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News Article | April 13, 2016
Site: http://www.cemag.us/rss-feeds/all/rss.xml/all

What if doctors could deliver anti-cancer drugs directly to tumors without making patients sick? Bringing this dream of targeted drug delivery closer to reality for pharmaceutical manufacturers, researchers at the National Institute of Standards and Technology (NIST) have received a patent for a method to create precisely sized nanometer-scale capsules. The NIST method employs microfluidics to create precise nanoscale spherical capsules. Made of lipids, the kinds of biomolecules that also comprise fats, the spherical capsules are known as liposomes. Essentially, liposomes are simplified artificial versions of cell membranes, the outer coverings of cells. The inside of a liposome could hold drugs, and the outside could be coated with receptors that bind to specific cancer cells. The method can produce liposomes with typical diameters of 100-400 nanometers, or billionths of a meter. This size range is useful for attaching to cells, whose size is typically 1 to 10 micrometers, or millionths of a meter. Typical methods for making liposomes include pushing a lipid solution through a filter, a process that can lead to wide variations in the size of the resulting liposomes. Furthermore, the methods can be wasteful, and can result in large amounts of expensive drugs not being captured inside the liposomes and being discarded. In the NIST technique, lipid material is dissolved in isopropyl alcohol. The resulting lipid-containing solution is then forced into a narrow channel and further constricted when it is squeezed by streams of water coming at it from multiple sides. Lipid molecules are repelled by water, so they clump together and coalesce into spherical liposomes. Adjusting the flow rate of the water can control the size of the liposomes that form. “We have precision control over making liposomes and changing their size by dialing in flow rates,” says Michael Gaitan, who works in NIST’s Physical Measurement Laboratory. Researchers could dissolve drugs or other molecules of interest into the water stream, Gaitan explains. Adjusting the concentrations of these molecules can determine the amount of the drug that ends up in the liposome, down to the single-molecule level. This method, which has received interest in being licensed by companies, originally developed from basic research. Gaitan and collaborator Laurie Locascio were looking for ways to enclose individual molecules of interest in fluid-filled capsules to study their behavior in a liquid environment. Previous methods had anchored individual molecules in glass slides, which are rather unnatural environments, as opposed to the more cell-like environment of a fluid-filled liposome. Once this technique was developed, researchers were able to create a variety of liposomes of many useful sizes, and the potential drug-delivery applications became clear. The researchers were awarded a patent for this work late last year. "This research and the resulting patent also have implications for the on-demand formulation of drugs in a way that’s applicable to personalized or precision medicine," says Laurie Locascio, director of NIST’s Material Measurement Laboratory. “The reason that this patent is so fundamental is that this is a process patent,” which is a more general form of patent, Gaitan explains. The method does not require a specific experimental configuration, but is a general approach that can be realized in many ways, he says. Moving forward, researchers at NIST’s Center for Nanoscale Science and Technology are continuing to develop this technique for more applications by creating capsules made of different types of nanoparticles. Size — and control — most definitely matter in nanotechnology. Being able to create precisely sized nanocontainers can open up many new applications, Gaitan says.


News Article
Site: http://www.rdmag.com/rss-feeds/all/rss.xml/all

Better thermometers might be possible as a result of a discovery at the National Institute of Standards and Technology (NIST), where physicists have found a way to calibrate temperature measurements by monitoring the tiny motions of a nanomechanical system that are governed by the often counterintuitive rules of quantum mechanics. While the method is not yet ready for commercialization, it reveals how an object’s thermal energy—its heat—can be determined precisely by observing its physical properties at the quantum scale. While the initial demonstration has an absolute accuracy only within a few percentage points, the NIST approach works over a wide temperature range encompassing cryogenic and room temperatures. It is also accomplished with a small, nanofabricated photonic device, which opens up possible applications that are not practical with conventional temperature standards. The NIST team’s approach arose from their efforts to observe the vibrations of a small transparent beam of silicon nitride using laser light. Thermal energy—often expressed as temperature—makes all objects vibrate; the warmer the object, the more pronounced the vibrations, though they are still on the order of just a picometer (trillionths of a meter) in size for the beam at room temperature. To observe these tiny perturbations, the team carved a small reflective cavity into the beam. When they shone a laser through the crystal, the light reflecting from the cavity experienced slight shifts in color or frequency due to the beam’s temperature-induced vibrations, making the light’s color change noticeably in time with the movement. But these were not the only vibrations the team members could see. The team also spotted the much more subtle vibrations that all objects possess due to a quantum-mechanical property called zero-point motion: Even at its lowest possible energy, the beam vibrates ever so slightly due to the inherent uncertainty at the heart of quantum mechanics. This motion is independent of temperature, and has a well-known amplitude fundamentally dictated by quantum mechanics. By comparing the relative size of the thermal vibration to the quantum motion, the absolute temperature can be determined. These intrinsic quantum fluctuations are thousands of times fainter and ordinarily get lost in the noise of the thermal energy-induced vibrations typical of ordinary temperatures, but the process of measuring the beam provides a method to distinguish quantum and thermal fluctuations. When photons from the laser bounce off the sides of the beam, they give it slight kicks, inducing correlations that make the quantum motion more pronounced. “Our technique allowed us to tease the quantum signals out from under the much larger thermal noise,” says the team’s Tom Purdy, a physicist at NIST’s Physical Measurement Laboratory and at the Joint Quantum Institute. “Now we can directly connect temperature to the quantum mechanical fluctuations of a particle. It sets the stage for a new approach to primary thermometry.” The power of this new method, when fully developed, will come when the beam is paired with other much more sensitive on-chip photonic thermometers also under development at NIST. Such devices offer the relative temperature sensitivity demanded by applications in pharmaceutical manufacturing, other high performance industrial applications, and climate monitoring, but require absolute calibration, and may drift over time. This new quantum thermometer will act as an integrated temperature standard, ready to keep the other thermometer on track over long periods of time. Purdy will present the team’s results on March 16, 2016, at the American Physical Society March Meeting in Baltimore, MD.


News Article
Site: http://phys.org/physics-news/

It won't be a minute too soon. The ampere (A) has long been a sort of metrological embarrassment. For one thing, its 70-year-old formal definition, phrased as a hypothetical, cannot be physically realized as written: "The ampere is that constant current which, if maintained in two straight parallel conductors of infinite length, of negligible circular cross-section, and placed 1 meter apart in vacuum, would produce between these conductors a force equal to 2 x 10–7 newton per meter of length." For another, the amp's status as a base unit is problematic. It is the only electrical unit among the seven SI base units. So you might logically expect that all other electrical units, including the volt and the ohm, will be derived from it. But that's not the case. In fact, the only practical way to realize the ampere to a suitable accuracy now is by measuring the nominally "derived" volt and ohm using quantum electrical standards and then calculating the ampere from those values. In 2018, however, the ampere is slated to be re-defined in terms of a fundamental invariant of nature: the elementary electrical charge (e). Direct ampere metrology will thus become a matter of counting the transit of individual electrons over time. One promising way to do so is with a nanoscale technique called single-electron transport (SET) pumping. Specially adapted at NIST for this application, it involves applying a gate voltage that prompts one electron from a source to tunnel across a high-resistance junction barrier and onto an "island" made from a microscopic quantum dot. The presence of this single extra electron on the dot electrically blocks any other electron from tunneling across until a gate voltage induces the first electron to move off the island, through another barrier, and into a drain. When the voltage returns to its initial value, another electron is allowed to tunnel onto the island; repeating this cycle generates a steady, measurable current of single electrons. There can be multiple islands in a very small space. The distance from source to drain is a few micrometers, and the electron channels are a few tens of nanometers wide and 200 nm to 300 nm long. And the energies involved are so tiny that that device has to be cooled to about 10 millikelvin in order to control and detect them reliably. Conventional, metallic SET devices, says NIST quantum-ampere project member Michael Stewart, can move and count single electrons with an uncertainty of a few parts in 108—in the uncertainty range of other electrical units—at a rate of tens of millions of cycles per second. "But the current in a single SET pump is on the order of picoamperes [10-12 A]," he says, "and that's many orders of magnitude too low to serve as a practical standard." So Stewart, colleague Neil Zimmerman, and co-workers are experimenting with ways to produce a current 10,000 times larger. By using all-silicon components instead of conventional metal/oxide materials, they believe that they will be able to increase the frequency at which the pump can be switched into the gigahertz range. And by running 100 pumps in parallel and combining their output, the researchers anticipate getting to a current of about 10 nanoamperes (10-9 A). Another innovation under development may allow them to reach a microampere (10-6 A), in the range that is needed to develop a working current standard. "At present, we are testing three device configurations of different complexity," Stewart says, "and we're trying to balance the fabrication difficulties with how accurate they can be." In addition to its use as an electrical current standard, a low-uncertainty, high-throughput SET pump would have two other significant benefits. The first is that it might be combined with ultra-miniature quantum standards for voltage or resistance into a single, quantum-based measurement suite that could be delivered to factory floors and laboratories. The overall effort to provide such standards for all the SI base units is known as "NIST-on-a-Chip," and is an ongoing priority of NIST's Physical Measurement Laboratory. The other advantage is that an SET pump could be used in conjunction with voltage and resistance standards to test Ohm's Law. Dating from the 1820s, it states that the amount of current (I) in a conductor is equal to the voltage (V) divided by the resistance (R): I=V/R. This relationship has been the basis for countless millions of electrical devices over the past two centuries. But metrologists are interested in testing Ohm's law with components which rely on fundamental constants. An SET pump could provide an all-quantum mechanical environment for doing so. In a separate effort, scientists at NIST's Boulder location are experimenting with an alternative technology that determines current by measuring the quantum "phase-slips" they engender while traveling through a very narrow superconducting wire. That work will be the subject of a later report.


News Article
Site: http://phys.org/physics-news/

While the method is not yet ready for commercialization, it reveals how an object's thermal energy—its heat—can be determined precisely by observing its physical properties at the quantum scale. While the initial demonstration has an absolute accuracy only within a few percentage points, the NIST approach works over a wide temperature range encompassing cryogenic and room temperatures. It is also accomplished with a small, nanofabricated photonic device, which opens up possible applications that are not practical with conventional temperature standards. The NIST team's approach arose from their efforts to observe the vibrations of a small transparent beam of silicon nitride using laser light. Thermal energy—often expressed as temperature—makes all objects vibrate; the warmer the object, the more pronounced the vibrations, though they are still on the order of just a picometer (trillionths of a meter) in size for the beam at room temperature. To observe these tiny perturbations, the team carved a small reflective cavity into the beam. When they shone a laser through the crystal, the light reflecting from the cavity experienced slight shifts in color or frequency due to the beam's temperature-induced vibrations, making the light's color change noticeably in time with the movement. But these were not the only vibrations the team members could see. The team also spotted the much more subtle vibrations that all objects possess due to a quantum-mechanical property called zero-point motion: Even at its lowest possible energy, the beam vibrates ever so slightly due to the inherent uncertainty at the heart of quantum mechanics. This motion is independent of temperature, and has a well-known amplitude fundamentally dictated by quantum mechanics. By comparing the relative size of the thermal vibration to the quantum motion, the absolute temperature can be determined. These intrinsic quantum fluctuations are thousands of times fainter and ordinarily get lost in the noise of the thermal energy-induced vibrations typical of ordinary temperatures, but the process of measuring the beam provides a method to distinguish quantum and thermal fluctuations. When photons from the laser bounce off the sides of the beam, they give it slight kicks, inducing correlations that make the quantum motion more pronounced. "Our technique allowed us to tease the quantum signals out from under the much larger thermal noise," says the team's Tom Purdy, a physicist at NIST's Physical Measurement Laboratory and at the Joint Quantum Institute. "Now we can directly connect temperature to the quantum mechanical fluctuations of a particle. It sets the stage for a new approach to primary thermometry." The power of this new method, when fully developed, will come when the beam is paired with other much more sensitive on-chip photonic thermometers also under development at NIST. Such devices offer the relative temperature sensitivity demanded by applications in pharmaceutical manufacturing, other high performance industrial applications, and climate monitoring, but require absolute calibration, and may drift over time. This new quantum thermometer will act as an integrated temperature standard, ready to keep the other thermometer on track over long periods of time. Purdy will present the team's results on March 16, 2016, at the American Physical Society March Meeting in Baltimore, Md. Explore further: Laser light used to cool object to quantum ground state


Shi W.L.,North University of China | Shi W.L.,Measurement Laboratory | Xue C.Y.,North University of China | Xue C.Y.,Measurement Laboratory | And 5 more authors.
Advanced Materials Research | Year: 2011

An experimental investigation has been carried out with clarifying the external mechanical stress effect on GaAs metal-semiconductor field-effect transistor (MESFET) I-V characteristic curve which as the sensitive element of micro-accelerometer in different condition. In this paper, we research different channel directions to explore the output characteristics of the GaAs MESFET which fabricated at the root of the cantilever. We design three channel directions which angled with the cantilever as 0 degree, 45 degree, 90 degree. We find that when the Channel direction parallel to the cantilever direction, ΔU has the maximum value of 12.13mv. The sensitivity of 0 degree is 0.04mv/g higher than the 90 degree. The dynamic result indicates that the channel direction parallel to the cantilever direction is the optimized design structure. © (2011) Trans Tech Publications, Switzerland. Source

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