Science and reality
The photos are presented seemingly as they were taken, with time-lapse captures taken through command module windows.
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An artist’s conception of an acoustic cell sorter is the cover image on the current issue of Lab on a Chip (credit: Huang Group/Penn State)
Penn State researchers have developed a new lab-on-a-chip cell sorting device based on acoustic waves that is capable of the kind of high sorting throughput necessary to compete with commercial fluorescence activated cell sorters, described in the cover story in the current issue of the British journal Lab on a Chip.
Commercial fluorescence activated cell sorters have been highly successful in the past 40 years at rapidly and accurately aiding medical diagnosis and biological studies, but they are bulky and too expensive ($200,000 -$1,000,000) for many labs or doctors’ offices.
“The current benchtop cell sorters are too expensive, too unsafe, and too high-maintenance. More importantly, they have very low biocompatibility. The cell-sorting process can reduce cell viability and functions by 30–99 percent for many fragile or sensitive cells such as neurons, stem cells, liver cells and sperm cells,” said Tony Jun Huang, Penn State professor of engineering science and mechanics and the paper’s corresponding author. “We are developing an acoustic cell sorter that has the potential to address all these problems.”
High-speed sorting
Schematic of the standing surface acoustic waves (SSAWs)-based sorter excited by focused interdigital transducers (FIDTs) (credit: Liqiang Ren et al./Lab on a Chip)
Microfluidic cell sorters are a promising new tool for single cell sequencing, rare cell isolation, and drug screening. However, many of them operate at only a few hundred cells per second, far too slow to compete with commercial devices that operate on the order of tens of thousands of operations per second. The Penn State system can sort about 3,000 cells per second, with the potential to sort more than 13,000 cells per second.
The speed is generated by using focused transducers to create standing surface acoustic waves (SSAWs). When the waves are not focused, the acoustic field spreads out, slowing the sorting process. The narrow field allows the sorting to take place at high speed while gently manipulating individual cells.
“Our high-throughput acoustic cell sorter is expected to maintain cell integrity by preserving not only high viability, but also other cellular features such as gene expression, post translational modification, and cell function,” said Huang.
“The acoustic power intensity and frequency used in our device are in a similar range as those used in ultrasonic imaging, which has proven to be extremely safe for health monitoring, even during various stages of pregnancy. With the gentle nature of low-power acoustic waves, I believe that our device has the best chance in preserving cell integrity, even for fragile, sensitive cells. Such an ability is important for numerous applications such as animal reproduction, cell immunotherapy and biological research.”
Because the device is built on a lab-on-a chip system, it is both compact and inexpensive — about the size and cost of a cell phone in its current configuration. With the addition of optics, the device would still be only as large as a book.
The acoustic cell sorter was fabricated in Penn State’s Nanofabrication Laboratory using standard lithography techniques and co-developed with Ascent Bio-Nano Technologies and the National Heart, Lung, and Blood Institute, a part of the National Institutes of Health.
In future work, the researchers plan to integrate their acoustic cell-sorting unit with an optical cell-detecting unit, with the goal of increasing throughput to 10,000 events per second.
Abstract of A high-throughput acoustic cell sorter
Acoustic-based fluorescence activated cell sorters (FACS) have drawn increased attention in recent years due to their versatility, high biocompatibility, high controllability, and simple design. However, the sorting throughput for existing acoustic cell sorters is far from optimum for practical applications. Here we report a high-throughput cell sorting method based on standing surface acoustic waves (SSAWs). We utilized a pair of focused interdigital transducers (FIDTs) to generate SSAW with high resolution and high energy efficiency. As a result, the sorting throughput is improved significantly from conventional acoustic-based cell sorting methods. We demonstrated the successful sorting of 10 μm polystyrene particles with a minimum actuation time of 72 μs, which translates to a potential sorting rate of more than 13800 events per second. Without using a cell-detection unit, we were able to demonstrate an actual sorting throughput of 3300 events per second. Our sorting method can be conveniently integrated with upstream detection units, and it represents an important development towards a functional acoustic-based FACS system.
From weighted brain networks (a), researchers estimate control points (b) whose large-scale regional activity can move the brain into new trajectories that traverse diverse cognitive functions (credit: Shi Gu et al./Nature Communications)
How does the brain determine which direction its thoughts travel? Looking for the mechanisms behind cognitive control of thought, researchers at the University of Pennsylvania, University of California, Riverside and Santa Barbara and United States Army Research Laboratory have used brain scans to shed new light on this question.
By using structural imaging techniques to convert brain scans into “wiring diagrams” of connections between brain regions, the researchers used the structure of these neural networks to reveal the fundamental rules that govern which parts of the brain are most able to exert “cognitive control” over thoughts and actions.
The work, published in an open-access paper in Nature Communications, weds cutting-edge neuroscience with the emerging field of network science, which is often used to study social systems. It applies control theory, a field traditionally used to study electrical and mechanical systems, to show that being on the “outskirts” of the brain is necessary for the frontal cortex to dynamically control the direction of thoughts and goal-directed behavior.
This fundamental understanding of how the brain controls its activity could help lead to better interventions for medical conditions associated with reduced cognitive control, such as autism, schizophrenia or dementia.
How the front cortex controls thoughts
According to Danielle Bassett, the Skirkanich Assistant Professor of Innovation in Penn’s School of Engineering and Applied Science and senior author on the study, “our results suggest that the human brain resembles a flock of birds. The flock comes to a consensus about which way to fly based on how close the birds are to one another and in what formation. Birds that fly at specific places in the flock can drive changes in the flock’s direction, being leaders in a so-called multi-agent system.
“Similarly, particular regions of your brain are predisposed to control your thoughts based on where they lie in relation to other regions.”
Cognitive psychologists and neuroscientists have long known that the frontal cortex is heavily involved in cognitive control. It is most active in experimental subjects asked to do tasks that require executive function, and damage to that region of the brain, through disease or injury, often results in loss of that function.
Applying control theory
The researchers were interested in developing a more fundamental understanding of how that region of the brain interacts with others to allow for executive function. Starting with detailed brain scans that show how neurons are physically connected to one another with one-millimeter precision, the scientists used a mathematical technique drawn from control theory in engineering.
By applying control theory equations to the “wiring diagrams” generated from brain scans, the researchers showed that the geographical and functional differences between regions of the brain are linked, with principles akin to large-scale dynamical network systems, such as power systems and robotic networks,
While the analysis cannot say whether the frontal cortex’s location or its role evolved first, it suggests that part of the frontal cortex’s ability to control executive function depends on its distance from other parts of the brain network.
Regions that are most interconnected, and therefore more internal to the network, are very good at moving the brain into nearby states, like from writing someone an email to talking to them on the phone. What’s particularly interesting is, if we look at where those inner nodes are, they’re all in ‘default mode’ regions, which are the regions that are active when you are resting. This makes sense, because if you were engineering an optimal system, you would want to put its baseline somewhere where it can get to most of the places it has to go pretty easily.”
This type of holistic understanding of the relationship between brain regions’ location and their roles is necessary for tailoring better treatments for people who have lost executive function due to disease or injury.
“We’re very interested in controlling brain networks with techniques like optogenetics, transcranial magnetic or direct-current stimulation, deep brain stimulation or even neurofeedback,” Bassett said, “but the problem has been that there is little theoretical basis to determine how these stimulations affect the dynamics of the whole brain. In most cases, stimulation is applied via trial and error. This research helps to build up an understanding of the impact of stimulation in one region on cognition as a whole.”
Future research will test whether “wiring” differences between people predict their performance on cognitive tasks. It will also underpin work on therapeutic and adaptive technologies that capitalize on brain networks’ unique advantages over their computerized counterparts.
Abstract of Controllability of structural brain networks
Cognitive function is driven by dynamic interactions between large-scale neural circuits or networks, enabling behaviour. However, fundamental principles constraining these dynamic network processes have remained elusive. Here we use tools from control and network theories to offer a mechanistic explanation for how the brain moves between cognitive states drawn from the network organization of white matter microstructure. Our results suggest that densely connected areas, particularly in the default mode system, facilitate the movement of the brain to many easily reachable states. Weakly connected areas, particularly in cognitive control systems, facilitate the movement of the brain to difficult-to-reach states. Areas located on the boundary between network communities, particularly in attentional control systems, facilitate the integration or segregation of diverse cognitive systems. Our results suggest that structural network differences between cognitive circuits dictate their distinct roles in controlling trajectories of brain network function.
Artist’s impression of the two-qubit logic gate device developed at UNSW. Each of the two electron qubits (red and blue) has a spin, or magnetic field, indicated by the arrow directions. Metal electrodes on the surface are used to manipulate the qubits, which interact to create an entangled quantum state. (credit: Tony Melov/UNSW)
University of New South Wales (UNSW) and Keio University engineers have built the first quantum logic gate in silicon, making calculations between two qubits* of information possible and clearing the final hurdle to making silicon quantum computers a reality.
The significant advance appears today (Oct. 5, 2015) in the journal Nature.
“What we have is a game changer,” said team leader Andrew Dzurak, Scientia Professor and Director of the Australian National Fabrication Facility at UNSW. “Because we use essentially the same device technology as existing computer chips, we believe it will be much easier to manufacture a full-scale processor chip than for any of the leading designs, which rely on more exotic technologies.”
University of New South Wales
“If quantum computers are to become a reality, the ability to conduct one- and two-qubits calculations are essential,” said Dzurak, who jointly led the team in 2012 that demonstrated the first ever silicon qubit, also reported in Nature.
Until now, using silicon, it had not been possible to make two quantum bits “talk” to each other and thereby create a logic gate. The new result means that all of the physical building blocks for a silicon-based quantum computer have now been successfully constructed, allowing engineers to finally begin the task of designing and building a functioning quantum computer, the researchers say.
Dzurak noted that the team had recently “patented a design for a full-scale quantum computer chip that would allow for millions of our qubits … using standard industrial manufacturing techniques to build the world’s first quantum processor chip. … That has major implications for the finance, security, and healthcare sectors.”
He said that a key next step for the project is to identify the right industry partners to work with to manufacture the full-scale quantum processor chip.
Dzurak’s research is supported by the Australian Research Council via the Centre of Excellence for Quantum Computation and Communication Technology, the U.S. Army Research Office, the State Government of New South Wales in Australia, the Commonwealth Bank of Australia, and the University of New South Wales. Veldhorst acknowledges support from the Netherlands Organisation for Scientific Research. The quantum logic devices were constructed at the Australian National Fabrication Facility, which is supported by the federal government’s National Collaborative Research Infrastructure Strategy (NCRIS).
* In classical computers, data is rendered as binary bits, which are always in one of two states: 0 or 1. A quantum bit (or ‘qubit’) can exist in both of these states at once, a condition known as a superposition. A qubit operation exploits this quantum weirdness by allowing many computations to be performed in parallel (a two-qubit system performs the operation on 4 values, a three-qubit system on 8, and so on).
Abstract of A two-qubit logic gate in silicon
Quantum computation requires qubits that can be coupled in a scalable manner, together with universal and high-fidelity one- and two-qubit logic gates. Many physical realizations of qubits exist, including single photons, trapped ions, superconducting circuits, single defects or atoms in diamond and silicon, and semiconductor quantum dots, with single-qubit fidelities that exceed the stringent thresholds required for fault-tolerant quantum computing. Despite this, high-fidelity two-qubit gates in the solid state that can be manufactured using standard lithographic techniques have so far been limited to superconducting qubits, owing to the difficulties of coupling qubits and dephasing in semiconductor systems. Here we present a two-qubit logic gate, which uses single spins in isotopically enriched silicon and is realized by performing single- and two-qubit operations in a quantum dot system using the exchange interaction, as envisaged in the Loss–DiVincenzo proposal. We realize CNOT gates via controlled-phase operations combined with single-qubit operations. Direct gate-voltage control provides single-qubit addressability, together with a switchable exchange interaction that is used in the two-qubit controlled-phase gate. By independently reading out both qubits, we measure clear anticorrelations in the two-spin probabilities of the CNOT gate.
An illustration of a tokamak with plasma (credit: ITER Organization)
Fusion reactors could become an economically viable means of generating electricity within a few decades, replacing conventional nuclear power stations, according to new research at Durham University and Culham Centre for Fusion Energy in Oxfordshire, U.K.
The research, published in the journal Fusion Engineering and Design, builds on earlier findings that a fusion power plant could generate electricity at a price similar to that of a fission plant and identifies new advantages in using new superconductor technology.
Such findings support the possibility that, within a generation or two, fusion reactors could offer an almost unlimited supply of energy without contributing to global warming or producing hazardous products on a significant scale.
No radioactive waste or leaks
Fusion reactors generate electricity by heating plasma to around 100 million degrees centigrade so that hydrogen atoms fuse together, releasing energy. Fission reactors work by splitting atoms at much lower temperatures.
The advantage of fusion reactors is that they create almost no radioactive waste and high-level radioactive material to potentially leak into the environment. That means disasters like Chernobyl or Fukushima are impossible because plasma simply fizzles out if it escapes.
Fusion energy would also not produce weapons-grade products that proliferate nuclear arms. It is fueled by deuterium (“heavy water”), which is extracted from seawater, and tritium, which is created within the reactor, so there is no problem with security of supply either.
A test fusion reactor based a tokamak design, the International Thermonuclear Experimental Reactor (ITER), is about 10 years away from operation in the South of France. Its aim is to prove the scientific and technological feasibility of fusion energy. MIT also plans to create new lower-cost, compact version of a tokamak fusion reactor, also based on improved superconductors, which are required to produce the high current needed to produce magnetic fields.
“Fission, fusion, or fossil fuels are the only practical options for reliable large-scale base-load energy sources,” said Professor Damian Hampshire, of the Centre for Material Physics at Durham University, who led the study. “Calculating the cost of a fusion reactor is complex, given the variations in the cost of raw materials and exchange rates. However, this work is a big step in the right direction” he said.
The potential for reducing the Cost of Electricity (CoE) by using High Temperature Superconductors (HTS) in the Toroidal Field (TF) coils of a fusion tokamak power plant has been investigated using a new HTS module in the PROCESS systems code. We report the CoE and the design of HTS tokamaks that have been optimised by minimising the major radius of the plasma. Potential future improvements in both the superconducting properties and the structural materials for TF coils operating at 4.8 K and 30 K are considered. Increasing the critical current density by a factor of 10 (with a commensurate reduction in costs kA−1 m−1) results in a CoE 4.4% less than equivalent tokamaks using current low temperature superconductors (LTS). If the yield strength of the TF casing material is increased by 40% to 1400 MPa, the CoE is further reduced by 3.4%. Implementing both improvements and operating the TF coils at 4.8 K leads to CoE of 19.1 (10.1) €cent kW−1 h−1 for a 500 MW (1.5 GW) HTS reactor compared to 20.7 (11.1) €cent kW−1 h−1 for an LTS reactor (2013 costs). Operating the HTS TF coils at 30 K with both improvements, gives a similar CoE for HTS and LTS tokamaks.
It's the middle of the road, but it's also the sweet spot. Take a moment to embrace the average.
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Strap on your space suit and fly into a dwarf moon's Danger Zone.
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This year's winners discovered their therapies by sifting through huge repositories of bacteria from soil samples and isolating active compounds from herbs.
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