Di seguito gli interventi pubblicati in questa sezione, in ordine cronologico.
Concrete pavements are made by mixing cement with water, sand, and "virgin aggregates" obtained from rock quarries located in the proximity of the construction site. In Indiana most of these aggregates are quarried limestone.
"Some parts of Indiana have plenty of quarries near highway construction sites," said Nancy Whiting, a scientist with the Applied Concrete Research Initiative at Purdue's School of Civil Engineering. "In other places, it's more difficult to find quality aggregate. If you have to drive 50 or 100 miles to get a good quality aggregate, it's going to be much more cost effective to use recycled materials by crushing the concrete you have in place."
Whiting is leading the concrete recycling project funded by INDOT through the Joint Transportation Research Program with Jan Olek, a Purdue professor of civil engineering, postdoctoral research associate Jitendra Jain and graduate research assistant Kho Pin Verian.
"If you are going to pave, you may have to remove the old concrete and break it into pieces anyway, so recycling makes sense," Olek said. "And you avoid putting it in landfills."
Jain gave a research presentation about the work earlier this month during a meeting of the American Concrete Institute in Tampa, Fla.
The researchers are testing concrete mixtures that contain varying percentages of recycled concrete. They also are developing cost-analysis software that will enable the state and construction contractors to estimate how much they could save by using recycled concrete. Crushing old concrete pavements into aggregate that can be recycled in new concrete can potentially reduce materials costs by 10 percent to 20 percent, depending on whether any quarries are located near construction sites.
"Whether that would mean a comparable reduction in overall construction costs is part of what our research will determine," Whiting said.
Also involved in the work are Mark Snyder, an engineering consultant based in Pittsburgh, and Tommy Nantung, a project administrator at INDOT. Indiana currently allows the use of "recycled concrete as aggregate," or RCA, as a base layer to support new pavements. However, no existing specifications allow for use of this material in new concrete mixtures. The goal of the research project is to extend the use of the crushed concrete for manufacturing of mixtures that can be used to construct the pavement itself.
The team will finalize a report early next year, providing guidelines and recommendations to help create design and material standards. Standards are needed to control the quality of RCA and its proper use in creating the new concrete.
"Various other states have used crushed concrete as aggregate, but there has been no standardization, so the end result hasn't always been good," Whiting said. "We are trying to show INDOT that it can work and how to be consistent about getting a good product."
One aim is to ensure resistance of the RCA to cracking due to freezing and thawing cycles the pavements are exposed to during winter. Some aggregates are more susceptible to cracking than others. The focus of the standards will be on test methods for freeze-thaw durability and absorption of water and deicing chemicals.
The researchers are working with industry to produce nearly 400 test specimens of varying sizes and shapes containing different percentages of recycled aggregate. Concrete taken from State Route 26 when it was recently repaved in Lafayette has been crushed for use as RCA for the project.
"Slabs of concrete have been crushed into aggregate by Milestone Contractors LP under the direction of J. Beland," said Whiting.
A commercial concrete plant in Lafayette operated by Irving Materials Inc. is mixing the material. In addition, Jay Snider and Calvin Kingery of Irving Materials as well as Dick Newell of Milestone Contractors are working alongside the researchers, helping with issues ranging from adjusting mixture proportions to placement of trial slabs in the field.
Industry partners helped found the Applied Concrete Research Initiative in 2008 along with INDOT and academia, and are providing their services free of charge.
"They are doing this as a courtesy to us," Olek said. "This type of collaboration with practitioners is critical with respect to implementation of laboratory derived materials and technologies in the field."
More information: Predicting Long Term Durability of Concretes with Recycled Concrete as Coarse Aggregates
The use of recycled concrete (RCA) as coarse aggregates in concrete is a sustainable, cost-effective alternative to disposing the old concrete pavements. Previous studies indicated that replacing up to 30% of the original (virgin) coarse aggregate in the mixture with RCA will have no negative effects on the freeze-thaw (F/T) resistance and mechanical properties of hardened concretes. In the present study, RCA was used in both plain and fly ash (20% of Class C fly ash) concretes to substitute for crushed limestone coarse virgin aggregates at four different replacement levels (0%, 30%, 50%, and 100%). The long-term durability of all concrete mixtures was evaluated by determining the F/T resistance (ASTM C666 procedure A), scaling resistance (ASTM C672), and rapid chloride penetration (RCP) resistance (ASTM C1202). In addition, the electrical impedance spectroscopy (EIS) measurements were performed on the same concrete specimens that were used for RCP test. EIS spectra were obtained using a Solartron™ 1260 gain-phase analyzer. A frequency range of 1 Hz–10 MHz using a 250 mV AC signal was employed, with 10 measurements per decade. The relationship between the values of final charge passed and bulk resistance obtained from EIS will be used to evaluate the effects of increase in temperature on charge passed during RCP for concretes with RCA. The different test results from this study would be useful to optimize the replacement levels as well as preferred tests to predict long-term durability of concretes with RCA.
Source: Physorg - Research Provided by Purdue University
Jack Kevorkian might be gone, but his spirit lives on -- well, maybe living isn't the best way to put it...
For the first time ever, this Friday night, a website will run a live broadcast of a terminally ill man ending his life in a case of assisted suicide.
Nikolai Ivanisovich, 62, is terminally ill with brain cancer. He will die before cameras and a worldwide audience at a clinic in Switzerland, with the use of lethal injection administered by a physician.
The filming of his death will be broadcast on BattleCam.com, a 24/7 Reality TV website where live events are regularly cast to a wide range of audiences.
The site is run by billionaire businessman Alki David, who purchased the exclusive rights to broadcast the process.
ALKI DAVID & NIKOLAI IVANISOVICH
"I am grateful to Mr. David and his team for making this possible," Ivanisovich told Russia Today. "My family will be able to live in prosperity after I pass. May God bless Mr. David for his kindness and generosity.
"Projecting the moral questions that will arise from this event, I would like to add that I find nothing wrong with this at all.
“Death is a fact of life... many governments throughout the western world, including Switzerland, Belgium and Luxembourg, recognize the importance the right to each individual's right to end their life, free of terminal pain."
The controversial event comes at a time the world is in the midst of a debate on assisted suicides: In the United States, it is legal only in the states of Oregon, Montana and Washington.
"This is a breakthrough in consciousness on what we watch,” BattleCam Operations VP Claude Haraser said, “and how we watch it."
In a paper published in Science, Los Alamos researchers Gang Wu, Christina Johnston, and Piotr Zelenay, joined by researcher Karren More of Oak Ridge National Laboratory, describe the use of a platinum-free catalyst in thecathode of a hydrogen fuel cell. Eliminating platinum—a precious metal more expensive than gold—would solve a significant economic challenge that has thwarted widespread use of large-scale hydrogen fuel cell systems.
Polymer-electrolyte hydrogen fuel cells convert hydrogen and oxygen into electricity. The cells can be enlarged and combined in series for high-power applications, including automobiles. Under optimal conditions, the hydrogen fuel cell produces water as a "waste" product and does not emit greenhouse gasses. However, because the use of platinum in catalysts is necessary to facilitate the reactions that produce electricity within a fuel cell, widespread use of fuel cells in common applications has been cost prohibitive. An increase in the demand for platinum-based catalysts could drive up the cost of platinum even higher than its current value of nearly $1,800 an ounce.
The Los Alamos researchers developed non-precious-metal catalysts for the part of the fuel cell that reacts with oxygen. The catalysts—which use carbon (partially derived from polyaniline in a high-temperature process), and inexpensive iron and cobalt instead of platinum—yielded high power output, good efficiency, and promising longevity. The researchers found that fuel cells containing the carbon-iron-cobalt catalyst synthesized by Wu not only generated currents comparable to the output of precious-metal-catalyst fuel cells, but held up favorably when cycled on and off—a condition that can damage inferior catalysts relatively quickly.
Moreover, the carbon-iron-cobalt catalyst fuel cells effectively completed the conversion of hydrogen and oxygen into water, rather than producing large amounts of undesirable hydrogen peroxide. Inefficient conversion of the fuels, which generates hydrogen peroxide, can reduce power output by up to 50 percent, and also has the potential to destroy fuel cell membranes. Fortunately, the carbon- iron-cobalt catalysts synthesized at Los Alamos create extremely small amounts of hydrogen peroxide, even when compared with state-of-the-art platinum-based oxygen-reduction catalysts.
Because of the successful performance of the new catalyst, the Los Alamos researchers have filed a patent for it.
"The encouraging point is that we have found a catalyst with a good durability and life cycle relative to platinum-based catalysts," said Zelenay, corresponding author for the paper. "For all intents and purposes, this is a zero-cost catalyst in comparison to platinum, so it directly addresses one of the main barriers to hydrogen fuel cells."
The next step in the team's research will be to better understand the mechanism underlying the carbon-iron-cobalt catalyst. Micrographic images of portions of the catalyst by researcher More have provided some insight into how it functions, but further work must be done to confirm theories by the research team. Such an understanding could lead to improvements in non-precious-metal catalysts, further increasing their efficiency and lifespan.
At first glance, the plans for the 10MW Tower have all the trappings of pre-crash Dubai: the improbable height, the flashy facade, the swagger of a newbie in a crowded skyline. On closer inspection, however, it’s an eco-machine. The A-shaped, 1,969-foot concept skyscraper is designed to turn out as much as 10 times the energy it needs, enough to power up to 4,000 nearby homes.
Dubai's 10MW Tower - Courtesy Robert Ferry/Studied Impact Design
Three separate systems make it work. First, a five-megawatt wind turbine in the hollow of the “A” generates energy in the powerful and unpredictable desert gusts. Second, mirrors dot the slanted, south-facing facade, beaming light to a molten-salt-filled collector that hangs off the building like an ultra-tall street lamp. Cooked to 932şF, the liquefied salt transfers heat to a convection loop that runs a three-megawatt steam turbine. Finally, a two-megawatt solar updraft tower produces additional energy in clear weather. Sunlight warms air in a two-foot-wide gap that runs the length of the southern face. The airflow from rising heat powers an internal wind turbine.
Reflective: The facade directs light to a power-producing salt-cooker. Courtesy Robert Ferry/Studied Impact Design
If it were built (at an estimated cost of $400 million), 10MW could pay off its energy debt in 20 years. Extra juice feeds the municipal grid, and other sources in the area would adjust for the tower’s output. The building could house offices or residences or both, says designer Robert Ferry, 35, who helms the Dubai architecture firm Studied Impact with his wife, Elizabeth Monoian. The pair became interested in energy-generating skyscrapers on moving to the United Arab Emirates, where there are superstructures in spades but few that are any greener than their brochures. With the 10MW Tower, they hope to someday create a power plant you can live in. It may sound fantastic, but, Ferry says, “it’s only a matter of time before something like this is built.”
Revolutionary: A five-megawatt turbine contributes to the building’s annual output of 20,000 megawatt-hours. Courtesy Robert Ferry/Studied Impact Design
Dr Steve Liddle, an expert in molecular depleted uranium chemistry, has created a new molecule containing two Uranium atoms which, if kept at a very low temperature, will maintain its magnetism. This type of single-molecule magnet (SMM) has the potential to increase data storage capacity by many hundreds, even thousands of times — as a result huge volumes of data could be stored in tiny places.
Dr Liddle, a Royal Society University Research Fellow and Reader in the School of Chemistry, has received numerous accolades for his ground breaking research. His latest discovery has just been published in the journal Nature Chemistry.
Dr Liddle said: “This work is exciting because it suggests a new way of generating SMM behaviour and it shines a light on poorly understood uranium phenomena. It could help point the way to making scientific advances with more technologically amenable metals such as the lanthanides. The challenge now is to see if we can build bigger clusters to improve the blocking temperatures and apply this more generally.
Computer hard discs are made up of magnetic material which record digital signals. The smaller you can make these tiny magnets the more information you can store.
Although it may have somewhat negative PR it seems depleted Uranium — a by-product from uranium enrichment and of no use in nuclear applications because the radioactive component has been removed — could now hold some of the key to their research. Dr Liddle has shown that by linking more than one uranium atom together via a bridging toluene molecule SMM behaviour is exhibited.
He said: “At this stage it is too early to say where this research might lead but single-molecule magnets have been the subject of intense study because of their potential applications to make a step change in data storage capacity and realise high performance computing techniques such as quantum information processing and spintronics.”
Dr Liddle said: “The inherent properties of uranium place it between popularly researched transition and lanthanide metals and this means it has the best of both worlds. It is therefore an attractive candidate for SMM chemistry, but this has never been realised in polymetallic systems which is necessary to make them work at room temperature.”
Dr Liddle is a regular contributor to the School of Chemistry’s award winning Periodic Table of Videos — periodicvideos.com. The website, created by Brady Haran, the University’s film maker in residence, won the 2008 IChemE Petronas Award for excellence in education and training.
Modeling crowd behavior can help engineers design buildings and other public spaces so as to prevent deaths and injuries during emergencies. But it is hard to design virtual crowds that realistically mimic real ones.
European researchers have now shown that a simple model based on one cognitive factor—vision—can predict pedestrian behavior in various types of crowds. It represents significant progress in a field that has been trying to move away from purely physics-based models.
"There's no clear way to describe the cognitive processes of each individual, but with this vision-based approach, it's actually very simple," says Dirk Helbing, of the Swiss Federal Institute of Technology in Zurich, who carried out the work with Mehdi Moussaïd and Guy Theraulaz, of Université Paul Sabatier in Toulouse, France.
The study, which appears in this week's issue of Proceedings of the National Academy of Sciences, was inspired by previous research that used eye-tracking data to determine how people predict the trajectory of an airborne ball in order to catch it. Numerous other studies have suggested that walking, like catching a ball, is primarily governed by vision. So the researchers hypothesized that using visual factors, mainly line of sight and visibility, would allow them to better model crowd behavior.
The researchers gave virtual crowd members the ability to "see" their surroundings and navigate accordingly. They found that their vision-based model predicted pedestrian behavior surprisingly well for both small and large crowds as long as the physical influence of the crowd as a whole was also considered. They suggest that the model could help avert such crowd disasters as the Love Parade incident that killed 19 concertgoers in Germany last summer, by providing designers with new information about how pedestrians will attempt to move quickly through a specific space.
The model primarily indicates how vision affects pedestrians' direction and speed—two forces that often compete when a person is navigating pedestrian traffic. The researchers predicted pedestrian trajectories using the model and then compared their predictions with data from real-life pedestrian scenarios. They found the trajectories matched up almost exactly.
To model crowd disasters, though, they had to consider involuntary as well as voluntary behaviors. What the pedestrian can see remains important, but sometimes the push and pull of the crowd can be even more so. "When the crowd becomes high-density, the simple model isn't enough," says Theraulaz. "You have to take into account the rules of physical contact."
Adding a physical-force component to the vision-based model allowed the study authors to predict pedestrian behavior in different types of overcrowding situations, such as a bottleneck around a blocked exit or a pileup that forms behind a fallen pedestrian.
When the study authors applied their modified model to a real-world bottleneck disaster, they were able to predict the location of the highest-risk areas and map out how pedestrian collisions would spread once the situation became critical. "This is the most dangerous type of case," says Helbing. "You can do video analysis afterward, but even then it's hard to see exactly what's going on, because people are hardly moving."
One of the biggest advantages of the vision-based model is its versatility, says Michael Batty, an urban planning researcher at University College London, who studies crowd modeling. "It's relevant to a whole range of pedestrian situations, and that's what makes it more testable," he says. The study authors suggest that the model could also be used to analyze crowd disasters in low-visibility cases, such as fires, and could help improve the design of crowd-navigating robots.
Source: Technology Review
Their work will help engineers develop a new generation of high-performance, energy-efficient lighting that could replace incandescent and fluorescent bulbs.
"Identifying the root cause of the problem is an indispensable first step toward devising solutions," says Chris Van de Walle, a professor in the Materials Department at UC Santa Barbara who heads the research group that carried out the work.
Van de Walle and his colleagues are working to improve the performance of nitride-based LEDs, which are efficient, non-toxic and long-lasting light sources. They investigated a phenomenon referred to as "droop"?the drop in efficiency that occurs in these LEDs when they're operating at the high powers required to illuminate a room. The cause of this decline has been the subject of considerable debate, but the UC Santa Barbara researchers say they've figured out the mechanism responsible for the effect by performing quantum-mechanical calculations.
LED droop, they conclude, can be attributed to Auger recombination, a process that occurs in semiconductors, in which three charge-carriers interact without giving off light. The researchers also discovered that indirect Auger effects, which involve a scattering mechanism, are significant?a finding that accounts for the discrepancy between the observed degree of droop and that predicted by other theoretical studies, which only accounted for direct Auger processes.
In nitride LEDs, "These indirect processes form the dominant contribution to the Auger recombination rate," says Emmanouil Kioupakis, a postdoctoral researcher at UC Santa Barbara and lead author of a paper published online April 19 in Applied Physics Letters. The other authors are Van de Walle, Patrick Rinke, now with the Fritz Haber Institute in Germany, and Kris Delaney, a project scientist at UC Santa Barbara.
LED droop can't be eliminated because Auger effects are intrinsic, but it could be minimized, the researchers say, by using thicker quantum wells in LEDs or growing devices along non-polar or semi-polar growth directions in order to keep carrier density low.
"With Auger recombination now established as the culprit, we can focus on creative approaches to suppress or circumvent this loss mechanism," Van de Walle says.
Several of Japan's nuclear power plants, especially the Fukushima Naiishi plant in northeastern Japan, are experiencing serious problems in the wake of earthquake and tsunami. If you've been following the news, you've seen some pretty alarming stuff going on at this plant--terms like "explosion," "partial meltdown," "evacuation," and "radiation exposure." With details sparse from the chaotic scene, here's what you need to know to understand and make sense of the news unfolding in Japan.
Fukushima Dai-ichi Nuclear Plant, March 14, 2011 - DigitalGlobe via Getty Images
What Is a Nuclear Reaction?
A nuclear reaction is at its most basic nothing more than a reaction process that occurs in an atomic nucleus. They typically take place when a nucleus of an atom gets smacked by either a subatomic particle (usually a "free neutron," a short-lived neutron not bound to an existing nucleus) or another nucleus. That reaction produces atomic and subatomic products different from either of the original two particles. To make the kind of nuclear reaction we want, a fission reaction (in which the nucleus splits apart), those two original particles have to be of a certain type: One has to be a very heavy elemental isotope, typically some form of uranium or plutonium, and the other has to be a very light "free neutron." The uranium or plutonium isotopes are referred to as "fissile," which means we can use them to induce fission by bombarding them with free neutrons.
In a fission reaction, the light particle (the free neutron) collides with the heavy particle (the uranium or plutonium isotope) which splits into two or three pieces. That fission produces a ton of energy in the form of both kinetic energy and electromagnetic radiation. Those new pieces include two new nuclei (byproducts), some photons (gamma rays), but also some more free neutrons, which is the key that makes nuclear fission a good candidate to generate energy. Those newly produced free neutrons zoom around and smack into more uranium or plutonium isotopes, which in turn produces more energy and more free neutrons, and the whole thing keeps going that way--a nuclear fission chain reaction.
Nuclear fission produces insane amounts of energy, largely in the form of heat--we're talking several million times more energy than you'd get from a similar mass of a more everyday fuel like gasoline.
Getting Usable Energy From Fission
There are several types of nuclear fission reactors in Japan, but we're going to focus on the Fukushima Naiishi plant, the most hard-hit facility in the country. Fukushima, run by the Tokyo Electric Power Company (TEPCO), has six separate reactor units, although numbers 4, 5, and 6 were shut down for maintenance at the time of the earthquake (and more importantly, the subsequent tsunami). Numbers 1, 2, and 3 are all "boiling water reactors," made by General Electric in the early- to mid-1970s. A boiling water reactor, or BWR, is the second-most-common reactor type in the world.
A BWR contains thousands of thin, straw-like tubes 12 feet in length, known as fuel rods, that in the case of Fukushima are made of a zirconium alloy. Inside those fuel rods is sealed the actual fuel, little ceramic pellets of uranium oxide. The fuel rods are bundled together in the core of the reactor. During a nuclear fission chain reaction, the tubes heat up to extremely high temperatures, and the way to keep them safe turns out to also be the way to extract useful energy from them. The rods are kept submerged in demineralized water, which serves as a coolant. The water is kept in a pressurized containment vessel, so it has a boiling point of around 550 °F. Even at such a high boiling point, the burning hot fuel rods produce large amounts of steam, which is actually what we want from this whole complicated arrangement—the high-pressure steam is used to turn the turbines on dynamos, producing electricity.
Boiling Water Reactor Schematic: 1. Reactor pressure vessel (RPV) 2. Nuclear fuel element 3. Control rods 4. Circulation pumps 5. Engine control rods 6. Steam 7. Feedwater 8. High pressure turbine (HPT) 9. Low pressure turbine 10. Generator 11. Exciter 12. Condenser 13. Coolant 14. Pre-heater 15. Feedwater pump 16. Cold water pump 17. Concrete enclosure 18. Mains connection Nicolas Lardot - Wikimedia Commons
Since lots of heat is being produced, as well as the production and use of lots of pretty nasty radioactive materials, nuclear plants employ a variety several safety efforts beyond simply the use of the cooling water (which itself is backed up by redundant diesel generators--more on that later). The plant's core, the fuel rods and the water, is encased in a steel reactor vessel. That reactor vessel is in turn encased in a giant reinforced concrete shell, which is designed to prevent any radioactive gases from escaping.
Isn't There an "Off" Switch?
Sure! But needless to say, safely shutting down and controlling a nuclear reactor is not at all as simple as unplugging a rogue kitchen appliance. This is due to the extreme heat still present well after fission has subsided--mostly due to chemical reactions inherent in the fission reaction.
A functioning fission plant employs a system of control rods, essentially structures that limit the rate of fission inside the fuel rods by absorbing roaming free neutrons. The rate of fission can be controlled--even stopped--by inserting and removing the control rods in the reactor. At the time of the quake, the Fukushima reactors' control rods functioned normally, shutting down the fission reaction. But even with the fission reaction stopped, the fuel rods remain at extremely high temperatures and require constant cooling.
Which isn't typically a problem, so long as the cooling system (and, failing that, its diesel-powered backup) is still intact. But after losing main power in the quake, the subsequent tsunami wave also destroyed Fukushima's diesel backup generators. Which is a serious problem; even though the fission had stopped, coolant is still very much required to keep the plant safe.
That's due to the heat that remains in the nuclear core, both from the recently-disabled but still-hot fuel rods and from the various byproducts of the fission process. Those byproducts include radioactive iodine and caesium, both of which produce what's called "decay heat"--residual heat that is very slow to dissipate. If the core isn't continuously cooled, there's still more than enough heat to cause a meltdown long after it's been "turned off."
In the case of the Fukushima plant, with both the main and backup coolant systems down for the count, TEPCO was forced to rig a method to flood the core with seawater laced with boric acid (the boric acid to stave off another fission reaction if one were to restart due to a meltdown--more on that below). That's a bad sign--it's a last-ditch effort to prevent catastrophe, as the salt in the seawater will corrode the machinery. It's also a temporary fix: TEPCO will need to pump thousands of gallons of seawater into the core every day, until they can get the coolant system back online. Without it, the seawater method might have to go on for weeks, even up to a year, as the decay heat slowly subsides.
The Dreaded Meltdown
First of all, a "meltdown" is not a precisely defined term, which makes it fairly useless as an indicator of what's going on. Even the terms "full meltdown" and "partial meltdown" are pretty unhelpful, which is partly why we've written this guide--you'll be able to understand what's actually happening without relying on spurious terms that the experts themselves are often loathe to use.
Anyway, let's start at some of the less severe (though still unsettling) things that can happen when the coolant liquid is no longer present in the core. When the fuel rods are left uncovered by water, they'll get far too hot--we're talking thousands of degrees Celsius here--and begin to oxidize, or rust. That oxidation will react with the water that's left, producing highly explosive hydrogen gas. This has already happened in reactor No. 1 at Fukushima (see the video below). The hydrogen gas can be vented in smallish doses into the containment building, but if they can't vent it fast enough, it'll explode, which is exactly what happened at reactor No. 1. Keep in mind, this is not a nuclear reaction, but a simple chemical explosion that often (as in this case) results in little or no radioactive material being leaked into the outside world.
TEPCO has announced that after the explosion, radiation levels in the area around the plant were still within "normal" parameters. This is an important distinction--not to say that a hydrogen explosion at a nuclear plant is particularly fun news, but it is not nearly as panic-inducing as a meltdown.
What people mean when they say "meltdown" can refer to several different things, all likely coming after a hydrogen explosion. A "full meltdown" has a more generally accepted definition than, say, a "partial meltdown." A full meltdown is a worst-case scenario: The zirconium alloy fuel rods and the fuel itself, along with whatever machinery is left in the nuclear core, will melt into a lava-like material known as corium. Corium is deeply nasty stuff, capable of burning right through the concrete containment vessel thanks to its prodigious heat and chemical force, and when all that supercharged nuclear matter gets together, it can actually restart the fission process, except at a totally uncontrollable rate. A breach of the containment vessel could lead to the release of all the awful radioactive junk the containment vessel was built to contain in the first place, which could lead to your basic Chernobyl-style destruction.
The problem with a full meltdown is that it's usually the end result of a whole boatload of other chaos--explosions, fires, general destruction. Even at Chernobyl, which (unbelievably, in retrospect) had no containment building at all, the damage was caused mostly by the destruction of the plant by explosion and a graphite fire which allowed the corium to escape to the outside world, not the physical melting of the nuclear core.
Over the weekend, Chief Cabinet Secretary Yukio Edano somewhat hesitatingly confirmed a "partial" meltdown. What does that mean? Nobody knows! The New York Times notes that a "partial" meltdown doesn't actually need to have any melting involved to qualify it as such--it could simply mean the fuel rods have been un-cooled long enough to corrode and crack, which given the hydrogen explosion, we know has already happened. But we'd advise against putting too much stock in any term relating to "meltdown"--it'll be much more informative to find out what's actually going on, rather than relying on a vague blanket term.
As TEPCO grapples with the damage the earthquake and tsunami did to the nuclear system, there's going to be lots of news--there could be more explosions, mass evacuations, and more "meltdowns" of one kind or another. All we can do is learn about what's going on, think calmly about the situation, and hope that TEPCO can eventually regain control of the plants
But we're fighting back, and winning! We played a key role in stopping Murdoch's grab for media control in the UK. Now we're taking our red-hot UK campaign global, to roll back the Murdoch menace everywhere with campaigns, investigations and legal action.
Hacking murdered children's phones, paying off police, destroying evidence of crimes, threatening politicians -- UK leaders say Rupert Murdoch's empire has "entered the criminal underworld". For decades, Murdoch has ruled with impunity -- making and breaking governments with his vast media holdings and scaring opponents into silence, but we're fighting back, and winning!
Murdoch at the World Economic Forum Annual Meeting in 2009.
Through almost 1 million actions, 7 campaigns, 30,000 phone calls, investigations and countless stunts and legal tactics, we've played a lead role and stopped Murdoch from buying over 50% of UK commercial media! Now we're taking our red-hot UK campaign global, to roll back the Murdoch menace everywhere.
Here's the plan: together we can a) hire investigators to expose Murdoch's corrupt tactics beyond the UK b) organize prominent voices to break the cycle of fear and speak out on this issue and c) mobilise people in key countries behind new laws and legal actions that stop Murdoch and clean up our media for good.
Avaaz members live in every country where Murdoch works, making our movement the only one that can truly take a campaign against his global empire and win. The time is now -- If just 20,000 of us donate a small amount each, we can seize this once-in-a-generation chance. Click below to chip in:
For weeks, nearly daily revelations have uncovered the extent of Murdoch media's corruption in the UK. His operatives hacked the phones of thousands of people, including grieving widows and soldiers who died in Iraq, stole a Prime Minister's bank information and harassed him for 10 years, paid huge sums to police officers, and Rupert's son, James Murdoch, himself authorized hush money to victims.
But this is the tip of the iceberg -- Murdoch is a global problem. He's famous for dictating editorial positions to his papers. He corrupts and controls democracies by pushing politicians to back his extremist ideas on war, torture and a host of other planetary ills, and destroying the careers of politicians with smear campaigns unless they do his bidding. In the US, he helped elect George W. Bush and has most of the Republican presidential candidates actually on his payroll (see sources below). His Fox News Network spread lies to promote the war in Iraq, pushed resentment of Muslims and immigrants and spawned the right-wing tea party. Maybe worst of all, he has helped block critical global action on climate change.
Murdoch's reign of fear is breaking down, and many are on the edge of speaking out against his tactics. The dam is about to break in the US, Australia and elsewhere, but we need to give it an urgent push by investigating Murdoch further, organising high profile opposition, and making sure that our politicians pass laws that will clean up our media for good. Let's make it happen together:
Our community kept campaigning on this issue when almost everyone else in the UK gave up hope. Because we're people-powered, we don't have the same fear of Murdoch that almost everyone else does. It's part of the promise that people power has for change in the world. Today, hope is breaking out in the UK -- let's take it global.
Ricken, Emma, Maria Paz, Giulia, Luis, Alice, Brianna and the rest of the Avaaz team
Decision on BSkyB takeover could take weeks after surge in online campaigning (Huffington Post)
BSkyB bid final clearance unlikely to be given before September (The Guardian)
Culture Secretary Jeremy Hunt will take 'several weeks' to review 100,000-plus submissions on News Corp/BSkyB takeover
Murdoch maimed by social media (The Scotsman)
Who is Rupert Murdoch? (Center for American Progess)
The global reach of Murdoch's News Corp (BBC)
Rebekah Brooks must go over Milly 'hacking' - Miliband (BBC)
Latest Updates on British Phone Hacking Scandal (New York Times)
Fox News 2012? Nearly All Potential GOP Presidential Candidates On FNC Payroll (Huffington Post)
Hydrogen gas is not only explosive but also very space-consuming. Storage in the form of very dense solid metal hydrides is a particularly safe alternative that accommodates the gas in a manageable volume. As the storage tank should also not be too heavy and expensive, solid-state chemists worldwide focus on hydrides containing light and abundant metals like magnesium.
Sjoerd Harder and his co-workers at the Universities of Groningen (Netherlands) and Duisburg-Essen (Germany) now take the molecular approach. As the researchers report in the journal Angewandte Chemie, extremely small clusters of molecular magnesium hydride could be a useful model substance for more precise studies about the processes involved in hydrogen storage.
Magnesium hydride (MgH2) can release hydrogen when needed and the resulting magnesium metal reacts back again to form the hydride by pressurizing with hydrogen at a "gas station". Unfortunately, this is an idealized picture. Not only is the speed of hydrogen release/uptake excessively slow (kinetics) but it also only operates at higher temperatures. The hydrides, the negatively charged hydrogen atoms (H-), are bound so strongly in the crystal lattice of magnesium cations (Mg2+) that temperatures of more than 300 ?C are needed to release the hydrogen gas.
Particularly intensive milling has made it possible to obtain nanocrystalline materials, which, on account of its larger surface, rapidly release or take up hydrogen. However, the high stability of the magnesium hydride still translates to rather high release temperatures. According to recent computer calculations, magnesium hydride clusters of only a few atoms possibly could generate hydrogen at temperatures far below 300 °C. Clusters with less than 20 Mg2+ions are smaller than one nanometer and behave differently from the bulk material. Their hydride ions have fewer Mg2+ neighbors and are more weakly bound. However, it is extremely difficult to obtain such tiny clusters by milling. In Harder's "bottom-up" approach, magnesium hydride clusters are made by starting from molecules. The challenge is to prevent such clusters from forming very stable bulk material. Using a special ligand system, they could trap a cluster that resembles a paddle wheel made of eight Mg2+ and ten H- ions. For the first time it was shown that molecular clusters indeed release hydrogen already at the temperature of 200 °C.
This largest magnesium hydride cluster reported to date is not practical for efficient hydrogen storage but shines new light on a current problem. It is easily studied by molecular methods and as a model system could provide detailed insights in hydrogen storage.