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Carbon Nanotubes as a SinglePhoton Source

first_img Explore further “A photon correlation experiment measures the probability of arrival of two photons with a given time delay,” Högele explained. “When two photons travel together, an ideal photon correlation setup would detect with a probability of one the arrival of one photon upon the arrival of another. When one of the two traveling photons is delayed, then the photons will arrive consecutively at the detector and the probability of simultaneous photon detection is zero. “The meaning of the vanishing peak at zero time delay is that photons ‘avoid’ each other, and that it is impossible to find a pulse that contains two or more photons. It has been shown previously that such photon statistics cannot be explained using classical Maxwell’s equations; a quantum description of light is necessary to understand the photon antibunching phenomenon.”The researchers found that two different mechanisms ensure the antibunching: Augur processes and low temperatures that suppress the motion of charged particles along the nanotube axis. Together, these two mechanisms lead to a two-photon emission probability as low as 3% at low temperatures. “We were quite puzzled by our first measurement that showed strong antibunching in the photo-emission of single carbon nanotubes,” said Högele. “In consecutive experiments, we identified two key mechanisms that ensure single-photon generation: first, non-linear Auger processes [which cause one out of two pairs of electrons and electron holes to annihilate non-radiatively] play an important role. Second, electron-hole pairs in carbon nanotubes appear to be strongly localized at low-temperatures by trapping centers. The result is a carbon nanotube quantum dot with an anharmonic spectrum.”The researchers hope that these observations could lead to the development of new single-photon sources for applications such as long-distance quantum communication and quantum cryptography. “The potential advantage of using CNTs as single-photon sources is the fact that their emission wavelength can be tuned into the optical communication wavelength window,” said Högele. “The emission wavelength of single-walled carbon nanotubes depends on the tube diameter and is tunable by growth in the range between around 1 and 2 microns.”More information: Högele, Alexander; Galland, Christophe; Winger, Martin; and Imamoğlu, Atac. “Photon Antibunching in the Photoluminescence Spectra of a Single Carbon Nanotube.” Physical Review Letters 100, 217401 (2008).Copyright 2008 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. 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. This atomic force microscope image shows a single-walled CNT with a height of 0.8 nm and length of 800 nm. Researchers found that, under low temperatures, CNTs emit one photon at a time, marking the first demonstration of non-classical optical emission from a CNT. Credit: Högele, Alexander, et al. Citation: Carbon Nanotubes as a Single-Photon Source (2008, June 12) retrieved 18 August 2019 from https://phys.org/news/2008-06-carbon-nanotubes-single-photon-source.htmlcenter_img For the first time, a team of researchers from the Institute of Quantum Electronics in Zurich, Switzerland, has observed photon antibunching (the characteristic signature of non-classical light) in CNT photoluminescence. The study, which is published in a recent issue of Physical Review Letters, provides the first demonstration of non-classical optical emission from a CNT. Over the past few years, researchers have identified several different systems that can act as single-photon sources. All these systems have a common feature: they confine the motion of charged particles to a very small space in all three dimensions. Physicists describe such systems with restricted particle motion as “quasi-zero-dimensional.” The corresponding phase-space of localized particles is made into discrete areas due to the laws of quantum mechanics. The Pauli Exclusion Principle prevents two particles from occupying identical quantum states, so that only one particle at a time can undergo a transition between two distinct states. The principle inhibits simultaneous two-photon generation, and ensures that the system generates only a single photon. Physical systems such as atoms, ions, molecules, and quantum dots are quasi-zero-dimensional and operate as single-photon sources. In the new study, the researchers show that the same principle applies to CNTs – despite the fact that nanotubes are spatially extended in one dimension.“The fact that carbon nanotubes are nearly-perfect single photon emitters is surprising,” lead author Alexander Högele told PhysOrg.com. “Single photon emission is characteristic of systems with quantum confinement in all spatial dimensions. Carbon nanotubes, however, are axially extended and represent a one-dimensional model system.”The single-walled CNTs that the team studied had diameters of just 0.8 nanometers, along with an average length of about 500 nanometers. The researchers used a laser to excite individual CNTs at temperatures as low as 4.2 K, and caused them to emit light with a wavelength of around 880 nanometers. At first, the researchers observed that individual CNTs emitted photons at a delay of a few nanoseconds, consistent with the repetition rate in the laser pulse train. The researchers then investigated statistic correlations between such consecutively emitted photons. Significantly, they did not detect any photon correlation at zero time delay (t=0), indicating strong photon antibunching. Carbon nanotubes, as true multi-purpose materials, have potential applications in everything from electrical circuits and drug delivery to golf clubs and space elevators. Recently, physicists have investigated single-walled carbon nanotubes (CNTs) for one more use: as a single-photon source, where they could help make quantum communication networks extremely secure and efficient. On-demand control of terahertz and infrared waveslast_img read more

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Mice Levitated for Space Research

first_img Citation: Mice Levitated for Space Research (2009, September 11) retrieved 18 August 2019 from https://phys.org/news/2009-09-mice-levitated-space.html (PhysOrg.com) — Scientists have managed to levitate young mice in research carried out for NASA. Levitated mice may help research on bone density loss during long exposures to low gravity, such as in space travel and missions to other planets. 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 researchers worked from a number of laboratories around the U.S., including the Jet Propulsion Laboratory in Pasadena, California and the University of Missouri. The research was done on behalf of NASA, and was published in the online journal Advances in Space Research on 6 September 2009.The scientists built a variable gravity simulator consisting of a superconducting magnet that could generate a magnetic field strong enough to levitate the water inside every cell in the mouse’s body. Water is weakly diamagnetic, which means that in the presence of a strong magnetic field the electrons in water rearrange orbit slightly, creating tiny currents in opposition to the external magnetic field. If the external magnet is strong enough, the diamagnetic repulsion of the water in the mouse tissue is enough to exactly balance the force of gravity on the body.Scientists have previously levitated live grasshoppers and frogs, but this is the first time a mammal has been levitated. The mice were confined to a plastic cage, which had a base with holes to allow waste to be removed, and an open top to allow in air, food, water, and to allow the proceedings to be filmed. The cage was not necessary for the levitation, but it did allow the scientists to compare the levitated mice with non-levitated subjects in identical cages.The first subject to be levitated was just three weeks old. The tiny mouse was disturbed and disoriented and began to spin when it kicked out as though trying to find something to hold on to. With no friction to stop the spinning, the mouse became even more disoriented, according to Jet Propulsion Lab physicist Yuanming Liu.The next young mouse was mildly sedated before being levitated, and it was less agitated by the experience. The levitation experiments were repeated a number of times, and showed that the mice quickly adjusted to the conditions, even eating and drinking normally after a few hours of levitation. Even without sedation, the mice became quite comfortable floating in zero gravity.The powerful magnetic field seemed to have no short term effects on the mice, and earlier studies on rats showed there were no ill effects even after 10 weeks’ exposure to strong magnetic fields.The researchers are now applying for research funding that will allow them to study the physiological effects of prolonged exposure to microgravity, and to try to develop countermeasures that astronauts could adopt.More information: Magnetic levitation of large water droplets and mice; Yuanming Liua, Da-Ming Zhub, Donald M. Strayera and Ulf E. Israelssona, Advances in Space Research, http://dx.doi.org/10.1016/j.asr.2009.08.033© 2009 PhysOrg.com Spinning Water Droplets Could Provide Insights into Black Holes, Atomic Nuclei Image credit: Da-Ming Zhulast_img read more

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Electrostatic netting opens a whole new world of malaria vector control

first_img Explore further Fighting mosquito resistance to insecticides More information: “Electrostatic coating enhances bioavailability of insecticides and breaks pyrethroid resistance in mosquitoes.” PNAS 2015 ; published ahead of print August 31, 2015, DOI: 10.1073/pnas.1510801112AbstractInsecticide resistance poses a significant and increasing threat to the control of malaria and other mosquito-borne diseases. We present a novel method of insecticide application based on netting treated with an electrostatic coating that binds insecticidal particles through polarity. Electrostatic netting can hold small amounts of insecticides effectively and results in enhanced bioavailability upon contact by the insect. Six pyrethroid-resistant Anopheles mosquito strains from across Africa were exposed to similar concentrations of deltamethrin on electrostatic netting or a standard long-lasting deltamethrin-coated bednet (PermaNet 2.0). Standard WHO exposure bioassays showed that electrostatic netting induced significantly higher mortality rates than the PermaNet, thereby effectively breaking mosquito resistance. Electrostatic netting also induced high mortality in resistant mosquito strains when a 15-fold lower dose of deltamethrin was applied and when the exposure time was reduced to only 5 s. Because different types of particles adhere to electrostatic netting, it is also possible to apply nonpyrethroid insecticides. Three insecticide classes were effective against strains of Aedes and Culex mosquitoes, demonstrating that electrostatic netting can be used to deploy a wide range of active insecticides against all major groups of disease-transmitting mosquitoes. Promising applications include the use of electrostatic coating on walls or eave curtains and in trapping/contamination devices. We conclude that application of electrostatically adhered particles boosts the efficacy of WHO-recommended insecticides even against resistant mosquitoes. This innovative technique has potential to support the use of unconventional insecticide classes or combinations thereof, potentially offering a significant step forward in managing insecticide resistance in vector-control operations. © 2015 Phys.org Citation: Electrostatic netting opens a whole new world of malaria vector control (2015, September 11) retrieved 18 August 2019 from https://phys.org/news/2015-09-electrostatic-netting-world-malaria-vector.html (Phys.org)—Mosquito-borne infectious diseases are a huge public health burden, which carry high human and economic costs. Malaria, Chikungunya, West Nile virus and dengue are difficult to treat, and controlling the disease vector—mosquitos—is imperative.center_img The WHO recommends the use of four classes of public health insecticides, but widespread use has inevitably resulted in the development of insecticide-resistant mosquitos. Additionally, larval exposure to low residual doses of agricultural insecticide has been a major driver of resistance in mosquitos. Thus, the WHO advises health officials to rotate the use of both agricultural and vector-targeting insecticides to assert control over the expression of resistant genes. Nonetheless, conventional methods of mosquito control are becoming less effective over time, and researchers seek alternatives to existing techniques in an effort to stay one step ahead of adaptation. Now, a group of health and ecological science researchers in Johannesburg, South Africa, and Liverpool, England, have reported in the Proceedings of the National Academy of Sciences the use of an electrostatic coating that binds insecticide particles. The authors report that the method delivers such high levels of insecticides to mosquitos that even those with high levels of resistance are killed effectively. It consists of a coating, originally developed to trap and bind airborne pollen, which is applied on different substrates, including conventional mosquito netting for deployment in households. The coating has an electrostatic charge that binds particles via polarity. Though such techniques have been effectively applied in agriculture, this study is the first to demonstrate efficacy against disease-carrying mosquitos. The researchers tested the electrostatic netting on six strains of Anopheles mosquitos with different methods of adaptive pyrethroid resistance from across Africa. Fluorescent dust tests with the netting showed visual support of high powder transfer efficiency to flying insects, even with very short contact. “Even with a mere 5-second contact and at 15-fold lower dose, the impact of deltamethrin on electrostatic netting was significantly higher than the impact of deltamethrin on a [standard] long-lasting insecticidal net,” the authors write.They applied multiple public health insecticides with the electrostatic coating, successfully transferring them to the polyester fibers of the netting. The researchers note that the application technique has a variety of potential uses and can be applied to other surfaces including walls, via paint. Additionally, electrostatic netting fibers can be washed up to 40 times while retaining their electrostatic charge, extending the active life of the netting. However, the electrostatic netting is not considered by the WHO to be suitable for bed nets, for which only pyrethroid impregnation techniques are approved. It is useful, however, for house-screening products that will not be handled frequently, and the researchers are investigating the use of such nets in Tanzanian households.”In conclusion,” the authors write, “the application of electrostatically adhered particles can boost the efficacy and provide resistance-breaking applications of currently recommended public health insecticides.” Credit: CDC Journal information: Proceedings of the National Academy of Sciences 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.last_img read more

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Hauling antiprotons around in a van

first_imgAntiprotons present a unique way to study the radioactive elements produced at CERN’s ISOLDE ion-beam facility.Credit: Julien Marius Ordan/CERN/Nature Journal information: Nature More information: Elizabeth Gibney. Physicists plan antimatter’s first outing—in a van, Nature (2018). DOI: 10.1038/d41586-018-02221-9 The antiprotons will be created the same way that they are currently made at what has become known as CERN’s antimatter factory, but they will be used in experiments in a nearby building. For that to happen, the antiprotons will have to be boxed up and shipped in a van.Antiprotons are, of course, the opposite twins of protons—they exist sometimes in nature, but do not last long, because when they come into contact with regular matter, they are annihilated. Researchers at CERN create them by firing a proton beam at a metal target—holding antiprotons in a vacuum chamber at just 4 degrees above absolute zero, comparable to intergalactic space, can protect them from annihilation for brief periods.The PUMA team are trying to learn more about the nuclei of large radioactive atoms, and to that end, want to fire antiprotons at them and then study the remnants after both are annihilated. But for that to happen, the team has to develop a means for transporting the antiprotons from the site where they are created to the site where they will be tested—from one lab to another just a few hundred meters away.The plan is to create a trap capable of holding a billion antiprotons for up to a week. The team estimates it is likely to take up to four years to get the trap just right. In addition to providing the workers at ISOLDE with a batch of antiprotons, the project will also establish a technique for other teams working at much greater distances. That will give researchers from perhaps all over the world access to antiproton batches for use in their own experiments. Explore further Citation: Hauling antiprotons around in a van (2018, February 22) retrieved 18 August 2019 from https://phys.org/news/2018-02-hauling-antiprotons-van.htmlcenter_img © 2018 Phys.org A team of researchers working on the antiProton Unstable Matter Annihilation (PUMA) project near CERN’s particle laboratory, according to a report in Nature, plans to capture a billion antiprotons, put them in a shipping container and transfer them to a lab that is conducting experiments collectively called ISOLDE. 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. CERN sets course for extra-low-energy antiprotonslast_img read more

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Phylogenomic analyses shows group of winged insects developed from terrestrial ancestor

first_imgVirtual model of the last common ancestor of Polyneoptera. Credit: Benjamin Wipfler and Evgeny V. Yan. Explore further Polyneoptera represents one of the most prominent lineages of winged insects (Pterygota). There are approximately 40,000 species of them in 10 orders. They include stoneflies, grasshoppers and roaches. The researchers note that they are the only major lineage of winged insects with a cloudy evolutionary history. In this new effort, the researchers sought to fill in many of the gaps that exist in their family tree by conducting a large-scale phylogenomic analyses of both Polyneoptera and Pterygota. This enabled them to trace phylogenetic relationships of 112 samples associated with the typical appearance and lifestyle of the winged insects. Their study also involved studying 106 species and 3014 genes.The researchers report that their analysis revealed that polyneoptera did not evolve from an initial sea creature, but instead, one that lived on the land. This finding contrasts sharply with the view that such insects evolved from creatures that swam into insects that buzzed above the water, such as dragonflies. Also, a sea evolution seemed logical, with wings developing from fins. The evolution of wings from a terrestrial creature would most likely have had to come about due to the advantage some received from falling from a higher place to one that was lower. The researchers furthermore contend that the early land-dweller evolved from an insect that had antennae and a segmented abdomen. Also, it had biting mouth parts that were located beneath the head capsule, which would have been similar to the modern dragonfly. It would also have had stiff forewings making flight difficult and necessitating the development of triangular rear wings.The researchers note that their work was part of the 1,000 Insect Transcriptome Evolution Project (1KITE) which brought together international teams of researchers for the purpose of better understanding the evolutionary history of insects. © 2019 Science X Network Insects took off when they evolved wings Journal information: Proceedings of the National Academy of Sciencescenter_img Citation: Phylogenomic analyses shows group of winged insects developed from terrestrial ancestor (2019, January 15) retrieved 18 August 2019 from https://phys.org/news/2019-01-phylogenomic-analyses-group-winged-insects.html An international team of researchers has found evidence that shows that many modern winged insects developed from a terrestrial ancestor, not from one that lived in the sea. In their paper published in Proceedings of the National Academy of Sciences, the group describe their large-scale phylogenomic analyses of both Polyneoptera and Pterygota and what they found. More information: Benjamin Wipfler et al. Evolutionary history of Polyneoptera and its implications for our understanding of early winged insects, Proceedings of the National Academy of Sciences (2019). DOI: 10.1073/pnas.1817794116 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.last_img read more

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3D culturing hepatocytes on a liveronachip device

first_imgDue to their wider adoption in academic and industrial settings, the bioreactors require optimized materials and conditions for high throughput fabrication. Conditions include replacing the common prototyping material polydimethylsiloxane (PDMS), integrating induced pluripotent stem cell (iPSC)-derived cells on a soft biomaterial that facilitates their growth and minimizing the large dead volume caused by microfluidics reservoirs and tubing of organ-on-chips devices.The novel biomaterial prepared in the study contained two main constituents crosslinked via SPAAC; a cycloocytne-modified hyaluronan (HA-BCN) and a multiarmed azide-modified PEG [p(N3)8]. The BCN reacted with azides (N3) on the 8-armed PEG polymer with terminating N3-moieties to form a stable 1,2,3-triazole. Christoffersson et al. completed chemical reactions under physiological conditions to form the hydrogels with tunable viscoelastic properties. The crosslinking strategy was ideal to fabricate hydrogels for 3D cell culture; as the cells could be encapsulated in the biomaterial without compromising their viability and were suitable for use in microfluidic devices. The scientists used excess SPAAC moieties on the novel biomaterial to attach different ligands including RGD peptides to promote interactions at the cell-material interface.Thereafter, the scientists varied the composition of the two main constituents to understand the resulting viscoelastic properties, such as the storage modulus (G’) and loss modulus (G”) of the hydrogels via oscillatory rheology (technique to measure the viscoelastic behavior of soft materials). They controlled the gelation kinetics of the novel hydrogel at increasing temperatures. Gelation kinetics of the new biomaterial was slow enough for homogenous cell distribution but rapid enough to prevent cell sedimentation. The ability to control gelation kinetics allowed the scientists to consider a variety of biofabrication strategies (e.g. bioprinting) and hydrogel assembly within the microfluidic systems for organ-on-chip applications. (a) Schematic representation of the formation of HA-PEG hydrogels through a strain-promoted alkyne-azide cycloaddition reaction. (b) Photograph of a HA-PEG hydrogel after formation. (c) Frequency sweeps of HA-PEG hydrogels with different BCN to N3 ratios. (d) Gelation time experiment showing the increase of G’ over time during gelation of HA-PEG hydrogels (10:1 BCN:N3) at different temperatures. Credit: Biofabrication, doi: https://doi.org/10.1088/1758-5090/aaf657 Journal information: Biofabrication , Nature Reviews Drug Discovery Liver-on-a-chip cell culture devices are attractive biomimetic models in drug discovery, toxicology and tissue engineering research. To maintain specific liver cell functions on a chip in the lab, adequate cell types and culture conditions must be met, which includes 3D cell orientation and a consistent supply of nutrients and oxygen. Compared with conventional 2D cell culture techniques, organ-on-a-chip devices offer versatility and effective biomimicry suited for advanced applications in drug discovery and medicine. Researchers create a more effective hydrogel for healing wounds More information: 1. Fabrication of modular hyaluronan-PEG hydrogels to support 3D cultures of hepatocytes in a perfused liver-on-a-chip device iopscience.iop.org/article/10. … 088/1758-5090/aaf657, Jonas Christoffersson et al. 27 December 2018, Biofabrication, IOP Science. 2. Controlling hydrogelation kinetics by peptide design for three-dimensional encapsulation and injectable delivery of cells www.pnas.org/content/104/19/7791 Haines-Butterick L. et al. May 2007, PNAS .3. Microfluidic organs-on-chips www.nature.com/articles/nbt.2989 Bhattia S. N and Ingber D.E. August 2014, Nature Biotechnology.4. Organs-on-chips at the frontiers of drug discovery, www.nature.com/articles/nrd4539 Esch E.W. et al. March 2015, Nature Reviews Drug Discovery. , Nature Biotechnology Explore further (a)–(c) Frequency sweeps of (a) agarose, (b) alginate and (c) HA-PEG hydrogels at different concentrations. (d)–(f) SEM micrographs of (d) agarose, (e) alginate and (f) HA-PEG hydrogels showing the morphology of each hydrogel. Credit: Biofabrication, doi: https://doi.org/10.1088/1758-5090/aaf657 Structure of a) HA-BCN with a ratio n/m of 0.19 and b) p(N3)8. Credit: Biofabrication, doi: https://doi.org/10.1088/1758-5090/aaf657 Christoffersson et al. next compared the HA-PEG hydrogels with the well-established 3D cell culture scaffolds – agarose and alginate hydrogels. In order to determine the final viscoelastic properties suited for 3D cell culture experiments, they used oscillatory rheology to examine the different polymer concentrations. The scientists analyzed the composition of the finalized materials using scanning electron microscopy (SEM) images.The liver-on-a-chip design and setup had to meet two key criteria in the study: 1. Allow perfusion (passage of fluid) of cell culture medium across the hydrogel surface for steady nutrient media exchange, to and from the encapsulated hepatocytes. 2. Allow sampling of the perfused media for experimental analysis during ongoing cell culture, without affecting the hepatocytes and the hydrogel.center_img (a) Schematic representation of the liver-on-a-chip device and setup. The device was put on an automatic rocker table to allow perfusion of media and nutrients during cell culture. (b) Depiction of the HepG2 3D cell culture experiments with HA-PEG hydrogels. The HepG2 cells were added to media-suspended p(N3)8 prior addition of HA-BCN. (c) Depiction of the hiPS-HEP 3D cell culture experiments with HA-PEG hydrogels. The hiPS-HEP cells were added to media-suspended p(N3)8 prior addition of HA-BCN. In experiments using either linRGD or cRGD peptide, the HA-BCN was preincubated with 1 μM of corresponding peptide for 1 h prior adding the HA-BCN(RGD) component to the hiPS-HEP/p(N3)8 mixture. Credit: Biofabrication, doi: https://doi.org/10.1088/1758-5090/aaf657 Based on the results, the scientists attributed the higher albumin quantity on the 2D HEP coat to the rate of albumin diffusion within hydrogels; transfer across 2D coat being faster than 3D. The higher concentration of albumin with cRGD motif bound hydrogels, correlated with the increased cell growth and viability observed on the cRGD bound biomaterial surfaces. As a result, the scientists intend to use cyclic forms of RGD peptide to assist hepatocyte stem cell culture on hydrogels prepared for liver-on-a-chip devices in the future. In this way, the study detailed the advantages of using hyaluronan-PEG based hydrogel modified with RGD peptides for 3D cultures of hepatocytes (approximating 13 days) in a liver-on-a-chip setup. As benchmarks of the study, Christofferfsson and co-workers used the commonly available alginate and agarose hydrogels. In the future, the scientists will optimize the viscoelastic properties and the concentration of cell adhesion motifs on the HA-PEG hydrogel system for biomimetic cytocompatibility. The optimized hydrogel system can be combined with the device setup to facilitate physiologically relevant liver-on-a-chip platforms for clinical research in drug toxicology, drug discovery and regenerative medicine. Citation: 3-D culturing hepatocytes on a liver-on-a-chip device (2019, January 17) retrieved 18 August 2019 from https://phys.org/news/2019-01-d-culturing-hepatocytes-liver-on-a-chip-device.html , Proceedings of the National Academy of Sciences (a) Viability and morphology of hiPS-HEP cells after 13 days of culture. Cell viability seems to be dependent on the cell’s ability to attach to the surface, the hydrogel, or to each other. Large structures of hiPS-HEPs were formed in HA-PEG(cRGD). (calcein, green), dead cells (ethidium homodimer-1, red), and nuclei (Hoechst 33 342, blue). (b) Z-stack of images obtained by confocal microscopy reveals the flat shape of hiPS-HEPS when cultured on a 2D substrate (left) compared to the 3D constructs of the cells in a HA-PEG(cRGD) hydrogel (right). The colours represent the height above the 3D cell culture device chamber bottom, i.e. the Z-axis, from 0 μm (red) to 40 μm (blue). (c) Albumin produced by hiPS-HEP on HEP Coat in 2D and in the different hydrogels. * indicates that the albumin concentration levels were too low for reliable quantification. Credit: Biofabrication, doi: https://doi.org/10.1088/1758-5090/aaf657 To meet these criteria, the scientists used a commercial 3D cell culture device (μ-Slide III 3D Perfusion IbiTreat) containing two consecutive chambers (2 x 30 µL) in three parallel arrays – each connected to media reservoirs to perfuse liquid. For effective perfusion, they mounted the device on an automatic rocking table by reversing the perfusate direction across the hydrogel-containing chambers. The experimental setup allowed perfusion through the device, fulfilling the first criteria. To fulfill the second criteria, the localized walls adjacent to the hydrogel chambers allowed the scientists to sample the perfusate without interfering the hydrogel or cell constituents. The scientists first investigated biofunctionalization of liver-on-a-chip devices in the study with HEPG2 cells (liver carcinoma cell line) encapsulated in hydrogels, after 3, 7 and 9 days of cell culture. They compared the cell morphology, viability and functionality with agarose and alginate hydrogels. The study included live/dead assays to confirm cell viability and further confirmed HepG2 functionality by detecting albumin and urea secretions in the supernatant of the cell culture. For improved cell functionality (surface attachment and mobility on materials), the scientists grafted cell adhesion motifs such as linear or cyclic RGD peptides (linear linRGD or cyclic cRGD) on to the hydrogels. In this instance, hiPS-HEP cells (hepatocyte stem cells) were cultured across different hydrogel compositions for 13 days to examine the morphology and viability (live/dead staining) after cell-material interactions. The scientists used six different hydrogel-based biomaterial surfaces in the experiments including; 2D (HEP coat), Agarose, Alginate, HA-PEG, HA-PEG (linRGD) and HA-PEG (cRGD). The hiPS-HEP cells encapsulated and cultured in the modified hydrogel grew within 2D and true 3D constructs. To test the functionality of the cultured hiPS-HEP cells (stem cells), the scientists quantified their albumin and urea excretion. The results showed that only the supernatants of stem cells cultured in 2D surfaces and in the presence of the cRGD motif hydrogels secreted albumin. Miniaturized bioreactors known as ‘organ-on-chips’, have recently emerged as alternative cell culture models that better mimic the in vivo biological microenvironment in the lab. The liver is a model of special interest in medical research due to drug hepatotoxicity observed at all phases of clinical drug development. Previous publications detail the use of organ-on-chips to predict the outcome of a drug’s impact in clinical trials and evaluate drug interactions with hepatocytes in the lab. © 2019 Science X Network In a recent study now published on Biofabrication, Jonas Christoffersson and colleagues demonstrated how hydrogels that mimic the extracellular matrix can support the functionality and viability of hepatocytes in a perfused liver-on-a-chip device. The interdisciplinary researchers in the division of biotechnology and molecular physics engineered a hydrogel system based on hyaluronan and poly(ethylene glycol) (HA-PEG) polymers. They developed the hydrogels using click chemistry. To enable the process, the scientists conducted a biorthogonal reaction (chemistry that occurs within living systems without the interference of native biochemical reactions) between a cyclooctyne moiety and alkyne azide-labelled reaction partner, known as strain-promoted alkyne azide cycloaddition (SPAAC).The new hydrogel materials were engineered and characterized in comparison with existing agarose and alginate hydrogels for cell compatibility (cytocompatibility). For biofunctionalization studies, the researchers used human induced-pluripotent stem cell derived hepatocytes (hiPS-HEPs). To improve surface cytocompatibility of the biomaterial, HA-PEG hydrogels were altered with azide-modified cell adhesion motifs to facilitate effective cell-material attachments. In the surface functionalized biomaterial, the hepatocyte stem cells migrated and grew in 3D orientations, with increased viability. The scientists observed higher albumin production on the novel material (characteristic liver protein), compared to cells cultured on other hydrogels. The flexible, SPAAC crosslinked hydrogel system with perfused 3D cell culture of hiPS-HEPs is a promising material to optimize liver-on-a-chip devices. 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.last_img read more

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Hydrogel based water purification system 12 times better than current systems

first_img Play Fabrication process of the h-LAH. Credit: Xingyi Zhou and Fei Zhao, UT Austin 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 world needs an inexpensive way to extract drinkable water from dirty water. Every day, millions of people are forced to drink water that is unfit for human consumption. In many cases, the places that need the water the most are not included in large purification efforts, thus, personal systems are needed. The most common way to purify water in small amounts is to make and use a solar-based water distillation system in which a bottle painted black on the bottom is exposed to the sun. As the water evaporates, it collects on the upper exposed surfaces of the bottle and trickles down into a container. While this method works quite well as a means of extracting clean water, it is very inefficient as evaporation starts only when the bottle and its entire contents are heated. In this new effort, the researchers developed a vastly more efficient systems.The new work by the team was based on work they did last year. In that effort, they created a sponge-like material made from two hydrogels—one was water-binding, the other light absorbing. When the sponge was placed atop the dirty water in a solar still, it forced the water inside to evaporate faster than normally. This was due to the layer of water that was touching the sponge forging weaker hydrogen bonds. That effort pushed the efficiency of the solar still to 3.2 L/h/m2 of water—which, the researchers claim, was more than twice the theoretical limit. In this new effort, the researchers improved that efficiency even more by adding chitosan (another polymer) to the mix. Doing so allowed the sponge to hold more water, leading to faster evaporation. This pushed the efficiency of the solar still to 3.6 L/h/m2, which, the researchers claim, is 12 times better than commercial units. 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 A team of researchers from the University of Texas at Austin, collaborating with a group from the Lockheed Martin Corporation, has developed a new hydrogel-based water purification system—it is approximately 12 times better than existing commercial systems. In their paper published in the journal Science Advances, the group describes their system and how well it tested. 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 Citation: Hydrogel based water purification system 12 times better than current systems (2019, July 1) retrieved 18 August 2019 from https://phys.org/news/2019-07-hydrogel-based-purification-current.html Solar-powered moisture harvester collects and cleans water from air Journal information: Science Advances © 2019 Science X Network Play Outdoor demo of the h-LAH based solar water purification. Credit: Xingyi Zhou and Fei Zhao, UT Austin More information: Xingyi Zhou et al. Architecting highly hydratable polymer networks to tune the water state for solar water purification, Science Advances (2019). DOI: 10.1126/sciadv.aaw5484last_img read more

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Usually unusual India

first_imgTina Chandroji’s oil on canvas paintings are like an arranged symphony. Garlands made of marigold, rose and jasmine, baskets full of petals and bouquets holding delicate stems, are all neatly arranged inside a flower shop. Chandroji’s painting looks so real that you can almost smell the scent of flowers. And that’s not all, her portrayal of Indian-ness in this most unusual way surfaces in the form of a bakery, music shop, vegetables and fruits shop, groceries’ shop, carpet shop, wine shop and even an office space. What connects all these paintings – apart from their stunningly real and meticulous depiction – is the presence of God in each work. Also Read – ‘Playing Jojo was emotionally exhausting’Mumbai-based Tina Chandroji, 34, believes that God is omnipresent and a part of every aspect of our lives and this is the thought behind her new body of works which will be exhibited in a show titled Cityscapes. Presented by Mumbai’s Art Space gallery, the show includes nineteen paintings in oil on canvas.Born in a Gujarati joint family of jewellers, Chandroji recalls that it was a childhood passion to paint that took her to JJ School of Art in 2001. ‘My mother is the religious one and I inherited the same from her,’ says Chandroji, ‘I have always been inspired by our cultural upbringing. Whether one lives in metros, villages or anywhere in the universe, one is in constant touch with God. My paintings connect us to the greatest gods of Indian culture. From roadside hawkers to offices of multinational companies, we are all connected to God.’ Also Read – Leslie doing new comedy special with NetflixHer ornately detailed works create an impact that only realism can. The work titled Antiques, for instance, is a delight to behold. Chandeliers and clocks, furniture and gramophone, artefacts and cabinets are so neatly arranged that every single element comes together to resemble a real shop. Or consider the work titled Vegetable Stall. Multi-coloured vegetables bunched together in artistic heaps, a transistor radio, photographs, hanging lamps, blue plastic bags hung on the wall – there is a photographic quality to each of her works. ‘As an Indian, you would have always seen shops like these,’ says Chandroji. ‘These are sights that I have grown up seeing in Mumbai, and these are present all over India. Religion and business is extremely intertwined. If you observe, you will see that every shop in India has a picture of God, another tradition, which is so unique to our culture,’ she says. ‘It’s common knowledge that bakeries are usually run by Christians or Parsis, grocery shops by West Indians, vegetable and fruits by North Indian and perfumes by Muslims and each of these places have a special place for their Gods.’.It is also like creating a film set. And that is what she did after completing her Bachelors in Fine Arts from JJ School of Art, Mumbai. She was the Assistant Art Director for the first season of Kaun Banega Crorepati and went on to become the Art Director for Salman Khan starrer Lucky- No Time For Love. With marriage in 2002 to art director and story board writer for Hindi and regional films, Chandroji was first initiated into the world of photography before she became a full-time artist. Her first solo show was at Lalit Kala Akademi, New Delhi in 2012.‘It takes me four to five months to complete a painting, though I work on three paintings at a time,’ she chuckles, as she recalls how viewers get so drawn to her work they want to touch and feel it!WHERE: Visual Arts Gallery, India Habitat CentreWHEN: 12 to 19 September, 10 am to 8 pmlast_img read more

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A wars homecoming

first_imgThrough mundane objects like matchboxes and utensils, rare monochromatic photographs of Indian soldiers cooking and a few silent movies depicting their life during the First World War an upcoming exhibition here will pay tribute to their unsung contribution during the Great War.The exhibition India and the First World War jointly organised by Roli Books, the French Embassy here and the Indira Gandhi National Centre for the Arts (IGNCA)will run from January 12 to February 10 to commemorate the 100th anniversary of the beginning of the War. Also Read – ‘Playing Jojo was emotionally exhausting’It wouldn’t be wrong to suggest that the exhibition is the brainchild of Roli Books publisher and CEO Pramod Kapoor, who first thought of thought of publishing a volume on the contribution of the Indian soldiers during the War when, at the Frankfurt Book Fair, several European exhibitors threw light on this lesser-known subject.After coming back he got in touch with Vedica Kant and Amarinder Singh, who researched and penned India and the First World War (prefaced with “If I die Here, who will remember me?” and Honour and Fidelity: India’s Military Contribution to the Great War 1914-1918. “That interaction with the exhibitors at the fair led to these two books because I realised these stories need to be told,” Kapoor told IANS. Also Read – Leslie doing new comedy special with NetflixBut what exactly shaped up this exhibition was a trip to Ypres and Lille in France, where he learned that Indian war heroes such as Khudadad Khan are household names and each family has a story to share about the warmth and bravery of the Indian troops stationed in this region. “It was so fascinating to see how many collectors had items used by the Indian soldiers while on the Western front. It was during the trip I realised the potential and gravity of this project,” said Kapoor. “I walked along the fields of Flanders where you can still pick out pieces of spent bullets embedded in the soil and was moved by the sight of the tricolour and Ashoka’s lion capital at Menin Gate,” he added. Kapoor then got in touch with the French Embassy, which made arrangements to bring the films and memorabilia to India for this exhibition. Apart from this, rare photographs of Indian soldiers will also be displayed.However, Kapoor hopes this exhibition reaches out to many people as books are read by aa few, but visual imaginary has the ability to reach out to many people. When: January 12 to February 10Where: IGNCAlast_img read more

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Council to announce HS results today

first_imgKolkata: The results of the Higher Secondary examination will be announced by the West Bengal Council of Higher Secondary Education (WBCHSE) on Friday. The results will be announced in a press conference which will be held at the office of the Council in Salt Lake at 10 am.Students can access their results from the officialwebsite of WBCHSE — wbresults.nic.in — from 11 am. The other websites through which the results can be accessed are www.indiaresults.com, www.exametc.com, www.schools9.com, www.jagranjosh.com etc. Students can also know their results by SMS option: WB12< Space> Roll number and send it to 58888.The marksheets would be distributed to the schools at 10.30 am. This year a total of 8,26,029 students appeared for the HS examination which was conducted from March 27 to April 11. The results are being published 58 days after the commencement of the examination. The HS Council has decided to introduce percentiles in the Class XII exam results this year to match boards like the CBSE.last_img read more

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