrogen, the same energy source for most plants here on Earth—a recent report by researchers studying data from Curiosity rover, describes nitrates found in the soil. In this new effort, King takes a different approach, he believes that carbon monoxide may hold the key to life on Mars.King took soil samples from three places here on Earth that have very dry climates and very salty soil, the Atacama desert in Chili, the Bonneville Salt Flats in Utah and a part of the big island in Hawaii. In studying the samples, he found that the soil did indeed pull carbon monoxide out of the air and held onto it. He suggests the same process could occur on Mars, as its atmosphere has more carbon monoxide in it than does ours. He goes further to suggest that the mysterious, recurring slope lineae—dark streaks that change color seasonally on Mars, might be due to carbon monoxide being pulled into the soil. He believes that carbon monoxide could represent the missing piece in the search for life on Mars: the energy source. As evidence of the possibility, he points out two microbes (Halorubrum str. BV1 and Alkalilimnicola ehrlichii MLHE-1) that live on Earth that use carbon monoxide as an energy source, one of which has also been shown able to tolerate salt concentrations that are similar to those found in Martian soil.Unfortunately, there is no mechanism for testing King’s ideas, neither of the rovers on Mars has the equipment needed for that kind of test. He will have to wait until 2021, when NASA plans to send a probe to the Red planet that is capable of detecting microbes in the soil. Explore further Valles Marineris, Mars. Credit: NASA (Phys.org)—Gary King, a biologist at Louisiana State University has put forth the idea that if life did exist on Mars, it very possibly could have survived by using carbon monoxide. In his paper published in Proceedings of the National Academy of Sciences, he discusses his study of microbes in soil samples collected here on Earth that are able to pull in carbon monoxide and why it might relate to life on Mars. Journal information: Proceedings of the National Academy of Sciences More information: Carbon monoxide as a metabolic energy source for extremely halophilic microbes: Implications for microbial activity in Mars regolith, Gary M. King, PNAS, DOI: 10.1073/pnas.1424989112AbstractCarbon monoxide occurs at relatively high concentrations (≥800 parts per million) in Mars’ atmosphere, where it represents a potentially significant energy source that could fuel metabolism by a localized putative surface or near-surface microbiota. However, the plausibility of CO oxidation under conditions relevant for Mars in its past or at present has not been evaluated. Results from diverse terrestrial brines and saline soils provide the first documentation, to our knowledge, of active CO uptake at water potentials (−41 MPa to −117 MPa) that might occur in putative brines at recurrent slope lineae (RSL) on Mars. Results from two extremely halophilic isolates complement the field observations. Halorubrum str. BV1, isolated from the Bonneville Salt Flats, Utah (to our knowledge, the first documented extremely halophilic CO-oxidizing member of the Euryarchaeota), consumed CO in a salt-saturated medium with a water potential of −39.6 MPa; activity was reduced by only 28% relative to activity at its optimum water potential of −11 MPa. A proteobacterial isolate from hypersaline Mono Lake, California, Alkalilimnicola ehrlichii MLHE-1, also oxidized CO at low water potentials (−19 MPa), at temperatures within ranges reported for RSL, and under oxic, suboxic (0.2% oxygen), and anoxic conditions (oxygen-free with nitrate). MLHE-1 was unaffected by magnesium perchlorate or low atmospheric pressure (10 mbar). These results collectively establish the potential for microbial CO oxidation under conditions that might obtain at local scales (e.g., RSL) on contemporary Mars and at larger spatial scales earlier in Mars’ history. Citation: Biologist suggests carbon monoxide as an energy source for microbes on Mars (2015, March 24) retrieved 18 August 2019 from https://phys.org/news/2015-03-biologist-carbon-monoxide-energy-source.html Video: What makes carbon monoxide so deadly? © 2015 Phys.org