Optically switchable photonic metasurfaces

DOE Office of Scientific and Technical Information (OSTI.GOV)

Waters, R. F.; MacDonald, K. F.; Hobson, P. A.

2015-08-24

We experimentally demonstrate an optically switchable gallium-based metasurface, in which a reversible light-induced transition between solid and liquid phases occurring in a confined nanoscale surface layer of the metal drives significant changes in reflectivity and absorption. The metasurface architecture resonantly enhances the metal's “active plasmonic” phase-change nonlinearity by an order of magnitude, offering high contrast all-optical switching in the near-infrared range at low, μW μm{sup −2}, excitation intensities.

Stimuli-Responsive DNA-Based Hydrogels: From Basic Principles to Applications.

PubMed

Kahn, Jason S; Hu, Yuwei; Willner, Itamar

2017-04-18

The base sequence of nucleic acids encodes structural and functional information into the DNA biopolymer. External stimuli such as metal ions, pH, light, or added nucleic acid fuel strands provide triggers to reversibly switch nucleic acid structures such as metal-ion-bridged duplexes, i-motifs, triplex nucleic acids, G-quadruplexes, or programmed double-stranded hybrids of oligonucleotides (DNA). The signal-triggered oligonucleotide structures have been broadly applied to develop switchable DNA nanostructures and DNA machines, and these stimuli-responsive assemblies provide functional scaffolds for the rapidly developing area of DNA nanotechnology. Stimuli-responsive hydrogels undergoing signal-triggered hydrogel-to-solution transitions or signal-controlled stiffness changes attract substantial interest as functional matrices for controlled drug delivery, materials exhibiting switchable mechanical properties, acting as valves or actuators, and "smart" materials for sensing and information processing. The integration of stimuli-responsive oligonucleotides with hydrogel-forming polymers provides versatile means to exploit the functional information encoded in the nucleic acid sequences to yield stimuli-responsive hydrogels exhibiting switchable physical, structural, and chemical properties. Stimuli-responsive DNA-based nucleic acid structures are integrated in acrylamide polymer chains and reversible, switchable hydrogel-to-solution transitions of the systems are demonstrated by applying external triggers, such as metal ions, pH-responsive strands, G-quadruplex, and appropriate counter triggers that bridge and dissociate the polymer chains. By combining stimuli-responsive nucleic acid bridges with thermosensitive poly(N-isopropylacrylamide) (pNIPAM) chains, systems undergoing reversible solution ↔ hydrogel ↔ solid transitions are demonstrated. Specifically, by bridging acrylamide polymer chains by two nucleic acid functionalities, where one type of bridging unit provides a stimuli-responsive element and the second unit acts as internal "bridging memory", shape-memory hydrogels undergoing reversible and switchable transitions between shaped hydrogels and shapeless quasi-liquid states are demonstrated. By using stimuli-responsive hydrogel cross-linking units that can assemble the bridging units by two different input signals, the orthogonally-triggered functions of the shape-memory were shown. Furthermore, a versatile approach to assemble stimuli-responsive DNA-based acrylamide hydrogel films on surfaces is presented. The method involves the activation of the hybridization chain-reaction (HCR) by a surface-confined promoter strand, in the presence of acrylamide chains modified with two DNA hairpin structures and appropriate stimuli-responsive tethers. The resulting hydrogel-modified surfaces revealed switchable stiffness properties and signal-triggered catalytic functions. By applying the method to assemble the hydrogel microparticles, substrate-loaded, stimuli-responsive microcapsules are prepared. The signal-triggered DNA-based hydrogel microcapsules are applied as drug carriers for controlled release. The different potential applications and future perspectives of stimuli responsive hydrogels are discussed. Specifically, the use of these smart materials and assemblies as carriers for controlled drug release and as shape-memory matrices for information storage and inscription and the use of surface-confined stimuli-responsive hydrogels, exhibiting switchable stiffness properties, for catalysis and controlled growth of cells are discussed.

Temperature-Switchable Agglomeration of Magnetic Particles Designed for Continuous Separation Processes in Biotechnology.

PubMed

Paulus, Anja S; Heinzler, Raphael; Ooi, Huey Wen; Franzreb, Matthias

2015-07-08

The purpose of this work was the synthesis and characterization of thermally switchable magnetic particles for use in biotechnological applications such as protein purification and enzymatic conversions. Reversible addition-fragmentation chain-transfer polymerization was employed to synthesize poly(N-isopropylacrylamide) brushes via a "graft-from" approach on the surface of magnetic microparticles. The resulting particles were characterized by infrared spectroscopy and thermogravimetric analysis and their temperature-dependent agglomeration behavior was assessed. The influence of several factors on particle agglomeration (pH, temperature, salt type, and particle concentration) was evaluated. The results showed that a low pH value (pH 3-4), a kosmotropic salt (ammonium sulfate), and a high particle concentration (4 g/L) resulted in improved agglomeration at elevated temperature (40 °C). Recycling of particles and reversibility of the temperature-switchable agglomeration were successfully demonstrated for ten heating-cooling cycles. Additionally, enhanced magnetic separation was observed for the modified particles. Ionic monomers were integrated into the polymer chain to create end-group functionalized particles as well as two- and three-block copolymer particles for protein binding. The adsorption of lactoferrin, bovine serum albumin, and lysozyme to these ion exchange particles was evaluated and showed a binding capacity of up to 135 mg/g. The dual-responsive particles combined magnetic and thermoresponsive properties for switchable agglomeration, easy separability, and efficient protein adsorption.

An Electrically Switchable Metal-Organic Framework

DOE Office of Scientific and Technical Information (OSTI.GOV)

Fernandez, CA; Martin, PC; Schaef, T

2014-08-19

Crystalline metal organic framework (MOF) materials containing interconnected porosity can be chemically modified to promote stimulus-driven (light, magnetic or electric fields) structural transformations that can be used in a number of devices. Innovative research strategies are now focused on understanding the role of chemical bond manipulation to reversibly alter the free volume in such structures of critical importance for electro-catalysis, molecular electronics, energy storage technologies, sensor devices and smart membranes. In this letter, we study the mechanism for which an electrically switchable MOF composed of Cu(TCNQ) (TCNQ = 7,7,8,8-tetracyanoquinodimethane) transitions from a high-resistance state to a conducting state in amore » reversible fashion by an applied potential. The actual mechanism for this reversible electrical switching is still not understood even though a number of reports are available describing the application of electric-field-induced switching of Cu(TCNQ) in device fabrication.« less

An Electrically Switchable Metal-Organic Framework

DOE Office of Scientific and Technical Information (OSTI.GOV)

Fernandez, Carlos A.; Martin, Paul F.; Schaef, Herbert T.

2014-08-19

Crystalline metal organic framework (MOF) materials containing interconnected porosity can be chemically modified to promote stimulus-driven (light, magnetic or electric fields) structural transformations that can be used in a number of devices. Innovative research strategies are now focused on understanding the role of chemical bond manipulation to reversibly alter the free volume in such structures of critical importance for electro-catalysis, molecular electronics, energy storage technologies, sensor devices and smart membranes. In this letter, we study the mechanism for which an electrically switchable MOF composed of Cu(TCNQ) (TCNQ 5 7,7,8,8-tetracyanoquinodimethane) transitions from a high-resistance state to a conducting state in amore » reversible fashion by an applied potential. The actual mechanism for this reversible electrical switching is still not understood even though a number of reports are available describing the application of electric-field-induced switching of Cu(TCNQ) in device fabrication.« less

An Electrically Switchable Metal-Organic Framework

NASA Astrophysics Data System (ADS)

Fernandez, Carlos A.; Martin, Paul C.; Schaef, Todd; Bowden, Mark E.; Thallapally, Praveen K.; Dang, Liem; Xu, Wu; Chen, Xilin; McGrail, B. Peter

2014-08-01

Crystalline metal organic framework (MOF) materials containing interconnected porosity can be chemically modified to promote stimulus-driven (light, magnetic or electric fields) structural transformations that can be used in a number of devices. Innovative research strategies are now focused on understanding the role of chemical bond manipulation to reversibly alter the free volume in such structures of critical importance for electro-catalysis, molecular electronics, energy storage technologies, sensor devices and smart membranes. In this letter, we study the mechanism for which an electrically switchable MOF composed of Cu(TCNQ) (TCNQ = 7,7,8,8-tetracyanoquinodimethane) transitions from a high-resistance state to a conducting state in a reversible fashion by an applied potential. The actual mechanism for this reversible electrical switching is still not understood even though a number of reports are available describing the application of electric-field-induced switching of Cu(TCNQ) in device fabrication.

Adhesion of Chlamydomonas microalgae to surfaces is switchable by light

NASA Astrophysics Data System (ADS)

Kreis, Christian Titus; Le Blay, Marine; Linne, Christine; Makowski, Marcin Michal; Bäumchen, Oliver

2018-01-01

Microalgae are photoactive microbes that live in liquid-infused environments, such as soil, temporary pools and rocks, where they encounter and colonize a plethora of surfaces. Their photoactivity manifests itself in a variety of processes, including light-directed motility (phototaxis), the growth of microalgal populations, and their photosynthetic machinery. Although microbial responses to light have been widely recognized, any influence of light on cell-surface interactions remains elusive. Here, we reveal that the unspecific adhesion of microalgae to surfaces can be reversibly switched on and off by light. Using a micropipette force spectroscopy technique, we measured in vivo single-cell adhesion forces and show that the microalga's flagella provide light-switchable adhesive contacts with the surface. This light-induced adhesion to surfaces is an active and completely reversible process that occurs on a timescale of seconds. Our results suggest that light-switchable adhesiveness is a natural functionality of microalgae to regulate the transition between the planktonic and the surface-associated state, which yields an adhesive adaptation to optimize the photosynthetic efficiency in conjunction with phototaxis.

A microfluidic study of liquid-liquid extraction mediated by carbon dioxide.

PubMed

Lestari, Gabriella; Salari, Alinaghi; Abolhasani, Milad; Kumacheva, Eugenia

2016-07-05

Liquid-liquid extraction is an important separation and purification method; however, it faces a challenge in reducing the energy consumption and the environmental impact of solvent (extractant) recovery. The reversible chemical reactions of switchable solvents (nitrogenous bases) with carbon dioxide (CO2) can be implemented in reactive liquid-liquid extraction to significantly reduce the cost and energy requirements of solvent recovery. The development of new effective switchable solvents reacting with CO2 and the optimization of extraction conditions rely on the ability to evaluate and screen the performance of switchable solvents in extraction processes. We report a microfluidic strategy for time- and labour-efficient studies of CO2-mediated solvent extraction. The platform utilizes a liquid segment containing an aqueous extractant droplet and a droplet of a solution of a switchable solvent in a non-polar liquid, with gaseous CO2 supplied to the segment from both sides. Following the reaction of the switchable solvent with CO2, the solvent becomes hydrophilic and transfers from the non-polar solvent to the aqueous droplet. By monitoring the time-dependent variation in droplet volumes, we determined the efficiency and extraction time for the CO2-mediated extraction of different nitrogenous bases in a broad experimental parameter space. The platform enables a significant reduction in the amount of switchable solvents used in these studies, provides accurate temporal characterization of the liquid-liquid extraction process, and offers the capability of high-throughput screening of switchable solvents.

Gadolinium nanoparticle based switchable mirrors: quenching of hydrogenation-dehydrogenation hysteresis.

PubMed

Aruna, I; Mehta, B R; Malhotra, L K

2007-06-01

A continuous and reversible 'structural, optical, and electronic' transition between the reflecting metallic dihydride and transparent semiconducting trihydride states observed in rare earth metals on hydrogenation make these materials and their hydrides suitable for switchable mirror, sensing, and other technological applications. Recently Pd capped Gd nanoparticle based 'new generation' switchable mirrors have been fabricated with extended color neutrality, better optical contrast, and faster kinetics in comparison to the polycrystalline, epitaxial, alloy, and multilayer films. The present report aims at investigating the effect of nanoparticle nature on the hydrogenation-dehydrogenation hysteresis in switchable mirrors by carrying out in situ measurement of optical transmittance and electrode potentials during electrochemical hydrogen loading-deloading of Gd nanoparticle samples. Interestingly, Gd nanoparticle samples were observed to exhibit quenched hysteresis. The quenching of hysteresis in hydrogen-induced properties has been attributed to the absence of structural transition upon hydrogenation, reduction in topographical interlocking of the grains and elimination of lateral clamping of the slack nanoparticle layer to the substrate.

Giant switchable photovoltaic effect in organometal trihalide perovskite devices

DOE PAGES

Xiao, Zhengguo; Yuan, Yongbo; Shao, Yuchuan; ...

2014-12-08

Organolead trihalide perovskite (OTP) materials are emerging as naturally abundant materials for low-cost, solution-processed and highly efficient solar cells. Here, we show that, in OTP-based photovoltaic devices with vertical and lateral cell configurations, the photocurrent direction can be switched repeatedly by applying a small electric field of <1 V μm –1. The switchable photocurrent, generally observed in devices based on ferroelectric materials, reached 20.1 mA cm –2 under one sun illumination in OTP devices with a vertical architecture, which is four orders of magnitude larger than that measured in other ferroelectric photovoltaic devices. This field-switchable photovoltaic effect can be explainedmore » by the formation of reversible p–i–n structures induced by ion drift in the perovskite layer. Furthermore, the demonstration of switchable OTP photovoltaics and electric-field-manipulated doping paves the way for innovative solar cell designs and for the exploitation of OTP materials in electrically and optically readable memristors and circuits.« less

Borophene as a Promising Material for Charge-Modulated Switchable CO2 Capture.

PubMed

Tan, Xin; Tahini, Hassan A; Smith, Sean C

2017-06-14

Ideal carbon dioxide (CO 2 ) capture materials for practical applications should bind CO 2 molecules neither too weakly to limit good loading kinetics nor too strongly to limit facile release. Although charge-modulated switchable CO 2 capture has been proposed to be a controllable, highly selective, and reversible CO 2 capture strategy, the development of a practical gas-adsorbent material remains a great challenge. In this study, by means of density functional theory (DFT) calculations, we have examined the possibility of conductive borophene nanosheets as promising sorbent materials for charge-modulated switchable CO 2 capture. Our results reveal that the binding strength of CO 2 molecules on negatively charged borophene can be significantly enhanced by injecting extra electrons into the adsorbent. At saturation CO 2 capture coverage, the negatively charged borophene achieves CO 2 capture capacities up to 6.73 × 10 14 cm -2 . In contrast to the other CO 2 capture methods, the CO 2 capture/release processes on negatively charged borophene are reversible with fast kinetics and can be easily controlled via switching on/off the charges carried by borophene nanosheets. Moreover, these negatively charged borophene nanosheets are highly selective for separating CO 2 from mixtures with CH 4 , H 2 , and/or N 2 . This theoretical exploration will provide helpful guidance for identifying experimentally feasible, controllable, highly selective, and high-capacity CO 2 capture materials with ideal thermodynamics and reversibility.

Reversible hydrogen storage using CO2 and a proton-switchable iridium catalyst in aqueous media under mild temperatures and pressures.

PubMed

Hull, Jonathan F; Himeda, Yuichiro; Wang, Wan-Hui; Hashiguchi, Brian; Periana, Roy; Szalda, David J; Muckerman, James T; Fujita, Etsuko

2012-03-18

Green plants convert CO(2) to sugar for energy storage via photosynthesis. We report a novel catalyst that uses CO(2) and hydrogen to store energy in formic acid. Using a homogeneous iridium catalyst with a proton-responsive ligand, we show the first reversible and recyclable hydrogen storage system that operates under mild conditions using CO(2), formate and formic acid. This system is energy-efficient and green because it operates near ambient conditions, uses water as a solvent, produces high-pressure CO-free hydrogen, and uses pH to control hydrogen production or consumption. The extraordinary and switchable catalytic activity is attributed to the multifunctional ligand, which acts as a proton-relay and strong π-donor, and is rationalized by theoretical and experimental studies.

Utilizing stretch-tunable thermochromic elastomeric opal films as novel reversible switchable photonic materials.

PubMed

Schäfer, Christian G; Lederle, Christina; Zentel, Kristina; Stühn, Bernd; Gallei, Markus

2014-11-01

In this work, the preparation of highly thermoresponsive and fully reversible stretch-tunable elastomeric opal films featuring switchable structural colors is reported. Novel particle architectures based on poly(diethylene glycol methylether methacrylate-co-ethyl acrylate) (PDEGMEMA-co-PEA) as shell polymer are synthesized via seeded and stepwise emulsion polymerization protocols. The use of DEGMEMA as comonomer and herein established synthetic strategies leads to monodisperse soft shell particles, which can be directly processed to opal films by using the feasible melt-shear organization technique. Subsequent UV crosslinking strategies open access to mechanically stable and homogeneous elastomeric opal films. The structural colors of the opal films feature mechano- and thermoresponsiveness, which is found to be fully reversible. Optical characterization shows that the combination of both stimuli provokes a photonic bandgap shift of more than 50 nm from 560 nm in the stretched state to 611 nm in the fully swollen state. In addition, versatile colorful patterns onto the colloidal crystal structure are produced by spatial UV-induced crosslinking by using a photomask. This facile approach enables the generation of spatially cross-linked switchable opal films with fascinating optical properties. Herein described strategies for the preparation of PDEGMEMA-containing colloidal architectures, application of the melt-shear ordering technique, and patterned crosslinking of the final opal films open access to novel stimuli-responsive colloidal crystal films, which are expected to be promising materials in the field of security and sensing applications. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Matsuo, Hiroki; Kitanaka, Yuuki; Inoue, Ryotaro

We investigate the mechanism of a switchable diode behavior observed in ferroelectric SrRuO{sub 3}/BiFeO{sub 3} (BFO)/SrRuO{sub 3} capacitors. We experimentally demonstrate that the switchable diode effect observed in the capacitors is induced by the polarization reversal in the BFO film. The conductivity in an Ohmic region in different oxidation states provides direct evidence that electron hole acts as the majority carrier, delivering p-type conduction. Density functional theory (DFT) calculations show that the p-type conduction arises from an unoccupied gap state of Fe{sup 4+} in an FeO{sub 5} pyramid which is derived from Bi vacancy. Our experimental and DFT study leadsmore » to the conclusion that the switchable diode effect originates from an asymmetric band bending in the top and bottom depletion layers modulated by ferroelectric polarization and oxygen vacancies.« less

Switchable cucurbituril-bipyridine beacons.

PubMed

Sinha, Mantosh K; Reany, Ofer; Parvari, Galit; Karmakar, Ananta; Keinan, Ehud

2010-08-09

4-Aminobipyridine derivatives form strong inclusion complexes with cucurbit[6]uril, exhibiting remarkably large enhancements in fluorescence intensity and quantum yields. The remarkable complexation-induced pK(a) shift (DeltapK(a)=3.3) highlights the strong charge-dipole interaction upon binding. The reversible binding phenomenon can be used for the design of switchable beacons that can be incorporated into cascades of binding networks. This concept is demonstrated herein by three different applications: 1) a switchable fluorescent beacon for chemical sensing of transition metals and other ligands; 2) direct measurement of binding constants between cucurbit[6]uril and various nonfluorescent guest molecules; and 3) quantitative monitoring of biocatalytic reactions and determination of their kinetic parameters. The latter application is illustrated by the hydrolysis of an amide catalyzed by penicillin G acylase and by the elimination reaction of a beta-cabamoyloxy ketone catalyzed by aldolase antibody 38C2.

Highly Sensitive Switchable Heterojunction Photodiode Based on Epitaxial Bi2FeCrO6 Multiferroic Thin Films.

PubMed

Huang, Wei; Chakrabartty, Joyprokash; Harnagea, Catalin; Gedamu, Dawit; Ka, Ibrahima; Chaker, Mohamed; Rosei, Federico; Nechache, Riad

2018-04-18

Perovskite multiferroic oxides are promising materials for the realization of sensitive and switchable photodiodes because of their favorable band gap (<3.0 eV), high absorption coefficient, and tunable internal ferroelectric (FE) polarization. A high-speed switchable photodiode based on multiferroic Bi 2 FeCrO 6 (BFCO)/SrRuO 3 (SRO)-layered heterojunction was fabricated by pulsed laser deposition. The heterojunction photodiode exhibits a large ideality factor ( n = ∼5.0) and a response time as fast as 68 ms, thanks to the effective charge carrier transport and collection at the BFCO/SRO interface. The diode can switch direction when the electric polarization is reversed by an external voltage pulse. The time-resolved photoluminescence decay of the device measured at ∼500 nm demonstrates an ultrafast charge transfer (lifetime = ∼6.4 ns) in BFCO/SRO heteroepitaxial structures. The estimated responsivity value at 500 nm and zero bias is 0.38 mA W -1 , which is so far the highest reported for any FE thin film photodiode. Our work highlights the huge potential for using multiferroic oxides to fabricate highly sensitive and switchable photodiodes.

Improved performance of Mg-Y alloy thin film switchable mirrors after coating with a superhydrophobic surface

NASA Astrophysics Data System (ADS)

La, Mao; Zhou, Huaijuan; Li, Ning; Xin, Yunchuan; Sha, Ren; Bao, Shanhu; Jin, Ping

2017-05-01

The magnesium based switchable mirrors can reversibly change their optical properties between the transparent and the reflective state as a result of hydrogenation and dehydrogenation. These films can potentially be applied as new energy-saving windows, by controlling the transmittance of solar radiation through the regulation of their reflective state. In this study, magnesium-yttrium (Mg-Y) alloy thin films were prepared using a DC magnetron sputtering method. However, the luminous transmittance in the transparent state and the switching durability of switchable mirrors are too poor to satisfy practical demands. In order to improve the films switching durability, luminous transmittance and the surface functionalization, polytetrafluoroethylene (PTFE) was coated with thermal vacuum deposition for use as the top layer of Mg-Y/Pd switchable mirrors. The PTFE layer had a porous network structure and exhibited a superhydrophobic surface with a water contact angle of approximately 152°. By characterization, PTFE thin films shows the excellent protection role against the oxidization of Mg, the switching durability of the films were improved 3 times, and also shows the antireflection role the luminous transmission of films was enhanced by 7% through the top covered with PTFE.

Conductive Graphitic Carbon Nitride as an Ideal Material for Electrocatalytically Switchable CO2 Capture

PubMed Central

Tan, Xin; Kou, Liangzhi; Tahini, Hassan A.; Smith, Sean C.

2015-01-01

Good electrical conductivity and high electron mobility of the sorbent materials are prerequisite for electrocatalytically switchable CO2 capture. However, no conductive and easily synthetic sorbent materials are available until now. Here, we examined the possibility of conductive graphitic carbon nitride (g-C4N3) nanosheets as sorbent materials for electrocatalytically switchable CO2 capture. Using first-principle calculations, we found that the adsorption energy of CO2 molecules on g-C4N3 nanosheets can be dramatically enhanced by injecting extra electrons into the adsorbent. At saturation CO2 capture coverage, the negatively charged g-C4N3 nanosheets achieve CO2 capture capacities up to 73.9 × 1013 cm−2 or 42.3 wt%. In contrast to other CO2 capture approaches, the process of CO2 capture/release occurs spontaneously without any energy barriers once extra electrons are introduced or removed, and these processes can be simply controlled and reversed by switching on/off the charging voltage. In addition, these negatively charged g-C4N3 nanosheets are highly selective for separating CO2 from mixtures with CH4, H2 and/or N2. These predictions may prove to be instrumental in searching for a new class of experimentally feasible high-capacity CO2 capture materials with ideal thermodynamics and reversibility. PMID:26621618

Switchable photosystem-II designer algae for photobiological hydrogen production

DOEpatents

Lee, James Weifu

2010-01-05

A switchable photosystem-II designer algae for photobiological hydrogen production. The designer transgenic algae includes at least two transgenes for enhanced photobiological H.sub.2 production wherein a first transgene serves as a genetic switch that can controls photosystem II (PSII) oxygen evolution and a second transgene encodes for creation of free proton channels in the algal photosynthetic membrane. In one embodiment, the algae includes a DNA construct having polymerase chain reaction forward primer (302), a inducible promoter (304), a PSII-iRNA sequence (306), a terminator (308), and a PCR reverse primer (310). In other embodiments, the PSII-iRNA sequence (306) is replaced with a CF.sub.1-iRNA sequence (312), a streptomycin-production gene (314), a targeting sequence (316) followed by a proton-channel producing gene (318), or a PSII-producing gene (320). In one embodiment, a photo-bioreactor and gas-product separation and utilization system produce photobiological H.sub.2 from the switchable PSII designer alga.

Switchable photovoltaic windows enabled by reversible photothermal complex dissociation from methylammonium lead iodide

DOE PAGES

Wheeler, Lance M.; Moore, David T.; Ihly, Rachelle; ...

2017-11-23

Materials with switchable absorption properties have been widely used for smart window applications to reduce energy consumption and enhance occupant comfort in buildings. In this work, we combine the benefits of smart windows with energy conversion by producing a photovoltaic device with a switchable absorber layer that dynamically responds to sunlight. Upon illumination, photothermal heating switches the absorber layer - composed of a metal halide perovskite-methylamine complex - from a transparent state (68% visible transmittance) to an absorbing, photovoltaic colored state (less than 3% visible transmittance) due to dissociation of methylamine. After cooling, the methylamine complex is re-formed, returning themore » absorber layer to the transparent state in which the device acts as a window to visible light. The thermodynamics of switching and performance of the device are described. In conclusion, this work validates a photovoltaic window technology that circumvents the fundamental tradeoff between efficient solar conversion and high visible light transmittance that limits conventional semitransparent PV window designs.« less

Adhesion of Photoactive Microalgae to Surfaces is Switchable by Light

NASA Astrophysics Data System (ADS)

Bäumchen, Oliver; Kreis, Christian; Le Blay, Marine; Linne, Christine; Makowski, Marcin

The natural habitats of many microorganisms are confined geometries, such as the interstitial space of rocks and soil, where interactions with interfaces and surfaces are of paramount importance. We performed in vivo force spectroscopy experiments on the unicellular biflagellated microalga Chlamydomonas, a prime model organism in cell- and microbiology, and discovered that the flagella-mediated adhesion to surfaces can be switched on and off by light. Time-resolved micropipette experiments show that the light-switchable adhesiveness of the flagella is a completely reversible process that is based on a redistribution of adhesion-promoting flagella-membrane proteins within seconds. Light-switchable adhesion enables the cell to regulate the transition between planktonic and surface-associated state, which possibly represents a significant biological advantage for photoactive microorganisms. In terms of the colonization of surfaces and the formation of biofilms, the findings might have immediate economic and environmental relevance in biotechnological settings, such as photo-bioreactors for the sustainable production of biofuels.

Switchable photovoltaic windows enabled by reversible photothermal complex dissociation from methylammonium lead iodide.

PubMed

Wheeler, Lance M; Moore, David T; Ihly, Rachelle; Stanton, Noah J; Miller, Elisa M; Tenent, Robert C; Blackburn, Jeffrey L; Neale, Nathan R

2017-11-23

Materials with switchable absorption properties have been widely used for smart window applications to reduce energy consumption and enhance occupant comfort in buildings. In this work, we combine the benefits of smart windows with energy conversion by producing a photovoltaic device with a switchable absorber layer that dynamically responds to sunlight. Upon illumination, photothermal heating switches the absorber layer-composed of a metal halide perovskite-methylamine complex-from a transparent state (68% visible transmittance) to an absorbing, photovoltaic colored state (less than 3% visible transmittance) due to dissociation of methylamine. After cooling, the methylamine complex is re-formed, returning the absorber layer to the transparent state in which the device acts as a window to visible light. The thermodynamics of switching and performance of the device are described. This work validates a photovoltaic window technology that circumvents the fundamental tradeoff between efficient solar conversion and high visible light transmittance that limits conventional semitransparent PV window designs.

Switchable photovoltaic windows enabled by reversible photothermal complex dissociation from methylammonium lead iodide

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wheeler, Lance M.; Moore, David T.; Ihly, Rachelle

Materials with switchable absorption properties have been widely used for smart window applications to reduce energy consumption and enhance occupant comfort in buildings. In this work, we combine the benefits of smart windows with energy conversion by producing a photovoltaic device with a switchable absorber layer that dynamically responds to sunlight. Upon illumination, photothermal heating switches the absorber layer - composed of a metal halide perovskite-methylamine complex - from a transparent state (68% visible transmittance) to an absorbing, photovoltaic colored state (less than 3% visible transmittance) due to dissociation of methylamine. After cooling, the methylamine complex is re-formed, returning themore » absorber layer to the transparent state in which the device acts as a window to visible light. The thermodynamics of switching and performance of the device are described. In conclusion, this work validates a photovoltaic window technology that circumvents the fundamental tradeoff between efficient solar conversion and high visible light transmittance that limits conventional semitransparent PV window designs.« less

Reversible optical switching of highly confined phonon-polaritons with an ultrathin phase-change material

NASA Astrophysics Data System (ADS)

Li, Peining; Yang, Xiaosheng; Maß, Tobias W. W.; Hanss, Julian; Lewin, Martin; Michel, Ann-Katrin U.; Wuttig, Matthias; Taubner, Thomas

2016-08-01

Surface phonon-polaritons (SPhPs), collective excitations of photons coupled with phonons in polar crystals, enable strong light-matter interaction and numerous infrared nanophotonic applications. However, as the lattice vibrations are determined by the crystal structure, the dynamical control of SPhPs remains challenging. Here, we realize the all-optical, non-volatile, and reversible switching of SPhPs by controlling the structural phase of a phase-change material (PCM) employed as a switchable dielectric environment. We experimentally demonstrate optical switching of an ultrathin PCM film (down to 7 nm, <λ/1,200) with single laser pulses and detect ultra-confined SPhPs (polariton wavevector kp > 70k0, k0 = 2π/λ) in quartz. Our proof of concept allows the preparation of all-dielectric, rewritable SPhP resonators without the need for complex fabrication methods. With optimized materials and parallelized optical addressing we foresee application potential for switchable infrared nanophotonic elements, for example, imaging elements such as superlenses and hyperlenses, as well as reconfigurable metasurfaces and sensors.

Review on electrochromic devices for automotive glazing

NASA Astrophysics Data System (ADS)

Demiryont, Hulya

1991-12-01

Electrochromic materials have been intensively studied for applications of various switchable optical systems. These materials exhibit adjustable optical absorption upon reversible oxidation/reduction processes. Since a reversible oxidation/reduction phenomenon is provided by electrically-driven electrochemical reactions, these materials are known as electrochromics. There are many publications including proceedings, books, and review articles written on electrochromic (EC) materials and their applications. This paper focuses on conventional and some new electrochromic devices (ECD), their specifications, and applications.

All-Silicon Switchable Magnetoelectric Effect through Interlayer Exchange Coupling.

PubMed

Liu, Hang; Sun, Jia-Tao; Fu, Hui-Xia; Sun, Pei-Jie; Feng, Y P; Meng, Sheng

2017-07-19

The magnetoelectric (ME) effect originating from the effective coupling between electric field and magnetism is an exciting frontier in nanoscale science such as magnetic tunneling junction (MTJ), ferroelectric/piezoelectric heterojunctions etc. The realization of switchable ME effect under external electric field in d0 semiconducting materials of single composition is needed especially for all-silicon spintronics applications because of its natural compatibility with current industry. We employ density functional theory (DFT) to reveal that the pristine Si(111)-3×3 R30° (Si3 hereafter) reconstructed surfaces of thin films with a thickness smaller than eleven bilayers support a sizeable linear ME effect with switchable direction of magnetic moment under external electric field. This is achieved through the interlayer exchange coupling effect in the antiferromagnetic regime, where the spin-up and spin-down magnetized density is located on opposite surfaces of Si3 thin films. The obtained coefficient for the linear ME effect can be four times larger than that of ferromagnetic Fe films, which fail to have the reversal switching capabilities. The larger ME effect originates from the spin-dependent screening of the spin-polarized Dirac fermion. The prediction will promote the realization of well-controlled and switchable data storage in all-silicon electronics. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

A facile route to steady redox-modulated nitroxide spin-labeled surfaces based on diazonium chemistry.

PubMed

Cougnon, Charles; Boisard, Séverine; Cador, Olivier; Dias, Marylène; Levillain, Eric; Breton, Tony

2013-05-18

A TEMPO derivative was covalently grafted onto carbon and gold surfaces via the diazonium chemistry. The acid-dependent redox properties of the nitroxyl group were exploited to elaborate electro-switchable magnetic surfaces. ESR characterization demonstrated the reversible and permanent magnetic character of the material.

Layer by layer assembled films between hemoglobin and multiwall carbon nanotubes for pH-switchable biosensing.

PubMed

Pan, Zhongqin; Liu, Xiaojun; Xie, Jing; Bao, Ning; He, Hong; Li, Xiaodong; Zeng, Jiang; Gu, Haiying

2015-05-01

Although pH-switchable behaviors have been reported based on multilayer films modified electrodes, their pH-switchable biosensing is still difficult due to the existence of the electroactive mediator. In this study, we report the pH-dependable determination of hydrogen peroxide (H2O2) based on a four-bilayer film fabricated through layer by layer assembly between hemoglobin (Hb) and multiwall carbon nanotubes (MWCNTs). We observed that response of electroactive probe Fe(CN)6(3-) at the multilayer films was very sensitive and reversible to pH values of phosphate buffer solutions phosphate buffer solution with cyclic voltammetry. The reduction peak height of Fe(CN)6(3-) at the multilayer film could reach ∼221μA at pH 3.0 while 0μA at pH 9.0. The linear range for the detection of H2O2 at pH 3.0 was from 12.5μM to 10.4mM, which was much wider than that at pH 9.0. Our results demonstrated that the detection of H2O2 with the proposed modified electrode is dependent on pH values of phosphate buffer solution. Moreover, the component of multilayer films has impacts on the performance of biosensors with pH-switchable behaviors. Copyright © 2015 Elsevier B.V. All rights reserved.

Stimuli-enabled zipper-like graphene interface for auto-switchable bioelectronics.

PubMed

Mishra, Sachin; Ashaduzzaman, Md; Mishra, Prashant; Swart, Hendrik C; Turner, Anthony P F; Tiwari, Ashutosh

2017-03-15

Graphene interfaces with multi-stimuli responsiveness are of particular interest due to their diverse super-thin interfacial behaviour, which could be well suited to operating complex physiological systems in a single miniaturised domain. In general, smart graphene interfaces switch bioelectrodes from the hydrophobic to hydrophilic state, or vice versa, upon triggering. In the present work, a stimuli encoded zipper-like graphene oxide (GrO)/polymer interface was fabricated with in situ poly(N-isopropylacrylamide-co-diethylaminoethylmethylacrylate), i.e., poly(NIPAAm-co-DEAEMA) directed hierarchical self-assembly of GrO and glucose oxidase (GOx). The designed interface exhibited reversible on/off-switching of bio-electrocatalysis on changing the pH between 5 and 8, via phase transition from super hydrophilic to hydrophobic. The study further indicated that the zipper-like interfacial bioelectrochemical properties could be tuned over a modest change of temperature (i.e., 20-40°C). The resulting auto-switchable interface has implications for the design of novel on/off-switchable biodevices with 'in-built' self-control. Copyright © 2016 Elsevier B.V. All rights reserved.

Conductive properties of switchable photoluminescence thermosetting systems based on liquid crystals.

PubMed

Tercjak, Agnieszka; Gutierrez, Junkal; Ocando, Connie; Mondragon, Iñaki

2010-03-16

Conductive properties of different thermosetting materials modified with nematic 4'-(hexyl)-4-biphenyl-carbonitrile (HBC) liquid crystal and rutile TiO(2) nanoparticles were successfully studied by means of tunneling atomic force miscroscopy (TUNA). Taking into account the liquid crystal state of the HBC at room temperature, depending on both the HBC content and the presence of TiO(2) nanoparticles, designed materials showed different TUNA currents passed through the sample. The addition of TiO(2) nanoparticles into the systems multiply the detected current if compared to the thermosetting systems without TiO(2) nanoparticles and simultaneously stabilized the current passed through the sample, making the process reversible since the absolute current values were almost the same applying both negative and positive voltage. Moreover, thermosetting systems modified with liquid crystals with and without TiO(2) nanoparticles are photoluminescence switchable materials as a function of temperature gradient during repeatable heating/cooling cycle. Conductive properties of switchable photoluminescence thermosetting systems based on liquid crystals can allow them to find potential application in the field of photoresponsive devices, with a high contrast ratio between transparent and opaque states.

SWITCHABLE POLARITY SOLVENTS AS DRAW SOLUTES FOR FORWARD OSMOSIS

DOE Office of Scientific and Technical Information (OSTI.GOV)

Frederick F. Stewart; Mark L. Stone; Aaron D. Wilson

2013-03-01

Switchable polarity solvents (SPS), mixtures of carbon dioxide, water, and tertiary amines, are presented as viable forward osmosis (FO) draw solutes allowing a novel SPS FO process. In this study substantial osmotic strengths of SPS are measured with freezing point osmometry and were demonstrated to induce competitive ?uxes at high salt concentrations on a laboratory-scale FO unit utilizing a ?at sheet cellulose triacetate (CTA) membrane. Under the experimental conditions the SPS degrades the CTA membrane; however experiments with polyamide reverse osmosis (RO) membranes display stability towards SPS. Once the draw is diluted the major fraction of the switchable polarity solventmore » can be mechanically separated from the puri?ed water after polar to nonpolar phase shift induced by introduction of 1 atm carbon dioxide to 1 atm of air or nitrogen with mild heating. Trace amounts of SPS can be removed from the separated water with RO in a process that avoids solution concentration polarization. The separated nonpolar phase can be regenerated to a full strength draw and recycled with the re-addition of 1 atm of carbon dioxide.« less

Photo-switchable microbial fuel-cells.

PubMed

Schlesinger, Orr; Dandela, Rambabu; Bhagat, Ashok; Adepu, Raju; Meijler, Michael M; Xia, Lin; Alfonta, Lital

2018-05-01

Regulation of Bio-systems in a clean, simple, and efficient way is important for the design of smart bio-interfaces and bioelectronic devices. Light as a non-invasive mean to control the activity of a protein enables spatial and temporal control far superior to other chemical and physical methods. The ability to regulate the activity of a catalytic enzyme in a biofuel-cell reduces the waste of resources and energy and turns the fuel-cell into a smart and more efficient device for power generation. Here we present a microbial-fuel-cell based on a surface displayed, photo-switchable alcohol dehydrogenase. The enzyme was modified near the active site using non-canonical amino acids and a small photo-reactive molecule, which enables reversible control of enzymatic activity. Depending on the modification site, the enzyme exhibits reversible behavior upon irradiation with UV and visible light, in both biochemical, and electrochemical assays. The change observed in power output of a microbial fuel cell utilizing the modified enzyme was almost five-fold, between inactive and active states. © 2018 Wiley Periodicals, Inc.

Charge-controlled switchable CO adsorption on FeN4 cluster embedded in graphene

NASA Astrophysics Data System (ADS)

Omidvar, Akbar

2018-02-01

Electrical charging of an FeN4 cluster embedded in graphene (FeN4G) is proposed as an approach for electrocatalytically switchable carbon monoxide (CO) adsorption. Using density functional theory (DFT), we found that the CO molecule is strongly adsorbed on the uncharged FeN4G cluster. Our results show that the adsorption energy of a CO molecule on the FeN4G cluster is dramatically decreased by introducing extra electrons into the cluster. Once the charges are removed, the CO molecule is spontaneously adsorbed on the FeN4G absorbent. In the framework of frontier molecular orbital (FMO) analysis, the enhanced sensitivity and reactivity of the FeN4G cluster towards the CO molecule can be interpreted in terms of interaction between the HOMO of CO molecule and the LUMO of FeN4G cluster. Therefore, this approach promises both facile reversibility and tunable kinetics without the need of specific catalysts. Our study indicates that the FeN4G nanomaterial is an excellent absorbent for controllable and reversible capture and release of the CO.

Switchable Underwater Bubble Wettability on Laser-Induced Titanium Multiscale Micro-/Nanostructures by Vertically Crossed Scanning.

PubMed

Jiao, Yunlong; Li, Chuanzong; Wu, Sizhu; Hu, Yanlei; Li, Jiawen; Yang, Liang; Wu, Dong; Chu, Jiaru

2018-05-16

We present here a kind of novel multiscale TiO 2 square micropillar arrays on titanium sheets through vertically crossed scanning of femtosecond laser. This multiscale micro-/nanostructure is ascribed to the combination of laser ablation/shock compression/debris self-deposition, which shows superaerophobicity in water with a very small sliding angle. The laser-induced sample displays switchable bubble wettability in water via heating in a dark environment and ultraviolet (UV) irradiation in alcohol. After heating in a dark environment (0.5 h), the ablated titanium surface shows superaerophilicity in water with a bubble contact angle (BCA) of ∼4°, which has a great ability of capturing bubbles in water. After UV irradiation in alcohol (1 h), the sample recovered its superaerophobicity in water and the BCA turns into 156°. The mechanism of reversible switching is believed as the chemical conversion between Ti-OH and Ti-O. It is worth noting that our proposed switching strategy is time-saving and the switch wetting cycle costs only 1.5 h. Then we repeat five switching cycles on the reversibility and the method shows excellent reproducibility and stability. Moreover, laser-induced samples with different scanning spacing (50-120 μm) are fabricated and all of them show switchable underwater bubble wettability via the above tunable methods. Finally, we fabricate hybrid-patterned microstructures to show different patterned bubbles in water on the heated samples. We believe the original works will provide some new insights to researchers in bubble manipulation and gas collection fields.

Switching wormlike micelles of selenium-containing surfactant using redox reaction.

PubMed

Zhang, Yongmin; Kong, Weiwei; Wang, Cheng; An, Pengyun; Fang, Yun; Feng, Yujun; Qin, Zhirong; Liu, Xuefeng

2015-10-14

A novel redox-switchable wormlike micellar system was developed based on a mixture of selenium-containing zwitterionic surfactant and commercially available anionic surfactant sodium dodecyl sulfate, which reversibly and quickly responds to H2O2 and vitamin C, and shows circulatory gel/sol transition, reflecting changes in aggregate morphology from entangled worms to vesicles.

Switchable solvents and methods of use thereof

DOEpatents

Jessop, Philip G.; Eckert, Charles A.; Liotta, Charles L.; Heldebrant, David J.

2013-08-20

A solvent that reversibly converts from a nonionic liquid mixture to an ionic liquid upon contact with a selected trigger, e.g., contact with CO.sub.2, is described. In preferred embodiments, the ionic solvent is readily converted back to the nonionic liquid mixture. The nonionic liquid mixture includes an amidine or guanidine or both, and water, alcohol, or a combination thereof. Single component amine solvents that reversibly convert between ionic and non-ionic states are also described. Some embodiments require increased pressure to convert; others convert at 1 atmosphere.

Switchable solvents and methods of use thereof

DOEpatents

Jessop, Philip G [Kingston, CA; Eckert, Charles A [Atlanta, GA; Liotta, Charles L [Atlanta, GA; Heldebrant, David J [Richland, WA

2011-07-19

A solvent that reversibly converts from a nonionic liquid mixture to an ionic liquid upon contact with a selected trigger, e.g., contact with CO.sub.2, is described. In preferred embodiments, the ionic solvent is readily converted back to the nonionic liquid mixture. The nonionic liquid mixture includes an amidine or guanidine or both, and water, alcohol, or a combination thereof. Single component amine solvents that reversibly convert between ionic and non-ionic states are also described. Some embodiments require increased pressure to convert; others convert at 1 atmosphere.

Switchable solvents and methods of use thereof

DOEpatents

Jessop, Philip G; Eckert, Charles A; Liotta, Charles L; Heldebrant, David J

2014-04-29

A solvent that reversibly converts from a nonionic liquid mixture to an ionic liquid upon contact with a selected trigger, e.g., contact with CO.sub.2, is described. In preferred embodiments, the ionic solvent is readily converted back to the nonionic liquid mixture. The nonionic liquid mixture includes an amidine or guanidine or both, and water, alcohol, or a combination thereof. Single component amine solvents that reversibly convert between ionic and non-ionic states are also described. Some embodiments require increased pressure to convert; others convert at 1 atmosphere.

Nanoporous membranes with electrochemically switchable, chemically stabilized ionic selectivity

NASA Astrophysics Data System (ADS)

Small, Leo J.; Wheeler, David R.; Spoerke, Erik D.

2015-10-01

Nanopore size, shape, and surface charge all play important roles in regulating ionic transport through nanoporous membranes. The ability to control these parameters in situ provides a means to create ion transport systems tunable in real time. Here, we present a new strategy to address this challenge, utilizing three unique electrochemically switchable chemistries to manipulate the terminal functional group and control the resulting surface charge throughout ensembles of gold plated nanopores in ion-tracked polycarbonate membranes 3 cm2 in area. We demonstrate the diazonium mediated surface functionalization with (1) nitrophenyl chemistry, (2) quinone chemistry, and (3) previously unreported trimethyl lock chemistry. Unlike other works, these chemistries are chemically stabilized, eliminating the need for a continuously applied gate voltage to maintain a given state and retain ionic selectivity. The effect of surface functionalization and nanopore geometry on selective ion transport through these functionalized membranes is characterized in aqueous solutions of sodium chloride at pH = 5.7. The nitrophenyl surface allows for ionic selectivity to be irreversibly switched in situ from cation-selective to anion-selective upon reduction to an aminophenyl surface. The quinone-terminated surface enables reversible changes between no ionic selectivity and a slight cationic selectivity. Alternatively, the trimethyl lock allows ionic selectivity to be reversibly switched by up to a factor of 8, approaching ideal selectivity, as a carboxylic acid group is electrochemically revealed or hidden. By varying the pore shape from cylindrical to conical, it is demonstrated that a controllable directionality can be imparted to the ionic selectivity. Combining control of nanopore geometry with stable, switchable chemistries facilitates superior control of molecular transport across the membrane, enabling tunable ion transport systems.Nanopore size, shape, and surface charge all play important roles in regulating ionic transport through nanoporous membranes. The ability to control these parameters in situ provides a means to create ion transport systems tunable in real time. Here, we present a new strategy to address this challenge, utilizing three unique electrochemically switchable chemistries to manipulate the terminal functional group and control the resulting surface charge throughout ensembles of gold plated nanopores in ion-tracked polycarbonate membranes 3 cm2 in area. We demonstrate the diazonium mediated surface functionalization with (1) nitrophenyl chemistry, (2) quinone chemistry, and (3) previously unreported trimethyl lock chemistry. Unlike other works, these chemistries are chemically stabilized, eliminating the need for a continuously applied gate voltage to maintain a given state and retain ionic selectivity. The effect of surface functionalization and nanopore geometry on selective ion transport through these functionalized membranes is characterized in aqueous solutions of sodium chloride at pH = 5.7. The nitrophenyl surface allows for ionic selectivity to be irreversibly switched in situ from cation-selective to anion-selective upon reduction to an aminophenyl surface. The quinone-terminated surface enables reversible changes between no ionic selectivity and a slight cationic selectivity. Alternatively, the trimethyl lock allows ionic selectivity to be reversibly switched by up to a factor of 8, approaching ideal selectivity, as a carboxylic acid group is electrochemically revealed or hidden. By varying the pore shape from cylindrical to conical, it is demonstrated that a controllable directionality can be imparted to the ionic selectivity. Combining control of nanopore geometry with stable, switchable chemistries facilitates superior control of molecular transport across the membrane, enabling tunable ion transport systems. Electronic supplementary information (ESI) available: Experimental procedures, synthesis, and characterization of molecules 1, 2 and 3. Explanation of the electrochemical method for approximating nanopore diameter. Additional XPS spectra. See DOI: 10.1039/C5NR02939B

A dual-stimuli-responsive fluorescent switch ultrathin film

NASA Astrophysics Data System (ADS)

Li, Zhixiong; Liang, Ruizheng; Liu, Wendi; Yan, Dongpeng; Wei, Min

2015-10-01

Stimuli-responsive fluorescent switches have shown broad applications in optical devices, biological materials and intelligent responses. Herein, we describe the design and fabrication of a dual-stimuli-responsive fluorescent switch ultrathin film (UTF) via a three-step layer-by-layer (LBL) technique: (i) encapsulation of spiropyran (SP) within an amphiphilic block copolymer (PTBEM) to give the (SP@PTBEM) micelle; (ii) the mixture of riboflavin (Rf) and poly(styrene 4-sulfonate) (PSS) to enhance the adhesion ability of small molecules; (iii) assembly of negatively charged SP@PTBEM and Rf-PSS with cationic layered double hydroxide (LDH) nanoplatelets to obtain the (Rf-PSS/LDH/SP@PTBEM)n UTFs (n: bilayer number). The assembly process of the UTFs and their luminescence properties, as monitored by fluorescence spectroscopy and scanning electron microscopy (SEM), present a uniform and ordered layered structure with stepwise growth. The resulting Rf-PSS/LDH/SP@PTBEM UTF serves as a three-state switchable multicolor (green, yellow, and red) luminescent system based on stimulation from UV/Vis light and pH, with an acceptable reversibility. Therefore, this work provides a facile way to fabricate stimuli-responsive solid-state film switches with tunable-color luminescence, which have potential applications in the areas of displays, sensors, and rewritable optical memory and fluorescent logic devices.Stimuli-responsive fluorescent switches have shown broad applications in optical devices, biological materials and intelligent responses. Herein, we describe the design and fabrication of a dual-stimuli-responsive fluorescent switch ultrathin film (UTF) via a three-step layer-by-layer (LBL) technique: (i) encapsulation of spiropyran (SP) within an amphiphilic block copolymer (PTBEM) to give the (SP@PTBEM) micelle; (ii) the mixture of riboflavin (Rf) and poly(styrene 4-sulfonate) (PSS) to enhance the adhesion ability of small molecules; (iii) assembly of negatively charged SP@PTBEM and Rf-PSS with cationic layered double hydroxide (LDH) nanoplatelets to obtain the (Rf-PSS/LDH/SP@PTBEM)n UTFs (n: bilayer number). The assembly process of the UTFs and their luminescence properties, as monitored by fluorescence spectroscopy and scanning electron microscopy (SEM), present a uniform and ordered layered structure with stepwise growth. The resulting Rf-PSS/LDH/SP@PTBEM UTF serves as a three-state switchable multicolor (green, yellow, and red) luminescent system based on stimulation from UV/Vis light and pH, with an acceptable reversibility. Therefore, this work provides a facile way to fabricate stimuli-responsive solid-state film switches with tunable-color luminescence, which have potential applications in the areas of displays, sensors, and rewritable optical memory and fluorescent logic devices. Electronic supplementary information (ESI) available. See DOI: 10.1039/c5nr05376e

NREL Develops Switchable Solar Window | News | NREL

Science.gov Websites

electricity at a high efficiency have been developed by scientists at the U.S. Department of Energy's National reversibly absorbed into the device. When solar energy heats up the device, the molecules are driven out, and the device is darkened. When the sun is not shining, the device is cooled back down, and the molecules

Tailoring superelasticity of soft magnetic materials

NASA Astrophysics Data System (ADS)

Cremer, Peet; Löwen, Hartmut; Menzel, Andreas M.

2015-10-01

Embedding magnetic colloidal particles in an elastic polymer matrix leads to smart soft materials that can reversibly be addressed from outside by external magnetic fields. We discover a pronounced nonlinear superelastic stress-strain behavior of such materials using numerical simulations. This behavior results from a combination of two stress-induced mechanisms: a detachment mechanism of embedded particle aggregates and a reorientation mechanism of magnetic moments. The superelastic regime can be reversibly tuned or even be switched on and off by external magnetic fields and thus be tailored during operation. Similarities to the superelastic behavior of shape-memory alloys suggest analogous applications, with the additional benefit of reversible switchability and a higher biocompatibility of soft materials.

Conductive Boron-Doped Graphene as an Ideal Material for Electrocatalytically Switchable and High-Capacity Hydrogen Storage.

PubMed

Tan, Xin; Tahini, Hassan A; Smith, Sean C

2016-12-07

Electrocatalytic, switchable hydrogen storage promises both tunable kinetics and facile reversibility without the need for specific catalysts. The feasibility of this approach relies on having materials that are easy to synthesize, possessing good electrical conductivities. Graphitic carbon nitride (g-C 4 N 3 ) has been predicted to display charge-responsive binding with molecular hydrogen-the only such conductive sorbent material that has been discovered to date. As yet, however, this conductive variant of graphitic carbon nitride is not readily synthesized by scalable methods. Here, we examine the possibility of conductive and easily synthesized boron-doped graphene nanosheets (B-doped graphene) as sorbent materials for practical applications of electrocatalytically switchable hydrogen storage. Using first-principle calculations, we find that the adsorption energy of H 2 molecules on B-doped graphene can be dramatically enhanced by removing electrons from and thereby positively charging the adsorbent. Thus, by controlling charge injected or depleted from the adsorbent, one can effectively tune the storage/release processes which occur spontaneously without any energy barriers. At full hydrogen coverage, the positively charged BC 5 achieves high storage capacities up to 5.3 wt %. Importantly, B-doped graphene, such as BC 49 , BC 7 , and BC 5 , have good electrical conductivity and can be easily synthesized by scalable methods, which positions this class of material as a very good candidate for charge injection/release. These predictions pave the route for practical implementation of electrocatalytic systems with switchable storage/release capacities that offer high capacity for hydrogen storage.

RGB-Switchable Porous Electrospun Nanofiber Chemoprobe-Filter Prepared from Multifunctional Copolymers for Versatile Sensing of pH and Heavy Metals.

PubMed

Liang, Fang-Cheng; Kuo, Chi-Ching; Chen, Bo-Yu; Cho, Chia-Jung; Hung, Chih-Chien; Chen, Wen-Chang; Borsali, Redouane

2017-05-17

Novel red-green-blue (RGB) switchable probes based on fluorescent porous electrospun (ES) nanofibers exhibiting high sensitivity to pH and mercury ions (Hg 2+ ) were prepared with one type of copolymer (poly(methyl methacrylatete-co-1,8-naphthalimide derivatives-co-rhodamine derivative); poly(MMA-co-BNPTU-co-RhBAM)) by using a single-capillary spinneret. The MMA, BNPTU, and RhBAM moieties were designed to (i) permit formation of porous fibers, (ii) fluoresce for Hg 2+ detection, and (iii) fluoresce for pH, respectively. The fluorescence emission of BNPTU (fluorescence resonance energy transfer (FRET) donor) changed from green to blue as it detected Hg 2+ . The fluorescence emission of RhBAM (FRET acceptor) was highly selective for pH, changing from nonfluorescent (pH 7) to exhibiting strong red fluorescence (pH 2). The full-color emission of the ES nanofibers included green, red, blue, purple, and white depending on the particular pH and Hg 2+ -concentration combination of the solution. The porous ES nanofibers with 30 nm pores were fabricated using hydrophobic MMA, low-boiling-point solvent, and at a high relative humidity (80%). These porous ES nanofibers had a higher surface-to-volume ratio than did the corresponding thin films, which enhanced their performance. The present study demonstrated that the FRET-based full-color-fluorescence porous nanofibrous membranes, which exhibit on-off switching and can be used as naked eye probes, have potential for application in water purification sensing filters.

Switchable Adhesion in Vacuum Using Bio-Inspired Dry Adhesives.

PubMed

Purtov, Julia; Frensemeier, Mareike; Kroner, Elmar

2015-11-04

Suction based attachment systems for pick and place handling of fragile objects like glass plates or optical lenses are energy-consuming and noisy and fail at reduced air pressure, which is essential, e.g., in chemical and physical vapor deposition processes. Recently, an alternative approach toward reversible adhesion of sensitive objects based on bioinspired dry adhesive structures has emerged. There, the switching in adhesion is achieved by a reversible buckling of adhesive pillar structures. In this study, we demonstrate that these adhesives are capable of switching adhesion not only in ambient air conditions but also in vacuum. Our bioinspired patterned adhesive with an area of 1 cm(2) provided an adhesion force of 2.6 N ± 0.2 N in air, which was reduced to 1.9 N ± 0.2 N if measured in vacuum. Detachment was induced by buckling of the structures due to a high compressive preload and occurred, independent of air pressure, at approximately 0.9 N ± 0.1 N. The switch in adhesion was observed at a compressive preload between 5.6 and 6.0 N and was independent of air pressure. The difference between maximum adhesion force and adhesion force after buckling gives a reasonable window of operation for pick and place processes. High reversibility of the switching behavior is shown over 50 cycles in air and in vacuum, making the bioinspired switchable adhesive applicable for handling operations of fragile objects.

Switchable Adhesion in Vacuum Using Bio-Inspired Dry Adhesives

PubMed Central

2015-01-01

Suction based attachment systems for pick and place handling of fragile objects like glass plates or optical lenses are energy-consuming and noisy and fail at reduced air pressure, which is essential, e.g., in chemical and physical vapor deposition processes. Recently, an alternative approach toward reversible adhesion of sensitive objects based on bioinspired dry adhesive structures has emerged. There, the switching in adhesion is achieved by a reversible buckling of adhesive pillar structures. In this study, we demonstrate that these adhesives are capable of switching adhesion not only in ambient air conditions but also in vacuum. Our bioinspired patterned adhesive with an area of 1 cm2 provided an adhesion force of 2.6 N ± 0.2 N in air, which was reduced to 1.9 N ± 0.2 N if measured in vacuum. Detachment was induced by buckling of the structures due to a high compressive preload and occurred, independent of air pressure, at approximately 0.9 N ± 0.1 N. The switch in adhesion was observed at a compressive preload between 5.6 and 6.0 N and was independent of air pressure. The difference between maximum adhesion force and adhesion force after buckling gives a reasonable window of operation for pick and place processes. High reversibility of the switching behavior is shown over 50 cycles in air and in vacuum, making the bioinspired switchable adhesive applicable for handling operations of fragile objects. PMID:26457864

Energy requirements of the switchable polarity solvent forward osmosis (SPS-FO) water purification process

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wendt, Daniel S.; Orme, Christopher J.; Mines, Gregory L.

A model was developed to estimate the process energy requirements of a switchable polarity solvent forward osmosis (SPS FO) system for water purification from aqueous NaCl feed solution concentrations ranging from 0.5 to 4.0 molal at an operational scale of 480 m3/day (feed stream). The model indicates recovering approximately 90% of the water from a feed solution with NaCl concentration similar to seawater using SPS FO would have total equivalent energy requirements between 2.4 and 4.3 kWh per m 3 of purified water product. The process is predicted to be competitive with current costs for disposal/treatment of produced water frommore » oil and gas drilling operations. As a result, once scaled up the SPS FO process may be a thermally driven desalination process that can compete with the cost of seawater reverse osmosis.« less

Energy requirements of the switchable polarity solvent forward osmosis (SPS-FO) water purification process

DOE PAGES

Wendt, Daniel S.; Orme, Christopher J.; Mines, Gregory L.; ...

2015-08-01

A model was developed to estimate the process energy requirements of a switchable polarity solvent forward osmosis (SPS FO) system for water purification from aqueous NaCl feed solution concentrations ranging from 0.5 to 4.0 molal at an operational scale of 480 m3/day (feed stream). The model indicates recovering approximately 90% of the water from a feed solution with NaCl concentration similar to seawater using SPS FO would have total equivalent energy requirements between 2.4 and 4.3 kWh per m 3 of purified water product. The process is predicted to be competitive with current costs for disposal/treatment of produced water frommore » oil and gas drilling operations. As a result, once scaled up the SPS FO process may be a thermally driven desalination process that can compete with the cost of seawater reverse osmosis.« less

The synthesis and the chemical and physical properties of non-aqueous silylamine solvents for carbon dioxide capture.

PubMed

Rohan, Amy L; Switzer, Jackson R; Flack, Kyle M; Hart, Ryan J; Sivaswamy, Swetha; Biddinger, Elizabeth J; Talreja, Manish; Verma, Manjusha; Faltermeier, Sean; Nielsen, Paul T; Pollet, Pamela; Schuette, George F; Eckert, Charles A; Liotta, Charles L

2012-11-01

Silylamine reversible ionic liquids were designed to achieve specific physical properties in order to address effective CO₂ capture. The reversible ionic liquid systems reported herein represent a class of switchable solvents where a relatively non-polar silylamine (molecular liquid) is reversibly transformed to a reversible ionic liquid (RevIL) by reaction with CO₂ (chemisorption). The RevILs can further capture additional CO₂ through physical absorption (physisorption). The effects of changes in structure on (1) the CO₂ capture capacity (chemisorption and physisorption), (2) the viscosity of the solvent systems at partial and total conversion to the ionic liquid state, (3) the energy required for reversing the CO₂ capture process, and (4) the ability to recycle the solvents systems are reported. Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Forward and reverse control system for induction motors

DOEpatents

Wright, J.T.

1987-09-15

A control system for controlling the direction of rotation of a rotor of an induction motor includes an array of five triacs with one of the triacs applying a current of fixed phase to the windings of the rotor and four of the triacs being switchable to apply either hot ac current or return ac current to the stator windings so as to reverse the phase of current in the stator relative to that of the rotor and thereby reverse the direction of rotation of the rotor. Switching current phase in the stator is accomplished by operating the gates of pairs of the triacs so as to connect either hot ac current or return ac current to the input winding of the stator. 1 fig.

Compatibility Study of Nanofiltration and Reverse Osmosis Membranes with 1 Cyclohexylpiperidenium Bicarbonate Solutions

DOE Data Explorer

Adhikari, Birendra; Jones, Michael G.; Orme, Christopher J.; Wendt, Daniel S.; Wilson, Aaron D.

2015-10-01

The switchable polarity solvent forward osmosis (SPS FO) desalination process requires use of a polishing filtration step to remove trace quantities of draw solution from the product water stream. Selected nanofiltration (NF) and reverse osmosis (RO) membranes were tested for their ability to recover water from 1-cyclohexylpiperidenium bicarbonate solutions in this application. This submission includes the experimental data used to calculate NF and RO membrane flux-normalized net driving pressure (FNNDP) and flux-normalized rejection (FNR) performance in recovering water from 1-cyclohexylpiperidenium bicarbonate solutions. This data is further described and visualized in the manuscript entitled "Compatibility study of nanofiltration and reverse osmosis membranes with 1 cyclohexylpiperidenium bicarbonate solutions" (see attached Compatibility Study Manuscript).

Dynamic Colloidal Molecules Maneuvered by Light-Controlled Janus Micromotors.

PubMed

Gao, Yirong; Mou, Fangzhi; Feng, Yizheng; Che, Shengping; Li, Wei; Xu, Leilei; Guan, Jianguo

2017-07-12

In this work, we propose and demonstrate a dynamic colloidal molecule that is capable of moving autonomously and performing swift, reversible, and in-place assembly dissociation in a high accuracy by manipulating a TiO 2 /Pt Janus micromotor with light irradiation. Due to the efficient motion of the TiO 2 /Pt Janus motor and the light-switchable electrostatic interactions between the micromotor and colloidal particles, the colloidal particles can be captured and assembled one by one on the fly, subsequently forming into swimming colloidal molecules by mimicking space-filling models of simple molecules with central atoms. The as-demonstrated dynamic colloidal molecules have a configuration accurately controlled and stabilized by regulating the time-dependent intensity of UV light, which controls the stop-and-go motion of the colloidal molecules. The dynamic colloidal molecules are dissociated when the light irradiation is turned off due to the disappearance of light-switchable electrostatic interaction between the motor and the colloidal particles. The strategy for the assembly of dynamic colloidal molecules is applicable to various charged colloidal particles. The simulated optical properties of a dynamic colloidal molecule imply that the results here may provide a novel approach for in-place building functional microdevices, such as microlens arrays, in a swift and reversible manner.

Stacked Switchable Element and Diode Combination

DOEpatents

Branz, H. M.; Wang, Q.

2006-06-27

A device (10) comprises a semiconductor diode (12) and a switchable element (14) positioned in stacked adjacent relationship so that the semiconductor diode (12) and the switchable element (14) are electrically connected in series with one another. The switchable element (14) is switchable from a low-conductance state to a high-conductance state in response to the application of a forming voltage to the switchable element (14).

Stacked switchable element and diode combination

DOEpatents

Branz, Howard M.; Wang, Qi

2006-06-27

A device (10) comprises a semiconductor diode (12) and a switchable element (14) positioned in stacked adjacent relationship so that the semiconductor diode (12) and the switchable element (14) are electrically connected in series with one another. The switchable element (14) is switchable from a low-conductance state to a high-conductance state in response to the application of a forming voltage to the switchable element (14).

Switchable bio-inspired adhesives

NASA Astrophysics Data System (ADS)

Kroner, Elmar

2015-03-01

Geckos have astonishing climbing abilities. They can adhere to almost any surface and can run on walls and even stick to ceilings. The extraordinary adhesion performance is caused by a combination of a complex surface pattern on their toes and the biomechanics of its movement. These biological dry adhesives have been intensely investigated during recent years because of the unique combination of adhesive properties. They provide high adhesion, allow for easy detachment, can be removed residue-free, and have self-cleaning properties. Many aspects have been successfully mimicked, leading to artificial, bio-inspired, patterned dry adhesives, and were addressed and in some aspects they even outperform the adhesion capabilities of geckos. However, designing artificial patterned adhesion systems with switchable adhesion remains a big challenge; the gecko's adhesion system is based on a complex hierarchical surface structure and on advanced biomechanics, which are both difficult to mimic. In this paper, two approaches are presented to achieve switchable adhesion. The first approach is based on a patterned polydimethylsiloxane (PDMS) polymer, where adhesion can be switched on and off by applying a low and a high compressive preload. The switch in adhesion is caused by a reversible mechanical instability of the adhesive silicone structures. The second approach is based on a composite material consisting of a Nickel- Titanium (NiTi) shape memory alloy and a patterned adhesive PDMS layer. The NiTi alloy is trained to change its surface topography as a function of temperature, which results in a change of the contact area and of alignment of the adhesive pattern towards a substrate, leading to switchable adhesion. These examples show that the unique properties of bio-inspired adhesives can be greatly improved by new concepts such as mechanical instability or by the use of active materials which react to external stimuli.

Stacked switchable element and diode combination with a low breakdown switchable element

DOEpatents

Wang, Qi [Littleton, CO; Ward, James Scott [Englewood, CO; Hu, Jian [Englewood, CO; Branz, Howard M [Boulder, CO

2012-06-19

A device (10) comprises a semiconductor diode (12) and a switchable element (14) positioned in stacked adjacent relationship. The semiconductor diode (12) and the switchable element (14) are electrically connected in series with one another. The switchable element (14) is switchable from a low-conductance state to a high-conductance state in response to the application of a low-density forming current and/or a low voltage.

Extensively Reversible Thermal Transformations of a Bistable, Fluorescence-Switchable Molecular Solid: Entry into Functional Molecular Phase-Change Materials.

PubMed

Srujana, P; Radhakrishnan, T P

2015-06-15

Functional phase-change materials (PCMs) are conspicuously absent among molecular materials in which the various attributes of inorganic solids have been realized. While organic PCMs are primarily limited to thermal storage systems, the amorphous-crystalline transformation of materials like Ge-Sb-Te find use in advanced applications such as information storage. Reversible amorphous-crystalline transformations in molecular solids require a subtle balance between robust supramolecular assembly and flexible structural elements. We report novel diaminodicyanoquinodimethanes that achieve this transformation by interlinked helical assemblies coupled with conformationally flexible alkoxyalkyl chains. They exhibit highly reversible thermal transformations between bistable (crystalline/amorphous) forms, along with a prominent switching of the fluorescence emission energy and intensity. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Four reversible and reconfigurable structures for three-phase emulsions: extended morphologies and applications

NASA Astrophysics Data System (ADS)

Ge, Xue-Hui; Geng, Yu-Hao; Zhang, Qiao-Chu; Shao, Meng; Chen, Jian; Luo, Guang-Sheng; Xu, Jian-Hong

2017-02-01

Here in this article, we classify and conclude the four morphologies of three-phase emulsions. Remarkably, we achieve the reversible transformations between every shape. Through theoretical analysis, we choose four liquid systems to form these four morphologies. Then monodispersed droplets with these four morphologies are formed through a microfluidic device and captured in a petri-dish. By replacing their ambient solution of the captured emulsions, in-situ morphology transformations between each shape are achieved. The process is well recorded through photographs and videos and they are systematical and reversible. Finally, we use the droplets structure to form an on-off switch to start and shut off the evaporation of one volatile phase to achieve the process monitoring. This could be used to initiate and quench a reaction, which offers a novel idea to achieve the switchable and reversible reaction control in multiple-phase reactions.

2000 survey of window manufacturers on the subject of switchable glass

NASA Astrophysics Data System (ADS)

LaPointe, Michael R.; Sottile, Gregory M.

2001-11-01

The results of a 2000 survey of United States window manufacturers on the subject of switchable glass are discussed. The areas covered in this paper include awareness of the overall product category of switchable glass and various types of switchable glass, attitudes toward specific features of switchable glass, expectations for manufacturer production of such products, expectations for market penetration rates among end-product consumers, levels of price sensitivity among window manufacturers regarding switchable glass, and expectations for the pace of new product development within the window industry over the next five years.

Switchable Pickering Emulsions Stabilized by Awakened TiO2 Nanoparticle Emulsifiers Using UV/Dark Actuation.

PubMed

Zhang, Qing; Bai, Rui-Xue; Guo, Ting; Meng, Tao

2015-08-26

In this work, switchable Pickering emulsions that utilize UV/dark manipulation employ a type of smart TiO2 nanoparticle as emulsifiers. The emulsifiers can be awakened when needed via UV-induced degradation of grafted silanes on TiO2 nanoparticles. By tuning the surface wettability of TiO2 nanoparticles in situ via UV/dark actuation, emulsions stabilized by the nanoparticles can be reversibly switched between the water-in-oil (W/O) type and oil-in-water (O/W) type for several cycles. Due to the convertible wettability, the smart nanoparticle emulsifiers can be settled in either the oil phase or the water phase as desired during phase separation, making it convenient for recycling. The present work provides a facile and noninvasive method to freely manipulate the formation, breakage, and switching of the emulsion; this method has promising potential as a powerful technique for use in energy-efficient and environmentally friendly industries.

Designing switchable near room-temperature multiferroics via the discovery of a novel magnetoelectric coupling

NASA Astrophysics Data System (ADS)

Feng, J. S.; Xu, Ke; Bellaiche, Laurent; Xiang, H. J.

2018-05-01

Magnetoelectric (ME) coupling is the key ingredient for realizing the cross-control of magnetism and ferroelectricity in multiferroics. However, multiferroics are not only rare, especially at room-temperature, in nature but also the overwhelming majority of known multiferroics do not exhibit highly-desired switching of the direction of magnetization when the polarization is reversed by an electric field. Here, we report group theory analysis and ab initio calculations demonstrating, and revealing the origin of, the existence of a novel form of ME coupling term in a specific class of materials that does allow such switching. This term naturally explains the previously observed electric field control of magnetism in the first known multiferroics, i.e., the Ni–X boracite family. It is also presently used to design a switchable near room-temperature multiferroic (namely, LaSrMnOsO6 perovskite) having rather large ferroelectric polarization and spontaneous magnetization, as well as strong ME coupling.

Warm/cool-tone switchable thermochromic material for smart windows by orthogonally integrating properties of pillar[6]arene and ferrocene.

PubMed

Wang, Sai; Xu, Zuqiang; Wang, Tingting; Xiao, Tangxin; Hu, Xiao-Yu; Shen, Ying-Zhong; Wang, Leyong

2018-04-30

Functional materials play a vital role in the fabrication of smart windows, which can provide a more comfortable indoor environment for humans to enjoy a better lifestyle. Traditional materials for smart windows tend to possess only a single functionality with the purpose of regulating the input of solar energy. However, different color tones also have great influences on human emotions. Herein, a strategy for orthogonal integration of different properties is proposed, namely the thermo-responsiveness of ethylene glycol-modified pillar[6]arene (EGP6) and the redox-induced reversible color switching of ferrocene/ferrocenium groups are orthogonally integrated into one system. This gives rise to a material with cooperative and non-interfering dual functions, featuring both thermochromism and warm/cool tone-switchability. Consequently, the obtained bifunctional material for fabricating smart windows can not only regulate the input of solar energy but also can provide a more comfortable color tone to improve the feelings and emotions of people in indoor environments.

Smart multifunctional nanoagents for in situ monitoring of small molecules with a switchable affinity towards biomedical targets

NASA Astrophysics Data System (ADS)

Shevchenko, Konstantin G.; Cherkasov, Vladimir R.; Nikitina, Irina L.; Babenyshev, Andrey V.; Nikitin, Maxim P.

2018-02-01

The great diversity of nanomaterials provides ample opportunities for constructing effective agents for biomedical applications ranging from biosensing to drug delivery. Multifunctional nanoagents that combine several features in a single particle are of special interest due to capabilities that substantially exceed those of molecular drugs. An ideal theranostic agent should simultaneously be an advanced biosensor to identify a disease and report the diagnosis and a biomedical actuator to treat the disease. While many approaches were developed to load a nanoparticle with various drugs for actuation of the diseased cells (e.g., to kill them), the nanoparticle-based approaches for the localized biosensing with real-time reporting of the marker concentration severely lag behind. Here, we show a smart in situ nanoparticle-based biosensor/actuator system that dynamically and reversibly changes its structural and optical properties in response to a small molecule marker to allow real-time monitoring of the marker concentration and adjustment of the system ability to bind its biomedical target. Using the synergistic combination of signal readout based on the localized surface plasmon resonance and an original method of fabrication of smart ON/OFF-switchable nanoagents, we demonstrate reversible responsiveness of the system to a model small molecule marker (antibiotic chloramphenicol) in a wide concentration range. The proposed approach can be used for the development of advanced multifunctional nanoagents for theranostic applications.

Temperature-responsive electrospun nanofibers for ‘on–off’ switchable release of dextran

PubMed Central

Kim, Young-Jin; Ebara, Mitsuhiro; Aoyagi, Takao

2012-01-01

We propose a new type of ‘smart’ nanofiber (NF) with dynamically and reversibly tunable properties for the ‘on–off’ controlled release of the polysaccharide dextran. The fibers are produced by electrospinning copolymers of N-isopropylacrylamide (NIPAAm) and N-hydroxymethylacrylamide (HMAAm). The OH groups of HMAAm are subsequently crosslinked by thermal curing. The copolymers were successfully fabricated into a well-defined nanofibrous structure with a diameter of about 600–700 nm, and the fibers preserved their morphology even after thermal curing. The resulting crosslinked NFs showed rapid and reversible volume changes in aqueous media in response to cycles of temperature alternation. The fibrous morphology was maintained for the crosslinked NFs even after the cycles of temperature alternation, while non-crosslinked NFs collapsed and dispersed quickly in the aqueous solution. Dextran-containing NFs were prepared by electrospinning the copolymers blended with fluorescein isothiocyanate (FITC)-dextran, and the ‘on–off’ switchable release of FITC-dextran from the crosslinked NFs was observed. Almost all the FITC-dextran was released from the NFs after six heating cycles, whereas only a negligible amount of FITC-dextran was evolved during the cooling process. The reported incorporation of smart properties into NFs takes advantage of their extremely large surface area and porosity and is expected to provide a simple platform for on–off drug delivery. PMID:27877530

Modifying Thermal Switchability of Liquid Crystalline Nanoparticles by Alkyl Ligands Variation

PubMed Central

Żuk, Maciej; Tupikowska, Martyna

2018-01-01

By coating plasmonic nanoparticles (NPs) with thermally responsive liquid crystals (LCs) it is possible to prepare reversibly reconfigurable plasmonic nanomaterials with prospective applications in optoelectronic devices. However, simple and versatile methods to precisely tailor properties of liquid-crystalline nanoparticles (LC NPs) are still required. Here, we report a new method for tuning structural properties of assemblies of nanoparticles grafted with a mixture of promesogenic and alkyl thiols, by varying design of the latter. As a model system, we used Ag and Au nanoparticles that were coated with three-ring promesogenic molecules and dodecanethiol ligand. These LC NPs self-assemble into switchable lamellar (Ag NPs) or tetragonal (Au NPs) aggregates, as determined with small angle X-ray diffraction and transmission electron microscopy. Reconfigurable assemblies of Au NPs with different unit cell symmetry (orthorombic) are formed if hexadecanethiol and 1H,1H,2H,2H-perfluorodecanethiol were used in the place of dodecanethiol; in the case of Ag NPs the use of 11-hydroxyundecanethiol promotes formation of a lamellar structure as in the reference system, although with substantially broader range of thermal stability (140 vs. 90 °C). Our results underline the importance of alkyl ligand functionalities in determining structural properties of liquid-crystalline nanoparticles, and, more generally, broaden the scope of synthetic tools available for tailoring properties of reversibly reconfigurable plasmonic nanomaterials. PMID:29518916

A dual-stimuli-responsive fluorescent switch ultrathin film.

PubMed

Li, Zhixiong; Liang, Ruizheng; Liu, Wendi; Yan, Dongpeng; Wei, Min

2015-10-28

Stimuli-responsive fluorescent switches have shown broad applications in optical devices, biological materials and intelligent responses. Herein, we describe the design and fabrication of a dual-stimuli-responsive fluorescent switch ultrathin film (UTF) via a three-step layer-by-layer (LBL) technique: (i) encapsulation of spiropyran (SP) within an amphiphilic block copolymer (PTBEM) to give the (SP@PTBEM) micelle; (ii) the mixture of riboflavin (Rf) and poly(styrene 4-sulfonate) (PSS) to enhance the adhesion ability of small molecules; (iii) assembly of negatively charged SP@PTBEM and Rf-PSS with cationic layered double hydroxide (LDH) nanoplatelets to obtain the (Rf-PSS/LDH/SP@PTBEM)n UTFs (n: bilayer number). The assembly process of the UTFs and their luminescence properties, as monitored by fluorescence spectroscopy and scanning electron microscopy (SEM), present a uniform and ordered layered structure with stepwise growth. The resulting Rf-PSS/LDH/SP@PTBEM UTF serves as a three-state switchable multicolor (green, yellow, and red) luminescent system based on stimulation from UV/Vis light and pH, with an acceptable reversibility. Therefore, this work provides a facile way to fabricate stimuli-responsive solid-state film switches with tunable-color luminescence, which have potential applications in the areas of displays, sensors, and rewritable optical memory and fluorescent logic devices.

Short-term hyperglycaemia causes non-reversible changes in arterial gene expression in a fully 'switchable' in vivo mouse model of diabetes.

PubMed

Zervou, S; Wang, Y-F; Laiho, A; Gyenesei, A; Kytömäki, L; Hermann, R; Abouna, S; Epstein, D; Pelengaris, S; Khan, M

2010-12-01

Irreversible arterial damage due to early effects of hypo- or hyperglycaemia could account for the limited success of glucose-lowering treatments in preventing cardiovascular disease (CVD) events. We hypothesised that even brief hypo- or hyperglycaemia could adversely affect arterial gene expression and that these changes, moreover, might not be fully reversible. By controlled activation of a 'switchable' c-Myc transgene in beta cells, adult pIns-c-MycER(TAM) mice were rendered transiently hypo- and then hyperglycaemic, after which they were allowed to recover for up to 3 months. Immediate and sequential changes in aortic global gene expression from normal glycaemia through hypo- and hyperglycaemia to recovery were assessed. Gene expression was compared with that of normoglycaemic transgenic and tamoxifen-treated wild-type controls. Overall, expression of 95 genes was significantly affected by moderate hypoglycaemia (glucose down to 2.5 mmol/l), whereas over 769 genes were affected by hyperglycaemia. Genes and pathways activated included several involved in atherogenic processes, such as inflammation and arterial calcification. Although expression of many genes recovered to initial pre-exposure levels when hyperglycaemia was corrected (74.9%), in one in four genes this did not occur. Quantitative reverse transcriptase PCR and immunohistochemistry verified the gene expression patterns of key molecules, as shown by global gene arrays. Short-term exposure to hyperglycaemia can cause deleterious and persistent changes in arterial gene expression in vivo. Brief hypoglycaemia also adversely affects gene expression, although less substantially. Together, these results suggest that early correction of hyperglycaemia and avoidance of hypoglycaemia may both be necessary to avoid excess CVD risk in diabetes.

A switchable digital microfluidic droplet dye-laser.

PubMed

Kuehne, Alexander J C; Gather, Malte C; Eydelnant, Irwin A; Yun, Seok-Hyun; Weitz, David A; Wheeler, Aaron R

2011-11-07

Digital microfluidic devices allow the manipulation of droplets between two parallel electrodes. These electrodes can act as mirrors generating a micro-cavity, which can be exploited for a droplet dye-laser. Three representative laser-dyes with emission wavelengths spanning the whole visible spectrum are chosen to show the applicability of this concept. Sub-microlitre droplets of laser-dye solution are moved in and out of a lasing site on-chip to down-convert the UV-excitation light into blue, green and red laser-pulses. This journal is © The Royal Society of Chemistry 2011

Optical properties of metal-hydride switchable films

NASA Astrophysics Data System (ADS)

Griessen, Ronald

2001-03-01

In 1996 we discovered that yttrium-, lanthanum-, and rare-earth-hydride (REHx) films [1] protected by a thin palladium layer, exhibit spectacular changes in their optical properties when the hydrogen concentration x is increased from 2 to 3. For example, a 500 nm thick YH2 film is metallic and shiny while YH3 is yellowish and transparent. The transition is reversible, fast [2, 3], and can simply be induced by adding or removing hydrogen from the gas phase, an electrolyte or from an H containing liquid. The optical switching that occurs near the metal-insulator transition of these hydrides is remarkably robust as it is not affected by structural or compositional disorder. It occurs in polycrystalline and epitaxial films, in alloys with cubic or hexagonal crystal structures,and deuterides [4] switch as well as hydrides. At small length scales epitaxial YHx films exhibit surprising structural properties which open the way to pixel-by-pixel optical switching [5]. Colour-neutral switchable mirrors based on RE-Mg alloys [6] can be used in all-solid-state switchable devices. Newest results for Rare-Earth free switchable mirrors will be presented. [1] J. N. Huiberts, R. Griessen, J. H. Rector, R. J. Wijngaarden, J. P. Dekker, D. G. de Groot and N. J. Koeman, Nature 380 (1996) 231; [2] S. J. van der Molen, J. W. J. Kerssemakers, J. H. Rector, N. J. Koeman, B. Dam, R. Griessen, J. Appl. Phys. 86 (1999) 6107; [3] F. J. A. den Broeder, S. J. van der Molen, et al., Nature 394 (1998)656; [4] A. T. M. van Gogh, E. S. Kooij, R. Griessen, Phys. Rev. Lett. 83 (1999) 4614; [5] J. W. J. Kerssemakers, S. J. van der Molen and R. Griessen, Nature 406 (2000) 489; [6] P. van der Sluis, M. Ouwerkerk and P. A. Duine, Appl. Phys. Lett. 70 (1997) 3356.

Mixed metal films with switchable optical properties

NASA Astrophysics Data System (ADS)

Richardson, T. J.; Slack, J. L.; Farangis, B.; Rubin, M. D.

2002-02-01

Thin, Pd-capped metallic films containing magnesium and first-row transition metals (Mn, Fe, Co) switch reversibly from their initial reflecting state to visually transparent states when exposed to gaseous hydrogen or following cathodic polarization in an alkaline electrolyte. Reversion to the reflecting state is achieved by exposure to air or by anodic polarization. The films were prepared by cosputtering from one magnesium target and one manganese, iron, or cobalt target. Both the dynamic optical switching range and the speed of the transition depend on the magnesium-transition metal ratio. Infrared spectra of films in the transparent, hydrided (deuterided) states support the presence of the intermetallic hydride phases Mg3MnH7, Mg2FeH6, and Mg2CoH5.

Field-Free Programmable Spin Logics via Chirality-Reversible Spin-Orbit Torque Switching.

PubMed

Wang, Xiao; Wan, Caihua; Kong, Wenjie; Zhang, Xuan; Xing, Yaowen; Fang, Chi; Tao, Bingshan; Yang, Wenlong; Huang, Li; Wu, Hao; Irfan, Muhammad; Han, Xiufeng

2018-06-21

Spin-orbit torque (SOT)-induced magnetization switching exhibits chirality (clockwise or counterclockwise), which offers the prospect of programmable spin-logic devices integrating nonvolatile spintronic memory cells with logic functions. Chirality is usually fixed by an applied or effective magnetic field in reported studies. Herein, utilizing an in-plane magnetic layer that is also switchable by SOT, the chirality of a perpendicular magnetic layer that is exchange-coupled with the in-plane layer can be reversed in a purely electrical way. In a single Hall bar device designed from this multilayer structure, three logic gates including AND, NAND, and NOT are reconfigured, which opens a gateway toward practical programmable spin-logic devices. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Phase-change memory function of correlated electrons in organic conductors

NASA Astrophysics Data System (ADS)

Oike, H.; Kagawa, F.; Ogawa, N.; Ueda, A.; Mori, H.; Kawasaki, M.; Tokura, Y.

2015-01-01

Phase-change memory (PCM), a promising candidate for next-generation nonvolatile memories, exploits quenched glassy and thermodynamically stable crystalline states as reversibly switchable state variables. We demonstrate PCM functions emerging from a charge-configuration degree of freedom in strongly correlated electron systems. Nonvolatile reversible switching between a high-resistivity charge-crystalline (or charge-ordered) state and a low-resistivity quenched state, charge glass, is achieved experimentally via heat pulses supplied by optical or electrical means in organic conductors θ -(BEDT-TTF)2X . Switching that is one order of magnitude faster is observed in another isostructural material that requires faster cooling to kinetically avoid charge crystallization, indicating that the material's critical cooling rate can be useful guidelines for pursuing a faster correlated-electron PCM function.

Charge Modulation in Graphitic Carbon Nitride as a Switchable Approach to High-Capacity Hydrogen Storage.

PubMed

Tan, Xin; Kou, Liangzhi; Tahini, Hassan A; Smith, Sean C

2015-11-01

Electrical charging of graphitic carbon nitride nanosheets (g-C4 N3 and g-C3 N4 ) is proposed as a strategy for high-capacity and electrocatalytically switchable hydrogen storage. Using first-principle calculations, we found that the adsorption energy of H2 molecules on graphitic carbon nitride nanosheets is dramatically enhanced by injecting extra electrons into the adsorbent. At full hydrogen coverage, the negatively charged graphitic carbon nitride achieves storage capacities up to 6-7 wt %. In contrast to other hydrogen storage approaches, the storage/release occurs spontaneously once extra electrons are introduced or removed, and these processes can be simply controlled by switching on/off the charging voltage. Therefore, this approach promises both facile reversibility and tunable kinetics without the need of specific catalysts. Importantly, g-C4 N3 has good electrical conductivity and high electron mobility, which can be a very good candidate for electron injection/release. These predictions may prove to be instrumental in searching for a new class of high-capacity hydrogen storage materials. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Effective Control of Bioelectricity Generation from a Microbial Fuel Cell by Logical Combinations of pH and Temperature

PubMed Central

Tang, Jiahuan; Liu, Ting; Yuan, Yong

2014-01-01

In this study, a microbial fuel cell (MFC) with switchable power release is designed, which can be logically controlled by combinations of the most physiologically important parameters such as “temperature” and “pH.” Changes in voltage output in response to temperature and pH changes were significant in which voltage output decreased sharply when temperature was lowered from 30°C to 10°C or pH was decreased from 7.0 to 5.0. The switchability of the MFC comes from the microbial anode whose activity is affected by the combined medium temperature and pH. Changes in temperature and pH cause reversible activation-inactivation of the bioanode, thus affecting the activity of the entire MFC. With temperature and pH as input signals, an AND logic operation is constructed for the MFC whose power density is controlled. The developed system has the potential to meet the requirement of power supplies producing electrical power on-demand for self-powered biosensors or biomedical devices. PMID:24741343

Dual switchable CRET-induced luminescence of CdSe/ZnS quantum dots (QDs) by the hemin/G-quadruplex-bridged aggregation and deaggregation of two-sized QDs.

PubMed

Hu, Lianzhe; Liu, Xiaoqing; Cecconello, Alessandro; Willner, Itamar

2014-10-08

The hemin/G-quadruplex-catalyzed generation of chemiluminescence through the oxidation of luminol by H2O2 stimulates the chemiluminescence resonance energy transfer (CRET) to CdSe/ZnS quantum dots (QDs), resulting in the luminescence of the QDs. By the cyclic K(+)-ion-induced formation of the hemin/G-quadruplex linked to the QDs, and the separation of the G-quadruplex in the presence of 18-crown-6-ether, the ON-OFF switchable CRET-induced luminescence of the QDs is demonstrated. QDs were modified with nucleic acids consisting of the G-quadruplex subunits sequences and of programmed domains that can be cross-linked through hybridization, using an auxiliary scaffold. In the presence of K(+)-ions, the QDs aggregate through the cooperative stabilization of K(+)-ion-stabilized G-quadruplex bridges and duplex domains between the auxiliary scaffold and the nucleic acids associated with the QDs. In the presence of 18-crown-6-ether, the K(+)-ions are eliminated from the G-quadruplex units, leading to the separation of the aggregated QDs. By the cyclic treatment of the QDs with K(+)-ions/18-crown-6-ether, the reversible aggregation/deaggregation of the QDs is demonstrated. The incorporation of hemin into the K(+)-ion-stabilized G-quadruplex leads to the ON-OFF switchable CRET-stimulated luminescence of the QDs. By the mixing of appropriately modified two-sized QDs, emitting at 540 and 610 nm, the dual ON-OFF activation of the luminescence of the QDs is demonstrated.

Temperature-Triggered Switchable Helix-Helix Inversion of Poly(phenylacetylene) Bearing l-Valine Ethyl Ester Pendants and Its Chiral Recognition Ability.

PubMed

Zhou, Yanli; Zhang, Chunhong; Qiu, Yuan; Liu, Lijia; Yang, Taotao; Dong, Hongxing; Satoh, Toshifumi; Okamoto, Yoshio

2016-11-21

A phenylacetylene containing the l-valine ethyl ester pendant (PAA-Val) was synthesized and polymerized by an organorhodium catalyst (Rh(nbd)BPh₄) to produce the corresponding one-handed helical cis -poly(phenylacetylene) (PPAA-Val). PPAA-Val showed a unique temperature-triggered switchable helix-sense in chloroform, while it was not observed in highly polar solvents, such as N , N '-dimethylformamide (DMF). By heating the solution of PPAA-Val in chloroform, the sign of the CD absorption became reversed, but recovered after cooling the solution to room temperature. Even after six cycles of the heating-cooling treatment, the helix sense of the PPAA-Val's backbone was still switchable without loss of the CD intensity. The PPAA-Val was then coated on silica gel particles to produce novel chiral stationary phases (CSPs) for high-performance liquid chromatography (HPLC). These novel PPAA-Val based CSPs showed a high chiral recognition ability for racemic mandelonitrile ( α = 2.18) and racemic trans - N , N '-diphenylcyclohexane-1,2-dicarboxamide ( α = 2.60). Additionally, the one-handed helical cis -polyene backbone of PPAA-Val was irreversibly destroyed to afford PPAA-Val-H by heating in dimethyl sulfoxide (DMSO) accompanied by the complete disappearance of the Cotton effect. Although PPAA-Val-H had the same l-valine ethyl ester pendants as its cis -isomer PPAA-Val, it showed no chiral recognition. It was concluded that the one-handed helical cis -polyene backbone of PPAA-Val plays an important role in the chiral recognition ability.

Dynamic Self-Assembly of Gold/Polymer Nanocomposites: pH-Encoded Switching between 1D Nanowires and 3D Nanosponges.

PubMed

Zhang, Qi; Xu, Tian-Yi; Zhao, Cai-Xin; Jin, Wei-Hang; Wang, Qian; Qu, Da-Hui

2017-10-05

The design of tunable dynamic self-assembly of nanoparticles with switchable assembled dimensions and morphologies is a challenging goal whose realization is vital for the evolution of smart nanomaterials. Herein, we report on chitosan polymer as an effective supramolecular "glue" for aldehyde-modified Au nanoparticles to reversibly modulate the states of self-assembled nanocomposites. By simultaneous integration of dynamic covalent Schiff base interactions and noncovalent hydrogen bonds, the chitosan/Au nanocomposites could reversibly transform their assembled morphologies from one-dimensional nanowires to three-dimensional nanosponges in response to the variation of pH value. Moreover, the obtained nanosponges could be used as an efficient pH-controlled cargo release system. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Tunable Porosities and Shapes of Fullerene-Like Spheres

PubMed Central

Dielmann, Fabian; Fleischmann, Matthias; Heindl, Claudia; Peresypkina, Eugenia V; Virovets, Alexander V; Gschwind, Ruth M; Scheer, Manfred

2015-01-01

The formation of reversible switchable nanostructures monitored by solution and solid-state methods is still a challenge in supramolecular chemistry. By a comprehensive solid state and solution study we demonstrate the potential of the fivefold symmetrical building block of pentaphosphaferrocene in combination with CuI halides to switch between spheres of different porosity and shape. With increasing amount of CuX, the structures of the formed supramolecules change from incomplete to complete spherically shaped fullerene-like assemblies possessing an Ih-C80 topology at one side and to a tetrahedral-structured aggregate at the other. In the solid state, the formed nano-sized aggregates reach an outer diameter of 3.14 and 3.56 nm, respectively. This feature is used to reversibly encapsulate and release guest molecules in solution. PMID:25759976

Thermoswitchable catalysis controlled by reversible dispersion/aggregation change of nanoreactors in the presence of α-CD polymers

NASA Astrophysics Data System (ADS)

Li, Yinfeng; Hu, Jie; Niu, Chengrong; Leng, Jinghang; Li, Songjun

2018-06-01

The present work was aimed at preparing a thermosensitive nanoreactor system which could adjust its dispersion/aggregation status according to external temperature change to achieve the switchable catalysis. The mesoporous silica nanoparticle (MSNP) was selected as the framework material of the nanoreactor, and Ag nanoparticles were encapsulated in the mesoporous silica by an in situ reaction. Dodecyl groups were introduced onto MSNP surface, which could transform reversibly between complexation and disassociation with α-cyclodextrin (CD) cavity upon temperature change. It was found that the nanoreactors aggregated and the catalysis was effectively switched ‘off’ in the presence of CD polymers at low temperature (20 °C). However, when the temperature increased to 50 °C, the nanoreactors redispersed and catalysis successfully switched ‘on’.

Thermoswitchable catalysis controlled by reversible dispersion/aggregation change of nanoreactors in the presence of α-CD polymers.

PubMed

Li, Yinfeng; Hu, Jie; Niu, Chengrong; Leng, Jinghang; Li, Songjun

2018-06-01

The present work was aimed at preparing a thermosensitive nanoreactor system which could adjust its dispersion/aggregation status according to external temperature change to achieve the switchable catalysis. The mesoporous silica nanoparticle (MSNP) was selected as the framework material of the nanoreactor, and Ag nanoparticles were encapsulated in the mesoporous silica by an in situ reaction. Dodecyl groups were introduced onto MSNP surface, which could transform reversibly between complexation and disassociation with α-cyclodextrin (CD) cavity upon temperature change. It was found that the nanoreactors aggregated and the catalysis was effectively switched 'off' in the presence of CD polymers at low temperature (20 °C). However, when the temperature increased to 50 °C, the nanoreactors redispersed and catalysis successfully switched 'on'.

Electrically switchable polymer stabilised broadband infrared reflectors and their potential as smart windows for energy saving in buildings.

PubMed

Khandelwal, Hitesh; Loonen, Roel C G M; Hensen, Jan L M; Debije, Michael G; Schenning, Albertus P H J

2015-07-01

Electrically switchable broadband infrared reflectors that are relatively transparent in the visible region have been fabricated using polymer stabilised cholesteric liquid crystals. The IR reflectors can change their reflection/transmission properties by applying a voltage in response to changes in environmental conditions. Simulations predict that a significant amount of energy can be saved on heating, cooling and lighting of buildings in places such as Madrid by using this switchable IR reflector. We have also fabricated a switchable IR reflector which can also generate electricity. These polymer based switchable IR reflectors are of high potential as windows of automobiles and buildings to control interior temperatures and save energy.

Electrically switchable polymer stabilised broadband infrared reflectors and their potential as smart windows for energy saving in buildings

PubMed Central

Khandelwal, Hitesh; Loonen, Roel C. G. M.; Hensen, Jan L. M.; Debije, Michael G.; Schenning, Albertus P. H. J.

2015-01-01

Electrically switchable broadband infrared reflectors that are relatively transparent in the visible region have been fabricated using polymer stabilised cholesteric liquid crystals. The IR reflectors can change their reflection/transmission properties by applying a voltage in response to changes in environmental conditions. Simulations predict that a significant amount of energy can be saved on heating, cooling and lighting of buildings in places such as Madrid by using this switchable IR reflector. We have also fabricated a switchable IR reflector which can also generate electricity. These polymer based switchable IR reflectors are of high potential as windows of automobiles and buildings to control interior temperatures and save energy. PMID:26132328

HMSIW-based switchable units using super compact loaded shunt stubs and its applications on SIW/HMSIW switches

NASA Astrophysics Data System (ADS)

Chen, Haidong; Che, Wenquan; Zhang, Tianyu; Cao, Yue; Feng, Wenjie

2018-06-01

Half-mode substrate integrated waveguide (HMSIW) switchable unit, built by HMSIW section with loaded single or multi-microstrip shunt stub(s), was proposed in this work. Both shorted and opened stubs were studied, investigated and compared, bandwidth enhancement method for proposed switchable units was proposed and demonstrated. Based on these switchable units, narrowband and broadband HMSIW single-pole-single-through (SPST) switches, SIW SPST switch and SIW/HMSIW-based single-pole-double-through (SPDT) switch were designed, fabricated and measured. Good performances were observed experimentally for these proposed circuits, showing the advantages of proposed concept and an excellent candidate for switchable or reconfigurable SIW/HMSIW circuits or systems.

Dynamic Coordination of Eu-Iminodiacetate to Control Fluorochromic Response of Polymer Hydrogels to Multistimuli.

PubMed

Weng, Gengsheng; Thanneeru, Srinivas; He, Jie

2018-03-01

New fluorochromic materials that reversibly change their emission properties in response to their environment are of interest for the development of sensors and light-emitting materials. A new design of Eu-containing polymer hydrogels showing fast self-healing and tunable fluorochromic properties in response to five different stimuli, including pH, temperature, metal ions, sonication, and force, is reported. The polymer hydrogels are fabricated using Eu-iminodiacetate (IDA) coordination in a hydrophilic poly(N,N-dimethylacrylamide) matrix. Dynamic metal-ligand coordination allows reversible formation and disruption of hydrogel networks under various stimuli which makes hydrogels self-healable and injectable. Such hydrogels show interesting switchable ON/OFF luminescence along with the sol-gel transition through the reversible formation and dissociation of Eu-IDA complexes upon various stimuli. It is demonstrated that Eu-containing hydrogels display fast and reversible mechanochromic response as well in hydrogels having interpenetrating polymer network. Those multistimuli responsive fluorochromic hydrogels illustrate a new pathway to make smart optical materials, particularly for biological sensors where multistimuli response is required. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

High sensitivity far infrared laser diagnostics for the C-2U advanced beam-driven field-reversed configuration plasmas

DOE Office of Scientific and Technical Information (OSTI.GOV)

Deng, B. H., E-mail: bdeng@trialphaenergy.com; Beall, M.; Schroeder, J.

2016-11-15

A high sensitivity multi-channel far infrared laser diagnostics with switchable interferometry and polarimetry operation modes for the advanced neutral beam-driven C-2U field-reversed configuration (FRC) plasmas is described. The interferometer achieved superior resolution of 1 × 10{sup 16} m{sup −2} at >1.5 MHz bandwidth, illustrated by measurement of small amplitude high frequency fluctuations. The polarimetry achieved 0.04° instrument resolution and 0.1° actual resolution in the challenging high density gradient environment with >0.5 MHz bandwidth, making it suitable for weak internal magnetic field measurements in the C-2U plasmas, where the maximum Faraday rotation angle is less than 1°. The polarimetry resolution datamore » is analyzed, and high resolution Faraday rotation data in C-2U is presented together with direct evidences of field reversal in FRC magnetic structure obtained for the first time by a non-perturbative method.« less

Photoswitching of glass transition temperatures of azobenzene-containing polymers induces reversible solid-to-liquid transitions.

PubMed

Zhou, Hongwei; Xue, Changguo; Weis, Philipp; Suzuki, Yasuhito; Huang, Shilin; Koynov, Kaloian; Auernhammer, Günter K; Berger, Rüdiger; Butt, Hans-Jürgen; Wu, Si

2017-02-01

The development of polymers with switchable glass transition temperatures (T g ) can address scientific challenges such as the healing of cracks in high-T g polymers and the processing of hard polymers at room temperature without using plasticizing solvents. Here, we demonstrate that light can switch the T g of azobenzene-containing polymers (azopolymers) and induce reversible solid-to-liquid transitions of the polymers. The azobenzene groups in the polymers exhibit reversible cis-trans photoisomerization abilities. Trans azopolymers are solids with T g above room temperature, whereas cis azopolymers are liquids with T g below room temperature. Because of the photoinduced solid-to-liquid transitions of these polymers, light can reduce the surface roughness of azopolymer films by almost 600%, repeatedly heal cracks in azopolymers, and control the adhesion of azopolymers for transfer printing. The photoswitching of T g provides a new strategy for designing healable polymers with high T g and allows for control over the mechanical properties of polymers with high spatiotemporal resolution.

CO2-Triggered Switchable Solvents, Surfactants, and Other Materials

DOE Office of Scientific and Technical Information (OSTI.GOV)

Jessop, Philip G.; Mercer, Sean; Heldebrant, David J.

2012-06-14

Waste CO2 at atmospheric pressure can be used to trigger dramatic changes in the properties of certain switchable materials. Compared to other triggers such as light, acids, oxidants, CO2 has the advantages that it is inexpensive, nonhazardous, non-accumulating in the system, easily removed, and it does not require the material to be transparent. Known CO2-triggered switchable materials 10 now include solvents, surfactants, solutes, catalysts, particles, polymers, and gels. The added flexibility of switchable materials represents a new strategy for minimizing energy and material consumption in process and product design.

Switchable Photonic Crystals Using One-Dimensional Confined Liquid Crystals for Photonic Device Application.

PubMed

Ryu, Seong Ho; Gim, Min-Jun; Lee, Wonsuk; Choi, Suk-Won; Yoon, Dong Ki

2017-01-25

Photonic crystals (PCs) have recently attracted considerable attention, with much effort devoted to photonic bandgap (PBG) control for varying the reflected color. Here, fabrication of a modulated one-dimensional (1D) anodic aluminum oxide (AAO) PC with a periodic porous structure is reported. The PBG of the fabricated PC can be reversibly changed by switching the ultraviolet (UV) light on/off. The AAO nanopores contain a mixture of photoresponsive liquid crystals (LCs) with irradiation-activated cis/trans photoisomerizable azobenzene. The resultant mixture of LCs in the porous AAO film exhibits a reversible PBG, depending on the cis/trans configuration of azobenzene molecules. The PBG switching is reliable over many cycles, suggesting that the fabricated device can be used in optical and photonic applications such as light modulators, smart windows, and sensors.

Two-Way Gold Nanoparticle Label-Free Sensing of Specific Sequence and Small Molecule Targets Using Switchable Concatemers.

PubMed

Zhu, Longjiao; Shao, Xiangli; Luo, Yunbo; Huang, Kunlung; Xu, Wentao

2017-05-19

A two-way colorimetric biosensor based on unmodified gold nanoparticles (GNPs) and a switchable double-stranded DNA (dsDNA) concatemer have been demonstrated. Two hairpin probes (H1 and H2) were first designed that provided the fuels to assemble the dsDNA concatemers via hybridization chain reaction (HCR). A functional hairpin (FH) was rationally designed to recognize the target sequences. All the hairpins contained a single-stranded DNA (ssDNA) loop and sticky end to prevent GNPs from salt-induced aggregation. In the presence of target sequence, the capture probe blocked in the FH recognizes the target to form a duplex DNA, which causes the release of the initiator probe by FH conformational change. This process then starts the alternate-opening of H1 and H2 through HCR, and dsDNA concatemers grow from the target sequence. As a result, unmodified GNPs undergo salt-induced aggregation because the formed dsDNA concatemers are stiffer and provide less stabilization. A light purple-to-blue color variation was observed in the bulk solution, termed the light-off sensing way. Furthermore, H1 ingeniously inserted an aptamer sequence to generate dsDNA concatemers with multiple small molecule binding sites. In the presence of small molecule targets, concatemers can be disassembled into mixtures with ssDNA sticky ends. A blue-to-purple reverse color variation was observed due to the regeneration of the ssDNA, termed the light-on way. The two-way biosensor can detect both nucleic acids and small molecule targets with one sensing device. This switchable sensing element is label-free, enzyme-free, and sophisticated-instrumentation-free. The detection limits of both targets were below nanomolar.

Direct observation of oxygen-vacancy-enhanced polarization in a SrTiO 3-buffered ferroelectric BaTiO 3 film on GaAs

DOE PAGES

Qiao, Q.; Zhang, Y.; Contreras-Guerrero, Rocio; ...

2015-11-16

The integration of functional oxide thin-films on compound semiconductors can lead to a class of reconfigurable spin-based optoelectronic devices if defect-free, fully reversible active layers are stabilized. However, previous first-principles calculations predicted that SrTiO 3 thin filmsgrown on Si exhibit pinned ferroelectric behavior that is not switchable, due to the presence of interfacial vacancies. Meanwhile, piezoresponse force microscopy measurements have demonstrated ferroelectricity in BaTiO 3 grown on semiconductor substrates. The presence of interfacial oxygen vacancies in such complex-oxide/semiconductor systems remains unexplored, and their effect on ferroelectricity is controversial. We also use a combination of aberration-corrected scanning transmission electron microscopy andmore » first-principles density functional theory modeling to examine the role of interfacial oxygen vacancies on the ferroelectricpolarization of a BaTiO 3 thin filmgrown on GaAs. Moreover, we demonstrate that interfacial oxygen vacancies enhance the polar discontinuity (and thus the single domain, out-of-plane polarization pinning in BaTiO 3), and propose that the presence of surface charge screening allows the formation of switchable domains.« less

Carbohydrate-actuated nanofluidic diode: switchable current rectification in a nanopipette

PubMed Central

Vilozny, Boaz; Wollenberg, Alexander L.; Actis, Paolo; Hwang, Daniel; Singaram, Bakthan

2013-01-01

Nanofluidic structures share many properties with ligand-gated ion channels. However, actuating ion conductance in artificial systems is a challenge. We have designed a system that uses a carbohydrate-responsive polymer to modulate ion conductance in a quartz nanopipette. The cationic polymer, a poly(vinylpyridine) quaternized with benzylboronic acid groups, undergoes a transition from swollen to collapsed upon binding to monosaccharides. As a result, the current rectification in nanopipettes can be reversibly switched depending on the concentration of monosaccharides. Such molecular actuation of nanofluidic conductance may be used in novel sensors and drug delivery systems. PMID:23934399

Carbohydrate-actuated nanofluidic diode: switchable current rectification in a nanopipette.

PubMed

Vilozny, Boaz; Wollenberg, Alexander L; Actis, Paolo; Hwang, Daniel; Singaram, Bakthan; Pourmand, Nader

2013-10-07

Nanofluidic structures share many properties with ligand-gated ion channels. However, actuating ion conductance in artificial systems is a challenge. We have designed a system that uses a carbohydrate-responsive polymer to modulate ion conductance in a quartz nanopipette. The cationic polymer, a poly(vinylpyridine) quaternized with benzylboronic acid groups, undergoes a transition from swollen to collapsed upon binding to monosaccharides. As a result, the current rectification in nanopipettes can be reversibly switched depending on the concentration of monosaccharides. Such molecular actuation of nanofluidic conductance may be used in novel sensors and drug delivery systems.

Self-organized layered hydrogenation in black Mg2NiHx switchable mirrors.

PubMed

Lohstroh, W; Westerwaal, R J; Noheda, B; Enache, S; Giebels, I A M E; Dam, B; Griessen, R

2004-11-05

In addition to a mirrorlike (Mg2Ni) and a transparent (Mg2NiH4) state, thin films of Mg2NiHx exhibit a remarkable black state with low reflection over the entire visible spectrum, essentially zero transmission and a low electrical resistivity. Such a black state is not explicable for a homogeneous layer since a large absorption coefficient always yields substantial reflection. We show that it results from a self-organized and reversible double layering of metallic Mg2NiH0.3 and semiconducting Mg2NiH4.

Light-induced metal-insulator transition in a switchable mirror.

PubMed

Hoekstra, A F; Roy, A S; Rosenbaum, T F; Griessen, R; Wijngaarden, R J; Koeman, N J

2001-06-04

Rare earth hydride films can be converted reversibly from metallic mirrors to insulating windows simply by changing the surrounding hydrogen gas pressure at room temperature. At low temperatures, in situ doping is not possible in this way as hydrogen cannot diffuse. However, our finding of persistent photoconductivity under ultraviolet illumination offers an attractive possibility to tune yttrium hydride through the T = 0 metal-insulator transition. Conductivity and Hall measurements are used to determine critical exponents. The unusually large value for the product of the static and dynamical critical exponents appears to signify the important role played by electron-electron interactions.

Pixel switching of epitaxial Pd/YHx/CaF2 switchable mirrors

PubMed

Kerssemakers; van der Molen SJ; Koeman; Gunther; Griessen

2000-08-03

Exposure of rare-earth films to hydrogen can induce a metal-insulator transition, accompanied by pronounced optical changes. This 'switchable mirror' effect has received considerable attention from theoretical, experimental and technological points of view. Most systems use polycrystalline films, but the synthesis of yttrium-based epitaxial switchable mirrors has also been reported. The latter form an extended self-organized ridge network during initial hydrogen loading, which results in the creation of micrometre-sized triangular domains. Here we observe homogeneous and essentially independent optical switching of individual domains in epitaxial switchable mirrors during hydrogen absorption. The optical switching is accompanied by topographical changes as the domains sequentially expand and contract; the ridges block lateral hydrogen diffusion and serve as a microscopic lubricant for the domain oscillations. We observe the correlated changes in topology and optical properties using in situ atomic force and optical microscopy. Single-domain phase switching is not observed in polycrystalline films, which are optically homogeneous. The ability to generate a tunable, dense pattern of switchable pixels is of technological relevance for solid-state displays based on switchable mirrors.

Light-induced protein degradation in human-derived cells.

PubMed

Sun, Wansheng; Zhang, Wenyao; Zhang, Chao; Mao, Miaowei; Zhao, Yuzheng; Chen, Xianjun; Yang, Yi

2017-05-27

Controlling protein degradation can be a valuable tool for posttranslational regulation of protein abundance to study complex biological systems. In the present study, we designed a light-switchable degron consisting of a light oxygen voltage (LOV) domain of Avena sativa phototropin 1 (AsLOV2) and a C-terminal degron. Our results showed that the light-switchable degron could be used for rapid and specific induction of protein degradation in HEK293 cells by light in a proteasome-dependent manner. Further studies showed that the light-switchable degron could also be utilized to mediate the degradation of secreted Gaussia princeps luciferase (GLuc), demonstrating the adaptability of the light-switchable degron in different types of protein. We suggest that the light-switchable degron offers a robust tool to control protein levels and may serves as a new and significant method for gene- and cell-based therapies. Copyright © 2017 Elsevier Inc. All rights reserved.

Four-Component Catalytic Machinery: Reversible Three-State Control of Organocatalysis by Walking Back and Forth on a Track.

PubMed

Mittal, Nikita; Özer, Merve S; Schmittel, Michael

2018-04-02

A three-component supramolecular walker system is presented where a two-footed ligand (biped) walks back and forth on a tetrahedral 3D track upon the addition and removal of copper(I) ions, respectively. The addition of N-methylpyrrolidine as a catalyst to the walker system generates a four-component catalytic machinery, which acts as a three-state switchable catalytic ensemble in the presence of substrates for a conjugate addition. The copper(I)-ion-initiated walking process of the biped ligand on the track regulates the catalytic activity in three steps: ON versus int ON (intermediate ON) versus OFF. To establish the operation of the four-component catalytic machinery in a mixture of all constituents, forward and backward cycles were performed in situ illustrating that both the walking process and catalytic action are fully reversible and reproducible.

Reversible adhesion switching of porous fibrillar adhesive pads by humidity.

PubMed

Xue, Longjian; Kovalev, Alexander; Dening, Kirstin; Eichler-Volf, Anna; Eickmeier, Henning; Haase, Markus; Enke, Dirk; Steinhart, Martin; Gorb, Stanislav N

2013-01-01

We report reversible adhesion switching on porous fibrillar polystyrene-block-poly(2-vinyl pyridine) (PS-b-P2VP) adhesive pads by humidity changes. Adhesion at a relative humidity of 90% was more than nine times higher than at a relative humidity of 2%. On nonporous fibrillar adhesive pads of the same material, adhesion increased only by a factor of ~3.3. The switching performance remained unchanged in at least 10 successive high/low humidity cycles. Main origin of enhanced adhesion at high humidity is the humidity-induced decrease in the elastic modulus of the polar component P2VP rather than capillary force. The presence of spongelike continuous internal pore systems with walls consisting of P2VP significantly leveraged this effect. Fibrillar adhesive pads on which adhesion is switchable by humidity changes may be used for preconcentration of airborne particulates, pollutants, and germs combined with triggered surface cleaning.

Reversible Modulation of DNA-Based Hydrogel Shapes by Internal Stress Interactions.

PubMed

Hu, Yuwei; Kahn, Jason S; Guo, Weiwei; Huang, Fujian; Fadeev, Michael; Harries, Daniel; Willner, Itamar

2016-12-14

We present the assembly of asymmetric two-layer hybrid DNA-based hydrogels revealing stimuli-triggered reversibly modulated shape transitions. Asymmetric, linear hydrogels that include layer-selective switchable stimuli-responsive elements that control the hydrogel stiffness are designed. Trigger-induced stress in one of the layers results in the bending of the linear hybrid structure, thereby minimizing the elastic free energy of the systems. The removal of the stress by a counter-trigger restores the original linear bilayer hydrogel. The stiffness of the DNA hydrogel layers is controlled by thermal, pH (i-motif), K + ion/crown ether (G-quadruplexes), chemical (pH-doped polyaniline), or biocatalytic (glucose oxidase/urease) triggers. A theoretical model relating the experimental bending radius of curvatures of the hydrogels with the Young's moduli and geometrical parameters of the hydrogels is provided. Promising applications of shape-regulated stimuli-responsive asymmetric hydrogels include their use as valves, actuators, sensors, and drug delivery devices.

Bio-inspired reversible underwater adhesive.

PubMed

Zhao, Yanhua; Wu, Yang; Wang, Liang; Zhang, Manman; Chen, Xuan; Liu, Minjie; Fan, Jun; Liu, Junqiu; Zhou, Feng; Wang, Zuankai

2017-12-20

The design of smart surfaces with switchable adhesive properties in a wet environment has remained a challenge in adhesion science and materials engineering. Despite intense demands in various industrial applications and exciting progress in mimicking the remarkable wet adhesion through the delicate control of catechol chemistry, polyelectrolyte complex, and supramolecular architectures, the full recapitulation of nature's dynamic function is limited. Here, we show a facile approach to synthesize bioinspired adhesive, which entails the reversible, tunable, and fast regulation of the wet adhesion on diverse surfaces. The smart wet adhesive takes advantage of the host-guest molecular interaction and the adhesive nature of catechol chemistry, as well as the responsive polymer, allowing for screening and activation of the interfacial interaction simply by a local temperature trigger in an on-demand manner. Our work opens up an avenue for the rational design of bioinspired adhesives with performances even beyond nature.

Reversible Structural Swell-Shrink and Recoverable Optical Properties in Hybrid Inorganic-Organic Perovskite.

PubMed

Zhang, Yupeng; Wang, Yusheng; Xu, Zai-Quan; Liu, Jingying; Song, Jingchao; Xue, Yunzhou; Wang, Ziyu; Zheng, Jialu; Jiang, Liangcong; Zheng, Changxi; Huang, Fuzhi; Sun, Baoquan; Cheng, Yi-Bing; Bao, Qiaoliang

2016-07-26

Ion migration in hybrid organic-inorganic perovskites has been suggested to be an important factor for many unusual behaviors in perovskite-based optoelectronics, such as current-voltage hysteresis, low-frequency giant dielectric response, and the switchable photovoltaic effect. However, the role played by ion migration in the photoelectric conversion process of perovskites is still unclear. In this work, we provide microscale insights into the influence of ion migration on the microstructure, stability, and light-matter interaction in perovskite micro/nanowires by using spatially resolved optical characterization techniques. We observed that ion migration, especially the migration of MA(+) ions, will induce a reversible structural swell-shrink in perovskites and recoverably affect the reflective index, quantum efficiency, light-harvesting, and photoelectric properties. The maximum ion migration quantity in perovskites was as high as approximately 30%, resulting in lattice swell or shrink of approximately 4.4%. Meanwhile, the evidence shows that ion migration in perovskites could gradually accelerate the aging of perovskites because of lattice distortion in the reversible structural swell-shrink process. Knowledge regarding reversible structural swell-shrink and recoverable optical properties may shed light on the development of optoelectronic and converse piezoelectric devices based on perovskites.

Genetic analysis of the roles of phytochromes A and B1 in the reversed gravitropic response of the lz-2 tomato mutant

NASA Technical Reports Server (NTRS)

Behringer, F. J.; Lomax, T. L.

1999-01-01

The lz-2 mutation in tomato (Lycopersicon esculentum) causes conditional reversal of shoot gravitropism by light. This response is mediated by phytochrome. To further elicit the mechanism by which phytochrome regulates the lz-2 phenotype, phytochrome-deficient lz-2 plants were generated. Introduction of au alleles, which severely block chromophore biosynthesis, eliminated the reversal of hypocotyl gravitropism in continuous red and far-red light. The fri1 and tri1 alleles were introduced to specifically deplete phytochromes A and B1, respectively. In dark-grown seedlings, phytochrome A was necessary for response to high-irradiance far-red light, a complete response to low fluence red light, and also mediated the effects of blue light in a far-red reversible manner. Loss of phytochrome B1 alone did not significantly affect the behaviour of lz-2 plants under any light treatment tested. However, dark-grown lz-2 plants lacking both phytochrome A and B1 exhibited reduced responses to continuous red and were less responsive to low fluence red light and high fluence blue light than plants that were deficient for phytochrome A alone. In high light, full spectrum greenhouse conditions, lz-2 plants grew downward regardless of the phytochrome deficiency. These results indicate that phytochromes A and B1 play significant roles in mediating the lz-2 phenotype and that at least one additional phytochrome is involved in reversing shoot gravitropism in this mutant.

Fabrication of ferroelectric polymer nanostructures on flexible substrates by soft-mold reverse nanoimprint lithography

NASA Astrophysics Data System (ADS)

Song, Jingfeng; Lu, Haidong; Li, Shumin; Tan, Li; Gruverman, Alexei; Ducharme, Stephen

2016-01-01

Conventional nanoimprint lithography with expensive rigid molds is used to pattern ferroelectric polymer nanostructures on hard substrate for use in, e.g., organic electronics. The main innovation here is the use of inexpensive soft polycarbonate molds derived from recordable DVDs and reverse nanoimprint lithography at low pressure, which is compatible with flexible substrates. This approach was implemented to produce regular stripe arrays with a spacing of 700 nm from vinylidene fluoride co trifluoroethylene ferroelectric copolymer on flexible polyethylene terephthalate substrates. The nanostructures have very stable and switchable piezoelectric response and good crystallinity, and are highly promising for use in organic electronics enhanced or complemented by the unique properties of the ferroelectric polymer, such as bistable polarization, piezoelectric response, pyroelectric response, or electrocaloric function. The soft-mold reverse nanoimprint lithography also leaves little or no residual layer, affording good isolation of the nanostructures. This approach reduces the cost and facilitates large-area, high-throughput production of isolated functional polymer nanostructures on flexible substrates for the increasing application of ferroelectric polymers in flexible electronics.

Fabrication of ferroelectric polymer nanostructures on flexible substrates by soft-mold reverse nanoimprint lithography.

PubMed

Song, Jingfeng; Lu, Haidong; Li, Shumin; Tan, Li; Gruverman, Alexei; Ducharme, Stephen

2016-01-08

Conventional nanoimprint lithography with expensive rigid molds is used to pattern ferroelectric polymer nanostructures on hard substrate for use in, e.g., organic electronics. The main innovation here is the use of inexpensive soft polycarbonate molds derived from recordable DVDs and reverse nanoimprint lithography at low pressure, which is compatible with flexible substrates. This approach was implemented to produce regular stripe arrays with a spacing of 700 nm from vinylidene fluoride co trifluoroethylene ferroelectric copolymer on flexible polyethylene terephthalate substrates. The nanostructures have very stable and switchable piezoelectric response and good crystallinity, and are highly promising for use in organic electronics enhanced or complemented by the unique properties of the ferroelectric polymer, such as bistable polarization, piezoelectric response, pyroelectric response, or electrocaloric function. The soft-mold reverse nanoimprint lithography also leaves little or no residual layer, affording good isolation of the nanostructures. This approach reduces the cost and facilitates large-area, high-throughput production of isolated functional polymer nanostructures on flexible substrates for the increasing application of ferroelectric polymers in flexible electronics.

Reversible non-volatile switch based on a TCNQ charge transfer complex

NASA Technical Reports Server (NTRS)

DiStefano, Salvador (Inventor); Moacanin, Jovan (Inventor); Nagasubramanian, Ganesan (Inventor)

1993-01-01

A solid-state synaptic memory matrix (10) having switchable weakly conductive connections at each node (24) whose resistances can be selectably increased or decreased over several orders of magnitude by control signals of opposite polarity, and which will remain stable after the signals are removed, comprises an insulated substrate (16), a set of electrical conductors (14) upon which is deposited a layer (18) of an organic conducting polymer, which changes from an insulator to a conductor upon the transfer of electrons, such as polymerized pyrrole doped with 7,7,8,8-tetracyanoquinodimethane (TCNQ), covered by a second set of conductors (20) laid at right angles to the first.

An Intrinsically Switchable Ladder-Type Ferroelectric BST-on-Si Composite FBAR Filter.

PubMed

Lee, Seungku; Mortazawi, Amir

2016-03-01

This paper presents a ladder-type bulk acoustic wave (BAW) intrinsically switchable filter based on ferroelectric thin-film bulk acoustic resonators (FBARs). The switchable filter can be turned on and off by the application of an external bias voltage due to the electrostrictive effect in thin-film ferroelectrics. In this paper, Barium Strontium Titanate (BST) is used as the ferroelectric material. A systematic design approach for switchable ladder-type ferroelectric filters is provided based on required filter specifications. A switchable filter is implemented in the form of a BST-on-Si composite structure to control the effective electromechanical coupling coefficient of FBARs. As an experimental verification, a 2.5-stage intrinsically switchable BST-on-Si composite FBAR filter is designed, fabricated, and measured. Measurement results for a typical BST-on-Si composite FBAR show a resonator mechanical quality factor (Q(m)) of 971, as well as a (Q(m)) × f of 2423 GHz. The filter presented here provides a measured insertion loss of 7.8 dB, out-of-band rejection of 26 dB, and fractional bandwidth of 0.33% at 2.5827 GHz when the filter is in the on state at a dc bias of 40 V. In its off state, the filter exhibits an isolation of 31 dB.

The 2D Selfassembly of Benzimidazole and its Co-crystallization

NASA Astrophysics Data System (ADS)

Costa, Paulo; Teeter, Jacob; Kunkel, Donna; Sinitskii, Alexander; Enders, Axel

Benzimidazoles (BI) are organic molecules that form ferroelectric crystals. Key to their ferroelectric behavior are the switchable N . . . HN type bonds and how they couple to the electron system of the molecules. We attempted to crystallize BI on various metal surfaces and studied them using STM. We observed that on Au and Ag, BI joins into zipper chains characteristic of its bulk structure that can pack into a continuous 2D layer. Because the dipole of BI lies in the direction of its switchable hydrogen bond, these zippers should in principle have reversible polarizations that point along the direction they run. BI's crystallization is reminiscent to how croconic acid (CA) crystallizes in 2D using O . . . HO bonding, suggesting that these molecules may be able to co-crystallize through OH . . . N bonds. This would present the opportunity to modify BI's properties, such as the energy needed to switch a hydrogen from a donor to acceptor site. When co-deposited, CA and BI successfully combine into a co-crystal formed by building blocks consisting of 2 CA and 2 BI molecules. These findings demonstrate the usefulness of using STM as a preliminary check to verify if two molecules are compatible with each other without having to attempt crystallization with multiple solvents and mixing methods.

Application of nanostructured biochips for efficient cell transfection microarrays

NASA Astrophysics Data System (ADS)

Akkamsetty, Yamini; Hook, Andrew L.; Thissen, Helmut; Hayes, Jason P.; Voelcker, Nicolas H.

2007-01-01

Microarrays, high-throughput devices for genomic analysis, can be further improved by developing materials that are able to manipulate the interfacial behaviour of biomolecules. This is achieved both spatially and temporally by smart materials possessing both switchable and patterned surface properties. A system had been developed to spatially manipulate both DNA and cell growth based upon the surface modification of highly doped silicon by plasma polymerisation and polyethylene grafting followed by masked laser ablation for formation of a pattered surface with both bioactive and non-fouling regions. This platform has been successfully applied to transfected cell microarray applications with the parallel expression of genes by utilising its ability to direct and limit both DNA and cell attachment to specific sites. One of the greatest advantages of this system is its application to reverse transfection, whereupon by utilising the switchable adsorption and desorption of DNA using a voltage bias, the efficiency of cell transfection can be enhanced. However, it was shown that application of a voltage also reduces the viability of neuroblastoma cells grown on a plasma polymer surface, but not human embryonic kidney cells. This suggests that the application of a voltage may not only result in the desorption of bound DNA but may also affect attached cells. The characterisation of a DNA microarray by contact printing has also been investigated.

Tunable and switchable all-fiber comb filter using a PBS-based two-stage cascaded Mach-Zehnder interferometer

NASA Astrophysics Data System (ADS)

Luo, Zhi-Chao; Luo, Ai-Ping; Xu, Wen-Cheng

2011-08-01

We propose and demonstrate a novel tunable and switchable all-fiber comb filter by employing a polarization beam splitter (PBS)-based two-stage cascaded Mach-Zehnder (M-Z) interferometer. The proposed comb filter consists of a rotatable polarizer, a fiber PBS, a non-3-dB coupler and a 3-dB coupler. By simply adjusting the polarization state of the input light, the dual-function of channel spacing tunable and wavelength switchable (interleaving) operations can be efficiently obtained. The theoretical analysis is verified by the experimental results. A comb filter with both the channel spacing tunable from 0.18 nm to 0.36 nm and the wavelength switchable functions is experimentally demonstrated.

Study on stimulus-responsive cellulose-based polymeric materials

NASA Astrophysics Data System (ADS)

Luo, Hongsheng

Stimulus-responsive cellulose-based polymeric materials were developed by physical and chemical approaches. The thermal, structural, mechanical and morphological properties of the samples were comprehensively investigated by multiple tools. Shape memory effect (SME), programming-structure-property relationship and underling mechanisms were emphasized in this study. Some new concepts, such as heterogeneous-twin-switch, path-dependent multi-shape, rapidly switchable water-sensitive SME were established. The samples were divided into two categories. For the first category, cellulose nano-whiskers (CNWs) were incorporated into crystalline shape memory polyurethane (SMPU) and thermal plastic polyurethane (TPU). The CNW-SMPU nano-composites had heterogeneous switches. Triple- and multi-shape effects were achieved for the CNW-SMPU nano-composites by applying into appropriate thermal-aqueous-mechanical programming. Furthermore, the thermally triggered shape recovery of the composites was found to be tuneable, depending on the PCN content. Theoretical prediction along with numerical analysis was conducted, providing evidence on the possible microstructure of the CNW-SMPU nano-composites. Rapidly switchable water-sensitive SME of the CNW-TPU nano-composites was unprecedentedly studied, which originated from the reversible regulation of hydrogen bonding by water. The samples in the second category consisted of cellulose-polyurethane (PU) blends, cellulose-poly(acrylic acid) (PAA) composites and modified cellulose with supramolecular switches, featuring the requirement of homogeneous cellulose solution in the synthesis process. The reversible behaviours of the cellulose-PU blends in wet-dry cycles as well as the underlying shape memory mechanism were characterized and disclosed. The micro-patterns of the blends were found to be self-similar in fractal dimensions. Cellulose-PAA semi-interpenetrating networks exhibited mechanical adaptability in wet-dry cycles. A type of thermally reversible quadruple hydrogen bonding units, ureidopyrimidinone (UPy), reacted with the cellulose as pendent side-groups, which may impart the modified cellulose with thermal sensitivity. It is the first attempt to explore the natural cellulose as smart polymeric materials systematically and comprehensively. The concepts originally created in the study provided new viewpoints and routes for the development of novel shape memory polymers. The findings significantly benefits extension of the potential application of the cellulose in smart polymeric materials field.

Wavelength-switchable C-band erbium-doped fibre laser incorporating all-fibre Fabry-Perot interferometer fabricated by chemical etching

NASA Astrophysics Data System (ADS)

He, Wei; Zhu, Lianqing; Dong, Mingli; Lou, Xiaoping; Luo, Fei

2018-04-01

A switchable and stable triple-wavelength, ring-cavity, erbium-doped fibre laser incorporating an all-fibre Fabry-Perot interferometer (FPI) is designed and experimentally demonstrated. In the proposed fibre laser, the all-fibre FPI is fabricated using the chemical etching method and is used to generate the filter effect. The laser threshold is 88 mW. Switchable single-wavelength lasing at 1529.9, 1545.1 and 1560.2 nm can be realized with a power fluctuation less than 0.64 dB under 20 min of scanning time at room temperature. In addition, the wavelength-switchable dual-wavelength lasers can be tuned by changing the polarization state in the experiment, and the maximum power fluctuations for the 1545.1 and 1560.2 nm lasers are less than 1.19 and 1.57 dB at 26 °C, respectively. Furthermore, a triple-wavelength laser is obtained by adjusting the polarization controller. The results demonstrate that switchable single-, dual-, or triple-wavelength lasers can be generated through the proposed fibre laser.

Switchable polarization in an unzipped graphene oxide monolayer.

PubMed

Noor-A-Alam, Mohammad; Shin, Young-Han

2016-08-14

Ferroelectricity in low-dimensional oxide materials is generally suppressed at the scale of a few nanometers, and has attracted considerable attention from both fundamental and technological aspects. Graphene is one of the thinnest materials (one atom thick). Therefore, engineering switchable polarization in non-polar pristine graphene could potentially lead to two-dimensional (2D) ferroelectric materials. In the present study, based on density functional theory, we show that an unzipped graphene oxide (UGO) monolayer can exhibit switchable polarization due to its foldable bonds between the oxygen atom and two carbon atoms underneath the oxygen. We find that a free standing UGO monolayer exhibits antiferroelectric switchable polarization. A UGO monolayer can be obtained as an intermediate product during the chemical exfoliation process of graphene. Interestingly, despite its dimensionality, our estimated polarization in a UGO monolayer is comparable to that in bulk ferroelectric materials (e.g., ferroelectric polymers). Our calculations could help realize antiferroelectric switchable polarization in 2D materials, which could find various potential applications in nanoscale devices such as sensors, actuators, and capacitors with high energy-storage density.

Switchable and non-switchable zero backscattering of dielectric nano-resonators

DOE PAGES

Wang, Feng; Wei, Qi -Huo; Htoon, Han

2015-02-27

Previous studies have shown that two-dimensional (2D) arrays of high-permittivity dielectric nanoparticles are capable of fully suppressing backward light scattering when the resonant frequencies of electrical and magnetic dipolar modes are coincident. In this paper, we numerically demonstrate that the zero-backscattering of 2D Si nanocuboid arrays can be engineered to be switchable or non-switchable in response to a variation in the environmental refractive index. For each cuboid width/length, there exist certain cuboid heights and orthogonal periodicity ratio for which the electrical and magnetic resonances exhibit similar spectra widths and equivalent sensitivities to the environmental index changes, so that the zero-backscatteringmore » is non-switchable upon environmental change. For some other cuboid heights and certain anisotropic periodicity ratios, the electric and magnetic modes exhibit different sensitivities to environmental index changes, making the zero-backscattering sensitive to environmental changes. We also show that by using two different types of nano-resonators in the unit cell, Fano resonances can be introduced to greatly enhance the switching sensitivity of zero-backscattering.« less

Switchable wavelength-selective and diffuse metamaterial absorber/emitter with a phase transition spacer layer

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wang, Hao; Yang, Yue; Wang, Liping, E-mail: liping.wang@asu.edu

2014-08-18

We numerically demonstrate a switchable metamaterial absorber/emitter by thermally turning on or off the excitation of magnetic resonance upon the phase transition of vanadium dioxide (VO{sub 2}). Perfect absorption peak exists around the wavelength of 5 μm when the excitation of magnetic resonance is supported with the insulating VO{sub 2} spacer layer. The wavelength-selective absorption is switched off when the magnetic resonance is disabled with metallic VO{sub 2} that shorts the top and bottom metallic structures. The resonance wavelength can be tuned with different geometry, and the switchable metamaterial exhibits diffuse behaviors at oblique angles. The results would facilitate the designmore » of switchable metamaterials for active control in energy and sensing applications.« less

In situ Charge Density Imaging of Metamaterials made with Switchable Two dimensionalElectron Gas at Oxide Heterointerfaces

DTIC Science & Technology

2017-11-28

AFRL-AFOSR-JP-TR-2018-0028 In-situ Charge-Density Imaging of Metamaterials from Switchable 2D electron gas CHANG BEOM EOM UNIVERSITY OF WISCONSIN...Imaging of Metamaterials made with Switchable Two-dimensional Electron Gas at Oxide Heterointerfaces 5a.  CONTRACT NUMBER 5b.  GRANT NUMBER FA2386-16-1...using pulsed laser deposition atomic with in-situ reflection high-energy electron diffraction (RHEED). We have also demonstrated that the inline

Effect of hydrogen-switchable mirrors on the Casimir force.

PubMed

Iannuzzi, Davide; Lisanti, Mariangela; Capasso, Federico

2004-03-23

We present systematic measurements of the Casimir force between a gold-coated plate and a sphere coated with a hydrogen-switchable mirror. Hydrogen-switchable mirrors are shiny metals that can become transparent upon hydrogenation. Despite such a dramatic change of the optical properties of the sphere, we did not observe any significant decrease of the Casimir force after filling the experimental apparatus with hydrogen. This counterintuitive result can be explained by the Lifshitz theory that describes the Casimir attraction between metallic and dielectric materials.

Effect of hydrogen-switchable mirrors on the Casimir force

PubMed Central

Iannuzzi, Davide; Lisanti, Mariangela; Capasso, Federico

2004-01-01

We present systematic measurements of the Casimir force between a gold-coated plate and a sphere coated with a hydrogen-switchable mirror. Hydrogen-switchable mirrors are shiny metals that can become transparent upon hydrogenation. Despite such a dramatic change of the optical properties of the sphere, we did not observe any significant decrease of the Casimir force after filling the experimental apparatus with hydrogen. This counterintuitive result can be explained by the Lifshitz theory that describes the Casimir attraction between metallic and dielectric materials. PMID:15024111

Transition Metal Switchable Mirror

ScienceCinema

None

2017-12-09

The switchable-mirrors technology was developed by Tom Richardson and Jonathan Slack of Berkeley Lab's Environmental Energy Technologies Division. By using transition metals rather than the rare earth metals used in the first metal-hydride switchable mirrors, Richardson and Slack were able to lower the cost and simplify the manufacturing process. Energy performance is improved as well, because the new windows can reflect or transmit both visible and infrared light. Besides windows for offices and homes, possible applications include automobile sunroofs, signs and displays, aircraft windows, and spacecraft.

Transition Metal Switchable Mirror

DOE Office of Scientific and Technical Information (OSTI.GOV)

None

2009-08-21

The switchable-mirrors technology was developed by Tom Richardson and Jonathan Slack of Berkeley Lab's Environmental Energy Technologies Division. By using transition metals rather than the rare earth metals used in the first metal-hydride switchable mirrors, Richardson and Slack were able to lower the cost and simplify the manufacturing process. Energy performance is improved as well, because the new windows can reflect or transmit both visible and infrared light. Besides windows for offices and homes, possible applications include automobile sunroofs, signs and displays, aircraft windows, and spacecraft.

Directly observed reversible shape changes and hemoglobin stratification during centrifugation of human and Amphiuma red blood cells.

PubMed

Hoffman, Joseph F; Inoué, Shinya

2006-02-21

This paper describes changes that occur in human and Amphiuma red blood cells observed during centrifugation with a special microscope. Dilute suspensions of cells were layered, in a centrifuge chamber, above an osmotically matched dense solution, containing Nycodenz, Ficoll, or Percoll (Pharmacia) that formed a density gradient that allowed the cells to slowly settle to an equilibrium position. Biconcave human red blood cells moved downward at low forces with minimum wobble. The cells oriented vertically when the force field was increased and Hb sedimented as the lower part of each cell became bulged and assumed a "bag-like" shape. The upper centripetal portion of the cell became thinner and remained biconcave. These changes occurred rapidly and were completely reversible upon lowering the centrifugal force. Bag-shaped cells, upon touching red cells in rouleau, immediately reverted to biconcave disks as they flipped onto a stack. Amphiuma red cells displayed a different type of reversible stratification and deformation at high force fields. Here the cells became stretched, with the nucleus now moving centrifugally, the Hb moving centripetally, and the bottom of the cells becoming thinner and clear. Nevertheless, the distribution of the marginal bands at the cells' rim was unchanged. We conclude that centrifugation, per se, while changing a red cell's shape and the distribution of its intracellular constituents, does so in a completely reversible manner. Centrifugation of red cells harboring altered or missing structural elements could provide information on shape determinants that are still unexplained.

Progressive myopia or hyperopia can be induced in chicks and reversed by manipulation of the chromaticity of ambient light.

PubMed

Foulds, Wallace S; Barathi, Veluchamy A; Luu, Chi D

2013-12-09

To determine whether progressive ametropia can be induced in chicks and reversed by manipulation of the chromaticity of ambient light. One-day-old chicks were raised in red light (90% red, 10% yellow-green) or in blue light (85% blue, 15% green) with a 12 hour on/off cycle for 14 to 42 days. Refraction was determined by streak retinoscopy, and by automated infrared photoretinoscopy and ocular biometry by A-scan ultrasonography. Red light induced progressive myopia (mean refraction ± SD at 28 days, -2.83 ± 0.25 diopters [D]). Progressive hyperopia was induced by blue light (mean refraction at 28 days, +4.55 ± 0.21 D). The difference in refraction between the groups was highly significant at P < 0.001. Induced myopia or hyperopia was axial as confirmed by ultrasound biometry. Myopia induced by 21 days of red light (-2.21 ± 0.21 D) was reversed to hyperopia (+2.50 ± 0.29 D) by subsequent 21 days of blue light. Hyperopia induced by 21 days of blue light (+4.21 ± 0.19 D) was reversed to myopia (-1.23 ± 0.12 D) by 21 days of red light. Rearing chicks in red light caused progressive myopia, while rearing in blue light caused progressive hyperopia. Light-induced myopia or hyperopia in chicks can be reversed to hyperopia or myopia, respectively, by an alteration in the chromaticity of ambient light. Manipulation of chromaticity may be applicable to the management of human childhood myopia.

Universal light-switchable gene promoter system

DOEpatents

Quail, Peter H.; Huq, Enamul; Tepperman, James; Sato, Sae

2005-02-22

An artificial promoter system that can be fused upstream of any desired gene enabling reversible induction or repression of the expression of the gene at will in any suitable host cell or organisms by light is described. The design of the system is such that a molecule of the plant photoreceptor phytochrome is targeted to the specific DNA binding site in the promoter by a protein domain that is fused to the phytochrome and that specifically recognizes this binding site. This bound phytochrome, upon activation by light, recruits a second fusion protein consisting of a protein that binds to phytochrome only upon light activation and a transcriptional activation domain that activates expression of the gene downstream of the promoter.

A switchable self-assembling and disassembling chiral system based on a porphyrin-substituted phenylalanine-phenylalanine motif

NASA Astrophysics Data System (ADS)

Charalambidis, Georgios; Georgilis, Evangelos; Panda, Manas K.; Anson, Christopher E.; Powell, Annie K.; Doyle, Stephen; Moss, David; Jochum, Tobias; Horton, Peter N.; Coles, Simon J.; Linares, Mathieu; Beljonne, David; Naubron, Jean-Valère; Conradt, Jonas; Kalt, Heinz; Mitraki, Anna; Coutsolelos, Athanassios G.; Balaban, Teodor Silviu

2016-09-01

Artificial light-harvesting systems have until now not been able to self-assemble into structures with a large photon capture cross-section that upon a stimulus reversibly can switch into an inactive state. Here we describe a simple and robust FLFL-dipeptide construct to which a meso-tetraphenylporphyrin has been appended and which self-assembles to fibrils, platelets or nanospheres depending on the solvent composition. The fibrils, functioning as quenched antennas, give intense excitonic couplets in the electronic circular dichroism spectra which are mirror imaged if the unnatural FDFD-analogue is used. By slightly increasing the solvent polarity, these light-harvesting fibres disassemble to spherical structures with silent electronic circular dichroism spectra but which fluoresce. Upon further dilution with the nonpolar solvent, the intense Cotton effects are recovered, thus proving a reversible switching. A single crystal X-ray structure shows a head-to-head arrangement of porphyrins that explains both their excitonic coupling and quenched fluorescence.

Controllable self-assembly of sodium caseinate with a zwitterionic vitamin-derived bolaamphiphile.

PubMed

Sun, Li-Hui; Sun, Yu-Long; Yang, Li-Jun; Zhang, Jian; Chen, Zhong-Xiu

2013-11-06

The control of self-assembly of sodium caseinate (SC) including the formation of mixed layers, microspheres, or nanoparticles is highly relevant to the microstructure of food and the design of promising drug delivery systems. In this paper, we designed a structure-switchable zwitterionic bolaamphiphile, 1,12-diaminododecanediorotate (DDO), from orotic acid, which has special binding sites and can guide the self-assembly of SC. Complexation between SC and DDO was investigated using dynamic light scattering, transmission electron microscopy, differential scanning calorimetry, and fluorescence spectra measurements. Monomeric DDO was bound to the negatively charged sites on the SC micelle and made the structure of SC more compact with decreased electrostatic repulsion between the head groups. Vesicular DDO led to reassociation of vesicles with enlarged size via preferable hydrophobic interactions. Moreover, the aggregation between SC and DDO was found to be temperature-dependent and reversible. This research provides an effective way to control the reversible self-assembly of SC by the zwitterionic vitamin-derived bolaamphiphile.

Transition Metal Switchable Mirror

ScienceCinema

None

2017-12-29

The switchable-mirrors technology was developed by Tom Richardson and Jonathan Slack of Berkeley Lab's Environmental Energy Technologies Division. By using transition metals rather than the rare earth metals used in the first metal-hydride switchable mirrors, Richardson and Slack were able to lower the cost and simplify the manufacturing process. Energy performance is improved as well, because the new windows can reflect or transmit both visible and infrared light. Besides windows for offices and homes, possible applications include automobile sunroofs, signs and displays, aircraft windows, and spacecraft. More information at: http://windows.lbl.gov/materials/chromogenics/default.htm

Transition Metal Switchable Mirror

DOE Office of Scientific and Technical Information (OSTI.GOV)

None

2009-08-21

The switchable-mirrors technology was developed by Tom Richardson and Jonathan Slack of Berkeley Lab's Environmental Energy Technologies Division. By using transition metals rather than the rare earth metals used in the first metal-hydride switchable mirrors, Richardson and Slack were able to lower the cost and simplify the manufacturing process. Energy performance is improved as well, because the new windows can reflect or transmit both visible and infrared light. Besides windows for offices and homes, possible applications include automobile sunroofs, signs and displays, aircraft windows, and spacecraft. More information at: http://windows.lbl.gov/materials/chromogenics/default.htm

In-situ Manipulation and Imaging of Switchable Two-dimensional Electron Gas at Oxide Heterointerfaces

DTIC Science & Technology

2016-11-30

AFRL-AFOSR-JP-TR-2017-0016 In-situ Manipulation and Imaging of Switchable Two-dimensional Electron Gas at Oxide Heterointerfaces CHANG BEOM EOM...Imaging of Switchable Two-dimensional Electron Gas at Oxide Heterointerfaces 5a.  CONTRACT NUMBER 5b.  GRANT NUMBER FA2386-15-1-4046 5c.  PROGRAM...NOTES 14. ABSTRACT The recent discovery of a two-dimensional electron gas (2DEG) at the interface between insulating perovskite oxides SrTiO3 and LaAlO3

Charge reversible gold nanoparticles for high efficient absorption and desorption of DNA

NASA Astrophysics Data System (ADS)

Wang, Can; Zhuang, Jiaqi; Jiang, Shan; Li, Jun; Yang, Wensheng

2012-10-01

Mercaptoundecylamine and mercaptoundecanoic acid co-modified Au nanoparticles were prepared by two-step ligand exchange of 6-mercaptohexanoic acid modified gold nanoparticles. Such particles terminated by appropriate ratios of the amine and carboxyl groups ( R N/C) were identified to show reversible charge on their surface, which were switchable by pH of the solution. The isoelectric point (IEP) of the particles is tunable by changing the ratios of the amine and carboxyl groups on the particle surfaces. The particles can absorb DNA effectively at pH lower than the IEP driven by the direct electrostatic interactions between DNA and the particle surface. When pH of the solutions was elevated to be higher than the IEP, the absorbed DNA can be released almost completely due to the electrostatic repulsion between the particle surface and DNA. With appropriate R N/C ratios of 0.8, the absorption and desorption efficiencies of DNA were 97 and 98 %, respectively, corresponding an extraction efficiency of 95 %. Such particles with reversible surface charges allow the high efficient extraction of DNA by simply changing pH instead of by changing salt concentration in the conventional salt bridge method.

A smart core-sheath nanofiber that captures and releases red blood cells from the blood.

PubMed

Shi, Q; Hou, J; Zhao, C; Xin, Z; Jin, J; Li, C; Wong, S-C; Yin, J

2016-01-28

A smart core-sheath nanofiber for non-adherent cell capture and release is demonstrated. The nanofibers are fabricated by single-spinneret electrospinning of poly(N-isopropylacrylamide) (PNIPAAm), polycaprolactone (PCL) and nattokinase (NK) solution blends. The self-assembly of PNIPAAm and PCL blends during the electrospinning generates the core-sheath PCL/PNIPAAm nanofibers with PNIPAAm as the sheath. The PNIPAAm-based core-sheath nanofibers are switchable between hydrophobicity and hydrophilicity with temperature change and enhance stability in the blood. When the nanofibers come in contact with blood, the NK is released from the nanofibers to resist platelet adhesion on the nanofiber surface, facilitating the direct capture and isolation of red blood cells (RBCs) from the blood above phase-transition temperature of PNIPAAm. Meanwhile, the captured RBCs are readily released from the nanofibers with temperature stimuli in an undamaged manner. The release efficiency of up to 100% is obtained while maintaining cellular integrity and function. This work presents promising nanofibers to effectively capture non-adherent cells and release for subsequent molecular analysis and diagnosis of single cells.

Low-Energy Water Recovery from Subsurface Brines

DOE Office of Scientific and Technical Information (OSTI.GOV)

Choi, Young Chul; Kim, Gyu Dong; Hendren, Zachary

A novel non-aqueous phase solvent (NAS) desalination process was proposed and developed in this research project. The NAS desalination process uses less energy than thermal processes, doesn’t require any additional chemicals for precipitation, and can be utilized to treat high TDS brine. In this project, our experimental work determined that water solubility changes and selective absorption are the key characteristics of NAS technology for successful desalination. Three NAS desalination mechanisms were investigated: (1) CO2 switchable, (2) high-temp absorption to low-temp desorption (thermally switchable), and (3) low-temp absorption to high-temp desorption (thermally switchable). Among these mechanisms, thermally switchable (low-temp absorption tomore » high-temp desorption) showed the highest water recovery and relatively high salt rejection. A test procedure for semi-continuous, bench scale NAS desalination process was also developed and used to assess performance under a range of conditions.« less

Multifunctional nanoparticle-protein conjugates with controllable bioactivity and pH responsiveness

NASA Astrophysics Data System (ADS)

Liu, Feng; Xue, Lulu; Yuan, Yuqi; Pan, Jingjing; Zhang, Chenjie; Wang, Hongwei; Brash, John L.; Yuan, Lin; Chen, Hong

2016-02-01

The modulation of protein activity is of significance for disease therapy, molecular diagnostics, and tissue engineering. Nanoparticles offer a new platform for the preparation of protein conjugates with improved protein properties. In the present work, Escherichia coli (E. coli) inorganic pyrophosphatase (PPase) and poly(methacrylic acid) (PMAA) were attached together to gold nanoparticles (AuNPs), forming AuNP-PPase-PMAA conjugates having controllable multi-biofunctionalities and responsiveness to pH. By treating with poly(2-(dimethylamino)ethyl methacrylate) (PDMAEMA) and regulating the pH, the bioactivity of the conjugate becomes ``on/off''-switchable. In addition, by taking advantage of the ability of AuNPs to undergo reversible aggregation/dispersion, the conjugates can be recycled and reused multiple times; and due to the shielding effect of the PMAA, the conjugated enzyme has high resistance to protease digestion. This approach has considerable potential in areas such as controlled delivery and release of drugs, biosensing, and biocatalysis.The modulation of protein activity is of significance for disease therapy, molecular diagnostics, and tissue engineering. Nanoparticles offer a new platform for the preparation of protein conjugates with improved protein properties. In the present work, Escherichia coli (E. coli) inorganic pyrophosphatase (PPase) and poly(methacrylic acid) (PMAA) were attached together to gold nanoparticles (AuNPs), forming AuNP-PPase-PMAA conjugates having controllable multi-biofunctionalities and responsiveness to pH. By treating with poly(2-(dimethylamino)ethyl methacrylate) (PDMAEMA) and regulating the pH, the bioactivity of the conjugate becomes ``on/off''-switchable. In addition, by taking advantage of the ability of AuNPs to undergo reversible aggregation/dispersion, the conjugates can be recycled and reused multiple times; and due to the shielding effect of the PMAA, the conjugated enzyme has high resistance to protease digestion. This approach has considerable potential in areas such as controlled delivery and release of drugs, biosensing, and biocatalysis. Electronic supplementary information (ESI) available. See DOI: 10.1039/c5nr07436c

Phototropin 1 and dim-blue light modulate the red light de-etiolation response.

PubMed

Wang, Yihai; M Folta, Kevin

2014-01-01

Light signals regulate seedling morphological changes during de-etiolation through the coordinated actions of multiple light-sensing pathways. Previously we have shown that red-light-induced hypocotyl growth inhibition can be reversed by addition of dim blue light through the action of phototropin 1 (phot1). Here we further examine the fluence-rate relationships of this blue light effect in short-term (hours) and long-term (days) hypocotyl growth assays. The red stem-growth inhibition and blue promotion is a low-fluence rate response, and blue light delays or attenuates both the red light and far-red light responses. These de-etiolation responses include blue light reversal of red or far-red induced apical hook opening. This response also requires phot1. Cryptochromes (cry1 and cry2) are activated by higher blue light fluence-rates and override phot1's influence on hypocotyl growth promotion. Exogenous application of auxin transport inhibitor naphthylphthalamic acid abolished the blue light stem growth promotion in both hypocotyl growth and hook opening. Results from the genetic tests of this blue light effect in auxin transporter mutants, as well as phytochrome kinase substrate mutants indicated that aux1 may play a role in blue light reversal of red light response. Together, the phot1-mediated adjustment of phytochrome-regulated photomorphogenic events is most robust in dim blue light conditions and is likely modulated by auxin transport through its transporters.

Direct and reverse pollen-mediated gene flow between GM rice and red rice weed

PubMed Central

Serrat, X.; Esteban, R.; Peñas, G.; Català, M. M.; Melé, E.; Messeguer, J.

2013-01-01

Potential risks of genetically modified (GM) crops must be identified before their commercialization, as happens with all new technologies. One of the major concerns is the proper risk assessment of adventitious presence of transgenic material in rice fields due to cross-pollination. Several studies have been conducted in order to quantify pollen-mediated gene flow from transgenic rice (Oryza sativa) to both conventional rice and red rice weed (O. sativa f. spontanea) under field conditions. Some of these studies reported GM pollen-donor rice transferring GM traits to red rice. However, gene flow also occurs in the opposite direction, in a phenomenon that we have called reverse gene flow, resulting in transgenic seeds that have incorporated the traits of wild red rice. We quantified reverse gene flow using material from two field trials. A molecular analysis based on amplified fragment length polymorphisms was carried out, being complemented with a phenotypic identification of red rice traits. In both field trials, the reverse gene flow detected was greater than the direct gene flow. The rate of direct gene flow varied according to the relative proportions of the donor (GM rice) and receptor (red rice) plants and was influenced by wind direction. The ecological impact of reverse gene flow is limited in comparison with that of direct gene flow because non-shattered and non-dormant seeds would be obtained in the first generation. Hybrid seed would remain in the spike and therefore most of it would be removed during harvesting. Nevertheless, this phenomenon must be considered in fields used for elite seed production and in developing countries where farmers often keep some seed for planting the following year. In these cases, there is a higher risk of GM red rice weed infestation increasing from year to year and therefore a proper monitoring plan needs to be established.

Switchable zero-index metamaterials by loading positive-intrinsic-negative diodes

DOE Office of Scientific and Technical Information (OSTI.GOV)

Xiang, Nan; Cheng, Qiang, E-mail: qiangcheng@emfield.org; Zhao, Jie

2014-02-03

We propose switchable zero-index metamaterials (ZIMs) implemented by split ring resonators (SRRs) loaded with positive-intrinsic-negative (PIN) diode switching elements. We demonstrate that ZIMs can be achieved at around 10 GHz when the PIN diode is switched off. When the PIN diode is switched on, however, the designed metamaterials have impedance matching to the free space, which is useful to reduce the reflections at the interface of two media. The switchable ZIMs are suitable for a wide variety of applications like the beam forming and directive radiation. Experimental results validate the switching ability of the proposed ZIMs.

Use of a conformational switching aptamer for rapid and specific ex vivo identification of central nervous system lymphoma in a xenograft model

NASA Astrophysics Data System (ADS)

Georges, Joseph F.; Liu, Xiaowei; Eschbacher, Jennifer; Nichols, Joshua; Mooney, Michael A.; Joy, Anna; Spetzler, Robert F.; Feuerstein, Burt G.; Anderson, Trent; Preul, Mark C.; Yan, Hao; Nakaji, Peter

2018-02-01

Improved tools for providing specific intraoperative diagnoses could improve patient care. In neurosurgery, intraoperatively differentiating non-operative lesions can be challenging, often necessitating immunohistochemical (IHC) procedures which require up to 24-48 hours. Here, we evaluate the feasibility of generating rapid ex vivo specific labeling using a novel lymphoma-specific fluorescent switchable aptamer. Our B-cell lymphoma-specific switchable aptamer produced only low-level fluorescence in its unbound conformation and generated an 8-fold increase in fluorescence once bound to its target on CD20-positive lymphoma cells. The aptamer demonstrated strong binding to B-cell lymphoma cells within 10 minutes of incubation. We applied the switchable aptamer to ex vivo xenograft tissue harboring B-cell lymphoma and astrocytoma, and within one hour specific visual identification of lymphoma was routinely possible. In this proof-of-concept study in human cell culture and orthotopic xenografts, we conclude that a fluorescent switchable aptamer can provide rapid and specific labeling of B-cell lymphoma, and that developing aptamer-based labeling approaches could simplify tissue staining and drastically reduce time to histopathological diagnoses compared with IHC-based methods. We propose that switchable aptamers could enhance expeditious, accurate intraoperative decision-making.

Switching "on" and "off" the adhesion in stimuli-responsive elastomers.

PubMed

Kaiser, S; Radl, S V; Manhart, J; Ayalur-Karunakaran, S; Griesser, T; Moser, A; Ganser, C; Teichert, C; Kern, W; Schlögl, S

2018-03-28

The present work aims at the preparation of dry adhesives with switchable bonding properties by using the reversible nature of the [4πs+4πs] cycloaddition of anthracenes. Photo-responsive hydrogenated carboxylated nitrile butadiene rubber with photo-responsive pendant anthracene groups is prepared by one-pot synthesis. The formation of 3D networks relies on the photodimerization of the anthracene moieties upon UV exposure (λ > 300 nm). Controlled cleavage of the crosslink sites is achieved by either deep UV exposure (λ = 254 nm) or thermal dissociation at 70 °C. The kinetics of the optical and thermal cleavage routes are compared in thin films using UV-vis spectroscopy and their influence on the reversibility of the network is detailed. Going from thin films to free standing samples the modulation of the network structure and thermo-mechanical properties over repeated crosslinking and cleavage cycles are characterized by low-field NMR spectroscopy and dynamic mechanical analysis. The applicability of the stimuli-responsive networks as adhesives with reversible bonding properties is demonstrated. The results evidence that the reversibility of the crosslinking reaction enables a controlled switching "on" and "off" of adhesion properties. The recovery of the adhesion force amounts to 75 and 80% for photo- and thermal dissociation, respectively. Spatial control of adhesion properties is evidenced by adhesion force mapping experiments of photo-patterned films.

Simple method for the extraction and reversed-phase high-performance liquid chromatographic analysis of carotenoid pigments from red yeasts (Basidiomycota, Fungi).

PubMed

Weber, Roland W S; Anke, Heidrun; Davoli, Paolo

2007-03-23

A simple method for the extraction of carotenoid pigments from frozen wet cells of red yeasts (Basidiomycota) and their analysis by reversed-phase HPLC using a C(18) column and a water/acetone solvent system is described. Typical red yeast carotenoids belonging to an oxidative series from the monocyclic gamma-carotene to 2-hydroxytorularhodin and from the bicyclic beta-carotene to astaxanthin were separated. Pigment identity was confirmed by LC-atmospheric pressure chemical ionisation (APCI) mass spectrometry using similar chromatographic conditions.

Mechanics of responsive polymers via conformationally switchable molecules

NASA Astrophysics Data System (ADS)

Brighenti, Roberto; Artoni, Federico; Vernerey, Franck; Torelli, Martina; Pedrini, Alessandro; Domenichelli, Ilaria; Dalcanale, Enrico

2018-04-01

Active materials are those capable of giving some physical reaction under external stimuli coming from the environment such as temperature, pH, light, mechanical stress, etc. Reactive polymeric materials can be obtained through the introduction of switchable molecules in their network, i.e. molecules having two distinct stable conformations: if properly linked to the hosting polymer chains, the switching from one state to the other can promote a mechanical reaction of the material, detectable at the macroscale, and thus enables us to tune the response according to a desired functionality. In the present paper, the main aspects of the mechanical behavior of polymeric materials with embedded switchable molecules-properly linked to the polymer's chains-are presented and discussed. Starting from the micro mechanisms occurring in such active material, a continuum model is developed, providing a straightforward implementation in computational approaches. Finally, some experimental outcomes related to a switchable molecules (known as quinoxaline cavitands) added to an elastomeric PDMS under chemical stimuli, are presented and quantitatively discussed through the use of the developed mechanical framework.

Phototropin 1 and dim-blue light modulate the red light de-etiolation response

PubMed Central

Wang, Yihai; M Folta, Kevin

2014-01-01

Light signals regulate seedling morphological changes during de-etiolation through the coordinated actions of multiple light-sensing pathways. Previously we have shown that red-light-induced hypocotyl growth inhibition can be reversed by addition of dim blue light through the action of phototropin 1 (phot1). Here we further examine the fluence-rate relationships of this blue light effect in short-term (hours) and long-term (days) hypocotyl growth assays. The red stem-growth inhibition and blue promotion is a low-fluence rate response, and blue light delays or attenuates both the red light and far-red light responses. These de-etiolation responses include blue light reversal of red or far-red induced apical hook opening. This response also requires phot1. Cryptochromes (cry1 and cry2) are activated by higher blue light fluence-rates and override phot1's influence on hypocotyl growth promotion. Exogenous application of auxin transport inhibitor naphthylphthalamic acid abolished the blue light stem growth promotion in both hypocotyl growth and hook opening. Results from the genetic tests of this blue light effect in auxin transporter mutants, as well as phytochrome kinase substrate mutants indicated that aux1 may play a role in blue light reversal of red light response. Together, the phot1-mediated adjustment of phytochrome-regulated photomorphogenic events is most robust in dim blue light conditions and is likely modulated by auxin transport through its transporters. PMID:25482790

Integrated, nonvolatile, high-speed analog random access memory

NASA Technical Reports Server (NTRS)

Katti, Romney R. (Inventor); Wu, Jiin-Chuan (Inventor); Stadler, Henry L. (Inventor)

1994-01-01

This invention provides an integrated, non-volatile, high-speed random access memory. A magnetically switchable ferromagnetic or ferrimagnetic layer is sandwiched between an electrical conductor which provides the ability to magnetize the magnetically switchable layer and a magneto resistive or Hall effect material which allows sensing the magnetic field which emanates from the magnetization of the magnetically switchable layer. By using this integrated three-layer form, the writing process, which is controlled by the conductor, is separated from the storage medium in the magnetic layer and from the readback process which is controlled by the magnetoresistive layer. A circuit for implementing the memory in CMOS or the like is disclosed.

Choice-Based Segmentation as an Enrollment Management Tool

ERIC Educational Resources Information Center

Young, Mark R.

2002-01-01

This article presents an approach to enrollment management based on target marketing strategies developed from a choice-based segmentation methodology. Students are classified into "switchable" or "non-switchable" segments based on their probability of selecting specific majors. A modified multinomial logit choice model is used to identify…

Use of a conformational switching aptamer for rapid and specific ex vivo identification of central nervous system lymphoma in a xenograft model.

PubMed

Georges, Joseph F; Liu, Xiaowei; Eschbacher, Jennifer; Nichols, Joshua; Mooney, Michael A; Joy, Anna; Spetzler, Robert F; Feuerstein, Burt G; Preul, Mark C; Anderson, Trent; Yan, Hao; Nakaji, Peter

2015-01-01

Improved tools for providing specific intraoperative diagnoses could improve patient care. In neurosurgery, intraoperatively differentiating non-operative lesions such as CNS B-cell lymphoma from operative lesions can be challenging, often necessitating immunohistochemical (IHC) procedures which require up to 24-48 hours. Here, we evaluate the feasibility of generating rapid ex vivo specific labeling using a novel lymphoma-specific fluorescent switchable aptamer. Our B-cell lymphoma-specific switchable aptamer produced only low-level fluorescence in its unbound conformation and generated an 8-fold increase in fluorescence once bound to its target on CD20-positive lymphoma cells. The aptamer demonstrated strong binding to B-cell lymphoma cells within 15 minutes of incubation as observed by flow cytometry. We applied the switchable aptamer to ex vivo xenograft tissue harboring B-cell lymphoma and astrocytoma, and within one hour specific visual identification of lymphoma was routinely possible. In this proof-of-concept study in human cell culture and orthotopic xenografts, we conclude that a fluorescent switchable aptamer can provide rapid and specific labeling of B-cell lymphoma, and that developing aptamer-based labeling approaches could simplify tissue staining and drastically reduce time to histopathological diagnoses compared with IHC-based methods. We propose that switchable aptamers could enhance expeditious, accurate intraoperative decision-making.

Light-switchable systems for remotely controlled drug delivery.

PubMed

Shim, Gayong; Ko, Seungbeom; Kim, Dongyoon; Le, Quoc-Viet; Park, Gyu Thae; Lee, Jaiwoo; Kwon, Taekhyun; Choi, Han-Gon; Kim, Young Bong; Oh, Yu-Kyoung

2017-12-10

Light-switchable systems have recently received attention as a new mode of remotely controlled drug delivery. In the past, a multitude of nanomedicine studies have sought to enhance the specificity of drug delivery to target sites by focusing on receptors overexpressed on malignant cells or environmental features of diseases sites. Despite these immense efforts, however, there are few clinically available nanomedicines. We need a paradigm shift in drug delivery. One strategy that may overcome the limitations of pathophysiology-based drug delivery is the use of remotely controlled delivery technology. Unlike pathophysiology-based active drug targeting strategies, light-switchable systems are not affected by the heterogeneity of cells, tissue types, and/or microenvironments. Instead, they are triggered by remote light (i.e., near-infrared) stimuli, which are absorbed by photoresponsive molecules or three-dimensional nanostructures. The sequential conversion of light to heat or reactive oxygen species can activate drug release and allow it to be spatio-temporally controlled. Light-switchable systems have been used to activate endosomal drug escape, modulate the release of chemical and biological drugs, and alter nanoparticle structures to control the release rates of drugs. This review will address the limitations of pathophysiology-based drug delivery systems, the current status of light-based remote-switch systems, and future directions in the application of light-switchable systems for remotely controlled drug delivery. Copyright © 2017 Elsevier B.V. All rights reserved.

Virtual screening on an α-helix to β-strand switchable region of the FGFR2 extracellular domain revealed positive and negative modulators.

PubMed

Diaz, Constantino; Corentin, Herbert; Thierry, Vermat; Chantal, Alcouffe; Tanguy, Bozec; David, Sibrac; Jean-Marc, Herbert; Pascual, Ferrara; Françoise, Bono; Edgardo, Ferran

2014-11-01

The secondary structure of some protein segments may vary between α-helix and β-strand. To predict these switchable segments, we have developed an algorithm, Switch-P, based solely on the protein sequence. This algorithm was used on the extracellular parts of FGF receptors. For FGFR2, it predicted that β4 and β5 strands of the third Ig-like domain were highly switchable. These two strands possess a high number of somatic mutations associated with cancer. Analysis of PDB structures of FGF receptors confirmed the switchability prediction for β5. We thus evaluated if compound-driven α-helix/β-strand switching of β5 could modulate FGFR2 signaling. We performed the virtual screening of a library containing 1.4 million of chemical compounds with two models of the third Ig-like domain of FGFR2 showing different secondary structures for β5, and we selected 32 compounds. Experimental testing using proliferation assays with FGF7-stimulated SNU-16 cells and a FGFR2-dependent Erk1/2 phosphorylation assay with FGFR2-transfected L6 cells, revealed activators and inhibitors of FGFR2. Our method for the identification of switchable proteinic regions, associated with our virtual screening approach, provides an opportunity to discover new generation of drugs with under-explored mechanism of action. © 2014 Wiley Periodicals, Inc.

Circadian Rhythm in the Expression of the mRNA Coding for the Apoprotein of the Light-Harvesting Complex of Photosystem II 1

PubMed Central

Tavladoraki, Paraskevi; Kloppstech, Klaus; Argyroudi-Akoyunoglou, Joan

1989-01-01

The mRNA coding for light-harvesting complex of PSII (LHC-II) apoprotein is present in etiolated bean (Phaseolus vulgaris L.) leaves; its level is low in 5-day-old leaves, increases about 3 to 4 times in 9- to 13-day-old leaves, and decreases thereafter. A red light pulse induces an increase in LHC-II mRNA level, which is reversed by far red light, in all ages of the etiolated tissue tested. The phytochrome-controlled initial increase of LHC-II mRNA level is higher in 9- and 13-day-old than in 5- and 17-day-old bean leaves. The amount of LHC-II mRNA, accumulated in the dark after a red light pulse, oscillates rhythmically with a period of about 24 hours. This rhythm is also observed in continuous white light and in the dark following exposure to continuous white light, and persists for at least 70 hours. A second red light pulse, applied 36 hours after initiation of the rhythm, induces a phase-shift, which is prevented by far red light immediately following the second red light pulse. A persistent, but gradually reduced, far red reversibility of the red light-induced increase in LHC-II mRNA level is observed. In contrast, far red reversibility of the red light-induced clock setting is only observed when far red follows immediately the red light. It is concluded that (a) the light-induced LHC-II mRNA accumulation follows an endogenous, circadian rhythm, for the appearance of which a red light pulse is sufficient, (b) the circadian oscillator is under phytochrome control, and (c) a stable Pfr form, which exists for several hours, is responsible for sustaining LHC-II gene transcription. Images Figure 1 Figure 2 Figure 8 PMID:16666825

Thermodynamic, energy efficiency, and power density analysis of reverse electrodialysis power generation with natural salinity gradients.

PubMed

Yip, Ngai Yin; Vermaas, David A; Nijmeijer, Kitty; Elimelech, Menachem

2014-05-06

Reverse electrodialysis (RED) can harness the Gibbs free energy of mixing when fresh river water flows into the sea for sustainable power generation. In this study, we carry out a thermodynamic and energy efficiency analysis of RED power generation, and assess the membrane power density. First, we present a reversible thermodynamic model for RED and verify that the theoretical maximum extractable work in a reversible RED process is identical to the Gibbs free energy of mixing. Work extraction in an irreversible process with maximized power density using a constant-resistance load is then examined to assess the energy conversion efficiency and power density. With equal volumes of seawater and river water, energy conversion efficiency of ∼ 33-44% can be obtained in RED, while the rest is lost through dissipation in the internal resistance of the ion-exchange membrane stack. We show that imperfections in the selectivity of typical ion exchange membranes (namely, co-ion transport, osmosis, and electro-osmosis) can detrimentally lower efficiency by up to 26%, with co-ion leakage being the dominant effect. Further inspection of the power density profile during RED revealed inherent ineffectiveness toward the end of the process. By judicious early discontinuation of the controlled mixing process, the overall power density performance can be considerably enhanced by up to 7-fold, without significant compromise to the energy efficiency. Additionally, membrane resistance was found to be an important factor in determining the power densities attainable. Lastly, the performance of an RED stack was examined for different membrane conductivities and intermembrane distances simulating high performance membranes and stack design. By thoughtful selection of the operating parameters, an efficiency of ∼ 37% and an overall gross power density of 3.5 W/m(2) represent the maximum performance that can potentially be achieved in a seawater-river water RED system with low-resistance ion exchange membranes (0.5 Ω cm(2)) at very small spacing intervals (50 μm).

Passive electrically switchable circuit element having improved tunability and method for its manufacture

DOE Office of Scientific and Technical Information (OSTI.GOV)

Mickel, Patrick R; James, Conrad D

2014-09-16

A resistive switching device and methods for making the same are disclosed. In the above said device, a resistive switching layer is interposed between opposing electrodes. The resistive switching layer comprises at least two sub-layers of switchable insulative material characterized by different ionic mobilities.

A smart core-sheath nanofiber that captures and releases red blood cells from the blood

NASA Astrophysics Data System (ADS)

Shi, Q.; Hou, J.; Zhao, C.; Xin, Z.; Jin, J.; Li, C.; Wong, S.-C.; Yin, J.

2016-01-01

A smart core-sheath nanofiber for non-adherent cell capture and release is demonstrated. The nanofibers are fabricated by single-spinneret electrospinning of poly(N-isopropylacrylamide) (PNIPAAm), polycaprolactone (PCL) and nattokinase (NK) solution blends. The self-assembly of PNIPAAm and PCL blends during the electrospinning generates the core-sheath PCL/PNIPAAm nanofibers with PNIPAAm as the sheath. The PNIPAAm-based core-sheath nanofibers are switchable between hydrophobicity and hydrophilicity with temperature change and enhance stability in the blood. When the nanofibers come in contact with blood, the NK is released from the nanofibers to resist platelet adhesion on the nanofiber surface, facilitating the direct capture and isolation of red blood cells (RBCs) from the blood above phase-transition temperature of PNIPAAm. Meanwhile, the captured RBCs are readily released from the nanofibers with temperature stimuli in an undamaged manner. The release efficiency of up to 100% is obtained while maintaining cellular integrity and function. This work presents promising nanofibers to effectively capture non-adherent cells and release for subsequent molecular analysis and diagnosis of single cells.A smart core-sheath nanofiber for non-adherent cell capture and release is demonstrated. The nanofibers are fabricated by single-spinneret electrospinning of poly(N-isopropylacrylamide) (PNIPAAm), polycaprolactone (PCL) and nattokinase (NK) solution blends. The self-assembly of PNIPAAm and PCL blends during the electrospinning generates the core-sheath PCL/PNIPAAm nanofibers with PNIPAAm as the sheath. The PNIPAAm-based core-sheath nanofibers are switchable between hydrophobicity and hydrophilicity with temperature change and enhance stability in the blood. When the nanofibers come in contact with blood, the NK is released from the nanofibers to resist platelet adhesion on the nanofiber surface, facilitating the direct capture and isolation of red blood cells (RBCs) from the blood above phase-transition temperature of PNIPAAm. Meanwhile, the captured RBCs are readily released from the nanofibers with temperature stimuli in an undamaged manner. The release efficiency of up to 100% is obtained while maintaining cellular integrity and function. This work presents promising nanofibers to effectively capture non-adherent cells and release for subsequent molecular analysis and diagnosis of single cells. Electronic supplementary information (ESI) available: Electrospinning of polymer nanofibers; FTIR spectra and XPS spectra of PCL, PNIPAAm and PCL/PNIPAAm nanofibers; SEM images of PCL/PNIPAAm nanofibers with varied composition; PNIPAAm content on the sheath of nanofibers; stability of core-sheath PCL/PNIPAAm nanofibers. Platelet adhesion on the PCL/PNIPAAm nanofibers in the presence of NK; Protein adsorption on nanofibers. See DOI: 10.1039/c5nr07070h

Tunable SPR-based remote actuation of bimetallic core-shell nanoparticles-coated stimuli responsive polymer for switchable chemo-photothermal synergistic cancer therapy.

PubMed

Amoli-Diva, Mitra; Sadighi-Bonabi, Rasoul; Pourghazi, Kamyar

2018-06-14

New dual light/temperature-responsive nanocarriers were synthesized using bimetallic plasmonic Au-Ag and Ag-Au nanoparticles (NPs) as cores of vehicles which subsequently functionalized with a UCST-based poly acrylamide-co-acrylonitrile using reversible addition-fragmentation chain transfer for spatiotemporally controlled chemo-photothermal synergistic cancer therapy. The bimetallic cores were assigned to sense wavelengths close to the localized SPR of monometallic NP shell to produce heat which not only can increase the surrounding temperature over the UCST of polymer to open the its valves and promote drug diffusion, but also can kill cancerous cells through photothermal effects with increasing in environment temperature nearly 18 °C after about 5 min radiation. The bimetallic NPs were shown good reusability even after five heating/cooling cycles and the efficiency of both photothermal/chemotherapic procedures can be modulated by manipulating carrier's concentration and radiation time. In addition, the cytotoxicity of drug-free nanocarriers on normal L929 fibroblast and letrozole-loaded nanocarriers on MDAMB 231 breast-cancer cell lines were investigated in the absence/presence of laser radiation. Finally, the prepared nanocomposites were exhibited switchable on/off drug release in two buffered solutions (pH 5.5 and 7.4) with light actuation. The results revealed that the prepared nanocarriers can be served as efficient delivery platforms for remote-control chemo-photothermal synergistic cancer therapy. Copyright © 2018. Published by Elsevier Inc.

First-principles Study of the Electronic Structure and Optical Properties of MgH2

NASA Astrophysics Data System (ADS)

Alford, Ashley; Chou, Mei-Yin

2003-03-01

It has been noticed that magnesium might play an interesting role in recently discovered switchable-mirror systems. For example, the films of rare earth and magnesium alloys are found to be superior to the pure rare-earth samples in maximum transparency and mirror-state reflectivity [1]. Moreover, the magnesium-rich Ni-Mg alloy films turned out to be a switchable-mirror system without rare earths [2]. In both cases, pure transparent MgH2 is reversibly formed when these alloys take up hydrogen. In order to model the optical properties of these films, we need to know the electronic and optical properties of MgH2. In this work, we investigate its bonding characteristics, band structure, and dielectric properties with first-principles theoretical methods. The stability of the crystal and the bonding are studied using density functional theory and pseudopotential methods. The excited state properties (the quasiparticle spectra) are studied by many-body perturbation theory within the so-called GW approximation in which the electronic self-energy is approximated by the full Green's function (G) times the screened Coulomb interaction (W). We will report the results for both the rutile-structured alpha-MgH2 and the low-symmetry gamma-MgH2. [1] P. van der Sluis, M. Ouwerkerk, and P. A. Duine, Appl. Phys. Lett. 70, 3356 (1997). [2] T. J. Richardson, J. L. Slack, R. D. armitage, R. Kostecki, B. Farangis, and M. D. Rubin, Appl. Phys. Lett. 78, 3047 (2001).

Tunable porosities and shapes of fullerene-like spheres.

PubMed

Dielmann, Fabian; Fleischmann, Matthias; Heindl, Claudia; Peresypkina, Eugenia V; Virovets, Alexander V; Gschwind, Ruth M; Scheer, Manfred

2015-04-13

The formation of reversible switchable nanostructures monitored by solution and solid-state methods is still a challenge in supramolecular chemistry. By a comprehensive solid state and solution study we demonstrate the potential of the fivefold symmetrical building block of pentaphosphaferrocene in combination with Cu(I) halides to switch between spheres of different porosity and shape. With increasing amount of CuX, the structures of the formed supramolecules change from incomplete to complete spherically shaped fullerene-like assemblies possessing an Ih -C80 topology at one side and to a tetrahedral-structured aggregate at the other. In the solid state, the formed nano-sized aggregates reach an outer diameter of 3.14 and 3.56 nm, respectively. This feature is used to reversibly encapsulate and release guest molecules in solution. © 2015 The Authors. Published by Wiley-VCH Verlag GmbH & Co. KGaA. This is an open access article under the terms of the Creative Commons Attribution Non-Commercial License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited and is not used for commercial purposes.

Biphasic Synergistic Gel Materials with Switchable Mechanics and Self-Healing Capacity.

PubMed

Zhao, Ziguang; Liu, Yuxia; Zhang, Kangjun; Zhuo, Shuyun; Fang, Ruochen; Zhang, Jianqi; Jiang, Lei; Liu, Mingjie

2017-10-16

A fabrication strategy for biphasic gels is reported, which incorporates high-internal-phase emulsions. Closely packed micro-inclusions within the elastic hydrogel matrix greatly improve the mechanical properties of the materials. The materials exhibit excellent switchable mechanics and shape-memory performance because of the switchable micro- inclusions that are incorporated into the hydrogel matrix. The produced materials demonstrated a self-healing capacity that originates from the noncovalent effect of the biphasic heteronetwork. The aforementioned characteristics suggest that the biphasic gels may serve as ideal composite gel materials with validity in a variety of applications, such as soft actuators, flexible devices, and biological materials. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Application of semiempirical electronic structure theory to compute the force generated by a single surface-mounted switchable rotaxane.

PubMed

Sohlberg, Karl; Bazargan, Gloria; Angelo, Joseph P; Lee, Choongkeun

2017-01-01

Herein we report a study of the switchable [3]rotaxane reported by Huang et al. (Appl Phys Lett 85(22):5391-5393, 1) that can be mounted to a surface to form a nanomechanical, linear, molecular motor. We demonstrate the application of semiempirical electronic structure theory to predict the average and instantaneous force generated by redox-induced ring shuttling. Detailed analysis of the geometric and electronic structure of the system reveals technical considerations essential to success of the approach. The force is found to be in the 100-200 pN range, consistent with published experimental estimates. Graphical Abstract A single surface-mounted switchable rotaxane.

Enhanced optical discrimination system based on switchable retroreflective films

NASA Astrophysics Data System (ADS)

Schultz, Phillip; Heikenfeld, Jason

2016-04-01

Reported herein is the design, characterization, and demonstration of a laser interrogation and response optical discrimination system based on large-area corner-cube retroreflective films. The switchable retroreflective films use light-scattering liquid crystal to modulate retroreflected intensity. The system can operate with multiple wavelengths (visible to infrared) and includes variable divergence optics for irradiance adjustments and ease of system alignment. The electronic receiver and switchable retroreflector offer low-power operation (<4 mW standby) on coin cell batteries with rapid interrogation to retroreflected signal reception response times (<15 ms). The entire switchable retroreflector film is <1 mm thick and is flexible for optimal placement and increased angular response. The system was demonstrated in high ambient lighting conditions (daylight, 18k lux) with a visible 10-mW output 635-nm source out to a distance of 400 m (naked eye detection). Nighttime demonstrations were performed using a 1.5-mW, 850-nm infrared laser diode out to a distance of 400 m using a night vision camera. This system could have tagging and conspicuity applications in commercial or military settings.

Phase-field modeling of switchable diode-like current-voltage characteristics in ferroelectric BaTiO{sub 3}

DOE Office of Scientific and Technical Information (OSTI.GOV)

Cao, Y., E-mail: yxc238@psu.edu; Randall, C. A.; Chen, L. Q.

2014-05-05

A self-consistent model has been proposed to study the switchable current-voltage (I-V) characteristics in Cu/BaTiO{sub 3}/Cu sandwiched structure combining the phase-field model of ferroelectric domains and diffusion equations for ionic/electronic transport. The electrochemical transport equations and Ginzburg-Landau equations are solved using the Chebyshev collocation algorithm. We considered a single parallel plate capacitor configuration which consists of a single layer BaTiO{sub 3} containing a single tetragonal domain orientated normal to the plate electrodes (Cu) and is subject to a sweep of ac bias from −1.0 to 1.0 V at 25 °C. Our simulation clearly shows rectifying I-V response with rectification ratios amount tomore » 10{sup 2}. The diode characteristics are switchable with an even larger rectification ratio after the polarization direction is flipped. The effects of interfacial polarization charge, dopant concentration, and dielectric constant on current responses were investigated. The switchable I-V behavior is attributed to the polarization bound charges that modulate the bulk conduction.« less

Smart Optical Composite Materials: Dispersions of Metal-Organic Framework@Superparamagnetic Microrods for Switchable Isotropic-Anisotropic Optical Properties.

PubMed

Mandel, Karl; Granath, Tim; Wehner, Tobias; Rey, Marcel; Stracke, Werner; Vogel, Nicolas; Sextl, Gerhard; Müller-Buschbaum, Klaus

2017-01-24

A smart optical composite material with dynamic isotropic and anisotropic optical properties by combination of luminescence and high reflectivity was developed. This combination enables switching between luminescence and angle-dependent reflectivity by changing the applied wavelength of light. The composite is formed as anisotropic core/shell particles by coating superparamagnetic iron oxide-silica microrods with a layer of the luminescent metal-organic framework (MOF) 3 ∞ [Eu 2 (BDC) 3 ]·2DMF·2H 2 O (BDC 2- = 1,4-benzenedicarboxylate). The composite particles can be rotated by an external magnet. Their anisotropic shape causes changes in the reflectivity and diffraction of light depending on the orientation of the composite particle. These rotation-dependent optical properties are complemented by an isotropic luminescence resulting from the MOF shell. If illuminated by UV light, the particles exhibit isotropic luminescence while the same sample shows anisotropic optical properties when illuminated with visible light. In addition to direct switching, the optical properties can be tailored continuously between isotropic red emission and anisotropic reflection of light if the illuminating light is tuned through fractions of both UV and visible light. The integration and control of light emission modes within a homogeneous particle dispersion marks a smart optical material, addressing fundamental directions for research on switchable multifunctional materials. The material can function as an optic compass or could be used as an optic shutter that can be switched by a magnetic field, e.g., for an intensity control for waveguides in the visible range.

A programmable nonlinear acoustic metamaterial

NASA Astrophysics Data System (ADS)

Yang, Tianzhi; Song, Zhi-Guang; Clerkin, Eoin; Zhang, Ye-Wei; Sun, Jia-He; Su, Yi-Shu; Chen, Li-Qun; Hagedorn, Peter

2017-09-01

Acoustic metamaterials with specifically designed lattices can manipulate acoustic/elastic waves in unprecedented ways. Whereas there are many studies that focus on passive linear lattice, with non-reconfigurable structures. In this letter, we present the design, theory and experimental demonstration of an active nonlinear acoustic metamaterial, the dynamic properties of which can be modified instantaneously with reversibility. By incorporating active and nonlinear elements in a single unit cell, a real-time tunability and switchability of the band gap is achieved. In addition, we demonstrate a dynamic "editing" capability for shaping transmission spectra, which can be used to create the desired band gap and resonance. This feature is impossible to achieve in passive metamaterials. These advantages demonstrate the versatility of the proposed device, paving the way toward smart acoustic devices, such as logic elements, diode and transistor.

Phase-selective vanadium dioxide (VO2) nanostructured thin films by pulsed laser deposition

NASA Astrophysics Data System (ADS)

Masina, B. N.; Lafane, S.; Wu, L.; Akande, A. A.; Mwakikunga, B.; Abdelli-Messaci, S.; Kerdja, T.; Forbes, A.

2015-10-01

Thin films of monoclinic nanostructured vanadium dioxide are notoriously difficult to produce in a selective manner. To date, post-annealing, after pulsed laser deposition (PLD), has been used to revert the crystal phase or to remove impurities, and non-glass substrates have been employed, thus reducing the efficacy of the transparency switching. Here, we overcome these limitations in PLD by optimizing a laser-ablation and deposition process through optical imaging of the laser-induced plasma. We report high quality monoclinic rutile-type vanadium dioxide (VO2) (M1) nanoparticles without post-annealing, and on a glass substrate. Our samples demonstrate a reversible metal-to-insulator transition at ˜43 °C, without any doping, paving the way to switchable transparency in optical materials at room temperature.

Achieving nonlinear optical modulation via four-wave mixing in a four-level atomic system

NASA Astrophysics Data System (ADS)

Li, Hai-Chao; Ge, Guo-Qin; Zubairy, M. Suhail

2018-05-01

We propose an accessible scheme for implementing tunable nonlinear optical amplification and attenuation via a synergetic mechanism of four-wave mixing (FWM) and optical interference in a four-level ladder-type atomic system. By constructing a cyclic atom-field interaction, we show that two reverse FWM processes can coexist via optical transitions in different branches. In the suitable input-field conditions, strong interference effects between the input fields and the generated FWM fields can be induced and result in large amplification and deep attenuation of the output fields. Moreover, such an optical modulation from enhancement to suppression can be controlled by tuning the relative phase. The quantum system can be served as a switchable optical modulator with potential applications in quantum nonlinear optics.

Reversible switching of wetting properties and erasable patterning of polymer surfaces using plasma oxidation and thermal treatment

NASA Astrophysics Data System (ADS)

Rashid, Zeeshan; Atay, Ipek; Soydan, Seren; Yagci, M. Baris; Jonáš, Alexandr; Yilgor, Emel; Kiraz, Alper; Yilgor, Iskender

2018-05-01

Polymer surfaces reversibly switchable from superhydrophobic to superhydrophilic by exposure to oxygen plasma and subsequent thermal treatment are demonstrated. Two inherently different polymers, hydrophobic segmented polydimethylsiloxane-urea copolymer (TPSC) and hydrophilic poly(methyl methacrylate) (PMMA) are modified with fumed silica nanoparticles to prepare superhydrophobic surfaces with roughness on nanometer to micrometer scale. Smooth TPSC and PMMA surfaces are also used as control samples. Regardless of their chemical structure and surface topography, all surfaces display completely reversible wetting behavior changing from hydrophobic to hydrophilic and back for many cycles upon plasma oxidation followed by thermal annealing. Influence of plasma power, plasma exposure time, annealing temperature and annealing time on the wetting behavior of polymeric surfaces are investigated. Surface compositions, textures and topographies are characterized by X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM) and white light interferometry (WLI), before and after oxidation and thermal annealing. Wetting properties of the surfaces are determined by measuring their static, advancing and receding water contact angle. We conclude that the chemical structure and surface topography of the polymers play a relatively minor role in reversible wetting behavior, where the essential factors are surface oxidation and migration of polymer molecules to the surface upon thermal annealing. Reconfigurable water channels on polymer surfaces are produced by plasma treatment using a mask and thermal annealing cycles. Such patterned reconfigurable hydrophilic regions can find use in surface microfluidics and optofluidics applications.

Switching single chain magnet behavior via photoinduced bidirectional metal-to-metal charge transfer† †Electronic supplementary information (ESI) available: Synthesis and physical measurement details. Crystal data in CIF format and additional figures (Fig. S1–S15). CCDC 1528877. For ESI and crystallographic data in CIF or other electronic format see DOI: 10.1039/c7sc03401f

PubMed Central

Jiang, Wenjing; Jiao, Chengqi; Meng, Yinshan; Zhao, Liang; Liu, Qiang

2017-01-01

The preparation of single-chain magnets (SCMs) with photo-switchable bistable states is essential for the development of high-density photo-recording devices. However, the reversible switching of the SCM behavior upon light irradiation is a formidable challenge. Here we report a well-isolated double zigzag chain {[Fe(bpy)(CN)4]2[Co(phpy)2]}·2H2O (bpy = 2,2′-bipyridine, phpy = 4-phenylpyridine), which exhibits reversible redox reactions with interconversion between FeIIILS(μ-CN)CoIIHS(μ-NC)FeIIILS (LS = low-spin, HS = high-spin) and FeIIILS(μ-CN)CoIIILS(μ-NC)FeIILS linkages under alternating irradiation with 808 and 532 nm lasers. The bidirectional photo-induced metal-to-metal charge transfer results in significant changes of anisotropy and intrachain magnetic interactions, reversibly switching the SCM behavior. The on-switching SCM behavior driven by light irradiation at 808 nm could be reversibly switched off by irradiation at 532 nm. The results provide an additional and independent way to control the bistable states of SCMs by switching in the 0 → 1 → 0 sequence, with potential applications in high density storage and molecular switches. PMID:29629126

Resistive Switching Memory Phenomena in PEDOT PSS: Coexistence of Switchable Diode Effect and Write Once Read Many Memory

PubMed Central

Nguyen, Viet Cuong; Lee, Pooi See

2016-01-01

We study resistive switching memory phenomena in conducting polymer PEDOT PSS. In the same film, there are two types of memory behavior coexisting; namely, the switchable diode effect and write once read many memory. This is the first report on switchable diode phenomenon based on conducting organic materials. The effect was explained as charge trapping of PEDOT PSS film and movement of proton. The same PEDOT PSS device also exhibits write once read many memory (WORM) phenomenon which arises due to redox reaction that reduces PEDOT PSS and renders it non-conducting. The revelation of these two types of memory phenomena in PEDOT PSS highlights the remarkable versatility of this conducting conjugated polymer. PMID:26806868

Enhanced spectral efficiency using bandwidth switchable SAW filtering for mobile satellite communications systems

NASA Technical Reports Server (NTRS)

Peach, Robert; Malarky, Alastair

1990-01-01

Currently proposed mobile satellite communications systems require a high degree of flexibility in assignment of spectral capacity to different geographic locations. Conventionally this results in poor spectral efficiency which may be overcome by the use of bandwidth switchable filtering. Surface acoustic wave (SAW) technology makes it possible to provide banks of filters whose responses may be contiguously combined to form variable bandwidth filters with constant amplitude and phase responses across the entire band. The high selectivity possible with SAW filters, combined with the variable bandwidth capability, makes it possible to achieve spectral efficiencies over the allocated bandwidths of greater than 90 percent, while retaining full system flexibility. Bandwidth switchable SAW filtering (BSSF) achieves these gains with a negligible increase in hardware complexity.

Electronic devices containing switchably conductive silicon oxides as a switching element and methods for production and use thereof

DOEpatents

Tour, James M.; Yao, Jun; Natelson, Douglas; Zhong, Lin; He, Tao

2015-09-08

In various embodiments, electronic devices containing switchably conductive silicon oxide as a switching element are described herein. The electronic devices are two-terminal devices containing a first electrical contact and a second electrical contact in which at least one of the first electrical contact or the second electrical contact is deposed on a substrate to define a gap region therebetween. A switching layer containing a switchably conductive silicon oxide resides in the gap region between the first electrical contact and the second electrical contact. The electronic devices exhibit hysteretic current versus voltage properties, enabling their use in switching and memory applications. Methods for configuring, operating and constructing the electronic devices are also presented herein.

Electronic devices containing switchably conductive silicon oxides as a switching element and methods for production and use thereof

DOEpatents

Tour, James M; Yao, Jun; Natelson, Douglas; Zhong, Lin; He, Tao

2013-11-26

In various embodiments, electronic devices containing switchably conductive silicon oxide as a switching element are described herein. The electronic devices are two-terminal devices containing a first electrical contact and a second electrical contact in which at least one of the first electrical contact or the second electrical contact is deposed on a substrate to define a gap region therebetween. A switching layer containing a switchably conductive silicon oxide resides in the the gap region between the first electical contact and the second electrical contact. The electronic devices exhibit hysteretic current versus voltage properties, enabling their use in switching and memory applications. Methods for configuring, operating and constructing the electronic devices are also presented herein.

Light-dependent reversion gravitropism of the moss Pohlia nutans

NASA Astrophysics Data System (ADS)

Khorkavtsiv, O.

Plants have evolved highly sensitive mechanisms adapting their growth to the environmental conditions. Light and gravity are critical importance factors, which exerts an essential and specific influence on the determination of the growth direction and regulation of the early stages of plants ontogeny, sometimes effects of these factors being independent. The negative gravitropic resp onse of moss protonemata causes their spatial orientation towards light, which in its turn is the source of photosynthetic efficiency and phototropism. The gravitropism system does not function independently of other sensory response systems in plants. The competence of protonemata to gravity might be altered and the gravitropic response be reversed from negative to positive by light. It has been shown that response of apical cells to light depend on wavelenght: red light (max = 660 nm) represses the gravitropism and blue ( = 450 nm) inverts the protonemal gravitropism. Light, has also been shown for seed plants to modulate gravitropism of roots and stems through the action of phy B in red/far-red reversible way and by phy A in a non-reversible, very - low-fluence response (Hangarter, 1997). In P. nutans blue light reversed the gravitropism protonemal filaments. The mean angle after 24 h blue irradiation was 83 0, like that of negative gravitropic protonemata in darkness. We compared the effect of blue light on gravitropism of chloronemal filaments of Funaria hygrometrica having very low sensitivity to gravity. After action of blue light, however, the positive gravitropism of F. hygrometrica chloronemata was fairly high - 370 . Among blue light spectrum the highest reversion effectiveness in P. nutans had the UV light ( = 350 nm) initiated bends in 90% of protonemata. If a far-red pulse (5 min per h) was added to the blue/UV the gravitropic growth of protonemata resembled that in the dark control. Phytochrome has maxima of absorption in blue and red spectrum region and in our experiments far-red pulse removed the action of the blue/UV light. This indicates to a participation of phytochrome in changing direction of gravitropism. Since red light inhibited the gravitropism it may be suggested that phytochrome is not directly responsible for positive direction of gravitropism. Probably phytochrome only modifies the activity of other receptors or signal systems participating in realization of the gravitropic reaction. Moveover, the competence of apical cells protonemata to grow in opposite directions might be genetically controlled via blue-light - dependent repressor proteins (Lamparter et al., 1998).

The Orange Side of Disperse Red 1: Humidity-Driven Color Switching in Supramolecular Azo-Polymer Materials Based on Reversible Dye Aggregation.

PubMed

Schoelch, Simon; Vapaavuori, Jaana; Rollet, Frédéric-Guillaume; Barrett, Christopher J

2017-01-01

Humidity detection, and the quest for low-cost facile humidity-sensitive indicator materials is of great interest for many fields, including semi-conductor processing, food transport and storage, and pharmaceuticals. Ideal humidity-detection materials for a these applications might be based on simple clear optical readout with no power supply, i.e.: a clear color change observed by the naked eye of any untrained observer, since it doesn't require any extra instrumentation or interpretation. Here, the introduction of a synthesis-free one-step procedure, based on physical mixing of easily available commercial materials, for producing a humidity memory material which can be easily painted onto a wide variety of surfaces and undergoes a remarkable color change (approximately 100 nm blue-shift of λ MAX ) upon exposure to various thresholds of levels of ambient humidity is reported. This strong color change, easily visible to as a red-to-orange color switch, is locked in until inspection, but can then be restored reversibly if desired, after moderate heating. By taking advantage of spontaneously-forming reversible 'soft' supramolecular bonds between a red-colored azo dye and a host polymer matrix, a reversible dye 'migration' aggregation appearing orange, and dis-aggregation back to red can be achieved, to function as the sensor. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Switchable dual-wavelength fiber laser based on PCF Sagnac loop and broadband FBG

NASA Astrophysics Data System (ADS)

Chen, Weiguo; Lou, Shuqin; Feng, Suchun; Wang, Liwen; Li, Honglei; Guo, Tieying; Jian, Shuisheng

2009-11-01

Switchable dual-wavelength fiber laser with photonic crystal fiber (PCF) Sagnac loop and broadband fiber Bragg grating (BFBG) at room temperature is demonstrated. By adjusting the polarization controller (PC) appropriately, the laser can be switched between the stable single- and dual-wavelength lasing operations by exploiting polarization hole burning (PHB) and spectral hole burning effects (SHB).

Switchable Shape Memory Alloys (SMA) Thermal Materials Project

NASA Technical Reports Server (NTRS)

Falker, John; Zeitlin, Nancy; Williams, Martha; Fesmire, James

2014-01-01

Develop 2-way switchable thermal systems for use in systems that function in cold to hot temperature ranges using different alloy designs for SMA system concepts. In this project, KSC will specifically address designs of two proof of concept SMA systems with transition temperatures in the 65-95 C range and investigate cycle fatigue and "memory loss" due to thermal cycling.

Switchable polarity solvent for liquid phase microextraction of Cd(II) as pyrrolidinedithiocarbamate chelates from environmental samples.

PubMed

Yilmaz, Erkan; Soylak, Mustafa

2015-07-30

A switchable polarity solvent was synthesized from triethylamine (TEA)/water/CO2 (Dry ice) via proton transfer reaction has been used for the microextraction of cadmium(II) as pyrrolidinedithiocarbamate (APDC) chelate. Cd(II)-APDC chelate was extracted into the switchable polarity solvent drops by adding 2 mL 10 M sodium hydroxide solution. Analytical parameters affecting the complex formation and microextraction efficiency such as pH, amount of ligand, volume of switchable polarity solvent and NaOH, sample volume were optimized. The effects of foreign ions were found tolerably. Under optimum conditions, the detection limit was 0.16 μg L(-1) (3Sb/m, n = 7) and the relative standard deviation was 5.4% (n = 7). The method was validated by the analysis of certified reference materials (TMDA-51.3 fortified water, TMDA-53.3 fortified water and SPS-WW2 waste water, 1573a Tomato Leaves and Oriental Basma Tobacco Leaves (INCT-OBTL-5)) and addition/recovery tests. The method was successfully applied to determination of cadmium contents of water, vegetable, fruit and cigarette samples. Copyright © 2015 Elsevier B.V. All rights reserved.

Polarization-switchable and wavelength-controllable multi-functional metasurface for focusing and surface-plasmon-polariton wave excitation.

PubMed

Ling, Yonghong; Huang, Lirong; Hong, Wei; Liu, Tongjun; Jing, Luan; Liu, Wenbin; Wang, Ziyong

2017-11-27

Realizing versatile functionalities in a single photonic device is crucial for photonic integration. We here propose a polarization-switchable and wavelength-controllable multi-functional metasurface. By changing the polarization state of incident light, its functionality can be switched between the flat focusing lens and exciting surface-plasmon-polariton (SPP) wave. Interestingly, by tuning the wavelength of incident light, the generated SPP waves can also be controlled at desired interfaces, traveling along the upper or lower interface of the metasurface, or along both of them, depending on whether the incident light satisfies the first or second Kerker condition. This polarization-switchable and wavelength-controllable multifunctional metasurface may provide flexibility in designing tunable or multifunctional metasurfaces and may find potential applications in highly integrated photonic systems.

pH-Driven Wetting Switchability of Electrodeposited Superhydrophobic Copolymers of Pyrene Bearing Acid Functions and Fluorinated Chains.

PubMed

Ramos Chagas, Gabriela; Kiryanenko, Denis; Godeau, Guilhem; Guittard, Frédéric; Darmanin, Thierry

2017-12-06

A smart stimuli-responsive surface was fabricated by the electro-copolymerization of pyrene monomers followed by base and acid treatment. Copolymers of pyrenes bearing fluorinated chains (Py-nF 6 ) and acid functions (Py-COOH) were produced with different molar concentrations of each monomer (0, 25, 50, 75, and 100 % of Py-nF 6 vs. Py-COOH) by an electrochemical process. Two different perfluorinated pyrenes containing ester and amide groups were used to reach superhydrophobic properties. The relation of those bonds with the final properties of the surface was explored. The pH-sensitive group of Py-COOH allowed the surfaces to be reversibly switched from superhydrophobic (water contact angle>θ w >150° and very low hysteresis) to hydrophilic (θ w <90°). The amide and ester bonds influenced the recovery of the original wettability after both base and acid treatment. Although the fluorinated homopolymer with ester bonds was insensitive to base and acid treatment due to its superhydrophobic properties with ultralow water adhesion, the recovery of the original wettability for the copolymers was much more important with amide bonds due to the amide functional groups be more resistant to the hydrolysis reaction. This strategy offered the opportunity to access superhydrophobic films with switchable wettability by simple pH treatment. The films proved to be a good tool for use in biological applications, for example, as a bacterial-resistant film if superhydrophobic and as a bacterial-adherent film if hydrophilic. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Effect of the Z- and Macro-R-Group on the Thermal Desulfurization of Polymers Synthesized with Acid/Base "Switchable" Dithiocarbamate RAFT Agents.

PubMed

Stace, Sarah J; Fellows, Christopher M; Moad, Graeme; Keddie, Daniel J

2018-05-11

Thermolysis is examined as a method for complete desulfurization of reversible addition-fragmentation chain transfer (RAFT)-synthesized polymers prepared with acid/base "switchable" N-methyl-N-pyridyldithiocarbamates [RS 2 CZ or RS 2 CZH + ]. Macro-RAFT agents from more activated monomers (MAMs) (i.e., styrene (St), N-isopropylacrylamide (NIPAm), and methyl methacrylate (MMA)) with RS 2 CZH + and less activated monomers (LAMs) (i.e., vinyl acetate (VAc) and N-vinylpyrolidone (NVP)) with RS 2 CZ are prepared by RAFT polymerization and analyzed by thermogravimetric analysis. In all cases, a mass loss consistent with loss of the end group (ZCS 2 H) is observed at temperatures lower than, and largely discrete from, that required for further degradation of the polymer. The temperatures for end group loss and the new end groups formed are strongly dependent on the identity of the R(P) n and the state of the pyridyl Z group; increasing in the series poly(MMA) < poly(St) ∼ poly(NIPAm) < poly(VAc) ∼ poly(NVP) for S 2 CZ and poly(MMA) < poly(St) ∼ poly(NIPAm) for S 2 CZH + . Clean end group removal is possible for poly(St) and poly(NVP). For poly(NIPAm), the thiocarbonyl chain end is removed, but the end group identity is less certain. For poly(MMA) and poly(VAc), some degradation of the polymer accompanies end group loss under the conditions used and further refinement of the process is required. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Beam steering for virtual/augmented reality displays with a cycloidal diffractive waveplate.

PubMed

Chen, Haiwei; Weng, Yishi; Xu, Daming; Tabiryan, Nelson V; Wu, Shin-Tson

2016-04-04

We proposed a switchable beam steering device with cycloidal diffractive waveplate (CDW) for eye tracking in a virtual reality (VR) or augmented reality (AR) display system. Such a CDW diffracts the incident circularly polarized light to the first order with over 95% efficiency. To convert the input linearly polarized light to right-handed or left-handed circular polarization, we developed a broadband polarization switch consisting of a twisted nematic liquid crystal cell and an achromatic quarter-wave retardation film. By cascading 2-3 CDWs together, multiple diffraction angles can be achieved. To suppress the color dispersion, we proposed two approaches to obtain the same diffraction angle for red, green, and blue LEDs-based full color displays. Our device exhibits several advantages, such as high diffraction efficiency, fast response time, low power consumption, and low cost. It holds promise for the emerging VR/AR displays.

Increasing Contact with Hepatitis E Virus in Red Deer, Spain

PubMed Central

Casas, Maribel; Martín, Marga; Vicente, Joaquín; Segalés, Joaquim; de la Fuente, José; Gortázar, Christian

2010-01-01

To describe the epidemiology of hepatitis E virus (HEV) in red deer in mainland Spain, we tested red deer for HEV RNA and antibodies. Overall, 10.4% and 13.6% of serum samples were positive by ELISA and reverse transcription–PCR, respectively. The increasing prevalence suggests a potential risk for humans. PMID:21122241

Integrating Reverse-Electrodialysis Stacks with Flow Batteries for Improved Energy Recovery from Salinity Gradients and Energy Storage.

PubMed

Zhu, Xiuping; Kim, Taeyoung; Rahimi, Mohammad; Gorski, Christopher A; Logan, Bruce E

2017-02-22

Salinity gradient energy can be directly converted into electrical power by using reverse electrodialysis (RED) and other technologies, but reported power densities have been too low for practical applications. Herein, the RED stack performance was improved by using 2,6-dihydroxyanthraquinone and ferrocyanide as redox couples. These electrolytes were then used in a flow battery to produce an integrated RED stack and flow battery (RED-FB) system capable of capturing, storing, and discharging salinity gradient energy. Energy captured from the RED stack was discharged in the flow battery at a maximum power density of 3.0 kW m -2 -anode, which was similar to the flow batteries charged by electrical power and could be used for practical applications. Salinity gradient energy captured from the RED stack was recovered from the electrolytes as electricity with 30 % efficiency, and the maximum energy density of the system was 2.4 kWh m -3 -anolyte. The combined RED-FB system overcomes many limitations of previous approaches to capture, store, and use salinity gradient energy from natural or engineered sources. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Synthesis of Thermally Switchable Chromatographic Materials with Immobilized Ti4+ for Enrichment of Phosphopeptides by Reversible Addition Fragmentation Chain Transfer Polymerization

NASA Astrophysics Data System (ADS)

Wang, Di; Cao, Zhihan; Pang, Xinzhu; Deng, Yulin; Li, Bo; Dai, Rongji

2018-01-01

Reversible phosphorylation of proteins is one of the most crucial types of post-translational modifications (PTMs). And it shows significant work in diversified biological processes. However, the separation technology of phosphorylated peptides is still an analytical challenge in phosphoproteomics, because phosphopeptides are alway in low stoichiometry. Thus, enrichment of phosphopeptides before detection is indispensable. In this study, a novel temperature regulated separation protocol was developed. Silica@p (NIPAAm-co-IPPA)-Ti4+, a new Ti(IV)-IMAC (Immobilized Metal Affinity chromatography) materials was synthesized by reversible addition fragmentation chain transfer polymerization (RAFT). By the unique thermally responsive properties of poly(N-isopropylacrylamide) (PNIPAAm), the captured phosphorylated peptides could be released by changing temperature only without applying any other eluant which could damage the phosphopeptides. We employed isopropanol phosphonic acid (IPPA) as an IMAC ligand for the immobilization of Ti(IV) which could increase the specific adsorption of phosphopeptides. The enrichment and release properties were examined by treatment with pyridoxal 5’-phosphate (PLP) and casein phosphopeptides (CPP). Two phosphorylated compounds above have temperature-stimulated binding to Ti4+. Finally, silica@p (NIPAAm-co-IPPA)-Ti4+ was successfully employed in pretreatment of phosphopeptides in a tryptic digest of a-casein and human serum albumin (HSA). The results indicated a great potential of this new temperature-responsive material in phosphoproteomics study.

Reversible switching of fluorophore property based on intrinsic conformational transition of adenylate kinase during its catalytic cycle.

PubMed

Fujii, Akira; Hirota, Shun; Matsuo, Takashi

2013-07-17

Adenylate kinase shows a conformational transition (OPEN and CLOSED forms) during substrate binding and product release to mediate the phosphoryl transfer between ADP and ATP/AMP. The protein motional characteristics will be useful to construct switching systems of fluorophore properties caused by the catalytic cycle of the enzyme. This paper demonstrates in situ reversible switching of a fluorophore property driven by the conformational transition of the enzyme. The pyrene-conjugated mutant adenylate kinase is able to switch the monomer/excimer emission property of pyrene on addition of ADP or P(1)P(5)-di(adenosine-5')pentaphosphate (Ap5A, a transition state analog). The observation under the dilute condition (~0.1 μM) indicates that the emission spectral change was caused by the motion of a protein molecule and not led by protein-protein interactions through π-π stacking of pyrene rings. The switching can be reversibly conducted by using hexokinase-coupling reaction. The fashion of the changes in emission intensities at various ligand concentrations is different between ADP, Mg(2+)-bound ADP, and Mg(2+)-bound Ap5A. The emission property switching is repeatable by a sequential addition of a substrate in a one-pot process. It is proposed that the property of a synthetic molecule on the enzyme surface is switchable in response to the catalytic cycle of adenylate kinase.

Phase-selective vanadium dioxide (VO{sub 2}) nanostructured thin films by pulsed laser deposition

DOE Office of Scientific and Technical Information (OSTI.GOV)

Masina, B. N., E-mail: BMasina@csir.co.za, E-mail: slafane@cdta.dz; School of Physics, University of KwaZulu-Natal, Private Bag X54001, Durban 4000; Lafane, S., E-mail: BMasina@csir.co.za, E-mail: slafane@cdta.dz

2015-10-28

Thin films of monoclinic nanostructured vanadium dioxide are notoriously difficult to produce in a selective manner. To date, post-annealing, after pulsed laser deposition (PLD), has been used to revert the crystal phase or to remove impurities, and non-glass substrates have been employed, thus reducing the efficacy of the transparency switching. Here, we overcome these limitations in PLD by optimizing a laser-ablation and deposition process through optical imaging of the laser-induced plasma. We report high quality monoclinic rutile-type vanadium dioxide (VO{sub 2}) (M1) nanoparticles without post-annealing, and on a glass substrate. Our samples demonstrate a reversible metal-to-insulator transition at ∼43 °C, withoutmore » any doping, paving the way to switchable transparency in optical materials at room temperature.« less

CO2-Switchable Membranes Prepared by Immobilization of CO2-Breathing Microgels.

PubMed

Zhang, Qi; Wang, Zhenwu; Lei, Lei; Tang, Jun; Wang, Jianli; Zhu, Shiping

2017-12-20

Herein, we report the development of a novel CO 2 -responsive membrane system through immobilization of CO 2 -responsive microgels into commercially available microfiltration membranes using a method of dynamic adsorption. The microgels, prepared from soap-free emulsion polymerization of CO 2 -responsive monomer 2-(diethylamino)ethyl methacrylate (DEA), can be reversibly expanded and shrunken upon CO 2 /N 2 alternation. When incorporated into the membranes, this switching behavior was preserved and further led to transformation between microfiltration and ultrafiltration membranes, as indicated from the dramatic changes on water flux and BSA rejection results. This CO 2 -regulated performance switching of membranes was caused by the changes of water transportation channel, as revealed from the dynamic water contact angle tests and SEM observation. This work represents a simple yet versatile strategy for making CO 2 -responsive membranes.

Integration methods for thermosensitive gel systems in garments

NASA Astrophysics Data System (ADS)

Reich, A.; Rödel, H.; Stoll, A.; Liske, A.; Zehm, D.

2017-10-01

Humans live and work under severe thermophysiological conditions, which are characterized by extreme temperatures and humidities. Furthermore, additional burdens can arise from physical activities of the human body or the work conditions (resulting in psychological stress) [1]. The thermoregulation of the human body compensates such situations and maintains the core body temperature at 37°C (98,6 °F). The currently used systems for supporting human thermoregulation, such as PCM-equipped surface structures or mobile water-based cooling units have the disadvantage that the running cooling process is neither switchable nor reversible. Another promising possibility for a personal cooling is the use of temperature-dependent superabsorbers (so-called LCST and UCST) in garments, which absorb the human sweat and transmit it to the environment by evaporation. Cooling during evaporation results in heat transfer from the human body.

Thermally switchable photonic band-edge to random laser emission in dye-doped cholesteric liquid crystals

NASA Astrophysics Data System (ADS)

Ye, Lihua; Wang, Yan; Feng, Yangyang; Liu, Bo; Gu, Bing; Cui, Yiping; Lu, Yanqing

2018-03-01

By changing the doping concentration of the chiral agent to adjust the relative position of the reflection band of cholesteric liquid crystals and the fluorescence emission spectrum of the dye, photonic band-edge and random lasing were observed, respectively. The reflection band of the cholesteric phase liquid crystal can also be controlled by adjusting the temperature: the reflection band is blue-shifted with increasing temperature, and a reversible switch from photonic band-edge to random lasing is obtained. Furthermore, the laser line width can be thermally adjusted from 1.1 nm (at 27 °C) to 4.6 nm (at 32.1 °C). A thermally tunable polarization state of a random laser from dual cells was observed, broadening the field of application liquid crystal random lasers.

Neutral Red and Ferroin as Reversible and Rapid Redox Materials for Redox Flow Batteries.

PubMed

Hong, Jeehoon; Kim, Ketack

2018-06-11

Neutral red and ferroin are used as redox indicators (RINs) in potentiometric titrations. The rapid response and reversibility that are prerequisites for RINs are also desirable properties for the active materials in redox flow batteries (RFBs). This study describes the electrochemical properties of ferroin and neutral red as a redox pair. The rapid reaction rates of the RINs allow a cell to run at a rate of 4 C with 89 % capacity retention after the 100 th  cycle. The diffusion coefficients, electrode reaction rates, and solubilities of the RINs were determined. The electron-transfer rate constants of ferroin and neutral red are 0.11 and 0.027 cm s -1 , respectively, which are greater than those of the components of all-vanadium and Zn/Br 2 cells. © 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Reversible mechanochromic luminescence at room temperature in cationic platinum(II) terpyridyl complexes.

PubMed

Han, Ali; Du, Pingwu; Sun, Zijun; Wu, Haotian; Jia, Hongxing; Zhang, Rui; Liang, Zhenning; Cao, Rui; Eisenberg, Richard

2014-04-07

Reversible mechanochromic luminescence in cationic platinum(II) terpyridyl complexes is described. The complexes [Pt(Nttpy)Cl]X2 (Nttpy = 4'-(p-nicotinamide-N-methylphenyl)-2,2':6',2″-terpyridine, X = PF6 (1), SbF6 (2), Cl (3), ClO4 (4), OTf (5), BF4 (6)) exhibit different colors under ambient light in the solid state, going from red to orange to yellow. All of these complexes are brightly luminescent at both room temperature and 77 K. Upon gentle grinding, the yellow complexes (4-6) turn orange and exhibit bright red luminescence. The red luminescence can be changed back to yellow by the addition of a few drops of acetonitrile to the sample. Crystallographic studies of the yellow and red forms of complex 5 suggest that the mechanochromic response is likely the result of a change in intermolecular Pt···Pt distances upon grinding.

Inducing and manipulating magnetization in 2D zinc–oxide by strain and external voltage

NASA Astrophysics Data System (ADS)

Taivansaikhan, P.; Tsevelmaa, T.; Rhim, S. H.; Hong, S. C.; Odkhuu, D.

2018-04-01

Two-dimensional (2D) structures that exhibit intriguing magnetic phenomena such as perpendicular magnetic anisotropy and its switchable feature are of great interests in spintronics research. Herein, the density functional theory studies reveal the critical impacts of strain and external gating on vacancy-induced magnetism and its spin direction in a graphene-like single layer of zinc oxide (ZnO). In contrast to the pristine and defective ZnO with an O-vacancy, the presence of a Zn-vacancy induces significant magnetic moments to its first neighboring O and Zn atoms due to the charge deficit. We further predict that the direction of magnetization easy axis reverses from an in-plane to perpendicular orientation under a practically achievable biaxial compressive strain of only ~1–2% or applying an electric field by means of the charge density modulation. This magnetization reversal is mainly driven by the strain- and electric-field-induced changes in the spin–orbit coupled d states of the first-neighbor Zn atom to a Zn-vacancy. These findings open interesting prospects for exploiting strain and electric field engineering to manipulate magnetism and magnetization orientation of 2D materials.

Thermal hysteresis kinetic effects of spin crossover nanoparticulated systems studied by FORC diagram method on an Ising-like model

NASA Astrophysics Data System (ADS)

Atitoaie, Alexandru; Stoleriu, Laurentiu; Tanasa, Radu; Stancu, Alexandru; Enachescu, Cristian

2016-04-01

The scientific community is manifesting a high research interest on spin crossover compounds and their recently synthesized nanoparticles, due to their various appealing properties, such as the bistability between a diamagnetic low spin state and a paramagnetic high spin state (HS), inter-switchable by temperature or pressure changes, light irradiation or magnetic field. The utility of these compounds showing hysteresis covers a broad area of applications, from the development of more efficient designs of temperature and pressure sensors to automotive and aeronautic industries and even a new type of molecular actuators. We are proposing in this work a study regarding the kinetic effects and the distribution of reversible and irreversible components on the thermal hysteresis of spin crossover nanoparticulated systems. We are considering here tridimensional systems with different sizes and also systems of nanoparticles with a Gaussian size distribution. The correlations between the kinetics of the thermal hysteresis, the distributions of sizes and intermolecular interactions and the transition temperature distributions were established by using the FORC (First Order Reversal Curves) method using a Monte Carlo technique within an Ising-like system.

Sequential decolorization of azo dye and mineralization of decolorization liquid coupled with bioelectricity generation using a pH self-neutralized photobioelectrochemical system operated with polarity reversion.

PubMed

Sun, Jian; Hu, Yongyou; Li, Wanjun; Zhang, Yaping; Chen, Jie; Deng, Feng

2015-05-30

A novel photobioelectrochemical system (PBES) was developed by acclimating algal-bacterial biofilm in both anode and cathode using Chlorella vulgaris and indigenous wastewater bacteria as inoculums. The PBES was operated in polarity reversion mode depend on dark/light alternate reaction to achieve simultaneous pH self-neutralization, azo dye degradation (Congo red) and bioelectricity generation. The anodic accumulated acidity and cathodic accumulated alkalinity were self-neutralized after polarity reversion and hence eliminate the membrane pH gradient. The Congo red was first decolored in the dark anode and the resultant decolorization liquid was subsequently mineralized after the dark anode changing to the photo-biocathode. The presence of C. vulgaris significantly enhanced the two-stage degradation of Congo red, with 93% increases in decolorization rates and 8% increases in mineralization compared to the algae-free BES. The PBES continuously generated stable voltage output over four months under repeatedly reversion of polarity. The maximum power density produced before and after polarity reversion was 78 and 61 mW/m(2), respectively. The synergy between C. vulgaris and mixed bacteria was responsible for the successful operation of the PBES which can be potentially applied to treat wastewater containing azo dye with benefits of enhanced azo dye degradation, high net power output and buffer minimization. Copyright © 2015 Elsevier B.V. All rights reserved.

Direct Imaging of Charge Density Modulation in Switchable Two-Dimensional Electron Gas at the Oxide Hetero-Interfaces by Using Electron Bean Inline Holography

DTIC Science & Technology

2015-08-16

Switchable Two-Dimensional Electron Gas at the Oxide Hetero-Interfaces by Using Electron Bean Inline Holography 5a. CONTRACT NUMBER FA2386-13-1-4136...Hetero-Interfaces by Using Electron Bean Inline Holography 5a. CONTRACT NUMBER FA2386-13-1-4136 5b. GRANT NUMBER 5c. PROGRAM ELEMENT NUMBER 61102F

Robust Quantum Computing using Molecules with Switchable Dipole

DTIC Science & Technology

2010-06-15

REPORT Robust quantum computing using molecules with switchable dipole 14. ABSTRACT 16. SECURITY CLASSIFICATION OF: Of the many systems studied to...Research Office P.O. Box 12211 Research Triangle Park, NC 27709-2211 15. SUBJECT TERMS Ultracold polar molecules, quantum computing , phase gates...From - To) 30-Aug-2006 Standard Form 298 (Rev 8/98) Prescribed by ANSI Std. Z39.18 - 31-Aug-2009 Robust quantum computing using molecules with

Switchable antifouling coatings and uses thereof

DOEpatents

Denton, Michele L. Baca; Dirk, Shawn M.; Johnson, Ross Stefan

2017-02-28

The present invention relates to antifouling coatings capable of being switched by using heat or ultraviolet light. Prior to switching, the coating includes an onium cation component having antimicrobial and antibacterial properties. Upon switching, the coating is converted to a conjugated polymer state, and the cationic component is released with any adsorbed biofilm layer. Thus, the coatings herein have switchable and releasable properties. Methods of making and using such coatings are also described.

Zipper-like magnetic molecularly imprinted microspheres for on/off-switchable recognition and extraction of 17β-estradiol from food samples.

PubMed

Zhu, Wenting; Peng, Hailong; Luo, Mei; Yu, Ningxiang; Xiong, Hua; Wang, Ronghui; Li, Yanbin

2018-09-30

Zipper-like on/off-switchable and magnetic molecularly imprinted microspheres (SM-MIMs) were constructed using acrylamide (AAm) and 2-acrylamide-2-methyl propanesulfonic acid (AMPS) as functional monomers for 17β-estradiol (17β-E 2 ) recognition and extraction. The imprinted polymer interactions between poly(AAm) (PAAm) and poly(AMPS) (PAMPS) with on/off-switchable property to temperature, exhibited dissociation at relatively higher temperatures (such as 30 °C) and helped 17β-E 2 enter into imprinted sites, leading to higher binding capability. Conversely, the interpolymer complexes between PAAm and PAMPS formed and blocked 17β-E 2 access to imprinted sites at lower temperature (such as 20 °C). SM-MIMs were used as dispersive solid phase extraction (SPE) adsorbent with HPLC for 17β-E 2 pretreatment and detection in food samples, and low limit detection (2.52 µg L -1 ) and quantification (10.76 µg L -1 ) with higher recovery were obtained. Therefore, SM-MIMs may be a promising adsorbent for 17β-E 2 pretreatment in food samples owing to its advantages of on/off-switchable recognition, eco-friendly elution, and efficient separation. Copyright © 2018. Published by Elsevier Ltd.

Reversibility of red blood cell deformation

NASA Astrophysics Data System (ADS)

Zeitz, Maria; Sens, P.

2012-05-01

The ability of cells to undergo reversible shape changes is often crucial to their survival. For red blood cells (RBCs), irreversible alteration of the cell shape and flexibility often causes anemia. Here we show theoretically that RBCs may react irreversibly to mechanical perturbations because of tensile stress in their cytoskeleton. The transient polymerization of protein fibers inside the cell seen in sickle cell anemia or a transient external force can trigger the formation of a cytoskeleton-free membrane protrusion of μm dimensions. The complex relaxation kinetics of the cell shape is shown to be responsible for selecting the final state once the perturbation is removed, thereby controlling the reversibility of the deformation. In some case, tubular protrusion are expected to relax via a peculiar “pearling instability.”

Reversibility of red blood cell deformation.

PubMed

Zeitz, Maria; Sens, P

2012-05-01

The ability of cells to undergo reversible shape changes is often crucial to their survival. For red blood cells (RBCs), irreversible alteration of the cell shape and flexibility often causes anemia. Here we show theoretically that RBCs may react irreversibly to mechanical perturbations because of tensile stress in their cytoskeleton. The transient polymerization of protein fibers inside the cell seen in sickle cell anemia or a transient external force can trigger the formation of a cytoskeleton-free membrane protrusion of μm dimensions. The complex relaxation kinetics of the cell shape is shown to be responsible for selecting the final state once the perturbation is removed, thereby controlling the reversibility of the deformation. In some case, tubular protrusion are expected to relax via a peculiar "pearling instability."

Bias-polarity-dependent UV/visible transferable electroluminescence from ZnO nanorod array LED with graphene oxide electrode supporting layer

NASA Astrophysics Data System (ADS)

Liu, Weizhen; Wang, Wei; Xu, Haiyang; Li, Xinghua; Yang, Liu; Ma, Jiangang; Liu, Yichun

2015-09-01

A simple top electrode preparation process, employing continuous graphene oxide films as electrode supporting layers, was adopted to fabricate a ZnO nanorod array/p-GaN heterojunction LED. The achieved LED demonstrated different electroluminescence behaviors under forward and reverse biases: a yellow-red emission band was observed under forward bias, whereas a blue-UV emission peak was obtained under reverse bias. Electroluminescence spectra under different currents and temperatures, as well as heterojunction energy-band alignments, reveal that the yellow-red emission under forward bias originates from recombinations related to heterointerface defects, whereas the blue-UV electroluminescence under reverse bias is ascribed to transitions from near-band-edge and Mg-acceptor levels in p-GaN.

Red cell surface changes in cold agglutination

PubMed Central

Salsbury, A. J.; Clarke, J. A.; Shand, W. S.

1968-01-01

Surface changes in red blood cells undergoing cold agglutination have been investigated using the Cambridge Stereoscan electron microscope. On incubation of red cells with a cold agglutinin of anti-I specificity at 4°C, circular shadows on the red cell membrane developed within 2 min. At the same time the membrane showed a granularity and processes began to develop on the surface. These processes increased in length, the processes of contiguous cells became interlinked and agglutination was complete after incubation of 1 hr. On warming an agglutinated specimen, the process was reversed with separation of red cells and retraction of the finger-like processes to yield discrete red cells of normal appearance. The addition of heparin in vivo prevented agglutination but did not inhibit surface changes completely. Complement appeared to play no part in the production of cold agglutination due to these antibodies or in the reversal of agglutination by warming. The significance of the surface changes described in relation to previous information on the mechanism of agglutination, has been discussed. ImagesFig. 1Fig. 2Fig. 3Fig. 4Fig. 5Fig. 6Fig. 7Fig. 8Fig. 9Fig. 10Fig. 11 PMID:5655472

Smart Mirrors for Photorefractive Control of Light with Tim Bunning, RX - Agile Filters Application

DTIC Science & Technology

2016-11-08

AFRL-AFOSR-UK-TR-2017-0008 Smart Mirrors for photorefractive control of light with Tim Bunning, RX-- Agile filters application Luciano De Sio...photorefractive control of light with Tim Bunning, RX-- Agile filters application 5a.  CONTRACT NUMBER 5b.  GRANT NUMBER FA9550-14-1-0050 5c.  PROGRAM...photorefractive, switchable optical filters , liquide crystalline composite materials, Switchable reflective holographic gratings, polymer-dispersed liquid

Switchable radioactive neutron source device

DOEpatents

Boyar, Robert E.; DeVolpi, Alexander; Stanford, George S.; Rhodes, Edgar A.

1989-01-01

This invention is a switchable neutron generating apparatus comprised of a pair of plates, the first plate having an alpha emitter section on it and the second plate having a target material portion on it which generates neutrons when its nuclei absorb an alpha particle. In operation, the alpha portion of the first plate is aligned with the neutron portion of the second plate to produce neutrons and brought out of alignment to cease production of neutrons.

Novel Material Systems and Methodologies for Transient Thermal Management

NASA Technical Reports Server (NTRS)

Oliva-Buisson, Yvette J.

2014-01-01

Development of multifunctional and thermally switchable systems to address reduced mass and components, and tailored for both structural and transient thermal applications. Active, passive, and novel combinations of the two functional approaches are being developed along two lines of research investigation: switchable systems and transient heat spreading. The approach is to build in thermal functionality to structural elements to lay the foundation for a revolution in the way high energy space systems are designed.

Sunlight-switchable light shutter fabricated using liquid crystals doped with push-pull azobenzene.

PubMed

Oh, Seung-Won; Baek, Jong-Min; Yoon, Tae-Hoon

2016-11-14

We propose a sunlight-switchable light shutter using liquid crystal/polymer composite doped with push-pull azobenzene. The proposed light shutter is switchable between the translucent and transparent states by application of an electric field or by UV irradiation. Switching by UV irradiation is based on the change of the liquid crystal (LC) clearing point by the photo-isomerization effect of push-pull azobenzene. Under sunlight, the light shutter can be switched from the translucent to the transparent state by the nematic-isotropic phase transition of the LC domains triggered by trans-cis photo-isomerization of the push-pull azobenzene molecules. When the amount of sunlight is low because of cloud cover or when there is no sunlight at sunset, the light shutter rapidly relaxes from its transparent state back to its initial translucent state by the isotropic-nematic phase transition induced by cis-trans back-isomerization of the push-pull azobenzene molecules.

Fast switchable ferroelectric liquid crystal gratings with two electro-optical modes

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ma, Ying; Srivastava, A. K., E-mail: abhishek-srivastava-lu@yahoo.co.in; Chigrinov, V. G.

In this article, we reveal a theoretical and experimental illustration of the Ferroelectric liquid crystal (FLC) grating fabricated by mean of patterned alignment based on photo-alignment. The complexity related to the mismatching of the predefined alignment domains on the top and bottom substrate has been avoided by incorporating only one side photo aligned substrate while the other substrate does not have any alignment layer. Depending on the easy axis in the said alignment domains and the azimuth plane of the impinging polarized light, the diffracting element can be tuned in two modes i.e. DIFF/OFF switchable and DIFF/TRANS switchable modes, whichmore » can be applied to different applications. The diffraction profile has been illustrated theoretically that fits well with the experimental finding and thus the proposed diffraction elements with fast response time and high diffraction efficiency could find application in many modern devices.« less

Switchable silver mirrors with long memory effects.

PubMed

Park, Chihyun; Seo, Seogjae; Shin, Haijin; Sarwade, Bhimrao D; Na, Jongbeom; Kim, Eunkyoung

2015-01-01

An electrochemically stable and bistable switchable mirror was achieved for the first time by introducing (1) a thiol-modified indium tin oxide (ITO) electrode for the stabilization of the metallic film and (2) ionic liquids as an anion-blocking layer, to achieve a long memory effect. The growth of the metallic film was denser and faster at the thiol-modified ITO electrode than at a bare ITO electrode. The electrochemical stability of the metallic film on the thiol-modified ITO was enhanced, maintaining the metallic state without rupture. In the voltage-off state, the metal film maintained bistability for a long period (>2 h) when ionic liquids were introduced as electrolytes for the switchable mirror. The electrical double layer in the highly viscous ionic liquid electrolyte seemed to effectively form a barrier to the bromide ions, to protect the metal thin film from them when in the voltage-off state.

Liquid-crystal-based switchable polarizers for sensor protection.

PubMed

Wu, C S; Wu, S T

1995-11-01

Linear polarizers are generally employed in conjunction with advanced liquid-crystal filters for the protection of human eyes and optical sensors. For detection sensitivity under a no-threat condition to be maximized, the polarizer should remain in a clear state with a minimum insertion loss. When threats are present, it should be quickly switched to function as a linear polarizer with a high extinction ratio. Two types of switchable polarizer for sensor protection are demonstrated. The polarization conversion type exhibits a high optical efficiency in its clear state, a high extinction ratio in the linear polarizer state, and a fast switching speed, except that its field of view is limited to approximately ±10°. In contrast, an improved switchable dichroic polarizer functions effectively over a much wider field of view. However, its extinction ratio and optical efficiency in its clear state are lower than those of the polarization conversion type.

Liquid-crystal-based switchable polarizers for sensor protection

NASA Astrophysics Data System (ADS)

Wu, Chiung-Sheng; Wu, Shin-Tson

1995-11-01

Linear polarizers are generally employed in conjunction with advanced liquid-crystal filters for the protection of human eyes and optical sensors. For detection sensitivity under a no-threat condition to be maximized, the polarizer should remain in a clear state with a minimum insertion loss. When threats are present, it should be quickly switched to function as a linear polarizer with a high extinction ratio. Two types of switchable polarizer for sensor protection are demonstrated. The polarization conversion type exhibits a high optical efficiency in its clear state, a high extinction ratio in the linear polarizer state, and a fast switching speed, except that its field of view is limited to approximately +/-10 deg In contrast, an improved switchable dichroic polarizer functions effectively over a much wider field of view. However, its extinction ratio and optical efficiency in its clear state are lower than those of the polarization conversion type.

Enhancement of Near-Real-Time Cloud Analysis and Related Analytic Support for Whole Sky Imagers

DTIC Science & Technology

2007-05-01

Red/ Blue Ratio Through the Sun on 3 Typical Days ................14 Fig. 11 Red/ Blue Ratio Through the Sun on Forward Bias Days ..........15 Fig...12 Red/ Blue Ratio Through the Sun on Reverse Bias Days ...........15 Fig. 13 No Moon Case in Oklahoma...the clear sky red/ blue ratios. Up until this time, we had been using the background from another site and instrument. As part of this contract, we

Photo-convertible fluorescent proteins as tools for fresh insights on subcellular interactions in plants.

PubMed

Griffiths, N; Jaipargas, E-A; Wozny, M R; Barton, K A; Mathur, N; Delfosse, K; Mathur, J

2016-08-01

Optical highlighters comprise photo-activatable, photo-switchable and photo-convertible fluorescent proteins and are relatively recent additions to the toolbox utilized for live cell imaging research. Here, we provide an overview of four photo-convertible fluorescent proteins (pcFP) that are being used in plant cell research: Eos, Kaede, Maple and Dendra2. Each of these proteins has a significant advantage over other optical highlighters since their green fluorescent nonconverted forms and red fluorescent converted forms are generally clearly visible at expression levels that do not appear to interfere with subcellular dynamics and plant development. These proteins have become increasingly useful for understanding the role of transient and sustained interactions between similar organelles. Tracking of single organelles after green-to-red conversion has provided novel insights on plastids and their stroma-filled extensions and on the formation of mega-mitochondria. Similarly colour recovery after photo-conversion has permitted the estimation of nuclear endo-reduplication events and is being developed further to image protein trafficking within the lumen of the endoplasmic reticulum. We have also applied photo-convertible proteins to create colour-differentiation between similar cell types to follow their development. Both the green and red fluorescent forms of these proteins are compatible with other commonly used single coloured FPs. This has allowed us to develop simultaneous visualization schemes for up to five types of organelles and investigate organelle interactivity. The advantages and caveats associated with the use of photo-convertible fluorescent proteins are discussed. © 2016 The Authors Journal of Microscopy © 2016 Royal Microscopical Society.

Photocontrol of germination in Amaranthus caudatus.

PubMed

Kendrick, R E; Frankland, B

1969-12-01

Germination of Amaranthus caudatus is inhibited by light, far-red being the most effective part of the spectrum. At temperatures of 25° and below there is a low final germination percentage under continuous far-red whereas above 25° there is only a delaying effect. In the presence of a saturating concentration of gibberellic acid (GA3) at 25° seeds germinate under continuous far-red although they are delayed. At 25° seeds exposed to 48 hr far-red fail to germinate when transferred to darkness. This induced dormancy can be broken by a single short exposure to red light given at any time after the far-red illumination. This effect of short red can be reversed by a subsequent short period of far-red indicating that the seeds are phytochrome controlled. Although most seeds have escaped from the reversing effect of short far-red after an intervening dark period of 5 hours, germination is greatly reduced by continuous far-red at this time. Results of exposing seeds to varying periods of far-red before and after dark imbibition are interpreted in terms of a continual production of phytochrome in its active P fr form and a requirement for P fr action over a long period of time. Effects of intermittent and continuous low intensity far-red on the inhibition of germination provides further evidence for a low energy photoreaction involving phytochrome. Effects on Germination Index of continuous illumination with various light sources maintaining different P fr /P total ratios have been investigated. The results suggest that the proportion of phytochrome in the P fr form is the most important factor in the regulation of germination. A scheme for the phytochrome control of germination in Amaranthus caudatus is presented and possible explanations for the dependence on P fr /P total ratio are discussed.

Isocratic non-aqueous reversed-phase high-performance liquid chromatographic separation of capsanthin and capsorubin in red peppers (Capsicum annuum L.), paprika and oleoresin.

PubMed

Weissenberg, M; Schaeffler, I; Menagem, E; Barzilai, M; Levy, A

1997-01-03

A simple, rapid high-performance liquid chromatography method has been devised in order to separate and quantify the xanthophylls capsorubin and capasanthin present in red pepper (Capsicum annuum L.) fruits and preparations made from them (paprika and oleoresin). A reversed-phase isocratic non-aqueous system allows the separation of xanthophylls within a few minutes, with detection at 450 nm, using methyl red as internal standard to locate the various carotenoids and xanthophylls found in plant extracts. The selection of extraction solvents, mild saponification conditions, and chromatographic features is evaluated and discussed. The method is proposed for rapid screening of large plant populations, plant selection, as well as for paprika products and oleoresin, and also for nutrition and quality control studies.

Comparison of hydrogen production and electrical power generation for energy capture in closed-loop ammonium bicarbonate reverse electrodialysis systems.

PubMed

Hatzell, Marta C; Ivanov, Ivan; Cusick, Roland D; Zhu, Xiuping; Logan, Bruce E

2014-01-28

Currently, there is an enormous amount of energy available from salinity gradients, which could be used for clean hydrogen production. Through the use of a favorable oxygen reduction reaction (ORR) cathode, the projected electrical energy generated by a single pass ammonium bicarbonate reverse electrodialysis (RED) system approached 78 W h m(-3). However, if RED is operated with the less favorable (higher overpotential) hydrogen evolution electrode and hydrogen gas is harvested, the energy recovered increases by as much ~1.5× to 118 W h m(-3). Indirect hydrogen production through coupling an RED stack with an external electrolysis system was only projected to achieve 35 W h m(-3) or ~1/3 of that produced through direct hydrogen generation.

Phenotypes on demand via switchable target protein degradation in multicellular organisms

PubMed Central

Faden, Frederik; Ramezani, Thomas; Mielke, Stefan; Almudi, Isabel; Nairz, Knud; Froehlich, Marceli S.; Höckendorff, Jörg; Brandt, Wolfgang; Hoehenwarter, Wolfgang; Dohmen, R. Jürgen; Schnittger, Arp; Dissmeyer, Nico

2016-01-01

Phenotypes on-demand generated by controlling activation and accumulation of proteins of interest are invaluable tools to analyse and engineer biological processes. While temperature-sensitive alleles are frequently used as conditional mutants in microorganisms, they are usually difficult to identify in multicellular species. Here we present a versatile and transferable, genetically stable system based on a low-temperature-controlled N-terminal degradation signal (lt-degron) that allows reversible and switch-like tuning of protein levels under physiological conditions in vivo. Thereby, developmental effects can be triggered and phenotypes on demand generated. The lt-degron was established to produce conditional and cell-type-specific phenotypes and is generally applicable in a wide range of organisms, from eukaryotic microorganisms to plants and poikilothermic animals. We have successfully applied this system to control the abundance and function of transcription factors and different enzymes by tunable protein accumulation. PMID:27447739

Switchable pH-responsive polymeric membranes prepared via block copolymer micelle assembly.

PubMed

Nunes, Suzana P; Behzad, Ali Reza; Hooghan, Bobby; Sougrat, Rachid; Karunakaran, Madhavan; Pradeep, Neelakanda; Vainio, Ulla; Peinemann, Klaus-Viktor

2011-05-24

A process is described to manufacture monodisperse asymmetric pH-responsive nanochannels with very high densities (pore density >2 × 10(14) pores per m(2)), reproducible in m(2) scale. Cylindric pores with diameters in the sub-10 nm range and lengths in the 400 nm range were formed by self-assembly of metal-block copolymer complexes and nonsolvent-induced phase separation. The film morphology was tailored by taking into account the stability constants for a series of metal-polymer complexes and confirmed by AFM. The distribution of metal-copolymer micelles was imaged by transmission electron microscopy tomography. The pH response of the polymer nanochannels is the strongest reported with synthetic pores in the nm range (reversible flux increase of more than 2 orders of magnitude when switching the pH from 2 to 8) and could be demonstrated by cryo-field emission scanning electron microscopy, SAXS, and ultra/nanofiltration experiments.

COHO - Utilizing Waste Heat and Carbon Dioxide at Power Plants for Water Treatment

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kaur, Sumanjeet; Wilson, Aaron; Wendt, Daniel

The COHO is a breakthrough water purification system that can concentrate challenging feed waters using carbon dioxide and low-grade heat. For this project, we studied feeds in a lab-scale system to simulate COHO’s potential to operate at coal- powered power plants. COHO proved successful at concentrating the highly scaling and challenging wastewaters derived from a power plant’s cooling towers and flue gas desulfurization units. We also found that COHO was successful at scrubbing carbon dioxide from flue gas mixtures. Thermal regeneration of the switchable polarity solvent forward osmosis draw solution ended up requiring higher temperatures than initially anticipated, but wemore » also found that the draw solution could be polished via reverse osmosis. A techno-economic analysis indicates that installation of a COHO at a power plant for wastewater treatment would result in significant savings.« less

Mechano-regulated surface for manipulating liquid droplets

NASA Astrophysics Data System (ADS)

Tang, Xin; Zhu, Pingan; Tian, Ye; Zhou, Xuechang; Kong, Tiantian; Wang, Liqiu

2017-04-01

The effective transfer of tiny liquid droplets is vital for a number of processes such as chemical and biological microassays. Inspired by the tarsi of meniscus-climbing insects, which can climb menisci by deforming the water/air interface, we developed a mechano-regulated surface consisting of a background mesh and a movable microfibre array with contrastive wettability. The adhesion of this mechano-regulated surface to liquid droplets can be reversibly switched through mechanical reconfiguration of the microfibre array. The adhesive force can be tuned by varying the number and surface chemistry of the microfibres. The in situ adhesion of the mechano-regulated surface can be used to manoeuvre micro-/nanolitre liquid droplets in a nearly loss-free manner. The mechano-regulated surface can be scaled up to handle multiple droplets in parallel. Our approach offers a miniaturized mechano-device with switchable adhesion for handling micro-/nanolitre droplets, either in air or in a fluid that is immiscible with the droplets.

Redox-Switchable Surface Wrinkling on Polyaniline Film.

PubMed

Xie, Jixun; Zong, Chuanyong; Han, Xue; Ji, Haipeng; Wang, Juanjuan; Yang, Xiu; Lu, Conghua

2016-04-01

Here the redox-driven switch between the wrinkled and dewrinkled states on poly-aniline (PANI) film is reported. This switch is derived from the reversible transition in different intrinsic redox states of polyaniline (e.g., between emeraldine salt (ES) and leucoemeraldine base (LEB) or between ES and pernigraniline base (PB)) that are involved in the redox reaction, coupled with the corresponding volume expansion/shrinkage. Interestingly, the as-wrinkled ES film becomes deswollen and dewrinkled when reduced to the LEB state or oxidized to the PB state. Conversely, oxidation of the LEB film or reduction of the PB film into the swollen ES film leads to the reoccurrence of surface wrinkling. Furthermore, the reducibility of the dewrinkled LEB film and the oxidizability of the dewrinkled PB film are well utilized respectively to yield various wrinkled PANI-based composite films. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Cell-Free Optogenetic Gene Expression System.

PubMed

Jayaraman, Premkumar; Yeoh, Jing Wui; Jayaraman, Sudhaghar; Teh, Ai Ying; Zhang, Jingyun; Poh, Chueh Loo

2018-04-20

Optogenetic tools provide a new and efficient way to dynamically program gene expression with unmatched spatiotemporal precision. To date, their vast potential remains untapped in the field of cell-free synthetic biology, largely due to the lack of simple and efficient light-switchable systems. Here, to bridge the gap between cell-free systems and optogenetics, we studied our previously engineered one component-based blue light-inducible Escherichia coli promoter in a cell-free environment through experimental characterization and mathematical modeling. We achieved >10-fold dynamic expression and demonstrated rapid and reversible activation of the target gene to generate oscillatory response. The deterministic model developed was able to recapitulate the system behavior and helped to provide quantitative insights to optimize dynamic response. This in vitro optogenetic approach could be a powerful new high-throughput screening technology for rapid prototyping of complex biological networks in both space and time without the need for chemical induction.

Dynamic patterns in a supported lipid bilayer driven by standing surface acoustic waves.

PubMed

Hennig, Martin; Neumann, Jürgen; Wixforth, Achim; Rädler, Joachim O; Schneider, Matthias F

2009-11-07

In the past decades supported lipid bilayers (SLBs) have been an important tool in order to study the physical properties of biological membranes and cells. So far, controlled manipulation of SLBs is very limited. Here we present a new technology to create lateral patterns in lipid membranes controllable in both space and time. Surface acoustic waves (SAWs) are used to generate lateral standing waves on a piezoelectric substrate which create local "traps" in the lipid bilayer and lead to a lateral modulation in lipid concentration. We demonstrate that pattern formation is reversible and does not affect the integrity of the lipid bilayer as shown by extracting the diffusion constant of fluid membranes. The described method could possibly be used to design switchable interfaces for the lateral transport and organization of membrane bound macromolecules to create dynamic bioarrays and control biofilm formation.

Anion Order and Spontaneous Polarization in LaTiO2N Oxynitride Thin Films

NASA Astrophysics Data System (ADS)

Vonrüti, Nathalie; Aschauer, Ulrich

2018-01-01

The perovskite oxynitride LaTiO2N is a promising material for photocatalytic water splitting under visible light. One of the obstacles towards higher efficiencies of this and similar materials stems from charge-carrier recombination, which could be suppressed by the surface charges resulting from the dipolar field in polar materials. In this study, we investigate the spontaneous polarization in epitaxially strained LaTiO2N thin films via density functional theory calculations. The effect of epitaxial strain on the anion order, resulting out-of-plane polarization, energy barriers for polarization reversal, and corresponding coercive fields are studied. We find that for compressive strains larger than 4% the thermodynamically stable anion order is polar along the out-of-plane direction and has a coercive field comparable to other switchable ferroelectrics. Our results show that strained LaTiO2N could indeed suppress carrier recombination and lead to enhanced photocatalytic activities.

A Smart Superwetting Surface with Responsivity in Both Surface Chemistry and Microstructure.

PubMed

Zhang, Dongjie; Cheng, Zhongjun; Kang, Hongjun; Yu, Jianxin; Liu, Yuyan; Jiang, Lei

2018-03-26

Recently, smart surfaces with switchable wettability have aroused much attention. However, only single surface chemistry or the microstructure can be changed on these surfaces, which significantly limits their wetting performances, controllability, and applications. A new surface with both tunable surface microstructure and chemistry was prepared by grafting poly(N-isopropylacrylamide) onto the pillar-structured shape memory polymer on which multiple wetting states from superhydrophilicity to superhydrophobicity can be reversibly and precisely controlled by synergistically regulating the surface microstructure and chemistry. Meanwhile, based on the excellent controllability, we also showed the application of the surface as a rewritable platform, and various gradient wettings can be obtained. This work presents for the first time a surface with controllability in both surface chemistry and microstructure, which starts some new ideas for the design of novel superwetting materials. © 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Near-infrared light-responsive dynamic wrinkle patterns.

PubMed

Li, Fudong; Hou, Honghao; Yin, Jie; Jiang, Xuesong

2018-04-01

Dynamic micro/nanopatterns provide an effective approach for on-demand tuning of surface properties to realize a smart surface. We report a simple yet versatile strategy for the fabrication of near-infrared (NIR) light-responsive dynamic wrinkles by using a carbon nanotube (CNT)-containing poly(dimethylsiloxane) (PDMS) elastomer as the substrate for the bilayer systems, with various functional polymers serving as the top stiff layers. The high photon-to-thermal energy conversion of CNT leads to the NIR-controlled thermal expansion of the elastic CNT-PDMS substrate, resulting in dynamic regulation of the applied strain (ε) of the bilayer system by the NIR on/off cycle to obtain a reversible wrinkle pattern. The switchable surface topological structures can transfer between the wrinkled state and the wrinkle-free state within tens of seconds via NIR irradiation. As a proof-of-concept application, this type of NIR-driven dynamic wrinkle pattern was used in smart displays, dynamic gratings, and light control electronics.

Performance through Deformation and Instability

NASA Astrophysics Data System (ADS)

Bertoldi, Katia

2015-03-01

Materials capable of undergoing large deformations like elastomers and gels are ubiquitous in daily life and nature. An exciting field of engineering is emerging that uses these compliant materials to design active devices, such as actuators, adaptive optical systems and self-regulating fluidics. Compliant structures may significantly change their architecture in response to diverse stimuli. When excessive deformation is applied, they may eventually become unstable. Traditionally, mechanical instabilities have been viewed as an inconvenience, with research focusing on how to avoid them. Here, I will demonstrate that these instabilities can be exploited to design materials with novel, switchable functionalities. The abrupt changes introduced into the architecture of soft materials by instabilities will be used to change their shape in a sudden, but controlled manner. Possible and exciting applications include materials with unusual properties such negative Poisson's ratio, phononic crystals with tunable low-frequency acoustic band gaps and reversible encapsulation systems.

An allosteric photoredox catalyst inspired by photosynthetic machinery

PubMed Central

Lifschitz, Alejo M.; Young, Ryan M.; Mendez-Arroyo, Jose; Stern, Charlotte L.; McGuirk, C. Michael; Wasielewski, Michael R.; Mirkin, Chad A.

2015-01-01

Biological photosynthetic machinery allosterically regulate light harvesting via conformational and electronic changes at the antenna protein complexes as a response to specific chemical inputs. Fundamental limitations in current approaches to regulating inorganic light-harvesting mimics prevent their use in catalysis. Here we show that a light-harvesting antenna/reaction centre mimic can be regulated by utilizing a coordination framework incorporating antenna hemilabile ligands and assembled via a high-yielding, modular approach. As in nature, allosteric regulation is afforded by coupling the conformational changes to the disruptions in the electrochemical landscape of the framework upon recognition of specific coordinating analytes. The hemilabile ligands enable switching using remarkably mild and redox-inactive inputs, allowing one to regulate the photoredox catalytic activity of the photosynthetic mimic reversibly and in situ. Thus, we demonstrate that bioinspired regulatory mechanisms can be applied to inorganic light-harvesting arrays displaying switchable catalytic properties and with potential uses in solar energy conversion and photonic devices. PMID:25817586

Polymeric surfaces exhibiting photocatalytic activity and controlled anisotropic wettability

NASA Astrophysics Data System (ADS)

Anastasiadis, Spiros H.; Frysali, Melani A.; Papoutsakis, Lampros; Kenanakis, George; Stratakis, Emmanuel; Vamvakaki, Maria; Mountrichas, Grigoris; Pispas, Stergios

2015-03-01

In this work we focus on surfaces, which exhibit controlled, switchable wettability in response to one or more external stimuli as well as photocatalytic activity. For this we are inspired from nature to produce surfaces with a dual-scale hierarchical roughness and combine them with the appropriate inorganic and/or polymer coating. The combination of the hierarchical surface with a ZnO coating and a pH- or temperature-responsive polymer results in efficient photo-active properties as well as reversible superhydrophobic / superhydrophilic surfaces. Furthermore, we fabricate surfaces with unidirectional wettability variation. Overall, such complex surfaces require advanced design, combining hierarchically structured surfaces with suitable polymeric materials. Acknowledgment: This research was partially supported by the European Union (European Social Fund, ESF) and Greek national funds through the ``ARISTEIA II'' Action (SMART-SURF) of the Operational Programme ``Education and Lifelong Learning,'' NSRF 2007-2013, via the General Secretariat for Research & Technology, Ministry of Education and Religious Affairs, Greece.

Supramolecular assembly/reassembly processes: molecular motors and dynamers operating at surfaces.

PubMed

Ciesielski, Artur; Samorì, Paolo

2011-04-01

Among the many significant advances within the field of supramolecular chemistry over the past decades, the development of the so-called "dynamers" features a direct relevance to materials science. Defined as "combinatorial dynamic polymers", dynamers are constitutional dynamic systems and materials resulting from the application of the principles of supramolecular chemistry to polymer science. Like supramolecular materials in general, dynamers are reversible dynamic multifunctional architectures, capable of modifying their constitution by exchanging, recombining, incorporating components. They may exhibit a variety of novel properties and behave as adaptive materials. In this review we focus on the design of responsive switchable monolayers, i.e. monolayers capable to undergo significant changes in their physical or chemical properties as a result of external stimuli. Scanning tunneling microscopy studies provide direct evidence with a sub-nanometre resolution, on the formation and dynamic response of these self-assembled systems featuring controlled geometries and properties.

Triply responsive films in bioelectrocatalysis with a binary architecture: combined layer-by-layer assembly and hydrogel polymerization.

PubMed

Yao, Huiqin; Hu, Naifei

2011-05-26

In this work, triply responsive films with a specific binary architecture combining layer-by-layer assembly (LbL) and hydrogel polymerization were successfully prepared. First, concanavalin A (Con A) and dextran (Dex) were assembled into {Con A/Dex}(5) LbL layers on electrode surface by the lectin-sugar biospecific interaction between them. The poly(N,N-diethylacrylamide) (PDEA) hydrogels with entrapped horseradish peroxidase (HRP) were then synthesized by polymerization on the surface of LbL inner layers, forming {Con A/Dex}(5)-(PDEA-HRP) films. The films demonstrated reversible pH-, thermo-, and salt-responsive on-off behavior toward electroactive probe Fe(CN)(6)(3-) in its cyclic voltammetric responses. This multiple stimuli-responsive films could be further used to realize triply switchable electrochemical reduction of H(2)O(2) catalyzed by HRP immobilized in the films and mediated by Fe(CN)(6)(3-) in solution. The responsive mechanism of the films was explored and discussed. The pH-sensitive property of the system was attributed to the electrostatic interaction between the {Con A/Dex}(5) inner layers and the probe at different pH, and the thermo- and salt-responsive behaviors should be ascribed to the structure change of PDEA hydrogels for the PDEA-HRP outermost layers under different conditions. The concept of binary architecture was also used to fabricate {Con A/Dex}(5)-(PDEA-GOD) films on electrodes, where GOD = glucose oxidase, which was applied to realize the triply switchable bioelectrocatalysis of glucose by GOD in the films with ferrocenedicarboxylic acid as the mediator in solution. This film system with the unique binary architecture may establish a foundation for fabricating a novel type of multicontrollable biosensors based on bioelectrocatalysis with immobilized enzymes.

Photo-switchable Donor-Acceptor (D-A) Dyad Interfacial Self-Assembled Monolayers for Organic Photovoltaic Cells

DTIC Science & Technology

2015-11-05

AFRL-AFOSR-VA-TR-2015-0396 (HBCU) Photo-switchable Donor-Acceptor for Organic Photovoltaic Cells Luis Echegoyen UNIVERSITY OF TEXAS AT EL PASO Final...Acceptor (D-A) Dyad Interfacial Self-Assembled Monolayers for Organic Photovoltaic Cells 5a.  CONTRACT NUMBER 5b.  GRANT NUMBER FA9550-12-1-0053 5c...demonstrated using impedance spectroscopy for several triphenylamine-fullerene dyads, but their performance in photovoltaic devices was not remarkable, likely

Switchable radioactive neutron source device

DOEpatents

Stanford, G.S.; Rhodes, E.A.; Devolpi, A.; Boyar, R.E.

1987-11-06

This invention is a switchable neutron generating apparatus comprised of a pair of plates, the first plate having an alpha emitter section on it and the second plate having a target material portion on it which generates neutrons when its nuclei absorb an alpha particle. In operation, the alpha portion of the first plate is aligned with the neutron portion of the second plate to produce neutrons and brought out of alignment to cease production of neutrons. 3 figs.

Electrical characteristics in reverse electrodialysis using nanoporous membranes

NASA Astrophysics Data System (ADS)

Chanda, Sourayon; Tsai, Peichun Amy

2017-11-01

We experimentally and numerically investigate the effects of concentration difference and flow velocity on sustainable electricity generation and associated fluid dynamics using a single reverse electrodialysis (RED) cell. By exploiting the charge-selective nature of nanoporous interfaces, electrical energy is generated by reverse electrodialysis harnessing chemical Gibbs energy via a salinity gradient. Experimentally, a RED cell was designed with two reservoirs, which are separated by a nanoporous, cation-selective membrane. We injected deionized water through one reservoir, whereas a solution of high salt concentration through the other. The gradient of salt concentration primarily drives the flow in the charged nano-pores, due to the interplay between charge selectivity, diffusion processes, and electro-migration. The current-voltage characteristics of the single RED cell shows a linear current-voltage relationship, similar to an electrochemical cell. The membrane resistance is increased with increasing salt concentration difference and external flow rate. The present experimental work was further analyzed numerically to better understand the detailed electrical and flow fields under different concentration gradients and external flows. NSERC Discovery, Accelerator, and CRC Programs.

Switchable and Tunable Bulk Acoustic Wave Devices Based on Ferroelectric Material

NASA Astrophysics Data System (ADS)

Mansour, Almonir

The explosive development of personal communications systems, navigation, satellite communications as well as personal computer and data processing systems together with the constant demand for higher speeds and larger bandwidths has driven fabrication technology to its limits. This, in turn, necessitates the development of novel functional materials for the fabrication of devices with superior performance and higher capacity at reduced manufacturing costs. Ferroelectric materials such as barium strontium titanate (BST) and strontium titanium oxide (STO) have received more attention by researchers and industry because of their field-induced piezoelectric property. This property gives these types of ferroelectric materials the ability to be switchable and tunable in the presence of an electric field. These features have allowed the ferroelectric materials to be used in many applications such as non-volatile memory and DRAMs, sensors, pyroelectric detectors, and tunable microwave devices. Therefore, with the ever increasing complexity in RF front-end receivers, and the demand for services (which in turn requires more functionalities), ferroelectric bulk acoustic wave (BAW) resonators and filters that are intrinsically switchable and tunable promise to reduce the size and complexity of component parts. In this work, we present the design, fabrication and experimental evaluation of switchable and tunable thin film bulk acoustic wave (BAW) resonators, filters and duplexers for radio frequency (RF) applications. The switchability and tunability of these devices come from utilizing the electrostrictive effect of ferroelectric materials such as barium strontium titanate (BST) with the application of an external DC-bias voltage. The BAW resonators, filters and duplexers in this work were fabricated on different substrates as solidly mounted resonator (SMR) structure with number of periodic layers of silicon dioxide and tantalum oxide as a Bragg reflector in order to acoustically isolate the resonator from the damping effect of the substrate, enhancing the quality factor and temperature compensation.

Integral physicochemical properties of reverse micelles of sodium bis(2-ethylhexyl) sulfosuccinate (AOT)

NASA Astrophysics Data System (ADS)

Fedyaeva, O. A.; Shubenkova, E. G.; Poshelyuzhnaya, E. G.; Lutaeva, I. A.

2016-08-01

The effect the degree of hydration has on optical and electrophysical properties of water/AOT/ n-hexane system is studied. It is found that AOT reverse micelles form aggregates whose dimensions grow along with the degree of hydration and temperature. Aggregation enhances their electrical conductivity and shifts the UV spectrum of AOT reverse emulsions to the red region. Four states of water are found in the structure of AOT reverse micelles.

Ferroelectric nanostructure having switchable multi-stable vortex states

DOEpatents

Naumov, Ivan I [Fayetteville, AR; Bellaiche, Laurent M [Fayetteville, AR; Prosandeev, Sergey A [Fayetteville, AR; Ponomareva, Inna V [Fayetteville, AR; Kornev, Igor A [Fayetteville, AR

2009-09-22

A ferroelectric nanostructure formed as a low dimensional nano-scale ferroelectric material having at least one vortex ring of polarization generating an ordered toroid moment switchable between multi-stable states. A stress-free ferroelectric nanodot under open-circuit-like electrical boundary conditions maintains such a vortex structure for their local dipoles when subject to a transverse inhomogeneous static electric field controlling the direction of the macroscopic toroidal moment. Stress is also capable of controlling the vortex's chirality, because of the electromechanical coupling that exists in ferroelectric nanodots.

Quenching of giant hysteresis effects in La(1-z)Y(z)Hx switchable mirrors

PubMed

van Gogh AT; Nagengast; Kooij; Koeman; Griessen

2000-09-04

The giant intrinsic hysteresis as a function of hydrogen concentration x in the optical and electrical properties of the archetypal switchable mirror YHx is eliminated by alloying Y with the chemically similar La. The La(1-z)Y(z)Hx films with z/=0.86 is the large uniaxial lattice expansion that accompanies their fcc to hexagonal phase transition in combination with lateral clamping.

New Materials for Smart Structures: a US: Japan Global Initiative

DTIC Science & Technology

2004-03-01

realization of the MPB in the Gallate:Scandate system and in the modified bismuth lanthanum ferrate lead titanate systems. A major puzzle in BiFeO3 which has...magnetization. A new major clue as to the origin of the high switchable polarization is provided by our most recent work on the modified bismuth lanthanum ...ferrate: gallate solid solutions with MPBs. In suitable composition switchability is only possible with limited electrode in a larger disk, and the fully

Simulation and Micro-Fabrication of Optically Switchable Split Ring Resonators

DTIC Science & Technology

2007-01-01

Simulation and micro-fabrication of optically switchable split ring resonators T.F. Gundogdu a,*, Mutlu Gökkavas b, Kaan Güven b, M. Kafesaki a...mail address: tamara@iesl.forth.gr (T.F. Gundogdu ). 1569-4410/$ – see front matter # 2007 Published by Elsevier B.V. doi:10.1016/j.photonics...ABSTRACT unclassified c. THIS PAGE unclassified Standard Form 298 (Rev. 8-98) Prescribed by ANSI Std Z39-18 T.F. Gundogdu et al. / Photonics and

A symmetry breaking phase transition-triggered high-temperature solid-state quadratic nonlinear optical switch coupled with a switchable dielectric constant in an organic-inorganic hybrid compound.

PubMed

Mei, Guang-Quan; Zhang, Han-Yue; Liao, Wei-Qiang

2016-09-25

An organic-inorganic hybrid compound, [NH3(CH2)5NH3]SbCl5, exhibits a switchable second harmonic generation (SHG) effect between SHG-OFF and SHG-ON states and tunable dielectric behaviors between high and low dielectric states, connected with the changes in the dynamics of 1,5-pentanediammonium cations during its centrosymmetric-to-noncentrosymmetric symmetry breaking phase transition at 365.4 K.

Red Raspberries and Their Bioactive Polyphenols: Cardiometabolic and Neuronal Health Links12

PubMed Central

Burton-Freeman, Britt M; Sandhu, Amandeep K; Edirisinghe, Indika

2016-01-01

Diet is an essential factor that affects the risk of modern-day metabolic diseases, including cardiovascular disease, diabetes mellitus, obesity, and Alzheimer disease. The potential ability of certain foods and their bioactive compounds to reverse or prevent the progression of the pathogenic processes that underlie these diseases has attracted research attention. Red raspberries (Rubus idaeus L.) are unique berries with a rich history and nutrient and bioactive composition. They possess several essential micronutrients, dietary fibers, and polyphenolic components, especially ellagitannins and anthocyanins, the latter of which give them their distinctive red coloring. In vitro and in vivo studies have revealed various mechanisms through which anthocyanins and ellagitannins (via ellagic acid or their urolithin metabolites) and red raspberry extracts (or the entire fruit) could reduce the risk of or reverse metabolically associated pathophysiologies. To our knowledge, few studies in humans are available for evaluation. We review and summarize the available literature that assesses the health-promoting potential of red raspberries and select components in modulating metabolic disease risk, especially cardiovascular disease, diabetes mellitus, obesity, and Alzheimer disease—all of which share critical metabolic, oxidative, and inflammatory links. The body of research is growing and supports a potential role for red raspberries in reducing the risk of metabolically based chronic diseases. PMID:26773014

Reversible near-infrared light directed reflection in a self-organized helical superstructure loaded with upconversion nanoparticles.

PubMed

Wang, Ling; Dong, Hao; Li, Yannian; Xue, Chenming; Sun, Ling-Dong; Yan, Chun-Hua; Li, Quan

2014-03-26

Adding external, dynamic control to self-organized superstructures with desired functionalities is an important leap necessary in leveraging the fascinating molecular systems for applications. Here, the new light-driven chiral molecular switch and upconversion nanoparticles, doped in a liquid crystal media, were able to self-organize into an optically tunable helical superstructure. The resulting nanoparticle impregnated helical superstructure was found to exhibit unprecedented reversible near-infrared (NIR) light-guided tunable behavior only by modulating the excitation power density of a continuous-wave NIR laser (980 nm). Upon irradiation by the NIR laser at the high power density, the reflection wavelength of the photonic superstructure red-shifted, whereas its reverse process occurred upon irradiation by the same laser but with the lower power density. Furthermore, reversible dynamic NIR-light-driven red, green, and blue reflections in a single thin film, achieved only by varying the power density of the NIR light, were for the first time demonstrated.

Long-term manure applications improve soil productivity and sustain high crop yield for acidic red soils

USDA-ARS?s Scientific Manuscript database

Intensive use of chemical nitrogen (N) fertilizers has resulted in severely reduced productivity of red soils (Ferralic Cambisol) due to accelerated acidification. Manure has been shown to be effective in improving soil productivity by preventing or reversing the acidification process, but little in...

Passband switchable microwave photonic multiband filter

PubMed Central

Ge, Jia; Fok, Mable P.

2015-01-01

A reconfigurable microwave photonic (MWP) multiband filter with selectable and switchable passbands is proposed and experimentally demonstrated, with a maximum of 12 simultaneous passbands evenly distributed from 0 to 10 GHz. The scheme is based on the generation of tunable optical comb lines using a two-stage Lyot loop filter, such that various filter tap spacings and spectral combinations are obtained for the configuration of the MWP filter. Through polarization state adjustment inside the Lyot loop filter, an optical frequency comb with 12 different comb spacings is achieved, which corresponds to a MWP filter with 12 selectable passbands. Center frequencies of the filter passbands are switchable, while the number of simultaneous passbands is tunable from 1 to 12. Furthermore, the MWP multiband filter can either work as an all-block, single-band or multiband filter with various passband combinations, which provide exceptional operation flexibility. All the passbands have over 30 dB sidelobe suppression and 3-dB bandwidth of 200 MHz, providing good filter selectivity. PMID:26521693

Passband switchable microwave photonic multiband filter.

PubMed

Ge, Jia; Fok, Mable P

2015-11-02

A reconfigurable microwave photonic (MWP) multiband filter with selectable and switchable passbands is proposed and experimentally demonstrated, with a maximum of 12 simultaneous passbands evenly distributed from 0 to 10 GHz. The scheme is based on the generation of tunable optical comb lines using a two-stage Lyot loop filter, such that various filter tap spacings and spectral combinations are obtained for the configuration of the MWP filter. Through polarization state adjustment inside the Lyot loop filter, an optical frequency comb with 12 different comb spacings is achieved, which corresponds to a MWP filter with 12 selectable passbands. Center frequencies of the filter passbands are switchable, while the number of simultaneous passbands is tunable from 1 to 12. Furthermore, the MWP multiband filter can either work as an all-block, single-band or multiband filter with various passband combinations, which provide exceptional operation flexibility. All the passbands have over 30 dB sidelobe suppression and 3-dB bandwidth of 200 MHz, providing good filter selectivity.

Switchable dual-wavelength SLM narrow linewidth fiber laser based on nonlinear amplifying loop mirror

NASA Astrophysics Data System (ADS)

Fu, Pan; Feng, Xiao-qiang; Lu, Baole; Qi, Xin-yuan; Chen, Haowei; Sun, Bo; Jiang, Man; Wang, Kaile; Bai, Jintao

2018-01-01

We demonstrate a stable switchable dual-wavelength single longitudinal mode (SLM) narrow linewidth ytterbium-doped fiber (YDF) laser using a nonlinear amplifying fiber loop mirror (NALM) at 1064 nm. The NALM of intensity-dependent transmission acts as a saturable absorber filter and an amplitude equalizer to suppress mode competition and the fiber Bragg grating (FBG) pair is used as one wavelength selection component. By properly adjusting the polarization controllers (PCs), the switchable dual-wavelength SLM fiber laser can be operated steadily at room temperature. The optical signal-to-noise ratio (OSNR) is better than 50 dB for both lasing wavelengths. Meanwhile, the linewidth of the fiber laser for each wavelength is approximate 17.07 kHz and 18.64 kHz with a 20 dB linewidth, which means the laser linewidth is approximate 853 Hz and 932 Hz FWHM. Correspondingly, the measured relative intensity noise (RIN) is less than -120 dB/Hz at frequencies over 5.0 MHz.

In situ alcoholysis of triacylglycerols by application of switchable-polarity solvents. A new derivatization procedure for the gas-chromatographic analysis of vegetable oils.

PubMed

Saliu, Francesco; Orlandi, Marco

2013-10-01

We describe a new use of switchable-polarity solvents for the simultaneous derivatization and extraction of triacylglycerols from vegetable oils before gas-chromatographic analysis. Different equimolecular mixtures of the commercially available amidine 1,8-diazabicyclo[5.4.0]undec-7-ene and n-alkyl alcohols were tested. Triolein was used as a model compound. Very good results were achieved by using butanol (recovery of butyl oleate was 89 ± 4%). The procedure was applied for the characterization of the fatty acid profile of different vegetable oils. No statistically significant differences from the results obtained with the application of two traditional methods were evidenced. Moreover, the use of switchable-polarity solvents showed many advantages: owing to the basicity of the amidines, no catalyst was required; the transterification reaction was conducted under mild conditions, one step and in situ; no particular matrix interferences were evidenced; the solvent was recovered.

A phytochrome/phototropin chimeric photoreceptor of fern functions as a blue/far-red light-dependent photoreceptor for phototropism in Arabidopsis.

PubMed

Kanegae, Takeshi; Kimura, Izumi

2015-08-01

In the fern Adiantum capillus-veneris, the phototropic response of the protonemal cells is induced by blue light and partially inhibited by subsequent irradiation with far-red light. This observation strongly suggests the existence of a phytochrome that mediates this blue/far-red reversible response; however, the phytochrome responsible for this response has not been identified. PHY3/NEO1, one of the three phytochrome genes identified in Adiantum, encodes a chimeric photoreceptor composed of both a phytochrome and a phototropin domain. It was demonstrated that phy3 mediates the red light-dependent phototropic response of Adiantum, and that phy3 potentially functions as a phototropin. These findings suggest that phy3 is the phytochrome that mediates the blue/far-red response in Adiantum protonemata. In the present study, we expressed Adiantum phy3 in a phot1 phot2 phototropin-deficient Arabidopsis line, and investigated the ability of phy3 to induce phototropic responses under various light conditions. Blue light irradiation clearly induced a phototropic response in the phy3-expressing transgenic seedlings, and this effect was fully inhibited by simultaneous irradiation with far-red light. In addition, experiments using amino acid-substituted phy3 indicated that FMN-cysteinyl adduct formation in the light, oxygen, voltage (LOV) domain was not necessary for the induction of blue light-dependent phototropism by phy3. We thus demonstrate that phy3 is the phytochrome that mediates the blue/far-red reversible phototropic response in Adiantum. Furthermore, our results imply that phy3 can function as a phototropin, but that it acts principally as a phytochrome that mediates both the red/far-red and blue/far-red light responses. © 2015 The Authors The Plant Journal © 2015 John Wiley & Sons Ltd.

All-optical materials design of chiral edge modes in transition-metal dichalcogenides

DOE PAGES

Claassen, Martin; Jia, Chunjing; Moritz, Brian; ...

2016-10-10

Monolayer transition-metal dichalcogenides are novel materials which at low energies constitute a condensed-matter realization of massive relativistic fermions in two dimensions. Here, we show that this picture breaks for optical pumping—instead, the added complexity of a realistic materials description leads to a new mechanism to optically induce topologically protected chiral edge modes, facilitating optically switchable conduction channels that are insensitive to disorder. In contrast to graphene and previously discussed toy models, the underlying mechanism relies on the intrinsic three-band nature of transition-metal dichalcogenide monolayers near the band edges. Photo-induced band inversions scale linearly in applied pump field and exhibit transitionsmore » from one to two chiral edge modes on sweeping from red to blue detuning. As a result, we develop an ab initio strategy to understand non-equilibrium Floquet–Bloch bands and topological transitions, and illustrate for WS 2 that control of chiral edge modes can be dictated solely from symmetry principles and is not qualitatively sensitive to microscopic materials details.« less

All-optical materials design of chiral edge modes in transition-metal dichalcogenides

PubMed Central

Claassen, Martin; Jia, Chunjing; Moritz, Brian; Devereaux, Thomas P.

2016-01-01

Monolayer transition-metal dichalcogenides are novel materials which at low energies constitute a condensed-matter realization of massive relativistic fermions in two dimensions. Here, we show that this picture breaks for optical pumping—instead, the added complexity of a realistic materials description leads to a new mechanism to optically induce topologically protected chiral edge modes, facilitating optically switchable conduction channels that are insensitive to disorder. In contrast to graphene and previously discussed toy models, the underlying mechanism relies on the intrinsic three-band nature of transition-metal dichalcogenide monolayers near the band edges. Photo-induced band inversions scale linearly in applied pump field and exhibit transitions from one to two chiral edge modes on sweeping from red to blue detuning. We develop an ab initio strategy to understand non-equilibrium Floquet–Bloch bands and topological transitions, and illustrate for WS2 that control of chiral edge modes can be dictated solely from symmetry principles and is not qualitatively sensitive to microscopic materials details. PMID:27721504

Ferroelectric Diodes with Charge Injection and Trapping

NASA Astrophysics Data System (ADS)

Fan, Zhen; Fan, Hua; Lu, Zengxing; Li, Peilian; Huang, Zhifeng; Tian, Guo; Yang, Lin; Yao, Junxiang; Chen, Chao; Chen, Deyang; Yan, Zhibo; Lu, Xubing; Gao, Xingsen; Liu, Jun-Ming

2017-01-01

Ferroelectric diodes with polarization-modulated Schottky barriers are promising for applications in resistive switching (RS) memories. However, they have not achieved satisfactory performance reliability as originally hoped. The physical origins underlying this issue have not been well studied, although they deserve much attention. Here, by means of scanning Kelvin probe microscopy we show that the electrical poling of ferroelectric diodes can cause significant charge injection and trapping besides polarization switching. We further show that the reproducibility and stability of switchable diode-type RS behavior are significantly affected by the interfacial traps. A theoretical model is then proposed to quantitatively describe the modifications of Schottky barriers by charge injection and trapping. This model is able to reproduce various types of hysteretic current-voltage characteristics as experimentally observed. It is further revealed that the charge injection and trapping can significantly modify the electroresistance ratio, RS polarity, and high- or low-resistance states initially defined by the polarization direction. Several approaches are suggested to suppress the effect of charge injection and trapping so as to realize high-performance polarization-reversal-induced RS. This study, therefore, reveals the microscopic mechanisms for the RS behavior comodulated by polarization reversal and charge trapping in ferroelectric diodes, and also provides useful suggestions for developing reliable ferroelectric RS memories.

In situ measurements of the optical absorption of dioxythiophene-based conjugated polymers

NASA Astrophysics Data System (ADS)

Hwang, J.; Schwendeman, I.; Ihas, B. C.; Clark, R. J.; Cornick, M.; Nikolou, M.; Argun, A.; Reynolds, J. R.; Tanner, D. B.

2011-05-01

Conjugated polymers can be reversibly doped by electrochemical means. This doping introduces new subband-gap optical absorption bands in the polymer while decreasing the band-gap absorption. To study this behavior, we have prepared an electrochemical cell allowing in situ measurements of the optical properties of the polymer. The cell consists of a thin polymer film deposited on gold-coated Mylar behind which is another polymer that serves as a counterelectrode. An infrared transparent window protects the upper polymer from ambient air. By adding a gel electrolyte and making electrical connections to the polymer-on-gold films, one may study electrochromism in a wide spectral range. As the cell voltage (the potential difference between the two electrodes) changes, the doping level of the conjugated polymer films is changed reversibly. Our experiments address electrochromism in poly(3,4-ethylenedioxythiophene) (PEDOT) and poly(3,4-dimethylpropylenedioxythiophene) (PProDOT-Me2). This closed electrochemical cell allows the study of the doping induced subband-gap features (polaronic and bipolaronic modes) in these easily oxidized and highly redox switchable polymers. We also study the changes in cell spectra as a function of polymer thickness and investigate strategies to obtain cleaner spectra, minimizing the contributions of water and gel electrolyte features.

Ultrafast water sensing and thermal imaging by a metal-organic framework with switchable luminescence

NASA Astrophysics Data System (ADS)

Chen, Ling; Ye, Jia-Wen; Wang, Hai-Ping; Pan, Mei; Yin, Shao-Yun; Wei, Zhang-Wen; Zhang, Lu-Yin; Wu, Kai; Fan, Ya-Nan; Su, Cheng-Yong

2017-06-01

A convenient, fast and selective water analysis method is highly desirable in industrial and detection processes. Here a robust microporous Zn-MOF (metal-organic framework, Zn(hpi2cf)(DMF)(H2O)) is assembled from a dual-emissive H2hpi2cf (5-(2-(5-fluoro-2-hydroxyphenyl)-4,5-bis(4-fluorophenyl)-1H-imidazol-1-yl)isophthalic acid) ligand that exhibits characteristic excited state intramolecular proton transfer (ESIPT). This Zn-MOF contains amphipathic micropores (<3 Å) and undergoes extremely facile single-crystal-to-single-crystal transformation driven by reversible removal/uptake of coordinating water molecules simply stimulated by dry gas blowing or gentle heating at 70 °C, manifesting an excellent example of dynamic reversible coordination behaviour. The interconversion between the hydrated and dehydrated phases can turn the ligand ESIPT process on or off, resulting in sensitive two-colour photoluminescence switching over cycles. Therefore, this Zn-MOF represents an excellent PL water-sensing material, showing a fast (on the order of seconds) and highly selective response to water on a molecular level. Furthermore, paper or in situ grown ZnO-based sensing films have been fabricated and applied in humidity sensing (RH<1%), detection of traces of water (<0.05% v/v) in various organic solvents, thermal imaging and as a thermometer.

Polydimethylsiloxane-Based Superhydrophobic Surfaces on Steel Substrate: Fabrication, Reversibly Extreme Wettability and Oil-Water Separation.

PubMed

Su, Xiaojing; Li, Hongqiang; Lai, Xuejun; Zhang, Lin; Liang, Tao; Feng, Yuchun; Zeng, Xingrong

2017-01-25

Functional surfaces for reversibly switchable wettability and oil-water separation have attracted much interest with pushing forward an immense influence on fundamental research and industrial application in recent years. This article proposed a facile method to fabricate superhydrophobic surfaces on steel substrates via electroless replacement deposition of copper sulfate (CuSO 4 ) and UV curing of vinyl-terminated polydimethylsiloxane (PDMS). PDMS-based superhydrophobic surfaces exhibited water contact angle (WCA) close to 160° and water sliding angle (WSA) lower than 5°, preserving outstanding chemical stability that maintained superhydrophobicity immersing in different aqueous solutions with pH values from 1 to 13 for 12 h. Interestingly, the superhydrophobic surface could dramatically switch to the superhydrophilic state under UV irradiation and then gradually recover to the highly hydrophobic state with WCA at 140° after dark storage. The underlying mechanism was also investigated by scanning electron microscopy, Fourier transform infrared spectroscopy, and X-ray photoelectron spectroscopy. Additionally, the PDMS-based steel mesh possessed high separation efficiency and excellent reusability in oil-water separation. Our studies provide a simple, fast, and economical fabrication method for wettability-transformable superhydrophobic surfaces and have the potential applications in microfluidics, the biomedical field, and oil spill cleanup.

Superstructures of chiral nematic microspheres as all-optical switchable distributors of light

PubMed Central

Aβhoff, Sarah J.; Sukas, Sertan; Yamaguchi, Tadatsugu; Hommersom, Catharina A.; Le Gac, Séverine; Katsonis, Nathalie

2015-01-01

Light technology is based on generating, detecting and controlling the wavelength, polarization and direction of light. Emerging applications range from electronics and telecommunication to health, defence and security. In particular, data transmission and communication technologies are currently asking for increasingly complex and fast devices, and therefore there is a growing interest in materials that can be used to transmit light and also to control the distribution of light in space and time. Here, we design chiral nematic microspheres whose shape enables them to reflect light of different wavelengths and handedness in all directions. Assembled in organized hexagonal superstructures, these microspheres of well-defined sizes communicate optically with high selectivity for the colour and chirality of light. Importantly, when the microspheres are doped with photo-responsive molecular switches, their chiroptical communication can be tuned, both gradually in wavelength and reversibly in polarization. Since the kinetics of the “on” and “off” switching can be adjusted by molecular engineering of the dopants and because the photonic cross-communication is selective with respect to the chirality of the incoming light, these photo-responsive microspheres show potential for chiroptical all-optical distributors and switches, in which wavelength, chirality and direction of the reflected light can be controlled independently and reversibly. PMID:26400584

pH-switchable electrochemical sensing platform based on chitosan-reduced graphene oxide/concanavalin a layer for assay of glucose and urea.

PubMed

Song, Yonghai; Liu, Hongyu; Tan, Hongliang; Xu, Fugang; Jia, Jianbo; Zhang, Lixue; Li, Zhuang; Wang, Li

2014-02-18

A facile and effective electrochemical sensing platform for the detection of glucose and urea in one sample without separation was developed using chitosan-reduced graphene oxide (CS-rGO)/concanavalin A (Con A) as a sensing layer. The CS-rGO/Con A with pH-dependent surface net charges exhibited pH-switchable response to negatively charged Fe(CN)6(3-). The principle for glucose and urea detection was essentially based on in situ pH-switchable enzyme-catalyzed reaction in which the oxidation of glucose catalyzed by glucose oxidase or the hydrolyzation of urea catalyzed by urease resulted in a pH change of electrolyte solution to give different electrochemical responses toward Fe(CN)6(3-). It was verified by cyclic voltammograms, differential pulse voltammograms, and electrochemical impedance spectroscopy. The resistance to charge transfer or amperometric current changed proportionally toward glucose concentration from 1.0 to 10.0 mM and urea concentration from 1.0 to 7.0 mM. On the basis of human serum experiments, the sensing platform was proved to be suitable for simultaneous assay of glucose and urea in a practical biosystem. This work not only gives a way to detect glucose and urea in one sample without separation but also provides a potential strategy for the detection of nonelectroactive species based on the enzyme-catalyzed reaction and pH-switchable biosensor.

Red, green and blue reflections enabled in an optically tunable self-organized 3D cubic nanostructured thin film.

PubMed

Lin, Tsung-Hsien; Li, Yannian; Wang, Chun-Ta; Jau, Hung-Chang; Chen, Chun-Wei; Li, Cheng-Chung; Bisoyi, Hari Krishna; Bunning, Timothy J; Li, Quan

2013-09-25

A new light-driven chiral molecular switch doped in a stable blue phase (BP) liquid crystal allows wide optical tunability of three-dimensional cubic nanostructures with a selective reflection wavelength that is reversibly tuned through the visible region. Moreover, unprecedented reversible light-directed red, green, and blue reflections of the self-organized three-dimensional cubic nanostructure in a single film are demonstrated for the first time. Additionally, unusual isothermal photo-stimulated less ordered BP II to more ordered BP I phase transition was observed in the system. © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Antiphase dual-color correlation in a reactant-product pair imparts ultrasensitivity in reaction-linked double-photoswitching fluorescence imaging.

PubMed

Wan, Wei; Zhu, Ming-Qiang; Tian, Zhiyuan; Li, Alexander D Q

2015-04-08

A pair of reversible photochemical reactions correlates their reactant and product specifically, and such a correlation uniquely distinguishes their correlated signal from others that are not linked by this reversible reaction. Here a nanoparticle-shielded fluorophore is photodriven to undergo structural dynamics, alternating between a green-fluorescence state and a red-fluorescence state. As time elapses, the fluorophore can be in either state but not both at the same time. Thus, the red fluorescence is maximized while the green fluorescence is minimized and vice versa. Such an antiphase dual-color (AD) corelationship between the red and green fluorescence maxima as well as between their minima can be exploited to greatly improve the signal-to-noise ratio, thus enhancing the ultimate detection limit. Potential benefits of this correlation include elimination of all interferences originating from single-color dyes and signal amplification of AD photoswitching molecules by orders of magnitude.

Red fluorescent protein with reversibly photoswitchable absorbance for photochromic FRET.

PubMed

Subach, Fedor V; Zhang, Lijuan; Gadella, Theodorus W J; Gurskaya, Nadya G; Lukyanov, Konstantin A; Verkhusha, Vladislav V

2010-07-30

We have developed the first red fluorescent protein, named rsTagRFP, which possesses reversibly photoswitchable absorbance spectra. Illumination with blue and yellow light switches rsTagRFP into a red fluorescent state (ON state) or nonfluorescent state (OFF state), respectively. The ON and OFF states exhibit absorbance maxima at 567 and 440 nm, respectively. Due to the photoswitchable absorbance, rsTagRFP can be used as an acceptor for a photochromic Förster resonance energy transfer (pcFRET). The photochromic acceptor facilitates determination of a protein-protein interaction by providing an internal control for FRET. Using pcFRET with EYFP as a donor, we observed an interaction between epidermal growth factor receptor and growth factor receptor-binding protein 2 in live cells by detecting the modulation of both the fluorescence intensity and lifetime of the EYFP donor upon the ON-OFF photoswitching of the rsTagRFP acceptor. 2010 Elsevier Ltd. All rights reserved.

Reconfigurable liquid metal circuits by Laplace pressure shaping

NASA Astrophysics Data System (ADS)

Cumby, Brad L.; Hayes, Gerard J.; Dickey, Michael D.; Justice, Ryan S.; Tabor, Christopher E.; Heikenfeld, Jason C.

2012-10-01

We report reconfigurable circuits formed by liquid metal shaping with <10 pounds per square inch (psi) Laplace and vacuum pressures. Laplace pressure drives liquid metals into microreplicated trenches, and upon release of vacuum, the liquid metal dewets into droplets that are compacted to 10-100× less area than when in the channel. Experimental validation includes measurements of actuation speeds exceeding 30 cm/s, simple erasable resistive networks, and switchable 4.5 GHz antennas. Such capability may be of value for next generation of simple electronic switches, tunable antennas, adaptive reflectors, and switchable metamaterials.

Thermally switchable dielectrics

DOEpatents

Dirk, Shawn M.; Johnson, Ross S.

2013-04-30

Precursor polymers to conjugated polymers, such as poly(phenylene vinylene), poly(poly(thiophene vinylene), poly(aniline vinylene), and poly(pyrrole vinylene), can be used as thermally switchable capacitor dielectrics that fail at a specific temperature due to the non-conjugated precursor polymer irreversibly switching from an insulator to the conjugated polymer, which serves as a bleed resistor. The precursor polymer is a good dielectric until it reaches a specific temperature determined by the stability of the leaving groups. Conjugation of the polymer backbone at high temperature effectively disables the capacitor, providing a `built-in` safety mechanism for electronic devices.

Switchable molecular magnets

PubMed Central

SATO, Osamu

2012-01-01

Various molecular magnetic compounds whose magnetic properties can be controlled by external stimuli have been developed, including electrochemically, photochemically, and chemically tunable bulk magnets as well as a phototunable antiferromagnetic phase of single chain magnet. In addition, we present tunable paramagnetic mononuclear complexes ranging from spin crossover complexes and valence tautomeric complexes to Co complexes in which orbital angular momentum can be switched. Furthermore, we recently developed several switchable clusters and one-dimensional coordination polymers. The switching of magnetic properties can be achieved by modulating metals, ligands, and molecules/ions in the second sphere of the complexes. PMID:22728438

Preparation of a Magnetically Switchable Bioelectrocatalytic System Employing Cross-Linked Enzyme Aggregates in Magnetic Mesocellular Carbon Foam

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lee, Jinwoo; Lee, Dohun; Oh, Eunkeu

2005-11-18

Nanostructured magnetic materials (NMMs)[1] have attracted much attention recently because of their broad biotechnological applications including support matrices for enzyme immobilization,[2] immunoassays,[3] drug delivery,[4] and biosensors.[ 5] Specifically, the easy separation and controlled placement of NMMs by means of an external magnetic field enables their application in the development of immobilized enzyme processes[2] and the construction of magnetically controllable bio-electrocatalytic systems.[5, 6] Herein, we demonstrate the use of immobilized enzymes in NMMs for magnetically switchable bio-electrocatalysis.

Blue light- and genetically-reversed gravitropic response in protonemata of the moss Ceratodon purpureus.

PubMed

Lamparter, T; Hughes, J; Hartmann, E

1998-09-01

In darkness, protonemal filaments of Ceratodon purpureus (Brid.) grow negatively gravitropically (upwards). Red light induces a positive phototropic response mediated by the photoreceptor phytochrome. A red light treatment also has an inhibitory effect on the gravitropic response, an effect also mediated by phytochrome. In this study the effects of blue light on phototropism and on gravitropism were analysed. Unilateral blue light resulted in only a weak phototropic response, but markedly randomised growth direction. Blue light given together with a gravitropic stimulus reversed the gravitropism, changing it from negative to positive (filaments grow downward). The effect of blue light was also analysed with the mutant ptr116, which is defective in the biosynthesis of the phytochrome chromophore, and in a newly isolated mutant wwr2, which is positively gravitropic in darkness. Blue light induced the same reversal of gravitropism in ptrll6 as in the wild type, indicating that phytochrome is not involved in this process. In wwr2 the direction of gravitropism was unaltered by the blue light treatment. Light also affects chlorophyll content and the size of plastids, potential statoliths for gravitropism. Red light induced an increase in plastid size and chlorophyll content in the wild type but not in ptr116. Blue light induced a similar change in wild type plastids. It seems as though light-induced alterations of gravitropism are not simply mediated by alterations in plastid properties, and that red light and blue light evoke fundamentally different responses.

Electrochemical methods for generation of a biological proton motive force

DOEpatents

Zeikus, Joseph Gregory [Okemos, MI; Shin, Hyoun S [Lansing, MI; Jain, Mahendra K [Lexington, KY

2008-12-02

Disclosed are methods using neutral red to mediate the interconversion of chemical and electrical energy. Electrically reduced neutral red has been found to promote cell growth and formation of reduced products by reversibly increasing the ratio of the reduced:oxidized forms of NAD(H) or NADP(H). Electrically reduced neutral red is able to serve as the sole source of reducing power for microbial cell growth. Neutral red is also able to promote conversion of chemical energy to electrical energy by facilitating the transfer of electrons from microbial reducing power to a fuel cell cathode.

Electrochemical methods for generation of a biological proton motive force and pyridine nucleotide cofactor regeneration

DOEpatents

Zeikus, Gregory J.; Shin, Hyoun S.; Jain, Mahendra K.

2002-01-01

Disclosed are methods using neutral red to mediate the interconversion of chemical and electrical energy. Electrically reduced neutral red has been found to promote cell growth and formation of reduced products by reversibly increasing the ratio of the reduced:oxidized forms of NAD(H) or NADP(H). Electrically reduced neutral red is able to serve as the sole source of reducing power for microbial, cell growth. Neutral red is also able to promote conversion of chemical energy to electrical energy by facilitating the transfer of electrons from microbial reducing power to a fuel cell cathode.

Electrochemical methods for generation of a biological proton motive force and pyridine nucleotide cofactor regeneration

DOEpatents

Zeikus, Joseph G.; Park, Doo

2001-01-01

Disclosed are methods using neutral red to mediate the interconversion of chemical and electrical energy. Electrically reduced neutral red has been found to promote cell growth and formation of reduced products by reversibly increasing the ratio of the reduced:oxidized forms of NAD(H) or NADP(H). Electrically reduced neutral red is able to serve as the sole source of reducing power for microbial cell growth. Neutral red is also able to promote conversion of chemical energy to electrical energy by facilitating the transfer of electrons from microbial reducing power to a fuel cell cathode.

Reversible switch between the nanoporous and the nonporous state of amphiphilic block copolymer films regulated by selective swelling.

PubMed

Yan, Nina; Wang, Yong

2015-09-21

Switchable nanoporous films, which can repeatedly alternate their porosities, are of great interest in a diversity of fields. Currently these intelligent materials are mostly based on polyelectrolytes and their porosities can change only in relatively narrow ranges, typically under wet conditions, severely limiting their applications. Here we develop a new system, which is capable of reversibly switching between a highly porous state and a nonporous state dozens of times regulated simply by exposure to selective solvents. In this system nanopores are created or reversibly eliminated in films of a block copolymer, polystyrene-block-poly(2-vinyl pyridine) (PS-b-P2VP), by exposing the films to P2VP-selective or PS-selective solvents, respectively. The mechanism of the switch is based on the selective swelling of the constituent blocks in corresponding solvents, which is a nondestructive and easily controllable process enabling the repeatable and ample switch between the open and the closed state. Systematic microscopic and ellipsometric characterization methods are performed to elucidate the pore-closing course induced by nonsolvents and the cycling between the pore-open and the pore-closed state up to 20 times. The affinity of the solvent for PS blocks is found to play a dominating role in determining the pore-closing process and the porosities of the pore-open films increase with the cycling numbers as a result of loose packing conditions of the polymer chains. We finally demonstrate the potential applications of these films as intelligent antireflection coatings and drug carriers.

Hierarchical self-assembly of switchable nucleolipid supramolecular gels based on environmentally-sensitive fluorescent nucleoside analogs

NASA Astrophysics Data System (ADS)

Nuthanakanti, Ashok; Srivatsan, Seergazhi G.

2016-02-01

Exquisite recognition and folding properties have rendered nucleic acids as useful supramolecular synthons for the construction of programmable architectures. Despite their proven applications in nanotechnology, scalability and fabrication of nucleic acid nanostructures still remain a challenge. Here, we describe a novel design strategy to construct new supramolecular nucleolipid synthons by using environmentally-sensitive fluorescent nucleoside analogs, based on 5-(benzofuran-2-yl)uracil and 5-(benzo[b]thiophen-2-yl)uracil cores, as the head group and fatty acids, attached to the ribose sugar, as the lipophilic group. These modified nucleoside-lipid hybrids formed organogels driven by hierarchical structures such as fibers, twisted ribbons, helical ribbons and nanotubes, which depended on the nature of fatty acid chain and nucleobase modification. NMR, single crystal X-ray and powder X-ray diffraction studies revealed the coordinated interplay of various non-covalent interactions invoked by modified nucleobase, sugar and fatty acid chains in setting up the pathway for the gelation process. Importantly, these nucleolipid gels retained or displayed aggregation-induced enhanced emission and their gelation behavior and photophysical properties could be reversibly switched by external stimuli such as temperature, ultrasound and chemicals. Furthermore, the switchable nature of nucleolipid gels to chemical stimuli enabled the selective two channel recognition of fluoride and Hg2+ ions through visual phase transition and fluorescence change. Fluorescent organogels exhibiting such a combination of useful features is rare, and hence, we expect that this innovative design of fluorescent nucleolipid supramolecular synthons could lead to the emergence of a new family of smart optical materials and probes.Exquisite recognition and folding properties have rendered nucleic acids as useful supramolecular synthons for the construction of programmable architectures. Despite their proven applications in nanotechnology, scalability and fabrication of nucleic acid nanostructures still remain a challenge. Here, we describe a novel design strategy to construct new supramolecular nucleolipid synthons by using environmentally-sensitive fluorescent nucleoside analogs, based on 5-(benzofuran-2-yl)uracil and 5-(benzo[b]thiophen-2-yl)uracil cores, as the head group and fatty acids, attached to the ribose sugar, as the lipophilic group. These modified nucleoside-lipid hybrids formed organogels driven by hierarchical structures such as fibers, twisted ribbons, helical ribbons and nanotubes, which depended on the nature of fatty acid chain and nucleobase modification. NMR, single crystal X-ray and powder X-ray diffraction studies revealed the coordinated interplay of various non-covalent interactions invoked by modified nucleobase, sugar and fatty acid chains in setting up the pathway for the gelation process. Importantly, these nucleolipid gels retained or displayed aggregation-induced enhanced emission and their gelation behavior and photophysical properties could be reversibly switched by external stimuli such as temperature, ultrasound and chemicals. Furthermore, the switchable nature of nucleolipid gels to chemical stimuli enabled the selective two channel recognition of fluoride and Hg2+ ions through visual phase transition and fluorescence change. Fluorescent organogels exhibiting such a combination of useful features is rare, and hence, we expect that this innovative design of fluorescent nucleolipid supramolecular synthons could lead to the emergence of a new family of smart optical materials and probes. Electronic supplementary information (ESI) available: Supplementary figures, tables, experimental procedures, crystallography data and NMR spectra. See DOI: 10.1039/c5nr07490h

Ultrasound extracted flavonoids from four varieties of Portuguese red grape skins determined by reverse-phase high-performance liquid chromatography with electrochemical detection.

PubMed

Novak, Ivana; Janeiro, Patricia; Seruga, Marijan; Oliveira-Brett, Ana Maria

2008-12-23

Several flavonoids present in red grape skins from four varieties of Portuguese grapes were determined by reverse-phase high-performance liquid chromatography (RP-HPLC) with electrochemical detection (ECD). Extraction of flavonoids from red grape skins was performed by ultrasonication, and hydrochloric acid in methanol was used as extraction solvent. The developed RP-HPLC method used combined isocratic and gradient elution with amperometric detection with a glassy carbon-working electrode. Good peak resolution was obtained following direct injection of a sample of red grape extract in a pH 2.20 mobile phase. Eleven different flavonoids: cyanidin-3-O-glucoside (kuromanin), delphinidin-3-O-glucoside (myrtillin), petunidin-3-O-glucoside, peonidin-3-O-glucoside, malvidin-3-O-glucoside (oenin), (+)-catechin, rutin, fisetin, myricetin, morin and quercetin, can be separated in a single run by direct injection of sample solution. The limit of detection obtained for these compounds by ECD was 20-90 pg/L, 1000 times lower when compared with photodiode array (PDA) limit of detection of 12-55 ng/L. RP-HPLC-ECD was characterized by an excellent sensitivity and selectivity, and appropriate for the simultaneous determination of these electroactive phenolic compounds present in red grape skins.

Light-regulated gravitropism in seedling roots of maize

NASA Technical Reports Server (NTRS)

Feldman, L. J.; Briggs, W. R.

1987-01-01

Red light-induced changes in the gravitropism of roots of Zea mays variety Merit is a very low fluence response with a threshold of 10(-9) moles per square meter and is not reversible by far red light. Blue light also affects root gravitropism but the sensitivity of roots to blue is 50 to 100 times less than to an equal fluence of red. In Z. mays Merit we conclude that phytochrome is the sole pigment associated with light-induced changes in root gravitropism.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Yee, J.P.

The following studies were conducted using the resistive pulse spectroscopy (RPS) technique: cumulative spectra and individual pulse forms for rigid latex polymer spheres; acquisition and analysis of RPS spectral data by means of special computer program; interaction of red blood cells with glutaraldehyde; membrane properties of erythrocytes undergoing abrupt osmotic hemolysis; reversible effects of the binding of chlorpromazine HCl at the red cell membrane surface; effects of high cholesterol diet on erythrocytes of guinea pigs; and multi-population analysis for a mixture of fetal and maternal red cells. (HLW)

Switchable silver mirrors with long memory effects† †Electronic supplementary information (ESI) available. See DOI: 10.1039/c4sc01912a Click here for additional data file. Click here for additional data file.

PubMed Central

Park, Chihyun; Seo, Seogjae; Shin, Haijin; Sarwade, Bhimrao D.; Na, Jongbeom

2015-01-01

An electrochemically stable and bistable switchable mirror was achieved for the first time by introducing (1) a thiol-modified indium tin oxide (ITO) electrode for the stabilization of the metallic film and (2) ionic liquids as an anion-blocking layer, to achieve a long memory effect. The growth of the metallic film was denser and faster at the thiol-modified ITO electrode than at a bare ITO electrode. The electrochemical stability of the metallic film on the thiol-modified ITO was enhanced, maintaining the metallic state without rupture. In the voltage-off state, the metal film maintained bistability for a long period (>2 h) when ionic liquids were introduced as electrolytes for the switchable mirror. The electrical double layer in the highly viscous ionic liquid electrolyte seemed to effectively form a barrier to the bromide ions, to protect the metal thin film from them when in the voltage-off state. PMID:28936310

Tunable and switchable dual-wavelength single polarization narrow linewidth SLM erbium-doped fiber laser based on a PM-CMFBG filter.

PubMed

Yin, Bin; Feng, Suchun; Liu, Zhibo; Bai, Yunlong; Jian, Shuisheng

2014-09-22

A tunable and switchable dual-wavelength single polarization narrow linewidth single-longitudinal-mode (SLM) erbium-doped fiber (EDF) ring laser based on polarization-maintaining chirped moiré fiber Bragg grating (PM-CMFBG) filter is proposed and demonstrated. For the first time as we know, the CMFBG inscribed on the PM fiber is applied for the wavelength-tunable and-switchable dual-wavelength laser. The PM-CMFBG filter with ultra-narrow transmission band (0.1 pm) and a uniform polarization-maintaining fiber Bragg grating (PM-FBG) are used to select the laser longitudinal mode. The stable single polarization SLM operation is guaranteed by the PM-CMFBG filter and polarization controller. A tuning range of about 0.25 nm with about 0.075 nm step is achieved by stretching the uniform PM-FBG. Meanwhile, the linewidth of the fiber laser for each wavelength is approximate 6.5 and 7.1 kHz with a 20 dB linewidth, which indicates the laser linewidth is approximate 325 Hz and 355 Hz FWHM.

Tunable and switchable dual-waveband ultrafast fiber laser with 100 GHz repetition-rate.

PubMed

Tan, Xiao-Mei; Chen, Hong-Jie; Cui, Hu; Lv, Yao-Kun; Zhao, Guan-Kai; Luo, Zhi-Chao; Luo, Ai-Ping; Xu, Wen-Cheng

2017-07-10

We demonstrate a tunable and switchable dual-waveband 100 GHz high-repetition-rate (HRR) ultrafast fiber laser based on dissipative four-wave-mixing (DFWM) mode-locked technique. Each waveband maintains HRR operation. The DFWM effect was realized by combining a Fabry-Perot (F-P) filter and a piece of highly nonlinear fiber (HNLF). The tunable and switchable operations were achieved by nonlinear polarization rotation (NPR) technique. Through appropriately controlling the filtering effect induced by NPR, the laser could operate at two kinds of tunable regimes. One is that the spacing between these two wavebands could be tuned while keeping their center at 1559 nm. The other is that the central position of the entire dual-waveband is tunable while with the same separation between these two wavebands of 13.2 nm. Moreover, the laser could switch between these two wavebands. Correspondingly, the center of the single-waveband has a tuning range of 15.2 nm. This versatile ultrafast fiber laser may find applications in fields of optical frequency combs, high speed optical communications, where HRR pulses are necessary.

Switchable multi-wavelength erbium-doped fiber ring laser based on a tapered in-line Mach–Zehnder interferometer

NASA Astrophysics Data System (ADS)

Zhou, Yuxin; Wang, Xin; Tang, Zijuan; Lou, Shuqin

2018-05-01

In this paper, a switchable multi-wavelength erbium-doped fiber ring laser based on a tapered in-line Mach–Zehnder interferometer is proposed. The in-line Mach–Zehnder interferometer is fabricated by splicing a large-core fiber between two segments of single mode fibers, in which the first splicing point is tapered and the second splicing point is connected directly. By carefully rotating the polarization controller, switchable single-, dual-, triple- and quad-wavelength lasing outputs can be obtained with a side mode suppression ratio higher than 50 dB. The maximal peak power difference of multi-wavelength lasing is 3.67 dB, demonstrating a good power equalization performance. Furthermore, the proposed laser is proven to be very stable at room temperature. The wavelength shifts and peak power fluctuations are less than 0.02 nm and 1.3 dB over half an hour. In addition, stable quintuple-wavelength lasing with a side mode suppression ratio higher than 50 dB can also be realized when the filter length is changed.

Frequency-Switchable Microfluidic CSRR-Loaded QMSIW Band-Pass Filter Using a Liquid Metal Alloy

PubMed Central

Eom, Seunghyun; Memon, Muhammad Usman; Lim, Sungjoon

2017-01-01

In this paper, we have proposed a frequency-switchable complementary split-ring resonator (CSRR)-loaded quarter-mode substrate-integrated-waveguide (QMSIW) band-pass filter. For frequency switching, a microfluidic channel and liquid metal are used. The liquid metal used is eutectic gallium-indium (EGaIn), consisting of 24.5% indium and 75.5% gallium. The microfluidic channels are built using the elastomer polydimethylsiloxane (PDMS) and three-dimensional-printed microfluidic channel frames. The CSRR-loaded QMSIW band-pass filter is designed to have two states. Before the injection of the liquid metal, the measured center frequency and fractional bandwidths are 2.205 GHz and 6.80%, respectively. After injection, the center frequency shifts from 2.205 GHz to 2.56 GHz. Although the coupling coefficient is practically unchanged, the fractional bandwidth changes from 6.8% to 9.38%, as the CSRR shape changes and the external quality factor decreases. After the removal of the liquid metal, the measured values are similar to the values recorded before the liquid metal was injected. The repeatability of the frequency-switchable mechanism is, therefore, verified. PMID:28350355

Reversible photoinduced spectral change in Eu2O3 at room temperature

NASA Astrophysics Data System (ADS)

Mochizuki, Shosuke; Nakanishi, Tauto; Suzuki, Yuya; Ishi, Kimihiro

2001-12-01

When Eu2O3 powder compact and film are irradiated with ultraviolet (UV) laser light in a vacuum, their photoluminescence (PL) spectra change from a red sharp-line structure to a white broad band, which can be clearly seen with the naked eye. After removing the UV laser light, the white PL continues for more than several months at room temperature under room light, in spite of any changes of atmosphere. By irradiating with the same UV laser light at room temperature under O2 gas atmosphere, the original red PL state reappears. Such a reversible phenomenon may well yield materials for white-light-emitting devices and erasable optical storage.

Experience reverses the red effect among Chinese stockbrokers.

PubMed

Zhang, Tengxiao; Han, Buxin

2014-01-01

Recent research has shown that the color red influences psychological functioning. Red is hypothesized to be linked to aggression and danger in evolution, and these links are enhanced by culture-specific uses of red. Thus, color meanings are thought to be grounded in biologically based proclivities and learned associations. However, to date, there has been no direct evidence for the influence of experience on the red effect. This study focused on whether experience could change the psychological effects of the color red. In the context of the Chinese stock market, contrary to the meaning generally associated with red as negative and green as positive, red represents a rise in stock price and green stands for a decrease. An experiment using a 2×2 between subjects factorial design demonstrated that red (compared with green) impaired Chinese college students' performance on an IQ test (in accordance with the red effect), but the opposite effect was found among stockbrokers. These results provide direct evidence of learned color meanings, in support of the general model of color effect.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Luo Hailu; Zhou Xinxing; Shu Weixing

We theorize an enhanced and switchable spin Hall effect (SHE) of light near the Brewster angle on reflection and demonstrate it experimentally. The obtained spin-dependent splitting reaches 3200 nm near the Brewster angle, which is 50 times larger than the previously reported values in refraction. We find that the amplifying factor in weak measurement is not a constant, which is significantly different from that in refraction. As an analogy of SHE in an electronic system, a switchable spin accumulation in SHE of light is detected. We were able to switch the direction of the spin accumulations by slightly adjusting themore » incident angle.« less

Smart window using a thermally and optically switchable liquid crystal cell

NASA Astrophysics Data System (ADS)

Oh, Seung-Won; Kim, Sang-Hyeok; Baek, Jong-Min; Yoon, Tae-Hoon

2018-02-01

Light shutter technologies that can control optical transparency have been studied extensively for developing curtain-free smart windows. We introduce thermally and optically switchable light shutters using LCs doped with push-pull azobenzene, which is known to speed up thermal relaxation. The liquid crystal light shutter can be switched between translucent and transparent states or transparent and opaque states by phase transition through changing temperature or photo-isomerization of doped azobenzene. The liquid crystal light shutter can be used for privacy windows with an initial translucent state or energy-saving windows with an initial transparent state.

Host-guest encapsulation of materials by assembled virus protein cages

NASA Astrophysics Data System (ADS)

Douglas, Trevor; Young, Mark

1998-05-01

Self-assembled cage structures of nanometre dimensions can be used as constrained environments for the preparation of nanostructured materials, and the encapsulation of guest molecules, with potential applications in drug delivery and catalysis. In synthetic systems the number of subunits contributing to cage structures is typically rather small,. But the protein coats of viruses (virions) commonly comprise hundreds of subunits that self-assemble into a cage for transporting viral nucleic acids. Many virions, moreover, can undergo reversible structural changes that open or close gated pores to allow switchable access to their interior. Here we show that such a virion - that of the cowpea chlorotic mottle virus - can be used as a host for the synthesis of materials. We report the mineralization of two polyoxometalate species (paratungstate and decavanadate) and the encapsulation of an anionic polymer inside this virion, controlled by pH-dependent gating of the virion's pores. The diversity in size and shape of such virus particles make this a versatile strategy for materials synthesis and molecular entrapment.

Optically triggering spatiotemporally confined GPCR activity in a cell and programming neurite initiation and extension

PubMed Central

Karunarathne, W. K. Ajith; Giri, Lopamudra; Kalyanaraman, Vani; Gautam, N.

2013-01-01

G-protein–coupled receptor (GPCR) activity gradients evoke important cell behavior but there is a dearth of methods to induce such asymmetric signaling in a cell. Here we achieved reversible, rapidly switchable patterns of spatiotemporally restricted GPCR activity in a single cell. We recruited properties of nonrhodopsin opsins—rapid deactivation, distinct spectral tuning, and resistance to bleaching—to activate native Gi, Gq, or Gs signaling in selected regions of a cell. Optical inputs were designed to spatiotemporally control levels of second messengers, IP3, phosphatidylinositol (3,4,5)-triphosphate, and cAMP in a cell. Spectrally selective imaging was accomplished to simultaneously monitor optically evoked molecular and cellular response dynamics. We show that localized optical activation of an opsin-based trigger can induce neurite initiation, phosphatidylinositol (3,4,5)-triphosphate increase, and actin remodeling. Serial optical inputs to neurite tips can refashion early neuron differentiation. Methods here can be widely applied to program GPCR-mediated cell behaviors. PMID:23479634

High-efficiency exfoliation of layered materials into 2D nanosheets in switchable CO2/Surfactant/H2O system

NASA Astrophysics Data System (ADS)

Wang, Nan; Xu, Qun; Xu, Shanshan; Qi, Yuhang; Chen, Meng; Li, Hongxiang; Han, Buxing

2015-11-01

Layered materials present attractive and important properties due to their two-dimensional (2D) structure, allowing potential applications including electronics, optoelectronics, and catalysis. However, fully exploiting the outstanding properties will require a method for their efficient exfoliation. Here we present that a series of layered materials can be successfully exfoliated into single- and few-layer nanosheets using the driving forces coming from the phase inversion, i.e., from micelles to reverse micelles in the emulsion microenvironment built by supercritical carbon dioxide (SC CO2). The effect of variable experimental parameters including CO2 pressure, ethanol/water ratio, and initial concentration of bulk materials on the exfoliation yield have been investigated. Moreover, we demonstrate that the exfoliated 2D nanosheets have their worthwhile applications, for example, graphene can be used to prepare conductive paper, MoS2 can be used as fluorescent label to perform cellular labelling, and BN can effectively reinforce polymers leading to the promising mechanical properties.

An allosteric photoredox catalyst inspired by photosynthetic machinery

DOE PAGES

Lifschitz, Alejo M.; Young, Ryan M.; Mendez-Arroyo, Jose; ...

2015-03-30

Biological photosynthetic machinery allosterically regulate light harvesting via conformational and electronic changes at the antenna protein complexes as a response to specific chemical inputs. Fundamental limitations in current approaches to regulating inorganic light-harvesting mimics prevent their use in catalysis. Here we show that a light-harvesting antenna/reaction centre mimic can be regulated by utilizing a coordination framework incorporating antenna hemilabile ligands and assembled via a high-yielding, modular approach. As in nature, allosteric regulation is afforded by coupling the conformational changes to the disruptions in the electrochemical landscape of the framework upon recognition of specific coordinating analytes. The hemilabile ligands enable switchingmore » using remarkably mild and redox-inactive inputs, allowing one to regulate the photoredox catalytic activity of the photosynthetic mimic reversibly and in situ. Furthermore, we demonstrate that bioinspired regulatory mechanisms can be applied to inorganic light-harvesting arrays displaying switchable catalytic properties and with potential uses in solar energy conversion and photonic devices.« less

Chiral modes and directional lasing at exceptional points

PubMed Central

Peng, Bo; Özdemir, Şahin Kaya; Liertzer, Matthias; Chen, Weijian; Kramer, Johannes; Yılmaz, Huzeyfe; Wiersig, Jan; Yang, Lan

2016-01-01

Controlling the emission and the flow of light in micro- and nanostructures is crucial for on-chip information processing. Here we show how to impose a strong chirality and a switchable direction of light propagation in an optical system by steering it to an exceptional point (EP)—a degeneracy universally occurring in all open physical systems when two eigenvalues and the corresponding eigenstates coalesce. In our experiments with a fiber-coupled whispering-gallery-mode (WGM) resonator, we dynamically control the chirality of resonator modes and the emission direction of a WGM microlaser in the vicinity of an EP: Away from the EPs, the resonator modes are nonchiral and laser emission is bidirectional. As the system approaches an EP, the modes become chiral and allow unidirectional emission such that by transiting from one EP to another one the direction of emission can be completely reversed. Our results exemplify a very counterintuitive feature of non-Hermitian physics that paves the way to chiral photonics on a chip. PMID:27274059

Coupled Molecular Switching Processes in Ordered Mono- and Multilayers of Stimulus-Responsive Rotaxanes on Gold Surfaces

PubMed Central

2015-01-01

Interfaces provide the structural basis for function as, for example, encountered in nature in the membrane-embedded photosystem or in technology in solar cells. Synthetic functional multilayers of molecules cooperating in a coupled manner can be fabricated on surfaces through layer-by-layer self-assembly. Ordered arrays of stimulus-responsive rotaxanes undergoing well-controlled axle shuttling are excellent candidates for coupled mechanical motion. Such stimulus-responsive surfaces may help integrate synthetic molecular machines in larger systems exhibiting even macroscopic effects or generating mechanical work from chemical energy through cooperative action. The present work demonstrates the successful deposition of ordered mono- and multilayers of chemically switchable rotaxanes on gold surfaces. Rotaxane mono- and multilayers are shown to reversibly switch in a coupled manner between two ordered states as revealed by linear dichroism effects in angle-resolved NEXAFS spectra. Such a concerted switching process is observed only when the surfaces are well packed, while less densely packed surfaces lacking lateral order do not exhibit such effects. PMID:25782057

Prediction of a native ferroelectric metal

PubMed Central

Filippetti, Alessio; Fiorentini, Vincenzo; Ricci, Francesco; Delugas, Pietro; Íñiguez, Jorge

2016-01-01

Over 50 years ago, Anderson and Blount discussed symmetry-allowed polar distortions in metals, spawning the idea that a material might be simultaneously metallic and ferroelectric. While many studies have ever since considered such or similar situations, actual ferroelectricity—that is, the existence of a switchable intrinsic electric polarization—has not yet been attained in a metal, and is in fact generally deemed incompatible with the screening by mobile conduction charges. Here we refute this common wisdom and show, by means of first-principles simulations, that native metallicity and ferroelectricity coexist in the layered perovskite Bi5Ti5O17. We show that, despite being a metal, Bi5Ti5O17 can sustain a sizable potential drop along the polar direction, as needed to reverse its polarization by an external bias. We also reveal striking behaviours, as the self-screening mechanism at work in thin Bi5Ti5O17 layers, emerging from the interplay between polar distortions and carriers in this compound. PMID:27040076

Intercorrelated In-Plane and Out-of-Plane Ferroelectricity in Ultrathin Two-Dimensional Layered Semiconductor In2Se3.

PubMed

Cui, Chaojie; Hu, Wei-Jin; Yan, Xingxu; Addiego, Christopher; Gao, Wenpei; Wang, Yao; Wang, Zhe; Li, Linze; Cheng, Yingchun; Li, Peng; Zhang, Xixiang; Alshareef, Husam N; Wu, Tom; Zhu, Wenguang; Pan, Xiaoqing; Li, Lain-Jong

2018-02-14

Enriching the functionality of ferroelectric materials with visible-light sensitivity and multiaxial switching capability would open up new opportunities for their applications in advanced information storage with diverse signal manipulation functions. We report experimental observations of robust intralayer ferroelectricity in two-dimensional (2D) van der Waals layered α-In 2 Se 3 ultrathin flakes at room temperature. Distinct from other 2D and conventional ferroelectrics, In 2 Se 3 exhibits intrinsically intercorrelated out-of-plane and in-plane polarization, where the reversal of the out-of-plane polarization by a vertical electric field also induces the rotation of the in-plane polarization. On the basis of the in-plane switchable diode effect and the narrow bandgap (∼1.3 eV) of ferroelectric In 2 Se 3 , a prototypical nonvolatile memory device, which can be manipulated both by electric field and visible light illumination, is demonstrated for advancing data storage technologies.

Strain-engineered diffusive atomic switching in two-dimensional crystals

PubMed Central

Kalikka, Janne; Zhou, Xilin; Dilcher, Eric; Wall, Simon; Li, Ju; Simpson, Robert E.

2016-01-01

Strain engineering is an emerging route for tuning the bandgap, carrier mobility, chemical reactivity and diffusivity of materials. Here we show how strain can be used to control atomic diffusion in van der Waals heterostructures of two-dimensional (2D) crystals. We use strain to increase the diffusivity of Ge and Te atoms that are confined to 5 Å thick 2D planes within an Sb2Te3–GeTe van der Waals superlattice. The number of quintuple Sb2Te3 2D crystal layers dictates the strain in the GeTe layers and consequently its diffusive atomic disordering. By identifying four critical rules for the superlattice configuration we lay the foundation for a generalizable approach to the design of switchable van der Waals heterostructures. As Sb2Te3–GeTe is a topological insulator, we envision these rules enabling methods to control spin and topological properties of materials in reversible and energy efficient ways. PMID:27329563

High-efficiency exfoliation of layered materials into 2D nanosheets in switchable CO2/Surfactant/H2O system.

PubMed

Wang, Nan; Xu, Qun; Xu, Shanshan; Qi, Yuhang; Chen, Meng; Li, Hongxiang; Han, Buxing

2015-11-16

Layered materials present attractive and important properties due to their two-dimensional (2D) structure, allowing potential applications including electronics, optoelectronics, and catalysis. However, fully exploiting the outstanding properties will require a method for their efficient exfoliation. Here we present that a series of layered materials can be successfully exfoliated into single- and few-layer nanosheets using the driving forces coming from the phase inversion, i.e., from micelles to reverse micelles in the emulsion microenvironment built by supercritical carbon dioxide (SC CO2). The effect of variable experimental parameters including CO2 pressure, ethanol/water ratio, and initial concentration of bulk materials on the exfoliation yield have been investigated. Moreover, we demonstrate that the exfoliated 2D nanosheets have their worthwhile applications, for example, graphene can be used to prepare conductive paper, MoS2 can be used as fluorescent label to perform cellular labelling, and BN can effectively reinforce polymers leading to the promising mechanical properties.

Giant and switchable surface activity of liquid metal via surface oxidation

PubMed Central

Khan, Mohammad Rashed; Eaker, Collin B.; Bowden, Edmond F.; Dickey, Michael D.

2014-01-01

We present a method to control the interfacial tension of a liquid alloy of gallium via electrochemical deposition (or removal) of the oxide layer on its surface. In sharp contrast with conventional surfactants, this method provides unprecedented lowering of surface tension (∼500 mJ/m2 to near zero) using very low voltage, and the change is completely reversible. This dramatic change in the interfacial tension enables a variety of electrohydrodynamic phenomena. The ability to manipulate the interfacial properties of the metal promises rich opportunities in shape-reconfigurable metallic components in electronic, electromagnetic, and microfluidic devices without the use of toxic mercury. This work suggests that the wetting properties of surface oxides—which are ubiquitous on most metals and semiconductors—are intrinsic “surfactants.” The inherent asymmetric nature of the surface coupled with the ability to actively manipulate its energetics is expected to have important applications in electrohydrodynamics, composites, and melt processing of oxide-forming materials. PMID:25228767

Near-infrared light–responsive dynamic wrinkle patterns

PubMed Central

Hou, Honghao; Yin, Jie

2018-01-01

Dynamic micro/nanopatterns provide an effective approach for on-demand tuning of surface properties to realize a smart surface. We report a simple yet versatile strategy for the fabrication of near-infrared (NIR) light–responsive dynamic wrinkles by using a carbon nanotube (CNT)–containing poly(dimethylsiloxane) (PDMS) elastomer as the substrate for the bilayer systems, with various functional polymers serving as the top stiff layers. The high photon-to-thermal energy conversion of CNT leads to the NIR-controlled thermal expansion of the elastic CNT-PDMS substrate, resulting in dynamic regulation of the applied strain (ε) of the bilayer system by the NIR on/off cycle to obtain a reversible wrinkle pattern. The switchable surface topological structures can transfer between the wrinkled state and the wrinkle-free state within tens of seconds via NIR irradiation. As a proof-of-concept application, this type of NIR-driven dynamic wrinkle pattern was used in smart displays, dynamic gratings, and light control electronics. PMID:29740615

A Janus cobalt-based catalytic material for electro-splitting of water

NASA Astrophysics Data System (ADS)

Cobo, Saioa; Heidkamp, Jonathan; Jacques, Pierre-André; Fize, Jennifer; Fourmond, Vincent; Guetaz, Laure; Jousselme, Bruno; Ivanova, Valentina; Dau, Holger; Palacin, Serge; Fontecave, Marc; Artero, Vincent

2012-09-01

The future of energy supply depends on innovative breakthroughs regarding the design of cheap, sustainable and efficient systems for the conversion and storage of renewable energy sources. The production of hydrogen through water splitting seems a promising and appealing solution. We found that a robust nanoparticulate electrocatalytic material, H2-CoCat, can be electrochemically prepared from cobalt salts in a phosphate buffer. This material consists of metallic cobalt coated with a cobalt-oxo/hydroxo-phosphate layer in contact with the electrolyte and mediates H2 evolution from neutral aqueous buffer at modest overpotentials. Remarkably, it can be converted on anodic equilibration into the previously described amorphous cobalt oxide film (O2-CoCat or CoPi) catalysing O2 evolution. The switch between the two catalytic forms is fully reversible and corresponds to a local interconversion between two morphologies and compositions at the surface of the electrode. After deposition, the noble-metal-free coating thus functions as a robust, bifunctional and switchable catalyst.

Switchable friction enabled by nanoscale self-assembly on graphene

DOE PAGES

Gallagher, Patrick; Lee, Menyoung; Amet, Francois; ...

2016-02-23

Graphene monolayers are known to display domains of anisotropic friction with twofold symmetry and anisotropy exceeding 200%. This anisotropy has been thought to originate from periodic nanoscale ripples in the graphene sheet, which enhance puckering around a sliding asperity to a degree determined by the sliding direction. Here we demonstrate that these frictional domains derive not from structural features in the graphene but from self-assembly of environmental adsorbates into a highly regular superlattice of stripes with period 4–6 nm. The stripes and resulting frictional domains appear on monolayer and multilayer graphene on a variety of substrates, as well as onmore » exfoliated flakes of hexagonal boron nitride. We show that the stripe-superlattices can be reproducibly and reversibly manipulated with submicrometre precision using a scanning probe microscope, allowing us to create arbitrary arrangements of frictional domains within a single flake. In conclusion, our results suggest a revised understanding of the anisotropic friction observed on graphene and bulk graphite in terms of adsorbates.« less

Focal switching of photochromic fluorescent proteins enables multiphoton microscopy with superior image contrast.

PubMed

Kao, Ya-Ting; Zhu, Xinxin; Xu, Fang; Min, Wei

2012-08-01

Probing biological structures and functions deep inside live organisms with light is highly desirable. Among the current optical imaging modalities, multiphoton fluorescence microscopy exhibits the best contrast for imaging scattering samples by employing a spatially confined nonlinear excitation. However, as the incident laser power drops exponentially with imaging depth into the sample due to the scattering loss, the out-of-focus background eventually overwhelms the in-focus signal, which defines a fundamental imaging-depth limit. Herein we significantly improve the image contrast for deep scattering samples by harnessing reversibly switchable fluorescent proteins (RSFPs) which can be cycled between bright and dark states upon light illumination. Two distinct techniques, multiphoton deactivation and imaging (MPDI) and multiphoton activation and imaging (MPAI), are demonstrated on tissue phantoms labeled with Dronpa protein. Such a focal switch approach can generate pseudo background-free images. Conceptually different from wave-based approaches that try to reduce light scattering in turbid samples, our work represents a molecule-based strategy that focused on imaging probes.

Focal switching of photochromic fluorescent proteins enables multiphoton microscopy with superior image contrast

PubMed Central

Kao, Ya-Ting; Zhu, Xinxin; Xu, Fang; Min, Wei

2012-01-01

Probing biological structures and functions deep inside live organisms with light is highly desirable. Among the current optical imaging modalities, multiphoton fluorescence microscopy exhibits the best contrast for imaging scattering samples by employing a spatially confined nonlinear excitation. However, as the incident laser power drops exponentially with imaging depth into the sample due to the scattering loss, the out-of-focus background eventually overwhelms the in-focus signal, which defines a fundamental imaging-depth limit. Herein we significantly improve the image contrast for deep scattering samples by harnessing reversibly switchable fluorescent proteins (RSFPs) which can be cycled between bright and dark states upon light illumination. Two distinct techniques, multiphoton deactivation and imaging (MPDI) and multiphoton activation and imaging (MPAI), are demonstrated on tissue phantoms labeled with Dronpa protein. Such a focal switch approach can generate pseudo background-free images. Conceptually different from wave-based approaches that try to reduce light scattering in turbid samples, our work represents a molecule-based strategy that focused on imaging probes. PMID:22876358

2D fluorescence spectroscopy for monitoring ion-exchange membrane based technologies - Reverse electrodialysis (RED).

PubMed

Pawlowski, Sylwin; Galinha, Claudia F; Crespo, João G; Velizarov, Svetlozar

2016-01-01

Reverse electrodialysis (RED) is one of the emerging, membrane-based technologies for harvesting salinity gradient energy. In RED process, fouling is an undesirable operation constraint since it leads to a decrease of the obtainable net power density due to increasing stack electric resistance and pressure drop. Therefore, early fouling detection is one of the main challenges for successful RED technology implementation. In the present study, two-dimensional (2D) fluorescence spectroscopy was used, for the first time, as a tool for fouling monitoring in RED. Fluorescence excitation-emission matrices (EEMs) of ion-exchange membrane surfaces and of natural aqueous streams were acquired during one month of a RED stack operation. Fouling evolvement on the ion-exchange membrane surfaces was successfully followed by 2D fluorescence spectroscopy and quantified using principal components analysis (PCA). Additionally, the efficiency of cleaning strategy was assessed by measuring the membrane fluorescence emission intensity before and after cleaning. The anion-exchange membrane (AEM) surface in contact with river water showed to be significantly affected due to fouling by humic compounds, which were found to cross through the membrane from the lower salinity (river water) to higher salinity (sea water) stream. The results obtained show that the combined approach of using 2D fluorescence spectroscopy and PCA has a high potential for studying fouling development and membrane cleaning efficiency in ion exchange membrane processes. Copyright © 2015 Elsevier Ltd. All rights reserved.

Electrical power from sea and river water by reverse electrodialysis: a first step from the laboratory to a real power plant.

PubMed

Veerman, Joost; Saakes, Michel; Metz, Sybrand J; Harmsen, G Jan

2010-12-01

Electricity can be produced directly with reverse electrodialysis (RED) from the reversible mixing of two solutions of different salinity, for example, sea and river water. The literature published so far on RED was based on experiments with relatively small stacks with cell dimensions less than 10 × 10 cm(2). For the implementation of the RED technique, it is necessary to know the challenges associated with a larger system. In the present study we show the performance of a scaled-up RED stack, equipped with 50 cells, each measuring 25 × 75 cm(2). A single cell consists of an AEM (anion exchange membrane) and a CEM (cation exchange membrane) and therefore, the total active membrane area in the stack is 18.75 m(2). This is the largest dimension of a reverse electrodialysis stack published so far. By comparing the performance of this stack with a small stack (10 × 10 cm(2), 50 cells) it was found that the key performance parameter to maximal power density is the hydrodynamic design of the stack. The power densities of the different stacks depend on the residence time of the fluids in the stack. For the large stack this was negatively affected by the increased hydrodynamic losses due to the longer flow path. It was also found that the large stack generated more power when the sea and river water were flowing in co-current operation. Co-current flow has other advantages, the local pressure differences between sea and river water compartments are low, hence preventing leakage around the internal manifolds and through pinholes in the membranes. Low pressure differences also enable the use of very thin membranes (with low electrical resistance) as well as very open spacers (with low hydrodynamic losses) in the future. Moreover, we showed that the use of segmented electrodes increase the power output by 11%.

Cluster analysis of historical and modern hard red spring wheat cultivars based on parentage and HPLC analysis of gluten forming proteins

USDA-ARS?s Scientific Manuscript database

In this study, 30 hard red spring (HRS) wheat cultivars released between 1910 and 2013 were analyzed to determine how they cluster in terms of parentage and protein data, analyzed by reverse-phase HPLC (RP-HPLC) of gliadins, and size-exclusion HPLC (SE-HPLC) of unreduced proteins. Dwarfing genes in...

Title: Studies on drug switchability showed heterogeneity in methodological approaches: a scoping review.

PubMed

Belleudi, Valeria; Trotta, Francesco; Vecchi, Simona; Amato, Laura; Addis, Antonio; Davoli, Marina

2018-05-16

Several drugs share the same therapeutic indication, including those undergoing patent expiration. Concerns on the interchangeability are frequent in clinical practice, challenging the evaluation of switchability through observational research. To conduct a scoping review of observational studies on drug switchability to identify methodological strategies adopted to deal with bias and confounding. We searched PubMed, EMBASE, and Web of Science (updated 1/31/2017) to identify studies evaluating switchability in terms of effectiveness/safety outcomes or compliance. Three reviewers independently screened studies extracting all characteristics. Strategies to address confounding, particularly, previous drug use and switching reasons were considered. All findings were summarized in descriptive analyses. Thirty-two studies, published in the last 10 years, met the inclusion criteria. Epilepsy, cardiovascular and rheumatology were the most frequently represented clinical areas. 75% of the studies reported data on effectiveness/safety outcomes. The most frequent study design was cohort (65.6%) followed by case-control (21.9%) and self-controlled (12.5%). Case-control and case-crossover studies showed homogeneous methodological strategies to deal with bias and confounding. Among cohort studies, the confounding associated with previous drug use was addressed introducing variables in multivariate model (47.3%) or selecting only adherent patients (14.3%). Around 30% of cohort studies did not report reasons for switching. In the remaining 70%, clinical parameters or previous occurrence of outcomes were measured to identify switching connected with lack of effectiveness or adverse events. This study represents a starting point for researchers and administrators who are approaching the investigation and assessment of issues related to interchangeability of drugs. Copyright © 2018. Published by Elsevier Inc.

Carbohydrate-actuated nanofluidic diode: switchable current rectification in a nanopipette

NASA Astrophysics Data System (ADS)

Vilozny, Boaz; Wollenberg, Alexander L.; Actis, Paolo; Hwang, Daniel; Singaram, Bakthan; Pourmand, Nader

2013-09-01

Nanofluidic structures share many properties with ligand-gated ion channels. However, actuating ion conductance in artificial systems is a challenge. We have designed a system that uses a carbohydrate-responsive polymer to modulate ion conductance in a quartz nanopipette. The cationic polymer, a poly(vinylpyridine) quaternized with benzylboronic acid groups, undergoes a transition from swollen to collapsed upon binding to monosaccharides. As a result, the current rectification in nanopipettes can be reversibly switched depending on the concentration of monosaccharides. Such molecular actuation of nanofluidic conductance may be used in novel sensors and drug delivery systems.Nanofluidic structures share many properties with ligand-gated ion channels. However, actuating ion conductance in artificial systems is a challenge. We have designed a system that uses a carbohydrate-responsive polymer to modulate ion conductance in a quartz nanopipette. The cationic polymer, a poly(vinylpyridine) quaternized with benzylboronic acid groups, undergoes a transition from swollen to collapsed upon binding to monosaccharides. As a result, the current rectification in nanopipettes can be reversibly switched depending on the concentration of monosaccharides. Such molecular actuation of nanofluidic conductance may be used in novel sensors and drug delivery systems. Electronic supplementary information (ESI) available: Experimental details on synthesis of polymer PVP-Bn, optical methods, 1H-NMR spectra, details on pH and ionic strength studies, and examples of current actuation with several different nanopores. See DOI: 10.1039/c3nr02105j

Ultrafast water sensing and thermal imaging by a metal-organic framework with switchable luminescence

PubMed Central

Chen, Ling; Ye, Jia-Wen; Wang, Hai-Ping; Pan, Mei; Yin, Shao-Yun; Wei, Zhang-Wen; Zhang, Lu-Yin; Wu, Kai; Fan, Ya-Nan; Su, Cheng-Yong

2017-01-01

A convenient, fast and selective water analysis method is highly desirable in industrial and detection processes. Here a robust microporous Zn-MOF (metal–organic framework, Zn(hpi2cf)(DMF)(H2O)) is assembled from a dual-emissive H2hpi2cf (5-(2-(5-fluoro-2-hydroxyphenyl)-4,5-bis(4-fluorophenyl)-1H-imidazol-1-yl)isophthalic acid) ligand that exhibits characteristic excited state intramolecular proton transfer (ESIPT). This Zn-MOF contains amphipathic micropores (<3 Å) and undergoes extremely facile single-crystal-to-single-crystal transformation driven by reversible removal/uptake of coordinating water molecules simply stimulated by dry gas blowing or gentle heating at 70 °C, manifesting an excellent example of dynamic reversible coordination behaviour. The interconversion between the hydrated and dehydrated phases can turn the ligand ESIPT process on or off, resulting in sensitive two-colour photoluminescence switching over cycles. Therefore, this Zn-MOF represents an excellent PL water-sensing material, showing a fast (on the order of seconds) and highly selective response to water on a molecular level. Furthermore, paper or in situ grown ZnO-based sensing films have been fabricated and applied in humidity sensing (RH<1%), detection of traces of water (<0.05% v/v) in various organic solvents, thermal imaging and as a thermometer. PMID:28665406

Geometry- and Length Scale-Dependent Deformation and Recovery on Micro- and Nanopatterned Shape Memory Polymer Surfaces

PubMed Central

Lee, Wei Li; Low, Hong Yee

2016-01-01

Micro- and nanoscale surface textures, when optimally designed, present a unique approach to improve surface functionalities. Coupling surface texture with shape memory polymers may generate reversibly tuneable surface properties. A shape memory polyetherurethane is used to prepare various surface textures including 2 μm- and 200 nm-gratings, 250 nm-pillars and 200 nm-holes. The mechanical deformation via stretching and recovery of the surface texture are investigated as a function of length scales and shapes. Results show the 200 nm-grating exhibiting more deformation than 2 μm-grating. Grating imparts anisotropic and surface area-to-volume effects, causing different degree of deformation between gratings and pillars under the same applied macroscopic strain. Full distribution of stress within the film causes the holes to deform more substantially than the pillars. In the recovery study, unlike a nearly complete recovery for the gratings after 10 transformation cycles, the high contribution of surface energy impedes the recovery of holes and pillars. The surface textures are shown to perform a switchable wetting function. This study provides insights into how geometric features of shape memory surface patterns can be designed to modulate the shape programming and recovery, and how the control of reversibly deformable surface textures can be applied to transfer microdroplets. PMID:27026290

Reconstruction of metabolic networks from high-throughput metabolite profiling data: in silico analysis of red blood cell metabolism.

PubMed

Nemenman, Ilya; Escola, G Sean; Hlavacek, William S; Unkefer, Pat J; Unkefer, Clifford J; Wall, Michael E

2007-12-01

We investigate the ability of algorithms developed for reverse engineering of transcriptional regulatory networks to reconstruct metabolic networks from high-throughput metabolite profiling data. For benchmarking purposes, we generate synthetic metabolic profiles based on a well-established model for red blood cell metabolism. A variety of data sets are generated, accounting for different properties of real metabolic networks, such as experimental noise, metabolite correlations, and temporal dynamics. These data sets are made available online. We use ARACNE, a mainstream algorithm for reverse engineering of transcriptional regulatory networks from gene expression data, to predict metabolic interactions from these data sets. We find that the performance of ARACNE on metabolic data is comparable to that on gene expression data.

Light-Regulated Gravitropism in Seedling Roots of Maize 1

PubMed Central

Feldman, Lewis J.; Briggs, Winslow R.

1987-01-01

Red light-induced changes in the gravitropism of roots of Zea mays variety Merit is a very low fluence response with a threshold of 10−9 moles per square meter and is not reversible by far red light. Blue light also affects root gravitropism but the sensitivity of roots to blue is 50 to 100 times less than to an equal fluence of red. In Z. mays Merit we conclude that phytochrome is the sole pigment associated with light-induced changes in root gravitropism. PMID:11539030

[Effect of red maca (Lepidium meyenii) on INF-γ levels in ovariectomized rats].

PubMed

Leiva-Revilla, Johanna; Guerra-Castañon, Félix; Olcese-Mori, Paola; Lozada, Iván; Rubio, Julio; Gonzales, Carla; Gonzales, Gustavo F

2014-01-01

Compare the effect of different doses of red maca on gamma interferon (IFN-γ) levels in ovariectomized rats (OVX). Adult female rats were randomly divided into the following six groups: Group 1: pseudo-ovariectomized rats (PO); Group 2: OVX rats; Group 3: OVX rats treated with 4 ug/kg estradiol; and Group 4, 5 and 6: OVX rats treated with red maca extracts with 2.15, 4.3 and 8.6 mg polyphenols/body weight kilogram, respectively. OVX rats showed low levels of IFN-γ compared to PO rats. Estradiol and red maca reversed the effect of ovariectomy on the IFN-γ levels. A positive dose-response effect of red maca on IFN-γ levels was shown (r = 0.57, p <0.05). Red maca administration increases levels of IFN-γ in ovariectomized rats.

A Red Sun Emerges: A Study of Nature in Japanese Culture.

ERIC Educational Resources Information Center

Trafton, Joyce

A collection of materials to help teachers and students learn how the relationship of the Japanese people to their natural surroundings is integral to an understanding of Japanese culture. The materials are organized into the following sections: (1) Introduction: Ura ni wa Ura ga iru (The reverse has its reverse side); Kami-sama no Kuni (Land of…

Minimal RED cell pairs markedly improve electrode kinetics and power production in microbial reverse electrodialysis cells.

PubMed

Cusick, Roland D; Hatzell, Marta; Zhang, Fang; Logan, Bruce E

2013-12-17

Power production from microbial reverse electrodialysis cell (MRC) electrodes is substantially improved compared to microbial fuel cells (MFCs) by using ammonium bicarbonate (AmB) solutions in multiple RED cell pair stacks and the cathode chamber. Reducing the number of RED membranes pairs while maintaining enhanced electrode performance could help to reduce capital costs. We show here that using only a single RED cell pair (CP), created by operating the cathode in concentrated AmB, dramatically increased power production normalized to cathode area from both acetate (Acetate: from 0.9 to 3.1 W/m(2)-cat) and wastewater (WW: 0.3 to 1.7 W/m(2)), by reducing solution and charge transfer resistances at the cathode. A second RED cell pair increased RED stack potential and reduced anode charge transfer resistance, further increasing power production (Acetate: 4.2 W/m(2); WW: 1.9 W/m(2)). By maintaining near optimal electrode power production with fewer membranes, power densities normalized to total membrane area for the 1-CP (Acetate: 3.1 W/m(2)-mem; WW: 1.7 W/m(2)) and 2-CP (Acetate: 1.3 W/m(2)-mem; WW: 0.6 W/m(2)) reactors were much higher than previous MRCs (0.3-0.5 W/m(2)-mem with acetate). While operating at peak power, the rate of wastewater COD removal, normalized to reactor volume, was 30-50 times higher in 1-CP and 2-CP MRCs than that in a single chamber MFC. These findings show that even a single cell pair AmB RED stack can significantly enhance electrical power production and wastewater treatment.

Solid-state structures and properties of scandium hydride; hydrogen storage and switchable mirrors application

NASA Astrophysics Data System (ADS)

Khodja, Khadidja; Bouhadda, Youcef; Seddik, Larbi; Benyelloul, Kamel

2016-05-01

First-principles calculation has been performed on the rare earth hydride ScH2 for hydrogen storage and switchable mirror applications, using the pseudo-potentials and plane waves based on the density-functional theory (DFT). The electronic and structural properties are studied within both local-density and generalized gradient approximations for exchange energy. The formation energy and the optical properties have been investigated and discussed. Our calculated results are generally in good agreement with theoretical and experimental data. Contribution to the topical issue "Materials for Energy Harvesting, Conversion and Storage (ICOME 2015) - Elected submissions", edited by Jean-Michel Nunzi, Rachid Bennacer and Mohammed El Ganaoui

Switchable dual-wavelength single-longitudinal-mode erbium fiber laser utilizing a dual-ring scheme with a saturable absorber

NASA Astrophysics Data System (ADS)

Yang, Zi-Qing; Huang, Tzu-Jung; Chang, Yao-Jen; Yeh, Chien-Hung; Chow, Chi-Wai; Chen, Jing-Heng; Chen, Kun-Huang

2018-06-01

In this work, we propose and demonstrate a switchable dual-wavelength erbium-doped fiber (EDF) ring laser with stable single-longitudinal-mode (SLM) output. Here, a dual-ring (DR) structure with an unpumped EDF of 2 m is designed to achieve SLM oscillation. Five fiber Bragg gratings (FBGs) are applied in the laser cavity serving as the reflective element to generate different dual-wavelength outputs. In the measurement, six sets of generated dual-wavelengths with various mode-spacing (Δλ) can be achieved via the five FBGs. Additionally, the stability performance of the proposed EDF DR laser is also demonstrated.

A power-efficient switchable CML driver at 10 Gbps

NASA Astrophysics Data System (ADS)

Peipei, Chen; Lei, Li; Huihua, Liu

2016-02-01

High static power limits the application of conventional current-mode logic(CML). This paper presents a power-efficient switchable CML driver, which achieves a significant current saving by 75% compared with conventional ones. Implemented in the 130 nm CMOS technology process, the proposed CML driver just occupies an area about 0.003 mm2 and provides a robust differential signal of 1600 mV for 10 Gbps optical line terminal (OLT) with a total current of 10 mA. The peak-to-peak jitter is about 4 ps (0.04TUI) and the offset voltage is 347.2 mV @ 1600 mVPP.

A Polarization Reconfigurable Slot Antenna with a Novel Switchable Feeding Network

NASA Astrophysics Data System (ADS)

Xie, Peng; Wang, Guang Ming

2017-12-01

A polarization reconfigurable slot antenna is proposed in this paper. The antenna consists of a microstrip line-to-slotline transition structure, two radiation slots and a switchable feeding network. The feeding network is a gradually changed ring slot with six switching diodes on it. By controlling the diodes states, the antenna can generate y-direction polarization, z-direction polarization, left-hand circular polarization and right-hand circular polarization. Detailed design considerations of the proposed antenna, simulated and measured results are presented and discussed. Measured results agree well with simulated. The results proved that the antenna can realize polarization reconfiguration effectively at 5 GHz.

Direct generation of vector vortex beams with switchable radial and azimuthal polarizations in a monolithic Nd:YAG microchip laser

NASA Astrophysics Data System (ADS)

He, Hong-Sen; Chen, Zhen; Dong, Jun

2017-05-01

A hollow focus lens (HFL) has been designed to effectively produce a focused annular beam for high-intensity pumping. By applying the central-dark pump beam, a monolithic Nd:YAG microchip laser without any extra optical elements is demonstrated to generate vector vortex beams with switchable radially polarized (RP) and azimuthally polarized (AP) states by easily controlling the pump power. The order and handedness of the output vortex beam remain stable during the switching of the RP and AP states. The monolithic Nd:YAG microchip laser provides a new laser source for applications such as material processing and optical manipulation.

Controlled higher-order transverse mode conversion from a fiber laser by polarization manipulation

NASA Astrophysics Data System (ADS)

Huang, Bin; Yi, Qian; Yang, Lingling; Zhao, Chujun; Wen, Shuangchun

2018-02-01

We report a vectorial fiber laser with controlled transverse mode conversion by intra-cavity polarization manipulation. By combining a q-plate and two quarter-wave plates (QWPs), we can generate a switchable polarization state output represented by the higher-order Poincaré sphere (l = +1, l = -1), and distinguish the fourfold degenerate LP11 mode. The four transverse vector modes can be obtained and switched in a flexible way, and the slope efficiency of the fiber laser can reach up to 39.4%. This compactness, high efficiency, and switchable operation potential will benefit a range of applications, such as materials processing, particle manipulation, etc.

On-demand Hydrogen Production from Organosilanes at Ambient Temperature Using Heterogeneous Gold Catalysts

NASA Astrophysics Data System (ADS)

Mitsudome, Takato; Urayama, Teppei; Kiyohiro, Taizo; Maeno, Zen; Mizugaki, Tomoo; Jitsukawa, Koichiro; Kaneda, Kiyotomi

2016-11-01

An environmentally friendly (“green”), H2-generation system was developed that involved hydrolytic oxidation of inexpensive organosilanes as hydrogen storage materials with newly developed heterogeneous gold nanoparticle catalysts. The gold catalyst functioned well at ambient temperature under aerobic conditions, providing efficient production of pure H2. The newly developed size-selective gold nanoparticle catalysts could be separated easily from the reaction mixture containing organosilanes, allowing an on/off-switchable H2-production by the introduction and removal of the catalyst. This is the first report of an on/off-switchable H2-production system employing hydrolytic oxidation of inexpensive organosilanes without requiring additional energy.

Mechanically switchable polymer fibers for sensing in biological conditions

NASA Astrophysics Data System (ADS)

McMillan, Sean; Rader, Chris; Jorfi, Mehdi; Pickrell, Gary; Foster, E. Johan

2017-02-01

The area of in vivo sensing using optical fibers commonly uses materials such as silica and polymethyl methacrylate, both of which possess much higher modulus than human tissue. The mechanical mismatch between materials and living tissue has been seen to cause higher levels of glial encapsulation, scarring, and inflammation, leading to failure of the implanted medical device. We present the use of a fiber made from polyvinyl alcohol (PVA) for use as an implantable sensor as it is an easy to work with functionalized polymer that undergoes a transition from rigid to soft when introduced to water. This ability to switch from stiff to soft reduces the severity of the immune response. The fabricated PVA fibers labeled with fluorescein for sensing applications showed excellent response to various stimuli while exhibiting mechanical switchability. For the dry fibers, a tensile storage modulus of 4700 MPa was measured, which fell sharply to 145 MPa upon wetting. The fibers showed excellent response to changing pH levels, producing values that were detectable in a range consistent with those seen in the literature and in proposed applications. The results show that these mechanically switchable fibers are a viable option for future sensing applications.

S- Cis Diene Conformation: A New Bathochromic Shift Strategy for Near-Infrared Fluorescence Switchable Dye and the Imaging Applications.

PubMed

Chen, Hsiang-Jung; Chew, Chee Ying; Chang, En-Hao; Tu, Yu-Wei; Wei, Li-Yu; Wu, Bo-Han; Chen, Chien-Hung; Yang, Ya-Ting; Huang, Su-Chin; Chen, Jen-Kun; Chen, I-Chia; Tan, Kui-Thong

2018-04-18

In this paper, we present a novel charge-free fluorescence-switchable near-infrared (IR) dye based on merocyanine for target specific imaging. In contrast to the typical bathochromic shift approach by extending π-conjugation, the bathochromic shift of our merocyanine dye to the near-IR region is due to an unusual S- cis diene conformer. This is the first example where a fluorescent dye adopts the stable S- cis conformation. In addition to the novel bathochromic shift mechanism, the dye exhibits fluorescence-switchable properties in response to polarity and viscosity. By incorporating a protein-specific ligand to the dye, the probes (for SNAP-tag and hCAII proteins) exhibited dramatic fluorescence increase (up to 300-fold) upon binding with its target protein. The large fluorescence enhancement, near-IR absorption/emission, and charge-free scaffold enabled no-wash and site-specific imaging of target proteins in living cells and in vivo with minimum background fluorescence. We believe that our unconventional approach for a near-IR dye with the S- cis diene conformation can lead to new strategies for the design of near-IR dyes.

On/off-switchable anti-neoplastic nanoarchitecture

NASA Astrophysics Data System (ADS)

Patra, Hirak K.; Imani, Roghayeh; Jangamreddy, Jaganmohan R.; Pazoki, Meysam; Iglič, Aleš; Turner, Anthony P. F.; Tiwari, Ashutosh

2015-09-01

Throughout the world, there are increasing demands for alternate approaches to advanced cancer therapeutics. Numerous potentially chemotherapeutic compounds are developed every year for clinical trial and some of them are considered as potential drug candidates. Nanotechnology-based approaches have accelerated the discovery process, but the key challenge still remains to develop therapeutically viable and physiologically safe materials suitable for cancer therapy. Here, we report a high turnover, on/off-switchable functionally popping reactive oxygen species (ROS) generator using a smart mesoporous titanium dioxide popcorn (TiO2 Pops) nanoarchitecture. The resulting TiO2 Pops, unlike TiO2 nanoparticles (TiO2 NPs), are exceptionally biocompatible with normal cells. Under identical conditions, TiO2 Pops show very high photocatalytic activity compared to TiO2 NPs. Upon on/off-switchable photo activation, the TiO2 Pops can trigger the generation of high-turnover flash ROS and can deliver their potential anticancer effect by enhancing the intracellular ROS level until it crosses the threshold to open the ‘death gate’, thus reducing the survival of cancer cells by at least six times in comparison with TiO2 NPs without affecting the normal cells.

An Ultrafast Switchable Terahertz Polarization Modulator Based on III-V Semiconductor Nanowires.

PubMed

Baig, Sarwat A; Boland, Jessica L; Damry, Djamshid A; Tan, H Hoe; Jagadish, Chennupati; Joyce, Hannah J; Johnston, Michael B

2017-04-12

Progress in the terahertz (THz) region of the electromagnetic spectrum is undergoing major advances, with advanced THz sources and detectors being developed at a rapid pace. Yet, ultrafast THz communication is still to be realized, owing to the lack of practical and effective THz modulators. Here, we present a novel ultrafast active THz polarization modulator based on GaAs semiconductor nanowires arranged in a wire-grid configuration. We utilize an optical pump-terahertz probe spectroscopy system and vary the polarization of the optical pump beam to demonstrate ultrafast THz modulation with a switching time of less than 5 ps and a modulation depth of -8 dB. We achieve an extinction of over 13% and a dynamic range of -9 dB, comparable to microsecond-switchable graphene- and metamaterial-based THz modulators, and surpassing the performance of optically switchable carbon nanotube THz polarizers. We show a broad bandwidth for THz modulation between 0.1 and 4 THz. Thus, this work presents the first THz modulator which combines not only a large modulation depth but also a broad bandwidth and picosecond time resolution for THz intensity and phase modulation, making it an ideal candidate for ultrafast THz communication.

Micropatterned photoalignment for wavefront controlled switchable optical devices

NASA Astrophysics Data System (ADS)

Glazar, Nikolaus

Photoalignment is a well-established technique for surface alignment of the liquid crystal director. Previously, chrome masks were necessary for patterned photoalignment but were difficult to use, costly, and inflexible. To extend the capabilities of photoalignment we built an automated maskless multi-domain photoalignment device based on a DMD (digital multimirror device) projection system. The device is capable of creating arbitrary photoalignment patterns with micron-sized features. Pancharatnam-Berry phase (PB-phase) is a geometric phase that arises from cyclic change of polarization state. By varying the azimuthal anchoring angle in a hybrid-aligned liquid crystal cell we can control the spatial variation of the PB-phase shift. Using our automated photoalignment device to align the liquid crystal arbitrary wave front manipulations are possible. The PB-phase shift effect is maximized when the cell is tuned to have a half-wave retardation and disappears at full-wave retardation, so the cell can be switched on and off by applying a voltage. Two wavefront controlled devices developed using this technique will be discussed: A switchable liquid crystal phase shift mask for creating sub-diffraction sized photolithographic features, and a transparent diffractive display that utilizes a switchable liquid crystal diffraction grating.

A switchable and stable single-longitudinal-mode, dual-wavelength erbium-doped fiber laser assisted by Rayleigh backscattering in tapered fiber

DOE Office of Scientific and Technical Information (OSTI.GOV)

Gu, Jian; Yang, Yanfu, E-mail: yangyanfu@hotmail.com; Zhang, Jianyu

We have proposed and demonstrated a novel switchable single-longitudinal-mode (SLM), dual-wavelength erbium-doped fiber laser (DWEDFL) assisted by Rayleigh backscattering (RBS) in a tapered fiber in a ring laser configuration. The RBS feedback in a tapered fiber is a key mechanism as linewidth narrowing for laser output. A compound laser cavity ensured that the EDFL operated in the SLM state and a saturable absorber (SA) is employed to form a gain grating for both filtering and improving wavelength stability. The fiber laser can output dual wavelengths simultaneously or operate at single wavelength in a switchable manner. Experiment results show that withmore » the proper SA, the peak power drift was improved from 1–2 dB to 0.31 dB and the optical signal to noise ratio was higher than 60 dB. Under the assistance of RBS feedback, the laser linewidths are compressed by around three times and the Lorentzian 3 dB linewidths of 445 Hz and 425 Hz are obtained at 1550 nm and 1554 nm, respectively.« less

On/off-switchable anti-neoplastic nanoarchitecture

PubMed Central

Patra, Hirak K.; Imani, Roghayeh; Jangamreddy, Jaganmohan R.; Pazoki, Meysam; Iglič, Aleš; Turner, Anthony P. F.; Tiwari, Ashutosh

2015-01-01

Throughout the world, there are increasing demands for alternate approaches to advanced cancer therapeutics. Numerous potentially chemotherapeutic compounds are developed every year for clinical trial and some of them are considered as potential drug candidates. Nanotechnology-based approaches have accelerated the discovery process, but the key challenge still remains to develop therapeutically viable and physiologically safe materials suitable for cancer therapy. Here, we report a high turnover, on/off-switchable functionally popping reactive oxygen species (ROS) generator using a smart mesoporous titanium dioxide popcorn (TiO2 Pops) nanoarchitecture. The resulting TiO2 Pops, unlike TiO2 nanoparticles (TiO2 NPs), are exceptionally biocompatible with normal cells. Under identical conditions, TiO2 Pops show very high photocatalytic activity compared to TiO2 NPs. Upon on/off-switchable photo activation, the TiO2 Pops can trigger the generation of high-turnover flash ROS and can deliver their potential anticancer effect by enhancing the intracellular ROS level until it crosses the threshold to open the ‘death gate’, thus reducing the survival of cancer cells by at least six times in comparison with TiO2 NPs without affecting the normal cells. PMID:26415561

Dipole pinning effect on photovoltaic characteristics of ferroelectric BiFeO3 films

NASA Astrophysics Data System (ADS)

Biswas, P. P.; Thirmal, Ch.; Pal, S.; Murugavel, P.

2018-01-01

Ferroelectric bismuth ferrite is an attractive candidate for switchable devices. The effect of dipole pinning due to the oxygen vacancy layer on the switching behavior of the BiFeO3 thin film fabricated by the chemical solution deposition method was studied after annealing under air, O2, and N2 environment. The air annealed film showed well defined and dense grains leading to a lower leakage current and superior electrical properties compared to the other two films. The photovoltage and transient photocurrent measured under positive and negative poling elucidated the switching nature of the films. Though the air and O2 annealed films showed a switchable photovoltaic response, the response was severely affected by oxygen vacancies in the N2 annealed film. In addition, the open circuit voltage was found to be mostly dependent on the polarization of BiFeO3 rather than the Schottky barriers at the interface. This work provides an important insight into the effect of dipole pinning caused by oxygen vacancies on the switchable photovoltaic effect of BiFeO3 thin films along with the importance of stoichiometric, defect free, and phase pure samples to facilitate meaningful practical applications.

Experience Reverses the Red Effect among Chinese Stockbrokers

PubMed Central

Zhang, Tengxiao; Han, Buxin

2014-01-01

Recent research has shown that the color red influences psychological functioning. Red is hypothesized to be linked to aggression and danger in evolution, and these links are enhanced by culture-specific uses of red. Thus, color meanings are thought to be grounded in biologically based proclivities and learned associations. However, to date, there has been no direct evidence for the influence of experience on the red effect. This study focused on whether experience could change the psychological effects of the color red. In the context of the Chinese stock market, contrary to the meaning generally associated with red as negative and green as positive, red represents a rise in stock price and green stands for a decrease. An experiment using a 2×2 between subjects factorial design demonstrated that red (compared with green) impaired Chinese college students’ performance on an IQ test (in accordance with the red effect), but the opposite effect was found among stockbrokers. These results provide direct evidence of learned color meanings, in support of the general model of color effect. PMID:24586587

All-optical spin switching: A new frontier in femtomagnetism — A short review and a simple theory

NASA Astrophysics Data System (ADS)

Zhang, G. P.; Latta, T.; Babyak, Z.; Bai, Y. H.; George, Thomas F.

2016-08-01

Using an ultrafast laser pulse to manipulate the spin degree of freedom has broad technological appeal. It allows one to control the spin dynamics on a femtosecond time scale. The discipline, commonly called femtomagnetism, started with the pioneering experiment by Beaurepaire and coworkers in 1996, who showed subpicosecond demagnetization occurs in magnetic Ni thin films. This finding has motivated extensive research worldwide. All-optical helicity-dependent spin switching (AO-HDS) represents a new frontier in femtomagnetism, where a single ultrafast laser pulse can permanently switch spin without any assistance from a magnetic field. This review summarizes some of the crucial aspects of this new discipline: key experimental findings, leading mechanisms, controversial issues, and possible future directions. The emphasis is on our latest investigation. We first develop the all-optical spin switching (AOS) rule that determines how the switchability depends on the light helicity. This rule allows one to understand microscopically how the spin is reversed and why the circularly polarized light appears more powerful than the linearly polarized light. Then we invoke our latest spin-orbit coupled harmonic oscillator model to simulate single spin reversal. We consider both continuous wave (cw) excitation and pulsed laser excitation. The results are in a good agreement with the experimental result (a MatLab code is available upon request from the author). We then extend the code to include the exchange interaction among different spin sites. We show where the “inverse-Faraday field” comes from and how the laser affects the spin reversal nonlinearly. Our hope is that this review will motivate new experimental and theoretical investigations and discussions.

Study of light signal receptor of Stephanopyxis palmeriana during sexual reproduction

NASA Astrophysics Data System (ADS)

Hu, Ren; Lin, Junmin; Lin, Qiuqi; Han, Boping

2005-09-01

We collected centric diatom Stephanopyxis palmeriana samples in coastal waters of Xiamen for characteristic red light/far red light (R/FR) phytochrome reactions to identify its photoreceptor in the course of sexual reproduction. The result showed that pre-illumination of 2 3h red light before darkness could induce sexualization of S. palmeriana, while the follow-up illumination of far red light could reverse the effect of red light, which is a featured reaction of phytochrome. The Southern Dot Blot was carried out to identify the type of phytochrome that induces the sexualization. The result also showed high homogeneity of DNA fragment of S. palmeriana with phyB, but phyA. This means the photoreceptor in the process of sexual reproduction of S. palmeriana is phytochrome B (phyB).

Solid-phase extraction and high-performance liquid chromatographic separation of pigments of red wines.

PubMed

Csiktusnádi Kiss, G A; Forgács, E; Cserháti, T; Candeias, M; Vilas-Boas, L; Bronze, R; Spranger, I

2000-08-11

The adsorption and desorption capacities of 11 different solid-phase extraction sorbents were tested for the preconcenration of pigments of various Hungarian red wines. The concentrates were evaluated by multiwavelengh spectrophotometry combined with a spectral mapping technique (SPM) and by reversed-phase high-performance liquid chromatography. The highest (10-fold) concentration of pigments was achieved on octadecylsilica sorbent. It can be used five times without losing adsorption and desorption characteristics. SPM indicated that multiwavelength spectrophotometry can be employed for the differentiation of red wines. Comparison of the chromatograms of pigments with and without preconcentration showed that preconcentration makes possible the separation and detection of pigments present in low concentration in red wines.

Light Requirement for Shoot Regeneration in Horseradish Hairy Roots 1

PubMed Central

Saitou, Tsutomu; Kamada, Hiroshi; Harada, Hiroshi

1992-01-01

Hairy roots of horseradish (Armoracia rusticana) were induced by inoculation with Agrobacterium rhizogenes harboring Ri plasmid and cultured on phytohormone-free Murashige and Skoog medium after eliminating the bacteria. Hairy roots grew vigorously and sometimes formed yellowish calli under dark conditions. On the other hand, growth of hairy roots stopped after several weeks of culture with light, then shoots were regenerated. Frequency of shoot formation from hairy roots increased as the culture period in light lengthened and the light intensity increased. The shoot regeneration was induced by treatment with white or red light, but not with far-red light. Shoot regeneration by red light was inhibited by following treatment with far-red light. Red and far-red light reversibly affected shoot regeneration. Excised roots of nontransformed plants grew quite slowly on phytohormone-free Murashige and Skoog medium and occasionally formed shoots under white light conditions. PMID:16669041

Light requirement for shoot regeneration in horseradish hairy roots.

PubMed

Saitou, T; Kamada, H; Harada, H

1992-08-01

Hairy roots of horseradish (Armoracia rusticana) were induced by inoculation with Agrobacterium rhizogenes harboring Ri plasmid and cultured on phytohormone-free Murashige and Skoog medium after eliminating the bacteria. Hairy roots grew vigorously and sometimes formed yellowish calli under dark conditions. On the other hand, growth of hairy roots stopped after several weeks of culture with light, then shoots were regenerated. Frequency of shoot formation from hairy roots increased as the culture period in light lengthened and the light intensity increased. The shoot regeneration was induced by treatment with white or red light, but not with far-red light. Shoot regeneration by red light was inhibited by following treatment with far-red light. Red and far-red light reversibly affected shoot regeneration. Excised roots of nontransformed plants grew quite slowly on phytohormone-free Murashige and Skoog medium and occasionally formed shoots under white light conditions.

Effect of Light on Anthocyanin Levels in Submerged, Harvested Cranberry Fruit

PubMed Central

Singh, Bal Ram

2004-01-01

Anthocyanins are a group of plant antioxidants known for their therapeutic use. The effects of natural light, red light, and far-red light on individual as well as total anthocyanin content in cranberry fruit (Vaccinium macrocarpon Ait) were examined in an experimental setting designed to mimic water-harvesting conditions. The reversed-phase high-performance liquid chromatography (HPLC) method was used to separate and analyze the anthocyanins. In contrast to the case of the control sample that was kept in the dark, natural light increased the total anthocyanin level by 75.3% and 87.2% after 24 and 48 hours of water immersion, respectively. Red light and far-red light increased the total anthocyanin level by 41.5% and 34.7%, respectively. The amount of each individual anthocyanin increased differently under natural light, red light, and far-red light, suggesting that expressions of enzymes that catalyze the anthocyanin biosynthesis are regulated differently by environments. PMID:15577187

Hemoglobin Function in Stored Blood.

DTIC Science & Technology

1977-12-31

reverse aide if neceseary and Identify by block number) Blood preservation, Red Cell Function, 2,3- Diphosphoglycerate , Adenine, Inosine, Methylene Blue...2,3-DPG, pH, and glucose levels of whole blood and packed cells studied in CPD-adenine with the following variables: pH, glucose concentrations...aimed directly at maintaining red cell 2,3-DPG levels during blood storage in order for transfused blood to deliver oxygen to the tissues immediately

Divalent Cation Removal by Donnan Dialysis for Improved Reverse Electrodialysis.

PubMed

Rijnaarts, Timon; Shenkute, Nathnael T; Wood, Jeffery A; de Vos, Wiebe M; Nijmeijer, Kitty

2018-05-07

Divalent cations in feedwater can cause significant decreases in efficiencies for membrane processes, such as reverse electrodialysis (RED). In RED, power is harvested from the mixing of river and seawater, and the obtainable voltage is reduced and the resistance is increased if divalent cations are present. The power density of the RED process can be improved by removing divalent cations from the fresh water. Here, we study divalent cation removal from fresh water using seawater as draw solution in a Donnan dialysis (DD) process. In this way, a membrane system with neither chemicals nor electrodes but only natural salinity gradients can be used to exchange divalent cations. For DD, the permselectivity of the cation exchange membrane is found to be crucial as it determines the ability to block salt leakage (also referred to as co-ion transport). Operating DD using a membrane stack achieved a 76% reduction in the divalent cation content in natural fresh water with residence times of just a few seconds. DD pretreated fresh water was then used in a RED process, which showed improved gross and net power densities of 9.0 and 6.3%, respectively. This improvement is caused by a lower fresh water resistance (at similar open circuit voltages), due to exchange of divalent for monovalent cations.

Global color variations on the Martian surface

USGS Publications Warehouse

Soderblom, L.A.; Edwards, K.; Eliason, E.M.; Sanchez, E.M.; Charette, M.P.

1978-01-01

Surface materials exposed throughout the equatorial region of Mars have been classified and mapped on the basis of spectral reflectance properties determined by the Viking II Orbiter vidicon cameras. Frames acquired at each of three wavelengths (0.45 ?? 0.03 ??m, 0.53 ?? 0.05 ??m, and 0.59 ?? 0.05 ??m) during the approach of Viking Orbiter II in Martian summer (Ls = 105??) were mosaicked by computer. The mosaics cover latitudes 30??N to 63??S for 360?? of longitude and have resolutions between 10 and 20 km per line pair. Image processing included Mercator transformation and removal of an average Martian photometric function to produce albedo maps at three wavelengths. The classical dark region between the equator and ???30??S in the Martian highlands is composed of two units: (i) and ancient unit consisting of topographic highs (ridges, crater rims, and rugged plateaus riddled with small dendritic channels) which is among the reddest on the planet (0.59/0.45 ??m {reversed tilde equals} 3); and (ii) intermediate age, smooth, intercrater volcanic plains displaying numerous mare ridges which are among the least red on Mars (0.59/0.45 ??m {reversed tilde equals} 2). The relatively young shield volcanoes are, like the oldest unit, dark and very red. Two probable eolian deposits are recognized in the intermediate and high albedo regions. The stratigraphically lower unit is intermediate in both color (0.59/ 0.45 ??m {reversed tilde equals} 2.5) and albedo. The upper unit has the highest albedo, is very red (0.59/0.45 ??m {reversed tilde equals} 3), and is apparently the major constituent of the annual dust storms as its areal extent changes from year to year. The south polar ice cap and condensate clouds dominate the southernmost part of the mosaics. ?? 1978.

Hmb(off/on) as a switchable thiol protecting group for native chemical ligation.

PubMed

Qi, Yun-Kun; Tang, Shan; Huang, Yi-Chao; Pan, Man; Zheng, Ji-Shen; Liu, Lei

2016-05-04

A new thiol protecting group Hmb(off/on) is described, which has a switchable activity that may be useful in the chemical synthesis of proteins. When placed on the side chain of Cys, Cys(Hmb(off)) is stable to trifluoroacetic acid (TFA) in the process of solid-phase peptide synthesis. When Cys(Hmb(off)) is treated with neutral aqueous buffers, it is cleanly converted to acid-labile Cys(Hmb(on)), which can later be fully deprotected by TFA to generate free Cys. The utility of Cys(Hmb(off/on)) is demonstrated by the chemical synthesis of an erythropoietin segment, EPO[Cys(98)-Arg(166)]-OH through native chemical ligation.

Self-alignment of plasmonic gold nanorods in reconfigurable anisotropic fluids for tunable bulk metamaterial applications.

PubMed

Liu, Qingkun; Cui, Yanxia; Gardner, Dennis; Li, Xin; He, Sailing; Smalyukh, Ivan I

2010-04-14

We demonstrate the bulk self-alignment of dispersed gold nanorods imposed by the intrinsic cylindrical micelle self-assembly in nematic and hexagonal liquid crystalline phases of anisotropic fluids. External magnetic field and shearing allow for alignment and realignment of the liquid crystal matrix with the ensuing long-range orientational order of well-dispersed plasmonic nanorods. This results in a switchable polarization-sensitive plasmon resonance exhibiting stark differences from that of the same nanorods in isotropic fluids. The device-scale bulk nanoparticle alignment may enable optical metamaterial mass production and control of properties arising from combining the switchable nanoscale structure of anisotropic fluids with the surface plasmon resonance properties of the plasmonic nanorods.

Switchable multi-wavelength fiber ring laser based on a compact in-fiber Mach-Zehnder interferometer with photonic crystal fiber

NASA Astrophysics Data System (ADS)

Chen, W. G.; Lou, S. Q.; Feng, S. C.; Wang, L. W.; Li, H. L.; Guo, T. Y.; Jian, S. S.

2009-11-01

Switchable multi-wavelength fiber ring laser with an in-fiber Mach-Zehnder interferometer incorporated into the ring cavity serving as wavelength-selective filter at room temperature is demonstrated. The filter is formed by splicing a section of few-mode photonic crystal fiber (PCF) and two segments of single mode fiber (SMF) with the air-holes on the both sides of PCF intentionally collapsed in the vicinity of the splices. By adjusting the states of the polarization controller (PC) appropriately, the laser can be switched among the stable single-, dual- and triple-wavelength lasing operations by exploiting polarization hole burning (PHB) effect.

Switchable dual-wavelength erbium-doped fiber laser based on the photonic crystal fiber loop mirror and chirped fiber Bragg grating

NASA Astrophysics Data System (ADS)

Chen, Wei-Guo; Lou, Shu-Qin; Wang, Li-Wen; Li, Hong-Lei; Guo, Tieying; Jian, Shui-Sheng

2010-03-01

The switchable dual-wavelength erbium-doped fiber laser (EDFL) with a two-mode photonic crystal fiber (PCF) loop mirror and a chirped fiber Bragg grating (CFBG) at room temperature is proposed and experimentally demonstrated. The two-mode PCF loop mirror is formed by inserting a piece of two-mode PCF into a Sagnac loop mirror, with the air-holes of the PCF intentionally collapsing at the splices. By adjusting the state of the polarization controller (PC) appropriately, the laser can be switched between the stable single- and dual-wavelength operations by means of the polarization hole burning (PHB) and spectral hole burning (SHB) effects.

Direct observation of fatigue in epitaxially grown Pb(Zr,Ti)O3 thin films using second harmonic piezoresponse force microscopy

NASA Astrophysics Data System (ADS)

Murari, Nishit M.; Hong, Seungbum; Lee, Ho Nyung; Katiyar, Ram. S.

2011-08-01

Here, we present a direct observation of fatigue phenomena in epitaxially grown Pb(Zr0.2Ti0.8)O3 (PZT) thin films using second harmonic piezoresponse force microscopy (SH-PFM). We observed strong correlation between the SH-PFM amplitude and phase signals with the remnant piezoresponse at different switching cycles. The SH-PFM results indicate that the average fraction of switchable domains decreases globally and the phase delays of polarization switching differ locally. In addition, we found that the fatigue developed uniformly over the whole area without developing region-by-region suppression of switchable polarization as in polycrystalline PZT thin films.

Frequency-Switchable Metamaterial Absorber Injecting Eutectic Gallium-Indium (EGaIn) Liquid Metal Alloy

PubMed Central

Ling, Kenyu; Kim, Hyung Ki; Yoo, Minyeong; Lim, Sungjoon

2015-01-01

In this study, we demonstrated a new class of frequency-switchable metamaterial absorber in the X-band. Eutectic gallium-indium (EGaIn), a liquid metal alloy, was injected in a microfluidic channel engraved on polymethyl methacrylate (PMMA) to achieve frequency switching. Numerical simulation and experimental results are presented for two cases: when the microfluidic channels are empty, and when they are filled with liquid metal. To evaluate the performance of the fabricated absorber prototype, it is tested with a rectangular waveguide. The resonant frequency was successfully switched from 10.96 GHz to 10.61 GHz after injecting liquid metal while maintaining absorptivity higher than 98%. PMID:26561815

Switchable narrow linewidth fiber laser with LP11 transverse mode output

NASA Astrophysics Data System (ADS)

Shen, Ya; Ren, Guobin; Yang, Yuguang; Yao, Shuzhi; Wu, Yue; Jiang, Youchao; Xu, Yao; Jin, Wenxing; Zhu, Bofeng; Jian, Shuisheng

2018-01-01

We experimentally demonstrate a switchable narrow linewidth single-longitudinal-mode (SLM) erbium-doped fiber (EDF) ring laser with LP11 transverse mode output. The laser is based on a mode selective all-fiber fused coupler which is composed of a single-mode fiber (SMF) and a two-mode fiber (TMF). By controlling the polarization state of the output light, the laser can provide narrow linewidth SLM output with LP11 transverse mode at two specific wavelengths, which correspond to two transmission peaks of the chirped moiré fiber grating (CMFBG). The 20 dB linewidth of the fiber laser for each wavelength is approximately 7.2 and 6.4 kHz.

Switchable Ni–Mn–Ga Heusler nanocrystals

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zayak, Alexey T.; Beckman, Scott P.; Tiago, Murilo L.

2008-10-02

Here, we examined bulk-like Heusler nanocrystals using real-space pseudopotentials constructed within density functional theory. The nanocrystals were made of various compositions of Ni-Mn-Ga in the size range from 15 up to 169 atoms. Among these compositions, the closest to the stoichiometric Ni 2MnGa were found to be the most stable. The Ni-based nanocrystals retained a tendency for tetragonal distortion, which is inherited from the bulk properties. Surface effects suppress the tetragonal structure in the smaller Ni-based nanocrystals, while bigger nanocrystals develop a bulk-like tetragonal distortion. We suggest the possibility of switchable Ni-Mn-Ga nanocrystals, which could be utilized for magnetic nano-shape-memorymore » applications.« less

Dynamically Babinet-invertible metasurface: a capacitive-inductive reconfigurable filter for terahertz waves using vanadium-dioxide metal-insulator transition

NASA Astrophysics Data System (ADS)

Urade, Yoshiro; Nakata, Yosuke; Okimura, Kunio; Nakanishi, Toshihiro; Miyamaru, Fumiaki; Takeda, Mitsuo W.; Kitano, Masao

2016-03-01

This paper proposes a reconfigurable planar metamaterial that can be switched between capacitive and inductive responses using local changes in the electrical conductivity of its constituent material. The proposed device is based on Babinet's principle and exploits the singular electromagnetic responses of metallic checkerboard structures, which are dependent on the local electrical conductivity. Utilizing the heating-induced metal-insulator transition of vanadium dioxide ($\\mathrm{VO}_2$), the proposed metamaterial is designed to compensate for the effect of the substrate and is experimentally characterized in the terahertz regime. This reconfigurable metamaterial can be utilized as a switchable filter and as a switchable phase shifter for terahertz waves.

Dynamically Babinet-invertible metasurface: a capacitive-inductive reconfigurable filter for terahertz waves using vanadium-dioxide metal-insulator transition.

PubMed

Urade, Yoshiro; Nakata, Yosuke; Okimura, Kunio; Nakanishi, Toshihiro; Miyamaru, Fumiaki; Takeda, Mitsuo W; Kitano, Masao

2016-03-07

This paper proposes a reconfigurable planar metamaterial that can be switched between capacitive and inductive responses using local changes in the electrical conductivity of its constituent material. The proposed device is based on Babinet's principle and exploits the singular electromagnetic responses of metallic checkerboard structures, which are dependent on the local electrical conductivity. Utilizing the heating-induced metal-insulator transition of vanadium dioxide (VO 2 ), the proposed meta-material is designed to compensate for the effect of the substrate and is experimentally characterized in the terahertz regime. This reconfigurable metamaterial can be utilized as a switchable filter and as a switchable phase shifter for terahertz waves.

Conformational fluctuations in a green fluorescent protein-like Akane family protein: a high-pressure fluorescence study at 0.1-700 MPa

NASA Astrophysics Data System (ADS)

Maeno, Akihiro; Kato, Yuko; Jimbo, Mitsuru; Amada, Kei; Mita, Hajime; Akasaka, Kazuyuki

2017-04-01

We have investigated conformational fluctuations in a new green fluorescent protein(GFP)-like protein rb-Akane found in a red-brown-colored octocoral, Scleronephthya gracillima (Kuekenthal)), with high pressure fluorescence spectroscopy at 0.1-700 MPa. Besides the green fluorescence at 510 nm, two red fluorescence peaks are observed at 590 and 629 nm, the relative intensity of which varies reversibly with pressure. The phenomenon is interpreted as representing the cis-trans isomerization of the chromophore accompanied by the conformational transition between two sub-states of the red fluorescence form of rb-Akane. The two sub-states are separated only marginally in free energy (ΔG0 = 1.9 ± 0.4 kJ mol-1), but significantly in partial molar volume (ΔV0 = -19.8 ± 1.4 ml mol-1) at 0.1 MPa (pH 7.5, 25°C). Above 500 MPa, the fluorescence at λmax 629 nm undergoes another reversible change with pressure, showing the onset of unfolding.

Lance Wheeler | NREL

Science.gov Websites

solution-phase phenomena of nanomaterials Switchable photovoltaics Solar thermochemical fuel production methylammonium lead halide perovskites during thermal processing from solution," Energy & Environmental

A Low Voltage Liquid Crystal Phase Grating with Switchable Diffraction Angles

PubMed Central

Chen, Haiwei; Tan, Guanjun; Huang, Yuge; Weng, Yishi; Choi, Tae-Hoon; Yoon, Tae-Hoon; Wu, Shin-Tson

2017-01-01

We demonstrate a simple yet high performance phase grating with switchable diffraction angles using a fringe field switching (FFS) liquid crystal (LC) cell. The LC rubbing angle is parallel to the FFS electrodes (i.e. α = 0°), leading to symmetric LC director distribution in a voltage-on state. Such a grating exhibits three unique features: 1) Two grating periods can be formed by controlling the applied voltage, resulting in switchable diffraction angles. In our design, the 1st diffraction order occurs at 4.3°, while the 2nd order appears at 8.6°. 2) The required voltage to achieve peak diffraction efficiency (η~32%) for the 1st order is only 4.4 V at λ = 633 nm as compared to 70 V for a conventional FFS-based phase grating in which α ≈ 7°, while the 2nd order (η~27%) is 15 V. 3). The measured rise and decay time for the 1st order is 7.62 ms and 6.75 ms, and for the 2nd order is 0.75 ms and 3.87 ms, respectively. To understand the physical mechanisms, we also perform device simulations. Good agreement between experiment and simulation is obtained. PMID:28054592

Maximal switchability of centralized networks

NASA Astrophysics Data System (ADS)

Vakulenko, Sergei; Morozov, Ivan; Radulescu, Ovidiu

2016-08-01

We consider continuous time Hopfield-like recurrent networks as dynamical models for gene regulation and neural networks. We are interested in networks that contain n high-degree nodes preferably connected to a large number of N s weakly connected satellites, a property that we call n/N s -centrality. If the hub dynamics is slow, we obtain that the large time network dynamics is completely defined by the hub dynamics. Moreover, such networks are maximally flexible and switchable, in the sense that they can switch from a globally attractive rest state to any structurally stable dynamics when the response time of a special controller hub is changed. In particular, we show that a decrease of the controller hub response time can lead to a sharp variation in the network attractor structure: we can obtain a set of new local attractors, whose number can increase exponentially with N, the total number of nodes of the nework. These new attractors can be periodic or even chaotic. We provide an algorithm, which allows us to design networks with the desired switching properties, or to learn them from time series, by adjusting the interactions between hubs and satellites. Such switchable networks could be used as models for context dependent adaptation in functional genetics or as models for cognitive functions in neuroscience.

Wideband-Switchable Metamaterial Absorber Using Injected Liquid Metal.

PubMed

Kim, Hyung Ki; Lee, Dongju; Lim, Sungjoon

2016-08-22

Metamaterial absorbers can provide good solutions for radar-cross-section (RCS) reduction. In spite of their attractive features of thinness, lightness, and low cost, resonant metamaterial absorbers have a drawback of narrow bandwidth. For practical radar applications, wideband absorbers are necessary. In this paper, we propose a wideband-switchable metamaterial absorber using liquid metal. In order to reduce RCS both for X-band and C-band, the switchable Jerusalem cross (JC) resonator is introduced. The JC resonator consists of slotted circular rings, chip resistors, and microfluidic channels. The JC resonator is etched on a flexible printed circuit board (FPCB), and the microfluidic channels are laser-etched on a polydimethylsiloxane (PDMS) material. The proposed absorber can switch the absorption frequency band by injecting a liquid metal alloy into the channels. The performance of the absorber was demonstrated through full-wave simulation and through measurements employing prototypes. The experimental results showed absorption ratios of over 90% from 7.43 GHz to 14.34 GHz, and from 5.62 GHz to 7.3 GHz, with empty channels and liquid metal-filled channels, respectively. Therefore, the absorption band was successfully switched between the C-band (4-8 GHz) and the X-band (8-12 GHz) by injecting liquid metal eutectic gallium indium alloy (EGaIn) into the channels.

Switchable skin window induced by optical clearing method for dermal blood flow imaging

NASA Astrophysics Data System (ADS)

Wang, Jing; Shi, Rui; Zhu, Dan

2013-06-01

Optical imaging techniques have shown tremendous potential for assessing cutaneous microcirculation, but the imaging depth and contrast is limited by the strong scattering of skin. Current skin windows have to be fulfilled by surgical operation and suffer from some side effects. In this study, a switchable skin window was developed by topical application of an optical clearing agent (OCA) and saline on rat skin in vivo. The validity of the skin window was evaluated by the laser speckle contrast imaging technique, and the safety of OCA to the body was tested through histologic examinations. The results indicated that administration of OCA or saline on rat skin in vivo can open or close the window of skin repeatedly for three days. With the repair effect of hyaluronic acid and Vaseline, it is able to repeatedly visualize the dermal blood vessels and flow distribution. Long-term observation shows that there is no abnormal reflection in micro-structure, body weight, organ coefficients, histopathologic lesions, or toxic reactions compared with a control group. This switchable window will provide an effective tool not only for cutaneous microcirculation with laser speckle contrast imaging, but also for diagnosis and treatment of peripheral vascular diseases, including tumor research with various optical imaging techniques.

Nanoscale Ultrasound-Switchable FRET-Based Liposomes for Near-Infrared Fluorescence Imaging in Optically Turbid Media.

PubMed

Zhang, Qimei; Morgan, Stephen P; Mather, Melissa L

2017-09-01

A new approach for fluorescence imaging in optically turbid media centered on the use of nanoscale ultrasound-switchable FRET-based liposome contrast agents is reported. Liposomes containing lipophilic carbocyanine dyes as FRET pairs with emission wavelengths located in the near-infrared window are prepared. The efficacy of FRET and self-quenching for liposomes with a range of fluorophore concentrations is first calculated from measurement of the liposome emission spectra. Exposure of the liposomes to ultrasound results in changes in the detected fluorescent signal, the nature of which depends on the fluorophores used, detection wavelength, and the fluorophore concentration. Line scanning of a tube containing the contrast agents with 1 mm inner diameter buried at a depth of 1 cm in a heavily scattering tissue phantom demonstrates an improvement in image spatial resolution by a factor of 6.3 as compared with images obtained in the absence of ultrasound. Improvements are also seen in image contrast with the highest obtained being 9% for a liposome system containing FRET pairs. Overall the results obtained provide evidence of the potential the nanoscale ultrasound-switchable FRET-based liposomes studied here have for in vivo fluorescence imaging. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Wideband-Switchable Metamaterial Absorber Using Injected Liquid Metal

NASA Astrophysics Data System (ADS)

Kim, Hyung Ki; Lee, Dongju; Lim, Sungjoon

2016-08-01

Metamaterial absorbers can provide good solutions for radar-cross-section (RCS) reduction. In spite of their attractive features of thinness, lightness, and low cost, resonant metamaterial absorbers have a drawback of narrow bandwidth. For practical radar applications, wideband absorbers are necessary. In this paper, we propose a wideband-switchable metamaterial absorber using liquid metal. In order to reduce RCS both for X-band and C-band, the switchable Jerusalem cross (JC) resonator is introduced. The JC resonator consists of slotted circular rings, chip resistors, and microfluidic channels. The JC resonator is etched on a flexible printed circuit board (FPCB), and the microfluidic channels are laser-etched on a polydimethylsiloxane (PDMS) material. The proposed absorber can switch the absorption frequency band by injecting a liquid metal alloy into the channels. The performance of the absorber was demonstrated through full-wave simulation and through measurements employing prototypes. The experimental results showed absorption ratios of over 90% from 7.43 GHz to 14.34 GHz, and from 5.62 GHz to 7.3 GHz, with empty channels and liquid metal-filled channels, respectively. Therefore, the absorption band was successfully switched between the C-band (4-8 GHz) and the X-band (8-12 GHz) by injecting liquid metal eutectic gallium indium alloy (EGaIn) into the channels.

Colloidal-Quantum-Dot Ring Lasers with Active Color Control.

PubMed

le Feber, Boris; Prins, Ferry; De Leo, Eva; Rabouw, Freddy T; Norris, David J

2018-02-14

To improve the photophysical performance of colloidal quantum dots for laser applications, sophisticated core/shell geometries have been developed. Typically, a wider bandgap semiconductor is added as a shell to enhance the gain from the quantum-dot core. This shell is designed to electronically isolate the core, funnel excitons to it, and reduce nonradiative Auger recombination. However, the shell could also potentially provide a secondary source of gain, leading to further versatility in these materials. Here we develop high-quality quantum-dot ring lasers that not only exhibit lasing from both the core and the shell but also the ability to switch between them. We fabricate ring resonators (with quality factors up to ∼2500) consisting only of CdSe/CdS/ZnS core/shell/shell quantum dots using a simple template-stripping process. We then examine lasing as a function of the optical excitation power and ring radius. In resonators with quality factors >1000, excitons in the CdSe cores lead to red lasing with thresholds at ∼25 μJ/cm 2 . With increasing power, green lasing from the CdS shell emerges (>100 μJ/cm 2 ) and then the red lasing begins to disappear (>250 μJ/cm 2 ). We present a rate-equation model that can explain this color switching as a competition between exciton localization into the core and stimulated emission from excitons in the shell. Moreover, by lowering the quality factor of the cavity we can engineer the device to exhibit only green lasing. The mechanism demonstrated here provides a potential route toward color-switchable quantum-dot lasers.

Structural tunability and switchable exciton emission in inorganic-organic hybrids with mixed halides

NASA Astrophysics Data System (ADS)

Ahmad, Shahab; Baumberg, Jeremy J.; Vijaya Prakash, G.

2013-12-01

Room-temperature tunable excitonic photoluminescence is demonstrated in alloy-tuned layered Inorganic-Organic (IO) hybrids, (C12H25NH3)2PbI4(1-y)Br4y (y = 0 to 1). These perovskite IO hybrids adopt structures with alternating stacks of low-dimensional inorganic and organic layers, considered to be naturally self-assembled multiple quantum wells. These systems resemble stacked monolayer 2D semiconductors since no interlayer coupling exists. Thin films of IO hybrids exhibit sharp and strong photoluminescence (PL) at room-temperature due to stable excitons formed within the low-dimensional inorganic layers. Systematic variation in the observed exciton PL from 510 nm to 350 nm as the alloy composition is changed, is attributed to the structural readjustment of crystal packing upon increase of the Br content in the Pb-I inorganic network. The energy separation between exciton absorption and PL is attributed to the modified exciton density of states and diffusion of excitons from relatively higher energy states corresponding to bromine rich sites towards the lower energy iodine sites. Apart from compositional fluctuations, these excitons show remarkable reversible flips at temperature-induced phase transitions. All the results are successfully correlated with thermal and structural studies. Such structural engineering flexibility in these hybrids allows selective tuning of desirable exciton properties within suitable operating temperature ranges. Such wide-range PL tunability and reversible exciton switching in these novel IO hybrids paves the way to potential applications in new generation of optoelectronic devices.

Redox-switchable copper(I) metallogel: a metal-organic material for selective and naked-eye sensing of picric acid.

PubMed

Sarkar, Sougata; Dutta, Soumen; Chakrabarti, Susmita; Bairi, Partha; Pal, Tarasankar

2014-05-14

Thiourea (TU), a commercially available laboratory chemical, has been discovered to introduce metallogelation when reacted with copper(II) chloride in aqueous medium. The chemistry involves the reduction of Cu(II) to Cu(I) with concomitant oxidation of thiourea to dithiobisformamidinium dichloride. The gel formation is triggered through metal-ligand complexation, i.e., Cu(I)-TU coordination and extensive hydrogen bonding interactions involving thiourea, the disulfide product, water, and chloride ions. Entangled network morphology of the gel selectively develops in water, maybe for its superior hydrogen-bonding ability, as accounted from Kamlet-Taft solvent parameters. Complete and systematic chemical analyses demonstrate the importance of both Cu(I) and chloride ions as the key ingredients in the metal-organic coordination gel framework. The gel is highly fluorescent. Again, exclusive presence of Cu(I) metal centers in the gel structure makes the gel redox-responsive and therefore it shows reversible gel-sol phase transition. However, the reversibility does not cause any morphological change in the gel phase. The gel practically exhibits its multiresponsive nature and therefore the influences of different probable interfering parameters (pH, selective metal ions and anions, selective complexing agents, etc.) have been studied mechanistically and the results might be promising for different applications. Finally, the gel material shows a highly selective visual response to a commonly used nitroexplosive, picric acid among a set of 19 congeners and the preferred selectivity has been mechanistically interpreted with density functional theory-based calculations.

Comparison of energy efficiency and power density in pressure retarded osmosis and reverse electrodialysis.

PubMed

Yip, Ngai Yin; Elimelech, Menachem

2014-09-16

Pressure retarded osmosis (PRO) and reverse electrodialysis (RED) are emerging membrane-based technologies that can convert chemical energy in salinity gradients to useful work. The two processes have intrinsically different working principles: controlled mixing in PRO is achieved by water permeation across salt-rejecting membranes, whereas RED is driven by ion flux across charged membranes. This study compares the energy efficiency and power density performance of PRO and RED with simulated technologically available membranes for natural, anthropogenic, and engineered salinity gradients (seawater-river water, desalination brine-wastewater, and synthetic hypersaline solutions, respectively). The analysis shows that PRO can achieve both greater efficiencies (54-56%) and higher power densities (2.4-38 W/m(2)) than RED (18-38% and 0.77-1.2 W/m(2)). The superior efficiency is attributed to the ability of PRO membranes to more effectively utilize the salinity difference to drive water permeation and better suppress the detrimental leakage of salts. On the other hand, the low conductivity of currently available ion exchange membranes impedes RED ion flux and, thus, constrains the power density. Both technologies exhibit a trade-off between efficiency and power density: employing more permeable but less selective membranes can enhance the power density, but undesired entropy production due to uncontrolled mixing increases and some efficiency is sacrificed. When the concentration difference is increased (i.e., natural → anthropogenic → engineered salinity gradients), PRO osmotic pressure difference rises proportionally but not so for RED Nernst potential, which has logarithmic dependence on the solution concentration. Because of this inherently different characteristic, RED is unable to take advantage of larger salinity gradients, whereas PRO power density is considerably enhanced. Additionally, high solution concentrations suppress the Donnan exclusion effect of the charged RED membranes, severely reducing the permselectivity and diminishing the energy conversion efficiency. This study indicates that PRO is more suitable to extract energy from a range of salinity gradients, while significant advancements in ion exchange membranes are likely necessary for RED to be competitive with PRO.

Neonatal nucleated red blood cell counts in small-for-gestational age fetuses with abnormal umbilical artery Doppler studies.

PubMed

Bernstein, P S; Minior, V K; Divon, M Y

1997-11-01

The presence of elevated nucleated red blood cell counts in neonatal blood has been associated with fetal hypoxia. We sought to determine whether small-for-gestational-age fetuses with abnormal umbilical artery Doppler velocity waveforms have elevated nucleated red blood cell counts. Hospital charts of neonates with the discharge diagnosis of small for gestational age (birth weight < 10th percentile) who were delivered between October 1988 and June 1995 were reviewed for antepartum testing, delivery conditions, and neonatal outcome. We studied fetuses who had an umbilical artery systolic/diastolic ratio within 3 days of delivery and a complete blood cell count on the first day of life. Multiple gestations, anomalous fetuses, and infants of diabetic mothers were excluded. Statistical analysis included the Student t test, chi 2 analysis, analysis of variance, and simple and stepwise regression. Fifty-two infants met the inclusion criteria. Those with absent or reversed end-diastolic velocity (n = 19) had significantly greater nucleated red blood cell counts than did those with end-diastolic velocity present (n = 33) (nucleated red blood cells/100 nucleated cells +/- SD: 135.5 +/- 138 vs 17.4 +/- 23.7, p < 0.0001). These infants exhibited significantly longer time intervals for clearance of nucleated red blood cells from their circulation (p < 0.0001). They also had lower birth weights (p < 0.05), lower initial platelet count (p = 0.0006), lower arterial cord blood pH (p < 0.05), higher cord blood base deficit (p < 0.05), and an increased likelihood of cesarean section for "fetal distress" (p < 0.05). Multivariate analysis demonstrated that absent or reversed end-diastolic velocity (p < 0.0001) and low birth weight (p < 0.0001) contributed to the elevation of the nucleated red blood cell count, whereas gestational age at delivery was not a significant contributor. We observed significantly greater nucleated red blood cell counts and lower platelet counts in small-for-gestational-age fetuses with abnormal umbilical artery Doppler studies. This may suggest that antenatal thrombotic events lead to an increased placental impedance. Fetal response to this chronic condition may result in an increased nucleated red blood cell count.

Comparison of Energy Efficiency and Power Density in Pressure Retarded Osmosis and Reverse Electrodialysis

DOE Office of Scientific and Technical Information (OSTI.GOV)

Yip, NY; Elimelech, M

Pressure retarded osmosis (PRO) and reverse electrodialysis (RED) are emerging membrane-based technologies that can convert chemical energy in salinity gradients to useful work. The two processes have intrinsically different working principles: controlled mixing in PRO is achieved by water permeation across salt-rejecting membranes, whereas RED is driven by ion flux across charged membranes. This study compares the energy efficiency and power density performance of PRO and RED with simulated technologically available membranes for natural, anthropogenic, and engineered salinity gradients (seawater-river water, desalination brine-wastewater, and synthetic hypersaline solutions, respectively). The analysis shows that PRO can achieve both greater efficiencies (54-56%) andmore » higher power densities (2.4-38 W/m(2)) than RED (18-38% and 0.77-1.2 W/m(2)). The superior efficiency is attributed to the ability of PRO membranes to more effectively utilize the salinity difference to drive water permeation and better suppress the detrimental leakage of salts. On the other hand, the low conductivity of currently available ion exchange membranes impedes RED ion flux and, thus, constrains the power density. Both technologies exhibit a trade-off between efficiency and power density: employing more permeable but less selective membranes can enhance the power density, but undesired entropy production due to uncontrolled mixing increases and some efficiency is sacrificed. When the concentration difference is increased (i.e., natural -> anthropogenic -> engineered salinity gradients), PRO osmotic pressure difference rises proportionally but not so for RED Nernst potential, which has logarithmic dependence on the solution concentration. Because of this inherently different characteristic, RED is unable to take advantage of larger salinity gradients, whereas PRO power density is considerably enhanced. Additionally, high solution concentrations suppress the Donnan exclusion effect of the charged RED membranes, severely reducing the permselectivity and diminishing the energy conversion efficiency. This study indicates that PRO is more suitable to extract energy from a range of salinity gradients, while significant advancements in ion exchange membranes are likely necessary for RED to be competitive with PRO.« less

Photoinduced fluorescence activation and nitric oxide release with biocompatible polymer nanoparticles.

PubMed

Deniz, Erhan; Kandoth, Noufal; Fraix, Aurore; Cardile, Venera; Graziano, Adriana C E; Lo Furno, Debora; Gref, Ruxandra; Raymo, Françisco M; Sortino, Salvatore

2012-12-03

A viable strategy to encapsulate a fluorophore/photochrome dyad and a nitric oxide photodonor within supramolecular assemblies of a cyclodextrin-based polymer in water was developed. The two photoresponsive guests do not interact with each other within their supramolecular container and can be operated in parallel under optical control. Specifically, the dyad permits the reversible switching of fluorescence on a microsecond timescale for hundreds of cycles, and the photodonor enables the irreversible release of nitric oxide. Furthermore, these supramolecular assemblies cross the membrane of human melanoma cancer cells and transport their cargo in the cytosol. The fluorescence of one component allows the visualization of the labeled cells, and its switchable character could, in principle, be used to acquire super-resolution images, while the release of nitric oxide from the other induces significant cell mortality. Thus, our design logic for the construction of biocompatible nanoparticles with dual functionality might evolve into the realization of valuable photoresponsive probes for imaging and therapeutic applications. Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Virus-based Photo-Responsive Nanowires Formed By Linking Site-Directed Mutagenesis and Chemical Reaction

NASA Astrophysics Data System (ADS)

Murugesan, Murali; Abbineni, Gopal; Nimmo, Susan L.; Cao, Binrui; Mao, Chuanbin

2013-05-01

Owing to the genetic flexibility and error-free bulk production, bio-nanostructures such as filamentous phage showed great potential in materials synthesis, however, their photo-responsive behaviour is neither explored nor unveiled. Here we show M13 phage genetically engineered with tyrosine residues precisely fused to the major coat protein is converted into a photo-responsive organic nanowire by a site-specific chemical reaction with an aromatic amine to form an azo dye structure on the surface. The resulting azo-M13-phage nanowire exhibits reversible photo-responsive properties due to the photo-switchable cis-trans isomerisation of the azo unit formed on the phage. This result shows that site-specific display of a peptide on bio-nanostructures through site-directed genetic mutagenesis can be translated into site-directed chemical reaction for developing advanced materials. The photo-responsive properties of the azo-M13-phage nanowires may open the door for the development of light controllable smart devices for use in non-linear optics, holography data storage, molecular antenna, and actuators.

Charge collection microscopy of in-situ switchable PRAM line cells in a scanning electron microscope: Technique development and unique observations

DOE Office of Scientific and Technical Information (OSTI.GOV)

Oosthoek, J. L. M.; Schuitema, R. W.; Brink, G. H. ten

2015-03-15

An imaging method has been developed based on charge collection in a scanning electron microscope (SEM) that allows discrimination between the amorphous and crystalline states of Phase-change Random Access Memory (PRAM) line cells. During imaging, the cells are electrically connected and can be switched between the states and the resistance can be measured. This allows for electrical characterization of the line cells in-situ in the SEM. Details on sample and measurement system requirements are provided which turned out to be crucial for the successful development of this method. Results show that the amorphous or crystalline state of the line cellsmore » can be readily discerned, but the spatial resolution is relatively poor. Nevertheless, it is still possible to estimate the length of the amorphous mark, and also for the first time, we could directly observe the shift of the amorphous mark from one side of the line cell to the other side when the polarity of the applied (50 ns) RESET pulse was reversed.« less

Endowing Hydrochromism to Fluorans via Bioinspired Alteration of Molecular Structures and Microenvironments and Expanding Their Potential for Rewritable Paper.

PubMed

Xi, Guan; Sheng, Lan; Zhang, Ivan; Du, Jiahui; Zhang, Ting; Chen, Qiaonan; Li, Guiying; Zhang, Ying; Song, Yue; Li, Jianhua; Zhang, Yu-Mo; Zhang, Sean Xiao-An

2017-11-01

Interest and effort toward new materials for rewritable paper have increased dramatically because of the exciting advantages for sustainable development and better nature life cycle. Inspired by how nature works within living systems, herein, we have used fluorans, as a concept verification, to endow original acidochromic, basochromic or photochromic molecules with broader properties, such as switchable with solvent, water, heat, electricity, stress, other force, etc., via simplified methods (i.e., via variation of submolecular structure or microenvironments). The hydrochromic visual change and reversible behavior of selected molecules have been explored, and the primary mechanism at the atomic or subatomic level has been hypothesized. In addition, several newly demonstrated hydrochromic fluorans have been utilized for water-jet rewritable paper (WJRP), which exhibit great photostability, high hydrochromic contrast, and fast responsive rate and which can be reused at least 30 times without significant variation. The water-jet prints have good resolution and various colors and can keep legibility after a few months or years. This improved performance is a major step toward practical applications of WJRP.

Virus-based Photo-Responsive Nanowires Formed By Linking Site-Directed Mutagenesis and Chemical Reaction

PubMed Central

Murugesan, Murali; Abbineni, Gopal; Nimmo, Susan L.; Cao, Binrui; Mao, Chuanbin

2013-01-01

Owing to the genetic flexibility and error-free bulk production, bio-nanostructures such as filamentous phage showed great potential in materials synthesis, however, their photo-responsive behaviour is neither explored nor unveiled. Here we show M13 phage genetically engineered with tyrosine residues precisely fused to the major coat protein is converted into a photo-responsive organic nanowire by a site-specific chemical reaction with an aromatic amine to form an azo dye structure on the surface. The resulting azo-M13-phage nanowire exhibits reversible photo-responsive properties due to the photo-switchable cis-trans isomerisation of the azo unit formed on the phage. This result shows that site-specific display of a peptide on bio-nanostructures through site-directed genetic mutagenesis can be translated into site-directed chemical reaction for developing advanced materials. The photo-responsive properties of the azo-M13-phage nanowires may open the door for the development of light controllable smart devices for use in non-linear optics, holography data storage, molecular antenna, and actuators. PMID:23673356

UV-driven microvalve based on a micro-nano TiO₂/SiO₂ composite surface for microscale flow control.

PubMed

Guo, Ting; Meng, Tao; Li, Wei; Qin, Jilong; Tong, Zhiping; Zhang, Qing; Li, Xueru

2014-03-28

This paper presents a novel ultraviolet (UV)-driven microvalve based on the concept of inserting a trimethyl chlorosilane (CTMS) modified TiO₂/SiO₂ composite patch of switchable wettability in a microfluidic system. A unique micro-nano hierarchical structure was designed and used to enhance the overall wetting contrast with the aim of improving the wetting-based valve performances. Field-emission scanning electron microscopy (FE-SEM) and x-ray photoelectron spectroscopy (XPS) were used to characterize the morphology and chemical composition of the surface. UV-driven wettability conversion on the patched microchannel was investigated using water column relative height tests, and the results confirmed the significant improvement of the hierarchical structure with the surface hydrophobic/hydrophilic conversion, which produced enhancements of 276% and 95% of the water-repellent and water-sucking pressures, respectively, compared with those of the single-scale TiO₂ nanopatterned structure. Accordingly, a good reversible and repeated on-off performance was identified by the valve tests, highlighting the potential application of the novel microvalve in the efficient control of microscale flow.

UV-driven microvalve based on a micro-nano TiO2/SiO2 composite surface for microscale flow control

NASA Astrophysics Data System (ADS)

Guo, Ting; Meng, Tao; Li, Wei; Qin, Jilong; Tong, Zhiping; Zhang, Qing; Li, Xueru

2014-03-01

This paper presents a novel ultraviolet (UV)-driven microvalve based on the concept of inserting a trimethyl chlorosilane (CTMS) modified TiO2/SiO2 composite patch of switchable wettability in a microfluidic system. A unique micro-nano hierarchical structure was designed and used to enhance the overall wetting contrast with the aim of improving the wetting-based valve performances. Field-emission scanning electron microscopy (FE-SEM) and x-ray photoelectron spectroscopy (XPS) were used to characterize the morphology and chemical composition of the surface. UV-driven wettability conversion on the patched microchannel was investigated using water column relative height tests, and the results confirmed the significant improvement of the hierarchical structure with the surface hydrophobic/hydrophilic conversion, which produced enhancements of 276% and 95% of the water-repellent and water-sucking pressures, respectively, compared with those of the single-scale TiO2 nanopatterned structure. Accordingly, a good reversible and repeated on-off performance was identified by the valve tests, highlighting the potential application of the novel microvalve in the efficient control of microscale flow.

Acid/Base and H2PO4(-) Controllable High-Contrast Optical Molecular Switches with a Novel BODIPY Functionalized [2]Rotaxane.

PubMed

Arumugaperumal, Reguram; Srinivasadesikan, Venkatesan; Ramakrishnam Raju, Mandapati V; Lin, Ming-Chang; Shukla, Tarun; Singh, Ravinder; Lin, Hong-Cheu

2015-12-09

A novel multifunctional mechanically interlocked switchable [2]rotaxane R4 containing two molecular stations and rotaxane arms terminated with boron-dipyrromethene (BODIPY) fluorophores and its derivatives were synthesized for the first time by CuAAC click reaction. The shuttling motion of macrocycle between the dibenzylammonium and triazolium recognition sites and the distance dependent photoinduced electron transfer process of R4 is demonstrated by utilizing external chemical stimuli (acid/base). Interestingly, the reversible self-assembly process of R4 was recognized by the acid-base molecular switch strategy. Notably, two symmetrical triazolium groups acted as molecular stations, H2PO4(-) receptors, and H-bonded donors. Both [2]rotaxane R4 and thread R2 demonstrated excellent optical responses and high selectivity toward H2PO4(-) ion. The specific motion and guest-host interactions of mechanically interlocked machines (MIMs) were also further explored by quantum mechanical calculations. The thread R2 also demonstrated to enable the detection of H2PO4(-) in RAW 264.7 cells successfully.

Effect of Divalent Cations on RED Performance and Cation Exchange Membrane Selection to Enhance Power Densities.

PubMed

Rijnaarts, Timon; Huerta, Elisa; van Baak, Willem; Nijmeijer, Kitty

2017-11-07

Reverse electrodialysis (RED) is a membrane-based renewable energy technology that can harvest energy from salinity gradients. The anticipated feed streams are natural river and seawater, both of which contain not only monovalent ions but also divalent ions. However, RED using feed streams containing divalent ions experiences lower power densities because of both uphill transport and increased membrane resistance. In this study, we investigate the effects of divalent cations (Mg 2+ and Ca 2+ ) on RED and demonstrate the mitigation of those effects using both novel and existing commercial cation exchange membranes (CEMs). Monovalent-selective Neosepta CMS is known to block divalent cations transport and can therefore mitigate reductions in stack voltage. The new multivalent-permeable Fuji T1 is able to transport divalent cations without a major increase in resistance. Both strategies significantly improve power densities compared to standard-grade CEMs when performing RED using streams containing divalent cations.

Pattern Switchable Antenna System Using Inkjet-Printed Directional Bow-Tie for Bi-Direction Sensing Applications

PubMed Central

Eom, Seung-Hyun; Seo, Yunsik; Lim, Sungjoon

2015-01-01

In this paper, we propose a paper-based pattern switchable antenna system using inkjet-printing technology for bi-direction sensor applications. The proposed antenna system is composed of two directional bow-tie antennas and a switching network. The switching network consists of a single-pole-double-throw (SPDT) switch and a balun element. A double-sided parallel-strip line (DSPSL) is employed to convert the unbalanced microstrip mode to the balanced strip mode. Two directional bow-tie antennas have different radiation patterns because of the different orientation of the reflectors and antennas. It is demonstrated from electromagnetic (EM) simulation and measurement that the radiation patterns of the proposed antenna are successfully switched by the SPDT switch. PMID:26690443

Wavelength switchable high-power diode-side-pumped rod Tm:YAG Laser around 2µm.

PubMed

Wang, Caili; Du, Shifeng; Niu, Yanxiong; Wang, Zhichao; Zhang, Chao; Bian, Qi; Guo, Chuan; Xu, Jialin; Bo, Yong; Peng, Qinjun; Cui, Dafu; Zhang, Jingyuan; Lei, Wenqiang; Xu, Zuyan

2013-03-25

We report a high-power diode-side-pumped rod Tm:YAG laser operated at either 2.07 or 2.02 µm depending on the transmission of pumped output coupler. The laser yields 115W of continuous-wave output power at 2.07 µm with 5% output coupling, which is the highest output power for all solid-state 2.07 μm cw rod Tm:YAG laser reported so far. With an output coupler of 10% transmission, the center wavelength of the laser is switched to 2.02 μm with an output power of 77.1 W. This is the first observation of high-power wavelength switchable diode-side-pumped rod Tm:YAG laser around 2 µm.

Compact Mach-Zehnder interferometer based on photonic crystal fiber and its application in switchable multi-wavelength fiber laser

NASA Astrophysics Data System (ADS)

Chen, Weiguo; Lou, Shuqin; Wang, Liwen; Li, Honglei; Guo, Tieying; Jian, Shuisheng

2009-08-01

The compact Mach-Zehnder interferometer is proposed by splicing a section of photonic crystal fiber (PCF) and two pieces of single mode fiber (SMF) with the air-holes of PCF intentionally collapsed in the vicinity of the splices. The depedence of the fringe spacing on the length of PCF is investigated. Based on the Mach-Zehnder interferometer as wavelength-selective filter, a switchable dual-wavelength fiber ring laser is demonstrated with a homemade erbiumdoped fiber amplifier (EDFA) as the gain medium at room temperature. By adjusting the states of the polarization controller (PC) appropriately, the laser can be switched among the stable single-and dual -wavelength lasing operations by exploiting polarization hole burning (PHB) effect.

Switchable and spacing-tunable dual-wavelength thulium-doped silica fiber laser based on a nonlinear amplifier loop mirror.

PubMed

Liu, Shuo; Yan, Fengping; Feng, Ting; Wu, Beilei; Dong, Ze; Chang, Gee-Kung

2014-08-20

A kind of switchable and spacing-tunable dual-wavelength thulium-doped silica fiber laser based on a nonlinear amplifier loop mirror is presented and experimentally demonstrated. By adjusting the polarization controllers (PCs), stable dual-wavelength operation is obtained at the 2 μm band. The optical signal-to-noise ratio (OSNR) is better than 56 dB. The wavelength tuning is performed by applying static strain into the fiber Bragg grating. A tuning range from 0 to 5.14 nm is achieved for the dual-wavelength spacing. By adjusting the PCs properly, the fiber laser can also operate in single-wavelength state with the OSNR for each wavelength more than 50 dB.

Pattern Switchable Antenna System Using Inkjet-Printed Directional Bow-Tie for Bi-Direction Sensing Applications.

PubMed

Eom, Seung-Hyun; Seo, Yunsik; Lim, Sungjoon

2015-12-10

In this paper, we propose a paper-based pattern switchable antenna system using inkjet-printing technology for bi-direction sensor applications. The proposed antenna system is composed of two directional bow-tie antennas and a switching network. The switching network consists of a single-pole-double-throw (SPDT) switch and a balun element. A double-sided parallel-strip line (DSPSL) is employed to convert the unbalanced microstrip mode to the balanced strip mode. Two directional bow-tie antennas have different radiation patterns because of the different orientation of the reflectors and antennas. It is demonstrated from electromagnetic (EM) simulation and measurement that the radiation patterns of the proposed antenna are successfully switched by the SPDT switch.

An L-section DC electric field switchable bulk acoustic wave solidly mounted resonator filter based on Ba0.5Sr0.5TiO3.

PubMed

Saddik, George N; York, Robert A

2012-09-01

This paper reports on the modeling, fabrication, and experimental results of a voltage switchable barium strontium titanate solidly mounted resonator filter at 6 GHz. The filter insertion loss was measured to be -4.26 dB and the return loss to be -13.5 dB. The 3-dB bandwidth was measured to be 72 MHz and the quality factor was calculated to be 83. The data were collected at a dc bias voltage of 10 V. Temperature data were also collected, and the filter demonstrated a 0.71-dB increase in insertion loss and a 7-MHz decrease in center frequency with increase in temperature.

Thermally Switchable Thin Films of an ABC Triblock Copolymer of Poly(n-butyl methacrylate)-poly(methyl methacrylate)-poly(2-fluoroethyl methacrylate)

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zhang, Shanju; Liu, Zhan; Bucknall, David G.

2011-01-01

The thermo-responsive behavior of polymer films consisting of novel linear triblock copolymers of poly(n-butyl methacrylate)-poly(methyl methacrylate)-poly(2-fluoroethyl methacrylate) (PnBuMA-PMMA-P2FEMA) are reported using differential scanning calorimetry (DSC), atomic forcing microscopy (AFM), X-ray photoelectron spectroscopy (XPS) and contacting angle (CA) measurements. The surface morphology, wettability and chemical structure of thin films of these triblock copolymers on silicon wafers as a function of temperature have been investigated. It has been shown that the wettability of the films is thermally switchable. Detailed structural analysis shows that thermo-responsive surface composition changes are produced. The underlying mechanism of the thermoresponsive behavior is discussed.

Switchable multi-wavelength fiber laser based on modal interference

NASA Astrophysics Data System (ADS)

Ma, Lin; Jiang, Sun; Qi, Yan-Hui; Kang, Ze-Xin; Jian, Shui-Sheng

2015-08-01

A comb fiber filter based on modal interference is proposed and demonstrated in this paper. Here two cascaded up-tapers are used to excite the cladding mode, and a core-offset jointing point is used to act as an interference component. Experimental results show that this kind of structure possesses a comb filter property in a range of the C-band. The measured extinction ratio is better than 12 dB with an insertion loss of about 11 dB. A switchable multi-wavelength erbium-doped fiber laser based on this novel comb filter is demonstrated. By adjusting the polarization controller, the output laser can be switched among single-, dual-, and three-wavelengths with a side mode suppression ratio of better than 45 dB.

Effects of aluminum on organic acid metabolism and secretion by red spruce cell suspension cultures and the reversal of Al effects on growth and polyamine metabolism by exogenous organic acids

Treesearch

Rakesh Minocha; Stephanie Long

2004-01-01

In the absence of added Al, the concentration of succinate in cultured red spruce (Picea rubens Sarg.) cells was 15-20 times higher (> 600 nmol g-1FW) than that of citrate or oxalate and 4-6 times higher than that of malate. Addition of AICIJ (effective monomeric Al concentrations of 0.23 and 0.48...

Nanoconfined phosphorus film coating on interconnected carbon nanotubes as ultrastable anodes for lithium ion batteries

NASA Astrophysics Data System (ADS)

Xu, Zhiwei; Zeng, Yan; Wang, Liyuan; Li, Nan; Chen, Cheng; Li, Cuiyu; Li, Jing; Lv, Hanming; Kuang, Liyun; Tian, Xu

2017-07-01

Elemental phosphorus (P) is extensively explored as promising anode candidates due to its abundance, low-cost and high theoretical specific capacity. However, it is of great challenge for P-based materials as practical high-energy-density and long-cycling anodes for its large volume expansion and low conductibility. Here, we significantly improve both cycling and rate performance of red P by cladding the nanoconfined P film on interconnected multi-walled carbon nanotube networks (P-MWCNTs composite) via facile wet ball-milling. The red P-MWCNTs anode presents a superior high reversible capacity of 1396.6 mAh g-1 on the basis of P-MWCNTs composite weight at 50 mA g-1 with capacity retention reaching at ∼90% over 50 cycles. Even at 1000 mA g-1, it still maintains remarkable specific reversible capacity of 934.0 mAh g-1. This markedly enhanced performance is ascribed to synergistic advantages of this unique structure: Intimate contacts between nanosized red P and entangled MWCNTs not only shorten the transmission routes of ions through MWCNTs toward red P, but also motivate the access with electrolyte to open structures of P film. Besides, the confined nanosized P film moderate volume expansions effectively and the entangled MWCNTs networks acted as conductive channels activate high ionic/electronic conductivity of the whole electrodes.

Candidate predators for biological control of the poultry red mite Dermanyssus gallinae.

PubMed

Lesna, Izabela; Wolfs, Peter; Faraji, Farid; Roy, Lise; Komdeur, Jan; Sabelis, Maurice W

2009-06-01

The poultry red mite, Dermanyssus gallinae, is currently a significant pest in the poultry industry in Europe. Biological control by the introduction of predatory mites is one of the various options for controlling poultry red mites. Here, we present the first results of an attempt to identify potential predators by surveying the mite fauna of European starling (Sturnus vulgaris) nests, by assessing their ability to feed on poultry red mites and by testing for their inability to extract blood from bird hosts, i.e., newly hatched, young starlings and chickens. Two genuine predators of poultry red mites are identified: Hypoaspis aculeifer and Androlaelaps casalis. A review of the literature shows that some authors suspected the latter species to parasitize on the blood of birds and mammals, but they did not provide experimental evidence for these feeding habits and/or overlooked published evidence showing the reverse. We advocate careful analysis of the trophic structure of arthropods inhabiting bird nests as a basis for identifying candidate predators for control of poultry red mites.

Red fluorescent proteins: advanced imaging applications and future design.

PubMed

Shcherbakova, Daria M; Subach, Oksana M; Verkhusha, Vladislav V

2012-10-22

In the past few years a large series of the advanced red-shifted fluorescent proteins (RFPs) has been developed. These enhanced RFPs provide new possibilities to study biological processes at the levels ranging from single molecules to whole organisms. Herein the relationship between the properties of the RFPs of different phenotypes and their applications to various imaging techniques are described. Existing and emerging imaging approaches are discussed for conventional RFPs, far-red FPs, RFPs with a large Stokes shift, fluorescent timers, irreversibly photoactivatable and reversibly photoswitchable RFPs. Advantages and limitations of specific RFPs for each technique are presented. Recent progress in understanding the chemical transformations of red chromophores allows the future RFP phenotypes and their respective novel imaging applications to be foreseen. Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Multicolor Super-Resolution Fluorescence Imaging via Multi-Parameter Fluorophore Detection

PubMed Central

Bates, Mark; Dempsey, Graham T; Chen, Kok Hao; Zhuang, Xiaowei

2012-01-01

Understanding the complexity of the cellular environment will benefit from the ability to unambiguously resolve multiple cellular components, simultaneously and with nanometer-scale spatial resolution. Multicolor super-resolution fluorescence microscopy techniques have been developed to achieve this goal, yet challenges remain in terms of the number of targets that can be simultaneously imaged and the crosstalk between color channels. Herein, we demonstrate multicolor stochastic optical reconstruction microscopy (STORM) based on a multi-parameter detection strategy, which uses both the fluorescence activation wavelength and the emission color to discriminate between photo-activatable fluorescent probes. First, we obtained two-color super-resolution images using the near-infrared cyanine dye Alexa 750 in conjunction with a red cyanine dye Alexa 647, and quantified color crosstalk levels and image registration accuracy. Combinatorial pairing of these two switchable dyes with fluorophores which enhance photo-activation enabled multi-parameter detection of six different probes. Using this approach, we obtained six-color super-resolution fluorescence images of a model sample. The combination of multiple fluorescence detection parameters for improved fluorophore discrimination promises to substantially enhance our ability to visualize multiple cellular targets with sub-diffraction-limit resolution. PMID:22213647

Electrically tunable superconducting terahertz metamaterial with low insertion loss and high switchable ratios

DOE Office of Scientific and Technical Information (OSTI.GOV)

Li, Chun; Zhang, Caihong, E-mail: chzhang@nju.edu.cn; Hu, Guoliang

2016-07-11

With the emergence and development of artificially structured electromagnetic materials, active terahertz (THz) metamaterial devices have attracted significant attention in recent years. Tunability of transmission is desirable for many applications. For example, short-range wireless THz communications and ultrafast THz interconnects require switches and modulators. However, the tunable range of transmission amplitude of existing THz metamaterial devices is not satisfactory. In this article, we experimentally demonstrate an electrically tunable superconducting niobium nitride metamaterial device and employ a hybrid coupling model to analyze its optical transmission characteristics. The maximum transmission coefficient at 0.507 THz is 0.98 and decreases to 0.19 when themore » applied voltage increases to 0.9 V. A relative transmittance change of 80.6% is observed, making this device an efficient narrowband THz switch. Additionally, the frequency of the peak is red shifted from 0.507 to 0.425 THz, which means that the device can be used to select the frequency. This study offers an alternative tuning method to existing optical, thermal, magnetic-field, and electric-field tuning, delivering a promising approach for designing active and miniaturized THz devices.« less

Behavioral and Functional Assays for Investigating Mechanisms of Noxious Cold Detection and Multimodal Sensory Processing in Drosophila Larvae

PubMed Central

Patel, Atit A.; Cox, Daniel N.

2017-01-01

To investigate cellular, molecular and behavioral mechanisms of noxious cold detection, we developed cold plate behavioral assays and quantitative means for evaluating the predominant noxious cold-evoked contraction behavior. To characterize neural activity in response to noxious cold, we implemented a GCaMP6-based calcium imaging assay enabling in vivo studies of intracellular calcium dynamics in intact Drosophila larvae. We identified Drosophila class III multidendritic (md) sensory neurons as multimodal sensors of innocuous mechanical and noxious cold stimuli and to dissect the mechanistic bases of multimodal sensory processing we developed two independent functional assays. First, we developed an optogenetic dose response assay to assess whether levels of neural activation contributes to the multimodal aspects of cold sensitive sensory neurons. Second, we utilized CaMPARI, a photo-switchable calcium integrator that stably converts fluorescence from green to red in presence of high intracellular calcium and photo-converting light, to assess in vivo functional differences in neural activation levels between innocuous mechanical and noxious cold stimuli. These novel assays enable investigations of behavioral and functional roles of peripheral sensory neurons and multimodal sensory processing in Drosophila larvae. PMID:28835907

Flow of Red Blood Cells in Stenosed Microvessels.

PubMed

Vahidkhah, Koohyar; Balogh, Peter; Bagchi, Prosenjit

2016-06-20

A computational study is presented on the flow of deformable red blood cells in stenosed microvessels. It is observed that the Fahraeus-Lindqvist effect is significantly enhanced due to the presence of a stenosis. The apparent viscosity of blood is observed to increase by several folds when compared to non-stenosed vessels. An asymmetric distribution of the red blood cells, caused by geometric focusing in stenosed vessels, is observed to play a major role in the enhancement. The asymmetry in cell distribution also results in an asymmetry in average velocity and wall shear stress along the length of the stenosis. The discrete motion of the cells causes large time-dependent fluctuations in flow properties. The root-mean-square of flow rate fluctuations could be an order of magnitude higher than that in non-stenosed vessels. Several folds increase in Eulerian velocity fluctuation is also observed in the vicinity of the stenosis. Surprisingly, a transient flow reversal is observed upstream a stenosis but not downstream. The asymmetry and fluctuations in flow quantities and the flow reversal would not occur in absence of the cells. It is concluded that the flow physics and its physiological consequences are significantly different in micro- versus macrovascular stenosis.

Flow of Red Blood Cells in Stenosed Microvessels

NASA Astrophysics Data System (ADS)

Vahidkhah, Koohyar; Balogh, Peter; Bagchi, Prosenjit

2016-06-01

A computational study is presented on the flow of deformable red blood cells in stenosed microvessels. It is observed that the Fahraeus-Lindqvist effect is significantly enhanced due to the presence of a stenosis. The apparent viscosity of blood is observed to increase by several folds when compared to non-stenosed vessels. An asymmetric distribution of the red blood cells, caused by geometric focusing in stenosed vessels, is observed to play a major role in the enhancement. The asymmetry in cell distribution also results in an asymmetry in average velocity and wall shear stress along the length of the stenosis. The discrete motion of the cells causes large time-dependent fluctuations in flow properties. The root-mean-square of flow rate fluctuations could be an order of magnitude higher than that in non-stenosed vessels. Several folds increase in Eulerian velocity fluctuation is also observed in the vicinity of the stenosis. Surprisingly, a transient flow reversal is observed upstream a stenosis but not downstream. The asymmetry and fluctuations in flow quantities and the flow reversal would not occur in absence of the cells. It is concluded that the flow physics and its physiological consequences are significantly different in micro- versus macrovascular stenosis.

Cytotoxic and multidrug resistance reversal activity of a vegetable, 'Anastasia Red', a variety of sweet pepper.

PubMed

Motohashi, Noboru; Wakabayashi, Hidetsugu; Kurihara, Teruo; Takada, Yuko; Maruyama, Shichiro; Sakagami, Hiroshi; Nakashima, Hideki; Tani, Satoru; Shirataki, Yoshiaki; Kawase, Masami; Wolfard, Kristina; Molnár, Joseph

2003-04-01

The vegetable, Anastasia Red, Capsicum annuum L. var. angulosum Mill. (Solanaceae) was successively extracted with hexane, acetone, methanol and 70% methanol, and the extracts were further separated into a total of 21 fractions by silica gel or octadecylsilane (ODS) column chromatography. The biological activities of extracts and fractions were determined. These extracts showed relatively higher cytotoxic activity against two human oral tumor cell lines (HSC-2, HSG) than against normal human gingival fibroblasts (HGF), suggesting a tumor-specific cytotoxic activity. The cytotoxic activity of these extracts was enhanced by fractionation on silica gel [H2, A2, M1-M3] or ODS column chromatography [70M]. Several fractions [H2, H4, H5, A1, A2, A3, A5, A6, A7, M2] reversed the multidrug resistance (MDR) phenotype with L5178 mouse lymphoma T cells, more efficiently than (+/-)-verapamil. The extracts and fractions did not show any detectable anti-human immunodeficiency virus (HIV) or anti-Helicobacter pylori activity. Thus, this study suggests the effective and selective antitumor potential of 'Anastasia Red' of sweet pepper for further phytochemical and biological investigation. Copyright 2003 John Wiley & Sons, Ltd.

Effect of flow rate and concentration difference on reverse electrodialysis system

NASA Astrophysics Data System (ADS)

Kwon, Kilsugn; Han, Jaesuk; Kim, Daejoong

2013-11-01

Various energy conversion technologies have been developed to reduce dependency on limited fossil fuels, including wind power, solar power, hydropower, ocean power, and geothermal power. Among them, reverse electrodialysis (RED), which is one type of salinity gradient power (SGP), has received much attention due to high reliability and simplicity without moving parts. Here, we experimentally evaluated the RED performance with several parameters like flow rate of concentrated and dilute solution, concentration difference, and temperature. RED was composed of endplates, electrodes, spacers, anion exchange membrane, and cation exchange membrane. Endplates are made by a polypropylene. It included the electrodes, flow field for the electrode rinse solution, and path to supply a concentrated and dilute solution. Titanium coated by iridium and ruthenium was used as the electrode. The electrode rinse solution based on hexacyanoferrate system is used to reduce the power loss generated by conversion process form ionic current to electric current. Maximum power monotonously increases as increasing flow rate and concentration difference. Net power has optimal point because pumping power consumption increases with flow rate. This work was supported by Basic Science Research Program (Grat No. NRF-2011-0009993) through the National Research Foundation of Korea.

A thermochromic silver nanocluster exhibiting dual emission character

NASA Astrophysics Data System (ADS)

Xu, Qing-Qing; Dong, Xi-Yan; Huang, Ren-Wu; Li, Bo; Zang, Shuang-Quan; Mak, Thomas C. W.

2015-01-01

A Ag12(SCH2C10H7)6(CF3CO2)6(CH3CN)6 (1) nanocluster modified using naphthalen-2-yl-methanethiol was synthesized and structurally characterized by single crystal X-ray analysis. The targeted luminescent nanocluster displays dual emission with the property of reversible thermochromism spanning from red to bright yellow.A Ag12(SCH2C10H7)6(CF3CO2)6(CH3CN)6 (1) nanocluster modified using naphthalen-2-yl-methanethiol was synthesized and structurally characterized by single crystal X-ray analysis. The targeted luminescent nanocluster displays dual emission with the property of reversible thermochromism spanning from red to bright yellow. Electronic supplementary information (ESI) available: Experimental section and supporting Fig. S1-S6. CCDC 1004246. For ESI and crystallographic data in CIF or other electronic format see DOI: 10.1039/c4nr05122j

Oxygen vacancies induced switchable and nonswitchable photovoltaic effects in Ag/Bi{sub 0.9}La{sub 0.1}FeO{sub 3} /La{sub 0.7}Sr{sub 0.3}MnO{sub 3} sandwiched capacitors

DOE Office of Scientific and Technical Information (OSTI.GOV)

Gao, R. L., E-mail: gaorongli2008@163.com, E-mail: jrsun@iphy.ac.cn; Beijing National Laboratory for Condensed Matter Physics and Institute of Physics, Chinese Academy of Science, Beijing 100190; Yang, H. W.

2014-01-20

The short circuit photocurrent (I{sub sc}) was found to be strongly dependent on the oxygen vacancies (V{sub Os}) distribution in Ag/Bi{sub 0.9}La{sub 0.1}FeO{sub 3}/La{sub 0.7}Sr{sub 0.3}MnO{sub 3} heterostructures. In order to manipulate the V{sub Os} accumulated at either the Ag/Bi{sub 0.9}La{sub 0.1}FeO{sub 3} or the Bi{sub 0.9}La{sub 0.1}FeO{sub 3}/La{sub 0.7}Sr{sub 0.3}MnO{sub 3} interface by pulse voltages, switchable or nonswitchable photocurrent can be observed without or with changing the polarization direction. The sign of photocurrent could be independent of the direction of polarization when the variation of diffusion current and the modulation of the Schottky barrier at the Ag/Bi{sub 0.9}La{sub 0.1}FeO{submore » 3} interface induced by oxygen vacancies are large enough to offset those induced by polarization. Our work provides deep insights into the nature of photovoltaic effects in ferroelectric films, and will facilitate the advanced design of switchable devices combining spintronic, electronic, and optical functionalities.« less

The Mechanisms and Biomedical Applications of an NIR BODIPY-Based Switchable Fluorescent Probe

PubMed Central

Cheng, Bingbing; Bandi, Venugopal; Yu, Shuai; D’Souza, Francis; Nguyen, Kytai T.; Hong, Yi; Tang, Liping; Yuan, Baohong

2017-01-01

Highly environment-sensitive fluorophores have been desired for many biomedical applications. Because of the noninvasive operation, high sensitivity, and high specificity to the microenvironment change, they can be used as excellent probes for fluorescence sensing/imaging, cell tracking/imaging, molecular imaging for cancer, and so on (i.e., polarity, viscosity, temperature, or pH measurement). In this work, investigations of the switching mechanism of a recently reported near-infrared environment-sensitive fluorophore, ADP(CA)2, were conducted. Besides, multiple potential biomedical applications of this switchable fluorescent probe have been demonstrated, including wash-free live-cell fluorescence imaging, in vivo tissue fluorescence imaging, temperature sensing, and ultrasound-switchable fluorescence (USF) imaging. The fluorescence of the ADP(CA)2 is extremely sensitive to the microenvironment, especially polarity and viscosity. Our investigations showed that the fluorescence of ADP(CA)2 can be switched on by low polarity, high viscosity, or the presence of protein and surfactants. In wash-free live-cell imaging, the fluorescence of ADP(CA)2 inside cells was found much brighter than the dye-containing medium and was retained for at least two days. In all of the fluorescence imaging applications conducted in this study, high target-to-noise (>5-fold) was achieved. In addition, a high temperature sensitivity (73-fold per Celsius degree) of ADP(CA)2-based temperature probes was found in temperature sensing. PMID:28208666

Detection of nitro-based and peroxide-based explosives by fast polarity-switchable ion mobility spectrometer with ion focusing in vicinity of Faraday detector.

PubMed

Zhou, Qinghua; Peng, Liying; Jiang, Dandan; Wang, Xin; Wang, Haiyan; Li, Haiyang

2015-05-29

Ion mobility spectrometer (IMS) has been widely deployed for on-site detection of explosives. The common nitro-based explosives are usually detected by negative IMS while the emerging peroxide-based explosives are better detected by positive IMS. In this study, a fast polarity-switchable IMS was constructed to detect these two explosive species in a single measurement. As the large traditional Faraday detector would cause a trailing reactant ion peak (RIP), a Faraday detector with ion focusing in vicinity was developed by reducing the detector radius to 3.3 mm and increasing the voltage difference between aperture grid and its front guard ring to 591 V, which could remove trailing peaks from RIP without loss of signal intensity. This fast polarity-switchable IMS with ion focusing in vicinity of Faraday detector was employed to detect a mixture of 10 ng 2,4,6-trinitrotoluene (TNT) and 50 ng hexamethylene triperoxide diamine (HMTD) by polarity-switching, and the result suggested that [TNT-H](-) and [HMTD+H](+) could be detected in a single measurement. Furthermore, the removal of trailing peaks from RIP by the Faraday detector with ion focusing in vicinity also promised the accurate identification of KClO4, KNO3 and S in common inorganic explosives, whose product ion peaks were fairly adjacent to RIP.

Observation of Switchable Photoresponse of a Monolayer WSe2-MoS2 Lateral Heterostructure via Photocurrent Spectral Atomic Force Microscopic Imaging.

PubMed

Son, Youngwoo; Li, Ming-Yang; Cheng, Chia-Chin; Wei, Kung-Hwa; Liu, Pingwei; Wang, Qing Hua; Li, Lain-Jong; Strano, Michael S

2016-06-08

In the pursuit of two-dimensional (2D) materials beyond graphene, enormous advances have been made in exploring the exciting and useful properties of transition metal dichalcogenides (TMDCs), such as a permanent band gap in the visible range and the transition from indirect to direct band gap due to 2D quantum confinement, and their potential for a wide range of device applications. In particular, recent success in the synthesis of seamless monolayer lateral heterostructures of different TMDCs via chemical vapor deposition methods has provided an effective solution to producing an in-plane p-n junction, which is a critical component in electronic and optoelectronic device applications. However, spatial variation of the electronic and optoelectonic properties of the synthesized heterojunction crystals throughout the homogeneous as well as the lateral junction region and the charge carrier transport behavior at their nanoscale junctions with metals remain unaddressed. In this work, we use photocurrent spectral atomic force microscopy to image the current and photocurrent generated between a biased PtIr tip and a monolayer WSe2-MoS2 lateral heterostructure. Current measurements in the dark in both forward and reverse bias reveal an opposite characteristic diode behavior for WSe2 and MoS2, owing to the formation of a Schottky barrier of dissimilar properties. Notably, by changing the polarity and magnitude of the tip voltage applied, pixels that show the photoresponse of the heterostructure are observed to be selectively switched on and off, allowing for the realization of a hyper-resolution array of the switchable photodiode pixels. This experimental approach has significant implications toward the development of novel optoelectronic technologies for regioselective photodetection and imaging at nanoscale resolutions. Comparative 2D Fourier analysis of physical height and current images shows high spatial frequency variations in substrate/MoS2 (or WSe2) contact that exceed the frequencies imposed by the underlying substrates. These results should provide important insights in the design and understanding of electronic and optoelectronic devices based on quantum confined atomically thin 2D lateral heterostructures.

Biomimetic DNA emulsions: specific, thermo-reversible and adjustable binding from a liquid-like DNA layer

NASA Astrophysics Data System (ADS)

Pontani, Lea-Laetitia; Feng, Lang; Dreyfus, Remi; Seeman, Nadrian; Chaikin, Paul; Brujic, Jasna

2013-03-01

We develop micron-sized emulsions coated with specific DNA sequences and complementary sticky ends. The emulsions are stabilized with phospholipids on which the DNA strands are grafted through biotin-streptavidin interactions, which allows the DNA to diffuse freely on the surface. We produce two complementary emulsions: one is functionalized with S sticky ends and dyed with red streptavidin, the other displays the complementary S' sticky ends and green streptavidin. Mixing those emulsions reveals specific adhesion between them due to the short-range S-S' hybridization. As expected this interaction is thermo-reversible: the red-green adhesive droplets dissociate upon heating and reassemble after cooling. Here the fluid phospholipids layer also leads to diffusive adhesion patches, which allows the bound droplets to rearrange throughout the packing structure. We quantify the adhesion strength between two droplets and build a theoretical framework that captures the observed trends through parameters such as the size of the droplets, the DNA surface density, the various DNA constructs or the temperature. This colloidal-scale, specific, thermo-reversible biomimetic emulsion offers a new versatile and powerful tool for the development of complex self-assembled materials.

Electrically switchable polymer liquid crystal and polymer birefringent flake in fluid host systems and optical devices utilizing same

DOEpatents

Marshall, Kenneth L.; Kosc, Tanya Z.; Jacobs, Stephen D.; Faris, Sadeg M.; Li, Le

2003-12-16

Flakes or platelets of polymer liquid crystals (PLC) or other birefringent polymers (BP) suspended in a fluid host medium constitute a system that can function as the active element in an electrically switchable optical device when the suspension is either contained between a pair of rigid substrates bearing transparent conductive coatings or dispersed as microcapsules within the body of a flexible host polymer. Optical properties of these flake materials include large effective optical path length, different polarization states and high angular sensitivity in their selective reflection or birefringence. The flakes or platelets of these devices need only a 3-20.degree. rotation about the normal to the cell surface to achieve switching characteristics obtainable with prior devices using particle rotation or translation.

Switchable focus using a polymeric lenticular microlens array and a polarization rotator.

PubMed

Ren, Hongwen; Xu, Su; Liu, Yifan; Wu, Shin-Tson

2013-04-08

We demonstrate a flat polymeric lenticular microlens array using a mixture of rod-like diacrylate monomer and positive dielectric anisotropy nematic liquid crystal (LC). To create gradient refractive index profile in one microlens, we generate fringing fields from a planar top electrode and two striped bottom electrodes. After UV stabilization, the film is optically anisotropic and can stand alone. We then laminate this film on a 90° twisted-nematic LC cell, which works as a dynamic polarization rotator. The static polymeric lenticular lens exhibits focusing effect only to the extraordinary ray, but no optical effect to the ordinary ray. Such an integrated lens system offers several advantages, such as low voltage, fast response time, and temperature insensitivity, and can be used for switchable 2D/3D displays.

Switchable polarization-sensitive surface plasmon resonance of highly stable gold nanorods liquid crystals composites

NASA Astrophysics Data System (ADS)

Liu, Qingkun; Qian, Jun; Cai, Fuhong; Smalyukh, Ivan I.; He, Sailing

2011-12-01

In this work, we demonstrate the bulk self-alignment of gold nanorods (GNRs) dispersed in lyotropic nematic liquid crystals (LCs) with high optical absorption coefficient at the surface plasmon resonant wavelength. The polymer-coated GNRs which show spontaneous long-range orientational ordering along the director of LC host exhibit long-term stability as well as high concentration. External magnetic field and shearing allow for alignment and realignment of the orientation of gold nanorods by changing the director of the liquid crystal matrix. This results in a switchable polarization-sensitive surface plasmon resonance exhibiting stark differences from that of the same nanorods in isotropic fluids. The devise-scale bulk nanoparticle alignment may enable optical metamaterial mass production and control of surface plasmon resonance of nanoparticles.

Switchable diode effect in oxygen vacancy-modulated SrTiO3 single crystal

NASA Astrophysics Data System (ADS)

Pan, Xinqiang; Shuai, Yao; Wu, Chuangui; Luo, Wenbo; Sun, Xiangyu; Zeng, Huizhong; Bai, Xiaoyuan; Gong, Chaoguan; Jian, Ke; Zhang, Lu; Guo, Hongliang; Tian, Benlang; Zhang, Wanli

2017-09-01

SrTiO3 (STO) single crystal wafer was annealed in vacuum, and co-planar metal-insulator-metal structure of Pt/Ti/STO/Ti/Pt were formed by sputtering Pt/Ti electrodes onto the surface of STO after annealing. The forming-free resistive switching behavior with self-compliance property was observed in the sample. The sample showed switchable diode effect, which is explained by a simple model that redistribution of oxygen vacancies (OVs) under the external electric field results in the formation of n-n+ junction or n+-n junction (n donated n-type semiconductor; n+ donated heavily doped n-type semiconductor). The self-compliance property is also interpreted by the formation of n-n+/n+-n junction caused by the migration of the OVs under the electric field.

Switchable multiwavelength erbium-doped photonic crystal fiber ring laser based on a length of polarization-maintaining photonic crystal fiber

NASA Astrophysics Data System (ADS)

Cheng, Jianqun; Ruan, Shuangchen

2011-11-01

A switchable multi-wavelength Erbium-doped photonic crystal fiber (ED-PCF) ring laser based on a length of polarization-maintaining photonic crystal fiber(PM-PCF) is presented and demonstrated experimentally. A segment of ED-PCF is used as linear gain medium in the resonant cavity. Due to the polarization hole burning (PHB) caused by the PM-PCF and a polarization controller (PC), the laser can operate in stable dual- or triple- wavelength modes at room temperature. The optical signal-to-noise ratio (OSNR) of the laser without any wavelength-selective components is greater than 30 dB. The amplitude variations of lasing peaks in ten minutes are less than 0.26dB for two different operating modes.

Switchable single-longitudinal-mode dual-wavelength erbium-doped fiber ring laser based on one polarization-maintaining fiber Bragg grating incorporating saturable absorber and feedback fiber loop

NASA Astrophysics Data System (ADS)

Feng, Suchun; Xu, Ou; Lu, Shaohua; Ning, Tigang; Jian, Shuisheng

2009-06-01

Switchable single-longitudinal-mode (SLM) dual-wavelength erbium-doped fiber ring laser based on one polarization-maintaining fiber Bragg grating (PMFBG) is demonstrated. Due to the enhancement of the polarization hole burning (PHB) by the PMFBG, the laser can be designed to operate in stable dual-wavelength or wavelength-switching modes with a wavelength spacing of 0.336 nm at room temperature by adjusting a polarization controller (PC). The stable SLM operation is guaranteed by a compound-ring cavity and a saturable absorber (SA). The optical signal-to-noise ratio (OSNR) is over 45 dB. The amplitude variation in nearly one and half an hour is less than 0.2 dB.

A 100 mW-level single-mode switchable dual-wavelength erbium-doped fiber laser

NASA Astrophysics Data System (ADS)

Cheng, Jianqun; Zhang, Liaolin; Sharafudeen, Kaniyarakkal; Qiu, Jianrong

2013-10-01

A switchable dual-wavelength CW erbium-doped fiber laser with two cascaded fiber Bragg gratings has been proposed and demonstrated experimentally at room temperature. The laser uses a linear resonant cavity configuration incorporating a Sagnac loop with a polarization controller (PC) and can switch flexibly to output a single wavelength or dual wavelengths based on the polarization hole burning (PHB) effect. The slope efficiency and maximum output power can reach 23% and 96 mW, respectively. The two lasing peaks of the laser, with a narrow linewidth output and an optical signal-to-noise ratio of more than 50 dB, are located in the C and L bands of the optical communication window, respectively. The laser shows good stability with respect to the wavelength and output power.

Switchable multiwavelength erbium-doped photonic crystal fiber ring laser based on a length of polarization-maintaining photonic crystal fiber

NASA Astrophysics Data System (ADS)

Cheng, Jianqun; Ruan, Shuangchen

2012-03-01

A switchable multi-wavelength Erbium-doped photonic crystal fiber (ED-PCF) ring laser based on a length of polarization-maintaining photonic crystal fiber(PM-PCF) is presented and demonstrated experimentally. A segment of ED-PCF is used as linear gain medium in the resonant cavity. Due to the polarization hole burning (PHB) caused by the PM-PCF and a polarization controller (PC), the laser can operate in stable dual- or triple- wavelength modes at room temperature. The optical signal-to-noise ratio (OSNR) of the laser without any wavelength-selective components is greater than 30 dB. The amplitude variations of lasing peaks in ten minutes are less than 0.26dB for two different operating modes.

Tunable and switchable dual-wavelength dissipative soliton generation in an all-normal-dispersion Yb-doped fiber laser with birefringence fiber filter.

PubMed

Zhang, Z X; Xu, Z W; Zhang, L

2012-11-19

We report the generation of tunable single- and dual-wavelength dissipative solitons in an all-normal-dispersion mode-locked Yb-doped fiber laser, to the best of our knowledge, for the first time. Besides single-wavelength mode-locking, dual-wavelength mode-locking was achieved using an in-line birefringence fiber filter with periodic multiple passbands, which not only allows multiple wavelengths to oscillate simultaneously but also performs spectrum modulation on highly chirped dissipative pulse. Furthermore, taking advantage of the tunability of the birefringence fiber filter, wavelength tuning for both single- and dual-wavelength dissipative soliton mode-locking was realized. The dual-wavelength operation is also switchable. The all-fiber dissipative laser with flexible outputs can meet diverse application needs.

Application of a 1,1,3,3-tetramethylguanidine (TMG)/MeOH-CO2 in situ derivatization procedure for the gas chromatographic characterization of the fatty acid profile in olive oil.

PubMed

Saliu, F; Anzano, M; Franzetti, A

2015-03-01

1,1,3,3-Tetramethylguanidine (TMG), methanol and carbon dioxide were investigated as switchable polarity solvents (SPS) in the simultaneous derivatization and extraction of triacylglycerols for the gas chromatographic (GC) characterization of olive oil. Three commercial olive oils were used as test samples. Results of the developed method did not differ statistically from those provided by reference derivatization procedures. The transesterification reaction was carried out under a very mild condition, one step and in situ, and no particular matrix interferences were evidenced. The method represented the first example of the use of a switchable polarity mixture for the preparation of methyl ester derivatives of fatty acids (FAME).

Digitally switchable multi-focal lens using freeform optics.

PubMed

Wang, Xuan; Qin, Yi; Hua, Hong; Lee, Yun-Han; Wu, Shin-Tson

2018-04-16

Optical technologies offering electrically tunable optical power have found a broad range of applications, from head-mounted displays for virtual and augmented reality applications to microscopy. In this paper, we present a novel design and prototype of a digitally switchable multi-focal lens (MFL) that offers the capability of rapidly switching the optical power of the system among multiple foci. It consists of a freeform singlet and a customized programmable optical shutter array (POSA). Time-multiplexed multiple foci can be obtained by electrically controlling the POSA to switch the light path through different segments of the freeform singlet rapidly. While this method can be applied to a broad range of imaging and display systems, we experimentally demonstrate a proof-of-concept prototype for a multi-foci imaging system.

Switchable hydrophilicity solvents for lipid extraction from microalgae for biofuel production.

PubMed

Boyd, Alaina R; Champagne, Pascale; McGinn, Patrick J; MacDougall, Karen M; Melanson, Jeremy E; Jessop, Philip G

2012-08-01

A switchable hydrophilicity solvent (SHS) was studied for its effectiveness at extracting lipids from freeze-dried samples of Botryococcus braunii microalgae. The SHS N,N-dimethylcyclohexylamine extracted up to 22 wt.% crude lipid relative to the freeze-dried cell weight. The solvent was removed from the extract with water saturated with carbon dioxide at atmospheric pressure and recovered from the water upon de-carbonation of the mixture. Liquid chromatography-mass spectrometry (LC-MS) showed that the extracted lipids contained high concentrations of long chain tri-, di- and mono-acylglycerols, no phospholipids, and only 4-8% of residual solvent. Unlike extractions with conventional organic solvents, this new method requires neither distillation nor the use of volatile, flammable or chlorinated organic solvents. Copyright © 2012 Elsevier Ltd. All rights reserved.

Integrated all-optical infrared switchable plasmonic quantum cascade laser.

PubMed

Kohoutek, John; Bonakdar, Alireza; Gelfand, Ryan; Dey, Dibyendu; Nia, Iman Hassani; Fathipour, Vala; Memis, Omer Gokalp; Mohseni, Hooman

2012-05-09

We report a type of infrared switchable plasmonic quantum cascade laser, in which far field light in the midwave infrared (MWIR, 6.1 μm) is modulated by a near field interaction of light in the telecommunications wavelength (1.55 μm). To achieve this all-optical switch, we used cross-polarized bowtie antennas and a centrally located germanium nanoslab. The bowtie antenna squeezes the short wavelength light into the gap region, where the germanium is placed. The perturbation of refractive index of the germanium due to the free carrier absorption produced by short wavelength light changes the optical response of the antenna and the entire laser intensity at 6.1 μm significantly. This device shows a viable method to modulate the far field of a laser through a near field interaction.

Optical frequency switching scheme for a high-speed broadband THz measurement system based on the photomixing technique.

PubMed

Song, Hajun; Hwang, Sejin; Song, Jong-In

2017-05-15

This study presents an optical frequency switching scheme for a high-speed broadband terahertz (THz) measurement system based on the photomixing technique. The proposed system can achieve high-speed broadband THz measurements using narrow optical frequency scanning of a tunable laser source combined with a wavelength-switchable laser source. In addition, this scheme can provide a larger output power of an individual THz signal compared with that of a multi-mode THz signal generated by multiple CW laser sources. A swept-source THz tomography system implemented with a two-channel wavelength-switchable laser source achieves a reduced time for acquisition of a point spread function and a higher depth resolution in the same amount of measurement time compared with a system with a single optical source.

High-speed switchable lens enables the development of a volumetric stereoscopic display

PubMed Central

Love, Gordon D.; Hoffman, David M.; Hands, Philip J.W.; Gao, James; Kirby, Andrew K.; Banks, Martin S.

2011-01-01

Stereoscopic displays present different images to the two eyes and thereby create a compelling three-dimensional (3D) sensation. They are being developed for numerous applications including cinema, television, virtual prototyping, and medical imaging. However, stereoscopic displays cause perceptual distortions, performance decrements, and visual fatigue. These problems occur because some of the presented depth cues (i.e., perspective and binocular disparity) specify the intended 3D scene while focus cues (blur and accommodation) specify the fixed distance of the display itself. We have developed a stereoscopic display that circumvents these problems. It consists of a fast switchable lens synchronized to the display such that focus cues are nearly correct. The system has great potential for both basic vision research and display applications. PMID:19724571

Photo-switchable two-dimensional nanofluidic ionic diodes.

PubMed

Wang, Lili; Feng, Yaping; Zhou, Yi; Jia, Meijuan; Wang, Guojie; Guo, Wei; Jiang, Lei

2017-06-01

The bottom-up assembly of ion-channel-mimetic nanofluidic devices and materials with two-dimensional (2D) nano-building blocks paves a straightforward way towards the real-world applications of the novel transport phenomena on a nano- or sub-nanoscale. One immediate challenge is to provide the 2D nanofluidic systems with adaptive responsibilities and asymmetric ion transport characteristics. Herein, we introduce a facile and general strategy to provide a graphene-oxide-based 2D nanofluidic system with photo-switchable ionic current rectification (ICR). The degree of ICR can be prominently enhanced upon UV irradiation and it can be perfectly retrieved under irradiation with visible light. A maximum ICR ratio of about 48 was achieved. The smart and functional nanofluidic devices have applications in energy conversion, chemical sensing, water treatment, etc .

Switchable Schottky diode characteristics induced by electroforming process in Mn-doped ZnO thin films

NASA Astrophysics Data System (ADS)

Nam, Yoonseung; Hwang, Inrok; Oh, Sungtaek; Lee, Sangik; Lee, Keundong; Hong, Sahwan; Kim, Jinsoo; Choi, Taekjib; Ho Park, Bae

2013-04-01

We investigated the asymmetric current-voltage (I-V) characteristics and accompanying unipolar resistive switching of pure ZnO and Mn(1%)-doped ZnO (Mn:ZnO) films sandwiched between Pt electrodes. After electroforming, a high resistance state of the Mn:ZnO capacitor revealed switchable diode characteristics whose forward direction was determined by the polarity of the electroforming voltage. Linear fitting of the I-V curves highlighted that the rectifying behavior was influenced by a Schottky barrier at the Pt/Mn:ZnO interface. Our results suggest that formation of conducting filaments from the cathode during the electroforming process resulted in a collapse of the Schottky barrier (near the cathode), and rectifying behaviors dominated by a remnant Schottky barrier near the anode.

High quality factor, fully switchable terahertz superconducting metasurface

DOE Office of Scientific and Technical Information (OSTI.GOV)

Scalari, G., E-mail: scalari@phys.ethz.ch; Maissen, C.; Faist, J.

2014-12-29

We present a complementary THz metasurface realised with Niobium thin film which displays a quality factor Q = 54 and a fully switchable behaviour as a function of the temperature. The switching behaviour and the high quality factor are due to a careful design of the metasurface aimed at maximising the ohmic losses when the Nb is above the critical temperature and minimising the radiative coupling. The superconductor allows the operation of the cavity with high Q and the use of inductive elements with a high aspect ratio. Comparison with three dimensional finite element simulations highlights the crucial role of the inductivemore » elements and of the kinetic inductance of the Cooper pairs in achieving the high quality factor and the high field enhancement.« less

Post-rift deformation of the Red Sea Arabian margin

NASA Astrophysics Data System (ADS)

Zanoni, Davide; Schettino, Antonio; Pierantoni, Pietro Paolo; Rasul, Najeeb

2017-04-01

Starting from the Oligocene, the Red Sea rift nucleated within the composite Neoproterozoic Arabian-Nubian shield. After about 30 Ma-long history of continental lithosphere thinning and magmatism, the first pulse of oceanic spreading occurred at around 4.6 Ma at the triple junction of Africa, Arabia, and Danakil plate boundaries and propagated southward separating Danakil and Arabia plates. Ocean floor spreading between Arabia and Africa started later, at about 3 Ma and propagated northward (Schettino et al., 2016). Nowadays the northern part of the Red Sea is characterised by isolated oceanic deeps or a thinned continental lithosphere. Here we investigate the deformation of thinned continental margins that develops as a consequence of the continental lithosphere break-up induced by the progressive oceanisation. This deformation consists of a system of transcurrent and reverse faults that accommodate the anelastic relaxation of the extended margins. Inversion and shortening tectonics along the rifted margins as a consequence of the formation of a new segment of ocean ridge was already documented in the Atlantic margin of North America (e.g. Schlische et al. 2003). We present preliminary structural data obtained along the north-central portion of the Arabian rifted margin of the Red Sea. We explored NE-SW trending lineaments within the Arabian margin that are the inland continuation of transform boundaries between segments of the oceanic ridge. We found brittle fault zones whose kinematics is consistent with a post-rift inversion. Along the southernmost transcurrent fault (Ad Damm fault) of the central portion of the Red Sea we found evidence of dextral movement. Along the northernmost transcurrent fault, which intersects the Harrat Lunayyir, structures indicate dextral movement. At the inland termination of this fault the evidence of dextral movement are weaker and NW-SE trending reverse faults outcrop. Between these two faults we found other dextral transcurrent systems that locally are associated with metre-thick reverse fault zones. Along the analysed faults there is evidence of tectonic reworking. Relict kinematic indicators or the sense of asymmetry of sigmoidal Miocene dykes may suggest that a former sinistral movement was locally accommodated by these faults. This evidence of inversion of strike-slip movement associated with reverse structures, mostly found at the inland endings of these lineaments, suggests an inversion tectonics that could be related to the progressive and recent oceanisation of rift segments. Schettino A., Macchiavelli C., Pierantoni P.P., Zanoni D. & Rasul N. 2016. Recent kinematics of the tectonic plates surrounding the Red Sea and Gulf of Aden. Geophysical Journal International, 207, 457-480. Schlische R.W., Withjack M.O. & Olsen P.E., 2003. Relative timing of CAMP, rifting, continental breakup, and basin inversion: tectonic significance, in The Central Atlantic Magmatic Province: Insights from Fragments of Pangea, eds Hames W., Mchone J.G., Renne P. & Ruppel C., American Geophysical Union, 33-59.

The influence of the chloride gradient across red cell membranes on sodium and potassium movements

PubMed Central

Cotterrell, D.; Whittam, R.

1971-01-01

1. A study has been made to see whether active and passive movements of sodium and potassium in human red blood cells are influenced by changing the chloride gradient and hence the potential difference across the cell membrane. 2. Chloride distribution was measured between red cells and isotonic solutions with a range of concentrations of chloride and non-penetrating anions (EDTA, citrate, gluconate). The cell chloride concentration was greater than that outside with low external chloride, suggesting that the sign of the membrane potential was reversed. The chloride ratio (internal/external) was approximately equal to the inverse of the hydrogen ion ratio at normal and low external chloride, and inversely proportional to external pH. These results show that chloride is passively distributed, making it valid to calculate the membrane potential from the chloride ratio. 3. Ouabain-sensitive (pump) potassium influx and sodium efflux were decreased by not more than 20 and 40% respectively on reversing the chloride gradient, corresponding to a change in membrane potential from -9 to +30 mV. In contrast, passive (ouabain-insensitive) movements were reversibly altered — potassium influx was decreased about 60% and potassium efflux was increased some tenfold. Sodium influx was unaffected by the nature of the anion and depended only on the external sodium concentration, whereas ouabain-insensitive sodium efflux was increased about threefold. When external sodium was replaced by potassium there was a decrease in ouabain-insensitive sodium efflux with normal chloride, but an increase in low-chloride medium. 4. Net movements of sodium and potassium were roughly in accord with the unidirectional fluxes. 5. The results suggest that reversing the chloride gradient and, therefore, the sign of the membrane potential, had little effect on the sodium pump, but caused a marked increase in passive outward movements of both sodium and potassium ions. PMID:4996368

Method of acetaldehyde measurement with minimal artifactual formation in red blood cells and plasma of actively drinking subjects with alcoholism.

PubMed

Hernandez-Munoz, R; Ma, X L; Baraona, E; Lieber, C S

1992-07-01

After alcohol consumption, a substantial amount of acetaldehyde that is reversibly bound to protein and nonprotein components of the red blood cells circulates in the blood and could cause extrahepatic toxicity. However, acetaldehyde measurement in human red blood cells is hampered by considerable ex vivo artifactual formation as a result of nonenzymatic oxidation of ethanol during protein precipitation. To eliminate this source of artifactual formation, free and reversibly bound acetaldehyde were trapped with semicarbazide from red blood cell hemolysates, and both the stroma and the hemoglobin were sequentially removed by centrifugation and ion-exchange chromatography in carboxymethyl Sephadex, respectively. The eluted semi-carbazone was dissociated with perchloric acid, and the acetaldehyde that was released in the protein-free supernatants was measured by head-space gas chromatography. Maximal retention of hemoglobin by carboxymethyl Sephadex and complete recovery of acetaldehyde and ethanol were achieved at a pH of 5.3. The artifactual formation decreased from 2.62 +/- 0.32 mumol of acetaldehyde per millimole of ethanol in the initial hemolysates to 1.38 +/- 0.20 mumol after removal of the stroma and to a level that is comparable to measurements in plasma (0.09 +/- 0.02 mumol) after removal of both the stroma and the hemoglobin. In 12 actively drinking subjects with alcoholism, with blood ethanol levels that ranged between 9 and 81 mmol/L, the concentrations of acetaldehyde in red blood cells (11.50 +/- 1.46 mumol/L; range: 7.5 to 22 mumol/L) were minimally affected by blood ethanol levels and were three times as high as those in the plasma (3.74 +/- 1.49 mumol/L).(ABSTRACT TRUNCATED AT 250 WORDS)

Individual variation in foraging behavior reveals a trade-off between flexibility and performance of a top predator

PubMed Central

McGhee, Katie E.; Roche, Daniel P.; Bell, Alison M.

2017-01-01

There is increasing evidence that behavioral flexibility is associated with the ability to adaptively respond to environmental change. Flexibility can be advantageous in some contexts such as exploiting novel resources, but it may come at a cost of accuracy or performance in ecologically relevant tasks, such as foraging. Such trade-offs may, in part, explain why individuals within a species are not equally flexible. Here, we conducted a reversal learning task and predation experiment on a top fish predator, the Northern pike (Esox lucius), to examine individual variation in flexibility and test the hypothesis that an individual’s behavioral flexibility is negatively related with its foraging performance. Pikes were trained to receive a food reward from either a red or blue cup and then the color of the rewarded cup was reversed. We found that pike improved over time in how quickly they oriented to the rewarded cup, but there was a bias toward the color red. Moreover, there was substantial variation among individuals in their ability to overcome this red bias and switch from an unrewarded red cup to the rewarded blue cup, which we interpret as consistent variation among individuals in behavioral flexibility. Furthermore, individual differences in behavioral flexibility were negatively associated with foraging performance on ecologically relevant stickleback prey. Our data indicate that individuals cannot be both behaviorally flexible and efficient predators, suggesting a trade-off between these two traits. PMID:29046598

Development and characterization of amorphous acrylate networks for use as switchable adhesives inspired from shapememory behavior

NASA Astrophysics Data System (ADS)

Lakhera, Nishant

Several types of insects and animals such as spiders and geckos are inherently able to climb along vertical walls and ceilings. This remarkable switchable adhesive behavior has been attributed to the fibrillar structures on their feet, with size ranging from few nanometers to a few micrometers depending on the species. Several studies have attempted to create synthetic micro-patterned surfaces trying to imitate this adhesive behavior seen in nature. The experimental procedures are scattered, with sole purpose of trying to increase adhesion, thereby making direct comparison between studies very difficult. There is a lack of fundamental understanding on adhesion of patterned surfaces. The influence of critical parameters like material modulus, glass transition temperature, viscoelastic effects, temperature and water absorption on adhesion is not fully explored and characterized. These parameters are expected to have a decisive influence on adhesion behavior of the polymer. Previous studies have utilized conventional "off-the-shelf" materials like epoxy, polyurethanes etc. It is however, impossible to change the material modulus, glass transition temperature etc. of these polymer systems without changing the base constituents itself, thereby explaining the gaps in the current research landscape. The purpose of this study was to use acrylate shape-memory polymers (SMPs) for their ability to be tailored to specific mechanical properties by control of polymer chemistry, without changing the base constituents. Polymer networks with tailorable glass transition, material modulus, water absorption etc. were developed and adhesion studies were performed to investigate the influence of temperature, viscoelastic effects, material modulus on the adhesion behavior of flat acrylate polymer surfaces. The knowledge base gained from these studies was utilized to better understand the fundamental mechanisms associated with adhesion behavior of patterned acrylate surfaces. Thermally induced switchable adhesion and water induced switchable adhesion of patterned acrylate surfaces was investigated. The viscoelastic energy dissipation occurring during the detachment phase was shown to dramatically increase adhesion under both thermally induced and water induced conditions. This effect was most pre-dominant at the glass transition temperature of the material. Increase in pre-load force and unloading velocity were also shown to increase the adhesive capability of the patterned acrylate SMPs.

Day light quality affects the night-break response in the short-day plant chrysanthemum, suggesting differential phytochrome-mediated regulation of flowering.

PubMed

Higuchi, Yohei; Sumitomo, Katsuhiko; Oda, Atsushi; Shimizu, Hiroshi; Hisamatsu, Tamotsu

2012-12-15

Chrysanthemum (Chrysanthemum morifolium) is a short-day plant, which flowers when the night length is longer than a critical minimum. Flowering is effectively inhibited when the required long-night phase is interrupted by a short period of exposure to red light (night break; NB). The reversal of this inhibition by subsequent exposure to far-red (FR) light indicates the involvement of phytochromes in the flowering response. Here, we elucidated the role of light quality in photoperiodic regulation of chrysanthemum flowering, by applying a range of different conditions. Flowering was consistently observed under short days with white light (W-SD), SD with monochromatic red light (R-SD), or SD with monochromatic blue light (B-SD). For W-SD, NB with monochromatic red light (NB-R) was most effective in inhibiting flowering, while NB with monochromatic blue light (NB-B) and NB with far-red light (NB-FR) caused little inhibition. In contrast, for B-SD, flowering was strongly inhibited by NB-B and NB-FR. However, when B-SD was supplemented with monochromatic red light (B+R-SD), no inhibition by NB-B and NB-FR was observed. Furthermore, the inhibitory effect of NB-B following B-SD was partially reversed by subsequent exposure to a FR light pulse. The conditions B-SD/NB-B (no flowering) and B+R-SD/NB-B (flowering) similarly affected the expression of circadian clock-related genes. However, only the former combination suppressed expression of the chrysanthemum orthologue of FLOWERING LOCUS T (CmFTL3). Our results suggest the involvement of at least 2 distinct phytochrome responses in the flowering response of chrysanthemum. Furthermore, it appears that the light quality supplied during the daily photoperiod affects the light quality required for effective NB. Copyright © 2012 Elsevier GmbH. All rights reserved.

Red Clover HCT2, a Hydroxycinnamoyl-Coenzyme A:Malate Hydroxycinnamoyl Transferase, Plays a Crucial Role in Biosynthesis of Phaselic Acid and Other Hydroxycinnamoyl-Malate Esters in Vivo1[OA

PubMed Central

Sullivan, Michael L.; Zarnowski, Robert

2011-01-01

In red clover (Trifolium pratense) leaves, phaselic acid (2-O-caffeoyl-l-malate) accumulates to several mmol kg−1 fresh weight and is a crucial component of a natural system that prevents protein breakdown during harvest and storage of this forage crop. Previously, we identified HCT2, a red clover gene encoding a hydroxycinnamoyl-Coenzyme A (CoA) hydroxycinnamoyl transferase capable of transferring p-coumaroyl and caffeoyl moieties from their CoA derivatives to malic acid to form the corresponding hydroxycinnamoyl-malate esters in vitro. Here, we carried out a detailed kinetic analysis of the enzyme and examined its in vivo function in red clover via reverse genetics. The kinetic analysis indicates that in vitro, despite similar Km values for the tested hydroxycinnamoyl-CoA derivatives, HCT2 favors transfer to malate of p-coumaroyl and feruloyl moieties over caffeoyl moieties by greater than 5-fold. Reverse reaction (transfer of hydroxycinnamoyl moieties from malate to CoA) by HCT2 was observed with p-coumaroyl-malate but not phaselic acid. Analysis of red clover plants down-regulated for HCT2 expression via RNA interference showed a significant and substantial correlation between HCT2 mRNA levels and phaselic acid accumulation (P < 0.005). In several of the HCT2-silenced plants, phaselic acid and p-coumaroyl-malate levels were reduced to <5% that of wild-type controls. These reductions resulted in easily observable phenotypes including reduced polyphenol oxidase-mediated browning and a reduction in blue epidermal fluorescence under ultraviolet light. These results demonstrate a crucial role for HCT2 in phaselic acid accumulation in red clover and define a previously undescribed pathway for the biosynthesis of hydroxycinnamoyl-malate esters in plants. PMID:21205620

Effects of different varieties of Maca (Lepidium meyenii) on bone structure in ovariectomized rats.

PubMed

Gonzales, Carla; Cárdenas-Valencia, Isaias; Leiva-Revilla, Johanna; Anza-Ramirez, Cecilia; Rubio, Julio; Gonzales, Gustavo F

2010-01-01

This study was designed to determine the effect of different varieties of maca (Lepidium meyenii) on bone structure in ovariectomized (OVX) rats. 36 female rats were randomly divided into 6 groups: sham and OVX rats treated with vehicle, estradiol (40 microg/kg), black, yellow or red maca (63 mg/ml) for 4 weeks. At the end of the treatment, uterine weight, femoral bone and lumbar vertebra histomorphology were assessed. Ovariectomy reduced weight, diameter and width of the femoral bone. Estradiol, black and red maca treatment reduced the effect of ovariectomy on these variables. Histological analyses revealed that estradiol, black and red maca treatments reversed the effect of ovariectomy by increasing the trabecular bone area in the second lumbar vertebra. Uterine weight was reduced in OVX rats, and estradiol but neither black nor red maca increased uterine weight. Red and black maca have protective effects on bone architecture in OVX rats without showing estrogenic effects on uterine weight. 2010 S. Karger AG, Basel.

Salt-responsive polyzwitterionic materials for surface regeneration between switchable fouling and antifouling properties.

PubMed

Chen, Hong; Yang, Jintao; Xiao, Shengwei; Hu, Rundong; Bhaway, Sarang M; Vogt, Bryan D; Zhang, Mingzhen; Chen, Qiang; Ma, Jie; Chang, Yung; Li, Lingyan; Zheng, Jie

2016-08-01

Development of smart regenerative surface is a highly challenging but important task for many scientific and industrial applications. Specifically, very limited research efforts were made for surface regeneration between bio-adhesion and antifouling properties, because bioadhesion and antifouling are the two highly desirable but completely opposite properties of materials. Herein, we developed salt-responsive polymer brushes of poly(3-(1-(4-vinylbenzyl)-1H-imidazol-3-ium-3-yl) propane-1-sulfonate) (polyVBIPS), which can be switched reversibly and repeatedly between protein capture/release and surface wettability in a controllable manner. PolyVBIPS brush has demonstrated its switching ability to resist both protein adsorption from 100% blood plasma/serum and bacterial attachment in multiple cycles. PolyVBIPS brush also exhibits reversible surface wettability from ∼40° to 25° between in PBS and in 1M NaCl solutions in multiple cycles. Overall, the salt-responsive behaviors of polyVBIPS brushes can be interpreted by the "anti-polyelectrolyte effect", i.e. polyVBIPS brushes adopt a collapsed chain conformation at low ionic strengths to achieve surface adhesive, but an extended chain conformation at high ionic strength to realize antifouling properties. We expect that polyVBIPS will provide a simple, robust, and promising system for the fabrication of smart surfaces with biocompatible, reliable, and regenerative properties. Unlike many materials with "one-time switching" capability for surface regeneration, we developed a new regenerative surface of zwitterionic polymer brush, which exhibits a reversible salt-induced switching property between a biomolecule-adhesive state and a biomolecule repellent state in complex media for multiple cycles. PolyVBIPS is easily synthesized and can be straightforward coated on the surface, which provides a simple, robust, and promising system for the fabrication of smart surfaces with biocompatible, reliable, regenerative properties. Copyright © 2016 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

Controlled protein adsorption on PMOXA/PAA based coatings by thermally induced immobilization

NASA Astrophysics Data System (ADS)

Mumtaz, Fatima; Chen, Chaoshi; Zhu, Haikun; Pan, Chao; Wang, Yanmei

2018-05-01

In this work, poly(2-methyl-2-oxazoline-random-glycidyl methacrylate) (PMOXA-r-GMA) and poly(acrylic acid)-block-poly(glycidyl methacrylate) (PAA-b-PGMA) copolymers were synthesized via cationic ring-opening polymerization (CROP) of 2-methyl-2-oxazoline (MOXA) and reversible addition-fragmentation chain transfer (RAFT) polymerization of acrylic acid (AA) followed by their random and block copolymerization with glycidyl methacrylate (GMA), respectively, and then characterized carefully. PMOXA/PAA based coatings were then prepared by simply spin coating the mixture of PMOXA-r-GMA and PAA-b-PGMA copolymer solutions onto silicon/glass substrates followed by annealing at 110 °C. The coatings were rigorously characterized by using X-ray photoelectron spectroscopy (XPS), the static water contact angle (WCA) test, ellipsometry and atomic force microscopy (AFM). The results demonstrated that the coating based mixed PMOXA/PAA brushes with desired surface composition could be attained by simply maintaining their percentage in the mixture of PMOXA-r-GMA and PAA-b-PGMA copolymer solutions. Finally, the switchable behavior of PMOXA/PAA based coatings toward bovine serum albumin (BSA) adsorption was investigated by fluorescein isothiocyanate-labelled BSA (FITC-BSA) assay and quartz crystal microbalance with dissipation monitoring (QCM-D), which indicated that the coating based mixed PMOXA/PAA brushes could control BSA adsorption/desorption from very low to high amount (>90% desorption) through adjusting the composition of PMOXA-r-GMA and PAA-b-PGMA solution used in preparing PMOXA/PAA based coatings upon pH and ionic strength change. Furthermore, PMOXA/PAA based coatings displayed efficient repeatability of reversible BSA adsorption/desorption cycles.

Water content and the conversion of phytochrome regulation of lettuce dormancy

NASA Technical Reports Server (NTRS)

Vertucci, C. W.; Vertucci, F. A.; Leopold, A. C.

1987-01-01

In an effort to determine which biological reactions can occur in relation to the water content of seeds, the regulation of lettuce seed dormancy by red and far red light was determined at various hydration levels. Far red light had an inhibiting effect on germination for seeds at all moisture contents from 4 to 32% water. Germination was progressively stimulated by red light as seed hydration increased from 8 to 15%, and reached a maximum at moisture contents above 18%. Red light was ineffective at moisture contents below 8%. Seeds that had been stimulated by red light and subsequently dried lost the enhanced germinability if stored at moisture contents above 8%. The contrast between the presumed photoconversion of phytochrome far red-absorbing (Pfr) to (Pr) occurring at any moisture content and the reverse reaction occurring only if the seed moisture content is greater than 8% may be explained on the basis of the existence of unstable intermediates in the Pr to Pfr conversion. Our results suggest that the initial photoreaction involved in phytochrome conversion is relatively independent of water content, while the subsequent partial reactions become increasingly facilitated as water content increases from 8 to 18%.

Colour break in reverse bicolour daffodils is associated with the presence of Narcissus mosaic virus

PubMed Central

2011-01-01

Background Daffodils (Narcissus pseudonarcissus) are one of the world's most popular ornamentals. They also provide a scientific model for studying the carotenoid pigments responsible for their yellow and orange flower colours. In reverse bicolour daffodils, the yellow flower trumpet fades to white with age. The flowers of this type of daffodil are particularly prone to colour break whereby, upon opening, the yellow colour of the perianth is observed to be 'broken' into patches of white. This colour break symptom is characteristic of potyviral infections in other ornamentals such as tulips whose colour break is due to alterations in the presence of anthocyanins. However, reverse bicolour flowers displaying colour break show no other virus-like symptoms such as leaf mottling or plant stunting, leading some to argue that the carotenoid-based colour breaking in reverse bicolour flowers may not be caused by virus infection. Results Although potyviruses have been reported to cause colour break in other flower species, enzyme-linked-immunoassays with an antibody specific to the potyviral family showed that potyviruses were not responsible for the occurrence of colour break in reverse bicolour daffodils. Colour break in this type of daffodil was clearly associated with the presence of large quantities of rod-shaped viral particles of lengths 502-580 nm in tepals. Sap from flowers displaying colour break caused red necrotic lesions on Gomphrena globosa, suggesting the presence of potexvirus. Red necrotic lesions were not observed in this indicator plant when sap from reverse bicolour flowers not showing colour break was used. The reverse transcriptase polymerase reactions using degenerate primers to carla-, potex- and poty-viruses linked viral RNA with colour break and sequencing of the amplified products indicated that the potexvirus Narcissisus mosaic virus was the predominant virus associated with the occurrence of the colour break. Conclusions High viral counts were associated with the reverse bicolour daffodil flowers that were displaying colour break but otherwise showed no other symptoms of infection. Narcissus mosaic virus was the virus that was clearly linked to the carotenoid-based colour break. PMID:21854646

Thermally switchable meta-material absorber involving vanadium dioxide semiconductor-metal transition for thermo photovoltaic conversion

NASA Astrophysics Data System (ADS)

Bendelala, Fathi; Cheknane, Ali; Hilal, Hikmat S.

2018-01-01

A new switchable absorber design using meta-materials for thermo photovoltaic applications is proposed here. Conventional absorbents are normally non-adjustable with narrow band-widths and polarization-dependence. The present study describes an alternative infrared absorber structure with tunable characteristics. The absorber is based on VO2 which exhibits transition from semiconductor to metallic conductor by thermal effect. With this design, the results show that wide-band absorption can be achieved. The absorption bandwidth can be improved from 15.94 to 36.75 THz. With 40.42% relative shift in the peak frequency, a maximum absorption efficiency of 99% can be achieved. This structure design is polarization-independent of normal incident radiations, and may accommodate radiations from wide oblique angles. These new features make the new thermally adjustable absorber potentially useful in thermo-photovoltaic conversion devices.

Thermoresponsive electrospun fibers for water harvesting applications

NASA Astrophysics Data System (ADS)

Thakur, Neha; Baji, Avinash; Ranganath, Anupama Sargur

2018-03-01

Temperature triggered switchable cellulose acetate-poly(N-isopropylacrylamide) (CA-PNIPAM) core-shell and blend nanofibers are fabricated for controlled moisture harvesting applications. Core-shell fibers are fabricated using a co-axial electrospinning setup whereas the conventional electrospinning setup is employed for fabricating the blend fibers. Investigation of their wettability behaviour demonstrated that the blend fibers are superhydrophilic whereas the core-shell fibers are hydrophilic at ambient temperature. Furthermore, both the samples have an ability to switch between the two states viz. hydrophilic to hydrophobic state based on thermal stimulus. The core-shell fibers are shown to have higher moisture sorption ability compared to the blend fibers. This study investigates the mechanism behind the switchable wettability behaviour of the core-shell fibers and demonstrates the crucial role played by the functional groups present on the surface layer of fibers in governing their moisture collection efficiency.

Perching and takeoff of a robotic insect on overhangs using switchable electrostatic adhesion.

PubMed

Graule, M A; Chirarattananon, P; Fuller, S B; Jafferis, N T; Ma, K Y; Spenko, M; Kornbluh, R; Wood, R J

2016-05-20

For aerial robots, maintaining a high vantage point for an extended time is crucial in many applications. However, available on-board power and mechanical fatigue constrain their flight time, especially for smaller, battery-powered aircraft. Perching on elevated structures is a biologically inspired approach to overcome these limitations. Previous perching robots have required specific material properties for the landing sites, such as surface asperities for spines, or ferromagnetism. We describe a switchable electroadhesive that enables controlled perching and detachment on nearly any material while requiring approximately three orders of magnitude less power than required to sustain flight. These electroadhesives are designed, characterized, and used to demonstrate a flying robotic insect able to robustly perch on a wide range of materials, including glass, wood, and a natural leaf. Copyright © 2016, American Association for the Advancement of Science.

Electrical Switchability and Dry-Wash Durability of Conductive Textiles

PubMed Central

Wu, Bangting; Zhang, Bowu; Wu, Jingxia; Wang, Ziqiang; Ma, Hongjuan; Yu, Ming; Li, Linfan; Li, Jingye

2015-01-01

There is growing interest in the area of conductive textiles in the scientific and industrial community. Herein, we successfully prepared a conductive textile via covalently grafting polyaniline (PANI) onto cotton by a multi-step treatment process. The conductivity of the resultant fabric could be tuned by immersing in water having different pH values. The conductive and insulating properties of the textile could be conveniently switched by alternately immersing in acidic and alkaline bath solutions. Most importantly, the resultant conductive fabrics were able to withstand 40 simulated dry-wash cycles, with almost no decay in the electrical conductivity, indicating their excellent dry-wash durability. The present strategy for fabricating conductive fabrics with excellent switchability of electrical properties and dry-wash durability is expected to provide inspiration for the production of multifunctional conductive textiles for use in hash or sensitive conditions. PMID:26066704

Design of protein switches based on an ensemble model of allostery.

PubMed

Choi, Jay H; Laurent, Abigail H; Hilser, Vincent J; Ostermeier, Marc

2015-04-22

Switchable proteins that can be regulated through exogenous or endogenous inputs have a broad range of biotechnological and biomedical applications. Here we describe the design of switchable enzymes based on an ensemble allosteric model. First, we insert an enzyme domain into an effector-binding domain such that both domains remain functionally intact. Second, we induce the fusion to behave as a switch through the introduction of conditional conformational flexibility designed to increase the conformational entropy of the enzyme domain in a temperature- or pH-dependent fashion. We confirm the switching behaviour in vitro and in vivo. Structural and thermodynamic studies support the hypothesis that switching result from an increase in conformational entropy of the enzyme domain in the absence of effector. These results support the ensemble model of allostery and embody a strategy for the design of protein switches.

Crack-Free, Soft Wrinkles Enable Switchable Anisotropic Wetting.

PubMed

Rhee, Dongjoon; Lee, Won-Kyu; Odom, Teri W

2017-06-01

Soft skin layers on elastomeric substrates are demonstrated to support mechano-responsive wrinkle patterns that do not exhibit cracking under applied strain. Soft fluoropolymer skin layers on pre-strained poly(dimethylsiloxane) slabs achieved crack-free surface wrinkling at high strain regimes not possible by using conventional stiff skin layers. A side-by-side comparison between the soft and hard skin layers after multiple cycles of stretching and releasing revealed that the soft skin layer enabled dynamic control over wrinkle topography without cracks or delamination. We systematically characterized the evolution of wrinkle wavelength, amplitude, and orientation as a function of tensile strain to resolve the crack-free structural transformation. We demonstrated that wrinkled surfaces can guide water spreading along wrinkle orientation, and hence switchable, anisotropic wetting was realized. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Characterization of an active metasurface using terahertz ellipsometry

DOE PAGES

Karl, Nicholas; Heimbeck, Martin S.; Everitt, Henry O.; ...

2017-11-06

Switchable metasurfaces fabricated on a doped epi-layer have become an important platform for developing techniques to control terahertz (THz) radiation, as a DC bias can modulate the transmission characteristics of the metasurface. To model and understand this performance in new device configurations accurately, a quantitative understanding of the bias-dependent surface characteristics is required. In this work, we perform THz variable angle spectroscopic ellipsometry on a switchable metasurface as a function of DC bias. By comparing these data with numerical simulations, we extract a model for the response of the metasurface at any bias value. Using this model, we predict amore » giant bias-induced phase modulation in a guided wave configuration. Lastly, these predictions are in qualitative agreement with our measurements, offering a route to efficient modulation of THz signals.« less

Chromogenic switchable glazing: Towards the development of the smart window

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lampert, C.M.

1995-06-01

The science and technology of chromogenic materials for switchable glazings in building applications is discussed. These glazings can be used for dynamic control of solar and visible energy. Currently many researchers and engineers are involved with the development of products in this field. A summary of activities in Japan, Europe, Australia, USA and Canada is made. The activities of the International Energy Agency are included. Both non-electrically activated and electrically activated glazings are discussed. Technologies covered in the first category are photochromics, and thermochromics and thermotropics. A discussion of electrically activated chromogenic glazings includes dispersed liquid crystals, dispersed particles andmore » electrochromics. A selection of device structures and performance characteristics are compared. A discussion of transparent conductors is presented. Technical issues concerning large-area development of smart windows are discussed.« less

Ferroelectrics: A pathway to switchable surface chemistry and catalysis

NASA Astrophysics Data System (ADS)

Kakekhani, Arvin; Ismail-Beigi, Sohrab; Altman, Eric I.

2016-08-01

It has been known for more than six decades that ferroelectricity can affect a material's surface physics and chemistry thereby potentially enhancing its catalytic properties. Ferroelectrics are a class of materials with a switchable electrical polarization that can affect surface stoichiometry and electronic structure and thus adsorption energies and modes; e.g., molecular versus dissociative. Therefore, ferroelectrics may be utilized to achieve switchable surface chemistry whereby surface properties are not fixed but can be dynamically controlled by, for example, applying an external electric field or modulating the temperature. Several important examples of applications of ferroelectric and polar materials in photocatalysis and heterogeneous catalysis are discussed. In photocatalysis, the polarization direction can control band bending at water/ferroelectric and ferroelectric/semiconductor interfaces, thereby facilitating charge separation and transfer to the electrolyte and enhancing photocatalytic activity. For gas-surface interactions, available results suggest that using ferroelectrics to support catalytically active transition metals and oxides is another way to enhance catalytic activity. Finally, the possibility of incorporating ferroelectric switching into the catalytic cycle itself is described. In this scenario, a dynamic collaboration of two polarization states can be used to drive reactions that have been historically challenging to achieve on surfaces with fixed chemical properties (e.g., direct NOx decomposition and the selective partial oxidation of methane). These predictions show that dynamic modulation of the polarization can help overcome some of the fundamental limitations on catalytic activity imposed by the Sabatier principle.

The use of the gonadotropin-releasing hormone analog deslorelin for short-term contraception in red pandas (Ailurus fulgens).

PubMed

Koeppel, Katja N; Barrows, Michelle; Visser, Katherine

2014-01-15

Red pandas (Ailurus fulgens) are threatened with extinction owing to habitat loss, exacerbated by their unique ecology and low fecundity. Regional breeding programs manage captive red panda populations. Recommendations not to breed may be made for various reasons, including genetic overrepresentation of certain individuals. No recommendations have been published on the use of contraception for red pandas. This article discusses the use of the GnRH analog deslorelin as a reversible method of contraception in both male and female pandas. The mean time from last contraception to conception was 3 years with a 4.6-mg deslorelin implant. The average dose of GnRH implant received was 1.09 mg/kg (range, 0.88-1.32). Males returned to breeding sooner than females. No reproductive side effects were noted with up to three consecutive annual GnRH implants. Copyright © 2014 Elsevier Inc. All rights reserved.

Photomorphogenesis in Sinningia speciosa, cv. Queen Victoria I. Characterization of Phytochrome Control.

PubMed

Satter, R L; Wetherell, D F

1968-06-01

The morphological development of Sinningia speciosa plants that were exposed to supplementary far red light was very different from that of plants receiving dark nights. After several nights of such irradiation, stems and petioles were elongated, petioles were angulated, leaf blade expansion was inhibited, plants were chlorotic and the accumulation of shoot dry weight was retarded.Red reversibility of the morphological changes potentiated by far red light indicated control by the phytochrome system. A high P(FR) level during the last half of the night inhibited stem elongation and promoted leaf blade expansion, but both of these processes were hardly affected by the P(FR) level during the first half of the night. Thus sensitivity to P(FR) was cyclic.The interpretation of our experiments was complicated by quantitative morphological differences resulting from long, as compared to short, far red irradiations.

A more than six orders of magnitude UV-responsive organic field-effect transistor utilizing a benzothiophene semiconductor and Disperse Red 1 for enhanced charge separation.

PubMed

Smithson, Chad S; Wu, Yiliang; Wigglesworth, Tony; Zhu, Shiping

2015-01-14

A more than six orders of magnitude UV-responsive organic field-effect transistor is developed using a benzothiophene (BTBT) semiconductor and strong donor-acceptor Disperse Red 1 as the traps to enhance charge separation. The device can be returned to its low drain current state by applying a short gate bias, and is completely reversible with excellent stability under ambient conditions. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Hematology and immunology studies

NASA Technical Reports Server (NTRS)

Kimzey, S. L.

1977-01-01

A coordinated series of experiments were conducted to evaluate immunologic and hemotologic system responses of Skylab crewmen to prolonged space flights. A reduced PHA responsiveness was observed on recovery, together with a reduced number of T-cells, with both values returning to normal 3 to 5 days postflight. Subnormal red cell count, hemoglobin concentration, and hematocrit values also returned gradually to preflight limits. Most pronounced changes were found in the shape of red blood cells during extended space missions with a rapid reversal of these changes upon reentry into a normal gravitational environment.

Assay of 6-thioinosinic acid and 6-thioguanine nucleotides, active metabolites of 6-mercaptopurine, in human red blood cells.

PubMed

Lennard, L

1987-12-25

A highly sensitive reversed-phase high-performance liquid chromatographic assay, with ultraviolet detection, for 6-thioinosinic acid and the 6-thioguanine nucleotides (6TGNs) was developed. The 6TGNs are major red blood cell metabolites of the immunosuppressive agent azathioprine and the cytotoxic drugs 6-thioguanine and 6-mercaptopurine. The assay is based on the specific extraction, via phenyl mercury adduct formation, of the thiopurine released on acid hydrolysis of the thionucleotide metabolite. Red blood cell 6TGN concentrations in eighteen leukaemic children receiving chronic 6-mercaptopurine chemotherapy were measured and compared to a previously published spectrophotofluorometric assay. Linear regression analysis gave r = 0.991; P less than 0.001; y = 40 + 0.94x.

Anthocyanin and flavonoid production from Perilla frutescens: pilot plant scale processing including cross-flow microfiltration and reverse osmosis.

PubMed

Meng, Linghua; Lozano, Yves; Bombarda, Isabelle; Gaydou, Emile; Li, Bin

2006-06-14

Extraction and concentration at a pilot plant scale of anthocyanins and flavonoids from Perilla frutescens var. frutescens harvested in the Guangzhou area of China were investigated. The study of extraction efficiency using mineral acids and organic acids showed that 0.01 mol/L nitric acid was the most suitable to extract flavonoids from this slightly red leaf cultivar. The red extract contained 12 mg/L (as cyanidin equivalent) anthocyanins and other flavones. The multistep process included cross-flow microfiltration (CFM) with a ceramic type membrane, reverse osmosis (RO), and rotating evaporation (RE). The filtration fluxes were high and constant for CFM (150 L/h/m2 at 0.6 b) and for RO (22 L/h/m2 at 40 b). The red extract was concentrated 9.4 times by RO and then 5.4 times by RE. It contained 422 mg/L anthocyanins, representing 77% of the total extracted anthocyanin. The proportion of flavonoids was found unchanged during processing. The concentrated extract showed a pH of 2.7, and its free acidity was found to be 46% of the acidity added for extraction, because of the buffering capacity of the extract. At the concentration level reached, a crystallized deposit occurred and was identified as tartrate.

Evolutionary innovation and diversification of carotenoid-based pigmentation in finches.

PubMed

Ligon, Russell A; Simpson, Richard K; Mason, Nicholas A; Hill, Geoffrey E; McGraw, Kevin J

2016-12-01

The ornaments used by animals to mediate social interactions are diverse, and by reconstructing their evolutionary pathways we can gain new insights into the mechanisms underlying ornamental innovation and variability. Here, we examine variation in plumage carotenoids among the true finches (Aves: Fringillidae) using biochemical and comparative phylogenetic analyses to reconstruct the evolutionary history of carotenoid states and evaluate competing models of carotenoid evolution. Our comparative analyses reveal that the most likely ancestor of finches used dietary carotenoids as yellow plumage colorants, and that the ability to metabolically modify dietary carotenoids into more complex pigments arose secondarily once finches began to use modified carotenoids to create red plumage. Following the evolutionary "innovation" that enabled modified red carotenoid pigments to be deposited as plumage colorants, many finch species subsequently modified carotenoid biochemical pathways to create yellow plumage. However, no reversions to dietary carotenoids were observed. The finding that ornaments and their underlying mechanisms may be operating under different selection regimes-where ornamental trait colors undergo frequent reversions (e.g., between red and yellow plumage) while carotenoid metabolization mechanisms are more conserved-supports a growing empirical framework suggesting different evolutionary patterns for ornaments and the mechanistic innovations that facilitate their diversification. © 2016 The Author(s). Evolution © 2016 The Society for the Study of Evolution.

Effect of temperature acclimation on red blood cell oxygen affinity in Pacific bluefin tuna (Thunnus orientalis) and yellowfin tuna (Thunnus albacares).

PubMed

Lilly, Laura E; Bonaventura, Joseph; Lipnick, Michael S; Block, Barbara A

2015-03-01

Hemoglobin-oxygen (Hb-O2) binding properties are central to aerobic physiology, and must be optimized for an animal's aerobic requirements and environmental conditions, both of which can vary widely with seasonal changes or acutely with diving. In the case of tunas, the matter is further complicated by large regional temperature differences between tissues within the same animal. This study investigates the effects of thermal acclimation on red blood cell Hb-O2 binding in Pacific bluefin tuna (T. orientalis) and yellowfin tuna (T. albacares) maintained in captive tanks at acclimation temperatures of 17°, 20° and 24 °C. Oxygen binding properties of acclimated tuna isolated red blood cells were examined under varying experimental temperatures (15°-35 °C) and CO2 levels (0%, 0.5% and 1.5%). Results for Pacific bluefin tuna produced temperature-independence at 17 °C- and 20 °C-acclimation temperatures and significant reverse temperature-dependence at 24 °C-acclimation in the absence of CO2, with instances of reverse temperature-dependence in 17 °C- and 24 °C-acclimations at 0.5% and 1.5% CO2. In contrast, yellowfin tuna produced normal temperature-dependence at each acclimation temperature at 0% CO2, temperature-independence at 0.5% and 1.5% CO2, and significant reverse temperature-dependence at 17 °C-acclimation and 0.5% CO2. Thermal acclimation of Pacific bluefin tuna increased O2 binding affinity of the 17 °C-acclimation group, and produced a significantly steeper oxygen equilibrium curve slope (nH) at 24 °C-acclimation compared to the other acclimation temperatures. We discuss the potential implications of these findings below. Copyright © 2014 Elsevier Inc. All rights reserved.

Novel robust cellulose-based foam with pH and light dual-response for oil recovery

NASA Astrophysics Data System (ADS)

Wang, Qian; Meng, Guihua; Wu, Jianning; Wang, Yixi; Liu, Zhiyong; Guo, Xuhong

2018-05-01

We fabricated pH and light dual-responsive adsorption materials which could induce the transition of surface wettability between hydrophobicity and hydrophilicity by using ATRP. The structure and morphology of adsorption materials were confirmed by ATR-FTIR, XPS, TGA and SEM. It showed that the modified cellulose (CE)-based foam was hydrophobic, which can adsorb a range of oils and organic solvents in water under pH = 7.0 or visible light irradiation (λ > 500 nm). Meanwhile, the wettability of robust CE-based foam can convert hydrophobicity into hydrophilicity and underwater oleophobicity under pH = 3.0 or UV irradiation (λ = 365 nm), giving rise to release oils and organic solvents. Most important of all, the adsorption and desorption processes of the modified CE-based foam could be switched by external stimuli. Furthermore, the modified CE-based foam was not damaged and still retained original performance after reversible cycle repeated for many times with variation of surface wettability. In short, it indicates that CE-based foam materials with switchable surface wettability are new responsive absorbent materials and have owned potential application in the treatment of oil recovery.

Solution-processed phase-change VO(2) metamaterials from colloidal vanadium oxide (VO(x)) nanocrystals.

PubMed

Paik, Taejong; Hong, Sung-Hoon; Gaulding, E Ashley; Caglayan, Humeyra; Gordon, Thomas R; Engheta, Nader; Kagan, Cherie R; Murray, Christopher B

2014-01-28

We demonstrate thermally switchable VO2 metamaterials fabricated using solution-processable colloidal nanocrystals (NCs). Vanadium oxide (VOx) NCs are synthesized through a nonhydrolytic reaction and deposited from stable colloidal dispersions to form NC thin films. Rapid thermal annealing transforms the VOx NC thin films into monoclinic, nanocrystalline VO2 thin films that show a sharp, reversible metal-insulator phase transition. Introduction of precise concentrations of tungsten dopings into the colloidal VOx NCs enables the still sharp phase transition of the VO2 thin films to be tuned to lower temperatures as the doping level increases. We fabricate "smart", differentially doped, multilayered VO2 films to program the phase and therefore the metal-insulator behavior of constituent vertically structured layers with temperature. With increasing temperature, we tailored the optical response of multilayered films in the near-IR and IR regions from that of a strong light absorber, in a metal-insulator structure, to that of a Drude-like reflector, characteristic of a pure metallic structure. We demonstrate that nanocrystal-based nanoimprinting can be employed to pattern multilayered subwavelength nanostructures, such as three-dimensional VO2 nanopillar arrays, that exhibit plasmonic dipolar responses tunable with a temperature change.

Switchable nanoassembly from an azobenzene-containing dye.

PubMed

Wang, Jing; Ha, Chang-Sik

2011-07-01

In this work, we investigated optical properties and the morphology of the amphiphilic azobenzene dye 1 containing hydroxyl azobenzene and C10 alkyl chains. Since the hydroxyl group on 1 has a pKa of 9.38, the deprotonation of the hydroxyl group occurs at pH > pKa (9.38) and thus the 1 nanoparticles are negatively charged. The deprotonated hydroxyl group is hydrophilic relative to the long alkyl chain that is hydrophobic, while the hydrophobic and hydrophilic parts are connected by covalent bonds. When such an azobenzene molecule 1 with both hydrophobic and hydrophilic groups exists in solution, "self-aggregation" may occur due to the hydrophobic interaction between the long alkyl chains. The scattered morphology at pH 7.0 (neutral state) and the aggregated morphology at pH 10.5 (anionic state) of 1 were demostrated by transmission electron microscopy (TEM) and atomic force microscopy (AFM) images. Formation of supramolecular aggregation-induced vesicular-like structures are highly interesting due to the ability to respond to external triggers, pH. The pH value can be reversed by adding acid or base to the system, that is, switching the aggregation "on" and "off" can be repeated.

Logic gate system with three outputs and three inputs based on switchable electrocatalysis of glucose by glucose oxidase entrapped in chitosan films.

PubMed

Liu, Shuang; Wang, Lei; Lian, Wenjing; Liu, Hongyun; Li, Chen-Zhong

2015-01-01

A logic-gate system with three outputs and three inputs was developed based on the bioelectrocatalysis of glucose by glucose oxidase (GOx) entrapped in chitosan films on the electrode surface by means of ferrocenedicarboxylic acid (Fc(COOH)2 ). Cyclic voltammetric (CV) signals of Fc(COOH)2 exhibited pH-triggered on/off behavior owing to electrostatic interactions between the film and the probe at different pH levels. The addition of glucose greatly increased the oxidation peak current (Ipa ) through the electrocatalytic reaction. pH and glucose were selected as two inputs. As a reversible inhibitor of GOx, Cu(2+) was chosen as the third input. The combination of three inputs led to Ipa with different values according to different mechanisms, which were defined as three outputs with two thresholds. The logic gate with three outputs by using one type of enzyme provided a novel model to build logic circuits based on biomacromolecules, which might be applied to the intelligent medical diagnostics as smart biosensors in the future. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Direct Laser Writing-Based Programmable Transfer Printing via Bioinspired Shape Memory Reversible Adhesive.

PubMed

Huang, Yin; Zheng, Ning; Cheng, Zhiqiang; Chen, Ying; Lu, Bingwei; Xie, Tao; Feng, Xue

2016-12-28

Flexible and stretchable electronics offer a wide range of unprecedented opportunities beyond conventional rigid electronics. Despite their vast promise, a significant bottleneck lies in the availability of a transfer printing technique to manufacture such devices in a highly controllable and scalable manner. Current technologies usually rely on manual stick-and-place and do not offer feasible mechanisms for precise and quantitative process control, especially when scalability is taken into account. Here, we demonstrate a spatioselective and programmable transfer strategy to print electronic microelements onto a soft substrate. The method takes advantage of automated direct laser writing to trigger localized heating of a micropatterned shape memory polymer adhesive stamp, allowing highly controlled and spatioselective switching of the interfacial adhesion. This, coupled to the proper tuning of the stamp properties, enables printing with perfect yield. The wide range adhesion switchability further allows printing of hybrid electronic elements, which is otherwise challenging given the complex interfacial manipulation involved. Our temperature-controlled transfer printing technique shows its critical importance and obvious advantages in the potential scale-up of device manufacturing. Our strategy opens a route to manufacturing flexible electronics with exceptional versatility and potential scalability.

Novel robust cellulose-based foam with pH and light dual-response for oil recovery

NASA Astrophysics Data System (ADS)

Wang, Qian; Meng, Guihua; Wu, Jianning; Wang, Yixi; Liu, Zhiyong; Guo, Xuhong

2018-06-01

We fabricated pH and light dual-responsive adsorption materials which could induce the transition of surface wettability between hydrophobicity and hydrophilicity by using ATRP. The structure and morphology of adsorption materials were confirmed by ATR-FTIR, XPS, TGA and SEM. It showed that the modified cellulose (CE)-based foam was hydrophobic, which can adsorb a range of oils and organic solvents in water under pH = 7.0 or visible light irradiation ( λ > 500 nm). Meanwhile, the wettability of robust CE-based foam can convert hydrophobicity into hydrophilicity and underwater oleophobicity under pH = 3.0 or UV irradiation ( λ = 365 nm), giving rise to release oils and organic solvents. Most important of all, the adsorption and desorption processes of the modified CE-based foam could be switched by external stimuli. Furthermore, the modified CE-based foam was not damaged and still retained original performance after reversible cycle repeated for many times with variation of surface wettability. In short, it indicates that CE-based foam materials with switchable surface wettability are new responsive absorbent materials and have owned potential application in the treatment of oil recovery.

Paleomagnetic evidence bearing on Tertiary tectonics of the Tihamat Asir coastal plain, southwestern Saudi Arabia

USGS Publications Warehouse

Kellogg, K.S.; Blank, H.R.

1982-01-01

Paleomagnetic directions determined for an upper Oligocene to lower Miocene dike swarm and from two lower Miocene layered gabbros in the Tihamat Asir coastal plain of southwestern Saudi Arabia are used to test several hypotheses concerning the tectonics of rifting along the eastern margin of the Red Sea. The dikes and gabbros were emplaced during the initial phases of Red Sea rifting and may mark the transition between continental and oceanic crust. Although these rocks have been hydrothermally altered to varying degrees, reliable remanent directions after alternating-field demagnetization were obtained for 23 dikes and for gabbros at Jabal at Tirf and Wadi Liyyah. Twelve of the dikes are reversely magnetized. After the directions of the reversely magnetized dikes are inverted 180?, the mean direction calculated for the normal dikes is approximately 24? more downward than that calculated for the reversed dikes. This result is similar to that found for the As Sarat volcanic field, 100 km to the north, and may be due to a displaced dipole source for the field. The unrotated mean remanent direction for the dikes (inverting reversed dike directions 180?) is D (declination) = 353.2? and I (inclination) = 6.8? with a95 (radius of the cone of 95 percent confidence) = 8.9? whereas directions from the Jabal at Tirf and Wadi Liyyah gabbros lie at D = 176.2?, I = -1.6? (a95 = 7 1 ?) and D = 17.1?, I = 16.3? (a 95 = 8.7?), respectively. Comparing these results with the results from the As Sarat volcanic field, all the paleomagnetic evidence supports a model for approximately 20 ? of westward tilting of the Wadi Damad and Wadi Jizan areas after the emplacement of the Jabal at Tiff gabbro. The Wadi Liyyah area may have been tilted even more toward the Red Sea. The paleomagnetic directions from three widely separated localities in the Jabal at Tirf gabbro are not significantly different, a fact which indicates that the body cooled in approximately its present bowl shape. Evidence suggests that the ratio of normal to reversed dikes may change significantly along a 6-km-long traverse normal to the trend of the dike swarm, possibly reflecting migration of .a spreading axis.

A Comparison of Red Cell Rejuvenation versus Mechanical Washing for the Prevention of Transfusion-associated Organ Injury in Swine.

PubMed

Woźniak, Marcin J; Qureshi, Saqib; Sullo, Nikol; Dott, William; Cardigan, Rebecca; Wiltshire, Michael; Nath, Mintu; Patel, Nishith N; Kumar, Tracy; Goodall, Alison H; Murphy, Gavin J

2018-02-01

We evaluated the effects of two interventions that modify the red cell storage lesion on kidney and lung injury in experimental models of transfusion. White-landrace pigs (n = 32) were allocated to receive sham transfusion (crystalloid), 14-day stored allogeneic red cells, 14-day red cells washed using the red cells washing/salvage system (CATS; Fresenius, Germany), or 14-day red cells rejuvenated using the inosine solution (Rejuvesol solution; Zimmer Biomet, USA) and washed using the CATS device. Functional, biochemical, and histologic markers of organ injury were assessed for up to 24 h posttransfusion. Transfusion of 14 day red cells resulted in lung injury (lung injury score vs. sham, mean difference -0.3 (95% CI, -0.6 to -0.1; P = 0.02), pulmonary endothelial dysfunction, and tissue leukocyte sequestration. Mechanical washing reduced red cell-derived microvesicles but increased cell-free hemoglobin in 14-day red cell units. Transfusion of washed red cells reduced leukocyte sequestration but did not reduce the lung injury score (mean difference -0.2; 95% CI, -0.5 to 0.1; P = 0.19) relative to 14-day cells. Transfusion of washed red cells also increased endothelial activation and kidney injury. Rejuvenation restored adenosine triphosphate to that of fresh red cells and reduced microvesicle concentrations without increasing cell-free hemoglobin release. Transfusion of rejuvenated red cells reduced plasma cell-free hemoglobin, leukocyte sequestration, and endothelial dysfunction in recipients and reduced lung and kidney injury relative to 14-day or washed 14-day cells. Reversal of the red cell storage lesion by rejuvenation reduces transfusion-associated organ injury in swine.

Alcohol consumption stimulates early steps in reverse cholesterol transport.

PubMed

van der Gaag, M S; van Tol, A; Vermunt, S H; Scheek, L M; Schaafsma, G; Hendriks, H F

2001-12-01

Alcohol consumption is associated with increased HDL cholesterol levels, which may indicate stimulated reverse cholesterol transport. The mechanism is, however, not known. The aim of this study was to evaluate the effects of alcohol consumption on the first two steps of the reverse cholesterol pathway: cellular cholesterol efflux and plasma cholesterol esterification. Eleven healthy middle-aged men consumed four glasses (40 g of alcohol) of red wine, beer, spirits (Dutch gin), or carbonated mineral water (control) daily with evening dinner, for 3 weeks, according to a 4 x 4 Latin square design. After 3 weeks of alcohol consumption the plasma ex vivo cholesterol efflux capacity, measured with Fu5AH cells, was raised by 6.2% (P < 0.0001) and did not differ between the alcoholic beverages. Plasma cholesterol esterification was increased by 10.8% after alcohol (P = 0.008). Changes were statistically significant after beer and spirits, but not after red wine consumption (P = 0.16). HDL lipids changed after alcohol consumption; HDL total cholesterol, HDL cholesteryl ester, HDL free cholesterol, HDL phospholipids and plasma apolipoprotein A-I all increased (P < 0.01). In conclusion, alcohol consumption stimulates cellular cholesterol efflux and its esterification in plasma. These effects were mostly independent of the kind of alcoholic beverage

Unveiling characteristics of a bioelectrochemical system with polarity reversion for simultaneous azo dye treatment and bioelectricity generation.

PubMed

Sun, Jian; Zhang, Yaping; Liu, Guoguang; Ning, Xunan; Wang, Yujie; Liu, Jingyong

2015-09-01

A novel bioelectrochemical system (BES) operated with polarity reversion was explored for simultaneous anaerobic/aerobic treatment of azo dye and production of bioelectricity under extremely low buffer. The Congo red was first decolorized in anode, with completed color removal in 35 h. The resultant decolorization intermediates were then mineralized after the anode reversed to aerobic biocathode, evidenced by 55 % chemical oxygen demand (COD) removal in 200 h. The mineralization efficiency was further increased to 70 % when the period of the half-cycle was prolonged to 375 h. Meanwhile, the BES produced a continuous stable positive/negative alternate voltage output under 5 mM phosphate buffer because of the self-neutralization of the accumulated protons and hydroxyl ions in electrolyte. The electrode performance was significantly improved, which was indicated by alleviated electrode polarization, due to in situ use of accumulated protons and hydroxyl ions and enhanced electron transfer in the presence of Congo red and its degradation intermediates, which resulted in 1.05-fold increases in maximum power density (67.5 vs. 32.9 mW/m(2)). An analysis of the microbial diversity in the biofilm revealed that the biofilm was dominated by facultative bacteria with functional roles in contaminant degradation and electricity generation.

The crystal structure of red fluorescent protein TagRFP-T reveals the mechanism of its superior photostability

DOE Office of Scientific and Technical Information (OSTI.GOV)

Liu, Rui; Liang, Qing-Nan; Du, Shu-Qi

2016-08-19

The red fluorescent protein variant TagRFP-T has greatly improved photostability over its parent molecule, TagRFP, but the underlying mechanism leading to this improvement is to date unknown. The 1.95 Å resolution crystallographic structure of TagRFP-T showed that its chromophore exists as a mixture of cis and trans coplanar isomers in roughly equal proportions. Interestingly, both isomers are able to fluoresce, a property that has never been observed in any other fluorescent protein. We propose a “circular restoration model” for TagRFP-T to explain its superior photostability: There are four co-existing chromophore states (cis/trans protonated/ionized state) that can be driven by light tomore » transform from one state into another. This model also explains how TagRPF-T essentially eliminates the temporary dark state (reversible photobleaching). - Highlights: • The 1.95 Å resolution crystal structure of TagRFP-T was determined. • The chromophore of TagRFP-T contains a mixture of cis and trans coplanar isomers. • A “circular restoration model” was proposed to explain the superior photostability. • The chromophore can reversibly convert between cis/trans protonated/ionized states. • The light-driven conversion reduce the dark state (reversible photobleaching).« less

Reversal of orbital angular momentum arising from an extreme Doppler shift

PubMed Central

Toninelli, Ermes; Horsley, Simon A. R.; Hendry, Euan; Phillips, David B.; Padgett, Miles J.

2018-01-01

The linear Doppler shift is familiar as the rise and fall in pitch of a siren as it passes by. Less well known is the rotational Doppler shift, proportional to the rotation rate between source and receiver, multiplied by the angular momentum carried by the beam. In extreme cases the Doppler shift can be larger than the rest-frame frequency and for a red shift, the observed frequency then becomes “negative.” In the linear case, this effect is associated with the time reversal of the received signal, but it can be observed only with supersonic relative motion between the source and receiver. However, the rotational case is different; if the radius of rotation is smaller than the wavelength, then the velocities required to observe negative frequencies are subsonic. Using an acoustic source at ≈100 Hz we create a rotational Doppler shift larger than the laboratory-frame frequency. We observe that once the red-shifted wave passes into the “negative frequency” regime, the angular momentum associated with the sound is reversed in sign compared with that of the laboratory frame. These low-velocity laboratory realizations of extreme Doppler shifts have relevance to superoscillatory fields and offer unique opportunities to probe interactions with rotating bodies and aspects of pseudorelativistic frame translation. PMID:29581257

Fluorescent reversible regulation based on the interactions of topotecan hydrochloride, neutral red and quantum dots

NASA Astrophysics Data System (ADS)

Wang, Linlin; Shen, Yizhong; Liu, Shaopu; Yang, Jidong; Liang, Wanjun; Li, Dan; He, Youqiu

2015-02-01

The interactions of topotecan hydrochloride (THC), neutral red (NR) and thioglycolic acid (TGA) capped CdTe/CdS quantum dots (QDs) built a solid base for the controlling of the fluorescent reversible regulation of the system. This study was developed by means of ultraviolet-visible (UV-vis) absorption, fluorescence (FL), resonance Rayleigh scattering (RRS) spectroscopy and transmission electron microscopy (TEM). Corresponding experimental results revealed that the fluorescence of TGA-CdTe/CdS QDs could be effectively quenched by NR, while the RRS of the QDs enhanced gradually with the each increment of NR concentration. After the addition of THC, the strong covalent conjugation between NR and THC which was in carboxylate state enabled NR to be dissociated from the surface of TGA-CdTe/CdS QDs to form more stable complex with THC, thereby enhancing the fluorescence of the TGA-CdTe/CdS QDs-NR system. What is more, through analyzing the optical properties and experimental data of the reaction between TGA-CdTe/CdS QDs and NR, the possible reaction mechanism of the whole system was discussed. This combination of multiple spectroscopic techniques could contribute to the investigation for the fluorescent reversible regulation of QDs and a method could also be established to research the interactions between camptothecin drugs and dyes.

Deep-Red Fluorescent Gold Nanoclusters for Nucleoli Staining: Real-Time Monitoring of the Nucleolar Dynamics in Reverse Transformation of Malignant Cells.

PubMed

Wang, Xiaojuan; Wang, Yanan; He, Hua; Ma, Xiqi; Chen, Qi; Zhang, Shuai; Ge, Baosheng; Wang, Shengjie; Nau, Werner M; Huang, Fang

2017-05-31

Nucleoli are important subnuclear structures inside cells. We report novel fluorescent gold nanoclusters (K-AuNCs) that are able to stain the nucleoli selectively and make it possible to explore the nucleolar morphology with fluorescence imaging technique. This novel probe is prepared through an easy synthesis method by employing a tripeptide (Lys-Cys-Lys) as the surface ligand. The properties, including deep-red fluorescence emission (680 nm), large Stocks shift, broad excitation band, low cytotoxicity, and good photostability, endow this probe with potential for bioanalytical applications. Because of their small size and their positively charged surface, K-AuNCs are able to accumulate efficiently at the nucleolar regions and provide precise morphological information. K-AuNCs are also used to monitor the nucleolar dynamics along the reverse-transformation process of malignant cells, induced by the agonist of protein A, 8-chloro-cyclic adenosine monophosphate. This gives a novel approach for investigating the working mechanism of antitumor drugs.

Reverse Engineering Applied to Red Human Hair Pheomelanin Reveals Redox-Buffering as a Pro-Oxidant Mechanism

PubMed Central

Kim, Eunkyoung; Panzella, Lucia; Micillo, Raffaella; Bentley, William E.; Napolitano, Alessandra; Payne, Gregory F.

2015-01-01

Pheomelanin has been implicated in the increased susceptibility to UV-induced melanoma for people with light skin and red hair. Recent studies identified a UV-independent pathway to melanoma carcinogenesis and implicated pheomelanin’s pro-oxidant properties that act through the generation of reactive oxygen species and/or the depletion of cellular antioxidants. Here, we applied an electrochemically-based reverse engineering methodology to compare the redox properties of human hair pheomelanin with model synthetic pigments and natural eumelanin. This methodology exposes the insoluble melanin samples to complex potential (voltage) inputs and measures output response characteristics to assess redox activities. The results demonstrate that both eumelanin and pheomelanin are redox-active, they can rapidly (sec-min) and repeatedly redox-cycle between oxidized and reduced states, and pheomelanin possesses a more oxidative redox potential. This study suggests that pheomelanin’s redox-based pro-oxidant activity may contribute to sustaining a chronic oxidative stress condition through a redox-buffering mechanism. PMID:26669666

Reverse Engineering Applied to Red Human Hair Pheomelanin Reveals Redox-Buffering as a Pro-Oxidant Mechanism.

PubMed

Kim, Eunkyoung; Panzella, Lucia; Micillo, Raffaella; Bentley, William E; Napolitano, Alessandra; Payne, Gregory F

2015-12-16

Pheomelanin has been implicated in the increased susceptibility to UV-induced melanoma for people with light skin and red hair. Recent studies identified a UV-independent pathway to melanoma carcinogenesis and implicated pheomelanin's pro-oxidant properties that act through the generation of reactive oxygen species and/or the depletion of cellular antioxidants. Here, we applied an electrochemically-based reverse engineering methodology to compare the redox properties of human hair pheomelanin with model synthetic pigments and natural eumelanin. This methodology exposes the insoluble melanin samples to complex potential (voltage) inputs and measures output response characteristics to assess redox activities. The results demonstrate that both eumelanin and pheomelanin are redox-active, they can rapidly (sec-min) and repeatedly redox-cycle between oxidized and reduced states, and pheomelanin possesses a more oxidative redox potential. This study suggests that pheomelanin's redox-based pro-oxidant activity may contribute to sustaining a chronic oxidative stress condition through a redox-buffering mechanism.

Test Excavations at 3LA128. An Early Caddo Occupation on the Red River.

DTIC Science & Technology

1982-04-15

aberact entered in Block 20, It different frot Report) IS. SUPPLEMENTARY NOTES It. KEY WORDS (Continue on reverse side It necessary end Identify by... block number) ! l SITNT’ (CCOlMnue as reverse shb N ne"myaj dad identify by block nmbet) t7The Arkansas Acheological Survey tested site 37.A128 under...Purchase Order DACW29-81-M-0165 on the Field Revetment for the New Orleans District Office of the U.S. Army Corps of Engineers to gather data for

Far-red light is needed for efficient photochemistry and photosynthesis.

PubMed

Zhen, Shuyang; van Iersel, Marc W

2017-02-01

The efficiency of monochromatic light to drive photosynthesis drops rapidly at wavelengths longer than 685nm. The photosynthetic efficiency of these longer wavelengths can be improved by adding shorter wavelength light, a phenomenon known as the Emerson enhancement effect. The reverse effect, the enhancement of photosynthesis under shorter wavelength light by longer wavelengths, however, has not been well studied and is often thought to be insignificant. We quantified the effect of adding far-red light (peak at 735nm) to red/blue or warm-white light on the photosynthetic efficiency of lettuce (Lactuca sativa). Adding far-red light immediately increased quantum yield of photosystem II (Φ PSII ) of lettuce by an average of 6.5 and 3.6% under red/blue and warm-white light, respectively. Similar or greater increases in Φ PSII were observed after 20min of exposure to far-red light. This longer-term effect of far-red light on Φ PSII was accompanied by a reduction in non-photochemical quenching of fluorescence (NPQ), indicating that far-red light reduced the dissipation of absorbed light as heat. The increase in Φ PSII and complementary decrease in NPQ is presumably due to preferential excitation of photosystem I (PSI) by far-red light, which leads to faster re-oxidization of the plastoquinone pool. This facilitates reopening of PSII reaction centers, enabling them to use absorbed photons more efficiently. The increase in Φ PSII by far-red light was associated with an increase in net photosynthesis (P n ). The stimulatory effect of far-red light increased asymptotically with increasing amounts of far-red. Overall, our results show that far-red light can increase the photosynthetic efficiency of shorter wavelength light that over-excites PSII. Copyright © 2016 Elsevier GmbH. All rights reserved.

Novel type of red-shifted chlorophyll a antenna complex from Chromera velia. I. Physiological relevance and functional connection to photosystems.

PubMed

Kotabová, Eva; Jarešová, Jana; Kaňa, Radek; Sobotka, Roman; Bína, David; Prášil, Ondřej

2014-06-01

Chromera velia is an alveolate alga associated with scleractinian corals. Here we present detailed work on chromatic adaptation in C. velia cultured under either blue or red light. Growth of C. velia under red light induced the accumulation of a light harvesting antenna complex exhibiting unusual spectroscopic properties with red-shifted absorption and atypical 710nm fluorescence emission at room temperature. Due to these characteristic features the complex was designated "Red-shifted Chromera light harvesting complex" (Red-CLH complex). Its detailed biochemical survey is described in the accompanying paper (Bina et al. 2013, this issue). Here, we show that the accumulation of Red-CLH complex under red light represents a slow acclimation process (days) that is reversible with much faster kinetics (hours) under blue light. This chromatic adaptation allows C. velia to maintain all important parameters of photosynthesis constant under both light colors. We further demonstrated that the C. velia Red-CLH complex is assembled from a 17kDa antenna protein and is functionally connected to photosystem II as it shows variability of chlorophyll fluorescence. Red-CLH also serves as an additional locus for non-photochemical quenching. Although overall rates of oxygen evolution and carbon fixation were similar for both blue and red light conditions, the presence of Red-CLH in C. velia cells increases the light harvesting potential of photosystem II, which manifested as a doubled oxygen evolution rate at illumination above 695nm. This data demonstrates a remarkable long-term remodeling of C. velia light-harvesting system according to light quality and suggests physiological significance of 'red' antenna complexes. Copyright © 2014 Elsevier B.V. All rights reserved.

Superphobicity/philicity Janus Fabrics with Switchable, Spontaneous, Directional Transport Ability to Water and Oil Fluids

PubMed Central

Zhou, Hua; Wang, Hongxia; Niu, Haitao; Lin, Tong

2013-01-01

Herein we demonstrate that switchable, spontaneous, directional-transport ability to both water and oil fluids can be created on fabric materials through wet-chemistry coating and successive UV irradiation treatment. When the fabric showed directional transport to a liquid, it prevented liquids of higher surface tension from penetration, but allowed liquids of lower surface tension to permeate, from either side. The directional transport ability can be switched from one fluid to another simply by heating the fabric at an elevated temperature and then re-irradiating the fabric with UV light for required period of time. By attaching liquid drops vertically upwards to a horizontally-laid fabric, we further demonstrated that this novel directional fluid transport was an automatic process driven by surface property alone, irrespective of gravity's effect. This novel fabric may be useful for development of “smart” textiles and functional membranes for various applications. PMID:24129357

Switchable in-line monitor for multi-dimensional multiplexed photonic integrated circuit.

PubMed

Chen, Guanyu; Yu, Yu; Ye, Mengyuan; Zhang, Xinliang

2016-06-27

A flexible monitor suitable for the discrimination of on-chip transmitted mode division multiplexed (MDM) and wavelength division multiplexed (WDM) signals is proposed and fabricated. By selectively extracting part of the incoming signals through the tunable wavelength and mode dependent drop filter, the in-line and switchable monitor can discriminate the wavelength, mode and power information of the transmitted signals. Being different from a conventional mode and wavelength demultiplexer, the monitor is specifically designed to ensure a flexible in-line monitoring. For demonstration, three mode and three wavelength multiplexed signals are successfully processed. Assisted by the integrated photodetectors (PDs), both the measured photo currents and eye diagrams validate the performance of the proposed device. The bit error ratio (BER) measurement results show less than 0.4 dB power penalty between different modes and ~2 dB power penalty for single wavelength and WDM cases under 10^-9 BER level.

2D-3D switchable display based on a passive polymeric lenticular lens array and electrically suppressed ferroelectric liquid crystal.

PubMed

Shi, Liangyu; Srivastava, Abhishek Kumar; Wai Tam, Alwin Ming; Chigrinov, Vladimir Grigorievich; Kwok, Hoi Sing

2017-09-01

We reveal a 2D-3D switchable lens unit that is based on a polarization-sensitive microlens array and a polarization selector unit made of an electrically suppressed helix ferroelectric liquid crystal (ESHFLC) cell. The ESHFLCs offer a high contrast ratio (∼10k∶1) between the crossed polarizers at a low applied electric field (∼1.7  V/μm) with a small switching time (<50  μs). A special driving scheme, to switch between a 2D and 3D mode, has been developed to avoid unwanted issues related to DC accumulation in the ferroelectric liquid crystal without affecting its optical quality. The proposed lens unit is characterized by low power consumption, ultrafast response, and 3D crosstalk <5%, and can therefore find application in TVs, cell phones, etc.

Microsecond switchable thermal antenna

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ben-Abdallah, Philippe, E-mail: pba@institutoptique.fr; Benisty, Henri; Besbes, Mondher

2014-07-21

We propose a thermal antenna that can be actively switched on and off at the microsecond scale by means of a phase transition of a metal-insulator material, the vanadium dioxide (VO{sub 2}). This thermal source is made of a periodically patterned tunable VO{sub 2} nanolayer, which support a surface phonon-polariton in the infrared range in their crystalline phase. Using electrodes properly registered with respect to the pattern, the VO{sub 2} phase transition can be locally triggered by ohmic heating so that the surface phonon-polariton can be diffracted by the induced grating, producing a highly directional thermal emission. Conversely, when heatingmore » less, the VO{sub 2} layers cool down below the transition temperature, the surface phonon-polariton cannot be diffracted anymore so that thermal emission is inhibited. This switchable antenna could find broad applications in the domain of active thermal coatings or in those of infrared spectroscopy and sensing.« less

Structure-Function Study of Tertiary Amines as Switchable Polarity Solvents

DOE Office of Scientific and Technical Information (OSTI.GOV)

Aaron D. Wilson; Frederick F. Stewart

2014-02-01

A series of tertiary amines have been screened for their function as switchable polarity solvents (SPS). The relative ratios of tertiary amine and carbonate species as well as maximum possible concentration were determined through quantitative 1H and 13C NMR spectroscopy. The viscosities of the polar SPS solutions were measured and ranged from near water in dilute systems through to gel formation at high concentrations. The van't Hoff indices for SPS solutions were measured through freezing point depression studies as a proxy for osmotic pressures. A new form of SPS with an amine : carbonate ratio significantly greater than unity hasmore » been identified. Tertiary amines that function as SPS at ambient pressures appear to be limited to molecules with fewer than 12 carbons. The N,N-dimethyl-n-alkylamine structure has been identified as important to the function of an SPS.« less

Rational Design of a Green-Light-Mediated Unimolecular Platform for Fast Switchable Acidic Sensing.

PubMed

Zhou, Yunyun; Zou, Qi; Qiu, Jing; Wang, Linjun; Zhu, Liangliang

2018-02-01

A controllable sensing ability strongly connects to complex and precise events in diagnosis and treatment. However, imposing visible light into the molecular-scale mediation of sensing processes is restricted by the lack of structural relevance. To address this critical challenge, we present the rational design, synthesis, and in vitro studies of a novel cyanostyryl-modified azulene system for green-light-mediated fast switchable acidic sensing. The advantageous features of the design include a highly efficient green-light-driven Z/E-isomerization (a quantum yield up to 61.3%) for fast erasing chromatic and luminescent expressions and a superior compatibility with control of ratiometric protonation. Significantly, these merits of the design enable the development of a microfluidic system to perform a green-light-mediated reusable sensing function toward a gastric acid analyte in a miniaturized platform. The results may provide new insights for building future integrated green materials.

Switchable and tunable dual-wavelength Er-doped fiber ring laser with single-frequency lasing wavelengths

NASA Astrophysics Data System (ADS)

Zhang, Haiwei; Shi, Wei; Bai, Xiaolei; Sheng, Quan; Xue, Lifang; Yao, Jianquan

2018-02-01

We obtain a switchable and tunable dual-wavelength single-frequency Er-doped ring fiber laser. In order to realize single-longitudinal output, two saturable-absorber-based tracking narrow-band filters are formed in 3- meter-long unpumped Er-doped fiber to narrow the linewidth via using the PM-FBG as a reflection filter. The maximum output power is 2.11 mW centered at 1550.16 nm and 1550.54 nm when the fiber laser operates in dual-wavelength mode. The corresponding linewidths of those two wavelengths are measured to be 769 Hz and 673 Hz, respectively. When the temperature around the PM-FBG is changed from 15 °C to 55 °C, the dual-wavelength single-frequency fiber laser can be tuned from 1550.12 nm to 1550.52 nm and from 1550.49 nm to 1550.82 nm, respectively.

Achieving dynamic switchable filter based on a transmutable metasurface using SMA

NASA Astrophysics Data System (ADS)

Chen, Xin; Gao, Jinsong; Kang, Bonan

2017-09-01

We propose a switchable filter composed of transmutable array using shape memory alloys (SMA). It could exhibit a temperature induced morphology change spontaneously like the biological excitability, acting as a shutter that allows the incident energy to be selectively transmitted or reflected with in excess of 12dB isolation at the certain frequencies for both polarizations. Equivalent circuit models describe the operational principle qualitatively and the switching effect is underpinned by the full-wave analysis. A further physical mechanism is shown by contrasting the distributions of electric field and surface current on the surface at the same frequency for the two working modes. The experimental results consist with the theoretical simulations, indicating that the metasurface could serve as one innovative solution for manipulating the electromagnetic waves and enlighten the next generation of advanced electromagnetic materials with more freedom in the processes of design and manufacturing.

Switchable single-longitudinal-mode dual-wavelength erbium-doped fiber laser based on one polarization-maintaining fiber Bragg grating incorporating saturable absorber

NASA Astrophysics Data System (ADS)

Feng, Suchun; Xu, Ou; Lu, Shaohua; Chen, Ming; Jian, Shuisheng

2009-08-01

Switchable single-longitudinal-mode (SLM) dual-wavelength erbium-doped fiber laser at room temperature is demonstrated. One fiber Bragg grating (FBG) directly written in a polarization-maintaining and photosensitive erbiumdoped fiber (PMPEDF) as the wavelength-selective component is used in a linear laser cavity. Due to the polarization hole burning (PHB) enhanced by the polarization-maintaining fiber Bragg grating (PMFBG), the laser can be designed to operate in stable dual-wavelength or wavelength-switching modes with a wavelength spacing of 0.202 nm by adjusting a polarization controller (PC). The stable SLM operation is guaranteed by a saturable absorber (SA). The optical signal-tonoise ratio (OSNR) of the laser is over 40 dB. The amplitude variation in nearly one and half an hour is less than 0.5 dB for both wavelengths.

Study of true-remanent polarization using remanent hysteresis task and resistive leakage analysis in ferroelectric 0.64Pb(Mg1/3Nb2/3)O3-0.36PbTiO3 ceramics

NASA Astrophysics Data System (ADS)

Joseph, Abhilash J.; Kumar, Binay

2018-03-01

The conventionally reported value of remanent polarization (Pr) contains contribution from non-remanent components which are not usable for memory device applications. This report presents techniques which extract the true-remanent (intrinsic) component of polarization after eliminating the non-remanent component in ferroelectric ceramics. For this, "remanent hysteresis task" and "positive-up-negative-down technique" were performed which utilized the switchable properties of polarizations to nullify the contributions from the non-remanent (non-switchable) components. The report also addresses the time-dependent leakage behavior of the ceramics focusing on the presence of resistive leakage (a time-dependent parameter) present in the ceramics. The techniques presented here are especially useful for polycrystalline ceramics where leakage current leads to an erroneous estimation of Pr.

Programmable Phase Transitions in a Photonic Microgel System: Linking Soft Interactions to a Temporal pH Gradient.

PubMed

Go, Dennis; Rommel, Dirk; Chen, Lisa; Shi, Feng; Sprakel, Joris; Kuehne, Alexander J C

2017-02-28

Soft amphoteric microgel systems exhibit a rich phase behavior. Crystalline phases of these material systems are of interest because they exhibit photonic stop-gaps, giving rise to iridescent color. Such microgel systems are promising for applications in soft, switchable, and programmable photonic filters and devices. We here report a composite microgel system consisting of a hard and fluorescently labeled core and a soft, amphoteric microgel shell. At pH above the isoelectric point (IEP), these colloids easily crystallize into three-dimensional colloidal assemblies. By adding a cyclic lactone to the system, the temporal pH profile can be controlled, and the microgels can be programmed to melt, while they lose charge. When the microgels gain the opposite charge, they recrystallize into assemblies of even higher order. We provide a model system to study the dynamic phase behavior of soft particles and their switchable and programmable photonic effects.

Dynamic control of chirality in phosphine ligands for enantioselective catalysis

PubMed Central

Zhao, Depeng; Neubauer, Thomas M.; Feringa, Ben L.

2015-01-01

Chirality plays a fundamental role in biology and chemistry and the precise control of chirality in a catalytic conversion is a key to modern synthesis most prominently seen in the production of pharmaceuticals. In enantioselective metal-based catalysis, access to each product enantiomer is commonly achieved through ligand design with chiral bisphosphines being widely applied as privileged ligands. Switchable phosphine ligands, in which chirality is modulated through an external trigger signal, might offer attractive possibilities to change enantioselectivity in a catalytic process in a non-invasive manner avoiding renewed ligand synthesis. Here we demonstrate that a photoswitchable chiral bisphosphine based on a unidirectional light-driven molecular motor, can be used to invert the stereoselectivity of a palladium-catalysed asymmetric transformation. It is shown that light-induced changes in geometry and helicity of the switchable ligand enable excellent selectivity towards the racemic or individual enantiomers of the product in a Pd-catalysed desymmetrization reaction. PMID:25806856

Superphobicity/philicity Janus Fabrics with Switchable, Spontaneous, Directional Transport Ability to Water and Oil Fluids

NASA Astrophysics Data System (ADS)

Zhou, Hua; Wang, Hongxia; Niu, Haitao; Lin, Tong

2013-10-01

Herein we demonstrate that switchable, spontaneous, directional-transport ability to both water and oil fluids can be created on fabric materials through wet-chemistry coating and successive UV irradiation treatment. When the fabric showed directional transport to a liquid, it prevented liquids of higher surface tension from penetration, but allowed liquids of lower surface tension to permeate, from either side. The directional transport ability can be switched from one fluid to another simply by heating the fabric at an elevated temperature and then re-irradiating the fabric with UV light for required period of time. By attaching liquid drops vertically upwards to a horizontally-laid fabric, we further demonstrated that this novel directional fluid transport was an automatic process driven by surface property alone, irrespective of gravity's effect. This novel fabric may be useful for development of ``smart'' textiles and functional membranes for various applications.

Guest-Induced Switchable Breathing Behavior in a Flexible Metal-Organic Framework with Pronounced Negative Gas Pressure.

PubMed

Shi, Yi-Xiang; Li, Wu-Xiang; Zhang, Wen-Hua; Lang, Jian-Ping

2018-06-29

Flexible metal-organic frameworks (MOFs) have attracted great interest for their dynamically structural transformability in response to external stimuli. Herein, we report a switchable "breathing" or "gate-opening" behavior associated with the phase transformation between a narrow pore (np) and a large pore (lp) in a flexible pillared-layered MOF, denoted as MOF-1 as, which is also confirmed by SCXRD and PXRD. The desolvated phase (MOF-1 des) features a unique stepwise adsorption isotherm for N 2 coupled with a pronounced negative gas adsorption pressure. For comparison, however, no appreciable CO 2 adsorption and gate-opening phenomenon with stepwise sorption can be observed. Furthermore, the polar micropore walls decorated with thiophene groups in MOF-1 des reveals the selective sorption of toluene over benzene and p-xylene associated with self-structural adjustment in spite of the markedly similar physicochemical properties of these vapor molecules.

Wavelength-switchable passively mode-locked fiber laser with mechanically exfoliated molybdenum ditelluride on side-polished fiber

NASA Astrophysics Data System (ADS)

Wang, Guomei

2017-11-01

We experimentally investigated the nonlinear saturable absorption characteristics of molybdenum ditelluride (MoTe2) and demonstrated a wavelength-switchable mode-locked erbium-doped fiber laser (EDFL) by using MoTe2 thin film on side-polished fiber (SPF) as saturable absorber. Here, the MoTe2 thin film was efficiently fabricated via mechanical exfoliation method and transferred onto the SPF with the assistance of polydimethylsiloxane (PDMS). MoTe2-covered SPF (MSPF) exhibits the nonlinear saturable absorption for pulses with different polarization states. Optical solitons with spectral bandwidth of 1.06 (1.31) nm centered at ∼1559 (∼1528) nm and pulse duration of 2.46 (2.04) ps can be obtained from the EDFL by adjusting the polarization controller (PC) properly. The time-bandwidth product (TBP) of the pulses was calculated as 0.322 (0.344).

Super-resolution photon-efficient imaging by nanometric double-helix point spread function localization of emitters (SPINDLE)

PubMed Central

Grover, Ginni; DeLuca, Keith; Quirin, Sean; DeLuca, Jennifer; Piestun, Rafael

2012-01-01

Super-resolution imaging with photo-activatable or photo-switchable probes is a promising tool in biological applications to reveal previously unresolved intra-cellular details with visible light. This field benefits from developments in the areas of molecular probes, optical systems, and computational post-processing of the data. The joint design of optics and reconstruction processes using double-helix point spread functions (DH-PSF) provides high resolution three-dimensional (3D) imaging over a long depth-of-field. We demonstrate for the first time a method integrating a Fisher information efficient DH-PSF design, a surface relief optical phase mask, and an optimal 3D localization estimator. 3D super-resolution imaging using photo-switchable dyes reveals the 3D microtubule network in mammalian cells with localization precision approaching the information theoretical limit over a depth of 1.2 µm. PMID:23187521

Low-cost, light-switched, forward-osmosis desalination system

DOE Office of Scientific and Technical Information (OSTI.GOV)

Warner, John C.

The looming water crisis is the second largest issue facing humanity after energy. In order to meet the increasing demand for clean water, new efficient and low-cost methods of water purification must be developed. A promising method for dry regions with sea borders is the desalination of seawater. While there remain many disadvantages to current desalination techniques, such as environmental pollution and high cost, there is a strong opportunity for new technology development in this area. In this Phase I program, the development of a light-switchable, low-cost desalination system was explored. The system requires photoselective switching of water solubility. Ninemore » new light-switchable spiropyran-based small molecule and polymeric materials were synthesized, and methods to evaluate their desalination potential were developed and utilized. Severable promising spiropyran analogues proved to be photoswitchable, but so far sufficient photoswitchablity of solubility for a commercial desalination system was not achieved. More development is required.« less

Sickle red cell dehydration: mechanisms and interventions.

PubMed

Bookchin, Robert M; Lew, Virgilio L

2002-03-01

A critical link between the single molecular defect in sickle cell anemia and the extensive pathology of this disease is the reversible increase in red cell membrane permeability generated by hemoglobin S polymers in the deoxygenated state. This permeability, usually described as P (sickle), triggers a chain of events in which two constitutive transporters of the red cell membrane become activated-the recently cloned intermediate conductance, Ca 2+ -sensitive K channel, and the electroneutral K:Cl cotransporter-leading to sickle cell dehydration. This article reviews knowledge of the dehydration mechanism, stressing the marked heterogeneity of dehydration rates in sickle cell populations, and discusses recent contributions to understanding of the function and regulation of P (sickle), Ca 2+ -sensitive K channel, and K:Cl cotransporter, and of therapies targeted at these transporters.

Determination of Microalgal Lipid Content and Fatty Acid for Biofuel Production

PubMed Central

Chen, Zhipeng; Wang, Lingfeng

2018-01-01

Biofuels produced from microalgal biomass have received growing worldwide recognition as promising alternatives to conventional petroleum-derived fuels. Among the processes involved, the downstream refinement process for the extraction of lipids from biomass greatly influences the sustainability and efficiency of the entire biofuel system. This review summarizes and compares the current techniques for the extraction and measurement of microalgal lipids, including the gravimetric methods using organic solvents, CO2-based solvents, ionic liquids and switchable solvents, Nile red lipid visualization method, sulfo-phospho-vanillin method, and the thin-layer chromatography method. Each method has its own competitive advantages and disadvantages. For example, the organic solvents-based gravimetric method is mostly used and frequently employed as a reference standard to validate other methods, but it requires large amounts of samples and is time-consuming and expensive to recover solvents also with low selectivity towards desired products. The pretreatment approaches which aimed to disrupt cells and support subsequent lipid extraction through bead beating, microwave, ultrasonication, chemical methods, and enzymatic disruption are also introduced. Moreover, the principles and procedures for the production and quantification of fatty acids are finally described in detail, involving the preparation of fatty acid methyl esters and their quantification and composition analysis by gas chromatography.

Multimodal Sensing Strategy Using pH Dependent Fluorescence Switchable System

NASA Astrophysics Data System (ADS)

Muthurasu, A.; Ganesh, V.

2016-12-01

Biomolecules assisted preparation of fluorescent gold nanoparticles (FL-Au NPs) has been reported in this work using glucose oxidase enzyme as both reducing and stabilizing agent and demonstrated their application through multimodal sensing strategy for selective detection of cysteine (Cys). Three different methods namely fluorescence turn OFF-ON strategy, naked eye detection and electrochemical methods are used for Cys detection by employing FL-Au NPs as a common probe. In case of fluorescence turn-OFF method a strong interaction between Au NPs and thiol results in quenching of fluorescence due to replacement of glucose oxidase by Cys at neutral pH. Second mode is based on fluorescence switch-ON strategy where initial fluorescence is significantly quenched by either excess acid or base and further addition of Cys results in appearance of rosy-red and green fluorescence respectively. Visual colour change and fluorescence emission arises due to etching of Au atoms on the surface by thiol leading to formation of Au nanoclusters. Finally, electrochemical sensing of Cys is also carried out using cyclic voltammetry in 0.1 M PBS solution. These findings provide a suitable platform for Cys detection over a wide range of pH and concentration levels and hence the sensitivity can also be tuned accordingly.

Sol-gel open tubular ODS columns with reversed electroosmotic flow for capillary electrochromatography.

PubMed

Hayes, J D; Malik, A

2001-03-01

Sol-gel chemistry was successfully used for the fabrication of open tubular columns with surface-bonded octadecylsilane (ODS) stationary-phase coating for capillary electrochromatography (OT-CEC). Following column preparations, a series of experiments were performed to investigate the performance of the sol-gel coated ODS columns in OT-CEC. The incorporation of N-octadecyldimethyl[3-(trimethoxysilyl)propyl]ammonium chloride as one of the sol-gel precursors played an important role in the electrochromatographic performance of the prepared columns. This chemical reagent possesses a chromatographically favorable, bonded ODS moiety, in conjunction with three methoxy groups allowing for sol-gel reactivity. In addition, a positively charged nitrogen atom is present in the molecular structure of this reagent and provides a positively charged capillary surface responsible for the reversed electroosmotic flow (EOF) in the columns during CEC operation. Comparative studies involving the EOF within such sol-gel ODS coated and uncoated capillaries were performed using acetonitrile and methanol as the organic modifiers in the mobile phase. The use of a deactivating reagent, phenyldimethylsilane, in the sol-gel solution was evaluated. Efficiency values of over 400,000 theoretical plates per meter were achieved in CEC on a 64 cm x 25 microm i.d. sol-gel ODS open tubular column. Test mixtures of polycyclic aromatic hydrocarbons, benzene derivatives, and aromatic aldehydes and ketones were used to evaluate the CEC performances of both nondeactivated and deactivated open tubular sol-gel columns. The effects of mobile-phase organic modifier contents and pH on EOF in such columns were evaluated. The prepared sol-gel ODS columns are characterized by switchable electroosmotic flow. A pH value of approximately 8.5 was found correspond to the isoelectric point for the prepared sol-gel ODS coatings.

Reversible biofunctionalization of surfaces with a switchable mutant of avidin.

PubMed

Pollheimer, Philipp; Taskinen, Barbara; Scherfler, Andreas; Gusenkov, Sergey; Creus, Marc; Wiesauer, Philipp; Zauner, Dominik; Schöfberger, Wolfgang; Schwarzinger, Clemens; Ebner, Andreas; Tampé, Robert; Stutz, Hanno; Hytönen, Vesa P; Gruber, Hermann J

2013-10-16

Label-free biosensors detect binding of prey molecules (″analytes″) to immobile bait molecules on the sensing surface. Numerous methods are available for immobilization of bait molecules. A convenient option is binding of biotinylated bait molecules to streptavidin-functionalized surfaces, or to biotinylated surfaces via biotin-avidin-biotin bridges. The goal of this study was to find a rapid method for reversible immobilization of biotinylated bait molecules on biotinylated sensor chips. The task was to establish a biotin-avidin-biotin bridge which was easily cleaved when desired, yet perfectly stable under a wide range of measurement conditions. The problem was solved with the avidin mutant M96H which contains extra histidine residues at the subunit-subunit interfaces. This mutant was bound to a mixed self-assembled monolayer (SAM) containing biotin residues on 20% of the oligo(ethylene glycol)-terminated SAM components. Various biotinylated bait molecules were bound on top of the immobilized avidin mutant. The biotin-avidin-biotin bridge was stable at pH ≥3, and it was insensitive to sodium dodecyl sulfate (SDS) at neutral pH. Only the combination of citric acid (2.5%, pH 2) and SDS (0.25%) caused instantaneous cleavage of the biotin-avidin-biotin bridge. As a consequence, the biotinylated bait molecules could be immobilized and removed as often as desired, the only limit being the time span for reproducible chip function when kept in buffer (2-3 weeks at 25 °C). As expected, the high isolectric pH (pI) of the avidin mutant caused nonspecific adsorption of proteins. This problem was solved by acetylation of avidin (to pI < 5), or by optimization of SAM formation and passivation with biotin-BSA and BSA.

Minimising reversion, using seawater and magnesium chloride, caused by the dissolution of tricalcium aluminate hexahydrate.

PubMed

Palmer, Sara J; Frost, Ray L; Smith, Matthew K

2011-01-15

The increase in pH and aluminium concentration after the neutralisation of bauxite refinery residues is commonly known as reversion. This investigation reports the extent of reversion in synthetic supernatant liquor and possible methods to reduce reversion. This work is based on bauxite refinery residues produced from alumina refineries, where reversion is a real life situation in neutralised refinery residues. Tricalcium aluminate hexahydrate, a common phase in bauxite refinery residues, has been found to cause reversion. It has been established that reductions in both pH and aluminium from the seawater neutralisation process are due to the formation of 'Bayer' hydrotalcite Mg(7)Al(2)(OH)(18)(CO(3)(2-),SO(4)(2-))·xH(2)O. This is the primary mechanism involved in the removal of aluminium from solution. Increasing the volume of seawater used for the neutralisation process minimises the extent of reversion for both synthetic supernatant liquor and red mud slurry. The addition of MgCl(2)·6H(2)O also showed a reduction in reversion and confirmed that the decrease in aluminium and hydroxyl ions is due to the formation of Bayer hydrotalcite and not simply a dilution effect. Copyright © 2010 Elsevier Inc. All rights reserved.

Long-run operation of a reverse electrodialysis system fed with wastewaters.

PubMed

Luque Di Salvo, Javier; Cosenza, Alessandro; Tamburini, Alessandro; Micale, Giorgio; Cipollina, Andrea

2018-07-01

The performance of a Reverse ElectroDialysis (RED) system fed by unconventional wastewater solutions for long operational periods is analysed for the first time. The experimental campaign was divided in a series of five independent long-runs which combined real wastewater solutions with artificial solutions for at least 10 days. The time evolution of electrical variables, gross power output and net power output, considering also pumping losses, was monitored: power density values obtained during the long-runs are comparable to those found in literature with artificial feed solutions of similar salinity. The increase in pressure drops and the development of membrane fouling were the main detrimental factors of system performance. Pressure drops increase was related to the physical obstruction of the feed channels defined by the spacers, while membrane fouling was related to the adsorption of foulants over the membrane surfaces. In order to manage channels partial clogging and fouling, different kinds of easily implemented in situ backwashings (i.e. neutral, acid, alkaline) were adopted, without the need for an abrupt interruption of the RED unit operation. The application of periodic ElectroDialysis (ED) pulses is also tested as fouling prevention strategy. The results collected suggest that RED can be used to produce electric power by unworthy wastewaters, but additional studies are still needed to characterize better membrane fouling and further improve system performance with these solutions. Copyright © 2018 Elsevier Ltd. All rights reserved.

Character displacement in the fighting colours of Hetaerina damselflies.

PubMed

Anderson, Christopher N; Grether, Gregory F

2010-12-07

Aggression between species is a seldom-considered but potentially widespread mechanism of character displacement in secondary sexual characters. Based on previous research showing that similarity in wing coloration directly influences interspecific territorial aggression in Hetaerina damselflies, we predicted that wing coloration would show a pattern of character displacement (divergence in sympatry). A geographical survey of four Hetaerina damselfly species in Mexico and Texas showed evidence for character displacement in both species pairs that regularly occurs sympatrically. Hetaerina titia, a species that typically has large black wing spots and small red wing spots, shifted to having even larger black spots and smaller red wing spots at sites where a congener with large red wing spots is numerically dominant (Hetaerina americana or Hetaerina occisa). Hetaerina americana showed the reverse pattern, shifting towards larger red wing spots where H. titia is numerically dominant. This pattern is consistent with the process of agonistic character displacement, but the ontogenetic basis of the shift remains to be demonstrated.

Reversibly pH-responsive polyurethane membranes for on-demand intravaginal drug delivery.

PubMed

Kim, Seungil; Chen, Yufei; Ho, Emmanuel A; Liu, Song

2017-01-01

To provide better protection for women against sexually transmitted infections, on-demand intravaginal drug delivery was attempted by synthesizing reversibly pH-sensitive polyether-polyurethane copolymers using poly(ethylene glycol) (PEG) and 1,4-bis(2-hydroxyethyl)piperazine (HEP). Chemical structure and thermo-characteristics of the synthesized polyurethanes were confirmed by attenuated total reflectance-Fourier transform infrared spectroscopy (ATR-FTIR), 1 H-nuclear magnetic resonance ( 1 H-NMR), and melting point testing. Membranes were cast by solvent evaporation method using the prepared pH-sensitive polyurethanes. The impact of varying pH on membrane swelling and surface morphology was evaluated via swelling ratio change and scanning electron microscopy (SEM). The prepared pH-responsive membranes showed two times higher swelling ratio at pH 4 than pH 7 and pH-triggered switchable surface morphology change. The anionic anti-inflammatory drug diclofenac sodium (NaDF) was used as a model compound for release studies. The prepared pH-responsive polyurethane membranes allowed continuous NaDF release for 24h and around 20% release of total NaDF within 3h at pH 7 but little-to-no drug release at pH 4.5. NaDF permeation across the prepared membranes demonstrated a reversible pH-responsiveness. The pH-responsive polyurethane membranes did not show any noticeable negative impact on vaginal epithelial cell viability or induction of pro-inflammatory cytokine production compared to controls. Overall, the non-cytotoxic HEP-based pH-responsive polyurethane demonstrated its potential to be used in membrane-based implants such as intravaginal rings to achieve on-demand "on-and-off" intravaginal drug delivery. A reversible and sharp switch between "off" and "on" drug release is achieved for the first time through new pH-sensitive polyurethane membranes, which can serve as window membranes in reservoir-type intravaginal rings for on-demand drug delivery to prevent sexually transmitted infections (STIs). Close to zero drug release occurs at the normal vaginal pH (4.5) for minimal side effects. Drug release is only triggered by elevation of pH to 7 during heterosexual intercourse. The reversibly sharp and fast "on-and-off" switch arises from the creative incorporation of a pH-sensitive monomer in the soft segment of polyurethane. This polyurethane biomaterial holds great potential to better protect women who are generally at higher risk and are more vulnerable to STIs. Copyright © 2016 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

Illumination with 630-nm red light reduces oxidative stress and restores memory by photo-activating catalase and formaldehyde dehydrogenase in SAMP8 mice.

PubMed

Zhang, Jingnan; Yue, Xiangpei; Luo, Hongjun; Jiang, Wenjing; Mei, Yufei; Ai, Li; Gao, Ge; Wu, Yan; Yang, Hui; An, Jieran; Ding, Shumao; Yang, Xu; Sun, Bingui; Luo, Wenhong; He, Rongqiao; Jia, Jianping; Lyu, Jihui; Tong, Zhiqian

2018-06-05

Pharmacological treatments for Alzheimer's disease (AD) have not resulted in desirable clinical efficacy over 100 years. Hydrogen peroxide (H2O2), a reactive and the most stable compound of reactive oxygen species (ROS), contributes to oxidative stress in AD patients. Here, we designed a medical device to emit red light at 630±15 nm from a light-emitting diode (LED-RL) and investigated whether the LED-RL reduces brain H2O2 levels and improves memory in senescence-accelerated prone 8 mouse (SAMP8) model of age-related dementia. We found that age-associated H2O2 directly inhibited formaldehyde dehydrogenase (FDH). FDH inactivity and semicarbazide-sensitive amine oxidase (SSAO) disorder resulted in endogenous formaldehyde (FA) accumulation. Unexpectedly, excess FA, in turn, caused acetylcholine (Ach) deficiency by inhibiting choline acetyltransferase (ChAT) activity in vitro and in vivo. Interestingly, the 630-nm red light can penetrate the skull and abdomen with light penetration rates: ~49% and ~43%, respectively. Illumination with LED-RL markedly activated both catalase and FDH in the brains, cultured cells and purified protein solutions, all reduced brain H2O2 and FA levels and restored brain Ach contents. Consequently, LED-RL not only prevented early-stage memory decline but also rescued late-stage memory deficits in SAMP8 mice. We developed a phototherapeutic device with 630-nm red light, and this LED-RL reduced brain H2O2 levels and reversed age-related memory disorders. The phototherapy of LED-RL has low photo toxicity and high rate of tissue penetration, and non-invasively reverses aging-associated cognitive decline. This finding opens a promising opportunity to translate LED-RL into clinical treatment for patients with dementia.

Red Versus White Wine as a Nutritional Aromatase Inhibitor in Premenopausal Women: A Pilot Study

PubMed Central

Shufelt, Chrisandra; Merz, C. Noel Bairey; Yang, YuChing; Kirschner, Joan; Polk, Donna; Stanczyk, Frank; Paul-Labrador, Maura

2012-01-01

Abstract Background An increased risk of breast cancer is associated with alcohol consumption; however, it is controversial whether red wine increases this risk. Aromatase inhibitors (AIs) prevent the conversion of androgens to estrogen and occur naturally in grapes, grape juice, and red, but not white wine. We tested whether red wine is a nutritional AI in premenopausal women. Methods In a cross-over design, 36 women (mean age [SD], 36 [8] years) were assigned to 8 ounces (237 mL) of red wine daily then white wine for 1 month each, or the reverse. Blood was collected twice during the menstrual cycle for measurement of estradiol (E2), estrone (E1), androstenedione (A), total and free testosterone (T), sex hormone binding globulin (SHBG), luteinizing hormone (LH), and follicle stimulating hormone (FSH). Results Red wine demonstrated higher free T vs. white wine (mean difference 0.64 pg/mL [0.2 SE], p=0.009) and lower SHBG (mean difference −5.0 nmol/L [1.9 SE], p=0.007). E2 levels were lower in red vs. white wine but not statistically significant. LH was significantly higher in red vs. white wine (mean difference 2.3 mIU/mL [1.3 SE], p=0.027); however, FSH was not. Conclusion Red wine is associated with significantly higher free T and lower SHBG levels, as well as a significant higher LH level vs. white wine in healthy premenopausal women. These data suggest that red wine is a nutritional AI and may explain the observation that red wine does not appear to increase breast cancer risk. PMID:22150098

Excitation-dependent local symmetry reversal in single host lattice Ba2A(BO3)2:Eu3+ [A = Mg and Ca] phosphors with tunable emission colours.

PubMed

Jayakiruba, S; Chandrasekaran, S Selva; Murugan, P; Lakshminarasimhan, N

2017-07-05

Eu 3+ activated phosphors are widely used as red emitters in various display devices and light emitting diodes (LEDs). The emission characteristics of Eu 3+ depend on the local site symmetry. The present study demonstrates the role of excitation-dependent local symmetry changes due to the structural reorganization on the emission colour tuning of Eu 3+ from orange-red to orange in single host lattices, Ba 2 Mg(BO 3 ) 2 and Ba 2 Ca(BO 3 ) 2 . The choice of these lattices was based on the difference in the extent of strain experienced by the oxygen atoms. The samples with Eu 3+ at Ba or Mg (Ca) sites were synthesized using the conventional high-temperature solid-state reaction method. The samples were characterized using powder XRD, 11 B MAS-NMR, FT-IR, and diffuse reflectance UV-Vis spectroscopic techniques. The room temperature photoluminescence (PL) recorded using different excitation wavelengths revealed a clear difference in the PL emission features due to symmetry reversal from non-inversion to inversion symmetry around Eu 3+ . The reorganization of highly strained oxygen atoms leads to such symmetry reversal. First-principles calculations were used to deduce the optimized structures of the two borate host lattices, and local geometries and their distortions upon Eu 3+ substitution. The outcomes of these calculations support the experimental findings.