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April 03, 2010

Dense Plasma Physics Update - A Great Month for Focus Fusion

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Lawrenceville Plasma Physics reports good progress in March, 2010.

At the beginning of March, good shots (those without pre-firing and with pinches) were a bit under 50% of the shots we fired. Since mid-month, we have increased that to 90% good shots. The two time-of-flight neutron detectors have produced more evidence that we are already duplicating the high ion energies achieved with higher currents in the Texas experiments. In our best shots, ion energies were measured in the range of 40-60 keV (the equivalent of 0.4-0.6 billion degrees K). The electron beam carried about 0.5 kJ of energy and the plasmoid held about 1 kJ of energy, nearly half that stored in the magnetic field of the device. So, this is evidence that a substantial part of the total energy available is being concentrated in the plasmoids and transferred to the beams.


We found that the control shots (with the magnetic coil turned off) were increasingly producing more neutrons (up to about 10 times) as the control shots in the beginning of our testing. It turns out the steel flanges that attach the vacuum chamber to the inner lower bus plate and the bus plate itself were both becoming permanently magnetized. This provides additional (though unintended) evidence that the predicted angular momentum effect is working. In the future, we may find it necessary to replace the flanges and bus plate with those made from non-magnetic alloys, but that will have to wait for now.

On March 18, Lerner gave an invited presentation on the DPF to an audience of physicists and engineers at Princeton Plasma Physics Laboratory, the nation's largest fusion lab. The Princeton physicists responded with interest and some friendly questions. The atmosphere was one of collaboration, not competition.

Finally, we received enough investment money to carry us through the end of summer, with additional funding pledged. This means we are almost halfway to our goal of raising $900K in this capital drive.

Lawrenceville Plasma Physics had eight objectives for their two year research program This work seems to show good progress on four of the eight objectives.





Advancing dense plasma focus fusion to about break even energy would enable a radical advance to fusion spaceplanes and rockets

If Lawrenceville Plasma Physics (LPP) achieves the full success, then a Focus Fusion reactor would produce electricity very differently. The energy from fusion reactions is released mainly in the form of a high-energy, pulsed beam of helium nuclei. Since the nuclei are electrically charged, this beam is already an electric current. All that is needed is to capture this electric energy into an electric circuit. This can be done by allowing the pulsed beam to generate electric currents in a series of coils as it passes through them. This is much the same way that a transformer works, stepping electric power down from the high voltage of a transmission line to the low voltage used in homes and factories. It is also like a particle accelerator run in reverse. Such an electrical transformation can be highly efficient, probably around 70%. What is most important is that it is exceedingly cheap and compact. The steam turbines and electrical generators are eliminated. A 5 MW Focus Fusion reactor may cost around $300,000 and produce electricity for 1/10th of a cent per kWh. This is fifty times less than current electric costs. Fuel costs will be negligible because a 5 MW plant will require only five pounds of fuel per year. [About 40 million kWh per year from a 5 MWe plant and 5 MWe is equal to 6705 horsepower]



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Spacecraft on a Chip Prototypes Should Be Launched This Year

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A swarm of "smart dust" spacecraft, positioned at a sweet spot between the Earth and the sun, could alert us to the approach of dangerous space storms well before a conventional craft can. The first prototypes are due for launch into low-Earth orbit this year, perhaps as early as May.

Mason Peck, a mechanical engineer at Cornell University in Ithaca, New York, and his colleague Justin Atchison have designed a 1-centimetre-square spacecraft that is 25 micrometres thick and weighs under 7.5 milligrams. The craft is modelled on the dust particles that orbit the sun and are propelled by the photons streaming out from the sun. The chips are essentially small solar panels with a radio antenna, and could act as a solar wind sensor. They can edge closer to the sun than a larger craft monitoring solar activity, buying an extra 13 minutes

At least one prototype should be launched in 2010 as proof of concept and feasibility of a spacecraft on a chip.

A passive, sun-pointing, millimeter-scale solar sail

Taking inspiration from the orbital dynamics of dust, we find that spacecraft length scaling is a means of enabling infinite-impulse orbits that require no feedback control. Our candidate spacecraft is a 25 μm thick, 1 cm square silicon chip equipped with signal transmitting circuitry. This design reduces the total mass to less than 7.5 mg and enables the spacecraft bus itself to serve as a solar sail with characteristic acceleration on the order of 0.1 mm/s2. It is passive in that it maneuvers with no closed-loop actuation of orbital or attitude states. The unforced dynamics that result from an insertion orbit and a launch-vehicle separation determine its subsequent state evolution. We have developed a system architecture that uses solar radiation torques to maintain a sun-pointing heading and can be fabricated with standard microfabrication processes. This architecture has potential applications in heliocentric, geocentric, and three-body orbits.



In collaboration with Sandia National Laboratories, we've developed our first prototype, dubbed "Sprite". Sprite uses a multi-chip module architecture to achieve a form factor of 2cm x 2cm x 2mm. The demo that follows the Sprite will be the system on a chip prototype

Using matched filtering techniques, it can close a communications link from a 500km orbit. A half century later, we expect to duplicate Sputnik’s achievement using less than one ten-millionth of its mass. Our design packages the traditional spacecraft systems (power, propulsion, communications, etc) onto a single silicon microchip smaller than a dime and unconstrained by onboard fuel.

The craft's miniature size would let it hitch a ride into space on the back of another satellite mission headed for the Lagrange point between the Earth and the sun.

The team envisage sending a whole swarm of these "smart dust" chips to the Lagrange point, where they would monitor the strength of the solar wind. They would also warn of any oncoming gusts of charged particles that could disrupt communications and electronics on Earth.

After the tiny craft has been dropped off at the Lagrange point, the effect of solar radiation moves it closer to the sun. Peck estimates that this could give an extra 13 minutes' notice of a storm compared with larger solar monitoring craft such as NASA's Advanced Composition Explorer.

A Passive Microscale Solar Sail (2008)

We consider spacecraft length scaling as a means of enabling achieving passive, feasible infinite-impulse orbits. Taking inspiration from the orbital dynamics of dust, this paper discusses the consequences of length scaling on acceleration due to solar radiation pressure and demonstrates its effectiveness on a candidate microscale spacecraft. We propose to fabricate this dime-sized spacecraft on a single ultra-thin substrate of silicon. This choice reduces the total mass to fewer than 7.5 mg and makes the spacecraft bus itself a solar sail, yielding a lightness number β of 0.0175. This architecture can provide passive solar sail formations and various passive methods of changing orbital energy. We also consider augmenting this architecture with traditional CP1 sail material (β of 0.1095) to reduce transfer times further. The paper surveys and compares passive methods of achieving a marginally stable sun-pointing attitude including the addition of fixed vanes and optical grating of the surface. The microscale infinite impulse (MII) spacecraft design replaces the traditional spacecraft subsystems with a single integrated circuit (IC). Our current fabrication efforts are directed at realizing this spacecraft as a simple sensing and transmitting circuit with standard IC tools.

This paper presents motivation, analytical evaluation, supporting simulation, and sample designs for a microscale infinite-impulse (MII) spacecraft with sufficiently low mass to enable solar sailing. The candidate bus is a 1cm x 1cm x 25 μm silicon IC that conservatively weighs less than 7.56 mg. Each conventional spacecraft subsystem is accounted for and described in the context of a Sputnik inspired temperature sensing mission.

If paired with two other MII spacecraft to form a corner cube, this design can passively reduce the effect of gravity by 1.0% via solar pressure, enabling unique formation opportunities. Using an optical grating scheme to produce stable sun-pointing attitudes, this acceleration can be improved up to 1.75% of gravity. If spin-stabilized and strategically coated with absorptive (η = 0.5, β = 0.0103) and reflective (η = 0.85, β = 0.0175) materials, the spacecraft can passively gain or remove energy and momentum in a simple circular orbit. Equipped with a 10 cm radius ultrathin CP-1 sail, such a spacecraft exhibits a lightness number of 0.1095. If coated, the sail-spacecraft system is shown to passively add or subtract 10% of its orbital energy in a single circular heliocentric orbit at 1 AU.

Table 1 lists this study’s two MII solar-sailing architectures along with two other well known designs. The geometry and performance of these four are compared. Although the lightness numbers are similar, the passive energy-change maneuver using different coatings is much less efficient than a simple logarithmic spiral trajectory.

As a result, a transfer from a circular orbit at 1 AU to the average orbital radius of Mars requires significantly more time with the passive MII design, even when augmented with the disc of thin CP1 material. Nevertheless, we emphasize that the difficult engineering challenges associated with a 22,700 m2 spacecraft introduce risk and cost that the 1 cm2 MII trades for small size.

Table 1. Solar Sail Design Comparison 
           MII Bus               MII – 10cm CP1       DLR/ JPL   Johns Hopkins 
          η1 = 0.50, η2 = 0.85  η1 = 0.50, η2 = 0.85  ODISSEE4   University4 
Design     Square               Disc                  Square     Disc 
Area       1 cm2                31.4 cm2              1600 m2    22,700 m2 
depth      25 μm                25 μm / 5 μm          7.5 μm     7.5 μm 
mass       7.5 mg               43 mg                 77 kg      180 kg 
β          β1 = 0.010           β1 = 0.064
           β2 = 0.018           β2 = 0.110            0.032      0.194 
Time to                                                          logarithmic 
Mars,yr     >100             different coatings,      logarithmic spiral
                                6                     spiral, 3    0.8

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IHS CERA Predicts 6.5 million barrels per day for Iraq Oil Production in 2020

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IHS CERA predicts Iraq oil production is 4.3 mbd in 2015 and 6.5 mbd in 2020.

Iraq’s current “highly ambitious plans” to expand oil production are unlikely to be fully realized given political, security, operational and infrastructure challenges, according to a new report, Fields of Dreams: The Great Iraqi Oil Rush—Its Potential, Challenges, and Limits by IHS Cambridge Energy Research Associates (IHS CERA). Iraq currently plans to expand production to as much as 12 million barrels per day (bpd) in the next six to seven years.



The report identifies infrastructure and logistics as “major challenges.” Iraq is responsible for providing the infrastructure needed to receive the extra oil but its plans for providing a “complex network of capital-intensive infrastructure”—from ports and roads to power and water crucial for operations—in synchronization with the development oil fields are not known, representing a major potential bottleneck.

“Iraq’s expansion timetable appears extraordinarily ambitious in comparison to the recently completed capacity increase in Saudi Arabia,” says Bahree. “Saudi Arabia has significant security and infrastructure advantages yet it took Saudi Arabia between four and five years to expand its net output capacity by some 2 million barrels per day. Iraq will certainly be challenged to match this pace, much less exceed it.”

Though Iraq is unlikely to meet its “very stretch target” of elevating its capacity to 12mbd in six to seven years, the expansion of its production capacity still represents a significant increase with strong implications for OPEC and the regional balance, the report finds.

IHS CERA’s 2009 reference case for global liquid productive capacity shows growth through 2030 to around 115 million barrels per day (mbd) and finds no evidence of a peak in supply appearing before that time

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NTT demoes 69 Terabit per Second Communication Over a 180 mile long Optical Fiber

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Nippon Telegraph and Telephone Corporation has successfully demonstrated an ultra-high-capacity optical transmission of 69.1 terabits per second (tera = one trillion) over a single 240 km-long optical fiber. The 69.1 Tb/s transmission, based on the wavelength division multiplexing (WDM) of 432 wavelengths with a capacity of 171 Gb/s, is the highest ever reported in the optical transmission field, and is twice the previous record of 32 Tb/s. The technologies used in this experiment will be useful for constructing future high-capacity optical backbone networks.



NTT Labs aim to realize high-capacity and long-distance optical transmission based on rates of over 100 Gb/s per wavelength and over 10 Tb/s per fiber, and to construct an optical backbone network that is superior in terms of economy and quality.

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Russia Increases Oil Production

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Russia, supplier of about 12 percent of the world’s oil, increased crude production in March to a post-Soviet record as TNK-BP tapped deposits and OAO Bashneft’s new owners squeezed more crude from older fields.

Crude output reached 10.12 million barrels a day, a gain of 3.3 percent from the same month last year and 0.4 percent from February, according to preliminary data released today by the Energy Ministry’s CDU-TEK unit. Exports rose 3 percent on the month to 5.38 million barrels a day.


“I think we’re going to see this continuing this year,” Artem Konchin, an oil and gas analyst at Unicredit SpA in Moscow, said by phone.

TNK-BP, BP Plc’s joint venture with four billionaires, increased output an annual 3.4 percent to 1.43 million barrels a day after starting production at the Verkhnechonsk, Kamennoye and Uvat deposits in Siberia. Bashneft, based in the Bashkortostan region near Kazakhstan, has increased output 21 percent to 280,000 barrels a day in the year since billionaire Vladimir Yevtushenkov’s AFK Sistema agreed to buy the company.

Further growth will probably be led by state-run OAO Rosneft and its smaller rival OAO Lukoil, Konchin said. Rosneft’s Vankor project, the largest new development in Russia, is about halfway to capacity, while Lukoil plans to start production in Russia’s section of the Caspian Sea this year.

Rosneft’s output in March fell an annual 1.5 percent to 2.24 million barrels a day after CDU-TEK stopped attributing to it the production at Tomskneft, a venture Rosneft jointly owns with OAO Gazprom Neft. Lukoil’s production fell an annual 1.8 percent to 1.83 million barrels a day.

Vankor started production in 2009 and is expected to reach 510,000 barrels of oil per day in 2011

The Vankor field has oil reserves 3,800 million barrels, of which 1,500 million barrels are proved reserves, and 95 billion cubic meters of natural gas. Rosneft produced 60 thousand barrels per day at Vankor in 2009 and expects 220 thousand barrels per day in 2010.

EIA profile of Russian oil

From 2008 - With production of 9.8 million bbl/d of liquids (not including oil products), and consumption of roughly 2.8 million bbl/d, Russia exported (in net) around 7 million bbl/d. According to the Oil and Gas Journal’s 2008 survey, Russia has proven oil reserves of 60 billion barrels, most of which are located in Western Siberia, between the Ural Mountains and the Central Siberian Plateau


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South Korea Electric Scooters Go up to 62 mph

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Korea-based electric vehicle maker Leo Motors, Inc has received a purchase order for 1,170 electric scooters from M&M Corp, Leo’s nationwide scooter distributor in Korea. M&M ordered Leo’s Hilless 1, Hilless 3 and Hilless 5 models which will be delivered by June 2010, for total revenues of 4.2 billion Korean Won (approximately US$3.73 million)

Hilless 1 - up to 37 mph and 37 mile range
Hilless 3 - up to 50 mph and 50 mile range
Hilless 5 - up to 62 mph and 62 mile range

the average price is $3500.



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April 02, 2010

Molten-salt based accelerator-driven subcritical reactor

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User clumma on the EnergyfromThorium discussion forum provides highlights of the Second Thorium Energy Alliance Conference


Andrew Hutton - Jefferson Lab (Nat'l Accel. Facility)
ADNA (Accelerator-Driven Neutron Applications) Corporation - GEM*STAR

These two were in the ADS (Accelerator-driven Systems) breakout session. I think it's safe to say that everyone in the room was blown away. Cost of neutrons in kg/Joule has gone down by SEVEN orders of magnitude since 1965. Thousands of accelerators using superconducting RF technology deployed worldwide.

ADNA is a company working on a molten-salt based accelerator-driven subcritical reactor. They claim to be ready to build a grid-connected 100MW demo plant in Los Alamos county. It will use a 180m linac (Linear Accelerator) to produce spallation neutrons. The accelerator is 25% of the plant cost. Electricity for $0.07/kWh, vs. $0.09/kWh Los Alamos county average. They have a site in mind.

The way they put it was extremely compelling: the perceived problems with fission have always stemmed from a shortage of neutrons. Well, if we can make neutrons effectively, these go away. No enrichment OR reprocessing. Burn fluorinated spent fuel, depleted uranium, Thorium, the works. Leave fission products in the reactor, just crank up the beam. They claim a net energy gain of 20-60 depending on the fuel mix.

They also showed VERY interesting work on graphite, which should interest anyone concerned about the LFTR "plumbing problem


Transmutation of Radioactive Materials using Thermal Neutrons

GEM*STAR is owned by Accelerator‐Driven Neutron Applications, ADNA Corp
– Goal is to build a pilot plant through private venture capital

A 44 page presentation at Oak Ridge by ADNA Pierson

ADNA estimates criticality at 8 tons with new graphite for a natural uranium graphite reactor



Gem*Star reactor Benefits

• Can use natural uranium as fuel
• Produces twice as much energy from mined uranium as LWRs
• Can use spent fuel from LWRs and get just as much energy out
• Recycling the molten salt fuel several times with supplemental neutrons reduces long‐lived waste by factor of 10
• Defers need for a geologic deposit for a century
• Divorces nuclear energy from nuclear weapons

Fission Energy With Waste Burn-up and Without Enrichment or Reprocessing

Adna asks - What would an optimized accelerator-driven nuclear-energy program look like?
If more neutrons were emitted in fission, there would be no need for enrichment or reprocessing, and much more of the mined uranium could be burned without proliferation-prone and expensive technologies. The purpose of enrichment and reprocessing is to make up for the limited neutrons from fission. The ADNA Corporation in collaboration with the physics staff of Duke University and Virginia Tech have embarked on an alternative approach to nuclear energy to reduce the non-beneficial loss of neutrons and to add external neutrons to sub-critical reactors from accelerators and ultimately fusion neutron sources. These external sources in combination with molten salt fuel enable the fuel to be recycled many times without separations that generate a waste stream. Because waste is not removed, waste is concurrently burned so that the ultimate waste storage requirements are reduced by about a factor of ten and delayed for generations. This approach, which works best with graphite-based reactors, will be cheaper than the combination of enrichment, reprocessing, and fast reactors and would not be burdened with proliferation concerns. Graphite systems were the original path for nuclear energy and we believe graphite systems should be brought back owing to many advantages that were not realized in early development. Our first step towards this concept was to study neutron diffusion in bulk quantities (an 8’x8’x8’cube) of modern graphite. Neutron losses in moving through certain modern graphites were found to be 40 % less than in older graphite. Neutron scattering studies on small samples of graphite at the Los Alamos National Laboratory revealed the physics basis. The consequences of reduced neutron loss are enhanced performance of graphite-based critical reactors and better performance with external neutron sources than previously thought.


GEM*STAR: The Alternative Reactor Technology Integrating Graphite, Molten Salt, and Accelerators

GEM*STAR, 8 page powerpoint presentation from Oct 2009

• sub-critical graphite moderated reactor driven by supplementary neutrons
– intrinsic safety: no critical mass ever present
– thermal neutrons: better tolerance to fission products
• molten-salt fuel in equilibrium throughout reactor life
– exceptional neutron economy: allows deeper burning
• high-temperature & low pressure operation
– higher thermal to electric conversion efficiency
– no high-pressure containment vessel

Virginia Tech budget for research which includes Gem*star is about $2 million/year














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Current Nuclear Reactor Fuel Research

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2010 LWR [Light water Reactor] Fuel Performance meeting will be held Sept 26-29, 2010. The link is to the list over one hundred abstracts.

What I found noteworthy:
Thermal-Hydraulic and Thermo-Mechanical Assessment of Dual-Cooled Annular Fuel for PWR Application

This paper discusses the work in South Korea to enable MIT annular fuel design to be adapted to Korean nuclear reactors to enable existing reactors to have power increased by 20% with minimal modification. More extensive modification would allow an increase in power of 50% for existing nuclear reactors.



A dual-cooled annular fuel for a pressurized water reactor (PWR) has been introduced for a significant amount of reactor power uprate. A previous study proposed a 13x13 annular fuel array replacing the 17x17 solid fuel in the Westinghouse PWR plant, which could increase the core power up to 50% with the considerable changes in the major reactor components. The Korea Atomic Energy Research Institute (KAERI) is conducting a research to develop a dual-cooled annular fuel for its employment in an optimized PWR in Korea, OPR1000. The dual-cooled fuel for the OPR1000 is targeted to increase the reactor power by 20% as well as reduce the fuel-pellet temperature by more than 30% without a change to the reactor components other than the fuel. Several technical issues exist for the application of the dual cooled annular fuel to the power uprate in the OPR1000. One of the important issues is the balance of heat split between the inner and outer channels since the coolant flows through the circular inner channel of annular fuel as well as the outer subchannels formed between the fuel rods. The dual-cooled fuel should be designed to maintain the heat split in reactor operation such that it does not exceed a specified acceptable fuel design limit, e.g., DNBR limit. It has been known that the heat split is largely dependent on the heat transfer in the inner and outer fuel gaps. This is because the thermal resistance in the fuel gap is very large due to a low thermal conductivity. The fuel gap is filled initially with helium gas and the heat is transferred by conduction and radiation. The heat transfer in the gap is governed by thermal gap conductance which decreases exponentially as the gap width increases. This study was performed to determine the acceptable range of gap conductance, i.e., gap width based on the DNBR analysis for the OPR1000 core with the dual-cooled fuel. The minimum DNBR (MDNBR) should be higher than the DNBR limit during anticipated operational occurrences (AOOs) as well as normal reactor operation. The DNBR calculations were made using the subchannel analysis method for the OPR1000 core with power uprate of 20%. For the wide range of the inner and outer gap conductance, the MDNBR values were predicted and compared with the DNBR limit to determine the acceptable range of the gap width. The MDNBR was found to occur in either inner channel or outer channel depending on the inner and outer gap conductance. This study also predicted the variation of the gap width using the thermo-mechanical analysis for the dual-cooled fuel in its life cycle. The outer gap width was found to reduce due to the thermal expansion while the inner one increased. The thermo-mechanical analysis included the effects of fuel swelling and creep as well. The inner and outer gap widths were predicted to vary within its acceptable region which is bounded by the DNBR limit.

Mechanical Design and Integrity of the Currently Designed Structural Components of a Dual Cooled Fuel

Dual cooled fuel is under developing for power uprating of an existing PWR (especially for OPR-1000 in our work). The most important feature of it is an additional coolant flow passage formed inside a fuel rod to increase the surface area of heat transfer. This makes the outer diameter of a fuel rod considerably increase compared with that of a conventional fuel. It inevitably affects the design of the structural components such as the spacer grids, top and bottom end pieces and guide tubes. Primary goal of the present work is to show the possibility of composing an actual fuel assembly through changing the component design without violating the design criteria and functional requirements of the components. Main ideas for them are: moving the support location of a fuel rod in the spacer grid due to narrow gap between the fuel rods; rearranging the flow hole pattern of the top and bottom end pieces; applying another bigger diameter tube outside the conventional guide tubes. First part of the present paper will show the design results. After the possibility is shown, mechanical integrity is concerned. So another part of the paper deals with the mechanical behavior and fretting wear performance of the dual cooled fuel. Flow-induced vibration (FIV) tests were conducted with the 4X4 partial assembly to investigate the vibration behavior. Two different types of the spacer grids were applied, which had different rod supporting force. The FIV characteristics were analyzed. By using the equation suggested by Yetisir el al., which correlates the workrate for wearing and the FIV parameters, the wear rate is to be predicted. Together with the fretting wear experiments, the fretting wear margin of a dual cooled fuel is to be discussed.
The South Korean previous work on dual cooled fuel and their capabilities to quickly build modular reactors was reviewed last year.

M5 (An Areva alloy that enables higher burnup in pressure water reactors) a breakthrough in Zr alloy

M5® is the reference alloy used as cladding tube and structure material for all AREVA PWR designs. As of July 2009, over 2.8 million M5® clad fuel rods loaded in 5800 fuel assemblies in designs from 14x14 to 18x18 have been irradiated in 73 commercial PWRs in 12 countries to fuel rod burn-up of 80GWd/tU. To demonstrate superiority of the M5® alloy at burn-ups beyond current licensing limits, M5® has been operated in PWR at fuel rod burn-ups exceeding 71 GWd/tU in the United States and 78 GWd/tU in Europe.

Westinghouse has its own advanced cladding material (Axiom) for high burnup



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Illusion Media - Generate Virtual Objects Using Realizable Metamaterials

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A simple scheme of an illusion medium layer that transforms the stereoscopic image of an object (a golden apple) into that of the illusion (two green apples). (a) The golden apple (the actual object) enclosed with the illusion medium layer in the physical space. (b) Two green apples (the illusion) in the virtual space. Both physical and virtual spaces share the same virtual boundary (dashed curves).

Arxiv - Illusion Media: Generate Virtual Objects Using Realizable Metamaterials (13 page pdf)

Transformation optics offers an unconventional strategy to the design of metamaterial devices. In this letter, we propose a class of optical transformation media, illusion media, which can render the enclosed object invisible and generate one or more virtual objects as desired. An arbitrary object enclosed by such an illusion medium layer appears to be one or more other objects. We apply the proposed method to design two devices, one of which transforms an actual object into two virtual objects, and the other of which transforms a complicated metallic object into a virtual dielectric object with arbitrary material properties. Both illusion devices exhibit unusual electromagnetic behaviors as verified by full-wave simulations. Different from the published illusion devices which are composed of left-handed materials with simultaneously negative permittivity and permeability, the illusion media proposed in this work have positive permittivity and permeability. We also propose a method of amending function to eliminate the singularities of medium parameters in the illusion media. Hence the designed devices could be realizable using artificial metamaterials. The proposed method presents a major step towards the realization of illusion media.

Illusion media will change the scattering patterns of the enclosed object to make it appear like another object or multiple virtual objects. The new illusion media design has an advantage over previously proposed illusion media, in that it should be easier to fabricate. All permittivity and permeability components of our illusion media are finite and positive. Hence the presented approach makes it possible to realize the illusion media using artificial metamaterials.”


This works follows up on earlier work to create illusions with metamaterials



The parameter distributions of the illusion medium layer, (a) μ1, (b) μ2, and (c) "z. The scattered electric-field distributions in the computational domain for (d) a metallic square cylinder without the illusion medium layer; (e) a metallic square cylinder with the illusion medium layer; and (f) two dielectric square cylinders when the plane waves are incident horizontally from the left to the right.

In summary, we have presented a class of optical transformation media, illusion media, which can create one or more virtual objects by using metamaterials. In such illusion media, all components of constitutive parameters in the principle coordinate system are positive, hence the illusion media could be realizable using artificial structures. Moreover, we proposed a method of amending function to eliminate the singularity of medium parameters for the illusion devices. However, the changing range of some parameters is still relatively large in the current version. In the future work, we will investigate the illusion media with further simplified medium parameters so that the illusion devices can be experimentally verified.

The parameter distributions of the illusion medium layer, (a) μ1, (b) μ2, and (c) "z. The scattered electric-field distributions in the computational domain for (d) a bronze of a woman model without the illusion medium layers; (e) a bronze of a woman model with the illusion medium layers; and (f) a woman with material parameters " = 3 and μ = 1 when the plane waves are incident in the horizontal direction from the left to the right.

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Radical research changes lab-on-a-chip design

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A University of Alberta mechanical engineering professor has developed a new model that could revolutionize the design of hand-held devices that provide reliable, nearly instant medical or environmental tests.

The model Mitra and Waghmare have developed takes both capillary action and electroosmosis into account and represents a radical shift in microfluidic chip design. The pair has introduced a new non-dimensional number, which describes the interplay between capillary force and electroosmotism, to help design highly efficient chips that make the most of both effects.

"We are now able to control the flow by suitably manipulating the capillary action and the electric field, rather than designing chips by trial and error, which can be expensive and time consuming," said Mitra.

The design, Mitra says, could lead to devices that test for virtually anything.

For example, people at risk of heart attacks could be given hand-held devices to test their own blood for elevated levels of myoglobin, a protein which floods the circulatory system in the minutes leading up to a heart attack. With the prick of a finger, patients feeling unwell would be able to tests their myoglobin levels and call for help if necessary.



"Lab-on-a-chip" technology has resulted in the development of new devices capable of testing samples of everything from water to blood. As the size of these devices decreases, designers have struggled to find reliable way to control fluid flow through microchannels, which are integral part of the technology.

Now, professor Sushanta Mitra and PhD student Prashant Waghmare have published research findings, which appear as a featured article in the March issue of the scientific journal Analytica Chemica Acta, that address the problem. In order to use the technology to analyze fluids such as blood, the fluid sample is stored in a tiny reservoir on a glass chip and transported through a microchannel to a detection site, where the sample is typically detected and analyzed.

But getting the fluid from one reservoir to another can be challenging. Sometimes, physical forces known as capillary action are not adequate to move fluid through these tiny channels and if the sample is transported too quickly or too slowly, the analysis is inaccurate. In such situations, designers have placed electrodes beneath the microchannels and have tried to manipulate the transport of fluid using electrical fields.



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Technology to accelerate scanning probe microscopes by a factor of 1000

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Physicists of Saarland University have developed a technology that could accelerate scanning probe microscopes by a factor of 1000.

A scanning probe microscope works like a record player. There, a needle follows the record track, mapping the fine structure of the track. The microscope uses a much smaller silicon needle instead, and direct contact with the surface is avoided. Surface structures are mapped by atomic forces, usually van-der-Waals interactions. "Even though the needle is tiny, there are still physical limits. Therefore we were looking for a component that is again a factor of 100 smaller than those used currently" explains Uwe Hartmann, Professor for Nanostructure Reasearch and Nanotechnology at Saarland University. With the nanocantilever, as it is called, surfaces will be mapped a lot faster and with higher precision.



State-of-the-art scanning probe microscopes operate at frequencies around 100 Kilohertz. "The processes nanotechnology is dealing with, however, have typical frequencies of gigahertz. These are one billion cycles per second. On the other hand, the velocity by which a hair is growing may well disturb the imaging process." Such are the dimensions of nanoresearch, as Uwe Hartmann describes. With his team's design, one hundred images per second and more and an increase in resolution will be possible. This is more than video rate.

The detector for the movements of the nanocantilever is separated from the nanocantilever by less than the wavelength of light, just one-fivehundredth of a hair's diameter. The result is a mapping of the surface with superior speed and precision.

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Venture launched to genetically boost aquaculture breeding

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Animal genetics firm MetaMorphix, Inc (MMI) and Stirius, Inc announced last week their jointly formed AquaAnimal Health, Inc to develop aquaculture technologies to augment output and advance disease resistance in farmed marine animals like finfish and crustaceans. AquaAnimal Health will use MMI’s Myostatin technology to maintain and enhance fish and crustacean quality across all aquaculture breeding.

Natural inhibition of myostatin in finfish was recently shown to produce greater muscle protein (15-20% more) and increase feed efficiency.






Terry Bradley, a professor of fisheries and aquaculture, said that his 10-year research into the inhibition of myostatin, a protein that slows muscle growth, has obtained "stunning results" in the last two years, with trout growing 15 to 20 per cent more muscle mass than standard fish, according to the University of Rhode Island (URI).

"Belgian blue cattle have a natural mutation in myostatin causing a 20 to 25 per cent increase in muscle mass, and mice overexpressing myostatin exhibit a two-fold increase in skeletal muscle mass," said Bradley.

Bradley and his team spent 500 hours injecting 20,000 rainbow trout eggs with DNA types designed to inhibit myostatin. Of the eggs that hatched, 300 carried the gene that led to increased muscle growth. After two years, most fish had the "six-pack ab" effect, even though fish lack standard abdominal muscles. They also have increased musculature throughout.

Some 500,000 metric tonnes of rainbow trout are raised every year in aquaculture facilities across the United States and Europe. In the US, some 1,000 trout farms produce around USD 80 million worth of trout annually.

Assuming Bradley's transgenic fish meet the regulations, it could provide a boost to the industry by enabling farmers to grow larger fish without increasing the amount of feed.

FURTHER READING

Transgenic fish status report from 2004/2005 (23 pages)

Transgenic fish studies in China from 2005 (10 pages)

Effects of the “all-fish” GH (growth hormone) transgene expression on resistance to Ichthyophthirius multifiliis infections in common carp, Cyprinus carpio L

Genetically modified fish has promoters driving an over-production of "all fish" growth hormone. This resulted in dramatic growth enhancement in several species, including salmonids, carps and tilapias.

1992). "Growth Enhancement in Transgenic Atlantic Salmon by the Use of an "All Fish" Chimeric Growth Hormone Gene Construct". Bio/Technology 10: 176–181. doi:10.1038/nbt0292-176. http://www.nature.com/nbt/journal/v10/n2/abs/nbt0292-176.html.

(15 February 2001). "Growth of domesticated transgenic fish". Nature 409 (6822): 781–782. doi:10.1038/35057314. http://www.nature.com/nature/journal/v409/n6822/full/409781a0.html.

(19 Apr 2005). "Growth and nutritional trials on transgenic Nile tilapia containing an exogenous fish growth hormone gene". Journal of Fish Biology 59 (1): 62–78. doi:10.1111/j.1095-8649.2001.tb02338.x. http://www3.interscience.wiley.com/journal/118974519/abstract?CRETRY=1&SRETRY=0.


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April 01, 2010

A Second Study Shows Rapamycin Extends Life of Mice and Rapamycin Prevents Alzheimer Effects and another Aging Gene Found

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If research results continue to be repeated and are turned into clinical trials, the drug Rapamycin already approved for some uses could be marshaled — sooner than we expect — to prevent Alzheimer's disease in humans and improve health to the end of life.

A few weeks after a report that rapamycin, a drug that extends lifespan in mice and that is currently used in transplant patients, curbed the effects of Alzheimer's disease in mice, a second group is announcing similar results in an entirely different mouse model of early Alzheimer's.

Both reports are from The University of Texas Health Science Center at San Antonio, where the rapamycin studies are conducted in the Sam and Ann Barshop Institute for Longevity and Aging Studies and in basic science departments.

The second report, released April 1 by the journal PLoS ONE, published by the Public Library of Science, , showed that administration of rapamycin improved learning and memory in a strain of mice engineered to develop Alzheimer's. The improvements in learning and memory were detected in a water maze activity test that is designed to measure learning and spatial memory. The improvements in learning and memory correlated with lower damage in brain tissue.

Rapamycin is the first pharmacologic intervention shown to extend life in an animal model of aging.

"The fact that we are seeing identical results in two vastly different mouse models of Alzheimer's disease," Dr. Galvan added, in reference to the recent study by Caccamo et al, "provides robust evidence that rapamycin treatment is effective and is acting by changing a basic pathogenic process of Alzheimer's that is common to both mouse models. This suggests that it may be an effective treatment for Alzheimer's in humans, who also have very diverse genetic makeup and life histories."



ournal of Molecular Cell Biology - Rapamycin: The Cure for all that Ails

Target of rapamycin (TOR) signaling stimulates cell growth by regulating protein synthesis in response to a variety of stimuli in a wide range of species and is inhibited by rapamycin, a naturally occurring antifungal compound produced by bacteria and discovered on Easter Island or in the local vernacular, Rapa Nui (rapamycin's namesake). Recently, rapamycin was shown to extend life span for mice, even when administered late in life, suggesting that inhibiting the mammalian TOR pathway may improve health span for people.

The target of rapamycin (TOR) pathway is key for this regulation thus, it is a good therapeutic target for life-span extension, but administration of TOR inhibitors may impart negative side effects, particularly if they are administered early in life at a time when growth is important for fitness. This notion is in accordance with evolutionary theories of aging which propose growth is essential for early life fitness that enables reproduction but may subsequently lead to age-related decline in health due to diminished selective pressure.

Interestingly, rapamycin extended life span even when chronic administration began in mice as old as 600 days (equivalent to 60 years in people). Thus, rapamycin or other mammalian TOR (mTOR) inhibitors may be efficacious for treating age-related illnesses in people without early or prolonged intervention; rapamycin may also be used as an aging prophylactic, assuming that chronic intervention is not toxic.

Could there be potential adverse side effects? This is a critical question to answer if mTOR inhibitors will be used to treat age-related diseases (especially if they are to be used prophylactically). One concern is that mTOR inhibitors may suppress the immune system. Rapamycin and other mTOR inhibitors have been used to prevent rejection of transplanted organs, since they are powerful immunosuppressants by reducing T-cell proliferation (Tsang et al., 2007). As a result, there is a history of using mTOR inhibitors in humans. At this time, organ transplant patients tolerate rapamycin at the doses given with minimal negative side effects. One of these side effects includes impaired glucose tolerance in kidney transplant patients. mTOR inhibitors may also prove valuable for treating autoimmune disease, since it is important for the survival of monocyte-derived dendritic cells and since rapamycin decreases MHC class II molecules on murine bone marrow-derived dendritic cells. Even though these immunosuppressant activities may have medical advantages, they may also have undesirable outcomes for people without the need to suppress their immune system, thus, limiting wide-spread prophylactic treatment.

These recently published results show that rapamycin-fed mice exhibit an extended life span when compared with control mice. The rapamycin-fed cohort exhibited the same spectrum of age-related diseases as the control cohort; thus, rapamycin seems to have a broad impact on ameliorating the aging process as opposed to resolving specific life-threatening illness endemic to these genetically heterogeneous mice used by the NIA-ITP study. This life-extending property was realized even when rapamycin treatment was initiated late in life. On the basis of these results, rapamycin is a strong candidate for attenuating the aging process, even when first administered to individuals at advanced age. This could be a boon for extending health span. Still major questions must be addressed to understand just how mTOR inhibition ameliorates aging. Since mTOR has many functions, it might be desirable to target downstream proteins with a more specific action. Also it will be important to fully realize negative side effects to determine if rapamycin or other mTOR inhibitors should be administered as an aging prophylactic or as a treatment for specific age-related illnesses.

2. Scientists funded by the Biotechnology and Biological Sciences Research Council (BBSRC) at the University of Birmingham have discovered that a gene called DAF-16 is strongly involved in determining the rate of ageing and average lifespan of the laboratory worm Caenorhabditis elegans (C. elegans) and its close evolutionary cousins. DAF-16 is found in many other animals, including humans. It is possible that this knowledge could open up new avenues for altering ageing, immunity and resistance to stresses in humans.

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Gene Therapy Restores Sight to Blind Mice and Increases Heart Attack Survival from 60 to 80% in Mice

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1. The researchers used a specially engineered virus to deliver extra copies of the gene for Nerve growth factor (NGF) into the hearts of mice. Thirty days after having a heart attack, 80 per cent of the mice that received this treatment were still alive, compared with only 60 per cent of mice that did not. The pumping ability of the heart was also significantly improved in mice that received the NGF gene.

In contrast, mice that were given an antibody that neutralised NGF fared significantly worse after they had a heart attack, with higher rates of cell death and more severely impaired heart function.



When the researchers looked at post mortem human hearts that had suffered a heart attack, they found that levels of NGF near the blood-starved part of the heart were higher than normal, suggesting that increasing NGF production is a normal part of the tissue's response to oxygen deprivation.

Dr Emanueli, Reader of Research in Experimental Cardiovascular Medicine Research in the Bristol Heart Institute (BHI) at the University of Bristol, said: "We've shown that in mice, NGF gene therapy improves survival rates after a heart attack, through both a direct protective effect on heart muscle cells and by stimulating the growth of new blood vessels.

"In the laboratory, we can deliver therapy directly to the heart at the time of the heart attack. But in a clinical context the therapy will have to be given hours or days later, ideally without the need for surgery. So next we need to see if we can get similar results in this situation.

"I'm convinced that NGF has huge potential for treating heart attack patients."

2. Scientists from Buffalo, Cleveland, and Oklahoma City made a huge step toward making the blind see, and they did it by using a form of gene therapy that does not involve the use of modified viruses.

Scientists described how they used a non-viral, synthetic nanoparticle carrier to improve and save the sight of mice with retinitis pigmentosa, an inherited disease characterized by progressive vision loss and eventual blindness.

"We hope the results of our study will be instrumental in generating a cure for the debilitating blindness associated with retinitis pigmentosa and other inherited and acquired retinal diseases," said Muna I. Naash, Ph.D., a researcher involved in the work from the Department of Cell Biology at the University of Oklahoma Health Sciences Center in Oklahoma City. "Compacted DNA nanoparticles are an exciting treatment strategy for these diseases and we look forward to exciting new developments."



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Stem Cell RNA Interference Treatment for HIV is Closer

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A novel stem cell therapy that arms the immune system with an intrinsic defence against HIV could be a powerful strategy to tackle the disease.

In the absence of an effective vaccine, daily administration of anti-retroviral drugs is the most effective treatment for HIV. However, low patient compliance rates combined with the virus's ability to easily mutate has led to the emergence of drug-resistant strains that are difficult to treat.



Professor Berkhout from the University of Amsterdam is investigating a novel gene therapy that has long-lasting effects even after a single treatment. It involves delivering antiviral DNA to the patients' own immune cells that arms them against viral infection. "This therapy would offer an alternative for HIV-infected patients that can no longer be treated with regular antivirals," he suggested.

The therapy involves extracting and purifying blood stem cells from the patient's bone marrow. Antiviral DNA is transferred to the cells in the laboratory, after which the cells are re-injected into the body. The DNA encodes tiny molecules called small RNAs that are the mirror image of key viral genes used by HIV to cause disease. The small RNAs float around inside the immune cell until they encounter viral genes which they can stick to like Velcro™. This mechanism, called 'RNA interference' can block the production of key viral components from these genes.

Transferring the antiviral DNA to stem cells would help to restore a large part of the patient's immune system. "Stem cells are the continually dividing 'master copy' cells from which all other immune cells are derived. By engineering the stem cells, the antiviral DNA is inherited by all the immune cells that are born from it," explained Professor Berkhout.

The group hopes to start clinical trials of the therapy within 3 years. "So far, very promising results have been obtained in the laboratory, and we are now testing the safety and efficacy in a pre-clinical mouse model," said Professor Berkhout.

Handheld HIV detector for $250 and other Cheap HIV tests

Researchers at California company Palo Alto Research Center have shrunk the laser technology inside large laboratory machines down to about the size of an iPod. Their cheap, handheld device promises to provide an immune system check-up on the spot and in less than 10 minutes.

The technology analyzes a small sample of blood drawn by a finger prick. Blood cells flow through a tiny channel, illuminated by a laser beam. A detector watches patterns in the light that bounces off the cells to identify them.

The detector looks for and counts CD4+ T cells, cells in the immune system that are killed by the HIV virus. The World Health Organization recommends that antiretroviral treatment begin when a patient's CD4 count drops below 250.

"The quality of their test is great," said researcher Bernhard Weigl of PATH, a non-profit reviewing a variety of CD4 testing technologies. "If you look at their graph, it pretty much looked like the graph you would get from a big instrument."

PARC's prototype cost about $250 to build, a hundred times cheaper than the large flow cytometers currently in use. Still, getting it to market may prove challenging.

Kiesel is competing against a dozen other groups vying to fill the need for cheap, portable CD4 tests. Other technologies have been under development for years, including a half-dozen recent projects funded by the Bill and Melinda Gates Foundation that include disposable CD4 tester kits as easy to use as a home pregnancy test. Kiesler's laboratory-tested device is a couple of years behind these projects, some of which have been tested in the field in African countries.

None of these devices is currently on the market. Many have been redesigned several times in the quest for commercialization, including a device by the Austin-based biotech company LabNow, which had hoped to have its technology on the market by 2006.

In the end, Weigl suspects that health workers will use some combination of these approaches in the field. Detectors like the one at PARC, with a low cost per person tested, make sense for areas with many cases of HIV, said Weigl. But disposable kits, which cost less initially and require no maintenance, may be a good solution for remote areas with fewer cases.

"I would be surprised if the first technologies aren't out by 2012," said Weigl. "The market is big; you're looking at many millions of users that have to get checked up every few months



A 20-year-old HIV-positive person starting antiretroviral (ARV) therapy today could expect to live, on average, to the age of 69, according to new calculations published July 26, 2008 in The Lancet. The study authors say this is a life expectancy increase of 37 percent over projections for 20-year-olds starting ARVs during the early years of combination treatment.


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Online Interview with Philip Moriarty Who is Experimenting to Validate or Disprove the Computational Work of Freitas and Merkle Molecular Tooltips

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There is a two part interview with Philip Moriarty at 10minus9 blog

I work in a variety of fields in nanoscience including self-assembly and pattern formation, fullerenes, synchrotron-based spectroscopy, and charge transport in nanoparticle assemblies, but my primary project at the moment focuses on an area which what at least one funding agency in the UK has termed “extreme nanotechnology”. The bulk of my funding is related to the development of atomic manipulation protocols on semiconductor and insulator surfaces (silicon and diamond). The aim is to explore to what extent it’s possible to fabricate nanostructures, atom-by-atom and automatically (i.e. under computer control), using scanning probes. A key aspect of this work is to move away from 2D manipulation (i.e. atom sliding/pushing/pulling) and to attempt fabrication of 3D structures. This is immensely challenging because it entails gaining fine control of an element of a scanning probe microscope which, although integral to its operation, is still generally a key unknown: the tip. Somewhat controversially, the project examines the extent to which Eric Drexler’s ideas regarding force-driven chemical reactions at the atomic/molecular scale (mechanosynthesis) can be realised and was inspired by a lengthy debate I had on the subject of Drexlarian nanotechnology with Chris Phoenix at the Centre for Responsible Nanotechnology a number of years ago.

Part 2 of the Philip Moriarty Interview

The Philip Moriarty five year project for experimentally work on mechanosynthesis was discussed here in August 2008


Finally experiments have been funded to test the viability of diamond mechanosynthesis as described in detail by Robert Freitas and Ralph Merkle. This is a major step towards achieving the long held vision of molecular nanotechnology as envisioned by Eric Drexler.



Moriarty is interested in testing the viability of positionally-controlled atom-by-atom fabrication of diamondoid materials as described in the Robert Freitas-Ralph Merkle minimal toolset theory paper. Moriarty’s efforts will be the first time that specific predictions of DFT in the area of mechanosynthesis will be rigorously tested by experiment. His work also directly addresses the requirement for “proof of principle” mechanosynthesis experiments requested in the 2006 National Nanotechnology Initiative (NNI) review, in the 2007 Battelle/Foresight nanotechnology roadmap, and by EPSRC’s Strategic Advisor for Nanotechnology, Richard Jones (Physics, Sheffield University, U.K.).

Robert Freitas and Ralph Merkle are the leading researchers of the direct to diamondoid pathway to molecular manufacturing

University of Nottingham Nanoscience Group Homepage

Latest Publications of the Nottingham Nanoscience Group

X-ray absorption and photoemission spectroscopy of zinc protoporphyrin adsorbed on rutile TiO2(110) prepared by in situ electrospray deposition
A. Rienzo, L. C. Mayor, G. Magnano, C. J. Satterley, E. Ataman, J. Schnadt, K. Schulte and J. N. O'Shea
J. Chem. Phys. 132, 084703 (2010)

Supramolecular Assemblies Formed on an Epitaxial Graphene Superstructure
A. J. Pollard, E. W. Perkins, N. A. Smith, A. Saywell, G. Goretzki, A. G. Phillips, S. P. Argent, H. Sachdev, F. Müller, S. Hüfner, S. Gsell, M. Fischer, M. Schreck, J. Osterwalder, T. Greber, S. Berner, N. R. Champness and P. H. Beton
Angew. Chem. Int. Ed., 49, 1794 –1799 (2010)

Theoretical and experimental comparison of SnPc, PbPc, and CoPc adsorption on Ag(111)
J. D. Baran, J. A. Larsson, R. A. J. Woolley, Yan Cong, P. J. Moriarty, A. A. Cafolla, K. Schulte and V. R. Dhanak
Phys. Rev. B, 81, 075413 (2010)

A combination of normal-incidence x-ray standing-wave (NIXSW) spectroscopy, x-ray photoelectron spectroscopy (XPS), scanning tunneling microscopy (STM), and density-functional theory (DFT) has been used to investigate the interaction of a number of phthalocyanine molecules (specifically, SnPc, PbPc, and CoPc) with the Ag(111) surface. The metal-surface distances predicted by the DFT calculations for SnPc/Ag(111) (2.48 Å) and CoPc/Ag(111) (2.88 Å) are in good agreement with our NIXSW experimental results for these systems (2.31±0.09 and 2.90±0.05 Å, respectively). Good agreement is also found between calculated partial density-of-states plots and STM images of CoPc on Ag(111). Although the DFT and Pb 4f NIXSW results for the Pb-Ag(111) distance are similarly in apparently good agreement, the Pb 4f core-level data suggest that a chemical reaction between PbPc and Ag(111) occurs due to the annealing procedure used in our experiments and that the similarity of the DFT and Pb 4f NIXSW values for the Pb-Ag(111) distance is likely to be fortuitous. We interpret the Pb 4f XPS data as indicating that the Pb atom can detach from the PbPc molecule when it is adsorbed in the “Pb-down” position, leading to the formation of a Pb-Ag alloy and the concomitant reduction in Pb from a Pb2+ state (in bulklike films of PbPc) to Pb0. In contrast to SnPc, neither PbPc nor CoPc forms a well-ordered monolayer on Ag(111) via the deposition and annealing procedures we have used. Our DFT calculations show that each of the phthalocyanine molecules donate charge to the silver surface, and that back donation from Ag to the metal atom (Co, Sn, or Pb) is only significant for CoPc

Above-barrier surface electron resonances induced by a molecular network
R. Stiufiuc, L. M. A. Perdigão, B. Grandidier, D. Deresmes, G. Allan, C. Delerue, D. Stiévenard, P. H. Beton, S. C. Erwin, M. Sassi, V. Oison and J. M. Debierre
Phys. Rev. B 81, 045421 (2010)

Patterns and Pathways in Nanoparticle Self-Organisation
M. O. Blunt, A. Stannard, E. Pauliac-Vaujour, C. P. Martin, I. Vancea, M. Šuvakov, U. Thiele, B. Tadic and P. Moriarty
in the Oxford Handbook of Nanoscience and Technology (Volume 1: Basic Aspects),
editors: A. V. Narlikar and Y. Y. Fu, ISBN: 978-0-19-953304-6 (Oxford University Press, 2010)

Their positional assembly page (may not be up to date)

FURTHER READING
Robert Freitas website
Ralph Merkle website

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