This document is subject to copyright. Apart from any fair dealing for the purpose of private study or research, no part may be reproduced without the written permission. The content is provided for information purposes only. Explore further For the first time, scientists have experimentally demonstrated that sound pulses can travel at velocities faster than the speed of light, c. William Robertson’s team from Middle Tennessee State University also showed that the group velocity of sound waves can become infinite, and even negative. To rephase the spectral components, the sound waves were sent through an asymmetric loop filter on a waveguide of PVC pipe, about 8 m long. The 0.65-meter loop split the sound waves into two unequal path lengths, resulting in destructive interference and standing wave resonances that together created transmission dips at regular frequencies. Due to anomalous dispersion (which changes the wave speed), sound pulses traveling through the loop filter arrived at the exit sooner than pulses traveling straight through the PVC. With this experiment, the group velocity could actually reach an infinitely small amount of time, although the individual spectral components still travel at the speed of sound. “We also achieved what is known as a ‘negative group velocity,’ a situation in which the peak of the output pulse exits the filter before the peak of the input pulse has reached the beginning of the filter,” explained Robertson. “Using the definition for speed as being equal to distance divided by time, we measured a negative time and thus realized a negative velocity.”It might not seem that a negative velocity would exceed the speed of light, but in this case, Robertson said, the speed of the pulse is actually much faster than c. “Consider the pulse speed in a slightly less dramatic case,” Robertson said. “Say the peak of the output pulse exits the filter at exactly the same time as the input pulse reaches the beginning. In this less dramatic case, the transit time is zero and the speed (distance divided by zero) is infinite. So we were beyond infinite! (‘To infinity and beyond,’ to steal a line from Toy Story.) In our experiment, we measured a negative transit time corresponding to a negative group velocity of -52 m/s.”Although such results may at first appear to violate special relativity (Einstein’s law that no material object can exceed the speed of light), the actual significance of these experiments is a little different. These types of superluminal phenomena, Robertson et al. explain, violate neither causality nor special relativity, nor do they enable information to travel faster than c. In fact, theoretical work had predicted that the superluminal speed of the group velocity of sound waves should exist.“The key to understanding this seeming paradox is that no wave energy exceeded the speed of light,” said Robertson. “Because we were passing the pulse through a filter, the sped-up pulse was much smaller (by more than a factor of 10) than the input pulse. Essentially, the pulse that made it through the filter was an exact (but smaller) replica of the input pulse. This replica is carved from the leading edge of the input pulse. At all times, the net energy of the wave crossing the filter region was equal to, or less than, the energy that would have arrived if the input pulse had been traveling in a straight pipe instead of through the filter.”Is this phenomenon simply the result of a clever set-up, or can it actually occur in the real world? According to the scientists, the interference that occurs in the loop filter is directly analogous to the “comb filtering” effect in architectural acoustics, where sound interference occurs between sound directly from a source and that reflected by a hard surface.“The superluminal acoustic effect we have described is likely a ubiquitous but imperceptible phenomenon in the everyday world,” the scientists conclude.Citation: Robertson, W., Pappafotis, J., Flannigan, P., Cathey, J., Cathey, B., and Klaus, C. “Sound beyond the speed of light: Measurement of negative group velocity in an acoustic loop filter.” Applied Physics Letters 90, 014102 (2007).By Lisa Zyga, Copyright 2006 PhysOrg.com. All rights reserved. This material may not be published, broadcast, rewritten or redistributed in whole or part without the express written permission of PhysOrg.com. Citation: ‘Mach c’? Scientists observe sound traveling faster than the speed of light (2007, January 17) retrieved 18 August 2019 from https://phys.org/news/2007-01-mach-scientists-faster.html The ‘pulse’ of a volcano can be used to predict its next eruption In this schematic of the acoustical test system, the scientists could create superluminal group velocity of sound waves, as well as negative group velocity. In the latter case, the peak of the output pulse traveling through the loop filter exited the filter before the peak of the input pulse had reached the beginning of the filter. Image credit: Bill Robertson, et al. Past experiments have demonstrated that the group velocities of other materials’ components—such as optical, microwave, and electrical pulses—can exceed the speed of light. But while the individual spectral components of these pulses have velocities very close to c, the components of sound waves are almost six orders of magnitude slower than light (compare 340 m/s to 300,000,000 m/s).“All of the interest in fast (and slow) wave velocity for all types of waves (optical, electrical, and acoustic) was initially to gain a fundamental understanding of the characteristics of wave propagation,” Robertson told PhysOrg.com. “Phase manipulation can change the phase relationship between these materials’ components. Using sound to create a group velocity that exceeds the speed of light is significant here because it dramatically illustrates this point, due to the large difference between the speeds of sound and light.”The experiment was conducted by two undergrads, an area high school teacher and two high school students, who received funding by an NSF STEP (Science, technology, engineering, math Talent Enhancement Program) grant. The grant aims to increase recruitment and retention of students to these subjects.In their experiment, the researchers achieved superluminal sound velocity by rephasing the spectral components of the sound pulses, which later recombine to form an identical-looking part of the pulse much further along within the pulse. So it’s not the actual sound waves that exceed c, but the waves’ “group velocity,” or the “length of the sample divided by the time taken for the peak of a pulse to traverse the sample.” “The sound-faster-than-light result will not be a surprise to the folks who work closely in this area because they recognize that the group velocity (the velocity that the peak of a pulse moves) is not merely connected to the velocity of all of the frequencies that superpose to create that pulse,” explained Robertson, “but rather to the manner in which a material or a filter changes the phase relationship between these components. By appropriate phase manipulation (rephasing) the group velocity can be increased or decreased.”
This document is subject to copyright. Apart from any fair dealing for the purpose of private study or research, no part may be reproduced without the written permission. The content is provided for information purposes only. The Santa Clara, Calfornia based company 8×8 Inc. has been awarded a patent for the arrangement of a telephone and an interface unit that interfaces with a standard switched system and Internet communication network. The Santa Clara, California based company 8×8 Inc. announced today the award of a patent on its new VoIP. The distinguishing features of this new patent relates to the arrangement of a telephone and an interface unit which interfaces the telephone to both a standard switched tele-communication system and an Internet communication network. The U.S. Patent 7,289, 491 was issued by the U.S. Patent Office on October 30, 2007. Since its inception in 1987 8X8 Inc. has been awarded 70 patents. It is known for its original development of the Packet8 Voice Over Internet Protocol and video communication services for residential and business customers. Their proprietary patents include a range of voice, video and storage technologies.The company offers telephony solutions for small to medium businesses and residential customers as well. 8X8 Inc. has a variety of VoIP service plans that suit the needs of small businesses and residential customers. One plans offers unlimited calling throughout the United States and eight additional countries.Another plan offers a video terminal adapter with a service plan. There is also a Packet8 Virtual Office that provides business solutions for budget conscious small and medium side businesses. There is a Packet8 Complete Contact Center that is a hosted multimedia call center distribution and management platform that works on any broadband network. The new patent announced today will provided business and residential customers with additional flexibility and resilience in meeting the challenges of the future in telephone communications. Citation: 8×8 Inc. Is Awarded VoIP Patent Allowing Standard & Internet Connection (2007, October 31) retrieved 18 August 2019 from https://phys.org/news/2007-10-8×8-awarded-voip-patent-standard.html
Digitally programmable perovskite nanowire-block copolymer composites Citation: Ultra-Fast Quantum-Dot Information Storage (2008, March 21) retrieved 18 August 2019 from https://phys.org/news/2008-03-ultra-fast-quantum-dot-storage.html Explore further This document is subject to copyright. Apart from any fair dealing for the purpose of private study or research, no part may be reproduced without the written permission. The content is provided for information purposes only. The information-storage market is dominated by two main types: Flash memory, used in memory sticks and cell phones, and dynamic random access memory (DRAM), which is the main memory in a personal computer. Both types have their advantages and disadvantages, but a new type of memory, based on tiny atom clusters, called quantum dots, may soon displace both of them. In research published in the March 4, 2008, online edition of Applied Physics Letters, scientists from the Technical University of Berlin, in Germany, and Istanbul University, in Turkey, describe how they created a type of quantum-dot-based memory device that can save information at speeds of only a few nanoseconds (billionths of a second).The paper’s lead author, Technical University of Berlin scientist Martin Geller, explained to PhysOrg.com, “Flash memory, which is today’s market-driver in the semiconductor industry, and which everybody knows from memory sticks, digital cameras, and mp3-players, has a slow write time. The semiconductor industry is seeking faster Flash memories, but hasn’t found an ultimate solution yet. Our quantum-dot-based memory may provide long storage time without power consumption of Flash memory, as wells as a fast write time and better scalability to real-life devices.”To be fair, the other established predecessor of quantum-dot memory, DRAM, does have some excellent qualities. It offers very fast information-access times—under 20 nanoseconds—and the information can be repeatedly written and rewritten on a DRAM; it has excellent so-called endurance. But a DRAM device has a big disadvantage: It is volatile, meaning the information has to be refreshed every ten milliseconds to be maintained, also resulting in a high power consumption.“The very first prototype of our new quantum-dot-based memory scheme is already almost as fast as DRAM,” said Andreas Marent, a physicist at the Technical University of Berlin who took part in the research. “And in contrast to DRAM or Flash, the physical characteristics of quantum dots limit the write time to the picosecond, or trillionth of a second, range. That means a better device prototype should be more than 100 times faster than today’s DRAM.”The prototype consists of quantum dots of indium arsenide (InAs), a compound of the metals indium and arsenic, embedded in a layer of gallium arsenide (GaAs; gallium is also a metal). The GaAs layer is “p-doped,” which means it contains impurity atoms that impart it with excess free positively charge called holes. This InAs/GaAs structure is topped with a layer of “n-doped” GaAs, which contains extra electrons. Altogether, the structure is a p-n diode, an electrical device that allows current to flow only in one direction.When a voltage is applied across this structure, the quantum dots become charged, which allows them to store bits of information, i.e. “0” or “1” values. Whether the quantum dots represent a 0 or 1 depends on the capacitance of the diode—how much charge it is holding. A larger capacitance indicates the quantum dots do not hold much positive charge, which equates to a “0.” A smaller capacitance means that the dots are filled with holes, representing a “1.”Geller, Marent, and their colleagues say that the write times of their quantum-dot schemes are currently limited by the experimental setup and certain physical characteristics of the memory structure. In the future, after they make improvements to the structure, they expect that write times faster than 1 nanosecond may be possible. Even picoseconds seem possible, since the structure’s physical limitation is in that range.Said Prof. Dieter Bimberg, who is the group’s leader at the Technical University of Berlin and co-author on the paper, “Our results and patents demonstrate that quantum dots like these we are studying might, in just a few years, revolutionize semiconductor memory.”Citation: Appl. Phys. Lett. 92, 092108 (2008)All rights reserved. This material may not be published, broadcast, rewritten or redistributed in whole or part without the express written permission of PhysOrg.com.
More information: Berkeley Bionics (PhysOrg.com) — Berkeley Bionics unveiled eLEGS exoskeleton at a press conference on October 7 in San Francisco. Berkeley Bionics’ CEO, Eythor Bender stated that their mission is to provide people with unprecedented mobility options. © 2010 PhysOrg.com eLEGS exoskeleton is a bionic device engineered to help paraplegics stand up and walk on their own. Citation: Paraplegics have been given new hope for walking (w/ Video) (2010, October 14) retrieved 18 August 2019 from https://phys.org/news/2010-10-paraplegics-video.html This document is subject to copyright. Apart from any fair dealing for the purpose of private study or research, no part may be reproduced without the written permission. The content is provided for information purposes only. Explore further The eLEGS exoskeleton is a bionic device engineered to help paraplegics stand up and walk on their own. At first the device will be offered to rehabilitation centers for use under medical supervision, and can be adjusted to fit most people between 5’2″ and 6’4″ and weighing 220 pounds or less.eLEGS is battery-powered and employs a gesture-based human-machine interface that incorporates sensors and monitors the gestures the user makes to determine their intentions and then acts accordingly. A real-time computer collects data from sensors and input devices to coordinate every aspect of a single step.The technology may prove to be extremely helpful to those who are newly injured and may still have retained muscle memory without their muscles significantly weakened. This early assistance can help patients get back on their feet and help prevent a host of minor health concerns associated with being in a wheelchair. This can range from digestive issues to poor circulation.According to Berkeley Bionics, there are approximately 6 million people with some form of paralysis in the U.S. who are bound to wheelchairs; many of whom may have been active and athletic before an injury damaged their spinal cord. This new technology will give some of them the mobility to move their bodies and free them from their wheelchair. In the above video Amanda Boxtel was injured in a skiing accident in 1993 and left paralyzed from the waist down. eLEGS has given Amanda her mobility back and now works as a motivational speaker.In an Engadget interview with Berkeley Bionics CEO Eythor Bender, the system is presently made of steel and carbon fiber with lithium-ion battery packs, weighs 45 pounds, and has enough power to run for six hours of continuous walking. While an exact price was not given, Bender said that they were shooting for $100,000 and that it would be very competitive.Clinical trials are about to begin shortly; thereafter the exoskeleton will be available to selected medical centers in July or August of 2011. Bender commented that the company is also working on a streamlined commercial version for all-day use, tentatively slated for 2013. N.Zealand inventors unveil bionic legs for paraplegics (w/ Video)
(Phys.org)—In response to a BBC report that proved that BMW cars built between 2006 and 2011 can be easily stolen by thieves using a device that takes advantage of the cars’ computer system, BMW has announced that all owners of such vehicles can bring them in for a free fix. At issue is the process BMW put in place for its cars during the period in question. Owners who lost their keys could bring the car into a dealer who would then connect a computer to the car’s computer, along with a new blank key, and a new electronic key would be produced. Because of the simplicity of the procedure and the high value of BMW cars, clever engineers began creating the same type of computer the dealer’s used and selling them on the Internet. That allowed thieves to purchase them which made stealing a BMW as easy as breaking a window to gain entry, attaching the computer to the port inside the vehicle, along with a blank, and creating a new key that when inserted into the dash port, allowed the car to be started and driven away. While certainly very high tech, the result is a vehicle being stolen just as easily as cars made back before all the fancy electronics were introduced.Putting computers in cars started with the engines, taking out carburetors and putting in small computers that more efficiently meted air and gas. After that came computers that controlled the door locks allowing people to use small handheld devices with buttons to lock and unlock their cars from a distance, making such mundane tasks a little easier and less messy in bad weather. This was followed by adding computers that allowed for automatically starting the engine of the car, allowing owners to warm things up before getting in, and eventually, for some brands, the disappearance of a metal key altogether. In such cars, programmed plastic keys are inserted into the dash, and the computer takes care of getting the car started, presumably saving wear and tear on the starter mechanism under the hood. That’s what BMW did and that’s where it ran into trouble. By including code in the cars computer to not only start the engine when a proper key was identified, but to zap a blank key to create a new one upon command by a special computer, the car company opened the door to thieves. And that, British police say has led to a rash of car thefts in that country.BMW owners who purchased cars during the period noted can call their local dealer to have the problem fixed with their vehicle, or as some have noted, can simply move the computer port inside their car to a new location using a simple screw driver so that thieves can’t find it. © 2012 Phys.org BMW shows hands-free driving on Autobahn (w/ video) Citation: BMW forced to respond to BBC report showing its cars at easy risk of being stolen (2012, September 14) retrieved 18 August 2019 from https://phys.org/news/2012-09-bmw-bbc-cars-easy-stolen.html Explore further This document is subject to copyright. Apart from any fair dealing for the purpose of private study or research, no part may be reproduced without the written permission. The content is provided for information purposes only.
(Left) A photograph of the PENG, (center) the PENG powers an LCD for more than 60 seconds, and (right) a green LED is powered by a Li-ion battery that was charged by the PENG. Image credit: Yang, et al. ©2012 American Chemical Society Explore further The scientists, Ya Yang and Sihong Wang from the Georgia Institute of Technology in Atlanta, Yan Zhang from the Georgia Institute of Technology and the Chinese Academy of Sciences in Beijing, and Zhong Lin Wang from both institutions, have published a paper on a pyroelectric nanogenerator in a recent issue of Nano Letters.The scientists call the device a pyroelectric nanogenerator (PENG) because it’s based on the pyroelectric effect, in which an anisotropic material’s polarization changes in response to temperature fluctuations, which can be used to harvest thermal energy. Unlike the Seebeck effect, which is used to harvest thermal energy based on the temperature difference between two ends of a device, the pyroelectric effect occurs in environments where the temperature is spatially uniform but changes over time.”Wasted heat is a rich source of energy that can be harvested,” Zhong Lin Wang told Phys.org. “In 2010, for example, more than 50 percent of the energy generated from all sources in the US was lost mainly in the form of wasted heat, which presents us with a great opportunity to harvest this type of energy using nanotechnology. Harvesting thermoelectric energy mainly relies on the Seebeck effect, which utilizes a temperature difference between two ends of the device for driving the diffusion of charge carriers. The presence of a temperature gradient is a must for the conventional thermoelectric cell. However, in an environment where the temperature is spatially uniform without a gradient, such as the outdoors in our daily life, the Seebeck effect is hardly useful for harvesting thermal energy arising from a time-dependent temperature fluctuation. In this case, the pyroelectric effect is the choice, which is about the spontaneous polarization in certain anisotropic solids as a result of temperature fluctuation, but there are few studies about using the pyroelectric effect for harvesting thermal energy.” More information: Ya Yang, et al. “Pyroelectric Nanogenerators for Driving Wireless Sensors.” Nano Letters. DOI: 10.1021/nl303755m (Phys.org)—The idea of harvesting ambient energy from the environment that would otherwise not be purposefully used is, in theory, a great way to produce green, renewable energy. But the biggest problem in this fairly new area of research is that scientists have yet to find a method that can harvest very large amounts of energy. However, the technology is steadily improving, as demonstrated by the development of a nanogenerator that can partially charge a Li-ion battery by harvesting energy from temperature fluctuations in the environment. Ancient effect harnessed to produce electricity from waste heat Journal information: Nano Letters To date, PENGs have had output voltages below 0.1 V and current below 1 nA, which are too low to drive any commercial electronics. Here, the researchers demonstrated that a PENG made of a lead zirconate titanate (PZT) thin film has an output voltage of up to 22 V, a current peak of 430 nA, and a current density of 171 nA/cm2 when exposed to a temperature change of 45 K at a rate of 0.2 K/second. The PZT thin film is 21 mm long, 12 mm wide, and 175 μm thick – about half the size of a postage stamp.With these improvements in voltage and current, a single output pulse of the PENG could continuously power an LCD for longer than 60 seconds; in comparison, a piezoelectric nanogenerator, which harvests mechanical energy from the environment, can power an LCD for about 2 seconds. To expand the potential applications of the PENG, the researchers wanted to store the electric energy it generated from temperature fluctuations. So they hooked it up to a Li-ion coin battery, and demonstrated that the PENG could charge the battery from 650 to 810 mV in about 3 hours. They then showed that this stored electric capacity could be used to power a green LED for a few seconds.Another potential application of PENGs is wireless sensors. The researchers explained that wireless sensors can be powered by a rechargeable Li-ion battery with a voltage of 2.8 V. However, the PENG fabricated here has too small of a current to do this, since the current cannot completely overtake the battery’s inherent self-discharge. The researchers predict that doubling the area of the PZT film would double the current, and increasing the thickness of the PZT film could also increase the current. These improvements could make the pyroelectric nanogenerators attractive for driving wireless sensors, LCDs, and other small electronic devices, just by harvesting the temperature changes in the environment.”In our living environment, temperature change can come from an air-flow-induced drop in room temperature, the cycled heat generation near an engine, sunlight illumination with a moving shadow, on and off hot water/air flow in a pipe, etc.” Zhong Lin Wang said.Currently, the researchers are continuing to improve the PENG’s output power and are also integrating the technology with some existing products to demonstrate its practical applications. Copyright 2012 Phys.org All rights reserved. This material may not be published, broadcast, rewritten or redistributed in whole or part without the express written permission of PhysOrg.com. Citation: Pyroelectric nanogenerator charges Li-ion battery with harvested energy (2012, November 20) retrieved 18 August 2019 from https://phys.org/news/2012-11-pyroelectric-nanogenerator-li-ion-battery-harvested.html This document is subject to copyright. Apart from any fair dealing for the purpose of private study or research, no part may be reproduced without the written permission. The content is provided for information purposes only.
Credit: Sam Osmanagich An archaeologist is looking at a rock with great interest, a sphere unearthed in a forest, believed to be part of ancient civilization. Or is it just a very big rock? © 2016 Phys.org Explore further Citation: Archaeologist sees Bosnia stone sphere as the most massive in Europe (2016, April 17) retrieved 18 August 2019 from https://phys.org/news/2016-04-archaeologist-bosnia-stone-sphere-massive.html Prehistoric rock art engraving discovered in Brecon Beacons A stone ball in Podubravlje village near Zavidovici, Bosnia and Herzegovina was seen earlier this month, in the ground, in a forest.What can it tell us? Archaeologist Sam Osmanagich, who called his Bosnian stone ball the most massive in Europe, has some interesting answers.”I’ve been researching prehistoric stone ball phenomenon for 15 years,” he blogged last month.”By the mid of March 2016, it became obvious that the most massive stone ball in Europe has been discovered. Name of the location is village Podubravlje.”He said actually less than half of the ball is uncovered. “Preliminary results show the radius to be between 1.2 – 1.5 meters. Materials have not been analyzed yet. However, brown and red color of the ball point to very high content of the iron. So, the density has to be very high, close to the iron which is 7,8 kg/m3. If we take value of only 5 kg/c.c. we have all the elements for the preliminary calculation of the mass. Mass comes to be over 30 tons!”Why does he view this discovery as significant? “First, it would be another proof that Southern Europe, Balkan and Bosnia in particular, were home for advanced civilizations from distant past and we have no written records about them. Secondly, they had high technology, different than ours. Finally, they knew the power of geometrical shapes, because the sphere is one of the most powerful shapes along with pyramidal and conical shapes. No wonder, that pyramids and tumulus phenomena can also be found in Bosnia.”News.com.au said Osmanagich had examined granite stone balls in southern Costa Rica, volcanic stone spheres in western Mexico and Easter Island, and then turned his attention to Bosnia.If the huge stone in Bosnia is found to be hewn by human hands, it would be the largest man-made stone ball ever found – twice as heavy as the Costa Rican ones, said MailOnline.Do other experts see the rock formation as proof of an ancient civilization which thrived there? Voice of America reported that some scientists said the rock was likely a natural formation and not a human construct.Experts were quoted in MailOnline as saying they believed the boulder was not man made. A lecturer at the University of Manchester School of Earth, Atmospheric and Environmental Sciences told MailOnline that the spherical stone may be an example of concretion. This is when a compact mass of rock is formed by the precipitation of natural mineral cement within the spaces between sediment grains. The result is often spherical in shape, with the process forming the famed Koutu boulders in New Zealand. Experts at the Geological Society, according to MailOnline, said the round shape of the rock could come from spheroidal weathering. This is a type of weathering affecting jointed bedrock. The result is formation of concentric or spherical layers of highly decayed rock. This document is subject to copyright. Apart from any fair dealing for the purpose of private study or research, no part may be reproduced without the written permission. The content is provided for information purposes only.
Quaternary-ammonium-salt linkers can be proteolytically or reductively cleaved on cell entry and tracelessly release tertiary and heteroaryl amines. Credit: (c) Nature Chemistry (2016) doi:10.1038/nchem.2635 (Phys.org)—Beyond designing a drug that will attack cancer cells or bacterial cells, drug design also involves figuring out how the drug can safely enter the body and find its target before doing its work. However, many drugs never make it to their desired target either because of solubility issues or inability to access certain parts of the cell. That is where carriers come in. Carriers are like molecular taxis that latch onto a small-molecule drug and transport it to its target location. Journal information: Nature Chemistry Citation: Targeted drug therapy with carrier links to tertiary and heteroaryl amines (2016, November 3) retrieved 18 August 2019 from https://phys.org/news/2016-11-drug-therapy-carrier-links-tertiary.html These molecular taxis need to connect to the drug in such a way that they safely take it to the location, but the connection must also be reversible so the carrier can eventually release the drug. There are very few types of chemical bonds that can do this and the ones that can are limited in scope.A group of scientists from Genentech, Inc. have devised a synthetic scheme that is generalizable, protecting-group free, and allows for a carrier linker to attach to tertiary or heteroaryl amines via a quaternary ammonium salt. Additionally, because it is a charged species, it is more water soluble than typical carrier molecules and, therefore, may alleviate the problems associated with aggregation. These linkers can be set up to be cleaved either by proteases in the lysosome or reducing agents in the cytosol. This work appears in Nature Chemistry.”Enabling the reversible connection of tertiary and heteroaryl amines allows us to consider many new drugs, previously unamenable for targeted therapy,” Dr. Thomas Pillow told Phys.org.The ability to attach a linker to a tertiary amine or a heteroaryl amine is of interest because there are several known anticancer and antibacterial drugs that that have these functional groups. These groups often cannot be converted to a secondary or primary amine because of synthetic complexities or diminished drug potency. These drugs require a carrier molecule in order to be most effective in the body, but most carrier molecules previously could only be connected to primary or secondary amines.Additionally, many anticancer and antibacterial drugs are hydrophobic. But, the body is a predominantly aqueous environment. This means that, upon entering the body, the hydrophobic molecules tend to aggregate, which can cause problems with bodily systems or protein uptake. Notably, when the Genentech scientists attached a tertiary amine to a linker via a quaternary ammonium salt, it became more hydrophilic suggesting that this might be a good option for countering the aggregation problem. The first step was to determine if a tertiary amine could be reversibly attached to a chemical linker. To test their proposed linker connection, a p-aminobenzyl quarternary ammonium salt, they chose a known dipeptide-cleavable trigger: valine-citrulline (ValCit) which cleaves in the presence of cathepsin B. Incubation of their linker in buffer demonstrated that the quaternary ammonium salts were stable, and exposure to cathepsin B resulted in cleavage at the aniline amide and generation of the tertiary amine as expected. Carbon-carbon bond formation at selective aliphatic carbon sites More information: Leanna R. Staben et al. Targeted drug delivery through the traceless release of tertiary and heteroaryl amines from antibody–drug conjugates, Nature Chemistry (2016). DOI: 10.1038/nchem.2635AbstractThe reversible attachment of a small-molecule drug to a carrier for targeted delivery can improve pharmacokinetics and the therapeutic index. Previous studies have reported the delivery of molecules that contain primary and secondary amines via an amide or carbamate bond; however, the ability to employ tertiary-amine-containing bioactive molecules has been elusive. Here we describe a bioreversible linkage based on a quaternary ammonium that can be used to connect a broad array of tertiary and heteroaryl amines to a carrier protein. Using a concise, protecting-group-free synthesis we demonstrate the chemoselective modification of 12 complex molecules that contain a range of reactive functional groups. We also show the utility of this connection with both protease-cleavable and reductively cleavable antibody–drug conjugates that were effective and stable in vitro and in vivo. Studies with a tertiary-amine-containing antibiotic show that the resulting antibody–antibiotic conjugate provided appropriate stability and release characteristics and led to an unexpected improvement in activity over the conjugates previously connected via a carbamate. Explore further This document is subject to copyright. Apart from any fair dealing for the purpose of private study or research, no part may be reproduced without the written permission. The content is provided for information purposes only. The next step was to optimize their synthesis to make it simple and generalizable so it can be used for drug screening. In particular, the synthesis could not involve the use of protecting groups and the carrier molecule needed to preferentially react with the tertiary amine on the small molecule drug. After developing the experimental conditions for their reaction, Staben et al. then tested the stability and release of their protease-cleavable linker with a variety of molecules containing tertiary and heteroaryl amines. Good stability and drug release was demonstrated with several of these conjugates.Thus far, Staben et al. have been looking at the cleavage of peptide bonds. Disulfide bonds are another bond that can be set up as a bioactive trigger that is reduced by intracellular GSH. They tested their system by cleaving the disulfide bond and were able to generate the free tubulysin drug. In the field of targeted therapies, antibody-drug conjugates have gained ground as a way to target cancer cells or invading bacteria. Prior research by this team demonstrated that an antibody-antibiotic conjugate was able to successfully clear methicillin-resistant S. aureus (MRSA) infections. For the current research, they linked the tertiary amine of a rifamycin analog to their quaternary ammonium salt linker and found that in vitro tests showed a large reduction in the number of intracellular MRSA bacteria, a typically difficult-to-treat bacterial infection. According to Dr. Pillow, “This novel linker connection expands the universe of drugs for targeted therapy, opening up new possibilities for the treatment of cancer and infectious disease.” © 2016 Phys.org
Combining pulsed laser with electron gun allows for capturing fast motion of nanoparticles in a liquid PausePlay% buffered00:0000:00UnmuteMuteDisable captionsEnable captionsSettingsCaptionsDisabledQuality0SpeedNormalCaptionsGo back to previous menuQualityGo back to previous menuSpeedGo back to previous menu0.5×0.75×Normal1.25×1.5×1.75×2×Exit fullscreenEnter fullscreen PausePlay% buffered00:0000:00UnmuteMuteDisable captionsEnable captionsSettingsCaptionsDisabledQuality0SpeedNormalCaptionsGo back to previous menuQualityGo back to previous menuSpeedGo back to previous menu0.5×0.75×Normal1.25×1.5×1.75×2×Exit fullscreenEnter fullscreen Journal information: Science Advances This document is subject to copyright. Apart from any fair dealing for the purpose of private study or research, no part may be reproduced without the written permission. The content is provided for information purposes only. Explore further Citation: Using four-dimensional electron microscopy to track diffusion of nanoparticles in a liquid (2017, August 28) retrieved 18 August 2019 from https://phys.org/news/2017-08-four-dimensional-electron-microscopy-track-diffusion.html A team of researchers at Caltech has developed a way to capture on film the superfast propulsive motion of Brownian objects, particularly those at the nanoscale. In their paper published on the open-access site Science Advances, the team describes using four-dimensional electron microscopy techniques to capture real-time imagery of gold nanoparticles as they diffused in a liquid. Play Tracing photoinduced nanoparticle diffusion. Credit: Xuewen Fu 4D imaging of nanoparticle diffusion in liquid. Credit: Xuewen Fu More information: Xuewen Fu et al. Photoinduced nanobubble-driven superfast diffusion of nanoparticles imaged by 4D electron microscopy, Science Advances (2017). DOI: 10.1126/sciadv.1701160 Tiny particles suspended in hot liquid are observed to move in a seemingly random fashion. Such movement was noted by Robert Brown in the early 19th century, a phenomenon thus called Brownian motion. In more recent times, researchers have focused on Brownian motion as it relates to even smaller particles—micro and nano particles. Unfortunately, due to technological limitations, it was previously impossible to capture the action on film—instead, researchers have pieced together stills taken using an electron microscope. In this new effort, the researchers report on a technique they have developed that overcomes this problem, offering a new way to study diffusion of extremely tiny particles.The new approach involves the use of four-dimensional microscopy, which entails using both extremely fast laser pulses and transmission electron microscopy—it is based, the researchers note, on a pump-probe working mechanism. The first of two lasers excites the particles, while the second takes a picture of the action—it happens so quickly that the results can be viewed as video.In their experiments, the researchers fired a first pulse at gold nanoparticles, then fired a second pulse that captured images of tiny bubbles forming near the surface of the nanoparticles and exciting them. Increasing the energy of the first pulse, the team noted, resulted in merging many of the tiny bubbles, causing different types of movement by the nanoparticles. The researchers suggest their technique could be used by other researchers to study dispersion systems, particularly those that are out of equilibrium. It could also lead the way, perhaps, to the development of light-powered nanorobots working inside liquid systems. Play Results of nanoparticle experiment. Credit: Xuewen Fu © 2017 Phys.org
He has been around the Capital’s music circuit for quite a while and is a name known in a good few circles of music lovers who frequent haunts that belt out unique talent.Meet Nikhil Mawkin. A professional musician for 10 years and counting, Mawkin has been around in the truest sense possible. With no formal training in music, Nikhil took on singing and the guitar when he was taking a break after school. A performance in a restaurant that happened to him by chance changed the game for him. Also Read – ‘Playing Jojo was emotionally exhausting’He has performed on and off in India and abroad, spending a lot of time in Boston where he says he learned the most about music. Looking back, Nikhil says: ‘I was stereotyped for performing Elvis’ songs for the longest time.’ He used to host Elvis tributes for almost four years and it stuck on. It took Nikhil quite a while to break the mould.‘If you have enough conviction in what you do, you will find the right people,’ says Nikhil talking about the innumerous ups and downs that the last decade has shown him. Right from the time he started in small joints across the Capital to a music project for a theatre embassy from Amsterdam and then his stint in Boston and finally to Red Mawkin. This vocalist, guitarist and drummer has indeed come a long way. Also Read – Leslie doing new comedy special with NetflixHe released an album last year and another is due by August this year, he announces. A part of the Red Mawkin project that he is working on, the latest album is made up of songs he defines as groove rock. While his first album was an eclectic mix of different genres, Nikhil says he has finally defined a strain for this album.A bit of drums, jazz, pop-rock and a lot of Indian music influences, Nikhil is also working on what he calls Bolly Jazz. So does he sing mainstream Bollywood songs? Nikhil laughs it off saying, ‘I have been adviced not to sing in Hindi,’ but he collaborates with other singers to produce some soulful jazz renditions of Bollywood songs and he is also not adverse to teaming up for something more commercial. He’ll take it as it comes, he says. While he works with a number of musicians, the team — Shikhar Prasad (Guitar), Clarence Gonsalves (Bass), Nikhil Vasudevan (Drums), Sarthak Mudgal (Percussion), Praachi Kumar (Vocals) and Sayontani Chatterjee (Vocals) — he performed with at Hard Rock Cafe on 14 February is a team that he has worked with for the last six months. Nikhil explains that musicians need to work together for a while to get used to each other, so the teams he gets together stick on for a year or more. Comprising people he has worked with before and new faces as well, Nikhil is on a steady path ahead. And optimism is on a high. If you misssed them on Thursday, keep an eye out for the next performance. It is totally worth it.