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Sample records for open cell metal

  1. Modeling hydrodynamic properties of open-cell metal foams

    NASA Astrophysics Data System (ADS)

    De Jaeger, P.; De Schampheleire, S.; Huisseune, H.; Ameel, B.; T'Joen, C.; De Paepe, M.

    2012-11-01

    Modeling the hydrodynamics of open-cell aluminum foam still is a challenging task because of the large range of length-scales, own to the physical phenomena which occur in the complex structure. Upscaling the classical conservation equations is a promising approach, but introduces the problem of modeling closure terms. This is dealt with via the well-known porous properties, i.e., permeability and inertial loss factor. Derivation of these properties is commonly done by linking pressure drop data to velocity via a second order interpolation. This, however, introduces significant deviation between the available data set, up to anorder of magnitude, which in turn results in difficulties to predict pressure drop during desing the desing phase of an applicaiton. As the closure terms have a well-defined physical meaning, it should be possible to compute them with better accuracy. This forms the topic of this paper.

  2. Metal foams application to enhance cooling of open cathode polymer electrolyte membrane fuel cells

    NASA Astrophysics Data System (ADS)

    Sajid Hossain, Mohammad; Shabani, Bahman

    2015-11-01

    Conventional channel flow fields of open cathode Polymer Electrolyte Membrane Fuel Cells (PEMFCs) introduce some challenges linked to humidity, temperature, pressure and oxygen concentration gradients along the conventional flow fields that reduce the cell performance. According to previous experimental reports, with conventional air flow fields, hotspot formation due to water accumulation in Gas Diffusion Layer (GDL) is common. Unlike continuous long flow passages in conventional channels, metal foams provide randomly interrupted flow passages. Re-circulation of fluid, due to randomly distributed tortuous ligaments, enhances temperature and humidity uniformity in the fluid. Moreover, the higher electrical conductivity of metal foams compared to non-metal current collectors and their very low mass density compared to solid metal materials are expected to increase the electrical performance of the cell while significantly reducing its weight. This article reviews the existing cooling systems and identifies the important parameters on the basis of reported literature in the air cooling systems of PEMFCs. This is followed by investigating metal foams as a possible option to be used within the structure of such PEMFCs as an option that can potentially address cooling and flow distribution challenges associated with using conventional flow channels, especially in air-cooled PEMFCs.

  3. Properties of open-cell porous metals and alloys for orthopaedic applications.

    PubMed

    Lewis, Gladius

    2013-10-01

    One shortcoming of metals and alloys used to fabricate various components of orthopaedic systems, such as the femoral stem of a total hip joint replacement and the tibial plate of a total knee joint replacement, is well-recognized. This is that the material modulus of elasticity (E') is substantially larger than that of the contiguous cancellous bone, a consequence of which is stress shielding which, in turn, has been postulated to be implicated in a cascade of events that culminates in the principal life-limiting phenomenon of these systems, namely, aseptic loosening. Thus, over the years, a host of research programs have focused on the synthesis of metallic biomaterials whose E' can be tailored to match that of cancellous bone. The present work is a review of the extant large volume of literature on these materials, which are called open-cell porous metals/alloys (or, sometimes, metal foams or cellular materials). As such, its range is wide, covering myriad aspects such as production methods, characterization studies, in vitro evaluations, and in vivo performance. The review also includes discussion of seven areas for future research, such as parametric studies of the influence of an assortment of process variables (such as the space holder material and the laser power in the space holder method and the laser-engineered net-shaping process, respectively) on various properties (notably, permeability, fatigue strength, and corrosion resistance) of a given porous metal/alloy, innovative methods of determining fatigue strength, and modeling of corrosion behavior.

  4. Cooling capacity of high porosity open-cell metal foams as passive cryogenic radiators

    NASA Astrophysics Data System (ADS)

    Dixit, Tisha; Ghosh, Indranil

    2017-06-01

    This work presents an innovative avenue for employment of high porosity open-cell metal foams as extended heat transfer surfaces in passive cryogenic radiators. Metal foams are known for being light in weight and possess high surface area density. In contrast to a solid surface, porosity of metal foams makes it feasible for penetration of radiation thereby resulting in higher radiatively interactive surface area. Two 20 PPI metal foams made of copper and aluminum with 94.9% and 90.3% porosity respectively have been chosen for this study. A laboratory-scale test rig measures the radiative cooling capacity of metal foams in vacuum (10-6 mbar) subjected to liquid nitrogen environment. Heat load to the foam has been provided by means of convective fluid loop. Simultaneously, a theoretical model based on radiation-conduction fin analysis has been developed to predict the foam cooling capacity at a specified temperature. The required radiation heat transfer coefficient has been obtained from a previous experiment wherein the foam samples are freely suspended in similar conditions but with no heat load. Lastly, performance of the foams under study has been expressed in terms of a commonly used performance parameter (surface area/cooling capacity) for passive cryogenic radiators.

  5. How to Study Thermal Applications of Open-Cell Metal Foam: Experiments and Computational Fluid Dynamics

    PubMed Central

    De Schampheleire, Sven; De Jaeger, Peter; De Kerpel, Kathleen; Ameel, Bernd; Huisseune, Henk; De Paepe, Michel

    2016-01-01

    This paper reviews the available methods to study thermal applications with open-cell metal foam. Both experimental and numerical work are discussed. For experimental research, the focus of this review is on the repeatability of the results. This is a major concern, as most studies only report the dependence of thermal properties on porosity and a number of pores per linear inch (PPI-value). A different approach, which is studied in this paper, is to characterize the foam using micro tomography scans with small voxel sizes. The results of these scans are compared to correlations from the open literature. Large differences are observed. For the numerical work, the focus is on studies using computational fluid dynamics. A novel way of determining the closure terms is proposed in this work. This is done through a numerical foam model based on micro tomography scan data. With this foam model, the closure terms are determined numerically. PMID:28787894

  6. Microtomography-based CFD Analysis of Transport in Open-Cell Aluminum Metal Foams

    NASA Astrophysics Data System (ADS)

    Ranut, Paola; Nobile, Enrico; Mancini, Lucia

    2014-04-01

    Nowadays, the need for developing more effective heat exchange technologies and innovative materials, capable of increasing performances while keeping power consumption, size and cost at reasonable levels, is well recognized. Under this perspective, metal foams have a great potential for enhancing the thermal efficiency of heat transfer devices, while allowing for the use of smaller and lighter equipments. However, for practical applications, it is necessary to compromise between the augmented heat transfer rate and the increased pressure drop induced by the tortuous flow passages. For design purposes, the estimation of the flow permeability and the thermal conductivity of the foam is fundamental, but far from simple. From this perspective, besides classical transport models and correlations, computational fluid dynamics (CFD) at the pore scale, although challenging, is becoming a promising approach, especially if coupled with a realistic description of the foam structure. For precisely recovering the microstructure of the foams, a 3D X-ray computed microtomography (μ-CT) can be adopted. In this work, the results of μ-CT-based CFD simulations performed on different open-cell aluminum foams samples, for laminar flow regime, will be discussed. The results demonstrate that open-cell aluminum foams are effective means for enhancing heat transfer.

  7. Comparison of elastic properties of open-cell metallic biomaterials with different unit cell types.

    PubMed

    Hedayati, Reza; Sadighi, Mojtaba; Mohammadi-Aghdam, Mohammad; Hosseini-Toudeshky, Hossein

    2017-02-06

    Additive manufacturing techniques have made it possible to create open-cell porous structures with arbitrary micro-geometrical characteristics. Since a wide range of micro-geometrical features is available for making an implant, having a comprehensive knowledge of the mechanical response of cellular structures is very useful. In this study, finite element simulations have been carried out to investigate the effect of structure unit cell type (cube, rhombic dodecahedron, Kelvin, Weaire-Phelan, and diamond), cross-section type (circular, square, and triangular), strut length, and relative density on the Young's modulus, shear modulus, yield stress, shear yield stress, and Poisson's ratio of open-cell tessellated cellular structures. It was desired to see whether or not and to what extent each of the aforementioned parameters affect the mechanical properties of a porous structure. It was seen that the strut cross-section type does not have a considerable effect on the structure Young's modulus while its effect on the structure yield stress is significant. The strut length was not effective on the mechanical properties if the relative density was kept constant. It was also observed that the structure unit cell type and relative density have a considerable effect on the elastic properties. The highest and the lowest stiffness and strength belonged to the cube and diamond unit cell types, respectively. The rhombic dodecahedron structure with circular cross-section had a high yielding strength (second among all the cases) while its Young's modulus was relatively low. Therefore, it is the best choice for applications with low stiffness requirements, such as biomedical implants. © 2017 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 2017.

  8. Numerical Study of Liquid Sloshing on Anti-sloshing Device Using Open Cell Metal Foams in Oil Tank

    NASA Astrophysics Data System (ADS)

    Zhang, Y.; Qu, Z. G.; Tao, W. Q.; Lu, T. J.

    2010-03-01

    A new baffle structure design named open-cell metal foams baffle for anti-sloshing device in oil tank is presented in this study. Numerical simulation study on the liquid sloshing with various baffles is carried out using FLUENT with the volume-of-fluid (VOF) model. Four types of baffles were studied, namely non-baffle (type A), conventional parallel-baffle (type B), cross-baffle (type C) and open- cell metal foams baffles (type D). The oil velocity distribution, centroid and oil occupancy in the sloshing process is revealed in the case of vehicle speeding up and turning respectively. It is found that type D reduce velocity of oil, increase the value of oil occupancy in the suction pipe entrance of the oil tank and lower the centroid of oil obviously comparing with the other types. As for the same open-cell metal foam pore density, lower open-cell metal foam porosity has much better effect of inhibition of liquid sloshing, but there is little deviation among different porosity for the absolute value. Moreover, according to the same porosity, the oil centroid can be lowered obviously with the increase of pore density. The results of type D show practical significance and referable guideline for baffles design to improve the safety and stability of vehicle.

  9. Increasing the Open-Circuit Voltage of Dye-Sensitized Solar Cells via Metal-Ion Coordination.

    PubMed

    Ogunsolu, Omotola O; Wang, Jamie C; Hanson, Kenneth

    2017-09-18

    Considerable efforts are dedicated to increasing the open-circuit voltage (Voc) of dye-sensitized solar cells (DSSCs) by slowing charge recombination dynamics using atomic layer deposition, alkyl-substituted dyes, coadsorbents, and other strategies. In this report, we introduce metal-ion coordination to a metal oxide bound dye as an alternative means of increasing Voc. Metal-ion coordination has minimal influence on the photophysical and electrochemical properties of the N3 dye, but presumably because of increased steric hindrance at the interface, it slows charge recombination kinetics and increases Voc by upwards of 130 mV relative to the parent N3 DSSC. With respect to the nature of the metal ion, the trend in decreasing short-circuit current (Jsc) and increasing Voc correlates with the charge of the coordinated metal ion (M(IV) → M(III) → M(II)). We attribute this trend to electrostatic interactions between the metal cation and I(-) or I3(-), with the more highly charged cations maintaining a higher concentration of mediator anions in proximity to the surface and, as a result, increasing the regeneration and recombination rates.

  10. Prospective of employing high porosity open-cell metal foams in passive cryogenic radiators for space applications

    NASA Astrophysics Data System (ADS)

    Tisha, Dixit; Indranil, Ghosh

    2017-02-01

    Passive cryogenic radiators work on the principle of dissipating heat to the outer space purely by radiation. High porosity open-cell metal foams are a relatively new class of extended surfaces. These possess the advantages of high surface area density and low weight, characteristics which the space industry looks for. In case of radiative heat transfer, the porous nature of metal foams permits a deeper penetration of the incident radiation. Consequently, the heat transfer area participating in radiative heat exchange increases thereby enhancing the heat transfer rate. However, effective heat conduction in between the foam struts reduces as a result of the void spaces. These two conflicting phenomenon for radiation heat transfer in metal foams have been studied in this work. Similar to the foam conduction-convection heat transfer analysis, a conduction-radiation heat transfer model has been developed for metal foams in analogy with the conventional solid fin theory. Metal foams have been theoretically represented as simple cubic structures. A comparison of the radiative heat transfer through metal foams and solid fins attached to a surface having constant temperature has been presented. Effect of changes in foam characteristic properties such as porosity and pore density have also been studied.

  11. Functional Characterization of Shape Memory CuZnAl Open-Cell Foams by Molten Metal Infiltration

    NASA Astrophysics Data System (ADS)

    Arnaboldi, S.; Bassani, P.; Passaretti, F.; Redaelli, A.; Tuissi, A.

    2011-07-01

    In the recent years, the research for novel materials with tailored mechanical properties, as well as functional properties, has encouraged the study of porous and cellular materials. Our previous work proposed and reported about the possibility to manufacture open-cell metal foams of CuZnAl shape memory alloy by liquid infiltration in a leachable bed of silica-gel particles. This innovative methodology is based on cheap commercial consumables and a simple technology, focusing on intermediate-density low-cost foams with interesting cost/benefits ratio. Microstructural analyses on foamed specimens showed uniform microstructure of ligaments and a very regular and well reproducible open-cell morphology. Moreover, calorimetric analysis detected a thermo-elastic martensitic transformation in the foamed material. In this study, a CuZnAl shape memory alloy was considered and tested to clarify possible effects of the foaming process on the functional properties of the material. Morphological, calorimetric, and thermo-mechanical analyses were carried out. The results show that it is possible to produce metal foams of CuZnAl shape memory alloy with different functional properties and able to recover mono-axial compressive strains up to 3%.

  12. Analytical and Numerical Modeling of Fluid Flow and Heat Transfer through Open-Cell Metal Foam Heat Exchangers

    NASA Astrophysics Data System (ADS)

    Taheri, Mehrdad

    In this thesis analytical and numerical investigations of fluid flow and heat transfer through open cell metal foam heat exchangers are presented. Primarily, different representative unit cell approximations, i.e, tetrakaidecahedron, dodecahedron and cubic are discussed. By applying the thermal resistance analogy, a novel formulation for evaluation of the effective thermal conductivity of metal foams is proposed. The model improves previous models based on cubic or hexagonal cells. By using computer tomography images of a nickel foam sample a realistic 3D geometry is created and the foam's geometrical properties (i.e., porosity and surface area to volume ratio) and effective thermal conductivity are obtained. By using the experimentally found values of permeability, Forchheimer coefficient and solid-fluid interfacial convection coefficient, mathematical models for fluid flow and heat transfer in metal foams are developed. Two different assumptions: local thermal equilibrium (LTE) and local thermal non-equilibrium (LTNE), are used. LTNE yields more accurate results. A three-dimensional computational fluid dynamics (CFD) model of metal foam is made and validated against the experimental data for a square cross sectional nickel foam heat exchanger channel heated from the side walls while cooling air passes through the foam. The simulations are carried out for constant temperature or heat flux and different foam materials with pore densities of 10 and 40 pores per inch. The results show that the bonding of the foam to the walls has a considerable impact on the heat transfer rate. Convective heat transfer coefficients in terms of Nusselt number as functions of Reynolds number are also obtained. The design and CFD modeling of metal foam cross flow heat exchangers are also discussed. The results indicate both effectiveness and number of transfer units (NTU) for the metal foam heat exchangers are higher than those of a hollow channel; however, the effectiveness-NTU curves

  13. Mechanical Properties of Open Celled Bulk Metallic Glass Foams Processed by Equal Channel Angular Extrusion

    NASA Astrophysics Data System (ADS)

    Cox, Marie Elizabeth

    The unique properties of metallic foams make them superior to their solid counterparts for many applications, including lightweight structures, impact protection, filtration and catalysis. This work extends the use of metallic foams for these applications by developing a novel solid state processing method to address some of the scalability and contamination issues that hinder common liquid state processing methods used to create metallic glass foams. Equal channel angular extrusion is used to consolidate a blend of amorphous Zr58.5Nb2.8Cu15.6Ni12.8Al1 0.3 (Vit106a) or Hf44.5Cu27Ni13.5Ti 5Al10 (ARLloy #1) powders and crystalline metal (Cu, Ni or W) powders into dense composites. Chemical dissolution of the crystalline phase results in amorphous foams with elongated pores, aligned at a ˜25° angle with respect to the extrusion direction. The extent of amorphous powder densification in the composites improves with the strength of the crystalline metallic powder, from low for Cu to high for W, with a concomitant improvement in foam compressive strength, ductility and energy absorption. High oxygen content in amorphous powders can greatly limit the bonding of the amorphous phase however increasing the processing temperature and decrease the extrusion rate reduces these affects. The presence of the prior powder boundaries in these foams create stress concentrators that influenced the path of fractures, resulting in more diffuse damage (determined by acoustic emission activity) leading to foams with energy absorbing properties comparable to foams without the prior powder boundaries. The alignment of the elongated pores leads to anisotropic mechanical properties. As the angle between the elongated pore and the direction of compressive loading increase from 0 to 68°, there is a significant decrease in loading stiffness and peak stress which is confirmed by finite element analysis. Foams with pores aligned 45-68° to the direction of loading show increased bending in

  14. Rule for structures of open metal surfaces.

    PubMed

    Sun, Y Y; Xu, H; Feng, Y P; Huan, A C H; Wee, A T S

    2004-09-24

    We present a clear and simple rule for determining the relaxation sequences on open (stepped, vicinal, or high-Miller-index) metal surfaces. At the bulk-truncated configuration of a surface, a surface slab is defined where the coordination of atoms is reduced from the bulk. The rule predicts that the interlayer spacings within this slab contract, while the interlayer spacing between this slab and the substrate expands. By first-principles calculations, we show that this rule is obeyed on all open Cu surfaces with interlayer spacings down to about 0.5 A. We also illustrate a direct relation of the relaxation sequences to the charge redistribution on these surfaces, which is demonstrated to be driving the multilayer relaxations. The applicability of the rule can be extended to other fcc and bcc metals, including unreconstructed and missing-row surfaces.

  15. Interface control of semiconducting metal oxide layers for efficient and stable inverted polymer solar cells with open-circuit voltages over 1.0 volt.

    PubMed

    Yin, Zhigang; Zheng, Qingdong; Chen, Shan-Ci; Cai, Dongdong

    2013-09-25

    Inverted polymer solar cells (PSCs) with high open-circuit voltages of 1.00-1.06 V are fabricated by using an indenofluorene-containing copolymer (PIFTBT8) as an electron donor material and [6,6]-phenyl-C71-butyric acid methyl ester (PC71BM) as an electron acceptor material. To improve the photovoltaic performance, interface control of various low-temperature processed ZnO films as cathode buffer layers is systematically investigated for effective electron transportation, while transition metal oxides including MoO3, WO3, NiO, and Cu2O are employed as anode buffer layers for hole-extraction. Incorporation of optimized semiconducting metal oxide interlayers can minimize interfacial power losses, which thus affords large open-circuit voltages (Voc), increased short-circuit current densities (Jsc), and fill factors (FF), eventually contributing to higher power conversion efficiencies (PCEs) as well as better device stability. Due to the improved interfacial contacts and fine-matching energy levels, inverted PSCs with a device configuration of ITO/ZnO/PIFTBT8:PC71BM/MoO3/Ag exhibit a high PCE of 5.05% with a large Voc of 1.04 V, a Jsc of 9.74 mA cm(-2), and an FF of 50.1%. For the single junction inverted PSCs with efficiencies over 5.0%, 1.04 V is the largest Voc ever achieved. By controlling the processing conditions of the active layer, the Voc can further be improved to 1.05 and 1.06 V, with PCEs of 4.70% and 4.18%, respectively. More importantly, the inverted PSCs are ascertained to maintain a PCE of 4.55% (>90% of its initial efficiency) and a Voc of 1.05 V over 180 days, demonstrating good long-term stability, which is much better than that of the conventional devices. The results suggest that the interface engineering of metal oxide interlayers is an important strategy to develop PSCs with good performance.

  16. Open-celled polyurethane foam

    NASA Technical Reports Server (NTRS)

    Russell, L. W.

    1970-01-01

    Open-celled polyurethane foam has a density of 8.3 pounds per cubic foot and a compressive strength of 295 to 325 psi. It is useful as a porous spacer in layered insulation and as an insulation material in vacuum tight systems.

  17. Closed cell metal foam method

    DOEpatents

    Patten, James W.

    1978-01-01

    Foamed metals and metal alloys which have a closed cellular structure are prepared by heating a metal body containing entrapped inert gas uniformly distributed throughout to a temperature above the melting point of the metal and maintaining the body at this temperature a period of time sufficient to permit the entrapped gas to expand, forming individual cells within the molten metal, thus expanding and foaming the molten metal. After cell formation has reached the desired amount, the foamed molten metal body is cooled to below the melting temperature of the metal. The void area or density of the foamed metal is controlled by predetermining the amount of inert gas entrapped in the metal body and by the period of time the metal body is maintained in the molten state. This method is useful for preparing foamed metals and metal alloys from any metal or other material of which a body containing entrapped inert gas can be prepared.

  18. On the metallicity of open clusters. III. Homogenised sample

    NASA Astrophysics Data System (ADS)

    Netopil, M.; Paunzen, E.; Heiter, U.; Soubiran, C.

    2016-01-01

    Context. Open clusters are known as excellent tools for various topics in Galactic research. For example, they allow accurately tracing the chemical structure of the Galactic disc. However, the metallicity is known only for a rather low percentage of the open cluster population, and these values are based on a variety of methods and data. Therefore, a large and homogeneous sample is highly desirable. Aims: In the third part of our series we compile a large sample of homogenised open cluster metallicities using a wide variety of different sources. These data and a sample of Cepheids are used to investigate the radial metallicity gradient, age effects, and to test current models. Methods: We used photometric and spectroscopic data to derive cluster metallicities. The different sources were checked and tested for possible offsets and correlations. Results: In total, metallicities for 172 open cluster were derived. We used the spectroscopic data of 100 objects for a study of the radial metallicity distribution and the age-metallicity relation. We found a possible increase of metallicity with age, which, if confirmed, would provide observational evidence for radial migration. Although a statistical significance is given, more studies are certainly needed to exclude selection effects, for example. The comparison of open clusters and Cepheids with recent Galactic models agrees well in general. However, the models do not reproduce the flat gradient of the open clusters in the outer disc. Thus, the effect of radial migration is either underestimated in the models, or an additional mechanism is at work. Conclusions: Apart from the Cepheids, open clusters are the best tracers for metallicity over large Galactocentric distances in the Milky Way. For a sound statistical analysis, a sufficiently large and homogeneous sample of cluster metallicities is needed. Our compilation is currently by far the largest and provides the basis for several basic studies such as the statistical

  19. Molecular machines open cell membranes.

    PubMed

    García-López, Víctor; Chen, Fang; Nilewski, Lizanne G; Duret, Guillaume; Aliyan, Amir; Kolomeisky, Anatoly B; Robinson, Jacob T; Wang, Gufeng; Pal, Robert; Tour, James M

    2017-08-30

    Beyond the more common chemical delivery strategies, several physical techniques are used to open the lipid bilayers of cellular membranes. These include using electric and magnetic fields, temperature, ultrasound or light to introduce compounds into cells, to release molecular species from cells or to selectively induce programmed cell death (apoptosis) or uncontrolled cell death (necrosis). More recently, molecular motors and switches that can change their conformation in a controlled manner in response to external stimuli have been used to produce mechanical actions on tissue for biomedical applications. Here we show that molecular machines can drill through cellular bilayers using their molecular-scale actuation, specifically nanomechanical action. Upon physical adsorption of the molecular motors onto lipid bilayers and subsequent activation of the motors using ultraviolet light, holes are drilled in the cell membranes. We designed molecular motors and complementary experimental protocols that use nanomechanical action to induce the diffusion of chemical species out of synthetic vesicles, to enhance the diffusion of traceable molecular machines into and within live cells, to induce necrosis and to introduce chemical species into live cells. We also show that, by using molecular machines that bear short peptide addends, nanomechanical action can selectively target specific cell-surface recognition sites. Beyond the in vitro applications demonstrated here, we expect that molecular machines could also be used in vivo, especially as their design progresses to allow two-photon, near-infrared and radio-frequency activation.

  20. Molecular machines open cell membranes

    NASA Astrophysics Data System (ADS)

    García-López, Víctor; Chen, Fang; Nilewski, Lizanne G.; Duret, Guillaume; Aliyan, Amir; Kolomeisky, Anatoly B.; Robinson, Jacob T.; Wang, Gufeng; Pal, Robert; Tour, James M.

    2017-08-01

    Beyond the more common chemical delivery strategies, several physical techniques are used to open the lipid bilayers of cellular membranes. These include using electric and magnetic fields, temperature, ultrasound or light to introduce compounds into cells, to release molecular species from cells or to selectively induce programmed cell death (apoptosis) or uncontrolled cell death (necrosis). More recently, molecular motors and switches that can change their conformation in a controlled manner in response to external stimuli have been used to produce mechanical actions on tissue for biomedical applications. Here we show that molecular machines can drill through cellular bilayers using their molecular-scale actuation, specifically nanomechanical action. Upon physical adsorption of the molecular motors onto lipid bilayers and subsequent activation of the motors using ultraviolet light, holes are drilled in the cell membranes. We designed molecular motors and complementary experimental protocols that use nanomechanical action to induce the diffusion of chemical species out of synthetic vesicles, to enhance the diffusion of traceable molecular machines into and within live cells, to induce necrosis and to introduce chemical species into live cells. We also show that, by using molecular machines that bear short peptide addends, nanomechanical action can selectively target specific cell-surface recognition sites. Beyond the in vitro applications demonstrated here, we expect that molecular machines could also be used in vivo, especially as their design progresses to allow two-photon, near-infrared and radio-frequency activation.

  1. Self-discharge in bimetallic cells containing alkali metal

    NASA Technical Reports Server (NTRS)

    Foster, M. S.; Hesson, J. C.; Shimotake, H.

    1969-01-01

    Theoretical analysis of thermally regenerative bimetallic cells with alkali metal anodes shows a relation between the current drawn and the rate of discharge under open-circuit conditions. The self-discharge rate of the cell is due to the dissolution and ionization of alkali metal atoms in the fused-salt electrolyte

  2. Mechanical behavior of open cell aluminum foams

    NASA Astrophysics Data System (ADS)

    Zhou, Jikou

    Open cell metallic foams are relatively new materials with increasingly applications due to their attractive combinations of physical, chemical, mechanical and optical properties. Since plastic deformation in the struts involves dislocation motion, dislocation slip bands are used to track the initiation/propagation and locations of plastic deformation in individual struts. We find that the onset of plastic deformation in struts is far beyond the observable strut/cell shape changes, and both plastic bending and buckling are strut deformation modes. To measure the strut mechanical properties, an existing micro-scale tensile tester was updated to test the individual struts extracted from foams using electro-discharged machining. The micro-tensile testing results show that the foam struts are typically more ductile and one time stronger than the corresponding fully dense alloy. To integrate the measured strut and foam properties, a four-strut structure unit is identified as a structural representative of the open cell foam structure. Based on the observed strut deformation modes, mechanics analysis is performed on the structure unit to predict the foam stiffness and strength. The predictions are in good agreement with the measured data, suggesting the significance of the studies on the foam strut properties and deformation. This model also predicts the bounds of the foam strengths. Under cyclic compression, foams fail due to damage accumulation in individual struts, in which surface cracks initiate and grow. At low stress levels, surface cracks are formed in multiple struts that are distributed across the foam block. This results in an abrupt strain jump due to the crush of foam block, upon foam failure. To meet applications requirements, open cell aluminum foams are usually annealed or strengthened. The studies are carried out in the foams in the as-fabricated (F), annealed (O) and T6-strengthed (T6) conditions. We find that annealing and T6 strengthening

  3. Open Zinc Freezing-Point Cell Assembly and Evaluation

    NASA Astrophysics Data System (ADS)

    Žužek, V.; Batagelj, V.; Drnovšek, J.; Bojkovski, J.

    2014-07-01

    An open metal freezing-point cell design has been developed in the Laboratory of Metrology and Quality. According to our design, a zinc cell was successfully assembled. The paper presents the needed parts for the cell, the cleaning process, and sealing of the cell. The assembled cell was then evaluated by comparison with two commercial closed zinc cells of different manufacturers. The freezing plateaus of the cells were measured, and a direct cell comparison was made. It was shown that the assembled open cell performed better than the used closed cell and was close to the brand new closed cell. The nominal purity of the zinc used for the open cell was 7 N, but the freezing plateau measurement suggests a higher impurity concentration. It was assumed that the zinc was contaminated to some extent during the process of cutting as its original shape was an irregular cylinder. The uncertainty due to impurities for the assembled cell is estimated to be 0.3 mK. Furthermore, the immersion profile and the pressure coefficient were measured. Both results are close to their theoretical values.

  4. Understanding hydrogen adsorption in metal-organic frameworks with open metal sites: a computational study.

    PubMed

    Yang, Qingyuan; Zhong, Chongli

    2006-01-19

    Recent experimental investigations show that the open metal sites may have a favorable impact on the hydrogen adsorption capacity of metal-organic frameworks (MOFs); however, no definite evidence has been obtained to date and little is known on the interactions between hydrogen and the pore walls of this kind of MOFs. In this work, a combined grand canonical Monte Carlo simulation and density functional theory calculation is performed on the adsorption of hydrogen in MOF-505, a recently synthesized MOF with open metal sites, to provide insight into molecular-level details of the underlying mechanisms. This work shows that metal-oxygen clusters are preferential adsorption sites for hydrogen, and the strongest adsorption of hydrogen is found in the directions of coordinatively unsaturated open metal sites, providing evidence that the open metal sites have a favorable impact on the hydrogen sorption capacity of MOFs. The storage capacity of hydrogen of MOF-505 at room temperature and moderate pressures is predicted to be low, in agreement with the outcome for hydrogen physisorption in other porous materials.

  5. Bandgap opening in bilayer graphene at metal contacts

    NASA Astrophysics Data System (ADS)

    Nouchi, Ryo

    A bandgap is opened in bilayer graphene (BLG) by introducing a potential difference between the two graphene layers, raising expectations for its application to a transistor channel. The potential difference can be introduced, for example by charge transfer from surface adsorbates. Thus, a finite bandgap is expected to be opened also at a metal contact, an inevitable component of transistors, where interfacial charge transfer occurs to align the Fermi levels of the metallic electrode and the underlying BLG. The bandgap at the metal-BLG interface can be detected by the superlinear current-voltage characteristics in back-gate field-effect transistors, caused by carriers propagating through the bandgap, i.e., by the band-to-band transport. The superlinearity was higher in the positively-gated region, attributed to hole doping from the Cr/Au electrodes. The control experiments using single-layer graphene (SLG) did not have a superlinearity, which is consistent with the fact that a sizeable bandgap is not expected at the metal-SLG interface. The current transport through the bandgap should be an additional source of electrode-contact resistance.

  6. Open source bioimage informatics for cell biology.

    PubMed

    Swedlow, Jason R; Eliceiri, Kevin W

    2009-11-01

    Significant technical advances in imaging, molecular biology and genomics have fueled a revolution in cell biology, in that the molecular and structural processes of the cell are now visualized and measured routinely. Driving much of this recent development has been the advent of computational tools for the acquisition, visualization, analysis and dissemination of these datasets. These tools collectively make up a new subfield of computational biology called bioimage informatics, which is facilitated by open source approaches. We discuss why open source tools for image informatics in cell biology are needed, some of the key general attributes of what make an open source imaging application successful, and point to opportunities for further operability that should greatly accelerate future cell biology discovery.

  7. Phytoplankton responses to atmospheric metal deposition in the coastal and open-ocean Sargasso Sea.

    PubMed

    Mackey, Katherine R M; Buck, Kristen N; Casey, John R; Cid, Abigail; Lomas, Michael W; Sohrin, Yoshiki; Paytan, Adina

    2012-01-01

    This study investigated the impact of atmospheric metal deposition on natural phytoplankton communities at open-ocean and coastal sites in the Sargasso Sea during the spring bloom. Locally collected aerosols with different metal contents were added to natural phytoplankton assemblages from each site, and changes in nitrate, dissolved metal concentration, and phytoplankton abundance and carbon content were monitored. Addition of aerosol doubled the concentrations of cadmium (Cd), cobalt (Co), copper (Cu), iron (Fe), manganese (Mn), and nickel (Ni) in the incubation water. Over the 3-day experiments, greater drawdown of dissolved metals occurred in the open ocean water, whereas little metal drawdown occurred in the coastal water. Two populations of picoeukaryotic algae and Synechococcus grew in response to aerosol additions in both experiments. Particulate organic carbon increased and was most sensitive to changes in picoeukaryote abundance. Phytoplankton community composition differed depending on the chemistry of the aerosol added. Enrichment with aerosol that had higher metal content led to a 10-fold increase in Synechococcus abundance in the oceanic experiment but not in the coastal experiment. Enrichment of aerosol-derived Co, Mn, and Ni were particularly enhanced in the oceanic experiment, suggesting the Synechococcus population may have been fertilized by these aerosol metals. Cu-binding ligand concentrations were in excess of dissolved Cu in both experiments, and increased with aerosol additions. Bioavailable free hydrated Cu(2+) concentrations were below toxicity thresholds throughout both experiments. These experiments show (1) atmospheric deposition contributes biologically important metals to seawater, (2) these metals are consumed over time scales commensurate with cell growth, and (3) growth responses can differ between distinct Synechococcus or eukaryotic algal populations despite their relatively close geographic proximity and taxonomic similarity.

  8. Phytoplankton responses to atmospheric metal deposition in the coastal and open-ocean Sargasso Sea

    PubMed Central

    Mackey, Katherine R. M.; Buck, Kristen N.; Casey, John R.; Cid, Abigail; Lomas, Michael W.; Sohrin, Yoshiki; Paytan, Adina

    2012-01-01

    This study investigated the impact of atmospheric metal deposition on natural phytoplankton communities at open-ocean and coastal sites in the Sargasso Sea during the spring bloom. Locally collected aerosols with different metal contents were added to natural phytoplankton assemblages from each site, and changes in nitrate, dissolved metal concentration, and phytoplankton abundance and carbon content were monitored. Addition of aerosol doubled the concentrations of cadmium (Cd), cobalt (Co), copper (Cu), iron (Fe), manganese (Mn), and nickel (Ni) in the incubation water. Over the 3-day experiments, greater drawdown of dissolved metals occurred in the open ocean water, whereas little metal drawdown occurred in the coastal water. Two populations of picoeukaryotic algae and Synechococcus grew in response to aerosol additions in both experiments. Particulate organic carbon increased and was most sensitive to changes in picoeukaryote abundance. Phytoplankton community composition differed depending on the chemistry of the aerosol added. Enrichment with aerosol that had higher metal content led to a 10-fold increase in Synechococcus abundance in the oceanic experiment but not in the coastal experiment. Enrichment of aerosol-derived Co, Mn, and Ni were particularly enhanced in the oceanic experiment, suggesting the Synechococcus population may have been fertilized by these aerosol metals. Cu-binding ligand concentrations were in excess of dissolved Cu in both experiments, and increased with aerosol additions. Bioavailable free hydrated Cu2+ concentrations were below toxicity thresholds throughout both experiments. These experiments show (1) atmospheric deposition contributes biologically important metals to seawater, (2) these metals are consumed over time scales commensurate with cell growth, and (3) growth responses can differ between distinct Synechococcus or eukaryotic algal populations despite their relatively close geographic proximity and taxonomic similarity. PMID

  9. The efficacy of magnetic field on the thermal behavior of MnFe2O4 nanofluid as a functional fluid through an open-cell metal foam tube

    NASA Astrophysics Data System (ADS)

    Amani, Mohammad; Ameri, Mohammad; Kasaeian, Alibakhsh

    2017-06-01

    In the present experimental study, the influence of permanent and alternating magnetic fields on the flow and thermal behavior of MnFe2O4 magnetic nanofluid flowing through a circular open-cell metal foam tube is investigated under homogeneous heat flux conditions. The experiments are performed at various nanoparticle concentrations, Reynolds numbers and magnetic fields with different strengths and frequencies. According to the observations, the heat transfer rate enhances directly relative to nanoparticle concentration and Reynolds number in attendance of magnetic field, whereas its maximum value of 16.4% is found for 2 wt% nanoparticles at Re = 200 under alternating field with 400 G strength and 20 Hz frequency. Moreover, it is observed that the influence of strength and frequency of magnetic field is insignificant for the pressure drop. Hydrothermal efficiency as the ratio of the Nusselt number to the ratio of the pressure drop is defined in order to evaluate the privilege of using MnFe2O4 nanofluids in practical applications. The maximum efficiency of 1.25 is observed at 2 wt% under magnetic field with 400 G and 20 Hz at Re = 1000.

  10. NGC 1252: a high altitude, metal poor open cluster remnant

    NASA Astrophysics Data System (ADS)

    de la Fuente Marcos, R.; de la Fuente Marcos, C.; Moni Bidin, C.; Carraro, G.; Costa, E.

    2013-09-01

    If stars form in clusters but most stars belong to the field, understanding the details of the transition from the former to the latter is imperative to explain the observational properties of the field. Aging open clusters are one of the sources of field stars. The disruption rate of open clusters slows down with age but, as an object gets older, the distinction between the remaining cluster or open cluster remnant (OCR) and the surrounding field becomes less and less obvious. As a result, finding good OCR candidates or confirming the OCR nature of some of the best candidates still remain elusive. One of these objects is NGC 1252, a scattered group of about 20 stars in Horologium. Here we use new wide-field photometry in the UBVI passbands, proper motions from the Yale/San Juan SPM 4.0 catalogue and high-resolution spectroscopy concurrently with results from N-body simulations to decipher NGC 1252's enigmatic character. Spectroscopy shows that most of the brightest stars in the studied area are chemically, kinematically and spatially unrelated to each other. However, after analysing proper motions, we find one relevant kinematic group. This sparse object is relatively close (˜1 kpc), metal poor and is probably not only one of the oldest clusters (3 Gyr) within 1.5 kpc from the Sun but also one of the clusters located farthest from the disc, at an altitude of nearly -900 pc. That makes NGC 1252 the first open cluster that can be truly considered a high Galactic altitude OCR: an unusual object that may hint at a star formation event induced on a high Galactic altitude gas cloud. We also conclude that the variable TW Horologii and the blue straggler candidate HD 20286 are unlikely to be part of NGC 1252. NGC 1252 17 is identified as an unrelated, Population II cannonball star moving at about 400 km s-1.

  11. Entrapment of Metal Clusters in MOF Channels by Extended Hooks Anchored at Open Metal Sites

    PubMed Central

    Zheng, Shou-Tian; Zhao, Xiang; Lau, Samuel; Fuhr, Addis; Feng, Pingyun; Bu, Xianhui

    2015-01-01

    Reported here is a new concept and its practical implementation that involves the novel utilization of open metal sites (OMS) for architectural pore design. Specifically, it is shown here that OMS can be used to run extended hooks (isonicotinate in this work) from the framework wall to channel centers to effect the capture of single metal ions or clusters, with the concurrent partition of the large channel space into multiple domains, alteration of host-guest charge relationship and associated guest-exchange properties, as well as the transfer of OMS from the wall to the channel centers. The concept of the extended hook, demonstrated here in the multi-component dual-metal and dual-ligand system, should be generally applicable to a range of framework types. PMID:23826752

  12. The old, metal-poor, anticentre open cluster Trumpler 5

    NASA Astrophysics Data System (ADS)

    Donati, P.; Cocozza, G.; Bragaglia, A.; Pancino, E.; Cantat-Gaudin, T.; Carrera, R.; Tosi, M.

    2015-01-01

    As part of a long-term programme, we analyse the evolutionary status and properties of the old and populous open cluster Trumpler 5 (Tr 5), located in the Galactic anticentre direction, almost on the Galactic plane. Tr 5 was observed with Wide Field Imager@MPG/ESO Telescope using the Bessel U, B, and V filters. The cluster parameters have been obtained using the synthetic colour-magnitude diagram (CMD) method, i.e. the direct comparison of the observational CMD with a library of synthetic CMDs generated with different stellar evolution sets (Padova, FRANEC, and FST). Age, reddening, and distance are derived through the synthetic CMD method using stellar evolutionary models with subsolar metallicity (Z = 0.004 or Z = 0.006). Additional spectroscopic observations with Ultraviolet VLT Echelle Spectrograph@Very Large Telescope of three red clump stars of the cluster were used to determine more robustly the chemical properties of the cluster. Our analysis shows that Tr 5 has subsolar metallicity, with [Fe/H] = -0.403 ± 0.006 dex (derived from spectroscopy), age between 2.9 and 4 Gyr (the lower age is found using stellar models without core overshooting), reddening E(B - V) in the range 0.60-0.66 mag complicated by a differential pattern (of the order of ˜±0.1 mag), and distance modulus (m - M)0 = 12.4 ± 0.1 mag.

  13. Open-cell and closed-cell clouds off Peru

    NASA Image and Video Library

    2017-09-27

    2010/107 - 04/17 at 21 :05 UTC. Open-cell and closed-cell clouds off Peru, Pacific Ocean Resembling a frosted window on a cold winter's day, this lacy pattern of marine clouds was captured off the coast of Peru in the Pacific Ocean by the MODIS on the Aqua satellite on April 19, 2010. The image reveals both open- and closed-cell cumulus cloud patterns. These cells, or parcels of air, often occur in roughly hexagonal arrays in a layer of fluid (the atmosphere often behaves like a fluid) that begins to "boil," or convect, due to heating at the base or cooling at the top of the layer. In "closed" cells warm air is rising in the center, and sinking around the edges, so clouds appear in cell centers, but evaporate around cell edges. This produces cloud formations like those that dominate the lower left. The reverse flow can also occur: air can sink in the center of the cell and rise at the edge. This process is called "open cell" convection, and clouds form at cell edges around open centers, which creates a lacy, hollow-looking pattern like the clouds in the upper right. Closed and open cell convection represent two stable atmospheric configurations — two sides of the convection coin. But what determines which path the "boiling" atmosphere will take? Apparently the process is highly chaotic, and there appears to be no way to predict whether convection will result in open or closed cells. Indeed, the atmosphere may sometimes flip between one mode and another in no predictable pattern. Satellite: Aqua NASA/GSFC/Jeff Schmaltz/MODIS Land Rapid Response Team To learn more about MODIS go to: rapidfire.sci.gsfc.nasa.gov/gallery/?latest NASA Goddard Space Flight Center is home to the nation's largest organization of combined scientists, engineers and technologists that build spacecraft, instruments and new technology to study the Earth, the sun, our solar system, and the universe.

  14. Open end protection for solid oxide fuel cells

    DOEpatents

    Zafred, Paolo R.; Dederer, Jeffrey T.; Tomlins, Gregory W.; Toms, James M.; Folser, George R.; Schmidt, Douglas S.; Singh, Prabhakar; Hager, Charles A.

    2001-01-01

    A solid oxide fuel cell (40) having a closed end (44) and an open end (42) operates in a fuel cell generator (10) where the fuel cell open end (42) of each fuel cell contains a sleeve (60, 64) fitted over the open end (42), where the sleeve (60, 64) extends beyond the open end (42) of the fuel cell (40) to prevent degradation of the interior air electrode of the fuel cell by fuel gas during operation of the generator (10).

  15. Metal-gas fuel cell

    SciTech Connect

    Struthers, R.C.

    1984-10-16

    A metal-gas fuel cell comprising an anode chamber filled with a base anolyte solution, a metallic anode plate immersed in the anolyte; an ion exchange chamber filled with a base ionolyte solution adjacent the anode chamber; a cationic membrane between the anode and ion exchange chambers separating the anolyte and ionolyte; a cathode plate adjacent the ion exchange chamber remote from the cationic membrane with one surface in contact with the ionolyte and another surface in contact with a cathode fuel gas. The cathode plate is a laminated structure including a layer of hydrophyllic material in contact with the ionolyte, a layer of gas permeable hydrophobic material in contact with the gas and a gas and liquid permeable current collector of inert material with catalytic surfaces within the layer of hydrophyllic material. The anode and cathode plates are connected with an external electric circuit which effects the flow of electrons from the anode plate to the cathode plate.

  16. Open-cell glass crystalline porous material

    DOEpatents

    Anshits, Alexander G.; Sharonova, Olga M.; Vereshchagina, Tatiana A.; Zykova, Irina D.; Revenko, Yurii A.; Tretyakov, Alexander A.; Aloy, Albert S.; Lubtsev, Rem I.; Knecht, Dieter A.; Tranter, Troy J.; Macheret, Yevgeny

    2002-01-01

    An open-cell glass crystalline porous material made from hollow microspheres which are cenospheres obtained from fly ash, having an open-cell porosity of up to 90 vol. % is produced. The cenospheres are separated into fractions based on one or more of grain size, density, magnetic or non-magnetic, and perforated or non-perforated. Selected fractions are molded and agglomerated by sintering with a binder at a temperature below the softening temperature, or without a binder at a temperature about, or above, the softening temperature but below the temperature of liquidity. The porous material produced has an apparent density of 0.3-0.6 g/cm.sup.3, a compressive strength in the range of 1.2-3.5 MPa, and two types of openings: through-flow wall pores in the cenospheres of 0.1-30 micrometers, and interglobular voids between the cenospheres of 20-100 micrometers. The porous material of the invention has properties useful as porous matrices for immobilization of liquid radioactive waste, heat-resistant traps and filters, supports for catalysts, adsorbents and ion-exchangers.

  17. Open-cell glass crystalline porous material

    DOEpatents

    Anshits, Alexander G.; Sharonova, Olga M.; Vereshchagina, Tatiana A.; Zykova, Irina D.; Revenko, Yurii A.; Tretyakov, Alexander A.; Aloy, Albert S.; Lubtsev, Rem I.; Knecht, Dieter A.; Tranter, Troy J.; Macheret, Yevgeny

    2003-12-23

    An open-cell glass crystalline porous material made from hollow microspheres which are cenospheres obtained from fly ash, having an open-cell porosity of up to 90 vol. % is produced. The cenospheres are separated into fractions based on one or more of grain size, density, magnetic or non-magnetic, and perforated or non-perforated. Selected fractions are molded and agglomerated by sintering with a binder at a temperature below the softening temperature, or without a binder at a temperature about, or above, the softening temperature but below the temperature of liquidity. The porous material produced has an apparent density of 0.3-0.6 g/cm.sup.3, a compressive strength in the range of 1.2-3.5 MPa, and two types of openings: through-flow wall pores in the cenospheres of 0.1-30 micrometers, and interglobular voids between the cenospheres of 20-100 micrometers. The porous material of the invention has properties useful as porous matrices for immobilization of liquid radioactive waste, heat-resistant traps and filters, supports for catalysts, adsorbents and ion-exchangers.

  18. Rethinking Guard Cell Metabolism1[OPEN

    PubMed Central

    2016-01-01

    Stomata control gaseous fluxes between the internal leaf air spaces and the external atmosphere and, therefore, play a pivotal role in regulating CO2 uptake for photosynthesis as well as water loss through transpiration. Guard cells, which flank the stomata, undergo adjustments in volume, resulting in changes in pore aperture. Stomatal opening is mediated by the complex regulation of ion transport and solute biosynthesis. Ion transport is exceptionally well understood, whereas our knowledge of guard cell metabolism remains limited, despite several decades of research. In this review, we evaluate the current literature on metabolism in guard cells, particularly the roles of starch, sucrose, and malate. We explore the possible origins of sucrose, including guard cell photosynthesis, and discuss new evidence that points to multiple processes and plasticity in guard cell metabolism that enable these cells to function effectively to maintain optimal stomatal aperture. We also discuss the new tools, techniques, and approaches available for further exploring and potentially manipulating guard cell metabolism to improve plant water use and productivity. PMID:27609861

  19. The Old, Super-Metal-Rich Open Cluster, NGC 6791

    NASA Astrophysics Data System (ADS)

    Boesgaard, Ann Merchant; Lum, Michael G. G.; Deliyannis, Constantine P.

    2015-08-01

    Stellar evolution and Galactic evolution have both been greatly advanced by the study of star clusters. In addition the elemental abundance results from clusters have revealed information about Galactic chemical evolution and nucleosynthesis. The cluster, NGC 6791, has a number of bizarre properties that make it especially interesting for comparative cluster studies. It is old (8.3 Gyr) yet metal-rich ([Fe/H] = +0.30). It has a heliocentric distance of 4 kpc and a galactic latitude of +11 degrees which makes it 1 kpc above the galactic plane. Its boxy orbit has a high eccentricity (~0.5) with a perigalactic distance of 3 kpc and an apogalactic distance of 10 kpc. The orbital period of ~130 Myr indicates that it has crossed the Galactic plane several times yet has remained as an intact cluster. We have determined abundances from high-resolution (R = 46,000) Keck/HIRES spectra of turn-off stars in this open cluster NGC 6791. We have a solid determination of [Fe/H] = +0.30 +/-0.02 from measurements of some 40 unblended, unsaturated lines of both Fe I and Fe II in eight turn-off stars. Our O abundances come from the O I triplet near 7774 Å and are corrected for small nLTE effects. We find consistent ratios of [O/Fe]n with a mean of -0.06 +/-0.02, indicating a single population of stars. Our results for the alpha elements [Mg/Fe], [Si/Fe], [Ca/Fe] and [Ti/Fe] are near solar and compare well with those of old, metal-rich field stars. The Fe-peak elements, Cr and Ni, have values of [Cr/Fe] = +0.05 +/-0.02 and [Ni/Fe] = +0.04 +/-0.01. Determinations of upper limits were found for Li by spectrum synthesis; this is consistent with the upper limits in this temperature range for turn-off/subgiant stars in the relatively old, super-metal-rich cluster NGC 6253. We speculate that no stars in NGC 6791 have retained the Li with which they formed.

  20. Laser-assisted solar cell metallization processing

    NASA Technical Reports Server (NTRS)

    Dutta, S.

    1984-01-01

    Laser assisted processing techniques utilized to produce the fine line, thin metal grid structures that are required to fabricate high efficiency solar cells are investigated. The tasks comprising these investigations are summarized. Metal deposition experiments are carried out utilizing laser assisted pyrolysis of a variety of metal bearing polymer films and metalloorganic inks spun onto silicon substrates. Laser decomposition of spun on silver neodecanoate ink yields very promising results. Solar cell comb metallization patterns are written using this technique.

  1. Laser-assisted solar cell metallization processing

    NASA Technical Reports Server (NTRS)

    Rohatgi, A.; Gupta, S.; Mcmullin, P. G.; Palaschak, P. A.

    1985-01-01

    Laser-assisted processing techniques for producing high-quality solar cell metallization patterns are being investigated, developed, and characterized. The tasks comprising these investigations are outlined.

  2. Metal-Insulator-Semiconductor Nanowire Network Solar Cells.

    PubMed

    Oener, Sebastian Z; van de Groep, Jorik; Macco, Bart; Bronsveld, Paula C P; Kessels, W M M; Polman, Albert; Garnett, Erik C

    2016-06-08

    Metal-insulator-semiconductor (MIS) junctions provide the charge separating properties of Schottky junctions while circumventing the direct and detrimental contact of the metal with the semiconductor. A passivating and tunnel dielectric is used as a separation layer to reduce carrier recombination and remove Fermi level pinning. When applied to solar cells, these junctions result in two main advantages over traditional p-n-junction solar cells: a highly simplified fabrication process and excellent passivation properties and hence high open-circuit voltages. However, one major drawback of metal-insulator-semiconductor solar cells is that a continuous metal layer is needed to form a junction at the surface of the silicon, which decreases the optical transmittance and hence short-circuit current density. The decrease of transmittance with increasing metal coverage, however, can be overcome by nanoscale structures. Nanowire networks exhibit precisely the properties that are required for MIS solar cells: closely spaced and conductive metal wires to induce an inversion layer for homogeneous charge carrier extraction and simultaneously a high optical transparency. We experimentally demonstrate the nanowire MIS concept by using it to make silicon solar cells with a measured energy conversion efficiency of 7% (∼11% after correction), an effective open-circuit voltage (Voc) of 560 mV and estimated short-circuit current density (Jsc) of 33 mA/cm(2). Furthermore, we show that the metal nanowire network can serve additionally as an etch mask to pattern inverted nanopyramids, decreasing the reflectivity substantially from 36% to ∼4%. Our extensive analysis points out a path toward nanowire based MIS solar cells that exhibit both high Voc and Jsc values.

  3. Three-electrode metal oxide reduction cell

    DOEpatents

    Dees, Dennis W.; Ackerman, John P.

    2008-08-12

    A method of electrochemically reducing a metal oxide to the metal in an electrochemical cell is disclosed along with the cell. Each of the anode and cathode operate at their respective maximum reaction rates. An electrolyte and an anode at which oxygen can be evolved, and a cathode including a metal oxide to be reduced are included as is a third electrode with independent power supplies connecting the anode and the third electrode and the cathode and the third electrode.

  4. Three-Electrode Metal Oxide Reduction Cell

    DOEpatents

    Dees, Dennis W.; Ackerman, John P.

    2005-06-28

    A method of electrochemically reducing a metal oxide to the metal in an electrochemical cell is disclosed along with the cell. Each of the anode and cathode operate at their respective maximum reaction rates. An electrolyte and an anode at which oxygen can be evolved, and a cathode including a metal oxide to be reduced are included as is a third electrode with independent power supplies connecting the anode and the third electrode and the cathode and the third electrode.

  5. Open cell fire-resistant foam

    NASA Technical Reports Server (NTRS)

    Thompson, J. E.; Wittman, J. W.; Reynard, K. A.

    1976-01-01

    Candidate polyphosphazene polymers were investigated to develop a fire-resistant, thermally stable and flexible open cell foam. The copolymers were prepared in several mole ratios of the substituent side chains and a (nominal) 40:60 derivative was selected for formulation studies. Synthesis of the polymers involved solution by polymerization of hexachlorophosphazene to soluble high molecular weight poly(dichlorophosphazene), followed by derivatization of the resultant polymer in a normal fashion to give polymers in high yield and high molecular weight. Small amounts of a cure site were incorporated into the polymer for vulcanization purposes. The poly(aryloxyphosphazenes) exhibited good thermal stability and the first polymer mentioned above exhibited the best thermal behavior of all the candidate polymers studied.

  6. Cell design for lithium alloy/metal sulfide battery

    DOEpatents

    Kaun, Thomas D.

    1985-01-01

    The disclosed lithium alloy/iron sulfide cell design provides loop-like positive and negative sheet metal current collectors electrically insulated from one another by separator means, the positive collector being located outwardly of the negative collector. The collectors are initially secured within an open-ended cell housing, which allows for collector pretesting for electrical shorts prior to adding any electrode materials and/or electrolyte to the cell. Separate chambers are defined outwardly of the positive collector and inwardly of the negative collector open respectively in opposite directions toward the open ends of the cell housing; and positive and negative electrode materials can be extruded into these respective chambers via the opposite open housing ends. The chambers and cell housing ends can then be sealed closed. A cross wall structurally reinforces the cell housing and also thereby defines two cavities, and paired positive and negative collectors are disposed in each cavity and electrically connected in parallel. The cell design provides for a high specific energy output and improved operating life in that any charge-discharge cycle swelling of the positive electrode material will be inwardly against only the positive collector to minimize shorts caused by the collectors shifting relative to one another.

  7. Improved cell design for lithium alloy/metal sulfide battery

    DOEpatents

    Kaun, T.D.

    1984-03-30

    The disclosed lithium alloy/iron sulfide cell design provides loop-like positive and negative sheet metal current collectors electrically insulated from one another by separator means, the positive collector being located outwardly of the negative collector. The collectors are initially secured within an open-ended cell housing, which allows for collector pretesting for electrical shorts prior to adding any electrode materials and/or electrolyte to the cell. Separate chambers are defined outwardly of the positive collector and inwardly of the negative collector open respectively in opposite directions toward the open ends of the cell housing; and positive and negative electrode materials can be extruded into these respective chambers via the opposite open housing ends. The chambers and cell housing ends can then be sealed closed. A cross wall structurally reinforces the cell housing and also thereby defines two cavities, and paired positive and negative collectors are disposed in each cavity and electrically connected in parallel. The cell design provides for a high specific energy output and improved operating life in that any charge-discharge cycle swelling of the positive electrode material will be inwardly against only the positive collector to minimize shorts caused by the collectors shifting relative to one another.

  8. Transition metal catalysis in the mitochondria of living cells

    NASA Astrophysics Data System (ADS)

    Tomás-Gamasa, María; Martínez-Calvo, Miguel; Couceiro, José R.; Mascareñas, José L.

    2016-09-01

    The development of transition metal catalysts capable of promoting non-natural transformations within living cells can open significant new avenues in chemical and cell biology. Unfortunately, the complexity of the cell makes it extremely difficult to translate standard organometallic chemistry to living environments. Therefore, progress in this field has been very slow, and many challenges, including the possibility of localizing active metal catalysts into specific subcellular sites or organelles, remain to be addressed. Herein, we report a designed ruthenium complex that accumulates preferentially inside the mitochondria of mammalian cells, while keeping its ability to react with exogenous substrates in a bioorthogonal way. Importantly, we show that the subcellular catalytic activity can be used for the confined release of fluorophores, and even allows selective functional alterations in the mitochondria by the localized transformation of inert precursors into uncouplers of the membrane potential.

  9. Transition metal catalysis in the mitochondria of living cells

    PubMed Central

    Tomás-Gamasa, María; Martínez-Calvo, Miguel; Couceiro, José R.; Mascareñas, José L.

    2016-01-01

    The development of transition metal catalysts capable of promoting non-natural transformations within living cells can open significant new avenues in chemical and cell biology. Unfortunately, the complexity of the cell makes it extremely difficult to translate standard organometallic chemistry to living environments. Therefore, progress in this field has been very slow, and many challenges, including the possibility of localizing active metal catalysts into specific subcellular sites or organelles, remain to be addressed. Herein, we report a designed ruthenium complex that accumulates preferentially inside the mitochondria of mammalian cells, while keeping its ability to react with exogenous substrates in a bioorthogonal way. Importantly, we show that the subcellular catalytic activity can be used for the confined release of fluorophores, and even allows selective functional alterations in the mitochondria by the localized transformation of inert precursors into uncouplers of the membrane potential. PMID:27600651

  10. Laser-assisted solar cell metallization processing

    NASA Technical Reports Server (NTRS)

    Dutta, S.

    1984-01-01

    Laser-assisted processing techniques utilized to produce the fine line, thin metal grid structures that are required to fabricate high efficiency solar cells are examined. Two basic techniques for metal deposition are investigated; (1) photochemical decomposition of liquid or gas phase organometallic compounds utilizing either a focused, CW ultraviolet laser (System 1) or a mask and ultraviolet flood illumination, such as that provided by a repetitively pulsed, defocused excimer laser (System 2), for pattern definition, and (2) thermal deposition of metals from organometallic solutions or vapors utilizing a focused, CW laser beam as a local heat source to draw the metallization pattern.

  11. Mechanisms of kidney cell injury from metals.

    PubMed Central

    Fowler, B A

    1993-01-01

    The most environmentally abundant toxic metals/metalloids (arsenic, cadmium, lead, and mercury) are each known to produce cell injury in the kidney but the molecular mechanisms underlying these events are now being elucidated. It is clear that the nephrotoxicity of these agents is due, in part, to the fact that urinary elimination is a major route of excretion from the body. The role(s) of molecular factors such as metal-binding proteins, inclusion bodies, and cell-specific receptorlike proteins that appear to influence renal tubule cell expression, have attracted increased interest as determinants that modulate cell populations as special risk for toxicity and renal cancer. The future of mechanistic toxicology studies with regard to how and why only certain renal cell populations become targets for toxicity from these metals/metalloids and other less common inorganic nephrotoxicants must focus on the molecular handling of these agents by target cell populations. Images FIGURE 1. FIGURE 3. PMID:8354182

  12. Mechanisms of kidney cell injury from metals

    SciTech Connect

    Fowler, B.A. )

    1993-04-01

    The most environmentally abundant toxic metals/metalloids (arsenic, cadmium, lead, and mercury) are each known to produce cell injury in the kidney but the molecular mechanisms underlying these events are now being elucidated. It is clear that the nephrotoxicity of these agents is due, in part, to the fact that urinary elimination is a major route of excretion from the body. The role(s) of molecular factors such as metal-binding proteins, inclusion bodies, and cell-specific receptorlike proteins that appear to influence renal tubule cell expression, have attracted increased interest as determinants that modulate cell populations as special risk for toxicity and renal cancer. The future of mechanistic toxicology studies with regard to how and why only certain renal cell populations become targets for toxicity from these metals/metalloids and other less common inorganic nephrotoxicants must focus on the molecular handling of these agents by target cell populations. 90 refs.

  13. Band gap opening in bilayer silicene by alkali metal intercalation

    NASA Astrophysics Data System (ADS)

    Liu, Hongsheng; Han, Nannan; Zhao, Jijun

    2014-11-01

    Recently, bilayer and multilayer silicene have attracted increased attention following the boom of silicene, which holds great promise for future applications in microelectronic devices. Herein we systematically investigate all stacking configurations of bilayer silicene and the corresponding electronic properties. Strong coupling is found between two silicene layers, which destroys the Dirac cones in the band structures of pristine silicene and makes bilayer silicene sheets metallic. However, intercalation of alkali metal (especially potassium) can effectively decouple the interaction between two silicene layers. In the K-intercalated bilayer silicene (KSi4), the Dirac cones are recovered with a small band gap of 0.27 eV located about 0.55 eV below the Fermi level. Furthermore, intercalation of K+ cations in bilayer silicene (K+Si4) results in a semiconductor with a moderate band gap of 0.43 eV, making it ideal for microelectronic applications.

  14. Metallic foil-assisted laser cell printing.

    PubMed

    Lin, Yafu; Huang, Yong; Chrisey, Douglas B

    2011-02-01

    Laser direct-write technology such as modified laser-induced forward transfer (LIFT) is emerging as a revolutionary technology for biological construct fabrication. While many modified LIFT-based cell direct writing successes have been achieved, possible process-induced cell injury and death is still a big hurdle for modified LIFT-based cell direct writing to be a viable technology. The objective of this study is to propose metallic foil-assisted LIFT using a four-layer structure to achieve better droplet size control and increase cell viability in direct writing of human colon cancer cells (HT-29). The proposed four layers include a quartz disk, a sacrificial and adhesive layer, a metallic foil, and a cell suspension layer. The bubble formation-induced stress wave is responsible for droplet formation. It is found that the proposed metallic foil-assisted LIFT approach is an effective cell direct-write technology and provides better printing resolution and high post-transfer cell viability when compared with other conventional modified LIFT technologies such as matrix-assisted pulsed-laser evaporation direct-write; at the same time, the possible contamination from the laser energy absorbing material is minimized using a metallic foil.

  15. Interaction of molecular hydrogen with open transition metal centers for enhanced binding in metal-organic frameworks: a computational study.

    PubMed

    Lochan, Rohini C; Khaliullin, Rustam Z; Head-Gordon, Martin

    2008-05-19

    Molecular hydrogen is known to form stable, "nonclassical" sigma complexes with transition metal centers that are stabilized by donor-acceptor interactions and electrostatics. In this computational study, we establish that strong H2 sorption sites can be obtained in metal-organic frameworks by incorporating open transition metal sites on the organic linkers. Using density functional theory and energy decomposition analysis, we investigate the nature and characteristics of the H2 interaction with models of exposed open metal binding sites {half-sandwich piano-stool shaped complexes of the form (Arene)ML(3- n)(H2)n [M=Cr, Mo, V(-), Mn(+); Arene = C6H5X (X=H, F, Cl, OCH3, NH2, CH3, CF3) or C6H3Y2X (Y=COOH, X=CF3, Cl; L=CO; n=1-3]}. The metal-H2 bond dissociation energy of the studied complexes is calculated to be between 48 and 84 kJ/mol, based on the introduction of arene substituents, changes to the metal core, and of charge-balancing ligands. Thus, design of the binding site controls the H2 binding affinity and could be potentially used to control the magnitude of the H2 interaction energy to achieve reversible sorption characteristics at ambient conditions. Energy decomposition analysis illuminates both the possibilities and present challenges associated with rational materials design.

  16. Metals Emissions from the Open Detonation Treatment of Energetic Wastes

    DTIC Science & Technology

    2004-10-01

    in the projectile body and nose tip and there are metal powders within the projectile. There is also lead styphnate , barium nitrate, antimony sulfide...1.375E-07 Barium nitra Ba 0.1946 0.011 1.45E-07 Antimony su Sb 0.12172 0.011 9.08E-08 Aluminum Al 0.08 0.048 2.60E-07 projectile 2.21 1043 steel Fe 99...constituents: 33g NC and 3.3g NG), 0.9g of lead, 0.53g chromium, 89.4g copper, 33.3g zinc, 4.1g aluminum, 67.3g iron, and 0.07g of barium . Test BB-OD2

  17. Fuel cells and the theory of metals.

    NASA Technical Reports Server (NTRS)

    Bocciarelli, C. V.

    1972-01-01

    Metal theory is used to study the role of metal catalysts in electrocatalysis, with particular reference to alkaline hydrogen-oxygen fuel cells. Use is made of a simple model, analogous to that used to interpret field emission in vacuum. Theoretical values for all the quantities in the Tafel equation are obtained in terms of bulk properties of the metal catalysts (such as free electron densities and Fermi level). The reasons why some processes are reversible (H-electrodes) and some irreversible (O-electrodes) are identified. Selection rules for desirable properties of catalytic materials are established.

  18. Fuel cells and the theory of metals.

    NASA Technical Reports Server (NTRS)

    Bocciarelli, C. V.

    1972-01-01

    Metal theory is used to study the role of metal catalysts in electrocatalysis, with particular reference to alkaline hydrogen-oxygen fuel cells. Use is made of a simple model, analogous to that used to interpret field emission in vacuum. Theoretical values for all the quantities in the Tafel equation are obtained in terms of bulk properties of the metal catalysts (such as free electron densities and Fermi level). The reasons why some processes are reversible (H-electrodes) and some irreversible (O-electrodes) are identified. Selection rules for desirable properties of catalytic materials are established.

  19. Finite Element Modeling of Metal Foam Structures Subject to Compressive Loading

    DTIC Science & Technology

    2001-12-01

    TERMS aluminum metal foam, composite metal foam, metal foam compressive loading, metal foam stiffness, metal foam strength 16. PRICE CODE 17...EXPERIMENTS........................................................................................................ 23 A. OPEN CELL ALUMINUM METAL FOAM...23 B. ALUMINUM METAL FOAM FILLED WITH ELASTO-PLASTIC MATERIAL

  20. A precious-metal free micro fuel cell accumulator

    NASA Astrophysics Data System (ADS)

    Bretthauer, C.; Müller, C.; Reinecke, H.

    2011-05-01

    In recent years, integrated fuel cell (FC) type primary and secondary batteries attracted a great deal of attention as integrated on-chip power sources due to their high theoretical power densities. Unfortunately, the costs of these devices have been rather high. This is partially due to the involved clean-room processes, but also due to the fact that these devices generally rely on expensive precious-metals such as Pd and Pt. Therefore we developed a novel integrated FC type accumulator that is based on non-precious-metals only. The key component of the presented accumulator is its alkaline polymer electrolyte membrane that allows not only the usage of a low-cost AB5 type hydrogen storage electrode, but also the usage of La0.6Ca0.4CoO3 as a precious-metal free bifunctional catalyst for the air-breathing electrode. Additionally the presented design requires only comparatively few cleanroom processes which further reduces the overall production costs. Although abdicating precious-metals, the presented accumulator shows an open circuit voltage of 0.81 V and a maximum power density of 0.66 mW cm-2 which is comparable or even superior to former precious-metal based cells.

  1. Development of nickel-metal hydride cell

    NASA Technical Reports Server (NTRS)

    Kuwajima, Saburo; Kamimori, Nolimits; Nakatani, Kensuke; Yano, Yoshiaki

    1993-01-01

    National Space Development Agency of Japan (NASDA) has conducted the research and development (R&D) of battery cells for space use. A new R&D program about a Nickel-Metal Hydride (Ni-MH) cell for space use from this year, based on good results in evaluations of commercial Ni-MH cells in Tsukuba Space Center (TKSC), was started. The results of those commercial Ni-MH cell's evaluations and recent status about the development of Ni-MH cells for space use are described.

  2. Open framework metal chalcogenides as efficient photocatalysts for reduction of CO2 into renewable hydrocarbon fuel.

    PubMed

    Sasan, Koroush; Lin, Qipu; Mao, Chengyu; Feng, Pingyun

    2016-06-07

    Open framework metal chalcogenides are a family of porous semiconducting materials with diverse chemical compositions. Here we show that these materials containing covalent three-dimensional superlattices of nanosized supertetrahedral clusters can function as efficient photocatalysts for the reduction of CO2 to CH4. Unlike dense semiconductors, metal cations are successfully incorporated into the channels of the porous semiconducting materials to further tune the physical properties of the materials such as electrical conductivity and band gaps. In terms of the photocatalytic properties, the metal-incorporated porous chalcogenides demonstrated enhanced solar energy absorption and higher electrical conductivity and improved photocatalytic activity.

  3. LITHIUM ABUNDANCES OF THE SUPER-METAL-RICH OPEN CLUSTER NGC 6253

    SciTech Connect

    Cummings, Jeffrey D.; Deliyannis, Constantine P.; Maderak, Ryan M.; Anthony-Twarog, Barbara; Twarog, Bruce E-mail: con@astro.indiana.edu E-mail: bjat@ku.edu

    2012-11-01

    High-resolution CTIO 4 m/HYDRA spectroscopy of the super-metal-rich open cluster NGC 6253 ([Fe/H] = +0.43 {+-} 0.01) has been used to study the stellar lithium (Li) abundances near the cluster's turnoff. NGC 6253 greatly expands the range of [Fe/H] for clusters that have a Li abundance analysis. This is important for studying the complicated effects of, and potential correlations with, stellar Fe abundance on surface Li abundance. Comparisons to the younger and less-metal-rich Hyades and to the similarly aged but solar-metallicity M67 show that NGC 6253's Li abundances are qualitatively consistent with the prediction, from Standard Stellar Evolution Theory, that higher-metallicity stars have a greater Li depletion. Comparison with M67 provides evidence that the more-metal-rich NGC 6253 had a higher initial Li, which is consistent with expectations from models of Galactic Li production. NGC 6253 is also compared to the intermediate-aged NGC 3680, NGC 752, and IC 4651 open clusters. Comparison of the Li-gap positions in all six clusters shows that (1) the gap's position in T{sub eff} is independent of metallicity, but (2) higher-metallicity clusters have their gaps in higher-mass stars. In addition, the Li gap's position is shown not to evolve with age, which provides an important constraint for the non-standard depletion mechanisms that may create the Li gap.

  4. Anticancer metal drugs and immunogenic cell death.

    PubMed

    Terenzi, Alessio; Pirker, Christine; Keppler, Bernhard K; Berger, Walter

    2016-12-01

    Conventional chemotherapeutics, but also innovative precision anticancer compounds, are commonly perceived to target primarily the cancer cell compartment. However, recently it was discovered that some of these compounds can also exert immunomodulatory activities which might be exploited to synergistically enhance their anticancer effects. One specific phenomenon of the interplay between chemotherapy and the anticancer immune response is the so-called "immunogenic cell death" (ICD). ICD was discovered based on a vaccination effect exerted by cancer cells dying from pretreatment with certain chemotherapeutics, termed ICD inducers, in syngeneic transplantation mouse models. Interestingly, only a minority of drugs is able to trigger ICD without a clear-cut relation to chemical structures or their primary modes-of-action. Nevertheless, generation of reactive oxygen species (ROS) and induction of endoplasmic reticulum (ER) stress are clearly linked to ICD. With regard to metal drugs, oxaliplatin but not cisplatin is considered a bona fide ICD inducer. Taken into account that several experimental metal compounds are efficient ROS and ER stress mediators, presence of potent ICD inducers within the plethora of novel metal complexes seems feasible and has occasionally been reported. In the light of recent successes in cancer immunotherapy, here we review existing literature regarding anticancer metal drugs and ICD induction. We recommend a more profound investigation of the immunogenic features of experimental anticancer metal drugs.

  5. Static impedance behavior of programmable metallization cells

    NASA Astrophysics Data System (ADS)

    Rajabi, S.; Saremi, M.; Barnaby, H. J.; Edwards, A.; Kozicki, M. N.; Mitkova, M.; Mahalanabis, D.; Gonzalez-Velo, Y.; Mahmud, A.

    2015-04-01

    Programmable metallization cell (PMC) devices work by growing and dissolving a conducting metallic bridge across a chalcogenide glass (ChG) solid electrolyte, which changes the resistance of the cell. PMC operation relies on the incorporation of metal ions in the ChG films via photo-doping to lower the off-state resistance and stabilize resistive switching, and subsequent transport of these ions by electric fields induced from an externally applied bias. In this paper, the static on- and off-state resistance of a PMC device composed of a layered (Ag-rich/Ag-poor) Ge30Se70 ChG film with active Ag and inert Ni electrodes is characterized and modeled using three dimensional simulation code. Calibrating the model to experimental data enables the extraction of device parameters such as material bandgaps, workfunctions, density of states, carrier mobilities, dielectric constants, and affinities.

  6. Metal electrode for amorphous silicon solar cells

    DOEpatents

    Williams, Richard

    1983-01-01

    An amorphous silicon solar cell having an N-type region wherein the contact to the N-type region is composed of a material having a work function of about 3.7 electron volts or less. Suitable materials include strontium, barium and magnesium and rare earth metals such as gadolinium and yttrium.

  7. How To Cut a Round and a Square Inside Opening in a Piece of Sheet Metal Using Aviation Snips. Sheet Metal 1-001. Lesson Plan No. 2.

    ERIC Educational Resources Information Center

    Shibayama, Guy T.

    As part of a 90-hour community college course in sheet metal working, this 50-minute lesson was designed to enable a student to: (1) identify and use right and left hand aviation snips; (2) cut out a 6-inch round opening in a piece of sheet metal using aviation snips; and (3) cut out a 6-by-6 inch square opening in a piece of sheet metal using…

  8. How To Cut a Round and a Square Inside Opening in a Piece of Sheet Metal Using Aviation Snips. Sheet Metal 1-001. Lesson Plan No. 2.

    ERIC Educational Resources Information Center

    Shibayama, Guy T.

    As part of a 90-hour community college course in sheet metal working, this 50-minute lesson was designed to enable a student to: (1) identify and use right and left hand aviation snips; (2) cut out a 6-inch round opening in a piece of sheet metal using aviation snips; and (3) cut out a 6-by-6 inch square opening in a piece of sheet metal using…

  9. Open-circuit voltage improvements in low resistivity solar cells

    NASA Technical Reports Server (NTRS)

    Godlewski, M. P.; Klucher, T. M.; Mazaris, G. A.; Weizer, V. G.

    1980-01-01

    Improvements in the open circuit voltage of 0.1 ohm-cm silicon solar cells were achieved using a multistep diffusion technique. Experimental details are given along with the results of an analysis that indicate that anomalous behavior of the electron mobility in the cell base limits attainment of higher voltages.

  10. Ozone Inhibits Guard Cell K+ Channels Implicated in Stomatal Opening

    NASA Astrophysics Data System (ADS)

    Torsethaugen, Gro; Pell, Eva J.; Assmann, Sarah M.

    1999-11-01

    Ozone (O3) deleteriously affects organisms ranging from humans to crop plants, yet little is understood regarding the underlying mechanisms. In plants, O3 decreases CO2 assimilation, but whether this could result from direct O3 action on guard cells remained unknown. Potassium flux causes osmotically driven changes in guard cell volume that regulate apertures of associated microscopic pores through which CO2 is supplied to the photosynthetic mesophyll tissue. We show in Vicia faba that O3 inhibits (i) guard cell K+ channels that mediate K+ uptake that drives stomatal opening; (ii) stomatal opening in isolated epidermes; and (iii) stomatal opening in leaves, such that CO2 assimilation is reduced without direct effects of O3 on photosynthetic capacity. Direct O3 effects on guard cells may have ecological and agronomic implications for plant productivity and for response to other environmental stressors including drought.

  11. White Dwarfs in the Metal-Rich Open Cluster NGC 6253

    NASA Astrophysics Data System (ADS)

    Jeffery, E. J.; Campos, F.; Romero, A.; Kepler, S. O.

    2017-03-01

    We have obtained 53 images with the g filter and 19 images with the i filter, each with 600-second exposures of the super metal rich open cluster NGC 6253 with the Gemini-South telescope to create deep images of the cluster to observe the cluster white dwarfs for the first time. We will analyze the white dwarf luminosity function to measure the cluster's white dwarf age, search for any anomalous features (as has been seen in the similarly metal rich cluster NGC 6791), and constrain the initial-final mass relation at high metallicities. We present an update on these observations and our program to study the formation of white dwarfs in super high metallicity environments.

  12. Cellular Dewetting: Opening of Macroapertures in Endothelial Cells

    NASA Astrophysics Data System (ADS)

    Gonzalez-Rodriguez, David; Maddugoda, Madhavi; Stefani, Caroline; Janel, Sebastien; Lafont, Frank; Cuvelier, Damien; Lemichez, Emmanuel; Brochard-Wyart, Francoise

    2011-11-01

    Pathogenic bacteria can cross from blood vessels to host tissues by opening transendothelial cell macroapertures. Here we model the opening of macroapertures as a new form of dewetting, driven by the cell's membrane tension. While liquid dewetting is irreversible, we show that cellular dewetting is transient. Our model predicts the minimum radius for hole nucleation, the maximum hole size, and the dynamics of opening, in good agreement with the experiments. The physical model is then coupled with biological experimental data to reveal that a certain curvature-sensing protein controls the line tension at the rim of the hole and opposes its opening. D.G.-R. is supported by Fondation Pierre-Gilles de Gennes.

  13. Lateral Programmable Metallization Cell Devices And Applications

    NASA Astrophysics Data System (ADS)

    Ren, Minghan

    2011-12-01

    Programmable Metallization Cell (PMC) is a technology platform which utilizes mass transport in solid or liquid electrolyte coupled with electrochemical (redox) reactions to form or remove nanoscale metallic electrodeposits on or in the electrolyte. The ability to redistribute metal mass and form metallic nanostructure in or on a structure in situ, via the application of a bias on laterally placed electrodes, creates a large number of promising applications. A novel PMC-based lateral microwave switch was fabricated and characterized for use in microwave systems. It has demonstrated low insertion loss, high isolation, low voltage operation, low power and low energy consumption, and excellent linearity. Due to its non-volatile nature the switch operates with fewer biases and its simple planar geometry makes possible innovative device structures which can be potentially integrated into microwave power distribution circuits. PMC technology is also used to develop lateral dendritic metal electrodes. A lateral metallic dendritic network can be grown in a solid electrolyte (GeSe) or electrodeposited on SiO2 or Si using a water-mediated method. These dendritic electrodes grown in a solid electrolyte (GeSe) can be used to lower resistances for applications like self-healing interconnects despite its relatively low light transparency; while the dendritic electrodes grown using water-mediated method can be potentially integrated into solar cell applications, like replacing conventional Ag screen-printed top electrodes as they not only reduce resistances but also are highly transparent. This research effort also laid a solid foundation for developing dendritic plasmonic structures. A PMC-based lateral dendritic plasmonic structure is a device that has metallic dendritic networks grown electrochemically on SiO2 with a thin layer of surface metal nanoparticles in liquid electrolyte. These structures increase the distribution of particle sizes by connecting pre-deposited Ag

  14. Exploration of Gate-Opening and Breathing Phenomena in a Tailored Flexible Metal-Organic Framework.

    PubMed

    Hyun, Sung-min; Lee, Jae Hwa; Jung, Gwan Yeong; Kim, Yun Kyeong; Kim, Tae Kyung; Jeoung, Sungeun; Kwak, Sang Kyu; Moon, Dohyun; Moon, Hoi Ri

    2016-02-15

    Flexible metal-organic frameworks (MOFs) show the structural transition phenomena, gate opening and breathing, upon the input of external stimuli. These phenomena have significant implications in their adsorptive applications. In this work, we demonstrate the direct capture of these gate-opening and breathing phenomena, triggered by CO2 molecules, in a well-designed flexible MOF composed of rotational sites and molecular gates. Combining X-ray single crystallographic data of a flexible MOF during gate opening/closing and breathing with in situ X-ray powder diffraction results uncovered the origin of this flexibility. Furthermore, computational studies revealed the specific sites required to open these gates by interaction with CO2 molecules.

  15. Highly effective hydrogen isotope separation in nanoporous metal-organic frameworks with open metal sites: direct measurement and theoretical analysis.

    PubMed

    Oh, Hyunchul; Savchenko, Ievgeniia; Mavrandonakis, Andreas; Heine, Thomas; Hirscher, Michael

    2014-01-28

    Separating gaseous mixtures that consist of very similar size is one of the critical issues in modern separation technology. Especially, the separation of the isotopes hydrogen and deuterium requires special efforts, even though these isotopes show a very large mass ratio. Conventionally, H/D separation can be realized through cryogenic distillation of the molecular species or the Girdler-sulfide process, which are among the most energy-intensive separation techniques in the chemical industry. However, costs can be significantly reduced by using highly mass-selective nanoporous sorbents. Here, we describe a hydrogen isotope separation strategy exploiting the strongly attractive open metal sites present in nanoporous metal-organic frameworks of the CPO-27 family (also referred to as MOF-74). A theoretical analysis predicts an outstanding hydrogen isotopologue separation at open metal sites due to isotopal effects, which has been directly observed through cryogenic thermal desorption spectroscopy. For H2/D2 separation of an equimolar mixture at 60 K, the selectivity of 12 is the highest value ever measured, and this methodology shows extremely high separation efficiencies even above 77 K. Our theoretical results imply also a high selectivity for HD/H2 separation at similar temperatures, and together with catalytically active sites, we propose a mechanism to produce D2 from HD/H2 mixtures with natural or enriched deuterium content.

  16. Laser-induced actuation of individual microsize liquid metal droplets on an open solid surface

    NASA Astrophysics Data System (ADS)

    Liu, Wei; Wang, Chunqing; Dou, Guangbin; Tian, Yanhong; Yang, Lei

    2017-01-01

    The actuation of microsize liquid metal droplets on an open solid surface with laser offset heating is reported in this work. The process allows the droplets to move towards the laser beam center. The analysis of the actuations showed that the droplets were predominantly driven by the thermally induced wettability alteration on the solid; in contrast, Marangoni flow and vapor recoil weakened the motion of the droplets. This indicates that a localized thermal gradient was the driving force for droplet motion and suggests that it may be an alternative actuation technique in manipulating liquid metal droplets for microsystems.

  17. Boundary conditions for the solution of the three-dimensional Poisson equation in open metallic enclosures

    SciTech Connect

    Biswas, Debabrata; Singh, Gaurav; Kumar, Raghwendra

    2015-09-15

    Numerical solution of the Poisson equation in metallic enclosures, open at one or more ends, is important in many practical situations, such as high power microwave or photo-cathode devices. It requires imposition of a suitable boundary condition at the open end. In this paper, methods for solving the Poisson equation are investigated for various charge densities and aspect ratios of the open ends. It is found that a mixture of second order and third order local asymptotic boundary conditions is best suited for large aspect ratios, while a proposed non-local matching method, based on the solution of the Laplace equation, scores well when the aspect ratio is near unity for all charge density variations, including ones where the centre of charge is close to an open end or the charge density is non-localized. The two methods complement each other and can be used in electrostatic calculations where the computational domain needs to be terminated at the open boundaries of the metallic enclosure.

  18. Tuning Metal-Organic Frameworks with Open-Metal Sites and Its Origin for Enhancing CO2 Affinity by Metal Substitution.

    PubMed

    Park, Joonho; Kim, Heejin; Han, Sang Soo; Jung, Yousung

    2012-04-05

    Reducing anthropogenic carbon emission is a problem that requires immediate attention. Metal-organic frameworks (MOFs) have emerged as a promising new materials platform for carbon capture, of which Mg-MOF-74 offers chemospecific affinity toward CO2 because of the open Mg sites. Here we tune the binding affinity of CO2 for M-MOF-74 by metal substitution (M = Mg, Ca, and the first transition metal elements) and show that Ti- and V-MOF-74 can have an enhanced affinity compared to Mg-MOF-74 by 6-9 kJ/mol. Electronic structure calculations suggest that the origin of the major affinity trend is the local electric field effect of the open metal site that stabilizes CO2, but forward donation from the lone-pair electrons of CO2 to the empty d-levels of transition metals as in a weak coordination bond makes Ti and V have an even higher binding strength than Mg, Ca, and Sc.

  19. The ODD Old, Super-Metal-Rich Open Cluster, NGC 6791

    NASA Astrophysics Data System (ADS)

    Boesgaard, Ann Merchant; Lum, Michael G.; Deliyannis, Constantine P.

    2017-03-01

    We report on the composition of turn-off stars in the intriguing open cluster, NGC 6791, which is old, but super-metal-rich using Keck/HIRES spectra. We find [Fe/H] = +0.30 +/-0.02[O/Fe]n -0.06 +/-0.02,[Mg/Fe], [Si/Fe], [Ca/Fe], and [Ti/Fe] near solar and the two Fe-peak elements, Cr and Ni, are consistent with Fe.

  20. Partial Multi-Walled Metal Parts Open Up New Technical Solutions

    NASA Astrophysics Data System (ADS)

    Gross, Heinz G.

    2011-01-01

    A new fabrication process was developed which allows to build totally new mechanical constructions. Metal parts having a homogeneous structure and a complex three dimensional shape can be produced with wall sections which are multi-walled. Such constructions are already widely used in extrusion dies to optimise the flow channel geometry while the process is running. Furthermore the broadened possibilities which the fabrication process opens up can be used to solve existing problems in nearly all fields of mechanical engineering.

  1. Voltage effects on cells cultured on metallic biomedical implants

    NASA Astrophysics Data System (ADS)

    Haerihosseini, Seyed Morteza

    Electrochemical voltage shifts in metallic biomedical implants occur in-vivo due to a number of processes including mechanically assisted corrosion. Surface potential of biomedical implants and excursions from resting open circuit potential (OCP), which is the voltage they attain while in contact with an electrolyte, can significantly change the interfacial properties of the metallic surfaces and alter the behavior of the surrounding cells, compromising the biocompatibility of metallic implants. Voltages can also be controlled to modulate cell function and fate. To date, the details of the physico-chemical phenomena and the role of different biomaterial parameters involved in the interaction between cells and metallic surfaces under cathodic bias have not been fully elucidated. In this work, changes in the interfacial properties of a CoCrMo biomedical alloy (ASTM F-1537) in phosphate-buffered saline (PBS) (pH 7.4) at different voltages was studied. Step polarization impedance spectroscopy technique was used to apply 50 mV voltage steps to samples, and the time-based current transients were recorded. A new equation was derived based on capacitive discharge through a Tafel element and generalized to deal with non-ideal impedance behavior. The new function compared to the KWW-Randles function, better matched the time-transient response. The results also showed a voltage dependent oxide resistance and capacitance behavior. Additionally, the in-vitro effect of static voltages on the behavior of MC3T3-E1 pre-osteoblasts cultured on CoCrMo alloy (ASTM-1537) was studied to determine the range of cell viability and mode of cell death beyond the viable range. Cell viability and morphology, changes in actin cytoskeleton, adhesion complexes and nucleus, and mode of cell death (necrosis, or intrinsic or extrinsic apoptosis) were characterized at different voltages ranging from -1000 to +500 mV (Ag/AgCl). Moreover, electrochemical currents and metal ion concentrations at each

  2. Scandium in the open ocean: A comparison with other group 3 trivalent metals

    NASA Astrophysics Data System (ADS)

    Parker, C. E.; Brown, M. T.; Bruland, K. W.

    2016-03-01

    Little is known about the distribution of scandium (Sc) in the open ocean. Since the 1970s there has been only one published depth profile of dissolved Sc. The work presented here reports depth profiles of dissolved Sc from GEOTRACES cruises in the North Atlantic, North Pacific, and South Pacific. This work also compares the reactivity of Sc with its trivalent periodic table groupmates in Group IIIB, yttrium (Y) and lanthanum (La), and Group IIIA, aluminum (Al) and gallium (Ga). Yttrium and La are classic nutrient-type metals that increase in concentration in aging deep water; Al and Ga are classic scavenged-type metals that do the opposite. Results indicate that Sc is a hybrid-type metal with an inferred residence time on the order of 1000 years, and that Sc's inorganic speciation and reactivity are similar to Fe's and have the potential to give insights into the nonnutrient side of oceanic Fe cycling.

  3. Open-cell cloud formation over the Bahamas

    NASA Technical Reports Server (NTRS)

    2002-01-01

    What atmospheric scientists refer to as open cell cloud formation is a regular occurrence on the back side of a low-pressure system or cyclone in the mid-latitudes. In the Northern Hemisphere, a low-pressure system will draw in surrounding air and spin it counterclockwise. That means that on the back side of the low-pressure center, cold air will be drawn in from the north, and on the front side, warm air will be drawn up from latitudes closer to the equator. This movement of an air mass is called advection, and when cold air advection occurs over warmer waters, open cell cloud formations often result. This MODIS image shows open cell cloud formation over the Atlantic Ocean off the southeast coast of the United States on February 19, 2002. This particular formation is the result of a low-pressure system sitting out in the North Atlantic Ocean a few hundred miles east of Massachusetts. (The low can be seen as the comma-shaped figure in the GOES-8 Infrared image from February 19, 2002.) Cold air is being drawn down from the north on the western side of the low and the open cell cumulus clouds begin to form as the cold air passes over the warmer Caribbean waters. For another look at the scene, check out the MODIS Direct Broadcast Image from the University of Wisconsin. Image courtesy Jacques Descloitres, MODIS Land Rapid Response Team at NASA GSFC

  4. Highly efficient separation of carbon dioxide by a metal-organic framework replete with open metal sites

    PubMed Central

    Britt, David; Furukawa, Hiroyasu; Wang, Bo; Glover, T. Grant; Yaghi, Omar M.

    2009-01-01

    Selective capture of CO2, which is essential for natural gas purification and CO2 sequestration, has been reported in zeolites, porous membranes, and amine solutions. However, all such systems require substantial energy input for release of captured CO2, leading to low energy efficiency and high cost. A new class of materials named metal-organic frameworks (MOFs) has also been demonstrated to take up voluminous amounts of CO2. However, these studies have been largely limited to equilibrium uptake measurements, which are a poor predictor of separation ability, rather than the more industrially relevant kinetic (dynamic) capacity. Here, we report that a known MOF, Mg-MOF-74, with open magnesium sites, rivals competitive materials in CO2 capture, with 8.9 wt. % dynamic capacity, and undergoes facile CO2 release at significantly lower temperature, 80 °C. Mg-MOF-74 offers an excellent balance between dynamic capacity and regeneration. These results demonstrate the potential of MOFs with open metal sites as efficient CO2 capture media. PMID:19948967

  5. Highly efficient separation of carbon dioxide by a metal-organic framework replete with open metal sites.

    PubMed

    Britt, David; Furukawa, Hiroyasu; Wang, Bo; Glover, T Grant; Yaghi, Omar M

    2009-12-08

    Selective capture of CO(2), which is essential for natural gas purification and CO(2) sequestration, has been reported in zeolites, porous membranes, and amine solutions. However, all such systems require substantial energy input for release of captured CO(2), leading to low energy efficiency and high cost. A new class of materials named metal-organic frameworks (MOFs) has also been demonstrated to take up voluminous amounts of CO(2). However, these studies have been largely limited to equilibrium uptake measurements, which are a poor predictor of separation ability, rather than the more industrially relevant kinetic (dynamic) capacity. Here, we report that a known MOF, Mg-MOF-74, with open magnesium sites, rivals competitive materials in CO(2) capture, with 8.9 wt. % dynamic capacity, and undergoes facile CO(2) release at significantly lower temperature, 80 degrees C. Mg-MOF-74 offers an excellent balance between dynamic capacity and regeneration. These results demonstrate the potential of MOFs with open metal sites as efficient CO(2) capture media.

  6. Predictive models of gas sorption in a metal-organic framework with open-metal sites and small pore sizes.

    PubMed

    Pham, Tony; Forrest, Katherine A; Franz, Douglas M; Guo, Zhiyong; Chen, Banglin; Space, Brian

    2017-07-19

    Simulations of CO2 and H2 sorption were performed in UTSA-20, a metal-organic framework (MOF) having zyg topology and composed of Cu(2+) ions coordinated to 3,3',3'',5,5',5''-benzene-1,3,5-triyl-hexabenzoate (BHB) linkers. Previous experimental studies have shown that this MOF displays remarkable CO2 sorption properties and exhibits one of the highest gravimetric H2 uptakes at 77 K/1.0 atm (2.9 wt%) [Z. Guo, et al. Angew. Chem., Int. Ed., 2011, 50, 3178-3181]. For both sorbates, the simulations were executed with the inclusion of explicit many-body polarization interactions, which was necessary to reproduce sorption onto the open-metal sites. Non-polarizable potentials were also utilized for simulations of CO2 sorption as a control. The simulated excess sorption isotherms for both CO2 and H2 are in very good agreement with the corresponding experimental data over a wide range of temperatures and pressures, thus demonstrating the accuracy and predictive power of the polarizable potentials used herein. The theoretical isosteric heat of adsorption (Qst) values are also in good agreement with the newly reported experimental Qst values for the respective sorbates in UTSA-20. Sorption onto the more positively charged Cu(2+) ion of the [Cu2(O2CR)4] cluster was observed for both CO2 and H2. However, a binding site with energetics comparable to that for an open-metal site was also discovered for both sorbates. A radial distribution function (g(r)) analysis about the preferential Cu(2+) ions for CO2 and H2 revealed that both sorbates display different trends for the relative occupancy about such sites upon increasing/decreasing the pressure in the MOF. Overall, this study provides insights into the CO2 and H2 sorption mechanisms in this MOF containing open-metal sites and small pore sizes for the first time through a classical polarizable force field.

  7. Laser-assisted solar-cell metallization processing

    NASA Technical Reports Server (NTRS)

    Dutta, S.

    1984-01-01

    A photolytic metal deposition system using a focused continuous wave ultraviolet laser, a photolytic metal deposition system using a mask and ultraviolet flood illumination, and a pyrolytic metal deposition system using a focused continuous wave laser were studied. Fabrication of solar cells, as well as characterization to determine the effects of transient heat on solar cell junctions were investigated.

  8. Sorption of H2 to open metal sites in a metal-organic framework: a symmetry-adapted perturbation theory analysis.

    PubMed

    Goings, Joshua J; Ohlsen, Suzanna M; Blaisdell, Kara M; Schofield, Daniel P

    2014-09-04

    Metal-organic frameworks (MOFs) show considerable promise as materials for gas storage and separation. Many MOF structures have open metal sites, which allow for coordination of gas molecules to the metal centers. In this work, we use coupled-cluster and symmetry-adapted perturbation theory to probe the interaction between hydrogen gas and unsaturated metal sites in mimic structures based on the MOF HKUST-1. The interactions are of a mixed electrostatic/dispersive nature, with the relative magnitudes of these components dependent on the metal center. The strongest binding was found for magnesium- and zinc-containing MOFs, with an overall interaction energy of -4.5 kcal mol(-1).

  9. Openings between Defective Endothelial Cells Explain Tumor Vessel Leakiness

    PubMed Central

    Hashizume, Hiroya; Baluk, Peter; Morikawa, Shunichi; McLean, John W.; Thurston, Gavin; Roberge, Sylvie; Jain, Rakesh K.; McDonald, Donald M.

    2000-01-01

    Leakiness of blood vessels in tumors may contribute to disease progression and is key to certain forms of cancer therapy, but the structural basis of the leakiness is unclear. We sought to determine whether endothelial gaps or transcellular holes, similar to those found in leaky vessels in inflammation, could explain the leakiness of tumor vessels. Blood vessels in MCa-IV mouse mammary carcinomas, which are known to be unusually leaky (functional pore size 1.2–2 μm), were compared to vessels in three less leaky tumors and normal mammary glands. Vessels were identified by their binding of intravascularly injected fluorescent cationic liposomes and Lycopersicon esculentum lectin and by CD31 (PECAM) immunoreactivity. The luminal surface of vessels in all four tumors had a defective endothelial monolayer as revealed by scanning electron microscopy. In MCa-IV tumors, 14% of the vessel surface was lined by poorly connected, overlapping cells. The most superficial lining cells, like endothelial cells, had CD31 immunoreactivity and fenestrae with diaphragms, but they had a branched phenotype with cytoplasmic projections as long as 50 μm. Some branched cells were separated by intercellular openings (mean diameter 1.7 μm; range, 0.3–4.7 μm). Transcellular holes (mean diameter 0.6 μm) were also present but were only 8% as numerous as intercellular openings. Some CD31-positive cells protruded into the vessel lumen; others sprouted into perivascular tumor tissue. Tumors in RIP-Tag2 mice had, in addition, tumor cell-lined lakes of extravasated erythrocytes. We conclude that some tumor vessels have a defective cellular lining composed of disorganized, loosely connected, branched, overlapping or sprouting endothelial cells. Openings between these cells contribute to tumor vessel leakiness and may permit access of macromolecular therapeutic agents to tumor cells. PMID:10751361

  10. Laser-assisted solar cell metallization processing

    NASA Technical Reports Server (NTRS)

    Meier, D. L.

    1986-01-01

    The status of the laser-assisted solar cell metallization processing is described. Metallo-organic silver films were spun-on by argon ion laser beam pyrolysis. The metallo-organic decomposition (MOD) film was spun-on an evaporated Ti/Pd film to produce tood adhesion. In a maskless process, the argon ion laser writes the contact pattern. The film is then built up to obtain the required conductivity using conventional silverplating process. The Ti/Pd film in the field is chemically etched using the plated silver film as the mask. The width of the contact pattern is determined by the power of the laser. Widths as thin as 20 microns were obtained using 0.66 W of laser power. Cells fabricated with the 50 micron line widths of 4 ohm-cm floating zone (Fz) silicon-produced efficiencies of 16.6% (no passivation) which were equivalent to the best cells using conventional metallization/lithography and no passivation.

  11. Metallicity effect on stellar granulation detected from oscillating red giants in open clusters

    NASA Astrophysics Data System (ADS)

    Corsaro, E.; Mathur, S.; García, R. A.; Gaulme, P.; Pinsonneault, M.; Stassun, K.; Stello, D.; Tayar, J.; Trampedach, R.; Jiang, C.; Nitschelm, C.; Salabert, D.

    2017-08-01

    Context. The effect of metallicity on the granulation activity in stars, and hence on the convective motions in general, is still poorly understood. Available spectroscopic parameters from the updated APOGEE-Kepler catalog, coupled with high-precision photometric observations from NASA's Kepler mission spanning more than four years of observation, make oscillating red giant stars in open clusters crucial testbeds. Aims: We aim to determine the role of metallicity on the stellar granulation activity by discriminating its effect from that of different stellar properties such as surface gravity, mass, and temperature. We analyze 60 known red giant stars belonging to the open clusters NGC 6791, NGC 6819, and NGC 6811, spanning a metallicity range from [Fe/H] ≃ - 0.09 to 0.32. The parameters describing the granulation activity of these stars and their frequency of maximum oscillation power, νmax, are studied while taking into account different masses, metallicities, and stellar evolutionary stages. We derive new scaling relations for the granulation activity, re-calibrate existing ones, and identify the best scaling relations from the available set of observations. Methods: We adopted the Bayesian code Diamonds for the analysis of the background signal in the Fourier spectra of the stars. We performed a Bayesian parameter estimation and model comparison to test the different model hypotheses proposed in this work and in the literature. Results: Metallicity causes a statistically significant change in the amplitude of the granulation activity, with a dependency stronger than that induced by both stellar mass and surface gravity. We also find that the metallicity has a significant impact on the corresponding time scales of the phenomenon. The effect of metallicity on the time scale is stronger than that of mass. Conclusions: A higher metallicity increases the amplitude of granulation and meso-granulation signals and slows down their characteristic time scales toward

  12. A RAVE investigation on Galactic open clusters. I. Radial velocities and metallicities

    NASA Astrophysics Data System (ADS)

    Conrad, C.; Scholz, R.-D.; Kharchenko, N. V.; Piskunov, A. E.; Schilbach, E.; Röser, S.; Boeche, C.; Kordopatis, G.; Siebert, A.; Williams, M.; Munari, U.; Matijevič, G.; Grebel, E. K.; Zwitter, T.; de Jong, R. S.; Steinmetz, M.; Gilmore, G.; Seabroke, G.; Freeman, K.; Navarro, J. F.; Parker, Q.; Reid, W.; Watson, F.; Gibson, B. K.; Bienaymé, O.; Wyse, R.; Bland-Hawthorn, J.; Siviero, A.

    2014-02-01

    Context. Galactic open clusters (OCs) mainly belong to the young stellar population in the Milky Way disk, but are there groups and complexes of OCs that possibly define an additional level in hierarchical star formation? Current compilations are too incomplete to address this question, especially regarding radial velocities (RVs) and metallicities ([M/H]). Aims: Here we provide and discuss newly obtained RV and [M/H] data, which will enable us to reinvestigate potential groupings of open clusters and associations. Methods: We extracted additional RVs and [M/H] from the RAdial Velocity Experiment (RAVE) via a cross-match with the Catalogue of Stars in Open Cluster Areas (CSOCA). For the identified OCs in RAVE we derived overlineRV and overline{[M/H]} from a cleaned working sample and compared the results with previous findings. Results: Although our RAVE sample does not show the same accuracy as the entire survey, we were able to derive reliable overlineRV for 110 Galactic open clusters. For 37 OCs we publish overlineRV for the first time. Moreover, we determined overline{[M/H]} for 81 open clusters, extending the number of OCs with overline{[M/H]} by 69. Tables 8 and 9 are only available at the CDS via anonymous ftp to http://cdsarc.u-strasbg.fr (ftp://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/562/A54

  13. Open-Shell Phenalenyl in Transition Metal-Free Catalytic C-H Functionalization.

    PubMed

    Paira, Rupankar; Singh, Bhagat; Hota, Pradip Kumar; Ahmed, Jasimuddin; Sau, Samaresh Chandra; Johnpeter, Justin P; Mandal, Swadhin K

    2016-03-18

    Open-shell phenalenyl chemistry has widely been explored in the last five decades demonstrating its potential in various applications including molecular switch, spin memory device, molecular battery, cathode material, etc. In this article, we have explored another new direction of open-shell phenalenyl chemistry toward transition metal-free catalytic C-H functionalization process. A phenalenyl ligand, namely, 9-methylamino-phenalen-1-one (4a), promoted chelation-assisted single electron transfer (SET) process, which facilitates the C-H functionalization of unactivated arenes to form the biaryl products. The present methodology offers a diverse substrate scope, which can be operated without employing any dry or inert conditions and under truly transition metal based catalyst like loading yet avoiding any expensive or toxic transition metal. This not only is the first report on the application of phenalenyl chemistry in C-H functionalization process but also provides a low-catalyst loading organocatalytic system (up to 0.5 mol % catalyst loading) as compared to the existing ones (mostly 20-40 mol %), which has taken advantage of long known phenalenyl based radical stability through the presence of its low-lying nonbonding molecular orbital.

  14. Lanthanide metals adsorbed in an open-cage Fullerene: first-principles calculations.

    PubMed

    Jun, Guo; Zhiguo, Liu; Xuehui, Zhao; Kelong, Huang

    2012-02-01

    In this paper, the properties of a 12-membered-ring open-cage fullerene, which encapsulate La, Ce, Pr, Nd, Pm, Sm, Eu or Gd, as a guest atom, were calculated using first-principle calculations. Calculations show that La etc. lanthanide metal atoms can be stably adsorbed on the openings of the fullerenes. The average adsorption energy is about -3.65 eV in which Pr and Nd have relatively large adsorption energy with -4.75 eV and -4.63 eV, respectively. The Gd is stably adsorbed on the side wall near bottom of the fullerene with adsorption energy of -3.05 eV. The PDOS of adsorbed lanthanides were analyzed, respectively. Magnetic property of adsorbed lanthanides was also discussed. From the calculation, it is proved that most of the adsorbed lanthanides keep good magnetic property. Finally, vertical ionization potential and vertical electron affinity of the complex compounds were researched. The results show that the possibility of donating electrons of the 12-membered-ring open-cage fullerene is significantly affected by the endohedral lanthanide metals. From our calculations, it is believed that the complex compounds could be promising candidates for medicine-carrier.

  15. Construction of an open tin cell at Inmetro

    NASA Astrophysics Data System (ADS)

    da Silva, R.; Teixeira, R. N.

    2013-09-01

    For the last decade, the Thermometry Laboratory of the National Institute of Metrology, Quality and Technology (INMETRO) has been developing its own primary standards. In late 2010, a brand new fixed point cell containing high purity tin (99.9999 %) was constructed as the continuation of a project for constructing metal fixed-point cells in the positive range, in accordance with the temperature fixed-points described by the International Temperature Scale of 1990 (ITS-90) [1]. This is the fourth temperature fixed-point constructed by the laboratory team, which enables the performance of some calibrations without having to rely solely on commercially available cells. The materials and their preparation, the design, the procedures for the construction of the cell, the equipment, the investigation on its performance and its results will be detailed in the present paper. In addition, it is worth mentioning that this cell has recently taken part in a bilateral comparison with the National Physical Laboratory - NPL.

  16. Development of Thin Heterojunction Solar Cells with High Open Circuit Voltage

    NASA Astrophysics Data System (ADS)

    Monga, Tanmay

    The aim of this thesis research is the development of thin silicon heterojunction solar cells with high open circuit voltage (Voc). Heterojunction solar cells are higher in efficiency than diffused junction c-Si solar cells, and they are less vulnerable to light degradation. Furthermore, the low temperature processing of heterojunction cells favour a decrease in production costs and improve cell performance at the same time. Since about 30 % of the module cost is a result of substrate cost, thin solar cells are of economic advantage than their thicker counterparts. This lead to the research for development of thin heterojunction solar cells. For high cell efficiencies and performance, it is important for cells to have a high operating voltage and Voc. Development of heterojunction cells with high Voc required a stable and repeatable baseline process on which further improvements could be made. Therefore a baseline process for heterojunction solar cells was developed and demonstrated as a pilot line at the Solar Power Lab at ASU. All the processes involved in fabrication of cells with the baseline process were optimized to have a stable and repeatable process. The cells produced with the baseline process were 19-20% efficient. The baseline process was further used as a backbone to improve and develop thin cells with even higher Voc. The process recipe was optimized with an aim to explore the limits of Voc that could be achieved with this structure on a much thinner substrate than used for the baseline process. A record Voc greater than 760mV was recorded at SPL using Suns-Voc tester on a 50 microns thick heterojunction cell without metallization. Furthermore, Voc of 754.2 mV was measured on a 50 microns thick cell with metallization by National Renewable Energy Laboratory (NREL), which is a record for Voc for heterojunction cells with metallization. High Voc corresponds to high cell efficiency and therefore, higher module voltage and power with using the same number

  17. A Search For Planets in the Metal-Rich Open Cluster Praesepe

    NASA Astrophysics Data System (ADS)

    White, Russel

    The most promising way to distinguish between competing theories of planet formation and subsequent migration is to find and determine the basic properties of short period (< 1 yr) planets with well-determined ages younger than 1 billion years. Open clusters are the most promising locations to do this, but disappointingly no main sequence open cluster stars are known to harbor planets. This is primarily a consequence of most clusters being too distant for precise radial velocity measurements at visual wavelength. A better determined frequency of planets within open clusters would also clarify if this environment inhibits their formation, as has recently been suggested. If confirmed, that would imply that most stars will not have planets since most stars are believed to form in dense clusters. Here we request funding to support a 2-year program to search for radial velocity planets in the 600 Myr Praesepe open cluster. Praesepe is the most metal rich open cluster within 1000 pc of the sun. Based on known planet frequency - metallicity correlations, its high metallicity suggests a planet frequency enhanced by nearly a factor of 4 relative to sun- like stars; approximately 1 in 20 of its members should harbor a short period (3-10 day) hot Jupiter-like planet, and 1 in 400 of its members should have a transiting planet. The observations will be carried out using the Mayall 4-m/Echelle and Keck/HIRES facilities; nearly 100 Praesepe FGK stars will be surveyed over a 1+ year baseline. Precise radial velocities will be obtained using telluric features as a wavelength reference. We have demonstrated this technique achieves a precision of at least 50 m/s, and anticipate a final precision of 10 m/s, similar to what has been previously achieved. This precision and proposed temporal sampling will enable us to confidently identify nearly all Jupiter-sized planets with periods less than ~1 yr. The discovery of the first planets orbiting dwarf stars within an open cluster with a

  18. Precious Metal Recovery from Fuel Cell MEA's

    SciTech Connect

    Shore, Lawrence

    2004-04-27

    In 2003, Engelhard Corporation received a DOE award to develop a cost-effective, environmentally friendly approach to recover Pt from fuel cell membrane electrode assemblies (MEA’s). The most important precious metal used in fuel cells is platinum, but ruthenium is also added to the anode electrocatalyst if CO is present in the hydrogen stream. As part of the project, a large number of measurements of Pt and Ru need to be made. A low-cost approach to measuring Pt is using the industry standard spectrophotometric measurement of Pt complexed with stannous chloride. The interference of Ru can be eliminated by reading the Pt absorbance at 450 nm. Spectrophotometric methods for measuring Ru, while reported in the literature, are not as robust. These slides will discuss the options for measuring Pt and Ru using the method of UV-VIS spectrophotometry

  19. Metal-chelating polymers by anionic ring-opening polymerization and their use in quantitative mass cytometry.

    PubMed

    Illy, Nicolas; Majonis, Daniel; Herrera, Isaac; Ornatsky, Olga; Winnik, Mitchell A

    2012-08-13

    Metal-chelating polymers (MCPs) are important reagents for multiplexed immunoassays based on mass cytometry. The role of the polymer is to carry multiple copies of individual metal isotopes, typically as lanthanide ions, and to provide a reactive functionality for convenient attachment to a monoclonal antibody (mAb). For this application, the optimum combination of chain length, backbone structure, end group, pendant groups, and synthesis strategy has yet to be determined. Here we describe the synthesis of a new type of MCP based on anionic ring-opening polymerization of an activated cyclopropane (the diallyl ester of 1,1-cyclopropane dicarboxylic acid) using a combination of 2-furanmethanethiol and a phosphazene base as the initiator. This reaction takes place with rigorous control over molecular weight, yielding a polymer with a narrow molecular weight distribution, reactive pendant groups for introducing a metal chelator, and a functional end group with orthogonal reactivity for attaching the polymer to the mAbs. Following the ring-opening polymerization, a two-step transformation introduced diethylenetriaminepentaacetic acid (DTPA) chelating groups on each pendant group. The polymers were characterized by NMR, size exclusion chromatography (SEC), and thermogravimetric analysis (TGA). The binding properties toward Gd(3+) as a prototypical lanthanide (Ln) ion were also studied by isothermal titration calorimetry (ITC). Attachment to a mAb involves a Diels-Alder reaction of the terminal furan with a bismaleimide, followed by a Michael addition of a thiol on the mAb, generated by mild reduction of a disulfide bond in the hinge region. Polymer samples with a number average degree of polymerization of 35, with a binding capacity of 49.5 ± 6 Ln(3+) ions per chain, were loaded with 10 different types of Ln ions and conjugated to 10 different mAbs. A suite of metal-tagged Abs was tested by mass cytometry in a 10-plex single cell analysis of human adult peripheral blood

  20. On the lithium dip in the metal poor open cluster NGC 2243

    SciTech Connect

    François, P.; Pasquini, L.; Palsa, R.; Biazzo, K.; Bonifacio, P.

    2014-05-02

    Lithium is a key element for studying the mixing mechanisms operating in stellar interiors. It can also be used to probe the chemical evolution of the Galaxy and the Big Bang nucleosynthesis. Measuring the abundance of Lithium in stars belonging to Open Clusters (hereafter OC) allows a detailed comparison with stellar evolutionary models. NGC 2243 is particularly interesting thanks to its relative low metallicity ([Fe/H]=−0.54 ± 0.10 dex). We performed a detailed analysis of high-resolution spectra obtained with the multi-object facility FLAMES at the VLT 8.2m telescope. Lithium abundance has been measured in 27 stars. We found a Li dip center of 1.06 M{sub ⊙}, which is significantly smaller than that observed in solar metallicity and metal-rich clusters. This finding confirms and strengthens the conclusion that the mass of the stars in the Li dip strongly depends on stellar metallicity. The mean Li abundance of the cluster is log n(Li) = 2.70 dex, which is substantially higher than that observed in 47 Tue. We derived an iron abundance of [Fe/H]=−0.54±0.10 dex for NGC 2243, in agreement (within the errors) with previous findings.

  1. Electrochemical analysis of transparent oxide-less photovoltaic cell with perforation patterned metal substrate

    NASA Astrophysics Data System (ADS)

    Kim, Myoung; You, In-Kyu; Lee, Kyoung-Won; Lee, In-Hwan; Yun, Ho-Gyeong

    2013-05-01

    In terms of electrochemical behaviour, a transparent conductive oxide (TCO)-less dye-sensitized solar cell (DSSC) with two metal foils was compared with those of a metal foil-based DSSC with a TCO-coated substrate. By virtue of electrochemical impedance spectroscopy, intensity modulated photocurrent spectroscopy, intensity modulated photovoltage spectroscopy, open-circuit voltage decay, and photocurrent transient measurements, it was clearly confirmed that the limited performance of the TCO-less DSSC was caused by the restricted transport of ion species in the electrolyte due to the perforation patterned metal foil.

  2. Microleakage of Four Dental Cements in Metal Ceramic Restorations With Open Margins

    PubMed Central

    Eftekhar Ashtiani, Reza; Farzaneh, Babak; Azarsina, Mohadese; Aghdashi, Farzad; Dehghani, Nima; Afshari, Aisooda; Mahshid, Minu

    2015-01-01

    Background: Fixed prosthodontics is a routine dental treatment and microleakage is a major cause of its failure. Objectives: The aim of this study was to assess the marginal microleakage of four cements in metal ceramic restorations with adapted and open margins. Materials and Methods: Sixty sound human premolars were selected for this experimental study performed in Tehran, Iran and prepared for full-crown restorations. Wax patterns were formed leaving a 300 µm gap on one of the proximal margins. The crowns were cast and the samples were randomly divided into four groups based on the cement used. Copings were cemented using zinc phosphate cement (Fleck), Fuji Plus resin-modified glass ionomer, Panavia F2.0 resin cement, or G-Cem resin cement, according to the manufacturers’ instructions. Samples were immersed in 2% methylene blue solution. After 24 hours, dye penetration was assessed under a stereomicroscope and analyzed using the respective software. Data were analyzed using ANOVA, paired t-tests, and Kruskal-Wallis, Wilcoxon, and Mann-Whitney tests. Results: The least microleakage occurred in the Panavia F2.0 group (closed margin, 0.18 mm; open margin, 0.64 mm) and the maximum was observed in the Fleck group (closed margin, 1.92 mm; open margin, 3.32 mm). The Fleck group displayed significantly more microleakage compared to the Fuji Plus and Panavia F2.0 groups (P < 0.001) in both closed and open margins. In open margins, differences in microleakage between the Fuji Plus and G-Cem as well as between the G-Cem and Panavia F2.0 groups were significant (P < 0.001). In closed margins, only the G-Cem group displayed significantly more microleakage as compared to the Panavia F2.0 group (P < 0.05). Paired t-test results showed significantly more microleakage in open margins compared to closed margins, except in the Fuji Plus group (P = 0.539). Conclusions: Fuji Plus cement exhibited better sealing ability in closed and open margins compared to G-Cem and Fleck

  3. Microleakage of Four Dental Cements in Metal Ceramic Restorations With Open Margins.

    PubMed

    Eftekhar Ashtiani, Reza; Farzaneh, Babak; Azarsina, Mohadese; Aghdashi, Farzad; Dehghani, Nima; Afshari, Aisooda; Mahshid, Minu

    2015-11-01

    Fixed prosthodontics is a routine dental treatment and microleakage is a major cause of its failure. The aim of this study was to assess the marginal microleakage of four cements in metal ceramic restorations with adapted and open margins. Sixty sound human premolars were selected for this experimental study performed in Tehran, Iran and prepared for full-crown restorations. Wax patterns were formed leaving a 300 µm gap on one of the proximal margins. The crowns were cast and the samples were randomly divided into four groups based on the cement used. Copings were cemented using zinc phosphate cement (Fleck), Fuji Plus resin-modified glass ionomer, Panavia F2.0 resin cement, or G-Cem resin cement, according to the manufacturers' instructions. Samples were immersed in 2% methylene blue solution. After 24 hours, dye penetration was assessed under a stereomicroscope and analyzed using the respective software. Data were analyzed using ANOVA, paired t-tests, and Kruskal-Wallis, Wilcoxon, and Mann-Whitney tests. The least microleakage occurred in the Panavia F2.0 group (closed margin, 0.18 mm; open margin, 0.64 mm) and the maximum was observed in the Fleck group (closed margin, 1.92 mm; open margin, 3.32 mm). The Fleck group displayed significantly more microleakage compared to the Fuji Plus and Panavia F2.0 groups (P < 0.001) in both closed and open margins. In open margins, differences in microleakage between the Fuji Plus and G-Cem as well as between the G-Cem and Panavia F2.0 groups were significant (P < 0.001). In closed margins, only the G-Cem group displayed significantly more microleakage as compared to the Panavia F2.0 group (P < 0.05). Paired t-test results showed significantly more microleakage in open margins compared to closed margins, except in the Fuji Plus group (P = 0.539). Fuji Plus cement exhibited better sealing ability in closed and open margins compared to G-Cem and Fleck cements. When using G-Cem and Fleck cements for full metal ceramic

  4. Methods for improving solar cell open circuit voltage

    DOEpatents

    Jordan, John F.; Singh, Vijay P.

    1979-01-01

    A method for producing a solar cell having an increased open circuit voltage. A layer of cadmium sulfide (CdS) produced by a chemical spray technique and having residual chlorides is exposed to a flow of hydrogen sulfide (H.sub.2 S) heated to a temperature of 400.degree.-600.degree. C. The residual chlorides are reduced and any remaining CdCl.sub.2 is converted to CdS. A heterojunction is formed over the CdS and electrodes are formed. Application of chromium as the positive electrode results in a further increase in the open circuit voltage available from the H.sub.2 S-treated solar cell.

  5. S-P coupling induced unusual open-shell metal clusters.

    PubMed

    Cheng, Shi-Bo; Berkdemir, Cuneyt; Melko, Joshua J; Castleman, A W

    2014-04-02

    Metal clusters featuring closed supershells or aromatic character usually exhibit remarkably enhanced stability in their cluster series. However, not all stable clusters are subject to these fundamental constraints. Here, by employing photoelectron imaging spectroscopy and ab initio calculations, we present experimental and theoretical evidence on the existence of unexpectedly stable open-shell clusters, which are more stable than their closed-shell and aromatic counterparts. The stabilization of these open-shell Al-Mg clusters is proposed to originate from the S-P molecular orbital coupling, leading to highly stable species with increased HOMO-LUMO gaps, akin to s-p hybridization in an organic carbon atom that is beneficial to form stable species. Introduction of the coupling effect highlighted here not only shows the limitations of the conventional closed-shell model and aromaticity but also provides the possibility to design valuable building blocks.

  6. Atom-by-Atom and Concerted Hopping of Adatom Pairs on an Open Metal Surface

    SciTech Connect

    Bogicevic, A.; Ovesson, S.; Lundqvist, B.I.; Jennison, D.R.

    1999-08-25

    Atom-by-atom and concerted hopping of ad-dimers on the open (100) surface of fcc metals are studied by means of density-functional calculations. The adatom interaction is relatively short-ranged, and beyond next-nearest neighbors ad-dimers are effectively dissociated. Diffusion takes place by a simple shearing process, favored because it maximizes adatom coordination at the transition state This holds for Al, Au, and Rh, and is likely a general result because geometrical arguments dominate over details of the electronic structure.

  7. Testing Metal Chlorides For Use In Sodium-Cell Cathodes

    NASA Technical Reports Server (NTRS)

    Bugga, Ratnakumar V.; Attia, Alan I.; Halpert, Gerald

    1992-01-01

    Cyclic voltammetric curves of transition-metal wires in molten NaAlCl4 electrolyte used to eliminate suitability of transition metals as cathodes in sodium cells. Cyclic voltammetry used in conjunction with measurement of galvanostatic polarization curves determines whether given metal chloride suitable as cathode material in such cell. Cells useful in such high-energy-density and high-power-density applications as leveling loads on electric-power plants, supplying power to electric ground vehicles, and aerospace applications.

  8. Testing Metal Chlorides For Use In Sodium-Cell Cathodes

    NASA Technical Reports Server (NTRS)

    Bugga, Ratnakumar V.; Attia, Alan I.; Halpert, Gerald

    1992-01-01

    Cyclic voltammetric curves of transition-metal wires in molten NaAlCl4 electrolyte used to eliminate suitability of transition metals as cathodes in sodium cells. Cyclic voltammetry used in conjunction with measurement of galvanostatic polarization curves determines whether given metal chloride suitable as cathode material in such cell. Cells useful in such high-energy-density and high-power-density applications as leveling loads on electric-power plants, supplying power to electric ground vehicles, and aerospace applications.

  9. Crystallographic Evidence for Direct Metal-Metal Bonding in a Stable Open-Shell La2 @Ih -C80 Derivative.

    PubMed

    Bao, Lipiao; Chen, Muqing; Pan, Changwang; Yamaguchi, Takahisa; Kato, Tatsuhisa; Olmstead, Marilyn M; Balch, Alan L; Akasaka, Takeshi; Lu, Xing

    2016-03-18

    Endohedral metallofullerenes (EMFs) have novel structures and properties that are closely associated with the internal metallic species. Benzyl radical additions have been previously shown to form closed-shell adducts by attaching an odd number of addends to open-shell EMFs (such as Sc3 C2 @Ih -C80 ) whereas an even number of groups are added to closed-shell EMFs (for example Sc3 N@Ih -C80 ). Herein we report that benzyl radical addition to the closed-shell La2 @Ih -C80 forms a stable, open-shell monoadduct instead of the anticipated closed-shell bisadduct. Single-crystal X-ray diffraction results show the formation of a stable radical species. In this species, the La-La distance is comparable to the theoretical value of a La-La covalent bond and is shorter than reported values for other La2 @Ih -C80 derivatives, providing unambiguous evidence for the formation of direct La-La bond.

  10. An Elongated Tetrakaidecahedron Model for Open-Celled Foams

    NASA Technical Reports Server (NTRS)

    Sullivan, Roy M.; Ghosn, Louis J.; Lerch, Bradley A.

    2007-01-01

    A micro-mechanics model for non-isotropic, open-celled foams is developed using an elongated tetrakaidecahedron (Kelvin model) as the repeating unit cell. The micro-mechanics model employs an elongated Kelvin model geometry which is more general than that employed by previous authors. Assuming the cell edges possess axial and bending rigidity, the mechanics of deformation of the elongated tetrakaidecahedron lead to a set of equations for the Young's modulus, Poisson's ratio and strength of the foam in the principal material directions. These equations are written as a function of the cell edge lengths and cross-section properties, the inclination angle and the strength and stiffness of the solid material. The model is applied to predict the strength and stiffness of several polymeric foams. Good agreement is observed between the model results and the experimental measurements.

  11. Molten metal electrodes in solid oxide fuel cells

    NASA Astrophysics Data System (ADS)

    Javadekar, Ashay Dileep

    Molten metal electrodes in solid oxide fuel cells are electrochemically characterized for their possible use in direct carbon oxidation and energy storage. The cells were operated in the battery mode at 973 K, without added fuel, in order to understand the oxidation characteristics of Sb alloys as anodes at electrolyte interfaces. The cells using 50-mol% In-Sb and Sn-Sb mixtures exhibited open-circuit voltages (OCV) of 1.0 and 0.93 V, values similar to those of cells with pure In and Sn anodes respectively, and insulating In2O3 and SnO2 layers formed at the electrolyte interface. The 50-mol% Sb-Bi cell had an OCV of 0.73 V initially, close to that with pure Sb anode. The OCV remained constant until all of the Sb had been oxidized, after which it dropped to 0.43 V, similar to the value for pure Bi. SEM analysis of the spent cell showed two distinct phases, with metallic Bi at the bottom and Sb2O3 at the top. The cell with 50-mol% Sb-Pb anode exhibited an OCV that changed continuously with conversion, from 0.73 V initially to 0.67 V following the addition of charge equivalent to oxidation of 120% the Sb. The total cell impedance remained low for this entire period. EDS measurements on the sectioned Sb-Pb cell suggested formation of a mixed oxide of Pb and Sb. An energy-storage concept using molten Sb as the fuel in a reversible solid-oxide electrochemical cell was tested using a button cell with a Sc-stabilized zirconia electrolyte at 973 K, by measuring the impedances under fuel-cell and electrolyzer conditions for a range of stirred Sb-Sb2O 3 compositions. The Sb-Sb2O3 electrode impedances were found to be on the order of 0.15 ohm.cm2 for both fuel-cell and electrolyzer conditions, for compositions up to 30% Sb and 70% Sb2O3. The OCVs were 0.75 V, independent of conversion. The use of molten neat Ag and alloyed Ag-Sb for direct-carbon anodes in SOFCs has been examined at 1273 K. For Ag, an OCV typical of that expected for carbon oxidation, 1.12 V, was observed when

  12. Synthesis of Highly Porous Coordination Polymers with Open Metal Sites for Enhanced Gas Uptake and Separation.

    PubMed

    Song, Kyung Seob; Kim, Daeok; Polychronopoulou, Kyriaki; Coskun, Ali

    2016-10-12

    Metal-containing amorphous microporous polymers are an emerging class of functional porous materials in which the surface properties and functions of polymers are dictated by the nature of the metal ions incorporated into the framework. In an effort to introduce coordinatively unsaturated metal sites into the porous polymers, we demonstrate herein an aqueous-phase synthesis of porous coordination polymers (PCPs) incorporating bis(o-diiminobenzosemiquinonato)-Cu(II) or -Ni(II) bridges by simply reacting hexaminotriptycene with CuSO4·5H2O [Cu(II)-PCP] or NiCl2·6H2O [Ni(II)-PCP] in H2O. The resulting polymers showed surface areas of up to 489 m(2) g(-1) along with a narrow pore size distribution. The presence of open metal sites significantly improved the gas affinity of these frameworks, leading to an exceptional isosteric heat of adsorption of 10.3 kJ·mol(-1) for H2 at zero coverage. The high affinities of Cu(II)- and Ni(II)-PCPs toward CO2 prompted us to investigate the removal of CO2 from natural and landfill gas conditions. We found that the higher affinity of Cu(II)-PCP compared to that of Ni(II)-PCP not only allowed for the tuning of the affinity of CO2 molecules toward the sorbent, but also led to an exceptional CO2/CH4 selectivity of 35.1 for landfill gas and 20.7 for natural gas at 298 K. These high selectivities were further verified by breakthrough measurements under the simulated natural and landfill gas conditions, in which both Cu(II)- and Ni(II)-PCPs showed complete removal of CO2. These results clearly demonstrate the promising attributes of metal-containing porous polymers for gas storage and separation applications.

  13. 'Open minded' cells: how cells can change fate.

    PubMed

    Costa, Silvia; Shaw, Peter

    2007-03-01

    It has long intrigued researchers why some but not all organisms can regenerate missing body parts. Plants are remarkable in that they can regenerate the entire organism from a small piece of tissue, or even a single cell. Epigenetic mechanisms that control chromatin organization are now known to regulate the cellular plasticity and reprogramming necessary for regeneration. Interestingly, although animals and plants have evolved different strategies and mechanisms to control developmental processes, they have maintained many similarities in the way they regulate chromatin organization. Given that plants can rapidly switch fate, we propose that an understanding of the mechanisms regulating this process in plant cells could provide a new perspective on cellular dedifferentiation in animals.

  14. Programmable Metallization Cell Devices for Flexible Electronics

    NASA Astrophysics Data System (ADS)

    Baliga, Sunil

    Programmable metallization cell (PMC) technology is based on an electrochemical phenomenon in which a metallic electrodeposit can be grown or dissolved between two electrodes depending on the voltage applied between them. Devices based on this phenomenon exhibit a unique, self-healing property, as a broken metallic structure can be healed by applying an appropriate voltage between the two broken ends. This work explores methods of fabricating interconnects and switches based on PMC technology on flexible substrates. The objective was the evaluation of the feasibility of using this technology in flexible electronics applications in which reliability is a primary concern. The re-healable property of the interconnect is characterized for the silver doped germanium selenide (Ag-Ge-Se) solid electrolyte system. This property was evaluated by measuring the resistances of the healed interconnect structures and comparing these to the resistances of the unbroken structures. The reliability of the interconnects in both unbroken and healed states is studied by investigating the resistances of the structures to DC voltages, AC voltages and different temperatures as a function of time. This work also explores replacing silver with copper for these interconnects to enhance their reliability. A model for PMC-based switches on flexible substrates is proposed and compared to the observed device behavior with the objective of developing a formal design methodology for these devices. The switches were subjected to voltage sweeps and their resistance was investigated as a function of sweep voltage. The resistance of the switches as a function of voltage pulse magnitude when placed in series with a resistance was also investigated. A model was then developed to explain the behavior of these devices. All observations were based on statistical measurements to account for random errors. The results of this work demonstrate that solid electrolyte based interconnects display self

  15. Removal of Machine Oil from Metal Surface by Mesoplasma Jet under Open Atmosphere

    NASA Astrophysics Data System (ADS)

    Saito, Haruki; Shiki, Hajime; Tsujii, Kenichi; Oke, Shinichiro; Suda, Yoshiyuki; Takikawa, Hirofumi; Okawa, Takashi; Yamanaka, Shigenobu

    2009-08-01

    An attempt was made to employ the plasma-energized jet (PEN-jet) generated by pulsed arc discharge, one of the atmospheric-pressure mesoplasmas, for removal of machine oil from the surface of electrically-grounded aluminum (Al) alloy substrate under open atmosphere. Three types of nozzle configurations were examined; a metal nozzle, ceramic nozzle, and electrically-floated metal nozzle. Electric input power to the pulsed arc plasma discharge was 700 W constant. First, free-burning of the PEN-jet was observed as a function of air gas flow. When the PEN-jets were irradiated to the clean substrate, the PEN-jet with the metal nozzle caused substrate damage by the arc spot due to transferring arc discharge. Then the PEN-jet with the ceramic nozzle was irradiated to the oily substrate. The adhesion strength of sealant and water contact angle of the treated surface were then measured. As a result, these values of the oily substrate treated by the PEN-jet were almost the same as those of clean substrate. The treated surface was analyzed by Fourier transform infrared spectroscopy, Raman spectroscopy, and reflectance spectroscopy. Their spectral profiles clearly indicated oil removal from the surface by PEN-jet.

  16. Cell Division, a new open access online forum for and from the cell cycle community.

    PubMed

    Kaldis, Philipp; Pagano, Michele

    2006-04-03

    Cell Division is a new, open access, peer-reviewed online journal that publishes cutting-edge articles, commentaries and reviews on all exciting aspects of cell cycle control in eukaryotes. A major goal of this new journal is to publish timely and significant studies on the aberrations of the cell cycle network that occur in cancer and other diseases.

  17. Openings

    PubMed Central

    Selwyn, Peter A.

    2015-01-01

    Reviewing his clinic patient schedule for the day, a physician reflects on the history of a young woman he has been caring for over the past 9 years. What starts out as a routine visit then turns into a unique opening for communication and connection. A chance glimpse out the window of the exam room leads to a deeper meditation on parenthood, survival, and healing, not only for the patient but also for the physician. How many missed opportunities have we all had, without even realizing it, to allow this kind of fleeting but profound opening? PMID:26195687

  18. Electrochemical cell utilizing molten alkali metal electrode-reactant

    DOEpatents

    Virkar, Anil V.; Miller, Gerald R.

    1983-11-04

    An improved electrochemical cell comprising an additive-modified molten alkali metal electrode-reactant and/or electrolyte is disclosed. Various electrochemical cells employing a molten alkali metal, e.g., sodium, electrode in contact with a cationically conductive ceramic membrane experience a lower resistance and a lower temperature coefficient of resistance whenever small amounts of selenium are present at the interface of the electrolyte and the molten alkali metal. Further, cells having small amounts of selenium present at the electrolyte-molten metal interface exhibit less degradation of the electrolyte under long term cycling conditions.

  19. A new method of metallization for silicon solar cells

    NASA Technical Reports Server (NTRS)

    Macha, M.

    1979-01-01

    The new metallization process based on Mo-Sn system was studied. The reaction mechanism of MoO3 and its mixture with Sn was examined. The basic ink composition was modified in order to obtain a low ohmic contact to the cell. The electrical characteristics of the cells were comparable with the existing metallization processes. However, in comparison with the standard processes using silver as the contacting metal, the saving obtained by the use of the new process was substantial.

  20. Atmospheric emissions of typical toxic heavy metals from open burning of municipal solid waste in China

    NASA Astrophysics Data System (ADS)

    Wang, Yan; Cheng, Ke; Wu, Weidong; Tian, Hezhong; Yi, Peng; Zhi, Guorui; Fan, Jing; Liu, Shuhan

    2017-03-01

    Municipal solid waste (MSW) contains considerable hazardous components and the widely-distributed open MSW burning in heavily-populated urban areas can cause direct exposure of hazardous materials to citizens. By determining the best available representation of composition-varying and time-varying emission factors with fuzzy mathematics method and S-shape curves, a comprehensive atmospheric emission inventories of 9 typical toxic heavy metals (THMs, e.g. mercury (Hg), arsenic (As), lead (Pb), cadmium (Cd), chromium (Cr), selenium (Se), copper (Cu), zinc (Zn), and nickel (Ni)) from open MSW burning activities in China is established during the period of 2000-2013 for the first time. Further, the emissions in 2013 are allocated at a high spatial resolution of 0.5° × 0.5° grid by surrogate indexes. The results show that 9 typical THMs emissions from open MSW burning are estimated at 21.25 t for Hg, 131.52 t for As, 97.12 t for Pb, 10.12 t for Cd, 50.58 t for Cr, 81.95 t for Se, 382.42 t for Cu, 1790.70 t for Zn, and 43.50 t for Ni, respectively. In terms of spatial variation, the majority of emissions are concentrated in relatively developed and densely-populated regions, especially for the eastern, central and southern regions. Moreover, future emissions are also projected for the period of 2015-2030 based on different scenarios of the independent and collaborative effects of control proposals including minimizing waste, improving MSW incineration ratio, and enhancing waste sorting and recycling, etc. The collaborative effect of the above proposals is expected to bring the most effective reduction to THMs emissions from open MSW burning in China except for Hg. The results will be supplementary to all anthropogenic emissions and useful for relevant policy-making and the improvement of urban air quality as well as human health.

  1. Cell surface engineering of microorganisms towards adsorption of heavy metals.

    PubMed

    Li, Peng-Song; Tao, Hu-Chun

    2015-06-01

    Heavy metal contamination has become a worldwide environmental concern due to its toxicity, non-degradability and food-chain bioaccumulation. Conventional physical and chemical treatment methods for heavy metal removal have disadvantages such as cost-intensiveness, incomplete removal, secondary pollution and the lack of metal specificity. Microbial biomass-based biosorption is one of the approaches gaining increasing attention because it is effective, cheap, and environmental friendly and can work well at low concentrations. To enhance the adsorption properties of microbial cells to heavy metal ions, the cell surface display of various metal-binding proteins/peptides have been performed using a cell surface engineering approach. The surface engineering of Gram-negative bacteria, Gram-positive bacteria and yeast towards the adsorption of heavy metals are reviewed in this article. The problems and future perspectives of this technology are discussed.

  2. Molybdenum-tin as a solar cell metallization system

    NASA Technical Reports Server (NTRS)

    Boyd, D. W.; Radics, C.

    1981-01-01

    The operations of solar cell manufacture are briefly examined. The formation of reliable, ohmic, low-loss, and low-cost metal contacts on solar cells is a critical process step in cell manufacturing. In a commonly used process, low-cost metallization is achieved by screen printing a metal powder-glass frit ink on the surface of the Si surface and the conductive metal powder. A technique utilizing a molybdenum-tin alloy for the metal contacts appears to lower the cost of materials and to reduce process complexity. The ink used in this system is formulated from MoO3 with Sn powder and a trace amount of titanium resonate. Resistive losses of the resulting contacts are low because the ink contains no frit. The MoO3 is finally melted and reduced in forming gas (N2+H2) to Mo metal. The resulting Mo is highly reactive which facilitates the Mo-Si bonding.

  3. Molybdenum-tin as a solar cell metallization system

    NASA Technical Reports Server (NTRS)

    Boyd, D. W.; Radics, C.

    1981-01-01

    The operations of solar cell manufacture are briefly examined. The formation of reliable, ohmic, low-loss, and low-cost metal contacts on solar cells is a critical process step in cell manufacturing. In a commonly used process, low-cost metallization is achieved by screen printing a metal powder-glass frit ink on the surface of the Si surface and the conductive metal powder. A technique utilizing a molybdenum-tin alloy for the metal contacts appears to lower the cost of materials and to reduce process complexity. The ink used in this system is formulated from MoO3 with Sn powder and a trace amount of titanium resonate. Resistive losses of the resulting contacts are low because the ink contains no frit. The MoO3 is finally melted and reduced in forming gas (N2+H2) to Mo metal. The resulting Mo is highly reactive which facilitates the Mo-Si bonding.

  4. Development of an all-metal thick film cost affective metallization system for solar cells

    NASA Technical Reports Server (NTRS)

    Ross, B.

    1981-01-01

    An economical thick film solar cell contact for high volume production of low cost silicon solar array modules was investigated. All metal screenable pastes using base metals were studied. Solar cells with junction depths varying by a factor of 3.3, with and without a deposited oxide coating were used. Cells were screened and fired by a two step firing process. Adhesion and metallurgical results are unsatisfactory. No electrical information is obtained due to inadequate contact adhesion.

  5. A novel microstructured metal-supported solid oxide fuel cell

    NASA Astrophysics Data System (ADS)

    Fernández-González, R.; Hernández, E.; Savvin, S.; Núñez, P.; Makradi, A.; Sabaté, N.; Esquivel, J. P.; Ruiz-Morales, J. C.

    2014-12-01

    An innovative design, alternative to the conventional metal supported fuel cells (MSC) is proposed. This new design of Solid Oxide Fuel Cell (SOFC), comprises a 200 μm layer of a honeycomb-metallic framework with hexagonal cells which supports a 250 μm layer of electrolyte. Each hexagonal cell is further functionalized with a thin 5-10 μm of Ni-YSZ anode. This new design allows a reduction of ∼65% of the metallic supporting material, rendering performances over 300 mW cm-2 under pure hydrogen at 850 °C, with an OCV of ∼1.1 V.

  6. The acoustical structure of highly porous open-cell foams

    NASA Technical Reports Server (NTRS)

    Lambert, R. F.

    1982-01-01

    This work concerns both the theoretical prediction and measurement of structural parameters in open-cell highly porous polyurethane foams. Of particular interest are the dynamic flow resistance, thermal time constant, and mass structure factor and their dependence on frequency and geometry of the cellular structure. The predictions of cell size parameters, static flow resistance, and heat transfer as accounted for by a Nusselt number are compared with measurement. Since the static flow resistance and inverse thermal time constant are interrelated via the 'mean' pore size parameter of Biot, only two independent measurements such as volume porosity and mean filament diameter are required to make the predictions for a given fluid condition. The agreements between this theory and nonacoustical experiments are excellent.

  7. The acoustical structure of highly porous open-cell foams

    NASA Technical Reports Server (NTRS)

    Lambert, R. F.

    1982-01-01

    This work concerns both the theoretical prediction and measurement of structural parameters in open-cell highly porous polyurethane foams. Of particular interest are the dynamic flow resistance, thermal time constant, and mass structure factor and their dependence on frequency and geometry of the cellular structure. The predictions of cell size parameters, static flow resistance, and heat transfer as accounted for by a Nusselt number are compared with measurement. Since the static flow resistance and inverse thermal time constant are interrelated via the 'mean' pore size parameter of Biot, only two independent measurements such as volume porosity and mean filament diameter are required to make the predictions for a given fluid condition. The agreements between this theory and nonacoustical experiments are excellent.

  8. A microporous Zn(II)-MOF with open metal sites: structure and selective adsorption properties.

    PubMed

    Zheng, Xiaofang; Huang, Yumei; Duan, Jingui; Wang, Chenggang; Wen, Lili; Zhao, Jinbo; Li, Dongfeng

    2014-06-14

    A three-dimensional microporous framework, Zn(II)-MOF [Zn(HPyImDC)(DMA)]n (1) (H3PyImDC = 2-(pyridine-4-yl)-1H-4,5-imidazoledicarboxylic, DMA = N,N'-dimethylacetamide), with open metal sites and small-sized pores, exhibits excellent selective capture of CO2 over N2 and CH4 at 273 K, as well as alcohols from water. The excellent CO2 adsorption selectivity of 1 allows its potential use in the capture of CO2 from industrial flue gas or the removal of CO2 from natural gas. More interestingly, compound represents the rare case of porous materials separating propanol isomers, which may be caused by the relative flexibility of the linear n-propanol considering that both n-propanol and i-propanol have similar kinetic diameters.

  9. A base-metal conductor system for silicon solar cells

    NASA Technical Reports Server (NTRS)

    Coleman, M. G.; Pryor, R. A.; Sparks, T. G.

    1980-01-01

    Solder, copper, and silver are evaluated as conductor layer metals for silicon solar cell metallization on the basis of metal price stability and reliability under operating conditions. Due to its properties and cost, copper becomes an attractive candidate for the conductor layer. It is shown that nickel operates as an excellent diffusion barrier between copper and silicon while simultaneously serving as an electrical contact and mechanical contact to silicon. The nickel-copper system may be applied to the silicon by plating techniques utilizing a variety of plating bath compositions. Solar cells having excellent current-voltage characteristics are fabricated to demonstrate the nickel-copper metallization system.

  10. The Design, Synthesis, and Characterization of Open Sites on Metal Clusters

    NASA Astrophysics Data System (ADS)

    Nigra, Michael Mark

    undercoordinated sites led me to synthesize small gold clusters consisting of a high fraction of coordinatively unsaturated open sites. This was enabled through an approach that utilized bulky calix[4]arene ligands that are bound to a gold core. Since the size of the calix[4]arene ligand is commensurate with the size of the gold cluster core, the calix[4]arene ligand does not pack closely together on the gold cluster surface. This in turn results in areas of accessible gold atom sites between ligands. Additionally, these calix[4]arene ligands prevent cluster aggregation and electronically tune the gold core in a manner conceptually similar to enzymes affecting reactivity through organic side-chains acting as ligands. I quantified the number of open sites that result from this packing problem on the gold cluster surface, using fluorescence probe chemisorption experiments. The results of these chemisorption measurements support the mechanical model of accessibility whereby accessibility is not dependent on the identity of the functional group, whether it be calixarene phosphines or N-heterocyclic carbenes, bound to the gold surface, but rather to the relative radii of curvature of bound ligands and the gold cluster core. Additional materials characterization was completed with transmission electron microscopy in both bright-field imaging of zeolites, in MCM-22 and delaminated ITQ-2 and UCB-1 materials, and in dark field imaging of glucan coatings on oxide particles. These materials could prove to be interesting materials as to use as supports for the calixarene-bound metal clusters described above or for other metal clusters.

  11. A novel shoe scanner using an open-access quadrupole resonance and metal sensor

    NASA Astrophysics Data System (ADS)

    Crowley, C.; Petrov, T.; Mitchell, O.; Shelby, R.; Ficke, L.; Kumar, S.; Prado, P.

    2007-04-01

    Airport security and efficiency are both compromised by the process of requiring passengers to remove their shoe. A novel shoe scanner developed at the GE Security San Diego Center of Excellence uses both Quadrupole Resonance (QR) and configuration-sensitive metal detection to identify threats hidden in shoes. The shoe scanner was developed with an open-access chassis and scanning chamber that allows passengers to stand in the system in a natural position during the scanning process. More traditional magnetic resonance systems are closed or partially closed and cannot be used for screening personnel because the scanning chambers confine the object in question. The shoe scanner's novelty lies in a particular chassis geometry that allows both QR and metal screening. The resulting scanning system achieves the same level of performance as a more confining system. The shoe scanner is small enough to allow integration with other sensors such as the GE Itemizer FX TM trace detection system. In fact, the first application of the novel shoe scanner is expected to be as a component in a multi-sensor verification and security system known as the Secure Registered Traveler (SRT) Kiosk. The SRT kiosk is designed to be used as part of the TSA's Registered Traveler Program.

  12. Organotemplate-free synthesis of two open-framework metal borophosphates.

    PubMed

    Zhang, Dan; Feng, Yuquan; Liu, Yunling; Zhang, Yuan; Li, Guanghua; Yuan, Hongming

    2015-10-21

    Two new isostructural metal borophosphates, |K2(H2O)|[CoB2P3O12(OH)] [M = Co (1), Ni (2)], have been hydrothermally synthesized with non-polluting K(+) ions instead of organic template-ethylenediamine. The two metal borophosphates are isostructural and constructed by the connection of tetrahedral layers and MO6 octahedra, giving rise to the 3-D intersecting 8-ring channels along the [010] direction. The negative charge of the framework is compensated by the K(+) ions located in the 8-ring channels. Like ethylenediamine, the K(+) ions also play an important structural directing role in the formation of the open framework. The framework shows a high thermal stability and is stable upon calcination at ca. 400 and 500 °C for 1 and 2, respectively. Considering the motion of K(+) ions, ionic conductivities of the two compounds were performed. The results indicated that they have similar activation energies of 0.94-1.09 eV and conductivities of 6.76 × 10(-8)-9.88 × 10(-8) S cm(-1) at 320 °C.

  13. Metal organic frameworks for enzyme immobilization in biofuel cells

    NASA Astrophysics Data System (ADS)

    Bodell, JaDee

    Interest in biofuel cells has been rapidly expanding as an ever-growing segment of the population gains access to electronic devices. The largest areas of growth for new populations using electronic devices are often in communities without electrical infrastructure. This lack of infrastructure in remote environments is one of the key driving factors behind the development of biofuel cells. Biofuel cells employ biological catalysts such as enzymes to catalyze oxidation and reduction reactions of select fuels to generate power. There are several benefits to using enzymes to catalyze reactions as compared to traditional fuel cells which use metal catalysts. First, enzymes are able to catalyze reactions at or near room temperature, whereas traditional metal catalysts are only efficient at very high temperatures. Second, biofuel cells can operate under mild pH conditions which is important for the eventual design of safe, commercially viable devices. Also, biofuel cells allow for implantable and flexible technologies. Finally, enzymes exhibit high selectivity and can be combined to fully oxidize or reduce the fuel which can generate several electrons from a single molecule of fuel, increasing the overall device efficiency. One of the main challenges which persist in biofuel cells is the instability of enzymes over time which tend to denature after hours or days. For a viable commercial biofuel cell to be produced, the stability of enzymes must be extended to months or years. Enzymes have been shown to have improved stability after being immobilized. The focus of this research was to find a metal organic framework (MOF) structure which could successfully immobilize enzymes while still allowing for electron transport to occur between the catalytic center of the enzyme and the electrode surface within a biofuel cell for power generation. Four MOF structures were successfully synthesized and were subsequently tested to determine the MOF's ability to immobilize the following

  14. NGC 6067: a young and massive open cluster with high metallicity

    NASA Astrophysics Data System (ADS)

    Alonso-Santiago, J.; Negueruela, I.; Marco, A.; Tabernero, H. M.; González-Fernández, C.; Castro, N.

    2017-08-01

    NGC 6067 is a young open cluster hosting the largest population of evolved stars among known Milky Way clusters in the 50-150 Ma age range. It thus represents the best laboratory in our Galaxy to constrain the evolutionary tracks of 5-7 M⊙ stars. We have used high-resolution spectra of a large sample of bright cluster members (45), combined with archival photometry, to obtain accurate parameters for the cluster as well as stellar atmospheric parameters. We derive a distance of 1.78 ± 0.12 kpc, an age of 90 ± 20 Ma and a tidal radius of 14.8^{+6.8}_{-3.2} arcmin. We estimate an initial mass above 5700 M⊙, for a present-day evolved population of two Cepheids, two A supergiants and 12 red giants with masses ≈6 M⊙. We also determine chemical abundances of Li, O, Na, Mg, Si, Ca, Ti, Ni, Rb, Y and Ba for the red clump stars. We find a supersolar metallicity, [Fe/H] = +0.19 ± 0.05, and a homogeneous chemical composition, consistent with the Galactic metallicity gradient. The presence of a Li-rich red giant, star 276 with A(Li) = 2.41, is also detected. An overabundance of Ba is found, supporting the enhanced s-process. The ratio of yellow to red giants is much smaller than 1, in agreement with models with moderate overshooting, but the properties of the cluster Cepheids do not seem consistent with current Padova models for supersolar metallicity.

  15. Radial Velocities, Metallicities, and Improved Fundamental Parameters of Outer Disk Open Clusters

    NASA Astrophysics Data System (ADS)

    Zasowski, Gail; Hamm, K.; Beaton, R.; Damke, G.; Carlberg, J. K.; Majewski, S. R.; Frinchaboy, P. M.

    2014-01-01

    Open stellar clusters have proven to be powerful tools for understanding the structure and stellar evolution of our Galaxy. Using photometry from 2MASS and the new Spitzer-IRAC GLIMPSE-360 surveys, Zasowski et al. (2013) identified and characterized more than a dozen new or poorly studied, heavily reddened open clusters in the outer Galactic disk. Here, we present follow-up spectroscopy for 11 of the clusters. Low resolution optical spectra were obtained with the DIS spectrograph on the Apache Point Observatory 3.5-meter telescope (R˜1200) for candidate members of seven clusters (GLM-CYGX 16, GLM-G360 18, GLM-G360 105, SAI 24, Berkeley 14, Berkeley 14a, and Czernik 20), and with the B&C spectrograph on the Las Campanas Observatory duPont telescope (R˜5400) for three clusters (GLM-G360 50, GLM-G360 75, and GLM-G360 79). High resolution (R˜22,500) infrared (H-band) spectra were also obtained for one cluster (GLM-G360 90) as part of an ancillary program for the SDSS-III/APOGEE survey. We use the mean chemical abundances and radial velocities (RVs) to identify likely cluster members and then revisit our previous isochrone fits. With reddening constrained by the Rayleigh-Jeans Color Excess method and mean metallicities by spectroscopy, the cluster distances and ages are estimated from improved isochrone fits to the stellar overdensity, weighted by confirmed RV and/or abundance members.

  16. Development of an all-metal thick film cost effective metallization system for solar cells

    NASA Astrophysics Data System (ADS)

    Ross, B.; Parker, J.

    1983-12-01

    Improved thick film solar cell contacts for the high volume production of low cost silicon solar arrays are needed. All metal screenable pastes made from economical base metals and suitable for application to low to high conductivity silicon were examined. Silver fluoride containing copper pastes and fluorocarbon containing copper pastes were discussed. The effect of hydrogen on the adhesion of metals to silicon was investigated. A cost analysis of various paste materials is provided.

  17. Development of an all-metal thick film cost effective metallization system for solar cells

    NASA Technical Reports Server (NTRS)

    Ross, B.; Parker, J.

    1983-01-01

    Improved thick film solar cell contacts for the high volume production of low cost silicon solar arrays are needed. All metal screenable pastes made from economical base metals and suitable for application to low to high conductivity silicon were examined. Silver fluoride containing copper pastes and fluorocarbon containing copper pastes were discussed. The effect of hydrogen on the adhesion of metals to silicon was investigated. A cost analysis of various paste materials is provided.

  18. Band-Gap Opening in Metallic Single-Walled Carbon Nanotubes by Encapsulation of an Organic Salt.

    PubMed

    Nieto-Ortega, Belén; Villalva, Julia; Vera-Hidalgo, Mariano; Ruiz-González, Luisa; Burzurí, Enrique; Pérez, Emilio M

    2017-09-25

    The encapsulation of viologen derivatives into metallic single-walled carbon nanotubes (SWNTs) results in the opening of a band gap, making the SWNTs semiconducting. Raman spectroscopy, thermogravimetric analysis, and aberration-corrected high-resolution transmission electron microscopy confirm the encapsulation process. Through the fabrication of field-effect transistor devices, the change of the electronic structure of the tubes from metallic to semiconducting upon the encapsulation is confirmed. The opening of a gap in the band structure of the tubes was not detected in supramolecular controls. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  19. Fuel cell with metal screen flow-field

    DOEpatents

    Wilson, Mahlon S.; Zawodzinski, Christine

    1998-01-01

    A polymer electrolyte membrane (PEM) fuel cell is provided with electrodes supplied with a reactant on each side of a catalyzed membrane assembly (CMA). The fuel cell includes a metal mesh defining a rectangular flow-field pattern having an inlet at a first corner and an outlet at a second corner located on a diagonal from the first corner, wherein all flow paths from the inlet to the outlet through the square flow field pattern are equivalent to uniformly distribute the reactant over the CMA. In a preferred form of metal mesh, a square weave screen forms the flow-field pattern. In a particular characterization of the present invention, a bipolar plate electrically connects adjacent fuel cells, where the bipolar plate includes a thin metal foil having an anode side and a cathode side; a first metal mesh on the anode side of the thin metal foil; and a second metal mesh on the cathode side of the thin metal foil. In another characterization of the present invention, a cooling plate assembly cools adjacent fuel cells, where the cooling plate assembly includes an anode electrode and a cathode electrode formed of thin conducting foils; and a metal mesh flow field therebetween for distributing cooling water flow over the electrodes to remove heat generated by the fuel cells.

  20. Fuel cell with metal screen flow-field

    DOEpatents

    Wilson, Mahlon S.; Zawodzinski, Christine

    2001-01-01

    A polymer electrolyte membrane (PEM) fuel cell is provided with electrodes supplied with a reactant on each side of a catalyzed membrane assembly (CMA). The fuel cell includes a metal mesh defining a rectangular flow-field pattern having an inlet at a first corner and an outlet at a second corner located on a diagonal from the first corner, wherein all flow paths from the inlet to the outlet through the square flow field pattern are equivalent to uniformly distribute the reactant over the CMA. In a preferred form of metal mesh, a square weave screen forms the flow-field pattern. In a particular characterization of the present invention, a bipolar plate electrically connects adjacent fuel cells, where the bipolar plate includes a thin metal foil having an anode side and a cathode side; a first metal mesh on the anode side of the thin metal foil; and a second metal mesh on the cathode side of the thin metal foil. In another characterization of the present invention, a cooling plate assembly cools adjacent fuel cells, where the cooling plate assembly includes an anode electrode and a cathode electrode formed of thin conducting foils; and a metal mesh flow field therebetween for distributing cooling water flow over the electrodes to remove heat generated by the fuel cells.

  1. Fuel cell with metal screen flow-field

    DOEpatents

    Wilson, M.S.; Zawodzinski, C.

    1998-08-25

    A polymer electrolyte membrane (PEM) fuel cell is provided with electrodes supplied with a reactant on each side of a catalyzed membrane assembly (CMA). The fuel cell includes a metal mesh defining a rectangular flow-field pattern having an inlet at a first corner and an outlet at a second corner located on a diagonal from the first corner, wherein all flow paths from the inlet to the outlet through the square flow field pattern are equivalent to uniformly distribute the reactant over the CMA. In a preferred form of metal mesh, a square weave screen forms the flow-field pattern. In a particular characterization of the present invention, a bipolar plate electrically connects adjacent fuel cells, where the bipolar plate includes a thin metal foil having an anode side and a cathode side; a first metal mesh on the anode side of the thin metal foil; and a second metal mesh on the cathode side of the thin metal foil. In another characterization of the present invention, a cooling plate assembly cools adjacent fuel cells, where the cooling plate assembly includes an anode electrode and a cathode electrode formed of thin conducting foils; and a metal mesh flow field there between for distributing cooling water flow over the electrodes to remove heat generated by the fuel cells. 11 figs.

  2. Metallic dental material biocompatibility in osteoblastlike cells: correlation with metal ion release.

    PubMed

    Cortizo, María C; De Mele, Mónica Fernández L; Cortizo, Ana M

    2004-08-01

    Ions released from metallic dental materials used in orthodontic appliances could induce undesirable effects on cells and tissues. This study evaluates the biocompatibility of two of the most labile components of metallic dental alloys on osteoblastlike cells. The influence of protein and ions on metal dissolution properties is also investigated using different electrolyte solutions. Morphological alterations, cell growth, and differentiation of osteoblasts were assessed after exposure to pure metals (Ag, Cu, Pd, Au) and Ni-Ti alloy and correlated with the kinetics of elements released into the culture media. Results showed that Cu and Ag were the most cytotoxic elements and the other metals were biocompatible with the osteoblasts. The parameters of biocompatibility were correlated with the levels of ions detected into the culture media. Metal ions induced cell death through early mitosis arrest, apoptotic phenomena, and necrotic processes. Voltammograms showed that anions and proteins interfered in the corrosion process. Fetal bovine serum (FBS) strongly affected the electrochemical process, decreasing the oxidation rate of the metals. In conclusion, copper and silver ions showed a time-dependent low biocompatibility, which correlated with the concentration of released ions. The dissolution of the metallic materials was dependent on the composition of the simulated biological media.

  3. Iron-copper metallization for flexible solar/cell arrays

    NASA Technical Reports Server (NTRS)

    Lavendel, H. W.

    1983-01-01

    The feasibility of a copper-base metallization for shallow-junction cells applied in flexible solar arrays in space is discussed. This type of metallization will reduce usage of precious metals (such as silver), increase case of bonding (by welding or by soldering) and eliminate heavy high Z interconnects (such as molybdenum). The main points of concern are stability against thermally induced diffusion of copper into silicon which causes degradation of shallow cell junctions, and low series resistance of the contact with semiconductor which promotes cell efficiency.

  4. Back contact to film silicon on metal for photovoltaic cells

    DOEpatents

    Branz, Howard M.; Teplin, Charles; Stradins, Pauls

    2013-06-18

    A crystal oriented metal back contact for solar cells is disclosed herein. In one embodiment, a photovoltaic device and methods for making the photovoltaic device are disclosed. The photovoltaic device includes a metal substrate with a crystalline orientation and a heteroepitaxial crystal silicon layer having the same crystal orientation of the metal substrate. A heteroepitaxial buffer layer having the crystal orientation of the metal substrate is positioned between the substrate and the crystal silicon layer to reduce diffusion of metal from the metal foil into the crystal silicon layer and provide chemical compatibility with the heteroepitaxial crystal silicon layer. Additionally, the buffer layer includes one or more electrically conductive pathways to electrically couple the crystal silicon layer and the metal substrate.

  5. Stabilizing metal components in electrodes of electrochemical cells

    DOEpatents

    Spengler, Charles J.; Ruka, Roswell J.

    1989-01-01

    Disclosed is a method of reducing the removal or transfer into a gas phase of a current carrying metal in an apparatus, such as an electrochemical cell 2 having a porous fuel electrode 6 containing metal particles 11, where the metal is subject to removal or transfer into a gaseous phase, the method characterized in that (1) a metal organic compound that decomposes to form an electronically conducting oxide coating when heated is applied to the metal and porous electrode, and (2) the compound on the metal is then heated to a temperature sufficient to decompose the compound into an oxide coating 13 by increasing the temperature at a rate that is longer than 1 hour between room temperature and 600.degree. C., resulting in at least one continuous layer 13, 14 of the oxide coating on the metal.

  6. Multiple Coordination Exchanges for Room-Temperature Activation of Open-Metal Sites in Metal-Organic Frameworks.

    PubMed

    Bae, Jinhee; Choi, Jae Sun; Hwang, Sunhyun; Yun, Won Seok; Song, Dahae; Lee, JaeDong; Jeong, Nak Cheon

    2017-07-26

    The activation of open coordination sites (OCSs) in metal-organic frameworks (MOFs), i.e., the removal of solvent molecules coordinated at the OCSs, is an essential step that is required prior to the use of MOFs in potential applications such as gas chemisorption, separation, and catalysis because OCSs often serve as key sites in these applications. Recently, we developed a "chemical activation" method involving dichloromethane (DCM) treatment at room temperature, which is considered to be a promising alternative to conventional thermal activation (TA), because it does not require the application of external thermal energy, thereby preserving the structural integrity of the MOFs. However, strongly coordinating solvents such as N,N-dimethylformamide (DMF), N,N-diethylformamide (DEF), and dimethyl sulfoxide (DMSO) are difficult to remove solely with the DCM treatment. In this report, we demonstrate a multiple coordination exchange (CE) process executed initially with acetonitrile (MeCN), methanol (MeOH), or ethanol (EtOH) and subsequently with DCM to achieve the complete activation of OCSs that possess strong extracoordination. Thus, this process can serve as an effective "chemical route" to activation at room temperature that does not require applying heat. To the best of our knowledge, no previous study has demonstrated the activation of OCSs using this multiple CE process, although MeOH and/or DCM has been popularly used in pretreatment steps prior to the TA process. Using MOF-74(Ni), we demonstrate that this multiple CE process can safely activate a thermally unstable MOF without inflicting structural damage. Furthermore, on the basis of in situ (1)H nuclear magnetic resonance ((1)H NMR) and Raman studies, we propose a plausible mechanism for the activation behavior of multiple CE.

  7. Novel fuel cell stack with coupled metal hydride containers

    NASA Astrophysics Data System (ADS)

    Liu, Zhixiang; Li, Yan; Bu, Qingyuan; Guzy, Christopher J.; Li, Qi; Chen, Weirong; Wang, Cheng

    2016-10-01

    Air-cooled, self-humidifying hydrogen fuel cells are often used for backup and portable power sources, with a metal hydride used as the hydrogen storage material. To provide a stable hydrogen flow to the fuel cell stack, heat must be provided to the metal hydride. Conventionally, the heat released from the exothermic reaction of hydrogen and oxygen in the fuel cell stack to the exhaust air is used to heat a separate metal hydride container. In this case, the heat is only partially used instead of being more closely coupled because of the heat transfer resistances in the system. To achieve better heat integration, a novel scheme is proposed whereby hydrogen storage and single fuel cells are more closely coupled. Based on this idea, metal hydride containers in the form of cooling plates were assembled between each pair of cells in the stack so that the heat could be directly transferred to a metal hydride container of much larger surface-to-volume ratio than conventional separate containers. A heat coupled fuel cell portable power source with 10 cells and 11 metal hydride containers was constructed and the experimental results show that this scheme is beneficial for the heat management of fuel cell stack.

  8. Cell Division and Targeted Cell Cycle Arrest Opens and Stabilizes Basement Membrane Gaps

    PubMed Central

    Matus, David Q.; Chang, Emily; Makohon-Moore, Sasha C.; Hagedorn, Mary A.; Chi, Qiuyi; Sherwood, David R.

    2014-01-01

    Large gaps in basement membrane (BM) occur during organ remodeling and cancer cell invasion. Whether dividing cells, which temporarily reduce their attachment to BM, influence these breaches is unknown. Here we analyse uterine-vulval attachment during development across 21 species of rhabditid nematodes and find that the BM gap that forms between these organs is always bounded by a non-dividing vulval cell. Through cell cycle manipulation and live cell imaging in Caenorhabditis elegans, we show that actively dividing vulval cells facilitate enlargement of this breach by promoting BM movement. In contrast, targeted cell-cycle arrest halts BM movement and limits gap opening. Further, we demonstrate that the BM component laminin accumulates at the BM gap edge and promotes increased integrin levels in non-dividing vulval cells, stabilizing gap position. Together, these studies reveal that cell division can be used as a mechanism to regulate BM breaches, thus controlling the exchange of cells between tissues. PMID:24924309

  9. Hypervelocity Impact Performance of Open Cell Foam Core Sandwich Panel Structures

    NASA Technical Reports Server (NTRS)

    Ryan, S.; Ordonez, E.; Christiansen, E. L.; Lear, D. M.

    2010-01-01

    Open cell metallic foam core sandwich panel structures are of interest for application in spacecraft micrometeoroid and orbital debris shields due to their novel form and advantageous structural and thermal performance. Repeated shocking as a result of secondary impacts upon individual foam ligaments during the penetration process acts to raise the thermal state of impacting projectiles ; resulting in fragmentation, melting, and vaporization at lower velocities than with traditional shielding configurations (e.g. Whipple shield). In order to characterize the protective capability of these structures, an extensive experimental campaign was performed by the Johnson Space Center Hypervelocity Impact Technology Facility, the results of which are reported in this paper. Although not capable of competing against the protection levels achievable with leading heavy shields in use on modern high-risk vehicles (i.e. International Space Station modules), metallic foam core sandwich panels are shown to provide a substantial improvement over comparable structural panels and traditional low weight shielding alternatives such as honeycomb sandwich panels and metallic Whipple shields. A ballistic limit equation, generalized in terms of panel geometry, is derived and presented in a form suitable for application in risk assessment codes.

  10. FIB/SEM cell sectioning for intracellular metal granules characterization

    NASA Astrophysics Data System (ADS)

    Milani, Marziale; Brundu, Claudia; Santisi, Grazia; Savoia, Claudio; Tatti, Francesco

    2009-05-01

    Focused Ion Beams (FIBs) provide a cross-sectioning tool for submicron dissection of cells and subcellular structures. In combination with Scanning Electron Microscope (SEM), FIB provides complementary morphological information, that can be further completed by EDX (Energy Dispersive X-ray Spectroscopy). This study focus onto intracellular microstructures, particularly onto metal granules (typically Zn, Cu and Fe) and on the possibility of sectioning digestive gland cells of the terrestrial isopod P. scaber making the granules available for a compositional analysis with EDX. Qualitative and quantitative analysis of metal granules size, amount and distribution are performed. Information is made available of the cellular storing pattern and, indirectly, metal metabolism. The extension to human level is of utmost interest since some pathologies of relevance are metal related. Apart from the common metal-overload-diseases (hereditary hemochromatosis, Wilson's and Menkes disease) it has been demonstrated that metal in excess can influence carcinogenesis in liver, kidney and breast. Therefore protocols will be established for the observation of mammal cells to improve our knowledge about the intracellular metal amount and distribution both in healthy cells and in those affected by primary or secondary metal overload or depletion.

  11. Hypervelocity Impact Performance of Open Cell Foam Core Sandwich Panel Structures

    NASA Technical Reports Server (NTRS)

    Ryan, Shannon; Christiansen, Eric; Lear, Dana

    2009-01-01

    Metallic foams are a relatively new class of materials with low density and novel physical, mechanical, thermal, electrical and acoustic properties. Although incompletely characterized, they offer comparable mechanical performance to traditional spacecraft structural materials (i.e. honeycomb sandwich panels) without detrimental through-thickness channeling cells. There are two competing types of metallic foams: open cell and closed cell. Open cell foams are considered the more promising technology due to their lower weight and higher degree of homogeneity. Leading micrometeoroid and orbital debris shields (MMOD) incorporate thin plates separated by a void space (i.e. Whipple shield). Inclusion of intermediate fabric layers, or multiple bumper plates have led to significant performance enhancements, yet these shields require additional non-ballistic mass for installation (fasteners, supports, etc.) that can consume up to 35% of the total shield weight [1]. Structural panels, such as open cell foam core sandwich panels, that are also capable of providing sufficient MMOD protection, represent a significant potential for increased efficiency in hypervelocity impact shielding from a systems perspective through a reduction in required non-ballistic mass. In this paper, the results of an extensive impact test program on aluminum foam core sandwich panels are reported. The effect of pore density, and core thickness on shielding performance have been evaluated over impact velocities ranging from 2.2 - 9.3 km/s at various angles. A number of additional tests on alternate sandwich panel configurations of comparable-weight have also been performed, including aluminum honeycomb sandwich panels (see Figure 1), Nomex honeycomb core sandwich panels, and 3D aluminum honeycomb sandwich panels. A total of 70 hypervelocity impact tests are reported, from which an empirical ballistic limit equation (BLE) has been derived. The BLE is in the standard form suitable for implementation in

  12. Environmental tests of metallization systems for terrestrial photovoltaic cells

    NASA Technical Reports Server (NTRS)

    Alexander, P., Jr.

    1985-01-01

    Seven different solar cell metallization systems were subjected to temperature cycling tests and humidity tests. Temperature cycling excursions were -50 deg C to 150 deg C per cycle. Humidity conditions were 70 deg C at 98% relative humidity. The seven metallization systems were: Ti/Ag, Ti/Pd/Ag, Ti/Pd/Cu, Ni/Cu, Pd/Ni/Solder, Cr/Pd/Ag, and thick film Ag. All metallization systems showed a slight to moderate decrease in cell efficiencies after subjection to 1000 temperature cycles. Six of the seven metallization systems also evidenced slight increases in cell efficiencies after moderate numbers of cycles, generally less than 100 cycles. The copper based systems showed the largest decrease in cell efficiencies after temperature cycling. All metallization systems showed moderate to large decreases in cell efficiencies after 123 days of humidity exposure. The copper based systems again showed the largest decrease in cell efficiencies after humidity exposure. Graphs of the environmental exposures versus cell efficiencies are presented for each metallization system, as well as environmental exposures versus fill factors or series resistance.

  13. Metal-air cell with ion exchange material

    DOEpatents

    Friesen, Cody A.; Wolfe, Derek; Johnson, Paul Bryan

    2015-08-25

    Embodiments of the invention are related to anion exchange membranes used in electrochemical metal-air cells in which the membranes function as the electrolyte material, or are used in conjunction with electrolytes such as ionic liquid electrolytes.

  14. Elastomers bonded to metal surfaces seal electrochemical cells

    NASA Technical Reports Server (NTRS)

    Sherfey, J. M.

    1964-01-01

    A leakproof seal secondary cell containing alkaline electrolytes was developed by bonding an alkali-resistant elastomer, such as neoprene, to metal contact surfaces. Test results of several different elastomers strongly indicate the feasibility of this sealing method.

  15. Highly Dispersed Metal Catalyst for Fuel Cell Electrodes

    SciTech Connect

    2009-03-01

    This factsheet describes a study that will bring industrial catalyst experience to fuel cell research. Specifically, industrial catalysts, such as those used in platforming, utilize precious metal platinum as an active component in a finely dispersed form.

  16. Positive-electrode current collector for liquid-metal cells

    DOEpatents

    Shimotake, H.; Bartholme, L.G.

    1982-09-27

    A current collector for the positive electrode of an electrochemical cell with a positive electrode including a sulfide. The cell also has a negative electrode and a molten salt electrolyte including halides of a metal selected from the alkali metals and the alkaline earth metals in contact with both the positive and negative electrodes. The current collector has a base metal of copper, silver, gold, aluminum or alloys thereof with a coating thereon of iron, nickel, chromium or alloys thereof. The current collector when subjected to cell voltage forms a sulfur-containing compound on the surface thereby substantially protecting the current collector from further attack by sulfur ions during cell operation. Both electroless and electrolytic processes may be used to deposit coatings.

  17. Positive electrode current collector for liquid metal cells

    DOEpatents

    Shimotake, Hiroshi; Bartholme, Louis G.

    1984-01-01

    A current collector for the positive electrode of an electrochemical cell with a positive electrode including a sulfide. The cell also has a negative electrode and a molten salt electrolyte including halides of a metal selected from the alkali metals and the alkaline earth metals in contact with both the positive and negative electrodes. The current collector has a base metal of copper, silver, gold, aluminum or alloys thereof with a coating thereon of iron, nickel, chromium or alloys thereof. The current collector when subjected to cell voltage forms a sulfur-containing compound on the surface thereby substantially protecting the current collector from further attack by sulfur ions during cell operation. Both electroless and electrolytic processes may be used to deposit coatings.

  18. OpenCFU, a new free and open-source software to count cell colonies and other circular objects.

    PubMed

    Geissmann, Quentin

    2013-01-01

    Counting circular objects such as cell colonies is an important source of information for biologists. Although this task is often time-consuming and subjective, it is still predominantly performed manually. The aim of the present work is to provide a new tool to enumerate circular objects from digital pictures and video streams. Here, I demonstrate that the created program, OpenCFU, is very robust, accurate and fast. In addition, it provides control over the processing parameters and is implemented in an intuitive and modern interface. OpenCFU is a cross-platform and open-source software freely available at http://opencfu.sourceforge.net.

  19. Heavy metals in the cell nucleus - role in pathogenesis.

    PubMed

    Sas-Nowosielska, Hanna; Pawlas, Natalia

    2015-01-01

    People are exposed to heavy metals both in an occupational and natural environment. The most pronounced effects of heavy metals result from their interaction with cellular genetic material packed in form of chromatin. Heavy metals influence chromatin, mimicking and substituting natural microelements in various processes taking place in the cell, or interacting chemically with nuclear components: nucleic acids, proteins and lipids. This paper is a review of current knowledge on the effects of heavy metals on chromatin, exerted at the level of various nuclear components.

  20. Electrochemical cell having an alkali-metal-nitrate electrode

    DOEpatents

    Roche, M.F.; Preto, S.K.

    1982-06-04

    A power-producing secondary electrochemical cell includes a molten alkali metal as the negative-electrode material and a molten-nitrate salt as the positive-electrode material. The molten material in the respective electrodes are separated by a solid barrier of alkali-metal-ion conducting material. A typical cell includes active materials of molten sodium separated from molten sodium nitrate and other nitrates in mixture by a layer of sodium ..beta..'' alumina.

  1. Open-cell and closed-cell clouds off Peru [detail

    NASA Image and Video Library

    2017-09-27

    2010/107 - 04/17 at 21 :05 UTC. Open-cell and closed-cell clouds off Peru, Pacific Ocean. To view the full fame of this image to go: www.flickr.com/photos/gsfc/4557497219/ Resembling a frosted window on a cold winter's day, this lacy pattern of marine clouds was captured off the coast of Peru in the Pacific Ocean by the MODIS on the Aqua satellite on April 19, 2010. The image reveals both open- and closed-cell cumulus cloud patterns. These cells, or parcels of air, often occur in roughly hexagonal arrays in a layer of fluid (the atmosphere often behaves like a fluid) that begins to "boil," or convect, due to heating at the base or cooling at the top of the layer. In "closed" cells warm air is rising in the center, and sinking around the edges, so clouds appear in cell centers, but evaporate around cell edges. This produces cloud formations like those that dominate the lower left. The reverse flow can also occur: air can sink in the center of the cell and rise at the edge. This process is called "open cell" convection, and clouds form at cell edges around open centers, which creates a lacy, hollow-looking pattern like the clouds in the upper right. Closed and open cell convection represent two stable atmospheric configurations — two sides of the convection coin. But what determines which path the "boiling" atmosphere will take? Apparently the process is highly chaotic, and there appears to be no way to predict whether convection will result in open or closed cells. Indeed, the atmosphere may sometimes flip between one mode and another in no predictable pattern. Satellite: Aqua NASA/GSFC/Jeff Schmaltz/MODIS Land Rapid Response Team To learn more about MODIS go to: rapidfire.sci.gsfc.nasa.gov/gallery/?latest NASA Goddard Space Flight Center is home to the nation's largest organization of combined scientists, engineers and technologists that build spacecraft, instruments and new technology to study the Earth, the sun, our solar system, and the universe.

  2. Open cluster Dolidze 25: Stellar parameters and the metallicity in the Galactic anticentre

    NASA Astrophysics Data System (ADS)

    Negueruela, I.; Simón-Díaz, S.; Lorenzo, J.; Castro, N.; Herrero, A.

    2015-12-01

    Context. The young open cluster Dolidze 25, in the direction of the Galactic anticentre, has been attributed a very low metallicity, with typical abundances between -0.5 and -0.7 dex below solar. Aims: We intend to derive accurate cluster parameters and accurate stellar abundances for some of its members. Methods: We have obtained a large sample of intermediate- and high-resolution spectra for stars in and around Dolidze 25. We used the fastwind code to generate stellar atmosphere models to fit the observed spectra. We derive stellar parameters for a large number of OB stars in the area, and abundances of oxygen and silicon for a number of stars with spectral types around B0. Results: We measure low abundances in stars of Dolidze 25. For the three stars with spectral types around B0, we find 0.3 dex (Si) and 0.5 dex (O) below the values typical in the solar neighbourhood. These values, even though not as low as those given previously, confirm Dolidze 25 and the surrounding H ii region Sh2-284 as the most metal-poor star-forming environment known in the Milky Way. We derive a distance 4.5 ± 0.3 kpc to the cluster (rG ≈ 12.3 kpc). The cluster cannot be older than ~3 Myr, and likely is not much younger. One star in its immediate vicinity, sharing the same distance, has Si and O abundances at most 0.15 dex below solar. Conclusions: The low abundances measured in Dolidze 25 are compatible with currently accepted values for the slope of the Galactic metallicity gradient, if we take into account that variations of at least ±0.15 dex are observed at a given radius. The area traditionally identified as Dolidze 25 is only a small part of a much larger star-forming region that comprises the whole dust shell associated with Sh2-284 and very likely several other smaller H ii regions in its vicinity. Based on observations made with the Nordic Optical Telescope, the Mercator Telescope, and the telescopes of the Isaac Newton Group.

  3. Thermal characterization of an AMTEC recirculating test cell. [Alkali Metal ThermoElectric Converter

    NASA Technical Reports Server (NTRS)

    Underwood, M. L.; O'Connor, D.; Williams, R. M.; Jeffries-Nakamura, B.; Ryan, M. A.; Bankston, C. P.

    1990-01-01

    An alkali metal thermoelectric converter (AMTEC) recirculating test cell has been operated in order to determine the magnitudes of the primary heat losses of the cell and the value of the emissivity of the condenser surface. The energy balance included radiation losses, conductive losses, and losses due to the flow of sodium into the cell. The radiative heat flux dominated the heat loss mechanism of the cell at open circuit, and the condenser emissivity was calculated to be about 0.1. It is shown that, if this emissivity can be reduced to 0.02, then parasitic losses in an AMTEC recirculating test cell operating near peak power would be less than 40 percent of the heat required by the cell. The condenser emissivity decreases with elapsed time, resulting in improved thermal performance of the cell.

  4. Metal catalyst technique for texturing silicon solar cells

    DOEpatents

    Ruby, Douglas S.; Zaidi, Saleem H.

    2001-01-01

    Textured silicon solar cells and techniques for their manufacture utilizing metal sources to catalyze formation of randomly distributed surface features such as nanoscale pyramidal and columnar structures. These structures include dimensions smaller than the wavelength of incident light, thereby resulting in a highly effective anti-reflective surface. According to the invention, metal sources present in a reactive ion etching chamber permit impurities (e.g. metal particles) to be introduced into a reactive ion etch plasma resulting in deposition of micro-masks on the surface of a substrate to be etched. Separate embodiments are disclosed including one in which the metal source includes one or more metal-coated substrates strategically positioned relative to the surface to be textured, and another in which the walls of the reaction chamber are pre-conditioned with a thin coating of metal catalyst material.

  5. An assessment of the levels of phthalate esters and metals in the Muledane open dump, Thohoyandou, Limpopo Province, South Africa

    PubMed Central

    Adeniyi, Adeleke; Dayomi, Matthew; Siebe, Pitso; Okedeyi, Olumuyiwa

    2008-01-01

    Background This work reports the determination of the levels of phthalate esters (dimethyl phthalate (DMP), diethyl phthalate (DEP), dibutyl phthalate (DBP), diethyl hexyl phthalate (DEHP)) and metals (lead, cadmium, manganese, zinc, iron, calcium) in composite soil samples. The soil samples were collected randomly within the Muledane open dump, Thohoyandou, Limpopo province, South Africa. Control samples were collected about 200 m away from the open dump. The phthalate esters were separated and determined by capillary gas chromatography with a flame ionization detector, whilst the metals were determined by atomic absorption spectrophotometry. Results Open dump values for the phthalate esters and metals to be generally higher in comparison to control samples for DMP, DEP, DBP and DEHP – the mean values calculated were 0.31 ± 0.12, 0.21 ± 0.05, 0.30 ± 0.07, and 0.03 ± 0.01 mg/kg, respectively, for the open dump soil samples. Nonetheless, the mean open dump values for lead, cadmium, manganese, zinc, iron and calcium were 0.07 ± 0.04, 0.003 ± 0.001, 5.02 ± 1.92, 0.31 ± 0.02, 11.62 ± 9.48 and 0.12 ± 0.13 mg/kg, respectively. The results were compared statistically. Conclusion Our results revealed that the discarding of wastes into the open dump is a potential source of soil contamination in the immediate vicinity and beyond, via dispersal. Increased levels of phthalate esters and metals in the soil pose a risk to public health, plants and animals. Sustained monitoring of these contaminants is recommended, in addition to upgrading the facility to a landfill. PMID:18474112

  6. Theory of metal/rare-gas clusters: aspects of open-shell atomic dopants

    NASA Astrophysics Data System (ADS)

    Boatz, J. A.; Hinde, R. J.; Sheehy, J. A.; Langhoff, P. W.

    2003-05-01

    Studies are reported of the structures and vibronic spectra of metal/rare-gas clusters and their ions employing new theoretical methods devised recently for these purposes. Particular attention is addressed to open-shell atomic dopants (B, Al,...), in which cases the theory must include anisotropic (M-Rg) and spin-orbit interactions in the ground states, the avoided crossings of nearly degenerate electronically excited potential energy surfaces, and significant fragmentation following the cluster ionization commonly employed in experimental detection schemes. Detailed computational applications of the theory are reported of AlArN clusters (N = 2 to 54), and comparisons made with the results of multi-photon excitation and ionization measurements. The significantly different structures of the neutral and ionic clusters predicted in these cases, in which Al is largely external to the Ar cluster and the Al^+ ion is inside the cluster, indicates that fragmentation plays a central role in the interpretation of the experiments. The cluster spectra are seen to be highly sensitive to the details of the atomic Ar arrangements around the Al chromophore, and, accordingly, the measurements provide useful spectroscopic probes of the nature and evolution of the Al trapping sites with increasing degree of solvation when the complex electronic and vibrational phenomena underlying the data are appropriately interpreted theoretically.

  7. A microporous metal-organic framework with both open metal and Lewis basic pyridyl sites for high C2H2 and CH4 storage at room temperature.

    PubMed

    Rao, Xingtang; Cai, Jianfeng; Yu, Jiancan; He, Yabing; Wu, Chuande; Zhou, Wei; Yildirim, Taner; Chen, Banglin; Qian, Guodong

    2013-08-04

    A new microporous metal-organic framework, Cu2(PDDI) (ZJU-5; H4PDDI = 5,5'-(pyridine-2,5-diyl)diisophthalic acid), was solvothermally synthesized and structurally characterized. With open metal sites, Lewis basic pyridyl sites and suitable pore space, the acetylene uptake in ZJU-5a reaches the highest value of 290 cm(3) g(-1) at 273 K and 1 bar. Furthermore, ZJU-5a exhibits high absolute methane storage of 190 cm(3) (STP) cm(-3) at 35 bar and 224 cm(3) (STP) cm(-3) at 60 bar at room temperature.

  8. Modulate Organic-Metal Oxide Heterojunction via [1,6] Azafulleroid for Highly Efficient Organic Solar Cells.

    PubMed

    Li, Chang-Zhi; Huang, Jiang; Ju, Huanxin; Zang, Yue; Zhang, Jianyuan; Zhu, Junfa; Chen, Hongzheng; Jen, Alex K-Y

    2016-09-01

    By creating an effective π-orbital hybridization between the fullerene cage and the aromatic anchor (addend), the azafulleroid interfacial modifiers exhibit enhanced electronic coupling to the underneath metal oxides. High power conversion efficiency of 10.3% can be achieved in organic solar cells using open-cage phenyl C61 butyric acid methyl ester (PCBM)-modified zinc oxide layer.

  9. Whole-Cell Bioreporters for the Detection of Bioavailable Metals

    NASA Astrophysics Data System (ADS)

    Hynninen, Anu; Virta, Marko

    Whole-cell bioreporters are living microorganisms that produce a specific, quantifiable output in response to target chemicals. Typically, whole-cell bioreporters combine a sensor element for the substance of interest and a reporter element coding for an easily detectable protein. The sensor element is responsible for recognizing the presence of an analyte. In the case of metal bioreporters, the sensor element consists of a DNA promoter region for a metal-binding transcription factor fused to a promoterless reporter gene that encodes a signal-producing protein. In this review, we provide an overview of specific whole-cell bioreporters for heavy metals. Because the sensing of metals by bioreporter microorganisms is usually based on heavy metal resistance/homeostasis mechanisms, the basis of these mechanisms will also be discussed. The goal here is not to present a comprehensive summary of individual metal-specific bioreporters that have been constructed, but rather to express views on the theory and applications of metal-specific bioreporters and identify some directions for future research and development.

  10. Recycled Cell Phones - A Treasure Trove of Valuable Metals

    USGS Publications Warehouse

    Sullivan, Daniel E.

    2006-01-01

    This U.S. Geological Survey (USGS) Fact Sheet examines the potential value of recycling the metals found in obsolete cell phones. Cell phones seem ubiquitous in the United States and commonplace throughout most of the world. There were approximately 1 billion cell phones in use worldwide in 2002. In the United States, the number of cell phone subscribers increased from 340,000 in 1985 to 180 million in 2004. Worldwide, cell phone sales have increased from slightly more than 100 million units per year in 1997 to an estimated 779 million units per year in 2005. Cell phone sales are projected to exceed 1 billion units per year in 2009, with an estimated 2.6 billion cell phones in use by the end of that year. The U.S. Environmental Protection Agency estimated that, by 2005, as many as 130 million cell phones would be retired annually in the United States. The nonprofit organization INFORM, Inc., anticipated that, by 2005, a total of 500 million obsolete cell phones would have accumulated in consumers' desk drawers, store rooms, or other storage, awaiting disposal. Typically, cell phones are used for only 1 1/2 years before being replaced. Less than 1 percent of the millions of cell phones retired and discarded annually are recycled. When large numbers of cell phones become obsolete, large quantities of valuable metals end up either in storage or in landfills. The amount of metals potentially recoverable would make a significant addition to total metals recovered from recycling in the United States and would supplement virgin metals derived from mining.

  11. Sorption of heavy metals by prepared bacterial cell surfaces

    SciTech Connect

    Churchill, S.A.; Walters, J.V.; Churchill, P.F.

    1995-10-01

    Prepared biomass from two Gram-negative and one Gram-positive bacterial strains was examined for single, binary, and quaternary mixtures of polyvalent metal cation binding to cell surfaces. The biosorption of {sub 24}Cr{sup 3+}, {sub 27}Co{sup 2+}, {sub 28}Ni{sup 2+}, and {sub 29}Cu{sup 2+} for each bacterial cell type was evaluated using a batch equilibrium method. The binding of each metal by all three bacterial cells could be described by the Freundlich sorption model. The isotherm binding constants suggest that E. coli cells are the most efficient at binding copper, chromium, and nickel; and M. luteus adsorbs cobalt most efficiently. The K-values for copper bound to P. aeruginosa and E. coli are > 2-fold and > 8-fold greater, respectively, than previous reported for intact cells. The general metal-affinity series observed was Cr{sup 3+} > Cu{sup 2+} > Ni{sup 2+} > Co{sup 2+}. There was a marked lower affinity of all biosorbents for Co{sup 2+} and Ni{sup 2+}. M. luteus and E. coli had a strong preference for Co{sup 2+} over Ni{sup 2+}. Metal-binding enhancement could be ascribed to increased cell barrier surface porosity to metal-bearing solutions.

  12. Effective Thermal Conductivity of High Porosity Open Cell Nickel Foam

    NASA Technical Reports Server (NTRS)

    Sullins, Alan D.; Daryabeigi, Kamran

    2001-01-01

    The effective thermal conductivity of high-porosity open cell nickel foam samples was measured over a wide range of temperatures and pressures using a standard steady-state technique. The samples, measuring 23.8 mm, 18.7 mm, and 13.6 mm in thickness, were constructed with layers of 1.7 mm thick foam with a porosity of 0.968. Tests were conducted with the specimens subjected to temperature differences of 100 to 1000 K across the thickness and at environmental pressures of 10(exp -4) to 750 mm Hg. All test were conducted in a gaseous nitrogen environment. A one-dimensional finite volume numerical model was developed to model combined radiation/conduction heat transfer in the foam. The radiation heat transfer was modeled using the two-flux approximation. Solid and gas conduction were modeled using standard techniques for high porosity media. A parameter estimation technique was used in conjunction with the measured and predicted thermal conductivities at pressures of 10(exp -4) and 750 mm Hg to determine the extinction coefficient, albedo of scattering, and weighting factors for modeling the conduction thermal conductivity. The measured and predicted conductivities over the intermediate pressure values differed by 13%.

  13. Blood Flow through an Open-Celled Foam

    NASA Astrophysics Data System (ADS)

    Ortega, Jason; Maitland, Duncan

    2011-11-01

    The Hazen-Dupuit-Darcy (HDD) equation is commonly used in engineering applications to model the pressure gradient of flow through a porous media. One major advantage of this equation is that it simplifies the complex geometric details of the porous media into two coefficients: the permeability, K, and form factor, C. However through this simplification, the flow details within the porous media are no longer accessible, making it difficult to study the phenomena that contribute to changes in K and C due to clotting of blood flow. To obtain a more detailed understanding of blood flow through a porous media, a direct assessment of the complex interstitial geometry and flow is required. In this study, we solve the Navier-Stokes equations for Newtonian and non-Newtonian blood flow through an open-celled foam geometry obtained from a micro-CT scan. The nominal strut size of the foam sample is of O(10e-5) m and the corresponding Reynolds number based upon this length ranges up to O(10). Fitting the pressure gradient vs. Darcy velocity data with the HDD equation demonstrates that both viscous and inertial forces play an important role in the flow through the foam at these Reynolds numbers. Recirculation zones are observed to form in the wake of the pore struts, producing regions of flow characterized by both low shear rates and long fluid residence times, factors of which have been shown in previous studies to promote blood clotting.

  14. Membership, binarity and metallicity of red giants in the southern open cluster NGC 2354

    NASA Astrophysics Data System (ADS)

    Clariá, J. J.; Mermilliod, J.-C.; Piatti, A. E.

    1999-01-01

    We present new Coravel radial-velocity observations and photoelectric photometry in the UBV, DDO and Washington systems for a sample of red giant candidates in the field of the intermediate-age open cluster NGC 2354. Photometric membership probabilities show very good agreement with those obtained from Coravel radial velocities. The analysis of the photometric and kinematical data allow us to confirm cluster membership for 9 red giants, one of them being a spectroscopic binary, while 4 confirmed spectroscopic binaries appear to be probable members. We have also discovered 4 spectroscopic binaries not belonging to the cluster. A mean radial velocity of (33.40 +/- 0.27) km s(-1) and a mean reddening E(B-V) = 0.13 +/- 0.03 were derived for the cluster giants. NGC 2354 has a mean ultraviolet excess = -0.03 +/- 0.01, relative to the field K giants, and a mean new cyanogen anomaly Delta CN = -0.035 +/- 0.007, both implying [Fe/H] ~ -0.3. The moderately metal-poor character of NGC 2354 is confirmed using five different metal abundance indicators of the Washington system. The cluster giant branch is formed by a well defined clump of 7 stars and 4 stars with high membership probabilities seem to define an ascending giant branch. The whole red giant locus cannot be reproduced by any theoretical track. Based on observations collected with the Danish\\protect\\linebreak 1.54-m telescope at the European Southern Observatory, La Silla (Chile); at Complejo Astronómico El Leoncito, which is operated under agreement between the Consejo Nacional de Investigaciones Científicas y Técnicas de la República Argentina and the National Universities of La Plata, Córdoba, and San Juan, Argentina, and at Cerro Tololo Inter-American Observatory, National Optical Astronomy Observatories, operated by the Association of Universities for Research in Astronomy, Inc., under contract with the National Science Foundation.

  15. Assessment and modelling of heavy metal contamination from Madneuli open-pit mine, Georgia

    NASA Astrophysics Data System (ADS)

    Tchelidze, T.; Melikadze, G.; Leveinen, J.; Kaija, J.; Kumpalainen, S.

    2003-04-01

    Acid mine drainage from banked waste rocks (150 million m^3) and sulfide ore tailings of the Madneuli Cu-Au open-pit mine have created major environmental pollution problem in Bolnisi district, Georgia. Intensive leaching of exposed rocks and direct discharge of mine waters to nearby watercourses have lead to strong heavy metal pollution of groundwater and Rivers Kazretula, Poladauri and Mashavera. Increased concentrations of Cu, Zn, Pb, Ni, Mn, Cr, Cd and Hg exceeding maximum permissible values by 3-2000 times, are registered almost everywhere. Polluted surface waters are used intensively for irrigation. Besides, contaminated groundwater is pumped for irrigation and drinking water supply in alluvial deposits along the rivers. Because the spread of contamination is a slow process, the adverse health effects may not yet have emerged in the investigation area. The transport modelling was used in the framework of risk assessment to estimate the direction, rate and extent of chemical migration in the contaminated site in order to support environmental management and decisionmaking involving identification of high-risk areas, protection from pollutants, and planning of remediation work. Geochemical and contamination transport modelling conducted in this study suggest that the present contamination levels will eventually reach the total investigation area causing serious health risks to the local population in long terms. Mineral lifetime estimates suggest that the contamination might continue for centuries with current pollution loads. Furthermore, geochemical modelling showed that there is no reason to expect the natural attenuation of the contamination. The potential impacts of preventive actions were studied by preparing a model scenario where the present heavy metal contamination level was lowered to 0.1 mg/l in two streams entering the model area. The model results suggest that within 5 years, already significant reduction of concentrations can be reached. The

  16. Monitoring metal concentrations in tissues and single cells using ultramicrosensors.

    PubMed Central

    Malinski, T; Grunfeld, S; Taha, Z; Tomboulian, P

    1994-01-01

    Intercellular and extracellular metal concentrations were measured using carbon fiber ultramicrosensors plated with mercury or with polymeric porphyrinic p-type semiconductors. Concentrations of unbound nickel and lead ions were studied within individual BC3H-1 myocytes, and H4-11-C3 rat hepatoma cells. Unbound ions are predominantly solvated inorganic ions not coordinated to biological cellular components. Fabrication of ultramicrosensors appropriate for the cells under investigation is described, including procedures for sharpening and waxing the microsensors in order to control the shape, area, and dimensions of the electroactive surface. Metal ion movement through cell membranes and intracellular ion diffusion in aorta tissue were studied. Images Figure 2. PMID:7843090

  17. Nanodisperse transition metal electrodes (NTME) for electrochemical cells

    SciTech Connect

    Striebel, Kathryn A.; Wen, Shi-Jie

    1998-12-01

    Disclosed are transition metal electrodes for electrochemical cells using gel-state and solid-state polymers. The electrodes are suitable for use in primary and secondary cells. The electrodes (either negative electrode or positive electrode) are characterized by uniform dispersion of the transition metal at the nanoscale in the polymer. The transition metal moiety is structurally amorphous, so no capacity fade should occur due to lattice expansion/contraction mechanisms. The small grain size, amorphous structure and homogeneous distribution provide improved charge/discharge cycling performance, and a higher initial discharge rate capability. The cells can be cycled at high current densities, limited only by the electrolyte conductivity. A method of making the electrodes (positive and negative), and their usage in electrochemical cells are disclosed.

  18. Nanodisperse transition metal electrodes (NTME) for electrochemical cells

    DOEpatents

    Striebel, Kathryn A.; Wen, Shi-Jie

    2000-01-01

    Disclosed are transition metal electrodes for electrochemical cells using gel-state and solid-state polymers. The electrodes are suitable for use in primary and secondary cells. The electrodes (either negative electrode or positive electrode) are characterized by uniform dispersion of the transition metal at the nanoscale in the polymer. The transition metal moiety is structurally amorphous, so no capacity fade should occur due to lattice expansion/contraction mechanisms. The small grain size, amorphous structure and homogeneous distribution provide improved charge/discharge cycling performance, and a higher initial discharge rate capability. The cells can be cycled at high current densities, limited only by the electrolyte conductivity. A method of making the electrodes (positive and negative), and their usage in electrochemical cells are disclosed.

  19. Schottky barrier amorphous silicon solar cell with thin doped region adjacent metal Schottky barrier

    DOEpatents

    Carlson, David E.; Wronski, Christopher R.

    1979-01-01

    A Schottky barrier amorphous silicon solar cell incorporating a thin highly doped p-type region of hydrogenated amorphous silicon disposed between a Schottky barrier high work function metal and the intrinsic region of hydrogenated amorphous silicon wherein said high work function metal and said thin highly doped p-type region forms a surface barrier junction with the intrinsic amorphous silicon layer. The thickness and concentration of p-type dopants in said p-type region are selected so that said p-type region is fully ionized by the Schottky barrier high work function metal. The thin highly doped p-type region has been found to increase the open circuit voltage and current of the photovoltaic device.

  20. Parasitic corrosion-resistant anode for use in metal/air or metal/O/sub 2/ cells

    DOEpatents

    Joy, R.W.; Smith, D.F.

    1982-09-20

    A consumable metal anode is described which is used in refuelable electrochemical cells and wherein at least a peripheral edge portion of the anode is protected against a corrosive alkaline environment of the cell by the application of a thin metal coating, the coating being formed of metals such as nickel, silver, and gold.

  1. Parasitic corrosion resistant anode for use in metal/air or metal/O.sub.2 cells

    DOEpatents

    Joy, Richard W.; Smith, David F.

    1983-01-01

    A consumable metal anode which is used in refuelable electrochemical cells and wherein at least a peripheral edge portion of the anode is protected against a corrosive alkaline environment of the cell by the application of a thin metal coating, the coating being formed of metals such as nickel, silver, and gold.

  2. The use of established skeletal muscle cell lines to assess potential toxicity from embedded metal fragments.

    PubMed

    Kane, Michele A; Kasper, Christine E; Kalinich, John F

    2009-03-01

    The use of novel materials on the modern battlefield, both in military munitions as well as in Improvised Explosive Devices, opens the possibility of wounds with embedded fragments whose health effects and toxicity characteristics have not been fully investigated, if at all. The costly and time-consuming nature of standard two-year lifespan studies prohibits the testing of many materials. In this report, we describe an in vitro system for rapidly assessing potential toxicity of metals and metal mixtures. Using rat L6 and mouse C2C12 skeletal muscle cells and tests for cellular viability, we have shown that two militarily relevant tungsten alloy mixtures (W/Ni/Co and W/Ni/Fe) significantly decreased the metabolic viability of rat L6 cells, whereas the viability of mouse C2C12 cells was not affected by W/Ni/Co and only slightly affected by W/Ni/Fe. In addition, viability assessed through lysosomal uptake of neutral red dye was not affected by either mixture in either cell line indicating that the mitochondria may be the target organelle of these unique metal mixtures. Development of this in vitro screening system may provide a procedure by which the potential toxicities of embedded metal fragments can be rapidly assessed.

  3. Metal binding proteins, recombinant host cells and methods

    DOEpatents

    Summers, Anne O.; Caguiat, Jonathan J.

    2004-06-15

    The present disclosure provides artificial heavy metal binding proteins termed chelons by the inventors. These chelons bind cadmium and/or mercuric ions with relatively high affinity. Also disclosed are coding sequences, recombinant DNA molecules and recombinant host cells comprising those recombinant DNA molecules for expression of the chelon proteins. In the recombinant host cells or transgenic plants, the chelons can be used to bind heavy metals taken up from contaminated soil, groundwater or irrigation water and to concentrate and sequester those ions. Recombinant enteric bacteria can be used within the gastrointestinal tracts of animals or humans exposed to toxic metal ions such as mercury and/or cadmium, where the chelon recombinantly expressed in chosen in accordance with the ion to be rededicated. Alternatively, the chelons can be immobilized to solid supports to bind and concentrate heavy metals from a contaminated aqueous medium including biological fluids.

  4. Type of cell death induced by seven metals in cultured mouse osteoblastic cells.

    PubMed

    Contreras, René García; Vilchis, José Rogelio Scougall; Sakagami, Hiroshi; Nakamura, Yuko; Nakamura, Yukio; Hibino, Yasushi; Nakajima, Hiroshi; Shimada, Jun

    2010-01-01

    The use of dental metal alloys in the daily clinic makes it necessary to evaluate the cytotoxicity of eluted metal components against oral cells. However, the cytotoxic mechanism and the type of cell death induced by dental metals in osteoblasts have not been well characterized. This study investigated the cytotoxicity of seven metals against the mouse osteoblastic cell line MC3T3-E1. alpha-MEM was used as a culture medium, since this medium provided much superior proliferation of MC3T3-E1 cells over DMEM. Ag (NH(3))(2)F was the most cytotoxic, followed by CuCl>CuCl(2) >CoCl(2), NiCl(2)>FeCl(3) and FeCl(2) (least toxic). None of the metals showed any apparent growth stimulating effect (so-called 'hormesis') at lower concentrations. A time course study demonstrated that two hours of contact between oral cells and Ag (NH(3))(2)F, CuCl, CoCl(2) or NiCl(2) induced irreversible cell death. Contact with these metals induced a smear pattern of DNA fragmentation without activation of caspase-3. Preincubation of MC3T3-E1 cells with either a caspase inhibitor (Z-VAD-FMK) or autophagy inhibitors (3-methyladenine, bafilomycin) failed to rescue them from metal cytotoxicity. These data suggest the induction of necrotic cell death rather than apoptosis and autophagy by metals in this osteoblastic cell line.

  5. Catalytic asymmetric ring-opening of meso-aziridines with malonates under heterodinuclear rare earth metal Schiff base catalysis.

    PubMed

    Xu, Yingjie; Lin, Luqing; Kanai, Motomu; Matsunaga, Shigeki; Shibasaki, Masakatsu

    2011-04-20

    Catalytic asymmetric ring-opening of meso-aziridines with malonates is described. The combined use of two rare earth metal sources with different properties promoted the desired ring-opening reaction. A 1:1:1 mixture of a heterobimetallic La(O-iPr)(3)/Yb(OTf)(3)/Schiff base 1a (0.25-10 mol %) efficiently promoted the reaction of five-, six-, and seven-membered ring cyclic meso-aziridines as well as acyclic meso-aziridines with dimethyl, diethyl, and dibenzyl malonates, giving chiral cyclic and acyclic γ-amino esters in 99-63% yield and >99.5-97% ee.

  6. Tuning the gate opening pressure of Metal-Organic Frameworks (MOFs) for the selective separation of hydrocarbons.

    PubMed

    Nijem, Nour; Wu, Haohan; Canepa, Pieremanuele; Marti, Anne; Balkus, Kenneth J; Thonhauser, Timo; Li, Jing; Chabal, Yves J

    2012-09-19

    Separation of hydrocarbons is one of the most energy demanding processes. The need to develop materials for the selective adsorption of hydrocarbons, under reasonable conditions, is therefore of paramount importance. This work unveils unexpected hydrocarbon selectivity in a flexible Metal-Organic Framework (MOF), based on differences in their gate opening pressure. We show selectivity dependence on both chain length and specific framework-gas interaction. By combining Raman spectroscopy and theoretical van der Waals Density Functional (vdW-DF) calculations, the separation mechanisms governing this unexpected gate-opening behavior are revealed.

  7. Adsorption and ring-opening of lactide on the chiral metal surface Pt(321)(S) studied by density functional theory.

    PubMed

    Franke, J-H; Kosov, D S

    2015-01-28

    We study the adsorption and ring-opening of lactide on the naturally chiral metal surface Pt(321)(S). Lactide is a precursor for polylactic acid ring-opening polymerization, and Pt is a well known catalyst surface. We study, here, the energetics of the ring-opening of lactide on a surface that has a high density of kink atoms. These sites are expected to be present on a realistic Pt surface and show enhanced catalytic activity. The use of a naturally chiral surface also enables us to study potential chiral selectivity effects of the reaction at the same time. Using density functional theory with a functional that includes the van der Waals forces in a first-principles manner, we find modest adsorption energies of around 1.4 eV for the pristine molecule and different ring-opened states. The energy barrier to be overcome in the ring-opening reaction is found to be very small at 0.32 eV and 0.30 eV for LL- and its chiral partner DD-lactide, respectively. These energies are much smaller than the activation energy for a dehydrogenation reaction of 0.78 eV. Our results thus indicate that (a) ring-opening reactions of lactide on Pt(321) can be expected already at very low temperatures, and Pt might be a very effective catalyst for this reaction; (b) the ring-opening reaction rate shows noticeable enantioselectivity.

  8. Adsorption and ring-opening of lactide on the chiral metal surface Pt(321)S studied by density functional theory

    NASA Astrophysics Data System (ADS)

    Franke, J.-H.; Kosov, D. S.

    2015-01-01

    We study the adsorption and ring-opening of lactide on the naturally chiral metal surface Pt(321)S. Lactide is a precursor for polylactic acid ring-opening polymerization, and Pt is a well known catalyst surface. We study, here, the energetics of the ring-opening of lactide on a surface that has a high density of kink atoms. These sites are expected to be present on a realistic Pt surface and show enhanced catalytic activity. The use of a naturally chiral surface also enables us to study potential chiral selectivity effects of the reaction at the same time. Using density functional theory with a functional that includes the van der Waals forces in a first-principles manner, we find modest adsorption energies of around 1.4 eV for the pristine molecule and different ring-opened states. The energy barrier to be overcome in the ring-opening reaction is found to be very small at 0.32 eV and 0.30 eV for LL- and its chiral partner DD-lactide, respectively. These energies are much smaller than the activation energy for a dehydrogenation reaction of 0.78 eV. Our results thus indicate that (a) ring-opening reactions of lactide on Pt(321) can be expected already at very low temperatures, and Pt might be a very effective catalyst for this reaction; (b) the ring-opening reaction rate shows noticeable enantioselectivity.

  9. Combined toxicity of heavy metal mixtures in liver cells.

    PubMed

    Lin, Xialu; Gu, Yuanliang; Zhou, Qi; Mao, Guochuan; Zou, Baobo; Zhao, Jinshun

    2016-09-01

    With rapid industrialization, China is now facing great challenges in heavy metal contamination in the environment. Human exposure to heavy metals through air, water and food commonly involves a mixture consisting of multiple heavy metals. In this study, eight common heavy metals (Pb, Cd, Hg, Cu, Zn, Mn, Cr, Ni) that cause environmental contamination were selected to investigate the combined toxicity of different heavy metal mixtures in HL7702 cells. Toxicity (24 h LC50 ) of each individual metal on the cells ranked Hg > Cr = Cd > Cu > Zn > Ni > Mn > Pb; toxicity of the different mixtures ranked: M5 > M3PbHgCd > M5+Mn > M5+Cu > M2CdNi > M4A > M8-Mn > M8 > M5+Zn > M4B > M8-Cr > M8-Zn > M8-Cu > M8-Pb > M8-Cd > M8-Hg > M8-Ni > M3PbHgNi > M3CuZnMn. The cytotoxicity data of individual metals were successfully used to build the additive models of two- to eight-component metal mixtures. The comparison between additive model and combination model or partly additive model was useful to evaluate the combined effects in mixture. Synergistic, antagonistic or additive effects of the toxicity were observed in different mixtures. These results suggest that the combined effects should be considered in the risk assessment of heavy metal co-exposure, and more comprehensive investigations on the combined effects of different heavy metal mixtures are needed in the future. Copyright © 2016 John Wiley & Sons, Ltd. Copyright © 2016 John Wiley & Sons, Ltd.

  10. Computational study of forced air-convection in open-cathode polymer electrolyte fuel cell stacks

    NASA Astrophysics Data System (ADS)

    Sasmito, A. P.; Lum, K. W.; Birgersson, E.; Mujumdar, A. S.

    A mathematical model for a polymer electrolyte fuel cell (PEFC) stack with an open-cathode manifold, where a fan provides the oxidant as well as cooling, is derived and studied. In short, the model considers two-phase flow and conservation of mass, momentum, species and energy in the ambient and PEFC stack, as well as conservation of charge and a phenomenological membrane and agglomerate model for the PEFC stack. The fan is resolved as an interfacial condition with a polynomial expression for the static pressure increase over the fan as a function of the fan velocity. The results suggest that there is strong correlation between fan power rating, the height of cathode flow-field and stack performance. Further, the placement of the fan - either in blowing or suction mode - does not give rise to a discernable difference in stack performance for the flow-field considered (metal mesh). Finally, it is noted that the model can be extended to incorporate other types of flow-fields and, most importantly, be employed for design and optimization of forced air-convection open-cathode PEFC stacks and adjacent fans.

  11. Cell surface reactivity of Synechococcus sp. PCC 7002: Implications for metal sorption from seawater

    NASA Astrophysics Data System (ADS)

    Liu, Yuxia; Alessi, D. S.; Owttrim, G. W.; Petrash, D. A.; Mloszewska, A. M.; Lalonde, S. V.; Martinez, R. E.; Zhou, Qixing; Konhauser, K. O.

    2015-11-01

    The past two decades have seen a significant advancement in our understanding of bacterial surface chemistry and the ability of microbes to bind metals from aqueous solutions. Much of this work has been aimed at benthic, mat-forming species in an effort to model the mechanisms by which microbes may exert control over metal contaminant transport in soils and groundwater. However, there is a distinct paucity of information pertaining to the surface chemistry of marine planktonic species, and their ability to bind trace metals from the ocean's photic zone. To this end, the surface properties of the cyanobacterium Synechococcus sp. PCC 7002 were studied as this genus is one of the dominant marine phytoplankton, and as such, contributes significantly to metal cycling in the ocean's photic zone. Zeta potential measurement indicates that the cell surfaces display a net negative charge. This was supported by potentiometric titration and Fourier transform infrared spectroscopy analyses demonstrating that the cells are dominated by surface proton releasing ligands, including carboxyl, phosphoryl and amino functional groups, with a total ligand density of 34.18 ± 1.62 mmol/g (dry biomass). Cd adsorption experiments further reveal that carboxyl groups play a primary role in metal adsorption, with 1.0 g of dry biomass binding an equivalent of 7.05 × 10-5 M of Cd from solution at pH = 8. To put this value into context, in 1 L of seawater, and with an open-ocean population of Synechococcus of 105 cells/mL in the photic zone, approximately 10 nmol of Cd could potentially be adsorbed by the cyanobacteria; an amount equivalent to seawater Cd concentrations. Although we have only focused on one microbial species and one metal cation, and we have not considered trace element assimilation, our results highlight the potential role of surface sorption by phytoplankton in the cycling of metals in the ocean.

  12. Open Gradient Magnetic Red Blood Cell Sorter Evaluation on Model Cell Mixtures

    PubMed Central

    Moore, Lee R.; Nehl, Franzisca; Dorn, Jenny; Chalmers, Jeffrey J.; Zborowski, Maciej

    2014-01-01

    The emerging applications of biological cell separation to rare circulating tumor cell (CTC) detection and separation from blood rely on efficient methods of red blood cell (RBC) debulking. The two most widely used methods of centrifugation and RBC lysis have been associated with the concomitant significant losses of the cells of interest (such as progenitor cells or circulating tumor cells). Moreover, RBC centrifugation and lysis are not well adapted to the emerging diagnostic applications, relying on microfluidics and micro-scale total analytical systems. Therefore, magnetic RBC separation appears a logical alternative considering the high iron content of the RBC (normal mean 105 fg) as compared to the white blood cell iron content (normal mean 1.6 fg). The typical magnetic forces acting on a RBC are small, however, as compared to typical forces associated with centrifugation or the forces acting on synthetic magnetic nanoparticles used in current magnetic cell separations. This requires a significant effort in designing and fabricating a practical magnetic RBC separator. Applying advanced designs to the low cost, high power permanent magnets currently available, and building on the accumulated knowledge of the immunomagnetic cell separation methods and devices, an open gradient magnetic red blood cell (RBC) sorter was designed, fabricated and tested on label-free cell mixtures, with potential applications to RBC debulking from whole blood samples intended for diagnostic tests. PMID:24910468

  13. Open Gradient Magnetic Red Blood Cell Sorter Evaluation on Model Cell Mixtures.

    PubMed

    Moore, Lee R; Nehl, Franzisca; Dorn, Jenny; Chalmers, Jeffrey J; Zborowski, Maciej

    2013-02-01

    The emerging applications of biological cell separation to rare circulating tumor cell (CTC) detection and separation from blood rely on efficient methods of red blood cell (RBC) debulking. The two most widely used methods of centrifugation and RBC lysis have been associated with the concomitant significant losses of the cells of interest (such as progenitor cells or circulating tumor cells). Moreover, RBC centrifugation and lysis are not well adapted to the emerging diagnostic applications, relying on microfluidics and micro-scale total analytical systems. Therefore, magnetic RBC separation appears a logical alternative considering the high iron content of the RBC (normal mean 105 fg) as compared to the white blood cell iron content (normal mean 1.6 fg). The typical magnetic forces acting on a RBC are small, however, as compared to typical forces associated with centrifugation or the forces acting on synthetic magnetic nanoparticles used in current magnetic cell separations. This requires a significant effort in designing and fabricating a practical magnetic RBC separator. Applying advanced designs to the low cost, high power permanent magnets currently available, and building on the accumulated knowledge of the immunomagnetic cell separation methods and devices, an open gradient magnetic red blood cell (RBC) sorter was designed, fabricated and tested on label-free cell mixtures, with potential applications to RBC debulking from whole blood samples intended for diagnostic tests.

  14. Admit One: How Essential and Nonessential Metals Gain Entrance into the Cell

    PubMed Central

    Martinez-Finley, Ebany J.; Chakraborty, Sudipta; Fretham, Stephanie; Aschner, Michael

    2016-01-01

    Metals can have a number of detrimental or beneficial effects in the cell, but first they must get in. Organisms have evolved transport mechanisms to get metals that are required, or essential into the cell. Nonessential metals often enter the cell through use of the machinery provided for essential metals. Much work has been done to advance our understanding of how these metals are transported across the plasma and organelle membranes. This review provides an overview of these metal transport processes. PMID:22337135

  15. Investigation of different contact geometries for partial rear metal contact of high-efficiency silicon solar cells

    NASA Astrophysics Data System (ADS)

    Mitra, Suchismita; Ghosh, Hemanta; Saha, Hiranmay; Datta, Swapan Kumar

    2015-11-01

    In this paper, we have investigated the dependence of the parameters of partial rear metal contact (PRC) solar cells on two commonly used geometrical configurations, viz. grid contact and square contact. It is demonstrated that while the geometry of rear metallic contact having the same fractional coverage changes the base spreading resistance significantly, rear surface passivation and back reflectance depend only on the fractional coverage of the real metal contact and are independent of the geometry of the contact. The performed analysis indicates that the base spreading resistance is much higher for square contact cells compared to that of grid contact cells having the same fractional coverage. While open-circuit voltage and short-circuit current are found to be essentially independent of the contact geometry, the fill factor is significantly affected by the geometry, indicating that the design of high-efficiency cells with partial rear grid contact is less critical in comparison to that of square contact cells for optimized performance. Results indicate that for a 180 μm cell, an efficiency enhancement of 14% is possible for  <10% fractional rear metallization over the baseline efficiency of about 19% for solar cells having full-area rear metallization. For 50 μm thin cells, the corresponding improvement in efficiency is 17%, leading to 22% efficiency solar cells.

  16. Highly Selective Adsorption of Ethylene over Ethane in a MOF Featuring the Combination of Open Metal Site and -Complexation

    DOE PAGES

    Zhang, Yiming; Li, Baiyan; Wu, Zili; ...

    2015-01-01

    The introduction of the combination of open metal site (OMS) and -complexation into MOF has led to very high ethylene/ethane adsorption selectivity at 318K, as illustrated in the context of MIL-101-Cr-SO3Ag. The interactions with ethylene from both OMS and -complexation in MIL-101-Cr-SO3Ag have been investigated by in situ IR spectroscopic studies and computational calculations, which suggest -complexation contributes dominantly to the high ethylene/ethane adsorption selectivity.

  17. Origin of Open-Circuit Voltage Loss in Polymer Solar Cells and Perovskite Solar Cells.

    PubMed

    Kim, Hyung Do; Yanagawa, Nayu; Shimazaki, Ai; Endo, Masaru; Wakamiya, Atsushi; Ohkita, Hideo; Benten, Hiroaki; Ito, Shinzaburo

    2017-06-14

    Herein, the open-circuit voltage (VOC) loss in both polymer solar cells and perovskite solar cells is quantitatively analyzed by measuring the temperature dependence of VOC to discuss the difference in the primary loss mechanism of VOC between them. As a result, the photon energy loss for polymer solar cells is in the range of about 0.7-1.4 eV, which is ascribed to temperature-independent and -dependent loss mechanisms, while that for perovskite solar cells is as small as about 0.5 eV, which is ascribed to a temperature-dependent loss mechanism. This difference is attributed to the different charge generation and recombination mechanisms between the two devices. The potential strategies for the improvement of VOC in both solar cells are further discussed on the basis of the experimental data.

  18. Metal bipolar plates for PEM fuel cell-A review

    NASA Astrophysics Data System (ADS)

    Tawfik, H.; Hung, Y.; Mahajan, D.

    The polymer electrolyte membrane (PEM) based fuel cells are clean alternative energy systems that hold excellent potential for cost effectiveness, durability, and relatively high overall efficiency. PEM fuel cell is recognized by the U.S. Department of Energy (DOE) as the main candidate to replace the internal combustion engine in transportation applications. Metallic bipolar plates and membrane electrode assembly (MEA) are two crucial components of a PEM power stack and their durability and fabrication cost must be optimized to allow fuel cells to penetrate the commercial market and compete with other energy sources. The bipolar plates perform as the current conductors between cells, provide conduits for reactant gases flow, and constitute the backbone of a power stack. They are commonly made of graphite composite for high corrosion resistance and good surface contact resistance; however their manufacturability, permeability, and durability for shock and vibration are unfavorable in comparison to metals. On the other hand, various methods and techniques must be developed to combat metallic corrosion and eliminate the passive layer that causes unacceptable reduction in contact resistance and possible fouling of the catalyst and the ionomer. Thus recently metallic bipolar plates have received considerable attention in the research community. This paper offers a comprehensive review of the research work conducted on metal bipolar plates to prevent corrosion while maintaining a low contact resistance.

  19. Correlation between oxidation potential and open-circuit voltage of composite solar cells based on blends of polythiophenes/ fullerene derivative

    NASA Astrophysics Data System (ADS)

    Gadisa, Abay; Svensson, Mattias; Andersson, Mats R.; Inganäs, Olle

    2004-03-01

    The photovoltaic parameters of donor/acceptor blend organic solar cells are highly influenced by several parameters, such as the strength of the acceptor species, the morphology of the film due to the solvent, and the mobility of the free charge carriers. In this work, the open-circuit voltage (Voc) of solar cells based on series of conjugated polythiophene polymers were measured and compared. In every cell, the donor polymer was blended with an electron acceptor fullerene molecule. The devices were constructed in a sandwich structure with indium tin oxide (ITO)/metallic polymer (PEDOT:PSS) acting as an anode and Al or LiF/Al acting as a cathode. Comparing the Voc of all the cells shows that this important photovoltaic parameter is systematically varying with the polymer. The variation of photovoltage is attributed to the variation of the oxidation potential of the donor conjugated polymers after due consideration of the different injection conditions in the varying polymers.

  20. Observations of solar-cell metallization corrosion

    NASA Technical Reports Server (NTRS)

    Mon, G. R.

    1983-01-01

    The Engineering Sciences Area of the Jet Propulsion Laboratory (JPL) Flat-Plate Solar Array Project is performing long term environmental tests on photovoltaic modules at Wyle Laboratories in Huntsville, Alabama. Some modules have been exposed to 85 C/85% RH and 40 C/93% RH for up to 280 days. Other modules undergoing temperature-only exposures ( 3% RH) at 85 C and 100 C have been tested for more than 180 days. At least two modules of each design type are exposed to each environment - one with, and the other without a 100-mA forward bias. Degradation is both visually observed and electrically monitored. Visual observations of changes in appearance are recorded at each inspection time. Significant visual observations relating to metallization corrosion (and/or metallization-induced corrosion) include discoloration (yellowing and browning) of grid lines, migration of grid line material into the encapsulation (blossoming), the appearance of rainbow-like diffraction patterns on the grid lines, and brown spots on collectors and grid lines. All of these observations were recorded for electrically biased modules in the 280-day tests with humidity.

  1. Photoelectrochemical cell for simultaneous electricity generation and heavy metals recovery from wastewater.

    PubMed

    Wang, Dawei; Li, Yi; Li Puma, Gianluca; Lianos, Panagiotis; Wang, Chao; Wang, Peifang

    2017-02-05

    The feasibility of simultaneous recovery of heavy metals from wastewater (e.g., acid mining and electroplating) and production of electricity is demonstrated in a novel photoelectrochemical cell (PEC). The photoanode of the cell bears a nanoparticulate titania (TiO2) film capped with the block copolymer [poly(ethylene glycol)-b-poly(propylene glycol)-b-poly(ethylene glycol)] hole scavenger, which consumed photogenerated holes, while the photogenerated electrons transferred to a copper cathode reducing dissolved metal ions and produced electricity. Dissolved silver Ag(+), copper Cu(2+), hexavalent chromium as dichromate Cr2O7(2-) and lead Pb(2+) ions in a mixture (0.2mM each) were removed at different rates, according to their reduction potentials. Reduced Ag(+), Cu(2+) and Pb(2+) ions produced metal deposits on the cathode electrode which were mechanically recovered, while Cr2O7(2-) reduced to the less toxic Cr(3+) in solution. The cell produced a current density Jsc of 0.23mA/cm(2), an open circuit voltage Voc of 0.63V and a maximum power density of 0.084mW/cm(2). A satisfactory performance of this PEC for the treatment of lead-acid battery wastewater was observed. The cathodic reduction of heavy metals was limited by the rate of electron-hole generation at the photoanode. The PEC performance decreased by 30% after 9 consecutive runs, caused by the photoanode progressive degradation.

  2. Metallic nanoparticle deposition techniques for enhanced organic photovoltaic cells

    NASA Astrophysics Data System (ADS)

    Cacha, Brian Joseph Gonda

    Energy generation via organic photovoltaic (OPV) cells provide many advantages over alternative processes including flexibility and price. However, more efficient OPVs are required in order to be competitive for applications. One way to enhance efficiency is through manipulation of exciton mechanisms within the OPV, for example by inserting a thin film of bathocuproine (BCP) and gold nanoparticles between the C60/Al and ZnPc/ITO interfaces, respectively. We find that BCP increases efficiencies by 330% due to gains of open circuit voltage (Voc) by 160% and short circuit current (Jsc) by 130%. However, these gains are complicated by the anomalous photovoltaic effect and an internal chemical potential. Exploration in the tuning of metallic nanoparticle deposition on ITO was done through four techniques. Drop casting Ag nanoparticle solution showed arduous control on deposited morphology. Spin-coating deposited very low densities of nanoparticles. Drop casting and spin-coating methods showed arduous control on Ag nanoparticle morphology due to clustering and low deposition density, respectively. Sputtered gold on glass was initially created to aid the adherence of Ag nanoparticles but instead showed a quick way to deposit aggregated gold nanoparticles. Electrodeposition of gold nanoparticles (AuNP) proved a quick method to tune nanoparticle morphology on ITO substrates. Control of deposition parameters affected AuNP size and distribution. AFM images of electrodeposited AuNPs showed sizes ranging from 39 to 58 nm. UV-Vis spectroscopy showed the presence of localized plasmon resonance through absorption peaks ranging from 503 to 614 nm. A linear correlation between electrodeposited AuNP size and peak absorbance was seen with a slope of 3.26 wavelength(nm)/diameter(nm).

  3. Microstructure based model for sound absorption predictions of perforated closed-cell metallic foams.

    PubMed

    Chevillotte, Fabien; Perrot, Camille; Panneton, Raymond

    2010-10-01

    Closed-cell metallic foams are known for their rigidity, lightness, thermal conductivity as well as their low production cost compared to open-cell metallic foams. However, they are also poor sound absorbers. Similarly to a rigid solid, a method to enhance their sound absorption is to perforate them. This method has shown good preliminary results but has not yet been analyzed from a microstructure point of view. The objective of this work is to better understand how perforations interact with closed-cell foam microstructure and how it modifies the sound absorption of the foam. A simple two-dimensional microstructural model of the perforated closed-cell metallic foam is presented and numerically solved. A rough three-dimensional conversion of the two-dimensional results is proposed. The results obtained with the calculation method show that the perforated closed-cell foam behaves similarly to a perforated solid; however, its sound absorption is modulated by the foam microstructure, and most particularly by the diameters of both perforation and pore. A comparison with measurements demonstrates that the proposed calculation method yields realistic trends. Some design guides are also proposed.

  4. Direct Structural Identification of Gas Induced Gate-Opening Coupled with Commensurate Adsorption in a Microporous Metal-Organic Framework.

    PubMed

    Banerjee, Debasis; Wang, Hao; Plonka, Anna M; Emge, Thomas J; Parise, John B; Li, Jing

    2016-08-08

    Gate-opening is a unique and interesting phenomenon commonly observed in flexible porous frameworks, where the pore characteristics and/or crystal structures change in response to external stimuli such as adding or removing guest molecules. For gate-opening that is induced by gas adsorption, the pore-opening pressure often varies for different adsorbate molecules and, thus, can be applied to selectively separate a gas mixture. The detailed understanding of this phenomenon is of fundamental importance to the design of industrially applicable gas-selective sorbents, which remains under investigated due to the lack of direct structural evidence for such systems. We report a mechanistic study of gas-induced gate-opening process of a microporous metal-organic framework, [Mn(ina)2 ] (ina=isonicotinate) associated with commensurate adsorption, by a combination of several analytical techniques including single crystal X-ray diffraction, in situ powder X-ray diffraction coupled with differential scanning calorimetry (XRD-DSC), and gas adsorption-desorption methods. Our study reveals that the pronounced and reversible gate opening/closing phenomena observed in [Mn(ina)2 ] are coupled with a structural transition that involves rotation of the organic linker molecules as a result of interaction of the framework with adsorbed gas molecules including carbon dioxide and propane. The onset pressure to open the gate correlates with the extent of such interaction.

  5. Retrieval of Au, Ag, Cu precious metals coupled with electric energy production via an unconventional coupled redox fuel cell reactor.

    PubMed

    Zhang, Hui-Min; Fan, Zheng; Xu, Wei; Feng, Xiao; Wu, Zu-Cheng

    2017-09-15

    The recovery of heavy metals from aqueous solutions or e-wastes is of upmost importance. Retrieval of Au, Ag, and Cu with electricity generation through building an ethanol-metal coupled redox fuel cells (CRFCs) is demonstrated. The cell was uniquely assembled on PdNi/C anode the electro-oxidation of ethanol takes place to give electrons and then go through the external circuit reducing metal ions to metallic on the cathode, metals are recovered. Taking an example of removal of 100mgL(-1) gold in 0.5M HAc-NaAc buffer solution as the catholyte, 2.0M ethanol in 1.0M alkaline solution as the anolyte, an open circuit voltage of 1.4V, more than 96% of gold removal efficiency in 20h, and equivalent energy production of 2.0kWhkg(-1) of gold can be readily achieved in this system. When gold and copper ions coexist, it was confirmed that metallic Cu is formed on the cathodic electrode later than metallic Au formation by XPS analysis. Thus, this system can achieve step by step electrodeposition of gold and copper while the two metal ions coexisting. This work develops a new approach to retrieve valuable metals from aqueous solution or e-wastes. Copyright © 2017 Elsevier B.V. All rights reserved.

  6. Low Cost PEM Fuel Cell Metal Bipolar Plates

    SciTech Connect

    Wang, Conghua

    2013-05-30

    Bipolar plate is an important component in fuel cell stacks and accounts for more than 75% of stack weight and volume. The technology development of metal bipolar plates can effectively reduce the fuel cells stack weight and volume over 50%. The challenge is the metal plate corrosion protection at low cost for the broad commercial applications. This project is aimed to develop innovative technological solutions to overcome the corrosion barrier of low cost metal plates. The feasibility of has been demonstrated and patented (US Patent 7,309,540). The plan is to further reduce the cost, and scale up the technology. The project is built on three pillars: 1) robust experimental evidence demonstrating the feasibility of our technology, 2) a team that consists of industrial leaders in fuel cell stack application, design, and manufactures; 3) a low-risk, significant-milestone driven program that proves the feasibility of meeting program objectives The implementation of this project will reduce the fuel cell stack metal bipolar separator plate cost which accounts 15-21% of the overall stack cost. It will contribute to the market adoption of fuel cell technologies. In addition, this corrosion protection technology can be used similar energy devices, such as batteries and electrolyzers. Therefore, the success of the project will be benefit in broad markets.

  7. Evaluation of Open Cell Foam Heat Transfer Enhancement for Liquid Rocket Engine

    NASA Technical Reports Server (NTRS)

    Chung, J. N.; Tully, Landon; Kim, Jung Hwan; Jones, Gregg W.; Watkins, William

    2006-01-01

    As NASA pursues the exploration mission, advanced propulsion for the next generation of spacecraft will be needed. These new propulsion systems will require higher performance and increased durability, despite current limitations on materials. A break-through technology is needed in the thrust chamber. In this paper the idea of using a porous metallic foam is examined for its potential cooling enhancement capabilities. The goal is to increase the chamber wall cooling without creating an additional pressure drop penalty. A feasibility study based on experiments at laboratory-scale conditions was performed and analysis at rocket conditions is underway. In the experiment, heat transfer and pressure drop data were collected using air as the coolant in a copper or nickel foam filled annular channel. The foam-channel performance was evaluated based on comparison with conventional microchannel cooling passages under equal pressure drop conditions. The heat transfer enhancement of the foam channel over the microchannel ranges from 130% to 172%. The enhancement is relatively independent of the pressure drop and increases with decreasing pore size. A direct numerical simulation model of the foam heat exchange has been built. The model is based on the actual metal foam microstructure of thin ligaments (0.2- 0.3 mm in diameter) that form a network of interconnected open-cells. The cell dimension is around 2 mm. The numerical model was built using the FLUENT CFD code. Comparison of the pressure drop results predicted by the current model with those experimental data of Leong and Jin [8] shows favorable comparisons. Pressure drop predictions have been made using hydrogen as a coolant at typical rocket conditions. Conjugate heat transfer analysis using the foam filled channel is planned for the future.

  8. Cell metal interactions: A comparison of natural uranium to other common metals in renal cells and bone osteoblasts

    NASA Astrophysics Data System (ADS)

    Milgram, S.; Carrière, M.; Thiebault, C.; Berger, P.; Khodja, H.; Gouget, B.

    2007-07-01

    Uranium acute intoxication has been documented to induce nephrotoxicity. Kidneys are the main target organs after short term exposures to high concentrations of the toxic, while chronic exposures lead to its accumulation in the skeleton. In this paper, chemical toxicity of uranium is investigated for rat osteoblastic bone cells and compared to results previously obtained on renal cells. We show that bone cells are less sensitive to uranium than renal cells. The influence of the chemical form on U cytotoxicity is demonstrated. For both cell types, a comparison of uranium toxicity with other metals or metalloids toxicities (Mn, Ni, Co, Cu, Zn, Se and Cd) permits classification of Cd, Zn, Se IV and Cu as the most toxic and Ni, Se VI, Mn and U as the least toxic. Chemical toxicity of natural uranium proves to be far less than that of cadmium. To try to explain the differences in sensitivities observed between metals and different cell types, cellular accumulations in cell monolayers are quantified by inductively coupled plasma-mass spectroscopy (ICP-MS), function of time or function of dose: lethal doses which simulate acute intoxications and sub-lethal doses which are more realistic with regard to environmentally metals concentrations. In addition to being more resistant, bone cells accumulated much more uranium than did renal cells. Moreover, for both cell models, Mn, U-citrate and U-bicarbonate are strongly accumulated whereas Cu, Zn and Ni are weakly accumulated. On the other hand, a strong difference in Cd behaviour between the two cell types is shown: whereas Cd is very weakly accumulated in bone cells, it is very strongly accumulated in renal cells. Finally, elemental distribution of the toxics is determined on a cellular scale using nuclear microprobe analysis. For both renal and osteoblastic cells, uranium was accumulated in as intracellular precipitates similar to those observed previously by SEM/EDS.

  9. Cell growth on metallic glasses: the interaction of amorphous metal alloys with cultured neuronal, osteoblast, endothelial, and fibroblast cells.

    PubMed

    McAuslan, B R; Johnson, G; Delamore, G W; Gibson, M A; Steele, J G

    1988-10-01

    Ferrous based, corrosion resistant amorphous alloys supported the adhesion and growth of cultured chick neuronal cells, human marrow stromal cells (presumptive osteoblasts), bovine aortal endothelial cells, and hamster kidney fibroblasts. Alloys of compositions Fe60Ni10Cr10P13C7, Fe70Cr10P13C7, and Fe70Cr10P13B7 were found to be suitable. In contrast the crystalline form of these alloys was markedly less effective. Outgrowth of neurites from neuronal cells was promoted by precoating the metal surface with either laminin or neurite promotion factor. The adhesion of osteoblasts and fibroblasts suggests that corrosion resistant metal glasses should be considered as biomaterials useful for orthopedic applications. The adhesion of neuronal cells accompanied by neurite outgrowth indicates that the system might provide a functional interface between the neuromuscular system and an electromagnetic material that could be useful in bionic engineering.

  10. Large Absorption Enhancement in Ultrathin Solar Cells Patterned by Metallic Nanocavity Arrays

    PubMed Central

    Wang, Wei; Zhang, Jiasen; Che, Xiaozhou; Qin, Guogang

    2016-01-01

    A new type of light trapping structure utilizing ring-shaped metallic nanocavity arrays is proposed for the absorption enhancement in ultrathin solar cells with few photonic waveguide modes. Dozens of times of broadband absorption enhancement in the spectral range of 700 to 1100 nm is demonstrated in an ultrathin Si3N4/c-Si/Ag prototype solar cell by means of finite-difference time-domain (FDTD) simulation, and this dramatic absorption enhancement can be attributed to the excitation of plasmonic cavity modes in these nanocavity arrays. The cavity modes optimally compensate for the lack of resonances in the longer wavelength range for ultrathin solar cells, and eventually a maximum Jsc enhancement factor of 2.15 is achieved under AM 1.5G solar illumination. This study opens a new perspective for light management in thin film solar cells and other optoelectronic devices. PMID:27703176

  11. Large Absorption Enhancement in Ultrathin Solar Cells Patterned by Metallic Nanocavity Arrays

    NASA Astrophysics Data System (ADS)

    Wang, Wei; Zhang, Jiasen; Che, Xiaozhou; Qin, Guogang

    2016-10-01

    A new type of light trapping structure utilizing ring-shaped metallic nanocavity arrays is proposed for the absorption enhancement in ultrathin solar cells with few photonic waveguide modes. Dozens of times of broadband absorption enhancement in the spectral range of 700 to 1100 nm is demonstrated in an ultrathin Si3N4/c-Si/Ag prototype solar cell by means of finite-difference time-domain (FDTD) simulation, and this dramatic absorption enhancement can be attributed to the excitation of plasmonic cavity modes in these nanocavity arrays. The cavity modes optimally compensate for the lack of resonances in the longer wavelength range for ultrathin solar cells, and eventually a maximum Jsc enhancement factor of 2.15 is achieved under AM 1.5G solar illumination. This study opens a new perspective for light management in thin film solar cells and other optoelectronic devices.

  12. Lithium metal oxide electrodes for lithium cells and batteries

    DOEpatents

    Thackeray, Michael M.; Johnson, Christopher S.; Amine, Khalil; Kim, Jaekook

    2004-01-13

    A lithium metal oxide positive electrode for a non-aqueous lithium cell is disclosed. The cell is prepared in its initial discharged state and has a general formula xLiMO.sub.2.(1-x)Li.sub.2 M'O.sub.3 in which 0cells or batteries are disclosed with anode, cathode and electrolyte as are batteries of several cells connected in parallel or series or both.

  13. Lithium metal oxide electrodes for lithium cells and batteries

    DOEpatents

    Thackeray, Michael M.; Johnson, Christopher S.; Amine, Khalil; Kim, Jaekook

    2006-11-14

    A lithium metal oxide positive electrode for a non-aqueous lithium cell is disclosed. The cell is prepared in its initial discharged state and has a general formula xLiMO.sub.2.(1-x)Li.sub.2M'O.sub.3 in which 0cells or batteries are disclosed with anode, cathode and electrolyte as are batteries of several cells connected in parallel or series or both.

  14. Molybdenum In Cathodes Of Sodium/Metal Chloride Cells

    NASA Technical Reports Server (NTRS)

    Bugga, Ratnakumar V.; Attia, Alan I.; Halpert, Gerald

    1992-01-01

    Cyclic voltammetric curves of molybdenum wire in NaAlCl4 melt indicate molybdenum chloride useful as cathode material in rechargeable sodium/metal chloride electrochemical cells. Batteries used in electric vehicles, for electric-power load leveling, and other applications involving high energy and power densities.

  15. Coated metal sintering carriers for fuel cell electrodes

    SciTech Connect

    Donelson, Richard; Bryson, E. S.

    1998-01-01

    A carrier for conveying components of a fuel cell to be sintered through a sintering furnace. The carrier comprises a metal sheet coated with a water-based carbon paint, the water-based carbon paint comprising water, powdered graphite, an organic binder, a wetting agent, a dispersing agent and a defoaming agent.

  16. Coated metal sintering carriers for fuel cell electrodes

    DOEpatents

    Donelson, R.; Bryson, E.S.

    1998-11-10

    A carrier is described for conveying components of a fuel cell to be sintered through a sintering furnace. The carrier comprises a metal sheet coated with a water-based carbon paint, the water-based carbon paint comprising water, powdered graphite, an organic binder, a wetting agent, a dispersing agent and a defoaming agent.

  17. Laser-assisted solar-cell metallization processing

    SciTech Connect

    Dutta, S.; Mcmullin, P.G.

    1984-03-01

    Laser assisted solar cell metallization processing which is a one step process is examined. The potential advantages of laser disposition techniques for photovoltaic systems are: a high resolution, no photolithography, clean and contamination free, in-situ sintering, and low contact resistance.

  18. Simultaneous presence of both open metal sites and free functional organic sites in a noncentrosymmetric dynamic metal-organic framework with bimodal catalytic and sensing activities.

    PubMed

    Saha, Rajat; Joarder, Biplab; Roy, Anupam Singha; Manirul Islam, Sk; Kumar, Sanjay

    2013-12-02

    Assimilation of open metal sites (OMSs) and free functional organic sites (FOSs) with a framework strut has opened up a new route for the fabrication of novel metal-organic materials, thereby providing a unique opportunity to explore their multiple functionalities. A new metal-organic framework (MOF), {[Cu(ina)2(H2O)][Cu(ina)2(bipy)]·2H2O}n (1) (ina=isonicotinate, bipy=4,4'-bipyridine), has been synthesized and characterized. Complex 1 is crystallized in the orthorhombic noncentrosymmetric space group Aba2 and consists of two different 2D coordination polymers, [Cu(ina)2(H2O)]n and [Cu(ina)2(bipy)]n, with entrapped solvent water molecules. Hydrogen-bonding interactions assemble these two different 2D coordination layers in a single-crystal structure with interdigitation of pendant 4,4'-bipy from one layer into the groove of another. Upon removal of guest molecules, 1 undergoes a structural transformation in single-crystal-to-single-crystal fashion with expansion of the effective void space. Each metal center is five-coordinated and thus can potentially behave as an OMS, and the free pyridyl groups of pendant 4,4'-bipy moieties and free -C=O groups can act as free FOSs. Thus, owing to presence of both OMSs and free FOSs, the framework exhibits multifunctional properties. Owing to the presence of OMSs, the framework can act as a Lewis acid catalyst as well as a small-molecule sensor material, and in a similar way, owing to the presence of free FOSs, it performs as a Lewis base catalyst and a cation sensor material. Furthermore, owing to noncentrosymmetry with large polarity along a particular direction, it shows strong second-harmonic generation/nonlinear optical (SHG-NLO) activity. Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  19. Cracking open cell death in the Drosophila ovary

    PubMed Central

    Pritchett, Tracy L.; Tanner, Elizabeth A.; McCall, Kimberly

    2010-01-01

    The Drosophila melanogaster ovary is a powerful yet simple system with only a few cell types. Cell death in the ovary can be induced in response to multiple developmental and environmental signals. These cell deaths occur at distinct stages of oogenesis and involve unique mechanisms utilizing apoptotic, autophagic and perhaps necrotic processes. In this review, we summarize recent progress characterizing cell death mechanisms in the fly ovary. PMID:19533361

  20. The cell biology of open and closed mitosis.

    PubMed

    Boettcher, Barbara; Barral, Yves

    2013-01-01

    Mitosis is the process of one cell dividing into two daughters, such that each inherits a single and complete copy of the genome of their mother. This is achieved through the equal segregation of the sister chromatids between the daughter cells. However, beyond this simple principle, the partitioning of other cellular components between daughter cells appears to follow a large variety of patterns. We discuss here how the organization of the nuclear envelope during mitosis influences cell division and, subsequently, cellular identity.

  1. Study of the migration phenomena of specific metals in canned tomato paste before and after opening. Validation of a new quality indicator for opened cans.

    PubMed

    Raptopoulou, Kalomoira G; Pasias, Ioannis N; Thomaidis, Nikolaos S; Proestos, Charalampos

    2014-07-01

    A method for the simultaneous determination of Cd-Pb, As-Cu, Cr-Ni and Fe-Mn in canned tomato paste samples by Electrothermal Atomic Absorption Spectrometry was developed and validated. The validation procedure was conducted according to the terms of the European regulation for the official control of contaminants in foods. The validated method was applied for the determination of these metals and metalloids in 13 different tomato paste samples and the results showed that Cd content was higher than the maximum permissible value of 0.050 mg kg(-1) as proposed in European Regulation (EC) No 1881/2006 concerning fresh fruits and vegetables. Furthermore, a new quality indicator was evaluated in order to provide information about tomato paste quality and the appropriate storage time of an opened canned tomato paste. Finally, a migration test was accomplished based on the calculation of mass balance and the comparison of the elemental content in canned tomato paste samples and in aseptic paper pack and it was proved that Fe and Pb were the main metals migrating in tomato paste samples.

  2. The Effect of Metallicity on Surface Lithium Abundance in Hyades-Aged Open Clusters

    NASA Astrophysics Data System (ADS)

    Gayetsky, Lisa; Cummings, J.; Deliyannis, C. P.; Steinhauer, A.; James, D.; Sarajedini, A.

    2007-12-01

    Two of the most important predictions from standard stellar evolution theory about the lithium depletion of solar-type F and G dwarfs are that it occurs primarily during the pre-main sequence and that it depends on metallicity. Abundant evidence from star clusters shows that Li depletion does indeed occur during the pre-main sequence, but then also continues during the main sequence, perhaps due to the effects of (non-standard) rotationally-induced or wave-induced mixing. However, little is known about whether Li depletion depends on metallicity. To test the predicted dependence of standard Li depletion on metallicity, a program has begun that compares the Li-Teff relation in Hyades-aged clusters of different metallicities. Here, we present high resolution results from WIYN/Hydra observations of IC 4756. We find, first, that our data qualitatively support the prediction that stars with higher metallicity have depleted more Li. Second, if a reasonable adjustment is made to the (unknown) initial cluster Li abundances that is consistent with knowledge of Galactic Li production from the field dwarf Li-Fe relation, then our data are also in good quantitative agreement with the metallicity-dependence of the Li depletion from standard theory. This work has been supported by the National Science Foundation under grants AST-0452975 and AST-0206202.

  3. (abstract) Alkali Metal Diffusion Through Porous Metal Electrodes in AMTEC Cells

    NASA Technical Reports Server (NTRS)

    Williams, R. M.; Jeffries-Nakamura, B.; Ryan, M. A.; Underwood, M. L.; O'Connor, D.; Kisor, A.; Kikkert, S.

    1993-01-01

    The mechanisms of mass transport of an alkali metal through porous metal electrodes in alkali metal thermal-to-electric converter AMTEC cells is important in optimizing these high current density devices, but also affords the opportunity to investigate a variety of simple mass transport modes at high temperatures via electrochemical techniques. We have previously reported evidence of ionic, free molecular flow, and surface transport of sodium in several types of AMTEC electrodes. Quantitative investigations of Na transport through WPt(sub 3.5) via surface or grain boundary diffusion, and K transport through porous Mo electrodes by free molecular flow, over large ranges of temperature have been performed. WPt(sub 3.5) has especially low transport impedance over the 950 to 1200K temperature range. New results are the Na through porous WPt(sub 3.5) and K through porous Mo diffusion rates and mechanisms.

  4. (abstract) Alkali Metal Diffusion Through Porous Metal Electrodes in AMTEC Cells

    NASA Technical Reports Server (NTRS)

    Williams, R. M.; Jeffries-Nakamura, B.; Ryan, M. A.; Underwood, M. L.; O'Connor, D.; Kisor, A.; Kikkert, S.

    1993-01-01

    The mechanisms of mass transport of an alkali metal through porous metal electrodes in alkali metal thermal-to-electric converter AMTEC cells is important in optimizing these high current density devices, but also affords the opportunity to investigate a variety of simple mass transport modes at high temperatures via electrochemical techniques. We have previously reported evidence of ionic, free molecular flow, and surface transport of sodium in several types of AMTEC electrodes. Quantitative investigations of Na transport through WPt(sub 3.5) via surface or grain boundary diffusion, and K transport through porous Mo electrodes by free molecular flow, over large ranges of temperature have been performed. WPt(sub 3.5) has especially low transport impedance over the 950 to 1200K temperature range. New results are the Na through porous WPt(sub 3.5) and K through porous Mo diffusion rates and mechanisms.

  5. Aluminum low temperature smelting cell metal collection

    DOEpatents

    Beck, Theodore R.; Brown, Craig W.

    2002-07-16

    A method of producing aluminum in an electrolytic cell containing alumina dissolved in an electrolyte. The method comprises the steps of providing a molten salt electrolyte in an electrolytic cell having an anodic liner for containing the electrolyte, the liner having an anodic bottom and walls including at least one end wall extending upwardly from the anodic bottom, the anodic liner being substantially inert with respect to the molten electrolyte. A plurality of non-consumable anodes is provided and disposed vertically in the electrolyte. A plurality of cathodes is disposed vertically in the electrolyte in alternating relationship with the anodes. The anodes are electrically connected to the anodic liner. An electric current is passed through the anodic liner to the anodes, through the electrolyte to the cathodes, and aluminum is deposited on said cathodes. Oxygen bubbles are generated at the anodes and the anodic liner, the bubbles stirring the electrolyte. Molten aluminum is collected from the cathodes into a tubular member positioned underneath the cathodes. The tubular member is in liquid communication with each cathode to collect the molten aluminum therefrom while excluding electrolyte. Molten aluminum is delivered through the tubular member to a molten aluminum reservoir located substantially opposite the anodes and cathodes. The molten aluminum is collected from the cathodes and delivered to the reservoir while avoiding contact of the molten aluminum with the anodic bottom.

  6. Incorporating metal into polarized 3He target cells

    NASA Astrophysics Data System (ADS)

    Katugampola, Sumudu K.; Matyas, Daniel J.; Wang, Yunxiao; Tobias, William A.; Nelyubin, Vladimir; Cates, Gordon D.

    2017-01-01

    An upcoming measurement at Jefferson Laboratory (JLab) of the electric form factor of the neutron will utilize a polarized 3He target at high luminosity. While polarized 3He targets at JLab have previously been made entirely of glass, we describe progress toward incorporating metal windows for the electron beam. Under the conditions of our targets, very few studies have been done on the spin-relaxation of nuclear-polarized 3He on metal surfaces. We have found good performance by using Oxygen Free High Conductivity (OFHC) copper substrates electroplated with gold. The glass-to-metal transitions within our test cells were based on Housekeeper seals. We have further established that Uranium glass (Canary glass) has excellent spin-relaxation properties, and can serve as a transition glass from Pyrex to Aluminosilicate glass (GE180). Another finding was that spin-relaxation properties were sensitive to the manner in which cells were annealed, an important issue because of constraints when annealing cells containing both metal and glass.

  7. Metal nano-grids for transparent conduction in solar cells

    DOE PAGES

    Muzzillo, Christopher P.

    2017-05-11

    A general procedure for predicting metal grid performance in solar cells was developed. Unlike transparent conducting oxides (TCOs) or other homogeneous films, metal grids induce more resistance in the neighbor layer. The resulting balance of transmittance, neighbor and grid resistance was explored in light of cheap lithography advances that have enabled metal nano-grid (MNG) fabrication. The patterned MNGs have junction resistances and degradation rates that are more favorable than solution-synthesized metal nanowires. Neighbor series resistance was simulated by the finite element method, although a simpler analytical model was sufficient in most cases. Finite-difference frequency-domain transmittance simulations were performed for MNGsmore » with minimum wire width (w) of 50 nm, but deviations from aperture transmittance were small in magnitude. Depending on the process, MNGs can exhibit increased series resistance as w is decreased. However, numerous experimental reports have already achieved transmittance-MNG sheet resistance trade-offs comparable to TCOs. The transmittance, neighbor and MNG series resistances were used to parameterize a grid fill factor for a solar cell. In conclusion, this new figure of merit was used to demonstrate that although MNGs have only been employed in low efficiency solar cells, substantial gains in performance are predicted for decreased w in all high efficiency absorber technologies.« less

  8. A New Method of Metallization for Silicon Solar Cells

    NASA Technical Reports Server (NTRS)

    Macha, M.

    1979-01-01

    A low cost ohmic contact on silicon solar cells based on molybdenum-tin metal systems was developed. The approach is based on the formulation of a screenable ink composed from molybdenum oxide and tin mixture. The reduction of Mo03 into Mo and the establishment of Mo 03:Sn ratio is studied. Both tasks were done in an experimental station constructed for this purpose. The results show that molybdenum was formed from its oxide at 800 C. and improved in bonding to silicon at 900 C. A 20% Mo03-80%Sn mixture was converted into metallic coating within this temperature range.

  9. Opening Study on the Development of a New Biosensor for Metal Toxicity Based on Pseudomonas fluorescens Pyoverdine

    PubMed Central

    Chiadò, Alessandro; Varani, Luca; Bosco, Francesca; Marmo, Luca

    2013-01-01

    To date, different kinds of biosensing elements have been used effectively for environmental monitoring. Microbial cells seem to be well-suited for this task: they are cheap, adaptable to variable field conditions and give a measurable response to a broad number of chemicals. Among different pollutants, heavy metals are still a major problem for the environment. A reasonable starting point for the selection of a biorecognition element to develop a biosensor for metals could be that of a microorganism that exhibits good mechanisms to cope with metals. Pseudomonads are characterized by the secretion of siderophores (e.g., pyoverdine), low-molecular weight compounds that chelate Fe3+ during iron starvation. Pyoverdine is easily detected by colorimetric assay, and it is suitable for simple online measurements. In this work, in order to evaluate pyoverdine as a biorecognition element for metal detection, the influence of metal ions (Fe3+, Cu2+, Zn2+), but also of temperature, pH and nutrients, on microbial growth and pyoverdine regulation has been studied in P. fluorescens. Each of these variables has been shown to influence the synthesis of siderophore: for instance, the lower the temperature, the higher the production of pyoverdine. Moreover, the concentration of pyoverdine produced in the presence of metals has been compared with the maximum allowable concentrations indicated in international regulations (e.g., 98/83/EC), and a correlation that could be useful to build a colorimetric biosensor has been observed. PMID:25586414

  10. Guard cell chloroplasts are essential for blue light-dependent stomatal opening in Arabidopsis.

    PubMed

    Suetsugu, Noriyuki; Takami, Tsuneaki; Ebisu, Yuuta; Watanabe, Harutaka; Iiboshi, Chihoko; Doi, Michio; Shimazaki, Ken-ichiro

    2014-01-01

    Blue light (BL) induces stomatal opening through the activation of H+-ATPases with subsequent ion accumulation in guard cells. In most plant species, red light (RL) enhances BL-dependent stomatal opening. This RL effect is attributable to the chloroplasts of guard cell, the only cells in the epidermis possessing this organelle. To clarify the role of chloroplasts in stomatal regulation, we investigated the effects of RL on BL-dependent stomatal opening in isolated epidermis, guard cell protoplasts, and intact leaves of Arabidopsis thaliana. In isolated epidermal tissues and intact leaves, weak BL superimposed on RL enhanced stomatal opening while BL alone was less effective. In guard cell protoplasts, RL enhanced BL-dependent H+-pumping and DCMU, a photosynthetic electron transport inhibitor, eliminated this effect. RL enhanced phosphorylation levels of the H+-ATPase in response to BL, but this RL effect was not suppressed by DCMU. Furthermore, DCMU inhibited both RL-induced and BL-dependent stomatal opening in intact leaves. The photosynthetic rate in leaves correlated positively with BL-dependent stomatal opening in the presence of DCMU. We conclude that guard cell chloroplasts provide ATP and/or reducing equivalents that fuel BL-dependent stomatal opening, and that they indirectly monitor photosynthetic CO2 fixation in mesophyll chloroplasts by absorbing PAR in the epidermis.

  11. Reduction of jaw opening (trismus) in giant cell arteritis

    PubMed Central

    Nir-Paz, R; Gross, A; Chajek-Shaul, T

    2002-01-01

    Methods: the prevalence of such symptoms in patients with GCA was evaluated by performing a retrospective analysis of all patients with GCA and polymyalgia rheumatica who were diagnosed during admission to Hadassah University Hospital. Ten patients reported previously in the literature were also evaluated. Results: Six patients out of 88 (6.8%) had complaints of reduction in jaw opening. These six patients seemed to have a much more abrupt onset of disease with shorter duration until diagnosis, higher prevalence of eye involvement (50% v 27%), and a higher rate of positive pathology (100%). Conclusions: Reduction in jaw opening in the appropriate setting may indicate the presence of GCA. This sign should not be overlooked in the presence of the claudication sign as it seems to reflect more severe GCA disease. PMID:12176811

  12. Heavy Metals Induce Iron Deficiency Responses at Different Hierarchic and Regulatory Levels1[OPEN

    PubMed Central

    2017-01-01

    In plants, the excess of several heavy metals mimics iron (Fe) deficiency-induced chlorosis, indicating a disturbance in Fe homeostasis. To examine the level at which heavy metals interfere with Fe deficiency responses, we carried out an in-depth characterization of Fe-related physiological, regulatory, and morphological responses in Arabidopsis (Arabidopsis thaliana) exposed to heavy metals. Enhanced zinc (Zn) uptake closely mimicked Fe deficiency by leading to low chlorophyll but high ferric-chelate reductase activity and coumarin release. These responses were not caused by Zn-inhibited Fe uptake via IRON-REGULATED TRANSPORTER (IRT1). Instead, Zn simulated the transcriptional response of typical Fe-regulated genes, indicating that Zn affects Fe homeostasis at the level of Fe sensing. Excess supplies of cobalt and nickel altered root traits in a different way from Fe deficiency, inducing only transient Fe deficiency responses, which were characterized by a lack of induction of the ethylene pathway. Cadmium showed a rather inconsistent influence on Fe deficiency responses at multiple levels. By contrast, manganese evoked weak Fe deficiency responses in wild-type plants but strongly exacerbated chlorosis in irt1 plants, indicating that manganese antagonized Fe mainly at the level of transport. These results show that the investigated heavy metals modulate Fe deficiency responses at different hierarchic and regulatory levels and that the interaction of metals with physiological and morphological Fe deficiency responses is uncoupled. Thus, this study not only emphasizes the importance of assessing heavy metal toxicities at multiple levels but also provides a new perspective on how Fe deficiency contributes to the toxic action of individual heavy metals. PMID:28500270

  13. Novel Approach for Selective Emitter Formation and Front Side Metallization of Crystalline Silicon Solar Cells

    SciTech Connect

    Xu, Baomin

    2010-07-26

    In this project we will explore the possibility of forming the front side metallization and selective emitter layer for the crystalline silicon solar cells through using selective laser ablation to create contact openings on the front surface and a screen printer to make connections with conductive paste. Using this novel approach we expect to reduce the specific contact resistance of the silver gridlines by about one order of magnitude compared to the state-of-art industrial crystalline silicon solar cells to below 1 mΩ∙cm2, and use lightly doped n+ emitter layer with sheet resistance of not smaller than 100 Ω. This represents an enabling improvement on crystalline silicon solar cell performance and can increase the absolute efficiency of the solar cell by about 1%. In this scientific report we first present our result on the selective laser ablation of the nitride layer to make contact openings. Then we report our work on the solar cell fabrication by using the laser ablated contact openings with self-doping paste. Through various electrical property characterization and SIMS analysis, the factors limiting the cell performance have been discussed. While through this proof-of-concept project we could not reach the target on cell efficiency improvement, the process to fabricate 125mm full-sized silicon solar cells using laser ablation and self-doping paste has been developed, and a much better understanding of technical challenges has been achieved. Future direction to realize the potential of the new technology has been clearly defined.

  14. Using CellML with OpenCMISS to Simulate Multi-Scale Physiology

    PubMed Central

    Nickerson, David P.; Ladd, David; Hussan, Jagir R.; Safaei, Soroush; Suresh, Vinod; Hunter, Peter J.; Bradley, Christopher P.

    2014-01-01

    OpenCMISS is an open-source modeling environment aimed, in particular, at the solution of bioengineering problems. OpenCMISS consists of two main parts: a computational library (OpenCMISS-Iron) and a field manipulation and visualization library (OpenCMISS-Zinc). OpenCMISS is designed for the solution of coupled multi-scale, multi-physics problems in a general-purpose parallel environment. CellML is an XML format designed to encode biophysically based systems of ordinary differential equations and both linear and non-linear algebraic equations. A primary design goal of CellML is to allow mathematical models to be encoded in a modular and reusable format to aid reproducibility and interoperability of modeling studies. In OpenCMISS, we make use of CellML models to enable users to configure various aspects of their multi-scale physiological models. This avoids the need for users to be familiar with the OpenCMISS internal code in order to perform customized computational experiments. Examples of this are: cellular electrophysiology models embedded in tissue electrical propagation models; material constitutive relationships for mechanical growth and deformation simulations; time-varying boundary conditions for various problem domains; and fluid constitutive relationships and lumped-parameter models. In this paper, we provide implementation details describing how CellML models are integrated into multi-scale physiological models in OpenCMISS. The external interface OpenCMISS presents to users is also described, including specific examples exemplifying the extensibility and usability these tools provide the physiological modeling and simulation community. We conclude with some thoughts on future extension of OpenCMISS to make use of other community developed information standards, such as FieldML, SED-ML, and BioSignalML. Plans for the integration of accelerator code (graphical processing unit and field programmable gate array) generated from CellML models is also

  15. Using CellML with OpenCMISS to Simulate Multi-Scale Physiology.

    PubMed

    Nickerson, David P; Ladd, David; Hussan, Jagir R; Safaei, Soroush; Suresh, Vinod; Hunter, Peter J; Bradley, Christopher P

    2014-01-01

    OpenCMISS is an open-source modeling environment aimed, in particular, at the solution of bioengineering problems. OpenCMISS consists of two main parts: a computational library (OpenCMISS-Iron) and a field manipulation and visualization library (OpenCMISS-Zinc). OpenCMISS is designed for the solution of coupled multi-scale, multi-physics problems in a general-purpose parallel environment. CellML is an XML format designed to encode biophysically based systems of ordinary differential equations and both linear and non-linear algebraic equations. A primary design goal of CellML is to allow mathematical models to be encoded in a modular and reusable format to aid reproducibility and interoperability of modeling studies. In OpenCMISS, we make use of CellML models to enable users to configure various aspects of their multi-scale physiological models. This avoids the need for users to be familiar with the OpenCMISS internal code in order to perform customized computational experiments. Examples of this are: cellular electrophysiology models embedded in tissue electrical propagation models; material constitutive relationships for mechanical growth and deformation simulations; time-varying boundary conditions for various problem domains; and fluid constitutive relationships and lumped-parameter models. In this paper, we provide implementation details describing how CellML models are integrated into multi-scale physiological models in OpenCMISS. The external interface OpenCMISS presents to users is also described, including specific examples exemplifying the extensibility and usability these tools provide the physiological modeling and simulation community. We conclude with some thoughts on future extension of OpenCMISS to make use of other community developed information standards, such as FieldML, SED-ML, and BioSignalML. Plans for the integration of accelerator code (graphical processing unit and field programmable gate array) generated from CellML models is also

  16. Evaluation of metal biouptake from the analysis of bulk metal depletion kinetics at various cell concentrations: theory and application.

    PubMed

    Rotureau, Elise; Billard, Patrick; Duval, Jérôme F L

    2015-01-20

    Bioavailability of trace metals is a key parameter for assessment of toxicity on living organisms. Proper evaluation of metal bioavailability requires monitoring the various interfacial processes that control metal partitioning dynamics at the biointerface, which includes metal transport from solution to cell membrane, adsorption at the biosurface, internalization, and possible excretion. In this work, a methodology is proposed to quantitatively describe the dynamics of Cd(II) uptake by Pseudomonas putida. The analysis is based on the kinetic measurement of Cd(II) depletion from bulk solution at various initial cell concentrations using electroanalytical probes. On the basis of a recent formalism on the dynamics of metal uptake by complex biointerphases, the cell concentration-dependent depletion time scales and plateau values reached by metal concentrations at long exposure times (>3 h) are successfully rationalized in terms of limiting metal uptake flux, rate of excretion, and metal affinity to internalization sites. The analysis shows the limits of approximate depletion models valid in the extremes of high and weak metal affinities. The contribution of conductive diffusion transfer of metals from the solution to the cell membrane in governing the rate of Cd(II) uptake is further discussed on the basis of estimated resistances for metal membrane transfer and extracellular mass transport.

  17. Burp Charging Nickel Metal Hydride Cells

    NASA Technical Reports Server (NTRS)

    Darcy, Eric; Pollard, Richard

    1997-01-01

    The SKYNET 4 constellation consists of three spacecraft which were launched between December 1988 and August 1990. The spacecraft are three-axis stabilized geostationary earth-orbiting military communications satellites with a design life of seven years on station. With the mission objective achieved all the batteries continue to give excellent performance. This paper presents a review of the history of the six batteries from cell procurement to the end of their design life and beyond. Differences in operational strategies are discussed and the lifetime trends in performance are analyzed. The combination of procurement acceptance criteria and the on-station battery management strategy utilized are presented as the prime factors in achieving completely successful battery performance throughout the mission.

  18. Comparison of selected metals content in Cambodian striped snakehead fish (Channa striata) using solar drying system and open sun drying.

    PubMed

    Basri, Dayang Fredalina; Abu Bakar, Nur Faizah; Fudholi, Ahmad; Ruslan, Mohd Hafidz; Saroeun, Im

    2015-01-01

    The content of 12 elements in Cambodian dried striped snakehead fish was determined using inductively coupled plasma mass spectrometry. The present study compares the level of the trace toxic metals and nutritional trace elements in the fish processed using solar drying system (SDS) and open sun drying (OSD). The skin of SDS fish has lower level of As, Pb, and Cd compared to the OSD sample. As such, the flesh of the fish accumulated higher amount of toxic metals during OSD compared to SDS. However, arsenic was detected in both samples within the safe limit. The nutritional elements (Fe, Mn, Mg, Se, Mo, Cu, Ni, and Cr) were higher in the skin sample SDS fish compared to OSD fish. These beneficial metals were not accumulated in the flesh sample SDS fish demonstrating lower level compared to drying under conventional system. The reddish coloration of the SDS fish was due to the presence of high Cu content in both the skin and flesh samples which possibly account for no mold formation 5 days after packaging. As conclusion, drying of Cambodian C. striata using solar-assisted system has proven higher content of the nutritious elements compared to using the conventional system despite only slight difference in the toxic metals level between the two systems.

  19. Soil criteria to protect terrestrial wildlife and open-range livestock from metal toxicity at mining sites

    USGS Publications Warehouse

    Ford, Karl L; Beyer, W. Nelson

    2014-01-01

    Thousands of hard rock mines exist in the western USA and in other parts of the world as a result of historic and current gold, silver, lead, and mercury mining. Many of these sites in the USA are on public lands. Typical mine waste associated with these sites are tailings and waste rock dumps that may be used by wildlife and open-range livestock. This report provides wildlife screening criteria levels for metals in soil and mine waste to evaluate risk and to determine the need for site-specific risk assessment, remediation, or a change in management practices. The screening levels are calculated from toxicity reference values based on maximum tolerable levels of metals in feed, on soil and plant ingestion rates, and on soil to plant uptake factors for a variety of receptors. The metals chosen for this report are common toxic metals found at mining sites: arsenic, cadmium, copper, lead, mercury, and zinc. The resulting soil screening values are well above those developed by the US Environmental Protection Agency. The difference in values was mainly a result of using toxicity reference values that were more specific to the receptors addressed rather than the most sensitive receptor.

  20. Soil criteria to protect terrestrial wildlife and open-range livestock from metal toxicity at mining sites.

    PubMed

    Ford, Karl L; Beyer, W Nelson

    2014-03-01

    Thousands of hard rock mines exist in the western USA and in other parts of the world as a result of historic and current gold, silver, lead, and mercury mining. Many of these sites in the USA are on public lands. Typical mine waste associated with these sites are tailings and waste rock dumps that may be used by wildlife and open-range livestock. This report provides wildlife screening criteria levels for metals in soil and mine waste to evaluate risk and to determine the need for site-specific risk assessment, remediation, or a change in management practices. The screening levels are calculated from toxicity reference values based on maximum tolerable levels of metals in feed, on soil and plant ingestion rates, and on soil to plant uptake factors for a variety of receptors. The metals chosen for this report are common toxic metals found at mining sites: arsenic, cadmium, copper, lead, mercury, and zinc. The resulting soil screening values are well above those developed by the US Environmental Protection Agency. The difference in values was mainly a result of using toxicity reference values that were more specific to the receptors addressed rather than the most sensitive receptor.

  1. Comparison of Selected Metals Content in Cambodian Striped Snakehead Fish (Channa striata) Using Solar Drying System and Open Sun Drying

    PubMed Central

    Abu Bakar, Nur Faizah; Fudholi, Ahmad; Ruslan, Mohd Hafidz; Saroeun, Im

    2015-01-01

    The content of 12 elements in Cambodian dried striped snakehead fish was determined using inductively coupled plasma mass spectrometry. The present study compares the level of the trace toxic metals and nutritional trace elements in the fish processed using solar drying system (SDS) and open sun drying (OSD). The skin of SDS fish has lower level of As, Pb, and Cd compared to the OSD sample. As such, the flesh of the fish accumulated higher amount of toxic metals during OSD compared to SDS. However, arsenic was detected in both samples within the safe limit. The nutritional elements (Fe, Mn, Mg, Se, Mo, Cu, Ni, and Cr) were higher in the skin sample SDS fish compared to OSD fish. These beneficial metals were not accumulated in the flesh sample SDS fish demonstrating lower level compared to drying under conventional system. The reddish coloration of the SDS fish was due to the presence of high Cu content in both the skin and flesh samples which possibly account for no mold formation 5 days after packaging. As conclusion, drying of Cambodian C. striata using solar-assisted system has proven higher content of the nutritious elements compared to using the conventional system despite only slight difference in the toxic metals level between the two systems. PMID:25688274

  2. Hybrid nanocatalysts containing enzymes and metallic nanoparticles for ethanol/O2 biofuel cell

    NASA Astrophysics Data System (ADS)

    Aquino Neto, S.; Almeida, T. S.; Palma, L. M.; Minteer, S. D.; de Andrade, A. R.

    2014-08-01

    We report the preparation of hybrid nanostructured bioanodes containing the enzyme alcohol dehydrogenase (ADH) with either Au, Pt, or Pt0.75Sn0.25 nanoparticles for use in ethanol/O2 hybrid biofuel cells. We describe two different methodologies for the preparation of the bioanodes: in a first case, multi walled carbon nanotubes (MWCNTs) were employed as a support for the metallic nanoparticles and TBAB-modified Nafion® aided enzyme immobilization. In the second case, we immobilized the enzymes using dendrimers-encapsulated nanoparticles as the agent for enzyme anchoring. The biofuel cell tests showed that the addition of metallic nanoparticles to the bioanode structure enhanced the overall biofuel cell performance. The bioelectrode containing Au nanoparticles displaying the best performance, with an open circuit potential of 0.61 ± 0.05 V and a maximum power density of 155 ± 11 μW cm-2. NADH cyclic voltammetric experiments indicated that Au nanoparticles behaved as a catalyst toward NADH oxidation. Comparing the two protocols we used to synthetized nanoparticles, the sample containing the Au nanoparticles supported on MWCNTs furnished fourfold higher values. Therefore, from the satisfactory results obtained, it can be inferred that the combination of small amounts of metallic nanoparticles with enzymes improve bioanode performance.

  3. Microwave detection of hairline surface-breaking cracks in metals using open-ended coaxial sensors: preliminary results

    NASA Astrophysics Data System (ADS)

    Zoughi, Reza; Hayes, Kent; Ganchev, Stoyan I.

    1996-11-01

    Recent microwave methods have shown to be capable of detecting and sizing surface slots and cracks in metals. These methods have incorporated the use of an open-ended rectangular waveguide probe for such measurements. A new microwave method utilizing an open-ended coaxial line sensor has been under investigation for some time now. Coaxial line sensors have certain features that make them quite attractive for surface crack detection. These features include their high level of sensitivity to the presence of very narrow cracks as will as the fact that their geometry may include complicated bends allowing access to hard to reach places. This paper presents and comments on some preliminary experimental results of using this sensor for hairline surface crack detection.

  4. Carbon-Carbon Bond Formation in a Weak Ligand Field: Leveraging Open Shell First Row Transition Metal Catalysts.

    PubMed

    Chirik, Paul James

    2017-01-12

    Unique features of Earth abundant transition metal catalysts are reviewed in the context of catalytic carbon-carbon bond forming reactions. Aryl-substituted bis(imino)pyridine iron and cobalt dihalide compounds, when activated with alkyl aluminum reagents, form highly active catalysts for the polymerization of ethylene. Open shell iron and cobalt alkyl complexes have been synthesized that serve as single component olefin polymerization catalysts. Reduced bis(imino)pyridine iron- and cobalt dinitrogen compounds have also been discovered that promote the unique [2+2] cycloaddition of unactivated terminal alkenes. Electronic structure studies support open shell intermediates, a deviation from traditional strong field organometallic compounds that promote catalytic C-C bond formation.

  5. Highly Selective Adsorption of Ethylene over Ethane in a MOF Featuring the Combination of Open Metal Site and -Complexation

    SciTech Connect

    Zhang, Yiming; Li, Baiyan; Wu, Zili; Ma, Shengqian

    2015-01-01

    The introduction of the combination of open metal site (OMS) and -complexation into MOF has led to very high ethylene/ethane adsorption selectivity at 318K, as illustrated in the context of MIL-101-Cr-SO3Ag. The interactions with ethylene from both OMS and -complexation in MIL-101-Cr-SO3Ag have been investigated by in situ IR spectroscopic studies and computational calculations, which suggest -complexation contributes dominantly to the high ethylene/ethane adsorption selectivity.

  6. Metal-Free Synthesis of N-Aryl Amides using Organocatalytic Ring-Opening Aminolysis of Lactones.

    PubMed

    Guo, Wusheng; Gómez, José Enrique; Martínez-Rodríguez, Luis; Bandeira, Nuno A G; Bo, Carles; Kleij, Arjan W

    2017-04-05

    Catalytic ring-opening of bio-sourced non-strained lactones with aromatic amines can offer a straightforward, 100 % atom-economical, and sustainable pathway towards relevant N-aryl amide scaffolds. Herein, the first general, metal-free, and highly efficient N-aryl amide formation is reported from poorly reactive aromatic amines and non-strained lactones under mild operating conditions using an organic bicyclic guanidine catalyst. This protocol has high application potential as exemplified by the formal syntheses of drug-relevant molecules.

  7. Automatic tracking of red blood cells in micro channels using OpenCV

    NASA Astrophysics Data System (ADS)

    Rodrigues, Vânia; Rodrigues, Pedro J.; Pereira, Ana I.; Lima, Rui

    2013-10-01

    The present study aims to developan automatic method able to track red blood cells (RBCs) trajectories flowing through a microchannel using the Open Source Computer Vision (OpenCV). The developed method is based on optical flux calculation assisted by the maximization of the template-matching product. The experimental results show a good functional performance of this method.

  8. Exploration of Metal Chloride Uptake for Improved Performance Characteristics of PbSe Quantum Dot Solar Cells

    SciTech Connect

    Marshall, Ashley R.; Young, Matthew R.; Nozik, Arthur J.; Beard, Matthew C.; Luther, Joseph M.

    2015-08-06

    We explored the uptake of metal chloride salts with +1 to +3 metals of Na+, K+, Zn2+, Cd2+, Sn2+, Cu2+, and In3+ by PbSe QD solar cells. We also compared CdCl2 to Cd acetate and Cd nitrate treatments. PbSe QD solar cells fabricated with a CdCl2 treatment are stable for more than 270 days stored in air. We studied how temperature and immersion times affect optoelectronic properties and photovoltaic cell performance. Uptake of Cd2+ and Zn2+ increase open circuit voltage, whereas In3+ and K+ increase the photocurrent without influencing the spectral response or first exciton peak position. Using the most beneficial treatments we varied the bandgap of PbSe QD solar cells from 0.78 to 1.3 eV and find the improved VOC is more prevalent for lower bandgap QD solar cells.

  9. Exploration of Metal Chloride Uptake for Improved Performance Characteristics of PbSe Quantum Dot Solar Cells.

    PubMed

    Marshall, Ashley R; Young, Matthew R; Nozik, Arthur J; Beard, Matthew C; Luther, Joseph M

    2015-08-06

    We explored the uptake of metal chloride salts with +1 to +3 metals of Na(+), K(+), Zn(2+), Cd(2+), Sn(2+), Cu(2+), and In(3+) by PbSe QD solar cells. We also compared CdCl2 to Cd acetate and Cd nitrate treatments. PbSe QD solar cells fabricated with a CdCl2 treatment are stable for more than 270 days stored in air. We studied how temperature and immersion times affect optoelectronic properties and photovoltaic cell performance. Uptake of Cd(2+) and Zn(2+) increase open circuit voltage, whereas In(3+) and K(+) increase the photocurrent without influencing the spectral response or first exciton peak position. Using the most beneficial treatments we varied the bandgap of PbSe QD solar cells from 0.78 to 1.3 eV and find the improved VOC is more prevalent for lower bandgap QD solar cells.

  10. Open questions: The disrupted circuitry of the cancer cell

    SciTech Connect

    Wiley, H. Steven

    2014-10-18

    Every new decade of biology brings with it a change in outlook driven by new technologies and fresh perspectives. Such is the case for cancer and how we consider the disease. The advent of molecular biology led to the identification of altered signaling molecules and 'oncogenes' that were proposed to drive uncontrolled cell proliferation. The rise of cell biology and new imaging and culturing technologies led to the idea that disruptions in the extracellular environment prime cells for transformation. In the current genomics era, cancer is most commonly seen as a genetic disorder where an unstable genome gives rise to a variety of different cell variants that are selected for proliferation and survival. All of these views are partially correct, of course, and are simply different ways of saying that genetic alterations in cancer cells result in a loss of growth homeostasis. They also take the view that molecular changes 'drive' a cell to grow uncontrollably, rather than tip the balance from one normal state (quiescence) to another (proliferation). Underlying this oversimplification is a profound ignorance of what controls homeostatic cell growth in the first place and how specific mutations impact it. Normal, proliferation-competent cells can accurately monitor their environment and respond appropriately to perturbation, whether it is a loss of neighbors or an inflammatory stimulus. Cancer cells either proliferate or refuse to die where and when they should not, which clearly indicates that they have problems in detecting or responding to their environment. Thus, an enormous amount of effort has gone into defining the signaling pathways that can trigger a proliferative response and the biochemical mechanisms underlying these pathways. Far less work has focused on understanding the higher-order logic of these pathways and the roles played by all of the components as part of an integrated system. In other words, we do not really understand how cells process

  11. Density functional theory embedding for correlated wavefunctions: improved methods for open-shell systems and transition metal complexes.

    PubMed

    Goodpaster, Jason D; Barnes, Taylor A; Manby, Frederick R; Miller, Thomas F

    2012-12-14

    Density functional theory (DFT) embedding provides a formally exact framework for interfacing correlated wave-function theory (WFT) methods with lower-level descriptions of electronic structure. Here, we report techniques to improve the accuracy and stability of WFT-in-DFT embedding calculations. In particular, we develop spin-dependent embedding potentials in both restricted and unrestricted orbital formulations to enable WFT-in-DFT embedding for open-shell systems, and develop an orbital-occupation-freezing technique to improve the convergence of optimized effective potential calculations that arise in the evaluation of the embedding potential. The new techniques are demonstrated in applications to the van-der-Waals-bound ethylene-propylene dimer and to the hexa-aquairon(II) transition-metal cation. Calculation of the dissociation curve for the ethylene-propylene dimer reveals that WFT-in-DFT embedding reproduces full CCSD(T) energies to within 0.1 kcal/mol at all distances, eliminating errors in the dispersion interactions due to conventional exchange-correlation (XC) functionals while simultaneously avoiding errors due to subsystem partitioning across covalent bonds. Application of WFT-in-DFT embedding to the calculation of the low-spin/high-spin splitting energy in the hexaaquairon(II) cation reveals that the majority of the dependence on the DFT XC functional can be eliminated by treating only the single transition-metal atom at the WFT level; furthermore, these calculations demonstrate the substantial effects of open-shell contributions to the embedding potential, and they suggest that restricted open-shell WFT-in-DFT embedding provides better accuracy than unrestricted open-shell WFT-in-DFT embedding due to the removal of spin contamination.

  12. Fracture Mechanical Analysis of Open Cell Ceramic Foams Under Thermal Shock Loading

    NASA Astrophysics Data System (ADS)

    Settgast, C.; Abendroth, M.; Kuna, M.

    2016-11-01

    Ceramic foams made by replica techniques containing sharp-edged cavities, which are potential crack initiators and therefore have to be analyzed using fracture mechanical methods. The ceramic foams made of novel carbon bonded alumina are used as filters in metal melt filtration applications, where the filters are exposed to a thermal shock. During the casting process the filters experience a complex thermo-mechanical loading, which is difficult to measure. Modern numerical methods allow the simulation of such complex processes. As a simplified foam structure an open Kelvin cell is used as a representative volume element. A three-dimensional finite element model containing realistic sharp-edged cavities and three-dimensional sub-models along these sharp edges are used to compute the transient temperature, stress and strain fields at the Kelvin foam. The sharp edges are evaluated using fracture mechanical methods like the J-integral technique. The results of this study describe the influence of the pore size, relative density of the ceramic foam, the heat transfer and selected material parameters on the fracture mechanical behaviour.

  13. ROS Regulation of Polar Growth in Plant Cells1[OPEN

    PubMed Central

    Mangano, Silvina; Juárez, Silvina Paola Denita

    2016-01-01

    Root hair cells and pollen tubes, like fungal hyphae, possess a typical tip or polar cell expansion with growth limited to the apical dome. Cell expansion needs to be carefully regulated to produce a correct shape and size. Polar cell growth is sustained by oscillatory feedback loops comprising three main components that together play an important role regulating this process. One of the main components are reactive oxygen species (ROS) that, together with calcium ions (Ca2+) and pH, sustain polar growth over time. Apoplastic ROS homeostasis controlled by NADPH oxidases as well as by secreted type III peroxidases has a great impact on cell wall properties during cell expansion. Polar growth needs to balance a focused secretion of new materials in an extending but still rigid cell wall in order to contain turgor pressure. In this review, we discuss the gaps in our understanding of how ROS impact on the oscillatory Ca2+ and pH signatures that, coordinately, allow root hair cells and pollen tubes to expand in a controlled manner to several hundred times their original size toward specific signals. PMID:27208283

  14. Ink jet printable silver metallization with zinc oxide for front side metallization for micro crystalline silicon solar cells

    NASA Astrophysics Data System (ADS)

    Jurk, Robert; Fritsch, Marco; Eberstein, Markus; Schilm, Jochen; Uhlig, Florian; Waltinger, Andreas; Michaelis, Alexander

    2015-12-01

    Ink jet printable water based inks are prepared by a new silver nanoparticle synthesis and the addition of nanoscaled ZnO particles. For the formation of front side contacts the inks are ink jet printed on the front side of micro crystalline silicon solar cells, and contact the cell directly during the firing step by etching through the wafers’ anti-reflection coating (ARC). In terms of Ag dissolution and precipitation the mechanism of contact formation can be compared to commercial glass containing thick film pastes. This avoids additional processing steps, like laser ablation, which are usually necessary to open the ARC prior to ink jet printing. As a consequence process costs can be reduced. In order to optimize the ARC etching and contact formation during firing, zinc oxide nanoparticles are investigated as an ink additive. By utilization of in situ contact resistivity measurements the mechanism of contacting was explored. Our results show that silver inks containing ZnO particles realize a specific contact resistance below 10 mΩṡcm2. By using a multi-pass ink jet printing and plating process a front side metallization of commercial 6  ×  6 inch2 standard micro crystalline silicone solar cells with emitter resistance of 60 Ω/◽ was achieved and showed an efficiency of 15.7%.

  15. INKJET PRINTING OF NICKEL AND SILVER METAL SOLAR CELL CONTACTS

    SciTech Connect

    Pasquarelli, R.; Curtis, C.; Van Hest, M.

    2008-01-01

    With about 125,000 terawatts of solar power striking the earth at any given moment, solar energy may be the only renewable energy resource with enough capacity to meet a major portion of our future energy needs. Thin-fi lm technologies and solution deposition processes seek to reduce manufacturing costs in order to compete with conventional coal-based electricity. Inkjet printing, as a derivative of the direct-write process, offers the potential for low-cost, material-effi cient deposition of the metals for photovoltaic contacts. Advances in contact metallizations are important because they can be employed on existing silicon technology and in future-generation devices. We report on the atmospheric, non-contact deposition of nickel (Ni) and silver (Ag) metal patterns on glass, Si, and ZnO substrates at 180–220°C from metal-organic precursor inks using a Dimatix inkjet printer. Near-bulk conductivity Ag contacts were successfully printed up to 4.5 μm thick and 130 μm wide on the silicon nitride antirefl ective coating of silicon solar cells. Thin, high-resolution Ni adhesion-layer lines were printed on glass and zinc oxide at 80 μm wide and 55 nm thick with a conductivity two orders of magnitude less than the bulk metal. Additionally, the ability to print multi-layered metallizations (Ag on Ni) on transparent conducting oxides was demonstrated and is promising for contacts in copper-indium-diselenide (CIS) solar cells. Future work will focus on further improving resolution, printing full contact devices, and investigating copper inks as a low-cost replacement for Ag contacts.

  16. Alkali corrosion resistant coatings and ceramic foams having superfine open cell structure and method of processing

    DOEpatents

    Brown, Jr., Jesse J.; Hirschfeld, Deidre A.; Li, Tingkai

    1993-12-07

    Alkali corrosion resistant coatings and ceramic foams having superfine open cell structure are created using sol-gel processes. The processes have particular application in creating calcium magnesium zirconium phosphate, CMZP, coatings and foams.

  17. Fatigue failure of an open cell and a closed cell aluminium alloy foam

    SciTech Connect

    Harte, A.M.; Fleck, N.A.; Ashby, M.F. . Engineering Dept.)

    1999-06-22

    The tension-tension and compression-compression cyclic properties are measured for an open cell Duocel foam of composition Al 6101-T6, and a closed cell Alporas foam of composition Al-5Ca-3Ti (wt%). the Duocel foam has a relatively uniform microstructure, and undergoes homogeneous straining in both monotonic and fatigue tests. In contrast, the Alporas foam is more irregular in microstructure, and exhibits crush-band formation at random locations under uniaxial compression; in compression-compression fatigue, a single crush band forms and broadens with additional fatigue cycles. Progressive shortening of the specimen in compression-compression fatigue, and progressive lengthening in tension-tension fatigue are due to a combination of low cycle fatigue failure and cyclic ratchetting. S-N fatigue curves are presented for the onset of progressive shortening in the compression tests, and material separation in the tension tests; it is envisaged that such curves will be of practical use in design.

  18. Perspectives on the metallic interconnects for solid oxide fuel cells.

    PubMed

    Zhu, Wei-Zhong; Yan, Mi

    2004-12-01

    The various stages and progress in the development of interconnect materials for solid oxide fuel cells (SOFCs) over the last two decades are reviewed. The criteria for the application of materials as interconnects are highlighted. In-terconnects based on lanthanum chromite ceramics demonstrate many inherent drawbacks and therefore are only useful for SOFCs operating around 1000 degrees C. The advance in the research of anode-supported flat SOFCs facilitates the replacement of ceramic interconnects with metallic ones due to their significantly lowered working temperature. Besides, interconnects made of metals or alloys offer many advantages as compared to their ceramic counterpart. The oxidation response and thermal expansion behaviors of various prospective metallic interconnects are examined and evaluated. The minimization of contact resistance to achieve desired and reliable stack performance during their projected lifetime still remains a highly challenging issue with metallic interconnects. Inexpensive coating materials and techniques may play a key role in pro-moting the commercialization of SOFC stack whose interconnects are constructed of some current commercially available alloys. Alternatively, development of new metallic materials that are capable of forming stable oxide scales with sluggish growth rate and sufficient electrical conductivity is called for.

  19. Metal cation uptake and reduction kinetics in microalgal cell culture

    NASA Astrophysics Data System (ADS)

    Kare, Anudeep

    This work was conducted to create a bio synthetic process for production of sustainable Nano materials, such as Noble metal nanoparticles with the use of living organisms as catalysts. Dactylococcus, Coelastrella and Chlamydomonas reinhardtii are the different species of algae used through which the Au and Ag nanoparticles are extracted. Under the appropriate bioprocess conditions phototrophic algal cell cultures can catalyze the conversion of soluble metal cations, such as trivalent gold cation (Au+3), to metallic gold nanoparticles (Au0 NP) and silver cation (Ag+) to metallic silver nanoparticles (Ag0 NP). The primary objective of this experiment is to identify the rate-limiting kinetics such as, mixing, biological, pH and so forth to see whether a scalable process can be proposed for production of these high valued materials. It is proposed in the literature that the reducing power required to drive this reaction is derived from the electron flux produced in the algae's photosynthetic apparatus. However, due to the lack of fundamental knowledge about the transport and kinetics, and therefore the bottlenecks and key process parameters, there is currently no scalable, controllable phototrophic system has been developed for the production of metallic nanoparticles.

  20. Open partial nephrectomy in renal cell cancer - Essential or obsolete?

    PubMed

    Anastasiadis, Eleni; O'Brien, Timothy; Fernando, Archana

    2016-12-01

    Since the first partial nephrectomy was first conducted 131 years ago, the procedure has evolved into the gold standard treatment for small renal masses. Over the past decade, with the introduction of minimally invasive surgery, open partial nephrectomy still retains a valuable role in the treatment of complex tumours in challenging clinical situations (e.g. hereditary renal cancer or single kidneys), and enables surgeons to push the boundaries of nephron-sparing surgery. In this article, we consider the origin of the procedure and how it has evolved over the past century, the surgical techniques involved, and the oncological and functional outcomes.

  1. Open questions: The disrupted circuitry of the cancer cell

    SciTech Connect

    Wiley, H. S.

    2014-10-24

    Every new decade of biology brings with it a change in outlook driven by new technologies and fresh perspectives. Such is the case for cancer and how we consider the disease. The advent of molecular biology led to the identification of altered signaling molecules and 'oncogenes' that were proposed to drive uncontrolled cell proliferation. The rise of cell biology and new imaging and culturing technologies led to the idea that disruptions in the extracellular environment prime cells for transformation. In the current genomics era, cancer is most commonly seen as a genetic disorder where an unstable genome gives rise to a variety of different cell variants that are selected for proliferation and survival. All of these views are partially correct, of course, and are simply different ways of saying that genetic alterations in cancer cells result in a loss of growth homeostasis. They also take the view that molecular changes 'drive' a cell to grow uncontrollably, rather than tip the balance from one normal state (quiescence) to another (proliferation). Underlying this oversimplification is a profound ignorance of what controls homeostatic cell growth in the first place and how specific mutations impact it.

  2. High reduction of interfacial charge recombination in colloidal quantum dot solar cells by metal oxide surface passivation.

    PubMed

    Chang, Jin; Kuga, Yuki; Mora-Seró, Iván; Toyoda, Taro; Ogomi, Yuhei; Hayase, Shuzi; Bisquert, Juan; Shen, Qing

    2015-03-12

    Bulk heterojunction (BHJ) solar cells based on colloidal QDs and metal oxide nanowires (NWs) possess unique and outstanding advantages in enhancing light harvesting and charge collection in comparison to planar architectures. However, the high surface area of the NW structure often brings about a large amount of recombination (especially interfacial recombination) and limits the open-circuit voltage in BHJ solar cells. This problem is solved here by passivating the surface of the metal oxide component in PbS colloidal quantum dot solar cells (CQDSCs). By coating thin TiO2 layers onto ZnO-NW surfaces, the open-circuit voltage and power conversion efficiency have been improved by over 40% in PbS CQDSCs. Characterization by transient photovoltage decay and impedance spectroscopy indicated that the interfacial recombination was significantly reduced by the surface passivation strategy. An efficiency as high as 6.13% was achieved through the passivation approach and optimization for the length of the ZnO-NW arrays (device active area: 16 mm2). All solar cells were tested in air, and exhibited excellent air storage stability (without any performance decline over more than 130 days). This work highlights the significance of metal oxide passivation in achieving high performance BHJ solar cells. The charge recombination mechanism uncovered in this work could shed light on the further improvement of PbS CQDSCs and/or other types of solar cells.

  3. Silicon solar cells with nickel/solder metallization

    NASA Technical Reports Server (NTRS)

    Petersen, R. C.; Muleo, A.

    1981-01-01

    The use of nickel plus solder is shown to be feasible for contact metallization for silicon solar cells by offering a relatively inexpensive method of making electrical contact with the cell surfaces. Nickel is plated on silicon solar cells using an electroless chemical deposition method to give contacts with good adhesion, and in some cases where adhesion is poor initially, sintering under relatively mild conditions will dramatically improve the quality of the bond without harming the p-n junction of the cell. The cells can survive terrestrial environment stresses, which is demonstrated by a 1000 hour test at 85 C and 85% relative humidity under constant forward bias of 0.45 volt.

  4. Silicon solar cells with nickel/solder metallization

    NASA Technical Reports Server (NTRS)

    Petersen, R. C.; Muleo, A.

    1981-01-01

    The use of nickel plus solder is shown to be feasible for contact metallization for silicon solar cells by offering a relatively inexpensive method of making electrical contact with the cell surfaces. Nickel is plated on silicon solar cells using an electroless chemical deposition method to give contacts with good adhesion, and in some cases where adhesion is poor initially, sintering under relatively mild conditions will dramatically improve the quality of the bond without harming the p-n junction of the cell. The cells can survive terrestrial environment stresses, which is demonstrated by a 1000 hour test at 85 C and 85% relative humidity under constant forward bias of 0.45 volt.

  5. Open questions: The disrupted circuitry of the cancer cell

    DOE PAGES

    Wiley, H. Steven

    2014-10-18

    Every new decade of biology brings with it a change in outlook driven by new technologies and fresh perspectives. Such is the case for cancer and how we consider the disease. The advent of molecular biology led to the identification of altered signaling molecules and 'oncogenes' that were proposed to drive uncontrolled cell proliferation. The rise of cell biology and new imaging and culturing technologies led to the idea that disruptions in the extracellular environment prime cells for transformation. In the current genomics era, cancer is most commonly seen as a genetic disorder where an unstable genome gives rise tomore » a variety of different cell variants that are selected for proliferation and survival. All of these views are partially correct, of course, and are simply different ways of saying that genetic alterations in cancer cells result in a loss of growth homeostasis. They also take the view that molecular changes 'drive' a cell to grow uncontrollably, rather than tip the balance from one normal state (quiescence) to another (proliferation). Underlying this oversimplification is a profound ignorance of what controls homeostatic cell growth in the first place and how specific mutations impact it. Normal, proliferation-competent cells can accurately monitor their environment and respond appropriately to perturbation, whether it is a loss of neighbors or an inflammatory stimulus. Cancer cells either proliferate or refuse to die where and when they should not, which clearly indicates that they have problems in detecting or responding to their environment. Thus, an enormous amount of effort has gone into defining the signaling pathways that can trigger a proliferative response and the biochemical mechanisms underlying these pathways. Far less work has focused on understanding the higher-order logic of these pathways and the roles played by all of the components as part of an integrated system. In other words, we do not really understand how cells process

  6. A sliding cell technique for diffusion measurements in liquid metals

    SciTech Connect

    Geng, Yongliang; Zhu, Chunao; Zhang, Bo

    2014-03-15

    The long capillary and shear cell techniques are the usual methods for diffusion measurements in liquid metals. Here we present a new “sliding cell technique” to measure interdiffusion in liquid alloys, which combines the merits of these two methods. Instead of a number of shear cells, as used in the shear cell method, only one sliding cell is designed to separate and join the liquid diffusion samples. Using the sliding cell technique, the influence of the heating process (which affects liquid diffusion measurements in the conventional long capillary method) can be eliminated. Time-dependent diffusion measurements at the same isothermal temperature were carried out in Al-Cu liquids. Compared with the previous results measured by in-situ X-ray radiography, the obtained liquid diffusion coefficient in this work is believed to be influenced by convective flow. The present work further supports the idea that to obtain accurate diffusion constants in liquid metals, the measurement conditions must be well controlled, and there should be no temperature gradients or other disturbances.

  7. A sliding cell technique for diffusion measurements in liquid metals

    NASA Astrophysics Data System (ADS)

    Geng, Yongliang; Zhu, Chunao; Zhang, Bo

    2014-03-01

    The long capillary and shear cell techniques are the usual methods for diffusion measurements in liquid metals. Here we present a new "sliding cell technique" to measure interdiffusion in liquid alloys, which combines the merits of these two methods. Instead of a number of shear cells, as used in the shear cell method, only one sliding cell is designed to separate and join the liquid diffusion samples. Using the sliding cell technique, the influence of the heating process (which affects liquid diffusion measurements in the conventional long capillary method) can be eliminated. Time-dependent diffusion measurements at the same isothermal temperature were carried out in Al-Cu liquids. Compared with the previous results measured by in-situ X-ray radiography, the obtained liquid diffusion coefficient in this work is believed to be influenced by convective flow. The present work further supports the idea that to obtain accurate diffusion constants in liquid metals, the measurement conditions must be well controlled, and there should be no temperature gradients or other disturbances.

  8. Reprogramming cancer cells in endocrine-related tumors: open issues.

    PubMed

    Tafani, M; Perrone, G A; Pucci, B; Russo, A; Bizzarri, M; Mechanick, J I; Carpi, A; Russo, M A

    2014-01-01

    Reprogramming technologies have been developed to revert somatic differentiated cells into pluripotent stem cells that can be differentiated into different lineages potentially useful in stem cell therapy. Reprogramming methods have been progressively refined to increase their efficiency, to obtain a cell population suitable for differentiation, and to eliminate viral plasmid which could be responsible for many unwanted side-effects when used in personalized medicine. All these methods are aimed to introduce into the cell genes or mRNAs encoding a set of four transcription factors (OCT- 4, SOX-2, KLF-4 and c-MYC) or a set of three lincRNAs (large intragenic non-coding RNAs) acting downstream of the reprogramming transcription factors OCT-4, SOX-2 and NANOG. Translational clinical applications in human pathologies and in developmental, repair and cancer biology have been numerous. Cancer cells can be, at least in principle, reprogrammed into a normal phenotype. This is a recently raised issue, rapidly advancing in many human tumors, especially endocrine-related cancers, such as breast, prostate and ovarian ca. The present review aims to describe basic phenomena observed in reprogramming tumor cells and solid tumors and to discuss their meaning in human hormone-related cancers. We will also discuss the fact that some of the targeted transcription factors are "normally" activated in a number of physiological processes, such as morphogenesis, hypoxia and wound healing, suggesting an in vivo role of reprogramming for development and homeostasis. Finally, we will review concerns and warnings raised for in vivo reprogramming of human tumors and for the use of induced pluripotent stem cells (iPSCs) in human therapy.

  9. Composite and Nanocomposite Metal Foams

    PubMed Central

    Duarte, Isabel; Ferreira, José M. F.

    2016-01-01

    Open-cell and closed-cell metal foams have been reinforced with different kinds of micro- and nano-sized reinforcements to enhance their mechanical properties of the metallic matrix. The idea behind this is that the reinforcement will strengthen the matrix of the cell edges and cell walls and provide high strength and stiffness. This manuscript provides an updated overview of the different manufacturing processes of composite and nanocomposite metal foams. PMID:28787880

  10. Composite and Nanocomposite Metal Foams.

    PubMed

    Duarte, Isabel; Ferreira, José M F

    2016-01-28

    Open-cell and closed-cell metal foams have been reinforced with different kinds of micro- and nano-sized reinforcements to enhance their mechanical properties of the metallic matrix. The idea behind this is that the reinforcement will strengthen the matrix of the cell edges and cell walls and provide high strength and stiffness. This manuscript provides an updated overview of the different manufacturing processes of composite and nanocomposite metal foams.

  11. CHARACTERIZATION OF EMISSIONS FROM THE SIMULATED OPEN-BURNING OF NON-METALLIC AUTOMOBILE SHREDDER RESIDUE

    EPA Science Inventory

    The report gives results of a study in which the open combustion of a nonmetallic waste product called "fluff" was simulated and the resulting emissions collected and characterized to gain insight into the types and quantities of these air pollutants. (NOTE: The reclamation proce...

  12. CHARACTERIZATION OF EMISSIONS FROM THE SIMULATED OPEN-BURNING OF NON-METALLIC AUTOMOBILE SHREDDER RESIDUE

    EPA Science Inventory

    The report gives results of a study in which the open combustion of a nonmetallic waste product called "fluff" was simulated and the resulting emissions collected and characterized to gain insight into the types and quantities of these air pollutants. (NOTE: The reclamation proce...

  13. Investigation of physicochemical characteristics and heavy metal distribution profile in groundwater system around the open dump site

    NASA Astrophysics Data System (ADS)

    Kanmani, S.; Gandhimathi, R.

    2013-06-01

    In this study, the characterization of solid waste and the effect of the leachate from an open dumping site in Ariyamangalam, Tiruchirappalli District, Tamil Nadu, on groundwater is investigated. A total of 14 groundwater samples and 20 leachate samples were collected for monitoring purpose. All the samples were analyzed for various physical and chemical parameters according to standard methods: this includes pH, electrical conductivity, total dissolved solids (TDS), total hardness, and total alkalinity, major cations such as Ca2+, Mg2+, and Fe2+, major anions such as NO3 -, Cl-, and SO4 2- and heavy metals such as Cd, Cu, Mn, Pb, and Zn. The results indicated that, very few parameters such as pH, sulfates and nitrates concentration in the groundwater samples are within the recommended maximum admissible limits approved by WHO (World Health Organization 940-949, 2002) and Bureau of Indian standards (IS 10500:1991). The TDS (range between 740 and 14,200 mg/L) in groundwater reveal the saline behavior of water and was found to be very high according to standards. The range of chlorides in all the locations under investigation is 215.15-4,098.73 mg/L. The contour plots also indicated that the groundwater was rigorously contaminated with various heavy metals. The presence of high concentration of Pb (0.59 mg/L) in groundwater samples nearby dumping site implies that groundwater samples were contaminated by leachate migration from an open dumping site.

  14. Giant-cell interstitial pneumonia and hard-metal pneumoconiosis. A clinicopathologic study of four cases and review of the literature

    SciTech Connect

    Ohori, N.P.; Sciurba, F.C.; Owens, G.R.; Hodgson, M.J.; Yousem, S.A.

    1989-07-01

    We report four cases of giant-cell interstitial pneumonia that occurred in association with exposure to hard metals. All patients presented with chronic interstitial lung disease and had open-lung biopsies that revealed marked interstitial fibrosis, cellular interstitial infiltrates, and prominent intraalveolar macrophages as well as giant cells displaying cellular cannibalism. We also review the literature to determine the sensitivity and specificity of giant-cell interstitial pneumonia for hard-metal pneumoconiosis. Although hard-metal pneumoconiosis may take the form of usual interstitial pneumonia, desquamative interstitial pneumonia, and giant-cell interstitial pneumonia, the finding of giant-cell interstitial pneumonia is almost pathognomonic of hard-metal disease and should provoke an investigation of occupational exposure. 25 references.

  15. Equivalent Thermal Conductivity of Open-Cell Ceramic Foams at High Temperatures

    NASA Astrophysics Data System (ADS)

    Li, J. E.; Wang, B.

    2014-01-01

    At high temperature, heat transfer in open-cell foams occurs by thermal radiation through the whole medium as well as by conduction through the solid matrix and air filling the pores. This paper applies the body-centered cubic cell model to predict radiative properties and the thermal conductivity of the open-cell foams. The model is validated by comparing the results with previous published works. Effects of structural characteristic parameters (cell diameter and porosity) and optical properties of the solid matrix (reflectivity and specularity parameter) on extinction coefficients and the radiative conductivity are discussed. The influence of temperature on the thermal conductivities including the effective, radiative, and the equivalent conductivity of open-cell ceramic foams are analyzed.

  16. Unexpected Anal Squamous Cells Carcinoma after Open Hemorrhoidectomy

    PubMed Central

    Luca, Navarra; Valentina, Abruzzese; Federico, Sista; Renato, Pietroletti

    2015-01-01

    We report a case of unexpected anal squamous cells carcinoma found in hemorrhoidectomy specimen. The patient had a 3-year history of prolapsing hemorrhoids. A prolapsing hemorrhoid was present at eleven o'clock in lithotomy. Milligan-Morgan was performed and gross examination of the specimen was unremarkable. Histopathologic evaluation showed noninvasive squamous cells carcinoma. The present case report evidences the opportunity of routine histopathologic analysis of hemorrhoidal specimens particularly in case of long-standing prolapse. Questions arise in the option of those techniques where no specimens are collected or tissue is excised far from deceased area. PMID:25922781

  17. Shear Modulus for Nonisotropic, Open-Celled Foams Using a General Elongated Kelvin Foam Model

    NASA Technical Reports Server (NTRS)

    Sullivan, Roy M.; Ghosn, Louis J.

    2008-01-01

    An equation for the shear modulus for nonisotropic, open-celled foams in the plane transverse to the elongation (rise) direction is derived using an elongated Kelvin foam model with the most general geometric description. The shear modulus was found to be a function of the unit cell dimensions, the solid material properties, and the cell edge cross-section properties. The shear modulus equation reduces to the relation derived by others for isotropic foams when the unit cell is equiaxed.

  18. CMOS standard cells characterization for open defects for test pattern generation

    NASA Astrophysics Data System (ADS)

    Wielgus, Andrzej; Pleskacz, Witold

    2016-12-01

    This paper presents an extended method of CMOS standard cells characterization for defect based voltage testing. It allows to estimate the probabilities of physical open defects occurrences in a cell, describes its faulty behavior caused by the defects and finds the test sequences that detect those faults. Finally, the minimal set of test sequences is selected to cover all detectable faults and the optimal complex test sequence is constructed. Experimental results for cells from industrial standard cell library are presented as well.

  19. Superhydrophobic and oleophilic open-cell foams from fibrillar blends of polypropylene and polytetrafluoroethylene.

    PubMed

    Rizvi, Ali; Chu, Raymond K M; Lee, Jung H; Park, Chul B

    2014-12-10

    Effective removal of oils from water is of global significance for environmental protection. In this study, we investigate the hydrophobicity and oleophilicity of open-cell polymer foams prepared in a continuous and scalable extrusion process. The material used to prepare the open-cell foams is a fibrillar blend of polypropylene (PP) and polytetrafluoroethylene (PTFE). Scanning electron microscopy (SEM) images of the morphology of the PP/PTFE fibrillar blend reveal that the PTFE has a fibrillar morphology in the PP matrix. SEM micrograph of the extruded foam shows the formation of an interconnected open-cell structure. Using nitrogen pycnometry, the open-cell content is estimated to be 97.7%. A typical bulk density of the open-cell foam is measured to be about 0.07 g cm(-3) corresponding to a void fraction of 92%. Thus, a large three-dimensional space is made available for oil storage. A drop of water on the cross-section of the extruded open-cell foam forms a contact angle of 160° suggesting that the open-cell foam exhibits superhydrophobicity. The open-cell foam can selectively absorb various petroleum products, such as octane, gasoline, diesel, kerosene, light crude oil, and heavy crude oil from water and the uptake capacities range from about 5 to 24 g g(-1). The uptake kinetics can be enhanced by exposing the open-cell foam to high intensity ultrasound which increases the surface porosity of the thin, impervious, foam "skin" layer. The reusability of the foam can be improved by using a matrix polymer which demonstrates superior elastic properties and prevents the foams from undergoing a large permanent deformation upon compression to "squeeze out" the oil. For example, when the PP homopolymer matrix is replaced with a PP random copolymer, the permanent deformation for 10 compressive cycles is reduced from about 30% to 10%. To the best of our knowledge, these PP-based open-cell foams outperform PP-based absorbents conventionally used for oil-spill cleanup

  20. Metal diffusion barriers for GaAs solar cells.

    PubMed

    van Leest, R H; Mulder, P; Bauhuis, G J; Cheun, H; Lee, H; Yoon, W; van der Heijden, R; Bongers, E; Vlieg, E; Schermer, J J

    2017-03-15

    In this study accelerated ageing testing (AAT), J-V characterization and TEM imaging in combination with phase diagram data from literature are used to assess the potential of Ti, Ni, Pd and Pt as diffusion barriers for Au/Cu-based metallization of III-V solar cells. Ni barriers show the largest potential as at an AAT temperature of 250 °C both cells with 10 and 100 nm thick Ni barriers show significantly better performance compared to Au/Cu cells, with the cells with 10 nm Ni barriers even showing virtually no degradation after 7.5 days at 250 °C (equivalent to 10 years at 100 °C at an Ea of 0.70 eV). Detailed investigation shows that Ni does not act as a barrier in the classical sense, i.e. preventing diffusion of Cu and Au across the barrier. Instead Ni modifies or slows down the interactions taking place during device degradation and thus effectively acts as an 'interaction' barrier. Different interactions occur at temperatures below and above 250 °C and for thin (10 nm) and thick (100 nm) barriers. The results of this study indicate that 10-100 nm thick Ni intermediate layers in the Cu/Au based metallization of III-V solar cells may be beneficial to improve the device stability upon exposure to elevated temperatures.

  1. Close the Textbook & Open "The Cell: An Image Library"

    ERIC Educational Resources Information Center

    Saunders, Cheston; Taylor, Amy

    2014-01-01

    Many students leave the biology classroom with misconceptions centered on cellular structure. This article presents an activity in which students utilize images from an online database called "The Cell: An Image Library" (http://www.cellimagelibrary. org/) to gain a greater understanding of the diversity of cellular structure and the…

  2. Close the Textbook & Open "The Cell: An Image Library"

    ERIC Educational Resources Information Center

    Saunders, Cheston; Taylor, Amy

    2014-01-01

    Many students leave the biology classroom with misconceptions centered on cellular structure. This article presents an activity in which students utilize images from an online database called "The Cell: An Image Library" (http://www.cellimagelibrary. org/) to gain a greater understanding of the diversity of cellular structure and the…

  3. Dipole-field-assisted charge extraction in metal-perovskite-metal back-contact solar cells.

    PubMed

    Lin, Xiongfeng; Jumabekov, Askhat N; Lal, Niraj N; Pascoe, Alexander R; Gómez, Daniel E; Duffy, Noel W; Chesman, Anthony S R; Sears, Kallista; Fournier, Maxime; Zhang, Yupeng; Bao, Qiaoliang; Cheng, Yi-Bing; Spiccia, Leone; Bach, Udo

    2017-09-20

    Hybrid organic-inorganic halide perovskites are low-cost solution-processable solar cell materials with photovoltaic properties that rival those of crystalline silicon. The perovskite films are typically sandwiched between thin layers of hole and electron transport materials, which efficiently extract photogenerated charges. This affords high-energy conversion efficiencies but results in significant performance and fabrication challenges. Herein we present a simple charge transport layer-free perovskite solar cell, comprising only a perovskite layer with two interdigitated gold back-contacts. Charge extraction is achieved via self-assembled monolayers and their associated dipole fields at the metal-perovskite interface. Photovoltages of ~600 mV generated by self-assembled molecular monolayer modified perovskite solar cells are equivalent to the built-in potential generated by individual dipole layers. Efficient charge extraction results in photocurrents of up to 12.1 mA cm(-2) under simulated sunlight, despite a large electrode spacing.Simplified device concepts may become important for the development of low cost photovoltaics. Lin et al. report solar cells based on interdigitated gold back-contacts and metal halide perovskites where charge extraction is assisted via a dipole field generated by self-assembled molecular monolayers.

  4. Metal-accelerated oxidation in plant cell death

    SciTech Connect

    Czuba, M. )

    1993-05-01

    Cadmium and mercury toxicity is further enhanced by external oxidizing conditions O[sub 3] or inherent plant processes. Lepidium sativum L, Lycopersicon esculentum Mill., or Phaseolus vulgaris L, were grown inpeat-lite to maturity under continuous cadmium exposure followed by one oxidant (O[sub 3]-6 hr. 30 pphm) exposure, with or without foliar calcium pretreatments. In comparison, Daucus carota, L and other species grown in a 71-V suspension, with or without 2,4-D were exposed continuously to low levels of methylmercury during exponential growth and analyzed in aggregates of distinct populations. Proteins were extracted and analyzed. Mechanisms of toxicity and eventual cell death are Ca-mediated and involve chloroplast, stomatal-water relations and changes in oxidant-anti-oxidant components in cells. Whether the metal-accelerated oxidative damage proceeds to cell death, depends on the species and its differential biotransformation system and cell association component.

  5. Lithium Metal Oxide Electrodes For Lithium Cells And Batteries

    DOEpatents

    Thackeray, Michael M.; Johnson, Christopher S.; Amine, Khalil; Kim, Jaekook

    2004-01-20

    A lithium metal oxide positive electrode for a non-aqueous lithium cell is disclosed. The cell is prepared in its initial discharged state and has a general formula xLiMO.sub.2.(1-x)Li.sub.2 M'O.sub.3 in which 0cells or batteries are disclosed with anode, cathode and electrolyte as are batteries of several cells connected in parallel or series or both.

  6. Lithium metal oxide electrodes for lithium cells and batteries

    DOEpatents

    Thackeray, Michael M.; Johnson, Christopher S.; Amine, Khalil

    2008-12-23

    A lithium metal oxide positive electrode for a non-aqueous lithium cell is disclosed. The cell is prepared in its initial discharged state and has a general formula xLiMO.sub.2.(1-x)Li.sub.2M'O.sub.3 in which 0cells or batteries are disclosed with anode, cathode and electrolyte as are batteries of several cells connected in parallel or series or both.

  7. Cell Death Control by Matrix Metalloproteinases1[OPEN

    PubMed Central

    Zimmermann, Dirk; Sieferer, Elke; Pfannstiel, Jens

    2016-01-01

    In contrast to mammalian matrix metalloproteinases (MMPs) that play important roles in the remodeling of the extracellular matrix in animals, the proteases responsible for dynamic modifications of the plant cell wall are largely unknown. A possible involvement of MMPs was addressed by cloning and functional characterization of Sl2-MMP and Sl3-MMP from tomato (Solanum lycopersicum). The two tomato MMPs were found to resemble mammalian homologs with respect to gelatinolytic activity, substrate preference for hydrophobic amino acids on both sides of the scissile bond, and catalytic properties. In transgenic tomato seedlings silenced for Sl2/3-MMP expression, necrotic lesions were observed at the base of the hypocotyl. Cell death initiated in the epidermis and proceeded to include outer cortical cell layers. In later developmental stages, necrosis spread, covering the entire stem and extending into the leaves of MMP-silenced plants. The subtilisin-like protease P69B was identified as a substrate of Sl2- and Sl3-MMP. P69B was shown to colocalize with Sl-MMPs in the apoplast of the tomato hypocotyl, it exhibited increased stability in transgenic plants silenced for Sl-MMP activity, and it was cleaved and inactivated by Sl-MMPs in vitro. The induction of cell death in Sl2/3-MMP-silenced plants depended on P69B, indicating that Sl2- and Sl3-MMP act upstream of P69B in an extracellular proteolytic cascade that contributes to the regulation of cell death in tomato. PMID:27208293

  8. Rapid enrichment of rare-earth metals by carboxymethyl cellulose-based open-cellular hydrogel adsorbent from HIPEs template.

    PubMed

    Zhu, Yongfeng; Wang, Wenbo; Zheng, Yian; Wang, Feng; Wang, Aiqin

    2016-04-20

    A series of monolithic open-cellular hydrogel adsorbents based on carboxymethylcellulose (CMC) were prepared through high internal phase emulsions (HIPEs) and used to enrich the rare-earth metals La(3+) and Ce(3+). The changes of pore structure, and the effects of pH, contact time, initial concentration on the adsorption performance were systematically studied. The results show that the as-prepared monolithic hydrogel adsorbents possess good open-cellular framework structure and have fast adsorption kinetics and high adsorption capacity for La(3+) and Ce(3+). The involved adsorption system can reach equilibrium within 30min and the maximal adsorption capacity is determined to be 384.62mg/g for La(3+) and 333.33mg/g for Ce(3+). Moreover, these porous hydrogel adsorbents show an excellent adsorptive reusability for La(3+) and Ce(3+) through five adsorption-desorption cycles. Such a pore hierarchy structure makes this monolithic open-cellular hydrogel adsorbent be an effective adsorbent for effective enrichment of La(3+) and Ce(3+) from aqueous solution.

  9. High-aspect-ratio silicon-cell metallization technical status report. Final report

    SciTech Connect

    Not Available

    1982-01-01

    Two features of the silicon concentrator solar cell are addressed which affect output at high concentration levels. The first is the development of narrow but high electroplated grid lines with improved conductivity. The object is a reduction in cell series resistance without increase in shadowing. This goal is accomplished by electroplating through a thick photo resist mask to produce lines .7 mil wide by .7 mil high. Advance pulse plating techniques are combined with pure silver plating baths to produce a deposit conductivity equal to the bulk silver conductivity (a 1.5 to 2 X improvement over conventional silver plating). The second feature is a double diffused selectively textured front surface. This development employs a deep diffusion in the silicon under the grid lines. Only the non grid line open area is selectively texture etched removing the deep junction. This open textured area is then given a second shallow diffusion for optimum cell efficiency. This selective procedure maintains the original highly polished wafer surface under the grid lines so that high resolution narrow grid lines are possible. The double diffusion protects the junction from metal diffusion while enabling the optimum shallow junction in the illuminated regions. Combining these two features has produced a large area concentrator cells (8 cm/sup 2/) with peak efficiency above 16% and exhibiting a broad peak efficiency extending from 50 to 175 suns above 15%.

  10. Ring Opening of Naphthenic Molecules Over Metal Containing Mesoporous Y Zeolite Catalyst.

    PubMed

    Lee, You-Jin; Kim, Eun Sang; Kim, Tae-Wan; Kim, Chul-Ung; Jeong, Kwang-Eun; Lee, Chang-Ha; Jeong, Soon-Yong

    2015-07-01

    Mesoporous Y zeolite (Meso-Y) with a uniform mesopore was synthesized via pseudomorphic syn- thesis. The Meso-Y supported Ni-W catalyst (NiW/Meso-Y) was introduced as a catalyst for the selective ring opening of naphthenic rings. The catalytic test for the ring opening of naphthalene as a model compound of multi-ring aromatics was performed using a batch-type reaction system with both sulfided 20 wt% NiW/Meso-Y and NiW/Y catalysts under different reaction conditions. The catalytic results reveal that the Meso-Y supported NiW catalyst experiences a naphthalene conversion similar to the NiW/Y catalyst, but the NiW/Meso-Y catalyst has higher product yields for BTEX (benzene, toluene, ethyl benzene, and xylene) and the middle distillate than those of the NiW/Y catalyst at a low reaction temperature. These results suggest that the mesoporosity of the NiW/Meso-Y catalyst is more advantageous for the ring opening reaction of multi-ring aromatics due to the easier access for the bulky molecules compared to the NiW/Y catalyst.

  11. Molecular design of the microbial cell surface toward the recovery of metal ions.

    PubMed

    Kuroda, Kouichi; Ueda, Mitsuyoshi

    2011-06-01

    The genetic engineering of microorganisms to adsorb metal ions is an attractive method to facilitate the environmental cleanup of metal pollution and to enrich the recovery of metal ions such as rare metal ions. For the recovery of metal ions by microorganisms, cell surface design is an effective strategy for the molecular breeding of bioadsorbents as an alternative to intracellular accumulation. The cell surface display of known metal-binding proteins/peptides and the molecular design of novel metal-binding proteins/peptides have been performed using a cell surface engineering approach. The adsorption of specific metal ions is the important challenge for the practical recovery of metal ions. In this paper, we discuss the recent progress in surface-engineered bioadsorbents for the recovery of metal ions. Copyright © 2011 Elsevier Ltd. All rights reserved.

  12. A closed molecular cube and an open book: two different products from assembly of the same metal salt and bridging ligand.

    PubMed

    Argent, Stephen P; Adams, Harry; Harding, Lindsay P; Ward, Michael D

    2006-01-28

    Reaction of the bis-bidentate bridging ligand L1 with Co(ClO4)2 or Zn(BF4)2 affords a mixture of complexes [M8(L1)12]X16 and [M6(L1)9]X12 having the same metal : ligand ratio: the former is a molecular cube with a metal ion at each vertex and a bridging ligand spanning each edge, whereas the latter has a metal framework like that of an 'open book' containing cross-linked double helical metal-ligand subunits.

  13. Embedded Metal Electrode for Organic-Inorganic Hybrid Nanowire Solar Cells.

    PubMed

    Um, Han-Don; Choi, Deokjae; Choi, Ahreum; Seo, Ji Hoon; Seo, Kwanyong

    2017-06-27

    We demonstrate here an embedded metal electrode for highly efficient organic-inorganic hybrid nanowire solar cells. The electrode proposed here is an effective alternative to the conventional bus and finger electrode which leads to a localized short circuit at a direct Si/metal contact and has a poor collection efficiency due to a nonoptimized electrode design. In our design, a Ag/SiO2 electrode is embedded into a Si substrate while being positioned between Si nanowire arrays underneath poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS), facilitating suppressed recombination at the Si/Ag interface and notable improvements in the fabrication reproducibility. With an optimized microgrid electrode, our 1 cm(2) hybrid solar cells exhibit a power conversion efficiency of up to 16.1% with an open-circuit voltage of 607 mV and a short circuit current density of 34.0 mA/cm(2). This power conversion efficiency is more than twice as high as that of solar cells using a conventional electrode (8.0%). The microgrid electrode significantly minimizes the optical and electrical losses. This reproducibly yields a superior quantum efficiency of 99% at the main solar spectrum wavelength of 600 nm. In particular, our solar cells exhibit a significant increase in the fill factor of 78.3% compared to that of a conventional electrode (61.4%); this is because of the drastic reduction in the metal/contact resistance of the 1 μm-thick Ag electrode. Hence, the use of our embedded microgrid electrode in the construction of an ideal carrier collection path presents an opportunity in the development of highly efficient organic-inorganic hybrid solar cells.

  14. Effects of metal salt catalysts on yeast cell growth in ethanol conversion

    Treesearch

    Chung-Yun Hse; Yin Lin

    2009-01-01

    The effects of the addition of metal salts and metal salt-catalyzed hydrolyzates on yeast cell growth in ethanol fermentation were investigated. Four yeast strains (Saccharomyces cerevisiae WT1, Saccharomyces cerevisiae MT81, Candida sp. 1779, and Klumaromyces fragilis), four metal salts (CuCl2, FeCl3, AgNO3, and I2), two metal salt-catalyzed hydrolyzates (...

  15. Metal-organic frameworks at interfaces in dye-sensitized solar cells.

    PubMed

    Li, Yafeng; Chen, Caiyun; Sun, Xun; Dou, Jie; Wei, Mingdeng

    2014-09-01

    ZIF-8, a kind of widely studied metal-organic frameworks, was used for the interfacial modification of dye-sensitized solar cells by a facile post-treatment strategy for the first time, which solved the problem of severely decreased short-circuit photocurrent in previous report. After the surface treatment, the performance of cells was obviously improved. The conditions for the deposition of ZIF-8 were optimized. The best photovoltaic property was obtained when the growth time of ZIF-8 was 7 min and the TiO2 photoanode was post-treated for 2 times. Besides the energy barrier effect of ZIF-8 that improved the open-circuit photovoltage and electron lifetime, the dyes adsorbed tightly on TiO2 surface was found to be a key point for the efficient electron injection and improved performance.

  16. Thermal Stress in HFEF Hot Cell Windows Due to an In-Cell Metal Fire

    DOE PAGES

    Solbrig, Charles W.; Warmann, Stephen A.

    2016-01-01

    This work investigates an accident during the pyrochemical extraction of Uranium and Plutonium from PWR spent fuel in an argon atmosphere hot cell. In the accident, the heavy metals (U and Pu) being extracted are accidentally exposed to air from a leaky instrument penetration which goes through the cell walls. The extracted pin size pieces of U and Pu metal readily burn when exposed to air. Technicians perform the electrochemical extraction using manipulators through a 4 foot thick hot cell concrete wall which protects them from the radioactivity of the spent fuel. Four foot thick windows placed in the wallmore » allow the technicians to visually control the manipulators. These windows would be exposed to the heat of the metal fire. As a result, this analysis determines if the thermal stress caused by the fire would crack the windows and if the heat would degrade the window seals allowing radioactivity to escape from the cell.« less

  17. Thermal Stress in HFEF Hot Cell Windows Due to an In-Cell Metal Fire

    SciTech Connect

    Solbrig, Charles W.; Warmann, Stephen A.

    2016-01-01

    This work investigates an accident during the pyrochemical extraction of Uranium and Plutonium from PWR spent fuel in an argon atmosphere hot cell. In the accident, the heavy metals (U and Pu) being extracted are accidentally exposed to air from a leaky instrument penetration which goes through the cell walls. The extracted pin size pieces of U and Pu metal readily burn when exposed to air. Technicians perform the electrochemical extraction using manipulators through a 4 foot thick hot cell concrete wall which protects them from the radioactivity of the spent fuel. Four foot thick windows placed in the wall allow the technicians to visually control the manipulators. These windows would be exposed to the heat of the metal fire. As a result, this analysis determines if the thermal stress caused by the fire would crack the windows and if the heat would degrade the window seals allowing radioactivity to escape from the cell.

  18. 77 FR 18243 - Hydrogen and Fuel Cell Technical Advisory Committee (HTAC); Notice of Open Meeting

    Federal Register 2010, 2011, 2012, 2013, 2014

    2012-03-27

    ... Hydrogen and Fuel Cell Technical Advisory Committee (HTAC); Notice of Open Meeting AGENCY: Office of Energy... announces a meeting of the Hydrogen and Fuel Cell Technical Advisory Committee (HTAC). The Federal Advisory...., Washington, DC 20585. SUPPLEMENTARY INFORMATION: Purpose of the Committee: The Hydrogen and Fuel...

  19. Studies of silicon p-n junction solar cells. [open circuit photovoltage

    NASA Technical Reports Server (NTRS)

    Lindholm, F. A.

    1976-01-01

    Single crystal silicon p-n junction solar cells made with low resistivity substrates show poorer solar energy conversion efficiency than traditional theory predicts. The physical mechanisms responsible for this discrepancy are identified and characterized. The open circuit voltage in shallow junction cells of about 0.1 ohm/cm substrate resistivity is investigated under AMO (one sun) conditions.

  20. Results of the safety run-in part of the METAL (METformin in Advanced Lung cancer) study: a multicentre, open-label phase I-II study of metformin with erlotinib in second-line therapy of patients with stage IV non-small-cell lung cancer.

    PubMed

    Morgillo, Floriana; Fasano, Morena; Della Corte, Carminia Maria; Sasso, Ferdinando Carlo; Papaccio, Federica; Viscardi, Giuseppe; Esposito, Giovanna; Di Liello, Raimondo; Normanno, Nicola; Capuano, Annalisa; Berrino, Liberato; Vicidomini, Giovanni; Fiorelli, Alfonso; Santini, Mario; Ciardiello, Fortunato

    2017-01-01

    Our previous works demonstrated the ability of metformin to revert resistance to gefitinib, a selective epidermal growth factor receptor (EGFR) tyrosine kinase inhibitor, in non-small-cell lung cancer (NSCLC) EGFR/LKB1 wild-type (WT) cell lines. However, the optimal dose of metformin to be used in non-diabetic patients still remains to be defined. The phase I-II trial METformin in Advanced Lung cancer (METAL) was designed to identify the maximum tolerated dose and to evaluate safety and activity of metformin combined with erlotinib in second-line treatment of patients with stage IV NSCLC, whose tumours harbour the WT EGFR gene. We report results from the safety run-in part designed to detect acute toxicities, to study pharmacokinetics and to identify the recommended phase II dose (RPD) to be used for the following phase of the study. In the run-in phase, metformin treatment was administered according to a dose escalation scheme and, subsequently, combined with erlotinib. Twelve patients were enrolled. Common adverse events were diarrhoea, decreased appetite, abdominal pain, vomiting and skin toxicity, mostly reversible with symptomatic medical treatment. Dose-limiting toxicities were vomiting and diarrhoea registered in the initial cohort receiving metformin 2000 mg plus erlotinib at 150 mg die, which was declared the maximum administered dose. Only one of nine patients treated at the next lower dose of 1500 mg of metformin plus erlotinib at 150 mg experienced G3 gastrointestinal toxicity. Metformin plasma-concentration profile confirmed the trend already observed in non-diabetic population. Glycemic profiles showed stability of the blood glucose level within the physiological range for non-diabetic subjects. At a follow-up of 30 weeks, six (50%) patients experienced a disease control (5 SD and 1 partial response). The RP2D of metformin dose was defined at 1500 mg/day to be combined with erlotinib 150 mg. EudraCT number: 2014-000349-59.

  1. A Robust Metal-Organic Framework Combining Open Metal Sites and Polar Groups for Methane Purification and CO2 /Fluorocarbon Capture.

    PubMed

    Chen, Cheng-Xia; Zheng, Shao-Ping; Wei, Zhang-Wen; Cao, Chen-Chen; Wang, Hai-Ping; Wang, Dawei; Jiang, Ji-Jun; Fenske, Dieter; Su, Cheng-Yong

    2017-02-08

    A 3D porous perchlorinated metal-organic framework (MOF), LIFM-26, featuring dual functionality, that is, functional polar groups and open metal sites, has been synthesized using perchlorinated linear dicarboxylate to link trigonal prismatic Fe3 (μ3 -O) units. LIFM-26 exhibits good thermal and chemical stability, and possesses high porosity with a BET surface area of 1513 m(2)  g(-1) , compared with isoreticular MOF-235 and Fe3 O(F4 BDC)3 (H2 O)3 (F4 BDC=2,3,5,6-tetrafluorobenzene-1,4-dicarboxylate). Most strikingly, LIFM-26 features good gas sorption/separation performance at 298 K and 1 atm with IAST selectivity values reaching up to 36, 93, 23, 11, 46, and 202 for CO2 /CH4 , CO2 /N2 , C2 H4 /CH4 , C2 H6 /CH4 , C3 H8 /CH4 , and R22/N2 (R22=CHClF2 ), respectively, showing potential for use in biogas/natural gas purification and CO2 /R22 capture.

  2. Collaborative Triple Framework Interpenetration and Immobilization of Open Metal Sites within a Microporous Mixed Metal-Organic Framework for Highly Selective Gas Adsorption

    SciTech Connect

    Zhang, Zhangjing; Xiang, Sheng-Chang; Hong, Kunlun; Das, Madhab; Arman, Hadi; Garcia, Maya; Mondal, Jalal; Chen, Banglin

    2012-01-01

    A three-dimensional triply interpenetrated mixed metal-organic framework, Zn{sub 2}(BBA){sub 2}(CuPyen) {center_dot} G{sub x} (M'MOF-20; BBA = biphenyl-4,4'-dicarboxylate; G = guest solvent molecules), of primitive cubic net was obtained through the solvothermal reaction of Zn(NO{sub 3}){sub 2}, biphenyl-4,4'-dicarboxylic acid, and the salen precursor Cu(PyenH{sub 2})(NO{sub 3}){sub 2} by a metallo-ligand approach. The triple framework interpenetration has stabilized the framework in which the activated M'MOF-20a displays type-I N{sub 2} gas sorption behavior with a Langmuir surface area of 62 m{sup 2} g{sup -1}. The narrow pores of about 3.9 {angstrom} and the open metal sites on the pore surfaces within M'MOF-20a collaboratively induce its highly selective C{sub 2}H{sub 2}/CH{sub 4} and CO{sub 2}/CH{sub 4} gas separation at ambient temperature.

  3. Insights into an intriguing gas sorption mechanism in a polar metal-organic framework with open-metal sites and narrow channels.

    PubMed

    Forrest, Katherine A; Pham, Tony; McLaughlin, Keith; Hogan, Adam; Space, Brian

    2014-07-14

    Simulations of H2 and CO2 sorption were performed in the metal-organic framework (MOF), [Cu(Me-4py-trz-ia)]. This MOF was recently shown experimentally to exhibit high uptake for H2 and CO2 sorption and this was reproduced and elucidated through the simulations performed herein. Consistent with experiment, the theoretical isosteric heat of adsorption, Q(st), values were nearly constant across all loadings for both sorbates. The simulations revealed that sorption directly onto the open-metal sites was not observed in this MOF, ostensibly a consequence of the low partial positive charges of the Cu(2+) ions as determined through electronic structure calculations. Sorption was primarily observed between adjacent carboxylate oxygen atoms (site 1) and between nearby methyl groups (site 2) of the organic linkers. In addition, saturation of the most energetically favorable sites (site 1) is possible only after filling a nearby site (site 2) first due to the MOF topology. This suggests that the lack of dependence on loading for the Q(st) is due to the concurrent filling of sites 1 and 2, leading to an observed average Q(st) value.

  4. VizieR Online Data Catalog: On the metallicity of open clusters. III. (Netopil+, 2016)

    NASA Astrophysics Data System (ADS)

    Netopil, M.; Paunzen, E.; Heiter, U.; Soubiran, C.

    2016-03-01

    In Paper II (Heiter et al., Paper II 2014A&A...561A..93H) we have evaluated available spectroscopic iron abundance determinations of open cluster stars and presented mean values for 78 open clusters. The results are based on high-resolution data (R>=25000) with high signal-to-noise ratios (S/N>=50). Furthermore, quality criteria were introduced by adopting only [Fe/H] measurements of stars with Teff=4400-6500K and logg>=2.0dex. We have to note that the mean iron abundance for Berkeley 29, listed in Paper II, also incorporates some measurements based upon lower S/N data. In the present paper we therefore list the correct values for the higher and lower quality data. Since publication of Paper II, some new studies were made (Boesgaard et al., 2013ApJ...775...58B; Bocek Topcu et al., 2015, Cat. J/MNRAS/446/3562; Carraro et al., 2014A&A...568A..86C; Donati et al., 2015, Cat. J/MNRAS/446/1411; Magrini et al.. 2014A&A...563A..44M, 2015A&A...580A..85M; Molenda-Zakowicz et al., 2014MNRAS.445.2446M; Monaco et al., 2014A&A...564L...6M; Reddy et al., 2015MNRAS.450.4301R), which we examined the same way as described in Paper II. This adds ten open clusters to our list (Berkeley 81, NGC 1342, NGC 1662, NGC 1912, NGC 2354, NGC 4337, NGC 4815, NGC 6811, Trumpler 5, and Trumpler 20) and supplementary data for NGC 752, NGC 2447, NGC 2632, and NGC 6705. (1 data file).

  5. From stimuli-responsive polymorphic organic dye crystals to photoluminescent cationic open-framework metal phosphate.

    PubMed

    Chang, Yu-Chuan; Wang, Sue-Lein

    2012-06-20

    Four photoluminescent dye crystals, TPB-n (n = 1-3) and TPCH, have been synthesized in isolation from carbon-carbon coupling of 4,4'-trimethylene-dipyridine (tmdp) in the absence of organic solvent and catalyst via in situ one-pot metal/ligand oxidative-dehydrogenation reactions. Large crystals have been obtained and readily separated from reaction products without the need for purification. Their structures were characterized: TPB and TPCH represent two dissimilar oxidized forms of tmdp dimers; TPCH was less oxidized but accompanied with partial hydrolysis with molecular formula further confirmed by FAB-MASS analysis. They exhibit distinct photoluminescence (PL) with quantum efficiency measured up to 42%. TPB-2 and TPB-3 are two polymorphic dihydrates, stimuli-responsive toward photoluminescence color changes; both can transform to TPB-1 upon gentle heating. Importantly, the three TPB-n crystals establish the first tetrapyridyl-type ligands adapted by metal phosphates to create a cationic luminescent framework, NTHU-12. This study serves as an inspiring route beyond conventional C-C bond formation reactions and has generated four tmdp dimers in isolation. The facile syntheses have resulted in ample production of a rare type of tetrapyridyl ligands, leading to the discovery of the first positively charged hybrid topology in nanoporous solids. The features of the four luminescent tmdp dimers and NTHU-12 embodied in synthesis, structure, and optical property are reported.

  6. Casting Protocols for the Production of Open Cell Aluminum Foams by the Replication Technique and the Effect on Porosity

    PubMed Central

    Elizondo Luna, Erardo M.; Barari, Farzad; Woolley, Robert; Goodall, Russell

    2014-01-01

    Metal foams are interesting materials from both a fundamental understanding and practical applications point of view. Uses have been proposed, and in many cases validated experimentally, for light weight or impact energy absorbing structures, as high surface area heat exchangers or electrodes, as implants to the body, and many more. Although great progress has been made in understanding their structure-properties relationships, the large number of different processing techniques, each producing material with different characteristics and structure, means that understanding of the individual effects of all aspects of structure is not complete. The replication process, where molten metal is infiltrated between grains of a removable preform material, allows a markedly high degree of control and has been used to good effect to elucidate some of these relationships. Nevertheless, the process has many steps that are dependent on individual “know-how”, and this paper aims to provide a detailed description of all stages of one embodiment of this processing method, using materials and equipment that would be relatively easy to set up in a research environment. The goal of this protocol and its variants is to produce metal foams in an effective and simple way, giving the possibility to tailor the outcome of the samples by modifying certain steps within the process. By following this, open cell aluminum foams with pore sizes of 1–2.36 mm diameter and 61% to 77% porosity can be obtained. PMID:25548938

  7. Casting protocols for the production of open cell aluminum foams by the replication technique and the effect on porosity.

    PubMed

    Elizondo Luna, Erardo M; Barari, Farzad; Woolley, Robert; Goodall, Russell

    2014-12-11

    Metal foams are interesting materials from both a fundamental understanding and practical applications point of view. Uses have been proposed, and in many cases validated experimentally, for light weight or impact energy absorbing structures, as high surface area heat exchangers or electrodes, as implants to the body, and many more. Although great progress has been made in understanding their structure-properties relationships, the large number of different processing techniques, each producing material with different characteristics and structure, means that understanding of the individual effects of all aspects of structure is not complete. The replication process, where molten metal is infiltrated between grains of a removable preform material, allows a markedly high degree of control and has been used to good effect to elucidate some of these relationships. Nevertheless, the process has many steps that are dependent on individual "know-how", and this paper aims to provide a detailed description of all stages of one embodiment of this processing method, using materials and equipment that would be relatively easy to set up in a research environment. The goal of this protocol and its variants is to produce metal foams in an effective and simple way, giving the possibility to tailor the outcome of the samples by modifying certain steps within the process. By following this, open cell aluminum foams with pore sizes of 1-2.36 mm diameter and 61% to 77% porosity can be obtained.

  8. A tomato stem cell extract, containing antioxidant compounds and metal chelating factors, protects skin cells from heavy metal-induced damages.

    PubMed

    Tito, Annalisa; Carola, Antonietta; Bimonte, Marida; Barbulova, Ani; Arciello, Stefania; de Laurentiis, Francesco; Monoli, Irene; Hill, Jacqueline; Gibertoni, Simone; Colucci, Gabriella; Apone, Fabio

    2011-12-01

    Heavy metals can cause several genotoxic effects on cells, including oxidative stress, DNA sequence breakage and protein modification. Among the body organs, skin is certainly the most exposed to heavy metal stress and thus the most damaged by the toxic effects that these chemicals cause. Moreover, heavy metals, in particular nickel, can induce the over-expression of collagenases (enzymes responsible for collagen degradation), leading to weakening of the skin extracellular matrix. Plants have evolved sophisticated mechanisms to protect their cells from heavy metal toxicity, including the synthesis of metal chelating proteins and peptides, such as metallothioneins and phytochelatins (PC), which capture the metals and prevent the damages on the cellular structures. To protect human skin cells from heavy metal toxicity, we developed a new cosmetic active ingredient from Lycopersicon esculentum (tomato) cultured stem cells. This product, besides its high content of antioxidant compounds, contained PC, effective in the protection of skin cells towards heavy metal toxicity. We have demonstrated that this new product preserves nuclear DNA integrity from heavy metal damages, by inducing genes responsible for DNA repair and protection, and neutralizes the effect of heavy metals on collagen degradation, by inhibiting collagenase expression and inducing the synthesis of new collagen. © 2011 Arterra Bioscience srl. ICS © 2011 Society of Cosmetic Scientists and the Société Française de Cosmétologie.

  9. The impact of atmospheric aerosols on trace metal chemistry in open ocean surface seawater: 2. Copper

    NASA Astrophysics Data System (ADS)

    Maring, H. B.; Duce, R. A.

    1989-01-01

    Atmospheric deposition contributes copper to the surface ocean. The biogeochemical importance and fate of this copper is poorly understood for open ocean regions. Atmospheric aerosols collected at Enewetak Atoll, in the tropical North Pacific, were exposed to seawater and artificial rainwater in laboratory experiments. Aerosol copper during the high-dust season at Enewetak Atoll is made up of aluminosilicate, oceanic, and possibly soil organic matter components. During the low-dust season, aerosol copper appears to be essentially all of oceanic origin. Virtually all nonaluminosilicate copper in marine aerosols collected at Enewetak is soluble in seawater. Dissolved organic matter and possibly cations in seawater increase the dissolution of aerosol copper. The net atmospheric flux of soluble copper to the tropical North Pacific near Enewetak is approximately 0.13 nmol cm-2 yr-1 out of a total net atmospheric copper flux of 0.14 nmol cm-2 yr-1. Atmospheric deposition supplies roughly the same quantity of soluble copper to tropical open North Pacific surface waters as does upwelling to eastern North Pacific surface waters. Atmospheric copper deposition, which appears to be primarily of natural origin, may be the most important input of copper to the surface waters of the central gyre of the North Pacific.

  10. Development of nickel-metal hydride cell: An update

    NASA Technical Reports Server (NTRS)

    Kuwajima, S.; Kusawake, Hiroaki; Nakatani, Kensuke; Yano, Y.

    1994-01-01

    This paper presents in viewgraph format an overview of NASDA's evaluation of commercial nickel metal-hydride (Ni-MH) cells and the development and testing of Ni-MH cells for use in space. The commercial cells are concluded to be feasible and suitable for use in LEO; for GEO, the durability for overcharge is needed because long-term charge retention is required. For the aerospace Ni-MH cell design, two activation procedures are applied to evaluate the effect of the difference in the amount of overcharge protection and precharge. Specific energy of the Ni-MH cell is nearly accomplished at 50 Wh/kg. Initial characteristics indicate the effect derived from precharge. Thirty-five amp-hour class Ni-MH cells have good performance for LEO cycle of 25 and 40 percent DOD up to 3000 cycles as similar to commercial cells. The effect of the difference in the amount of overcharge protection will appear in life test.

  11. Metal nanoparticles amplify photodynamic effect on skin cells in vitro

    NASA Astrophysics Data System (ADS)

    Bauer, Brigitte; Chen, Si; Käll, Mikael; Gunnarsson, Linda; Ericson, Marica B.

    2011-03-01

    We report on an investigation aimed to increase the efficiency of photodynamic therapy (PDT) through the influence of localized surface plasmon resonances (LSPR's) in metal nanoparticles. PDT is based on photosensitizers that generate singlet oxygen at the tumour site upon exposure to visible light. Although PDT is a well-established treatment for skin cancer, a major drawback is the low quantum yield for singlet-oxygen production. This motivates the development of novel methods that enhance singlet oxygen generation during treatment. In this context, we study the photodynamic effect on cultured human skin cells in the presence or absence of gold nanoparticles with well established LSPR and field-enhancement properties. The cultured skin cells were exposed to protoporphyrin IX and gold nanoparticles and subsequently illuminated with red light. We investigated the differences in cell viability by tuning different parameters, such as incubation time and light dose. In order to find optimal parameters for specific targeting of tumour cells, we compared normal human epidermal keratinocytes with a human squamous skin cancer cell line. The study indicates significantly enhanced cell death in the presence of nanoparticles and important differences in treatment efficiency between normal and tumour cells. These results are thus promising and clearly motivate further development of nanoparticle enhanced clinical PDT treatment.

  12. Open-source computational model of a solid oxide fuel cell

    NASA Astrophysics Data System (ADS)

    Beale, Steven B.; Choi, Hae-Won; Pharoah, Jon G.; Roth, Helmut K.; Jasak, Hrvoje; Jeon, Dong Hyup

    2016-03-01

    The solid oxide fuel cell is an electro-chemical device which converts chemical energy into electricity and heat. To compete in today's market, design improvements, in terms of performance and life cycle, are required. Numerical prototypes can accelerate design and development progress. In this programme of research, a three-dimensional solid oxide fuel cell prototype, openFuelCell, based on open-source computational fluid dynamics software was developed and applied to a single cell. Transport phenomena, combined with the solution to the local Nernst equation for the open-circuit potential, as well as the Kirchhoff-Ohm relationship for the local current density, allow local electro-chemistry, fluid flow, multi-component species transport, and multi-region thermal analysis to be considered. The underlying physicochemical hydrodynamics, including porous-electrode and electro-chemical effects are described in detail. The openFuelCell program is developed in an object-oriented open-source C++ library. The code is available at http://openfuelcell.sourceforge.net/. The paper also describes domain decomposition techniques considered in the context of highly efficient parallel programming.

  13. Relationship between the blue response and open-circuit voltage of high performance silicon solar cells

    NASA Technical Reports Server (NTRS)

    Green, M. A.; Blakers, A. W.

    1983-01-01

    The relationship between the response at blue wavelengths and the open-circuit voltage of high performance silicon solar cells with a virtually 'transparent' emitter is analyzed. It is shown that a one-dimensional cell model cannot simultaneously model the optical collection properties and operating characteristics of such cells. The analysis highlights the importance of surface conditions and shows that previous conclusions regarding bounds on Auger coefficients imposed by correlating these parameters must be treated with caution.

  14. Final Scientific Report : Development of Transition Metal/ Chalcogen Based Cathode Catalysts for PEM Fuel Cells

    SciTech Connect

    Campbell, Stephen, A.

    2008-02-29

    The aim of this project was to investigate the potential for using base metal sulfides and selenides as low cost replacements for precious metal catalysts, such as platinum, currently being used in PEM fuel cells. The approach was to deposit thin films of the materials to be evaluated onto inert electrodes and evaluate their activity for the cathode reaction (oxygen reduction) as well as ex-situ structural and compositional characterization. The most active materials identified are CoS2 and the 50:50 solid solution (Co,Ni)S2. However, the OCP of these materials is still considered too low, at 0.83V and 0.89V vs. RHE respectively, for testing in fuel cells. The methods employed here were necessary to compare with the activity of platinum as, when nano-dispersed on carbon supports, the active surface area of these materials is difficult to measure, making comparisons inaccurate. This research adds to the knowledge of potential candidates for platinum replacement in order to reduce the cost of PEM fuel cell technology and promote commercialization. Although the fabrication methods employed here are strictly experimental, methods were also developed to produce nano-dispersed catalysts with similar compositions, structure and activity. Cycling of these catalysts to highly oxidizing potentials resulted in an increase of the open circuit voltage to approach that of platinum, however, it proved difficult to determine why using these dispersed materials. The potential for non-precious, non-metallic, low cost, compound catalysts for PEM fuel cells has been investigated and demonstrated.

  15. Spatial, Hysteretic, and Adaptive Host-Guest Chemistry in a Metal-Organic Framework with Open Watson-Crick Sites.

    PubMed

    Cai, Hong; Li, Mian; Lin, Xiao-Rong; Chen, Wei; Chen, Guang-Hui; Huang, Xiao-Chun; Li, Dan

    2015-09-01

    Biological and artificial molecules and assemblies capable of supramolecular recognition, especially those with nucleobase pairing, usually rely on autonomous or collective binding to function. Advanced site-specific recognition takes advantage of cooperative spatial effects, as in local folding in protein-DNA binding. Herein, we report a new nucleobase-tagged metal-organic framework (MOF), namely ZnBTCA (BTC=benzene-1,3,5-tricarboxyl, A=adenine), in which the exposed Watson-Crick faces of adenine residues are immobilized periodically on the interior crystalline surface. Systematic control experiments demonstrated the cooperation of the open Watson-Crick sites and spatial effects within the nanopores, and thermodynamic and kinetic studies revealed a hysteretic host-guest interaction attributed to mild chemisorption. We further exploited this behavior for adenine-thymine binding within the constrained pores, and a globally adaptive response of the MOF host was observed.

  16. Extreme carbon dioxide sorption hysteresis in open-channel rigid metal-organic frameworks.

    PubMed

    Bezuidenhout, Charl X; Smith, Vincent J; Bhatt, Prashant M; Esterhuysen, Catharine; Barbour, Leonard J

    2015-02-09

    A systematic study is presented of three closely related microporous metal-organic frameworks the pore dimensions of which vary according to the choice of 4,4'-bipyridyl linker. The tunable linker allows exploration of the effect of increasing pore dimensions on the sorption behavior of the frameworks. The MOFs described capture CO2 under supercritical conditions and continue to sequester the gas under ambient conditions. Gas sorption isotherms for CO2 are compared with thermogravimetric data, and the CO2 molecules in the channels of the frameworks could be modeled using single-crystal X-ray diffraction analysis. Crystallographic data were used to construct a theoretical model based on DFT methods to calculate framework electrostatic potential maps with a view to understanding the nature of the sorbate-sorbent interactions.

  17. Metallized polymeric foam material

    NASA Technical Reports Server (NTRS)

    Birnbaum, B. A.; Bilow, N.

    1974-01-01

    Open-celled polyurethane foams can be coated uniformly with thin film of metal by vapor deposition of aluminum or by sensitization of foam followed by electroless deposition of nickel or copper. Foam can be further processed to increase thickness of metal overcoat to impart rigidity or to provide inert surface with only modest increase in weight.

  18. WIYN Open Cluster Study. LXXII. A uvbyCaHβ CCD Analysis of the Metal-deficient Open Cluster NGC 2506

    NASA Astrophysics Data System (ADS)

    Anthony-Twarog, Barbara J.; Deliyannis, Constantine P.; Twarog, Bruce A.

    2016-12-01

    Precision uvbyCaHβ photometry of the metal-deficient, old open cluster NGC 2506 is presented. The survey covers an area of 20\\prime × 20\\prime and extends to V˜ 18 for b - y and Hβ and to V˜ 17.0 for c 1 and hk. For V brighter than 16.0, photometric scatter among the indices leads to the recovery of six known variables within the cluster core and five new variables in the outer 5\\prime of the survey field. Proper motions, radial velocities, and precise multicolor indices are used to isolate a highly probable sample of cluster members from the very rich color-magnitude diagram. From 257 highly probable members at the cluster turnoff, we derive a reddening estimate of E(b-y)=0.042+/- 0.001 (E(B-V)=0.058+/- 0.001), where the errors refer to the internal standard errors of the mean. [Fe/H] is derived from the A/F dwarf members using both m 1 and hk, leading to [Fe/H] = -0.296 ± 0.011 (sem) and -0.317 ± 0.004 (sem), respectively. The weighted average, heavily dominated by hk, is [Fe/H] = -0.316 ± 0.033. Based on red giant members, we place an upper limit of ±0.010 on the variation in the reddening across the face of the cluster. We also identify two dozen potential red giant cluster members outside the cluster core. Victoria-Regina isochrones on the Strömgren system produce an excellent match to the cluster for an apparent modulus of (m-M)=12.75+/- 0.1 and an age of 1.85 ± 0.05 Gyr.

  19. The impact of atmospheric aerosols on trace metal chemistry in open ocean surface seawater, 1. Aluminum

    NASA Astrophysics Data System (ADS)

    Maring, H. B.; Duce, R. A.

    1987-08-01

    Significant quantities of aerosol aluminum are transported from continental regions through the atmosphere to the oceans. Enrichments in the concentration of dissolved aluminum in open ocean surface seawater suggest that dissolution of aerosol aluminum is an important source of dissolved aluminum to these waters. Atmospheric aerosols collected at Enewetak Atoll were exposed to seawater and artificial rain water to determine directly the importance of atmospheric deposition as a source of marine dissolved aluminum. The results of these experiments indicate that ˜ 8-10% of the aluminum in atmospheric aerosols of crustal origin over the North Pacific is soluble in seawater. Approximately 5-6% dissolves very rapidly ( < 0.6 hr). An additional 3-4% dissolves within 60 hr. This bimodal dissolution of aerosol aluminum of crustal origin suggests that this aluminum is present in two forms. The rapidly dissolving fraction is likely aluminum already weathered from primary minerals, while the more slowly dissolving fraction is probably aluminum from the aluminosilicate matrix. Nearly the same amount of aerosol aluminum dissolved in artificial rain water ( pH= 5.5) in 6 hr as dissolved in seawater ( pH= 8) in 60 hr. The lower pH appears to not only increase the dissolution rate but may also increase the quantity of aerosol aluminum that dissolves. Dissolved organic matter in seawater appears to have relatively little effect on aerosol aluminum dissolution. Considering measured total aerosol aluminum fluxes, aluminum dissolution of 5-10% would constitute the major source for dissolved aluminum in surface waters of the open North Pacific. The calculated residence time of dissolved aluminum in the upper 100 m of the tropical North Pacific ranges from 2 to 6 years.

  20. Development of Low-Cost, Clad Metal Bipolar Plates for PEM Fuel Cells

    SciTech Connect

    Weil, K Scott; Yang, Zhenguo; Xia, Guanguang; Kim, Jin Yong; Hardy, Michael; Chang, Steve

    2006-05-18

    The bipolar plate is the most bulky component in the PEMFC stack (in both weight and volume) and one of the most expensive to manufacture. It serves not only as the electrical junction between serially connected cells, but also performs several other key functions in the device: • Distribute the fuel and oxidant uniformly over the active areas of the cells. • Facilitate water management of the membrane to keep it humidified, yet mitigate flooding. • Act as an impermeable barrier between the fuel and oxidant streams (particularly H2) to maintain the hydrogen gradient across the membrane necessary for high power output. • Provide some measure of structural support for the stack. • Remove heat from the active areas of the cells. The use of metal-based bipolar plates in PEMFC stacks potentially offers a number advantages particularly for transportation applications including: low-cost, mass-production via stamping or embossing of sheet product; fabrication in very thin form (< 200μm) to reduce weight and volume in the overall stack; impermeability to fuel, oxidant and water vapor; and in general, excellent thermal conduction properties and good mechanical robustness, even as a thin stamped foil. The primary challenge with metal interconnects is surface corrosion, and the current drive to increase the operating temperature of the stack will only exacerbate this problem. Corrosion of the bipolar plate leads to a release of metal ions that can contaminate the electrolyte membrane and poison the electrode catalysts. In addition, the formation of a passivating oxide or oxyhydroxide layer on the surface of the metal will increase the contact resistance between the bipolar plate and the adjacent graphite electrode backing layer by many orders of magnitude. Both conditions can significantly degrade stack performance. A number of researchers have investigated various schemes for protecting metallic bipolar plates, most of which rely on a thin, inert yet electrically

  1. Determination of phase equilibria in confined systems by open pore cell Monte Carlo method.

    PubMed

    Miyahara, Minoru T; Tanaka, Hideki

    2013-02-28

    We present a modification of the molecular dynamics simulation method with a unit pore cell with imaginary gas phase [M. Miyahara, T. Yoshioka, and M. Okazaki, J. Chem. Phys. 106, 8124 (1997)] designed for determination of phase equilibria in nanopores. This new method is based on a Monte Carlo technique and it combines the pore cell, opened to the imaginary gas phase (open pore cell), with a gas cell to measure the equilibrium chemical potential of the confined system. The most striking feature of our new method is that the confined system is steadily led to a thermodynamically stable state by forming concave menisci in the open pore cell. This feature of the open pore cell makes it possible to obtain the equilibrium chemical potential with only a single simulation run, unlike existing simulation methods, which need a number of additional runs. We apply the method to evaluate the equilibrium chemical potentials of confined nitrogen in carbon slit pores and silica cylindrical pores at 77 K, and show that the results are in good agreement with those obtained by two conventional thermodynamic integration methods. Moreover, we also show that the proposed method can be particularly useful for determining vapor-liquid and vapor-solid coexistence curves and the triple point of the confined system.

  2. Optimizing Open Iron Sites in Metal-Organic Frameworks for Ethane Oxidation: A First-Principles Study.

    PubMed

    Liao, Peilin; Getman, Rachel B; Snurr, Randall Q

    2017-04-10

    Activation of the C-H bonds in ethane to form ethanol is a highly desirable, yet challenging, reaction. Metal-organic frameworks (MOFs) with open Fe sites are promising candidates for catalyzing this reaction. One advantage of MOFs is their modular construction from inorganic nodes and organic linkers, allowing for flexible design and detailed control of properties. In this work, we studied a series of single-metal atom Fe model systems with ligands that are commonly used as MOF linkers and tried to understand how one can design an optimal Fe catalyst. We found linear relationships between the binding enthalpy of oxygen to the Fe sites and common descriptors for catalytic reactions, such as the Fe 3d energy levels in different reaction intermediates. We further analyzed the three highest-barrier steps in the ethane oxidation cycle (including desorption of the product) with the Fe 3d energy levels. Volcano relationships are revealed with peaks toward higher Fe 3d energy and stronger electron-donating group functionalization of linkers. Furthermore, we found that the Fe 3d energy levels positively correlate with the electron-donating strength of functional groups on the linkers. Finally, we validated our hypotheses on larger models of MOF-74 iron sites. Compared with MOF-74, functionalizing the MOF-74 linkers with NH2 groups lowers the enthalpic barrier for the most endothermic step in the reaction cycle. Our findings provide insight for catalyst optimization and point out directions for future experimental efforts.

  3. UB CCD PHOTOMETRY OF THE OLD, METAL-RICH, OPEN CLUSTERS NGC 6791, NGC 6819, AND NGC 7142

    SciTech Connect

    Carraro, G.; Buzzoni, A.; Bertone, E.; Buson, L. E-mail: alberto.buzzoni@oabo.inaf.it E-mail: lucio.buson@oapd.inaf.it

    2013-11-01

    We report on a UV-oriented imaging survey in the fields of the old, metal-rich open clusters NGC 6791, NGC 6819, and NGC 7142. With their super-solar metallicity and ages ∼> 3-8 Gyr, these three clusters represent both very near and ideal stellar aggregates to match the distinctive properties of the evolved stellar populations, as in elliptical galaxies and bulges of spirals. Following a first discussion of NGC 6791 observations in an accompanying paper, here we complete our analysis, also presenting for NGC 6819 and NGC 7142 the first-ever U CCD photometry. The color-magnitude diagram of the three clusters is analyzed in detail, with special emphasis on the hot stellar component. We report, in this regard, one new extreme horizontal-branch star candidate in NGC 6791. For NGC 6819 and 7142, the stellar luminosity function clearly points to a looser radial distribution of faint lower main sequence stars, either as a consequence of cluster dynamical interaction with the Galaxy or as an effect of an increasing fraction of binary stars toward the cluster core, as also observed in NGC 6791. Compared to a reference theoretical model for the Galaxy disk, the analysis of the stellar field along the line of sight of each cluster indicates that a more centrally concentrated thick disk, on a scale length shorter than ∼2.8 kpc, might better reconcile the lower observed fraction of bright field stars and their white-dwarf progeny.

  4. UB CCD Photometry of the Old, Metal-rich, Open Clusters NGC 6791, NGC 6819, and NGC 7142

    NASA Astrophysics Data System (ADS)

    Carraro, G.; Buzzoni, A.; Bertone, E.; Buson, L.

    2013-11-01

    We report on a UV-oriented imaging survey in the fields of the old, metal-rich open clusters NGC 6791, NGC 6819, and NGC 7142. With their super-solar metallicity and ages >~ 3-8 Gyr, these three clusters represent both very near and ideal stellar aggregates to match the distinctive properties of the evolved stellar populations, as in elliptical galaxies and bulges of spirals. Following a first discussion of NGC 6791 observations in an accompanying paper, here we complete our analysis, also presenting for NGC 6819 and NGC 7142 the first-ever U CCD photometry. The color-magnitude diagram of the three clusters is analyzed in detail, with special emphasis on the hot stellar component. We report, in this regard, one new extreme horizontal-branch star candidate in NGC 6791. For NGC 6819 and 7142, the stellar luminosity function clearly points to a looser radial distribution of faint lower main sequence stars, either as a consequence of cluster dynamical interaction with the Galaxy or as an effect of an increasing fraction of binary stars toward the cluster core, as also observed in NGC 6791. Compared to a reference theoretical model for the Galaxy disk, the analysis of the stellar field along the line of sight of each cluster indicates that a more centrally concentrated thick disk, on a scale length shorter than ~2.8 kpc, might better reconcile the lower observed fraction of bright field stars and their white-dwarf progeny.

  5. Protonation of metal-bound ?-hydroxycarboxylate ligand and implication for the role of homocitrate in nitrogenase: Computational study of the oxy-bidentate chelate ring opening

    NASA Astrophysics Data System (ADS)

    Cao, Zexing; Jin, Xi; Zhou, Zhaohui; Zhang, Qianer

    Protonation of the metal-bound oxy-bidentate ligand in the model complexes of [(HS)3(NH3)M(OCH2COO)]q (M = Mo, Fe, V, Co; q = -2, -1) in the gas phase and in solutions of water and acetonitrile has been explored by the density functional approach. Calculations show that protonation of the carboxyl oxygen can open the ?-hydroxycarboxylate chelate ring ligated to a transition-metal center under specific oxidation and spin states. The feasibility of the chelate ring opening by protonation depends on the electronic nature of the metal site in tune with conversion of a six-coordinate with a five-coordinate metal atom. Such selective dissociation of the metal-bound chelate ligand manipulates the availability of an empty site at the metal center and significantly affects reactivity of the metal-mediated chemical processes. Protonation changes the stability of species with different spin multiplicities and impels spin transition at the metal center in dissociation of the oxy-bidentate ligand. Solvent environments of water and acetonitrile play an important role in stabilizing the negatively charged species.

  6. The Biomechanisms of Metal and Metal-Oxide Nanoparticles’ Interactions with Cells

    PubMed Central

    Teske, Sondra S.; Detweiler, Corrella S.

    2015-01-01

    Humans are increasingly exposed to nanoparticles (NPs) in medicine and in industrial settings, where significant concentrations of NPs are common. However, NP interactions with and effects on biomolecules and organisms have only recently been addressed. Within we review the literature regarding proposed modes of action for metal and metal-oxide NPs, two of the most prevalent types manufactured. Iron-oxide NPs, for instance, are used as tracers for magnetic resonance imaging of oncological tumors and as vehicles for therapeutic drug delivery. Factors and theories that determine the physicochemical and biokinetic behaviors of NPs are discussed, along with the observed toxicological effects of NPs on cells. Key thermodynamic and kinetic models that explain the sources of energy transfer from NPs to biological targets are summarized, in addition to quantitative structural activity relationship (QSAR) modeling efforts. Future challenges for nanotoxicological research are discussed. We conclude that NP studies based on cell culture are often inconsistent and underestimate the toxicity of NPs. Thus, the effect of NPs needs to be examined in whole animal systems. PMID:25648173

  7. Electronic fine structure calculation of metal complexes with three-open-shell s, d, and p configurations.

    PubMed

    Ramanantoanina, Harry; Daul, Claude

    2017-08-01

    The ligand field density functional theory (LFDFT) algorithm is extended to treat the electronic structure and properties of systems with three-open-shell electron configurations, exemplified in this work by the calculation of the core and semi-core 1s, 2s, and 3s one-electron excitations in compounds containing transition metal ions. The work presents a model to non-empirically resolve the multiplet energy levels arising from the three-open-shell systems of non-equivalent ns, 3d, and 4p electrons and to calculate the oscillator strengths corresponding to the electric-dipole 3d (m)  → ns (1)3d (m) 4p (1) transitions, with n = 1, 2, 3 and m = 0, 1, 2, …, 10 involved in the s electron excitation process. Using the concept of ligand field, the Slater-Condon integrals, the spin-orbit coupling constants, and the parameters of the ligand field potential are determined from density functional theory (DFT). Therefore, a theoretical procedure using LFDFT is established illustrating the spectroscopic details at the atomic scale that can be valuable in the analysis and characterization of the electronic spectra obtained from X-ray absorption fine structure or electron energy loss spectroscopies.

  8. Influence of a MoOx interlayer on the open-circuit voltage in organic photovoltaic cells

    NASA Astrophysics Data System (ADS)

    Zou, Yunlong; Holmes, Russell J.

    2013-07-01

    Metal-oxides have been used as interlayers at the anode-organic interface in organic photovoltaic cells (OPVs) to increase the open-circuit voltage (VOC). We examine the role of MoOx in determining the maximum VOC in a planar heterojunction OPV and find that the interlayer strongly affects the temperature dependence of VOC. Boron subphthalocyanine chloride (SubPc)-C60 OPVs that contain no interlayer show a maximum VOC of 1.2 V at low temperature, while those with MoOx show no saturation, reaching VOC > 1.4 V. We propose that the MoOx-SubPc interface forms a Schottky junction that provides an additional contribution to VOC at low temperature.

  9. Platinum redispersion on metal oxides in low temperature fuel cells.

    PubMed

    Tripković, Vladimir; Cerri, Isotta; Nagami, Tetsuo; Bligaard, Thomas; Rossmeisl, Jan

    2013-03-07

    We have analyzed the aptitude of several metal oxide supports (TiO(2), SnO(2), NbO(2), ZrO(2), SiO(2), Ta(2)O(5) and Nb(2)O(5)) to redisperse platinum under electrochemical conditions pertinent to the Proton Exchange Membrane Fuel Cell (PEMFC) cathode. The redispersion on oxide supports in air has been studied in detail; however, due to different operating conditions it is not straightforward to link the chemical and the electrochemical environment. The largest differences reflect in (1) the oxidation state of the surface (the oxygen species coverage), (2) temperature and (3) the possibility of platinum dissolution at high potentials and the interference of redispersion with normal working potential of the PEMFC cathode. We have calculated the PtO(x) (x = 0, 1, 2) adsorption energies on different metal oxides' surface terminations as well as inside the metal oxides' bulk, and we have concluded that NbO(2) might be a good support for platinum redispersion at PEMFC cathodes.

  10. Preventing interfacial recombination in colloidal quantum dot solar cells by doping the metal oxide.

    PubMed

    Ehrler, Bruno; Musselman, Kevin P; Böhm, Marcus L; Morgenstern, Frederik S F; Vaynzof, Yana; Walker, Brian J; Macmanus-Driscoll, Judith L; Greenham, Neil C

    2013-05-28

    Recent research has pushed the efficiency of colloidal quantum dot solar cells toward a level that spurs commercial interest. Quantum dot/metal oxide bilayers form the most efficient colloidal quantum dot solar cells, and most studies have advanced the understanding of the quantum dot component. We study the interfacial recombination process in depleted heterojunction colloidal quantum dot (QD) solar cells formed with ZnO as the oxide by varying (i) the carrier concentration of the ZnO layer and (ii) the density of intragap recombination sites in the QD layer. We find that the open-circuit voltage and efficiency of PbS QD/ZnO devices can be improved by 50% upon doping of the ZnO with nitrogen to reduce its carrier concentration. In contrast, doping the ZnO did not change the performance of PbSe QD/ZnO solar cells. We use X-ray photoemission spectroscopy, ultraviolet photoemission spectroscopy, transient photovoltage decay measurements, transient absorption spectroscopy, and intensity-dependent photocurrent measurements to investigate the origin of this effect. We find a significant density of intragap states within the band gap of the PbS quantum dots. These states facilitate recombination at the PbS/ZnO interface, which can be suppressed by reducing the density of occupied states in the ZnO. For the PbSe QD/ZnO solar cells, where fewer intragap states are observed in the quantum dots, the interfacial recombination channel does not limit device performance. Our study sheds light on the mechanisms of interfacial recombination in colloidal quantum dot solar cells and emphasizes the influence of quantum dot intragap states and metal oxide properties on this loss pathway.

  11. Application of fuel cell for pyrite and heavy metal containing mining waste

    NASA Astrophysics Data System (ADS)

    Keum, H.; Ju, W. J.; Jho, E. H.; Nam, K.

    2015-12-01

    Once pyrite and heavy metal containing mining waste reacts with water and air it produces acid mine drainage (AMD) and leads to the other environmental problems such as contamination of surrounding soils. Pyrite is the major source of AMD and it can be controlled using a biological-electrochemical dissolution method. By enhancing the dissolution of pyrite using fuel cell technology, not only mining waste be beneficially utilized but also be treated at the same time by. As pyrite-containing mining waste is oxidized in the anode of the fuel cell, electrons and protons are generated, and electrons moves through an external load to cathode reducing oxygen to water while protons migrate to cathode through a proton exchange membrane. Iron-oxidizing bacteria such as Acidithiobacillus ferrooxidans, which can utilize Fe as an electron donor promotes pyrite dissolution and hence enhances electrochemical dissolution of pyrite from mining waste. In this study mining waste from a zinc mine in Korea containing 17 wt% pyrite and 9% As was utilized as a fuel for the fuel cell inoculated with A. ferrooxidans. Electrochemically dissolved As content and chemically dissolved As content was compared. With the initial pH of 3.5 at 23℃, the dissolved As concentration increased (from 4.0 to 13 mg/L after 20 d) in the fuel cell, while it kept decreased in the chemical reactor (from 12 to 0.43 mg/L after 20 d). The fuel cell produced 0.09 V of open circuit voltage with the maximum power density of 0.84 mW/m2. Dissolution of As from mining waste was enhanced through electrochemical reaction. Application of fuel cell technology is a novel treatment method for pyrite and heavy metals containing mining waste, and this method is beneficial for mining environment as well as local community of mining areas.

  12. Photoluminescence imaging for determining the spatially resolved implied open circuit voltage of silicon solar cells

    NASA Astrophysics Data System (ADS)

    Hallam, Brett; Augarten, Yael; Tjahjono, Budi; Trupke, Thorsten; Wenham, Stuart

    2014-01-01

    Photoluminescence imaging has widely been used as a characterisation tool for the development of silicon solar cells. However, photoluminescence images typically only give qualitative information due to the presence of an unknown calibration constant. In this work, quasi-steady-state photoconductance measurements on partially processed solar cells and I-V measurements on finished solar cells are used to determine the calibration constants to yield spatially resolved implied open circuit voltage images. This technique is then applied to determine the implied open circuit voltage of laser doped selective emitter solar cells at various stages of cell fabrication after the formation of the full area aluminium back surface field when other characterisation techniques such as photoconductance cannot be used.

  13. Surface acoustic admittance of highly porous open-cell, elastic foams

    NASA Technical Reports Server (NTRS)

    Lambert, R. F.

    1983-01-01

    This work presents a comprehensive study of the surface acoustic admittance properties of graded sizes of open-cell foams that are highly porous and elastic. The intrinsic admittance as well as properties of samples of finite depth were predicted and then measured for sound at normal incidence over a frequency range extending from about 35-3500 Hz. The agreement between theory and experiment for a range of mean pore size and volume porosity is excellent. The implications of fibrous structure on the admittance of open-cell foams is quite evident from the results.

  14. Rhodococcus erythropolis cells adapt their fatty acid composition during biofilm formation on metallic and non-metallic surfaces.

    PubMed

    Rodrigues, Carlos J C; de Carvalho, Carla C C R

    2015-12-01

    Several parameters are involved in bacterial adhesion and biofilm formation including surface type, medium composition and cellular surface hydrophobicty. When the cells are placed inside tubes, parameters such as oxygen availability should also influence cell adhesion. To understand which cellular lipids are involved in the molecular events of biofilm formation in Rhodococcus erythropolis, cell adhesion was promoted on different metallic and non-metallic surfaces immersed in culture media. These cells were able to modulate the fatty acid composition of the cell membrane in response to both the surface to which they adhered and the growth medium used. To assess the response of the cells to both surfaces and operational conditions, biofilms were also promoted inside a reactor built with five different types of tubes and with medium recirculation. The biofilm biomass could be directly related not to the hydrophobicity of the tubes used but to the oxygen permeability of the tubes. Besides this, cell age influenced the adhesion of the R. erythropolis cells to the tubes. Principal component analysis showed that the lipid composition of the cells could separate cells attached to metallic from those on non-metallic surfaces in the plane formed by PC1 and PC2, and influence biofilm biomass.

  15. Construction of robust open metal-organic frameworks with chiral channels and permanent porosity.

    PubMed

    Sun, Daofeng; Ke, Yanxiong; Collins, David J; Lorigan, Gary A; Zhou, Hong-Cai

    2007-04-02

    Four new metal-organic frameworks (MOFs) containing chiral channels have been synthesized using an achiral, triazine-based trigonal-planar ligand, 4,4',4' '-s-triazine-2,4,6-triyltribenzoate (TATB), and an hourglass secondary building unit (SBU): Zn3(TATB)2(H2O)2.4DMF.6H2O (1); Cd3(TATB)2(H2O)2.7DMA.10H2O (2); [H2N(CH3)2][Zn3(TATB)2(HCOO)].HN(CH3)2.3DMF.3H2O (3); [H2N(CH3)2][Cd3(TATB)2(CH3COO)].HN(CH3)2.3DMA.4H2O (4). MOFs 1 and 2 are isostructural and possess (10,3)-a nets containing large chiral channels of 20.93 and 21.23 A, respectively, but are thermally unstable due to the easy removal of coordinated water molecules on the SBU. Replacement of these water molecules by formate or acetate generated in situ leads to 3 and 4, respectively. Formate or acetate links SBUs to form infinite helical chains bridged by TATB to create three-dimensional anionic networks, in which one of the two oxygen atoms of the formate or acetate is uncoordinated and points into the void of the channels. This novel SBU-stabilization and channel-functionalization strategy may have general implications in the preparation of new MOFs. Thermogravimetric analysis (TGA) shows that solvent-free 3' is thermally stable to 410 degrees C, while TGA studies on samples vapor-diffused with water, methanol, and chloroform show reversible adsorption. MOF 3 also has permanent porosity with a large Langmuir surface area of 1558 m2/g. All complexes exhibit similar strong luminescence with a lambdamax of approximately 423 nm upon excitation at 268.5 nm.

  16. Chemical and aerosol processes in the transition from closed to open cells during VOCALS-REx

    NASA Astrophysics Data System (ADS)

    Kazil, J.; Wang, H.; Feingold, G.; Clarke, A. D.; Snider, J. R.; Bandy, A. R.

    2011-02-01

    Chemical and aerosol processes in the transition from closed- to open-cell circulation in the remote, cloudy marine boundary layer are explored. It has previously been shown that precipitation can initiate a transition from the closed- to the open-cellular state, but that the boundary layer cannot maintain this open-cell state without a resupply of cloud condensation nuclei (CCN). Potential sources include wind-driven production of sea salt particles from the ocean, nucleation from the gas phase, and entrainment from the free troposphere. In order to investigate aerosol sources in the marine boundary layer and their role in supplying new particles, we have coupled in detail chemical, aerosol, and cloud processes in the WRF/Chem model, and added state-of-the-art representations of sea salt emissions and aerosol nucleation. We introduce the new features of the model and conduct simulations of the marine boundary layer in the transition from a closed- to an open-cell state. Results are compared with observations in the Southeast Pacific boundary layer during the VAMOS Ocean-Cloud-Atmosphere-Land Study Regional Experiment (VOCALS-REx). The transition from the closed- to the open-cell state generates conditions that are conducive to nucleation by forming a cloud-scavenged, ultra-clean layer below the inversion base. Open cell wall updrafts loft dimethyl sulfide from the ocean surface into the ultra-clean layer, where it is oxidized during daytime to SO2 and subsequently to H2SO4. Low H2SO4 condensation sink values in the ultra-clean layer allow H2SO4 to rise to concentrations at which aerosol nucleation proceeds efficiently. The existence of the ultra-clean layer is confirmed by observations. We find that the observed DMS flux from the ocean in the VOCALS-REx region can support a nucleation source of aerosol in open cells that exceeds sea salt emissions in terms of the number of particles produced. The freshly nucleated, nanometer-sized aerosol particles need, however

  17. Effect of Structure, Temperature, and Metal Work Function on Performance of Organometallic Perovskite Solar Cells

    NASA Astrophysics Data System (ADS)

    Hossain, M. I.; Aïssa, B.

    2017-01-01

    The impact of hole transport materials (HTMs) on the performance of methylammonium lead halide (CH3NH3PbI3)-based perovskite solar cells has been investigated using computational analysis. The main objective is to replace the HTM with the aim of enhancing the lifetime and decreasing the overall cost of the device. As the CH3NH3PbI3 absorber layer shows an absorption coefficient as high as 105/cm, all photons with incident energy larger the material bandgap are absorbed within only a 400-nm-thick layer. Also, all the electronic and optical properties of such an absorber layer are suitable for use in photovoltaic (PV) devices. Hence, the effects of the HTM thickness, operating temperature, incident light spectrum, and metal electrode work function on the charge collection were studied numerically. For a cell with Cu2O as HTM, efficiency exceeding 25% is predicted for a 350-nm-thick absorber layer. Also, a fully optimized device architecture without HTM shows the possibility of fabricating a perovskite solar cell with PV efficiency exceeding 15%. We expect considerable minimization of the energy loss in this structure due to charge transfer across the heterojunction. Moreover, the effect of temperature on perovskite solar cells and potential electrodes with different work functions has been investigated. Our results are believed to help open an experimental avenue to achieve optimum results for perovskite solar cells with various structures.

  18. An exploration of plastic deformation dependence of cell viability and adhesion in metallic implant materials.

    PubMed

    Uzer, B; Toker, S M; Cingoz, A; Bagci-Onder, T; Gerstein, G; Maier, H J; Canadinc, D

    2016-07-01

    The relationship between cell viability and adhesion behavior, and micro-deformation mechanisms was investigated on austenitic 316L stainless steel samples, which were subjected to different amounts of plastic strains (5%, 15%, 25%, 35% and 60%) to promote a variety in the slip and twin activities in the microstructure. Confocal laser scanning microscopy (CLSM) and field emission scanning electron microscopy (FESEM) revealed that cells most favored the samples with the largest plastic deformation, such that they spread more and formed significant filopodial extensions. Specifically, brain tumor cells seeded on the 35% deformed samples exhibited the best adhesion performance, where a significant slip activity was prevalent, accompanied by considerable slip-twin interactions. Furthermore, maximum viability was exhibited by the cells seeded on the 60% deformed samples, which were particularly designed in a specific geometry that could endure greater strain values. Overall, the current findings open a new venue for the production of metallic implants with enhanced biocompatibility, such that the adhesion and viability of the cells surrounding an implant can be optimized by tailoring the surface relief of the material, which is dictated by the micro-deformation mechanism activities facilitated by plastic deformation imposed by machining.

  19. Effect of Structure, Temperature, and Metal Work Function on Performance of Organometallic Perovskite Solar Cells

    NASA Astrophysics Data System (ADS)

    Hossain, M. I.; Aïssa, B.

    2017-03-01

    The impact of hole transport materials (HTMs) on the performance of methylammonium lead halide (CH3NH3PbI3)-based perovskite solar cells has been investigated using computational analysis. The main objective is to replace the HTM with the aim of enhancing the lifetime and decreasing the overall cost of the device. As the CH3NH3PbI3 absorber layer shows an absorption coefficient as high as 105/cm, all photons with incident energy larger the material bandgap are absorbed within only a 400-nm-thick layer. Also, all the electronic and optical properties of such an absorber layer are suitable for use in photovoltaic (PV) devices. Hence, the effects of the HTM thickness, operating temperature, incident light spectrum, and metal electrode work function on the charge collection were studied numerically. For a cell with Cu2O as HTM, efficiency exceeding 25% is predicted for a 350-nm-thick absorber layer. Also, a fully optimized device architecture without HTM shows the possibility of fabricating a perovskite solar cell with PV efficiency exceeding 15%. We expect considerable minimization of the energy loss in this structure due to charge transfer across the heterojunction. Moreover, the effect of temperature on perovskite solar cells and potential electrodes with different work functions has been investigated. Our results are believed to help open an experimental avenue to achieve optimum results for perovskite solar cells with various structures.

  20. Ring-opening polymerization of cyclic esters by phenoxy-thioether complexes derived from biocompatible metals.

    PubMed

    Pilone, Alessia; Lamberti, Marina; Mazzeo, Mina; Milione, Stefano; Pellecchia, Claudio

    2013-09-28

    A series of novel Mg(II) and Zn(II) complexes of the form LMX or L2M, supported by phenoxy-thioether ligands bearing different substituents at the ortho position of the thiophenol rings [L(-) = 4,6-tBu2-OC6H2-2-CH2S(2-R-C6H4)(-)] [M = Zn, R = H, X = N(SiMe3)2 (1) and X = Et (2); M = Mg, X = n-Bu, R = H (3), R = CH3 (4), R = Br (5); M = Mg, R = H (6)], were synthesized and characterized. Reaction of the proper zinc precursor (Zn[N(SiHMe2)2]2 or ZnEt2) with one equivalent of the phenoxy-thioether proligand produced the corresponding amido (1) and ethyl (2) zinc complexes in high yields. The monoalkylmagnesium complexes (3-5) were all obtained by butane elimination reaction of the dialkylmagnesium reagent, Mg(n-Bu)2, with one equivalent of the proligand in good yields. The homoleptic complex 6 was obtained by reaction of 0.5 equivalent of Mg(n-Bu)2 and the proper proligand. Variable temperature (1)H NMR studies performed on 2 and 3 demonstrated that the named complexes are involved in fluxional processes concerning a fast conformational change of the six-membered metallacycle. DOSY (Diffusion Ordered SpectroscopY) (1)H experiments and ligand scrambling strongly suggested that complexes 1-6 exist as dimeric species in solution. All complexes were active as catalysts in the ring-opening polymerization of cyclic esters. In particular, magnesium complexes showed superior ε-caprolactone and lactide ROP behavior in terms of activity, control of molecular weights and molecular weight distributions.

  1. Density Functional Theory of Open-Shell Systems. The 3d-Series Transition-Metal Atoms and Their Cations.

    PubMed

    Luo, Sijie; Averkiev, Boris; Yang, Ke R; Xu, Xuefei; Truhlar, Donald G

    2014-01-14

    The 3d-series transition metals (also called the fourth-period transition metals), Sc to Zn, are very important in industry and biology, but they provide unique challenges to computing the electronic structure of their compounds. In order to successfully describe the compounds by theory, one must be able to describe their components, in particular the constituent atoms and cations. In order to understand the ingredients required for successful computations with density functional theory, it is useful to examine the performance of various exchange-correlation functionals; we do this here for 4s(N)3d(N') transition-metal atoms and their cations. We analyze the results using three ways to compute the energy of the open-shell states: the direct variational method, the weighted-averaged broken symmetry (WABS) method, and a new broken-symmetry method called the reinterpreted broken symmetry (RBS) method. We find the RBS method to be comparable in accuracy with the WABS method. By examining the overall accuracy in treating 18 multiplicity-changing excitations and 10 ionization potentials with the RBS method, 10 functionals are found to have a mean-unsigned error of <5 kcal/mol, with ωB97X-D topping the list. For local density functionals, which are more practical for extended systems, the M06-L functional is the most accurate. And by combining the results with our previous studies of p-block and 4d-series elements as well as databases for alkyl bond dissociation, main-group atomization energies, and π-π noncovalent interactions, we find five functionals, namely, PW6B95, MPW1B95, M08-SO, SOGGA11-X, and MPWB1K, to be highly recommended. We also studied the performance of PW86 and C09 exchange functionals, which have drawn wide interest in recent studies due to their claimed ability to reproduce Hartree-Fock exchange at long distance. By combining them with four correlation functionals, we find the performance of the resulting functionals disappointing both for 3d

  2. High performance, high durability non-precious metal fuel cell catalysts

    DOEpatents

    Wood, Thomas E.; Atanasoski, Radoslav; Schmoeckel, Alison K.

    2016-03-15

    This invention relates to non-precious metal fuel cell cathode catalysts, fuel cells that contain these catalysts, and methods of making the same. The fuel cell cathode catalysts are highly nitrogenated carbon materials that can contain a transition metal. The highly nitrogenated carbon materials can be supported on a nanoparticle substrate.

  3. Metal nanoparticle fluorophore: a powerful fluorescence probe in single cell imaging

    NASA Astrophysics Data System (ADS)

    Zhang, Jian; Fu, Yi; Zhao, Richard Y.; Lakowicz, Joseph R.

    2010-02-01

    Metal nanoparticle fluorophores have been developed using metal-enhanced fluorescence (MEF) principle. Compared with the conventional organic fluorophores, the metal fluorophores display the increasing brightness and shortening lifetime as well as the lengthening photostability and reducing photoblinking. Conjugated the metal fluorophores on the surfaces of cell lines, the cell images were recorded on a scanning confocal microscopy in the either emission intensity or lifetime. The emission spots by the conjugated metal fluorophores were isolated distinctly from the cell images because of their brighter signals and shorter lifetimes. Collected in the three-dimension, the total number of emission signals could be counted quantitatively and the distribution could be described on the cell surfaces. It was noticed that the emission intensity over the cell image was increased with an increase of the number of metal fluorophore on the cell surface and simultaneously the lifetime was altered. A quantitative regression curve was achieved between the amount of metal fluorophore on the cell surface and the emission intensity or lifetime over the entire cell image. Based on this regression curve, the target molecules on the cell surfaces could be quantified readily through the cell intensity and/or lifetime at the single cell level instead of the direct count to the emission spots. As novel molecule imaging agents, these metal fluorophores are being applied in the quantification and distribution of target molecule on the cell surface for the clinical diagnostic research.

  4. Metal Preferences and Metallation*

    PubMed Central

    Foster, Andrew W.; Osman, Deenah; Robinson, Nigel J.

    2014-01-01

    The metal binding preferences of most metalloproteins do not match their metal requirements. Thus, metallation of an estimated 30% of metalloenzymes is aided by metal delivery systems, with ∼25% acquiring preassembled metal cofactors. The remaining ∼70% are presumed to compete for metals from buffered metal pools. Metallation is further aided by maintaining the relative concentrations of these pools as an inverse function of the stabilities of the respective metal complexes. For example, magnesium enzymes always prefer to bind zinc, and these metals dominate the metalloenzymes without metal delivery systems. Therefore, the buffered concentration of zinc is held at least a million-fold below magnesium inside most cells. PMID:25160626

  5. Technology of GaAs metal-oxide-semiconductor solar cells

    NASA Technical Reports Server (NTRS)

    Stirn, R. J.; Yeh, Y. C. M.

    1977-01-01

    The growth of an oxide interfacial layer was recently found to increase the open-circuit voltage (OCV) and efficiency by up to 60 per cent in GaAs metal-semiconductor solar cells. Details of oxidation techniques to provide the necessary oxide thickness and chemical structure and using ozone, water-vapor-saturated oxygen, or oxygen gas discharges are described, as well as apparent crystallographic orientation effects. Preliminary results of the oxide chemistry obtained from X-ray, photoelectron spectroscopy are given. Ratios of arsenic oxide to gallium oxide of unity or less seem to be preferable. Samples with the highest OVC predominantly have As(+3) in the arsenic oxide rather than As(+5). A major difficulty at this time is a reduction in OCV by 100-200 mV when the antireflection coating is vacuum deposited.

  6. Improve the operational stability of the inverted organic solar cells using bilayer metal oxide structure.

    PubMed

    Chang, Jingjing; Lin, Zhenhua; Jiang, Changyun; Zhang, Jie; Zhu, Chunxiang; Wu, Jishan

    2014-11-12

    Operational stability is a big obstacle for the application of inverted organic solar cells (OSCs), however, less talked about in the research reports. Due to photoinduced degradation of the metal oxide interlayer, which can cause shunts generation and degeneration in ZnO interlayer, a significant degradation of open circuit voltage (Voc) and fill factor (FF) has been observed by in situ periodic measurements of the device current density-voltage (J-V) curves with light illumination. By combining TiOx and ZnO to form bilayer structures on ITO, the photovoltaic performance is improved and the photoinduced degradation is reduced. It was found that the device based on ZnO/TiOx bilayer structure achieved better operational stability as compared to that with ZnO or TiOx interlayer.

  7. Technology of GaAs metal-oxide-semiconductor solar cells

    NASA Technical Reports Server (NTRS)

    Stirn, R. J.; Yeh, Y. C. M.

    1977-01-01

    The growth of an oxide interfacial layer was recently found to increase the open-circuit voltage (OCV) and efficiency by up to 60 per cent in GaAs metal-semiconductor solar cells. Details of oxidation techniques to provide the necessary oxide thickness and chemical structure and using ozone, water-vapor-saturated oxygen, or oxygen gas discharges are described, as well as apparent crystallographic orientation effects. Preliminary results of the oxide chemistry obtained from X-ray, photoelectron spectroscopy are given. Ratios of arsenic oxide to gallium oxide of unity or less seem to be preferable. Samples with the highest OVC predominantly have As(+3) in the arsenic oxide rather than As(+5). A major difficulty at this time is a reduction in OCV by 100-200 mV when the antireflection coating is vacuum deposited.

  8. Action Spectra for Guard Cell Rb+ Uptake and Stomatal Opening in Vivia faba

    PubMed Central

    Hsiao, Theodore C.; Allaway, W. G.; Evans, L. T.

    1973-01-01

    Abaxial epidermal strips, containing guard cells as the only viable cells, were prepared from leaves of Vicia faba following a period in darkness, and floated, under CO2-free air, on 2 mm RbCl + 0.1 mm CaCl2 labeled with 86Rb+. Under white light (high pressure mercury vapor lamp), stomatal opening in these strips approached its maximum at less than 0.02 calorie per square centimeter per minute. Under light of different wavelengths, 20 nanometers apart, and at a low quantum flux density of 7 × 1014 quanta per square centimeter per second, Rb+ uptake and stomatal opening were activated only in the blue and long ultraviolet regions, with a peak at 420 to 460 nanometers. The action spectrum suggests that the underlying process is not photosynthesis. At higher quantum flux density (38 × 1014 quanta per square centimeter per second), uptake and opening also responded to red (600-680 nanometers) and somewhat to green light, with a minimum at 540 to 560 nanometers, indicating a possible involvement of the photosynthetic process. This light-induced opening appeared not to be mediated by a lowering of CO2 concentration, since CO2-free air was used in all treatments and controls. Stomatal opening paralleled Rb+ uptake in all cases. This constitutes further evidence for the potassium transport hypothesis of stomatal movement. In the abaxial surface of leaf discs under air of normal CO2 concentration, stomatal opening in white light approached its maximum at an intensity similar to that for epidermal strips. At both quantum flux densities, the action spectra for opening in leaf discs were very similar to those for epidermal strips. Thus, these light-linked processes for stomatal opening are likely to be the same in leaves as in epidermal strips. PMID:16658302

  9. Kinetics of Open Circuit Processes in Undischarged Li/SOC12 Cells

    NASA Technical Reports Server (NTRS)

    Hansen, L. D.; Frank, H.

    1984-01-01

    The kinetics of the heat producing processes in undischarged Li/SOCl2 cells under open circuit conditions were measured by heat-conduction microcalorimetry. The cells studied, Honeywell type G2666 reserve cells, were activated as needed and the rate of open circuit heat output determined as a function of time since activation and temperature. The results at each temperature can be described by an equation of the form q = Bktx where q is the rate of heat output, B is the heat produced per unit of reaction, k and x are empirical constants, and t is the time since activation. Both x and k are found to be functions of temperature; therefore, accelerated testing at elevated temperatures is probably not valid for these cells until the processes involved are better understood.

  10. Absorption Spectroscopy of Rubidium in an Alkali Metal Dispenser Cell and Bleached Wave Analysis

    DTIC Science & Technology

    2015-03-26

    ABSORPTION SPECTROSCOPY OF RUBIDIUM IN AN ALKALI METAL DISPENSER CELL AND BLEACHED WAVE ANALYSIS THESIS JAMES M. ROSENTHAL, 2 nd Lt...102 ABSORPTION SPECTROSCOPY OF RUBIDIUM IN AN ALKALI METAL DISPENSER CELL AND BLEACHED WAVE ANALYSIS THESIS Presented to the Faculty...SPECTROSCOPY OF RUBIDIUM IN AN ALKALI METAL DISPENSER CELL AND BLEACHED WAVE ANALYSIS James M. Rosenthal, BA 2 nd Lt, USAF Committee Membership

  11. Effect of chemical surface treatments on non-native (Bi/sub 2/O/sub 3/) GaAs metal-insulator-semiconductor solar cells

    SciTech Connect

    Wang, E.Y.; Pandelisev, K.A.

    1981-07-01

    GaAs metal-insulator-semiconductor solar cells with a physically deposited Bi/sub 2/O/sub 3/ interfacial layer have been investigated. The deposition techniques used in the study were electron beam and boat thermal evaporation. The cells fabricated with interfacial layers of Bi/sub 2/O/sub 3/ showed a substantial improvement in open-circuit voltage over cells made without the physically deposited oxide layer. An etch has been used which yields an irregular ''textured'' surface. Cells employing this surface had a higher short-circuit current than those made with smooth, polished surfaces. The open-circuit voltages of these textured cells were lower than those with smooth surfaces. Calculations of the dependence of open-circuit voltage on pinhole density are in agreement with these results since a rough surface has a greater probability of pinholes.

  12. HOT CELL BUILDING, TRA632, INTERIOR. OPEN CORRIDOR ALONG SOUTH WALL ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    HOT CELL BUILDING, TRA-632, INTERIOR. OPEN CORRIDOR ALONG SOUTH WALL OF BUILDING. CAMERA IS NEAR HOT CELL NO. 1, FACES WEST TOWARDS WALL OF TEST-TRAIN ASSEMBLY (TRA-632A). NOTE MOTORIZED RAIL CRANE ABOVE STAIRWAY. INL NEGATIVE NO. HD46-29-3. Mike Crane, Photographer, 2/2005 - Idaho National Engineering Laboratory, Test Reactor Area, Materials & Engineering Test Reactors, Scoville, Butte County, ID

  13. Y3+, La3+, and some bivalent metals inhibited the opening of the Tl+-induced permeability transition pore in Ca2+-loaded rat liver mitochondria.

    PubMed

    Korotkov, Sergey; Konovalova, Svetlana; Emelyanova, Larisa; Brailovskaya, Irina

    2014-12-01

    We showed earlier that diminution of 2,4-dinitrophenol (DNP)-stimulated respiration and increase of both mitochondrial swelling and electrochemical potential (ΔΨmito) dissipation in medium containing TlNO3 and KNO3 were caused by opening of Tl(+)-induced mitochondrial permeability transition pore (MPTP) in the inner membrane of Ca(2+)-loaded rat liver mitochondria. The MPTP opening was studied in the presence of bivalent metal ions (Sr(2+), Ba(2+), Mn(2+), Co(2+) and Ni(2+)), trivalent metal ions (Y(3+) and La(3+)), and ruthenium red. We found that these metal ions (except Ba(2+) and Co(2+)) as well as ruthenium red inhibited to the MPTP opening that manifested in preventing both diminution of the DNP-stimulated respiration and increase of the swelling and of the ΔΨmito dissipation in medium containing TlNO3, KNO3, and Ca(2+). Inhibition of the MPTP opening by Sr(2+) and Mn(2+) is suggested because of their interaction with high affinity Ca(2+) sites, facing the matrix side and participating in the MPTP opening. The inhibitory effects of metal ions (Y(3+), La(3+), and Ni(2+)), and ruthenium red are accordingly discussed in regard to competitive and noncompetitive inhibition of the mitochondrial Ca(2+)-uniporter. High concentrations (50μM) of Y(3+) and La(3+) favored of MPTP opening in the inner membrane of rat liver mitochondria in Ca(2+) free medium containing TlNO3. The latter MPTP opening was markedly eliminated by MPTP inhibitors (cyclosporine A and ADP).

  14. Enhanced Fluorescence Cell Imaging with Metal-Coated Slides

    PubMed Central

    Moal, E. Le; Fort, E.; Lévêque-Fort, S.; Cordelières, F. P.; Fontaine-Aupart, M.-P.; Ricolleau, C.

    2007-01-01

    Fluorescence labeling is the prevailing imaging technique in cell biology research. When they involve statistical investigations on a large number of cells, experimental studies require both low magnification to get a reliable statistical population and high contrast to achieve accurate diagnosis on the nature of the cells' perturbation. Because microscope objectives of low magnification generally yield low collection efficiency, such studies are limited by the fluorescence signal weakness. To overcome this technological bottleneck, we proposed a new method based on metal-coated substrates that enhance the fluorescence process and improve collection efficiency in epifluorescence observation and that can be directly used with a common microscope setup. We developed a model based on the dipole approximation with the aim of simulating the optical behavior of a fluorophore on such a substrate and revealing the different mechanisms responsible for fluorescence enhancement. The presence of a reflective surface modifies both excitation and emission processes and additionally reshapes fluorescence emission lobes. From both theoretical and experimental results, we found the fluorescence signal emitted by a molecular cyanine 3 dye layer to be amplified by a factor ∼30 when fluorophores are separated by a proper distance from the substrate. We then adapted our model to the case of homogeneously stained micrometer-sized objects and demonstrated mean signal amplification by a factor ∼4. Finally, we applied our method to fluorescence imaging of dog kidney cells and verified experimentally the simulated results. PMID:17172306

  15. Cell openness manipulation of low density polyurethane foam for efficient sound absorption

    NASA Astrophysics Data System (ADS)

    Hyuk Park, Ju; Suh Minn, Kyung; Rae Lee, Hyeong; Hyun Yang, Sei; Bin Yu, Cheng; Yeol Pak, Seong; Sung Oh, Chi; Seok Song, Young; June Kang, Yeon; Ryoun Youn, Jae

    2017-10-01

    Satisfactory sound absorption using a low mass density foam is an intriguing desire for achieving high fuel efficiency of vehicles. This issue has been dealt with a microcellular geometry manipulation. In this study, we demonstrate the relationship between cell openness of polyurethane (PU) foam and sound absorption behaviors, both theoretically and experimentally. The objective of this work is to mitigate a threshold of mass density by rendering a sound absorber which shows a satisfactory performance. The cell openness, which causes the best sound absorption performance in all cases considered, was estimated as 15% by numerical simulation. Cell openness of PU foam was experimentally manipulated into desired ranges by adjusting rheological properties in a foaming reaction. Microcellular structures of the fabricated PU foams were observed and sound absorption coefficients were measured using a B&K impedance tube. The fabricated PU foam with the best cell openness showed better sound absorption performance than the foam with double mass density. We envisage that this study can help the manufacture of low mass density sound absorbing foams more efficiently and economically.

  16. Photorespiration and temperature dependence of oxygen evolution in tomato plants monitored by open photoacoustic cell technique

    NASA Astrophysics Data System (ADS)

    Vargas-Luna, M.; Madueño, L.; Gutiérrez-Juárez, G.; Bernal-Alvarado, J.; Sosa, M.; González-Solís, J. L.; Sánchez-Rocha, S.; Olalde-Portugal, V.; Alvarado-Gil, J. J.; Campos, P.

    2003-01-01

    The open photoacoustic cell was used to monitor the evolution rate of oxygen from tomato leaves. Estimates of the relative amount of released oxygen in vivo and in situ conditions as influenced by ambient temperature are being presented. Photorespiration phenomenon is shown to dominate above a critical temperature. The evolution of this critical point is analyzed as a function of the environmental temperature.

  17. Electrokinetic transport of nanoparticles to opening of nanopores on cell membrane during electroporation

    NASA Astrophysics Data System (ADS)

    Movahed, Saeid; Li, Dongqing

    2013-04-01

    Nanoparticle transport to the opening of the single nanopore created on the cell membrane during the electroporation is studied. First, the permeabilization of a single cell located in a microchannel is investigated. When the nanopores are created, the transport of the nanoparticles from the surrounding liquid to the opening of one of the created nanopores is examined. It was found that the negatively charged nanoparticles preferably move into the nanopores from the side of the cell membrane that faces the negative electrode. Opposite to the electro-osmotic flow effect, the electrophoretic force tends to draw the negatively charged nanoparticles into the opening of the nanopores. The effect of the Brownian force is negligible in comparison with the electro-osmosis and the electrophoresis. Smaller nanoparticles with stronger surface charge transport more easily to the opening of the nanopores. Positively charged nanoparticles preferably enter the nanopores from the side of the cell membrane that faces the positive electrode. On this side, both the electrophoretic and the electro-osmotic forces are in the same directions and contribute to bring the positively charged particles into the nanopores.

  18. Shape and Dynamics of Adhesive Cells: Mechanical Response of Open Systems

    NASA Astrophysics Data System (ADS)

    Yang, Yuehua; Jiang, Hongyuan

    2017-05-01

    Cell adhesion is an essential biological process. However, previous theoretical and experimental studies ignore a key variable, the changes of cellular volume and pressure, during the dynamic adhesion process. Here, we treat cells as open systems and propose a theoretical framework to investigate how the exchange of water and ions with the environment affects the shape and dynamics of cells adhered between two adhesive surfaces. We show that adherent cells can be either stable (convex or concave) or unstable (spontaneous rupture or collapse) depending on the adhesion energy density, the cell size, the separation of two adhesive surfaces, and the stiffness of the flexible surface. Strikingly, we find that the unstable states vanish when cellular volume and pressure are constant. We further show that the detachments of convex and concave cells are very different. The mechanical response of adherent cells is mainly determined by the competition between the loading rate and the regulation of the cellular volume and pressure. Finally, we show that as an open system the detachment of adherent cells is also significantly influenced by the loading history. Thus, our findings reveal a major difference between living cells and nonliving materials.

  19. On-chip fabrication of alkali-metal vapor cells utilizing an alkali-metal source tablet

    NASA Astrophysics Data System (ADS)

    Tsujimoto, K.; Ban, K.; Hirai, Y.; Sugano, K.; Tsuchiya, T.; Mizutani, N.; Tabata, O.

    2013-11-01

    We describe a novel on-chip microfabrication technique for the alkali-metal vapor cell of an optically pumped atomic magnetometer (OPAM), utilizing an alkali-metal source tablet (AMST). The newly proposed AMST is a millimeter-sized piece of porous alumina whose considerable surface area holds deposited alkali-metal chloride (KCl) and barium azide (BaN6), source materials that effectively produce alkali-metal vapor at less than 400 °C. Our experiments indicated that the most effective pore size of the AMST is between 60 and 170 µm. The thickness of an insulating glass spacer holding the AMST was designed to confine generated alkali metal to the interior of the vapor cell during its production, and an integrated silicon heater was designed to seal the device using a glass frit, melted at an optimum temperature range of 460-490 °C that was determined by finite element method thermal simulation. The proposed design and AMST were used to successfully fabricate a K cell that was then operated as an OPAM with a measured sensitivity of 50 pT. These results demonstrate that the proposed concept for on-chip microfabrication of alkali-metal vapor cells may lead to effective replacement of conventional glassworking approaches.

  20. A microporous Cu-MOF with optimized open metal sites and pore spaces for high gas storage and active chemical fixation of CO2.

    PubMed

    Gao, Chao-Ying; Tian, Hong-Rui; Ai, Jing; Li, Lei-Jiao; Dang, Song; Lan, Ya-Qian; Sun, Zhong-Ming

    2016-09-25

    A microporous Cu-MOF with optimized open metal sites and pore space was constructed based on a designed bent ligand; it exhibits high-capacity multiple gas storage under atmospheric pressure and efficient catalytic activity for chemical fixation of CO2 under mild conditions.

  1. Rubisco activity in guard cells compared with the solute requirement for stomatal opening. [Pisum sativum

    SciTech Connect

    Reckmann, U.; Scheibe, R.; Raschke, K. )

    1990-01-01

    We investigated whether the reductive pentose phosphate path in guard cells of Pisum sativum had the capacity to contribute significantly to the production of osmotica during stomatal opening in the light. Amounts of ribulose 1,5-bisphophate carboxylase/oxygenase (Rubisco) were determined by the ({sup 14}C) carboxyarabinitol bisphosphate assay. A guard cell contained about 1.2 and a mesophyll cell about 324 picograms of the enzyme; the ratio was 1:270. The specific activities of Rubisco in guard cells and in mesophyll cells were equal; there was no indication of a specific inhibitor of Rubisco in guard cells. Rubisco activity was 115 femtomol per guard-cell protoplast and hour. This value was different from zero with a probability of 0.99. After exposure of guard-cell protoplasts to {sup 14}CO{sub 2} for 2 seconds in the light, about one-half of the radioactivity was in phosphorylated compounds and <10% in malate. Guard cells in epidermal strips produced a different labelling pattern; in the light, <10% of the label was in phosphorylated compounds and about 60% in malate. The rate of solute accumulation in intact guard cells was estimated to have been 900 femto-osmol per cell and hour. If Rubisco operated at full capacity in guard cells, and hexoses were produced as osmotica, solutes could be supplied at a rate of 19femto-osmol per cell and hour, which would constitute 2% of the estimated requirement. The capacity of guard-cell Rubisco to meet the solute requirement for stomatal opening in leaves of Pisum sativum is insignificant.

  2. Rubisco Activity in Guard Cells Compared with the Solute Requirement for Stomatal Opening 1

    PubMed Central

    Reckmann, Udo; Scheibe, Renate; Raschke, Klaus

    1990-01-01

    We investigated whether the reductive pentose phosphate path in guard cells of Pisum sativum had the capacity to contribute significantly to the production of osmotica during stomatal opening in the light. Amounts of ribulose 1,5-bisphophate carboxylase/oxygenase (Rubisco) were determined by the [14C]carboxyarabinitol bisphosphate assay. A guard cell contained about 1.2 and a mesophyll cell about 324 picograms of the enzyme; the ratio was 1:270. The specific activities of Rubisco in guard cells and in mesophyll cells were equal; there was no indication of a specific inhibitor of Rubisco in guard cells. Rubisco activity was 115 femtomol per guard-cell protoplast and hour. This value was different from zero with a probability of 0.99. After exposure of guard-cell protoplasts to 14CO2 for 2 seconds in the light, about one-half of the radioactivity was in phosphorylated compounds and <10% in malate. Guard cells in epidermal strips produced a different labelling pattern; in the light, <10% of the label was in phosphorylated compounds and about 60% in malate. The rate of solute accumulation in intact guard cells was estimated to have been 900 femto-osmol per cell and hour. If Rubisco operated at full capacity in guard cells, and hexoses were produced as osmotica, solutes could be supplied at a rate of 19 femto-osmol per cell and hour, which would constitute 2% of the estimated requirement. The capacity of guard-cell Rubisco to meet the solute requirement for stomatal opening in leaves of Pisum sativum is insignificant. Images Figure 1 PMID:16667255

  3. Transition-Metal Additives For Long-Life Na/NiCI(2) Cells

    NASA Technical Reports Server (NTRS)

    Bugga, Ratnakumar V.; Surampudi, Subbarao; Halpert, Gerald

    1995-01-01

    Transition-metal additives in cathodes of Na/NiCI(2) high-temperature, rechargeable electrochemical cells found to slow premature fading of charge/discharge capacity. Decline in capacity of cell attributed to agglomeration of Ni particles at cathode: this agglomeration reduces electrochemical area of cathode. Depending on choice of transition-metal additive for particular cell, additive might even participate in desired electrochemical reactions in cell, contributing to specific energy of cell.

  4. Ionothermal synthesis of open-framework metal phosphates with a Kagome lattice network exhibiting canted anti-ferromagnetism

    SciTech Connect

    Wang, Guangmei; Valldor, Martin; Mallick, Bert; Mudring, Anja-Verena

    2014-01-01

    Four open-framework transition-metal phosphates; (NH4)2Co3(HPO4)2F4 (1), (NH4)Co3(HPO4)2(H2PO4)F2 (2), KCo3(HPO4)2(H2PO4)F2 (3), and KFe3(HPO4)2(H2PO4)F2 (4); are prepared by ionothermal synthesis using pyridinium hexafluorophosphate as the ionic liquid. Single-crystal X-ray diffraction analyses reveal that the four compounds contain cobalt/iron–oxygen/fluoride layers with Kagomé topology composed of interlinked face-sharing MO3F3/MO4F2 octahedra. PO3OH pseudo-tetrahedral groups augment the [M3O6F4] (1)/[M3O8F2] layers on both sides to give M3(HPO4)2F4 (1) and M3(HPO4)2F2 (2–4) layers. These layers are stacked along the a axis in a sequence AA…, resulting in the formation of a layer structure for (NH4)2Co3(HPO4)2F4(1). In NH4Co3(HPO4)2(H2PO4)F2 and KM3(HPO4)2(H2PO4)F2, the M3(HPO4)2F2 layers are stacked along the a axis in a sequence AAi… and are connected by [PO3(OH)] tetrahedra, giving rise to a 3-D open framework structure with 10-ring channels along the [001] direction. The negative charges of the inorganic framework are balanced by K+/NH4+ ions located within the channels. The magnetic transition metal cations themselves form layers with stair-case Kagomé topology. Magnetic susceptibility and magnetization measurements reveal that all four compounds exhibit a canted anti-ferromagnetic ground state (Tc = 10 or 13 K for Co and Tc = 27 K for Fe) with different canting angles. The full orbital moment is observed for both Co2+ and Fe2+.

  5. Radial velocities and metallicities from infrared Ca ii triplet spectroscopy of open clusters. II. Berkeley 23, King 1, NGC 559, NGC 6603, and NGC 7245

    NASA Astrophysics Data System (ADS)

    Carrera, R.; Casamiquela, L.; Ospina, N.; Balaguer-Núñez, L.; Jordi, C.; Monteagudo, L.

    2015-06-01

    Context. Open clusters are key to studying the formation and evolution of the Galactic disc. However, there is a deficiency of radial velocity and chemical abundance determinations for open clusters in the literature. Aims: We intend to increase the number of determinations of radial velocities and metallicities from spectroscopy for open clusters. Methods: We acquired medium-resolution spectra (R ~ 8000) in the infrared region Ca ii triplet lines (~8500 Å) for several stars in five open clusters with the long-slit IDS spectrograph on the 2.5 m Isaac Newton Telescope (Roque de los Muchachos Observatory, Spain). Radial velocities were obtained by cross-correlation fitting techniques. The relationships available in the literature between the strength of infrared Ca ii lines and metallicity were also used to derive the metallicity for each cluster. Results: We obtain ⟨Vr⟩ = 48.6 ± 3.4, -58.4 ± 6.8, 26.0 ± 4.3, and -65.3 ± 3.2 km s-1 for Berkeley 23, NGC 559, NGC 6603, and NGC 7245, respectively. We found [ Fe/H ] = -0.25 ± 0.14 and -0.15 ± 0.18 for NGC 559 and NGC 7245, respectively. Berkeley 23 has low metallicity, [ Fe/H ] = -0.42 ± 0.13, which is similar to other open clusters in the outskirts of the Galactic disc. In contrast, we derived high metallicity ([ Fe/H ] = +0.43 ± 0.15) for NGC 6603, which places this system among the most metal-rich known open clusters. To our knowledge, this is the first determination of radial velocities and metallicities from spectroscopy for these clusters, except NGC 6603, for which radial velocities had been previously determined. We have also analysed ten stars in the line of sight to King 1. Because of the large dispersion obtained in both radial velocity and metallicity, we cannot be sure that we have sampled true cluster members. Based on observations made with the 2.5 m Isaac Newton Telescope operated on the island of La Palma by the Isaac Newton Group in the Spanish Observatorio del Roque de los Muchachos of the

  6. Metal-cluster-sensitized solar cells. A new class of thiolated gold sensitizers delivering efficiency greater than 2%.

    PubMed

    Chen, Yong-Siou; Choi, Hyunbong; Kamat, Prashant V

    2013-06-19

    A new class of metal-cluster sensitizers has been explored for designing high-efficiency solar cells. Thiol-protected gold clusters which exhibit molecular-like properties have been found to inject electrons into TiO2 nanostructures under visible excitation. Mesoscopic TiO2 films modified with gold clusters deliver stable photocurrent of 3.96 mA/cm(2) with power conversion efficiencies of 2.3% under AM 1.5 illumination. The overall absorption features and cell performance of metal-cluster-sensitized solar cells (MCSCs) are comparable to those of CdS quantum-dot-based solar cells (QDSCs). The relatively high open-circuit voltage of 832 mV and fill factor of 0.7 for MCSCs as compared to QDSCs show the viability of these new sensitizers as alternatives to semiconductor QDs and sensitizing dyes in the next generation of solar cells. The superior performance of MCSCs discussed in this maiden study lays the foundation to explore other metal clusters with broader visible absorption.

  7. High reduction of interfacial charge recombination in colloidal quantum dot solar cells by metal oxide surface passivation

    NASA Astrophysics Data System (ADS)

    Chang, Jin; Kuga, Yuki; Mora-Seró, Iván; Toyoda, Taro; Ogomi, Yuhei; Hayase, Shuzi; Bisquert, Juan; Shen, Qing

    2015-03-01

    Bulk heterojunction (BHJ) solar cells based on colloidal QDs and metal oxide nanowires (NWs) possess unique and outstanding advantages in enhancing light harvesting and charge collection in comparison to planar architectures. However, the high surface area of the NW structure often brings about a large amount of recombination (especially interfacial recombination) and limits the open-circuit voltage in BHJ solar cells. This problem is solved here by passivating the surface of the metal oxide component in PbS colloidal quantum dot solar cells (CQDSCs). By coating thin TiO2 layers onto ZnO-NW surfaces, the open-circuit voltage and power conversion efficiency have been improved by over 40% in PbS CQDSCs. Characterization by transient photovoltage decay and impedance spectroscopy indicated that the interfacial recombination was significantly reduced by the surface passivation strategy. An efficiency as high as 6.13% was achieved through the passivation approach and optimization for the length of the ZnO-NW arrays (device active area: 16 mm2). All solar cells were tested in air, and exhibited excellent air storage stability (without any performance decline over more than 130 days). This work highlights the significance of metal oxide passivation in achieving high performance BHJ solar cells. The charge recombination mechanism uncovered in this work could shed light on the further improvement of PbS CQDSCs and/or other types of solar cells.Bulk heterojunction (BHJ) solar cells based on colloidal QDs and metal oxide nanowires (NWs) possess unique and outstanding advantages in enhancing light harvesting and charge collection in comparison to planar architectures. However, the high surface area of the NW structure often brings about a large amount of recombination (especially interfacial recombination) and limits the open-circuit voltage in BHJ solar cells. This problem is solved here by passivating the surface of the metal oxide component in PbS colloidal quantum dot solar

  8. Lightweight Cellular Metals with High Structural Efficiency

    DTIC Science & Technology

    2003-09-01

    10-2 10-1 0.01 0.1 Open-Cell Closed-Cell ERG Fraunhofer Alulight Alporas Cymat Relative Density, ρ* /ρ s Closed-Cell Open-Cell 10-4 10-3 10-2 10-1...0.01 0.1 Open-Cell Closed-Cell ERG Fraunhofer Alulight Alporas Cymat Relative Density, ρ* /ρ s Closed-Cell Open-Cell Stochastic Foams: Modulus and...Structures NATO ARW 22 Stiffness limited design at minimum weight Applications of Cellular Metals Cymat , Inc. Messiah College Beams (free area), columns

  9. High photovoltage multiple-heterojunction organic solar cells incorporating interfacial metallic nanoclusters

    NASA Astrophysics Data System (ADS)

    Yakimov, A.; Forrest, S. R.

    2002-03-01

    We demonstrate high open circuit voltage (Voc) organic photovoltaic (PV) cells that incorporate two, three, or five stacked, thin heterojunctions (HJs) consisting of Cu-phthalocyanine as a donor, and 3,4,9,10 perylenetetracarboxylic bis-benzimidazole as an acceptor. Ultrathin (˜5 Å average thickness) layers of Ag clusters are placed between each HJ to serve as recombination centers for unpaired charges that are photogenerated in the device's interior. High power conversion efficiencies with high Voc have been demonstrated in cells containing up to five optically active HJs and four interstitial metallic recombination regions. The power conversion efficiencies of the two and three HJ cells under one sun, AM 1.5 illumination are ηp=2.5±0.1% and ηp 2.3±0.1%, with Voc=0.93±0.05 and 1.20±0.05 V, respectively. These values of ηp are more than twice that of a comparable single-junction cell based on the same materials, where ηp=1.1±0.1%.

  10. HOT CELL SYSTEM FOR DETERMINING FISSION GAS RETENTION IN METALLIC FUELS

    SciTech Connect

    Sell, D. A.; Baily, C. E.; Malewitz, T. J.; Medvedev, P. G.; Porter, D. L.; Hilton, B. A.

    2016-09-01

    A system has been developed to perform measurements on irradiated, sodium bonded-metallic fuel elements to determine the amount of fission gas retained in the fuel material after release of the gas to the element plenum. During irradiation of metallic fuel elements, most of the fission gas developed is released from the fuel and captured in the gas plenums of the fuel elements. A significant amount of fission gas, however, remains captured in closed porosities which develop in the fuel during irradiation. Additionally, some gas is trapped in open porosity but sealed off from the plenum by frozen bond sodium after the element has cooled in the hot cell. The Retained fission Gas (RFG) system has been designed, tested and implemented to capture and measure the quantity of retained fission gas in characterized cut pieces of sodium bonded metallic fuel. Fuel pieces are loaded into the apparatus along with a prescribed amount of iron powder, which is used to create a relatively low melting, eutectic composition as the iron diffuses into the fuel. The apparatus is sealed, evacuated, and then heated to temperatures in excess of the eutectic melting point. Retained fission gas release is monitored by pressure transducers during the heating phase, thus monitoring for release of fission gas as first the bond sodium melts and then the fuel. A separate hot cell system is used to sample the gas in the apparatus and also characterize the volume of the apparatus thus permitting the calculation of the total fission gas release from the fuel element samples along with analysis of the gas composition.

  11. Protection of open-metal V(III) sites and their associated CO₂/CH₄/N₂/O₂/H₂O adsorption properties in mesoporous V-MOFs.

    PubMed

    Yang, Jiangfeng; Wang, Yong; Li, Libo; Zhang, Zhuoming; Li, Jinping

    2015-10-15

    Metal-organic frameworks with open metal site are potential sorbents for the separation of gas mixtures; however, low valence metal will bind to oxygen in the open air causing a decrease in adsorption ability. We now report open-metal sites V(III) on both MIL-100V(III/IV) and MIL-101V(III/IV) that can be protected with water molecules, and which associated CO2/CH4/N2/O2 adsorption properties on these two mesoporous V-MOFs were investigated. The protective properties of water were investigated and evaluated using density functional theory simulations. The binding energy of single O2 on open-metal V(III) site was 93.278 kJ/mol, which decreased to 26.5 kJ/mol when H2O occupies the site. When the water coating is removed, the X-ray photoelectron spectroscopy pattern of V2p showed that the V-MOF changes to MIL-100V(IV) and MIL-101V(IV) at 298 K because of the action of O2. Under these conditions, O2 binds strongly on the open V site significantly reducing the BET (Brunauer-Emmett-Teller) surface and CH4 adsorption volume of the V-MOFs. From the ideal adsorbed solution theory calculated, the adsorption selectivity of CH4/N2 is higher before than after binding of O2 (with V(III) site). In contrast, the adsorption selectivity of CO2/CH4 is higher after than before O2 binding (with no more V(III) sites). Copyright © 2015 Elsevier Inc. All rights reserved.

  12. Thermocleavable materials for polymer solar cells with high open circuit voltage-a comparative study.

    PubMed

    Tromholt, Thomas; Gevorgyan, Suren A; Jørgensen, Mikkel; Krebs, Frederik C; Sylvester-Hvid, Kristian O

    2009-12-01

    The search for polymer solar cells giving a high open circuit voltage was conducted through a comparative study of four types of bulk-heterojunction solar cells employing different photoactive layers. As electron donors the thermo-cleavable polymer poly-(3-(2-methylhexyloxycarbonyl)dithiophene) (P3MHOCT) and unsubstituted polythiophene (PT) were used, the latter of which results from thermo cleaving the former at 310 degrees C. As reference, P3HT solar cells were built in parallel. As electron acceptors, either PCBM or bis-[60]PCBM were used. In excess of 300 solar cells were produced under as identical conditions as possible, varying only the material combination of the photo active layer. It was observed that on replacing PCBM with bis[60]PCBM, the open circuit voltage on average increased by 100 mV for P3MHOCT and 200 mV for PT solar cells. Open circuit voltages approaching 1 V were observed for the PT:bis[60]PCBM solar cells and a maximum conversion efficiency of 1.3% was obtained for solar cells with P3MHOCT:PCBM as the photoactive material. For the reference solar cells maximum efficiencies of 2.1 and 2.4% were achieved for P3HT:PCBM and P3HT:bis[60]PCBM, respectively. Despite special measures taken in terms of substrate design and device processing, a substantial spread in the photovoltaic properties was generally observed. This spread could not be correlated with the optical properties of the solar cells, the thickness of the photo active layer or the electrode deposition conditions of the aluminum top electrode.

  13. The emerging multiple metal nanostructures for enhancing the light trapping of thin film organic photovoltaic cells.

    PubMed

    Choy, Wallace C H

    2014-10-18

    Recently, various metal nanostructures have been introduced into organic solar cells (OSCs) for performance enhancement. Here, we review the recent progress in OSCs incorporated with multiple metal nanostructures including various metal nanopatterns and metal nanomaterials. Multiple physical effects arise from these incorporated nanostructures, which require careful distinction. Changes induced by the metal nanostructures are examined in detail from the optical and electrical aspects. With the comprehensive understanding of the physical mechanisms for various metal nanostructures, further improvement in device performance and emerging applications can be expected for the new class of nanostructure-incorporated OSCs.

  14. An investigation of the microstructure and strength of open-cell 6101 aluminum foams

    NASA Astrophysics Data System (ADS)

    Zhou, J.; Mercer, C.; Soboyejo, W. O.

    2002-05-01

    This article presents the results of a study of the microstructure and strength of open-cell 6101 aluminum alloy fans with three different levels of pore size (measured in pores per inch (PPI)). The macrostructures and microstructures of open-cell foam struts are characterized using a combination of optical and scanning electron microscopy (SEM). The compositions of the individual phases are also determined via energy-dispersive spectroscopy (EDS). The variations in strut microhardness are then measured using Vickers microindentation techniques. Following the measurement of the mechanical properties of foams, a modified model is used to estimate the relative density from measured strut dimensions. The mechanisms of compressive deformation are then elucidated before presenting a discussion on unit-cell modeling, strut plastic deformation, and the relationships between strut microstructure and microhardness.

  15. Metal ion bombardment of onion skin cell wall

    SciTech Connect

    Sangyuenyongpipat, S.; Vilaithong, T.; Yu, L.D.; Verdaguer, A.; Ratera, I.; Ogletree, D.F.; Monteiro, O.R.; Brown, I.G.

    2004-05-10

    Ion bombardment of living cellular material is a novel subfield of ion beam surface modification that is receiving growing attention from the ion beam and biological communities. Although it has been demonstrated that the technique is sound, in that an adequate fraction of the living cells can survive both the vacuum environment and energetic ion bombardment, there remains much uncertainty about the process details. Here we report on our observations of onion skin cells that were subjected to ion implantation, and propose some possible physical models that tend to support the experimental results. The ion beams used were metallic (Mg, Ti, Fe, Ni, Cu), mean ion energy was typically 30keV, and the implantation fluence was in the range 1014 1016 ions/cm2. The cells were viewed using Atomic Force Microscopy, revealing the formation of microcrater-like structures due to ion bombardment. The implantation depth profile was measured with Rutherford backscattering spectrometry and compared to the results of the TRIM, T-DYN and PROFILE computer codes.

  16. Metal ion bombardment of onion skin cell wall

    NASA Astrophysics Data System (ADS)

    Sangyuenyongpipat, S.; Vilaithong, T.; Yu, L. D.; Verdaguer, A.; Ratera, I.; Ogletree, D. F.; Monteiro, O. R.; Brown, I. G.

    2005-01-01

    Ion bombardment of living cellular material is a novel subfield of ion beam surface modification that is receiving growing attention from the ion beam and biological communities. Although it has been demonstrated that the technique is sound, in that an adequate fraction of the living cells can survive both the vacuum environment and energetic ion bombardment, there remains much uncertainty about the process details. Here we report on our observations of onion skin cells that were subjected to ion implantation, and propose some possible physical models that tend to support the experimental results. The ion beams used were metallic (Mg, Ti, Fe, Ni, Cu), mean ion energy was typically 30 keV, and the implantation fluence was in the range 1014-1016 ions/cm2. The cells were viewed using Atomic Force Microscopy, revealing the formation of microcrater-like structures due to ion bombardment. The implantation depth profile was measured with Rutherford backscattering spectrometry and compared to the results of the TRIM, T-DYN and PROFILE computer codes.

  17. Moderate temperature sodium cells. I - Transition metal disulfide cathodes

    NASA Technical Reports Server (NTRS)

    Abraham, K. M.; Pitts, L.; Schiff, R.

    1980-01-01

    TiS2, VS2, and Nb(1.1)S2 transition metal disulfides were evaluated as cathode materials for a moderate temperature rechargeable Na cell operating at 130 C. The 1st discharge of TiS2 results in a capacity of 0.85 eq/mole; approximately half of the Na in the 1st phase spanning the Na range from zero to 0.30 and almost all the Na in the 2nd phase spanning the 0.37 to 0.80 range are rechargeable. VS2 intercalates up to one mole of Na/mole of VS2 in the 1st discharge; the resulting Na(x)VS2 ternary consists of 3 phases in the 3 ranges of Na from zero to 1. Niobium disulfide undergoes a phase change in the 1st discharge; the average rechargeable capacity in extended cycling of this cathode is 0.50 eq/mole.

  18. Screenable silver and base metal solar cell contacts

    NASA Technical Reports Server (NTRS)

    Ross, B.

    1980-01-01

    The metallurgical soundness of the all-metal screenable thick film electrode system is established for silver and copper electrodes. Silver fluoride was identified as a successful etchant material and is found most effective in the liquid phase (435-460 C). Best results were achieved with the eutectic alloys of dopants and semiconductors. The air-fired silver inks were strongly adherent, rugged, and solderable, whereas the hydrogen-fired silver inks had very poor adhesion. A two-step firing process was devised in which copper inks containing silver fluoride were activated in a nitrogen atmosphere, with sintering done at the same or higher temperatures in hydrogen. Good solar cells were made using the copper paste back contacts demonstrating that the electrodes are not the limiting factors in efficiency.

  19. Metal-sulfur type cell having improved positive electrode

    NASA Astrophysics Data System (ADS)

    Dejonghe, Lutgard C.; Visco, Steven J.; Mailhe, Catherine C.; Armand, Michel B.

    1988-03-01

    A novel metal-sulfur type cell operable at a temperature of 200 C or less with an energy density of 150 Whrs/Kg or better is disclosed characterized by an organo-sulfur cathode formed from an organic-sulfur compound having the general formula, in its charged state, of (R(S) sub y) n wherein y = 1 to 6; n = 2 to 20; and R is one or more different aliphatic or aromatic organic moieties having 1 to 20 carbon atoms, which may include one or more oxygen, sulfur, or nitrogen heteroatoms when R comprises one or more aromatic rings, or one or more oxygen, sulfur, nitrogen, or fluorine atoms associated with the chain when R comprises an aliphatic chain, wherein the aliphatic group may be linear or branched, saturated or unsaturated, and wherein either the aliphatic chain or the aromatic ring may have substituted groups thereon.

  20. Metal-sulfur type cell having improved positive electrode

    DOEpatents

    DeJonghe, L.C.; Visco, S.J.; Mailhe, C.C.; Armand, M.B.

    1988-03-31

    A novel metal-sulfur type cell operable at a temperature of 200/degree/C or less with an energy density of 150 Whrs/Kg or better is disclosed characterized by an organo-sulfur cathode formed from an organic-sulfur compound having the general formula, in its charged state, of (R(S)/sub y/)n wherein y = 1 to 6; n = 2 to 20; and R is one or more different aliphatic or aromatic organic moieties having 1 to 20 carbon atoms, which may include one or more oxygen, sulfur, or nitrogen heteroatoms when R comprises one or more aromatic rings, or one or more oxygen, sulfur, nitrogen, or fluorine atoms associated with the chain when R comprises an aliphatic chain, wherein the aliphatic group may be linear or branched, saturated or unsaturated, and wherein either the aliphatic chain or the aromatic ring may have substituted groups thereon. 4 figs.

  1. Metal-sulfur type cell having improved positive electrode

    DOEpatents

    Dejonghe, Lutgard C.; Visco, Steven J.; Mailhe, Catherine C.; Armand, Michel B.

    1989-01-01

    An novel metal-sulfur type cell operable at a temperature of 200.degree. C. or less with an energy density of 150 Whrs/Kg or better is disclosed characterized by an organo-sulfur cathode formed from an organic-sulfur compound having the general formula, in its charged state, of (R(S).sub.y).sub.n wherein y=1 to 6; n=2 to 20; and R is one or more different aliphatic or aromatic organic moieties having 1 to 20 carbon atoms, which may include one or more oxygen, sulfur, or nitrogen heteroatoms when R comprisises one of more aromatic rings, or one or more oxygen, sulfur, nitrogen, or fluorine atoms associtated with the chain when R comprises an aliphatic chain, wherein the aliphatic group may be linear or branched, saturated or unsaturated, and wherein either the aliphatic chain or the aromatic ring may have substituted groups thereon.

  2. Differential biofilms characteristics of Shewanella decolorationis microbial fuel cells under open and closed circuit conditions.

    PubMed

    Yang, Yonggang; Sun, Guoping; Guo, Jun; Xu, Meiying

    2011-07-01

    Biofilms formation capacities of Shewanella species in microbial fuel cells (MFCs) and their roles in current generation have been documented to be species-dependent. Understandings of the biofilms growth and metabolism are essential to optimize the current generation of MFCs. Shewanella decolorationis S12 was used in both closed-circuit and open-circuit MFCs in this study. The anodic S. decolorationis S12 biofilms could generate fivefold more current than the planktonic cells, playing a dominant role in current generation. Anodic biofilms viability was sustained at 98 ± 1.2% in closed-circuit while biofilms viability in open-circuit decreased to 72 ± 7% within 96 h. The unviable domain in open-circuit MFCs biofilms majorly located at the inner layer of biofilm. The decreased biofilms viability in open-circuit MFCs could be recovered by switching into closed-circuit, indicating that the current-generating anode in MFCs could serve as a favorable electron acceptor and provide sufficient energy to support cell growth and metabolism inside biofilms.

  3. Investigation of the open-circuit voltage in solar cells doped with quantum dots

    PubMed Central

    Tayagaki, Takeshi; Hoshi, Yusuke; Usami, Noritaka

    2013-01-01

    Quantum dots (QDs) have attracted much attention for use in photovoltaic applications because of their potential for overcoming the limits of conventional single-junction devices. One problem associated with solar cells using QDs is that the open-circuit voltage (Voc) always decreases with the addition of QDs with respect to the reference cell without QDs. Here, we report the investigation of current–voltage characteristics in Ge/Si QD solar cells in the temperature range from 100 to 300 K. We show that even though Voc decreases with increasing temperature, it depends on the nominal Ge thickness, indicating that Voc reduction is primarily caused by a decrease in the bandgap energy of the cell. From photoluminescence decay measurements, we found that rapid carrier extraction from QDs occurred in the solar cells; this process eliminates the quasi-Fermi energy splitting between the QDs and the host semiconductor and causes Voc reduction in QD solar cells. PMID:24067805

  4. High Open-Circuit Voltage Solar Cells Based on Organic-Inorganic Lead Bromide Perovskite.

    PubMed

    Edri, Eran; Kirmayer, Saar; Cahen, David; Hodes, Gary

    2013-03-21

    Mesoscopic solar cells, based on solution-processed organic-inorganic perovskite absorbers, are a promising avenue for converting solar to electrical energy. We used solution-processed organic-inorganic lead halide perovskite absorbers, in conjunction with organic hole conductors, to form high voltage solar cells. There is a dire need for low-cost cells of this type, to drive electrochemical reactions or as the high photon energy cell in a system with spectral splitting. These perovskite materials, although spin-coated from solution, form highly crystalline materials. Their simple synthesis, along with high chemical versatility, allows tuning their electronic and optical properties. By judicious selection of the perovskite lead halide-based absorber, matching organic hole conductor, and contacts, a cell with a ∼ 1.3 V open circuit voltage was made. While further study is needed, this achievement provides a general guideline for additional improvement of cell performance.

  5. The effect of hydrogen crossover on open-circuit voltage in polymer electrolyte membrane fuel cells

    NASA Astrophysics Data System (ADS)

    Vilekar, Saurabh A.; Datta, Ravindra

    Even though the measured open-circuit voltage in a H 2-O 2 PEM fuel cell is invariably about 200-250 mV lower than that predicted from thermodynamics (1.229 V at 25 °C), there is no unequivocal explanation of this phenomenon available in the literature, although several hypotheses exist. Based on a theoretical model of mixed potential with a priori parameters, it is shown here that this voltage loss under open-circuit conditions can be attributed exclusively to hydrogen crossover and the resulting oxygen reduction reaction overpotential at the cathode. The analytical model predictions agree well with available experimental results.

  6. Solar cells in bulk InP using an open tube diffusion process

    NASA Technical Reports Server (NTRS)

    Parat, K. K.; Bothra, S.; Borrego, J. M.; Ghandhi, S. K.

    1987-01-01

    A simple open tube diffusion technique for the fabrication of n+p junction solar cells is described. Large area (greater than 0.25 square cm) solar cells have been made by this process with a photovoltaic conversion efficiency of 15.2 percent under simulated AMO illumination. An ideality factor is 1.04 and a saturation current density of 9.6 times 10 to the minus 16th power A/square cm have been observed for these cells. These are the lowest (best) values reported to date for diffused structures in bulk InP.

  7. Defining the Velocity Field of Root Cells in Arabidopsis Seedlings Using Open Source Image Processing Tools

    NASA Astrophysics Data System (ADS)

    Craig, Amy E.; Higgins, Brad R.; Guy, Tracy; Durham Brooks, Tessa; Wentworth, Christopher D.

    2011-11-01

    The velocity field for cells in a growing root is a function of a cell's position with respect to the root apex and time. For many species of plant this function has the same general sigmoid shape described by a modified logistics curve. In this investigation we obtain microscopic images of Arabidopsis seedling roots over a 20 minute period of time, measure the velocity field for root cells using an application developed with the open source mathematics application Octave, and test whether the velocity field can be described by the modified logistics function. We find support for describing the velocity field by the modified logistics function.

  8. Solvothermal synthesis of new open-framework metal phosphites with structure-directing agents generated in situ

    NASA Astrophysics Data System (ADS)

    Xue, Li; Luo, Daibing; Luo, Xiuchao; Zeng, Hongmei; Lin, Zhien

    2013-05-01

    By using amide molecules and a urea derivative as the source of structure-directing agents (SDAs), three open-framework metal phosphites, (CH3NH3)2·[Be3(HPO3)4] (1), (CH3CH2NH3)2·[Be3(HPO3)4] (2), and [(CH3)2NH2]1.5·(H3O)0.5·[Al4(HPO3)7(H2O)3]·(H2O)0.5 (3), have been synthesized under solvothermal conditions. Compound 1 has left- and right-handed helical channels running along the [001] directions. Compound 2 possesses zigzag 12-ring channels running along the [001] direction. Compound 3 contains multidirectional 12-ring channels running along the [100], [010], and [110] directions. It is noteworthy that the direct use of methylamine, ethylamine and dimethylamine as SDAs can't produce corresponding single crystals of compounds 1-3, demonstrating the slow release of amines from amide molecules and urea derivative is a key process for the crystal growth.

  9. Mechanistic Investigations of the Stereoselective Rare Earth Metal-Mediated Ring-Opening Polymerization of β-Butyrolactone.

    PubMed

    Altenbuchner, Peter T; Kronast, Alexander; Kissling, Stefan; Vagin, Sergei I; Herdtweck, Eberhardt; Pöthig, Alexander; Deglmann, Peter; Loos, Robert; Rieger, Bernhard

    2015-09-21

    Poly(3-hydroxybutyrate) (PHB) is produced by numerous bacteria as carbon and energy reserve storage material. Whereas nature only produces PHB in its strictly isotactic (R) form, homogeneous catalysis, when starting from racemic (rac) β-butyrolactone (BL) as monomer, can in fact produce a wide variety of tacticities. The variation of the metal center and the surrounding ligand structure enable activity as well as tacticity tuning. However, no homogeneous catalyst exists to date that is easy to modify, highly active, and able to produce PHB with high isotacticities from rac-β-BL. Therefore, in this work, the reaction kinetics of various 2-methoxyethylamino-bis(phenolate) lanthanide (Ln=Sm, Tb, Y, Lu) catalysts are examined in detail. The order in monomer and catalyst are determined to elucidate the reaction mechanism and the results are correlated with DFT calculations of the catalytic cycle. Furthermore, the enthalpies and entropies of the rate-determining steps are determined through temperature-dependent in situ IR measurements. Experimental and computational results converge in one specific mechanism for the ring-opening polymerization of BL and even allow us to rationalize the preference for syndiotactic PHB.

  10. Comparative study on open system digestion and microwave assisted digestion methods for metal determination in shrimp sludge compost.

    PubMed

    Nemati, Keivan; Abu Bakar, Nor Kartini; Bin Abas, Mhd Radzi; Sobhanzadeh, Elham; Low, Kah Hin

    2010-10-15

    The aim of this work was to evaluate two different digestion methods for the determination of the total concentration of metals (Zn, Cu, Cr, Ni, Pb and Cd) in shrimp sludge compost. The compost made from shrimp aquaculture sludge co-composted with organic materials (peat, crushed bark and manure) was used as an organic growing medium for crop. Open system digestion and microwave assisted digestion procedures were employed in sample preparation. Various combinations and volumes of hydrofluoric, nitric and hydrochloric acids were evaluated for the efficiency of both methods. A certified reference material (CRM 146) was used in the comparison of these two digestion methods. The results revealed a good agreement between both procedures and the certified valued. The best recoveries were found in the range between 95% and 99% for microwave assisted digestion with a mixture of 2 ml of HF, 6 ml of HNO(3) and 2 ml of HCl. This procedure was recommended as the method for digestion the compost herein based on the recovery analysis and time taken.

  11. Optical design of transparent metal grids for plasmonic absorption enhancement in ultrathin organic solar cells.

    PubMed

    Kim, Inho; Lee, Taek Seong; Jeong, Doo Seok; Lee, Wook Seong; Kim, Won Mok; Lee, Kyeong-Seok

    2013-07-01

    Transparent metal grid combining with plasmonic absorption enhancement is a promising replacement to indium tin oxide thin films. We numerically demonstrate metal grids in one or two dimension lead to plasmonic absorption enhancements in ultrathin organic solar cells. In this paper, we study optical design of metal grids for plasmonic light trapping and identify different plasmonic modes of the surface plasmon polaritons excited at the interfaces of glass/metal grids, metal grids/active layers, and the localized surface plasmon resonance of the metal grids using numerical calculations. One dimension metal grids with the optimal design of a width and a period lead to the absorption enhancement in the ultrathin active layers of 20 nm thickness by a factor of 2.6 under transverse electric polarized light compared to the case without the metal grids. Similarly, two dimensional metal grids provide the absorption enhancement by a factor of 1.8 under randomly polarized light.

  12. Facilitation of trace metal uptake in cells by inulin coating of metallic nanoparticles

    PubMed Central

    Santillán-Urquiza, Esmeralda; Arteaga-Cardona, Fernando; Torres-Duarte, Cristina; Cole, Bryan; Wu, Bing; Méndez-Rojas, Miguel A.

    2017-01-01

    Trace elements such as zinc and iron are essential for the proper function of biochemical processes, and their uptake and bioavailability are dependent on their chemical form. Supplementation of trace metals through nanostructured materials is a new field, but its application raises concerns regarding their toxicity. Here, we compared the intracellular zinc uptake of different sources of zinc: zinc sulfate, and ZnO and core-shell α-Fe2O3@ZnO nanoparticles, coated or uncoated with inulin, an edible and biocompatible polysaccharide. Using mussel haemocytes, a well-known model system to assess nanomaterial toxicity, we simultaneously assessed zinc accumulation and multiple cellular response endpoints. We found that intracellular zinc uptake was strongly enhanced by inulin coating, in comparison to the uncoated nanoparticles, while no significant effects on cell death, cell viability, mitochondrial membrane integrity, production of reactive oxygen species or lysosome abundance were observed at concentrations up to 20 ppm. Since no significant increments in toxicity were observed, the coated nanomaterials may be useful to increase in vivo zinc uptake for nutritional applications. PMID:28989755

  13. Facilitation of trace metal uptake in cells by inulin coating of metallic nanoparticles.

    PubMed

    Santillán-Urquiza, Esmeralda; Arteaga-Cardona, Fernando; Torres-Duarte, Cristina; Cole, Bryan; Wu, Bing; Méndez-Rojas, Miguel A; Cherr, Gary N

    2017-09-01

    Trace elements such as zinc and iron are essential for the proper function of biochemical processes, and their uptake and bioavailability are dependent on their chemical form. Supplementation of trace metals through nanostructured materials is a new field, but its application raises concerns regarding their toxicity. Here, we compared the intracellular zinc uptake of different sources of zinc: zinc sulfate, and ZnO and core-shell α-Fe2O3@ZnO nanoparticles, coated or uncoated with inulin, an edible and biocompatible polysaccharide. Using mussel haemocytes, a well-known model system to assess nanomaterial toxicity, we simultaneously assessed zinc accumulation and multiple cellular response endpoints. We found that intracellular zinc uptake was strongly enhanced by inulin coating, in comparison to the uncoated nanoparticles, while no significant effects on cell death, cell viability, mitochondrial membrane integrity, production of reactive oxygen species or lysosome abundance were observed at concentrations up to 20 ppm. Since no significant increments in toxicity were observed, the coated nanomaterials may be useful to increase in vivo zinc uptake for nutritional applications.

  14. An open-chamber flow-focusing device for focal stimulation of micropatterned cells

    PubMed Central

    Chang, Tim C.; Bhattacharjee, Nirveek; Folch, Albert

    2016-01-01

    Microfluidic devices can deliver soluble factors to cell and tissue culture microenvironments with precise spatiotemporal control. However, enclosed microfluidic environments often have drawbacks such as the need for continuous culture medium perfusion which limits the duration of experiments, incongruity between microculture and macroculture, difficulty in introducing cells and tissues, and high shear stress on cells. Here, we present an open-chamber microfluidic device that delivers hydrodynamically focused streams of soluble reagents to cells over long time periods (i.e., several hours). We demonstrate the advantage of the open chamber by using conventional cell culture techniques to induce the differentiation of myoblasts into myotubes, a process that occurs in 7–10 days and is difficult to achieve in closed chamber microfluidic devices. By controlling the flow rates and altering the device geometry, we produced sharp focal streams with widths ranging from 36 μm to 187 μm. The focal streams were reproducible (∼12% variation between units) and stable (∼20% increase in stream width over 10 h of operation). Furthermore, we integrated trenches for micropatterning myoblasts and microtraps for confining single primary myofibers into the device. We demonstrate with finite element method (FEM) simulations that shear stresses within the cell trench are well below values known to be deleterious to cells, while local concentrations are maintained at ∼22% of the input concentration. Finally, we demonstrated focused delivery of cytoplasmic and nuclear dyes to micropatterned myoblasts and myofibers. The open-chamber microfluidic flow-focusing concept combined with micropatterning may be generalized to other microfluidic applications that require stringent long-term cell culture conditions. PMID:27158290

  15. Gravure-Offset Printed Metallization of Multi-Crystalline Silicon Solar Cells with Low Metal-Line Width for Mass Production.

    PubMed

    Lee, Jonghwan; Jeong, Chaehwan

    2016-05-01

    The gravure offset method has been developed toward an industrially viable printing technique for electronic circuitry. In this paper, a roller type gravure offset manufacturing process was developed to fabricate fine line for using front electrode for solar cells. In order to obtain the optimum metallization printing lines, thickness of 20 μm which is narrow line is required. The main targets are the reduction of metallized area to reduce the shading loss, and a high conductivity to transport the current as loss free as possible out of the cell. However, it is well known that there is a poor contact resistance between the front Ag electrode and the n(+) emitter. Nickel plating was conducted to prevent the increase of contact resistance and the increase of fill factor (FF). The performance of n-Si/Ag (seed layer)/Ni solar cells were observed in 609 mV of open circuit voltage, 35.54 mA/cm2 of short circuit current density, 75.75% of fill factor, and 16.04% of conversion efficiency.

  16. Correlation of open cell-attached and excised patch clamp techniques.

    PubMed

    Filipovic, D; Hayslett, J P

    1995-11-01

    The excised patch clamp configuration provides a unique technique for some types of single channel analyses, but maintenance of stable, long-lasting preparations may be confounded by rundown and/or rapid loss of seal. Studies were performed on the amiloride-sensitive Na+ channel, located on the apical surface of A6 cells, to determine whether the nystatin-induced open cell-attached patch could serve as an alternative configuration. Compared to excised inside-out patches, stable preparations were achieved more readily with the open cell-attached patch (9% vs. 56% of attempts). In both preparations, the current voltage (I-V) relation was linear, current amplitudes were equal at opposite equivalent clamped voltages, and Erev was zero in symmetrical Na+ solutions, indicating similar Na+ activities on the cytosolic and external surfaces of the patch. Moreover, there was no evidence that nystatin altered channel activity in the patch because slope conductance (3-4pS) and Erev (75 mV), when the bath was perfused with a high K:low Na solution (ENa = 80 mV), were nearly equal in both patch configurations. Our results therefore indicate that the nystatin-induced open cell-attached patch can serve as an alternative approach to the excised inside-out patch when experiments require modulation of univalent ions in the cytosol.

  17. Fluorescent metal nanoshell and CK19 detection on single cell image

    SciTech Connect

    Zhang, Jian; Fu, Yi; Li, Ge; Lakowicz, Joseph R.; Zhao, Richard Y.

    2011-09-16

    Highlights: {yields} Novel metal nanoshell as fluorescence imaging agent. {yields} Fluorescent mAb-metal complex with enhanced intensity and shortened lifetime. {yields} Immuno-interactions of mAb-metal complexes with CK19 molecules on CNCAP and HeLa cell surfaces. {yields} Isolation of conjugated mAb-metal complexes from cellular autofluorescence on cell image. -- Abstract: In this article, we report the synthesis strategy and optical properties of a novel type of fluorescence metal nanoshell when it was used as imaging agent for fluorescence cell imaging. The metal nanoshells were made with 40 nm silica cores and 10 nm silver shells. Unlike typical fluorescence metal nanoshells which contain the organic dyes in the cores, novel metal nanoshells were composed of Cy5-labelled monoclonal anti-CK19 antibodies (mAbs) on the external surfaces of shells. Optical measurements to the single nanoparticles showed that in comparison with the metal free labelled mAbs, the mAb-Ag complexes displayed significantly enhanced emission intensity and dramatically shortened lifetime due to near-field interactions of fluorophores with metal. These metal nanoshells were found to be able to immunoreact with target cytokeratin 19 (CK19) molecules on the surfaces of LNCAP and HeLa cells. Fluorescence cell images were recorded on a time-resolved confocal microscope. The emissions from the metal nanoprobes could be clearly isolated from the cellular autofluorescence backgrounds on the cell images as either individuals or small clusters due to their stronger emission intensities and shorter lifetimes. These emission signals could also be precisely counted on single cell images. The count number may provide an approach for quantifying the target molecules in the cells.

  18. Induced Pluripotent Stem Cells Restore Function in a Human Cell Loss Model of Open-Angle Glaucoma

    PubMed Central

    Abu-Hassan, Diala W; Li, Xinbo; Ryan, Eileen I; Acott, Ted S; Kelley, Mary J

    2015-01-01

    Normally, trabecular meshwork (TM) and Schlemm's canal inner wall endothelial cells within the aqueous humor outflow pathway maintain intraocular pressure within a narrow safe range. Elevation in intraocular pressure, because of the loss of homeostatic regulation by these outflow pathway cells, is the primary risk factor for vision loss due to glaucomatous optic neuropathy. A notable feature associated with glaucoma is outflow pathway cell loss. Using controlled cell loss in ex vivo perfused human outflow pathway organ culture, we developed compelling experimental evidence that this level of cell loss compromises intraocular pressure homeostatic function. This function was restored by repopulation of the model with fresh TM cells. We then differentiated induced pluripotent stem cells (iPSCs) and used them to repopulate this cell depletion model. These differentiated cells (TM-like iPSCs) became similar to TM cells in both morphology and expression patterns. When transplanted, they were able to fully restore intraocular pressure homeostatic function. This successful transplantation of TM-like iPSCs establishes the conceptual feasibility of using autologous stem cells to restore intraocular pressure regulatory function in open-angle glaucoma patients, providing a novel alternative treatment option. Stem Cells 2015;33:751–761 PMID:25377070

  19. Induced pluripotent stem cells restore function in a human cell loss model of open-angle glaucoma.

    PubMed

    Abu-Hassan, Diala W; Li, Xinbo; Ryan, Eileen I; Acott, Ted S; Kelley, Mary J

    2015-03-01

    Normally, trabecular meshwork (TM) and Schlemm's canal inner wall endothelial cells within the aqueous humor outflow pathway maintain intraocular pressure within a narrow safe range. Elevation in intraocular pressure, because of the loss of homeostatic regulation by these outflow pathway cells, is the primary risk factor for vision loss due to glaucomatous optic neuropathy. A notable feature associated with glaucoma is outflow pathway cell loss. Using controlled cell loss in ex vivo perfused human outflow pathway organ culture, we developed compelling experimental evidence that this level of cell loss compromises intraocular pressure homeostatic function. This function was restored by repopulation of the model with fresh TM cells. We then differentiated induced pluripotent stem cells (iPSCs) and used them to repopulate this cell depletion model. These differentiated cells (TM-like iPSCs) became similar to TM cells in both morphology and expression patterns. When transplanted, they were able to fully restore intraocular pressure homeostatic function. This successful transplantation of TM-like iPSCs establishes the conceptual feasibility of using autologous stem cells to restore intraocular pressure regulatory function in open-angle glaucoma patients, providing a novel alternative treatment option. © 2014 The Authors. STEM CELLS Published by Wiley Periodicals, Inc. on behalf of AlphaMed Press.

  20. Autoimmunity-inducing metals (Hg, Au and Ag) modulate mast cell signaling, function and survival.

    PubMed

    Suzuki, Yoshihiro; Inoue, Toshio; Ra, Chisei

    2011-11-01

    The three heavy metals, mercury, gold and silver commonly and specifically induce aberrant immunological responses leading to autoimmune disorders in genetically susceptible animals and humans. The disorders are characterized by autoantibody production, increases in serum IgG and IgE, polyclonal activation of B and T lymphocytes and renal immune complex deposition and glomerulonephritis. Mast cells play key roles in allergic and inflammatory reactions. A growing body of evidence suggests that mast cells are key players in innate and adaptive immunity and involved in autoimmune diseases. Mast cells are also direct targets for autoimmunity-inducing metals both in vitro and in vivo and play a role in the development of metal-induced autoimmune disorders. The three metals specifically modulate mast cell function, including degranulation and secretion of arachidonic acid metabolites and cytokines such as interleukin-4. Divergent signaling components, including mitogen-activated protein kinase activation, reactive oxygen and nitric oxide generation and Ca2+ influx are modulated by the metals. Furthermore, the metals have considerable impacts on mast cell survival, which also species seems to be involved in the development of metal-induced autoimmune disorders. In this review, we provide an overview of recent advances in our understanding of the impacts of the three metals on mast cell signaling, function and survival and their possible roles in the pathologies of metal-induced autoimmunity.

  1. Enhanced fluorescence cell imaging with metal-coated slides

    NASA Astrophysics Data System (ADS)

    Le Moal, Eric; Fort, Emmanuel; Lévêque-Fort, Sandrine; Janin, Anne; Murata, Hideyuki; Cordelières, Fabrice P.

    2007-07-01

    The last decade has witnessed momentous advances in fluorescence microscopy. The introduction of novel fluorescent markers, together with the development of original microscopy techniques, made it possible to study biomolecular interactions in living cells and to examine the structure and function of living tissues. The emergence of these innovative techniques had a remarkable impact on all the life sciences. However, many biological and medical applications involve the detection of minute quantities of biomolecules, and are limited by the signal weakness in common observation conditions. Here, we show that silver and gold-coated microscope slides can be used as mirror substrates to efficiently improve detection sensitivity when fluorescence microscopy is applied to micrometer-thick biological samples. We report a fourfold enhancement of the fluorescence signal and a noticeable strengthening of the image contrast, when mirror substrates are used with standard air microscope objectives. We demonstrate that metal-coated substrates provide the means to get sensitivity-enhanced fluorescence detection with dry optics, while keeping a wide field observation and a large depth of field. This is a crucial advantage for automated and high-throughput applications to cell and tissue diagnostic analysis.

  2. Development of high performance sodium/metal chloride cells

    NASA Astrophysics Data System (ADS)

    Vissers, D. R.; Bloom, I. D.; Hash, M. C.; Redey, L.; Hammer, C. L.; Dees, D. W.; Nelson, P. A.

    Sodium/metal chloride (MCl2) cells and batteries are being studied at Argonne National Laboratory (ANL) for stationary energy storage and transportation applications. The work is being directed toward (1) development of thin, high capacity density electrodes and inexpensive beta double prime alumina-glass composite electrolyte materials to replace beta double prime alumina, and (2) the development of models to project MCl2 system performances. In our NiCl2 electrode work, the effects of charge/discharge rates, temperature, electrode porosity, and sulfur content on electrode performance were determined using annular electrodes fabricated in the uncharged state. Of all electrode design parameters mentioned, electrode porosity, sulfur content, and charge rates have the greatest effect on utilization and on the area-specific impedance. The beta double prime alumina-glass composite electrolyte work has led to the development of a highly conductive (3.3 x 10(exp -2)S/cm at 250 C) composite material. Preliminary modeling studies indicate that the performance of the MCl2 electrodes can be fitted by a mathematic model very successfully and that cell electrolyte configurations of either multiple tubes joined at a header or compartmented flat structures of either beta double prime alumina or of the composite material would result in high performance batteries with power-to-energy ratios of about 5.

  3. Metal-Free Sensitizers for Dye-Sensitized Solar Cells.

    PubMed

    Chaurasia, Sumit; Lin, Jiann T

    2016-06-01

    This review focuses on our work on metal-free sensitizers for dye-sensitized solar cells (DSSCs). Sensitizers based on D-A'-π-A architecture (D is a donor, A is an acceptor, A' is an electron-deficient entity) exhibit better light harvesting than D-π-A-type sensitizers. However, appropriate molecular design is needed to avoid excessive aggregation of negative charge at the electron-deficient entity upon photoexcitation. Rigidified aromatics, including aromatic segments comprising fused electron-excessive and -deficient units in the spacer, allow effective electronic communication, and good photoinduced charge transfer leads to excellent cell performance. Sensitizers with two anchors/acceptors, D(-π-A)2 , can more efficiently harvest light, inject electrons, and suppress dark current compared with congeners with a single anchor. Appropriate incorporation of heteroaromatic units in the spacer is beneficial to DSSC performance. High-performance, aqueous-based DSSCs can be achieved with a dual redox couple comprising imidazolium iodide and 2,2,6,6-tetramethylpiperidin-N-oxyl, and/or using dyes of improved wettability through the incorporation of a triethylene oxide methyl ether chain.

  4. A metallic interconnect for a solid oxide fuel cell stack

    NASA Astrophysics Data System (ADS)

    England, Diane Mildred

    A solid oxide fuel cell (SOFC) electrochemically converts the chemical energy of reaction into electrical energy. The commercial success of planar, SOFC stack technology has a number of challenges, one of which is the interconnect that electrically and physically connects the cathode of one cell to the anode of an adjacent cell in the SOFC stack and in addition, separates the anodic and cathodic gases. An SOFC stack operating at intermediate temperatures, between 600°C and 800°C, can utilize a metallic alloy as an interconnect material. Since the interconnect of an SOFC stack must operate in both air and fuel environments, the oxidation kinetics, adherence and electronic resistance of the oxide scales formed on commercial alloys were investigated in air and wet hydrogen under thermal cycling conditions to 800°C. The alloy, Haynes 230, exhibited the slowest oxidation kinetics and the lowest area-specific resistance as a function of oxidation time of all the alloys in air at 800°C. However, the area-specific resistance of the oxide scale formed on Haynes 230 in wet hydrogen was unacceptably high after only 500 hours of oxidation, which was attributed to the high resistivity of Cr2O3 in a reducing atmosphere. A study of the electrical conductivity of the minor phase manganese chromite, MnXCr3-XO4, in the oxide scale of Haynes 230, revealed that a composition closer to Mn2CrO4 had significantly higher electrical conductivity than that closer to MnCr 2O4. Haynes 230 was coated with Mn to form a phase closer to the Mn2CrO4 composition for application on the fuel side of the interconnect. U.S. Patent No. 6,054,231 is pending. Although coating a metallic alloy is inexpensive, the stringent economic requirements of SOFC stack technology required an alloy without coating for production applications. As no commercially available alloy, among the 41 alloys investigated, performed to the specifications required, a new alloy was created and designated DME-A2. The oxide scale

  5. Outdoor cultivation of lutein-rich cells of Muriellopsis sp. in open ponds.

    PubMed

    Blanco, Antonio M; Moreno, José; Del Campo, José A; Rivas, Joaquín; Guerrero, Miguel G

    2007-01-01

    The growth performance of the chlorophycean microalga Muriellopsis sp. outdoors in open tanks agitated with a paddlewheel and its ability to accumulate carotenoids have been evaluated throughout the year. The cells grown in the open system had free lutein as the main carotenoid, with violaxanthin, beta-carotene, and neoxanthin also present. Lutein content of the dry biomass ranged from 0.4 to 0.6%, depending on the growth and environmental conditions. In addition, the biomass of Muriellopsis sp. had a high content in both protein and lipids with about half of the fatty acids being of the polyunsaturated type, with alpha-linolenic acid accounting for almost 30% of the total fatty acids. The effect of determinant parameters on the performance of the cultures in open tanks was evaluated. Operating conditions that allow the maintenance of productive cultures were established under semicontinuous regime for 9 months throughout the year. Biomass and lutein yields in the open system were not far from those in closed tubular photobioreactors, and reached productivity values of 20 g dry biomass, containing around 100 mg lutein m(-2) day(-1) in summer. The outdoor culture of Muriellopsis sp. in open ponds thus represents a real alternative to established systems for the production of lutein.

  6. Influences of current collector foils with different opening ratios in passive polymer electrolyte membrane fuel cells

    NASA Astrophysics Data System (ADS)

    Krumbholz, S.; Kaiser, J.; Weiland, M.; Hahn, R.; Reichl, H.

    Even if many fuel cell applications are ready to start into the market, more research needs to be done to improve the currently achieved power density further. In the power range of about 10-20 W micro-PEM fuel cells have a high improvement potential concerning the current collector design and the design of the passive air supply. These two points have a high impact on the water management of a PEM fuel cell and allow a significant decrease of the fuel cell system in size and weight. The current work shows calculations for the fuel cell impedance based on a mathematical resistance model which was already presented for similarly constructed direct methanol fuel cells (DMFCs) [4]. Selected publications on water uptake and membrane humidification for the used Gore MEAs [6,7] are taken into account. The model is evaluated with realized versions of cathode side current collector designs, which influence the maximum power density and the self-heating of the fuel cell stack. Several measurement results are presented, which can confirm the validity of the used model. A very low opening ratio of less than 0.1 induces a very high concentration gradient of the generated water in relation to the net water outtake. From this it follows that the cell impedance is very low and the membrane has a very high ionic conductivity. Additionally it can be shown that the power density of these fuel cells is twice as high as for the cells with an opening ratio greater than 0.45.

  7. Effects of CoCr metal wear debris generated from metal-on-metal hip implants and Co ions on human monocyte-like U937 cells.

    PubMed

    Posada, Olga M; Tate, Rothwelle J; Grant, M Helen

    2015-03-01

    Hip resurfacing with cobalt-chromium (CoCr) alloy was developed as a surgical alternative to total hip replacement. However, the biological effects of nanoparticles generated by wear at the metal-on-metal articulating surfaces has limited the success of such implants. The aim of this study was to investigate the effects of the combined exposure to CoCr nanoparticles and cobalt ions released from a resurfacing implant on monocytes (U937 cells) and whether these resulted in morphology changes, proliferation alterations, toxicity and cytokine release. The interaction between prior exposure to Co ions and the cellular response to nanoparticulate debris was determined to simulate the situation in patients with metal-on-metal implants receiving a second implant. Effects on U937 cells were mainly seen after 120h of treatment. Prior exposure to Co ions increased the toxic effects induced by the debris, and by Co ions themselves, suggesting the potential for interaction in vivo. Increased TNF-α secretion by resting cells exposed to nanoparticles could contribute to osteolysis processes in vivo, while increased IFN-γ production by activated cells could represent cellular protection against tissue damage. Data suggest that interactions between Co ions and CoCr nanoparticles would occur in vivo, and could threaten the survival of a CoCr metal implant. Copyright © 2014 Elsevier Ltd. All rights reserved.

  8. In-channel printing-device opening assay for micropatterning multiple cells and gene analysis.

    PubMed

    Zhou, Hao; Zhao, Liang; Zhang, Xueji

    2015-02-17

    Herein we report an easy but versatile method for patterning different cells on a single substrate by using a microfluidic approach that allows not only spatial and temporal control of multiple microenvironments but also retrieval of specific treated cells to profile their expressed genetic information at around 10-cell resolution. By taking advantages of increased surface area of gold nanoparticles on a poly(dimethylsiloxane) (PDMS) coated substrate, cell adhesive-promotive protein, human fibronectin (hFN) can be significantly accumulated on designed regions where cells can recognize the protein and spread out. Moreover, the whole device can be easily opened by hand without any loss of patterned cells which could be retrieved by mouth-pipet. Consequently, we demonstrate the possibility of analyzing the difference of gene expression patterns between wild type MCF-7 cell and MCF/Adr (drug-resistant cell line) from less than 400 cells in total for a single comprehensive assay, including parallel experiments, controls, and multiple dose treatments. Certain genes, especially the P-glycoprotein coding gene (ABCB1), show high expression level in resistant cells compared with the wild type, suggesting a possible pathway that may contribute to the antidrug mechanism.

  9. Open-Porous Hydroxyapatite Scaffolds for Three-Dimensional Culture of Human Adult Liver Cells

    PubMed Central

    Schmelzer, Eva; Over, Patrick; Nettleship, Ian; Gerlach, Joerg C.

    2016-01-01

    Liver cell culture within three-dimensional structures provides an improved culture system for various applications in basic research, pharmacological screening, and implantable or extracorporeal liver support. Biodegradable calcium-based scaffolds in such systems could enhance liver cell functionality by providing endothelial and hepatic cell support through locally elevated calcium levels, increased surface area for cell attachment, and allowing three-dimensional tissue restructuring. Open-porous hydroxyapatite scaffolds were fabricated and seeded with primary adult human liver cells, which were embedded within or without gels of extracellular matrix protein collagen-1 or hyaluronan. Metabolic functions were assessed after 5, 15, and 28 days. Longer-term cultures exhibited highest cell numbers and liver specific gene expression when cultured on hydroxyapatite scaffolds in collagen-1. Endothelial gene expression was induced in cells cultured on scaffolds without extracellular matrix proteins. Hydroxyapatite induced gene expression for cytokeratin-19 when cells were cultured in collagen-1 gel while culture in hyaluronan increased cytokeratin-19 gene expression independent of the use of scaffold in long-term culture. The implementation of hydroxyapatite composites with extracellular matrices affected liver cell cultures and cell differentiation depending on the type of matrix protein and the presence of a scaffold. The hydroxyapatite scaffolds enable scale-up of hepatic three-dimensional culture models for regenerative medicine applications. PMID:27403430

  10. Open-Porous Hydroxyapatite Scaffolds for Three-Dimensional Culture of Human Adult Liver Cells.

    PubMed

    Finoli, Anthony; Schmelzer, Eva; Over, Patrick; Nettleship, Ian; Gerlach, Joerg C

    2016-01-01

    Liver cell culture within three-dimensional structures provides an improved culture system for various applications in basic research, pharmacological screening, and implantable or extracorporeal liver support. Biodegradable calcium-based scaffolds in such systems could enhance liver cell functionality by providing endothelial and hepatic cell support through locally elevated calcium levels, increased surface area for cell attachment, and allowing three-dimensional tissue restructuring. Open-porous hydroxyapatite scaffolds were fabricated and seeded with primary adult human liver cells, which were embedded within or without gels of extracellular matrix protein collagen-1 or hyaluronan. Metabolic functions were assessed after 5, 15, and 28 days. Longer-term cultures exhibited highest cell numbers and liver specific gene expression when cultured on hydroxyapatite scaffolds in collagen-1. Endothelial gene expression was induced in cells cultured on scaffolds without extracellular matrix proteins. Hydroxyapatite induced gene expression for cytokeratin-19 when cells were cultured in collagen-1 gel while culture in hyaluronan increased cytokeratin-19 gene expression independent of the use of scaffold in long-term culture. The implementation of hydroxyapatite composites with extracellular matrices affected liver cell cultures and cell differentiation depending on the type of matrix protein and the presence of a scaffold. The hydroxyapatite scaffolds enable scale-up of hepatic three-dimensional culture models for regenerative medicine applications.

  11. Orthotropic Laminated Open-cell Frameworks Retaining Strong Auxeticity under Large Uniaxial Loading

    NASA Astrophysics Data System (ADS)

    Tanaka, Hiro; Suga, Kaito; Iwata, Naoki; Shibutani, Yoji

    2017-01-01

    Anisotropic materials form inside living tissue and are widely applied in engineered structures, where sophisticated structural and functional design principles are essential to employing these materials. This paper presents a candidate laminated open-cell framework, which is an anisotropic material that shows remarkable mechanical performance. Using additive manufacturing, artificial frameworks are fabricated by lamination of in-plane orthotropic microstructures made of elbowed beam and column members; this fabricated structure features orthogonal anisotropy in three-dimensional space. Uniaxial loading tests reveal strong auxeticity (high negative Poisson’s ratios) in the out-of-plane direction, which is retained reproducibly up to the nonlinear elastic region, and is equal under tensile and compressive loading. Finite element simulations support the observed auxetic behaviors for a unit cell in the periodic framework, which preserve the theoretical elastic properties of an orthogonal solid. These findings open the possibility of conceptual materials design based on geometry.

  12. Orthotropic Laminated Open-cell Frameworks Retaining Strong Auxeticity under Large Uniaxial Loading.

    PubMed

    Tanaka, Hiro; Suga, Kaito; Iwata, Naoki; Shibutani, Yoji

    2017-01-04

    Anisotropic materials form inside living tissue and are widely applied in engineered structures, where sophisticated structural and functional design principles are essential to employing these materials. This paper presents a candidate laminated open-cell framework, which is an anisotropic material that shows remarkable mechanical performance. Using additive manufacturing, artificial frameworks are fabricated by lamination of in-plane orthotropic microstructures made of elbowed beam and column members; this fabricated structure features orthogonal anisotropy in three-dimensional space. Uniaxial loading tests reveal strong auxeticity (high negative Poisson's ratios) in the out-of-plane direction, which is retained reproducibly up to the nonlinear elastic region, and is equal under tensile and compressive loading. Finite element simulations support the observed auxetic behaviors for a unit cell in the periodic framework, which preserve the theoretical elastic properties of an orthogonal solid. These findings open the possibility of conceptual materials design based on geometry.

  13. Propagation of sound in highly porous open-cell elastic foams

    NASA Technical Reports Server (NTRS)

    Lambert, R. F.

    1983-01-01

    This work presents both theoretical predictions and experimental measurements of attenuation and progressive phase constants of sound in open-cell, highly porous, elastic polyurethane foams. The foams are available commercially in graded pore sizes for which information about the static flow resistance, thermal time constant, volume porosity, dynamic structure factor, and speed of sound is known. The analysis is specialized to highly porous foams which can be efficient sound absorbers at audio frequencies. Negligible effect of internal wave coupling on attenuation and phase shift for the frequency range 16-6000 Hz was predicted and no experimentally significant effects were observed in the bulk samples studied. The agreement between predictions and measurements in bulk materials is excellent. The analysis is applicable to both the regular and compressed elastic open-cell foams.

  14. Structure and compressive strength of silicon open-cell foam obtained by a centrifugal separation method

    NASA Astrophysics Data System (ADS)

    Cho, Ju-Young; Kim, Ki-Young

    2013-03-01

    The present study describes a new way to make an open-cell silicon foam from an Al-Si alloy melt by centrifugation during its solidification. The effects of the silicon content and the chute diameter of the crucible on the morphology, the density and the compressive strength of the silicon foams were investigated. A vertical-type centrifugal separator was designed to push the unfrozen Al-Si melt outside, leaving only the silicon foam inside the crucible during rotation. Alloys in the Al-Si system with silicon contents of 40 and 50 wt% were prepared by an electrical resistance furnace, and the revolution of the centrifugal separator was controlled to fabricate the foam. Open-cell silicon foams could be obtained successfully. The apparent density and the compressive strength were in the ranges of 620-820 kg/m3 and 7.5-14.5 MPa, respectively.

  15. Characterization of compressive and short beam shear strength of bamboo opened cell foam core sandwich composites

    NASA Astrophysics Data System (ADS)

    Setyawan, Paryanto Dwi; Sugiman, Saputra, Yudhi

    2016-03-01

    The paper presents the compressive and the short beam shear strength of a sandwich composite with opened cell foam made of bamboo fiber as the core and plywood as the skins. The core thickness was varied from 10 mm to 40 mm keeping the volume fraction of fiber constant. Several test s were carried out including the core density, flatwise compressive and the short beam shear testing in three point bending. The results show that the density of bamboo opened cell foam is comparable with commercial plastic foam, such as polyurethane foam. The compressive strength tends to increase linearly with increasing the core thickness. The short beam shear failure load of the sandwich composite increases with the increase of core thickness, however on the contrary, the short beam shear strength which tends to sharply decrease from the thickness of 10 mm to 30 mm and then becomes flat.

  16. Polymer defect states modulate open-circuit voltage in bulk-heterojunction solar cells

    SciTech Connect

    Ripolles, Teresa S.; Guerrero, Antonio; Garcia-Belmonte, Germà

    2013-12-09

    Defect states influence the operation of organic solar cells altering transport, recombination, and energetic mechanisms. This work investigates how processing conditions induce morphology-related, electrically active defects in the donor polymer of bulk-heterojunction solar cells. Structural order is inferred from absorption and X-ray diffraction data, while defect density is determined from capacitance methods. A correlation is observed between the polymer nanocrystallite size, the defect concentration, and the output voltage. For the case of poly(3-hexylthiophene), processing that promote crystallinity is beneficial for the device performance as it decreases the defect density (energy disorder) that finally enlarges the maximum achievable open-circuit voltage. Defect states within the effective bandgap modulate the downshift of the hole Fermi level upon illumination that in turn establishes the achievable open-circuit voltage.

  17. a Vibrational Model of Open Celled Polyurethane Foam Automotive Seat Cushions

    NASA Astrophysics Data System (ADS)

    Patten, W. N.; Sha, S.; Mo, C.

    1998-10-01

    A mechanistic model of a seat cushion is developed. The work relates the kinematic motion of the seat to the geometric and constitutive properties of the cellular foam used in the seat. The model includes the influence of pneumatic damping caused by friction between the gas within the open-celled foam and matrix polymer. A continuous shape function is introduced to characterize the piecewise continuous stress-strain characteristic of flexible open-celled foam. After some simplification, a non-linear dynamic automotive seat cushion model is derived, which relies explicitly on the constitutive properties of polyurethane foams and on the geometry of the seat cushion. Experimental and analytical models of the two automotive seats are compared to verify the model. The comparisons indicate that the new model is able to predict the dynamic performance of an automotive seat cushion with fidelity.

  18. Method for cleaning a solar cell surface opening made with a solar etch paste

    DOEpatents

    Rohatgi, Ajeet; Meemongkolkiat, Vichai

    2010-06-22

    A thin silicon solar cell having a back dielectric passivation and rear contact with local back surface field is described. Specifically, the solar cell may be fabricated from a crystalline silicon wafer having a thickness from 50 to 500 micrometers. A barrier layer and a dielectric layer are applied at least to the back surface of the silicon wafer to protect the silicon wafer from deformation when the rear contact is formed. At least one opening is made to the dielectric layer. An aluminum contact that provides a back surface field is formed in the opening and on the dielectric layer. The aluminum contact may be applied by screen printing an aluminum paste having from one to 12 atomic percent silicon and then applying a heat treatment at 750 degrees Celsius.

  19. Fabrication of Open-Cell Al Foams and Evaluation of their Mechanical Response under Tension

    NASA Astrophysics Data System (ADS)

    Michailidis, N.; Stergioudi, F.; Omar, H.; Tsipas, D. N.

    2010-01-01

    In the present paper a novel procedure for describing the solid geometry of open cell foams is introduced, facilitating the establishment of a corresponding FEM model for simulating the material behaviour in micro-tension. Open-cell Al-foams were fabricated using the polymer impregnating method. A serial sectioning image-based process is described to capture, reproduce and visualize the exact three-dimensional (3D) microstructure of the examined foam. The generated 3D geometry of the Al-foam, derived from the synthesis of digital cross sectional images of the foam, was appropriately adjusted to build a FE model simulating the deformation conditions of the Al-foam under micro-tension loads. The obtained results enabled the visualisation of the stress fields in the Al-foam, allowing for a full investigation of its mechanical behaviour.

  20. Characterization of compressive and short beam shear strength of bamboo opened cell foam core sandwich composites

    SciTech Connect

    Setyawan, Paryanto Dwi Sugiman,; Saputra, Yudhi

    2016-03-29

    The paper presents the compressive and the short beam shear strength of a sandwich composite with opened cell foam made of bamboo fiber as the core and plywood as the skins. The core thickness was varied from 10 mm to 40 mm keeping the volume fraction of fiber constant. Several test s were carried out including the core density, flatwise compressive and the short beam shear testing in three point bending. The results show that the density of bamboo opened cell foam is comparable with commercial plastic foam, such as polyurethane foam. The compressive strength tends to increase linearly with increasing the core thickness. The short beam shear failure load of the sandwich composite increases with the increase of core thickness, however on the contrary, the short beam shear strength which tends to sharply decrease from the thickness of 10 mm to 30 mm and then becomes flat.

  1. Orthotropic Laminated Open-cell Frameworks Retaining Strong Auxeticity under Large Uniaxial Loading

    PubMed Central

    Tanaka, Hiro; Suga, Kaito; Iwata, Naoki; Shibutani, Yoji

    2017-01-01

    Anisotropic materials form inside living tissue and are widely applied in engineered structures, where sophisticated structural and functional design principles are essential to employing these materials. This paper presents a candidate laminated open-cell framework, which is an anisotropic material that shows remarkable mechanical performance. Using additive manufacturing, artificial frameworks are fabricated by lamination of in-plane orthotropic microstructures made of elbowed beam and column members; this fabricated structure features orthogonal anisotropy in three-dimensional space. Uniaxial loading tests reveal strong auxeticity (high negative Poisson’s ratios) in the out-of-plane direction, which is retained reproducibly up to the nonlinear elastic region, and is equal under tensile and compressive loading. Finite element simulations support the observed auxetic behaviors for a unit cell in the periodic framework, which preserve the theoretical elastic properties of an orthogonal solid. These findings open the possibility of conceptual materials design based on geometry. PMID:28051133

  2. Static Behavior of Chalcogenide Based Programmable Metallization Cells

    NASA Astrophysics Data System (ADS)

    Rajabi, Saba

    Nonvolatile memory (NVM) technologies have been an integral part of electronic systems for the past 30 years. The ideal non-volatile memory have minimal physical size, energy usage, and cost while having maximal speed, capacity, retention time, and radiation hardness. A promising candidate for next-generation memory is ion-conducting bridging RAM which is referred to as programmable metallization cell (PMC), conductive bridge RAM (CBRAM), or electrochemical metallization memory (ECM), which is likely to surpass flash memory in all the ideal memory characteristics. A comprehensive physics-based model is needed to completely understand PMC operation and assist in design optimization. To advance the PMC modeling effort, this thesis presents a precise physical model parameterizing materials associated with both ion-rich and ion-poor layers of the PMC's solid electrolyte, so that captures the static electrical behavior of the PMC in both its low-resistance on-state (LRS) and high resistance off-state (HRS). The experimental data is measured from a chalcogenide glass PMC designed and manufactured at ASU. The static on- and off-state resistance of a PMC device composed of a layered (Ag-rich/Ag-poor) Ge30Se70 ChG film is characterized and modeled using three dimensional simulation code written in Silvaco Atlas finite element analysis software. Calibrating the model to experimental data enables the extraction of device parameters such as material bandgaps, workfunctions, density of states, carrier mobilities, dielectric constants, and affinities. The sensitivity of our modeled PMC to the variation of its prominent achieved material parameters is examined on the HRS and LRS impedance behavior. The obtained accurate set of material parameters for both Ag-rich and Ag-poor ChG systems and process variation verification on electrical characteristics enables greater fidelity in PMC device simulation, which significantly enhances our ability to understand the underlying physics of

  3. Stereorigid OSSO-Type Group 4 Metal Complexes in the Ring-Opening Polymerization of rac-Lactide.

    PubMed

    Lapenta, Rosita; Buonerba, Antonio; De Nisi, Assunta; Monari, Magda; Grassi, Alfonso; Milione, Stefano; Capacchione, Carmine

    2017-03-20

    The synthesis and characterization of a series of group 4 metal complexes of general formula {OSSOX}M(OR)2 (X = R = (t)Bu, M = Zr (1); X = cumyl, M = Zr, R = (t)Bu (2); X = cumyl, M = Ti, R = (i)Pr (4); X = cumyl, M = Hf, R = (t)Bu (5)) and {OSSOX}2Zr (X = Cl (3)) supported by o-phenylene-bridged bis(phenolato) ligands (OSSOtBu-H = 6,6'-((1,2-phenylenebis(sulfanediyl))bis(methylene))bis(2,4-di-tert-butyphenol); OSSOCum-H = 6,6'-((1,2-phenylenebis(sulfanediyl))bis(methylene))bis(2,4-bis(2-phenylpropan-2-yl)phenol); OSSOCl-H = 6,6'-((1,2-phenylenebis(sulfanediyl))bis(methylene))bis(2,4-dichlorophenol)) are described herein. Complexes 1-5 were readily obtained by σ-bond metathesis reactions between the proligand and the appropriate homoleptic metal precursor. The reaction with OSSOCl yielded the bis-ligand complex{OSSOCl}2Zr (3) regardless of the OSSOCl-H/Zr(O(t)Bu)4 molar ratio or experimental conditions. All complexes were characterized in solution using NMR spectroscopy and, in the case of 2, by single-crystal X-ray diffraction experiments. These complexes show a fac-fac ligand wrapping and a cis relationship between the other two monodentate ligands; zirconium and hafnium complexes 1-3 and 5 are configurationally stable, whereas titanium complex 4 is fluxional in solution at room temperature. The complexes tested in the ring-opening polymerization (ROP) of racemic-lactide showed, except in the case of 3, moderate rates and good levels of polymerization control. Upon addition of an exogenous alcohol (isopropyl alcohol or tert-butyl alcohol) efficient binary catalytic systems were achieved. Polymerizations were well-controlled, as testified by the linear growth of the molecular weight as polymerization proceeded, narrow polydispersity indices, and molecular weights close to those expected on the basis of added alcohol amounts. Experimental and theoretical evidence is provided that ROP reactions operate according to an activated monomer mechanism.

  4. Cellular responses of osteoblast-like cells to 17 elemental metals.

    PubMed

    Zhang, Dongmei; Wong, Cynthia S; Wen, Cuie; Li, Yuncang

    2017-01-01

    Elemental metals have been widely used to alloy metallic orthopedic implants. However, there is still insufficient research data elucidating the cell responses of osteoblastic cells to alloying elemental metals, which impedes the development of new metallic implant materials. In this study, the cellular responses of osteoblast-like cells (SaOS2) to 17 pure alloying elemental metals, that is, titanium (Ti), zirconium (Zr), hafnium (Hf), vanadium (V), niobium (Nb), tantalum (Ta), chromium (Cr), molybdenum (Mo), manganese (Mn), iron (Fe), ruthenium (Ru), cobalt (Co), nickel (Ni), copper (Cu), zinc (Zn), silicon (Si), and tin (Sn) were comparatively investigated in vitro. Cellular responses including intracellular total protein synthesis and collagen content, cell adhesion, cell proliferation, and alkaline phosphatase (ALP) activity on these elemental metals were systematically assessed and compared. It was found that these elemental metals could be categorized into three groups based on the cellular functions on them. Group 1, including Ti, Zr, Hf, Nb, Ta, Cr, Ru, and Si, showed excellent cell proliferation and varied ALP activity for SaOS2 cells. Cells exposed to Group 2, including Mo and Sn, although initially attached and grew, did not proliferate over time. In contrast, Group 3, including V, Mn, Fe, Co, Ni, Cu, and Zn, showed severe cytotoxicity toward SaOS2 cells. It is vital to consider the cell responses to the elemental metals when designing a new metallic implant material and the findings of this study provide insights into the biological performance of the elemental metals. © 2016 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 105A: 148-158, 2017.

  5. Nonfullerene Tandem Organic Solar Cells with High Open-Circuit Voltage of 1.97 V.

    PubMed

    Liu, Wenqing; Li, Shuixing; Huang, Jiang; Yang, Shida; Chen, Jiehuan; Zuo, Lijian; Shi, Minmin; Zhan, Xiaowei; Li, Chang-Zhi; Chen, Hongzheng

    2016-11-01

    Small-molecule nonfullerene-based tandem organic solar cells (OSCs) are fabricated for the first time by utilizing P3HT:SF(DPPB)4 and PTB7-Th:IEIC bulk heterojunctions as the front and back subcells, respectively. A power conversion efficiency of 8.48% is achieved with an ultrahigh open-circuit voltage of 1.97 V, which is the highest voltage value reported to date among efficient tandem OSCs.

  6. Transmissive metallic contact for amorphous silicon solar cells

    DOEpatents

    Madan, A.

    1984-11-29

    A transmissive metallic contact for amorphous silicon semiconductors includes a thin layer of metal, such as aluminum or other low work function metal, coated on the amorphous silicon with an antireflective layer coated on the metal. A transparent substrate, such as glass, is positioned on the light reflective layer. The metallic layer is preferably thin enough to transmit at least 50% of light incident thereon, yet thick enough to conduct electricity. The antireflection layer is preferably a transparent material that has a refractive index in the range of 1.8 to 2.2 and is approximately 550A to 600A thick.

  7. Enhanced bioaccumulation of heavy metal ions by bacterial cells due to surface display of short metal binding peptides

    SciTech Connect

    Kotrba, P.; Ruml, T.; Doleckova, L.; Lorenzo, V. de

    1999-03-01

    Metal binding peptides of sequences Gly-His-His-Pro-His-Gly (named HP) and Gly-Cys-Gly-Cys-Pro-Cys-Gly-Cys-Gly (named CP) were genetically engineered into LamB protein and expressed in Escherichia coli. The Cd{sup 2+}-to-HP and Cd{sup 2+}-to-CP stoichiometries of peptides were 1:1 and 3:1, respectively. Hybrid LamB proteins were found to be properly folded in the outer membrane of E. coli. Isolated cell envelopes of E. coli bearing newly added metal binding peptides showed an up to 1.8-fold increase in Cd{sup 2+} binding capacity. The bioaccumulation of Cd{sup 2+}, Cu{sup 2+}, and Zn{sup 2+} by E. coli was evaluated. Surface display of CP multiplied the ability of E. coli to bind Cd{sup 2+} from growth medium fourfold. Display of HP peptide did not contribute to an increase in the accumulation of Cu{sup 2+} and Zn{sup 2+}. However, Cu{sup 2+} ceased contribution of HP for Cd{sup 2+} accumulation, probably due to the strong binding of Cu{sup 2+} to HP. Thus, considering the cooperation of cell structures with inserted peptides, the relative affinities of metal binding peptide and, for example, the cell wall to metal ion should be taken into account in the rational design of peptide sequences possessing specificity for a particular metal.

  8. Different arrangements of simplified models to predict effective thermal conductivity of open-cell foams

    NASA Astrophysics Data System (ADS)

    Kumar, Prashant; Topin, Frédéric

    2017-02-01

    It is often desirable to predict the effective thermal conductivity (ETC) of a homogenous material like open-cell foams based on its composition, particularly when variations in composition are expected. A combination of five fundamental simplified thermal conductivity bounds and models (series, parallel, Hashin-Shtrikman, effective medium theory, and reciprocity models) is proposed to predict ETC of open-cell foams. Usually, these models use a parameter as the weighted mean to account the proportion of each bound arranged in arithmetic and geometric schemes. Based on ETC data obtained on numerous virtual Kelvin-like foam samples, the dependence of this parameter has been deduced as a function of morphology and phase thermal conductivity ratio. Various effective thermal conductivity correlations are derived based on material properties and foam structure. This is valid for open-cell foams filled with any arbitrary working fluid over a solid conductivity of materials range (λs /λf = 10-30,000) and over a wide range of porosity (0.60 < &epsilono < 0.95). Arrangement of series and parallel models together using the simplest models for both, arithmetic and geometric schemes, is found to predict excellent results among all the generic combinations.

  9. Percutaneous biliary drainage using open cell stents for malignant biliary hilar obstruction.

    PubMed

    Ahn, Sun Jun; Bae, Jae Ik; Han, Tae Sun; Won, Je Hwan; Kim, Ji Dae; Kwack, Kyu-Sung; Lee, Jae Hee; Kim, Young Chul

    2012-01-01

    To evaluate the feasibility, safety and the effectiveness of the complex assembly of open cell nitinol stents for biliary hilar malignancy. During the 10 month period between January and October 2007, 26 consecutive patients with malignant biliary hilar obstruction underwent percutaneous insertion of open cell design nitinol stents. Four types of stent placement methods were used according to the patients' ductal anatomy of the hilum. We evaluated the technical feasibility of stent placement, complications, patient survival, and the duration of stent patency. Bilobar biliary stent placement was conducted in 26 patients with malignant biliary obstruction-T (n = 9), Y (n = 7), crisscross (n = 6) and multiple intersecting types (n = 4). Primary technical success was obtained in 24 of 26 (93%) patients. The crushing of the 1st stent during insertion of the 2nd stent occurred in two cases. Major complications occurred in 2 of 26 patients (7.7%). One case of active bleeding from hepatic segmental artery and one case of sepsis after procedure occurred. Clinical success was achieved in 21 of 24 (87.5%) patients, who were followed for a mean of 141.5 days (range 25-354 days). The mean primary stent patency period was 191.8 days and the mean patient survival period was 299 days. Applying an open cell stent in the biliary system is feasible, and can be effective, especially in multiple intersecting stent insertions in the hepatic hilum.

  10. Different arrangements of simplified models to predict effective thermal conductivity of open-cell foams

    NASA Astrophysics Data System (ADS)

    Kumar, Prashant; Topin, Frédéric

    2017-08-01

    It is often desirable to predict the effective thermal conductivity (ETC) of a homogenous material like open-cell foams based on its composition, particularly when variations in composition are expected. A combination of five fundamental simplified thermal conductivity bounds and models (series, parallel, Hashin-Shtrikman, effective medium theory, and reciprocity models) is proposed to predict ETC of open-cell foams. Usually, these models use a parameter as the weighted mean to account the proportion of each bound arranged in arithmetic and geometric schemes. Based on ETC data obtained on numerous virtual Kelvin-like foam samples, the dependence of this parameter has been deduced as a function of morphology and phase thermal conductivity ratio. Various effective thermal conductivity correlations are derived based on material properties and foam structure. This is valid for open-cell foams filled with any arbitrary working fluid over a solid conductivity of materials range (λs /λf = 10-30,000) and over a wide range of porosity (0.60 < ɛo < 0.95). Arrangement of series and parallel models together using the simplest models for both, arithmetic and geometric schemes, is found to predict excellent results among all the generic combinations.

  11. Percutaneous Biliary Drainage Using Open Cell Stents for Malignant Biliary Hilar Obstruction

    PubMed Central

    Ahn, Sun Jun; Han, Tae Sun; Won, Je Hwan; Kim, Ji Dae; Kwack, Kyu-Sung; Lee, Jae Hee; Kim, Young Chul

    2012-01-01

    Objective To evaluate the feasibility, safety and the effectiveness of the complex assembly of open cell nitinol stents for biliary hilar malignancy. Materials and Methods During the 10 month period between January and October 2007, 26 consecutive patients with malignant biliary hilar obstruction underwent percutaneous insertion of open cell design nitinol stents. Four types of stent placement methods were used according to the patients' ductal anatomy of the hilum. We evaluated the technical feasibility of stent placement, complications, patient survival, and the duration of stent patency. Results Bilobar biliary stent placement was conducted in 26 patients with malignant biliary obstruction-T (n = 9), Y (n = 7), crisscross (n = 6) and multiple intersecting types (n = 4). Primary technical success was obtained in 24 of 26 (93%) patients. The crushing of the 1st stent during insertion of the 2nd stent occurred in two cases. Major complications occurred in 2 of 26 patients (7.7%). One case of active bleeding from hepatic segmental artery and one case of sepsis after procedure occurred. Clinical success was achieved in 21 of 24 (87.5%) patients, who were followed for a mean of 141.5 days (range 25-354 days). The mean primary stent patency period was 191.8 days and the mean patient survival period was 299 days. Conclusion Applying an open cell stent in the biliary system is feasible, and can be effective, especially in multiple intersecting stent insertions in the hepatic hilum. PMID:23118579

  12. DEVELOPING A CAPE-OPEN COMPLIANT METAL FINISHING FACILITY POLLUTION PREVENTION TOOL (CO-MFFP2T)

    EPA Science Inventory

    The USEPA is developing a Computer Aided Process Engineering (CAPE) software tool for the metal finishing industry that helps users design efficient metal finishing processes that are less polluting to the environment. Metal finishing process lines can be simulated and evaluated...

  13. DEVELOPING A CAPE-OPEN COMPLIANT METAL FINISHING FACILITY POLLUTION PREVENTION TOOL (CO-MFFP2T)

    EPA Science Inventory

    The USEPA is developing a Computer Aided Process Engineering (CAPE) software tool for the metal finishing industry that helps users design efficient metal finishing processes that are less polluting to the environment. Metal finishing process lines can be simulated and evaluated...

  14. Pea Border Cell Maturation and Release Involve Complex Cell Wall Structural Dynamics1[OPEN

    PubMed Central

    2017-01-01

    The adhesion of plant cells is vital for support and protection of the plant body and is maintained by a variety of molecular associations between cell wall components. In some specialized cases, though, plant cells are programmed to detach, and root cap-derived border cells are examples of this. Border cells (in some species known as border-like cells) provide an expendable barrier between roots and the environment. Their maturation and release is an important but poorly characterized cell separation event. To gain a deeper insight into the complex cellular dynamics underlying this process, we undertook a systematic, detailed analysis of pea (Pisum sativum) root tip cell walls. Our study included immunocarbohydrate microarray profiling, monosaccharide composition determination, Fourier-transformed infrared microspectroscopy, quantitative reverse transcription-PCR of cell wall biosynthetic genes, analysis of hydrolytic activities, transmission electron microscopy, and immunolocalization of cell wall components. Using this integrated glycobiology approach, we identified multiple novel modes of cell wall structural and compositional rearrangement during root cap growth and the release of border cells. Our findings provide a new level of detail about border cell maturation and enable us to develop a model of the separation process. We propose that loss of adhesion by the dissolution of homogalacturonan in the middle lamellae is augmented by an active biophysical process of cell curvature driven by the polarized distribution of xyloglucan and extensin epitopes. PMID:28400496

  15. CellStress - open source image analysis program for single-cell analysis

    NASA Astrophysics Data System (ADS)

    Smedh, Maria; Beck, Caroline; Sott, Kristin; Goksör, Mattias

    2010-08-01

    This work describes our image-analysis software, CellStress, which has been developed in Matlab and is issued under a GPL license. CellStress was developed in order to analyze migration of fluorescent proteins inside single cells during changing environmental conditions. CellStress can also be used to score information regarding protein aggregation in single cells over time, which is especially useful when monitoring cell signaling pathways involved in e.g. Alzheimer's or Huntington's disease. Parallel single-cell analysis of large numbers of cells is an important part of the research conducted in systems biology and quantitative biology in order to mathematically describe cellular processes. To quantify properties for single cells, large amounts of data acquired during extended time periods are needed. Manual analyses of such data involve huge efforts and could also include a bias, which complicates the use and comparison of data for further simulations or modeling. Therefore, it is necessary to have an automated and unbiased image analysis procedure, which is the aim of CellStress. CellStress utilizes cell contours detected by CellStat (developed at Fraunhofer-Chalmers Centre), which identifies cell boundaries using bright field images, and thus reduces the fluorescent labeling needed.

  16. Screenable all-metal solar cell electrodes of nickel and copper

    NASA Technical Reports Server (NTRS)

    Ross, B.; Bickler, D. B.

    1981-01-01

    Screenable thick film solar cell electrodes are made using the all-metal electrode system, which eliminates the commonly used glass frit and substitutes an oxide scavenger such as silver fluoride. The low temperature firing copper metal systems give good results on solar cells obtaining cell efficiencies of 13% AM1, and adhering sintered structures are demonstrated with nickel systems. The potential effect of copper upon cell performance at elevated temperatures over long periods of time is determined, and it is found that the formation of a copper-silicon eutectic at 550 C produces needle-like structures with broad bases on the silicon, extending into and occasionally through the metallization layer.

  17. Gate-opening upon CO2 adsorption on a metal-organic framework that mimics a natural stimuli-response system.

    PubMed

    Tseng, T W; Lee, L W; Luo, T T; Chien, P H; Liu, Y H; Lee, S L; Wang, C M; Lu, K L

    2017-09-28

    A dynamic metal-organic framework that consists of d-champhorate-based homochiral protuberant-grid-type networks can successively participate in gate-opening and closing processes for many cycles, which were triggered by the stimuli of the adsorption and desorption of CO2 to highly and specifically recognize CO2 over N2 and H2 with a high CO2 uptake of 90 mg g(-1) under 35 bar at 298 K. It is highly thermally stable and the structure remains intact at least for ten reversible gate-opening and -closing processes. Thus, it is a potential candidate for industrial CO2 capture and facile release.

  18. Adsorption and ring-opening of lactide on the chiral metal surface Pt(321){sup S} studied by density functional theory

    SciTech Connect

    Franke, J.-H.; Kosov, D. S.

    2015-01-28

    We study the adsorption and ring-opening of lactide on the naturally chiral metal surface Pt(321){sup S}. Lactide is a precursor for polylactic acid ring-opening polymerization, and Pt is a well known catalyst surface. We study, here, the energetics of the ring-opening of lactide on a surface that has a high density of kink atoms. These sites are expected to be present on a realistic Pt surface and show enhanced catalytic activity. The use of a naturally chiral surface also enables us to study potential chiral selectivity effects of the reaction at the same time. Using density functional theory with a functional that includes the van der Waals forces in a first-principles manner, we find modest adsorption energies of around 1.4 eV for the pristine molecule and different ring-opened states. The energy barrier to be overcome in the ring-opening reaction is found to be very small at 0.32 eV and 0.30 eV for LL- and its chiral partner DD-lactide, respectively. These energies are much smaller than the activation energy for a dehydrogenation reaction of 0.78 eV. Our results thus indicate that (a) ring-opening reactions of lactide on Pt(321) can be expected already at very low temperatures, and Pt might be a very effective catalyst for this reaction; (b) the ring-opening reaction rate shows noticeable enantioselectivity.

  19. Enhanced Open-Circuit Voltage of PbS Nanocrystal Quantum Dot Solar Cells

    NASA Astrophysics Data System (ADS)

    Yoon, Woojun; Boercker, Janice E.; Lumb, Matthew P.; Placencia, Diogenes; Foos, Edward E.; Tischler, Joseph G.

    2013-07-01

    Nanocrystal quantum dots (QD) show great promise toward improving solar cell efficiencies through the use of quantum confinement to tune absorbance across the solar spectrum and enable multi-exciton generation. Despite this remarkable potential for high photocurrent generation, the achievable open-circuit voltage (Voc) is fundamentally limited due to non-radiative recombination processes in QD solar cells. Here we report the highest open-circuit voltages to date for colloidal QD based solar cells under one sun illumination. This Voc of 692 +/- 7 mV for 1.4 eV PbS QDs is a result of improved passivation of the defective QD surface, demonstrating as a function of the QD bandgap (Eg). Comparing experimental Voc variation with the theoretical upper-limit obtained from one diode modeling of the cells with different Eg, these results clearly demonstrate that there is a tremendous opportunity for improvement of Voc to values greater than 1 V by using smaller QDs in QD solar cells.

  20. Enhanced open-circuit voltage of PbS nanocrystal quantum dot solar cells.

    PubMed

    Yoon, Woojun; Boercker, Janice E; Lumb, Matthew P; Placencia, Diogenes; Foos, Edward E; Tischler, Joseph G

    2013-01-01

    Nanocrystal quantum dots (QD) show great promise toward improving solar cell efficiencies through the use of quantum confinement to tune absorbance across the solar spectrum and enable multi-exciton generation. Despite this remarkable potential for high photocurrent generation, the achievable open-circuit voltage (Voc) is fundamentally limited due to non-radiative recombination processes in QD solar cells. Here we report the highest open-circuit voltages to date for colloidal QD based solar cells under one sun illumination. This Voc of 692 ± 7 mV for 1.4 eV PbS QDs is a result of improved passivation of the defective QD surface, demonstrating Voc(mV)=553Eg/q-59 as a function of the QD bandgap (Eg). Comparing experimental Voc variation with the theoretical upper-limit obtained from one diode modeling of the cells with different Eg, these results clearly demonstrate that there is a tremendous opportunity for improvement of Voc to values greater than 1 V by using smaller QDs in QD solar cells.

  1. Single-nanowire, low-bandgap hot carrier solar cells with tunable open-circuit voltage.

    PubMed

    Limpert, Steven; Burke, Adam; Chen, I-Ju; Anttu, Nicklas; Lehmann, Sebastian; Fahlvik, Sofia; Bremner, Stephen; Conibeer, Gavin J; Thelander, Claes; Pistol, Mats-Erik; Linke, Heiner

    2017-08-31

    Compared to traditional pn-junction photovoltaics, hot carrier solar cells offer potentially higher efficiency by extracting work from the kinetic energy of photogenerated "hot carriers" before they cool to the lattice temperature. Hot carrier solar cells have been demonstrated in high-bandgap ferroelectric insulators and GaAs/AlGaAs heterostructures, but so far not in low-bandgap materials, where the potential efficiency gain is highest. Recently, a high open-circuit voltage was demonstrated in an illuminated wurtzite InAs nanowire with a low bandgap of 0.39 eV, and was interpreted in terms of a photothermoelectric effect. Here, we point out that this device is a hot carrier solar cell and discuss its performance in those terms. In the demonstrated devices, InP heterostructures are used as energy filters in order to thermoelectrically harvest the energy of hot electrons photogenerated in InAs absorber segments. The obtained photovoltage depends on the heterostructure design of the energy filter and is therefore tunable. By using a high-resistance, thermionic barrier, an open-circuit voltage is obtained that is in excess of the Shockley-Queisser limit. These results provide generalizable insight into how to realize high voltage hot carrier solar cells in low-bandgap materials, and therefore are a step towards the demonstration of higher efficiency hot carrier solar cells. © 2017 IOP Publishing Ltd.

  2. Edaravone protects osteoblastic cells from dexamethasone through inhibiting oxidative stress and mPTP opening.

    PubMed

    Sun, Wen-xiao; Zheng, Hai-ya; Lan, Jun

    2015-11-01

    Existing evidences have emphasized an important role of oxidative stress in dexamethasone (Dex)-induced osteoblastic cell damages. Here, we investigated the possible anti-Dex activity of edaravone in osteoblastic cells, and studied the underlying mechanisms. We showed that edaravone dose-dependently attenuated Dex-induced death and apoptosis of established human or murine osteoblastic cells. Further, Dex-mediated damages to primary murine osteoblasts were also alleviated by edaravone. In osteoblastic cells/osteoblasts, Dex induced significant oxidative stresses, tested by increased levels of reactive oxygen species and lipid peroxidation, which were remarkably inhibited by edaravone. Meanwhile, edaravone repressed Dex-induced mitochondrial permeability transition pore (mPTP) opening, or mitochondrial membrane potential reduction, in osteoblastic cells/osteoblasts. Significantly, edaravone-induced osteoblast-protective activity against Dex was alleviated with mPTP inhibition through cyclosporin A or cyclophilin-D siRNA. Together, we demonstrate that edaravone protects osteoblasts from Dex-induced damages probably through inhibiting oxidative stresses and following mPTP opening.

  3. Enhanced Open-Circuit Voltage of PbS Nanocrystal Quantum Dot Solar Cells

    PubMed Central

    Yoon, Woojun; Boercker, Janice E.; Lumb, Matthew P.; Placencia, Diogenes; Foos, Edward E.; Tischler, Joseph G.

    2013-01-01

    Nanocrystal quantum dots (QD) show great promise toward improving solar cell efficiencies through the use of quantum confinement to tune absorbance across the solar spectrum and enable multi-exciton generation. Despite this remarkable potential for high photocurrent generation, the achievable open-circuit voltage (Voc) is fundamentally limited due to non-radiative recombination processes in QD solar cells. Here we report the highest open-circuit voltages to date for colloidal QD based solar cells under one sun illumination. This Voc of 692 ± 7 mV for 1.4 eV PbS QDs is a result of improved passivation of the defective QD surface, demonstrating as a function of the QD bandgap (Eg). Comparing experimental Voc variation with the theoretical upper-limit obtained from one diode modeling of the cells with different Eg, these results clearly demonstrate that there is a tremendous opportunity for improvement of Voc to values greater than 1 V by using smaller QDs in QD solar cells. PMID:23868514

  4. Potential for leaching of heavy metals in open-burning bottom ash and soil from a non-engineered solid waste landfill.

    PubMed

    Gwenzi, Willis; Gora, Dorcas; Chaukura, Nhamo; Tauro, Tonny

    2016-03-01

    Bottom ash from open-burning of municipal waste practised in developing countries poses a risk of heavy metal leaching into groundwater. Compared to incineration ash, there is limited information on heavy metal leaching from open-burning ash and soil from non-engineered landfills. Batch and column experiments were conducted to address three specific objectives; (1) to determine aqua regia extractable concentrations of heavy metals in fresh ash, old ash and soil from beneath the landfill, (2) to determine the relationship between heavy metal leaching, initial and final pH of leaching solution, and aqua regia extractable concentrations, and (3) to determine the breakthrough curves of heavy metals in ashes and soil. Aqua regia extractable concentrations of Cd, Zn, Mn, Cu, Ni and Pb were significantly higher (p < 0.05) in fresh and old ashes than soil beneath landfill and uncontaminated soil (control). Increasing initial solution pH from 5 and 7 to 9 significantly reduced the mobility of Pb, Zn and Cu but not Cd whose mobility peaked at pH 7 and 9. Concentrations of desorbed heavy metals were not correlated with aqua regia extractable concentrations. Final pH of leachate rebounded to close to original pH of the material, suggesting a putative high buffering capacity for all materials. Both batch and column leaching showed that concentrations of leached heavy metals were disproportionately lower (<5%) than aqua regia extractable concentrations in most cases. The retardation of heavy metals was further evidenced by sigmoidal breakthrough curves. Heavy metal retention was attributed to precipitation, pH-dependent adsorption and formation of insoluble organo-metallic complexes at near-neutral to alkaline pH. Overall, the risk of heavy metal leaching from ash and soil from the waste dump into groundwater was low. The high pH and the presence of Zn, Fe, Mn and Cu make ash an ideal low-cost liming material and source of micronutrients particularly on acidic soils prevalent

  5. Finite element analysis of a three-dimensional open-celled model for trabecular bone.

    PubMed

    Beaupre, G S; Hayes, W C

    1985-08-01

    Based on a regular array of cubic unit cells, each containing a body-centered spherical void, we created an idealized three-dimensional model for both subchondral trabecular bone and a class of porous foams. By considering only face-to-face stacking of unit cells, the inherent symmetry was such that, except at the surface, the displacements and stresses within any one unit cell were representative of the entire porous structure. Using prescribed displacements the model was loaded in both uniaxial compressive strain and uniaxial shear strain. Based on the response to these loads, we found the tensor of elastic constants for an equivalent homogeneous elastic solid with cubic symmetry. We then compared the predicted modulus with our experimental values for bovine trabecular bone and literature values for an open-celled latex rubber foam.

  6. MRP proteins as potential mediators of heavy metal resistance in zebrafish cells.

    PubMed

    Long, Yong; Li, Qing; Wang, Youhui; Cui, Zongbin

    2011-04-01

    Acquired resistance of mammalian cells to heavy metals is closely relevant to enhanced expression of several multidrug resistance-associated proteins (MRP), but it remains unclear whether MRP proteins confer resistance to heavy metals in zebrafish. In this study, we obtained zebrafish (Danio rerio) fibroblast-like ZF4 cells with resistance to toxic heavy metals after chronic cadmium exposure and selection for 6months. These cadmium-resistant cells (ZF4-Cd) were maintained in 5μM cadmium and displayed cross-resistance to cadmium, mercury, arsenite and arsenate. ZF4-Cd cells remained the resistance to heavy metals after protracted culture in cadmium-free medium. In comparison with ZF4-WT cells, ZF4-Cd cells exhibited accelerated rate of cadmium excretion, enhanced activity of MRP-like transport, elevated expression of abcc2, abcc4 and mt2 genes, and increased content of cellular GSH. Inhibition of MRP-like transport activity, GSH biosynthesis and GST activity significantly attenuated the resistance of ZF4-Cd cells to heavy metals. The results indicate that some of MRP transporters are involved in the efflux of heavy metals conjugated with cellular GSH and thus play crucial roles in heavy metal detoxification of zebrafish cells.

  7. Large-conductance K+ channel openers induce death of human glioma cells.

    PubMed

    Debska-Vielhaber, G; Godlewski, M M; Kicinska, A; Skalska, J; Kulawiak, B; Piwonska, M; Zablocki, K; Kunz, W S; Szewczyk, A; Motyl, T

    2009-12-01

    Large-conductance Ca(2+)-activated K(+) channels (BKCa channels) are highly expressed in human glioma cells. It has been reported that BK(Ca) channels are present in the inner mitochondrial membrane of the human glioma cell line LN229. In the present study we investigated whether BK(Ca)-channel openers, such as CGS7181 (ethyl 2-hydroxy-1-[[(4-methylphenyl)amino]oxo]-6-trifluoromethyl-1H-indole-3-carboxylate) and CGS7184 (ethyl 1-[[(4-chlorophenyl)amino]oxo]-2-hydroxy-6-trifluoromethyl-1H-indole-3-carboxylate), affect the functioning of LN229 glioma cell mitochondria in situ. In the micromolar concentration range CGS7181 and CGS7184 induced glioma cell death. Morphological and cytometric analyses confirmed that both substances trigger the glioma cell death. This effect was not inhibited by the pan-caspase inhibitor z-VAD-fmk. Lack of DNA laddering, PARP cleavage, and caspase 3 activation suggested that glioma cell death was not of the apoptotic type. We examined the effect of CGS7184 on mitochondrial membrane potential and mitochondrial respiration. Potassium channel opener CGS7184 increased cell respiration and induced mitochondrial membrane depolarization. The latter was dependent on the presence of Ca(2+) in the external medium. It was shown that CGS7184 induced an increase of cytosolic Ca(2+) concentration due to endoplasmic reticulum store depletion. In conclusion, our results show that CGS7181 and CGS7184 induce glioma cell death by increasing the cytosolic calcium concentration followed by activation of calpains.

  8. Fluorescent metal nanoshell and CK19 detection on single cell image.

    PubMed

    Zhang, Jian; Fu, Yi; Li, Ge; Lakowicz, Joseph R; Zhao, Richard Y

    2011-09-16

    In this article, we report the synthesis strategy and optical properties of a novel type of fluorescence metal nanoshell when it was used as imaging agent for fluorescence cell imaging. The metal nanoshells were made with 40 nm silica cores and 10nm silver shells. Unlike typical fluorescence metal nanoshells which contain the organic dyes in the cores, novel metal nanoshells were composed of Cy5-labelled monoclonal anti-CK19 antibodies (mAbs) on the external surfaces of shells. Optical measurements to the single nanoparticles showed that in comparison with the metal free labelled mAbs, the mAb-Ag complexes displayed significantly enhanced emission intensity and dramatically shortened lifetime due to near-field interactions of fluorophores with metal. These metal nanoshells were found to be able to immunoreact with target cytokeratin 19 (CK19) molecules on the surfaces of LNCAP and HeLa cells. Fluorescence cell images were recorded on a time-resolved confocal microscope. The emissions from the metal nanoprobes could be clearly isolated from the cellular autofluorescence backgrounds on the cell images as either individuals or small clusters due to their stronger emission intensities and shorter lifetimes. These emission signals could also be precisely counted on single cell images. The count number may provide an approach for quantifying the target molecules in the cells.

  9. Metal ion transport quantified by ICP-MS in intact cells

    PubMed Central

    Figueroa, Julio A. Landero; Stiner, Cory A.; Radzyukevich, Tatiana L.; Heiny, Judith A.

    2016-01-01

    The use of ICP-MS to measure metal ion content in biological tissues offers a highly sensitive means to study metal-dependent physiological processes. Here we describe the application of ICP-MS to measure membrane transport of Rb and K ions by the Na,K-ATPase in mouse skeletal muscles and human red blood cells. The ICP-MS method provides greater precision and statistical power than possible with conventional tracer flux methods. The method is widely applicable to studies of other metal ion transporters and metal-dependent processes in a range of cell types and conditions. PMID:26838181

  10. Metal ion transport quantified by ICP-MS in intact cells.

    PubMed

    Figueroa, Julio A Landero; Stiner, Cory A; Radzyukevich, Tatiana L; Heiny, Judith A

    2016-02-03

    The use of ICP-MS to measure metal ion content in biological tissues offers a highly sensitive means to study metal-dependent physiological processes. Here we describe the application of ICP-MS to measure membrane transport of Rb and K ions by the Na,K-ATPase in mouse skeletal muscles and human red blood cells. The ICP-MS method provides greater precision and statistical power than possible with conventional tracer flux methods. The method is widely applicable to studies of other metal ion transporters and metal-dependent processes in a range of cell types and conditions.

  11. Visualizing metal ions in cells: an overview of analytical techniques, approaches, and probes

    PubMed Central

    Dean, Kevin M.; Qin, Yan; Palmer, Amy E.

    2012-01-01

    Quantifying the amount and defining the location of metal ions in cells and organisms are critical steps in understanding metal homeostasis and how dyshomeostasis causes or is a consequence of disease. A number of recent advances have been made in the development and application of analytical methods to visualize metal ions in biological specimens. Here, we briefly summarize these advances before focusing in more depth on probes for examining transition metals in living cells with high spatial and temporal resolution using fluorescence microscopy. PMID:22521452

  12. CellAnimation: an open source MATLAB framework for microscopy assays.

    PubMed

    Georgescu, Walter; Wikswo, John P; Quaranta, Vito

    2012-01-01

    Advances in microscopy technology have led to the creation of high-throughput microscopes that are capable of generating several hundred gigabytes of images in a few days. Analyzing such wealth of data manually is nearly impossible and requires an automated approach. There are at present a number of open-source and commercial software packages that allow the user to apply algorithms of different degrees of sophistication to the images and extract desired metrics. However, the types of metrics that can be extracted are severely limited by the specific image processing algorithms that the application implements, and by the expertise of the user. In most commercial software, code unavailability prevents implementation by the end user of newly developed algorithms better suited for a particular type of imaging assay. While it is possible to implement new algorithms in open-source software, rewiring an image processing application requires a high degree of expertise. To obviate these limitations, we have developed an open-source high-throughput application that allows implementation of different biological assays such as cell tracking or ancestry recording, through the use of small, relatively simple image processing modules connected into sophisticated imaging pipelines. By connecting modules, non-expert users can apply the particular combination of well-established and novel algorithms developed by us and others that are best suited for each individual assay type. In addition, our data exploration and visualization modules make it easy to discover or select specific cell phenotypes from a heterogeneous population. CellAnimation is distributed under the Creative Commons Attribution-NonCommercial 3.0 Unported license (http://creativecommons.org/licenses/by-nc/3.0/). CellAnimationsource code and documentation may be downloaded from www.vanderbilt.edu/viibre/software/documents/CellAnimation.zip. Sample data are available at www

  13. Enhancement of the third-order nonlinear optical properties in open-shell singlet transition-metal dinuclear systems: effects of the group, of the period, and of the charge of the metal atom.

    PubMed

    Fukui, Hitoshi; Inoue, Yudai; Yamada, Taishi; Ito, Soichi; Shigeta, Yasuteru; Kishi, Ryohei; Champagne, Benoît; Nakano, Masayoshi

    2012-06-07

    Metal-metal multiply bonded complexes in their singlet state have been predicted to form a novel class of "σ-dominant" third-order nonlinear optical compounds based on the results of dichromium(II) and dimolybdenum(II) systems (H. Fukui et al. J. Phys. Chem. Lett.2011, 2, 2063) whose second hyperpolarizabilities (γ) are enhanced by the contribution of the dσ electrons with an intermediate diradical character. In this study, using the spin-unrestricted coupled-cluster method with singles and doubles as well as with perturbative triples, we investigate the dependences of γ on the group and on the period of the transition metals as well as on their atomic charges in several open-shell singlet dimetallic systems. A significant enhancement of γ is observed in those dimetallic systems composed of (i) transition metals with a small group number, (ii) transition metals with a large periodic number, and (iii) transition metals with a small positive charge. From the decomposition of the γ values into the contributions of dσ, dπ, and dδ electrons, the γ enhancements are shown to originate from the dσ contribution, because it corresponds to the intermediate diradical character region. Furthermore, the amplitude of dσ contribution turns out to be related to the size of the d(z(2)) atomic orbital of the transition metal, which accounts for the dependence of γ on the group, on the period, and on the charge of the metal atoms. These dependences provide a guideline for an effective molecular design of highly efficient third-order nonlinear optical (NLO) systems based on the metal-metal bonded systems.

  14. Mapping local deformation behavior in single cell metal lattice structures

    DOE PAGES

    Carlton, Holly D.; Lind, Jonathan; Messner, Mark C.; ...

    2017-02-08

    The deformation behavior of metal lattice structures is extremely complex and challenging to predict, especially since strain is not uniformly distributed throughout the structure. Understanding and predicting the failure behavior for these types of light-weighting structures is of great interest due to the excellent scaling of stiffness- and strength-to weight ratios they display. Therefore, there is a need to perform simplified experiments that probe unit cell mechanisms. This study reports on high resolution mapping of the heterogeneous structural response of single unit cells to the macro-scale loading condition. Two types of structures, known to show different stress-strain responses, were evaluatedmore » using synchrotron radiation micro-tomography while performing in-situ uniaxial compression tests to capture the local micro-strain deformation. These structures included the octet-truss, a stretch-dominated lattice, and the rhombic-dodecahedron, a bend-dominated lattice. The tomographic analysis showed that the stretch- and bend-dominated lattices exhibit different failure mechanisms and that the defects built into the structure cause a heterogeneous localized deformation response. Also shown here is a change in failure mode for stretch-dominated lattices, where there appears to be a transition from buckling to plastic yielding for samples with a relative density between 10 and 20%. In conclusion, the experimental results were also used to inform computational studies designed to predict the mesoscale deformation behavior of lattice structures. Here an equivalent continuum model and a finite element model were used to predict both local strain fields and mechanical behavior of lattices with different topologies.« less

  15. Cell Culture in Microgravity: Opening the Door to Space Cell Biology

    NASA Technical Reports Server (NTRS)

    Pellis, Neal R.; Dawson, David L. (Technical Monitor)

    1999-01-01

    Adaptational response of human cell populations to microgravity is investigated using simulation, short-term Shuttle experiments, and long-term microgravity. Simulation consists of a clinostatically-rotated cell culture system. The system is a horizontally-rotated cylinder completely filled with culture medium. Low speed rotation results in continuous-fall of the cells through the fluid medium. In this setting, cells: 1) aggregate, 2) propagate in three dimensions, 3) synthesize matrix, 4) differentiate, and 5) form sinusoids that facilitate mass transfer. Space cell culture is conducted in flight bioreactors and in static incubators. Cells grown in microgravity are: bovine cartilage, promyelocytic leukemia, kidney proximal tubule cells, adrenal medulla, breast and colon cancer, and endothelium. Cells were cultured in space to test specific hypotheses. Cartilage cells were used to determine structural differences in cartilage grown in space compared to ground-based bioreactors. Results from a 130-day experiment on Mir revealed that cartilage grown in space was substantially more compressible due to insufficient glycosaminoglycan in the matrix. Interestingly, earth-grown cartilage conformed better to the dimensions of the scaffolding material, while the Mir specimens were spherical. The other cell populations are currently being analyzed for cell surface properties, gene expression, and differentiation. Results suggest that some cells spontaneously differentiate in microgravity. Additionally, vast changes in gene expression may occur in response to microgravity. In conclusion, the transition to microgravity may constitute a physical perturbation in cells resulting in unique gene expressions, the consequences of which may be useful in tissue engineering, disease modeling, and space cell biology.

  16. Cell Culture in Microgravity: Opening the Door to Space Cell Biology

    NASA Technical Reports Server (NTRS)

    Pellis, Neal R.; Dawson, David L. (Technical Monitor)

    1999-01-01

    Adaptational response of human cell populations to microgravity is investigated using simulation, short-term Shuttle experiments, and long-term microgravity. Simulation consists of a clinostatically-rotated cell culture system. The system is a horizontally-rotated cylinder completely filled with culture medium. Low speed rotation results in continuous-fall of the cells through the fluid medium. In this setting, cells: 1) aggregate, 2) propagate in three dimensions, 3) synthesize matrix, 4) differentiate, and 5) form sinusoids that facilitate mass transfer. Space cell culture is conducted in flight bioreactors and in static incubators. Cells grown in microgravity are: bovine cartilage, promyelocytic leukemia, kidney proximal tubule cells, adrenal medulla, breast and colon cancer, and endothelium. Cells were cultured in space to test specific hypotheses. Cartilage cells were used to determine structural differences in cartilage grown in space compared to ground-based bioreactors. Results from a 130-day experiment on Mir revealed that cartilage grown in space was substantially more compressible due to insufficient glycosaminoglycan in the matrix. Interestingly, earth-grown cartilage conformed better to the dimensions of the scaffolding material, while the Mir specimens were spherical. The other cell populations are currently being analyzed for cell surface properties, gene expression, and differentiation. Results suggest that some cells spontaneously differentiate in microgravity. Additionally, vast changes in gene expression may occur in response to microgravity. In conclusion, the transition to microgravity may constitute a physical perturbation in cells resulting in unique gene expressions, the consequences of which may be useful in tissue engineering, disease modeling, and space cell biology.

  17. Biodegradable, polymer encapsulated, metal oxide particles for MRI-based cell tracking

    PubMed Central

    Shapiro, Erik M.

    2014-01-01

    Metallic particles have shaped the use of MRI for molecular and cellular imaging. While these particles have generally been developed for extracellular residence, either as blood pool contrast agents or targeted contrast agents, the coopted use of these particles for intracellular labeling has grown over the last 20 years. Coincident with this growth has been the development of metal oxide particles specifically intended for intracellular residence, and innovations in the nature of the metallic core. One promising nanoparticle construct for MRI-based cell tracking is polymer encapsulated metal oxide nanoparticles. Rather than a polymer coated metal oxide nanocrystal of the core:shell type, polymer encapsulated metal oxide nanoparticles cluster many nanocrystals within a polymer matrix. This nanoparticle composite more efficiently packages inorganic nanocrystals, affording the ability to label cells with more inorganic material. Further, for magnetic nanocrystals, the clustering of multiple magnetic nanocrystals within a single nanoparticle enhances r2 and r2* relaxivity. Methods for fabricating polymer encapsulated metal oxide nanoparticles are facile, yielding both varied compositions and synthetic approaches. This review presents a brief history into the use of metal oxide particles for MRI-based cell tracking and details the development and use of biodegradable, polymer encapsulated, metal oxide nano- and microparticles for MRI-based cell tracking. PMID:24753150

  18. Biodegradable, polymer encapsulated, metal oxide particles for MRI-based cell tracking.

    PubMed

    Shapiro, Erik M

    2015-01-01

    Metallic particles have shaped the use of magnetic resonance imaging (MRI) for molecular and cellular imaging. Although these particles have generally been developed for extracellular residence, either as blood pool contrast agents or targeted contrast agents, the coopted use of these particles for intracellular labeling has grown over the last 20 years. Coincident with this growth has been the development of metal oxide particles specifically intended for intracellular residence, and innovations in the nature of the metallic core. One promising nanoparticle construct for MRI-based cell tracking is polymer encapsulated metal oxide nanoparticles. Rather than a polymer coated metal oxide nanocrystal of the core: shell type, polymer encapsulated metal oxide nanoparticles cluster many nanocrystals within a polymer matrix. This nanoparticle composite more efficiently packages inorganic nanocrystals, affording the ability to label cells with more inorganic material. Further, for magnetic nanocrystals, the clustering of multiple magnetic nanocrystals within a single nanoparticle enhances r2 and r2* relaxivity. Methods for fabricating polymer encapsulated metal oxide nanoparticles are facile, yielding both varied compositions and synthetic approaches. This review presents a brief history into the use of metal oxide particles for MRI-based cell tracking and details the development and use of biodegradable, polymer encapsulated, metal oxide nanoparticles and microparticles for MRI-based cell tracking.

  19. Efficient Nanostructured 'Black' Silicon Solar Cell by Copper-Catalyzed Metal-Assisted Etching

    SciTech Connect

    Toor, Fatima; Oh, Jihun; Branz, Howard M.

    2014-09-13

    Here, we produce low-reflectivity nanostructured ‘black’ silicon (bSi) using copper (Cu) nanoparticles as the catalyst for metal-assisted etching and demonstrate a 17.0%-efficient Cu-etched bSi solar cell without any vacuum-deposited anti-reflection coating. We found that the concentration ratio of HF to H2O2 in the etch solution provides control of the nanostructure morphology. The solar-spectrum-weighted average reflection (Rave) for bSi is as low as 3.1% on Cu-etched planar samples; we achieve lower reflectivity by nanostructuring of micron-scale pyramids. Successful Cu-based anti-reflection etching requires a concentration ratio [HF]/[H2O2] ≥ 3. Our 17.0%-efficient Cu-etched bSi photovoltaic cell with a pyramid-texture has a Rave of 3% and an open circuit voltage (Voc) of 616 mV that might be further improved by reducing near-surface phosphorus (P) densities.

  20. Correlation of energy disorder and open-circuit voltage in hybrid perovskite solar cells

    NASA Astrophysics Data System (ADS)

    Shao, Yuchuan; Yuan, Yongbo; Huang, Jinsong

    2016-01-01

    Organometal trihalide perovskites have been demonstrated as excellent light absorbers for high-efficiency photovoltaic applications. Previous approaches to increasing the solar cell efficiency have focused on optimization of the grain morphology of perovskite thin films. Here, we show that the structural order of the electron transport layers also has a significant impact on solar cell performance. We demonstrate that the power conversion efficiency of CH3NH3PbI3 planar heterojunction photovoltaic cells increases from 17.1 to 19.4% when the energy disorder in the fullerene electron transport layer is reduced by a simple solvent annealing process. The increase in efficiency is the result of the enhancement in open-circuit voltage from 1.04 to 1.13 V without sacrificing the short-circuit current and fill factor. These results shed light on the origin of open-circuit voltage in perovskite solar cells, and provide a path to further increase their efficiency.

  1. Correlation of energy disorder and open-circuit voltage in hybrid perovskite solar cells

    DOE PAGES

    Shao, Yuchuan; Yuan, Yongbo; Huang, Jinsong

    2016-01-11

    Organometal trihalide perovskites have been demonstrated as excellent light absorbers for high efficiency photovoltaic applications. Previous approaches to increasing the solar cell efficiency have focussed on optimisation of the grain morphology of perovskite thin films. Here, we show that the structural order of the electron-transport layers also has a significant impact on solar cell performance. We demonstrate that the power conversion efficiency of CH3NH3PbI3 planar-heterojunction photovoltaic cells increases from 17.1% to 19.4% when the energy disorder in the fullerene electron-transport layer is reduced by a simple solvent annealing process. The increase in efficiency is the result of the enhancement inmore » open-circuit voltage from 1.04 V to 1.13 V without sacrificing the short-circuit current and fill factor. Finally, these results shed light on the origin of open-circuit voltage in perovskite solar cells, and provide a new path to further increase their efficiency« less

  2. Correlation of energy disorder and open-circuit voltage in hybrid perovskite solar cells

    SciTech Connect

    Shao, Yuchuan; Yuan, Yongbo; Huang, Jinsong

    2016-01-11

    Organometal trihalide perovskites have been demonstrated as excellent light absorbers for high efficiency photovoltaic applications. Previous approaches to increasing the solar cell efficiency have focussed on optimisation of the grain morphology of perovskite thin films. Here, we show that the structural order of the electron-transport layers also has a significant impact on solar cell performance. We demonstrate that the power conversion efficiency of CH3NH3PbI3 planar-heterojunction photovoltaic cells increases from 17.1% to 19.4% when the energy disorder in the fullerene electron-transport layer is reduced by a simple solvent annealing process. The increase in efficiency is the result of the enhancement in open-circuit voltage from 1.04 V to 1.13 V without sacrificing the short-circuit current and fill factor. Finally, these results shed light on the origin of open-circuit voltage in perovskite solar cells, and provide a new path to further increase their efficiency

  3. OpenRBC: A Fast Simulator of Red Blood Cells at Protein Resolution

    NASA Astrophysics Data System (ADS)

    Tang, Yu-Hang; Lu, Lu; Li, He; Evangelinos, Constantinos; Grinberg, Leopold; Sachdeva, Vipin; Karniadakis, George Em

    2017-05-01

    We present OpenRBC, a coarse-grained molecular dynamics code, which is capable of performing an unprecedented in silico experiment --- simulating an entire mammal red blood cell lipid bilayer and cytoskeleton as modeled by 4 million mesoscopic particles --- using a single shared memory commodity workstation. To achieve this, we invented an adaptive spatial-searching algorithm to accelerate the computation of short-range pairwise interactions in an extremely sparse 3D space. The algorithm is based on a Voronoi partitioning of the point cloud of coarse-grained particles, and is continuously updated over the course of the simulation. The algorithm enables the construction of the key spatial searching data structure in our code, i.e. a lattice-free cell list, with a time and space cost linearly proportional to the number of particles in the system. The position and shape of the cells also adapt automatically to the local density and curvature. The code implements OpenMP parallelization and scales to hundreds of hardware threads. It outperforms a legacy simulator by almost an order of magnitude in time-to-solution and more than 40 times in problem size, thus providing a new platform for probing the biomechanics of red blood cells.

  4. Correlation of energy disorder and open-circuit voltage in hybrid perovskite solar cells

    DOE PAGES

    Shao, Yuchuan; Yuan, Yongbo; Huang, Jinsong

    2016-01-11

    Organometal trihalide perovskites have been demonstrated as excellent light absorbers for high efficiency photovoltaic applications. Previous approaches to increasing the solar cell efficiency have focussed on optimisation of the grain morphology of perovskite thin films. Here, we show that the structural order of the electron-transport layers also has a significant impact on solar cell performance. We demonstrate that the power conversion efficiency of CH3NH3PbI3 planar-heterojunction photovoltaic cells increases from 17.1% to 19.4% when the energy disorder in the fullerene electron-transport layer is reduced by a simple solvent annealing process. The increase in efficiency is the result of the enhancement inmore » open-circuit voltage from 1.04 V to 1.13 V without sacrificing the short-circuit current and fill factor. Lastly, these results shed light on the origin of open-circuit voltage in perovskite solar cells, and provide a new path to further increase their efficiency.« less

  5. Correlation of energy disorder and open-circuit voltage in hybrid perovskite solar cells

    SciTech Connect

    Shao, Yuchuan; Yuan, Yongbo; Huang, Jinsong

    2016-01-11

    Organometal trihalide perovskites have been demonstrated as excellent light absorbers for high efficiency photovoltaic applications. Previous approaches to increasing the solar cell efficiency have focussed on optimisation of the grain morphology of perovskite thin films. Here, we show that the structural order of the electron-transport layers also has a significant impact on solar cell performance. We demonstrate that the power conversion efficiency of CH3NH3PbI3 planar-heterojunction photovoltaic cells increases from 17.1% to 19.4% when the energy disorder in the fullerene electron-transport layer is reduced by a simple solvent annealing process. The increase in efficiency is the result of the enhancement in open-circuit voltage from 1.04 V to 1.13 V without sacrificing the short-circuit current and fill factor. Lastly, these results shed light on the origin of open-circuit voltage in perovskite solar cells, and provide a new path to further increase their efficiency.

  6. Stem Cell-Based Cell Carrier for Targeted Oncolytic Virotherapy: Translational Opportunity and Open Questions.

    PubMed

    Kim, Janice; Hall, Robert R; Lesniak, Maciej S; Ahmed, Atique U

    2015-11-27

    Oncolytic virotherapy for cancer is an innovative therapeutic option where the ability of a virus to promote cell lysis is harnessed and reprogrammed to selectively destroy cancer cells. Such treatment modalities exhibited antitumor activity in preclinical and clinical settings and appear to be well tolerated when tested in clinical trials. However, the clinical success of oncolytic virotherapy has been significantly hampered due to the inability to target systematic metastasis. This is partly due to the inability of the therapeutic virus to survive in the patient circulation, in order to target tumors at distant sites. An early study from various laboratories demonstrated that cells infected with oncolytic virus can protect the therapeutic payload form the host immune system as well as function as factories for virus production and enhance the therapeutic efficacy of oncolytic virus. While a variety of cell lineages possessed potential as cell carriers, copious investigation has established stem cells as a very attractive cell carrier system in oncolytic virotherapy. The ideal cell carrier desire to be susceptible to viral infection as well as support viral infection, maintain immunosuppressive properties to shield the loaded viruses from the host immune system, and most importantly possess an intrinsic tumor homing ability to deliver loaded viruses directly to the site of the metastasis-all qualities stem cells exhibit. In this review, we summarize the recent work in the development of stem cell-based carrier for oncolytic virotherapy, discuss the advantages and disadvantages of a variety of cell carriers, especially focusing on why stem cells have emerged as the leading candidate, and finally propose a future direction for stem cell-based targeted oncolytic virotherapy that involves its establishment as a viable treatment option for cancer patients in the clinical setting.

  7. Stem Cell-Based Cell Carrier for Targeted Oncolytic Virotherapy: Translational Opportunity and Open Questions

    PubMed Central

    Kim, Janice; Hall, Robert R.; Lesniak, Maciej S.; Ahmed, Atique U.

    2015-01-01

    Oncolytic virotherapy for cancer is an innovative therapeutic option where the ability of a virus to promote cell lysis is harnessed and reprogrammed to selectively destroy cancer cells. Such treatment modalities exhibited antitumor activity in preclinical and clinical settings and appear to be well tolerated when tested in clinical trials. However, the clinical success of oncolytic virotherapy has been significantly hampered due to the inability to target systematic metastasis. This is partly due to the inability of the therapeutic virus to survive in the patient circulation, in order to target tumors at distant sites. An early study from various laboratories demonstrated that cells infected with oncolytic virus can protect the therapeutic payload form the host immune system as well as function as factories for virus production and enhance the therapeutic efficacy of oncolytic virus. While a variety of cell lineages possessed potential as cell carriers, copious investigation has established stem cells as a very attractive cell carrier system in oncolytic virotherapy. The ideal cell carrier desire to be susceptible to viral infection as well as support viral infection, maintain immunosuppressive properties to shield the loaded viruses from the host immune system, and most importantly possess an intrinsic tumor homing ability to deliver loaded viruses directly to the site of the metastasis—all qualities stem cells exhibit. In this review, we summarize the recent work in the development of stem cell-based carrier for oncolytic virotherapy, discuss the advantages and disadvantages of a variety of cell carriers, especially focusing on why stem cells have emerged as the leading candidate, and finally propose a future direction for stem cell-based targeted oncolytic virotherapy that involves its establishment as a viable treatment option for cancer patients in the clinical setting. PMID:26633462

  8. Cooling Earth's temperature by seeding marine stratocumulus clouds for increasing cloud cover by closing open cells

    NASA Astrophysics Data System (ADS)

    Daniel, R.

    2008-12-01

    The transition from open to closed cellular convection in marine stratocumulus is very sensitive to small concentrations of cloud condensation nuclei (CCN) aerosols. Addition of small amounts of CCN (about 100 cm-3) to the marine boundary layer (MBL) can close the open cells and by that increase the cloud cover from about 40% to nearly 100%, with negative radiative forcing exceeding 100 wm-2. We show satellite measurements that demonstrate this sensitivity by inadvertent experiments of old and diluted ship tracks. With the methodology suggested by Salter and Latham for spraying sub-micron sea water drops that serve as CCN, it is possible to close sufficiently large area of open cells for achieving the negative radiative forcing that is necessary to balance the greenhouse gases positive forcing. We show calculations of the feasibility of such an undertaking, and suggest that this is an economically feasible method with the least potential risks, when compared to seeding marine stratocumulus for enhancing their albedo or with seeding the stratosphere with bright or dark aerosols. Global Circulation models coupled with the ocean and the ice are necessary to calculate the impact and the possible side effects.

  9. Solar cell degradation under open circuit condition in out-doors-in desert region

    NASA Astrophysics Data System (ADS)

    Boussaid, M.; Belghachi, A.; Agroui, K.; Abdelaoui, M.; Otmani, M.

    The reliability of solar cells is an important parameter in the design of photovoltaic systems and particularly for cost estimation. Solar cell degradation is the result of various operating conditions; temperature is one of most important factors. Installed PV modules in desert regions are subjected to various temperature changes with significant gradient leading to accelerated degradation. In the present work, we demonstrate the influence of open-circuit condition on the degradation of PV modules. The experiment is carried out in the desert region of ADRAR (southern Algeria) using two modules IJISEL of single-crystal silicon. A continuous monitoring allows analysis of both performances of modules for duration of 330 days. The module in open-circuit condition reaches higher temperature means than the module in charging condition; therefore, it undergoes a higher degradation. By simulation, we found that the life of a PV module (whose power output is close to 50%) in a condition of an open-circuit in the desert region could be reduced to 4 years, and that has a significant impact on economy.

  10. Engineered metal nanoparticles in the sub-nanomolar levels kill cancer cells

    PubMed Central

    Vodyanoy, Vitaly; Daniels, Yasmine; Pustovyy, Oleg; MacCrehan, William A; Muramoto, Shin; Stan, Gheorghe

    2016-01-01

    Background Small metal nanoparticles obtained from animal blood were observed to be toxic to cultured cancer cells, whereas noncancerous cells were much less affected. In this work, engineered zinc and copper metal nanoparticles were produced from bulk metal rods by an underwater high-voltage discharge method. The metal nanoparticles were characterized by atomic force microscopy and X-ray photoelectron spectroscopy. The metal nanoparticles, with estimated diameters of 1 nm–2 nm, were determined to be more than 85% nonoxidized. A cell viability assay and high-resolution light microscopy showed that exposure of RG2, cultured rat brain glioma cancer cells, to the zinc and copper nanoparticles resulted in cell morphological changes, including decreased cell adherence, shrinking/rounding, nuclear condensation, and budding from cell bodies. The metal-induced cell injuries were similar to the effects of staurosporine, an active apoptotic reagent. The viability experiments conducted for zinc and copper yielded values of dissociation constants of 0.22±0.08 nmol/L (standard error [SE]) and 0.12±0.02 nmol/L (SE), respectively. The noncancerous astrocytes were not affected at the same conditions. Because metal nanoparticles were lethal to the cancer cells at sub-nanomolar concentrations, they are potentially important as nanomedicine. Purpose Lethal concentrations of synthetic metal nanoparticles reported in the literature are a few orders of magnitude higher than the natural, blood-isolated metal nanoparticles; therefore, in this work, engineered metal nanoparticles were examined to mimic the properties of endogenous metal nanoparticles. Materials and methods RG2, rat brain glioma cells CTX TNA2 brain rat astrocytes, obtained from the American Type Culture Collection, high-voltage discharge, atomic force microscope, X-ray photoelectron spectroscopy, high-resolution light microscopy, zeta potential measurements, and 3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyltetrazolium

  11. Tanacetum vulgare as a bioindicator of trace-metal contamination: a study of a naturally colonized open-pit lignite mine.

    PubMed

    Jasion, Mateusz; Samecka-Cymerman, Aleksandra; Kolon, Krzysztof; Kempers, Alexander J

    2013-10-01

    We investigated the possibility of use of Tanacetum vulgare (tansy) as an ecological indicator of metal concentration in a naturally colonized open-pit lignite mine in Bełchatów (Poland). Tanacetum vulgare is the only species growing abundantly and spontaneously in the lignite mine waste dumps. Metal concentrations in roots, stems, leaves, flowers, and soil were measured in dump sites differing in type and time of reclamation and therefore differing in pollution levels. Tanacetum vulgare appeared to be an accumulator of chromium and iron in roots, whereas highest concentrations of manganese and zinc were found in leaves. A high bioaccumulation factor for cadmium (Cd) was observed in dumps and control sites, indicating that even small amounts of Cd in the environment may result in significant uptake by the plant. The lowest concentrations of metals were found in plants from sites situated on dumps reclaimed with argillaceous limestone.

  12. Designing a metallic nanoconcentrator for a lateral multijunction photovoltaic cell

    NASA Astrophysics Data System (ADS)

    Wang, Trudie; Peumans, Peter

    2011-06-01

    A lateral multijunction photovoltaic (PV) concept is introduced that explores the unique ability of plasmonic nanoantennas to locally concentrate optical energy and spectrally filter incoming light at the subwavelength level. This electromagnetic field enhancement near the localized plasmon resonance modes of the metallic nanoantennas can be used to selectively increase light absorption in semiconductor nanowires at specific spectral and spatial regions. In our geometry, we take advantage of the ring antenna's ability to excite two distinct plasmon modes in order to carry out spectral splitting and concentration of the electromagnetic field. A localized dipolar surface plasmon mode near the material resonance of the silver nanoantenna results from the ring behaving as an effective disk in the visible region and focuses the field on the external surface of the ring while a dipolar bonding resonance mode dependent on the coupling of modes excited on the inner and outer surface of the ring geometry in the near infrared (NIR) region focuses energy in the cavity of the ring. Using finite difference time domain (FDTD) simulations, we describe the basic mechanisms at work and demonstrate that the subwavelength ring antennas can couple incident light into semiconductor nanowires placed both inside and outside the ring through the two modes with minimal loss in the metal. The modes are used to laterally split different spectral regions of broadband incident light optimized to the material bandgap of the nanowires located in the regions of field enhancement to produce the lateral multijunction effect. We demonstrate that, for example, a ring antenna with both an internal diameter and a thickness of 40 nm can enhance absorption by 6x in the visible region for a 100 nm tall AlAs nanowire placed just outside the ring and by 380x in the NIR region for a geometrically similar GaAs nanowire placed inside the ring. Both enhancements occur just above the material band gaps of the

  13. Modeling quorum sensing trade-offs between bacterial cell density and system extension from open boundaries

    NASA Astrophysics Data System (ADS)

    Marenda, Mattia; Zanardo, Marina; Trovato, Antonio; Seno, Flavio; Squartini, Andrea

    2016-12-01

    Bacterial communities undergo collective behavioural switches upon producing and sensing diffusible signal molecules; a mechanism referred to as Quorum Sensing (QS). Exemplarily, biofilm organic matrices are built concertedly by bacteria in several environments. QS scope in bacterial ecology has been debated for over 20 years. Different perspectives counterpose the role of density reporter for populations to that of local environment diffusivity probe for individual cells. Here we devise a model system where tubes of different heights contain matrix-embedded producers and sensors. These tubes allow non-limiting signal diffusion from one open end, thereby showing that population spatial extension away from an open boundary can be a main critical factor in QS. Experimental data, successfully recapitulated by a comprehensive mathematical model, demonstrate how tube height can overtake the role of producer density in triggering sensor activation. The biotic degradation of the signal is found to play a major role and to be species-specific and entirely feedback-independent.

  14. Stem cell research funding policies and dynamic innovation: a survey of open access and commercialization requirements.

    PubMed

    Lévesque, Maroussia; Kim, Jihyun Rosel; Isasi, Rosario; Knoppers, Bartha Maria; Plomer, Aurora; Joly, Yann

    2014-08-01

    This article compares and contrasts the pressures of both open access data sharing and commercialization policies in the context of publicly funded embryonic stem cell research (SCR). First, normative guidelines of international SCR organizations were examined. We then examined SCR funding guidelines and the project evaluation criteria of major funding organizations in the EU, the United Kingdom (UK), Spain, Canada and the United States. Our survey of policies revealed subtle pressures to commercialize research that include: increased funding availability for commercialization opportunities, assistance for obtaining intellectual property rights (IPRs) and legislation mandating commercialization. In lieu of open access models, funders are increasingly opting for limited sharing models or "protected commons" models that make the research available to researchers within the same region or those receiving the same funding. Meanwhile, there still is need for funding agencies to clarify and standardize terms such as "non-profit organizations" and "for-profit research," as more universities are pursuing for-profit or commercial opportunities.

  15. Modeling quorum sensing trade-offs between bacterial cell density and system extension from open boundaries.

    PubMed

    Marenda, Mattia; Zanardo, Marina; Trovato, Antonio; Seno, Flavio; Squartini, Andrea

    2016-12-14

    Bacterial communities undergo collective behavioural switches upon producing and sensing diffusible signal molecules; a mechanism referred to as Quorum Sensing (QS). Exemplarily, biofilm organic matrices are built concertedly by bacteria in several environments. QS scope in bacterial ecology has been debated for over 20 years. Different perspectives counterpose the role of density reporter for populations to that of local environment diffusivity probe for individual cells. Here we devise a model system where tubes of different heights contain matrix-embedded producers and sensors. These tubes allow non-limiting signal diffusion from one open end, thereby showing that population spatial extension away from an open boundary can be a main critical factor in QS. Experimental data, successfully recapitulated by a comprehensive mathematical model, demonstrate how tube height can overtake the role of producer density in triggering sensor activation. The biotic degradation of the signal is found to play a major role and to be species-specific and entirely feedback-independent.

  16. High open circuit voltages of solar cells based on quantum dot and dye hybrid-sensitization

    SciTech Connect

    Zhao, Yujie; Zhao, Wanyu; Chen, Jingkuo; Li, Huayang; Fu, Wuyou E-mail: fuwy56@163.com; Sun, Guang; Cao, Jianliang; Zhang, Zhanying; Bala, Hari E-mail: fuwy56@163.com

    2014-01-06

    A type of solar cell based on quantum dot (QD) and dye hybrid-sensitized mesoporous TiO{sub 2} film electrode was designed and reported. The electrode was consisted of a TiO{sub 2} nanoparticle (NP) thin film layer sensitized with CdS quantum dot (QD) and an amorphous TiO{sub 2} coated TiO{sub 2} NP thin film layer that sensitized with C106 dye. The amorphous TiO{sub 2} layer was obtained by TiCl{sub 4} post-treatment to improve the properties of solar cells. Research showed that the solar cells fabricated with as-prepared hybrid-sensitized electrode exhibited excellent photovoltaic performances and a fairly high open circuit voltage of 796 mV was achieved.

  17. Organic-silicon heterojunction solar cells: Open-circuit voltage potential and stability

    NASA Astrophysics Data System (ADS)

    Schmidt, Jan; Titova, Valeriya; Zielke, Dimitri

    2013-10-01

    We characterize the electronic properties of crystalline silicon (c-Si)/poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) junctions by means of contactless carrier lifetime measurements. The measurements demonstrate that this type of heterojunction has an unexpectedly high open-circuit voltage (Voc) potential exceeding 690 mV, making it relevant for the implementation into high-efficiency c-Si solar cells. Hybrid n-type c-Si solar cells featuring a PEDOT:PSS hole-transport layer on the front reach an energy conversion efficiency of 12.3%. We observe a humidity-related degradation in cell efficiency during storage in air. The degradation is reduced by capping the entire device by an atomic-layer-deposited aluminum oxide film and is completely avoided in a dehumidified environment.

  18. Remote replacement of materials open-test assembly specimens at the FFTF/IEM cell

    SciTech Connect

    Gibbons, P.W.; Ramsey, E.B.

    1990-01-01

    The Fast Flux Test Facility (FFTF) interim examination and maintenance (IEM) cell is used for the remote disassembly of irradiated fuel and materials experiments. The materials open-test assembly (MOTA) is brought to the IEM cell for materials test specimen removal. The specimens are shipped to the materials laboratory for sorting and installation in new specimen holders and then returned within 10 days to the IEM cell where they are installed in a new MOTA vehicle for further irradiation. Reconstituting a MOTA is a challenging remote operation involving dozens of steps and two separate facilities. Handling and disassembling sodium-wetted components pose interesting handling, cleaning, and disposal challenges. The success of this system is evidenced by its timely completion in the critical path of FFTF outage schedules.

  19. Metal complex-based electron-transfer mediators in dye-sensitized solar cells

    DOEpatents

    Elliott, C. Michael; Sapp, Shawn A.; Bignozzi, Carlo Alberto; Contado, Cristiano; Caramori, Stefano

    2006-03-28

    This present invention provides a metal-ligand complex and methods for using and preparing the same. In particular, the metal-ligand complex of the present invention is of the formula: L.sub.a-M-X.sub.b where L, M, X, a, and b are those define herein. The metal-ligand complexes of the present invention are useful in a variety of applications including as electron-transfer mediators in dye-sensitized solar cells and related photoelectrochromic devices.

  20. Myosin 2 Maintains an Open Exocytic Fusion Pore in Secretory Epithelial Cells

    PubMed Central

    Bhat, Purnima

    2009-01-01

    Many studies have implicated F-actin and myosin 2 in the control of regulated secretion. Most recently, evidence suggests a role for the microfilament network in regulating the postfusion events of vesicle dynamics. This is of potential importance as postfusion behavior can influence the loss of vesicle content and may provide a new target for drug therapy. We have investigated the role of myosin 2 in regulating exocytosis in secretory epithelial cells by using novel assays to determine the behavior of the fusion pore in individual granules. We immunolocalize myosin 2A to the apical region of pancreatic acinar cells, suggesting it is this isoform that plays a role in granule exocytosis. We further show myosin 2 phosphorylation increased on cell stimulation, consistent with a regulatory role in secretion. Importantly, in a single-cell, single-granule secretion assay, neither the myosin 2 inhibitor (−)-blebbistatin nor the myosin light chain kinase inhibitor ML-9 had any effect on the numbers of granules stimulated to fuse after cell stimulation. These data indicate that myosin 2, if it has any action on secretion, must be targeting postfusion granule behavior. This interpretation is supported by direct study of fusion pore opening in which we show that (−)-blebbistatin and ML-9 promote fusion pore closure and decrease fusion pore lifetimes. Our work now adds to a growing body of evidence showing that myosin 2 is an essential regulator of postfusion granule behavior. In particular, in the case of the secretory epithelial cells, myosin 2 activity is necessary to maintain fusion pore opening. PMID:19158378

  1. Isolation of Cells Specialized in Anticancer Alkaloid Metabolism by Fluorescence-Activated Cell Sorting1[OPEN

    PubMed Central

    Guimarães, Ana Luísa; Martínez-Cortés, Teresa; Guedes, Joana G.; Lopes, Telma; Andrade, Cláudia; Bispo, Cláudia; Andrade, Paula; Rodrigues, José A.

    2016-01-01

    Plant specialized metabolism often presents a complex cell-specific compartmentation essential to accomplish the biosynthesis of valuable plant natural products. Hence, the disclosure and potential manipulation of such pathways may depend on the capacity to isolate and characterize specific cell types. Catharanthus roseus is the source of several medicinal terpenoid indole alkaloids, including the low-level anticancer vinblastine and vincristine, for which the late biosynthetic steps occur in specialized mesophyll cells called idioblasts. Here, the optical, fluorescence, and alkaloid-accumulating properties of C. roseus leaf idioblasts are characterized, and a methodology for the isolation of idioblast protoplasts by fluorescence-activated cell sorting is established, taking advantage of the distinctive autofluorescence of these cells. This achievement represents a crucial step for the development of differential omic strategies leading to the identification of candidate genes putatively involved in the biosynthesis, pathway regulation, and transmembrane transport leading to the anticancer alkaloids from C. roseus. PMID:27356972

  2. Thin-Film Solar Cell Fabricated on a Flexible Metallic Substrate

    DOEpatents

    Tuttle, J. R.; Noufi, R.; Hasoon, F. S.

    2006-05-30

    A thin-film solar cell (10) is provided. The thin-film solar cell (10) comprises a flexible metallic substrate (12) having a first surface and a second surface. A back metal contact layer (16) is deposited on the first surface of the flexible metallic substrate (12). A semiconductor absorber layer (14) is deposited on the back metal contact. A photoactive film deposited on the semiconductor absorber layer (14) forms a heterojunction structure and a grid contact (24) deposited on the heterjunction structure. The flexible metal substrate (12) can be constructed of either aluminium or stainless steel. Furthermore, a method of constructing a solar cell is provided. The method comprises providing an aluminum substrate (12), depositing a semiconductor absorber layer (14) on the aluminum substrate (12), and insulating the aluminum substrate (12) from the semiconductor absorber layer (14) to inhibit reaction between the aluminum substrate (12) and the semiconductor absorber layer (14).

  3. Thin-film solar cell fabricated on a flexible metallic substrate

    DOEpatents

    Tuttle, John R.; Noufi, Rommel; Hasoon, Falah S.

    2006-05-30

    A thin-film solar cell (10) is provided. The thin-film solar cell (10) comprises a flexible metallic substrate (12) having a first surface and a second surface. A back metal contact layer (16) is deposited on the first surface of the flexible metallic substrate (12). A semiconductor absorber layer (14) is deposited on the back metal contact. A photoactive film deposited on the semiconductor absorber layer (14) forms a heterojunction structure and a grid contact (24) deposited on the heterjunction structure. The flexible metal substrate (12) can be constructed of either aluminium or stainless steel. Furthermore, a method of constructing a solar cell is provided. The method comprises providing an aluminum substrate (12), depositing a semiconductor absorber layer (14) on the aluminum substrate (12), and insulating the aluminum substrate (12) from the semiconductor absorber layer (14) to inhibit reaction between the aluminum substrate (12) and the semiconductor absorber layer (14).

  4. Environmental sensing of heavy metals through whole cell microbial biosensors: a synthetic biology approach.

    PubMed

    Bereza-Malcolm, Lara Tess; Mann, Gülay; Franks, Ashley Edwin

    2015-05-15

    Whole cell microbial biosensors are offering an alternative means for rapid, on-site heavy metal detection. Based in microorganisms, biosensing constructs are designed and constructed to produce both qualitative and quantitative outputs in response to heavy metal ions. Previous microbial biosensors designs are focused on single-input constructs; however, development of multiplexed systems is resulting in more flexible designs. The movement of microbial biosensors from laboratory based designs toward on-site, functioning heavy metal detectors has been hindered by the toxic nature of heavy metals, along with the lack of specificity of heavy metals promoter elements. Applying a synthetic biology approach with alternative microbial chassis may increase the robustness of microbial biosensors and mitigate these issues. Before full applications are achieved, further consideration has to be made regarding the risk and regulations of whole cell microbial biosensor use in the environment. To this end, a standard framework for future whole cell microbial biosensor design and use is proposed.

  5. On the prospects of using runaway electron beams generated in an open discharge for the pumping of metal-vapor lasers

    SciTech Connect

    Arlantsev, S.V.; Borovich, B.L.; Yurchenko, N.I.

    1995-03-01

    The excitation of gas lasers with the help of electron beams (e-beams) is, at the present time, one of the most promising methods of pumping. In most of the conventional methods, an electron beam is produced as a result of a collisionless acceleration of electrons due to the low gas density in a diode of an accelerator. Because of this, an accelerative gap should be hermetically isolated from a laser cell, which makes the technique of e-beam injection into the active region quite complicated. A radical solution to the problem would be the production of an e-beam in the gas whose density in the accelerative gap corresponds to the working pressure of the laser. This would allow one to place an accelerator in one chamber with the laser. The generation of a beam in a high-density gas would become possible when one provides the conditions for an effective transition of electrons into the runaway regime. Such a motion of electrons can be achieved in a strong electric field as a result of the decreasing cross section of the electron-atom interaction as sufficiently high energy. The runaway effect is manifested in the case where the electrons moving under the action of a strong external field obtain kinetic energy comparable with the potential difference. The kinetic energy is many times greater than that spent in one collision. Despite the considerable number of collisions, the electrons are transmitted into the steady acceleration regime, and their motion becomes almost directed, thus forming a beam. The present paper is devoted to the development of a physical-mathematical model of an open discharge, the calculation of its characteristics, and the estimation of the potentialities of e-beam pumping of metal-vapor lasers.

  6. A Novel Mechanism, Linked to Cell Density, Largely Controls Cell Division in Synechocystis1[OPEN

    PubMed Central

    Esteves-Ferreira, Alberto A.; Fort, Antoine; Fleming, Gerard T.A.; Araújo, Wagner L.; Fernie, Alisdair R.

    2017-01-01

    Many studies have investigated the various genetic and environmental factors regulating cyanobacterial growth. Here, we investigated the growth and metabolism of Synechocystis sp. PCC 6803 under different nitrogen sources, light intensities, and CO2 concentrations. Cells grown on urea showed the highest growth rates. However, for all conditions tested, the daily growth rates in batch cultures decreased steadily over time, and stationary phase was obtained with similar cell densities. Unexpectedly, metabolic and physiological analyses showed that growth rates during log phase were not controlled primarily by the availability of photoassimilates. Further physiological investigations indicated that nutrient limitation, quorum sensing, light quality, and light intensity (self-shading) were not the main factors responsible for the decrease in the growth rate and the onset of the stationary phase. Moreover, cell division rates in fed-batch cultures were positively correlated with the dilution rates. Hence, not only light, CO2, and nutrients can affect growth but also a cell-cell interaction. Accordingly, we propose that cell-cell interaction may be a factor responsible for the gradual decrease of growth rates in batch cultures during log phase, culminating with the onset of stationary phase. PMID:28646084

  7. Lacking chloroplasts in guard cells of crumpled leaf attenuates stomatal opening: both guard cell chloroplasts and mesophyll contribute to guard cell ATP levels.

    PubMed

    Wang, Shu-Wei; Li, Ying; Zhang, Xiao-Lu; Yang, Hai-Qiang; Han, Xue-Fei; Liu, Zhao-Hui; Shang, Zhong-Lin; Asano, Tomoya; Yoshioka, Yasushi; Zhang, Chun-Guang; Chen, Yu-Ling

    2014-09-01

    Controversies regarding the function of guard cell chloroplasts and the contribution of mesophyll in stomatal movements have persisted for several decades. Here, by comparing the stomatal opening of guard cells with (crl-ch) or without chloroplasts (crl-no ch) in one epidermis of crl (crumpled leaf) mutant in Arabidopsis, we showed that stomatal apertures of crl-no ch were approximately 65-70% those of crl-ch and approximately 50-60% those of wild type. The weakened stomatal opening in crl-no ch could be partially restored by imposing lower extracellular pH. Correspondingly, the external pH changes and K(+) accumulations following fusicoccin (FC) treatment were greatly reduced in the guard cells of crl-no ch compared with crl-ch and wild type. Determination of the relative ATP levels in individual cells showed that crl-no ch guard cells contained considerably lower levels of ATP than did crl-ch and wild type after 2 h of white light illumination. In addition, guard cell ATP levels were lower in the epidermis than in leaves, which is consistent with the observed weaker stomatal opening response to white light in the epidermis than in leaves. These results provide evidence that both guard cell chloroplasts and mesophyll contribute to the ATP source for H(+) extrusion by guard cells. © 2014 John Wiley & Sons Ltd.

  8. Development of inexpensive metal macrocyclic complexes for use in fuel cells

    SciTech Connect

    Doddapaneni, N.; Ingersoll, D.; Kosek, J.A.; Cropley, C.C.; Hamdan, M.

    1998-01-01

    Several metal macrocyclic complexes were synthesized for use as catalysts in fuel cells. An initial evaluation of their ability to catalyze the fuel cell reactions were completed. Based on this initial evaluation, one metal macrocyclic catalyst was selected and long-term stability testing in a fuel cell was initiated. The fuel cell employing this catalyst was operated continuously for one year with little signs of catalyst degradation. The effect of synthetic reformates on the performance of the catalyst in the fuel cell environment also demonstrated high tolerance of this catalyst for common contaminants and poisons.

  9. Development of an all-metal thick film cost effective metallization system for solar cells

    NASA Technical Reports Server (NTRS)

    Ross, B.

    1981-01-01

    The objectives of the investigation were to provide all-metal screenable pastes using economical base metals, suitable for application to low-to-high conductivity silicon of either conductivity type and possibly to aluminum surfaces. Experiments were conducted with variations in paste parameters, firing conditions, including gas ambients, furnace furniture, silicon surface and others. A liquid medium, intended to provide transport during the carbon fluoride decomposition was incorporated in the paste with promising results.

  10. Adenovirus Type 5 E4 Open Reading Frame 4 Protein Induces Apoptosis in Transformed Cells

    PubMed Central

    Shtrichman, Ronit; Kleinberger, Tamar

    1998-01-01

    Adenovirus type 5 E4 open reading frame 4 (E4orf4) protein has been previously shown to counteract transactivation of the junB and c-fos genes by cyclic AMP plus E1A protein and to interact with protein phosphatase 2A (PP2A). Here, we show that the wild-type E4orf4 protein induces apoptosis in the E1A-expressing 293 cells, in NIH 3T3 cells transformed with v-Ras, and in the lung carcinoma cell line H1299. The induction of apoptosis is not accompanied by enhanced levels of p53 in 293 cells and occurs in the absence of p53 in H1299 cells, indicating involvement of a p53-independent pathway. A mutant E4orf4 protein that had lost the ability to induce apoptosis also lost its ability to bind PP2A. We suggest that E4orf4 antagonizes continuous signals to proliferate, like those given by E1A or v-Ras, and that the conflicting signals lead to the induction of cell death. PMID:9525619

  11. Open data set of live cyanobacterial cells imaged using an X-ray laser.

    PubMed

    van der Schot, Gijs; Svenda, Martin; Maia, Filipe R N C; Hantke, Max F; DePonte, Daniel P; Seibert, M Marvin; Aquila, Andrew; Schulz, Joachim; Kirian, Richard A; Liang, Mengning; Stellato, Francesco; Bari, Sadia; Iwan, Bianca; Andreasson, Jakob; Timneanu, Nicusor; Bielecki, Johan; Westphal, Daniel; Nunes de Almeida, Francisca; Odić, Duško; Hasse, Dirk; Carlsson, Gunilla H; Larsson, Daniel S D; Barty, Anton; Martin, Andrew V; Schorb, Sebastian; Bostedt, Christoph; Bozek, John D; Carron, Sebastian; Ferguson, Ken; Rolles, Daniel; Rudenko, Artem; Epp, Sascha W; Foucar, Lutz; Rudek, Benedikt; Erk, Benjamin; Hartmann, Robert; Kimmel, Nils; Holl, Peter; Englert, Lars; Loh, N Duane; Chapman, Henry N; Andersson, Inger; Hajdu, Janos; Ekeberg, Tomas

    2016-08-01

    Structural studies on living cells by conventional methods are limited to low resolution because radiation damage kills cells long before the necessary dose for high resolution can be delivered. X-ray free-electron lasers circumvent this problem by outrunning key damage processes with an ultra-short and extremely bright coherent X-ray pulse. Diffraction-before-destruction experiments provide high-resolution data from cells that are alive when the femtosecond X-ray pulse traverses the sample. This paper presents two data sets from micron-sized cyanobacteria obtained at the Linac Coherent Light Source, containing a total of 199,000 diffraction patterns. Utilizing this type of diffraction data will require the development of new analysis methods and algorithms for studying structure and structural variability in large populations of cells and to create abstract models. Such studies will allow us to understand living cells and populations of cells in new ways. New X-ray lasers, like the European XFEL, will produce billions of pulses per day, and could open new areas in structural sciences.

  12. Open data set of live cyanobacterial cells imaged using an X-ray laser

    NASA Astrophysics Data System (ADS)

    van der Schot, Gijs; Svenda, Martin; Maia, Filipe R. N. C.; Hantke, Max F.; Deponte, Daniel P.; Seibert, M. Marvin; Aquila, Andrew; Schulz, Joachim; Kirian, Richard A.; Liang, Mengning; Stellato, Francesco; Bari, Sadia; Iwan, Bianca; Andreasson, Jakob; Timneanu, Nicusor; Bielecki, Johan; Westphal, Daniel; Nunes de Almeida, Francisca; Odić, Duško; Hasse, Dirk; Carlsson, Gunilla H.; Larsson, Daniel S. D.; Barty, Anton; Martin, Andrew V.; Schorb, Sebastian; Bostedt, Christoph; Bozek, John D.; Carron, Sebastian; Ferguson, Ken; Rolles, Daniel; Rudenko, Artem; Epp, Sascha W.; Foucar, Lutz; Rudek, Benedikt; Erk, Benjamin; Hartmann, Robert; Kimmel, Nils; Holl, Peter; Englert, Lars; Loh, N. Duane; Chapman, Henry N.; Andersson, Inger; Hajdu, Janos; Ekeberg, Tomas

    2016-08-01

    Structural studies on living cells by conventional methods are limited to low resolution because radiation damage kills cells long before the necessary dose for high resolution can be delivered. X-ray free-electron lasers circumvent this problem by outrunning key damage processes with an ultra-short and extremely bright coherent X-ray pulse. Diffraction-before-destruction experiments provide high-resolution data from cells that are alive when the femtosecond X-ray pulse traverses the sample. This paper presents two data sets from micron-sized cyanobacteria obtained at the Linac Coherent Light Source, containing a total of 199,000 diffraction patterns. Utilizing this type of diffraction data will require the development of new analysis methods and algorithms for studying structure and structural variability in large populations of cells and to create abstract models. Such studies will allow us to understand living cells and populations of cells in new ways. New X-ray lasers, like the European XFEL, will produce billions of pulses per day, and could open new areas in structural sciences.

  13. Open data set of live cyanobacterial cells imaged using an X-ray laser

    PubMed Central

    van der Schot, Gijs; Svenda, Martin; Maia, Filipe R.N.C.; Hantke, Max F.; DePonte, Daniel P.; Seibert, M. Marvin; Aquila, Andrew; Schulz, Joachim; Kirian, Richard A.; Liang, Mengning; Stellato, Francesco; Bari, Sadia; Iwan, Bianca; Andreasson, Jakob; Timneanu, Nicusor; Bielecki, Johan; Westphal, Daniel; Nunes de Almeida, Francisca; Odić, Duško; Hasse, Dirk; Carlsson, Gunilla H.; Larsson, Daniel S.D.; Barty, Anton; Martin, Andrew V.; Schorb, Sebastian; Bostedt, Christoph; Bozek, John D.; Carron, Sebastian; Ferguson, Ken; Rolles, Daniel; Rudenko, Artem; Epp, Sascha W.; Foucar, Lutz; Rudek, Benedikt; Erk, Benjamin; Hartmann, Robert; Kimmel, Nils; Holl, Peter; Englert, Lars; Loh, N. Duane; Chapman, Henry N.; Andersson, Inger; Hajdu, Janos; Ekeberg, Tomas

    2016-01-01

    Structural studies on living cells by conventional methods are limited to low resolution because radiation damage kills cells long before the necessary dose for high resolution can be delivered. X-ray free-electron lasers circumvent this problem by outrunning key damage processes with an ultra-short and extremely bright coherent X-ray pulse. Diffraction-before-destruction experiments provide high-resolution data from cells that are alive when the femtosecond X-ray pulse traverses the sample. This paper presents two data sets from micron-sized cyanobacteria obtained at the Linac Coherent Light Source, containing a total of 199,000 diffraction patterns. Utilizing this type of diffraction data will require the development of new analysis methods and algorithms for studying structure and structural variability in large populations of cells and to create abstract models. Such studies will allow us to understand living cells and populations of cells in new ways. New X-ray lasers, like the European XFEL, will produce billions of pulses per day, and could open new areas in structural sciences. PMID:27479514

  14. Metallic sulfide additives for positive electrode material within a secondary electrochemical cell

    DOEpatents

    Walsh, William J.; McPheeters, Charles C.; Yao, Neng-ping; Koura, Kobuyuki

    1976-01-01

    An improved active material for use within the positive electrode of a secondary electrochemical cell includes a mixture of iron disulfide and a sulfide of a polyvalent metal. Various metal sulfides, particularly sulfides of cobalt, nickel, copper, cerium and manganese, are added in minor weight proportion in respect to iron disulfide for improving the electrode performance and reducing current collector requirements.

  15. Proliferation of the synovial lining cell layer in suggested metal hypersensitivity.

    PubMed

    Burkandt, Andreas; Katzer, Alexander; Thaler, Karlheinz; Von Baehr, Volker; Friedrich, Reinhard E; Rüther, Wolfgang; Amling, Michael; Zustin, Jozef

    2011-01-01

    Synovial tissues in joints with prostheses display characteristic morphological changes in cases with aseptic failure, particularly macrophage infiltration. Since proliferation of the synovial lining cell layer represents a feature characteristic of autoimmune joint diseases, the possibility of morphological changes of the synovial lining cell layer in periprosthetic tissues was investigated. Synovial biopsies from five groups of morphologically well-defined lesions (osteoarthritis, rheumatoid arthritis, aseptic loosened metal-on-polyethylene and metal-on-metal arthroplasty and suggested metal hypersensitivity) were compared using a conventional staining method and immunohistochemistry. The synovial lining cell layer was substantially enlarged in both rheumatoid arthritis and cases suggestive of metal hypersensitivity. Macrophage infiltrates were apparent in rheumatoid arthritis and all specimens from retrieved hip arthroplasties. Although both synovial and subsynovial macrophages were positive for CD163 (indicating synovial M2 macrophages), the remaining fibroblast-like synoviocytes and scattered stromal fibroblasts showed a positive reaction with the D2-40 antibody (indicating fibroblast-like synoviocytes). Furthermore, in contrast to CD163-positive macrophages, the enlarged D2-40-positive fibroblast-like synoviocytes displayed cytoplasmatic tubular projections. Proliferation of the periprosthetic synovial lining cell layer occurred in cases with unexplained groin pain following metal-on-metal hip resurfacing arthroplasty, suggestive of hypersensitivity. Despite some important study limitations, the present observation adds to the evidence that metal hypersensitivity shares characteristic morphological features with autoimmune diseases of the joints.

  16. Metallic Nickel Nanoparticles May Exhibit Higher Carcinogenic Potential than Fine Particles in JB6 Cells

    PubMed Central

    Bowman, Linda; Zou, Baobo; Mao, Guochuan; Xu, Jin; Castranova, Vincent; Zhao, Jinshun; Ding, Min

    2014-01-01

    While numerous studies have described the pathogenic and carcinogenic effects of nickel compounds, little has been done on the biological effects of metallic nickel. Moreover, the carcinogenetic potential of metallic nickel nanoparticles is unknown. Activator protein-1 (AP-1) and nuclear factor-κB (NF-κB) have been shown to play pivotal roles in tumor initiation, promotion, and progression. Mutation of the p53 tumor suppressor gene is considered to be one of the steps leading to the neoplastic state. The present study examines effects of metallic nickel fine and nanoparticles on tumor promoter or suppressor gene expressions as well as on cell transformation in JB6 cells. Our results demonstrate that metallic nickel nanoparticles caused higher activation of AP-1 and NF-κB, and a greater decrease of p53 transcription activity than fine particles. Western blot indicates that metallic nickel nanoparticles induced a higher level of protein expressions for R-Ras, c-myc, C-Jun, p65, and p50 in a time-dependent manner. In addition, both metallic nickel nano- and fine particles increased anchorage-independent colony formation in JB6 P+ cells in the soft agar assay. These results imply that metallic nickel fine and nanoparticles are both carcinogenetic in vitro in JB6 cells. Moreover, metallic nickel nanoparticles may exhibit higher carcinogenic potential, which suggests that precautionary measures should be taken in the use of nickel nanoparticles or its compounds in nanomedicine. PMID:24691273

  17. Simplified process for leaching precious metals from fuel cell membrane electrode assemblies

    DOEpatents

    Shore, Lawrence; Matlin, Ramail

    2009-12-22

    The membrane electrode assemblies of fuel cells are recycled to recover the catalyst precious metals from the assemblies. The assemblies are cryogenically embrittled and pulverized to form a powder. The pulverized assemblies are then mixed with a surfactant to form a paste which is contacted with an acid solution to leach precious metals from the pulverized membranes.

  18. Metal Hydrides as hot carrier cell absorber materials

    NASA Astrophysics Data System (ADS)

    Wang, Pei; Wen, Xiaoming; Shrestha, Santosh; Conibeer, Gavin; Aguey-Zinsou, Kondo-Francois

    2016-09-01

    The hot Carrier Solar Cell (HCSC) allows the photon-induced hot carriers (the carriers with energy larger than the band gap) to be collected before they completely thermalise. The absorber of the HCSC should have a large phononic band gap to supress Klemens Decay, which results in a slow carrier cooling speed. In fact, a large phononic band gap likely exists in a binary compound whose constituent elements have a large mass ratio between each other. Binary hydrides with their overwhelming mass ratio of the constituent elements are important absorber candidates. Study on different types of binary hydrides as potential absorber candidates is presented in this paper. Many binary transition metal hydrides have reported theoretical or experimental phonon dispersion charts which show large phononic band gaps. Among these hydrides, the titanium hydride (TiHX) is outstanding because of its low cost, easy fabrication process and is relatively inert to air and water. A TiHX thin film is fabricated by directly hydrogenating an evaporated titanium thin film. Characterisation shows good crystal quality and the hydrogenation process is believed to be successful. Ultrafast transient absorption (TA) spectroscopy is used to study the electron cooling time of TiHX. The result is very noisy due to the low absorption and transmission of the sample. The evolution of the TA curves has been explained by band to band transition using the calculated band structure of TiH2. Though not reliable due to the high noise, decay time fitting at 700nm and 600nm shows a considerably slow carrier cooling speed of the sample.

  19. Effects of heavy metals (Fe3+/Cr6+) on low-level energy generation in a microbial fuel cell

    NASA Astrophysics Data System (ADS)

    Caparanga, A. R.; Balatbat, A. S.; Tayo, L.

    2017-06-01

    A dual-chamber microbial fuel cell (MFC) was constructed with Pseudomonas aeruginosa as biocatalyst to facilitate substrate conversion and, consequently, low-level energy generation. To simulate a wastewater situation with BOD and heavy metals contamination, glucose and Fe3+ and Cr6+ were used as substrate and heavy-metal spikes, respectively. The effects of varying substrate concentrations (150 ppm, 300 ppm, 600 ppm) and heavy metal loads (10 ppm, 50 ppm, 100 ppm) on overall power generation were evaluated. The presence of Cr6+ in the anode compartment decreased the potential from 565 to 201 mV (i.e., lowest value achieved at highest Cr6+ concentration of 300 ppm). On the other hand, replacing Cr6+ with Fe3+ as electron acceptor resulted in substantial increase in measured potential (i.e., from 565 to 703 mV). Increasing glucose concentrations resulted in longer time to reach constant open circuit voltage. A maximum potential of 606 mV was achieved at 1200 ppm glucose. Incorporating Pseudomonas aeruginosa increased the potential from 256 to 592 mV. On the basis of these results, a microbial fuel cell feeding on wastewater can be an important potential technology for generating low-level energy

  20. Acceleration of a Particle-in-Cell Code for Space Plasma Simulations with OpenACC

    NASA Astrophysics Data System (ADS)

    Peng, Ivy Bo; Markidis, Stefano; Vaivads, Andris; Vencels, Juris; Deca, Jan; Lapenta, Giovanni; Hart, Alistair; Laure, Erwin

    2015-04-01

    We simulate space plasmas with the Particle-in-cell (PIC) method that uses computational particles to mimic electrons and protons in solar wind and in Earth magnetosphere. The magnetic and electric fields are computed by solving the Maxwell's equations on a computational grid. In each PIC simulation step, there are four major phases: interpolation of fields to particles, updating the location and velocity of each particle, interpolation of particles to grids and solving the Maxwell's equations on the grid. We use the iPIC3D code, which was implemented in C++, using both MPI and OpenMP, for our case study. By November 2014, heterogeneous systems using hardware accelerators such as Graphics Processing Unit (GPUs) and the Many Integrated Core (MIC) coprocessors for high performance computing continue growth in the top 500 most powerful supercomputers world wide. Scientific applications for numerical simulations need to adapt to using accelerators to achieve portability and scalability in the coming exascale systems. In our work, we conduct a case study of using OpenACC to offload the computation intensive parts: particle mover and interpolation of particles to grids, in a massively parallel Particle-in-Cell simulation code, iPIC3D, to multi-GPU systems. We use MPI for inter-node communication for halo exchange and communicating particles. We identify the most promising parts suitable for GPUs accelerator by profiling using CrayPAT. We implemented manual deep copy to address the challenges of porting C++ classes to GPU. We document the necessary changes in the exiting algorithms to adapt for GPU computation. We present the challenges and findings as well as our methodology for porting a Particle-in-Cell code to multi-GPU systems using OpenACC. In this work, we will present the challenges, findings and our methodology of porting a Particle-in-Cell code for space applications as follows: We profile the iPIC3D code by Cray Performance Analysis Tool (CrayPAT) and identify