The key to using silicon in electronic devices such as transistors and solar cells lies in doping, or adding in small quantities of other elements, to create an excess of electrons (n-type) or positively charged holes (p-type) that change the material's conductivity. N-type and p-type silicon are butted together to form p-n junctions, the basic building blocks of electronic devices such as solar cells, light-emitting diodes, and transistors.
For years, researchers have tried to do something similar with quantum dots, tiny semiconductor crystals a few nanometers in diameter. Now, a team of Israeli researchers has reported success. They have doped indium arsenide quantum dots to create n-type and p-type materials. The advance, published in the journal Science, could lead to new types of efficient, cheap, and printable thin-film solar cells.
Quantum dots hold promise for low-cost solar cells because they can be made using simple, inexpensive chemical reactions. Scientists have calculated that quantum dots could be used to make thin-film photovoltaics that are at least as efficient as conventional silicon cells, and possibly more efficient. The higher possible efficiency is because nanocrystals made of certain semiconductors can emit more than one electron for every photon absorbed. Plus, tweaking their size and shape changes the colors of light they absorb. "We could tune the nanocrystal absorption to match the solar spectrum," says Uri Banin, a professor of chemistry at the Hebrew University of Jerusalem who led the new work.
Despite these advantages, no one has succeeded in making efficient quantum-dot solar cells. For that, you need n-type and p-type nanocrystals, says Eran Rabani, a chemistry professor at Tel Aviv University who was involved in the new work. In solar cells, the electrons and holes that are created when photons are absorbed have to be separated so that the electrons can travel out of the semiconductor to the external electric circuit. Some electrons and holes inevitably combine, but they combine much faster in quantum dots than in large silicon crystals. Doping semiconductor nanocrystals would provide a way for creating p-n junctions that separate electrons and holes efficiently, Rabani says.
Silicon is typically doped with phosphorus or boron atoms, but these materials do not work with quantum dots because the dots are so small. A 4-nanometer-wide nanocrystal contains about 1,000 atoms. Adding a few dopant atoms .can lead to their being expelled from the nanocrystals.
Some quantum-dot doping efforts have succeeded. Researchers have, for instance, doped them with magnetic manganese ions, but this technique does not introduce excess electrons or holes. Others have been able to make undoped nanocrystals n-type by injecting electrons into them. Still others have been able to dope thin films of nanocrystals.
The Israeli team, by contrast, is able to dope freestanding nanoparticles. "This is a major breakthrough here," says Y. Charles Cao, a chemistry professor at the University of Florida in Gainesville. "The major advantage here is you [have] the building blocks for the bottom-up assembly of nanocrystal electronic devices." Another plus, adds Cao, is that the method used to make the dots is easy and inexpensive and could be scaled up to make devices in large quantities.
Although the lungless salamander and some frog species have developed ballistic tongues, the chameleon's ballistic tongue is the fastest, the longest, and the one that can catch the heaviest prey. A chameleon’s tongue can elongate more than six times its rest length, zipping forward at speeds of 3.5-10.5 meters/second – faster than a human eye can follow. The tongue is called ballistic because, like all ballistic objects, it moves freely without any applied force during its forward motion. Once the chameleon's accordion-like tongue is ejected, it continues moving forward under its own inertia.
With the aim to mimic the mechanisms and performance of the chameleon’s tongue, researcher Alexis Debray of Canon, Inc., in Tokyo, Japan, has developed four ballistic robotic manipulators. Each of the four manipulators excels at copying a certain part of the chameleon’s tongue, and insights from each design could eventually be combined to create a more advanced chameleon tongue that could have manufacturing applications. Debray’s study is published in a recent issue of Bioinspiration & Biomimetics.
“As far as I know, this is the first published demonstration of manipulators based on the chameleon tongue,” Debray told PhysOrg.com. “The particular mechanism of the tongue of the chameleon allows for fast accelerations and velocities and also applies no force during most of the motion.
As Debray explains, what we normally think of as the tongue of the chameleon is actually a larger system called the hyolingual apparatus. The tongue is just a small component on the front tip of the hyolingual apparatus. The majority of the hyolingual apparatus consists of the long, thin hyoglossus complex, which is the part that folds up like an accordion inside the chameleon’s mouth.
The rapid movement of the chameleon’s hyolingual apparatus involves three phases: projection, catching, and retraction. Each of these three phases is controlled by a different system. The tongue (tip of the hyolingual apparatus) contains the accelerator muscle and collagens that control the projection. When the chameleon is ready to project, it slowly protrudes its tongue out of its mouth. Then, the tongue’s accelerator muscle projects the tongue off a bone inside the chameleon’s mouth. No applied force is needed to keep the tongue – and the rest of the hyolingual apparatus – moving forward. When the tongue reaches its prey, a tongue pad containing a small suction on the tip of the tongue can stick to the prey. Finally, the hyoglossus muscle in the accordion-like hyoglossus complex retracts the tongue at a constant velocity. Although the three phases are controlled by different systems, they occur in a single smooth, continuous motion.
Like the chameleon tongue, Debray’s robotic manipulators use different specialized systems for projection, catching, and retraction. To project, all four manipulators use a coilgun in place of the chameleon tongue’s accelerator muscle. Elastomers and/or cotton string is used in place of the chameleon’s hyolingual apparatus. Instead of folding up like an accordion, the elastomers and string are wound around a reel. As for catching, the robotic manipulators use magnets on the tip of the elastomers, which attract magnetic “prey.” For retraction, the manipulators use either an elastomer, a DC motor connected to a reel and string, or a combination of both. One of the manipulators also had wings on the mobile part, which could allow researchers to take advantage of aerodynamic effects.
“In the future, movable wings will allow controlling the trajectory after the ejection of the tongue, which is not possible now,” Debray said. “In our experiments, the wings are not movable. However, their aerodynamic effect on the trajectory of the tongue has been demonstrated experimentally. So far, aerodynamic effects have been poorly studied in the field of manipulators.”
Using a high-speed camera, Debray could track the manipulators in motion. The results showed that the robotic manipulators could reach a projection velocity of 3.8 meters/second without the need for a continuously applied force, which is similar to the velocity of the chameleon tongue. In addition, the robotic manipulators could reach an acceleration of 919 meters/second2, which exceeds that of the chameleon (374 meters/second2). The manipulators that used a DC motor and string for retraction had the same extension ability as the chameleon tongue, and could also adapt to variations in the targets’ distances, as chameleons can.
By incorporating various end effectors onto the robotic manipulators, the devices could have a variety of applications, especially for products passing on a factory line. For example, manipulators with sensors could be used to sense data on products. Stamps and catching devices could be used to deposit patterns and manipulate objects, respectively. Using a mechanism based on the chameleon’s ballistic tongue could provide certain advantages compared with other manipulators due to the small size and flexibility. Further, because ballistic manipulators do not apply a continuous force during their forward motion, an accidental collision would be less severe and likely cause less damage compared to a device being pushed forward. As Debray explained, the current manipulators lack reliability, and so they cannot yet be put to practical use.
“The work presented in the paper is a first step towards manipulators inspired by the chameleon tongue,” Debray said. “Further development is needed in order to use them in factory lines. However, the ultimate goal of this work is the manufacture of Canon products such as cameras and printers, among others.”
Economic theory assumes resource scarcity as an important premise, and there is a general consensus that scarce resources are best allocated by means of a market. However, a new doctoral thesis from the University of Gothenburg, Sweden, shows that there may be alternative solutions to the allocation problem.
Economic theory generally assumes that there will never be enough food, water, cars, money etc. to satisfy people's wants. This means that inequalities, conflict and poverty are inevitable parts of society. Many economists feel that scarcity is best dealt with through the presence of a market – the highest bidders gain access to a society's scarce resources.
Yet, economic sociologists do not necessarily see resource scarcity as inevitable, and neither do they always agree with the mainstream solution to the economic problem. There are indeed enough resources, they might argue, but people are for various reasons denied access. For example, there is enough food in the world, but people are still starving. Why is that?
'The market as an allocation mechanism has not been able to distribute food to everyone – every sixth person in the world does not have access to enough food,' says Adel Daoud, author of the thesis.
So, do we need the market?
'Maybe we do, given the present economic system, but we should at the same time ask ourselves whether any alternative allocation models could help us manage the world's resources better, not least considering the climate threat. A so-called economic democracy could be one such solution. In an economic democracy, citizens get to have a say about what and how much of various products and services should be produced,' says Daoud.
One of the main contributions of the thesis is to show the importance of using alternative perspectives, such as economic sociology, to deal with the notion of resource scarcity rather than simply seeing scarcity as inevitable.
High school students who feel they do not fit in are less likely to attend college — particularly girls who are gay or obese — according to new research from The University of Texas at Austin.
"Because social experiences in high school have such demonstrable effects on academic progress and attending college, the social concerns of teenagers are educational concerns for school," says sociologist Robert Crosnoe.
Crosnoe has completed one of the most comprehensive studies of the long-term effects on teenagers who say they don't fit in. He used national statistics from 132 high schools and spent more than a year inside a high school in Texas with 2,200 students, observing and interviewing teenagers. His findings will be published in his new book "Fitting In, Standing Out" (Cambridge University Press, April 11).
"Kids who have social problems — often because they are overweight or gay are at greater risk of missing out on going to college simply because of the social problems they have and how it affects them emotionally," says Crosnoe, a Sociology Department professor and Population Research Center affiliate. "Not because of anything to do with intelligence or academic progress."
Girls were 57 percent and boys 68 percent less likely than peers of the same race, social class and academic background to attend college if they had feelings of not fitting in, according to the study. Particularly at risk were girls who are obese, who are 78 percent less likely to attend college than non-obese girls, and those who are gay, who are 50 percent less likely to attend.
Crosnoe found feelings of not fitting in led to increased depression, marijuana use and truancy over time. Those coping strategies interrupt the education process — the classes teenagers take, the grades they make — which, in turn, affect their ability to go to college.
"Teenagers cope with the discomforts of not fitting in, including being bullied, in ways that are protective in the short term, but disastrous in the long term," says Crosnoe.
His research, funded by the National Institutes of Health and William T. Grant Foundation, has resulted in recommendations for how parents, teachers and policymakers can ensure that the social side of high school supports, rather than undermines, academics. It comes at a time when state lawmakers and federal policymakers are tackling bullying — often a cause of teenage social problems — as a national crisis.
Hundreds of thousands of individuals globally celebrate today (May 5, 2011 - TA note) the confirmation that their efforts to end the torturous pre-trial confinement conditions inflicted upon US Army PFC Bradley Manning have been successful. Manning's lead defense attorney, David E. Coombs of Rhode Island, has personally verified that Manning is indeed being held in Medium Custody confinement at the Joint Regional Corrections Facility (JRCF) at Fort Leavenworth, Kansas, as claimed by the Army last week.
"We won this battle because 600,000 individuals took the time to write letters and sign petitions, because thousands called the White House switchboard, because 300 of America's top legal scholars decried Bradley's pre-trial conditions as a clear violation of our Constitution's 5th and 8th Amendments," declared Jeff Paterson of Courage to Resist and the Bradley Manning Support Network. "We won this battle because over a hundred concerned citizens engaged in civil disobedience at the White House and at Quantico, and because our grassroots campaign shows no sign of slowing."
These new conditions reflect a dramatic improvement for Manning following his transfer to Fort Leavenworth on April 20, 2011, after having suffered extreme solitary-like confinement at US Marine Corps Base Quantico, Virginia. During the nine months at Quantico, Manning was denied meaningful exercise, social interaction, sunlight, and was at times kept completely naked. These conditions were unique to Manning and were illegal under US military law as they clearly amounted to pre-trial punishment.
"I was able to tour the (Fort Leavenworth) facility and meet with PFC Manning last week. PFC Manning is now being held in Medium Custody. He is no longer under.harsh pretrial confinement conditions. Unlike at Quantico, PFC Manning's cell has a large window that provides adequate natural light....PFC Manning is able to have all of his personal items in his cell, which include his clothing, his legal materials, books and letters from family and friends....Each pre-trial area (including PFC Manning's) has four cells, and each pre-trial detainee is assigned to his own cell. The cells are connected to a shared common area, with a table, a treadmill, a television and a shower area....PFC Manning and his group are taken to the outdoor recreation area [for approximately two hours daily]," explained Coombs on his blog at www.armycourtmartialdefense.info hours ago.
"President Obama's recent pronouncement that Bradley Manning 'broke the law' amounts to Unlawful Command Influence, something clearly prohibited because it's devastating to the military justice system. Manning will eventually be judged by a jury of career military officers and noncommissioned officers. Will they be able to set aside the declaration of their commander in chief?" explains attorney Kevin Zeese, a member of the Bradley Manning Support Network. "Along with the illegal pre-trial punishment already inflicted upon Bradley, the government has more than enough legal basis to drop the prosecution. Instead, the death penalty or life in prison hangs over Manning's head."
After nearly a year in confinement, the Army is expected to soon announce Manning's first public hearing, an Article 32 pre-trail proceeding, which will be held in the Washington DC area. Scores of international solidarity events are already being planned.
US Army intelligence analyst Private First Class Bradley E. Manning, 23-years-old, was arrested in Iraq on May 26, 2010. He still awaits his first public court hearing, now expected to begin in June 2011. Over 4,300 individuals have contributed over $333,000 towards PFC Manning's legal fees and related public education efforts. The Bradley Manning Support Network is dedicated to thwarting the military's attempts to hold a secret court martial, and to eventually winning the freedom of PFC Manning.
Researchers at the Hebrew University of Jerusalem have achieved a breakthrough in the field of nanoscience by successfully altering nanocrystal properties with impurity atoms -- a process called doping – thereby opening the way for the manufacture of improved semiconductor nanocrystals.
Semiconductor nanocrystals consist of tens to thousands of atoms and are 10,000 times smaller than the width of a human hair. These tiny particles have uses in a host of fields, such as solid-state lighting, solar cells and bio-imaging. One of the main potential applications of these remarkable materials is in the semiconductor industry, where intensive miniaturization has been taking place for the last 50 years and is now in the nanometer range.
However, these semiconductors are poor electrical conductors, and in order to use them in electronic circuits, their conductivity must be tuned by the addition of impurities. In this process, foreign atoms, called impurities, are introduced into the semiconductor, causing an improvement in its electrical conductivity.
Today, the semiconductor industry annually spends billions of dollars in efforts to intentionally add impurities into semiconductor products, which is a major step in the manufacturing of numerous electronic products, including computer chips, light emitting diodes and solar cells.
Due to the importance of doping to the semiconductor industry, researchers worldwide have made continuing attempts at doping nanocrystals in order to achieve ever greater miniaturization and to improve production methods for electronic devices. Unfortunately, these tiny crystals are resistant to doping, as their small size causes the impurities to be expelled. An additional problem is the lack of analytical techniques available to study small amounts of dopants in nanocrystals. Due to this limitation, most of the research in this area has focused on introducing magnetic impurities, which can be analyzed more easily. However, the magnetic impurities don't really improve the conductivity of the nanocrystal.
Prof. Uri Banin and his graduate student, David Mocatta, of the Hebrew University Center for Nanoscience and Nanotechnology, have achieved a breakthrough in their development of a straightforward, room- temperature chemical reaction to introduce impurity atoms of metals into the semiconductor nanocrystals. They saw new effects not previously reported. However, when the researchers tried to explain the results, they found that the physics of doped nanocrystals was not very well understood.
Bit by bit, in collaboration with Prof. Oded Millo of the Hebrew University and with Guy Cohen and Prof. Eran Rabani of Tel Aviv University, they built up a comprehensive picture of how the impurities affect the properties of nanocrystals. The initial difficulty in explaining this process proved to be a great opportunity, as they discovered that the impurity affects the nanocrystal in unexpected ways, resulting in new and intriguing physics.
"We had to use a combination of many techniques that when taken together make it obvious that we managed to dope the nanocrystals. It took five years but we got there in the end," said Mocatta.
This breakthrough was reported recently in the prestigious journal Science. It sets the stage for the development of many potential applications with nanocrystals, ranging from electronics to optics, from sensing to alternative energy solutions. Doped nanocrystals can be used to make new types of nanolasers, solar cells, sensors and transistors, meeting the exacting demands of the semiconductor industry.
A consortium of scientists is developing a new type of large fluid battery that will be able to store enough renewable energy to power 2,000 homes. One of the roadblocks to large-scale renewable energy adoption is that it is intermittent — if the sun isn’t shining or the wind isn’t blowing power can’t be generated, so there is a tremendous need for systems that store excess power to be released as needed. These new batteries are based on redox flow technology — which converts chemical energy to electrical currents very quickly — and each one will be the size of a handball court.
The scientists have already developed a working 2 kilowatt battery and are hoping to scale the model up to 20 megawatt hours. “The process already works reliably,” notes Dr. Christian Dötsch, business unit manager for a participating institute, Energy Efficiency Technologies at UMSICHT. “The challenge lies in the upscale version, the enlargement of these plants.”
In principle the scientists believe they can build an 80 kW battery with their present technology, and they hope to get a 20 kW system up and running by the end of this year. They are working on new membranes and battery designs that have the potential to create batteries with megawatt capacities in about five years. Though they’ve got a long way to go to reach their desired capacity, this technology is a promising candidate for large-scale renewable power storage facilities.
ZM Global Radio is a weekly radio show presented by various active coordinators of The Zeitgeist Movement in a rotational fashion. These broadcasts discuss the developments and aims of The Zeitgeist Movement.
This wednesday May 4th 2011 at 4pm EDT Cliff Faber, coordinator of the Canadian Chapter, will host The Zeitgeist Movement's Global Radio show.
He will talk about the upcoming Zeitgeist media Festival and will look at chapters and their continued goal of reaching the masses through continued awareness campaigns. A couple guests will be on hand to talk about some very effective campaign strategies that they are using for spreading the message of a Resource Based Economy to the global public.
On May 1, 2011 Pres. Barack Obama appeared on national television with the spontaneous announcement that Osama bin Laden, the purported organizer of the tragic events of September 11th 2001, was killed by military forces in Pakistan.
Within moments, a media blitz ran across virtually all television networks in what could only be described as a grotesque celebratory display, reflective of a level of emotional immaturity that borders on cultural psychosis. Depictions of people running through the streets of New York and Washington chanting jingoistic American slogans, waving their flags like the members of some cult, praising the death of another human being, reveals yet another layer of this sickness we call modern society.
It is not the scope of this response to address the political usage of such an event or to illuminate the staged orchestration of how public perception was to be controlled by the mainstream media and the United States Government. Rather the point of this article is to express the gross irrationality apparent and how our culture becomes so easily fixed and emotionally charged with respect to surface symbology, rather than true root problems, solutions or rational considerations of circumstance.
The first and most obvious point is that the death of Osama bin Laden means nothing when it comes to the problem of international terrorism. His death simply serves as a catharsis for a culture that has a neurotic fixation on revenge and retribution. The very fact that the Government which, from a psychological standpoint, has always served as a paternal figure for it citizens, reinforces the idea that murdering people is a solution to anything should be enough for most of us to take pause and consider the quality of the values coming out of the zeitgeist itself.
However, beyond the emotional distortions and tragic, vindictive pattern of rewarding the continuation of human division and violence comes a more practical consideration regarding what the problem really is and the importance of that problem with respect to priority.
The death of any human being is of an immeasurable consequence in society. It is never just the death of the individual. It is the death of relationships, companionship, support and the integrity of familial and communal environments. The unnecessary deaths of 3000 people on September 11, 2001 is no more or no less important than the deaths of those during the World Wars, via cancer and disease, accidents or anything else.
As a society, it is safe to say that we seek a world that strategically limits all such unnecessary consequences through social approaches that allow for the greatest safety our ingenuity can create. It is in this context that the neurotic obsession with the events of September 11th, 2001 become gravely insulting and detrimental to progress. An environment has now been created where outrageous amounts of money, resources and energy is spent seeking and destroying very small subcultures of human beings that pose ideological differences and act on those differences through violence.
Yet, in the United States alone each year, roughly 30,000 people die from automobile accidents, the majority of which could be stopped by very simple structural changes. That's ten 9/11's each year... yet no one seems to pine over this epidemic. Likewise, over 1 million Americans die from heart disease and cancer annually - causes of which are now easily linked to environmental influences in the majority. Yet, regardless of the over 330 9/11's occurring each year in this context, the governmental budget allocations for research on these illnesses is only a small fraction of the money spent on “anti-terrorism” operations.
Such a list could go on and on with regard to the perversion of priority when it comes to what it means to truly save and protect human life and I hope many out there can recognize the severe imbalance we have at hand with respect to our values.
So, coming back to the point of revenge and retribution, I will conclude this response with a quote from Dr. Martin Luther King Jr., likely the most brilliant intuitive mind when it came to conflict and the power of non-violence. On September 15, 1963 a Birmingham Alabama church was bombed, killing four little girls attending Sunday school.
In a public address, Dr. King stated:
“What murdered these four girls? Look around. You will see that many people that you never thought about participated in this evil act. So tonight all of us must leave here with a new determination to struggle. God has a job for us to do. Maybe our mission is to save the soul of America. We can't save the soul of this nation throwing bricks. We can't save the soul of this nation getting our ammunitions and going out shooting physical weapons. We must know that we have something much more powerful. Just take up the ammunition of love.”
Future buildings may use heat to cool off more efficiently, using new materials developed at Pacific Northwest National Laboratory. The materials could enable compact adsorption chillers inside homes and office buildings.
Adsorption chillers are a type of air conditioner that runs on waste heat, requiring very little electricity. But they’re big and expensive, which has limited their use to large, hot places like power plants or industrial spaces, as Technology Review explains.
PNNL received a grant last summer from the DOE’s Advanced Research Projects Agency, ARPA-E, to build smaller adsorption chillers based on PNNL-developed nanostructured metal-organic heat carriers, or MOHCs. The material is more porous than existing adsorption materials, which makes them more efficient. PNNL researchers displayed the new material at a recent conference.
Adsorption is the binding of molecules or particles to a surface. In an adsorption chiller, hot water drives the cooling process instead of electricity. An evaporated refrigerant (in this case, water) binds to the surface of silica gel. The gel acts as a sponge for water vapor, and when the gel is heated, the water molecules are released, condensing into water droplets when the pressure rises.
The nanostructured MOHCs are even better sponges, trapping three or four times more water by weight, which can reduce the size of the system. They are also more efficient at releasing the water molecules, further reducing the chiller’s size; Tech Review gives the full breakdown here.
PNNL says a variety of heat sources can be used to warm up the MOHCs and free the water vapor, such as burning natural gas or other fuels, heating with solar thermal, or capturing engine or fuel cell system waste heat.