Friday, June 3, 2011

Air Liquide Arabia will invest more than 35 million US dollars in two Air Separation Units

The Kingdom of Saudi Arabia is the largest economy in the Middle East. Growth is driven by the expansion of the refining and petrochemical industries and the development of infrastructure projects. Air Liquide announces new successes in this growth region.

Saudi Aramco and Air Liquide Arabia announce that they have signed a new long-term nitrogen supply agreement for Saudi Aramco’s operations in Qurayyah, in the Eastern Province. This nitrogen will be used by Saudi Aramco in the processing of seawater related to oil production.

Under the terms of the agreement, Air Liquide Arabia will invest more than 35 million US dollars (more than €25 million) in two Air Separation Units with a total production capacity of 500 tonnes per day. The facility will be designed and built by Air Liquide Engineering teams and commissioned in 2012. It will also support growing industrial merchant needs in the Eastern Province.

This new contract follows Air Liquide Arabia’s signature of a hydrogen supply agreement in September 2010 for Saudi Aramco’s large-scale refinery in Yanbu.

Also in Saudi Arabia, Air Liquide Al Khafrah Industrial Gases has started up a new high purity filling center in Dammam to deliver specialty gases to its key petrochemical customers. The investment amount for these new capabilities and the supply chain for bulk gases is 10 million US dollars (more than €7 million).

Pierre Dufour, Senior Executive Vice-President of the Air Liquide Group supervising the Middle East Zone, commented: “With those new investments, Air Liquide demonstrates its capacity to accompany its customers at all stages of their industrial processes particularly in the main industrial hubs. These investments also reinforce our growing presence in all aspects of the Saudi Arabia economy, where we continue to develop our industrial gas infrastructure in support, not only of the energy sector, a growth driver for Air Liquide, but also in the evolving non-energy sector.”

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Where no lab has gone before: Single-Molecule Electrokinetic Traps

To study the behavior of large protein complexes and long DNA chains in solution, researchers use so-called molecular traps. However, earlier traps have proven ineffective when working with small molecules due to the latter’s high diffusion. This limitation was first addressed through single-molecule immobilization techniques such as surface attachment and laser tweezers, but there were drawbacks: the former can disrupt biochemical structures, while the latter require molecules to be attached to large beads. A later trap developed at Stanford University used computer-based image capture and processing to track a single molecule’s Brownian motion, which it then cancels by applying variable voltage feedback. Now, however, Harvard University researchers have devised an Anti-Brownian ELectrokinetic (ABEL) trap that couples fluorescence microscopy to real-time electrokinetic feedback to trap any soluble fluorescence-capable molecule up to 800 times less massive than was previously possible.

Developed at Harvard University by Prof. Adam E. Cohen in the Departments of Physics and of Chemistry and Chemical Biology, and Alex Fields, his student in the Biophysics Program, the ABEL trap works by following the Brownian motion of a particle, and then applying feedback forces to the particle to suppress this Brownian motion. The system uses fluorescence (from a dye molecule attached to that particle) to track the Brownian motion of the particle with a high degree of precision without damaging it.

Molecular traps face a basic challenge that has been historically difficult to overcome – namely, the differences in behavior between atoms in a low-temperature vacuum, which follow Newton’s laws of inertia and momentum, and those in solution. In the latter case, molecules collide every few picoseconds (as opposed to billions of times per second in a gas at atmospheric pressure, and only once every few seconds for typical atom trapping done at ultra-high vacuum), making it very difficult to track and analyze their positions and trajectories. This therefore requires a very different molecular trapping strategy.

While fluorescence has been employed in single-molecule imaging since the 1990s, these early systems required molecules to be immobilized on the surface of a slide using a chemical tether. Unfortunately, the tether often perturbed or modified the particle being trapped, so that there was no guarantee that it was behaving as it would if free in solution. Other early traps required molecules to be attached to small bead-like structures in order to be immobilized, which also often perturbed the molecule under study.

However, Cohen’s work with W. E. Moerner at Stanford University in 2005 led to traps that connected a CCD camera to a computer and determined the molecule's position via real-time image fitting. The computer then applied a time-varying feedback voltage to the solution so that the electrophoretic and electroosmotic drifts combined to cancel the Brownian motion.

Despite the significant progress made, the system’s speed was limited by software speed and the frame-rate of the camera. During his last year at Stanford, however, Cohen updated the trap with custom hardware that by having single-photon sensitivity allowed not only more precise measurement but the ability to determine where a photon had originated.

“The key to making ABEL work,” says Cohen, “is to do the feedback as quickly and accurately as possible. However, as we try to trap ever-smaller particles, this task becomes challenging for two reasons. First, smaller particles diffuse faster – the amount of diffusion is inversely proportional to the radius of the particle, so a 1 nm particle diffuses 10 times faster than a 10 nm particle. Second, smaller particles tend to be dimmer – and in the limit of having just one fluorescent dye molecule, we don't get very many photons from it. So in the end, we're trying to follow the motion of this incredibly quickly moving, dim object, and we need to do this with sub-millisecond resolution in time and micron-scale resolution in space. That's hard to do.”

The primary innovation that allows the ABEL trap to trap single dye molecules is a statistically rigorous tracking algorithm that makes nearly optimal use of the information in every detected photon, which Fields designed and implemented in custom digital hardware (called a Field Programmable Gate Array, or FPGA). “The FPGA can run the algorithm tens of thousands of times per second,” explains Cohen, “so every time we detect a photon from a trapped molecule, the algorithm incorporates this information into its estimate of where the particle was, generates the appropriate feedback signals, and then waits until the next photon detection.”

This video is not supported by your browser at this time.

A series of Alexa 647 molecules are trapped until photobleaching or diffusional escape. The movie is shown in real time. Video (c) PNAS, DOI:10.1073/pnas.1103554108

The result is an imaging and detection system that performs the fastest and most sensitive tracking to date by combining all photon information in a statistically optimal way that generates the most likely estimate of the location of a photon’s source. Moreover, implementing the algorithm on the FPGA runs the algorithm in 9 µs, which is significantly less than the typical interval between photon emissions. (By way of comparison, the CCD camera-based system took 4.5 ms to process emitted photon data, and the algorithm prior to that developed by Fields required 25 µs.)

Cohen acknowledges that despite these advances, ABEL is not perfect. “One limitation to that ABEL can only trap for a few seconds because the oxygen-sensitive dye molecule is subject to laser-induced photobleaching. Optical excitation has a small probability of resulting in a photochemical change that disrupts the dye molecule.” However, he adds that photobleaching can be minimized by adding chemicals that consume oxygen, as well as other chemicals that decrease its impact, such as antioxidants and free- radical scavengers.

Going forward, Cohen is interested in layering other kinds of spectroscopy on top of the trapping. “We want to shine different colors of light onto the trapped molecule, and so get more information out of the photons – their polarization, wavelength, and precise timing – that the molecule emits. This additional information will give us a more detailed picture of what the one molecule is doing inside the trap”

Cohen also is investigating the addition of various fluidics to facilitate the inflow and outflow of different reagents. “It would be great if we could trap an enzyme, say, and then flow in substrate or ATP, and see how the dynamics of the enzyme change.”

Regarding applications, Cohen is hoping in the near term to study the dynamics of short pieces of and DNA-protein interactions. “DNA has been incredibly well studied, of course; but there are still really fundamental and important things we don't know,” he points out. “For example, we don't know what happens to DNA if you bend it very sharply, or how the mechanical properties of DNA depend on its underlying sequence. These questions are important to the function of DNA in a cell, because DNA in a cell is often highly bent around histones or by DNA-binding proteins. We also don't fully understand how DNA-binding proteins find their specific binding sites on the molecule. It's possible that the proteins are probing the local mechanical properties of the molecule as part of their search.”

In the longer term, the team would like to study the internal dynamics of a wide range of proteins and molecular machines. “Now that we can trap nearly any molecule without tethering it to a surface, we can hope to look at the dynamics of many individual that thus far have been impossible to study at the single-molecule level.”

More information:
• Electrokinetic trapping at the one nanometer limit, PNAS Published online before print May 11, 2011, DOI:10.1073/pnas.1103554108
Cohen Lab at Harvard University

Copyright 2011
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Making materials to order: Fine-tuning mechanical, electrical, thermal, other properties of composites

 A team of researchers at MIT has found a way to make complex composite materials whose attributes can be fine-tuned to give various desirable combinations of properties such as stiffness, strength, resistance to impacts and energy dissipation.

The key feature of the new composites is a “co-continuous” structure of two different with very different properties, creating a material combining aspects of both. The co-continuous structure means that the two interleaved materials each form a kind of three-dimensional lattice whose pieces are fully connected to each other from side to side, front to back, and top to bottom.

The research — by postdoc Lifeng Wang, who worked with undergraduate Jacky Lau and professors Mary Boyce and Edwin Thomas — was published in April in the journal Advanced Materials. The research was funded by the U.S. Army through MIT’s Institute for Soldier Nanotechnologies.

The initial objective of the research was to “try to design a material that can absorb energy under extreme loading situations,” Wang explains. Such a material could be used as shielding for trucks or aircraft, he says: “It could be lightweight and efficient, flexible, not just a solid mantle” like most present-day armor.

In most conventional materials — even modern advanced composites — once cracks start to form they tend to propagate through the material, Wang says. But in the new co-continuous materials, crack propagation is limited within the microstructure, he says, making them highly “damage tolerant” even when subjected to many crack-producing events.

Some existing composite materials, such as carbon-carbon composites that use fibers embedded in another material, can have great strength in the direction parallel to the fibers, but not much strength in other directions. Because of the continuous 3-D structure of the new composites, their strength is nearly equal in all dimensions, Wang says.

Thomas, the Morris Cohen Professor of Materials Science and Engineering and head of MIT’s Department of Materials Science and Engineering, says that in most existing , the fibers form disordered mass with “zero continuity,” while the other material — typically a resin that fills the space and then hardens — is continuous and connected in three dimensions. The material that forms the continuous structure “tends to dominate the properties” of the composite, he says. “But when both materials are continuous, you can get benefits that are surprisingly synergistic, not just additive.”

In their experiments, the MIT researchers combined two polymer materials with quite different properties: one that is glass-like, strong but brittle, and another that is rubber-like, not so strong, but tough and resilient. The result, Thomas says, was a material “that is stiff, strong and tough.”

In the quest for new materials with specific combinations of properties, Thomas says, “we’ve pretty much exhausted the natural homogeneous materials,” but the new fabrication techniques developed in this research can “take to another level” the material development process.

The researchers designed the new materials through computer simulations, then made samples that were tested under laboratory conditions. The simulations and the experimental data “agree nicely,” Thomas says. While this initial research focused on tuning the material’s mechanical properties, the same principles could be applied to controlling a material’s electrical, thermal, optical or other properties, the researchers say.

The process could even be used to make materials with "tunable" properties: for example, to allow certain frequencies of phonons — waves of heat or sound — to pass through while blocking others, with the selection of frequencies tuned through changes in mechanical pressure. It could also be used to make materials with shape-memory properties, which could be compressed and then spring back to a specific form.

Richard Vaia, acting chief of the Nanostructured and Biological Materials Branch at Wright-Patterson Air Force Base in Ohio, says this work is “an exciting demonstration of the crucial importance of architecture in materials-by-design concepts.”

Vaia says this work “provides an example of the future of composite and hybrid materialstechnology where direct-write fabrication, printing technologies and complex fiber-weaving techniques are not simply manufacturing tools, but an integral part of a robust, implementable digital design and manufacturing paradigm.”

The next step in the research, Thomas says, is to make co-continuous composites out of pairs of materials whose are even more drastically different than those used in the initial experiments, such as metal with ceramic, or polymer with metal. Such composites could be very different from any materials made before, he says.
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