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Record-smashing new shield creates a large volume with a magnetic field even smaller than that found in the depths of outer space, making certain types of searches for physics beyond the Standard Model possible for the first time
The Standard Model of particle physics, sometimes called "The Theory of Almost Everything," is the best set of equations to date that describes the universe's fundamental particles and how they interact. Yet the theory has holes -- including the absence of an adequate explanation for gravity, the inability to explain the asymmetry between matter and antimatter in the early universe, which gave rise to the stars and galaxies, and the failure to identify fundamental dark matter particles or account for dark energy.
Technische Universität Müchen
This image shows the inner three layers of the magnetic shield (also known as the insert), and the cylindrical layer with 780 copper rods. The cylindrical layer is used to generate a very uniform magnetic field, which is necessary for EDM experiments. Also shown are two measurement devices: A mercury magnetometer is placed between the wooden support structure, and a high precision pendulum device, which is used for the absolute alignment of conventional magnetic field probes, is on top of the support table.
Researchers now have a new tool to aid in the search for physics beyond the good, but yet incomplete Standard Model. An international team of scientists has designed and tested a magnetic shield that is the first to achieve an extremely low magnetic field over a large volume. The device provides more than 10 times better magnetic shielding than previous state-of-the art shields. The record-setting performance makes it possible for scientists to measure certain properties of fundamental particles at higher levels of precision -- which in turn could reveal previously hidden physics and set parameters in the search for new particles.
The researchers describe the new magnetic shield in a paper in the Journal of Applied Physics, from AIP Publishing.
High precision measurements are one of three frontiers to search for physics beyond the Standard Model, explained Tobias Lins, a doctoral student who worked on the new magnetic shield in the research lab of Professor Peter Fierlinger at the Technische Universität München in Germany. The precision measurements complement other methods to search for new physics, including slamming particles together in a collider to generate new, high-energy particles, and peering into space to catch signals from the early universe.
"Precision experiments are able to probe nature up to energy scales which might not be accessible by current and next generation collider experiments," Lins said. That's because the existence of exotic new particles can slightly alter the properties of already known particles. A tiny deviation from the expected properties may indicate that an as-yet-undiscovered fundamental particle inhabits the "particle zoo."
Constructing the Shield
The researchers built the new shield out of several layers of a special alloy, composed of nickel and iron, that has a high degree of magnetic permeability -- meaning it can act like a sponge to absorb and redirect an applied magnetic field, like the earth's own magnetic field or fields generated by equipment such as motors and transformers.
"The apparatus might be compared to cuboid Russian nesting dolls," Lins said. "Like the dolls, most layers can be used individually and with an increasing number of layers the inside is more and more protected."
The team's big breakthrough came from in-depth numerical modeling of the arrangement of the precision treated magnetizable alloy, resulting in significantly optimized design details, like thickness, connections and spacing of layers.
The materials in magnetic shields change their magnetization due to environmental influences, like temperature changes and vibrations caused by passing cars, and these shifts can be passed to the inside of the shield. The thinner sheets in the new design enabled a better balancing of the magnetic field in the metal, resulting in the smallest and most homogenous magnetic field ever created within the shielded space, even beating the average ambient magnetic field of the interstellar medium.
New Experiments Ahead
Plans are already underway to use the new magnetic shield in an experiment to test limits for the distribution of charges (called the electric dipole moment, or EDM) of an isotope of xenon. An EDM that is higher than predicted by the Standard Model could signal the existence of a new particle whose mass is linked to the amount by which the EDM deviates from the expected value.
The researchers also want to use a modified SQUID detector -- which can detect extremely subtle magnetic fields -- to search for long theorized, but never detected magnetic monopoles. Within the magnetically quiet space inside the shield, a monopole passing by the SQUID might produce a magnetic field higher than the background noise level, Lins said.
The article, "A large-scale magnetic shield with 10^6 damping at millihertz frequencies," is authored by I. Altarev, M. Bales, D. H. Beck, T. Chupp, K. Fierlinger, P. Fierlinger, F. Kuchler, T. Lins, M. G. Marino, B. Niessen, G. Petzoldt, U. Schläpfer, A. Schnabel, J. T. Singh, R. Stoepler, S. Stuiber, M. Sturm, B. Taubenheim and J. Voigt. It will be published in the Journal of Applied Physics on May 12, 2015 (DOI: 10.1063/1.4919366). After that date, it can be accessed at: http://scitation.aip.org/content/aip/journal/jap/117/18/10.1063/1.4919366
The authors of this paper are affiliated with the universities Technische Universität Müchen, the University of Illinois at Urbana-Champaign, the University of Michigan and Physikalisch-Technische Bundesanstalt Berlin and the industry partner IMEDCO AG as manufacturer of the shield.
ABOUT THE JOURNAL
Journal of Applied Physics is an influential international journal publishing significant new experimental and theoretical results of applied physics research. See: http://jap.aip.org
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One of the more common combustion reactions is the combustion of an alkane in the presence of oxygen.
A general strategy for balancing these combustion reactions is to first balance the carbon (C) atom, followed by the hydrogen atoms (H) and then then oxygen (O) atoms.
Remember: C H O
The combustion of alkanes in the presences of oxygen will produce carbon dioxide and water. Here is the reaction for the combustion of propane , an alkane containing 3 carbon atoms.
Here is the balanced equation for the combustion of propane , an alkane
containing 3 carbon atoms:
C3H8 + 5 O2 -----> 3 CO2 + 4 H2O
Let's examine how this combustion reaction was balanced.
Strategy for balancing a combustion reaction
1. Write the reaction.
C3H8 + O2 -----> CO2 + H2O
2. Next balance the carbon atoms ( C) by placing a 3 in front of the CO2 in the products.
C3H8 + O2 -----> 3 CO2 + H2O
3. Then balance the hydrogen atoms (H) by placing a 4 in front of the H2O in the products.
C3H8 + O2 -----> 3 CO2 + 4 H2O
4. Finally balance the the oxygen atoms (O) by placing a 5 in front of the O2 in the reactants.
C3H8 + 5 O2-----> 3 CO2 + 4 H2O
If the alkane contains an even number of carbon atoms, you will need to alter your strategy slightly.
You still use C H O; however when you attempt to balance the oxygens in the end you will get stuck.
A simple strategy for balancing alkanes that have an even number of hydrogens is to simply place a 2 in front of the alkane before you begin to balance.
Balancing combustion reactions with an even number of carbons in the alkane.
1) Let's first write the reaction.
C2H6 + O2 -----> CO2 + H2O
2) Arbitrarily place a 2 in front of the C2H6 in the reactants.
2 C2H6 + O2 -----> CO2 + H2O
3) Now balance the carbon atoms by placing a 4 in front of CO2 in the products.
2 C2H6 + O2 -----> 4 CO2 + H2O
4) Balance the hydrogen atoms by placing a 6 in front of H2O in the products.
2 C2H6 + O2 -----> 4 CO2 + 6 H2O
5) Now balance the oxygen atoms by placing a 7 in front of the O2 in the reactants.
2 C2H6 + 7 O2 -----> 4 CO2 + 6 H2O | <urn:uuid:3c2ae95b-bd70-4d94-8878-9edd451d628f> | 3.953125 | 601 | Tutorial | Science & Tech. | 74.303154 | 95,628,668 |
July 27th, 2016 by Clem Miege
Our team got out of the field a few days ago after a successful field campaign with a lot of great data to analyze! For the coming blog posts, we will be sharing with you the different kind of measurements we made during our stay at the ice camp and but also describe the wide range of instrumentation being used.
For this blog entry, I am going to talk about the surveys we did with a ground-penetrating radar (also known by its acronym: GPR) and the shallow ice cores we collected to help calibrating the radar data by identify the depths of subsurface features. The main of goal of this radar data is to quantify spatial changes in the weathering crust. This crust corresponds to a relatively thin layer (1-2 meters thick) of ice and water starting from the ice surface. It is strongly influenced and shaped by weather variations (sunny days vs. cloudy days, air temperature, melt intensity…)
But before going in those details, here is a photo of our camp in relation to the supra-glacial lake and river to get you situated.
General view of our ice camp with a close up on Rio Behar at the bottom of the photo. Photo by Clem Miege.
For the ground-penetrating radar measurements, we brought to the ice camp a radar designed by GSSI, a company specialized into geophysical measurements. The radar basically acts as our eyes to explore the features located in the ice, below the surface. With a 400 MHz antenna, we are limited to look at the first 50m of the ice thickness with a vertical resolution of about 10-20 cm. Any changes in the ice density, stratigraphy or changes in its dielectric properties create internal reflections. We then follow and trace those continuous reflections (also called internal layers) and look at their spatial distribution. In addition, the presence of water within the ice generates a sharp and bright radar reflection because of the significant dielectric contrast between the solid and the liquid phase of the water molecule.
The radar system is made of an antenna and a control unit. It is relatively light and portable, making it possible to use with only one person. To geolocate the radar scans in relation to the ice surface, we carry a precise GPS.
The radar setup with the GPS antenna. Photo by Charlie Kershner.
The radar in action. Photo by Lincoln Pitcher.
In addition to the GPR work, we have been drilling 10 boreholes from the ice surface. Big thanks to Bob Hawley at Dartmouth for letting us borrow his coring drill. We extracted 75-mm-width ice cores in the top part of the ice column (1 to 2 meters depth) which reveal the ice stratigraphy and densities below the surface. We also measured the height of the water in the borehole (if any) which will be helpful to establish an accurate depth profile for the radar data.
Asa is operating the coring drill from the surface to retrieve ice cores. Photo by Clem Miege.
Clem is processing the first meter of the ice cores, logging mainly stratigraphy and densities. Photo by Matt Cooper.
Back at the office, we will have quite a bit of work to process all the data collected and connect the ice-core data with the radar data. This dataset will become very helpful to understand the formation of the weathering crust as well as the water being stored in it.
That is it for this post! Thanks for following us and there will be more blog entries soon so you can learn about the other instruments deployed on the ice.
All the best,
July 26th, 2016 by Clem Miege
In the last two weeks, we’ve wrapped up the test flights and major preparations for NASA’s ATom mission. ATom is an airborne science experiment aboard the DC-8 flying laboratory that will study the most remote parts of the Earth’s atmosphere. We want to learn how much pollution reaches areas most people would consider untouched by human influence, and to understand how pollutant chemicals in these distant regions affect things we care about.
I’m Steve Wofsy, an atmospheric scientist at Harvard University and ATom’s Principal Investigator. I couldn’t be more excited to get underway. ATom is the realization of an idea to sample cross-sections of the world’s atmosphere that I have dreamed about for more than 20 years. The idea for ATom started in the 1990’s, when I participated in a series of aircraft missions that characterized the chemistry of the Earth’s stratosphere, spanning from the Arctic to the Antarctic. Our images of global chemical changes were immensely powerful in helping us to understand depletion of stratospheric ozone. Together with my colleagues in those stratospheric missions, Paul Newman of NASA’s Goddard Space Flight Center and Michael Prather of University of California, we started to think about how we might undertake such a study in the troposphere, where we all live.
The Los Angeles skyline is hazy with smog generated from air pollutants emitted by cars. The air pollution doesn’t stay in the city, however, but will eventually travel to other parts of the world. Credit: Michael Prather
The chemistry of the atmosphere is very important for human beings and for all creatures on Earth. In the ATom study we want to understand air pollution and climate change. Air pollution has immediate and long-term consequences for human health, agriculture, and ecosystems. Climate change in the era of fossil fuel emissions and industry is being driven mostly by the gases we pump into the atmosphere.
To understand the chemistry of the atmosphere, we have to be able to measure many different chemicals in tiny amounts. The only way to do that is by going out in the atmosphere itself. We can’t make the measurements only at the ground, because the atmosphere extends far above the surface. Some measurements can be made using satellites that look down into the atmosphere, but many measurements must be made directly in the air, because the concentrations of many important gases are far too small, and the patterns we need to observe are too fine, to be measured from space.
Scientists have been using airplanes to sample the atmosphere since the 1940’s, when Britain’s Royal Air Force flew missions to understand the occurrence of contrails, which are simply water vapor that condenses behind an aircraft in certain atmospheric conditions. Today’s modern flying laboratories take sophisticated instrumentation throughout the atmosphere, in locations remote and nearby, polluted and nearly unpolluted. It is a very exacting, challenging endeavor, but one that pays off for both our understanding of the planet and for protecting it and the people on the ground.
Some of the most daring measurements of atmospheric chemistry were made in the stratospheric missions I mentioned before, between 1985 and 2000. We used the high-flying ER-2 aircraft carrying extremely sensitive instruments to measure very reactive “free radical” chemical species – in particular the chemicals responsible for the hole in stratospheric ozone that was forming each year over Antarctica. The measurements cannot be done by capturing air and taking it back to the lab – these chemicals are constantly generated by sunlight, and then they react and vanish in seconds, minutes, or hours.
NASA’s ER-2 aircraft takes scientific measurements from 65,000 feet. It was instrumental in understanding the depletion of stratospheric ozone. Credit: NASA Armstrong Flight Research Center
The insights scientists were able to gain because of those data sets led to huge societal changes, including the Montreal Protocol, the international treaty banning a whole class of industrial chemicals that were harming Earth. The amazing global consensus to ban these chemicals could not have happened without the ER-2 aircraft measurements.
Those data did not come easily. Scientists had to develop a whole new class of instruments that had to operate autonomously, since only the pilot is on board the ER-2. The plane had to go to the limit of its capability to sample in very inhospitable locations. Pilots, engineers and scientists worked very closely together to ensure safe execution of these flights.
ATom’s Principal Investigator Steve Wofsy in front of NASA’s DC-8. Credit: Tom Ryerson
The equipment on board the DC-8 in ATom likewise has to be very carefully engineered to be both safe and exquisitely sensitive and accurate. Because the chemistry of the troposphere is much more complex than that of the stratosphere, the number of independent instruments has multiplied to 22. The crew has to manage this very complex payload, with many possible hazards. The plane will often be flying very low to the ocean surface, and it will cross some of the most remote and inhospitable areas on the planet. Many of the instruments in ATom have their heritage in those flights of the ER-2.
The preparation of the DC-8 and the science payload has been meticulous. The planning of flights and logistics around the globe for our ten stopovers was undertaken to meet multiple constraints of safety, cost, and science objectives. We don’t know yet what we’ll see, but it will be the most detailed slice of the atmosphere we’ve ever measured. We hope to find out how human beings are changing the global atmosphere, what are the effects on climate, and what these changes may mean for the health and welfare of human beings and global ecosystems. We are confident in our readiness, eager to head out on our adventure, and ready to report back.
July 22nd, 2016 by Clem Miege
I’m Christina Williamson, a postdoctoral scientist at CIRES CU-Boulder/NOAA-ESRL interested in Atmospheric Aerosols, the small particles in the air that cause haze, and on which clouds are formed.
I’m working with a few colleagues from NOAA to take a suite of instruments on NASA’s ATom mission that will measure the number and size of particles in the air as we fly around the world. We’re interested in this because aerosols in the atmosphere affect how much of the energy from the sun is absorbed and how much is reflected back to space by clouds and by the aerosols themselves.
My research team in our lab at NOAA ESRL setting up our flight rack for ATom. From left to right, Frank Erdesz, engineer with CIRES/NOAA, Charles Brock, Principal Investigator from NOAA, Agneiszka Kupc, research scientist with NOAA/University of Vienna, and Christina Williamson, research scientist with CIRES/NOAA. (Credit: Nick Wagner)
Over the past few weeks we’ve brought our instruments down from NOAA’s Earth-Science Research Laboratory in Boulder, Colorado to NASA Armstrong in California, integrated them onto the plane and tested how they perform while the plane is flying. We’re running five instruments, measuring aerosols in different size ranges, which, after modifying to optimize performance for ATom conditions, and testing in the lab, we put together in a flight rack. Everything we fly is secured in the rack with aircraft grade hardware so that it cannot shake loose or be propelled out during flight, and the rack is then screwed to the seat tracks of the plane.
Assembling the instrument rack in the lab at NASA Armstrong. From left to right, Charles Brock, Principal Investigator from NOAA, Agneiszka Kupc, research scientist with NOAA/University of Vienna, and Christina Williamson, research scientist with CIRES/NOAA. (Credit: Maximilian Dollner)
We sample aerosols in flight by pulling air in through an inlet tube that is mounted on a plate where the window would normally be. We plumbed this to our instruments taking care to route the flow to minimize the number of aerosol particles that get lost by sticking to the walls of the tubing on their way from outside to the instruments.
Instrument inlets (where air is pulled into the instruments inside for sampling) on the NASA DC-8. Ours is the curvy one third from the right. (Credit: NASA Armstrong)
On the plane we tested the instrument set-up while it was still in the hangar, checking for leaks and that particles were being transmitted well, as well as other things like electrical connections and communications. I ran some calibrations to check that nothing had shifted in the instrument performance in the move from the lab. We also spend a good deal of time neatly tying down all of the cabling and plumbing, securing it to the rack and the body of the plane and making sure everything in the rack will hold fast during even the most turbulent of flights.
The AMP (aerosol microphysical processes) rack installed on the DC8. We run all five instruments from this monitor, and check the data as it comes in during the flights. (Credit: Christina Williamson)
The AMP (aerosol microphysical processes) rack being integrated on the DC8. You can see there’s some work to be done neatening and tying down the cabling. The instruments on the top are two Nucleation Mode Aerosol Size Spectrometers (NMASSs), which measure aerosol size distributions between 3 and 60nm. Lower in the rack are two Ultra High Sensitivity Aerosol Spectrometers (UHSASs), which measure particles between 60 and 800nm, and a Laser Aerosol Spectrometer, getting the size distribution from 90nm up to 7.5μm. (Credit: Christina Williamson)
All this involved many days working on the plane in the hangar. Palmdale, where the Armstrong base is located, can get above 40C (104F) this time of year. The air-conditioning from the plane’s ground unit cannot quite compete with combination of heat from outside and from electrical scientific equipment operating inside (not to mention a lot of busy scientists and crew), so it gets pretty hot. We’re working often in the cramped spaces between two instruments, or a rack and the wall, or laying cabling and plumbing along the floor, so it’s hot, awkward and dirty work, but the excitement of working on the plane and seeing everything come together for the flights more than compensates for that.
The crew conducted a shakedown flight without scientists just to check that everything was integrated safely, and then we went up for out first test flight on July 12. This was my first time flying in a research plane. Some more experienced scientists delighted in telling me horror-stories of maneuvers and low-flying turbulence making people ill before we took off. I was nervous, mainly about how my instruments would perform, as there are controls for things like pressure and flow that I can’t test on the ground, and also because I didn’t want to embarrass myself by getting ill on the test flight.
Christina Williamson (i.e. me), research scientist with CIRES/NOAA boarding the DC-8 for our first test flight at NASA Armstrong. (Credit: Agnieszka Kupc)
We flew from the base out over the Pacific, then back inland over the LA-Basin and back to base. The ATom mission flights will be constantly profiling between about 0.2 and 12km (650 feet to 7 miles) altitude, so we did a lot of ascending and descending to check that the instruments can cope with it and to look at the fuel performance of the plane with this payload. To really test every instrument, the pilots did some really fast ascents and descents (for example, flow into the inlets is affected by the incline). I had to be up out of my seat testing some things on the instrument during part of this: the crew really weren’t joking when they said to hang on.
Our instruments behaved well, needing just one or two quick software fixes that I was able to implement as we flew, and I started to relax and enjoy the flight. We can stream video from cameras in the cockpit and one looking directly down below the plane, which is great. We also have a window by my seat, so I can look out.
Once over the Pacific and out of the LA-area high air traffic we dropped seriously low — had there been a whale breaching below I would have easily seen it. We also did some very low flying over the Central Valley, which produced interesting data and interesting views (although also a reasonable amount of turbulence).
Photo from the DC-8 flying low over the Pacific Ocean on the first ATom test flight. (Credit: Christina Williamson)
During the flight we had to do some maneuvers. These are used to calibrate instruments measuring wind-speed. The crew advised us to sit down for these, and I’m glad I did, as some of them had my body weight almost out of the seat and pulling on the seatbelt. If you throw a small object in the air during one of the maneuvers you can watch it appear to hover as it falls under gravity but then you and the plane also move down away from it. It felt a bit like being in a roller coaster, and by the end of all the maneuvers I was glad to return to more normal flight. It can make you a little queasy, but just eating something or walking about the cabin afterwards really helps.
Agneiszka Kupc, research scientist with NOAA/University of Vienna, monitoring data during the first ATom test flight. (Credit: Christina Williamson)
The aircraft is noisy in flight, partly because there is less insulation on it than on a normal passenger plane, and partly because of all the pumps and fans etc. on our instruments. We therefore all wear headsets, which cancel background noise and enable us to communicate with other scientists and the crew. We get some bleed-over from the channel the pilots are on, which is quite fun.
Christina Williamson (yup, me again), research scientist with CIRES/NOAA on the DC-8 during the first ATom test flight. (Credit: Christina Williamson)
I was quite surprised when we arrived back already, four hours of flight goes by so quickly when you’re operating instruments and concentrating on the science behind what you’re seeing compared to a passenger flight. It was a good feeling to have a successful flight under the belt, to see that the instruments worked as expected and that my body coped fine with the flying conditions. We have one more test-flight just before we take off for the mission-proper. I’m looking forward to it!
Christina Williamson blogs regularly about the ATom Mission and other adventures in atmospheric science at christinajwilliamson.wordpress.com and tweets as @chasingcloudsCW.
July 21st, 2016 by Clem Miege
Take 78 percent nitrogen, 21 percent oxygen, 0.9 percent argon, 0.03 percent carbon dioxide – that’s 99.93 percent of the atmosphere. But the trace gases and airborne particles that make up that last approximately 0.07 percent are what NASA’s Atmospheric Tomography (ATom) mission is interested in.
ATom is a chemistry mission to study the movement and chemical processes that affect the top three greenhouse agents after carbon dioxide – methane, tropospheric ozone, and black carbon. In addition, it’s the first time scientists are going to do a comprehensive survey of over 200 gases and aerosol particles all over the world. And to do that a team of university and NASA scientists are going on a 26-day journey from pole to pole and back again.
NASA’s DC-8 aircraft has intake valves on the window ports to suck in the air it’s flying through. Photo taken July 11 in Palmdale, California, before ATom’s first test flight. Credit: Michael Prather (UCI)
Over the next few weeks a handful of ATom scientists will be blogging about their around-the-world journey on NASA’s DC-8 flying laboratory – a plane the size of a midsize commercial airliner stuffed with 22 scientific instruments for sampling the air. They’ll collect data that not only shows where these hundreds of trace gases are hanging out and where they’re going, but also how they interact with each other – creating new compounds or destroying others, like methane, and effectively removing them from the atmosphere. Taken together, the data will give the science community a better understanding of how these gases, many of which are pollutants, affect global climate change.
The majority of the air sampled will be over the Pacific and Atlantic oceans. This summer’s trip will be the first of four deployments, one in each season over the next three years.
To learn more about ATom’s science goals and its ten-leg flight path, stay tuned.
Comments Off on ATom Mission to Sample the Atmosphere is Ready for Take Off
July 20th, 2016 by Clem Miege
We are ready for the big day! Tomorrow (Wednesday) we will start our put-in to the field. With a total of 5 helicopter flights all our gear, science equipment and the entire team will be flown to our field site, approx. 130 km northwest of Kulusuk. However, we have to take the weather in account; if it is foggy on the ice sheet the helicopter will not be able to land and the put-in will be postponed. So, fingers crossed!
View from the village of Kulusuk. Great weather!
During the past three days, the team arrived according to plan: Rick and Kip on Sunday morning and, last but not least, Nick on Monday morning. Having the entire team in Kulusuk made the organization of the equipment rather quick and smooth. To give you an idea of the preparations we have done: we checked and strengthened about 100 bamboo stakes, repaired tears in the tents, tested the generators, checked the gasoline on contamination with water, charged ~20 batteries, and every group sorted and tested their own science equipment. In the end, we had 132 packed and weighted items ready to be taken to the field.
This afternoon the BlueWest helicopter arrived from Reykjavik with our two pilots Johannes and Nicola. They crossed the ocean from Iceland to Greenland on the narrowest part as that is about the maximum distance the helo can fly. From there they followed the Greenland coast southward till Kulusuk. On the way, they saw seals and a group of 10 whales from the helicopter. That must have been an awesome sight!
Kip replacing the coupling on the borehole liners.
Packing the first sling load with the BlueWest helicopter on the right.
Today, we also had time to test and practice our drone-flying skills! This year, we brought a drone with us for both a serious and less serious goal. First the serious one, we will use it to scan the lowest section of our study area for crevasses. These cracks in the ice are very dangerous as they can be very deep, so it is not advisable to go close to them! However, as the ice sheet is very flat you sometimes cannot see them until you are dangerously close. With the drone we hope to spot them earlier and keep a safe distance. Next to this, the drone will be able to make a number of priceless pictures and videos of us doing science.
Photo from the drone: Nick, Stefan, and Rick in front of Hotel Kulusuk.
Now it is time to finish packing, take a last shower and go to sleep. Tomorrow, there are three flights scheduled: first our camping equipment will be flown in by sling, followed by a part of the team who will set up camp. The science equipment will be flown in next. The next day, the snow mobile and fuel are brought in followed by the last passenger flight. At least that is the plan, the weather can still change everything…!
Greetings from Kulusuk! Olivia, Nick, Clem, Rick, Kip, and Stefan. | <urn:uuid:6533e20d-2ef2-4e44-a7f1-dfcd773a23dd> | 3.21875 | 4,984 | Personal Blog | Science & Tech. | 50.606971 | 95,628,669 |
World’s Oldest Colors Shed Light On Ancient Life
6 hari ago kesimpulan 0
What is happening in our world? Who is discovering what? What is going on now? These are questions that will be answered. Enjoy.
World’s Oldest Colors Shed Light On Ancient Life
Bright pink 1.1-billion-year-old molecules from deep beneath the Sahara desert are now the oldest biological colors that scientists have discovered so far, and could shed light on why complex, multicellular life took so long to evolve on Earth.
This discovery “really came as a fluke,” said study senior author Jochen Brocks, a paleobiogeochemist at the Australian National University in Canberra. “About 10 years ago, a petroleum company looking for oil in the Sahara was exploring the black shales of the Taoudeni Basin in Mauritania when they hit upon something date 1.1 billion years in age. Our lab is renowned for analyzing the oldest molecules in the world, so they sent us a few samples to analyze.”
The scientists crushed the rock they were given to powder and suspended it within an organic solvent. “It was just like working with a coffee machine — instead of pumping water through a powder to get coffee, we ran a solvent through the rock powder to get a brown to black extract,” Brocks said.
This sample was unusually rich in carbon — “so rich and black that it would burn in an oven,” Brocks said. When they separated the different molecules in the extract within a gel, study lead author Nur Gueneli screamed, came into the office, and showed Brocks that it wasn’t just a typical brown or black oil at all, but had an amazing pink band in it.
The researchers had discovered ancient chlorophyll, the pigment that plants and other photosynthetic life use to convert sunlight into biological energy. The normal blue-green color of chlorophyll is due largely to magnesium, “which sits like a wobbly tooth in chlorophyll — it’s not very stable inside,” Brocks said. However, when an organism dies, other metals can replace this magnesium.
“Every single black shale that can preserve these molecules has all sorts of heavy metals in it,” Brocks said. “If that metal is nickel, the chlorophyll becomes blood-red; if vanadium, it becomes purple, and if that gets diluted, that’s how you get pink.”
Until now, the oldest pigment molecules scientists had found were about 500 million years old. “This is older by about 600 million years,” Brocks said. “These molecules are just exceedingly rare, and unlikely to find. We looked at just about every conceivable rock of this age before and found nothing. I’m not sure we’re going to find anything older ever, and I’m not sure we’re going to find any molecules filling in the gap between 500 million years ago and 1.1 billion years ago.”
Pigments of Life
These molecules are more than just a pretty color — they are now also shedding light on ancient oceans. When the scientists analyzed these compounds, they discovered they were unusually rich in the isotope nitrogen-15. Isotopes of an element vary in how many neutrons they possess in their atomic nuclei — the most common nitrogen isotope, nitrogen-14, has seven neutrons in its nucleus, while nitrogen-15 has eight.
Previous research found that different photosynthetic organisms consistently have different, specific levels of nitrogen-15 in their photosynthetic pigments. It remains a mystery why this is — “what we do know is that this suggests these pigments we found belonged to cyanobacteria and not algae,” Brocks said.
Cyanobacteria are microbes that were likely among the first photosynthetic life on Earth. They were later joined in ancient oceans by algae, which like plants and animals but unlike cyanobacteria are eukaryotes — that is, they have nuclei in their cells.
The scientists found this sample was overwhelmingly cyanobacterial in nature. “That surprised me — it wasn’t, like 50 percent cyanobacteria and 50 percent algae, it was really strongly cyanobacterial,” Brocks said. The researchers also saw the sample had a dearth of molecules known as steranes that are typical of eukaryotes but not of bacteria.
These findings suggest that about 1.1 billion years ago, Earth’s oceans were dominated by cyanobacteria and not algae. “These ancient oceans were really bacterial oceans,” Brocks said. “We do have eukaryotic fossils from this time, but ecologically, they were really unimportant.”
The Mystery Of Complexity
As such, “the beautiful pink molecule could help answer a major question — why did large multicelullar complex animals on Earth take so long to develop?” Brocks said.
“Earth is 4.6 billion years old, and it’s well-established without a doubt it had life by 3.5 billion years, and it probably emerged earlier,” Brocks said. “But the first complex multicellular creatures big enough to see with the eye did not emerge until about 600 million years ago. So why did it take about 3 billion years of evolution before something complex and multicellular emerged?”
One possible explanation was that relatively large animals could not appear until large, nutritious photosynthetic microbes such as algae evolved. These animals then supported the evolution of carnivores that preyed on these herbivores, and life on Earth exploded with complexity.
“These pigments we found suggested that at 1.1 billion years, there were no algae, only cyanobacteria, which supports the idea that animals could not exist in such oceans because the food sources were not sufficient,” Brocks said.
The scientists detailed their findings online July 9 in the Proceedings of the National Academy of Sciences. | <urn:uuid:77fec66b-2474-4f23-a084-ee820b671eaf> | 3.046875 | 1,279 | News Article | Science & Tech. | 46.730268 | 95,628,670 |
Using a combination of camera traps, along with interviews with park guards and subsistence hunters, WCS estimates at least 14,500 lowland tapirs in the region. The population bridges five connected national parks in northwest Bolivia and southeastern Peru.
Wildlife Conservation Society scientists have documented a thriving population of lowland tapirs -- the strange forest and grassland-dwelling herbivore with the trunk-like snout -- living in a network of remote national parks spanning the Peru-Bolivia border.
Credit: Mileniusz Spanowics/WCS
The WCS findings were described in the December issue of the journal Integrative Zoology. Authors include Robert Wallace, Guido Ayala, and Maria Viscara of WCS's Greater Madidi-Tambopata Landscape Program.
The study synthesizes 12 years of research on lowland tapirs in the region. Together with WCS studies on jaguars, the results underscore the importance of this protected area complex for the conservation of Latin America's most charismatic terrestrial wildlife species.
"The Madidi-Tambopata landscape is estimated to hold a population of at least 14,500 lowland tapirs making it one of the most important strongholds for lowland tapir conservation in the continent," said the study's lead author Robert Wallace. "These results underline the fundamental importance of protected areas for the conservation of larger species of wildlife threatened by hunting and habitat loss."
The lowland tapir is the largest terrestrial mammal in South America, weighing up to 300 kg (661 pounds). Its unusual prehensile proboscis or snout is used to reach leaves and fruit. Tapirs are found throughout tropical forests and grasslands in South America. However, they are threatened by habitat loss and especially unsustainable hunting due to their large size, low reproductive rate (1 birth every 2-3 years), and ease of detection at mineral licks in the rainforest. Lowland tapirs are considered Vulnerable by the IUCN.
WCS collected and systematized 1,255 lowland tapir distribution records in the region. These records came from research observations and camera trap photographs as well as interviews with park guards of Madidi, Pilón Lajas and Apolobamba National Parks in Bolivia, and Bahuaja Sonene and Tambopata National Parks in neighboring Peru, and subsistence hunters from 19 Takana and Tsimane' communities.
Camera trap data revealed that lowland tapir abundance was higher at sites under protection than sites outside protected areas. At one site sampled over time, the Tuichi River, camera trapping has revealed that lowland tapir populations have been recovering following the creation of Madidi National Park in 1995. Prior to the creation of the park, loggers had hunted heavily in this area.
Madidi National Park contains 11 percent of the world's birds, more than 200 species of mammals, 300 types of fish, and 12,000 plant varieties. The 19,000 square-kilometer (7,335 square mile) park is known for its array of altitudinal gradients and habitats from lowland tropical forests of the Amazon to snow-capped peaks of the High Andes.
Working with government partners in Bolivia and Peru, the Greater Madidi-Tambopata Landscape Conservation Program aims to develop local capacity to conserve the landscape and mitigate a variety of threats to biodiversity and wildlife including lowland tapirs, including road construction, logging, unsustainable natural resource use, and agricultural expansion.
Julie Kunen, WCS Director of Latin America and Caribbean Programs said: "WCS commends our government and indigenous partners for their commitment to the Madidi-Tambopata Landscape. Their dedication is clearly paying off with well-managed protected areas and more wildlife."
WCS's conservation research in the Madidi-Tambopata Landscape has been made possible by the Gordon and Betty Moore Foundation, The John D. and Catherine T. MacArthur Foundation, the blue moon fund, USAID, the Beneficia Foundation, the Disney Worldwide Conservation Fund, Woodland Park Zoo, and other generous supporters.The Wildlife Conservation Society saves wildlife and wild places worldwide. We do so through science, global conservation, education and the management of the world's largest system of urban wildlife parks, led by the flagship Bronx Zoo. Together these activities change attitudes towards nature and help people imagine wildlife and humans living in harmony. WCS is committed to this mission because it is essential to the integrity of life on Earth. Visit www.wcs.org.
Further reports about: > Amazon basin > Conservation Science > Gates Foundation > WCS > Wildlife > Wildlife Conservation > Wildlife Conservation Society > global conservation > habitat loss > landscape > population of lowland tapirs > protected areas > tapir > terrestrial wildlife species > tropical forest > trunk-like snout > wildlife park
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Temporal range: Late Devonian–Triassic
|Impression of the head and body of X. sessilis at the Museum für Naturkunde, Berlin|
Type Species: Xenacanthus decheni
Pleuracanthus Agassiz 1837
Xenacanthus is a genus of prehistoric sharks. The first species of the genus lived in the later Devonian period, and they survived until the end of the Triassic, 202 million years ago. Fossils of various species have been found worldwide.
Xenacanthus had a number of features that distinguished it from modern sharks. This freshwater shark was about one meter (three feet) in length. The dorsal fin was ribbonlike and ran the entire length of the back and round the tail, where it joined with the anal fin. This arrangement resembles that of modern conger eels, and Xenacanthus probably swam in a similar manner. A distinctive spine projected from the back of the head and gave the genus its name. The spike has even been speculated to have been venomous, perhaps in a similar manner to a sting ray. This is quite plausible as the rays are close relatives to the sharks. The teeth had an unusual "V" shape, and it probably fed on small crustaceans and heavily scaled palaeoniscid fishes.
As with all fossil sharks, Xenacanthus is mainly known because of fossilised teeth and spines.
In popular culture
Xenacanthus was shown in the forty-third episode of River Monsters, labeled "Prehistoric Terror", wherein it was nicknamed the "eel shark" (which also occasionally is a name used for the frilled shark). The show's host, Jeremy Wade, goes into an in-depth investigation into the habits of the animal, exploring its probable nature as an ambush predator that hunted in fresh water.
- Gaines, Richard M. (2001). Coelophysis. ABDO Publishing Company. p. 17. ISBN 1-57765-488-9.
- Palmer, D., ed. (1999). The Marshall Illustrated Encyclopedia of Dinosaurs and Prehistoric Animals. London: Marshall Editions. p. 27. ISBN 1-84028-152-9.
- Victor E. Pauliv; Eliseu V. Dias; Fernando A. Sedor; Ana Maria Ribeiro (2014). "A new Xenacanthiformes shark (Chondrichthyes, Elasmobranchii) from the Late Paleozoic Rio do Rasto Formation (Paraná Basin), Southern Brazil". Anais da Academia Brasileira de Ciências. 86 (1): 135–145. doi:10.1590/0001-37652014107612.
- "Prehistoric Terror". River Monsters. 19 April 2015. Animal Planet. | <urn:uuid:8c12482e-6b32-4f48-b030-0c012e3c4fe8> | 3.78125 | 590 | Knowledge Article | Science & Tech. | 57.153685 | 95,628,697 |
Enabling bioengineers to design new molecular machines for nanotechnology applications is one of the possible outcomes of a study by University of Montreal researchers that was published in Nature Structural and Molecular Biology today.
Vallée-Bélisle and Michnick have developed a new approach to visualize how proteins assemble, which may also significantly aid our understanding of diseases such as Alzheimer’s and Parkinson’s, which are caused by errors in assembly. Here shown are two different assembly stages (purple and red) of the protein ubiquitin and the fluorescent probe used to visualize these stage (tryptophan: see yellow). Print resolution available on request. Credit: Credit: Peter Allen
The protein assembly process is not the end of its journey, as a protein can change, through chemical modifications or with age, to take on different forms and functions. "Understanding how a protein goes from being one thing to becoming another is the first step towards understanding and designing protein nanomachines for biotechnologies such as medical and environmental diagnostic sensors, drug synthesis of delivery," Vallée-Bélisle said.
This research was supported by the Natural Sciences and Engineering Research Council of Canada and Le fond de recherché du Québec, Nature et Technologie. The article, "Visualizing transient protein folding intermediates by tryptophan scanning mutagenesis," published in Nature Structural & Molecular Biology, was coauthored by Alexis Vallée-Bélisle and Stephen W. Michnick of the Département de Biochimie de l'Université de Montréal. The University of Montreal is known officially as Université de Montréal.
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For the first time ever, scientists have determined the cosmic origin of highest-energy neutrinos. A research group led by IceCube scientist Elisa Resconi, spokesperson of the Collaborative Research Center SFB1258 at the Technical University of Munich (TUM), provides an important piece of evidence that the particles detected by the IceCube neutrino telescope at the South Pole originate from a galaxy four billion light-years away from Earth.
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For the first time a team of researchers have discovered two different phases of magnetic skyrmions in a single material. Physicists of the Technical Universities of Munich and Dresden and the University of Cologne can now better study and understand the properties of these magnetic structures, which are important for both basic research and applications.
Whirlpools are an everyday experience in a bath tub: When the water is drained a circular vortex is formed. Typically, such whirls are rather stable. Similar...
Physicists working with Roland Wester at the University of Innsbruck have investigated if and how chemical reactions can be influenced by targeted vibrational excitation of the reactants. They were able to demonstrate that excitation with a laser beam does not affect the efficiency of a chemical exchange reaction and that the excited molecular group acts only as a spectator in the reaction.
A frequently used reaction in organic chemistry is nucleophilic substitution. It plays, for example, an important role in in the synthesis of new chemical...
Optical spectroscopy allows investigating the energy structure and dynamic properties of complex quantum systems. Researchers from the University of Würzburg present two new approaches of coherent two-dimensional spectroscopy.
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Ultra-short, high-intensity X-ray flashes open the door to the foundations of chemical reactions. Free-electron lasers generate these kinds of pulses, but there is a catch: the pulses vary in duration and energy. An international research team has now presented a solution: Using a ring of 16 detectors and a circularly polarized laser beam, they can determine both factors with attosecond accuracy.
Free-electron lasers (FELs) generate extremely short and intense X-ray flashes. Researchers can use these flashes to resolve structures with diameters on the...
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What mass of ammonia can theoretically be formed when 1kg of nitrogen reacts with 0.5kg of hydrogen?
N2 + 3N2 -> 2NH3
I got 2428.59g but the answers sheet says 1210g. I have exams when I get back from college break and can’t get hold of my teacher can anyone explain how you get that answer?
Turn on thread page Beta
Chemistry problem watch
- Thread Starter
- 17-10-2017 16:43
- 17-10-2017 18:44
can we see your calculations? It's hard to know where you're going wrong without them. A screenshot is fine rather than typing it all.
- 17-10-2017 18:45
How many mol of each do you have?
Which is the limiting reagent, given the balanced equation? | <urn:uuid:fe9aa0fb-0c4f-4065-abdf-82ff6db97a10> | 2.546875 | 177 | Comment Section | Science & Tech. | 96.0115 | 95,628,703 |
why is 1 mol of cu2+ equivalent to 1 mol of s2o3 2-
the question is: a 0.5g sample of brass is reacted with concentrated nitric acid to form a solution containing cu2+ and zn2+ ions. the solution is then neutralised. excess KI (aq) is added. the resulting iodine solution is titrated with 0.2 mol dm3 sodium thiosulfate and 25.2cm3 are required to reach the end point calculate the percentage by mass of copper and zinc in the brass.
i got the half equations for cu2+ and thisoulfate to be:
cu2+ 2e- ----> cu
2S2O3 2- ----> S4O6 2- +2e-
as you can see from my half equations there are 2 moles of thiosulfate and 1 mole of copper
someone explain to me please
Turn on thread page Beta
redox titration- problem with the moles ? watch
- Thread Starter
- 18-10-2017 18:03
- Official Rep
- 21-10-2017 17:16
Sorry you've not had any responses about this. Are you sure you've posted in the right place? Here's a link to our subject forum which should help get you more responses if you post there. | <urn:uuid:d56a3006-0a2d-4d6f-8be8-e0c1a7faa837> | 3.125 | 283 | Comment Section | Science & Tech. | 76.595455 | 95,628,704 |
What is it? T_T
Turn on thread page Beta
What is Aliasing?-physics watch
- Thread Starter
- 24-10-2017 14:33
- 30-10-2017 23:17
Aliasing is a sampling problem.
This is a phenomenon which occurs when you simply do not obey the nyquist sampling frequency criterion.
According to Nyquist, in order to successfully record the information from a continuous signal (analogue to digital conversion), you must collect samples at a frequency which is double that of the main signal itself. The idea is for you to be able to sample a wave at least twice within one complete wavelength.
If you decide to do anything less than that, you will end up sampling the wave at non identical phase positions within consecutive wavelengths. What this means is that you would end up with recording a totally distorted and inconsistent signal copy of the main signal. This would seem a bit like some random noise except that the actual information is totally lost for good.
This can be solved by anti-aliasing, either by slowing down the main signal, or speeding up the sampler. For this reason, we use coupling capacitors.
- Study Helper
- 31-10-2017 08:38
When reconstructing a digitised data stream (D to A conversion), if the sampling rate applied to the original analogue signal is less than twice the maximum frequency of the sampled signal (Nyquist sampling rate), a true representation of the original will be impossible to reproduce.
A classic analogy is the strobe effect. When viewing a rotating wheel spokes under a strobe light, the wheel appears to rotate backwards but the wheel is in reality, moving forwards.
Below, the diagram shows what happens when the sampling rate (black dots) is less than the original analogue signal frequency (red sinusoid). The reconstructed analogue signal (blue sinusoid) is produced from the stored samples as an 'alias' and erroneously lower frequency. There is no way of recovering the original from the stored samples because not enough information is available.
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Thanks to the cooler temperatures, the diversity of marine fauna ballooned, as paleontologists from the University of Zurich have reconstructed. The warmer climate, coupled with a high CO2 level in the atmosphere, initially gave rise to new, short-lived species. In the longer term, however, this climate change had an adverse effect on biodiversity and caused species to become extinct.
Amonoids peaked earlier after the vast mass extiction.
Feeding apparatus (reconstruction) of a Conodont.
Until now, it was always assumed that it took flora and fauna a long time to recover from the vast mass extinction at the end of the Permian geological period 252 million years ago. According to the scientific consensus, complex ecological communities only began to reappear in the Middle Triassic, so 247 million years ago. Now, however, a Swiss team headed by paleontologist Hugo Bucher from the University of Zurich reveals that marine animal groups such as ammonoids and conodonts (microfossils) already peaked three or four million years earlier, namely still during the Early Triassic.
The scientists chart the temperature curves in detail in Nature Geoscience, demonstrating that the climate and the carbon dioxide level in the atmosphere fluctuated greatly during the Early Triassic and what impact this had on marine biodiversity and terrestrial plants.
Alternate cooler and very warm phases
For their climate reconstruction, Bucher and his colleagues analyzed the composition of the oxygen isotopes in conodonts, the remains of chordates that once lived in the sea. According to the study, the climate at the beginning of the Triassic 249 million years ago was cool. This cooler phase was followed by a brief very warm climate phase. At the end of the Early Triassic, namely between 247.9 and 245.9 million years ago, cooler conditions resumed.
Climate and carbon cycle influence biodiversity
The scientists then examined the impact of the climate on the development of flora and fauna. “Biodiversity increased most in the cooler phases,” explains paleontologist Bucher. “The subsequent extremely warm phase, however, led to great changes in the marine fauna and a major ecological shift in the flora.” Bucher and his team can reveal that this decline in biodiversity in the warm phases correlates with strong fluctuations in the carbon isotope composition of the atmosphere. These, in turn, were directly related to carbon dioxide gases, which stemmed from volcanic eruptions in the Siberian Large Igneous Province.
Species emerge and die out
Through the climatic changes, conodont and ammonoid faunae were initially able to recover very quickly during the Early Triassic as unusually short-lived species emerged. However, the removal of excess CO2 by primary producers such as algae and terrestrial plants had adverse effects in the long run: The removal of these vast amounts of organic matter used up the majority of the oxygen in the water. Due to the lack of oxygen in the oceans, many marine species died out. “Our studies reveal that greater climatic changes can lead to both the emergence and extinction of species. Thus, it is important to consider both extinction rates and the rate at which new species emerged,” says Bucher.
Bucher and his colleagues are convinced that climate changes and the emission of volcanic gases were key drivers of biotic recovery in the oceans during the Early Triassic: Cooler climate phases encourage biological diversification. Warmer climate phases and very high CO2 levels in the atmosphere, however, can have a harmful impact on biodiversity.Literature:
Beat Müller | idw
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A new manufacturing technique uses a process similar to newspaper printing to form smoother and more flexible metals for making ultrafast electronic devices.
The low-cost process, developed by Purdue University researchers, combines tools already used in industry for manufacturing metals on a large scale, but uses...
For the first time ever, scientists have determined the cosmic origin of highest-energy neutrinos. A research group led by IceCube scientist Elisa Resconi, spokesperson of the Collaborative Research Center SFB1258 at the Technical University of Munich (TUM), provides an important piece of evidence that the particles detected by the IceCube neutrino telescope at the South Pole originate from a galaxy four billion light-years away from Earth.
To rule out other origins with certainty, the team led by neutrino physicist Elisa Resconi from the Technical University of Munich and multi-wavelength...
For the first time a team of researchers have discovered two different phases of magnetic skyrmions in a single material. Physicists of the Technical Universities of Munich and Dresden and the University of Cologne can now better study and understand the properties of these magnetic structures, which are important for both basic research and applications.
Whirlpools are an everyday experience in a bath tub: When the water is drained a circular vortex is formed. Typically, such whirls are rather stable. Similar...
Physicists working with Roland Wester at the University of Innsbruck have investigated if and how chemical reactions can be influenced by targeted vibrational excitation of the reactants. They were able to demonstrate that excitation with a laser beam does not affect the efficiency of a chemical exchange reaction and that the excited molecular group acts only as a spectator in the reaction.
A frequently used reaction in organic chemistry is nucleophilic substitution. It plays, for example, an important role in in the synthesis of new chemical...
Optical spectroscopy allows investigating the energy structure and dynamic properties of complex quantum systems. Researchers from the University of Würzburg present two new approaches of coherent two-dimensional spectroscopy.
"Put an excitation into the system and observe how it evolves." According to physicist Professor Tobias Brixner, this is the credo of optical spectroscopy....
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The sun's atmosphere dances. Giant columns of solar material – made of gas so hot that many of the electrons have been scorched off the atoms, turning it into a form of magnetized matter we call plasma – leap off the sun's surface, jumping and twisting. Sometimes these prominences of solar material, shoot off, escaping completely into space, other times they fall back down under their own weight.
Such structures are but one of many that the roiling magnetic fields and million-degree plasma create in the sun's atmosphere, the corona, but they are an important one as they can be the starting point of what's called a coronal mass ejection, or CME. CMEs are billion-ton clouds of material from the sun’s atmosphere that erupt out into the solar system and can interfere with satellites and radio communications near Earth when they head our way.
"We don't really know what gets these CMEs going," says Terry Kucera, a solar scientist at NASA's Goddard Space Flight Center in Greenbelt, Md. "So we want to understand their structure before they even erupt, because then we might have a better clue about why it's erupting and perhaps even get some advance warning on when they will erupt."
Kucera and her colleagues have published a paper in the Sept. 20, 2012, issue of The Astrophysical Journal on the temperatures of the coronal cavities. This is the third in a series of papers -- the first discussed cavity geometry and the second its density -- collating and analyzing as much data as possible from a cavity that appeared over the upper left horizon of the sun on Aug. 9, 2007 (below). By understanding these three aspects of the cavities, that is the shape, density and temperature, scientists can better understand the space weather that can disrupt technologies near Earth.
The Aug. 9 cavity lay at a fortuitous angle that maximized observations of the cavity itself, as opposed to the prominence at its base or the surrounding plasma. Together the papers describe a cavity in the shape of a croissant, with a giant inner tube of looping magnetic fields -- think something like a slinky -- helping to define its shape. The cavity appears to be 30% less dense than the streamer surrounding it, and the temperatures vary greatly throughout the cavity, but on average range from 1.4 million to 1.7 million Celsius (2.5 to 3 million Fahrenheit), increasing with height.
Trying to describe a cavity, a space that appears empty from our viewpoint, from 93 million miles away is naturally a tricky business. "Our first objective was to completely pin down the morphology," says Sarah Gibson, a solar scientist at the High Altitude Observatory at the National Center for Atmospheric Research (NCAR) in Boulder, Colo. who was an author on all three cavity papers. "When you see such a crisp clean shape like this, it’s not an accident. That shape is telling you something about the physics of the magnetic fields creating it, and understanding those magnetic fields can also help us understand what’s at the heart of CMEs."
To do this, the team collected as much data from as many instruments from as many perspectives as they could, including observations from NASA’s Solar Terrestrial Relations Observatory (STEREO), ESA and NASA’s Solar and Heliospheric Observatory (SOHO), the JAXA/NASA mission Hinode, and NCAR's Mauna Loa Solar Observatory.
They collected this information for the cavity’s entire trip across the face of the sun along with the sun’s rotation. Figuring out, for example, why the cavity was visible on the left side of the sun but couldn’t be seen as well on the right held important clues about the structure’s orientation, suggesting a tunnel shape that could be viewed head on from one perspective, but was misaligned for proper viewing from the other. The cavity itself looked like a tunnel in a crescent shape, not unlike a hollow croissant. Magnetic fields loop through the croissant in giant circles to support the shape, the way a slinky might look if it were narrower on the ends and tall in the middle – the entire thing draped in a sheath of thick plasma. The paper describing this three-dimensional morphology appeared in The Astrophysical Journal on Dec. 1, 2010.
Next up, for the second paper, was the cavity’s density. Figuring out density and temperature was a trickier prospect since one’s point of view of the sun is inherently limited. Because the sun’s corona is partially transparent, it is difficult to tease out differences of density and temperature along one’s line of sight; all the radiation from a given line hits an instrument at the same time in a jumble, information from one area superimposed upon every other.
Using a variety of techniques to tease density out from temperature, the team was able to determine that the cavity was 30% less than that of the surrounding streamer. This means that there is, in fact, quite a bit of material in the cavity. It simply appears dim to our eyes when compared with the denser, brighter areas nearby. The paper on the cavity’s density appeared in The Astrophysical Journal on May 20, 2011.
"With the morphology and the density determined, we had found two of the main characteristics of the cavity, so next we focused on temperature," says Kucera. "And it turned out to be a much more complicated problem. We wanted to know if it was hotter or cooler than the surrounding material – the answer is that it is both."
Ultimately, what Kucera and her colleagues found was that the temperature of the cavity was not – on average – hotter or cooler than the surrounding plasma.
However, it was much more varied, with hotter and cooler areas that Kucera thinks link the much colder 10,000 degrees Celsius (17,000 F) prominence at the bottom to the million to two million degrees Celsius (1.8 million to 3.6 million degrees Fahrenheit) corona at the top. Other observations of cavities show that cavity features are constantly in motion creating a complicated flow pattern that the team would like to study further.
While these three science papers focused on just the one cavity from 2007, the scientists have already begun comparing this test case to other cavities and find that the characteristics are fairly consistent. More recent cavities can also be studied using the high-resolution images from NASA’s Solar Dynamics Observatory (SDO), which launched in 2010.
"Our point with all of these research projects into what might seem like side streets, is ultimately to figure out the physics of magnetic fields in the corona," says Gibson. "Sometimes these cavities can be stable for days and weeks, but then suddenly erupt into a CME. We want to understand how that happens. We’re accessing so much data, so it’s an exciting time – with all these observations, our understanding is coming together to form a consistent story." | <urn:uuid:577360c5-8292-4ae8-a908-2e1de10ab60b> | 3.75 | 1,463 | Nonfiction Writing | Science & Tech. | 45.155904 | 95,628,735 |
Presentation on theme: "Introduction to Maven 2.0 An open source build tool for Enterprise Java projects Mahen Goonewardene."— Presentation transcript:
Introduction to Maven 2.0 An open source build tool for Enterprise Java projects Mahen Goonewardene
History Make – Not the best tool for building Java projects Platform-dependent Not easy to use Ant – A revolutionary build tool Platform-independent Uses XML configuration file (build.xml) XML configuration file is extremely abstract High learning curve (syntax) Maven 1.0 – Replacement for Ant? Uses Ant at its core
Features Standardized project layout and project structure generator Standardized dependency-management mechanism Multiple project support Instant downloads of new plug-ins and features as the developer needs them Website generation for up-to-date project information
Project Object Model (POM) The POM file is a set of instructions for Maven that tells it how to build the project and includes other special instructions The POM takes the form of an XML file (pom.xml) Maven includes the JUnit dependency by default to encourage unit testing
Dependency Management Transitive Dependencies Maven will take care of the libraries that your libraries need Dependency Scopes compile: Available in all phases (default value) provided: Used to compile the application but will not be deployed runtime: Needed only for execution and not for compilation (eg: JDBC drivers) test: Needed only to compile and run tests (eg: JUnit)
Structure src/main/java: Java source code src/main/resources: Other resources src/main/filters: Resource filters in the form of properties files, which may be used to define variables only known at runtime src/main/config: Configuration files src/main/webapp: The Web application directory for a WAR project
Structure src/test/java: Unit tests src/test/resources: Resources to be used for unit tests, but will not be deployed src/test/filters: Resource filters to be used for unit tests, but will not be deployed src/site: Files used to generate the Maven project Website
Project Life Cycle Default Build Phases validate: Validate the project is correct and all necessary information is available compile: Compiles project source code test: Test the compiled source code using a suitable unit testing framework such as JUnit. These tests should not require the code be packaged or deployed package: Take the compiled code and package it in its distributable format, such as a WAR, JAR etc.
Project Life Cycle Default Build Phases integration-test: Process and deploy the package if necessary into an environment where integration tests can be run verify: Run any checks to verify the package is valid and meets quality criteria install: Install the package into the local repository, for use as a dependency in other projects locally deploy: Copies the final package to the remote repository for sharing with other developers and projects (done in an integration or release environment).
Maven Site Generation Build Phase site: Generates the project website Project Management Reports General project information (source repositories, defect tracking, team members, etc.) Unit test and test coverage reports (Corbetura plug-in) Automatic code reviews (Checkstyle plug-in) Configuration and version information Dependencies Java-docs Source code in indexed and cross-referenced HTML format Team member list
Conclusion Maven 2.0 is... A powerful tool that greatly simplifies and standardizes the build process Promotes a standard project outline and incorporates recommended best practices Standard plug-ins such as the site generator provide valuable team-oriented project tools with little extra effort | <urn:uuid:ea57ad21-7f57-402c-8618-a0d3e62c113a> | 2.578125 | 746 | Audio Transcript | Software Dev. | 8.543303 | 95,628,762 |
4. Related Rates
by M. Bourne
If 2 variables both vary with respect to time and have a relation between them, we can express the rate of change of one in terms of the other.
We need to differentiate both sides w.r.t. (with respect to) time.
That is, we'll be finding `(df)/(dt)` for some function `f(t)`.
Recall from implicit differentiation the following for some function `x` of `t`:
We use this concept throughout this section on related rates.
A `20\ "m"` ladder leans against a wall. The top slides down at a rate of 4 ms-1. How fast is the bottom of the ladder moving when it is 16 m from the wall?
- Make a sketch of the problem
- Identify constant and variable quantities
- Establish relationship between quantities.
- Differentiate w.r.t time.
- Evaluate at point of interest.
Here's the sketch of the situation. The variables `x` and `y` vary as time varies.
(We regard UP as being the POSITIVE direction.)
Now the relation between x and y is:
x2 + y2 = 202
Differentiating throughout with respect to time (since the value of x and y depends on t):
Now, we know
and we need to know the horizontal velocity (`dx/(dt)`) when
`x = 16`.
The only other unknown is y, which we obtain using Pythagoras' Theorem:
Please support IntMath!
A stone is dropped into a pond, the ripples forming concentric circles which expand. At what rate is the area of one of these circles increasing when the radius is `4\ "m"` and increasing at the rate of 0.5 ms-1?
The area of a circle with radius `r` is:
Differentiate w.r.t. time, and then substitute known values:
An earth satellite moves in a path that can be described by
where x and y are in thousands of kilometres.
If `dx/dt = 12900\ "km/h"` for `x = 3200\ "km"` and `y > 0`, find `dy/dt`.
Here is the path of the satellite. It is an ellipse, but is very nearly circular.
Elliptical path of the satellite.
We can see from the above that `(dy)/(dt)` should be a negative value (as it is going "down" in this reference frame).
We differentiate the expression with respect to t:
We need to find y. We do this by substituting `x = 3.2` (because `x` is in 1000s of kilometers) into the original expression:
Solving this gives:
The question tells us to take the positive value only. Substituting our known values gives:
`(dy)/(dt)=-5.195`This means the velocity in the y-direction is −5195 km/h (since the units are 1000s of kilometers).
Easy to understand math videos:
The tuning frequency f of an electronic tuner is inversely proportional to the square root of the capacitance `C` in the circuit.
If f = 920 kHz for C = 3.5 pF, find how fast f is changing at this frequency if `(dC)/(dt) =0.3\ "pF/s"`.
and substituting our given values, we have that
and this gives `k = 1.721`.
We need to find `(df)/(dt)`.
We are told that `C = 3.5\ "pF"` and `(dC)/(dt) =0.3\ "pF/s"`.
`=-39424.8\ "Hz s"^-1`
So the frequency of the electronic tuner is decreasing at the rate of 39.4 kHz s-1.
Please support IntMath! | <urn:uuid:f9a9eec5-22e9-4665-a633-70f8d9360a5e> | 4.15625 | 861 | Tutorial | Science & Tech. | 84.443428 | 95,628,765 |
Atmospheric Science Department, Colorado State University, Ft. Collins 80523
Growing global population pressures and predicted future food and energy shortages dictate that man fully explore his potential use of solar energy. This paper investigates the possibility of beneficial weather modification through artificial solar energy absorption. A variety of physical ideas related to artificial heat sources on different scales of motion are considered. Interest is concentrated on the feasibility of mesoscale (100–300 km) weather modification through solar energy absorption by carbon aerosol particles of size 0.1 μm or less. Particles of this size maximize solar energy absorption per unit mass.
It is hypothesized that significant beneficial influences can be derived through judicious exploitation of the solar absorption potential of carbon black dust. There is an especially high potential for this in the boundary layer over tropical oceans and in the formation of cirrus clouds and the consequent alteration of the tropospheric IR energy budget. If dispersed in sizes 0.1 μm, solar energy absorption amounts as high as 2 × 1010 cal lb−1 per 10 h or about 4 × 1011 cal per dollar per 10 h can be obtained. This is a tremendously powerful heat source, especially if it stimulates additional radiation energy gains from extra cloud formation and/or enhanced surface evaporation. Preliminary observational and modeling information indicates that this artificial heat source can be employed on the mesoscale (100–300 km) to achieve significant economic gains by means of precipitation enhancement and tropical storm destruction alleviation. It may also be possible to use carbon dust to enhance precipitation over interior land areas, alter extratropical cyclones, inhibit high daytime summer temperatures and severe weather, prevent frosts, and speed up springtime snowmelt in agriculturally marginal regions.
A discussion of this physical hypothesis from the meteorological, radiational, engineering and ecological points of view is made. | <urn:uuid:7b95f114-d9e9-4eac-9096-21238105641a> | 3.21875 | 378 | Academic Writing | Science & Tech. | 15.609781 | 95,628,768 |
Changes in weather and climate extremes over Korea and possible causes: A review
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Weather and climate extremes exert devastating influence on human society and ecosystem around the world. Recent observations show increase in frequency and intensity of climate extremes around the world including East Asia. In order to assess current status of the observed changes in weather and climate extremes and discuss possible mechanisms, this study provides an overview of recent analyses on such extremes over Korea and East Asia. It is found that the temperature extremes over the Korean Peninsula exhibit long-term warming trends with more frequent hot events and less frequent cold events, along with sizeable interannual and decadal variabilities. The comprehensive review on the previous literature further suggests that the weather and climate extremes over East Asia can be affected by several climate factors of external and internal origins. It has been assessed that greenhouse warming leads to increase in warm extremes and decrease in cold extremes over East Asia, but recent Arctic sea-ice melting and associated warming tends to bring cold snaps to East Asia during winter. Internal climate variability such as tropical intraseasonal oscillation and El Niño-Southern Oscillation can also exert considerable impacts on weather and climate extremes over Korea and East Asia. It is, however, noted that our current understanding is far behind to estimate the effect of these climate factors on local weather and climate extremes in a quantitative sense.
Key wordsWeather extremes climate extremes climate variability and change Korea and East Asia
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Genetics as it applies to evolution, molecular biology, and medical aspects.
Moderators: honeev, Leonid, amiradm, BioTeam
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What is the role of a DNA polymerase?
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microbiologist, climber, snowboarder.
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The role of DNA polymerase is to add complementary nucleotides to the DNA molecule being replicated. However, DNA polymerase can only add free nucleotides to the hydroxyl end, provided by the RNA primer.
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posted by mike
A 2.5 kg block of ice at a temperature of 0.0 degrees Celcius and an initial speed of 5.7 m/s slides across a level floor. If 3.3 x 10^5 J are required to melt 1.0 kg of ice, how much ice melts, assuming that the initial kinetic energy of the ice block is entirely converted to the ice's internal energy?
(Our teacher doesn't teach us, plus I'm not really geared towards physics. Any help provided would be appreciated.)
What does your teacher do?
Compute the initial kinetic energy (KE) of the ice using
KE = (1/2) M V^2
You should get 40.6 Joules
Divide that by 3.3*10^5 J/kg to get the number of kg's that melt.
Very little ice melts compared to the mass of the block. No energy goes into raising the temperature because it stays at 0C until it all melts.
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posted by Alisa
In really stormy weather and with the right conditions, the sky would dump a bunch of hail, making the roads rather hazardous. A choir director was driving his car in these conditions and going a tad fast under the circumstances. His car began to slip on the balls of ice in the road towards two music students walking in front of him, so he leaned on his horn to warn the students to jump out of the way. Since he has career in music, his car horn is set to emit a frequency at exactly Tenor C – 523 Hz. The students have perfect pitch and are able to determine that the frequency that they hear is now 554 Hz (a semitone sharp for any musicians in the room). Since they have also taken Physics with Algebra, they were able to determine the choir director’s speed. What was that speed?
Isn't there a standard formula for doppler , stationary listner, moving source?
Source moving towards observer:
and you are looking to compute vs | <urn:uuid:47feb88c-f223-454e-8ba6-cf8695027f51> | 3.265625 | 210 | Personal Blog | Science & Tech. | 60.969773 | 95,628,789 |
Many of our actions are guided by past experiences combined with insight into the future. A major mystery of biology involves understanding how brain cells can create a representation that extends backward and forward through time. A new study conducted by researchers at Mount Sinai School of Medicine published in the December 18th issue of Neuron begins to unravel the brain activity that underlies concurrent processing of the recent past, the present and the imminent future.
Memories that are organized by time and context are known as episodic memory. Dr. Matthew L. Shapiro, Associate Professor of Neurobiology at Mount Sinai School of Medicine and leader of the study offers the following example. "Imagine driving to work, parking your car, and taking an elevator to your office. During the day you may take the elevator several times without thinking of your car. Only when the end of the day arrives and you descend in the elevator to go home do you remember where your car is parked. In the present moment in the elevator, the past guides your future action." To examine the brain processes involved in such episodic memories, Drs. Shapiro and Ferbinteanu examined cellular activity within the brain while rats searched for food in a maze where the starting and ending point was varied.
The researchers examined activity in the hippocampus, a brain region that is key for memory. The hippocampus contains cells, called place cells, which become more active in response to a particular spatial location. "We found that the activity of the place cells showed something very interesting while the rats performed the task. Some cells signaled location alone but others were additionally sensitive to recent or impending events," explains Dr. Ferbinteanu. "These cells maintained spatial selectivity, but this activity depended upon where the animal had just been or where it intended to go." Therefore, the hippocampus can support episodic memory by creating patterns of cellular activity for events within a temporal context.
Debra Kaplan | EurekAlert!
NYSCF researchers develop novel bioengineering technique for personalized bone grafts
18.07.2018 | New York Stem Cell Foundation
Pollen taxi for bacteria
18.07.2018 | Technische Universität München
For the first time ever, scientists have determined the cosmic origin of highest-energy neutrinos. A research group led by IceCube scientist Elisa Resconi, spokesperson of the Collaborative Research Center SFB1258 at the Technical University of Munich (TUM), provides an important piece of evidence that the particles detected by the IceCube neutrino telescope at the South Pole originate from a galaxy four billion light-years away from Earth.
To rule out other origins with certainty, the team led by neutrino physicist Elisa Resconi from the Technical University of Munich and multi-wavelength...
For the first time a team of researchers have discovered two different phases of magnetic skyrmions in a single material. Physicists of the Technical Universities of Munich and Dresden and the University of Cologne can now better study and understand the properties of these magnetic structures, which are important for both basic research and applications.
Whirlpools are an everyday experience in a bath tub: When the water is drained a circular vortex is formed. Typically, such whirls are rather stable. Similar...
Physicists working with Roland Wester at the University of Innsbruck have investigated if and how chemical reactions can be influenced by targeted vibrational excitation of the reactants. They were able to demonstrate that excitation with a laser beam does not affect the efficiency of a chemical exchange reaction and that the excited molecular group acts only as a spectator in the reaction.
A frequently used reaction in organic chemistry is nucleophilic substitution. It plays, for example, an important role in in the synthesis of new chemical...
Optical spectroscopy allows investigating the energy structure and dynamic properties of complex quantum systems. Researchers from the University of Würzburg present two new approaches of coherent two-dimensional spectroscopy.
"Put an excitation into the system and observe how it evolves." According to physicist Professor Tobias Brixner, this is the credo of optical spectroscopy....
Ultra-short, high-intensity X-ray flashes open the door to the foundations of chemical reactions. Free-electron lasers generate these kinds of pulses, but there is a catch: the pulses vary in duration and energy. An international research team has now presented a solution: Using a ring of 16 detectors and a circularly polarized laser beam, they can determine both factors with attosecond accuracy.
Free-electron lasers (FELs) generate extremely short and intense X-ray flashes. Researchers can use these flashes to resolve structures with diameters on the...
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Published on Oct 25, 2013
An optical transform can be used to compare possible trial structures with the observed x-ray diffraction pattern from DNA. A pocket laser and masks mimic the process by which the architecture of DNA was determined. | <urn:uuid:73f908c5-8f43-4136-9eca-0d7eb9b27e4b> | 2.578125 | 72 | Truncated | Science & Tech. | 55.763475 | 95,628,804 |
Site-specific climatic signals in stable isotope records from Swedish pine forests
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Pinus sylvestris tree-ring δ13C and δ18O records from locally moist sites in central and northern Sweden contain consistently stronger climate signals than their dry site counterparts.
We produced twentieth century stable isotope data from Pinus sylvestris trees near lakeshores and inland sites in northern Sweden (near Kiruna) and central Sweden (near Stockholm) to evaluate the influence of changing microsite conditions on the climate sensitivity of tree-ring δ13C and δ18O. The data reveal a latitudinal trend towards lower C and O isotope values near the Arctic tree line (− 0.8‰ for δ13C and − 2.4‰ for δ18O relative to central Sweden) reflecting widely recognized atmospheric changes. At the microsite scale, δ13C decreases from the dry inland to the moist lakeshore sites (− 0.7‰ in Kiruna and − 1.2‰ in Stockholm), evidence of the importance of groundwater access to this proxy. While all isotope records from northern and central Sweden correlate significantly against temperature, precipitation, cloud cover and/or drought data, climate signals in the records from moist microsites are consistently stronger, which emphasizes the importance of site selection when producing stable isotope chronologies. Overall strongest correlations are found with summer temperature, except for δ18O from Stockholm correlating best with instrumental drought indices. These findings are complemented by significant positive correlations with temperature-sensitive ring width data in Kiruna, and inverse (or absent) correlations with precipitation-sensitive ring width data in Stockholm. A conclusive differentiation between leading and co-varying forcings is challenging based on only the calibration against often defective instrumental climate data, and would require an improved understanding of the physiological processes that control isotope fractionation at varying microsites and joined application of forward modelling.
Keywordsδ13C δ18O Pinus sylvestris L. Microsite Dendrochronology Sweden
We thank Florian Benninghoff, Willy Dindorf, Elisabeth Düthorn, Susanne Koch, Markus Kochbeck, Oliver Konter, Michael Maus, Maria Mischel and Jutta Sonnberg for field and laboratory support.
Compliance with ethical standards
Conflict of interest
All authors declare no conflict of interest.
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We can treat a single ion channel as a cylindrical pore through the cell membrane. The channel is of length L = 5 nm and is filled with water. The concentration differences of sodium ions across the membrane is â??c = 100 mM. This concentration difference produces a flux of ions through the channel, given by Fickâ??s Law. For small ions like sodium, the diffusion constant, D, in water is of the order of 1 µm2/ms.
a.Assuming that the channel cross-section has an area A = 1 nm2, use Fickâ??s Law to calculate the number of sodium ions that pass through the channel every second due to diffusion.
b.Figure 2 shows current recording from a single channel. Use this figure to estimate the number of ions passing through the channel per second, when it is open. Assume that each sodium ion carries an elemental charge, q.
See attached pic© BrainMass Inc. brainmass.com July 20, 2018, 10:21 am ad1c9bdddf
Fick's first law of diffusion tells us how the flux varies with the concentration gradient:
J = -D*dc/dx
Where D is a diffusion coefficient (given in the problem as 1 µm^2/ms) that represents how easily the particles in question move through the medium (or to look at it another way, how fast the sodium ions can move in the water).
Here the concentration gradient is given as well: 100 mM over 5 nm.
So we can find the flux, J, in a fairly straightforward way. The trickiest part at this point is going to be keeping the units straight. I highly recommend explicitly writing out the units at every step.
J = -D*dc/dx
J = -(1 µm^2/ms) * (100 mM / 5 nm)
Fick's first law of diffusion is thoroughly exemplified. | <urn:uuid:e29c6baf-0e7e-451c-a93e-b2ab8de89a6b> | 4.09375 | 403 | Q&A Forum | Science & Tech. | 83.829 | 95,628,821 |
#7 - What's so nice about it is you, and I assume he, don't confuse things by using the generic "Observer effect" wording, but go right to how an instrument effects a change. It's that simple next step that clarifies. Otherwise a student is left with "instruments" "analysis" and "observing" - and coming up with "how in the world would something I do every day mess up just seeing?"
On a more macroscopic level, sometimes I just pause in the kitchen and watch a dust particle drift into the beam of LED light (counter pendants) and take off downward in a blaze of speed.
#8 | Posted by YAV at 2018-06-17 12:51 PM | Reply | Newsworthy 1
The dust movement there is most likely caused by air currents set up by the lights. The light pressure from lights like that is unlikely to be observable on something as large as a dust particle. More likely, the heat from the lights has set up a convection cell near the lights, or something else has set up some kind of air current there - AC/heat, change in the shape of the ceiling or walls, or something.
There is enough of it in space to matter, though. One of the proposed methods of space travel is with a "light sail". It had to be accounted for in calculating trajectories for long distance space probes as well. See this article for some information: Radiation Pressure (Wikipedia)
I am unable to read the article itself - Forbes doesn't seem to like me - but the statement that, for example, supersymmetry doesn't have any evidence for it isn't really correct. There is support for it, as it explains some things the standard model has difficulty with. At the same time, the discovery of the Higgs Boson has placed some strain on supersymmetry because it is fairly heavy for the model. Overall, I would class supersymmetry as still only a hypothesis, but I'm not really in the particle physics world. There are other hypothesis out there, but they aren't as able to explain as many of the disconnects with the standard model.
#1 - about QM telling us "weird" is the answer: I think you are misunderstanding what is meant by "beauty". QM is "beautiful" in its mathematics as well. The weirdness of QM is a directly predicted by the simple mathematics. Almost all of QM falls out of group theory with a few basic assumptions. That relationship wasn't necessarily what started the theory, but that is how it is expressed today. I remember finding it much easier to follow QM once I was taught "bra-ket" notation, as it made the connection with group theory and algebras much easier to grasp. Then again, I had courses in, and really enjoyed, abstract algebra and other abstract mathematics. | <urn:uuid:84ae321a-df2e-421f-b5b0-0e8302e6c4dc> | 2.75 | 598 | Comment Section | Science & Tech. | 55.793911 | 95,628,839 |
The US Forest Service has proposed new regulations under the National Forest Management Act that would replace a long-standing requirement that the agency manage its lands "to maintain viable populations of existing native and desired non-native vertebrate species." In its place, the Forest Service would be obligated merely to assess ecosystem and species diversity. A landscape assessment process would rely on ecosystem-level surrogate measures, such as maps of vegetation communities and soils, to estimate species diversity. Reliance on such "coarse-filter" assessment techniques is problematic because there tends to be poor concordance between species distributions predicted by vegetation models and observations from species surveys. The proposed changes would increase the likelihood of continued declines in biodiversity and fail to address the original intent of the act. We contend that responsible stewardship requires a comprehensive strategy that includes not only coarse-filter, ecosystem-level assessment but also fine-filter, species-level assessments and viability assessments for at-risk species.
Mendeley saves you time finding and organizing research
Choose a citation style from the tabs below | <urn:uuid:ad541b29-ae5b-482c-84e7-6483e51b375d> | 2.90625 | 210 | Academic Writing | Science & Tech. | 0.045042 | 95,628,843 |
Yeast cells are members of the Fungus Kingdom. They are single celled microorganisms (eukaryotic) classified under phyla Ascomycota (sac fungi) and Basidiomyota (higher fungi) both of which fall under the subkingdom Dikarya.
* Budding yeast, also referred to as true yeast fall under the Phylum Acomycota and in the Order Saccharomycetales
Yeast are very diverse (over 1,500 species) with most forming the phylum Ascomycota while only a few are classified as Basidiomycota. Yeast reproduce through budding or binary fission which are both methods of asexual reproduction (Horst, 2010).
Budding - A new cell is formed through mitotic cell division and remains attached as a bud on the old cell until it splits and becomes independent. Here, the parent cell produces an outgrowth that finally splits to become an independent identical cell as the parent cell.
Binary fission - In binary fission, no outgrowth (bud) is formed. Rather, through mitosis, the genome replicates and divides followed by the formation of a new plasma membrane and ultimately the cell dividing in to two to form two new cells from the parent cell.
* Some of the fungi referred to as dimorphic tend to alternate between the yeast and hyphal phase which means that they can also grow as hyphae (thread like)
Because they are very diverse, yeast can be found in a wide variety of habitats particularly in environments with sugar-rich materials. They are likely to be found on flowers, plant leaves, and fruits as well as on soil, deep-sea environments, skin surface and even intestinal tracts of animals (warm blooded).
While they can be found in many
environments, yeast require moist environments with sufficient amounts of simple
and soluble nutrients to support growth and multiplication (Horst, 2010).
While such yeast as the Candica can cause infections (Candidiasis) there are useful yeast such as:
Yeast cake contains Saccharomyces Cerevisiae (sugar-eating fungus) and can therefore be used to obtain the yeast to observe under the microscope. The following is a procedure that can be used to prepare the specimen for observation.
When viewing the specimen under high
magnification (1000x and above) one will see oval (egg shaped) organism, which
are the yeast. It is also possible to observe the buds, which can be seen on
some of the cells.
If the solution had some sugar, one will also notice some bubbles in the specimen, which are as a result of the fermentation process by the microorganisms.
More about Brightfield Microscopy here.
Fluorescence microscopy can be used for the purposes of observing the organelles inside the yeast cells. This is particularly a great method through which students can get to view the intracellular distribution of the cell and identify the different types of cell organelle. However, this may prove a little challenging when it comes to yeast given that they are very small in size (compared to other cells) and have a cell wall (Chalfie and Kain, 2005).
For living yeast cells, a number of dyes have to be used in order to increase contrast and be able to differentiate the different organelles in the cells. These include:
Yeast are among the smallest eukaryotic cells with diameters of between 5 and 10um. For this reason, it is important to view them under high magnification using fluorescence microscopy. Here, 60x or 100x objectives with numerical aperture of 1.4 are recommended for visual observation and maximum brightness and resolution respectively.
If recording using a digital camera (e.g. using a 6.8 x 6.8 um sq pixel camera) then a magnification of 60x would be recommended with numerical aperture of 1.4 (Hašek, 2006).
Martin Chalfie and Steven R. Kain (2005) Green Fluorescent Protein: Properties, Applications and Protocols.
Jiří Hašek (2006) Yeast Fluorescence Microscopy. Volume 313 of the series Methods in Molecular Biology pp 85-96.
Feldmann, Horst (2010). Yeast. Molecular and Cell bio.
Jul 18, 18 10:57 AM
The genus Claviceps is a fungi species that can be found in the ovaries of grasses and rye (as well as other related plants). This has been shown to be the primary characteristic of these species.
Jul 11, 18 02:16 PM
Pezizomycotina is the largest subphylum of phylum Ascomycota (also known as sac fungi). With well over 100, 000 species (over 30,000 of these species have been well described), subphylum Pezizomycotin…
Jul 11, 18 01:04 PM
San Antonio, Texas, based Living Slides (www.theliveslide.com) is pleased to announce the launch of an innovative new microscope slide, LiveSlide®, developed in San Antonio and proudly manufactured in…
MicroscopeMaster.com is a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means to earn fees by linking to Amazon.com and affiliated sites. | <urn:uuid:58578889-7f5d-41e8-ad11-6d35f7eada6f> | 4.125 | 1,114 | Knowledge Article | Science & Tech. | 42.951504 | 95,628,845 |
"Orbital commensurabilities among planets are fundamentally fragile, so the present-day configuration of the K2-138 planets clearly points to a rather gentle and laminar formation environment of these distant worlds". There's no way water would exist on the surface, as portrayed here.
Back in California, Crossfield and Christiansen joined NASA astronomer Geert Barentsen, who was in Australia, in examining results as they came in.
"We're looking forward to more discoveries in the near future", Crossfield says. The central star is slightly smaller and cooler than our Sun. Their orbits around their parent star appear to be concentric circles, unlike the elliptical ones we are familiar with in the solar system. The appearance of most systems containing planets with similar sizes and regularly spaced orbits suggests they have been mostly undisturbed since formation. They are all being classified as super-Earths, weighing in at about two to three times larger than our planet.
These planets are orbiting in a resonance, a mathematical term for when each planet takes nearly exactly 50 percent longer to orbit the star than the next planet further in.
Sorting through the upvoted, crowdsourced data, Christiansen eventually found a star with four planets orbiting it. Christainsen and the Expoplanet Explorers had stumbled upon the first system of exo-planets that was discovered entirely by crowdsourcing. "So, we made a decision to look for a multi-planet system because it's very hard to get an accidental false signal of several planets". But the story of how K2-138 was discovered is also pretty neat.
Citizen scientists have discovered five tightly packed planets outside our solar system, almost 620 light years from Earth, using data from NASA's Kepler Space Telescope.
Using data from some of the thousands of exoplanets located using Kepler, Weiss and her team used the W. M. Keck Observatory in Mauna Kea, Hawaii to obtain high-resolution spectral data of 1,305 stars hosting 2,025 planets. Typically, computer programs flag the stars with these brightness dips, then astronomers look at each one and decide whether or not they truly could host a planet candidate. A dip in starlight indicates a possible transit, or crossing, of an object such as a planet in front of its star. Known as the C12 dataset, this represents a disgusting amount of data for scientists to sift through.
Another batch of 2017 Kepler data was recently uploaded to Exoplanet Explorers for citizen scientists to peer through. Dr. Christina formed that People from anywhere across the globe can log on and learn what real signals coming from exoplanet look like, and then look through actual data collected from the Kepler telescope to vote on whether or not to classify a given signal as a transit, or just noise. For the signals to get confirmed for further analysis by researchers, at least ten users should look at a potential signal and then ninety percent of users should have to vote "yes" for that signal.
During the Stargazing Live series, results from more than 10,000 viewers were collected by the Exoplanet Explorers. Astronomers have not yet searched through most of it for planets. "What's exciting is that we found this unusual system with the help of the general public". "So, we chose to look for a multi-planet system because it's very hard to get an accidental false signal of several planets".
They also found only a very weak correlation between star mass and planet radius, which means it's probably not stellar mass that enforces planet size. Three of the four planets received "yes" votes from 100 per cent of participants, while the remaining planet got "yes" votes from 92 per cent. Citizen scientists and astronomers are now searching through the new data trove, indicating that more new exciting discoveries may be in the offing.
Citizen scientists have struck again.
"The clockwork-like orbital architecture of this planetary system is keenly reminiscent of the Galilean satellites of Jupiter", says Konstantin Batygin, assistant professor of planetary science and Van Nuys Page Scholar, who was not involved with the study, said in a statement.
Wynn Resorts, Limited (NASDAQ:WYNN) Holdings Lowered by Allianz Asset Management GmbH
Tiaa Cref Inv Mngmt Limited Com invested 0.09% in Wynn Resorts, Limited (NASDAQ:WYNN). 5,024 are held by Natixis Asset Mgmt. The investor is now holding $5.12 million shares due in part to a decrease of 1.61 million new shares in their portfolio. | <urn:uuid:286947f4-1819-4fe2-ae26-80edca78b2ce> | 3.78125 | 954 | News Article | Science & Tech. | 46.16734 | 95,628,851 |
Radiocarbon decays slowly in a living organism, and the amount lost is continually replenished as long as the organism takes in air or food.
Once the organism dies, however, it ceases to absorb carbon-14, so that the amount of the radiocarbon in its tissues steadily decreases.
I have tried here to answer some of the frequently asked questions that I receive from students via email, as well as providing some basic information about scientific dating methods.
"Everything which has come down to us from heathendom is wrapped in a thick fog; it belongs to a space of time we cannot measure.
Since 1947, scientists have reckoned the ages of many old objects by measuring the amounts of radioactive carbon they contain.
New research shows, however, that some estimates based on carbon may have erred by thousands of years.
They used pottery and other materials in sites to date 'relatively'.
They thought that sites which had the same kinds of pots and tools would be the same age.
The aim here is to provide clear, understandable information relating to radiocarbon dating for the benefit of K12 students, as well as lay people who are not requiring detailed information about the method of radiocarbon dating itself.
Since its first use in the 1940s radiocarbon dating has been the most accurate method of dating ancient objects and artifacts.
Radiocarbon, present in living organisms, decays at a constant rate in dead tissue.
Carbon-14 has a half-life of 5,730 ± 40 years— during the succeeding 5,730 years.
Because carbon-14 decays at this constant rate, an estimate of the date at which an organism died can be made by measuring the amount of its residual radiocarbon. | <urn:uuid:aa8619d7-452c-408d-a7fc-4a666894ac83> | 3.75 | 362 | Knowledge Article | Science & Tech. | 42.989393 | 95,628,870 |
Inner cities as well as suburbs show distinctly warmer temperatures--known as the urban heat island effect--than rural areas as a result of land use and human activities, which can affect rainfall, air quality and public health.
A University of Georgia study using a new method for calculating urban heat island intensities clarifies the conflict on whether urban density or sprawl amplify these effects more. It also provides a ranking of the top urban heat island cities among the 50 largest metropolitan statistical areas.
The urban heat island effect describes how the spatial configuration of cities, the materials in them (such as asphalt), lack of vegetation and waste heat can modify temperature.
The study, published in the journal Computers, Environment and Urban Systems, identifies Salt Lake City, Miami and Louisville as the top three urban heat island cities in the U.S.
Urban morphology--the patterns of a city's physical configuration and the process of its development--has long been associated with the formation of urban heat islands. By examining the UHI intensities of 50 cities with various urban morphologies, the researchers evaluated the degree to which city configuration influences the UHI effect.
"The overall goal of our study was to clarify which urban form--sprawl or more-dense development--is most appropriate for UHI mitigation," said the study's lead author Neil Debbage, doctoral student in the Franklin College of Arts and Sciences' department of geography.
The study establishes a method for estimating UHI intensities using PRISM--Parameter-elevation Relationships on Independent Slopes Model--climate data, an analytical model that creates gridded estimates by incorporating climatic variables (temperature and precipitation), expert knowledge of climatic events (rain shadows, temperature inversions and coastal regimes) and digital elevation.
The use of spatially gridded temperature data, rather than urban versus rural point comparisons, represents a new method for calculating a city's canopy heat island intensity. The results identify the spatial contiguity of developed areas as a significant factor influencing the magnitude of the heat island effect.
"Not just whether cities have high-density development, but how the built infrastructure is connected--and disconnected by green spaces--has a great impact on heat island intensity," said study co-author Marshall Shepherd, the UGA Athletic Association Distinguished Professor of Geography and Atmospheric Sciences.
"We found that more contiguous sprawling and dense urban development both enhanced UHI intensities. In other words, it does not appear to be a simplistic either-or situation regarding sprawl or density," Debbage said.
The researchers hope the results can help influence local governments and city planners in the formulation of effective codes and policies to mitigate the urban heat island effect.
"It's crucial to work toward a better understanding of the complex processes at the intersection of urbanization, climate and human health," Shepherd said. "Current and future cities will be modified or designed with weather and climate in mind, and research at UGA will play a key role.
The study on "The Urban Heat Island Effect and City Contiguity" is available at http://www.
Neil Debbage | EurekAlert!
New research calculates capacity of North American forests to sequester carbon
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16.07.2018 | Earth Sciences | <urn:uuid:baac4a1e-6701-4d8c-8cc4-082ae2c9c4f5> | 3.4375 | 1,269 | Content Listing | Science & Tech. | 32.119734 | 95,628,892 |
Elements: Assembly Language Programming
An assembly language provides the following three basic facilities that simplify programming:
Mnemonic operation codes
The mnemonic operation codes for machine instructions (also called mnemonic opcodes) are easier to remember and use than numeric operation codes. Their use also enables the assembler to detect the use of invalid operation codes in a program.
A programmer can associate symbolic names with data or instructions and use these symbolic names as operands in assembly statements. Moreover, This facility frees the programmer from having to think of numeric addresses in a program. We use the term symbolic name only in formal contexts; elsewhere we simply say a name.
Data can be declared in a variety of notations, including the decimal notation. Also, It avoids the need to manually specify constants in representations that a computer can understand, for example, specify -5 as (11111011)2 in the two’s complement representation.
An assembly language statement has the following format:
[Label] <Opcode> <operand specification>[,<operand specification>..]
where the notation [..] indicates that the enclosed specification is optional. If a label is specified in a statement, it associated as a symbolic name with the memory word generated for the statement.
Moreover, If more than one memory word generated for a statement, the label would be associated with the first of these memory words.
<operand specification> has the following syntax:
<symbolic name> [± <displacement> ] [(<index register>)]
Thus, some possible operand forms as follows: The operand AREA refers to the memory word with which the name AREA associated.
- The operand AREA+5 refers to the memory word that is 5 words away from the word with the name AREA. Here ‘5’ the displacement or offset from AREA.
- The operand AREA(4) implies indexing the operand AREA with index register 4—that is, the operand address obtained by adding the contents of index register 4 to the address of AREA.
- The operand AREA+5 (4) is a combination of the previous two specifications. | <urn:uuid:d70b56e0-57a2-4a45-a5c6-7755243cfea1> | 4.46875 | 459 | Documentation | Software Dev. | 25.928939 | 95,628,899 |
Low pressure centers associated with a summer monsoon trough have repeatedly drenched Australia from central Queensland to northern New South Wales. The clockwise rotation of these low pressure centers have continued to pump warm moist air from the Coral Sea over these areas resulting in severe flooding. Thousands of Australians have been displaced by this flooding.
TRMM satellite rainfall estimates for the state of Queensland are shown above for the ten day period from January 27 to February 6, 2012. The highest amounts of extreme rainfall (shown in purple), totaling more than 520 mm (~20.5 inches), extend from the Gulf of Carpentaria over the Cape York Peninsula. This analysis shows another area south of Mackay along Australia's coast with rainfall totaling over 480 mm (~18.9 inches). Credit: SSAI/NASA, Hal Pierce
A Tropical cyclone called Jasmine originated as a low pressure center over the Cape York Peninsula. Jasmine was upgraded to a tropical cyclone on February 6, 2012. Jasmine is in the Coral Sea well east of Australia, moving eastward and is predicted to strike Vanuatu on February 8th, 2012.
Data from the TRMM satellite are used to calibrate rainfall data merged from various satellite sources. This TRMM-based, near-real time Multi-satellite Precipitation Analysis (TMPA) at the NASA Goddard Space Flight Center, Greenbelt, Md. is used to monitor rainfall over the global Tropics. TMPA rainfall estimates for the state of Queensland were calculated for the ten day period from January 27 to February 6, 2012. The highest amounts of extreme rainfall (shown in purple), totaling more than 520 mm (~20.5 inches), extend from the Gulf of Carpentaria over the Cape York Peninsula. This analysis shows another area south of Mackay along Australia's coast with rainfall totaling over 480 mm (~18.9 inches).
Parts of the town on St George in southern Queensland were advised to evacuate. Runoff from extreme rainfall has swollen the Balonne River.
The current La Nina conditions are predicted to continue causing heavier than normal rainfall over northeastern Australia.Text Credit: Hal Pierce and Steve Lang
Rob Gutro | EurekAlert!
New research calculates capacity of North American forests to sequester carbon
16.07.2018 | University of California - Santa Cruz
Scientists discover Earth's youngest banded iron formation in western China
12.07.2018 | University of Alberta
For the first time ever, scientists have determined the cosmic origin of highest-energy neutrinos. A research group led by IceCube scientist Elisa Resconi, spokesperson of the Collaborative Research Center SFB1258 at the Technical University of Munich (TUM), provides an important piece of evidence that the particles detected by the IceCube neutrino telescope at the South Pole originate from a galaxy four billion light-years away from Earth.
To rule out other origins with certainty, the team led by neutrino physicist Elisa Resconi from the Technical University of Munich and multi-wavelength...
For the first time a team of researchers have discovered two different phases of magnetic skyrmions in a single material. Physicists of the Technical Universities of Munich and Dresden and the University of Cologne can now better study and understand the properties of these magnetic structures, which are important for both basic research and applications.
Whirlpools are an everyday experience in a bath tub: When the water is drained a circular vortex is formed. Typically, such whirls are rather stable. Similar...
Physicists working with Roland Wester at the University of Innsbruck have investigated if and how chemical reactions can be influenced by targeted vibrational excitation of the reactants. They were able to demonstrate that excitation with a laser beam does not affect the efficiency of a chemical exchange reaction and that the excited molecular group acts only as a spectator in the reaction.
A frequently used reaction in organic chemistry is nucleophilic substitution. It plays, for example, an important role in in the synthesis of new chemical...
Optical spectroscopy allows investigating the energy structure and dynamic properties of complex quantum systems. Researchers from the University of Würzburg present two new approaches of coherent two-dimensional spectroscopy.
"Put an excitation into the system and observe how it evolves." According to physicist Professor Tobias Brixner, this is the credo of optical spectroscopy....
Ultra-short, high-intensity X-ray flashes open the door to the foundations of chemical reactions. Free-electron lasers generate these kinds of pulses, but there is a catch: the pulses vary in duration and energy. An international research team has now presented a solution: Using a ring of 16 detectors and a circularly polarized laser beam, they can determine both factors with attosecond accuracy.
Free-electron lasers (FELs) generate extremely short and intense X-ray flashes. Researchers can use these flashes to resolve structures with diameters on the...
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The hunting of the Majorana fermions - particles that are their own antiparticles - in topological superconductors is one of paramount research targets in condensed matter physics today. Recently, a research team led by Professor Qi-Kun Xue of Tsinghua University in China has succeeded to reveal experimental evidence of topological superconductivity near the surface of epitaxial β-Bi2Pd films, and possible Majorana zero modes at magnetic vortices.
A topological superconductor is superconducting inside the bulk like usual superconductors, while on the boundary/surface it harbors the long-sought Majorana fermions. Such unusual particles obey non-Abelian braiding statistics and could be potential for fault-tolerant quantum computing, which can operate much more efficiently than any current computers.
Topological superconductivity and Majorana zero modes of epitaxial β-Bi2Pd films by molecular beam epitaxy. (a) Topographic image of β-Bi2Pd films, with the insert as the schematic crystal structure of β-Bi2Pd. (b) Typical differential conductance dI/dV spectrum at 0.4 K, revealing two distinct superconducting gaps from bulk (Δb) and topological surface (Δs) states, respectively. (c) Zero-bias conductance map, showing an individual magnetic vortex (bright yellow region). (d) Tunneling conductance dI/dV spectrum taken at the vortex center, signifying a salient zero bias conductance peak. (e) The dI/dV spectra acquired at positions with varying radial distance r from the vortex center. The peaks shows no splitting and is invariably fixed to the zero energy, anticipated for Majorana zero modes.
Credit: ©Science China Press
A handful of topological superconductors have hitherto been proposed in topological insulators or other systems with strong spin-orbital coupling when they are interfaced with a superconductor or driven into the superconducting states by chemical doping. However, little attention is paid to the other way of thinking, to wit, searching for topologically nontrivial band structure in classical s-wave superconductors.
Tetragonal β-Bi2Pd was found to be superconducting below 5.4 K in 1957. Just recently, it was revealed from angle-resolved photoemission spectroscopy that topologically protected surface bands cross the Fermi level of β-Bi2Pd.
The two major ingredients of realizing topological superconductivity are coincidently existing in this single-component compound. Subsequent experimental search for the buried topological superconductivity in β-Bi2Pd all fell flat. The researchers in Tsinghua University have caught the rare opportunity and unmasked the veil of topologically nontrivial superconducting states in β-Bi2Pd.
"We are motivated to unravel why the topological superconductivity failed to be observed in all previous studies of β-Bi2Pd crystals, it is now known that tuning the chemical potential to isolate the topological surface states from bulk bands near the Fermi level is the key to observe such topologically nontrivial superconducting states," said Yanfeng Lv, the first author of this study, now is a postdoctoral researcher at Texas Center for Superconductivity, University of Houston.
Published in the journal of Science Bulletin, the study utilized a state-of-the-art molecular beam epitaxy technique under ultrahigh vacuum to prepare successfully high-quality β-Bi2Pd thin films on SrTiO3 substrates, which was then in-situ transferred to a cryogenic scanning tunneling microscopy chamber.
The tunneling spectrum revealed a pronounced and impurity-resistant superconducting gap opening on the surface, which appears much larger than the bulk on owing to Dirac-fermion enhanced parity mixing of surface pair potential. The direct visualization of superconducting gap opening on the topological surface states, as well as its expected variation with the Fermi level, compellingly reveals β-Bi2Pd as a promising candidate for topological superconductor. Salient zero bias conductance peaks, probably from Majorana zero modes supported by such superconducting states, were identified at the end of magnetic vortex lines.
"This research provides the convincing evidence of topological superconductivity on β-Bi2Pd and signature of Majorana zero modes at vortices," said the researchers, "and more importantly points to a novel avenue for searching topological pairing states on usual superconductors that might exhibit topologically nontrivial band structure by the engineering of Fermi level."
This work was financially supported by National Science Foundation, Ministry of Science and Technology and Ministry of Education of China, the National Thousand-Young-Talents Program and the Tsinghua University Initiative Scientific Research Program.
See the article:
Yan-Feng Lv, Wen-Lin Wang, Yi-Min Zhang, Hao Ding, Wei Li, Lili Wang, Ke He, Can-Li Song, Xu-Cun Ma, Qi-Kun Xue. Experimental signature of topological superconductivity and Majorana zero modes on β-Bi2Pd thin films. Science Bulletin 2017, 62(12): 852-856. https:/
Can-Li Song | EurekAlert!
Computer model predicts how fracturing metallic glass releases energy at the atomic level
20.07.2018 | American Institute of Physics
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For the first time a team of researchers have discovered two different phases of magnetic skyrmions in a single material. Physicists of the Technical Universities of Munich and Dresden and the University of Cologne can now better study and understand the properties of these magnetic structures, which are important for both basic research and applications.
Whirlpools are an everyday experience in a bath tub: When the water is drained a circular vortex is formed. Typically, such whirls are rather stable. Similar...
Physicists working with Roland Wester at the University of Innsbruck have investigated if and how chemical reactions can be influenced by targeted vibrational excitation of the reactants. They were able to demonstrate that excitation with a laser beam does not affect the efficiency of a chemical exchange reaction and that the excited molecular group acts only as a spectator in the reaction.
A frequently used reaction in organic chemistry is nucleophilic substitution. It plays, for example, an important role in in the synthesis of new chemical...
Optical spectroscopy allows investigating the energy structure and dynamic properties of complex quantum systems. Researchers from the University of Würzburg present two new approaches of coherent two-dimensional spectroscopy.
"Put an excitation into the system and observe how it evolves." According to physicist Professor Tobias Brixner, this is the credo of optical spectroscopy....
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Red-cockaded woodpeckers are named for the line of red feathers sported by males between their black caps and white cheeks. When the birds were given a name about two centuries ago, cockades—ribbons or ornaments worn in hats—were quite popular, and the decorative feathers on the male were reminiscent of one. The red cockade is one of the only features that distinguishes a male from a female. Both males and females have grayish-white bellies and black-and-white striped backs. Red-cockaded woodpeckers are 7.8 to 9.1 inches (20 to 23 centimeters) in length with a 14-inch (36-centimeter) wingspan.
Red-cockaded woodpeckers have been extirpated from the northern part of their range. They are now found in a patchy distribution from Virginia south to Florida and west to Arkansas, Oklahoma, and Texas.
The woodpeckers live in mature pine forests that are maintained by fire. Mature trees are preferred over young ones for two reasons. First, young trees may not be large enough in diameter for cavity excavation. Second, mature trees are more likely to be infected with a fungus called red heart disease. This makes the wood of the tree softer and easier for the woodpecker to remove. Fire is important because it keeps the forest midstory from getting too tall. It’s thought that when the midstory rises too high, predators and nest competitors have easier access to woodpecker cavities. Red-cockaded woodpeckers drill sap wells near the entrance to their nests to deter rat snakes, a major tree-climbing predator. The woodpeckers must also watch out for several other bird and mammal species that seize their nest cavities while they’re still in use.
Most of the red-cockaded woodpecker's diet is comprised of insects and spiders foraged from under loose pine bark. They supplement their insectivorous diet with seeds and berries.
Red-cockaded woodpeckers are cooperative breeders, meaning multiple birds take care of the young. Females lay their eggs in the roost cavities of their male mates. The male and several helper birds, which are usually relatives of the breeding pair, incubate the eggs. The whole family sticks together while the young are raised. Red-cockaded woodpeckers have been recorded living up to 12 years, but the average lifespan is lower.
Red-cockaded woodpeckers now occupy a much smaller portion of their original range, and they are federally listed as endangered. Red-cockaded woodpeckers have a preference for longleaf pine forests, but these have been extensively logged and replaced with other pine species. The woodpeckers will nest in shortleaf, slash, and loblolly pines, but it takes the young, replanted trees years to mature to the level at which they become habitable for the woodpeckers. Additionally, natural, beneficial fires have been suppressed in the forests, which results in more habitat for predators of the woodpeckers.
When red-cockaded woodpeckers begin excavating a nest cavity, they remove wood at an upward angle so sap drains out and rainwater doesn’t flood the hollow. Once they drill past the outer sapwood, the nest cavity starts to take shape in the heartwood.
Khan, M., & Walters, J. (2002). Effects of helpers on breeder survival in the red-cockaded woodpecker (Picoides borealis). Behavioral Ecology and Sociobiology, 51(4), 336–344.
South Carolina Department of Natural Resources
The Cornell Lab of Ornithology
The IUCN Red List of Threatened Species
U.S. Fish & Wildlife Service
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Weiss and colleagues dreamed up the idea behind a massive antenna so sensitive it detects faint, invisible ripples in space from 1.3 billion years ago - offering evidence of Einstein's theory of general relativity.
When he was 19, Mark Everett’s father died. But his big idea, a surprising interpretation of quantum mechanics, lived on. And if that idea is right, he might still be alive … somewhere.
For decades, astronauts have had to drink from plastic bags to keep their water and coffee from floating away. Now NASA is trying out a new "zero-gravity cup" that uses physics to simulate taking a normal sip back on the ground. | <urn:uuid:07ff9cc7-40d0-434c-8efd-84ccd4e08623> | 2.828125 | 133 | Content Listing | Science & Tech. | 53.217727 | 95,628,984 |
Doubts in Physics answered
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If electrons are caused to fall through a potential difference of 100000volt find the final speed of them if they were initially at rest?
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Please use the formula
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The NASA/ESA Hubble Space Telescope is famous for its jaw-dropping snapshots of the cosmos. At first glance this Picture of the Week appears to be quite the opposite, showing just a blur of jagged spikes, speckled noise, and weird, clashing colors -- but once you know what you are looking at, images like this one are no less breathtaking.
This shows a distant galaxy -- visible as the smudge to the lower right -- as it begins to align with and pass behind a star sitting nearer to us within the Milky Way. This is an event known as a transit. The star is called HD 107146, and it sits at the center of the frame.
This shows a distant galaxy -- visible as the smudge to the lower right -- as it begins to align with and pass behind a star sitting nearer to us within the Milky Way. This is an event known as a transit. The star is called HD 107146, and it sits at the center of the frame. Its light has been blocked in this image to make its immediate surroundings and the faint galaxy visible -- the position of the star is marked with a green circle.
Credit: ESA/Hubble & NASA
Its light has been blocked in this image to make its immediate surroundings and the faint galaxy visible -- the position of the star is marked with a green circle.
The concentric orange circle surrounding HD 107146 is a circumstellar disk -- a disk of debris orbiting the star. In the case of HD 107146 we see the disk face-on. As this star very much resembles our sun, it is an interesting scientific target to study: its circumstellar disk could be analogous to the asteroids in our Solar System and the Kuiper belt.
A detailed study of this system is possible because of the much more distant galaxy -- nicknamed the "Vermin Galaxy" by some to reflect their annoyance at its presence -- as the star passes in front of it.
The unusual pairing was first observed in 2004 by Hubble's Advanced Camera for Surveys, and again in 2011 by Hubble's Space Telescope Imaging Spectrograph.
The latter image is shown here, as the Vermin Galaxy began its transit behind HD 107146. The galaxy will not be fully obscured until around 2020, but interesting science can be done even while the galaxy is only partly obscured.
Light from the galaxy will pass through the star's debris disks before reaching our telescopes, allowing us to study the properties of the light and how it changes, and thus infer the characteristics of the disk itself.
Rob Gutro | EurekAlert!
Computer model predicts how fracturing metallic glass releases energy at the atomic level
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What happens when we heat the atomic lattice of a magnet all of a sudden?
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To rule out other origins with certainty, the team led by neutrino physicist Elisa Resconi from the Technical University of Munich and multi-wavelength...
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Whirlpools are an everyday experience in a bath tub: When the water is drained a circular vortex is formed. Typically, such whirls are rather stable. Similar...
Physicists working with Roland Wester at the University of Innsbruck have investigated if and how chemical reactions can be influenced by targeted vibrational excitation of the reactants. They were able to demonstrate that excitation with a laser beam does not affect the efficiency of a chemical exchange reaction and that the excited molecular group acts only as a spectator in the reaction.
A frequently used reaction in organic chemistry is nucleophilic substitution. It plays, for example, an important role in in the synthesis of new chemical...
Optical spectroscopy allows investigating the energy structure and dynamic properties of complex quantum systems. Researchers from the University of Würzburg present two new approaches of coherent two-dimensional spectroscopy.
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SOUTH AUSTRALIAN SUN-MOTHS
Synemon 'Flinders Ranges' (Flinders Ranges Sun-moth)
Male 38mm from Wilpena (left), female 38mm from Yunta
|Another un-studied species, belonging in the Chrysopogon/Cymbopogon
(Poaceae) feeding complex of Synemon species, particularly Synemon austera and S. brontias, and may
even be a form of the latter species. This complex is more commonly found in
tropical and sub-tropical latitudes. It is a pretty moth, characterised by having a
hindwing that is nearly all yellow-orange coloured, and is presently documented from S.A.
in only the Frome Basin along ephemeral creeks containing its tussock host-grass Cymbopogon
ambiguus (Lemon-scented or Kerosene Grass). It requires its hostplant to grow in
the open and to not be congested by other plants, particularly feral weeds and grasses
that tend to grow in the creeks that have a more reliable supply of water. Hence, this
sun-moth does not occur in the temperate areas of SA even though its Cymbopogon
hostplants may occur. It is not known what the consequences are for the early stages when
there is an extended wet period in the habitat area and the creeks are flowing water.
It has a wing expanse of 30-40mm and flies in spring during October-early November. The range of this species may be more extensive than presently recorded as the larval host Cymbopogon also occurs in the Southern Flinders and Gawler Ranges, and the Far North-west Regions, or perhaps there may even be another new species to be discovered in S.A. as other sun-moths are known to utilise this grass in neighbouring Australian states.
It flies during the heat of the day, but by 3.00pm starts to look for a place to hide for the night. It often uses large cracks in the creek cliffs to hide in, which would seem to be an inhospitable environment as such places also tend to contain spiders and lizards and other nasties. Males often remain inactive on the ground during the day, possibly tending their territorial areas (leks).
Females spend their time laying eggs. The eggs are laid on the stems of the hostplant near its base, which the female accesses by landing on the ground near the plant then walking in under its tussocky leaves to its base. After each egg is laid, the females rest nearby on the ground in an open wing position. They do not feed from flowers as they do not possess a functional proboscis. They carry a lot of fat in their bodies to survive on, derived from their earlier larva and pupa stages, and in museum specimens this fat tends to seep into the wings discolouring them. Newly laid eggs are about 2.3x1.0mm, white coloured and have six longitudinal ridges. Other early stage details have yet to be documented.
It is threatened by over-grazing pastoral practices and locust spraying.
Resting female (after laying egg); 'tent' position
left; open wing position right,
showing the exaggerated hindwing flash colours.
Ungrazed Cymbopogon ambiguus in an ephemeral
creek at Wilpena.
The moths retire to cracks in the cliff by late afternoon, then emerge again the following late morning.
Cymbopogon ambiguus (Lemon-scented or Kerosene grass) (Poaceae) at Wilpena.
Cymbopogon ambiguus in Yunta Ck.
Cymbopogon ambiguus in a small ephemeral creek near Olary.
Egg of Synemon 'Flinders' having 6 longitudinal ridges. Egg on left is partially dehydrated.
Photography by R. Grund
Author: R. GRUND, © copyright 12 April 2011, all rights reserved.
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Quagga mussels (Dreissena rostriformis bugensis) have created economic and ecological impacts in the western United States since their discovery in 2007. This study focuses on chemical control for preventing the spread of these mussels. The effectiveness of EarthTec® in killing quagga mussels (adults, juveniles, and veligers) in Lake Mead, Nevada-Arizona, was evaluated over time across six concentrations: 0, 1, 5, 10, 17, and 83 ppm. One hundred percent mortality of adult and juvenile mussels was achieved after 96 h with 17 ppm and 5 ppm (respectively), and 100% veliger mortality occurred within 30 min at 3 ppm. From December 2010 to February 2011, the effectiveness of EarthTec® in preventing veliger colonization was also evaluated and the results showed that 2.8 ppm was effective in preventing veliger colonization on fiberglass panels. This study indicates that EarthTec® has the potential to be an effective control agent against the invasive quagga mussel, and more specifically, in preventing the colonization of veligers.
- Introduced aquatic organisms,
- West (U.S.)
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Cyclacenes are hoop-like polycyclic compounds where aromatic moieties are fused together to form the ring structures. Because of their interesting electronic and structural properties as well as their potential applications in supramolecular chemistry and molecular recognition, cyclacenes have drawn much attention from organic chemists and been viewed as interesting yet challenging synthetic targets. Pioneering efforts by Fraser Stoddart and co-workers in the late 1980s and following work from other groups embarked on the synthesis of various cyclacenes. Figure 1 shows two examples of cyclacenes that have been synthesized.
Cyclacenes are synthesized usually via interactive reactions to construct the repetitive units in the ring structure. Stoddart and co-workers synthesized 12cyclacene through interactive Diels-Alder reactions. Reacting 7-oxoanorbornene derivative A with bisdienophile B generated intermediate C in good yield (Fig. 2). Compound C further reacted with A under high pressure to close the ring structure and afforded compound D with 12 consecutive six-membered rings fused together. To convert compound D to 12cyclacene, Stoddart and co-workers used a two-step process where the 6 ether linkages in D were removed and additional double bonds were generated to afford the -systems in the final product.
- Kohnke, F. H.; Slawin, A. M. Z.; Stoddart, J. F.; Williams, D. J. Angew. Chem., Int. Ed. 1987, 26, 892-894.
- Ashton, P. R.; Isaacs, N. S.; Kohnke, F. H.; Slawin, A. M. Z.; Spencer, C. M.; Stoddart, J. F.; Williams, D. J. Angew. Chem., Int. Ed. 1988, 27, 966-969. | <urn:uuid:b83ef5e2-401f-4156-afda-6c12b3968d24> | 3.125 | 394 | Knowledge Article | Science & Tech. | 57.157639 | 95,629,014 |
Ar ar dating method ppt
That is, a fresh mineral grain has its K-Ar "clock" set at zero.The method relies on satisfying some important assumptions: Given careful work in the field and in the lab, these assumptions can be met.An Ar age of 542.62 ± 0.38 Ma (1 sigma, full external precision, Renne et al., 2011) for metalliferous alteration clays in Scotland shows that this event occurred immediately prior to the Precambrian–Cambrian boundary.A negative δCr isotopic signature for the clay is consistent with mobilization on land of redox sensitive metals by oxidative terrestrial weathering.This unprecedented flushing of metals from the weathered Precambrian surface would have contributed to the chemistry of the earliest Cambrian ocean at a time of marked faunal evolution.Your access to the NCBI website at gov has been temporarily blocked due to a possible misuse/abuse situation involving your site.The amount of Argon sublimation that occurs is a function of the purity of the sample, the composition of the mother material, and a number of other factors.These factors introduce error limits on the upper and lower bounds of dating, so that final determination of age is reliant on the environmental factors during formation, melting, and exposure to decreased pressure and/or open-air.
What simplifies things is that potassium is a reactive metal and argon is an inert gas: Potassium is always tightly locked up in minerals whereas argon is not part of any minerals. So assuming that no air gets into a mineral grain when it first forms, it has zero argon content.
Potassium–argon dating, abbreviated K–Ar dating, is a radiometric dating method used in geochronology and archaeology. | <urn:uuid:d12796ab-06af-41c3-9ba6-bbcaf6512c3a> | 3.390625 | 366 | Knowledge Article | Science & Tech. | 37.744355 | 95,629,017 |
10 relations: American Association of Variable Star Observers, Apparent magnitude, Aquila (constellation), Bright Star Catalogue, Constellation, Durchmusterung, Henry Draper Catalogue, Hipparcos, Mira variable, Smithsonian Astrophysical Observatory Star Catalog.
Since its founding in 1911, the American Association of Variable Star Observers (AAVSO) has coordinated, collected, evaluated, analyzed, published, and archived variable star observations made largely by amateur astronomers and makes the records available to professional astronomers, researchers, and educators.
The apparent magnitude of a celestial object is a number that is a measure of its brightness as seen by an observer on Earth.
New!!: R Aquilae and Apparent magnitude ·
Aquila is a constellation on the celestial equator.
New!!: R Aquilae and Aquila (constellation) ·
The Bright Star Catalogue, also known as the Yale Catalogue of Bright Stars or Yale Bright Star Catalogue, is a star catalogue that lists all stars of stellar magnitude 6.5 or brighter, which is roughly every star visible to the naked eye from Earth.
New!!: R Aquilae and Bright Star Catalogue ·
A constellation is a group of stars that are considered to form imaginary outlines or meaningful patterns on the celestial sphere, typically representing animals, mythological people or gods, mythological creatures, or manufactured devices.
New!!: R Aquilae and Constellation ·
In astronomy, Durchmusterung or Bonner Durchmusterung (BD), is the comprehensive astrometric star catalogue of the whole sky, compiled by the Bonn Observatory (Germany) from 1859 to 1903.
New!!: R Aquilae and Durchmusterung ·
The Henry Draper Catalogue (HD) is an astronomical star catalogue published between 1918 and 1924, giving spectroscopic classifications for 225,300 stars; it was later expanded by the Henry Draper Extension (HDE), published between 1925 and 1936, which gave classifications for 46,850 more stars, and by the Henry Draper Extension Charts (HDEC), published from 1937 to 1949 in the form of charts, which gave classifications for 86,933 more stars.
New!!: R Aquilae and Henry Draper Catalogue ·
Hipparcos was a scientific satellite of the European Space Agency (ESA), launched in 1989 and operated until 1993.
New!!: R Aquilae and Hipparcos ·
Mira variables ("Mira", Latin, adj. - feminine form of adjective "wonderful"), named for the prototype star Mira, are a class of pulsating variable stars characterized by very red colours, pulsation periods longer than 100 days, and amplitudes greater than one magnitude in infrared and 2.5 magnitude at visual wavelengths.
New!!: R Aquilae and Mira variable ·
The Smithsonian Astrophysical Observatory Star Catalog is an astrometric star catalogue. | <urn:uuid:36daca3b-6671-445b-ab43-f8843ec713ad> | 3.5 | 613 | Structured Data | Science & Tech. | 28.498257 | 95,629,032 |
Ant nests in tank bromeliads — an example of non-specific interaction
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Four species of epiphytic tank bromeliads on an island in the Orinoco river in Venezuelan Amazonia were inhabited by 13 ant species from four subfamilies. None of these ant species are known as specialised plant-ants. A Monte Carlo randomisation test showed that ants were randomly distributed among host plants: (1) there was no association between particular ant species and bromeliad species, and (2) there was no vertical stratification of the ant community between bromeliads sampled on the ground and at two height classes in trees. This contrasts with the few published data on the distribution of ants on terrestrial myrmecophytes and epiphytes, respectively, to which we applied the same analytical method.
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It was one of the greatest mysteries in modern science: a series of brief but extremely bright flashes of ultra-high energy light coming from somewhere out in space. These gamma ray bursts were first spotted by spy satellites in the 1960s. It took three decades and a revolution in high-energy astronomy for scientists to figure out what they were.
Far out in space, in the center of a seething cosmic maelstrom. Extreme heat. High velocities. Atoms tear, and space literally buckles. Photons fly out across the universe, energized to the limits found in nature. Billions of years later, they enter the detectors of spacecraft stationed above our atmosphere. Our ability to record them is part of a new age of high-energy astronomy, and a new age of insights into nature at its most extreme. What can we learn by witnessing the violent birth of a black hole?
The outer limits of a black hole, call the event horizon, is subject to what Albert Einstein called frame dragging, in which space and time are pulled along on a path that leads into the black hole. As gas, dust, stars or planets fall into the hole, they form into a disk that spirals in with the flow of space time, reaching the speed of light just as it hits the event horizon. The spinning motion of this so-called “accretion disk” can channel some of the inflowing matter out into a pair of high-energy beams, or jets.
How a jet can form was shown in a supercomputer simulation of a short gamma ray burst. It was based on a 40-millisecond long burst recorded by Swift on May 9, 2005. It took five minutes for the afterglow to fade, but that was enough for astronomers to capture crucial details. It had come from a giant galaxy 2.6 billion light years away, filled with old stars.
Scientists suspected that this was a case of two dead stars falling into a catastrophic embrace. Orbiting each other, they moved ever closer, gradually gaining speed. At the end of the line, they began tearing each other apart, until they finally merged. NASA scientists simulated the final 35 thousandths of a second, when a black hole forms.
Chaos reigns. But the new structure becomes steadily more organized, and a magnetic field takes on the character of a jet. Within less than a second after the black hole is born, it launches a jet of particles to a speed approaching light.
A similar chain of events, in the death of a large star, is responsible for longer gamma ray bursts. Stars resist gravity by generating photons that push outward on their enormous mass. But the weight of a large star’s core increases from the accumulation of heavy elements produced in nuclear fusion. In time, its outer layers cannot resist the inward pull… and the star collapses. The crash produces a shock wave that races through the star and obliterates it.
In the largest of these dying stars, known as collapsars or hypernovae, a black hole forms in the collapse. Matter flowing in forms a disk. Charged particles create magnetic fields that twist off this disk, sending a portion out in high-speed jets.
Simulations show that the jet is powerful enough to plow its way through the star. In so doing, it may help trigger the explosion. The birth of a black hole does not simply light up the universe. It is a crucial event in the spread of heavy elements that seed the birth of new solar systems and planets.
But the black hole birth cries that we can now register with a fleet of high-energy telescopes are part of wider response to gravity’s convulsive power.
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+44 1803 865913
By: John Wright
419 pages, Figs
Undergraduate textbook offering an accessible introduction to chemical principles and concepts, and applies them to relevant environmental situations and issues.
'This is a timely and much needed text for students of environmental science or related subjects who need an appreciation of the importance and relevance of environmental chemistry to their studies.' - I David J. Harwood, Director, Institute of Science Education, University of Plymouth
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Authors: Bingzhuo Liu
Through the long-term extensive research on the experimental data of the fundamental physical constants and the mass of elementary particles such as charged leptons and neutrinos, the present study defines the source of "generation" difference generated from leptons, which thereby allows the accurate expression of the lepton mass to be derived. It is particularly important to point out that the data at the best fitting point Δm^2_32= 1.59·10^-3 eV^2 obtained in "Study of the wave packet treatment of neutrino oscillation at Daya Bay" reached an accuracy of 96%.
Comments: 6 Pages.
[v1] 2017-06-29 05:07:49
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ratio of the weight of a given volume of a substance to the weight of an equal volume of some reference substance, or, equivalently, the ratio of the masses of equal volumes of the two substances.
Unlike density, which has units of mass per volume, specific gravity is a pure number, i.e., it has no associated unit of measure. If the densities of the substance of interest and the reference substance are known in the same units (e.g., both in g/cm3 or lb/ft3), then the specific gravity of the substance is equal to its density divided by that of the reference substance. Similarly, if the specific gravity of a substance is known and the density of the reference substance is known in some particular units, then the density of the substance of interest, in those units, is equal to the product of its specific gravity and the density of the reference substance.
The most widely used reference substance for determining the specific gravities of solids and liquids is water. Because the density of water is very nearly 1 g/cm3, the density of any substance in g/cm3 is nearly the same numerically as its specific gravity relative to water. In the English system of units the density of water is about 62.4 lb/ft3, so the near equality between specific gravity and density is not preserved in this system. Specific gravities of gases are often given with dry air as the reference substance. Because the densities of all substances vary with temperature and pressure, the temperature and (particularly for gases) the pressure for both the reference substance and the substance of interest are often included when precise values of specific gravities are given.
A number of experimental methods for determining the specific gravities of solids, liquids, and gases have been devised. A solid is weighed first in air, then while immersed in water; the difference in the two weights, according to Archimedes' principle, is the weight of the water displaced by the volume of the solid. If the solid is less dense than water, some means must be adopted to fully submerge it, e.g., a system of pulleys or a sinker of known mass and volume. The specific gravity of the solid is the ratio of its weight in air to the difference between its weight in air and its weight immersed in water.
Two methods are commonly used for determining the specific gravities of liquids. One method uses the hydrometer, an instrument that gives a specific gravity reading directly. A second method, called the bottle method, uses a "specific-gravity bottle," i.e., a flask made to hold a known volume of liquid at a specified temperature (usually 20 degrees Celsius). The bottle is weighed, filled with the liquid whose specific gravity is to be found, and weighed again. The difference in weights is divided by the weight of an equal volume of water to give the specific gravity of the liquid. For gases a method essentially the same as the bottle method for liquids is used. Specific gravities of gases are usually converted mathematically to their value at standard temperature and pressure (see STP).
A physical measure, the weight of a given volume relative to the same volume of water at the same temperature and pressure. Because fat (adipose...
The ratio of an object’s or substance’s weight to that of an equal volume of water. The property is useful in, for example, sink float separation...
ratio of the mass of a substance to its volume, expressed, for example, in units of grams per cubic centimeter or pounds per cubic foot. The density | <urn:uuid:4494cdf2-db02-4365-ac7a-a2bdcc281aa9> | 4.0625 | 737 | Knowledge Article | Science & Tech. | 42.100925 | 95,629,090 |
Cycloalkanes (also called naphthenes, but distinct from naphthalene) are types of hydrocarbon compounds that have one or more rings of carbonatoms in the chemical structure of their molecules. Alkanes are types of organichydrocarboncompounds that have only single chemical bonds in their chemical structure. Cycloalkanes consist of only carbon (C) and hydrogen (H) atoms and are saturated because there are no multiple C-C bonds to hydrogenate (add more hydrogen to). A general chemical formula forpila cycloalkanes would be CnH2(n+1-g) where n = number of C atoms and g= number of rings in the molecule. For those cycloalkanes that have one ring in their molecules, cycloalkanes can be treated as isomers of their alkene counterparts, for example, cyclopropane and propene both have the chemical formula C3H6. Cycloalkanes with a single ring are named analogously to their normal alkane counterpart of the same carbon count: cyclopropane, cyclobutane, cyclopentane, cyclohexane, etc. The larger cycloalkanes, with greater than 20 carbon atoms are typically called cycloparaffins. | <urn:uuid:89940ff4-11ed-4a88-9dab-e553cda718da> | 3.734375 | 266 | Knowledge Article | Science & Tech. | 14 | 95,629,091 |
heterothallism defined in 1951 yearheterothallism - heterothallism;
heterothallism - (Of fungi, algae) condition in which sexual reproduction occurs only through participation of two thalli, each of which is self-sterile. In Fungi, includes morphological heterothallism where sexes are segregated, some thalli being male, others female; and physiological heterothallism where interacting thalli, often labelled plus and minus strains, show no morphological difference such as might be recognized as a difference in sex. Includes forms in which both thalli bear male and female sex organs and others which have no sex organs, union between strains depending on hyphal fusions. Compare with: Homothallism.
near heterothallism in Knolik
definition of word "heterothallism" was readed 2489 times | <urn:uuid:0ac6e342-c60d-4de8-a4de-a2c421ae73cd> | 2.875 | 178 | Knowledge Article | Science & Tech. | 0.493409 | 95,629,095 |
Defining and Using Classes
Defining Class Projections
This chapter discusses class projections, which provide a way to customize what happens when a class is compiled or removed. It discusses the following topics:
When viewing this book online, use the preface
of this book to quickly find related topics.
Class projections provide a way to customize what happens when a class is compiled or removed. A class projection associates a class definition with a projection class. The projection class (derived from the %Projection.AbstractProjection
class) provides methods that InterSystems IRIS™ uses to automatically generate additional code at two times:
When the class is compiled
When the class is deleted
This mechanism is used by the Java and C++ projections (hence the origin of the term projection
) to automatically generate the necessary client binding code (Java or C++) whenever a class is compiled.
To add a projection to a class definition, use the Projection statement within a class definition:
class MyApp.Person extends %Persistent
Projection JavaClient As %Projection.Java(ROOTDIR="c:\java");
A class can have multiple uniquely named projections. In the case of multiple projections, the methods of each projection class will be invoked when a class is compiled or deleted. The order in which multiple projections are handled is undefined.
InterSystems IRIS provides the following projection classes:
You can also create your own projection classes and use them in the same way as you would any built-in projection class.
Class MyApp.MyProjection Extends %Projection.AbstractProjection
/// This method is invoked when a class is compiled
ClassMethod CreateProjection(cls As %String, ByRef params) As %Status
// code here...
/// This method is invoked when a class is 'uncompiled'
ClassMethod RemoveProjection(cls As %String, ByRef params, recompile as %Boolean) As %Status
// code here...
Every projection class implements the projection interface
, a set of methods that are called in response to certain events during the life cycle of a class. This interface consists of the following methods:
method is a class method that is invoked by the class compiler after it completes the compilation of a class definition. This method is passed the name of the class being compiled as well as an array containing the parameter values (subscripted by parameter name) defined for the projection.
When a class definition is deleted
At the start of a recompilation of the class
This method is passed the name of the class being removed, an array containing the parameter values (subscripted by parameter name) defined for the projection, and a flag indicating whether the method is being called as part of a recompilation or because the class definition is being deleted.
When a class definition containing a projection is compiled, the following events occur:
If the class has been compiled previously, it will be uncompiled
before the new compile begins; that is, all the results of the previous compilation are removed. At this time, the compiler invokes the RemoveProjection()
method for every projection with a flag indicating that a recompilation is about to occur.
Note that you cannot call methods of the associated class from within the RemoveProjection()
method, because the class does not exist at this point.
Also note that if you add a new projection definition to a class that had been previously compiled (without the projection), then the compiler will call the RemoveProjection()
method on the next compilation even though the CreateProjection()
method has never been called. Implementers of the RemoveProjection()
method must plan for this possibility.
After the class is completely compiled (that is, it is ready for use), the compiler will invoke the CreateProjection()
method for every projection.
When a class definition is deleted, the RemoveProjection()
method is invoked for every projection with a flag indicating that a deletion has occurred. | <urn:uuid:6f7abc8b-8a09-40ad-9bfb-2a3d950a10b9> | 3 | 827 | Documentation | Software Dev. | 30.214915 | 95,629,111 |
This could cause an imbalance in the food web as well as decrease ocean CO2 uptake, an important regulator of global climate. The results of the study, conducted off the coast of Svalbard, Norway, in 2010, are now compiled in a special issue published in Biogeosciences, a journal of the European Geosciences Union.
Scientists checking the mesocosms off the coast of Svalbard (Credit: Ulf Riebesell/GEOMAR)
“If the tiny plankton blooms, it consumes the nutrients that are normally also available to larger plankton species,” explains Ulf Riebesell, a professor of biological oceanography at the GEOMAR Helmholtz Centre for Ocean Research Kiel in Germany and head of the experimental team. This could mean the larger plankton run short of food.
Large plankton play an important role in carbon export to the deep ocean, but in a system dominated by the so-called pico- and nanoplankton, less carbon is transported out of surface waters. “This may cause the oceans to absorb less CO2 in the future,” says Riebesell.
The potential imbalance in the plankton food web may have an even bigger climate impact. Large plankton are also important producers of a climate-cooling gas called dimethyl sulphide, which stimulates cloud-formation over the oceans. Less dimethyl sulphide means more sunlight reaches the Earth’s surface, adding to the greenhouse effect. “These important services of the ocean may thus be significantly affected by acidification.”
Ecosystems in the Arctic are some of the most vulnerable to acidification because the cold temperatures here mean that the ocean absorbs more carbon dioxide. “Acidification is faster there than in temperate or tropical regions,” explains the coordinator of the European Project on Ocean Acidification (EPOCA), Jean-Pierre Gattuso of the Laboratory of Oceanography of Villefranche-sur-Mer of the French National Centre for Scientific Research (CNRS).
The increasing acidity is known to affect some calcifying organisms in the Arctic, including certain sea snails, mussels and other molluscs. But scientists did not know until now how ocean acidification alters both the base of the marine food web and carbon transport in the ocean.
The five-week long field study conducted in the Kongsfjord off the Arctic archipelago of Svalbard, under the EPOCA framework, intended to close this knowledge gap. For the experiment, the scientists deployed nine large ‘mesocosms’, eight-metre long floatation frames carrying plastic bags with a capacity of 50 cubic metres. These water enclosures, developed at GEOMAR, allow researchers to study plankton communities in their natural environment under controlled conditions, rather than in a beaker in the lab. Few studies have looked at whole communities before.
The scientists gradually added CO2 to the mesocom water so that it reached acidity levels expected in 20, 40, 60, 80 and 100 years, with two bags left as controls. They also added nutrients to simulate a natural plankton bloom, as reported in the Biogeosciences special issue.
The team found that, where CO2 was elevated, pico- and, to a lesser extent, nanoplankton grew, drawing down nutrients so there were less available to larger plankton. “The different responses we observed made it clear that the communities’ sensitivity to acidification depends strongly on whether or not nutrients are available,” Riebesell summarises.
“Time and [time] again the tiniest plankton benefits from the surplus CO2, they produce more biomass and more organic carbon, and dimethyl sulphide production and carbon export are decreasing,” he concludes.
With 35 participants from 13 European institutions, the GEOMAR-coordinated mesocosm experiment was the largest project of EPOCA, a large EU-funded research initiative on ocean acidification that ran from 2008 to 2012. It was supported by the French-German Arctic Research Base.
The research results obtained in the mesocosm study are presented in the special issue ‘Arctic ocean acidification: pelagic ecosystem and biogeochemical responses during a mesocosm study’ of the EGU open access journal Biogeosciences. The papers on the special issue were published between March and August 2013. Please mention the publication if reporting on this story and, if reporting online, include a link to the special issue or to the journal website.
The scientific articles that make up the special issue are available online, free of charge, at http://www.biogeosciences.net/special_issue120.html.
The issue was edited by U. Riebesell (GEOMAR Helmholtz Centre for Ocean Research Kiel, Germany), J.-P. Gattuso (CNRS Laboratory of Oceanography of Villefranche sur Mer and Université Pierre et Marie Curie-Paris 6, France), T. F. Thingstad (Department of Biology, University of Bergen, Norway) and J. J. Middelburg (Faculty of Geosciences, Utrecht University, the Netherlands).
For additional high-resolution images and video footage of the experiment, please email Maike Nicolai (GEOMAR Communication & Media) at email@example.com.
The European Geosciences Union (EGU) is Europe’s premier geosciences union, dedicated to the pursuit of excellence in the Earth, planetary, and space sciences for the benefit of humanity, worldwide. It is a non-profit interdisciplinary learned association of scientists founded in 2002. The EGU has a current portfolio of 15 diverse scientific journals, which use an innovative open access format, and organises a number of topical meetings, and education and outreach activities. Its annual General Assembly is the largest and most prominent European geosciences event, attracting over 11,000 scientists from all over the world. The meeting’s sessions cover a wide range of topics, including volcanology, planetary exploration, the Earth’s internal structure and atmosphere, climate, energy, and resources. The 2014 EGU General Assembly is taking place is Vienna, Austria from 27 April to 2 May 2014. For information regarding the press centre at the meeting and media registration, please check http://media.egu.eu closer to the time of the conference.
If you wish to receive our press releases via email, please use the Press Release Subscription Form at http://www.egu.eu/news/subscribe/. Subscribed journalists and other members of the media receive EGU press releases under embargo (if applicable) 24 hours in advance of public dissemination.Links
Bárbara Ferreira | European Geosciences Union (EGU)
Upcycling of PET Bottles: New Ideas for Resource Cycles in Germany
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For the first time ever, scientists have determined the cosmic origin of highest-energy neutrinos. A research group led by IceCube scientist Elisa Resconi, spokesperson of the Collaborative Research Center SFB1258 at the Technical University of Munich (TUM), provides an important piece of evidence that the particles detected by the IceCube neutrino telescope at the South Pole originate from a galaxy four billion light-years away from Earth.
To rule out other origins with certainty, the team led by neutrino physicist Elisa Resconi from the Technical University of Munich and multi-wavelength...
For the first time a team of researchers have discovered two different phases of magnetic skyrmions in a single material. Physicists of the Technical Universities of Munich and Dresden and the University of Cologne can now better study and understand the properties of these magnetic structures, which are important for both basic research and applications.
Whirlpools are an everyday experience in a bath tub: When the water is drained a circular vortex is formed. Typically, such whirls are rather stable. Similar...
Physicists working with Roland Wester at the University of Innsbruck have investigated if and how chemical reactions can be influenced by targeted vibrational excitation of the reactants. They were able to demonstrate that excitation with a laser beam does not affect the efficiency of a chemical exchange reaction and that the excited molecular group acts only as a spectator in the reaction.
A frequently used reaction in organic chemistry is nucleophilic substitution. It plays, for example, an important role in in the synthesis of new chemical...
Optical spectroscopy allows investigating the energy structure and dynamic properties of complex quantum systems. Researchers from the University of Würzburg present two new approaches of coherent two-dimensional spectroscopy.
"Put an excitation into the system and observe how it evolves." According to physicist Professor Tobias Brixner, this is the credo of optical spectroscopy....
Ultra-short, high-intensity X-ray flashes open the door to the foundations of chemical reactions. Free-electron lasers generate these kinds of pulses, but there is a catch: the pulses vary in duration and energy. An international research team has now presented a solution: Using a ring of 16 detectors and a circularly polarized laser beam, they can determine both factors with attosecond accuracy.
Free-electron lasers (FELs) generate extremely short and intense X-ray flashes. Researchers can use these flashes to resolve structures with diameters on the...
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The Big Bell Test was an experiment conducted on November 30th, 2016. More than 100,000 people participated in a simple video game that required users to generate ones and zeros (bits) randomly. That information was sent to twelve laboratories in which scientist of all continents oriented their studies on atoms, photons and superconducting devices. Through these actions, the objective was to save what is known as loophole from freedom of action.
In Argentina, the laboratory that participated was the Laboratorio de Óptica Cuántica del Instituto de Investigaciones Científicas y Técnicas para la Defensa (CITEDEF, CONICET- Ministerio de Defensa), with researchers from the Faculty of Exact and Natural Sciences of the UBA. The laboratory is in charge of Miguel Larotonda, independent researcher of the Council.
Over the last century, experts raised the discussion about the view of quantum mechanics which states that particles “change” when they are observed –they are in one state and in the other at the same time-, and they’re not determined for their properties so the measurement cannot change it. For Einstein, there were unmeasured variables that produced that effect. Niels Bohr, however, states that the observable properties did not make sense until they were measured.
“This experiment tends to close the gap between the general public and the ‘strange’ and anti-intuitive concepts of quantum mechanics as it attracts and encourages participants from all parts of the world to produce bits unpredictable sequences, which feed simultaneous and cutting edge technological experiments in a number of laboratories from all the world”, Larotonda affirms.
In 1964, physicist John Stewart Bell proposed a series of conditions for one experiment that could close the methodological traps likely to affect the measures at a quantum level. “Bell proposed a kind of correlations estimator that a system would need to comply with if it worked according to quantum mechanics”, Larotonda explains. Different loopholes were created throughout previous research, but there was last variable missing: freedom of action.
In the measurements on interlaced particles, such as photon, scientists generate and send different locations and analyze some properties of those particles such as color, arrival time or polarization. If the results of those measurements tend to coincide, regardless of what properties we want to measure, that fact would explain that a particle affects the other particle immediately despite being separated by kilometers. This contradicts Einstein’s worldview: the universe would not be independent of our observations.
The results, which were published in Nature, tend to confirm once more that the theory of quantum mechanics is accurate against the local realism proposed by Einstein.
Se abre la convocatoria para el Premio L’Oréal-UNESCO en colaboración con el CONICET
Hasta el 20 de julio podrán postularse investigadoras y becarias postdoctorales que lleven a cabo sus trabajos científicos en el área de las Ciencias de la Materia.
El CONICET fue parte del desarrollo del segundo magnetómetro criogénico del mundo, clave para la industria petrolera
Es el Cri.Ar que mide el paleomagnetismo en rocas.
Inundaciones: un novedoso enfoque para evaluar la percepción social del riesgo
Expertos del CONICET y la UNLP relevaron notas periodísticas sobre los eventos ocurridos en la región entre 1911 y 2014. Proponen una app colaborativa.
Científicos del CONICET trabajan sobre Acidificación de los Océanos
Maria Soledad Yusseppone, becaria postdoctoral fue seleccionada para la realización de una capacitación intensiva sobre "Oceanic Acidification Practical Training - From experimental design to data analysis".
El genocidio invisible de los pueblos indígenas en Argentina
A través de distintas líneas de estudio, investigadores del CONICET en el Instituto de Investigaciones Geohistóricas del Chaco, producen conocimiento -junto con comunidades de la región- acerca de cómo se perpetúan los mecanismos opresivos. | <urn:uuid:3e62b556-d4bb-476c-9899-e799d6be49ca> | 3.421875 | 969 | News (Org.) | Science & Tech. | 11.199559 | 95,629,138 |
Visual Basic Reference
Unloads a form or control from memory.
The object placeholder is the name of a Form object or control array element to unload.
Unloading a form or control may be necessary or expedient in some cases where the memory used is needed for something else, or when you need to reset properties to their original values.
Before a form is unloaded, the Query_Unload event procedure occurs, followed by the Form_Unload event procedure. Setting the cancel argument to True in either of these events prevents the form from being unloaded. For MDIForm objects, the MDIForm object's Query_Unload event procedure occurs, followed by the Query_Unload event procedure and Form_Unload event procedure for each MDI child form, and finally the MDIForm object's Form_Unload event procedure.
When a form is unloaded, all controls placed on the form at run time are no longer accessible. Controls placed on the form at design time remain intact; however, any run-time changes to those controls and their properties are lost when the form is reloaded. All changes to form properties are also lost. Accessing any controls on the form causes it to be reloaded.
*Note* When a form is unloaded, only the displayed component is unloaded. The code associated with the form module remains in memory.
Only control array elements added to a form at run time can be unloaded with the Unload statement. The properties of unloaded controls are reinitialized when the controls are reloaded. | <urn:uuid:8f745849-a762-4643-bc0b-3f2191689d37> | 2.796875 | 313 | Documentation | Software Dev. | 37.281066 | 95,629,144 |
Hypoxia Tolerance and Metabolic Suppression in Oxygen Minimum Zone Euphausiids: Implications for Ocean Deoxygenation and Biogeochemical Cycles
KAUST DepartmentRed Sea Research Center (RSRC)
MetadataShow full item record
AbstractThe effects of regional variations in oxygen and temperature levels with depth were assessed for the metabolism and hypoxia tolerance of dominant euphausiid species. The physiological strategies employed by these species facilitate prediction of changing vertical distributions with expanding oxygen minimum zones and inform estimates of the contribution of vertically migrating species to biogeochemical cycles. The migrating species from the Eastern Tropical Pacific (ETP), Euphausia eximia and Nematoscelis gracilis, tolerate a Partial Pressure (PO2) of 0.8 kPa at 10 °C (∼15 µM O2) for at least 12 h without mortality, while the California Current species, Nematoscelis difficilis, is incapable of surviving even 2.4 kPa PO2 (∼32 µM O2) for more than 3 h at that temperature. Euphausia diomedeae from the Red Sea migrates into an intermediate oxygen minimum zone, but one in which the temperature at depth remains near 22 °C. Euphausia diomedeae survived 1.6 kPa PO2 (∼22 µM O2) at 22 °C for the duration of six hour respiration experiments. Critical oxygen partial pressures were estimated for each species, and, for E. eximia, measured via oxygen consumption (2.1 kPa, 10 °C, n = 2) and lactate accumulation (1.1 kPa, 10 °C). A primary mechanism facilitating low oxygen tolerance is an ability to dramatically reduce energy expenditure during daytime forays into low oxygen waters. The ETP and Red Sea species reduced aerobic metabolism by more than 50% during exposure to hypoxia. Anaerobic glycolytic energy production, as indicated by whole-animal lactate accumulation, contributed only modestly to the energy deficit. Thus, the total metabolic rate was suppressed by ∼49–64%. Metabolic suppression during diel migrations to depth reduces the metabolic contribution of these species to vertical carbon and nitrogen flux (i.e., the biological pump) by an equivalent amount. Growing evidence suggests that metabolic suppression is a widespread strategy among migrating zooplankton in oxygen minimum zones and may have important implications for the economy and ecology of the oceans. The interacting effects of oxygen and temperature on the metabolism of oceanic species facilitate predictions of changing vertical distribution with climate change.
CitationSeibel BA, Schneider JL, Kaartvedt S, Wishner KF, Daly KL (2016) Hypoxia Tolerance and Metabolic Suppression in Oxygen Minimum Zone Euphausiids: Implications for Ocean Deoxygenation and Biogeochemical Cycles. Integrative and Comparative Biology 56: 510–523. Available: http://dx.doi.org/10.1093/icb/icw091.
SponsorsThis project was funded by National Science Foundation grants (0852138 to B.A.S., 0526502 and 1459243 to B.A.S. and K.W., 0526545 to K.L.D.), and by the King Abdullah University of Science and Technology.
PublisherOxford University Press (OUP)
- Metabolic suppression during protracted exposure to hypoxia in the jumbo squid, Dosidicus gigas, living in an oxygen minimum zone.
- Authors: Seibel BA, Häfker NS, Trübenbach K, Zhang J, Tessier SN, Pörtner HO, Rosa R, Storey KB
- Issue date: 2014 Jul 15
- Life at stable low oxygen levels: adaptations of animals to oceanic oxygen minimum layers.
- Authors: Childress JJ, Seibel BA
- Issue date: 1998 Apr
- Critical oxygen levels and metabolic suppression in oceanic oxygen minimum zones.
- Authors: Seibel BA
- Issue date: 2011 Jan 15
- Aerobic and anaerobic metabolism in oxygen minimum layer fishes: the role of alcohol dehydrogenase.
- Authors: Torres JJ, Grigsby MD, Clarke ME
- Issue date: 2012 Jun 1
- Metabolic suppression in the pelagic crab, Pleuroncodes planipes, in oxygen minimum zones.
- Authors: Seibel BA, Luu BE, Tessier SN, Towanda T, Storey KB
- Issue date: 2017 Dec 27 | <urn:uuid:54ef1521-da2d-4a1e-8bff-9d054b62a62a> | 2.5625 | 961 | Academic Writing | Science & Tech. | 31.587415 | 95,629,145 |
A breakthrough in perovskite solar cells could be the solution to the UK’s longstanding energy shortage. Scientists attending the Materials Research Society conference in Boston, Massachusetts last December were treated to news of vast improvements in the efficiency of photovoltaics.
Currently sunlight is converted into electricity through silicon solar cells which are not only expensive but perform at a low rate of conductivity. The recent improvements to perovskite solar cells could result in a valid alternative to silicon with the efficiency to utilise the 1% of British sunlight needed to fulfil current energy demands.
Speakers at the Rump Session for Organo-metal Halide Perovskite-based Solar Cells revealed that size and orientation of the material’s crystals will determine future developments of perovskite performance. The findings were collected through X-ray scatterings, the research reports stating, “Our findings underscored the importance of full characterizing and controlling the nanostructured components for improved solar cell efficiency.”
With further developments in large-scale conversion, developments in photovoltaic technologies could provide a cost-effective source of British energy with the efficiency to compete and even override the use of fossil fuels.
Source: Intelligent Building Today
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Transcript of Atoms
Rutherford's Gold Foil Experiment
Bohr's Atomic Model
Friday, October 2, 2015
Vol XCIII, No. 311
Dalton's Atomic Theory
Schrodinger's Wave Mechanical Model
History & Timeline
The experiment was inspired from these factors and outcomes, which are:
His discovery of alpha particle.
His previous study about x-ray.
Rejection of Thomson model from scientists.
The experiment was conducted from 1908 to 1913 under Rutherford's direction.
His initial hypothesis was supported by the experiment's outcome, which was published in 1911 and again in 1913 to give further information discovered.
Who is Ernest Rutherford?
Why did he initiate the experiment?
What is Rutherford's Gold Foil Experiment
Ernest Rutherford was a New Zealander whose parents relocated from England.
In 1895, he gained permission to work and study at the University of Cambridge in England.
In 1907, he decided to move permanently to England.
During WWI, he worked on a top secret project to figure out a way to detect submarines.
During his lifetime, he achieved many awards for his contribution to science, specifically chemistry and physics.
Where did he proceed the experiment?
How was the experiment performed?
The Significance of Rutherford's Gold Foil Experiment
The experiment proved and supported Rutherford's initial hypothesis and rejected Thomson model of an atom.
The experiment proved the existence of a nucleus within an atom and further developed the structure like what it is currently today.
It proved that the nucleus is positively charged and is surrounded with an empty space.
Alpha particles are shot directly onto the thin gold sheet.
A radioactive source is prepared and is placed in a lead box to prevent radiation from spreading out.
A ring of detector is placed around a thin sheet of gold foil to detect alpha particles from the radioactive source.
In 1907, Ernest Rutherford, a new physics professor at the University of Manchester, received a visit from Hans Geiger and Ernest Marsden.
They would later assist him with the experiment.
Rutherford's Gold Foil Experiment was a series of experiments whose purpose is to discover and to prove that every atom contains a positively charged nucleus.
They eventually achieved their original purpose by performed and measured how alpha particle is scattered when comes in contact with a thin gold foil.
Alik Manoogian, Hayden Gallina, and Viet Tran
All matter is made of atoms. Atoms are indivisible and indestructible.
All atoms of a given element are identical in mass and properties.
Compounds are formed by a combination of two or more different kinds of atoms.
A chemical reaction is a rearrangement of atoms.
John Dalton was of Quaker bakground and an English chemist
Known primarily for his atomic theory, although he made many other discoveries in the field of chemistry
study of colorblindness (Daltonism)
a pioneer meteorologist
fascination with the weather and atmosphere= further research into the nature of gasses
History & Timeline
The Significance of J.J. Thomson's Experiment
The experiment was proceeded at the Victoria University of Manchester (today University of Manchester).
Atomism (the atom and void)
4th century BCE in India- Kanada
five elements were air, water, earth, fire, and space
5th century BCE in Greece- Leucippus and Democritus
all matter composed of small indivisible particles called atoms
acceptance of the four elements of air, water, earth, and fire, but not atomic theory
up until the 16th century CE Aristotelian philosophy was most widely accepted
18th century in Europe- Isaac Newton and John Locke
ideology that puts reality and change in terms of corpuscles
unlike atomism, corpuscles could be divided
Law of Conservation of Mass (1789)
Law of Definite Proportions (1799)
Joseph Louis Proust
In 1897, J.J. Thomson discovered electrons by experimenting and measuring cathode rays.
England's Lake District (Cumberland) and Manchester
In 1904, because of his discovery of electrons, he suggested the Thomson Model.
In 1894, he began studying about cathode rays.
A theory proposed in 1808 stating...
Interest in meteorology>>
Further research into gasses
Evaporated water exists as its own gas
Air occupies the same space as the water
Solids cannot occupy the same space as each other, and the gasses must therefore be composed of small particles
He wanted to explain how and why these elements could compine in ratios
Initial observations of gasses
Water absorbed carbon dioxide better than it did nitrogen
Water and air particles were able to coexist and mix together
These paired with the Law of Conservation of Mass and the Law of Definite Proportions allowed him to develop the Law of Multiple Proportions
Additionally, he hypothesized that different elements combined at different fixed rations due to their different atomic weights and complexities
His atomic theory explained why the Law of Multiple Proportions was valid
The establishment of a first scientific theory of an atom
Basis to nearly all other advances in the study of atoms
Dalton's Atom Model
Dalton believed atoms to be single units that could not be broken down, and therefore saw them as solid spheres
Bohr realized that electrons moving around impacted physical and chemical characteristics of atoms. (3)
Bohr's atomic model has had a
huge impact on the world. His model gave us a better understanding of what atoms look like, and how they are built up. Although parts of his model are incorrect, he still has had a large impact on the world. (1) (2)
A British physicist who discovered the electron with experiments created to study the electric discharge in a cathode tube. (3)
A well-known Cavendish lab in Cambridge, England
Objective: Prove that cathode rays carried a negative charge
Bohr worked with J.J. Thompson and was introduced to Rutherford. Rutherford's model showed electrons moving in random motion, and Bohr had evidence that the electrons moved in stable orbits around the nucleus. (2) (1)
Neils Bohr was a Danish physicist who contributed heavily to peoples understanding of the atomic theory and structure.. (2)
Bohr conducted his experiments to prove that electrons move in a stable motion around the nucleus. He wanted to help people understand what atoms look like. (1)
Bohr made his discoveries while working with and under J.J. Thompson in England. (2)
Bohr's model is a model that shows how electrons move in a stable motion around the nucleus. (1)
(1): Rutherford's Experiment - Part I: 1906 to Early 1911
(2): Rutherford's Experiment - Part II: The Paper of 1911
(3): Ernest Rutherford Biography
Objective: Measure charge and mass of particles
Series of experiments (3): designed to study the nature of electric discharge in a cathode-ray tube
Objective: Prove that the rays emitted by the cathode were inseparable
Cathode ray tube with metal cylinder, two slits that led to electrometer, and electrometers that measured the electrical charges.
After improvement of the quality of the cathode ray tube and vacuum, positive and negative plates placed on the tube
Determine the charge and mass by how much different electrical currents of varying strengths bent them
Electrometers measured no charge when there was a magnetic field; cathode rays were charged and were deflected by magnets; thus charges and rays were intertwined and together.
Rays deflected by electric plates; positive plate attracted them, and negative plate deflected them; thus, charges bound to the rays and consisted of "corpuscles" or electrons that were negatively charged.
Charge-to-Mass ratio was very large, so either the charge of particles was very large or mass was very small.
"Plum Pudding Model"
1): Elements and Atoms: Chapter 16
1) Atomism before Dalton by Leopold May http://pubs.acs.org/doi/abs/10.1021/bk-2010-1044.ch003
2) John Dalton's Atomic Model by Matt Williams http://www.universetoday.com/38169/john-daltons-atomic-model/
3) John Dalton by Sydney Ross http://www.britannica.com/biography/John-Dalton
4) Dalton's Atomic Theory http://www.iun.edu/~cpanhd/C101webnotes/composition/dalton.html
(6): Alpha Particles and the Atom
(7): Rutherford's Gold Foil Experiment
2) JJ Thomson's Experiments with Cathode Ray Tubes http://ericsaltchemistry.blogspot.com/2010/10/jj-thomsons-experiments-with-cathode.html
1) ERWIN SCHR÷DINGER (1887 - 1961) http://www.physicsoftheuniverse.com/scientists_schrodinger.html
2) The Cloud Model http://www.regentsprep.org/Regents/physics/phys05/catomodel/cloud.htm
3) Atomic Theory http://www.msnucleus.org/membership/html/jh/physical/atomictheory/lesson1/atomic1g.html
4) Historical Models of the Atom http://www.commonsensescience.org/atom_models.html
5) Modern Atomic Theory: Models http://www.abcte.org/files/previews/chemistry/s1_p6.html
6) The Physics Behind Schrödinger's Cat Paradox by Melody Kramer http://news.nationalgeographic.com/news/2013/08/130812-physics-schrodinger-erwin-google-doodle-cat-paradox-science/
7) Schrodinger Equation http://hyperphysics.phy-astr.gsu.edu/hbase/quantum/schr.html
Erwin Schrödinger was an Austrian physicist who is one of the founders of quantum mechanics.
Developed the "electron cloud model"
Developed the Schrödinger Equation
Austria (mainly Vienna) and England (Oxford University)
The quantum mechanical model of an atom that does not provide an exact path of the electrons, but predicts the odds of the location of the electron.
Predicts the behavior of a complex system
As a wavefunction, it predicts the outcomes and possibilities precisely
the outcome can be a large number of events and the equation predicts the distribution of results
Had the help of Werner Heisenburg, and they used the mathematical equation of the behavior of waves developed by Louis de Broglie, a French theorist.
As a theoretical physicist who studied under many people, Schrodinger was interested in Bohr's model. He developed the idea in a slightly different direction creating a mathematical model that incorporated de Broglie's ideas and it was based on quantum mechanics.
Schrodinger's Cat is a paradox that was developed in order to illustrate the nature of wave particles in quantum mechanics.
Just as Schrodinger's Cat explains all the possible existences of the cat, at the heart of quantum theory with wave function is the explanation of all the possible states that particles can have, such as the electrons.
Thus, the idea is that without observation, we cannot know exactly what something is doing, only the probabilities, no matter how small each probability is.
1) Bohr Atomic Model http://abyss.uoregon.edu/~js/glossary/bohr_atom.html
3) Joseph John Thompson http://www.chemheritage.org/discover/online-resources/chemistry-in-history/themes/atomic-and-nuclear-structure/thomson.aspx
In cathode tubes, switching on voltage could make fluorescent lines of electricity travel from the bottom to the top of the tube. The problem was that nobody had any idea how it worked. J.J. Thompson wanted to find out how it worked. (4)
4) Discovery of the Electron http://www.pbs.org/transistor/science/events/electron.html
2) Neils Bohr-Important Scientists http://www.physicsoftheuniverse.com/scientists_bohr.html
Does not show function of atoms, but their structure
Basis of the Quantum Mechanical Model of the atom
Represents the beginning of the modern atomic theory
5) J.J. Thomson Biographyhttp://www.biography.com/people/jj-thomson-40039
It acts as one of the stepping stones of modern atomic theory.
(3) Neils Bohr: Odyssey of the Atom https://www.msu.edu/~ramseys3/lbs171h/index.htm | <urn:uuid:f7ffc9bf-16f2-4dc4-8c52-14a6d5847334> | 3.65625 | 2,842 | Truncated | Science & Tech. | 44.940991 | 95,629,164 |
The far-reaching importance of tropical forests, from stabilising regional climate to underpinning rural economies, has not protected them from rapacious deforestation.
Tropical deforestation during a single year (to July 2016) in a single country (Brazil) amounted to 7,893 square kilometres, an area which would almost cover the island of Cyprus. After a long period of significant reduction in deforestation in the Brazilian Amazon region, the rate has been rising since 2012. This disappointing trend has continued into 2015 and 2016, escalating by 60% over those two years.
This picture in Brazil, together with that in Indonesia, contributed 50% of all tropical deforestation in 2016. The overall scale and trend in global tropical deforestation remains immensely sensitive to fickle political developments in these two major rainforest countries, as well as the Democratic Republic of Congo (DRC). Brazil is home to 40% of the Amazon rainforest, the largest in the world, while DRC hosts 60% of the Congo Basin forest.
Currently, the politics in these countries is the source of much concern for forest campaigners. In Brazil, the government of Michel Temer has surprised even the most conservative landowners with its enthusiastic abolition of regulations for land use, apparently content to scramble a decade of progress. In the DRC, an increasingly unstable government granted vast concessions totalling 6,500 square kilometres to Chinese companies in 2017, violating its own moratorium that has been largely observed since 2002.
The rate of deforestation in sub-Saharan Africa generally, as well as DRC, has been relatively modest over that period, due to inaccessibility and political risk. But there are signs of increasing vulnerability as the continent opens up to foreign investment.
This rising global trend for deforestation is a major disappointment after a generation of environmental activism to protect tropical forests, supported by billions of aid dollars. For the purpose of its statistics, the UN Food and Agriculture Organization defines deforestation as the complete conversion of an area of forest to a different land use. It considers land to be forest if it has minimum canopy cover of 10% and “the absence of other predominant land uses.”
However, reports submitted by individual countries do not necessarily follow this approach and the quality of data is notoriously suspect in the forest sector. The rapid advance of satellite technology, such as Global Forest Watch, now offers real-time accuracy within 100 metres of resolution, the data openly available.
Forest degradation is the term which expresses less drastic loss of forest cover. Where industrial logging is selective in its approach, it may be assessed as forest degradation. Carbon dioxide emissions caused by rainforest degradation amount to as much as one-third of those arising from deforestation.
In temperate regions of the world, forest cover is increasing. Deforestation is countered by extensive programmes of replanting and forest regeneration, especially in China and India.
more Forests briefings (updated April 2018)
Importance of Tropical Forests
Tropical Forests and Climate Change
Causes of Deforestation
Sustainable Development Goal for Deforestation
Consumer Solutions to Deforestation
Rights-based Solutions to Deforestation
Market-based Solutions to Deforestation
Source material and useful links | <urn:uuid:eeda810f-313f-446e-92a9-ab60e9671234> | 3.828125 | 642 | Knowledge Article | Science & Tech. | 17.492734 | 95,629,174 |
Assessing and monitoring coral reef sponges: Why and how?
Functional roles of sponges in coral reef ecosystems include: increasing coral survival by binding live corals to the reef frame and preventing access to their skeletons by excavating organisms; mediating regeneration of physically damaged reefs by temporary stabilization of carbonate rubble; reworking of solid carbonate through bioerosion; recycling nutrients and adding to primary production through microbial symbionts with special biochemical capabilities; clearing the water column of procaryotic plankton; serving as food for a variety of megafauna; and attracting support for responsible human stewardship of coral reefs with aesthetically appealing colors and morphologies. Nevertheless, sponges tend to be avoided in assessment and monitoring of coral reefs because they are not easy to quantify or identify, and because we have only recently begun to understand the importance of their many functional roles. As we gain more understanding of these roles of sponges in coral reefs, the need to carefully assess and monitor changes in sponges is becoming more clear. Focus on functional roles dictates choice of methods for assessing and monitoring sponges, as follows: (1) volume will generally be the most useful way to quantify sponge populations; (2) accurate identification to genus, family, or even order, combined with a brief description and reference to voucher specimens, is preferable to guesses on species names, in cases for which identification can't be verified by specialists; (3) permanently marked sites must be monitored over time in order to be able to detect community changes and to distinguish beneficial from detrimental effects of sponges on corals.
No Supplementary Data.
No Article Media
Document Type: Research Article
Publication date: 01 September 2001
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- The Bulletin of Marine Science is dedicated to the dissemination of high quality research from the world's oceans. All aspects of marine science are treated by the Bulletin of Marine Science, including papers in marine biology, biological oceanography, fisheries, marine affairs, applied marine physics, marine geology and geophysics, marine and atmospheric chemistry, and meteorology and physical oceanography.
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Why is such network needed? As of now, it is not possible to compare pH values of solutions made in different solvents, as every solvent has its own pH scale. This situation is highly unfortunate, since it causes confusion and inaccuracies into many fields, extending far beyond the specific field of acid-base chemistry. Examples are industrial catalytic processes, food chemistry, liquid chromatograpy, etc. The central goal of UnipHied is to overcome this situation by putting the new theoretical concept of the recently introduced unified pHabs scale on a metrologically well-founded basis into practice.
The most important specific objectives of UnipHied are (1) to develop and validate a reliable and universally applicable measurement procedure that enables the measurement of pHabs; (2) to create a reliable method for the experimental or computational evaluation of the liquid junction potential between aqueous and non-aqueous solutions; (3) to develop a coherent and validated suite of calibration standards for standardizing routine measurement systems in terms of pHabs values for a variety of widespread systems (e.g., industrial mixtures, soils/waters, food products, biomaterials).
The first version of the pHabs measurement procedure has been created by Agnes Heering (Suu) in the framework of her PhD thesis. The main experimental difficulty is evaluation of the liquid junction potential (LJP), which will be thoroughly addressed by UnipHied. The first important steps towards this goal have very recently been made and published as two back-to-back papers: Angew. Chem. Int. Ed. 2018, 57, 2344–2347 and Angew. Chem. Int. Ed. 2018, 57, 2348–2352
The key achievement described in the papers is finding an ionic liquid, namely [N2225][NTf2], that can be used as salt bridge electrolyte and has such properties that two out of three main sources of LJP are eliminated.
The partners of the UnipHied network are LNE (France, coordinator), BFKH (Hungary), CMI (Czech Republic), DFM (Denmark), IPQ (Portugal), PTB (Germany), SYKE (Finland), TÜBITAK-UME (Turkey), Freiburg University (Germany), ANBSensors (United Kingdom), FCiencias.ID (Portugal), UT (Estonia). | <urn:uuid:6a01ea3c-fdd8-4677-ab76-01415721d0b1> | 2.515625 | 500 | About (Org.) | Science & Tech. | 36.529189 | 95,629,183 |
20 Oct , 2017 by Matt Williams
According to a new analysis, the number of undiscovered and potentially-hazardous asteroids could be lower than previously thought.
19 Oct , 2017 by Matt Williams
A team of astronomers from the University of Arizona’s Lunar and Planetary Laboratory has confirmed that Earth’s “temporary Moon” is an asteroid, and not space junk.
Space stories from across the internet, sent to you by email. | <urn:uuid:eca10fcc-d71f-45ee-89df-83efba38daec> | 2.734375 | 94 | Content Listing | Science & Tech. | 40.540238 | 95,629,188 |
Ocean scientists have long known that juvenile coral reef fishes use coastal seagrass and mangrove habitats as nurseries, later moving as adults onto coral reefs.
But the fishes' movements, and the connections between different tropical habitats, are much more complex than previously realized, according to a study published September 3 in Proceedings of the National Academy of Sciences. The findings have important implications for management and protection of coral reefs and other marine environments.
A number of studies have demonstrated a strong relationship between the presence of coastal wetlands and offshore fish abundance and fisheries yield, but it has proved difficult to develop quantitative assessment of habitat use by fish or their movement among different habitats.
"The rationale for this study,"says Simon Thorrold, a biologist at Woods Hole Oceanographic Institution (WHOI), "was to determine the relative importance of different nursery habitats to reef fishes that spend their adult lives on coral reefs but may spend at least part of their juvenile residency elsewhere."
The study also advances understanding of the functional connectivity of coral reef fish in a tropical seascape, says WHOI biologist and study lead author Kelton McMahon. "Traditional methods of assessing nursery habitats – visual surveys of abundance and size of fish in different locations – provide important but indirect evidence of connectivity among essential habitats. We developed a quantitative method that identifies essential nursery habitat, and allows reconstruction of migration within the seascape."
The method analyzes isotopic signatures recorded in fish tissue. These signatures, unique to each environment in which a fish lives and feeds, are laid down in its otoliths, or ear bones, creating a record similar to that of tree rings.
"Otoliths are constantly and permanently recording the conditions a fish is experiencing at any time," explains Thorrold. What a fish eats can be traced back to a particular food web, which makes it possible to track where a fish went throughout its life.
Thorrold, McMahon, and Michael Berument of King Abdullah University of Science and Technology in Saudi Arabia first analyzed food webs in five specific habitats in the Red Sea off the northern coast of Saudi Arabia: coastal wetlands, coastal reefs near the shoreline, reefs on the continental shelf less than 60 meters deep, patch reefs around a continental offshore island, and oceanic reefs surrounded by deep open water. They used those data to create an isoscape, or map of the unique isotope signature of each location.
They then collected adult Ehrenberg's snapper (Lutjanus ehrenbergii), a commercially important snapper widespread throughout tropical and subtropical waters. With gas chromatography, the researchers measured compounds in otoliths of individual fish, working their way back to layers created when each was a juvenile. They matched each fish's signature to one on the isoscape, identifying with a high degree of accuracy the habitat an individual fish occupied as a juvenile.
This made it possible to look at movement of juvenile fish within the seascape at a level never before possible, revealing a few surprises. "We found that a number of juveniles had settled directly onto reefs, despite the fact that in several years of regular work in this area, we'd never visually observed them there," says Thorrold. "If you just observed distribution of juveniles, you would say the only important nursery habitat is coastal wetlands. But that's not true. Some fish settle right on the reefs, and the continental island proved to be very important habitat as well."
In other words, coastal wetlands are important juvenile nursery habitat for snapper in the Red Sea, but snapper are not obligated to use them, as was previously thought. Instead, the fish showed surprising plasticity, using a wide variety of habitats. "Our results showed remarkable complexity in the use of different habitats and movement patterns among them," McMahon says. Fish movements, the study makes clear, are more complex than a linear model of coastal fish moving out onto reefs.
The analysis also showed that seascape configuration plays an important and perhaps underappreciated role in determining the connectivity among essential habitats. "We found that coral reef fish made remarkable long-distance migrations from coastal wetlands across deep open water – long considered a hard migration barrier for coral reef fish – to offshore reefs," McMahon says. "That was, for me, the most surprising finding. Migration capability was far greater than we originally appreciated. It underscores the potential of significant connectivity within a large and complex tropical seascape." These results are particularly timely, given the increasing use of spatial management approaches in coral reef ecosystems, including networked marine protected areas.
The implication is that it isn't enough to protect adult habitat on coral reefs. Habitats that supply those reefs and the migration corridors that connect them also need protection. "As human activity continues to degrade and fragment tropical seascape habitats, quantitative understanding of the connectivity among them becomes increasingly important," says McMahon.
"Protecting the reef protects the adult fishes, but not an important component of their life history, as juveniles," says Thorrold. "It won't work to protect the reef but, for example, allow a hotel to be built on the seagrass beds and mangroves."
The study's quantitative method also provides a way to estimate ecosystem services that specific habitats provide to fisheries yields within a seascape, allowing for a more accurate accounting of these services and potentially providing a way to determine suitable value for mitigation and remediation purposes.
"We haven't known the value of those habitats to the reefs themselves when considering development," says Thorrold. "This technique allows us to quantify the importance of different habitats, and that makes it possible to come up with reasonable biological valuations for them. It hasn't been done yet, but is an important implication of the work going forward."
An important next step, the researchers say, is to analyze other globally important coral reef or tropical seascapes to see how general these patterns are.
This research was based on work supported by awards from King Abdullah University of Science and Technology, with additional funding provided by WHOI, an International Society for Reef Studies-Conservancy Coral Reef Fellowship, and the National Science Foundation Graduate Research Fellowship Program. Dream Divers, Jeddah, Saudi Arabia provided boat and dive operation assistance.
The Woods Hole Oceanographic Institution is a private, independent organization in Falmouth, Mass., dedicated to marine research, engineering, and higher education. Established in 1930 on a recommendation from the National Academy of Sciences, its primary mission is to understand the oceans and their interaction with the Earth as a whole, and to communicate a basic understanding of the oceans' role in the changing global environment.
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A new manufacturing technique uses a process similar to newspaper printing to form smoother and more flexible metals for making ultrafast electronic devices.
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For the first time a team of researchers have discovered two different phases of magnetic skyrmions in a single material. Physicists of the Technical Universities of Munich and Dresden and the University of Cologne can now better study and understand the properties of these magnetic structures, which are important for both basic research and applications.
Whirlpools are an everyday experience in a bath tub: When the water is drained a circular vortex is formed. Typically, such whirls are rather stable. Similar...
Physicists working with Roland Wester at the University of Innsbruck have investigated if and how chemical reactions can be influenced by targeted vibrational excitation of the reactants. They were able to demonstrate that excitation with a laser beam does not affect the efficiency of a chemical exchange reaction and that the excited molecular group acts only as a spectator in the reaction.
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Once, thousands of years ago, all humans were supported directly and entirely by nature. Our food, water, and everything else came directly from natural ecosystems as our ancestors, hunter-gatherers, went about their business for a million or more years. We cannot go back easily to that state because of population growth, for natural ecosystems alone could probably support no more than a few hundreds of millions of people. Today fossil-fueled systems of agriculture, water supply, and waste disposal support seven billion people on the planet. Most humans live in environments of concrete, boards, and macadam largely disconnected from the natural world. Although nature remains very popular in zoos and on television, and lucky youngsters still go camping with their parents, our population is increasingly disconnected from experiencing real nature or even rural agricultural landscapes, or from understanding our dependence upon these systems. Food comes from markets, water from faucets, entertainment from electronics encased in plastic boxes, and so on. But in fact all of these resources and toys and much more are all ultimately derived from nature, and their provision is usually associated with some degradation of nature and diminishment of natural resources. In general we do not pay for nature’s goods and services but only for the energy, labor, and equipment to extract them. In fact we might argue that it is only because we do not pay for these things that we can afford to live at all, or certainly at the present level of general affluence.
KeywordsEcosystem Service Sport Fish Horizontal Drilling Ecosystem Service Concept Ecological Footprint Analysis
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- 3.Hall, M.H., R. Germain, and M. Tyrrell. 2010. Predicting Future Water Quality from Land Use Change Projections in the Catskill-Delaware Watersheds. Final report to the NY State Department of Environmental Conservation, Albany, NY. http://redir.aspx?C=95f13948884f410183203d8059421dca&URL=http%3a%2f%2fwww.esf.edu%2fes%2fhall%2fwater.pdf” http://www.esf.edu/es/hall/water.pdf and HYPERLINK “redir.aspx?C=95f13948884f410183203d8059421dca & URL=http%3a%2f%2fresearch.yale.edu%2fgisf%2fCatskill_report%2findex.htm” http://research.yale.edu/gisf/Catskill_report/index.htm.
- 4.Hall, C.A.S. 1977. The Hudson River striped bass example. In Hall, C. A. S. and J. W. Day. Ecosystem modeling in theory and practice. Wiley Interscience.Google Scholar
- 5.Hagens, N., K. Mulder and N. Fisher. 2010. Burning water: Energy return on water invested. AMBIO Volume 39, Number 1/February, 2010.Google Scholar | <urn:uuid:6028ccc0-6a59-47b1-992e-2102e92f65e3> | 2.96875 | 731 | Academic Writing | Science & Tech. | 58.405191 | 95,629,205 |
The Highest and Lowest Points of the Lithosphere Essay Sample
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Introduction of TOPIC
The Highest and Lowest points of the Lithosphere are both found at the Earths plate boundaries, with reference to the process of plate tectonics, explain why this is so.
The process of plate tectonics, also known as Orogenesis, has shaped Planet Earth to what it is today. The four different spheres; Lithosphere, Hydrosphere, Atmosphere, and Biosphere, have worked together to create a beautiful a gigantic Ecosystem where Fauna, Flora, Detritus Feeders (Bacteria and other Micro-organisms) and Decomposers have created a world to live in with the highest and smartest known species; the Human. Plate Tectonics has not only build our world but also helped to destroy it and to rebuild it in different shapes and forms.
The Earths Landmasses used to be joined together known under the name of Pangea. After millions of year the art of plate tectonics has moved this large landmass apart into smaller landmasses known as Continents and Islands. It is already estimated what the “Next Pangea” will look like, that would be 250 Million years from now (Figure 4.1). Through this process many new landscapes have been created. There are seven major plates that move between the earths surface and core, which is named the Asthenosphere. They are the Pacific Plate, Indo-Australian Plate, African Plate, North American Plate, South American Plate, Antarctic Plate, and the Eurasian Plate (Figure 6.1). The structure of the Earth can be easily shown in a diagram which is shown in (Figure 1.1) at the end of this document. The plates which are moved by the convection currents in different directions have therefore created and destroyed parts of the lithosphere, also known as Denudation (Process of breaking down the Lithosphere). These convection cells and their currents have moved these major plates in different directions through all this time. These movements have different names too. They are describes like this and diagrams are shown in (Figure 2.1) and
(Figure 3.1) at the end of the Document:
Constructive Margins- is when two plates move apart and away from each other
letting Magma (the molten rock which belies under the earths crust) reach the surface where its then
Destructive Margins- is when two plates move together and one plate is pushed under the other plate. This only happens when a Continental Plate and a Oceanic Plate move together. The Oceanic Plate is pushed under the Continental Plate because of it’s heavy mass of Ocean Water. As it slides under the lighter Continental Plate it creates a Subduction Zone which is the point where the Oceanic Plate is swallowed by the magma and melts to create more magma. One way for the pressure to be released is by Volcanoes which are very evident at the site of Destruction. Example: Andes Ranges, South America.
Collison Zones- is when two continental plates move together in equal force to create mountain chains, often known as Fold Mountains. None of the plates are pushed under like in the Destructive Margin because they both have no Ocean Mass on it and they move together with equal force which makes both plates fold upwards to create new mountain chains. Example: Mt. Everest, Himalayas.
Conservative (Passive) Margin- is when two plates move parallel to each other sliding next to each other without moving away or towards each other. These are also called Transform Faults. Example: San Andreas Fault, California.
These different methods of Orogenesis have created the earths upper layer on which we live on with all the other species. The earths highest and lowest points are therefore found on the plate boundaries because those are the areas where the plates interact to form and construct these higher and lower points. The higher and lower points are created by different methods of Orogenisis. For Example the Hawaiian Islands where not formed by any of these Margins. The Hawaiian Islands and its Volcanoes are Hot Spots (Figure 5.1). This means that at that particular spot the Lithosphere is very thin which lets Magma escape and therefore create Volcanoes and add new landmasses, Islands.
The Highest Point of the Earths Crust which is Mt. Everest in Nepal, has been created by the process of Collision Zones. The highest point of the earths crust that is Mt. Everest has been created when the Eurasian Plate and Indo-Australian Plate have moved together to collide and fold upwards. Mt. Everest has a height of 8,848 meters or 29,029 feet altitude. It is the highest point of the Earths Crust.
The Lowest Point of the Earths Crust which is the Mariana Trench in the Pacific Ocean has a depth of 10,920 meters or 35,827 feet. It was created by the process of Constructive Margins or Sea-Floor Spreading. The Eurasian Plate has moved away from the North American plate which spreaded the Sea Floor in the Pacific Ocean ceating the Mariana Trench; the lowest point of the Lithosphere.
Therefore, the process of Orogenesis created the Highest and Lowest points of the Lithosphere and because of the Plate’s Locations thanks to Convection Currents has created those wonders on the Plate Boundaries. There are more diagrams shown at the end of this Informative Document. | <urn:uuid:bea86bb0-b60f-4321-a186-0fc922ac1827> | 3.515625 | 1,206 | Academic Writing | Science & Tech. | 48.252281 | 95,629,212 |
Boulder, Colo., USA: The biggest landslides on Earth aren't on land, but on the seafloor. These mega-slides can move thousands of cubic kilometers of material, and sometimes trigger tsunamis. Yet, remarkably, they occur on nearly flat slopes of less than three degrees.
Morelia Urlaub, a marine geoscientist at the Geomar Helmholtz Center for Ocean Research in Kiel, Germany, voices the obvious question: "How can you fail on a slope that is so flat?" Now, Urlaub and colleagues may have discovered the answer. The smoking -- or in this case, oozing -- gun is a layer of siliceous microfossils called diatoms.
The study, published online ahead of print for the Geological Society of America's journal Geology, is the first to identify the weak layer responsible for a submarine mega-slide. Although the nature of these critical weak layers has been highly debated, studying them has been nearly impossible because they are typically destroyed along with the slides.
Urlaub was compiling ocean drilling data from 1980 when she realized that the core sampled the seafloor just outside the Cap Blanc slide, a 149,000 year-old mega-slide off the coast of northwest Africa. She correlated that data with high resolution seismic reflection data recorded in the same area in 2009. Together, these data revealed diatom-rich layers, up to ten meters thick, that traced directly from the core to the base of slide layers within the mega-slide complex.
What's more, each diatom layer was topped by a layer of clay-rich sediment. That clay is apparently key. "Diatom layers are very compressible and water rich," Urlaub says. As pressure builds, she explains, water would be squeezed from the diatom layer into the clay. Ultimately the clay or the interface between the clay and diatoms fails, sending the sediments above sliding.
At the Cap Blanc slide, the seafloor slopes at just 2.8 degrees. Yet when it broke loose, the slide transported over 30 cubic kilometers of material, and extended at least 35 kilometers. Another submarine mega-slide 8,500 years ago off Norway moved a staggering 3,000 cubic kilometers, causing a damaging tsunami. And some scientists speculate that the 2011 Tohoku tsunami in Japan may have been amplified by a submarine mega-slide.
Although such slides don't occur very often, says Urlaub, their size makes them quite significant. "One-fifth of all tsunamis may be caused by undersea mega-slides," she says. If diatom layers are a major factor, then understanding where paleoclimate conditions may have favored diatom growth might help reveal potential mega-slide sites.
Diatom ooze: Crucial for the generation of submarine megaslides?
M. Urlaub, Jacob Geersen, Sebastian Krastel, and Tilmann Schwenk. Geology: https:/
GEOMAR Helmholtz Centre for Ocean Research Kiel, Kiel
GEOLOGY articles are online http://geology. | <urn:uuid:1ac6fc0b-fca1-48c3-9f23-4883308094e0> | 4.1875 | 652 | Knowledge Article | Science & Tech. | 46.191552 | 95,629,220 |
brown dwarf planet 88.
(photo credit: )
Israeli and German astronomers have detected and become the first to directly image a "brown dwarf" companion to a star that also has a planet.
The feat of detecting a solar system's faintest-known companions - carried out by Profs. Markus Mugrauer and Ralph Neuh user of the Friedrich-Schiller University of Jena, Andreas Seifahrt of the European Space Observatory and Tsevi Mazeh of Tel Aviv University - yields important information on the conditions under which planets form.
"Brown dwarfs" are sub-stellar objects with a mass below that necessary to maintain hydrogen-burning nuclear fusion reactions in their cores.
"Such a system is an interesting example that might prove that planet and brown dwarf can form around the same star," said Mugrauer, lead author of the paper presenting the discovery. These results were first presented at the recent International Astronomy Union general assembly in Prague and will soon be published in the Monthly Notices of the Royal Astronomical Society.
The star HD 3651 is slightly less massive than our sun, located 36 light-years away in the constellation Pisces. For several years, it has been known to harbor a planet less massive than Saturn located closer to its parent star than Mercury is from the Sun; the planet accomplishes a full circle every 62 days.
The brown dwarf was named HD 3651B. Comparing its characteristics with theoretical models, the astronomers inferred that the object has a mass between 20 and 60 Jupiter masses and a temperature between 500 and 600 degrees Celsius. It is thus 10 times colder and 300,000 times less luminous than the Sun. These properties place it in the category of "cool T brown dwarfs."
Due to their faintness even in the infrared range, cool T dwarfs are very difficult to find, said Mugrauer. "Only two other brown dwarfs with similar brightness are presently known."
The study will provide important insights on the atmospheric properties of cool sub-stellar objects," said Mugrauer.
He and his colleagues first spotted the faint companion in 2003 on images from the United Kingdom Infrared Telescope (UKIRT), which is 3.8 meters in diameter and located in Hawaii. Observations in 2004 and 2006 using ESO's 3.6-meter-wide New Technology Telescope (NTT) at La Silla provided the crucial confirmation that the speck of light is not a spurious background star, but indeed a true companion.
HD 3651B is 16 times further away from HD 3651 than Neptune is from the Sun. As it is not detected on the photographic plates of the Palomar All Sky Survey, the companion must be even fainter in the visible spectral range than in the infrared, meaning it is a very cool low-mass sub-stellar object, he said.
More than 170 stars outside of the solar system are known to have planets. In some cases, these stars were also found to have one or several stellar companions, showing that planet formation can also take place in a more complex environment compared a system like our own solar system where planet formation occurred around a single isolated star.
In 2001, Mugrauer and colleagues started an observational program to find out whether these "exoplanet host stars" are "single," that is with no large companions other than planets, or "married," that is a system that has a large companion that is not a planet, such as a brown or white dwarf. In this program, known exoplanet host stars are systematically imaged is at two different periods, at least several months apart.
True companions can be distinguished from coincidental background objects as only they move together with the stars over time.
With this effective search strategy several new companions of exoplanet host stars have been detected. Most of the detected companions are low-mass stars in the same evolutionary state as the Sun.
In two cases, however, the astronomers found the companions to be "white dwarfs," that is, stars at the end of their life. These intriguing systems bear evidence that planets can even survive the troubled last moments in the life of a nearby star. | <urn:uuid:37e42b0e-e01b-49ba-8ec1-aebb8fbe175c> | 3.6875 | 851 | News Article | Science & Tech. | 46.082687 | 95,629,232 |
Can RNA Turn Genes On?
Researchers at the University of Texas Southwestern Medical Center have found that RNA may be a potential tool in activating dormant genes.
This week, more than 700 scientists have flocked to the ski resort of Keystone, Colorado, for five days. But it’s not the snow that’s brought them together. Rather, it’s something they find much more exciting: RNA–a tiny cousin of DNA that may be the key to developing genetic therapies for a huge range of diseases, including cancer, neurological and respiratory diseases, and HIV.
Nearly eight years ago, researchers Craig Mello, of the University of Massachusetts Medical School, and Andrew Fire, of Stanford University’s School of Medicine, discovered that RNA plays a crucial role in regulating gene expression: the ability to turn genes off. They won a Nobel Prize for their work in 2006 identifying the mechanism for a process called RNA interference, or RNAi. They found that RNA blocks a gene from delivering its message to proteins, essentially shutting down that gene. Since then, scientists around the world have run with the idea, finding ways for RNAi to turn off a variety of genes–in particular, those that cause disease. It’s RNA’s role in switching off genes that dominates the talks at this week’s conference, titled “RNAi for Target Validation and as a Therapeutic.”
However, not much is known about RNA’s role, if any, in turning genes on. It’s a phenomenon that researchers Bethany Janowski and David Corey stumbled upon a couple years ago, almost by accident. Their study, published in Nature Chemical Biology, provides evidence of RNA’s genetic “on” switch, and they’ve presented their findings at this week’s conference.
In 2005, Janowski and Corey, both at the University of Texas Southwestern Medical Center, were studying the effects of RNA in turning off certain genes related to breast cancer. Specifically, they found that injecting RNA strands into cultures of human breast-cancer cells with high levels of progesterone receptors inhibited the gene that controlled for that receptor. (It’s been found that varying levels of the hormone progesterone affects the growth of cancer cells.) As a result, the team observed a reduced level of progesterone production.
After a closer look, Janowski and Corey also found that a small number of RNA strands had the opposite effect, causing a slight increase in gene activation–an effect they did not expect. Investigating further, they isolated the activating RNA strands, then injected them into a culture of cancer cells with low levels of progesterone receptors. The result: RNA actually turned up gene expression for these receptors, stimulating the gene to produce more progesterone.
“It really goes against the dogma out there,” says Janowski, assistant professor of pharmacology and lead author of the study. “The idea that RNA can be a major regulator is something that people have to get used to. But on a biological level, it makes perfect sense. If RNA can silence, it should be able to turn on.”
The ability to turn genes both on and off may have major implications for the treatment of diseases. For example, the development of cancer may be partially due to mutations in genes that control cell growth. The body contains genes that are natural tumor suppressors. Mutations that silence these genes may result in uncontrolled cancer growth. Janowski and Corey believe that finding a way to turn these genes back on may stem the growth of tumor cells.
However, they say it’s not clear exactly how RNA’s genetic “on” switch works. In their experiments, the researchers injected RNA directly into cancer cells, where it interacted with specific genes to turn them on. Janowski says this may be a more direct method compared with conventional RNAi techniques, in which scientists inject RNA strands outside a cell to block messenger RNA–an intermediary molecule that delivers genetic information out of a cell to surrounding proteins that act out a gene’s instructions.
“It’s easier to turn something off by acting like a roadblock so the transcriptional machinery can’t get past it,” says Janowski. “But to activate it is harder to do.”
Gordon Carmichael, professor of genetics and developmental biology at the University of Connecticut Health Center, studies RNA’s role in regulating disease. While Carmichael did not attend the conference, he is familiar with the team’s work and says the research is interesting, although puzzling. “The question arises as to whether the observed effects are general and, if so, how general?” he says. “There appear to be few genes that can be regulated this way.”
In future studies, Janowski and Corey plan to explore the exact mechanism for RNA’s genetic activating potential. They will also explore RNA’s effect in turning on a variety of genes, including tumor suppressor genes, and they hope eventually to experiment on animal models. However, Janowski acknowledges that the team’s work and its conclusions are preliminary.
Phillip Sharp, MIT professor and Nobel Prize-winning cancer researcher, advises a wait-and-see approach. Speaking from the RNAi conference in Colorado, Sharp says it may be a while before RNA’s genetic “on” switch is as scientifically confirmed as its “off” switch. “There will have to be a lot of additional work before one can judge the importance of this finding,” he says.
The University of Texas team, meanwhile, is optimistic. “Anything new will be a test of time,” says Janowski. “People are pretty open to new ideas, but because this has been so entrenched, it will take people a while to get a handle on this.”
Couldn't make it to EmTech Next to meet experts in AI, Robotics and the Economy?Go behind the scenes and check out our video | <urn:uuid:3bce51c5-b2df-4bce-b074-feb9592a4537> | 3.53125 | 1,258 | News Article | Science & Tech. | 42.188153 | 95,629,242 |
A) Draw the Lewis structure of chlorine nitrate.
b) Write out the chemical equations showing how chlorine nitrate is formed in the stratosphere and for the reactions that convert it back to active chlorine compounds. Include reactions that occur in polar stratospheric clouds.
Calculate the rate constants at 220 K for Reactions 1 and 2.
Offer an explanation for why Reaction 2 has an activation energy of approximately zero.
Consider the net reaction in Question 2:
O + O3 O2 + O2
The standard enthalpies of formation of O and O3 are 249.2 and 142.7 kJ mol−1, respectively. Calculate the reaction enthalpy. Why does this reaction not proceed on its own, to any appreciable extent, in the stratosphere?
In particulate sampling, air is drawn through a filter, which collects the particulates. In one sampling, the initial weight of the filter was 3.347 g. The final filter weight was 3.762 g. If the average flow rate of air through the filter was 49 cubic feet per minute, and the sample was collected over 24 hours, what is the TSP concentration in μg/m3 for this sample?
(1 cubic foot = 0.02832 m3)
Write out the steps for the atmospheric oxidation of ethane.
Write out the steps for the atmospheric oxidation of propylene.
The atmospheric residence time of methane in the atmosphere is 12 years. If global methane emissions total 600 Mt (megatonnes) per year, what is the steady state concentration of methane in the atmosphere in Mt??in ppm?
Note: The total mass of the atmosphere is 5.1 ?1018 kg, and the average molar mass is 29.0 g/mol.
A) In petroleum production, the term "solution gas" refers to gases that are dissolved in the petroleum reservoir because of the high pressure conditions underground, but become gaseous when the oil is brought to the surface. In 2007 in Alberta, 3.25 ?108 m3 of solution gas was flared (burned off) from crude oil and crude bitumen batteries. Assuming that the solution gas was 100% methane, how many moles of CO2 are produced from this flaring? What is the increase in global concentration of CO2 in the atmosphere, in ppmv, resulting from this activity?
Note: The total mass of the atmosphere is 5.1 ?1018 kg, and the average molar mass is
b) In 2005, Alberta used 26 Mt (megatonnes) of coal to generate electricity. Assuming that 100% of the coal is converted to CO2, how many moles of CO2 are produced? What is the increase in global concentration of CO2 in the atmosphere, in ppmv, caused by this activity?
At the Braidwood nuclear power plant in Illinois, between 1996 and 2000,millions of litres of radioactive cooling water were leaked on the site, and groundwater is now contaminated with high levels of tritium. Tritium is a beta emitter with a half life of 12.3 years. Monitoring wells on the site have found groundwater radioactivity of up to 282,000 pCi/L. The EPA drinking water standard is 20,000 pCi/L. If the contaminated groundwater remained static and there was no decrease in tritium levels resulting from groundwater flow, how many years would it take for the radioactivity to decrease from 282,000 pCi/L to 20,000 pCi/L?© BrainMass Inc. brainmass.com July 21, 2018, 9:23 pm ad1c9bdddf
1a) See attached picture, and replace the lines with dots. Note that chlorine nitrate has two different structures here because they are in resonance with one another. See images.jpeg
b) Formation: Cl2O+N2O5 ---> 2ClONO2
It can be decomposed with heat to give...
2ClONO2---> Cl2 + NOx, (a variety of different NO compounds are formed)
Metal Chlorides also will change it back to chlorine gas, such as titanium (IV) chloride:
4ClONO2 + TiCl4 ---> Ti(NO3)4 + 4Cl2
In polar stratospheric clouds, Chlorine nitrates have been shown to react with water or hydrogen chloride gas (Tolbert, et al. 1987 Science vol 238)
ClONO2 + H2O --->HOCl + HNO3
ClONO2 + HCl ----> Cl2 + HNO3
2a) k=Ae^(-Ea/RT), units are in brackets for clarity. Ea converted to joules from kJ to line up with the gas constant
Reaction 1: k=1.8x10^-12 * e^(-11400[J/mol]/8.314[J/K.mol]*220)
k=1.8x10^-12 * e^(-6.85)
Reaction 2: Since Ea is 0, the "e" term is e^0, or 1. Thus, k=9.3x10^-12
b) Reaction two could be the intermediate between reaction 1 ...
In this solution we consider the kinetics and concentrations calculations associated with a variety of environmental chemistry concepts. These include the formation of chlorine nitrate and its kinetics (along with how to calculate rate constants given empirical data), the concept of activation energy and why a reaction may have an activation energy close to zero, and calculation of reaction enthalpies in the case where standard enthalpies of formation are given.
In addition, the calculation of TSP is considered, along with how ethane and propylene are oxidized in the atmosphere. We also show you how to solve a steady-state concentration problem on the global scale with regard to methane.
Finally, we also consider increases in global CO2 concentrations due to fossil fuel combustion before ending with a calculation using half-life of tritium, specifically referring to how many years it will take to reach a certain level of radioactivity.
This solution is a tour de force in environmental chemistry and has good application in a variety of general chemistry concepts! Do not miss it if you are having trouble! | <urn:uuid:e071d1f0-4506-4d98-9a2d-f18e25a7ab22> | 3.546875 | 1,332 | Tutorial | Science & Tech. | 62.203636 | 95,629,275 |
With some chemical knowledge, you can fairly easily guess if a molecule will be polar or not. Each atom will have a different level of electronegativity, or ability to attract electrons. Actually calculating the polarity of a molecule precisely, however, requires determining the shape of the molecule and performing vector addition. The length of each vector will correspond to the electronegativity of the atom in each bond. The direction of the vector will correspond to molecular shape.
Draw the molecule in standard chemical format, with all atoms and free electrons shown in the drawing.
Determine the shape of the molecule. With one or two bonded atoms, the molecule will be linear. With two bonded atoms and unbonded electrons, the molecule will be angular. With three bonded atoms and no free electrons, the molecule will be flat triangular. With three bonded atoms and a set of free electrons, the molecule will be triangular, pyramidal. With four bonded atoms, the molecule will be pyramidal.
Determine the electronegativity of each atom in the molecule. Use a standard measurement, such as a centimeter per whole unit of electronegativity, to determine the length of each vector.
Draw a vector of the appropriate length for each atom that you determined vector length. Draw them facing the direction they would face in the molecule, according to the shape determined in Step 2.
Line up the vectors end to end. The distance between your starting point and the final vector is the measurement of polarity in the molecule. For example, if you used 1 cm per whole unit of electronegativity, and your final distance between the last vector and your starting point is 5 mm, the molecule has a polarity of 0.5 in that direction.
Many chemistry books list polarity measurements of common molecules.
If estimating polarity, look for atoms like oxygen or fluorine, which have strong electronegativity. If they are on one side of the molecule and not the other, it is likely that the molecule is polar in that direction.
Calculating polarity of a molecule becomes increasingly complicated as a molecule increases in size and is typically calculated with a computer. This technique primarily works for small molecules. | <urn:uuid:76631986-b9be-4434-ab38-7a94a9a0233b> | 4.46875 | 454 | Tutorial | Science & Tech. | 31.753398 | 95,629,278 |
Rotation and revolution are often confused, but there are distinct differences between the two. Each describes a different process altogether, and understanding these differences can help clarify your perception of the way our solar system is organized, and how our planet relates to it. For a simple reference, remember that the Earth rotates around its axis and revolves around the Sun.
Rotation is when a planet moves on its own axis. One rotation is completed when a planet turns on its axis once. During rotation, a planet's position changes only with respect to its axis, not to other celestial bodies. An axis can not be seen, but is an imaginary line that runs through a planet. On Earth, the axis of rotation is located in a straight line between the North and South poles. Though the Earth is tilted about 15 degrees, it rotates along this imaginary line as if it were a straight line.
A revolution describes when a planet moves around a central celestial body, such as the Sun. The word revolution comes from the 1500s astronomer Copernicus, who published a theory titled "On the Revolution of Planets." In this theory, he described what we now know to be true, that the planets in our solar system revolve around the Sun and not the Earth. For this reason, the revolution of planets is named after his theory.
The Earth takes 365 days to revolve around the sun, but only 24 hours to rotate on its axis. Armed with this knowledge, it may seem as if a revolution always takes much longer than a rotation, but this is not the case. For instance, the moon rotates around its axis and revolves around the Earth in the same amount of time, 27 days. This is the reason we always see the same side of the moon at all times of the year.
Both revolution and rotation are essential to the way that our planet functions. The revolution of our planet around the Sun provides us with the various seasons throughout the year, as our elliptical orbit moves us closer and farther away from the Sun. The Earth's rotation is responsible for the distinctions between night and day; as it spins different parts of the planet are exposed to the Sun. | <urn:uuid:fb1e316f-697f-4d92-9cd8-871aaeb779f7> | 4.03125 | 440 | Knowledge Article | Science & Tech. | 51.911327 | 95,629,279 |
Join Patrick Royal for an in-depth discussion in this video Solution overview, part of Code Clinic: Java (2014).
- The solution to this problem…has a lot of complicated details and syntax.…But the overall structure is easy to undertand.…The first step is to load the picture into Java.…There are a number of different ways to…represent images in Java,…so it's important to find a way…where we can easily get information…about the image for comparison.…Next, we need to find some way of…matching up the two images.…Essentially, we need to compare the…smaller image to every possible equal…size subset of the larger image…and see if they are the same.…
Third, we need an algorithm to…actually perform the comparisons.…If the images were identical pixel for pixel,…this would be easy.…However, the process of cropping…changes how the smaller image is represented.…So we will have to use more complicated comparisons.…Finally, we need to interpret these results to determine…whether one picture is a subset of the other.…My solution is structured to…meet these four main objectives.…The main method loads in two images…from their file name and compares their size.…
Patrick introduces challenges and provide an overview of his solutions in Java. Challenges include topics such as statistical analysis, searching directories for images, and accessing peripheral devices.
Visit other courses in the series to see how to solve the exact same challenges in languages like C#, C++, PHP, Python, and Ruby.
Skill Level Intermediate
Q: I am unable to access the Lake Pend Oreille data from outside the U.S.
A: A static copy of this data is provided here for lynda.com members outside of the U.S
Problem One: Exploring Lake Pend Oreille
Problem Two: Image Analysis
Problem Three: Eight Queens
Problem Four: Accessing Peripherals
Problem Five: Recursion and Directories
Problem Six: Building the Web
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- Open Access
Geographic variation in sexual selection and implications for speciation in the Barn Swallow
© Scordato and Safran; licensee BioMed Central. 2014
Received: 26 November 2014
Accepted: 27 November 2014
Published: 24 December 2014
Barn Swallows (Hirundo rustica), a group of passerine birds comprised of six closely related subspecies, are well known throughout their nearly worldwide distribution, in part because of their close association with human settlements. A tractable species for both individual-based and population-level studies, Barn Swallows are a prominent model system in evolutionary, ecological, and behavioral research. Here we review work on sexual selection and population divergence in this species complex, focusing on comparative studies among populations and subspecies. We summarize variation in the targets of mate choice and in the information conveyed by sexually selected traits, and conclude that the benefits advertised by different traits may vary geographically. Finally, we consider the role of sexual selection as a driver of population divergence in this widespread and phenotypically variable species complex.
A spring and summer inhabitant of the Holarctic, the Barn Swallow (Hirundo rustica) is the most widespread species of the swallow family, Hirundinidae. The extensive breeding range of the Barn Swallow is believed to be due in part to their close association with human populations. Based on patterns of human colonization in Eurasia and recent phylogenetic studies in swallows, it appears that this association with humans has persisted for millennia (Zink et al. ). Indeed, swallows will nest nearly everywhere there are barns or bridges, especially if these are situated near water and fields. In addition to human structures providing nest sites, swallows benefit from agriculture: the insects surrounding livestock are an excellent food source for these aerial insectivores. The Barn Swallow is thus well known and easily recognizable throughout rural areas worldwide, and has been the subject of extensive behavioral, ecological, and evolutionary research since the early part of the 20th century (reviewed in Møller [1994a]; Turner ).
The first studies of sexual selection in Barn Swallows were conducted in European populations of H. r. rustica, and focused primarily on the role of tail streamer length in mate choice. However, when research began on North American H. r. erythrogaster in the 1990s, it became apparent that streamer length played a different role in reproductive success in this subspecies than it did in Europe, although sample sizes for these studies were small (Smith and Montgomerie ; Smith et al. ). Geographic variation in the targets of mate choice has subsequently drawn attention to the role that sexual selection may play in population divergence and speciation in the Barn Swallow complex. Here, we first review what is known about the evolution and social function of streamer length and ventral coloration in different subspecies of Barn Swallow; these two traits have been the subject of the most extensive research. We also consider the role of song in sexual selection, which is less well studied than color and streamer length but nonetheless seems to play a role in both male competition and mate choice. We summarize data related to sexual selection on these traits in the different subspecies, and then consider the role of geographic variation in sexual selection pressures in population divergence and speciation. We do not discuss traits that have been studied in only a single subspecies of Barn Swallows (e.g., nest size, asymmetry, senescence), as there is no comparative data available. We conclude by highlighting future directions for ecological and evolutionary research on this species complex.
Sexually selected traits in the Barn Swallow
Sexual selection was originally conceived by Darwin () to explain the widespread presence in nature of elaborate and conspicuous traits that do not contribute to an organism’s survival, and indeed often seem detrimental to its fitness. Darwin postulated that these traits evolve because they are attractive to members of the opposite sex and/or aid in competition for mates; hence, costly and elaborate traits could persist because they enhanced an individual’s mating success, if not its survival. A sexually selected trait is therefore defined as any trait that assists an individual in the acquisition of mates or fertilizations (Andersson ). These traits can evolve via female choice (i.e., females mate with males that display the most elaborate traits), or by male-male competition (i.e., males with the most elaborate traits are best able to monopolize access to fertile females). Both cases result in directional selection on traits because males with the most elaborate sexually selected traits are often those that enjoy the greatest reproductive fitness.
A central question in sexual selection research is why females prefer males that display showy and presumably costly traits. The most common explanation is that elaborate male traits advertise benefits a female may obtain by mating with that male. These benefits fall into two categories: direct benefits which affect female fitness, such as a male’s ability to provide resources, good paternal care or high quality territories to his mate (Price et al. ; Kirkpatrick ); and indirect, or genetic benefits, which advertise a male’s ability to produce attractive, healthy, or high-quality offspring (Iwasa et al. ; Kirkpatrick ). Both types of benefits models rely on sexual signals being “honest indicators” of male quality (Zahavi ); that is, only the highest quality males have the surplus resources available to bear the costs associated with developing and maintaining elaborate traits (Grafen ). More elaborate signals therefore advertise higher quality males who can provide better benefits, and females should choose to mate with males that exhibit the most elaborate version of the preferred trait (Grafen ). A major focus of sexual selection studies is thus identifying the costs and benefits (both direct and indirect) associated with putative sexually selected traits.
Determining whether or not a trait is sexually selected requires extensive empirical work. Although it is often tempting to assume that any elaborate or sexually dimorphic trait (e.g., bright colors, ornamental feathers, or weapons) is sexually selected, these traits can also evolve for other purposes, such as mimicry, aposematic signaling, and species recognition (e.g., Jiggins et al. ; Maan and Cummings ; Price ). To show that a trait is subject to sexual selection, a causal relationship between trait variation and reproductive success must be demonstrated. The best way to do this is using field experiments that manipulate a trait to be more or less exaggerated than average and then measuring the effects of this manipulation on some aspect of fitness, such as timing of breeding, pairing success, or number of offspring. Barn Swallows are a favored model system in sexual selection studies, as their most obvious sexually selected traits, tail streamers and color, are both relatively easy to manipulate (e.g., tail streamers: Møller , ; color: Safran et al. ). Substantial work has thus been devoted to identifying the costs and benefits advertised by these traits.
Tail streamers in European H. r. rustica
The best studied of the Barn Swallow’s sexually selected traits are the tail streamers. Since this trait is strongly sexually dimorphic in European populations, scientists studying H. r. rustica quickly suspected that these traits were under sexual selection in males. To determine whether there is a relationship between tail streamer length and male mating success, Møller () artificially elongated and shortened streamer length and examined whether this affected a male’s ability to attract a mate. Males with artificially elongated tail streamers mated earlier than their short-streamered neighbors - the first demonstration of a causal relationship between male tail length and female mate choice in Barn Swallows. Indeed, since that initial study and the dozens that have followed (reviewed in Møller et al. [1998a]; Turner ), tail streamers in European H. r. rustica have become a textbook example of sexual selection. Further experimental and correlational studies confirmed that females prefer males with the longest tail streamers: long-tailed males produce the most offspring (in their first clutches and total number of young per season) each year because they pair and breed earlier and successfully fledge more broods than shorter-tailed males (reviewed in Møller [1994a]; Møller et al. [1998a]). Naturally long-streamered males likely breed earlier because they are in better condition and arrive on the breeding grounds earlier than shorter-streamered males (Møller [1994a]; Møller et al. ; Ninni et al. ), which gives them an advantage for obtaining high quality nest sites and mates, as well as producing more broods.
Barn Swallows are socially monogamous and exhibit biparental care (Møller [1994a]). However, they also pursue extra-pair matings. This means that in any given nest, some offspring are likely not genetically related to the male caring for them, and counting the number of chicks in a nest is thus not necessarily an accurate reflection of the male nest owner’s reproductive output. Molecular parentage analyses provide a definitive measure of a male’s reproductive success, and allow a more accurate assessment of the strength of sexual selection associated with different traits. In European populations of Barn Swallows, the proportion of extra-pair young (EPY) in a nest averages 17.8–34% (Saino et al. [1997b]; Møller et al. [1998b]). Møller’s () tail manipulation study was replicated in Europe and confirmed that males with the longest streamers obtained a significantly greater share of genetic paternity in their nests and in the nests of others, relative to their short-streamered neighbors (Møller and Tegelström ; Saino et al. [1997b]).
Tail streamers are a particularly interesting sexually selected trait because they have a clear function unrelated to mating. As aerial insectivores, Barn Swallows must fly efficiently, a task that is substantially aided (or hindered) by the shape of their tails. Thus, rather than evolving under directional sexual selection alone (as would be predicted if the longest-streamered males always had the highest fitness), this trait is predicted to be shaped by a balance between sexual and natural (viability) selection. This appears to be borne out by empirical data: individuals with longer streamers suffer from impaired aerodynamic performance that may result in lower foraging efficiency (Møller et al. [1998a]; Bro-Jørgensen et al. ), and population-level survival is lower when male streamer length is longer on average (Møller and de Lope ). There is some evidence that high condition males with naturally longer tails have higher survival (Møller [1991a]; Møller [1994a]), although more recent mark-recapture analyses of annual population means shows that males with naturally longer tails have lower survival (Møller and Szép ). Swallows with too short a set of streamers also suffer from reduced flight skills (Buchanan and Evans ; Rowe et al. ). The balance between tail feathers that are too long or too short implies that there is a naturally- selected optima for tail length, and that sexual selection may drive tail length away from this optima (Møller et al. ; Evans and Thomas ; Buchanan and Evans ; Bro-Jørgensen et al. ).
The apparent costs associated with elongated tail streamers led researchers to hypothesize that tail length is an honest signal of male quality: only high condition males can bear the costs of elongated tails. If this is true, females should gain benefits from mating with longer-tailed males, which leads to directional sexual selection on streamer length that will ultimately be opposed by viability selection when the survival costs of long tails outweigh the benefits from increased mating success. There is some evidence for the type of “quality” that long-tailed males might be signaling: European males with longer tails had fewer ectoparasites (Saino and Møller ) and more robust immune responses (Saino et al. [1997a], ), suggesting that tail length advertises information about immune system quality. Experimental data manipulating tail length also found that long-tailed males were better able to cope with the immune costs of their elaborate traits (Saino and Møller ). Some aspects of the immune response appear to be heritable, as a positive correlation was found between ectoparasite loads on fathers and sons (Møller ; Møller et al. ), meaning that females paired to long-tailed males may gain indirect benefits in the form of healthy sons. Females may gain direct benefits from mating with healthy, long-tailed males as well, via less exposure to contagious ectoparasites.
Long tails seem to advertise additional qualities besides immune function: males with longer tails had higher levels of circulating testosterone, which may be related to competitive ability (Saino and Møller ), and the sons of long-tailed males had greater longevity than those of short-tailed males (Møller [1994b]), which could be due to good genes, better parental care in nests with long-tailed fathers, or other heritable components of longevity. These latter effects are difficult to partition, particularly because long-tailed males obtained high-quality females as mates (Møller [1991b]), high quality females also had long tails (Møller [1991b]; Cuervo et al. [1996b]), and females mated to attractive, long-tailed males invested more in reproductive effort (de Lope and Møller ). Thus, some of the benefits experienced by the offspring of long-tailed males are likely due to their high-quality mothers, although offspring may also suffer due to reduced investment from their long-tailed fathers (de Lope and Møller ). Taken together, long tail streamers seem to be indicators primarily of indirect benefits: females mated to long-streamered males do not obtain better paternal care (indeed, elevated testosterone and longer tails resulted in poorer parental care, de Lope and Møller ; Saino and Møller [1995a]), but they produce healthy, long-lived offspring and long- streamered sons.
However, another hypothesis suggests that tail streamer length is not an honest signal of a male’s ability to withstand a “too long” streamer, but rather is optimized to individual-specific flight performance and thus subject to natural selection (Cuervo et al. [1996a]; Evans and Thomas ; Buchanan and Evans ). To differentiate these alternatives, Bro-Jørgensen et al. () utilized an individual-based approach to study flight performance as a function of streamer length. They analyzed aerodynamic performance after manipulating tail streamers to multiple different lengths, and found no evidence to support the view that the sexually selected component of this trait reflects individual variation in flight performance. Instead, the optimal streamer length for efficient flight varied among males, but beyond a certain point, any additional length to the streamer, presumably caused by sexual selection, did not vary among individuals. The conclusion is that the naturally, rather than the sexually, selected component of the streamer conveys information about a male's flight and foraging performance, leaving open the question of why streamers are elongated past this optimal value. Bro-Jørgensen et al. () speculate that tail streamer lengths may simply serve to signal the age and sex of the individual (adult male vs. female or juvenile), and indeed, older males typically have longer tails, although the benefits associated with streamer length are still found when controlling for the effect of age (Møller et al. [1998a]). The relative roles of natural and sexual selection in shaping elongated tail streamers thus remain debated (e.g., Evans , ; Hedenström and Møller ; Evans ; Evans et al. ; Aparicio and Møller ), particularly because an explicit link between flight performance and fitness has not been demonstrated. Further experimental studies that adopt a within-individual experimental approach with additional treatments related to mate-selection may provide a definitive test for understanding the relative contributions of sexual and natural selection to variation in streamer length.
Geographical variation in sexual selection on tail streamers
All of the above studies were conducted in European populations of H. r. rustica. However, there are five other Barn Swallow subspecies, and there is mounting evidence that the function of tail streamers is not the same in all groups. This may to some extent be predicted by variation in streamer length among subspecies: for example, despite some latitudinal variation, tail streamers are on average shorter in North American than European populations, and the extent of sexual dimorphism in streamer length is much reduced (Safran and McGraw ). This leads to the a priori suggestion that this trait may be subject to weaker sexual selection in North America compared to Europe.
Available correlational and experimental data generally bear out this prediction. For example, in contrast to European H. r. rustica, streamer variation in males and females did not significantly predict patterns of assortative pairing in North American H. r. erythrogaster (Safran and McGraw ). Male streamer length was not a significant predictor of measures of seasonal reproductive success in some correlational data sets (Safran and McGraw ; Neuman et al. ), but in a Canadian population males with naturally long streamers bred earlier (Smith and Montgomerie ) and had increased extra-pair mating success compared to shorter-streamered males (Kleven et al. ). In the same Canadian population, a positive correlation was found between streamer length and fertilization success, but much of this relationship was explained by the age-dependence of streamer length: older males had both greater fertilization success and longer streamers, making it difficult to separate these effects on reproductive success (Lifjeld et al. ).
Additional components of reproductive success vary with respect to streamer length between European and North American populations. In Europe, there is a significant positive association between streamer length and the proportion of offspring sired in first breeding attempts (Saino et al. [1997b]), whereas no such significant association was found between these two variables using the same test statistic in North American population (Neuman et al. ). Likewise, males with longer tails sired more offspring in their own nests in Europe (Saino et al. [1997b]) but the relationship was not significant in North America (Neuman et al. ). A negative correlation was found between the proportion of broods being sired by extra-pair males and the streamer length of the male nest owner in a population in Denmark (Møller and Tegelström ), indicating that longer-tailed males are less likely to be cuckolded, but no such correspondence between a male’s streamer length and his probability of being cuckolded was found in New York with the same test statistic (Neuman et al. ). Finally, a study that replicated the experimental design of Møller’s () tail manipulation study in Europe did not find a significant effect of artificial streamer elongation on male reproductive success in a North American population of swallows (Safran et al. in review).
Despite latitudinal variation in streamer lengths within Europe, the function of streamers, in terms benefits related to social and genetic reproductive success, vary little among European populations of H. r. rustica (Møller ). By contrast, male H. r. erythrogaster with elongated streamers in New York did not obtain the same reproductive benefits as males with elongated streamers in Italy (see above). Considered in concert, the results of studies in North America and Europe demonstrate that the pattern of sexual selection on tail streamers varies among subspecies.
Two other Barn Swallow subspecies have been the subjects of additional sexual selection studies: H. r. transitiva in Israel, and H. r. gutturalis in Japan. Again, there appears to be variation in sexual selection on tail streamers among these subspecies. Male H. r. transitiva have tail streamers that are nearly as long as those in H. r. rustica, and, accordingly, males with longer streamers breed earlier and have fewer extra pair young in their nests in both correlational (Vortman et al. ) and experimental (Vortman et al. ) studies. By contrast, male H. r. gutturalis, which have much shorter streamers than H. r. rustica and H. r. transitiva, do not gain any significant reproductive benefits based on tail length in correlational datasets (Kojima et al. ; Hasegawa et al. ).
Ventral coloration in North America
Although North American swallows have shorter tail streamers than their European counterparts, they have much darker ventral coloration. Accordingly, ventral coloration, not streamer length, was found to correlate with patterns of pairing and seasonal reproductive success in two populations of North American Barn Swallows (Safran and McGraw ; Neuman et al. ; Eikenaar et al. [2011a]), but not in another (Lifjeld et al. ), suggesting that darker coloration may be a target of mate choice in some H. r. erythrogaster populations. Experimental manipulations of male coloration further demonstrated that females use ventral color to assess male quality. In North American populations, males with experimentally darkened ventral color gained greater paternity relative to the amount obtained in their first breeding attempts, prior to the color manipulation (Safran et al. ), but experimentally elongated tail streamers did not predict increased paternity allocation; in fact, males with reduced streamer lengths actually obtained greater paternity (Safran et al. in review).
It is unclear why females favor the use of color for mate selection in some populations and streamer length in others. Feather color in Barn Swallows is not as obvious a “costly signal” as elongated streamers, as darker ventral color probably doesn’t hinder foraging ability, and darker birds are unlikely to be more conspicuous to predators (as is the case for some costly, bright-colored signals). There is evidence in other systems that bright red and orange carotenoid-based colors are costly and/or honest signals, because carotenoid pigments must be obtained from the diet and physiologically modified before deposition in tissues (reviewed in Hill and McGraw ). However, the orange-brown throat and ventral color in Barn Swallows is caused by eu- and phaeomelanin pigments rather than carotenoids, which can be synthesized endogenously (McGraw et al. ) and are not generally believed to be costly to produce (Hubbard et al. ). However, recent studies have revealed that there may indeed be costs to deposition of melanin pigments. In addition to stimulating melanogenesis in external tissue, the melanocortin pathway serves non-signaling functions such as regulation of stress and immune responses via binding of peptide derivatives to different melanocortin receptors (Ducrest et al. ). Allocation of melanocortins to different receptors may result in a tradeoff between pigment deposition and hormonal function (e.g. Roulin et al. ). Melanin-based signals can also be sensitive to oxidative stress (Galván and Alonso-Alvarez , ), and thus have the potential to function as an honest signal of antioxidant levels.
Several recent studies have illuminated some of the physiological mechanisms underlying color variation, and shed light on the type of information that darker males may be signaling to prospective mates and competitors. Dark melanin pigmentation appears to be linked to hormonal state: in North American populations, artificially darkened females adjusted their physiological state to have lower levels of testosterone and reactive oxidative metabolites than prior to manipulation (Vitousek et al. ). Likewise, naturally darker males were found to have higher levels of circulating testosterone, and experimentally darkening an individual’s color increased his testosterone levels (Safran et al. ). These experimental findings demonstrate feedbacks between external phenotype and physiological state: experimentally darkened birds likely had different types of social interactions than when they had lighter feathers, resulting in an adjustment of hormonal state to match their new phenotype.
It may be beneficial for naturally dark-colored males to advertise their high levels of testosterone. If these dark, high-testosterone males are more aggressive, they could be more competitive in obtaining high quality nesting territories early in the breeding season (Safran et al. ), making them more attractive to females. Indeed, females paired to darker males increased feeding rates of their chicks, although dark males themselves did not give more paternal care than lighter males (Maguire and Safran ). This finding suggests that females invest more in their offspring when paired to attractive mates. If darker males can obtain and defend better nest sites, this represents a direct benefit to their mates; however, there is also a potential cost in that high-testosterone males tend to be poorer parents in both Barn Swallows and other bird species (e.g., Ketterson et al. ; Saino and Møller [1995a], but see Eikenaar et al. [2011b]). In both Europe and North America, therefore, there is evidence that the main target of female choice (tail length and ventral color, respectively) is linked to high levels of circulating testosterone and may advertise a male’s competitive ability. Dark coloration in North America is also heritable to some extent (Hubbard et al. in review), suggesting that females paired to dark colored males may obtain indirect benefits in the form of attractive offspring.
Plumage coloration in other populations
Darker ventral color is also associated with greater breeding success in Middle Eastern swallows (H. r. transitiva), a subspecies that exhibits elongated tail streamers and dark ventral color. Experimental work in this subspecies has shown that both ventral color and tail streamer length predict different aspects of breeding success, with darker males raising more young over the course of a season, and males with longer tail streamers breeding earlier and having fewer extra-pair chicks in their nests (Vortman et al. , ).
Ventral color needn’t be the only target of sexual selection on plumage- indeed, in a subspecies with pale ventral coloration, it appears that the size of the dark orange-brown throat patch is the trait most preferred by females. In a Japanese population of H. r. gutturalis, females preferred males with larger throat patches, and, accordingly, the throat patch is on average twice as large in H. r. gutturalis as in the closely related H. r. rustica (Hasegawa et al. ; Hasegawa and Arai [2013a]). Males with larger, darker throat patches obtained high-quality females who initiated clutches earlier than females paired to lighter males (Hasegawa et al. , Hasegawa and Arai [2013b]). Darker-throated males also had greater survival probability (Hasegawa et al. ), and obtained higher quality territories and reduced their paternal care (Hasegawa et al. ), relative to small- and pale-throated males. Male tail streamer length was linked to survival rate but unrelated to measures of reproductive success (Kojima et al. ; Hasegawa et al. ), consistent with the relatively short length of male streamers in this population.
Studies of melanin-based coloration in European populations of Barn Swallows have thus far focused primarily on the potential for melanic signals to advertise information about viability, immunocompetence, and stress. These populations have paler ventral coloration in comparison to males in other subspecies (e.g., H. r. gutturalis, H. r. transitiva, and H. r. erythrogaster), and studies show that paler males have higher survival between years (Saino et al. [2013b]). Moreover, naturally paler birds have a stronger primary immune response, but not cell-mediated immune response (Saino et al. [2013a]), suggesting a possible immune cost to darker ventral plumage in this population. If darker coloration is associated with poorer immune response, this may be an important source of “honesty” in melanin-based signals. Interestingly, although birds with darker ventral color have a weaker immune response, individuals with darker throat color have higher survival in a Danish population (Galván and Møller ), similar to Japanese H. r. gutturalis (Hasegawa et al. ). Melanic throat color is heritable in Italian populations (Saino et al. [2013c]), suggesting that different color patches could advertise different information.
There may also be a relationship between the stress hormone corticosterone and coloration, but this only emerged in experimentally stress-reduced males in Europe (i.e., among males with artificially reduced brood sizes, paler males had less corticosterone and may thus have been less stressed, Saino et al. [2013a]). Moreover, a North American study of melanin color in males (both nestlings and adults) found no correlation between color and different measures of corticosterone (Jenkins et al. ). The relationship between stress and melanin-based color thus remains unclear. Some of the complication in interpreting the costs of melanin production and deposition comes from the different physiological pathways associated with producing eu- vs. phaeomelanin (Saino et al. [2013a], [b]), which remain poorly understood in most natural populations. Additionally, feathers are a static signal that likely reflect the hormonal state of the individual when the feathers were grown; thus, measuring hormones months after the trait has developed may not provide useful information about the costs or benefits being signaled. Further research on the relative signaling roles of the two different melanin pigments, as well as on temporal variation in hormone responses, will help elucidate the role of melanin-based ornaments in sexual selection.
Additional plumage characters that have been the focus of some research are the white spots on the underside of the tail feathers. These are sexually dimorphic, and area of white spots is significantly correlated with streamer length. In European populations, males with experimentally reduced white spot sizes fledged fewer offspring, likely because they were less likely to have second broods (Kose and Møller ). The white portions of the feather are more prone to breakage (Kose and Møller ) and are also the preferred feeding sites of feather lice, although males with larger white spots have fewer lice (Kose et al. ). This suggests white spots could signal ectoparasite infestations (Kose et al. ). In Japanese H. r. gutturalis, males with larger white tail spots bred earlier in the season, suggesting this trait may be sexually selected in these populations as well (Hasegawa et al. ).
Song in mate choice and male competition
Studies of European Barn Swallow song suggest that different song features serve different functions and advertise different information. For example, males with more neighbors produced longer rattles, and shorter, less complex songs; additionally, males with longer rattles had higher levels of circulating testosterone, and these song features may therefore be involved in competitive interactions (Galeotti et al. ). Further, experiments showed that males with artificially elongated tails produced longer rattles (Saino et al. ), and immune challenged males reduced the lengths of their rattles (Dreiss et al. ), indicating that this trait is somewhat plastic and can respond to social and physiological cues. Longer rattles and longer tails are both linked to higher levels of circulating testosterone (Saino and Møller ; Galeotti et al. , respectively), suggesting that a hormone-mediated social feedback loop similar to the one demonstrated with color in North American birds (Safran et al. ; Vitousek et al. ) may exist for song as well.
There is also some evidence that females consider song in mating decisions. Males with both long tails and higher song rates had fewer extra pair young in their nests (Møller et al. [1998b]); however, the effect of tail was much more important in this relationship, indicating that short-tailed males cannot compensate for their unattractiveness by singing at higher rates. Additionally, males that sang overall longer songs paired more successfully and had lower ectoparasite loads (Garamszegi et al. ). Together, these data suggest that in European populations, some song components are used in territory defense and intrasexual competition, while other components may advertise condition and have a role in mate choice. Since clear links between tail streamer length and male-male competition have not been demonstrated in H. r. rustica (e.g. Saino and Møller [1995b]), males may use different signaling modalities to communicate with potential mates vs. competitors.
Thus far there has been little research on song in non-European Barn Swallow populations. However, recent work in North America found that some song features are important for male-male competition and while other components are used in female choice (Wilkins ), possibly implicating a greater role for song in mate choice in this short-streamered subspecies. Future comparative work on the information conveyed by song and melanin-based traits should further illuminate the costs and benefits associated with different types of signals across subspecies.
From geographic variation in sexual selection to speciation
It is clear that many traits, at least some of which are sexually selected, vary among the different Barn Swallow subspecies. But what causes geographic variation in phenotype? And what are the consequences of this variation for population divergence and speciation? Answering these questions entails examining the roles of selective and non-selective processes in shaping phenotypic variation and patterns of reproductive isolation. New species form when individuals from different populations no longer recognize one another as potential mates, or opportunities for mating become limited by differences in habitat use or reproductive schedules (Mayr ). In these cases, individuals are reproductively isolated and thus do not exchange genes; this is the first step towards speciation. Work in the field of speciation frequently focuses on identifying the processes that create barriers to gene flow among divergent populations. In this section we discuss the potential roles of natural selection, sexual selection, and drift in forming these barriers and driving phenotypic and population divergence in the Barn Swallow complex.
Speciation by natural selection, or “ecological speciation”, occurs when populations living in different environments undergo adaptive evolutionary change via divergent natural selection. This process can form barriers to gene flow when divergent selection results in individuals being physically isolated from each other (i.e., in different ecological niches) or on different reproductive schedules (reviewed in Nosil ). Ecological speciation can often be inferred if ecologically divergent pairs of populations exhibit greater reproductive isolation than ecologically similar pairs of populations of similar age (e.g. Funk et al. ). Moreover, in cases of ecological speciation, the traits involved in divergent ecological adaptation should also contribute to reproductive isolation, and levels of gene flow in nature should decrease as ecological differences between populations increase (Nosil ).
Reproductive isolation can also emerge via divergent sexual selection (Panhuis et al. ; Ritchie ). In this scenario, divergence in traits related to reproductive success contributes to barriers to gene flow among populations. If reproductive isolation is caused by divergent sexual selection, pairs of populations might be expected to be ecologically similar but possess divergent mating traits (Panhuis et al. ).
Controversy has surrounded the role of sexual selection in speciation, particularly with respect to its relationship with divergent natural selection. At the center of this discussion is whether sexual selection alone can drive speciation, or whether ecological divergence is a prerequisite for the completion of reproductive isolation (Panhuis et al. ; Bussière et al. ; Safran et al. ). Although there are some cases in which sexual or natural selection is the dominant process driving divergence (reviewed in (Kraaijeveld et al. )), the most common scenario is that sexual and natural selection act together to drive variation in the traits used in reproductive isolation (Safran et al. ; Scordato et al. ). The pertinent question then becomes not which process is most important in causing speciation, but how the two processes interact, how the phenotypic traits used in mate selection and reproductive isolation are shaped by this interaction, and if interactions are consistent or predictable across systems (Arnegard et al. ; Wagner et al. ; Safran et al. ).
Finally, some models of speciation do not include selection as a driver of divergence and reproductive isolation, but rather invoke a key role for chance events. These cases include speciation by genetic drift and founder-events/population bottlenecks. Although such models have a long history in speciation research, for example in the context of small populations colonizing islands, clear empirical support is relatively limited (reviewed in Coyne and Orr ). However, when examining the causes of divergence and reproductive isolation among populations, adaptive divergence via selection cannot be assumed, and ruling out a role for random processes is critical.
Divergent ecological and sexual selection in Barn Swallows
Because the Barn Swallow complex has been the subject of extensive sexual selection research for decades and has several phenotypically variable subspecies that are tractable subjects for field studies, it is an ideal system in which to investigate the relative roles of ecological selection, sexual selection, and random processes in population divergence.
Several ecological variables could contribute to population and phenotypic divergence in Barn Swallows. There is variation in migratory distance among subspecies: some subspecies embark on migrations of many thousands of miles (i.e. European and North American populations), where as others are short-distance migrants or entirely sedentary (Middle Eastern populations; Møller [1994a]; Turner ). Variation in migratory distance can exert natural selection on morphological factors like body size (Alerstam et al. ) and the shape of the wings (Mönkkönen ; Lockwood et al. ). Moreover, different wintering grounds and migratory routes can result in variation in the length and timing of the breeding season: birds that migrate longer distances typically have shorter and more synchronous breeding seasons than short-distance migrants (Garamszegi et al. ), which can translate into variation in selection on life history traits such as clutch size and incubation time, as well as mating strategies and parental care. Divergence in any of these traits could contribute to reproductive barriers, particularly if hybrids are unfit; for example, there is some evidence that the hybrid offspring of populations with different migratory pathways follow intermediate and maladaptive migration routes (Irwin ).
Geographic variation in sexual selection pressures may also drive phenotypic divergence and generate reproductive barriers in Barn Swallows. As we have discussed in this review, decades of work on the different sexually selected traits in this species show that the relative roles of streamer length, coloration, and possibly song in mate choice and male-male competition vary among subspecies. Even among European populations there is variation the strength of selection on tail length, although it remains consistently positive among populations (Møller et al. ). Likewise, the information conveyed by these traits varies geographically, with some evidence suggesting that long tail streamers in Europe advertise indirect benefits (Møller [1994a]; Møller et al. [1998a]); but see (Bro-Jørgensen et al. ) for alternative explanations), whereas coloration has been suggested to advertise direct and indirect benefits in Japan(Kojima et al. ; Hasegawa et al. ), and could relate to both direct and indirect benefits in North America (Safran and McGraw ; Safran et al. ). If the relative importance of different types of benefits varies among populations, this may result in mate choice, and consequent directional selection, on different traits, leading to phenotypic divergence and reproductive isolation based on sexually selected signals.
There is some evidence that sexually selected traits act as reproductive barriers in Barn Swallows: in an Israeli population of H. r. transitiva, males with color and tail length manipulated to look like the geographically proximate H. r. savignii were not attractive to females, suggesting there may be some selection against heterotypic matings in this populations (Vortman et al. ). These reproductive barriers are not complete, however: there is evidence for hybridization between H. r. rustica and H. r. tytleri in central Siberia, between H. r. tytleri and H. r. gutturalis in eastern Siberia (Turner ), and between H. r. rustica and H. r. transitiva in Israel (Dor et al. ), despite morphological differences between all these subspecies. Hybridization, if substantial, has the potential to reverse incipient differences among Barn Swallow subspecies. For example, it has been suggested that formerly geographically isolated subspecies in Asia may have been brought into contact by recent human settlement (Turner ). If reproductive barriers are porous, there may be an eventual loss of differentiation between subspecies, resulting in a uniform hybrid swarm.
To understand the action of ecological and sexual selection and their relative roles in generating (or breaking down) reproductive barriers, we ultimately need to study the substrates on which selection acts; that is, sexually and naturally selected traits and, in the case of sexual selection, their associated preferences. Future work explicitly measuring natural and sexual selection on different aspects of the phenotype will continue to shed light on how these processes operate in the Barn Swallow system. New techniques for obtaining genome-wide estimates of selection are greatly advancing our ability to study the loci involved in reproductive isolation and identify signatures of divergence via adaptation versus random processes.
Conclusions and future directions
Here we have reviewed sexual selection research in Barn Swallows dating back nearly 30 years. Although this vast body of work has made Barn Swallows a model system in evolutionary biology, recent comparative studies show that much remains to be discovered in this species complex. Future comparative research addressing the relative roles of tail streamers, plumage coloration, and song in mating decisions across the different subspecies, as well as determining the information conveyed by these different signals, would help illuminate why the targets of female preferences appear to vary geographically. This work would be enhanced by ecological studies that focus on how different mating traits are shaped by natural selection as well as sexual selection, and by carefully designed experiments that can test the relative contributions of different selective processes to variation within and among subspecies. Finally, advances in genomic methods for detecting ongoing gene flow and the genetic basis of reproductive isolation present the possibility of studying reproductive barriers and causes of diversification among the different subspecies. Integrations of experimental, geographic, ecological, and genomic approaches are likely to yield new insight into sexual selection and speciation in the Barn Swallow complex over the coming decades.
We thank W. Liang for the invitation to write this review, and A. Hund and M. Wilkins for comments on the manuscript. Support was provided by the National Science Foundation (DEB-CAREER 1149942 to RJS).
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Large Eddy Simulation
The behaviour of fluids can be described by the well-known mathematical model known as the Navier-Stokes equations. The original equations include formulations for the conservation of momentum, energy and mass, therefore leading to three momentum equations, one energy equation and one continuity equation. The form presented below is a simplification of these equations for incompressible flows and a constant viscosity. For a detailed derivation of the Navier-Stokes equations as well as the simplifications applied for incompressibility, many textbooks on fluid dynamics are available, eg. , or .
KeywordsResidual Stress Turbulence Model Large Eddy Simulation Momentum Equation Direct Numerical Simulation
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Daily news articles relating Drought. The Earth times and pollution with daily updates on breaking news. Stay informed, learn how you can take action to reverse global warming. A drought is a period of below-average precipitation in a given region, resulting in prolonged shortages in the water supply, whether atmospheric, surface water or ground water. A drought can last for months or years, or may be declared after as few as 15 days. It can have a substantial impact on the ecosystem and agriculture of the affected region and harm to the local economy. Annual dry seasons in the tropics significantly increase the chances of a drought developing and subsequent bush fires. Periods of heat can significantly worsen drought conditions by hastening evaporation of water vapour. Many plant species, such as those in the family Cactaceae (or cacti), have drought tolerance adaptations like reduced leaf area and waxy cuticles to enhance their ability to tolerate drought. Some others survive dry periods as buried seeds. Semi-permanent drought produces arid biomes such as deserts and grasslands. Prolonged droughts have caused mass migrations and humanitarian crisis. Most arid ecosystems have inherently low productivity. The most prolonged drought ever in the world in recorded history occurred in the Atacama Desert in Chile (400 Years). >> Tell Us << You are witnessing of Pollution, tell us how you feel after witnessing this major event in history of the earth. | <urn:uuid:f96ca746-f3b4-4fc5-8890-6631fb2e48db> | 3.65625 | 289 | Knowledge Article | Science & Tech. | 36.985615 | 95,629,313 |
Is the Earth actually a living 'creature'? Chemical clues could finally prove claims our planet is a single organic system
- 'Gaia Hypothesis' claims earth is self-regulating 'organic' system that maintains life
- Sulphur could be key to understanding cycles of Earth
- Gaia idea initially scorned by scientists but now taken seriously
In the 70s, James Lovelock and Lynn Margulis claimed that Earth's physical and biological processes 'link' to form a self-regulating, basically 'self-aware' system
In the 70s, James Lovelock and Lynn Margulis claimed that Earth's physical and biological processes 'link' to form a self-regulating, basically 'self-aware' system.
Their book became a cult classic, and the idea that the Earth is a giant chemical system, almost like an 'organism' persists to this day - although it's never been proved.
In 2010, a poll of 400 academics placed the Gaia Hypothesis the sixth greatest British academic breakthrough of all time.
Now a new chemical clue - sulphur - could allow scientists to work out whether Earth is in fact 'alive' - a huge chemical system that in turn sustains us all.
The Gaia hypothesis doesn't claim that the earth is actually 'alive' - but that all living organisms and their non-living surroundings are bound together into a 'system' that maintains the conditions for life.
One of the early predictions of Lovelock's theory - known as the Gaia - hypothesis was that there should be a sulphur compound made by organisms in the oceans that would transfer to the air and thus to the land.
Scientists are on the brink of testing this theory - and proving the existence of at least one part of a 'system' of the Earth.
The most likely candidate for this role was deemed to be dimethyl sulphide.
Harry Oduro of the University of Maryland has created a tool for tracing and measuring the movement of sulphur through ocean organisms, the atmosphere and the land in ways that may help prove or disprove the controversial Gaia theory.
Sulphur, the tenth most abundant element in the universe, is part of many inorganic and organic compounds.
Sulphur cycles sulphur through the land, atmosphere and living things and plays critical roles in both climate and in the health of organisms and ecosystems.
‘Dimethylsulfide emissions play a role in climate regulation through transformation to aerosols that are thought to influence the earth's radiation balance,’ says Oduro, who conducted the research while completing a Ph.D. in geology & earth system sciences at Maryland and now is a postdoctoral fellow at the Massachusetts Institute of Technology.
Their book became a cult classic, and the idea that the Earth is a giant 'organism' persists to this day - although it's never been proved
IS THE EARTH REALLY 'ALIVE'? THE 'GAIA HYPOTHESIS'
The Gaia hypothesis - first proposed in the 70s - doesn't claim that the earth is actually 'alive' - but that all living organisms and their non-living surroundings are bound together into a 'system' that maintains the conditions for life.
It was initially scorned by scientists, but is now being seriously investigated by Earth scientists and scientists in other disciplines - observing how the evolution of life have contributed to the stability of temperature and ocean salinity.
It's also inspired various political and religious movements - with many interpreting the hypothesis as a claim that the Earth actually IS alive.
'We show that differences in composition of dimethylsulfide may vary in ways that will help us to refine estimates of its emission into the atmosphere and of its cycling in the oceans.’
As with many other chemical elements, sulphur consists of different isotopes.
All isotopes of an element are characterised by having the same number of electrons and protons but different numbers of neutrons.
Therefore, isotopes of an element are characterized by identical chemical properties, but different mass and nuclear properties.
As a result, it can be possible for scientists to use unique combinations of an element's radioactive isotopes as isotopic signatures through which compounds with that element can be traced.
‘Harry's work establishes that we should expect to see variability in the sulfur isotope signatures of these compounds in the oceans under different environmental conditions and for different organisms,' says UMD geochemist James Farquhar.
'I think this will ultimately be very important for using isotopes to trace the cycling of these compounds in the surface oceans as well as the flux of dimethylsulfide to the atmosphere. It may even help us to better trace connections between dimethylsulfide emissions and sulfate aerosols, ultimately testing a coupling in the Gaia hypothesis,’ Farquhar says
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Conducting polymers can be exploited as an excellent tool for the preparation of nanocomposites with nano-scaled biomolecules. Polypyrrole (Ppy) is one of the most extensively used conducting polymers in design of bioanalytical sensors. In this review article significant attention is paid to immobilization of biologically active molecules within Ppy during electrochemical deposition of this polymer. Such unique properties of this polymer as prevention of some undesirable electrochemical interactions and facilitation of electron transfer from some redox enzymes are discussed. Recent advances in application of polypyrrole in immunosensors and DNA sensors are presented. Some new electrochemical target DNA and target protein detection methods based on changes of semiconducting properties of electrochemically generated Ppy doped by affinity agents are introduced. Recent progress and problems in development of molecularly imprinted polypyrrole are considered. (c) 2006 Elsevier Ltd. All rights reserved.
Mendeley saves you time finding and organizing research
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Robot probe Philae uploaded a slew of data to Earth Friday from a deep-space comet that it drilled into long after its onboard battery was feared to have died.
Data started streaming in as soon as late-night contact was reestablished between Europe’s robot lab and its orbiting mothership Rosetta — ending an anxious wait by mission controllers worried they might never hear from it again.
Philae’s data collection from a comet travelling at 18 kilometres (11 miles) per second, currently at a distance of 510 million kilometres (320 million miles) from Earth, crowns a 10-year mission to study the origins of Solar System some 4.6 billion years ago, and maybe even life on Earth.
“Science from an alien world” said an official tweet from ESA (European Space Agency) Operations around 2300 GMT. “Info now flowing from .”
In the latest in a series of jaw-dropping achievements, the robot lab which landed in a dark ditch after a bouncy touchdown Wednesday, also managed to lift itself four centimetres (1.5 inches) and rotate its solar panels to absorb as much energy as possible to be stored for a possible wakeup later.
It was too late to recharge Philae’s batteries sufficiently for an immediate life extension, and the lander was expected to go into hibernation very soon.
“So much hard work…getting tired… my battery voltage is approaching the limit soon now,” said a tweet around midnight GMT.
But mission engineers hope they may be able to revive the lander for renewed contact in the coming months as the comet, with Philae still perched on its surface, moves closer to the Sun.
Philae landed Wednesday after a nail-biting seven-hour, 20-km descent from Rosetta, which had travelled more than a decade and 6.5 billion kilometres (four billion miles) to meet up with comet 67P/Churyumov-Gerasimenko in August this year.
The touchdown did not go entirely as planned, when Philae’s duo of anchoring harpoons failed to deploy and it lifted off again twice.
The lander finally settled in a crevice in a location that remains a mystery, but data revealed it was shadowed from battery-boosting sunlight that could have extended its 60-hour core mission.
– ‘First comet drilling’ –
Among the most anticipated data from Philae is chemical analysis of a sub-surface drill sample which scientists hope will shed light on the origins of the Solar System 4.6 billion years ago, and maybe even life on Earth.
The ESA confirmed that Philae had drilled into the comet Friday, though it did not specify whether a sample had been obtained.
“I confirm that my (drill) went all the way DOWN and UP again!!” said a tweet in the robot’s name. “First comet drilling is a fact!”
The lander and its mothership, which relays Philae’s messages to Earth, have only two communications windows per day — the last opened around 2130 GMT Friday.
Mission managers on Earth had to wait hours after the morning window closed to see whether the probe would have enough power from its fading 60-hour onboard battery to check in one last time.
The Rosetta-Philae team said Friday they were ecstatic with the results.
All 10 instruments on board the 100-kilogramme (220-pound) lab kicked into action, enabling Philae to send back the first-ever photos taken on a comet, and probed its surface density, temperature and composition.
The 1.3-billion-euro ($1.6-billion) mission aims to unlock the secrets of comets, which some astrophysicists believe may have “seeded” Earth with some of the ingredients for life.
Rosetta, with Philae riding piggyback, was hoisted into space in 2004, and reached its target in August this year, having used the gravitational pull of Earth and Mars as slingshots to build up speed. | <urn:uuid:79fe9923-0627-405e-ace8-82fbba9ed098> | 3.03125 | 855 | News Article | Science & Tech. | 51.629585 | 95,629,348 |
Public sightings suggest increase in basking sharks in British waters
Public sightings suggest increase in basking sharks in British waters MCS data reveals more people are spotting these marine giants - and they’re getting bigger! The number of basking sharks recorded in Britain’s seas could be increasing, decades after being protected from commercial hunting in the late 20th century.
Public sightings suggest increase in basking sharks in British waters MCS data reveals more people are spotting these marine giants - and they’re getting bigger! The number of basking sharks recorded in Britain’s seas could be increasing, decades after being protected from commercial hunting in the late 20th century. The most comprehensive analysis ever undertaken of basking shark sightings in UK waters, by the University of Exeter, MCS, Cornwall Wildlife Trust (CWT) and Wave Action, is published in the journal Marine Ecology Progress Series. The northeast Atlantic hosted an extensive commercial fishery for basking sharks, mainly in Norway, Ireland and Scotland, where more than 81,000 were killed between 1952 and 2004, hunted largely for their liver oil. Large-scale hunting ended in the UK in the middle of the twentieth century, though it continued at low levels in Norway until 2000. Protected under UK legislation since 1998 and more recently under international conservation agreements, basking sharks are regularly seen off the coast of the UK during the summer, but very little is known about where and how they live for the rest of the year. The research team set about understanding patterns in summer basking shark sightings in UK waters. They analysed 20-years-worth of data from public sightings - a total of 11,781 records - from databases generated by MCS and Cornwall Wildlife Trust. They combined these data with records from dedicated boat-based basking shark surveys to complete the largest study of its kind. Their analysis showed a rise in the number of sightings from the 1980s through to the 2000’s. It also suggests an increase in the proportion of medium and large-sized animals, suggesting an increase in the number of older sharks. Basking shark populations are believed to recover slowly from over-exploitation due to their slow growth to maturity and the relatively few offspring they produce in comparison to other fish species. These new results show that long-term protection may well be paying off, with UK basking shark populations showing increasing body size: a classic sign of recovery for over-exploited fish stocks. The researchers identified three hotspots for sightings off the coasts of South West England, Western Scotland and the Isle of Man. Each year, the earliest records were of sharks off South West England’s coastline in April, with the latest being in Scottish waters in August. This could mean that sharks are moving northwards during the summer, possibly following the arrival of the plankton which they feed on, or may suggest the existence of different groups of sharks in each location. Dr Jean Luc Solandt, Senior Biodiversity Policy Officer.of the Marine Conservation Society said: “These exciting results show that long-term protection for basking sharks seems to be paying off - great news to celebrate the 25th anniversary of MCS Basking Shark Watch, which has been supported by thousands of people across the UK. It is only through public participation that we can see this positive change - citizen science works! The industrial demand for basking shark oil is now over, but the large basking shark gatherings we see each summer in our seas are proving to be popular wildlife spectacles. This conservation success means that these harmless giants will be here to be enjoyed by generations to come.” Professor Brendan Godley of the University of Exeter’s Centre for Ecology and Conservation said: “Our research shows that basking sharks could be recovering from the extensive hunting that took place in the 20th century. We are also helping to shed light on their key habitats in British waters: important information as the use of our seas changes and grows. It is notoriously challenging to carry out long-term monitoring of marine wildlife but with the help of many hundreds of volunteers reporting their records, we have made a leap forward. Anyone who has had the experience of seeing a basking shark from our coastline will know what awe-inspiring creatures they are and our research suggests that more of us may be fortunate enough to see them in the future.” Ruth Williams, Marine Conservation Manager for Cornwall Wildlife Trust said: “This research has proved the value of data collected by members of the public and our volunteers, and highlights the importance of public engagement with such recording schemes. It is hugely encouraging to see the positive trend in numbers of basking sharks in our waters. Collaborative working between conservation organisations and academic institutions makes the most of available resources and the results are vital to help us actively conserve and protect these magnificent animals for the future.” This study was funded by the Natural Environment Research Council (NERC).
Actions you can take
Help protect 40% of English seas
Let the government know they must protect our ocean and marine wildlife before it’s too late. | <urn:uuid:f60bb977-6f58-4dbe-b6ed-35ec6ba491f4> | 2.8125 | 1,036 | News (Org.) | Science & Tech. | 36.640696 | 95,629,358 |
An integrated, interdisciplinary, intensive study of three forested watersheds in the Adirondack Park region of New York State was started in 1977 to quantify the relationship between the deposition of atmospheric acids and surface water acidity. A general mechanistic theory of lake-watershed acidification that takes into account the production and consumption of acidity by watershed processes, as well as atmospheric inputs of acidity, was developed. This theory is formulated as a mathematical simulation model.Model and data analyses establish the importance of using an integrated ecosystem perspective to assess the vulnerability of surface waters to acidification by acidic deposition. The acid-base status of surface waters is determined by the interaction of many factors: soil, hydrologic, vegetation, geologic, climatic, atmospheric. The absolute and relative contribution of any given factor can be highly variable, both geographically and temporally; hence, lake sensitivity to changes in the quality and quantity of atmospheric deposition is also highly variable.
Weitere Kapitel dieses Buchs durch Wischen aufrufen
- Integrated Lake-Watershed Acidification Study: Summary
Robert A. Goldstein
Carl W. Chen
Steven A. Gherini
- Springer Netherlands
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Understanding cell segregation mechanisms which help prevent cancer spread
Scientists have uncovered how cells are kept in the right place as the body develops, which may shed light on what causes invasive cancer cells to migrate.
In order for organs to develop properly, cells from different tissues need to be separated by sharp borders that persist throughout our lifetime. The mechanisms that keep cells in the right place are lost in cancer cells, allowing them to invade other cell populations and spread to different tissues.
Researchers at the Francis Crick Institute have worked out how major players in border formation between tissues — cell-surface proteins called ephrins and their Eph receptors — keep cells in the right places. The findings are published in The Journal of the Royal Society Interface.
In many tissues, ephrins are present in one cell population and Eph receptors in the other. When these cells come into contact, ephrins bind to their receptors, triggering signalling inside both cells that stops them from mixing. However, it was not previously known whether this was because cells preferentially stick to 'like' cells of the same type, if they repelled other 'non-like' cells, or both.
To investigate this problem, the team labelled ephrin-expressing and receptor-expressing cells with different fluorescent colours, mixed them together, and observed their interactions under a microscope as the two populations separated out.
The team used their measurements to develop a computer model of the cell interactions to help understand how they become organised.
"We found that when cells of different types contacted each other, they rebounded in opposite directions," says co-author Anaïs Khuong, Postdoctoral Training Fellow at the Francis Crick Institute. "Our simulations suggest that this repulsion is the main force separating the cell types to form sharp borders."
The team also found that when they reduced the expression of a molecule called N-cadherin that keeps 'like' cells together, the different cell types did not separate as normal. Instead, 'like' cells repelled each other and broke into small clusters that mixed with 'non-like' cells. These findings were replicated in the computer simulations and suggest that under normal circumstances, N-cadherin suppresses repulsion between 'like' cells. This suppression is vital for 'like' cells to stick together, and to prevent them from invading 'non-like' cells enabling a sharp border to form between different cell populations.
Co-senior author David Wilkinson, Group Leader of the Neural Development Lab at the Francis Crick Institute, says: "This collaborative research between mathematical biology and developmental biology has given us new insights into how ephrins and their receptors work to keep cells in the right places, and the critical role of N-cadherin to keep like-cells together. Understanding how this signalling works will help us to figure out what might be going wrong in cancer cells to allow them to cross borders and spread through the body. Scientists are looking at potential therapeutic effects of targeting ephrin-signalling in tumours."
Co-senior author Willie Taylor, Group Leader of the Computational Cell and Molecular Biology Lab at the Francis Crick Institute, says "The collaborative ethos of the Institute brought about this project, when we realised that simulations that I had developed for interactions of molecules could be adapted to model cell interactions. The environment at the Crick is enhancing such collaboration between labs."
The paper 'Cell segregation and border sharpening by Eph receptor: ephrin-mediated heterotypic repulsion' is published in The Journal of the Royal Society Interface. | <urn:uuid:78b2960e-3819-4ff7-9cd6-b8fc53240e8b> | 4.0625 | 738 | News Article | Science & Tech. | 28.379357 | 95,629,371 |
Genetic Variability in Cell Bank Lots
News Jul 27, 2016
In a surprise finding, researchers working with breast cancer cells purchased at the same time from the same cell bank discovered that the cells responded differently to chemicals, even though the researchers had not detected any difference when they tested them for authenticity at the time of purchase.
Had the cells been the same, the exposure to chemicals would have produced similar results in the cells. Instead, identical experiments in two different laboratories – one at the Johns Hopkins Bloomberg School of Public Health and another at Brown University – produced very different results, even when the researchers swapped out the cells and replicated their experiment to rule out issues at the respective laboratories. Upon further testing, however, the researchers discovered that the cells had been genetically different from the time they acquired them.
Researchers have long worked under the assumption that cells purchased from the same lot of a cell bank are clones — after all, they presumably result from divisions of a single cell, and therefore should all carry the same DNA. The reliability of cells is the foundation of much scientific research.
The findings, being published online July 26 in the journal Scientific Reports and discussed at the EuroScience Open Forum (ESOF) in Manchester, England, were made by a research team led by scientists at the Johns Hopkins Bloomberg School of Public Health. Even if this was one bad batch, the discovery raises uncertainty about the reproducibility of experiments using cells that researchers have assumed were the same and contained the same DNA. For the researchers, the flawed cells cost them several years of work and close to $1 million in research funding from the National Institutes of Health.
“Every researcher believes that if they use cells from the same line of cells, particularly cells from the same lot of a cell bank, then they have clones that should look and act the same,” says study leader Thomas Hartung, MD, PhD, a professor in the Bloomberg School’s departments of Environmental Health Sciences and Molecular Microbiology and Immunology. “We learned in this study that that is not always the case.”
Cell irregularities are not unprecedented. Last year, Italian researchers reported instances of genetic instability in another tumor cell line from different laboratories. However, they did not detect instability in cells from the same lot from a single cell bank, as the Bloomberg School researchers did. Separately, three years ago, an international study using the same cell line as the Bloomberg School researchers, also failed because the cells were inconsistent, but this was not traced back to the cell source but blamed on the university laboratories.
The discovery came about when Hartung and other researchers at the Bloomberg School and Brown University were performing experiments for the Human Toxome Project, a large effort led by Hartung and taking place at six study centers across the country to better understand the toxicity of various chemicals by testing them on cell cultures.
For this experiment, the researchers worked with cells from the MCF-7 (Michigan Cancer Foundation-7) line, a well-established breast cancer line isolated in 1970. It has been used in original research published in more than 23,000 scientific articles. Many cancer cell lines, including this one, are “immortalized”—meaning that they’ve lost the natural stop of dividing over time, creating limitless numbers of cells of the same type.
To perform identical experiments at the two different schools, researchers from the Bloomberg School and Brown purchased frozen vials of cells of the same lot from the same cell bank. As a standard precaution to make sure that the cells they’d purchased weren’t contaminated with others of a different type, the researchers at each school performed a test that sampled short segments of the genome, called short tandem repeats. The test suggested that the cells were genetically identical.
However, when the researchers began comparing notes from their experiments, they found that cells at the two different schools looked and behaved in vastly different ways, says Hartung, who also directs the Center for Alternatives to Animal Testing at the Bloomberg School.
The MCF-7 cells at the Bloomberg School grew flat, with a cobblestone-like appearance, while those at Brown grew in large, heap-like aggregations. When the cells were exposed to estrogen, those at Brown proliferated wildly but those at the Bloomberg School remained static. Further tests at the two schools showed that the different batches of cells produced different amounts of metabolic byproducts and had different patterns of gene activation.
As noted above, to rule out whether dissimilarities between the two labs’ techniques were responsible for these variations, the schools swapped cells and tried the experiments again—with identical results to the original experiments at the opposite school.
When the researchers performed another, more thorough test — called comparative genomic hybridization (CGH) — to check for genomic differences, they found that the two batches of cells were riddled with variations, presumably the cause for their host of differences. Fortunately, both laboratories had an additional vial of the same lot as obtained from the cell bank in their freezers that they’d never touched. The big surprise: They already showed the same genetic differences, before they’d been exposed to anything.
The findings shed light on a potentially huge problem for the reproducibility of scientific experiments that use tumor cell cultures, Hartung explains. “This might explain, why three years ago a big international study using this very cell line failed because of lacking reproducibility,” he says.
The results are a call to action for cell banks to rethink quality assurance procedures, Hartung says. By using detailed genetic testing, such as CGH, cell banks and their scientist customers can be reassured that cells from the same lot are indeed genetically identical, helping to reassure that they’ll behave the same in identical experiments.
Hartung and colleagues have previously called for tighter quality controls. In 2005, he led a team that published recommendations for Good Cell Culture Practice aimed at quality standards for cell banks and researchers. These eventually led to the founding of the International Good Cell Culture Practice Collaboration, which has representatives from organizations and agencies from around the world and is formally launching at ESOF 2016.
“It is our goal to develop internationally agreed-upon standards for quality assurance of cell cultures and how we report on our experiments,” Hartung says.
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A key signaling protein, known as heme-regulated inhibitor (HRI), has been identified as a potential therapeutic target for the development of drugs to treat sickle cell disease, using a CRISPR screening approach.READ MORE
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40 subtypes of retinal ganglion cells classified, raising questions about what constitutes a cell type or subtypeREAD MORE | <urn:uuid:1afd08ef-7a65-4e09-a25b-aa0aea4c4056> | 2.59375 | 1,400 | News Article | Science & Tech. | 24.763283 | 95,629,379 |
Researchers study ice to learn about wildfire
August 28, 2017
With the recent occurrence of wildfires on the rise, researchers at the Desert Research Institute in Reno may have uncovered important data in understanding how human-caused climate change compares with what the Earth was like thousands of years ago.
In a study published by the Journal of Geophysical Research last month, scientists identified a link between climate conditions and the concentration of wildfire black carbon emissions found in Antarctic ice cores.
"This is the longest ice core black carbon record published to date, and it tells us a fascinating story about wildfire," said DRI Assistant Research Professor Monica Arienzo in a statement.
In the study, which was funded by the National Science Foundation and NASA, scientists measured b Theylack carbon concentrations in two Antarctic ice cores to understand what was in the atmosphere at the time the snow fell. They compared the findings with other records such as lake and marine sediment to develop a record of air quality dating as far back as 14,000 years ago.
"Our analysis gives us a sense of what climate-fire relationships were like before significant human-caused changes to the climate," said the study's coauthor, Joe McConnell, in a statement. "Knowing what climate-fire relationships were like in the past will help scientists make more accurate climate models because they can account for BC (black carbon) contributions from wildfires in addition to those from human sources."
Black carbon, which is present in soot, is component of particulate matter formed by the incomplete combustion of fossil fuels, biofuels and biomass, according to the Environmental Protection Agency's website.
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The black carbon found in Antarctic ice cores from thousands of years ago, was created by wildfires burning biomass, or plant matter. According to the EPA, humans have since become the leading cause of black carbon emissions into the atmosphere.
"Given that BC (black carbon) emissions from human sources are predicted to increase, our findings are an important factor for climate predictions involving BC (black carbon) impacts," Arienzo said.
Amanda Rhoades is a news, environment and business reporter for the Sierra Sun. She can be reached at email@example.com or 530-550-2653. Follow her on Twitter, Facebook and Instagram @akrhoades.
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Low-voltage electron microscope
Low-voltage electron microscope (LVEM) is an electron microscope which operates at accelerating voltages of a few kiloelectronvolts or less. Traditional electron microscopes use accelerating voltages in the range of 10-1000 keV.
Low voltage imaging in transmitted electrons is possible in many new scanning electron detector.
Low cost alternative is dedicated table top low voltage transmission electron microscope. While its architecture is very similar to a conventional transmission electron microscope, it has a few key changes that enable it to take advantage of a 5 keV electron source, but trading off many advantages of higher voltage operations, including higher resolution, possibility of X-ray microanalysis and EELS, etc... Recently a new low voltage transmission electron microscope has been introduced that operates at variable voltage ranges between 6-25kV.
A substantial decrease of electron energy allows for a significant improvement of contrast of light elements. The comparison images below show that decreasing the acceleration voltage from 80 kV to 5 kV significantly enhances the contrast of test samples. The improved contrast is a direct result of increased electron scattering associated with a reduced accelerating voltage.
LVEM brings an enhancement of imaging contrast nearly twenty times higher than for 100 kV. This is very promising for biological specimens which are composed from light elements and don't exhibit sufficient contrast in classical TEMs.
Further, a relatively low mean free path (15 nm) for organic samples at 5 kV means that for samples with constant thickness, high contrast will be obtained from small variations in density. For example, for 5% contrast in the LVEM bright field image, we will only need to have a difference in density between the phases of 0.07 g/cm3. This means that the usual need to stain polymers for enhanced contrast in the TEM (typically done with osmium or ruthenium tetraoxide) may not be necessary with the low voltage electron microscopy technique.
Stain not required
The improved contrast allows for the significant reduction, or elimination, of the heavy metal negative staining step for TEM imaging of light elements (H, C, N, O, S, P). While staining is beneficial for experiments aimed at high resolution structure determination, it is highly undesirable in certain protein sample preparations, because it could destabilize the protein sample due to its acid pH and relatively high heavy metal concentration. The addition of stain to sectioned samples such as biological materials or polymers can also introduce imaging artifacts.
LVEM experiments carried out on an extracted membrane protein sample that was analyzed with and without the staining procedure show a marked improvement in the appearance of the sample when standard staining is omitted. Results show that LVEM could be even more useful than conventional EM for this particular application because it avoids the potentially disrupting staining step, thus providing an undisturbed image of the protein’s aggregation state.
Additionally, The ability to eliminate the staining step could aid to improve safety in the lab, as common heavy metal stains, such as uranyl acetate do have associated health risks.
The first low-voltage electron microscopes were capable of spatial resolutions of about 2.5 nm in TEM, 2.0 nm in STEM, and 3.0 nm in SEM modes. The SEM resolution has been improved to ~1.2 nm at 800 eV by 2010, while a 0.14 nm TEM resolution at 15 keV has been reported in 2016.
Currently available low voltage microscopes are only able to obtain resolutions of 1.0–3 nanometers. While this is well beyond resolutions possible from optical (light) microscopes, they are not yet able to compete with the atomic resolution obtainable from conventional (higher voltage) electron microscopes.
Low voltage limits the maximum thickness of samples which can be studied in the TEM or STEM mode. Whereas it is about 50-90 nm in conventional TEM, it decreases to around 20–65 nanometers for LVEM @ 5kV. However, thicknesses of the order of 20 nm or less are required to attain the maximal resolution in the TEM and STEM modes 5kV.. These thickness are sometimes achievable with the use of an ultramicrotome.
in 2015 these limitations were overcome with a 25kV low voltage electron microscope that can produce high quality results with thin sectioned samples up to around 100nm+.
- Electron microscope
- Transmission Electron Microscope (TEM)
- High-resolution transmission electron microscopy (HRTEM)
- Scanning electron microscope (SEM)
- Scanning transmission electron microscope (STEM)
- Electron diffraction
LVEM is especially efficient for the following applications.
- LVEM5 from Delong America
- LVEM25 from Delong America
- Nebesářová1, Jana; Vancová, Marie (2007). "How to Observe Small Biological Objects in Low Voltage Electron Microscope". Microscopy and Microanalysis. 13 (3): 248–249. doi:10.1017/S143192760708124X (inactive 2017-02-06).
- Drummy, Lawrence, F.; Yang, Junyan; Martin, David C. (2004). "Low-voltage electron microscopy of polymer and organic molecular thin films". Ultramicroscopy. 99 (4): 247–256. doi:10.1016/j.ultramic.2004.01.011. PMID 15149719.
- Asmar, G.A.; Hanson, M.A.; Ward, A.B.; Lasalde, J.A.; Stevens, R.C.; Potter, C.; Kuhn, P. M. (2004). "Low-Voltage Electron Microscopy (LVEM) as a probe for solubilized membrane protein aggregation states". Microscopy and Microanalysis. 10 (2): 1492–1493. doi:10.1017/S1431927604886069.
- Lundstrom, Kenneth (2006). Structural genomics on membrane proteins. CRC Press. pp. 271–274. ISBN 1-57444-526-X.
- Van Aken, R. H.; Maas, D. J.; Hagen, C. W.; Barth, J. E.; Kruit, P (2010). "Design of an aberration corrected low-voltage SEM". Ultramicroscopy. 110 (11): 1411–9. doi:10.1016/j.ultramic.2010.07.012. PMID 20728276.
- Morishita, Shigeyuki; Mukai, Masaki; Suenaga, Kazu; Sawada, Hidetaka (2016). "Atomic Resolution Imaging at an Ultralow Accelerating Voltage by a Monochromatic Transmission Electron Microscope". Physical Review Letters. 117 (15). doi:10.1103/PhysRevLett.117.153004. | <urn:uuid:349a2da7-c6e5-4db0-9f51-edb2aef92797> | 3.21875 | 1,458 | Knowledge Article | Science & Tech. | 49.100039 | 95,629,418 |
A new study suggests that while NASA is touting its recent discovery of organic molecules on the surface of Mars, the space agency actually first made the discovery more than 40 years ago but accidentally destroyed the proof.
The "ancient organic matter" discovered on the Red Planet represents possible proof "the planet could have supported ancient life" and additional evidence dealing with the question concerning any current life on Mars.
The paper was published in New Scientist, and it suggests that NASA's iconic twin Viking landers may have both been responsible for the discovery and the destruction of it. It highlights the surprise behind the Viking mission's failure to provide proof of organic matter on Mars.
The paper's lead author, Chris McKay is a scientist at the space agency's Ames Research Center in Silicon Valley. He suggests that when testing the soil on the surface of Mars, the Viking landers would heat them to release vapors it could further analyze. McKay believes that when doing this, the landers accidentally ignited a flammable salt called perchlorate.
McKay, in the paper, says they found evidence of chlorobenzene in some soil samples which is a compound only produced when carbon molecules burn with the flammable salt.
The Daily Mail reports Melissa Guzman, a scientist at the LATMOS research center in France, said that the chlorobenzene found in the samples could have come from things carried on the probe from Earth.
"NASA's Viking Project found a place in history when it became the first U.S. mission to land a spacecraft safely on the surface of Mars and return images of the surface," the space agency reports on its website.
"Two identical spacecraft, each consisting of a lander and an orbiter, were built. Each orbiter-lander pair flew together and entered Mars orbit; the landers then separated and descended to the planet's surface."
Viking 1 is said to have made its final transmission to Earth in November 1982, and that the last data received from Viking 2 occurred in April 1980.
This paper published a little more than a month removed from NASA's hyped up announcement that its Curiosity rover found evidence Mars was once able to support "ancient life."
Thomas Zurbuchen, NASA's associate administrator for the Science Mission Directorate, said at the time of the findings that these discoveries should be viewed as Mars "telling us to stay the course and keep searching for evidence of life." The space agency still has not been able to discover the exact source of the organic molecules found.
Jen Eigenbrode, of NASA's Goddard Space Flight Center, has said these findings "bode well" in its attempts to unlock the Red Planet's history and formation.
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3 June 2018 | <urn:uuid:4dbf36e1-e685-4ec1-8fcb-497eb4e71894> | 3.671875 | 562 | News Article | Science & Tech. | 40.698729 | 95,629,427 |
Introduction to Complex Analysis
by W W L Chen
Publisher: Macquarie University 2003
Number of pages: 194
A set of notes suitable for an introduction to some of the basic ideas in complex analysis: complex numbers; foundations of complex analysis; complex differentiation; complex integrals; Cauchy's integral theorem; Cauchy's integral formula; Taylor series, uniqueness and the maximum principle; isolated singularities and Laurent series; Cauchy's integral theorem revisited; residue theory; evaluation of definite integrals; harmonic functions and conformal mappings; Möbius transformations; Schwarz-Christoffel transformations; uniform convergence.
Download or read it online for free here:
by B. Ya. Levin - American Mathematical Society
This monograph aims to expose the main facts of the theory of entire functions and to give their applications in real and functional analysis. The general theory starts with the fundamental results on the growth of entire functions of finite order.
by H. Maass - Tata institute of Fundamental Research
This is an elementary introduction to the theory of modular functions and modular forms. Basic facts from the theory of functions of a complex variable and some properties of the elementary transcendental functions are the only prerequisites.
by E. G. Phillips - Oliver And Boyd
This book is concerned essentially with the application of the methods of the differential and integral calculus to complex numbers. Limitations of space made it necessary for me to confine myself to the more essential aspects of the theory ...
by Alfred Cardew Dixon - Macmillan
This textbook will supply the wants of those students who, for reasons connected with examinations or otherwise, wish to have a knowledge of the elements of Elliptic Functions, not including the Theory of Transformations and the Theta Functions. | <urn:uuid:d66a1290-14d0-4e27-8b75-cc89dc85573f> | 2.703125 | 363 | Content Listing | Science & Tech. | 24.388806 | 95,629,446 |
Crystal structure of Cd2Os2O7The metal-insulator transition (MIT) is a phenomenon in which certain (electricity-conducting) metals make a sudden transition to become a (non-conducting) insulator when cooled below a given temperature. Unlike pure insulators such as silicon and germanium, and pure conductors such as gold and silver, metals with MITs are by their nature unstable and difficult to characterize. This instability is also their strength: complex materials with MITs such as semiconductors form the building blocks for much of our modern technology.
Elucidating the physical basis for MIT, one of the oldest and least well-understood phenomena in condensed matter physics, would shed light on the electron transport properties of a wide range of potentially useful materials. Among these materials, the compound Cd2Os2O7, first discovered more than 30 years ago, has recently attracted renewed attention. Cd2Os2O7 has the intriguing property that when cooled to 227K (-46 °C), it undergoes both a metal-insulator transition and a magnetic transition to a state in which all its electron spins are aligned. This spin alignment, which makes the material magnetic, is useful for a wide array of applications, notably information storage.
Previous efforts to elucidate this magnetic structure, however, have been complicated by another property of Cd2Os2O7: its propensity to absorb neutrons, which interferes with standard neutron scattering techniques used to analyze magnetism. To get around this problem, the researchers employed an alternative technique known as resonant x-ray scattering (RXS) using synchrotron radiation from the RIKEN SPring-8 facility, the world's most powerful synchrotron light source. Their results show that at 227K, Cd2Os2O7 structures itself into a tetrahedral network of osmium atoms with electron spins in each tetrahedron pointing in one of two directions: all inward, or all outward (Figure 1). The structure of this unusual "all-in-all-out" arrangement is such that the spins cancel each other out, so that the material as a whole is not magnetic.
Cd2Os2O7 thus has all the makings of a new kind of information storage medium, one whose binary bits of information ("all-in" and "all-out" spin arrangements) would, unlike present-day computer memory, be largely unaffected by surrounding magnetic fields. The results also provide fundamental insights into how electron spin can influence a material's transport properties, with broad applications in condensed matter physics.For more information, please contact
RIKEN is Japan's flagship research institute devoted to basic and applied research. Over 2500 papers by RIKEN researchers are published every year in reputable scientific and technical journals, covering topics ranging across a broad spectrum of disciplines including physics, chemistry, biology, medical science and engineering. RIKEN's advanced research environment and strong emphasis on interdisciplinary collaboration has earned itself an unparalleled reputation for scientific excellence in Japan and around the world.
About the RIKEN SPring-8 Center
The RIKEN SPring-8 Center, located in Harima, Japan, is home to SPring-8 (the Super Photon ring-8 GeV), the most powerful synchrotron radiation facility in the world. The RIKEN SPring-8 Center was established to support frontier research initiatives applying SPring-8's unique radiation to a wide variety of fields, notably structural biology and materials science. The center also focuses on the development of technology for producing high-quality synchrotron radiation sources and on development of the new SACLA X-ray Free Electron Laser project.
RIKEN Global Relations Office | EurekAlert!
Subaru Telescope helps pinpoint origin of ultra-high energy neutrino
16.07.2018 | National Institutes of Natural Sciences
Nano-kirigami: 'Paper-cut' provides model for 3D intelligent nanofabrication
16.07.2018 | Chinese Academy of Sciences Headquarters
For the first time ever, scientists have determined the cosmic origin of highest-energy neutrinos. A research group led by IceCube scientist Elisa Resconi, spokesperson of the Collaborative Research Center SFB1258 at the Technical University of Munich (TUM), provides an important piece of evidence that the particles detected by the IceCube neutrino telescope at the South Pole originate from a galaxy four billion light-years away from Earth.
To rule out other origins with certainty, the team led by neutrino physicist Elisa Resconi from the Technical University of Munich and multi-wavelength...
For the first time a team of researchers have discovered two different phases of magnetic skyrmions in a single material. Physicists of the Technical Universities of Munich and Dresden and the University of Cologne can now better study and understand the properties of these magnetic structures, which are important for both basic research and applications.
Whirlpools are an everyday experience in a bath tub: When the water is drained a circular vortex is formed. Typically, such whirls are rather stable. Similar...
Physicists working with Roland Wester at the University of Innsbruck have investigated if and how chemical reactions can be influenced by targeted vibrational excitation of the reactants. They were able to demonstrate that excitation with a laser beam does not affect the efficiency of a chemical exchange reaction and that the excited molecular group acts only as a spectator in the reaction.
A frequently used reaction in organic chemistry is nucleophilic substitution. It plays, for example, an important role in in the synthesis of new chemical...
Optical spectroscopy allows investigating the energy structure and dynamic properties of complex quantum systems. Researchers from the University of Würzburg present two new approaches of coherent two-dimensional spectroscopy.
"Put an excitation into the system and observe how it evolves." According to physicist Professor Tobias Brixner, this is the credo of optical spectroscopy....
Ultra-short, high-intensity X-ray flashes open the door to the foundations of chemical reactions. Free-electron lasers generate these kinds of pulses, but there is a catch: the pulses vary in duration and energy. An international research team has now presented a solution: Using a ring of 16 detectors and a circularly polarized laser beam, they can determine both factors with attosecond accuracy.
Free-electron lasers (FELs) generate extremely short and intense X-ray flashes. Researchers can use these flashes to resolve structures with diameters on the...
13.07.2018 | Event News
12.07.2018 | Event News
03.07.2018 | Event News
16.07.2018 | Physics and Astronomy
16.07.2018 | Life Sciences
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MIT researchers uncover the secrets behind a marine creature's defensive armor -- 1 that is exceptionally tough, yet optically clear
The shells of a sea creature, the mollusk Placuna placenta, are not only exceptionally tough, but also clear enough to read through. Now, researchers at MIT have analyzed these shells to determine exactly why they are so resistant to penetration and damage — even though they are 99 percent calcite, a weak, brittle mineral.
The shells' unique properties emerge from a specialized nanostructure that allows optical clarity, as well as efficient energy dissipation and the ability to localize deformation, the researchers found. The results are published this week in the journal Nature Materials, in a paper co-authored by MIT graduate student Ling Li and professor Christine Ortiz.
Ortiz, the Morris Cohen Professor of Materials Science and Engineering (and MIT's dean for graduate education), has long analyzed the complex structures and properties of biological materials as possible models for new, even better synthetic analogs.
Engineered ceramic-based armor, while designed to resist penetration, often lacks the ability to withstand multiple blows, due to large-scale deformation and fracture that can compromise its structural integrity, Ortiz says. In transparent armor systems, such deformation can also obscure visibility.
Creatures that have evolved natural exoskeletons — many of them ceramic-based — have developed ingenious designs that can withstand multiple penetrating attacks from predators. The shells of a few species, such as Placuna placenta, are also optically clear.
To test exactly how the shells — which combine calcite with about 1 percent organic material — respond to penetration, the researchers subjected samples to indentation tests, using a sharp diamond tip in an experimental setup that could measure loads precisely. They then used high-resolution analysis methods, such as electron microscopy and diffraction, to examine the resulting damage.
The material initially isolates damage through an atomic-level process called "twinning" within the individual ceramic building blocks: Part of the crystal shifts its position in a predictable way, leaving two regions with the same orientation as before, but with one portion shifted relative to the other. This twinning process occurs all around the stressed region, helping to form a kind of boundary that keeps the damage from spreading outward.
The MIT researchers found that twinning then activates "a series of additional energy-dissipation mechanisms … which preserve the mechanical and optical integrity of the surrounding material," Li says. This produces a material that is 10 times more efficient in dissipating energy than the pure mineral, Li adds.
The properties of this natural armor make it a promising template for the development of bio-inspired synthetic materials for both commercial and military applications — such as eye and face protection for soldiers, windows and windshields, and blast shields, Ortiz says.
The work was supported by the National Science Foundation; the U.S. Army Research Office through the MIT Institute for Soldier Nanotechnologies; the National Security Science and Engineering Faculty Fellowships Program; and the Office of the Assistant Secretary of Defense for Research and Engineering.
Written by David Chandler, MIT News Office
Andrew Carleen | EurekAlert!
Research finds new molecular structures in boron-based nanoclusters
13.07.2018 | Brown University
3D-Printing: Support structures to prevent vibrations in post-processing of thin-walled parts
12.07.2018 | Fraunhofer-Institut für Produktionstechnologie IPT
For the first time ever, scientists have determined the cosmic origin of highest-energy neutrinos. A research group led by IceCube scientist Elisa Resconi, spokesperson of the Collaborative Research Center SFB1258 at the Technical University of Munich (TUM), provides an important piece of evidence that the particles detected by the IceCube neutrino telescope at the South Pole originate from a galaxy four billion light-years away from Earth.
To rule out other origins with certainty, the team led by neutrino physicist Elisa Resconi from the Technical University of Munich and multi-wavelength...
For the first time a team of researchers have discovered two different phases of magnetic skyrmions in a single material. Physicists of the Technical Universities of Munich and Dresden and the University of Cologne can now better study and understand the properties of these magnetic structures, which are important for both basic research and applications.
Whirlpools are an everyday experience in a bath tub: When the water is drained a circular vortex is formed. Typically, such whirls are rather stable. Similar...
Physicists working with Roland Wester at the University of Innsbruck have investigated if and how chemical reactions can be influenced by targeted vibrational excitation of the reactants. They were able to demonstrate that excitation with a laser beam does not affect the efficiency of a chemical exchange reaction and that the excited molecular group acts only as a spectator in the reaction.
A frequently used reaction in organic chemistry is nucleophilic substitution. It plays, for example, an important role in in the synthesis of new chemical...
Optical spectroscopy allows investigating the energy structure and dynamic properties of complex quantum systems. Researchers from the University of Würzburg present two new approaches of coherent two-dimensional spectroscopy.
"Put an excitation into the system and observe how it evolves." According to physicist Professor Tobias Brixner, this is the credo of optical spectroscopy....
Ultra-short, high-intensity X-ray flashes open the door to the foundations of chemical reactions. Free-electron lasers generate these kinds of pulses, but there is a catch: the pulses vary in duration and energy. An international research team has now presented a solution: Using a ring of 16 detectors and a circularly polarized laser beam, they can determine both factors with attosecond accuracy.
Free-electron lasers (FELs) generate extremely short and intense X-ray flashes. Researchers can use these flashes to resolve structures with diameters on the...
13.07.2018 | Event News
12.07.2018 | Event News
03.07.2018 | Event News
16.07.2018 | Physics and Astronomy
16.07.2018 | Transportation and Logistics
16.07.2018 | Agricultural and Forestry Science | <urn:uuid:16718d5b-0a0e-4860-a33d-7b131b1ba2b1> | 3.390625 | 1,307 | Content Listing | Science & Tech. | 29.675199 | 95,629,543 |
Ask yourself an important question: What is resonance? If you're having trouble coming up with an answer for this question, you're not alone. We'll explain what resonace is and how to draw both simple resonance structures. A separate tutorial will be created for more complex forms of resonance pertaining to organic chemistry.
Resonance is a bookkeeping trick used to represent delocalization of electrons on paper. By delocalization, I mean electrons spread out throughout the molecule. Lewis structures show the electrons being fixed (localized) on certain atoms; but often times, molecules can have their electrons spread out (delocalized) onto many different atoms.
Let's draw the carbonate anion CO32- and its resonance forms
It looks like we just rotated the molecule and obtained the other two resonace forms, but this is NOT the case. Each of those oxygen atoms is different and the double bond lies between all three oxygen atoms. Consider the color coded picture below:
The oxygen atoms are color coded so you can see they are different. Notice that the double bond is present between each oxygen atom. What does this mean? This shows us that the electrons are capable of moving all over the molecule. If we were to condense the three structures above into one structure, it would look like this
This structure says that the electrons are on all three of the oxygen atoms at all times. The dashed bonds show this "electron highway" where the electrons are free to move. Each resonace form only represents one piece of this "highway", but when you put them altogether, you get the complete electron highway.
IMPORTANT: Resonance is a concept, not a process. This means that resonace is purely conceptual-it represents an electron highway and nothing else. When looking at the individual resonance forms, it's important to note that the electrons are not switching from one form to another, but simply represent a piece of the electron highway. The electrons actually exist in all 3 resonance forms at all instances in time, forming the superhighway.
Also note: ONLY pi electrons and lone pairs play the resonance game. Single bonds don't change-these electrons are locked between two atoms.
Draw resonance forms for the following: SO42- , benzene, HCN, acetone, styrene (google structure if you have to)
Message Kyle1990 for solutions | <urn:uuid:8189f56c-beef-4509-9c29-11c2767d8938> | 4.28125 | 484 | Tutorial | Science & Tech. | 38.485637 | 95,629,552 |
Continuous monitoring since 2002.
Earthquake Monitoring Along the Fairweather Fault
A seismic station has been monitoring earthquakes in Glacier Bay National Park and Preserve for over a decade. Are earthquakes common here?
Did You Know?
Alaska is by far the most seismically active state in the U.S. Every year about 35,000 earthquakes are recorded here. Three of the 10 largest quakes ever recorded in the world, and 10 of the 15 largest ever recorded in the U.S., occurred in Alaska. The biggest was a magnitude 9.2 that ruptured the Prince William Sound area on March 27, 1964.
The Alaska Earthquake Information Center (AEIC) was established as a partnership among the State of Alaska, the University of Alaska Fairbanks Geophysical Institute, and the U.S. Geological Survey in 1986. AEIC’s mission is to monitor earthquake activity throughout Alaska in real time and to provide the public and government agencies with timely location and magnitude information in the event of a significant seismic event. Data from a network of more than 400 seismic stations around the state are received and processed at the AEIC.
A seismic station was established in the Deception Hills (DCPH) on the outer coast of Glacier Bay National Park and Preserve in August 2002. Due to the remoteness of the area and difficult access, only a handful of seismic stations have been established in that region. DCPH is located in close proximity to the Fairweather Fault, a notable tectonic feature in Southeast Alaska. In 1958 this fault ruptured in a magnitude 7.8 earthquake that triggered a massive landslide into the ocean which in turn generated a devastating giant wave in Lituya Bay. Site DCPH provides crucial data for locating earthquakes in Southeast Alaska and for understanding local tectonics.
Methods and Findings
On the Web: The Alaska Earthquake Information Center website is at | <urn:uuid:fd4a945a-46bd-4a94-8336-c53f35d5d8f1> | 3.59375 | 386 | Knowledge Article | Science & Tech. | 45.51392 | 95,629,559 |
Scientists at the Broad Institute of MIT and Harvard have discovered that a mysterious class of large RNAs plays a central role in embryonic development, contrary to the dogma that proteins alone are the master regulators of this process. The research, published online August 28 in the journal Nature, reveals that these RNAs orchestrate the fate of embryonic stem (ES) cells by keeping them in their fledgling state or directing them along the path to cell specialization.
Broad scientists discovered several years ago that the human and mouse genomes encode thousands of unusual RNAs — termed large, intergenic non-coding RNAs (lincRNAs) —but their role was almost entirely unknown. By studying more than 100 lincRNAs in ES cells, the researchers now show that these RNAs help regulate development by physically interacting with proteins to coordinate gene expression and suggest that lincRNAs may play similar roles in most cells.
"There's been a lot of debate about what lincRNAs are doing," said Eric Lander, director of the Broad Institute and the senior author of the paper. "It's now clear that they play critical roles in regulating developmental decisions — that is, cell fate. This was a big surprise, because specific types of proteins have been thought to be the master controls of development."
"This is the first global study of lincRNAs," said Mitchell Guttman, first author of the paper and a graduate student at MIT and the Broad Institute. "We picked embryonic stem cells in particular because they are so important to development and so well understood. This allowed us to dissect the role of lincRNAs within the circuitry of a cell."
The researchers used genetic tools to inhibit more than 100 lincRNAs and found that the vast majority — more than 90 percent — had a significant impact on embryonic stem cells, indicating that the RNAs play a key role in the cells' circuitry.
Embryonic stem cells can follow one of two main routes. They can either differentiate, becoming cells of a specific lineage such as blood cells or neurons, or they can stay in a pluripotent state, duplicating themselves without losing the ability to become any cell in the body. When the researchers turned off each lincRNA in turn, they found dozens that suppress genes that are important only in specific kinds of cells. They also found dozens of lincRNAs that cause the stem cells to exit the pluripotent state.
"It's a balancing act," said Guttman. "To maintain the pluripotent state, you need to repress differentiation genes."
The researchers also uncovered a critical clue about how lincRNAs carry out their important job. Through biochemical analysis, they found that lincRNAs physically interact with key proteins involved in influencing cell fate to coordinate their responses.
"The lincRNAs appear to play an organizing role, acting as a scaffold to assemble a diverse group of proteins into functional units," said John Rinn, an author on the paper, an assistant professor at Harvard University and Medical School, and a senior associate member of the Broad Institute. "lincRNAs are like team captains, bringing together the right players to get a job done."
"By understanding how these interactions form, we may be able to engineer these RNAs to do what we want them to do," said Guttman. "This could make it possible to target key genes that are improperly regulated in disease."
Aviv Regev, an author on the paper, a core member of the Broad Institute, and associate professor at MIT, sees the team's approach to studying the lincRNAs as important for the field. "Many people are interested in lincRNAs, but they need a comprehensive view of the whole collection of lincRNAs," said Regev. "The large-scale data and technology from this study will be useful for scientists worldwide in studying both lincRNAs as well as many other RNAs in the cell."
This project marks a collaborative effort involving experts in embryonic stem cells and lincRNAs as well as computational biologists and researchers in the Broad's RNAi Platform, which developed the tools needed to systematically silence lincRNAs. Other researchers who contributed to this work include Julie Donaghey, Bryce W. Carey, Manuel Garber, Jennifer K. Grenier, Glen Munson, Geneva Young, Anne Bergstrom Lucas, Robert Ach, Xiaoping Yang, Ido Amit, Alexander Meissner, and David E. Root. This work was funded by the National Human Genome Research Institute, the Richard Merkin Foundation for Stem Cell Research at the Broad Institute, and funds from the Broad Institute of MIT and Harvard.
-Written by Haley Bridger, Broad Institute
Guttman M et al. lincRNAs act in the circuitry controlling pluripotency and differentiation. Nature. August 28, 2011 DOI: 10.1038/nature10398
About the Broad Institute of Harvard and MIT
The Eli and Edythe L. Broad Institute of Harvard and MIT was launched in 2004 to empower this generation of creative scientists to transform medicine. The Broad Institute seeks to describe all the molecular components of life and their connections; discover the molecular basis of major human diseases; develop effective new approaches to diagnostics and therapeutics; and disseminate discoveries, tools, methods and data openly to the entire scientific community.
Founded by MIT, Harvard and its affiliated hospitals, and the visionary Los Angeles philanthropists Eli and Edythe L. Broad, the Broad Institute includes faculty, professional staff and students from throughout the MIT and Harvard biomedical research communities and beyond, with collaborations spanning over a hundred private and public institutions in more than 40 countries worldwide. For further information about the Broad Institute, go to http://www.broadinstitute.org.
About the Richard Merkin Foundation for Stem Cell Research at the Broad Institute
The Richard Merkin Foundation for Stem Cell Research at the Broad Institute seeks to fund Broad Institute-affiliated scientists to develop a novel and comprehensive "toolbox" of experimental methods and computational algorithms and to apply those tools to understand cellular circuitry in stem cells, with the goal of being able to manipulate those circuits for both biological knowledge and medical applications.
For more information, contact:Broad Institute of MIT and Harvard
Haley Bridger | EurekAlert!
Pollen taxi for bacteria
18.07.2018 | Technische Universität München
Biological signalling processes in intelligent materials
18.07.2018 | Albert-Ludwigs-Universität Freiburg im Breisgau
For the first time ever, scientists have determined the cosmic origin of highest-energy neutrinos. A research group led by IceCube scientist Elisa Resconi, spokesperson of the Collaborative Research Center SFB1258 at the Technical University of Munich (TUM), provides an important piece of evidence that the particles detected by the IceCube neutrino telescope at the South Pole originate from a galaxy four billion light-years away from Earth.
To rule out other origins with certainty, the team led by neutrino physicist Elisa Resconi from the Technical University of Munich and multi-wavelength...
For the first time a team of researchers have discovered two different phases of magnetic skyrmions in a single material. Physicists of the Technical Universities of Munich and Dresden and the University of Cologne can now better study and understand the properties of these magnetic structures, which are important for both basic research and applications.
Whirlpools are an everyday experience in a bath tub: When the water is drained a circular vortex is formed. Typically, such whirls are rather stable. Similar...
Physicists working with Roland Wester at the University of Innsbruck have investigated if and how chemical reactions can be influenced by targeted vibrational excitation of the reactants. They were able to demonstrate that excitation with a laser beam does not affect the efficiency of a chemical exchange reaction and that the excited molecular group acts only as a spectator in the reaction.
A frequently used reaction in organic chemistry is nucleophilic substitution. It plays, for example, an important role in in the synthesis of new chemical...
Optical spectroscopy allows investigating the energy structure and dynamic properties of complex quantum systems. Researchers from the University of Würzburg present two new approaches of coherent two-dimensional spectroscopy.
"Put an excitation into the system and observe how it evolves." According to physicist Professor Tobias Brixner, this is the credo of optical spectroscopy....
Ultra-short, high-intensity X-ray flashes open the door to the foundations of chemical reactions. Free-electron lasers generate these kinds of pulses, but there is a catch: the pulses vary in duration and energy. An international research team has now presented a solution: Using a ring of 16 detectors and a circularly polarized laser beam, they can determine both factors with attosecond accuracy.
Free-electron lasers (FELs) generate extremely short and intense X-ray flashes. Researchers can use these flashes to resolve structures with diameters on the...
13.07.2018 | Event News
12.07.2018 | Event News
03.07.2018 | Event News
18.07.2018 | Life Sciences
18.07.2018 | Life Sciences
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We consider a three-dimensional network of aqueous droplets joined by single lipid bilayers to form a cohesive, tissuelike material. The droplets in these networks can be programed to have distinct osmolarities so that osmotic gradients generate internal stresses via local fluid flows to cause the network to change shape. We discover, using molecular dynamics simulations, a reversible folding-unfolding process by adding an osmotic interaction with the surrounding environment which necessarily evolves dynamically as the shape of the network changes. This discovery is the next important step towards osmotic robotics in this system. We also explore analytically and numerically how the networks become faceted via buckling and how quasi-one-dimensional networks become three dimensional.
Mendeley saves you time finding and organizing research
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Funded by the National Science Foundation (NSF) and led by scientists at Harvard University, the team reports on its work this week in the journal Science.
The new findings--based on an analysis of ancient tropical rocks that are now found in remote northwestern Canada--bolster the theory that our planet has, at times in the past, been ice-covered at all latitudes.
"This is the first time that the Sturtian glaciation has been shown to have occurred at tropical latitudes, providing direct evidence that this particular glaciation was a 'snowball Earth' event," says lead author Francis Macdonald, a geologist at Harvard University.
"Our data also suggest that the Sturtian glaciation lasted a minimum of five million years."
According to Enriqueta Barrera, program director in NSF's Division of Earth Sciences, which supported the research, the Sturtian glaciation, along with the Marinoan glaciation right after it, are the greatest ice ages known to have taken place on Earth. "Ice may have covered the entire planet then," says Barrera, "turning it into a 'snowball Earth.'"
The survival of eukaryotes--life forms other than microbes such as bacteria--throughout this period suggests that sunlight and surface water remained available somewhere on Earth's surface. The earliest animals arose at roughly the same time.
Even in a snowball Earth, Macdonald says, there would be temperature gradients, and it is likely that sea ice would be dynamic: flowing, thinning and forming local patches of open water, providing refuge for life.
"The fossil record suggests that all of the major eukaryotic groups, with the possible exception of animals, existed before the Sturtian glaciation," Macdonald says. "The questions that arise from this are: If a snowball Earth existed, how did these eukaryotes survive? Did the Sturtian snowball Earth stimulate evolution and the origin of animals?"
"From an evolutionary perspective," he adds, "it's not always a bad thing for life on Earth to face severe stress."
The rocks Macdonald and his colleagues analyzed in Canada's Yukon Territory showed glacial deposits and other signs of glaciation, such as striated clasts, ice-rafted debris, and deformation of soft sediments.
The scientists were able to determine, based on the magnetism and composition of these rocks, that 716.5 million years ago the rocks were located at sea-level in the tropics, at about 10 degrees latitude.
"Climate modeling has long predicted that if sea ice were ever to develop within 30 degrees latitude of the equator, the whole ocean would rapidly freeze over," Macdonald says. "So our result implies quite strongly that ice would have been found at all latitudes during the Sturtian glaciation."
Scientists don't know exactly what caused this glaciation or what ended it, but Macdonald says its age of 716.5 million years closely matches the age of a large igneous province--made up of rocks formed by magma that has cooled--stretching more than 1,500 kilometers (932 miles) from Alaska to Ellesmere Island in far northeastern Canada.
This coincidence could mean the glaciation was either precipitated or terminated by volcanic activity.
Macdonald's co-authors on the Science paper are Phoebe A. Cohen, David T. Johnston, and Daniel P. Schrag at Harvard; Mark D. Schmitz and James L. Crowley of Boise State University; Charles F. Roots of the Geological Survey of Canada; David S. Jones of Washington University in St. Louis; Adam C. Maloof of Princeton University; and Justin V. Strauss.
This work also was supported by the Polar Continental Shelf Project.
Cheryl Dybas | EurekAlert!
Global study of world's beaches shows threat to protected areas
19.07.2018 | NASA/Goddard Space Flight Center
NSF-supported researchers to present new results on hurricanes and other extreme events
19.07.2018 | National Science Foundation
A new manufacturing technique uses a process similar to newspaper printing to form smoother and more flexible metals for making ultrafast electronic devices.
The low-cost process, developed by Purdue University researchers, combines tools already used in industry for manufacturing metals on a large scale, but uses...
For the first time ever, scientists have determined the cosmic origin of highest-energy neutrinos. A research group led by IceCube scientist Elisa Resconi, spokesperson of the Collaborative Research Center SFB1258 at the Technical University of Munich (TUM), provides an important piece of evidence that the particles detected by the IceCube neutrino telescope at the South Pole originate from a galaxy four billion light-years away from Earth.
To rule out other origins with certainty, the team led by neutrino physicist Elisa Resconi from the Technical University of Munich and multi-wavelength...
For the first time a team of researchers have discovered two different phases of magnetic skyrmions in a single material. Physicists of the Technical Universities of Munich and Dresden and the University of Cologne can now better study and understand the properties of these magnetic structures, which are important for both basic research and applications.
Whirlpools are an everyday experience in a bath tub: When the water is drained a circular vortex is formed. Typically, such whirls are rather stable. Similar...
Physicists working with Roland Wester at the University of Innsbruck have investigated if and how chemical reactions can be influenced by targeted vibrational excitation of the reactants. They were able to demonstrate that excitation with a laser beam does not affect the efficiency of a chemical exchange reaction and that the excited molecular group acts only as a spectator in the reaction.
A frequently used reaction in organic chemistry is nucleophilic substitution. It plays, for example, an important role in in the synthesis of new chemical...
Optical spectroscopy allows investigating the energy structure and dynamic properties of complex quantum systems. Researchers from the University of Würzburg present two new approaches of coherent two-dimensional spectroscopy.
"Put an excitation into the system and observe how it evolves." According to physicist Professor Tobias Brixner, this is the credo of optical spectroscopy....
13.07.2018 | Event News
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Chapter 13: Fluids. A fluid is a gas or a liquid. A gas expands to fill any container A liquid (at fixed pressure and temperature), has a fixed volume, but deforms to the shape of its container. The density r of any substance is its mass M per volume V :. Pressure.
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A fluid isa gas or a liquid.
A gas expands to fill any container
A liquid (at fixed pressure and temperature), has a fixed volume, but deforms to the shape of its container.
The densityr of any substance is its mass M per volume V:
PressureP is the amount of force F per unit area A:
By the Action-Reaction principle, Pressure is the inward force per unit area that the container exerts on the fluid.
Pressure is the outward force per unit area that the fluid exerts on its container.
Atmospheric pressure comes from the weight of the column of air above us. At sea level, atmospheric pressure is (up to 10% lower during hurricanes!)
Pat = 1.01 105 N/m2
= 1.01 105Pa1 Pascal= 1 N/m2
= 14.7 lb/in2
= 1 bar (tire pressure gauges in Europe read 1, 2, …. bar)
The mass of the column of atmosphere above each square meter of the surface of the earth is
M = A P/g = [1m2] [1.01 105 N/m2 ] / [9.81 m /s2 ]
= 10.3 103 kg
This is huge, the mass of 1 m3 of water is only 103 kg
The density of air is about 1.0 kg/ m3.
The mass of a column of air of height h is M=rAh.
The equivalent height of the atmosphere is
h = (M/A)/r = [10.3 103 kg /m2]/[1.0 kg/ m3] 10 km
Actual height is >100 km because density decreases with height
Pressure in a fluid depends only on the depth h below the surface.
P = Pat + rgh r = density of fluid
Weight/Area of fluid
Weight/Area of atmosphere above fluid
IF the density of the fluid is constant and it has atmospheric pressure (Pat) at its surface.
Mass of fluid above depth h is
(density)(volume) = rhA
Force of gravity on fluid above depth h: W=rghA
To what depth in water must you dive to double the pressure exerted on your body?
P = Pat + rgh
rgh = Pat , h= Pat /rg
The variation in pressure at two different depths is given by:
P2 = P1 + rgh
When a hole is made in the side of a container holding water, water flows out and follows a parabolic trajectory. If the the container is dropped in free fall, the water flow
2. stops altogether.
3. goes out in a straight line.
4. curves upward.
A Force F1 is applied to area A1, displacing the fluid by a distance d1.
The pressure increase in the fluid is P=F1/A1.
The Pressure F1/A1 creates a force on the car F2= A2 (F1/A1).
The volume of fluid displaced on the left is V=d1 A1.
This equals the volume increase on the right V=d2A2.
Thus the work done by F1: W1 = F1d1 ,
is the same as the work done by the hydraulic system on the car:
W2=F2d2= d2(A2 F1/A1)=(d2A2 )(F1/A1)=( d1 A1)(F1/A1)= F1d1 = W1 :
Because the pressure in a fluid is greater below the object than above, there is an upward buoyant force Fb on any object in a fluid.
The upward buoyant force on an object is equal to the weight of the displaced fluid.
Nota bene: r is the density of the (displaced) fluid, not the density of the object (in green).
This result does not depend upon the shape of the immersed object.
F2/A = F1 /A + rgh
F2 = F1 + rghA
When an object floats, the magnitude of the upward buoyant force equals its weight. Therefore an object floats when it displaces an amount of fluid equal to its weight.
In order to float, an object must have a density less than or equal to that of the fluid in which it is immersed.
W=Mg = rblockVg, V = volume of block
F = fraction of block submerged
Volume displaced = fV
Weight of displaced water = rwaterfVg=Fb
Fb-W = Ma=0 (equilibrium)
Fb= W rwaterf Vg = rblockVg
f = rblock/rwater
How do steel ships float?
A boat is floating in a lake. The boat has a large rock in it. If the rock is thrown overboard, does the level of the water in the lake h increase, decrease or remain the same?
Inside the boat,
The rock displaces a volume of water equal in mass to the rock.
At the bottom of the lake, the rock displaces only a volume of water equal in mass to the rock. The density of the rock is about 4 times larger than the density of water. The height h of the water on the shore (not on the side of the boat) goes DOWN when you through the rock overboard.
A 0.12-kg balloon is filled with helium (density = 0.179 kg/m3). If the balloon is a sphere with a radius of 5.2 m, what is the maximum weight it can lift?
Density of air = 1.29 kg/m3.
If you have continuous flow of a fluid, then the rate of mass flow is the same at every point.
r1A1v1 = r2A2v2(general case: all liquids and gasses)
If the density does not change, which is true for most liquids:
A1v1 = A2v2 (liquids)
Conservation of energy in a flowing fluid leads to Bernoulli’s Equation: (work done by pressure = change in mechanical energy of a small volume of fluid)
P1 + ½rv12 + rgy1 = P2 + ½rv22 + rgy2
Here we assume that the density does not change.
Example: lift on an airplane wing
A horizontal pipe contains water at a pressure of 110 kPa flowing with a speed of 1.4 m/s. When the pipe narrows to one-half its original diameter, what is (a) the speed and (b) the pressure of the water? | <urn:uuid:a4687ae1-5388-437b-bae0-352d3949e018> | 4.125 | 1,557 | Truncated | Science & Tech. | 79.251467 | 95,629,618 |
Date of Award
Bachelor of Science (Hons.)
Faculty of Computing, Health and Science.
Professor H.F. Recher
The birds of grazed paddocks, early revegetation (less than three years in age), three to seven year old revegetation, older revegetation (greater than seven years in age) and remnant vegetation were surveyed over the course of one year to determine whether revegetation recovers avian biodiversity in agricultural landscapes. Habitat features that were useful to the birds, and those that were missing from revegetation, were identified in order to broaden the knowledge base of faunal use of farmland revegetation, and aid in the devising of successful revegetation strategies. Notable differences in the abundance and composition of birds were found between the five vegetation classes studied. The bird communities advanced from paddock sites through to remnant areas, with a pattern of increasing species richness and abundance. Differences were found in the guild structure and microhabitat utilisation by birds of the five vegetation classes. The birds recorded in paddocks and early revegetation were characteristic of open areas. As the revegetation advanced, species with more specific requirements became apparent. However, remnant vegetation attracted a suite of species not recorded in the other vegetation classes. Many species that are known to have declined in range and/or abundance were recorded utilising revegetation in this study. These results indicate that revegetation is a valuable resource for declining species. Although it is likely that some of these species were not resident in planted sites, revegetation provides foraging habitats and thus enlarges the food resources available to many birds in agricultural landscapes. Specific recommendations for future revegetation projects that resulted from this study include the planting of understorey shrubs, inclusion of nest boxes and dead wood (such as logs) into revegetation sites and the integration of remnant vegetation into future plantings.
Heath, R. (2003). The recovery of birds through farmland revegetation in the Shire of Goomalling, Western Australia. Retrieved from http://ro.ecu.edu.au/theses_hons/136 | <urn:uuid:2c700864-dbe4-451b-aecb-f61f04ad3c43> | 3.03125 | 443 | Academic Writing | Science & Tech. | 19.999453 | 95,629,623 |
Reaction of particles of grades S and KLZ graphites with an iron matrix during heating
Theory and Technology of Sintering, Thermal, and Chemicothermal Treatment Processes
KeywordsIron Graphite Iron Matrix
These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.
Unable to display preview. Download preview PDF.
- 1.R. Z. Vlasyuk, I. D. Radomysel'skii, and M. L. Gorb, “Characteristics of graphite and cast iron particle dissolution in iron during sintering,” Poroshk. Metall., No. 10, 15–21 (1977).Google Scholar
- 2.A. P. Gulyaev, Metal Science [in Russian], Oborongiz, Moscow (1963).Google Scholar
- 3.G. B. Skripchenko, Z. V. Grigor'eva, T. M. Khrenkova, É. G. Spiridonov, and V. I. Kasatochkin, “Graphite transformation during comminution,” in: Structural Chemistry of Carbon and Coal [in Russian], Nauka, Moscow (1969), pp. 78–87.Google Scholar
- 4.F. Walker (editor), Chemical and Physical Properties of Carbon [Russian translation], Mir, Moscow (1969).Google Scholar
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Using a new cooling technique MPQ scientists succeed at observing collisions in a dense beam of cold and slow dipolar molecules.
How do chemical reactions proceed at extremely low temperatures? The answer requires the investigation of molecular samples that are cold, dense, and slow at the same time. Scientists around Dr. Martin Zeppenfeld from the Quantum Dynamics Division of Prof. Gerhard Rempe at the Max Planck Institute of Quantum Optics in Garching have now taken an important step in this direction by developing a new cooling method: the so-called “cryofuge” combines cryogenic buffer-gas cooling with a special kind of centrifuge in which rotating electric fields decelerate the precooled molecules down to velocities of less than 20 metres per second.
Due to the high flux densities that were attained the team succeeded in observing collisions between the cold molecules. For two chemical compounds with a strong electric dipole moment, the collision probability as well as its dependence on velocity and flux density was thereby determined (Science, 13 October 2017).
The new technique is a milestone for the emerging field of cold chemistry and could open the perspective towards controlling and manipulating chemical pathways at extremely low temperatures.
The production of cold molecules has proven to be a big challenge: laser-cooling – a very efficient method for atoms – in general doesn’t work for molecules because they exhibit vibrational and rotational states in addition to the electronic states. On the other hand, a large number of molecules, e.g. water (H2O), possess an uneven electric charge distribution. Molecules with such an electric dipole moment can be influenced and hence decelerated by electric fields.
The MPQ team has mostly experimented with fluoromethane (CH3F) and deuterated ammonia (ND3). Initially, the molecules have a temperature of around 200 Kelvin and a velocity of several hundred metres per second. As a first step, the molecules thermalize with a helium or neon buffer-gas in the cryogenic buffer-gas cell and get cooled down to 6 Kelvin (helium) and 17 Kelvin (neon) respectively.
They are extracted from the cryogenic environment by a bent electrostatic quadrupole guide. When they exit the buffer-gas cell, their speed has been reduced to 50 to 100 metres per second. “However, it is not only the velocity that matters”, emphasizes Dr. Martin Zeppenfeld, leader of the project. “Regarding the molecular collisions that we aim to observe it is crucial that during this cooling process also the internal states are being cooled. We can prove that only very few and low rotational and vibrational states are excited.”
By a straight guide the molecules are transferred to the second part of the cooling device, the centrifuge decelerator. “Varying the guiding voltage on the straight guide we can control the trap depth and thereby the molecular beam densities,” explains Thomas Gantner, doctoral candidate at the experiment. “The higher the voltage, the higher the beam density. This kind of control is necessary in order to get a better understanding of the mechanisms behind the cold dipolar collisions that we are going to measure after the deceleration process.”
Entering the centrifuge, the molecules first propagate around the periphery in a stationary storage ring with a diameter of 40 centimetres composed of two static and two rotating electrodes. Then a rotating electric quadrupole guide picks up the molecules almost at any point around the storage ring and pushes them along its spiral shape towards the rotation axis. Thus, while the electric fields make the molecules move into the centre of the disc, they constantly have to counteract the centrifugal force induced by the quadrupole guide that rotates at 30 Hertz, thereby continuously slowing the molecules down.
A final straight guide brings the molecules to a quadrupole mass spectrometer where they are analysed regarding their velocity. “The molecules spend about 25 milliseconds inside the quadrupole guide,” says Thomas Gantner. “This is plenty of time for them to interact, and in these collisions, molecules are being lost. The analysis reveals that the losses increase for decreasing velocities and increasing beam densities. The evaluation of the data relies to a large extent on model calculations that were done by Xing Wu, who is first author of this work and achieved his doctoral degree on this experiment.”
“The observation of cold molecular collisions is a milestone for the field of cold chemistry,” emphasizes Dr. Zeppenfeld. “The generic principle underlying the cryofuge enables its application to a wide range of dipolar compounds. We envision the possibility that in the future chemical reactions with long interaction times can be realized at very low temperatures.”
Furthermore, the cryofuge could extend the range of research topics that experiments with cold molecules offer. For instance, the cold and slow beam of methanol produced could be ideally suited for measuring variations in the proton-to-electron mass ratio. According to theoretical predictions these could be caused by interaction with dark matter. The cryofuge could also serve as a perfect source for ongoing experiments with laser-coolable diatomic molecules. On the other hand, the long-range and anisotropic dipole coupling mediates interactions over micrometre distances. This renders cold polar molecules particularly suitable for applications in quantum simulation or quantum computing. “The very first observation of collisions in a cold gas of naturally occurring molecules brings us closer to the dream of achieving a complex quantum gas such as a Bose Einstein condensate of water molecules,” says Prof. Gerhard Rempe. Olivia Meyer-Streng
Xing Wu, Thomas Gantner, Manuel Koller, Martin Zeppenfeld, Sotir Chervenkov, Gerhard Rempe
A cryofuge for cold-collision experiments with slow polar molecules
Science, 13. Oktober 2017, DOI:10.1126/science.aan3029
Dr. Martin Zeppenfeld
Max Planck Institute of Quantum Optics
85748 Garching, Germany
Phone: +49 (0)89 / 32 905 - 726
Prof. Dr. Gerhard Rempe
Direktor at the Max Planck Institute of Quantum Optics
85748 Garching, Germany
Phone: +49 (0)89 / 32 905 - 701
Dr. Olivia Meyer-Streng
Press & Public Relations
Max Planck Institute of Quantum Optics
Phone: +49 (0)89 / 32 905 - 213
Dr. Olivia Meyer-Streng | Max-Planck-Institut für Quantenoptik
First evidence on the source of extragalactic particles
13.07.2018 | Technische Universität München
Simpler interferometer can fine tune even the quickest pulses of light
12.07.2018 | University of Rochester
For the first time ever, scientists have determined the cosmic origin of highest-energy neutrinos. A research group led by IceCube scientist Elisa Resconi, spokesperson of the Collaborative Research Center SFB1258 at the Technical University of Munich (TUM), provides an important piece of evidence that the particles detected by the IceCube neutrino telescope at the South Pole originate from a galaxy four billion light-years away from Earth.
To rule out other origins with certainty, the team led by neutrino physicist Elisa Resconi from the Technical University of Munich and multi-wavelength...
For the first time a team of researchers have discovered two different phases of magnetic skyrmions in a single material. Physicists of the Technical Universities of Munich and Dresden and the University of Cologne can now better study and understand the properties of these magnetic structures, which are important for both basic research and applications.
Whirlpools are an everyday experience in a bath tub: When the water is drained a circular vortex is formed. Typically, such whirls are rather stable. Similar...
Physicists working with Roland Wester at the University of Innsbruck have investigated if and how chemical reactions can be influenced by targeted vibrational excitation of the reactants. They were able to demonstrate that excitation with a laser beam does not affect the efficiency of a chemical exchange reaction and that the excited molecular group acts only as a spectator in the reaction.
A frequently used reaction in organic chemistry is nucleophilic substitution. It plays, for example, an important role in in the synthesis of new chemical...
Optical spectroscopy allows investigating the energy structure and dynamic properties of complex quantum systems. Researchers from the University of Würzburg present two new approaches of coherent two-dimensional spectroscopy.
"Put an excitation into the system and observe how it evolves." According to physicist Professor Tobias Brixner, this is the credo of optical spectroscopy....
Ultra-short, high-intensity X-ray flashes open the door to the foundations of chemical reactions. Free-electron lasers generate these kinds of pulses, but there is a catch: the pulses vary in duration and energy. An international research team has now presented a solution: Using a ring of 16 detectors and a circularly polarized laser beam, they can determine both factors with attosecond accuracy.
Free-electron lasers (FELs) generate extremely short and intense X-ray flashes. Researchers can use these flashes to resolve structures with diameters on the...
13.07.2018 | Event News
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13.07.2018 | Materials Sciences
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The new findings, which are being published the week of February 12 in an online edition of the Proceedings of the National Academy of Sciences, offer significant insights into normal folding mechanisms as well as those that lead to abnormal amyloid fibril conversion. The new insights may lead to the discovery of novel therapeutic targets for neurodegenerative diseases.
Intriguingly, certain prions and amyloids can play beneficial roles. The subject of the new study, Sup35, enables protein-based inheritance in yeast. When this prion protein misfolds, it converts into self-perpetuating amyloid fibrils, thus altering its function in an inheritable manner. The research team used a combination of advanced biophysical methods to investigate these processes.
"By focusing on single unfolded prions, we were able to define the dynamics of two distinct regions or domains that determine conversion dynamics," said Ashok A. Deniz, a Scripps Research scientist who led the study. "Our research techniques can now be used to probe the structures of other amyloidogenic proteins. This could prove important in understanding the basic biology of amyloid formation, as well as in designing strategies against misfolding diseases."
Interestingly, the new study revealed that yeast prion protein Sup35 lacks a specific, static structure in its native collapsed state. Instead, the compact protein fluctuates among several different structures before forming intermediate shapes during the amyloid assembly process.
The intermediate stages of the process are critically important, Deniz noted: "No single native unfolded protein is capable of initiating the amyloid cascade because of this constant shape-shifting. To start the amyloid conversion process, it has to first convert to an intermediate species, consisting of multiple protein molecules. This insight may be important to finding potential new therapeutic targets for disease-causing amyloids."
To define the dynamic structural details of individual prions, Deniz and his colleagues employed several novel technologies including single-molecule fluorescence resonance energy transfer (SM-FRET) and fluorescence correlation spectroscopy (FCS).
Fluorescence resonance energy transfer is a highly sensitive tool used to measure molecular structure and dynamics such as in single proteins at the angstrom level, a measurement unit used to define molecular distances (a 10th of a millionth of a millimeter). Fluorescence correlation spectroscopy is a high resolution technique that measures time fluctuations in fluorescent emissions from tagged proteins, which provided information about changes in shape of Sup35 taking place on the nanosecond timescale (billionths of seconds).
A third technology, single molecule fluorescence coincidence, was used in an unusual way-to prove that the protein species under scrutiny were not oligomeric (consisting of multiple proteins in an aggregate). The technology, based on measuring fluorescence bursts from individual tagged proteins, enabled the scientists to determine that the proteins being studied were, in fact, single monomers and not aggregates.
Deniz said that future work with yeast prion mutants might resolve some of the questions that remain unanswered. "Our laboratory has spent a great deal of time in improving these techniques, and we have used them to uncover some very intriguing information about this particular monomer," he said. "This combination of techniques can now be used to study other amyloidogenic proteins, including prions, particularly small assemblies and intermediate stages of the aggregation process. These are currently considered the most toxic forms of amyloid-disease associated proteins."
While mammalian prion proteins are different from those of yeast in their amino acid sequence, they do share some basic features, including their ability to catalyze the conversion to amyloid fibers. Some studies suggest that prions may also play key roles in certain critical processes such as long-term memory. Other authors of the study, A Natively Unfolded Yeast Prion Monomer Adopts An Ensemble of Collapsed and Rapidly Fluctuating Structures, are Samrat Mukhopadhyay and Edward A. Lemke of The Scripps Research Institute; and Susan Lindquist and Rajaraman Krishnan of the Whitehead Institute for Biomedical Research.
Marisela Chevez | EurekAlert!
World’s Largest Study on Allergic Rhinitis Reveals new Risk Genes
17.07.2018 | Helmholtz Zentrum München - Deutsches Forschungszentrum für Gesundheit und Umwelt
Plant mothers talk to their embryos via the hormone auxin
17.07.2018 | Institute of Science and Technology Austria
For the first time ever, scientists have determined the cosmic origin of highest-energy neutrinos. A research group led by IceCube scientist Elisa Resconi, spokesperson of the Collaborative Research Center SFB1258 at the Technical University of Munich (TUM), provides an important piece of evidence that the particles detected by the IceCube neutrino telescope at the South Pole originate from a galaxy four billion light-years away from Earth.
To rule out other origins with certainty, the team led by neutrino physicist Elisa Resconi from the Technical University of Munich and multi-wavelength...
For the first time a team of researchers have discovered two different phases of magnetic skyrmions in a single material. Physicists of the Technical Universities of Munich and Dresden and the University of Cologne can now better study and understand the properties of these magnetic structures, which are important for both basic research and applications.
Whirlpools are an everyday experience in a bath tub: When the water is drained a circular vortex is formed. Typically, such whirls are rather stable. Similar...
Physicists working with Roland Wester at the University of Innsbruck have investigated if and how chemical reactions can be influenced by targeted vibrational excitation of the reactants. They were able to demonstrate that excitation with a laser beam does not affect the efficiency of a chemical exchange reaction and that the excited molecular group acts only as a spectator in the reaction.
A frequently used reaction in organic chemistry is nucleophilic substitution. It plays, for example, an important role in in the synthesis of new chemical...
Optical spectroscopy allows investigating the energy structure and dynamic properties of complex quantum systems. Researchers from the University of Würzburg present two new approaches of coherent two-dimensional spectroscopy.
"Put an excitation into the system and observe how it evolves." According to physicist Professor Tobias Brixner, this is the credo of optical spectroscopy....
Ultra-short, high-intensity X-ray flashes open the door to the foundations of chemical reactions. Free-electron lasers generate these kinds of pulses, but there is a catch: the pulses vary in duration and energy. An international research team has now presented a solution: Using a ring of 16 detectors and a circularly polarized laser beam, they can determine both factors with attosecond accuracy.
Free-electron lasers (FELs) generate extremely short and intense X-ray flashes. Researchers can use these flashes to resolve structures with diameters on the...
13.07.2018 | Event News
12.07.2018 | Event News
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17.07.2018 | Information Technology
17.07.2018 | Materials Sciences
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Blog / Laetitia Navarro / December 15, 2016
The world has agreed that we live on a planet under threat and we need to sustain the rich diversity of life on Earth. Commitments came through the 1992 Convention on Biological Diversity signed by government leaders; and the 20 time bound, measurable targets agreed by those parties in 2010.
The Aichi Targets are now being translated into national strategies by all countries – and we at GEO BON are there to remind all 193 parties to the convention that they can’t set targets without assessing the status and trends of biodiversity, through observation.
I attended the 13th Conference of the Parties this month in Mexico to raise awareness about the importance of biodiversity observation networks. Consistent biodiversity monitoring is fundamental – and GEO BON is helping countries to work on improving consistency.
In collaboration with the Alexander von Humboldt Institute in Colombia we developed BON in a Box, an online toolkit for technology transfer. BON in a Box is a mechanism for capacity building to assist countries in the development of biodiversity observation.
GEO BON is also working on the development of the Essential Biodiversity Variables and on biodiversity change indicators to assess progress to specific Aichi targets which rely on the availability of repeated biodiversity observations in time but also on a better geographical coverage.
As isolated science research programmes start to become more uniform and connected through GEO BON, we can build up a more accurate picture of the world today, and how to manage it for tomorrow.
Watch the GEO BON side event on Periscope, by the Humboldt Institut, Colombia.
Blog post: Earth Observations for Urban Resilience: Takeaways from ICLEI’s 2018 Resilient Cities Congress
Blog post: World Day to Combat Desertification and Drought 2018 – GEO Land Degradation Neutrality Activity | <urn:uuid:df326cc0-0e59-46ba-bb15-bd04676bb124> | 2.96875 | 386 | News (Org.) | Science & Tech. | 19.735998 | 95,629,671 |
At the U.S. Department of Energy’s (DOE) Brookhaven National Laboratory, a team of researchers has generated extremely short light pulses using a new technique that could be used in the next generation of light source facilities around the world to catch molecules and atoms in action.
Published on January 19, 2007 in Physical Review Letters, the research team’s findings describe the use of a laser to control the pulse duration of light from a free electron laser (FEL), a type of light source with a brightness up to one billion times higher than that of ordinary synchrotron light. The team also reports the first experimental observation of a phenomenon called superradiance.
Most of the world’s light sources – facilities such as Brookhaven’s National Synchrotron Light Source (NSLS) that produce x-ray, ultraviolet, and infrared light for research in fields ranging from biology to nanotechnology – produce a broad range of wavelengths, or colors of light. This is ideal for hosting a wide variety of experiments, but to understand how molecules change their structure in chemical and biological systems, scientists need extremely short pulses of light (shorter than one trillionth of a second) with short wavelengths. This is where FELs are valuable, as they can provide pulses of light that are a thousand times shorter than those produced at existing light sources and contain a million more photons per pulse. Like a strobe flash, the ultra-short FEL allows scientists to take time-resolved images of biological and chemical processes and various other atomic-scale events.
"In existing light sources, we just take a static snapshot of a sample,” said NSLS physicist Takahiro Watanabe, one of the paper’s authors. “We get the location of the pieces, but what happens if the pieces move? You don’t know how they actually got there. What you want is to take images along the way to see these things move, and that’s where these ultra-fast sources come into play.”
Synchrotron light is produced by accelerating of a beam of electrons and sending it through a magnetic field. Generally, the pulse duration of both synchrotron and FEL light is determined by that of the electron beam. Tremendous effort has been devoted to generating short electron pulses, but scientists have been unable to shorten the electron pulse past a certain point because of forces that repel the electrons in the beam away from each other. At Brookhaven’s Source Development Lab (SDL), researchers found a way to generate a very short FEL pulse that doesn’t depend on the length of the electron pulse. This was done using a titanium-sapphire laser that combines a femtoseconds pulse of light with the much longer electron beam. A femtosecond is extremely fast – one billionth of one millionth of a second. This leads to a femtosecond FEL pulse that keeps growing in intensity and shortening in time duration, which is attributed to a phenomenon called superradiance.
“The electron beam and the laser beam don’t move at the same speed, they slip a little bit,” Watanabe said. “So this scenario provides new areas on the electron beam for the interaction to continue and allows the intensity of light to keep growing.”
Superradiance was first proposed in 1954 as the most efficient way to extract energy from either atomic or molecular systems, but the SDL research group is the first to experimentally observe its effects in this type of FEL setup. Understanding how to produce these intense, ultrafast pulses of light could help scientists around the world as they begin to construct the next generation of light source facilities.
Other members of the group include James Murphy, Xijie Wang, James Rose, Yuzhen Shen, and Thomas Tsang of Brookhaven National Laboratory; Luca Giannessi of the ENEA, Frascati, Italy; Pietro Musumeci of the National Institute of Nuclear Physics, Italy; and Sven Reiche of the University of California, Los Angeles. The Office of Naval Research provided funding for this study. NSLS operations are funded by the DOE’s Basic Energy Sciences program within the Office of Science.
Karen McNulty Walsh | EurekAlert!
What happens when we heat the atomic lattice of a magnet all of a sudden?
18.07.2018 | Forschungsverbund Berlin
Subaru Telescope helps pinpoint origin of ultra-high energy neutrino
16.07.2018 | National Institutes of Natural Sciences
For the first time ever, scientists have determined the cosmic origin of highest-energy neutrinos. A research group led by IceCube scientist Elisa Resconi, spokesperson of the Collaborative Research Center SFB1258 at the Technical University of Munich (TUM), provides an important piece of evidence that the particles detected by the IceCube neutrino telescope at the South Pole originate from a galaxy four billion light-years away from Earth.
To rule out other origins with certainty, the team led by neutrino physicist Elisa Resconi from the Technical University of Munich and multi-wavelength...
For the first time a team of researchers have discovered two different phases of magnetic skyrmions in a single material. Physicists of the Technical Universities of Munich and Dresden and the University of Cologne can now better study and understand the properties of these magnetic structures, which are important for both basic research and applications.
Whirlpools are an everyday experience in a bath tub: When the water is drained a circular vortex is formed. Typically, such whirls are rather stable. Similar...
Physicists working with Roland Wester at the University of Innsbruck have investigated if and how chemical reactions can be influenced by targeted vibrational excitation of the reactants. They were able to demonstrate that excitation with a laser beam does not affect the efficiency of a chemical exchange reaction and that the excited molecular group acts only as a spectator in the reaction.
A frequently used reaction in organic chemistry is nucleophilic substitution. It plays, for example, an important role in in the synthesis of new chemical...
Optical spectroscopy allows investigating the energy structure and dynamic properties of complex quantum systems. Researchers from the University of Würzburg present two new approaches of coherent two-dimensional spectroscopy.
"Put an excitation into the system and observe how it evolves." According to physicist Professor Tobias Brixner, this is the credo of optical spectroscopy....
Ultra-short, high-intensity X-ray flashes open the door to the foundations of chemical reactions. Free-electron lasers generate these kinds of pulses, but there is a catch: the pulses vary in duration and energy. An international research team has now presented a solution: Using a ring of 16 detectors and a circularly polarized laser beam, they can determine both factors with attosecond accuracy.
Free-electron lasers (FELs) generate extremely short and intense X-ray flashes. Researchers can use these flashes to resolve structures with diameters on the...
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Ribosomal RNA integrity and rate of seed germination
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The integrity of ribosomal RNA (the percentage of complete, un-nicked molecules) in seeds was studied by electrophoresis under denaturing conditions. Two batches of carrot seed, harvested at different stages of maturity, and four batches ofNicotiana seed stored for various times were used. Within each species, there was a correlation between the integrity of the rRNA of the dry seed and the rate of germination of that seed. In carrot seed, there was extensive degradation of existing rRNA in both the embryo and endosperm during the first two days of imbibition.
Key wordsDaucus Germination (seeds) Nicotinana rRNA Seed ageing Seed germination
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NASA was scheduled to launch a new, next-generation weather satellite early Wednesday morning, but unfavorable weather conditions forced the postponement of the launch.
A new launch date for the satellite, which will help improve the accuracy of weather forecasting, has been set for Saturday, Nov. 18 at 4:47 a.m. EST.
The satellite is the first of four weather satellites in the Joint Polar Satellite System (JPSS) and has been named JPSS-1.
“The new JPSS satellite will join GOES-16 as we are confronting one of the most tragic hurricane seasons in the past decade,” said Secretary of Commerce Wilbur Ross.
“The JPSS satellite system will provide advanced forecasting on not only hurricanes but also dangerous weather events threatening communities across the United States,” Ross added.
Here are three things to know about the new weather satellite:
1. JPSS-1 will be much different from GOES-16
Last November, GOES-16 (formerly GOES-R) made headlines by being the first of the next generation of geostationary weather satellites.
GOES-16 orbits the Earth around 22,000 miles above the equator and remains fixed over the same area of the globe at all times.
This satellite has sent back incredible images of snowstorms, hurricanes and severe thunderstorms, but since it is fixed over the same area of the world, it is unable so send back information for areas such as Africa or Asia.
JPSS-1 is in a different family of satellites and will be launched into a polar orbit, circling the globe 14 times a day from pole to pole.
Being in a polar orbit, JPSS-1 will gather data from around the world from a distance of around 520 miles. This provides meteorologists with much different information than GOES-16.
“Using polar satellite data, we have been able to provide emergency managers with more accurate forecasts, allowing them to pre-position equipment and resources days before a storm. JPSS will continue this trend,” said Louis W. Uccellini, Ph.D., director of NOAA’s National Weather Service.
2. How the instruments on JPSS-1 will help to improve weather forecasts
Polar-orbiting satellites supply 85 percent of the data used in weather prediction computer models, so the weather observations taken by the five advanced instruments on JPSS-1 will supply these models with more comprehensive information.
“The satellite will provide meteorologists with a variety of observations, such as atmospheric temperature and moisture, sea-surface temperature, ocean color, sea ice cover, volcanic ash and fire detection,” NOAA said.
Other polar-orbiting weather satellites currently in use collect similar data, but the instruments on board JPSS-1 will be more advanced and able to gather data at a higher resolution.
Specifically, the Advanced Technology Microwave Sounder (ATMS) instrument on JPSS-1 will offer more channels, better resolution and a wider swath than older weather satellites to improve the accuracy of short- and medium-term forecasting.
The high-resolution observations will help to provide meteorologists with more information during severe weather events, including hurricanes, blizzards and severe thunderstorm outbreaks.
“JPSS-1 is going to bring the latest, most advanced technology that NOAA has ever flown in polar orbit to produce accurate three- to seven-day weather forecasts,” said Greg Mandt, director of the JPSS program at NOAA.
3. Long-term observations to help climate scientists
Data collected by JPSS-1 and subsequent satellites help to improve not only short- and medium-range forecasts but also long-term climate studies.
The Cross-Track Infrared Sounder (CrIS) instrument will collect high-vertical-resolution temperature and water vapor information and detect changes in greenhouse gasses.
Over a long period of time, these observations can help climate scientists improve climate prediction, as well as better understand long-duration weather phenomenon such as El Niño and La Niña.
JPSS-1 launched before dawn on Tuesday atop a Delta II rocket form Vandenberg Air Force Base, California.
Although JPSS-1 has launched, it will not become operational until 2018. Once it does become operational, it will be renamed NOAA-20.
The satellite's primary mission is designed to last for seven years, but it may remain in service longer if the instruments continue to function properly.
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An uptick in monsoon rainfall is expected to heighten the flood threat across eastern and northern India this week.
The threat for damaging thunderstorms will shift into the southeastern United States as the weekend kicks off.
Three people were injured after severe weather tore from Indiana to Kentucky and Tennessee to end the week.
A new round of severe weather is threatening lives from Ohio through Tennessee and will continue into Saturday morning.
In select regions of the world, people can live long enough to make some wonder if these countries have discovered the heavily sought-after fountain of youth.
A town in Iowa was severely damaged by a tornado on Thursday, while strong storms led to a tour boat disaster in Missouri that killed 17. | <urn:uuid:4222fb5a-aabb-490d-9507-1cb0afc5575c> | 2.796875 | 1,125 | News Article | Science & Tech. | 38.875914 | 95,629,718 |
Lacustrine Features (Mars)
Living reference work entry
Sites of putative long-standing bodies of water on Mars.
Flat regions in commonly breached closed or open depressions or topographic lows.
Open-basin lake area ranges between ∼2 and ∼500,000 km2 (Fassett and Head 2008).
Subtypes of lacustrine features in relation to associated observable valley(s):
Open-basin lake (Cabrol and Grin 1999): possible lake where outlet is observed. Water must have ponded to the “level of the surface adjacent to the outlet valley head before breaching and overflowing the basin, requiring a period of sustained fluvial activity on the surface of Mars” (Fassett and Head 2008; Goudge et al. 2012).
Closed-basin lake (Cabrol and...
KeywordsCrater Lake Impact Crater Lacustrine Basin Thermokarst Lake Lacustrine Plain
These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.
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