Fully printed carbon nanotube transistor circuits for displays

ScienceDaily (Nov. 30, 2011) — Since the invention of liquid crystal displays in the mid-1960s, display electronics have undergone rapid transformation. Recently developed organic light-emitting diodes (OLEDs) have shown several advantages over LCDs, including their light weight, flexibility, wide viewing angles, improved brightness, high power efficiency and quick response.

OLED-based displays are now used in cell phones, digital cameras and other portable devices. But developing a lower-cost method for mass-producing such displays has been complicated by the difficulties of incorporating thin-film transistors that use amorphous silicon and polysilicon into the production process.

Now, researchers from Aneeve Nanotechnologies, a startup company at UCLA's on-campus technology incubator at the California NanoSystems Institute (CNSI), have used low-cost ink-jet printing to fabricate the first circuits composed of fully printed back-gated and top-gated carbon nanotube-based electronics for use with OLED displays. 

The startup includes collaborators from the departments of materials science and electrical engineering at the UCLA Henry Samueli School of Engineering and Applied Science and the department of electrical engineering at the University of Southern California.

In this innovative study, the team made carbon nanotube thin-film transistors with high mobility and a high on-off ratio, completely based on ink-jet printing. They demonstrated the first fully printed single-pixel OLED control circuits, and their fully printed thin-film circuits showed significant performance advantages over traditional organic-based printed electronics.

"This is the first practical demonstration of carbon nanotube-based printed circuits for display backplane applications," said Kos Galatsis, an associate adjunct professor of materials science at UCLA Engineering and a co-founder of Aneeve. "We have demonstrated carbon nanotubes' viable candidacy as a competing technology alongside amorphous silicon and metal-oxide semiconductor solution as a low-cost and scalable backplane option."

This distinct process utilizes an ink-jet printing method that eliminates the need for expensive vacuum equipment and lends itself to scalable manufacturing and roll-to-roll printing. The team solved many material integration problems, developed new cleaning processes and created new methods for negotiating nano-based ink solutions.

For active-matrix OLED applications, the printed carbon nanotube transistors will be fully integrated with OLED arrays, the researchers said. The encapsulation technology developed for OLEDs will also keep the carbon nanotube transistors well protected, as the organics in OLEDs are very sensitive to oxygen and moisture.

The technology incubator at the CNSI was established two years ago to nurture early-stage research and to help speed the commercial translation of technologies developed at UCLA. Aneeve Nanotechnologies LLC has been conducting proof-of-concept work at the tech incubator with the mission of developing superior, low-cost, high-performance electronics using nanotechnology solutions that bridge the gap between emerging and traditional platforms.

The research was published this month in the journal Nano Letters.

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Pochiang Chen, Yue Fu, Radnoosh Aminirad, Chuan Wang, Jialu Zhang, Kang Wang, Kosmas Galatsis, Chongwu Zhou. Fully Printed Separated Carbon Nanotube Thin Film Transistor Circuits and Its Application in Organic Light Emitting Diode Control. Nano Letters, 2011; : 111122151948003 DOI: 10.1021/nl202765b

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Cancer cells' DNA repair disrupted to increase radiation sensitivity

ScienceDaily (Dec. 1, 2011) — Shortening end caps on chromosomes in human cervical cancer cells disrupts DNA repair signaling, increases the cells' sensitivity to radiation treatment and kills them more quickly, according to a study in Cancer Prevention Research.

Researchers would to like see their laboratory findings -- published in the journal's Dec. 5 print edition -- lead to safer, more effective combination therapies for hard-to-treat pediatric brain cancers like medulloblastoma and high-grade gliomas. To this end, they are starting laboratory tests on brain cancer cells.

"Children with pediatric brain cancers don't have very many options because progress to find new treatments has been limited the last 30 years," said Rachid Drissi, PhD, principal investigator on the study and a researcher in the Division of Oncology at Cincinnati Children's. "The ability to make cancer cells more sensitive to radiation could allow physicians to use lower radiation doses to lessen side effects. Too many children with brain cancer can develop disabilities or die from treatment."

Before treating cells with ionizing radiation, the researchers blocked an enzyme called telomerase, found in over 90 percent of cancer cells but barely detectable in most normal human cells. In cancer cells, telomerase helps maintain the length of caps on the ends of chromosomes called telomeres. This helps cancer cells replicate indefinitely, grow and spread, Drissi said.

Unraveling DNA stability

Found on chromosomes in both cancerous and normal cells, telomeres are analogous to plastic caps that keep shoestring ends from unraveling. Telomeres help preserve DNA stability in cells by containing genetic miscues. This helps explain why cells with maintained or long telomeres appear to be more resistant to radiation.

In normal cells lacking the telomerase enzyme, telomeres get shorter each time cells divide. They continue doing so until normal cells stop dividing, reaching a condition called senescence. If this first cell-cycle "stop sign" is bypassed, cells continue dividing until telomeres become critically short and reach a second stopping point, when most cells die. In rare instances, cells bypass this second "stop sign" and survive. This survival is often associated with telomerase activation and the onset of cancer.

This was the basis for experiments Drissi and his colleagues conducted to compare the radiation sensitivity and survivability of cells based on telomere length. They also monitored DNA repair responses in the cells by looking for specific biochemical signs that indicate whether the repair systems are working.

The tests involved normal human foreskin cells -- called fibroblasts -- and human cervical carcinoma cells. They exposed the cells to ionizing radiation and analyzed DNA repair responses as telomeres became progressively shorter. In the cervical cancer cells, researchers blocked the telomerase enzyme before radiation treatment to induce progressively shorter telomeres.

Both late-stage noncancerous cells with shorter telomeres, and cancer cells with induced shorter telomeres, were more radiosensitive and died more quickly, according to the study.

Among cancer cells with maintained telomere length, close to 10 percent receiving the maximum dose of ionizing radiation used in the study (8 Gy, or Gray Units) survived the treatment. None of the cancer cells with the shortest telomeres survived that exposure.

Researchers said the cancer cells became more radiosensitive because material inside the chromosomes -- called chromatin -- compacted as telomeres became shorter. Compacted chromatin then disrupted the biochemical signaling of a protein called ATM (ataxiatelangeietasia mutated).

ATM is a master regulator of DNA repair and cell division. It sends signals to activate other biochemical targets (H2AX, SMC1, NBS1 and p53) that help direct DNA repair and preserve genetic stability. In telomere-shortened cancer cells, the compacted chromatin inhibited ATM signaling to all of the chromatin-bound targets tested in the study. This disrupted DNA repair responses and increased radiation sensitivity.

Testing brain cancer cells

The researchers are now testing their findings in cells from hard-to-treat pediatric brain tumors. These tests begin as Drissi's laboratory also leads correlative cancer biology studies of tumor samples from a current clinical trial. The trial is evaluating telomere shortening as a stand-alone therapy for pediatric cancer.

Managed through the National Institutes of Health's Children's Oncology Group (COG), the multi-institutional Phase 1 trial is testing the safety and tumor response capabilities of the drug Imetelstat, which blocks telomerase in cancer cells. Drissi serves on the clinical trial committee along with Maryam Fouladi, MD, MSc, and medical director of Neuro-Oncology at Cincinnati Children's. She leads the medical center's clinical participation in the trial.

Drissi and Fouladi are starting preparatory work to develop, and seek approvals for, a possible clinical trial to test telomere shortening and radiation treatment as a safer, more effective treatment for pediatric brain tumors.

Funding support for the current study in Cancer Prevention Research -- published by the American Society for Cancer Research -- came from the National Institutes of Health, the American Lebanese Syrian Associated Charities of St. Jude Children's Research Hospital and Cincinnati Children's Hospital Medical Center. Also collaborating were researchers from Children's National Medical Center in Washington, D.C., and from St. Jude. Funding support for the Drissi lab's correlative studies on the COG clinical trial comes from CancerFree Kids Pediatric Cancer Research Alliance and from Children's Cancer Research Fund.

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R. Drissi, J. Wu, Y. Hu, C. A. Bockhold, J. S. Dome. Telomere shortening alters the kinetics of the DNA damage response after ionizing radiation in human cells. Cancer Prevention Research, 2011; DOI: 10.1158/1940-6207.CAPR-11-0069

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Scientists propose new names for elements 114 and 116

ScienceDaily (Dec. 1, 2011) — The International Union of Pure and Applied Chemistry (IUPAC) have recommended new proposed names for elements 114 and 116, the latest heavy elements to be added to the periodic table.

Scientists of the Lawrence Livermore National Laboratory (LLNL)-Dubna collaboration proposed the names as Flerovium for element 114 and Livermorium for element 116.

In June 2011, the IUPAC officially accepted elements 114 and 116 as the heaviest elements, more than 10 years after scientists from the Joint Institute for Nuclear Research in Dubna and Lawrence Livermore chemists discovered them.

Flerovium (atomic symbol Fl) was chosen to honor Flerov Laboratory of Nuclear Reactions, where superheavy elements, including element 114, were synthesized. Georgiy N. Flerov (1913-1990) was a renowned physicist who discovered the spontaneous fission of uranium and was a pioneer in heavy-ion physics. He is the founder of the Joint Institute for Nuclear Research. In 1991, the laboratory was named after Flerov -- Flerov Laboratory of Nuclear Reactions (FLNR).

Livermorium (atomic symbol Lv) was chosen to honor Lawrence Livermore National Laboratory (LLNL) and the city of Livermore, Calif. A group of researchers from the Laboratory, along with scientists at the Flerov Laboratory of Nuclear Reactions, participated in the work carried out in Dubna on the synthesis of superheavy elements, including element 116. (Lawrencium -- Element 103 -- was already named for LLNL's founder E.O. Lawrence.)

In 1989, Flerov and Ken Hulet (1926-2010) of LLNL established collaboration between scientists at LLNL and scientists at FLNR; one of the results of this long-standing collaboration was the synthesis of elements 114 and 116.

"Proposing these names for the elements honors not only the individual contributions of scientists from these laboratories to the fields of nuclear science, heavy element research, and superheavy element research, but also the phenomenal cooperation and collaboration that has occurred between scientists at these two locations," said Bill Goldstein, associate director of LLNL's Physical and Life Sciences Directorate.

LLNL scientists Ken Moody, Dawn Shaughnessy, Jackie Kenneally and Mark Stoyer were critical members of the team along with a team of retired LLNL scientists including John Wild, Ron Lougheed and Jerry Landrum. Former LLNL scientists Nancy Stoyer, Carola Gregorich, Jerry Landrum, Joshua Patin and Philip Wilk also were on the team. The research was supported by LLNL Laboratory Research and Development funds (LDRD).

Scientists at LLNL have been involved in heavy element research since the Laboratory's inception in 1952 and have been collaborators in the discovery of six elements -- 113,114,115,116,117 and 118.

Livermore also has been at the forefront of investigations into other areas related to nuclear science such as cross-section measurements, nuclear theory, radiochemical diagnostics of laser-induced reactions, separations chemistry including rapid automated aqueous separations, actinide chemistry, heavy-element target fabrication, and nuclear forensics.

The creation of elements 116 and 114 involved smashing calcium ions (with 20 protons each) into a curium target (96 protons) to create element 116. Element 116 decayed almost immediately into element 114. The scientists also created element 114 separately by replacing curium with a plutonium target (94 protons).

The creation of elements 114 and 116 generate hope that the team is on its way to the "island of stability," an area of the periodic table in which new heavy elements would be stable or last long enough for applications to be found.

The new names were submitted to the IUPAC in late October and now remain in the public domain. The new names will not be official until about five months from now when the public comment period is over.

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New switch could improve electronics

ScienceDaily (Dec. 1, 2011) — Researchers at the University of Pittsburgh have invented a new type of electronic switch that performs electronic logic functions within a single molecule. The incorporation of such single-molecule elements could enable smaller, faster, and more energy-efficient electronics. The research findings, supported by a $1 million grant from the W.M. Keck Foundation, were published online in the Nov. 14 issue of Nano Letters.

"This new switch is superior to existing single-molecule concepts," said Hrvoje Petek, principal investigator and professor of physics and chemistry in the Kenneth P. Dietrich School of Arts and Sciences and codirector of the Petersen Institute for NanoScience and Engineering (PINSE) at Pitt. "We are learning how to reduce electronic circuit elements to single molecules for a new generation of enhanced and more sustainable technologies."

The switch was discovered by experimenting with the rotation of a triangular cluster of three metal atoms held together by a nitrogen atom, which is enclosed entirely within a cage made up entirely of carbon atoms. Petek and his team found that the metal clusters encapsulated within a hollow carbon cage could rotate between several structures under the stimulation of electrons. This rotation changes the molecule's ability to conduct an electric current, thereby switching among multiple logic states without changing the spherical shape of the carbon cage. Petek says this concept also protects the molecule so it can function without influence from outside chemicals.

Because of their constant spherical shape, the prototype molecular switches can be integrated as atom-like building blocks the size of one nanometer (100,000 times smaller than the diameter of a human hair) into massively parallel computing architectures.

The prototype was demonstrated using an Sc3N@C80 molecule sandwiched between two electrodes consisting of an atomically flat copper oxide substrate and an atomically sharp tungsten tip. By applying a voltage pulse, the equilateral triangle-shaped Sc3N could be rotated predictably among six logic states.

The research was led by Petek in collaboration with chemists at the Leibnitz Institute for Solid State Research in Dresden, Germany, and theoreticians at the University of Science and Technology of China in Hefei, People's Republic of China. The experiments were performed by postdoctoral researcher Tian Huang and research assistant professor Min Feng, both in Pitt's Department of Physics and Astronomy.

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Tian Huang, Jin Zhao, Min Feng, Alexey A. Popov, Shangfeng Yang, Lothar Dunsch, Hrvoje Petek. A Molecular Switch Based on Current-Driven Rotation of an Encapsulated Cluster within a Fullerene Cage. Nano Letters, 2011; : 111123145903006 DOI: 10.1021/nl2028409

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Strange new 'species' of ultra-red galaxy discovered

ScienceDaily (Dec. 1, 2011) — In the distant reaches of the universe, almost 13 billion light-years from Earth, a strange species of galaxy lay hidden. Cloaked in dust and dimmed by the intervening distance, even the Hubble Space Telescope couldn't spy it. It took the revealing power of NASA's Spitzer Space Telescope to uncover not one, but four remarkably red galaxies. And while astronomers can describe the members of this new "species," they can't explain what makes them so ruddy.

"We've had to go to extremes to get the models to match our observations," said Jiasheng Huang of the Harvard-Smithsonian Center for Astrophysics (CfA). Huang is lead author on the paper announcing the find, which was published online by the Astrophysical Journal.

Spitzer succeeded where Hubble failed because Spitzer is sensitive to infrared light -- light so red that it lies beyond the visible part of the spectrum. The newfound galaxies are more than 60 times brighter in the infrared than they are at the reddest colors Hubble can detect.

Galaxies can be very red for several reasons. They might be very dusty. They might contain many old, red stars. Or they might be very distant, in which case the expansion of the universe stretches their light to longer wavelengths and hence redder colors (a process known as redshifting). All three reasons seem to apply to the newfound galaxies.

All four galaxies are grouped near each other and appear to be physically associated, rather than being a chance line-up. Due to their great distance, we see them as they were only a billion years after the Big Bang -- an era when the first galaxies formed.

"Hubble has shown us some of the first protogalaxies that formed, but nothing that looks like this. In a sense, these galaxies might be a 'missing link' in galactic evolution" said co-author Giovanni Fazio of the CfA.

Next, researchers hope to measure an accurate redshift for the galaxies, which will require more powerful instruments like the Large Millimeter Telescope or Atacama Large Millimeter Array. They also plan to search for more examples of this new "species" of extremely red galaxies.

"There's evidence for others in other regions of the sky. We'll analyze more Spitzer and Hubble observations to track them down," said Fazio.

NASA's Jet Propulsion Laboratory, Pasadena, Calif., manages the Spitzer mission for NASA's Science Mission Directorate. Science operations are conducted at the Spitzer Science Center at the California Institute of Technology in Pasadena. NASA's Goddard Space Flight Center built Spitzer's Infrared Array Camera, which took the observations. The instrument's principal investigator is Giovanni Fazio of CfA.

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J.-S. Huang, X. Z. Zheng, D. Rigopoulou, G. Magdis, G. G. Fazio, T. Wang. FOUR IRAC SOURCES WITH AN EXTREMELY RED H – [3.6] COLOR: PASSIVE OR DUSTY GALAXIES ATz> 4.5? The Astrophysical Journal, 2011; 742 (1): L13 DOI: 10.1088/2041-8205/742/1/L13

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Using radiation to sterilize insect pests may protect California fruits and vegetables

ScienceDaily (Nov. 30, 2011) — A new study published in the Journal of Economic Entomology shows that radiation can be used to effectively sterilize the light brown apple moth (LBAM), an insect pest found in Australia, New Zealand, California, Hawaii, Sweden, and the British Isles. The light brown apple moth, Epiphyas postvittana (Walker), feeds on apples, pears, stonefruits, citrus, grapes, berries and many other plants. A native of Australia, it has been found in California since 2007. The California Department of Food and Agriculture has spent more than $70 million in CDFA and USDA funds to eradicate the LBAM, and estimates that failure to eradicate it could cost California growers over $133 million per year.

Using similar methodologies in two different laboratories, the authors coordinated radiation biology studies between two geographically isolated LBAM populations from Australia and New Zealand. The results showed that for both populations, an irradiation dose of 250 Gy administered to LBMA pupae induced >95% sterility in females and >90% sterility in males. These results can be used to initiate a suppression program against the LBMA where sterile males are released, mate with wild females, and no offspring are produced. If successful, this technique can largely eliminate the need for pesticides.

"These results suggest that a sterile insect technique (SIT) or F1 sterility program can be applied to control an infestation of Epiphyas postvittana, but these would still be reliant on complementary information such as physical fitness and modeling of overflooding ratios." according to the authors. "The challenge now is to identify the dose of radiation that would provide a balance between insect sterility and field competitiveness."

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Rajendra Soopaya, Lloyd D. Stringer, Bill Woods, Andrea E. A. Stephens, Ruth C. Butler, Ian Lacey, Amandip Kaur, and David M. Suckling. Radiation Biology and Inherited Sterility of Light Brown Apple Moth (Lepidoptera: Tortricidae): Developing a Sterile Insect Release Program. J. Econ. Entomol., 104(6): 1999?2008 (2011) DOI: 10.1603/EC11049

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China's demand for oil will equal US demand by 2040

ScienceDaily (Dec. 1, 2011) — Despite aggressive demand-management policies announced in recent years, China's oil use could easily reach levels comparable to today's U.S. levels by 2040, according to a new energy study by the Baker Institute.

The study's authors said this finding has timely significance because China's growing energy use could continue to pose a major challenge for global climate deliberations in South Africa this week.

The study, "The Rise of China and Its Energy Implications," finds that China's recent efforts at centralizing energy policy do not appear to be significantly more successful than the makeshift patchwork of energy initiatives devised by the United States. In fact, the study said, the U.S. system of open and competitive private sector investment is stimulating more innovation in the American energy sector than in the Chinese energy industry, especially in the area of unconventional oil and gas.

That, ironically, is attracting Chinese state investment to U.S. shores and prompting Beijing to consider further opening of its oil and gas exploration activities to partnerships with U.S. firms, the study said.

China, like the United States, has substantial potential shale gas resources but faces technical, regulatory and market infrastructure challenges that are likely to delay rapid development. Were China to mobilize investments in shale gas more quickly, the study said, it could greatly reduce the country's expected large import needs for liquefied natural gas (LNG) from Australia and the Middle East and contribute to a future glut in global natural gas markets.

Despite sporadic government policies to discourage private car ownership, the growth in the number of vehicles on the road in China has more than quadrupled in recent years to more than 50 million. The Baker Institute report projects that this number could increase to more than 200 million vehicles by 2020 and 770 million by 2040 under a scenario where China's real gross domestic product growth averages 6 percent between now and 2030. Even under a scenario where the number of electric cars rises to 5 million a year by 2030, which is in line with ambitious targets announced by China's National Development and Reform Commission, China's oil use from the transportation sector will grow significantly, the Baker Institute study said.

"Given the scale of vehicle stock growth in China, it is going to be extremely difficult to move the needle of the country's rising transport fuel outlook," said Kenneth Medlock, a study author and the James A. Baker III and Susan G. Baker Fellow in Energy and Resource Economics at the Baker Institute.

The study noted that China's "going abroad" strategy has also encountered recent difficulties in light of geopolitical events and rising global political risks in oil-producing regions.

"China is learning that owning equity oil in risky regions may not be as effective an energy security strategy as it had previously imagined," said Amy Myers Jaffe, an author of the study and the Wallace S. Wilson Fellow for Energy Studies at the Baker Institute. "China is now finding itself mired in more energy-related foreign diplomacy than it bargained for.

"But this could be good news for the United States," Jaffe said. "It may mean China will be more inclined to act in concert with other members of the international community in conflict-prone regions."

The study noted that China has tried to offset some of this risk by increasing investments in the United States and Canada, which gives the U.S. more leverage in seeking China's collaboration in international diplomatic matters.

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