Citation: Soapy property improves electron mobility in organic semiconductors (2008, October 28) retrieved 18 August 2019 from https://phys.org/news/2008-10-soapy-property-electron-mobility-semiconductors.html Taking a step toward that goal, physicists have made an important advance in the development of organic semiconductors in terms of their electron mobility. Generally, organic semiconductors have low electron mobility, meaning that the overall motion of their electrons is too random and not directed enough to provide a good electric current and conductivity. The physicists demonstrated how to improve the electron mobility of liquid crystalline semiconductors to 0.27cm2/ V•s, which is 10 times higher than the current highest level for room-temperature columnar liquid crystalline materials. The physicists, from the University of Tokyo, Kyoto University, Osaka University, and the Japan Synchrotron Radiation Research Institute, published their study in a recent issue of the Journal of the American Chemical Society.The scientists modified a molecule known as a condensed porphyrin copper complex to make it self-assemble into a liquid crystalline state at room temperature (throughout a wide range from -17 to 99°C). They achieved the record mobility at a temperature of 16°C.The key modification was adding hydrophobic side chains to one side of the molecule and hydrophilic side chains to the other. By being both hydrophobic and hydrophilic, the molecule has now become “amphiphilic.” Other common amphiphilic substances include soaps and detergents, which have molecules that can both attach to grease and easily be washed away by water.The amphiphilic property is useful for improving electron mobility because amphiphilic molecules tend to gather together in an orderly manner. Specifically, the amphiphilic molecular design enhanced the ð-stacking interaction, and molecules with larger ð-conjugated cores tend to have higher electron mobility. The physicists explain that ð-stacking is improved due to a nanoscale phase separation caused by the incompatibility between the hydrophobic and hydrophilic side chains of the molecules.The scientists also noted that the new organic semiconductor is especially efficient at absorbing visible light, which could make them useful for organic thin-film solar cells.More information: Sakurai, Tsuneaki, et al. “Prominent Electron Transport Property Observed for Triply Fused Metalloporphyrin Dimer: Directed Columnar Liquid Crystalline Assembly by Amphiphilic Molecular Design.” J. Am. Chem. Soc., 130 (42), 13812-13813, 2008. 10.1021/ja8030714.via: Tech-On! Polarized optical micrograph of a condensed porphyrin copper complex molecule with hydrophobic and hydrophilic side chains. Image credit: Tsuneaki Sakurai, et al. Physicists use nanostructures to free photons for highly efficient white OLEDs (PhysOrg.com) — Organic semiconductors are a main component in a variety of future organic electronics, such as flexible flat-panel displays, inexpensive solar cells, and other unique devices. Because of their advantages – which include being energy-efficient, inexpensive, and lightweight – organic electronics are expected to compose a multi-billion industry. 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.
A modified LEGI model and computer simulation that reproduces both persistent cell migration and oscillations. A diagram of the modified LEGI model that involves the production of both excitation and inhibitory signals in the frontal region, followed by the transport of inhibitory signals away from the front to maintain frontal protrusions and cell polarity in control cells. In nocodazole-treated cells, the impairment of the transport and the resulting accumulation of inhibitory signals at the front act against the excitation signals and cause the head to switch into a tail (A). Computer simulation of this mechanism for cells in 1D successfully reproduces both persistent migration (kymograph in B) and oscillations (kymograph in C). Diagrams of cell location and shape, colored to show the heat map of net signals, show the dynamics of net signals before and after the treatment of nocodazole (D). In addition, the period of oscillation increases upon the impairment of the generation of inhibitory signals (by increasing the delay), which mimics the effect of blebbistatin (kymograph in E). a.u. stands for an arbitrary unit used in computer simulation. See also Fig. S6 and Movies S4–S6. Credit: Zhang J et al. (2014) Microtubules stabilize cell polarity by localizing rear signals. Proc Natl Acad Sci USA 111(46):16383-16388. Explore further (Phys.org)—Microtubules – tubular polymers of tubulin (a globular protein) that are a component of the cytoskeleton found throughout cell cytoplasm – are involved in a range of cellular functions, including the movement of secretory vesicles, organelles, and intracellular substances; cell division (mitosis and meiosis), including the formation of mitotic spindles; and cell polarity, which refers to spatial differences in cellular shape, structure and function. However, the nature of the role of microtubules in cell polarity has yet to be clarified. At the same time, cell migration plays an essential role in many important physiological processes, such as embryogenesis, wound healing, and immune responses; in engineering applications such as tissue regeneration; and, when defective, in causing severe problems such as birth defects, vascular disease and tumor metastasis. A key area for investigation in the linkage between cell polarity and cell migration is that directional cell migration requires a defined polarity, generated by an integrated network of signals, adhesions (the protein-based binding of a cell to a surface or substrate) and cytoskeleton. Play A representative RPE-1 cell expressing RFP-zyxin and migrating on 1D strip, treated with nocodazole to induce oscillations. The movie shows the redistribution of zyxin upon nocodazole treatment. Related to Fig. 2. Credit: Zhang J et al. (2014) Microtubules stabilize cell polarity by localizing rear signals. Proc Natl Acad Sci USA 111(46):16383-16388. Moving forward, Wang tells Phys.org, the researchers would like to drill down the molecular mechanism and cellular structures for polarity control. “We found that a focal adhesion protein, zyxin, has some unique properties that parallel cell polarity, suggesting that it may be a key ‘readout’ of the LEGI mechanism as well as the control factor for cell polarity – and we’re now in the process of elucidating its functional role in cell polarity. In addition,” he continues, “while centrosomes have long been speculated to control cell polarity, we’re trying to establish a logical connection between centrosomes and the LEGI mechanism.” (The centrosome is an organelle that serves as the main microtubule organizing center, or MTOC, of the animal cell, where microtubules are nucleated.) Wang adds that they may also investigate fine regulation of cell migration based on the manipulation of microtubules or motor molecules without total depolymerization of microtubules, and a ‘biological clock’ based on oscillating polarity.Wang says that there are other areas of research that might benefit from their study. “Understanding the control mechanism of cell migration can greatly facilitate migration dependent processes such as tissue engineering and cancer treatment3,4. In addition, the elegant switch between positive and negative feedback may impact bio-inspired engineering, in which a man-made machine may use a biomimetic control mechanism to achieve innovative functions.”Specifically, Phys.org asked Wang if their findings might pertain to the observation that metastasis and neuroneogenic targeting have similar behavioral properties, and may share what has been termed an ancient genetic toolkit5 that plays a role in cancer. “Yes,” Wang affirmed. “Metastasis is driven by the migration of tumor cells. Our findings improve the understanding of the internal control circuit for cell migration, which will benefit the understanding and treatment of metastasis, – such that conditions that reduce the stability of tumor cell migration may be deployed for cancer treatment.” RPE-1 cells in 50 μM ciliobrevin D. Kymograph shows a representative RPE-1 cell treated with ciliobrevin D oscillating in a manner similar to those treated with nocodazole. (Scale bar, 50 μm, 60 min.) See also Figs. S1 and S7 and Movie S1.Credit: Zhang J et al. (2014) Microtubules stabilize cell polarity by localizing rear signals. See also Figs. S1 and S7 and Movie S1. Proc Natl Acad Sci USA 111(46):16383-16388. More information: Microtubules stabilize cell polarity by localizing rear signals, Proceedings of the National Academy of Sciences (2014) 111(46):16383-16388, doi:10.1073/pnas.1410533111Related:1Quantitative Studies of the Growth of Mouse Embryo Cells in Culture and their Development into Established Lines, Journal of Cell Biology (1963) 17(2):299–313, doi:10.1083/jcb.17.2.2992Periodic migration in a physical model of cells on micropatterns, Physical Review Letters (2013) 111(15):158102, doi:10.1103/PhysRevLett.111.1581023Race to the top: Decoding metastasis, Medical Xpress April 29, 20114Probing the invasiveness of prostate cancer cells in a 3D microfabricated landscape, Proceedings of the National Academy of Sciences (2011) 108(17):6853-6856, doi:10.1073/pnas.11028081085Cancer tumors as Metazoa 1.0: tapping genes of ancient ancestors, Physical Biology (2011) 8:015001, doi:10.1088/1478-3975/8/1/015001 Recently, scientists in the Department of Biomedical Engineering at Carnegie Mellon University, Pittsburgh obtained a series of analytical and experimental results showing that:Cells on micropatterned linear strips change from highly persistent migration into striking oscillations upon the disassembly of microtubulesPositive feedback in the local-excitation-global-inhibition, or LEGI, mechanism – which is responsible for migration persistence, and in which the response to a stimulus (such as chemotaxis, the movement of an organism in response to a chemical stimulus) is mediated through the balance between a fast, local excitation and a slower, global inhibition process – might be converted into negative feedback to drive oscillations upon the disassembly of microtubulesMicrotubules facilitate the transport of inhibitory signals and their global distributionFeedback in the integrated control circuit may be either positive or negative, depending on the relative position of excitation and inhibitory signalsThe scientists therefore concluded that these findings provide valuable insights into the role of microtubules in the control circuit of cell migration.Prof. Yu-Li Wang discussed the paper that he, Graduate Research Assistant Jian Zhang and Project Scientist Wei-Hui Guo published in Proceedings of the National Academy of Sciences, starting with the challenges involved in the team finding that depolymerization of microtubules caused cells to change from persistent to oscillatory migration. The issue, Wang tells Phys.org, is that without confining cell migration along a one-dimensional (1D) strip, depolymerization of microtubules simply causes cells to lose directional migration without showing recognizable oscillations – so confinement to 1D is required for the highly persistent migration before microtubule depolymerization as well as the oscillatory migration after depolymerization. “This is most likely due to limiting cell migration to two opposite directions,” he explains. “Oscillations become difficult to observe when the cell is able to switch among many different directions. Moreover,” he adds, “our observation was also facilitated by using the RPE-1 cell line, which has a relatively short oscillation period such that multiple cycles of oscillation may be observed before the cell enters division phase. RPE-1 cells therefore allowed unambiguous confirmation of the initial observation made with NIH/3T3 cells.” The retinal pigment epithelium, or RPE, is the pigmented cell layer just outside the neurosensory retina that nourishes retinal visual cells, and is firmly attached to the underlying choroid and overlying retinal visual cells. 3T3 cells – from a cell line originally established in 1962, and published1 in 1963, by George J. Todaro and Howard Green at New York University School of Medicine – has become the standard fibroblast cell line. (Fibroblasts are the most common connective tissue cell in animals.) 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 Play Persistent migration and oscillation of RPE-1 cells. The movie shows representative RPE-1 cells migrating persistently as a control or showing oscillations when treated with nocodazole or ciliobrevin D on 1D strips. Related to Figs. 1, 2, and 6. Credit: Zhang J et al. (2014) Microtubules stabilize cell polarity by localizing rear signals. Proc Natl Acad Sci USA 111(46):16383-16388. The second analytic conclusion was based on a primary difference between cells and man-made machines – the former involve dynamic localization of structures and signals, while the latter usually consist of components with a fixed location and geometrical relationship – so depending on the relative position of excitation and inhibitory signals in cells, the resulting feedback in the integrated control circuit may be either positive or negative. In contrast, the lack of dynamic localization in most man-made machines keeps them from exhibiting this conversion. “Although rarely realized in man-made machines, transport-dependent conversion between positive and negative feedback in the cell makes intuitive sense for regulating dynamically localized activities.” Wang points out. “When negative signals are transported away from positive signals, it creates a positive feedback by suppressing the activities elsewhere that may compete with the existing frontal end. Conversely, when negative signals are allowed to accumulate in the vicinity of positive signals, they cause negative feedback by overpowering positive signals.”The scientists suggest that microtubules are required not for the generation, but rather for the maintenance, of cell polarity by mediating the global distribution of inhibitory signals. “We found that after the depolymerization of microtubules, cells are still able to move directionally for more than an hour before reversing the direction,” Wang says. “Therefore, cells without microtubules are able to establish a direction of migration but are not able to maintain the polarity for an extended period of time as control cells do. The defect may be explained by the inability to remove the accumulating inhibitory signals at the leading edge, which eventually overpower the excitation signals required for maintaining frontal protrusion activities.”A key finding discussed in the paper is that disassembly of microtubules induces cell oscillation by allowing inhibitory signals to accumulate at the front, which stops frontal protrusion and allows the polarity to reverse. “According to the LEGI model, frontal protrusion activities are determined by the balance between excitation and inhibitory signals,” Wang explains. “Upon the loss of microtubules and the associated transport mechanism, the cell is no longer able to move inhibitory signals away from the leading edge where they are generated, and therefore cannot achieve their global distribution.” Specifically, the accumulating inhibitory signals eventually overcome the excitation signal to stop frontal protrusion activities – and at the same time, the suppression of protrusion activities elsewhere also becomes compromised due to the defective global transport. “Spontaneously-generated excitation signals are then allowed to accumulate and cause the formation of a new front,” Wang adds, “which in the case of cells confined to 1D translates into the reversal of polarity.” The researchers also found that in addition to oscillation, their modified LEGI mechanism can create a range of possible cell behaviors as a result of different relative dynamics of excitation and inhibitory signals – and thereby, the variable interplay between shape, mechanics, and polarity. “The magnitude of inhibitory signals is determined by the relative rate between the generation and transport-mediated depletion.” Wang adds. “Our model accounts for the key elements between signal generation and transport – and while previous models, such as that created by Brian Camley and his colleagues2, incorporate some of the relevant parameters such as cell adhesion and shape to generate oscillation, they are unable to generate as wide a range of activities.”Wang notes that their mathematical model is capable of generating testable, verifiable predictions. One of the primary predictions was that longer cells should oscillate with a longer period; another prediction was that inhibition of dynein (one of many proteins that bind to microtubules, in this case a motor protein responsible for the transports of cargos away from the cell front) should cause similar oscillations as those caused by microtubule disassembly. Wang emphasizes that both of these predictions were verified with experiments. , Physical Review Letters The scientists also faced a hurdle when applying computer modeling to understand how positive LEGI feedback might be converted into negative feedback to drive oscillations upon microtubule disassembly. “The main challenge was to model not only excitation and inhibitory signals at different locations, but also a transport process responsible for delivering the inhibitory signals away from the frontal region for global distribution,” Wang explains, “because the oscillation phenomenon can be produced only when the model includes all the essential elements.” © 2014 Phys.org , Physical Biology 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: Going places: Microtubule-mediated transport of inhibitory signals critical in stabilizing cell migration polarity (2014, December 9) retrieved 18 August 2019 from https://phys.org/news/2014-12-microtubule-mediated-inhibitory-critical-stabilizing-cell.html Journal information: Proceedings of the National Academy of Sciences Persistent migration of cells on 1D strips and the corresponding localization of focal adhesion proteins. Related to Fig. 1. Immunofluorescence staining of tensin in a representative RPE-1 cell (A; scale bar, 25 μm) shows no apparent polarization. Kymograph (B; scale bar, 50 μm, 60 min) and time series (C; 90-min interval; scale bar, 100 μm; arrow indicates the direction of migration) of representative NIH 3T3 fibroblasts exhibiting persistent migration on 1D strips. RFP-zyxin in NIH 3T3 cells migrating on 1D strips localizes to the tail region (D). (Scale bar, 50 μm.) Credit: Zhang J et al. (2014) Microtubules stabilize cell polarity by localizing rear signals. Proc Natl Acad Sci USA 111(46):16383-16388. , Journal of Cell Biology A new mechanism affecting cell migration found Despite the complexity of their investigation, the researchers addressed these challenges in a number of ways. They showed that microtubules play a key role in maintaining the positive feedback in the LEGI mechanism, and as described above that positive feedback of the LEGI mechanism for persistent migration may be readily converted into a negative feedback for oscillations. “We found that, in order to generate oscillation, the production of inhibitory signals must lag behind the production of excitation signals,” Wang tells Phys.org. “This is consistent with the general understanding that delay differential equations have the capability to generate oscillations.” In addition, he continues, they used a highly reliable micropatterning method, developed in their lab, which grafts linear polyacrylamide on glass surfaces to block cell migration for confining cell migration to a 1D strip. “We also used a computer model – also implemented in our lab – that simulates not only the control circuit, but also its effect on cell migration.”The paper presents two analytic conclusions, the first being that microtubules facilitate the transport of inhibitory signals and their global distribution. “Our reasoning was guided by the conversion from persistent migration – known to depend on LEGI-based positive feedback – to oscillation, which in general requires negative feedback,” Wang says. “The simplest way for this conversion to occur involves the inhibition of global distribution of negative signals, which fits perfectly with the well-documented function of microtubules in intracellular transport.” Wang points out that this type of reverse reasoning – where an intuitive hypothesis to provide a simple explanation of a biological phenomenon is made before seeking experimental evidence or computational verification – is widely practiced for understanding complex biological phenomenon that are too difficult to address through forward dissection. “Our results further imply that a cell is able to measure its own length based on the time required for end-to-end microtubule-mediated transport,” Wang continues. “Other cellular processes may be similarly affected by the time for the transport of molecular signals along the cell length.” 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.
© 2019 Science X Network ABF locally perturbs fluid flow. (A) Schematic of a 200-μm-wide microfluidic channel with suspended ABF (36 μm long, 10 μm in diameter) positioned at the channel center (x,y,z) = (0,0,0). The upper channel contains water, whereas the lower channel contains 200-nm fluorescent NPs. (B) Snapshot of ABF in a 200-μm-wide channel perturbing the tracked paths of the 200-nm fluorescent NPs indicating fluid flow. Scale bar (top), 10 μm. A numerical simulation of two-fluid flow with an ABF at the interface, with color indicating concentration distribution (red, 1 mol/m3; blue, 0 mol/m3) of molecular species (bottom). (C) Velocity profile at positions upstream and downstream of the ABF. For the control, at x = +3 mm, an unperturbed laminar profile with peak velocity of 50 μm/s was simulated. At both x = +50 μm (upstream) and x = −50 μm (downstream), an increase in peak velocities is predicted, with the peak shifted closer toward the channel wall for the upstream case. (D) Simulation results for the y velocity component uy (orthogonal to and out of the channel) at the same positions as (C). In the vicinity of the ABF, a push directed orthogonal to the flow direction toward the channel wall is predicted. Credit: Science Advances, doi: 10.1126/sciadv.aav4803 Explore further Tiny robots powered by magnetic fields could help drug-delivery nanoparticles reach their targets Generally, NP transport is affected by surface charge, hydrophobicity and surface biochemistry; properties that can be actively optimized in research work for more effective in vivo trafficking. Scientists have used external energy sources such as magnetic and acoustic forces to create wirelessly controlled microbots and shuttle the therapies to diseased tissue for improved diffusive transport. However, these methods still relied on diffusive transport after releasing their onboard cargo, while the need remains for more distinct strategies of transport into a defined location. Control of green fluorescently labeled MTB in microfluidic device, when RMF is on/off. Credit: Science Advances, doi: 10.1126/sciadv.aav4803 Conceptual overview of magnetically controlled micropropellers for convection-enhanced NP transport. (A) Conceptual schematic depicting a single microrobot, the artificial bacterial flagellum (ABF), enhancing mass transport of nanoparticles (NPs) at the vessel-tissue interface (left), and swarms of magnetotactic bacteria (MTB) generating convective flow to improve mass transport (right). ECM, extracellular matrix. (B) Schematic of magnetofluidic platform for NP mass transport studies using magnetically induced convection. The microfluidic chip is placed between the objective lens of an inverted optical microscope and the electromagnets (left). A schematic depicts the chip, consisting of an upper channel filled with NPs (red) and a lower water channel (blue) that both border a collagen matrix (gray) along restricting trapezoidal posts made of PDMS. NPs can passively diffuse into the collagen matrix along their concentration gradient toward the water channel. Credit: Science Advances, doi: 10.1126/sciadv.aav4803 Ferrohydrodynamic pumping with controlled swarms of MTB. (A) Transmission electron micrograph of M. magnetic strain AMB-1. Scale bar, 0.5 μm. The magnetosomes are clearly visible, here formed in two distinct strings of iron oxide crystals. (B) Control of AMB-1 under static magnetic fields (top) and magnetic fields rotating in-plane at 1 Hz. Scale bar (bottom), 5 μm. (C) Postprocessed images of tracked, co-suspended, nonmagnetic, fluorescent NPs used to observe flow fields generated by a swarm of MTB exposed to a 12-mT magnetic field rotating at 10 Hz in the y-z plane. Traces in green correspond to traveled trajectories over 12 frames (~1 s). Positions are computed using band-pass filter with 25-pixel diameter, followed by peak finding (top). Bacterial motion can be steered by changing the direction of the vector of the rotating magnetic field, because the MTB translate within the plane of rotation (bottom). For an RMF vector around the x axis, bacteria rotate along y, generating a flow that transports NPs along y. (D) Translational velocity is plotted versus applied rotational frequency at two different magnetic field strengths. Translational velocity increases with frequency initially, but at sufficiently high frequencies, it decreases because fluidic drag torque overcomes the magnetic torque to prevent them from keeping up with the rotation of the field. The maximum synchronized frequency, also corresponding to the maximum translational velocity, is referred to as the step-out frequency ωmax. When the magnetic field strength is increased, the step-out frequency increases, as observed. Credit: Science Advances, doi: 10.1126/sciadv.aav4803 , Advanced Materials The scientists also developed a single-fluid flow model in a microchannel to form a bioinspired microvessel with biomimetic scales and fluid flow rates. The model contained concentrated collagen in the center that mimicked the native extracellular matrix. Using the device, Schuerle et al. quantified the fluorescent intensity in the biomimetic matrix to test if the magnetically controlled ABF could enhance the mass transport of fluorescently labelled NPs into the tissue-mimicking matrix. The results indicated that ABFs were limited as a convective micropropller in smaller vessels, but this can be changed by scaling the ABF structure to suit the channel size in the future.The scientists considered the effects of a whole swarm of smaller microrobot propellers next. For this, Schuerle et al. selected the wild type MTB strain AMB-1 (Magnetospirillum magneticum) to form magnetosomes. The microorganisms naturally produced chains of iron oxide particles in lipid bilayers of the plasma membrane for manipulated movement using external magnetic fields. While researchers had used MTBs in previous studies as potential vehicles of drug delivery with external magnetic fields, Schuerle et al. used rotational magnetic fields (RMFs) in the present work. The RMFs forced the movement of an MTB swarm to drive their motion via magnetic torque. , Nature Nanotechnology The scientists lowered the average distance between the bacteria by using a high concentration of MTBs to press the cell neighbors forward in 3-D swarms dominated by hydrodynamic forces. They did not observe clustering or aggregation of the MTB magnetosomes when exposed to RMFs since the magnetosomes were inherently shielded by the bacterial cell membranes for controlled fluid flow. Schuerle et al. repeated the experiments for biomimicry using a microfluidic device containing collagen to show that MTB swarms could penetrate collagen, when sufficiently high concentrations of MTBs were used. In this way, using two experimental strategies Schuerle et al. improved the mass transport of NPs, via convective flow generated by magnetically controlled micropropellers. The microrobotic experiments showed that ABF mimicked a bacterial flagellum to assist NP accumulation and penetration into a dense collagen matrix – when acted upon by RMFs. Schuerle et al. propose to include such stationary ABFs into stents to trigger drug release and improve penetration at a site of interest to counteract inflammation on demand. With the second strategy, they focused on generating the same technique but with magnetotactic bacterial strains (MTBs). Based on the present work and the existing tumor-homing properties of MTBs, the scientists envision magnetically controlled swarms of 3-D MTBs to transport NPs in the interstitial fluid space of tumor microenvironments. The scientists will optimize the density of bacteria for a compatible dose in vivo and the work will pave the way forward to further studies on micro- and nanomaterials for magnetically enhanced NP transport in clinical nanomedicine. They used rotating magnetic fields (RMFs) to power the devices and create local fluid convection to overcome the diffusion-limited transport of nanoparticles. During the first experimental approach, they used a single synthetic magnetic microrobot as an artificial bacterial flagellum (ABF) and then used swarms of a naturally occurring magnetotactic bacteria (MTB) to create a “living ferrofluid” by exploiting the ferrohydrodynamics. Using both approaches the scientists enhanced the transport of NPs in a microfluidic model of blood extravasation (movement of a drug from blood vessels to the external tissue) and tissue penetration in microchannels surrounded by a collagen matrix to create a biomimetic tissue-vessel interface in the lab. The results of the study are now published in Science Advances. Nanoparticles (NPs) are increasingly popular in nanomedicine due to biomedical research potential as carriers in drug delivery that surpass the limits of conventional medicine. While NPs are designed to alter the pharmacokinetics and biodistribution of existing drugs, they are impeded by physiological barriers, which prevent successful accumulation at the sites of disease, limiting their therapeutic effects in vivo. During cancer therapy, for instance, drug carriers encounter abnormal vessels that surround the tumor architecture for ineffective intravenous drug release. Since delivering NPs into tissues is strongly influenced by their physiochemical properties, scientists have re-designed the NP shapes and sizes to optimize their transport kinetics through vessel walls to reach tissues. Researchers had previously proposed multistage approaches for optimized drug delivery, either by shrinking nanoparticles in time, or fragmenting them to disperse and reach a site of interest only after encountering microenvironmental cues of disease in vivo. , Science Schuerle et al. engineered the magnetic ABF using three-dimensional (3-D) lithography and metal deposition, as previously reported. The bioinspired microrobots mimicked the rotating flagella for efficient propulsion-based locomotion at the microscale—where viscous drag forces dominate. They controlled the ABF motion with uniform magnetic fields in 3-D rotation using a wireless magnetic control setup containing electromagnets arranged around a single hemisphere. Then they mounted the setup on an inverted microscope to track the movements of the controlled microrobots. The rotating magnetic fields (RMFs) allowed forward propulsion and convective flow in the surrounding fluid and when the scientists immersed the ABF in a suspension of fluorescent NPs, they observed controlled flow for mass transport of the NPs.In the experiment, they constructed the bottom layer of the microfluidic channel to contain the 200 nm NPs similar to the size used in clinical applications, while on the top fluid layer they maintained a suspension of pure aqueous medium. The scientists stationed the ABF at the center of the setup to sustain its position against the flow by controlling the fluid flow in the setup. This arrangement of the ABF in a microfluidic channel disrupted the laminar flow to produce convection, which transported NPs from the fluid layer at the bottom to the upper layer—to reach the channel wall, i.e., the location of interest. The artificial bacterial flagellum (ABF) in a microvessel-like one-fluid flow device. Credit: Science Advances, doi: 10.1126/sciadv.aav4803 Nanoparticles (NPs) are a promising platform for drug delivery to treat a variety of diseases including cancer, cardiovascular disease and inflammation. Yet the efficiency of NP transfer to the diseased tissue of interest is limited due to an assortment of physiological barriers. One significant hurdle is the transport of NPs to precisely reach the target tissue of interest. In a recent study, S. Schuerle and a team of interdisciplinary researchers at the departments of Translational Medicine, Biophysics, Engineering Robotics, Nanomedicine and Electronics, in Switzerland, the U.K. and the U.S. developed two distinct microrobot-based micro-propellers to address the challenge. More information: S. Schuerle et al. Synthetic and living micropropellers for convection-enhanced nanoparticle transport, Science Advances (2019). DOI: 10.1126/sciadv.aav4803 R. Blakemore. Magnetotactic bacteria, Science (2006). DOI: 10.1126/science.170679 Ouajdi Felfoul et al. Magneto-aerotactic bacteria deliver drug-containing nanoliposomes to tumour hypoxic regions, Nature Nanotechnology (2016). DOI: 10.1038/nnano.2016.137 Soichiro Tottori et al. Magnetic Helical Micromachines: Fabrication, Controlled Swimming, and Cargo Transport, Advanced Materials (2012). DOI: 10.1002/adma.201103818 In the present work, Schuerle et al. detailed two distinct strategies to generate wirelessly localized convective flow to prevent the invasiveness of implanted nanoparticles. Inspired by the field of microrobots (microbots), the scientists used (1) a single, synthetic, bacteria-inspired microrobot, or (2) large swarms of living bacteria to drive localized NP transport. The artificial and natural micropropellers assisted the process by promoting magnetically driven convection into a defined location in a magnetofluidic setup with potential for therapeutic applications. The synthetic microbot imitated bacterial propulsion using an artificial bacterial flagellum (ABF), while the dense swarms of magnetotactic bacteria (MTB) harnessed by Schuerle et al. occurred naturally as gram-negative prokaryotes (Magnetospirillum magneticum) with magnetic properties. The scientists expect the results to overcome existing transport barriers for enhanced NP tissue penetration via wireless control and spatiotemporally precise local convection in the future. Journal information: Science Advances Citation: Synthetic and living micropropellers support convection-enhanced nanoparticle transport (2019, May 7) retrieved 18 August 2019 from https://phys.org/news/2019-05-synthetic-micropropellers-convection-enhanced-nanoparticle.html This document is subject to copyright. Apart from any fair dealing for the purpose of private study or research, no part may be reproduced without the written permission. The content is provided for information purposes only.
When the Muses Strike: Creative Ideas of Physicists and Writers Routinely Occur During Mind WanderingShelly L. Gable, Elizabeth A. Hopper, and Jonathan W. Schooler Conceptually Rich, Perceptually Sparse: Object Representations in 6-Month-Old Infants’ Working MemoryMelissa M. Kibbe and Alan M. Leslie Read about the latest research published in Psychological Science: A Tight Spot: How Personality Moderates the Impact of Social Norms on Sojourner AdaptationNicolas Geeraert, Ren Li, Colleen Ward, Michele Gelfand, and Kali A. Demes How do contextual factors and personality traits affect how individuals adapt to a new culture when they temporarily move to a different country? To answer this question, Geeraert and colleagues analyzed data from a longitudinal acculturation project that measured young adults’ personality and cultural adaptation during and after a temporary move to a different country. These measures were collected on three occasions: 3 months before departure as well as 2 weeks and 5 months after arrival to the host country. Overall, participants who moved to a tight culture (i.e., one with strong norms and little tolerance for deviance) showed less adaptation than those who moved to a loose culture (i.e., one with less rigid norms), but participants originally from a tight culture showed more adaptation than those from a loose culture. Participants who scored higher on agreeableness and honesty-humility were less likely to feel the negative effects of cultural tightness or to return early to their home country. These results may help ensure a good fit between individuals’ personalities and their destination culture, which will increase the benefits of the rapid increase in international mobility. Do infants remember conceptual information about an object (e.g., the object is a ball) even when they do not remember perceptual information (e.g., the object is round and green)? This study indicates that they do. Six-month-old infants were familiarized with a yellow and red striped ball and a doll’s head with brown skin and eyes. The two objects were then hidden one at a time in separate locations. One of the objects then reappeared at the location where the first object was hidden; critically, this object could be the same one that had been hidden there or the other object. The experimenters measured the time that infants spent looking at this object. Infants looked longer when the object had been swapped, indicating that they remembered the hidden object’s conceptual information. This effect did not occur when the doll’s head was inverted and therefore not processed as a face. It also did not occur when the ball was swapped for a green ball with red polka dots or when the doll’s head was swapped for a doll’s head with pink skin and blue eyes, indicating that infants’ memory for the first object hidden relied on conceptual details (e.g., is the object a ball or a head?) but not on perceptual details (e.g., does the object have brown or blue eyes?). These results suggest that infants may encode the conceptual category of a hidden object, even when perceptual features are lost. Mind wandering, which involves thoughts that are both independent from the task at hand and different from one’s previous thoughts on the matter, can generate creative ideas experienced as “aha” moments, this study suggests. Every day for 1 or 2 weeks, physicists and writers listed their most important creative idea of the day, described what they were thinking and doing when the idea occurred, and rated the importance of the idea and whether it felt like an “aha” moment or not. Participants reported that about 20% of their most important ideas occurred when their minds were wandering, and these ideas were rated as being equally important and creative as the ideas formed while working on task. After 3 or 6 months, they rated all these previous ideas as slightly more creative but less important. Overall, ideas generated during mind wandering were more likely to be rated as “aha” moments, compared with ideas generated while working. Hence, profession-related ideas that occur outside of work when people are not thinking about the topic can be inventive and create sudden insights, showing a positive side of mind wandering.
A store recently launched its heritage bridal collection at a star property in central Delhi. The fash frat attended the fashion show over high tea. We saw Narendra Kumar, Poonam Bhagat, publisher Archana Pillai, Kavita Bhartia, Aki Narula, Fleur Xavier, Deepika Jindal and Anisha Munjal among others. Take a look
Here’s just the thing for the people who love their classical arts. ICCR, Sangeet Natak, Academy and Kalahetu presents Windows Into Indian Dance 2013 – a series of programmes celebrating nature through Indian music and dance. The evening will witness performances by several well known names in Indian dance and music including – Parveen Gangani (Kathak), Mukesh Gangani (Kathak), Kalpana Verma (Sufi Kathak) and the group Kalahetu and vocalist Fareed Hassan. WHEN: 7 August, 6:30 om onwards WHERE: ICCR, Azad Bhavan
Dresden police on Sunday said they had received information from federal and state counterparts indicating a “concrete threat” against the right-wing populist group “Patriotic Europeans Against the Islamisation of the Occident”.There had been calls for would-be “assassins to mingle among the protesters and to murder an individual member of the organising team of the PEGIDA demonstrations”, police said in a notice on the 24-hour ban.This was consistent with “an Arabic-language Tweet that called the PEGIDA demonstrations an enemy of Islam,” it said. Also Read – Pro-Govt supporters rally as Hong Kong’s divisions deepenThe PEGIDA marches — which have voiced anger against Islam and “criminal asylum seekers” and vented a host of other grievances — began in Dresden in October with several hundred supporters and have since steadily grown.They drew a record 25,000 people last Monday, in the wake of the attacks by radical Islamists in Paris in which 17 people were killed.Also last Monday, some 100,000 Germans marched in nationwide counter-demonstrations against PEGIDA. Also Read – Pak Army ‘fully prepared’ to face any challenge: Army spokesmanDresden police said that after the latest information “and given the characteristics of terrorist attacks, we must assume the use of homicidal means and an immediate threat to life and limb of all participants of the demonstrations.”Because there were no individual suspects, Dresden police said it saw no alternative to the temporary suspension of the constitutional right to free assembly within city limits.However, PEGIDA earlier told its followers on Facebook that its 13th planned rally had been scrapped, citing a threat from the Islamic State jihadist group, and portraying the cancellation as its own decision. “What in police jargon is called an ‘abstract threat’ has changed to a ‘concrete death threat’ against a member of the organising team. IS terrorists have ordered his assassination,” it said in a statement.It had decided to call off the Dresden event as it could not guarantee the security of marchers and feared “collateral damage”.In a later press release, it said that after having failed to agree with police on a way to secure the march, it had “considered it irresponsible to expose our sympathisers and our city to incalculable risks.”
Incoming England and Wales Cricket Board (ECB) chairman Colin Graves has given Kevin Pietersen a glimmer of hope that he may yet be able to resurrect his England career. Pietersen, 34, has not played for England since the ECB effectively called time on his international career following the disastrous Ashes tour of 2013-14.But with England toiling at the World Cup and Pietersen having spoken of his eagerness to return to the team, Graves has suggested that a return to English county cricket could open the door for a dramatic comeback. “The first thing he has to do if he wants to get back is start playing county cricket. The selectors and the coaches are not going to pick him if he’s not playing. It’s as simple as that. I’ll leave it at that,” Graves told BBC Radio 5 on Sunday. Also Read – Khel Ratna for Deepa and Bajrang, Arjuna for JadejaPietersen is currently without a county after leaving Surrey and although Graves is not an ECB selector, he believes a county return would help the outspoken South Africa-born batsman’s cause. Asked if he was in favour of Pietersen returning for England, Graves replied: “At the end of the day it’s down to the selectors and coaches and what they feel is best for English cricket. They will make the decisions and I will support their decisions.”
“We are the first state government in the country which has decided to legalise hawking. This will ensure you are not evicted by anybody. We have formulated a policy for the hawkers. We are the first in the country to start the process of registering vendors and hawkers,” Banerjee said after a meeting with hawkers. Banerjee said the process of registration will begin on July 15 and continue for three months, and dedicated counters will be set up for the process.”The process of verifying the applications will be carried outfirst. Once, verified, you will be given a registration certificate and free trade licence. But this facility is available only for the existing hawkers,” announcedBanerjee. Also Read – Need to understand why law graduate’s natural choice is not legal profession: CJIThe whole process will be monitored by a committee comprising the KMC, the state Government and the police. The Chief Minister also urged the hawkers not to encroach on the shop keepers or inconvenience pedestrians. About 5000 licensed shopkeepers—on strike in the New market area–have been contending that it was becoming difficult for them to stay in business as hawkers, apart from competing with cheaper goods, block shop facades preventing the entry of shoppers in the market.
With Bollywood films now exploring new heights in terms of domestic and overseas incomes, which are soaring sky-high, is it hard to analyse the success and popularity of Indian film-making business? The latest example of proliferation of Bollywood films in Australia is explained by Pat Fiske, where she said that the aboriginal community of Ramingining in northern Australia