Month: August 2019

Two new studies suggest ways of improving traffic flow

first_img Traffic control systems © 2010 PhysOrg.com Citation: Two new studies suggest ways of improving traffic flow (2010, September 21) retrieved 18 August 2019 from https://phys.org/news/2010-09-ways-traffic.html (PhysOrg.com) — Two studies have just been published that may help improve traffic flows. The first, presented as a Santa Fe Institute working paper for September, concluded that if traffic lights responded to measured traffic flow instead of being timed. The second, published in a special edition of Philosophical Transactions of the Royal Society, looked at how driver behavior affects traffic flow. Traffic congestion is a growing problem globally, and minimizing it would save money and cut emissions, as well as reducing stress and frustration in drivers. Traffic lights are usually controlled by an “optimal” timed cycle maximized to suit an expected flow of traffic for the time of day, but the problem is the large variability of traffic volume and the direction vehicles travel on leaving an intersection even on a “typical” day. This can lead to gridlocks or traffic congestion if too many vehicles are made to wait too long, and to frustration if drivers are made to wait at red lights when no vehicles are present on the intersecting road to take advantage of the green.Co-author of the first study, Dirk Helbing of the Swiss Federal Institute of Technology in Zurich, said the current method of top-down control is not optimal because the average situation for which it is designed rarely occurs. With colleague Stefan Lämmer of the Dresden University of Technology, Helbing studied crowd movements through a narrow space and discovered a natural “traffic light” develops with many people from one side moving through the space and then the flow reversing suddenly and those waiting at the other side moving through.Helbing said the natural movement oscillation is the result of build-up of pressure on the side where people are waiting, and they wondered if the same principle could be used to control traffic, so the traffic flow controls the light rather than the opposite.They ran a simulation in Dresden city center, fitting two sensors to each traffic light to detect incoming and outgoing traffic flows. Each traffic light communicated only with its nearest neighbors, so that “platoons” of vehicles could be detected in enough time to give the next set of lights time to prepare and avoid stopping the large number of vehicles. The area covered in their experiment included 13 sets of traffic lights, 68 pedestrian crossings, seven bus and tram lines crossing the network every 10 minutes, and a train station handling over 13,000 passengers a day.The results of the experiment showed traffic flow was improved for all vehicles and pedestrians, with trams and buses spending 56 percent less time waiting in traffic, other vehicles spending nine percent less time stuck, and a 36 percent reduction for pedestrians.Adopting traffic light systems that improve the flow addresses only one part of the problem because vehicles are driven by humans and their behavior can have a significant effect on traffic flows. The second study found that drivers who are too aggressive are a major cause of traffic jams, because of their habits of driving too fast, tailgating, and frequently slamming on the brakes. Timid drivers also cause traffic to slow because they leave too big a space in front of them and “send a wave of deceleration” behind them.The paper’s author, Dr Jorge Laval, of the Georgia Institute of Technology in Atlanta, said “stop and go” driving behavior is a frustration for drivers, which affects safety, and it increases fuel consumption and emissions. With colleague Ludovic Leclercq of the University of Lyon in France, Laval studied traffic on stretches of freeway in Los Angeles and near San Francisco, and then created a mathematical model to match their observations.Their results showed that changes of speed passed like a wave backwards through traffic, and the slowdown was worsened by aggressive drivers, who kept too small a gap between vehicles, causing them to frequently brake hard at the last moment and then drive more slowly to open up a gap. Traffic speed also slowed with timid drivers, because they deliberately drove even more slowly to increase the gap between their vehicle and the one in front.The responsive traffic light system will soon be implemented in Dresden, and Zurich is also considering adopting the system. Laval and Leclercq suggest the driver behavior problems could be addressed by an increasing use of adaptive cruise control (ACC) that can keep the gap between cars at a set distance.center_img 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. More information: A special edition of Philosophical Transactions of the Royal Society: ‘Traffic jams: dynamics and control’: rsta.royalsocietypublishing.or … content/368/1928.toclast_img read more

Team uses fractal geometry to build lighter structures

first_img Physics duo create tractor beam using dual Bessel beams Citation: Team uses fractal geometry to build lighter structures (2012, December 3) retrieved 18 August 2019 from https://phys.org/news/2012-12-team-fractal-geometry-lighter.html Journal information: Physical Review Letters © 2012 Phys.org (Phys.org)—A team made up of members from several European countries has published a paper in Physical Review Letters describing a technique they’ve developed for using fractal geometry to build structures that maintain their strength despite weighing significantly less. Fractal frame. This construction shows the similarity of different scales (“self-similarity”) in a generation-2 hierarchical structure. Due to manufacturing limitations, the scaffolding here is made of solid rather than hollow beams (inset). Credit: D. Rayneau-Kirkhope et al., Phys. Rev. Lett. (2012)center_img The researchers began their study by noting that many structures in the world already demonstrate some degree of fractal geometry. The Eifel Tower for example, they note was essentially built using a single type of metal rod that is replicated in different sizes throughout the tower to minimize weight. What’s not been the case however, they add is a predefined way to implement fractal geometry into structures in general. To rectify that, they have come up with a process that allows for creating metal beams that take advantage of fractal properties.The first step is to create a hollow metal beam of the size desired for a given project. Next, reengineer the beam by changing its diameter and thickness such that the beam weighs as little as possible but is still able to withstand the weight or pressure it will be subjected to as a final structure. Once that is achieved, label it generation-0. The next step is to create a larger beam made out of generation-0 beams arranged using triangular subdivisions. This next beam is labeled a generation-1 beam. Generation-2 beams would be constructed by replacing all of the generation-1 beams with full scale versions of itself, only in a larger construct. Theoretically, the process can be repeated as many times as is desired or is possible, depending on scale.The resulting structures weigh less than those made with solid steal because they contain less of it – the more generations used, the lighter the structure becomes proportionally to one made of solid steel. As an example the researchers suggest that a solar sail made with a solid metal 100 meter boom (not that anyone is proposing that) could be made to be 10,000 times lighter if a generation-3 beam were used instead.The overall idea the team reiterates, is that it appears possible to use a standard methodology that includes fractal elements in building new structures, rather than borrowing fractal ideas and adding them in an ad hoc fashion, to achieve lighter weight constructs. Explore further More information: Ultralight Fractal Structures from Hollow Tubes, Phys. Rev. Lett. 109, 204301 (2012) DOI: 10.1103/PhysRevLett.109.204301AbstractA fractal design is shown to be highly efficient both as a load bearing structure and as a general metamaterial. Through changing the hierarchical order of the structure, the scaling of material required for stability against loading can be manipulated. We show that the transition from solid to hollow beams changes the scaling in a manner analogous to increasing the hierarchical order by one. An example second order solid beam frame is constructed using rapid prototyping techniques. The optimal hierarchical order of the structure is found for different values of loading. Possible fabrication methods and applications are then discussed.Physics Focus 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

What makes Champagne bubbly

first_imgMolecular dynamics simulations and NMR spectroscopy measurements show that ethanol is the main molecule, apart from water, that is responsible for the value of the CO2 diffusion coefficients (and subsequent tasting sensations) in typical Champagne wines. Credit: Bonhommeau, et al. ©2014 American Chemical Society 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. Journal information: Journal of Physical Chemistry Letters To better understand this bubble formation process, the researchers in the current study investigated the interplay between CO2 and ethanol molecules in Champagne wines and, unlike in some previous research, took account of the influence of temperature on the CO2 dynamics. Their molecular dynamics simulations showed that CO2 diffuses more rapidly at higher temperatures, in agreement with their NMR spectroscopy measurements. Their results also show that CO2 diffusion coefficients are about twice as large as ethanol diffusion coefficients. This is because, compared to CO2 molecules, ethanol molecules form at least five times more hydrogen bonds with the surrounding water molecules, making ethanol molecules less mobile. From this perspective, ethanol molecules and water molecules react to form a bonding network, while CO2 molecules can be considered a spectator species, having more freedom to float to the top.Because the value of CO2 diffusion coefficients depends mainly on ethanol, the results suggest that there should be no major correlation between the taste of sparkling wines, which is mainly due to acids, sugars, and proteins, and the formation and growth dynamics of bubbles.”For industrial companies, [our results show] that modifying the composition of Champagne wines—in which ethanol concentration is fixed to 12.5% v/v in champagnes—will probably have little effect on the formation and growth dynamics of bubbles that is believed to have an influence on tasting sensations,” Bonhommeau said.In addition, the researchers showed that the molecular dynamics simulations validate results from previous research. Specifically, the simulations show that an empirical method of determining the CO2 radius is sufficiently accurate to be used to approximate or evaluate diffusion coefficients or viscosities in liquids. This approach could be used to study a variety of transport phenomena in supersaturated solutions or water/alcohol mixtures, which are often used as solvents in chemistry research.”The Stokes-Einstein relationship connecting the diffusion coefficient of a species and the viscosity of the liquid depends on the species hydrodynamic radius (the species being assumed spherical),” Bonhommeau said. “It is hard to exactly know the value of this effective radius. We proved in the paper that using the rms (root mean squared) distance of the species atoms with respect to its center of mass leads to a reliable first guess for this radius, at least for relatively small molecules. This means that researchers running molecular dynamics simulations could straightforwardly evaluate diffusion coefficients (resp. viscosity) from the knowledge of viscosity (resp. diffusion coefficients) by only applying the Stokes-Einstein formula, although this formula is only rigorously valid for more macroscopic systems.”Finally, the same approach used to model Champagne used here could be applied to many other applications.”Although Champagne is a multicomponent liquid by nature (that is, composed of a number of different molecules), CO2 diffusion can be simply modeled by applying methods commonly used for binary mixtures,” Bonhommeau said. “Such an approach could be extended to the investigation of the diffusion of small molecules in other supersaturated liquids such as brines (i.e., water in oceans) or maybe in amorphous solids (molecules trapped in ice for atmospheric or astrochemical applications). It is sometimes believed that convergence may be hard to reach with such simple models, but we proved, by comparing our results to NMR measurements, that excellent agreement can be achieved by using standard molecular dynamics simulations provided that suitable water models and appropriate techniques for evaluating diffusion coefficients are employed.” The science of champagne fizz: How many bubbles are in your bubbly? More information: David A. Bonhommeau, et al. “Unveiling the Interplay Between Diffusing CO2 and Ethanol Molecules in Champagne Wines by Classical Molecular Dynamics and 13C NMR Spectroscopy.” The Journal of Physical Chemistry Letters. DOI: 10.1021/jz502025e © 2014 Phys.org The researchers, David A. Bonhommeau, et al., from the University of Reims Champagne-Ardenne, have published their findings in a recent issue of The Journal of Physical Chemistry Letters. The work was supported by the Bull company, experts in HPC (High-Performance Computing); and ANRT (the Association Nationale de la Recherche et de la Technologie).”The greatest theoretical significance of this work is to demonstrate, by extensive comparison with nuclear magnetic resonance (NMR) and viscometry measurements, that the diffusion and viscosity in supersaturated multicomponent liquids such as Champagnes can be investigated at various temperatures by standard molecular dynamics simulations,” Bonhommeau told Phys.org. “Moreover, the temperature dependence of the CO2 diffusion coefficient is useful information to better apprehend the kinetics of CO2 release under standard tasting conditions, i.e., to better apprehend how long a Champagne or a sparkling wine keeps its so much sought-after effervescence.”As the scientists explain, previous research has shown that two phenomena are responsible for the emission of CO2 bubbles in sparkling beverages such as Champagne wines. The first phenomenon arises because these beverages are supersaturated with CO2, and CO2 emission occurs at the interface between a supersaturated aqueous solution and a gas phase (the air above the glass). The second phenomenon responsible for CO2 bubble emission is effervescence, which refers to the formation of bubbles from tiny gas pockets trapped within immersed particles, such as cellulose fibers, crystals, or even within scratches or etchings on the glass surface. When the radius of the gas pocket trapped within the particle or scratch exceeds a critical size (about 0.2 µm at the opening of a Champagne bottle), dissolved CO2 can diffuse into the gas pocket and make the bubble grow. As the CO2 diffuses, many CO2 bubbles are released in the Champagne in the form of bubble trains. Explore further Citation: What makes Champagne bubbly? (2014, December 9) retrieved 18 August 2019 from https://phys.org/news/2014-12-champagne.html (Phys.org)—Just in time for the holidays, scientists have unraveled some of the chemistry behind the diffusion of CO2 molecules in a glass of Champagne. Among their findings, they discovered that ethanol is the main molecule (along with water) responsible for the value of CO2 diffusion coefficients in Champagne, and is therefore an essential molecule to better understand the CO2 bubble formation and growth in these beverages. Besides shedding light on the bubble dynamics and subsequent tasting sensations of Champagne, the results could also have applications for evaluating the diffusion of CO2 molecules in water/alcohol mixtures that are commonly used in physical chemistry.last_img read more

Bacteria used to create superfluids

first_img(Phys.org)—A team of researchers with Université Paris-Sud and Université P.M. Curie/Université Paris-Diderot, both in France, has discovered that putting certain types of bacteria into an ordinary fluid, can cause it to become a superfluid. In their paper published in the journal Physical Review Letters, the team describes how they modified an old rheometer to conduct the tests, their readings and their ideas on why the bacteria caused a change in viscosity. © 2015 Phys.org Citation: Bacteria used to create superfluids (2015, July 13) retrieved 18 August 2019 from https://phys.org/news/2015-07-bacteria-superfluids.html Explore further New model of cosmic stickiness favors ‘Big Rip’ demise of universe Journal information: Physical Review Letters Escherichia coli. Credit: Rocky Mountain Laboratories, NIAID, NIH , arXiv A fluid’s viscosity is its state of thickness as can be demonstrated when it is poured out—water will run out much faster than oil, for example. Viscosity comes about due to friction among the ingredients that make up the fluid. Scientists have suspected for a number of years that bacteria in a fluid can cause a change in its viscosity, but until now, it has not been proven. To do so, the researchers pulled out a rheometer (a device used to measure viscosity) that was built several decades ago—they modified it to allow for connecting to a computer. They then added various amounts of E. Coli to a water/nutrient solution and then tested its viscosity at different rotation speeds. Their modified instrument showed that the bacteria did indeed cause a change in viscosity, it lowered it. Adding more bacteria led to a viscosity reading of zero, and then to negative viscosity. They also proved that their results were due to some action on the part of the bacteria rather than their mere presence causing the change—when the E. Coli were killed, the viscosity readings did not go down. Fluids with no viscosity are called superfluids because they flow with no friction whatsoever.The team explains that they had to modify the old rheometer because modern devices are only capable of measuring high viscosity, which means using a high spin rate. They also suggest that it is likely the bacteria caused changes to viscosity by the movement of their tails against the current. They note that it might be possible to somehow harness the viscosity lowering ability of bacteria by inserting tiny rotors into a fluid that would be dragged around, perhaps powering a small device. More information: Turning Bacteria Suspensions into Superfluids, Phys. Rev. Lett. 115, 028301 – Published 7 July 2015. dx.doi.org/10.1103/PhysRevLett.115.028301 . On Arxiv: arxiv.org/abs/1503.05511ABSTRACTThe rheological response under simple shear of an active suspension of Escherichia coli is determined in a large range of shear rates and concentrations. The effective viscosity and the time scales characterizing the bacterial organization under shear are obtained. In the dilute regime, we bring evidence for a low-shear Newtonian plateau characterized by a shear viscosity decreasing with concentration. In the semidilute regime, for particularly active bacteria, the suspension displays a “superfluidlike” transition where the viscous resistance to shear vanishes, thus showing that, macroscopically, the activity of pusher swimmers organized by shear is able to fully overcome the dissipative effects due to viscous loss. 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

Engineering ECMlike fibers with bioactive silk for 3D cell culture

first_imgSpreading and expansion of cells within FN-silk compared to when encapsulated in an RGD-coupled hydrogel. (a) Representative graph (mean and standard deviation) of Alamar Blue viability assay showing metabolic activity of fibroblasts (HDF) within FN-silk foam (circle), a very low viscosity (VLVG) alginate hydrogel coupled with RGD (square), and a medium viscosity (MVG) alginate hydrogel coupled with RGD (triangle) during two weeks of culture. Insert shows a zoomed in view of the lower intensities. Statistics (students t-test at each time point): **** indicates p < 0.0001 (n = 12) (b) Representative live (green) and dead (red) staining of human mesenchymal stem cells (HMSC) in FN-silk foam (upper) and RGD-coupled alginate VLVG (lower) at day 14. Scale bars = 100 µm. (c) Confocal scans of HMSCs integrated into FN-silk foam (left panel), and RGD coupled alginate hydrogel MVG (right panel) after 1 h, 4 days and 7 days. Actin filaments are visualized by phalloidin staining (green) and cell nuclei are stained with DAPI (blue). Scale bars = 20 µm. (d) Schematic description of the hypothesis for the reason behind the observed difference in interactions between cells and silk (left) versus RGD-coupled alginate hydrogels (right). Several integrin pairs (green) can adhere and gather to the silk microfibers, forming focal adhesions at the edge of actin filaments, enabling the cells to spread and proliferate. In the alginate hydrogel, a single integrin pair (green) can bind to the coupled RGD-motif, but the thin alginate chains restrict subsequent gathering into focal adhesions. Inserts show examples of a cell (fibroblast) after 3 h in FN-silk foam (left) and a low viscosity (VLVG) alginate hydrogel coupled with RGD (right). Actin filaments are visualized by phalloidin staining (green), and focal adhesions can be seen where this is co-localized with staining for vinculin (red, marked with arrow). Cell nuclei are stained with DAPI (blue). Credit: Scientific Reports, doi: 10.1038/s41598-019-42541-y Based on the encouraging preliminary results, the scientists conducted parallel experiments to compare cell growth in silk vs. cell growth in hydrogel to determine cytocompatibility of the two materials. They chose alginate to represent the hydrogel during cell culture and observed dissimilarities between alginate vs silk, recording clear cell expansion in silk, while cells in alginate remained in a steady metabolic state. Using confocal microscopy, they investigated reasons for the observed difference in cell growth at the level of the microenvironment. The results showed prompt cell attachment (seen with elongated cells) in the silk constructs, while the alginate constructs contracted during cell culture, which may have stressed the cells to detach. Biomechanical studies – characterizing the new materialsThey determined material surface stiffness to be a crucial component that affected cell fate. To verify this observation, Johansson et al. tested biomechanical behavior of the silk constructs to ensure they adequately mimicked native tissue. They conducted tensile testing in a physiological buffer to obtain the results, which proved that the mechanical properties of silk containing cells matched those of connective tissue such as arterial walls. Johansson et al. were able to demonstrate high extendibility of the microfibers to indicate force transition into and throughout the cells attached to the new biomaterial – confirming adequate cell attachment. Biofunctionalization studies – investigating surface biocompatibility in vitro Previously, Johansson and Widhe et al. had developed a scalable process to engineer the recombinant spider silk protein known as 4RepCT for bioinspired cell culture in the lab, which self-assembled into biodegradable and biocompatible microfibers in aqueous, physiological buffers at room temperature. They functionalized the novel construct using a cell adhesion motif from fibronectin (FN) to form the FN-silk material and promote firm cell attachment. Although cells proliferated along the new material surfaces, they remained on the surface alone, unable to proliferate in to the constructs to adequately mimic tissue-like properties in vitro. In the present work, the scientists therefore developed a new method, to efficiently embed cells in to the silk material during the assembly of FN-silk for encapsulated and viable 3-D cell culture that adequately mimicked the extracellular matrix in vitro. After establishing biomechanical stability, the scientists tested if the stem cells that grew on the silk scaffolds could differentiate (mature) on the same material. For this, they used pluripotent and multipotent human embryonic stem cells in the cell culture assays, followed by quantifying gene expression of biological markers of cell growth; FOXA2 (metabolic genes), SOX17 (genes for embryonic development and cell fate determination), CER1 (bone morphogenetic protein antagonists) and NANOG (embryonic stem cell proliferation, pluripotency and renewal). In the results, both SOX17 and CER1 showed robust upregulation, while the biomarker of pluripotency (NANOG) decreased due to cell maturity as a result of the loss of pluripotency. The scientists tested surface biofunctionalization for diverse cell types, including human skeletal muscle satellite cells (HSkMSC) and bone marrow-derived human mesenchymal stem cells (hMSC). After cell expansion on the constructs, the scientists could steer the fate of the hMSCs into either adipogenic or osteogenic cell lineages. Additionally, after two weeks of cell culture, Johansson et al. showed myogenic differentiation of the HSkMSCs to form prominent actin filaments, and express the muscle-specific marker desmin, to verify in vitro myotube maturation. Engineering biological vessels in the labThe scientists then combined endothelial cells in the 3-D vascular network to form connective tissue that mimicked inherent cellular organization of micro-vessels in the lab. They followed the same protocol using silk assembly with cell integration and added a fraction of endothelial cells to engineer the connective tissue. In two weeks, they observed the cells gather and form millimeter long branched sprouts and vessel-like structures with prominent rings of endothelial cells in the silk fibers. The scientists could increase the size of the constructs to-scale and determine the alignment and aggregation of diverse cell types. In this way, Johansson and Widhe et al. demonstrated a new strategy and developed a protocol to fit in functional cells within 3-D networks that mimicked the fibrous architecture of the native extracellular matrix (ECM). To mediate the experiment, they used self-assembling recombinant silk proteins and showed that a variety of cells could be embedded in the 3-D constructs. The setup and protocol are simple and cost-effective, unlike 3-D printing the process is frugal and hands-on, without expensive machinery. The scientists aim to optimize and standardize this protocol to develop biocompatible, advanced silk materials in tissue engineering. The experimental work will have a wide range of applications in materials science as miniature in vitro models for drug development and as larger bioengineered tissue constructs in regenerative medicine. Citation: Engineering ECM-like fibers with bioactive silk for 3-D cell culture (2019, April 29) retrieved 18 August 2019 from https://phys.org/news/2019-04-ecm-like-fibers-bioactive-silk-d.html , Nature Materials Silk-assembly to integrate cells into a 3D network of microfibers. (a) Schematic description of the formation of silk foam with ingrained cells. Cells suspended in culture medium (pink) are added to a defined drop of FN-silk protein solution (blue) placed in the middle of a non-treated culture well (I). Air bubbles are quickly introduced (5–10 sec) through a pipette tip (II), to give rise to a 3D foam with cells. After 30 minutes in the cell incubator, additional culture medium is added to cover the foam completely (III). Day 1 after formulation, the silk foam with cells looks almost transparent, although harboring some remaining air bubbles (that disappear with time) (IV). After 2 weeks of culture, the foam with integrated cells shows a denser and whiter appearance (V). Already at day 3 the foam is filled with well-spread cells (here mouse mesenchymal stem cells (MMSC) are shown) (VI). Actin filaments are visualized by phalloidin (green) and cell nuclei by DAPI staining (blue). Scale bar IV-V = 1 mm, VI = 100 µm. (b) Schematic description of silk fibers formed with integrated cells. Cells suspended in medium (pink) are added to the FN-silk protein solution (blue) (I). During gentle repeated uniaxial tilting for 1–3 hours (II) the silk proteins assemble at the air-liquid interface into a macroscopic bundle of microfibers with incorporated cells (III). The silk fibers with cells are easily retrieved (IV) and can be placed in a well for further culture, whereby the thickness increases over 2 weeks (V). At day 3, aligned cells (here MMSC) are found spread integrated in the fiber bundle (VI). Actin filaments are visualized by phalloidin (green) and cell nuclei by DAPI staining (blue). Scale bar IV-V = 1 mm, VI = 100 µm. (c) Differential Interference Contrast (DIC) micrographs of the silk microfibers (white) in a fiber (left) and a foam (right) with integrated cells (MMSC). Actin filaments are visualized by phalloidin (green) and cell nuclei by DAPI staining (blue). Scale bar = 50 µm (left) and 100 µm (right). Credit: Scientific Reports, doi: 10.1038/s41598-019-42541-y Proliferation and viability of cells integrated in 3D silk. Representative graphs of Alamar blue viability assay show increasing metabolic activity during the first 2 weeks within (a) foam (N = 3–4, n = 3–7), and (b) fibers (N = 1–9, n = 2–13), reflecting growth of the various integrated cell types (HaCaT; human keratinocyte cell line, HDF; human dermal fibroblasts, MDMEC; mouse dermal microvascular endothelial cells, MIN6m9;insulin-secreting mouse pancreatic β-cell line). (c) Cell division occurs deep within the 3D silk. Cryosection of a fiber with integrated fibroblasts (HDF) fixed at day 11 and stained with FITC-anti BrdU for newly synthesized DNA (green) and DAPI (blue). The silk shows a dim autofluorescence in the blue/green range. (d) Representative live (green) and dead (red) staining of mouse mesenchymal stem cells (MMSC) in foam (left) and HDF in fiber (right) at day 14. The fiber shows a dim autofluorescence in the red range. Scale bars = 100 µm. (e) Viability (%, mean and standard deviation) after 14 days culture of different cell types (see Suppl. Table 1) in foam (left graph), and in fibers (right graph) (N = 1–3, n = 4). (f) Long time cultures of cells integrated into fibers maintained metabolic activity (Alamar blue) during the entire study period (up to 97 days). Credit: Scientific Reports, doi: 10.1038/s41598-019-42541-y Tissue engineering cell-embedded silk constructs in the labDuring the experiments, Johansson and Widhe et al., first added a drop of dispersed stem cells (mesenchymal mouse stem cells, MMSC) to the FN-silk protein solution prior to solution assembly. After incubation, the newly formed network remained stable in culture media and the encapsulated cell number increased in the constructs throughout the period of culture. After three days, the cells spread across all dimensions of the foam, which the scientists observed using differential interference contrast (DIC) microscopy. Advanced biomaterials with silk fibroin-bioactive glass to engineer patient-specific 3-D bone grafts In a recent study, Ulrika Johansson, Mona Widhe and co-workers at the interdisciplinary departments of Biotechnology, Biomaterials Chemistry, and Immunology in Sweden developed a method to include mammalian cells into a silk solution before assembling silk into constructs, to form uniform cell-integrated tissue-like microfibers. The resulting 3-D scaffold constructs showed improved cell proliferation (growth) and homogenous cell spreading compared to cells encapsulated in hydrogel. The results of the study are now published in Scientific Reports. The scientists confirmed cell attachment on fibronectin-silk constructs (FN-Silk) in the work by observing filamentous actin and by defining focal adhesion points of the attached, elongated cells. They maintained cell viability for 90 days in the cell-FN/silk surfaces and showed scalability of the method to macro-sized 3-D cell cultures. The silk microfiber bundles with encapsulated cells maintained biomechanical strength and extendibility much like human arterial walls. The protocol developed by Johansson and Widhe et al. also allowed stem cells to differentiate inside the 3-D constructs to assist the growth of diverse cell co-cultures. They showed that endothelial cells could be included into the bioinspired materials to form vessel-like structures throughout the tissue constructs. The scientists envision using the ECM-like network as a foundation for future efforts to engineer functional biological tissues in the lab. In vitro mammalian cell culture is an indispensable experimental technique in basic research and industrial applications, although the existing process relies on 2-D hard plastic or glass surfaces for convenience—impairing the native biological response. Since biological cells are naturally accustomed to receiving signals from the 3-D environment, tissue engineers have formed new experimental strategies using 3-D cell cultures. The experimental conditions maintained cell adhesion, proliferation and differentiation to recreate and sustain cell metabolism and functionality in the lab. They directed the cell alignment to form a random 3-D network of microfibers that successfully mimicked biological tissues by forming a macroscopic bundle of microfibers during the timeline of cell culture, followed by cell to ECM ratio examination. The scientists varied the ECM to cell composition to mimic or match a range of tissue types, including cell sparse and high-density tissues of the liver. The method is therefore also suited for 3-D cell culture with minute cell quantities. Testing cell viability on the silk scaffolds – cytocompatibility studiesThe scientists used growth profiles to map the diverse cell types embedded in both foam and fibers of the silk assembly. They observed an increased signal from the metabolic activity to represent cell proliferation in the 3-D silk scaffolds and in time they showed increased cell density in the innermost cell-silk scaffold. Johansson et al. investigated cell proliferation using BrdU staining, where positive results proved deeper proliferation and cell spreading in the silk fibers to maintain cell viability after 2 weeks of encapsulation, and during long-term cell culture periods that spanned one to three months. Comparing the cytocompatibility of silk vs. hydrogel biomaterials Differentiation of cells in 3D silk. (a) After initial expansion of stem cells integrated to 3D silk, differentiation into various tissue types can be triggered by addition of appropriate factors. (b) Differentiation of pluripotent stem cells. Left: Human embryonic stem cells (hESC) visualized by mCherry detection at 48 h after cell integration into FN-silk foam. Scale bar = 50 µm. Middle: Immunostaining for endodermal markers SOX17 (green) and FOX2A (red) after 3 days of differentiation. Scale bars = 200 µm. Right: Gene expression (SOX17, CER1, NANOG) of hESC in a FN-silk foam compared to 2D culture, analyzed by RT-qPCR at day 3 of endodermal induction. Bars represent the mean fold change ± standard deviation (n = 4). (c) Differentiation of multipotent adult stem cells. Left: Human mesenchymal stem cells (HMSC) in FN-silk foam differentiated into the adipogenic linage containing lipids, visualized by Red Oil staining (red) (N = 2, n = 4). Scale bar = 100 µm. Right: HMSCs differentiated into the osteogenic linage, probed with osteogenic marker for calcium content (Alizarin Red S (red) in FN-silk fiber (right, scale bar = 200 µm), (N = 2, n = 4). Inset shows photo of a whole fiber (right), scale bar = 1 mm). (d) Differentiation of adult precursor cells. Left: After 14 days in differentiation media, skeletal muscle satellite cells (HSkMSC) within a FN-silk fiber show prominent actin filaments, as visualized by phalloidin staining (green). Right: Myogenic differentiation of skeletal muscle satellite cells (HSkMSC) visualized by Desmin staining (green). DAPI-stained nuclei in blue. (N = 9, n = 4). Scale bars = 200 µm. A closeup of the area of a multinucleated myotube is shown in the upper right corner. Credit: Scientific Reports, doi: 10.1038/s41598-019-42541-y 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. More information: Ulrika Johansson et al. Assembly of functionalized silk together with cells to obtain proliferative 3-D cultures integrated in a network of ECM-like microfibers, Scientific Reports (2019). DOI: 10.1038/s41598-019-42541-y Brendon M. Baker et al. Cell-mediated fibre recruitment drives extracellular matrix mechanosensing in engineered fibrillar microenvironments, Nature Materials (2015). DOI: 10.1038/nmat4444 Darren Rodenhizer et al. A three-dimensional engineered tumour for spatial snapshot analysis of cell metabolism and phenotype in hypoxic gradients, Nature Materials (2015). DOI: 10.1038/nmat4482Young's moduli and shear moduli in cortical bone. Proceedings of the Royal Society Series B: Biological Sciences. doi.org/10.1098/rspb.1996.0044 Journal information: Scientific Reports Biological tissues are built when cells anchor to specific sites on a 3-D microfiber network in an extracellular matrix (ECM). Scientists are keen to recreate biological tissues in the lab using bioinspired tissue engineering and genetic engineering, to form functional ECM motifs fused to recombinant silk proteins. Under adequate physiological conditions, bioengineered silk proteins and fibronectin-silk (FN-silk) can self-assemble into microfiber networks that mimic native ECM. Provided by Science X Network Uni-axial tensile testing of silk fibers with integrated mesenchymal stem cells. (a) Illustration of the experimental set-up for tensile tests performed in PBS buffer at 37 °C in order to maintain viable cells. (b) Representative First Piola-Kirchhoff stress versus strain curve of a FN-silk fiber with integrated mesenchymal stem cells (MMSC) subjected to tensile testing after 14 days of culture. Stress-strain curve illustrates a rather linear (and probably elastic) phase that is followed by a plastic-like (irreversible) deformation phase until the maximum stress is reached, and the fiber breaks. For comparison, grey areas represent ranges of stress strain properties in tendons and ligaments (i), artery walls (ii), and brain tissue (iii). Roman numbers refer to images (c) taken during the tensile test, i.e. during start (I), extension (II) and breakage (III) of the fibers. Scale bar = 5 mm. (d) Micrographs of the breaking point of fibers with MMSCs after tensile testing. Actin filaments are visualized by phalloidin staining (green) and cell nuclei are stained with DAPI (blue). Scale bars = 200 µm. Credit: Scientific Reports, doi: 10.1038/s41598-019-42541-y Explore further © 2019 Science X Networklast_img read more

Truth of life

first_imgThe Capital is soon going to see a play which depicts how a person tries to overcome all the questions raised in one’s own mind about one’s own nature, but all in a comic manner. The play titled Death…On Stage will be showcasing how individuals surrounds themselves with an envelope of illusion to justify their actions even though they are contradictory to one’s own nature. The play is scripted designed and directed by Devesh Nigam. The journey begins on a hilarious note when announcer comes on stage, annoyed with the so called illusionary method of theatre. Subsequently, the myth of life is being created by the actors emulating a train journey. Everything goes as per the ‘script’ till ‘Death’ enters the stage! The play is a comic drama with a relative absurdness critical to the plot.The cast of the play are – Radha Bhatt, Ashish Mishra, Rohit Kapur, Deep Singh, Komal Gupta, Rishi Sharma, Atul, Sahil Verma, Sonu, Navdeep Batra, Abhishek Sehgal, Neelesh.When: 14 June Time: 7pm Where: Akshara Theatre, Baba Kharag Singh Marg Tickets: Rs 200 –  300last_img read more

As old warlords fight for survival

first_imgThe emergence of Narendra Modi as the prime minister and a national leader has changed the contours of Indian politics and it is a time of repositioning for the leaders of other parties to maintain their clout and relevance in the changed political scenario. Leaders of the Hindi heartland of Uttar Pradesh, Bihar and Haryana are among those, who find themselves to be in wilderness after the 2014 Lok Sabha elections. They were rejoicing at the reverses of BJP in by-elections, which were held in Uttarakhand, Bihar and UP just after the Lok Sabha elections. Most of the seats had fallen vacant because of the victory of BJP MLAs in Lok Sabha elections and in subsequent by-elections, BJP failed to retain most of those seats. This gave reasons to cheer to leaders like Lalu, Nitish and Mulayam. But after the assembly elections of Haryana and Maharashtra, the picture has turned gloomy again for them and they are now convinced that this Modi phenomenon is to stay for now. Also Read – Gateway of criminal justiceThis realisation has made the leaders of these three states of UP, Bihar and Haryana to talk about the unity of the Janata Dal Parivar. The leaders, who are trying to forge unity to face forces of marginalisation, have been in the party named Janata Dal, which itself was the result of unification of many parties in 1988-89. Even earlier, they were together in 1977 in its earlier avatar named Janata Party. Naturally these leaders are hoping to recreate a new Janata experiment so as to make themselves relevant in the changed political scenario. Also Read – Turning a blind eyeThe question is will they succeed in repeating the experiment of 1977 or 1989. The answer is negative. The reason is simple. In 1977, almost all opposition parties of Northern India (except left) have joined hands to form Janata Party and it attracted leaders from almost all parts of India. The unification was preceded by emergency and a strong movement against Indira Gandhi’s rule. The move was succeeded because it had backing of a big movement. Once, Janata Party came to power, the constituent parties started colliding among themselves and that was the end of the Janata Party experiment. In 1988-89, India witnessed Janata Dal experiment. The experiment was not as huge as what it was in 1977. Some parties merged themselves as Janata Dal. Janata Dal entered into alliance with BJP in one side and left on the other. After election, Janata Dal emerged as the second largest party after Congress, which had failed to get majority. The Dal formed government with the outside support of BJP and left parties. Again Janata Dal cracked from inside and it started splitting.We have over a dozen fragments of Janata Dal, which was once led by V P Singh. In fact the present exercise to forge unity is confined only among these fragments. Out of these fragments Biju Janata Dal is in power in Odisha and Samajwadi Party is in Uttar Pradesh.The reasons for failures of the experiments are many. First of all, the leaders lack a valid issue to unite against Modi. In 1977 Janata Party was formed after unification to save democracy, which had been endangered by the emergency imposed by Indira Gandhi. In 1988-89 the unification took place with the slogan of movement against corruption. Corruption was the main issue agitating the minds of people at that time. Now the issue raised by leaders like Nitish and Lalu is communalism. They had raised this issue in the last Lok Sabha election as well, but they could not succeed preventing BJP from coming to power. Now they think that their combined strength will defeat Narendra Modi. This issue is not going to click in the caste sensitive states of Uttar Pradesh and Bihar, because people have understood that by raising the bogey of communalism, they are not promoting any noble cause, but trying to get Muslim votes only. These leaders acquire their political clout because of being OBCs and they have fanned caste politics to gain power. Narendra Modi is also an OBC and BJP under him is reaping the harvest. They get power with the help of OBC votes, but serve the interests of their own castes and Muslims. These feelings have reached the weaker sections of OBCs. Hence, the slogan of secularism only furthered the cause of BJP, which got votes of weaker OBCs in the last Lok Sabha election. This happened in Haryana too. That is the single most important reason for BJP in getting the majority in Haryana election. Hence the issue of communalism vouched by them to unite against Modi I may not fully work in their favour. The success of Lalu- Nitish combine in Bihar by- elections should not be taken seriously, because a sizable number of people vote for party in power in such elections. The second reason for the likely failure of the experiment is the credibility of these leaders. They no longer inspire people by their speech, because they have failed to meet the expectations of their supporters and sympathisers. They are forging unity to defeat Modi, but they have explanation why they had separated from each other causing multiple fragmentations of the Janata Dal, which is being claimed by them as their parivar (family). People have come to know that they unite for their survival and divide to gain more plums of power.Third reason is that they may talk of unity, but they are as disunited as before. Haryana Assembly election is the recent example. Nitish Kumar of Janata Dal (U) was campaigning for the INLD (Indian National Lok Dal of Chautala) candidates and Rabri Devi of RJD was campaigning for Congress candidate Ajay Yadav, who happens to be the father in law of her daughter, though both claim to be in the same camp in Bihar now. There is a history that whenever there is conflict between the collective interests and their personal interests, they choose personal interests to pursue. All Janata leaders have this weakness and all know that others would desert the unity or its talks, once their own personal interests are at stake. All of them are suspicious of one another on this count. The fourth reason is the influence areas of these leaders. Nitish and Lalu have no influence outside Bihar. So they are not going to help Mulayam electorally in UP or Chautala in Haryana. Similarly, Mulayam is not going to help Lalu- Nitish getting more votes in Bihar. HD Deve Gowda has also joined the unity talks, but he is not going to benefit by this unity in Karnataka nor he is of any benefit to Hindi state leaders, so far as raising the vote percentage is concerned. Hence, the unity moves of Janata Dal Parivar might continue for some time but it is difficult to finally form a cohesive party which will give electoral dividends.last_img read more

Ahead of his time

first_imgWhat happens to a man who gives all his life for something he loves? Is an individual really free in this world to do what he wants? The Asmita theatre group’s play Hanoosh chronicles the life of an individual who devotes his life to fulfill his wish of creating a clock about which he had heard in his childhood. Based in ancient Greece, the play shows how people around Hanoosh question, doubt and even try to encash over his invention. After all it was all to see the first machine that measured time. The play also manages to portray issues both contemporary and gender related in a subtle manner through the character and also gives an idea about the intensity of social pressure a common individual faces irrespective of time. Religion is also an important component which finds its way within the play. The power struggle between different groups and an innocent individual’s obsession are amalgamated in way which enables the audience thinks about the prevalent contemporary issues.  Also Read – ‘Playing Jojo was emotionally exhausting’The direction is intense and Arvind Gaur, the director, is successful in captivating his audience. The lead role is played by Gaurav Mishra who smoothly incorporated the character of an innocent but obsessive locksmith who dreams of making a clock. Katya is of a strong-willed woman who works for the family and make the ends meet, while lashing out at Hanoosh for indulging in clock-making, which seems to be a Herculean task. Shilpi, with her powerful voice, enacts the role of Katya, making the crowd cheer for her.  Also Read – Leslie doing new comedy special with NetflixThe props played an important role in this play and they were diligently used, especially the clock. The prototype of the clock becomes the symbol of the struggles which the initial makers in the early centuries might have gone through. The cultural setting is not introduced through the props but words are used instead. This method enables the audience to guess the exact historical context while they watch the play. This play was performed in Shriram Centre on May 9 and was also telecasted live on the online platform www.viewmyshow.in. It became the first play ever in Delhi to have an online broadcast. The Asmita Theatre group has donated their earning amount for Nepal quake relief. The theatre artists themselves have bought items and also have visited villages of Nepal to ensure the needs of our neighbours are met. They plan to continue the relief work by going there every week. With good cause and excellent performance, this play manages to keep audience glued to their seats.last_img read more

JU students demand Sarkars expulsion

first_imgKolkata: The controversy surrounding Jadavpur University professor Kanak Sarkar took a dramatic turn on Tuesday with a section of students submitting a deputation to Vice-Chancellor Suranjan Das and Internal Complaints’ Committee (ICC) of the varsity seeking strong action against him and demanding his expulsion. Sarkar, a professor with the International Relations department, had recently posted on social media regarding his logic about women and their virginity and subsequent marriage prospects. The West Bengal Women’s Commission sent a notice to him on Tuesday seeking an explanation and directing him to depose before the Commission’s within seven days. Also Read – 3 injured, flight, train services hit as rains lash BengalThe National Commission for Women has taken suo motu cognisance of Sarkar’s comments, calling it “shockingly misogynistic”. It’s chairperson Rekha Sharma wrote to the state Director General of Police requesting him to investigate the matter and take appropriate action. United Students’ Democratic Front (USDF) staged protest in the JU campus condemning the misogynistic statement objectifying women on his Facebook page. “This is not an incident in isolation as he has been harassing students from all marginalised identities for years now,” said Dwaipayan Sarkar, a member of the USDF. Also Read – Speeding Jaguar crashes into Mercedes car in Kolkata, 2 pedestrians killedOne of Sarkar’s former students narrated her ordeal during his class and expressed relief that he had been exposed now. “I had no option but bunk ALL his classes when I was in JU,” she mentioned on social media. Jadavpur University Vice-Chancellor Suranjan Das condemned the incident and said: “If we find evidence of such actions of Sarkar within the campus it will be referred to the ICC and steps will be taken as per rules.” Sarkar had withdrawn his post within an hour of publication.last_img read more

Centre asks state govt to inquire about role of 5 top cops

first_imgKolkata: The Union Home ministry has sent a letter to the Bengal government to inquire about the role of five IPS officers who allegedly attended Chief Minister Mamata Banerjee’s ‘dharna’ on Sunday. However, it may be noted that the officers did not go to the sit-in protest at any point in time and were not seen sharing the stage with the Chief Minister.According to sources, after Governor Keshari Nath Tripathi sent a report regarding the conflict between Kolkata Police and the Central Bureau of Investigation (CBI), Ministry of Home Affairs (MHA) issued the letter to the state government, asking the latter to find out about the role of these police personnel. Also Read – Bose & Gandhi: More similar than apart, says Sugata BoseThe five IPS officers include Virendra, Director General of Police (DGP), West Bengal; Additional Director General (ADG), Law and Order (L&O) Anuj Sharma; Director Security in the rank of ADG, Vineet Kumar Goyal; Commissioner of Police (CP), Bidhannagar, Gyanwant Singh and Additional Commissioner of Police (Addl CP) III, Kolkata Police, Supratim Sarkar. It is important to mention that these police officers had only met the Chief Minister for a discussion when she went to the Metro Channel to begin the ‘dharna’ and left soon after. Incidentally, Goyal is in-charge of the Chief Minister’s security. All had gone to meet the Chief Minister to finalise the arrangements for the Bengal Global Business Summit, scheduled just two days later with more than 4,000 delegates and foreign dignitaries taking part. Sarkar is responsible for traffic and had gone to finalise the arrangements for Monday’s Investiture Ceremony where Banerjee gave away the annual awards for the state and Kolkata Police. The function was held at a makeshift stage next to the ‘dharna manch’, separately constructed for the awards event.last_img read more