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Sample records for active layer absorption

  1. Solar cells based on particulate structure of active layer: Investigation of light absorption by an ordered system of spherical submicron silicon particles

    NASA Astrophysics Data System (ADS)

    Miskevich, Alexander A.; Loiko, Valery A.

    2015-12-01

    Enhancement of the performance of photovoltaic cells through increasing light absorption due to optimization of an active layer is considered. The optimization consists in creation of particulate structure of active layer. The ordered monolayers and multilayers of submicron crystalline silicon (c-Si) spherical particles are examined. The quasicrystalline approximation (QCA) and the transfer matrix method (TMM) are used to calculate light absorption in the wavelength range from 0.28 μm to 1.12 μm. The integrated over the terrestial solar spectral irradiance "Global tilt" ASTM G173-03 absorption coefficient is calculated. In the wavelength range of small absorption index of c-Si (0.8-1.12 μm) the integral absorption coefficient of monolayer can be more than 20 times higher than the one of the plane-parallel plate of the equivalent volume of material. In the overall considered range (0.28-1.12 μm) the enhancement factor up to ~1.45 for individual monolayer is observed. Maximum value of the spectral absorption coefficient approaches unity for multilayers consisting of large amount of sparse monolayers of small particles. Multilayers with variable concentration and size of particles in the monolayer sequences are considered. Absorption increasing by such gradient multilayers as compared to the non-gradient ones is illustrated. The considered structures are promising for creation of high efficiency thin-film solar cells.

  2. nBn and pBp infrared detectors with graded barrier layer, graded absorption layer, or chirped strained layer super lattice absorption layer

    NASA Technical Reports Server (NTRS)

    Gunapala, Sarath D. (Inventor); Ting, David Z. (Inventor); Hill, Cory J. (Inventor); Bandara, Sumith V. (Inventor)

    2010-01-01

    An nBn detector is described where for some embodiments the barrier layer has a concentration gradient, for some embodiments the absorption layer has a concentration gradient, and for some embodiments the absorption layer is a chirped strained layer super lattice. The use of a graded barrier or absorption layer, or the use of a chirped strained layer super lattice for the absorption layer, allows for design of the energy bands so that the valence band may be aligned across the device. Other embodiments are described and claimed.

  3. Coherent absorption and enhanced photoluminescence in thin layers of nanorods

    NASA Astrophysics Data System (ADS)

    Pirruccio, G.; Lozano, G.; Zhang, Y.; Rodriguez, S. R. K.; Gomes, R.; Hens, Z.; Rivas, Jaime Gómez

    2012-04-01

    We demonstrate a large light absorptance (80%) in a nanometric layer of quantum dots in rods (QRs) with a thickness of 23 nm. This behavior is explained in terms of the coherent absorption by interference of the light incident at a certain angle onto the very thin QR layer. We exploit this coherent light absorption to enhance the photoluminescent emission from the QRs. Up to a seven- and fivefold enhancement of the photoluminescence is observed for p- and s-polarized incident light, respectively.

  4. nBn Infrared Detector Containing Graded Absorption Layer

    NASA Technical Reports Server (NTRS)

    Gunapala, Sarath D.; Ting, David Z.; Hill, Cory J.; Bandara, Sumith V.

    2009-01-01

    It has been proposed to modify the basic structure of an nBn infrared photodetector so that a plain electron-donor- type (n-type) semiconductor contact layer would be replaced by a graded n-type III V alloy semiconductor layer (i.e., ternary or quarternary) with appropriate doping gradient. The abbreviation nBn refers to one aspect of the unmodified basic device structure: There is an electron-barrier ("B" ) layer between two n-type ("n" ) layers, as shown in the upper part of the figure. One of the n-type layers is the aforementioned photon-absorption layer; the other n-type layer, denoted the contact layer, collects the photocurrent. The basic unmodified device structure utilizes minority-charge-carrier conduction, such that, for reasons too complex to explain within the space available for this article, the dark current at a given temperature can be orders of magnitude lower (and, consequently, signal-to-noise ratios can be greater) than in infrared detectors of other types. Thus, to obtain a given level of performance, less cooling (and, consequently, less cooling equipment and less cooling power) is needed. [In principle, one could obtain the same advantages by means of a structure that would be called pBp because it would include a barrier layer between two electron-acceptor- type (p-type) layers.] The proposed modifications could make it practical to utilize nBn photodetectors in conjunction with readily available, compact thermoelectric coolers in diverse infrared- imaging applications that could include planetary exploration, industrial quality control, monitoring pollution, firefighting, law enforcement, and medical diagnosis.

  5. Implanted Silicon Resistor Layers for Efficient Terahertz Absorption

    NASA Technical Reports Server (NTRS)

    Chervenak, J. A.; Abrahams, J.; Allen, C. A.; Benford, D. J.; Henry, R.; Stevenson, T.; Wollack, E.; Moseley, S. H.

    2005-01-01

    Broadband absorption structures are an essential component of large format bolometer arrays for imaging GHz and THz radiation. We have measured electrical and optical properties of implanted silicon resistor layers designed to be suitable for these absorbers. Implanted resistors offer a low-film-stress, buried absorber that is robust to longterm aging, temperature, and subsequent metals processing. Such an absorber layer is readily integrated with superconducting integrated circuits and standard micromachining as demonstrated by the SCUBA II array built by ROE/NIST (1). We present a complete characterization of these layers, demonstrating frequency regimes in which different recipes will be suitable for absorbers. Single layer thin film coatings have been demonstrated as effective absorbers at certain wavelengths including semimetal (2,3), thin metal (4), and patterned metal films (5,6). Astronomical instrument examples include the SHARC II instrument is imaging the submillimeter band using passivated Bi semimetal films and the HAWC instrument for SOFIA, which employs ultrathin metal films to span 1-3 THz. Patterned metal films on spiderweb bolometers have also been proposed for broadband detection. In each case, the absorber structure matches the impedance of free space for optimal absorption in the detector configuration (typically 157 Ohms per square for high absorption with a single or 377 Ohms per square in a resonant cavity or quarter wave backshort). Resonant structures with -20% bandwidth coupled to bolometers are also under development; stacks of such structures may take advantage of instruments imaging over a wide band. Each technique may enable effective absorbers in imagers. However, thin films tend to age, degrade or change during further processing, can be difficult to reproduce, and often exhibit an intrinsic granularity that creates complicated frequency dependence at THz frequencies. Thick metal films are more robust but the requirement for

  6. Infrared sensor with precisely patterned Au black absorption layer

    NASA Astrophysics Data System (ADS)

    Hirota, Masaki; Morita, Shinichi

    1998-10-01

    Thermoelectric infrared sensors has been fabricated by adding to the CMOS process a surface micromachining technique and a highly accurate process for forming an infrared radiation absorbing layer. The sensor, or thermopile, consists of alternating areas of p-type and n-type polysilicon connected in series on a Si3N4 layer. An anisotropic etching technique using hydrazine is employed to form a thermally isolated membrane. While a Au-black layer for infrared radiation absorption provides the best absorption efficiency over a broad infrared wavelength region, it has been difficult to pattern the layer precisely. Patterning is accomplished by forming the Au-black layer by a low-pressure vapor deposition technique on amorphous Si and a PSG sacrificial layer and then removing it on PSG by the lift-off technique or wet etching PSG. This technique makes it possible to obtain a Au-black pattern with the same degree of accuracy as with the CMOS process. As a result, sensor performance has been improved and a device array has also been achieved. A simple sensor design method has been established by which simulations are easily conducted using a thermal equivalent circuit based on the CMOS process. Prototype sensors, having external dimensions of 160 micrometer X 160 micrometer, achieved responsivity of 300, 149 and 60 V/W and a time constant of 2.0, 0.46 and 0.27 msec in the air, respectively. These performance figures surpass the performance reported to date for thermoelectric infrared sensors.

  7. Asymmetric perfectly matched layer for the absorption of waves

    SciTech Connect

    Vay, Jean-Luc

    2002-02-10

    The Perfectly Matched Layer (PML) has become a standard for comparison in the techniques that have been developed to close the system of Maxwell equations (more generally wave equations) when simulating an open system. The original Berenger PML formulation relies on a split version of Maxwell equations with numerical electric and magnetic conductivities. They present here an extension of this formulation which introduces counterparts of the electric and magnetic conductivities affecting the term which is spatially differentiated in the equations. they phase velocity along each direction is also multiplied by an additional coefficient. They show that, under certain constraints on the additional numerical coefficients, this ''medium'' does not generate any reflection at any angle and any frequency and is then a Perfectly Matched Layer. Technically it is a super-set of Berenger's PML to which it reduces for a specific set of parameters and like it, it is anisotropic. However, unlike the PML, it introduces some asymmetry in the absorption rate and is therefore labeled an APML for Asymmetric Perfectly Matched Layer. They present here the numerical considerations that have led them to introduce such a medium as well as its theory. Several finite-different numerical implementations are derived (in one, two and three dimensions) and the performance of the APML is contrasted with that of the PML in one and two dimensions. Using plane wave analysis, they show that the APML implementations lead to higher absorption rates than the considered PML implementations. Although they have considered in this paper the finite-different discretization of Maxwell-like equations only, the APML system of equations may be used with other discretization schemes, such as finite-elements, and may be applied to other equations, for applications beyond electromagnetics.

  8. Broadband absorption enhancement in organic solar cells with an antenna layer through surface-plasmon mediated energy transfer

    NASA Astrophysics Data System (ADS)

    Jin, Yu; Feng, Jing; Zhang, Xu-Lin; Xu, Ming; Chen, Qi-Dai; Wu, Zhi-Jun; Sun, Hong-Bo

    2015-06-01

    We demonstrated a strategy to realize broadband enhanced absorption in the top-incident inverted organic solar cells (OSCs) by employing an external antenna layer on top of the periodic corrugated metallic anode. Surface-plasmon polaritons (SPPs) are excited on the opposite interfaces of the periodic corrugated metallic anode, which mediate the energy transfer from the antenna layer to the active layer through the anode. The absorption of the OSCs is significantly broadened and enhanced by tuning the SPP resonance to coincide with both the emission of the antenna and the absorption of the active material. The power conversion efficiency exhibits an enhancement of 16% compared to that of the OSCs without the antenna layer.

  9. Metaporous layer to overcome the thickness constraint for broadband sound absorption

    SciTech Connect

    Yang, Jieun; Lee, Joong Seok; Kim, Yoon Young

    2015-05-07

    The sound absorption of a porous layer is affected by its thickness, especially in a low-frequency range. If a hard-backed porous layer contains periodical arrangements of rigid partitions that are coordinated parallel and perpendicular to the direction of incoming sound waves, the lower bound of the effective sound absorption can be lowered much more and the overall absorption performance enhanced. The consequence of rigid partitioning in a porous layer is to make the first thickness resonance mode in the layer appear at much lower frequencies compared to that in the original homogeneous porous layer with the same thickness. Moreover, appropriate partitioning yields multiple thickness resonances with higher absorption peaks through impedance matching. The physics of the partitioned porous layer, or the metaporous layer, is theoretically investigated in this study.

  10. Microwave absorption properties of double-layer absorber based on carbonyl iron/barium hexaferrite composites

    NASA Astrophysics Data System (ADS)

    Ren, Xiaohu; Fan, Huiqing; Cheng, Yankui

    2016-05-01

    The microwave absorption properties of BaCo0.4Zn1.6Fe16O27 ferrite and carbonyl iron powder with single-layer and double-layer composite absorbers were investigated based on the electromagnetic transmission line theory in the frequency range from 1 to 14 GHz. XRD was used to characterize the structure of prepared absorbing particles. SEM was used to examine the micromorphology of the particles and composites. The complex permittivity and permeability of composites were measured by using a vector network analyzer. The reflection loss of the single-layer and double-layer absorbers with different thicknesses and orders was investigated. The results show that double-layer absorbers have better microwave absorption properties than single-layer absorbers. The microwave absorption properties of the double-layer structure are influenced by the coupling interactions between the matching and absorption layers. As the pure ferrite used as matching layer and the composite of BF-5CI used as absorption, the minimum RL of absorber can achieve to -55.4 dB and the bandwidth of RL <-10 dB ranged from 5.6 to 10.8 GHz when the thicknesses of matching layer and absorption layer were 0.9 and 1.4 mm, respectively.

  11. Fabrication of multi-layered absorption structure for high quantum efficiency photon detectors

    SciTech Connect

    Fujii, Go; Fukuda, Daiji; Numata, Takayuki; Yoshizawa, Akio; Tsuchida, Hidemi; Fujino, Hidetoshi; Ishii, Hiroyuki; Itatani, Taro; Zama, Tatsuya; Inoue, Shuichiro

    2009-12-16

    We report on some efforts to improve a quantum efficiency of titanium-based optical superconducting transition edge sensors using the multi-layered absorption structure for maximizing photon absorption in the Ti layer. Using complex refractive index values of each film measured by a Spectroscopic Ellipsometry, we designed and optimized by a simulation code. An absorption measurement of fabricated structure was in good agreement with the design and was higher than 99% at optimized wavelength of 1550 nm.

  12. Structure, Optical Absorption, and Performance of Organic Solar Cells Improved by Gold Nanoparticles in Buffer Layers.

    PubMed

    Yang, Yingguo; Feng, Shanglei; Li, Meng; Wu, Zhongwei; Fang, Xiao; Wang, Fei; Geng, Dongping; Yang, Tieying; Li, Xiaolong; Sun, Baoquan; Gao, Xingyu

    2015-11-11

    11-Mercaptoundecanoic acid (MUA)-stabilized gold nanoparticles (AuNPs) embedded in copper phthalocyanine (CuPc) were used as a buffer layer between a poly(3-hexyl-thiophene) (P3HT)/[6,6]-phenyl C61-butyric acid methyl ester (PCBM) bulk heterojunction and anodic indium-tin oxide (ITO) substrate. As systematic synchrotron-based grazing incidence X-ray diffraction (GIXRD) experiments demonstrated that the AuNPs present in the buffer layer can improve the microstructure of the active layer with a better lamella packing of P3HT from the surface to the interior, UV-visible absorption spectrum measurements revealed enhanced optical absorption due to the localized surface plasma resonance (LSPR) generated by the AuNPs. The device of ITO/poly(3,4-ethylenedioxythiophene):polystyrenesulfonate/CuPc:MUA-stabilized AuNPs/P3HT:PCBM/LiF/Al was found with over 24% enhancement of power conversion efficiency (PCE) in comparison with reference devices without AuNPs. This remarkable improvement in PCE should be partially attributed to LSPR generated by the AuNPs and partially to improved crystallization as well as preferred orientation order of P3HT due to the presence of the AuNPs, which would promote more applications of metal NPs in the organic photovoltaic devices and other organic multilayer devices. PMID:26477556

  13. Properties of multilayer optical systems formed by layers with small absorption in inclined falling of radiation

    NASA Astrophysics Data System (ADS)

    Karyaev, Konstantin V.; Zhoga, Eugene V.; Putilin, Eduard S.

    2000-10-01

    Multilayer dielectric systems find wide employment in different fields of science and engineering. Dielectric systems, formed by layers with small absorption, attract particular interest. Value of absorption, as a rule, depends on structure of the system (order and optical thickness of layers), angle of incidence and wavelength of radiation. Experiment shows that there are peaks of absorption on certain angles of incidence and wavelength, but behavior of absorption wasn't studied well. Model of a system, formed by isotropic layers settled on semiinfinite substate proved to be a good approximation for many of real optical systems. We studied pecularities in spectral dependencies of reflection, transmission and absorption coefficients in dependance on the angle of incidence and wavelength of falling radiation with flat wave front. Problem was solved on the basis of Maxwell equations and corresponding boundary conditions.

  14. Measurements of the optical absorption coefficient of Ar8+ ion implanted silicon layers using the photothermal radiometry and the modulated free carrier absorption methods

    NASA Astrophysics Data System (ADS)

    Chrobak, Ł.; Maliński, M.; Pawlak, M.

    2014-11-01

    This paper presents a method of the measurement of the optical absorption coefficient of the Ar8+ ions implanted layers in the p-type silicon substrate. The absorption coefficient is calculated using a value of the attenuation of amplitudes of a photothermal radiometry (PTR) and/or a modulation free carrier absorption (MFCA) signals and the implanted layer thickness calculated by means of the TRIM program. The proposed method can be used to indicate the amorphization of the ions implanted layers.

  15. Absorption of THz electromagnetic wave in two mono-layers of graphene

    NASA Astrophysics Data System (ADS)

    Reynolds, Cole B.; Shoufie Ukhtary, M.; Saito, Riichiro

    2016-05-01

    Nearly 100% absorption of an electromagnetic (EM) wave in terahertz (THz) frequency is proposed for a system consisting of two mono-layers of graphene. Here, we demonstrate that the system can almost perfectly absorb an EM wave with frequency of 2 THz, even though we have a low electron mobility of roughly 1000 cm2  Vs‑1. The absorption probability is calculated by using the transfer matrix method. We show that the two mono-layers of the graphene system is needed to obtain nearly 100% absorption when the graphene has a relatively low Fermi energy. The absorption dependence on the distance between the graphene layers is also discussed.

  16. Systems having optical absorption layer for mid and long wave infrared and methods for making the same

    SciTech Connect

    Kuzmenko, Paul J

    2013-10-01

    An optical system according to one embodiment includes a substrate; and an optical absorption layer coupled to the substrate, wherein the optical absorption layer comprises a layer of diamond-like carbon, wherein the optical absorption layer absorbs at least 50% of mid wave infrared light (3-5 .mu.m wavelength) and at least 50% of long wave infrared light (8-13 .mu.m wavelength). A method for applying an optical absorption layer to an optical system according to another embodiment includes depositing a layer of diamond-like carbon of an optical absorption layer above a substrate using plasma enhanced chemical vapor deposition, wherein the optical absorption layer absorbs at least 50% of mid wave infrared light (3-5 .mu.m wavelength) and at least 50% of long wave infrared light (8-13 .mu.m wavelength). Additional systems and methods are also presented.

  17. Analysis of absorption performances of anechoic layers with steel plate backing.

    PubMed

    Meng, Hao; Wen, Jihong; Zhao, Honggang; Lv, Linmei; Wen, Xisen

    2012-07-01

    Rubber layers with air-filled cavities or local resonance scatters can be used as anechoic coatings. A lot of researches have focused on the absorption mechanism of the anechoic coatings. As the anechoic coatings are bonded to the hull of submarine, the vibration of the hull should not be neglected when the analysis of the absorption characters is carried out. Therefore, it is more reasonable to treat the anechoic coating and the backing as a whole when the acoustic performance is analyzed. Considering the effects of the steel plate backing, the sound absorption performances on different models of anechoic coatings are investigated in this paper. The Finite Element Method is used to illustrate the vibrational behaviors of the anechoic coatings under the steel backings by which the displacement contours is obtained for analysis. The theoretical results show that an absorption peak is induced by the resonance of the steel slab and rubber layer. At the frequency of this absorption peak, the steel plate and the coating vibrates longitudinally like a mass-spring system in which the steel slab serves for mass and the coating layer is the spring. To illuminate the effects of the steel slab backing on the acoustic absorption, the thicknesses of the steel slab and the anechoic layer are discussed. Finally, an experiment is performed and the results show a good agreement with the theoretical analysis. PMID:22779456

  18. Optical measurements of absorption changes in two-layered diffusive media

    NASA Astrophysics Data System (ADS)

    Fabbri, Francesco; Sassaroli, Angelo; Henry, Michael E.; Fantini, Sergio

    2004-04-01

    We have used Monte Carlo simulations for a two-layered diffusive medium to investigate the effect of a superficial layer on the measurement of absorption variations from optical diffuse reflectance data processed by using: (a) a multidistance, frequency-domain method based on diffusion theory for a semi-infinite homogeneous medium; (b) a differential-pathlength-factor method based on a modified Lambert-Beer law for a homogeneous medium and (c) a two-distance, partial-pathlength method based on a modified Lambert-Beer law for a two-layered medium. Methods (a) and (b) lead to a single value for the absorption variation, whereas method (c) yields absorption variations for each layer. In the simulations, the optical coefficients of the medium were representative of those of biological tissue in the near-infrared. The thickness of the first layer was in the range 0.3-1.4 cm, and the source-detector distances were in the range 1-5 cm, which is typical of near-infrared diffuse reflectance measurements in tissue. The simulations have shown that (1) method (a) is mostly sensitive to absorption changes in the underlying layer, provided that the thickness of the superficial layer is ~0.6 cm or less; (2) method (b) is significantly affected by absorption changes in the superficial layer and (3) method (c) yields the absorption changes for both layers with a relatively good accuracy of ~4% for the superficial layer and ~10% for the underlying layer (provided that the absorption changes are less than 20-30% of the baseline value). We have applied all three methods of data analysis to near-infrared data collected on the forehead of a human subject during electroconvulsive therapy. Our results suggest that the multidistance method (a) and the two-distance partial-pathlength method (c) may better decouple the contributions to the optical signals that originate in deeper tissue (brain) from those that originate in more superficial tissue layers.

  19. Vortex mediated microwave absorption in superclean layered superconductors

    NASA Astrophysics Data System (ADS)

    Koulakov, A. A.; Larkin, A. I.

    1998-03-01

    In the superclean case the spectrum of vortex core excitations in the presence of disorder is not random but consists of two series of equally-spaced levels. (A.I. Larkin, Yu.N. Ovchinnikov, preprint cond-mat/9708202 (1997).) The I-V characteristics of such superconductors displays many interesting phenomena. A series of resonances is predicted at frequencies commensurate with the spacing of the vortex excitations. These resonances reveal an even-odd anomaly. In the presence of even one weak impurity the excitation levels can approach each other and even cross. Absorption at very low frequencies is identified with the resonances arising in this case. The results of such microscopic theory coincide up to the order of magnitude with both a theory employing kinetic equation(N. B. Kopnin and V. E. Kravtsov, JETP Lett. 23), 578 (1976); Sov. Phys. JETP 44, 861 (1986). and the experiment. (Y. Matsuda, N. P. Ong, J. M. Harris, J. B. Peterson, and Y. F. Yan, Phys. Rev. B 49), 4380 (1994). Numerous non-linear effects associated with Zener transitions in such crossings are studied. These phenomena can be used as a probe of vortex core excitations.

  20. Direct characterization and removal of interfering absorption trends in two-layer turbid media.

    PubMed

    Saager, Rolf B; Berger, Andrew J

    2005-09-01

    We propose a method to isolate absorption trends confined to the lower layer of a two-layer turbid medium, as is desired in near-infrared spectroscopy (NIRS) of cerebral hemodynamics. Several two-layer Monte Carlo simulations of NIRS time series were generated using a physiologically relevant range of optical properties and varying the absorption coefficients due to bottom-layer, top-layer, and/or global fluctuations. Initial results showed that by measuring absorption trends at two source-detector separations and performing a least-squares fit of one to the other, processed signals strongly resemble the simulated bottom-layer absorption properties. Through this approach, it was demonstrated that fitting coefficients can be estimated within less than +/- 2% of the ideal value without any a priori knowledge of the optical properties present in the model. An analytical approximation for the least-squares coefficient provides physical insight into the nature of errors and suggests ways to reduce them. PMID:16211814

  1. Absorption and quasiguided mode analysis of organic solar cells with photonic crystal photoactive layers.

    PubMed

    Tumbleston, John R; Ko, Doo-Hyun; Samulski, Edward T; Lopez, Rene

    2009-04-27

    We analyze optical absorption enhancements and quasiguided mode properties of organic solar cells with highly ordered nanostructured photoactive layers comprised of the bulk heterojunction blend, poly-3-hexylthiophene/[6,6]-phenyl-C61-butyric acid methyl ester (P3HT:PCBM) and a low index of refraction conducting material (LICM). This photonic crystal geometry is capable of enhancing spectral absorption by approximately 17% in part due to the excitation of quasiguided modes near the band edge of P3HT:PCBM. A nanostructure thickness between 200 nm and 300 nm is determined to be optimal, while the LICM must have an index of refraction approximately 0.3 lower than P3HT:PCBM to produce absorption enhancements. Quasiguided modes that differ in lifetime by an order of magnitude are also identified and yield absorption that is concentrated in the P3HT:PCBM flash layer. PMID:19399146

  2. A multidistance probe arrangement NIRS for detecting absorption changes in cerebral gray matter layer

    NASA Astrophysics Data System (ADS)

    Yamada, Toru; Umeyama, Shinji; Matsuda, Keiji

    2010-02-01

    We provide theoretical validation of the brain-functional detection using multidistance probe arrangement based on Monte Carlo simulations of five-layered model in which both scattering and absorption changes occur. It shows that optimized multidistance probe arrangement can be effective in removing interferences by scattering and absorption changes in upper layers and extracting absorption change in the gray matter layer. Using newly designed probes and their holder system, both conventional and proposed fNIRS measurements were implemented with non-functional (body and head movements and respiratory change) and functional (finger opposition) tasks. Artifacts, even if it correlate with task sequence, were well reduced. Functional signals were well localized at lateralized cerebral functional area.

  3. Strain- and twist-engineered optical absorption of few-layer black phosphorus

    NASA Astrophysics Data System (ADS)

    Jia, Qian; Kong, XiangHua; Qiao, JingSi; Ji, Wei

    2016-09-01

    Density functional and many-body perturbation theories calculations were carried out to investigate fundamental and optical bandgap, exciton binding energy and optical absorption property of normal and strain- and twist-engineered few-layer black phosphorus (BP). We found that the fundamental bandgaps of few layer BP can be engineered by layer stacking and in-plane strain, with linear relationships to their associated exciton binding energies. The strain-dependent optical absorption behaviors are also anisotropic that the position of the first absorption peak monotonically blue-shifts as the strain applies to either direction for incident light polarized along the armchair direction, but this is not the case for that along the zigzag direction. Given those striking properties, we proposed two prototype devices for building potentially more balanced light absorbers and light filter passes, which promotes further applications and investigations of BP in nanoelectronics and optoelectronics.

  4. Millimeter and terahertz wave absorption in a lossy conducting layer

    SciTech Connect

    Shen, M. K.; Chiang, W. Y.; Wu, K. L.; Chu, K. R.

    2013-10-15

    Relativistic electronics research in recent years has produced powerful millimeter waves on the MW level, while also extending the frequency range into the terahertz (THz) region and beyond. These developments have opened up new horizons in applications. The current study is motivated by the associated need for high-power absorbers not readily available at such frequencies. Our focus is on effective absorber schemes which can handle high power while also possessing a structural simplicity for easy implementation. In and above the THz region, the electrical conductivity can no longer be treated as a real constant. We begin with a derivation of the field penetration depth applicable to all frequencies. Requirements to meet the intended criteria are then determined from the wave penetration and reflection properties. Design examples in the 1–1000 GHz range are illustrated, which consist of a thin lossy conducting layer on the surface of a pyramidal shaped metal base. It is shown in theory that such structures can function effectively in the millimeter and THz regions.

  5. Vacuum heating versus skin layer absorption of intense femtosecond laser pulses

    SciTech Connect

    Bauer, D.; Mulser, P.

    2007-02-15

    The crossing of the narrow skin layer in solid targets by electrons in a time shorter than a laser cycle represents one of the numerous collisionless absorption mechanisms of intense laser-matter interaction. This kinetic effect is studied at normal and oblique laser beam incidence and particle injection by a test particle approach in an energy interval extending into the relativistic domain. Three main results obtained are the strong dependence of the energy gain by the single particle on the instant of injection relative to the phase of the light wave, the reflection of the particles primarily contributing to absorption well in front of the target rather than in the Debye layer, and the low degree of absorption hardly exceeding the 10% limit. The simulation results offer a more unambiguous interpretation of the absorption mechanism often referred to as ''vacuum heating.'' In particular, it is clearly revealed that the absorption in the vacuum region prevails on that originating from the skin layer. Relativistic ponderomotive effects are also tested, however their contribution to absorption is not significant.

  6. Microwave absorption properties of carbon nanocoils coated with highly controlled magnetic materials by atomic layer deposition.

    PubMed

    Wang, Guizhen; Gao, Zhe; Tang, Shiwei; Chen, Chaoqiu; Duan, Feifei; Zhao, Shichao; Lin, Shiwei; Feng, Yuhong; Zhou, Lei; Qin, Yong

    2012-12-21

    In this work, atomic layer deposition is applied to coat carbon nanocoils with magnetic Fe(3)O(4) or Ni. The coatings have a uniform and highly controlled thickness. The coated nanocoils with coaxial multilayer nanostructures exhibit remarkably improved microwave absorption properties compared to the pristine carbon nanocoils. The enhanced absorption ability arises from the efficient complementarity between complex permittivity and permeability, chiral morphology, and multilayer structure of the products. This method can be extended to exploit other composite materials benefiting from its convenient control of the impedance matching and combination of dielectric-magnetic multiple loss mechanisms for microwave absorption applications. PMID:23171130

  7. Electronic absorption band broadening and surface roughening of phthalocyanine double layers by saturated solvent vapor treatment

    SciTech Connect

    Kim, Jinhyun; Yim, Sanggyu

    2012-10-15

    Variations in the electronic absorption (EA) and surface morphology of three types of phthalocyanine (Pc) thin film systems, i.e. copper phthalocyanine (CuPc) single layer, zinc phthalocyanine (ZnPc) single layer, and ZnPc on CuPc (CuPc/ZnPc) double layer film, treated with saturated acetone vapor were investigated. For the treated CuPc single layer film, the surface roughness slightly increased and bundles of nanorods were formed, while the EA varied little. In contrast, for the ZnPc single layer film, the relatively high solubility of ZnPc led to a considerable shift in the absorption bands as well as a large increase in the surface roughness and formation of long and wide nano-beams, indicating a part of the ZnPc molecules dissolved in acetone, which altered their molecular stacking. For the CuPc/ZnPc film, the saturated acetone vapor treatment resulted in morphological changes in mainly the upper ZnPc layer due to the significantly low solubility of the underlying CuPc layer. The treatment also broadened the EA band, which involved a combination of unchanged CuPc and changed ZnPc absorption.

  8. Use of laminar flow and unstirred layer models to predict intestinal absorption in the rat.

    PubMed Central

    Levitt, M D; Kneip, J M; Levitt, D G

    1988-01-01

    Carbon monoxide (CO) and [14C]warfarin were used to measure the preepithelial diffusion resistance resulting from poor luminal stirring (RL) in the constantly perfused rat jejunum at varying degrees of distension (0.05, 0.1, and 0.2 ml/cm). RL was much greater than epithelial cell resistance, indicating that poor stirring was the limiting factor in absorption and that an appropriate model of stirring should accurately predict absorption. A laminar flow model accurately predicted the absorption rate of both probes at all levels of gut distension, as well as the absorption of glucose when RL was the rate-limiting factor in absorption. In contrast, an unstirred layer model would not have predicted that gut distension would have little influence on absorption, and would have underestimated [14C]warfarin absorption relative to CO. We concluded that in the perfused rat jejunum, laminar flow accurately models luminal stirring and an unstirred layer should be considered to be a unit of resistance in laminar flow, rather than a model of luminal stirring. PMID:3366899

  9. Enhancing sound absorption and transmission through flexible multi-layer micro-perforated structures.

    PubMed

    Bravo, Teresa; Maury, Cédric; Pinhède, Cédric

    2013-11-01

    Theoretical and experimental results are presented into the sound absorption and transmission properties of multi-layer structures made up of thin micro-perforated panels (ML-MPPs). The objective is to improve both the absorption and insulation performances of ML-MPPs through impedance boundary optimization. A fully coupled modal formulation is introduced that predicts the effect of the structural resonances onto the normal incidence absorption coefficient and transmission loss of ML-MPPs. This model is assessed against standing wave tube measurements and simulations based on impedance translation method for two double-layer MPP configurations of relevance in building acoustics and aeronautics. Optimal impedance relationships are proposed that ensure simultaneous maximization of both the absorption and the transmission loss under normal incidence. Exhaustive optimization of the double-layer MPPs is performed to assess the absorption and/or transmission performances with respect to the impedance criterion. It is investigated how the panel volumetric resonances modify the excess dissipation that can be achieved from non-modal optimization of ML-MPPs. PMID:24180777

  10. Extreme light absorption by multiple plasmonic layers on upgraded metallurgical grade silicon solar cells.

    PubMed

    Lee, Duck Hyun; Kwon, Jae Young; Maldonado, Stephen; Tuteja, Anish; Boukai, Akram

    2014-01-01

    We fabricate high-efficiency, ultrathin (∼12 μm), flexible, upgraded metallurgical-grade polycrystalline silicon solar cells with multiple plasmonic layers precisely positioned on top of the cell to dramatically increase light absorption. This scalable approach increases the optical absorptivity of our solar cells over a broad range of wavelengths, and they achieve efficiencies η ≈ 11%. Detailed studies on the electrical and optical properties of the developed solar cells elucidate the light absorption contribution of each individual plasmonic layer. Finite-difference time-domain simulations were also performed to yield further insights into the obtained results. We anticipate that the findings from this work will provide useful design considerations for fabricating a range of different solar cell systems. PMID:24611793

  11. Monitoring of amorfization of the oxygen implanted layers in silicon wafers using photothermal radiometry and modulated free carrier absorption methods

    NASA Astrophysics Data System (ADS)

    Maliński, M.; Pawlak, M.; Chrobak, Ł.; Pal, S.; Ludwig, A.

    2015-03-01

    This paper presents experimental results that characterize implanted layers in silicon being the result of a high energy implantation of O+6 ions. We propose a simple relation between attenuation of photothermal radiometry and/or modulated free carrier absorption amplitudes, the implanted layer thickness and its optical absorption coefficient. The thickness of the implanted layers was determined from capacitance-voltage characteristics and computations with the TRIM program. The obtained results allowed to estimate changes of the optical absorption coefficient of the oxygen implanted layers indicating the amorfization of the layers.

  12. Broadband ultrafast nonlinear absorption and nonlinear refraction of layered molybdenum dichalcogenide semiconductors.

    PubMed

    Wang, Kangpeng; Feng, Yanyan; Chang, Chunxia; Zhan, Jingxin; Wang, Chengwei; Zhao, Quanzhong; Coleman, Jonathan N; Zhang, Long; Blau, Werner J; Wang, Jun

    2014-09-21

    A series of layered molybdenum dichalcogenides, i.e., MoX₂ (X = S, Se and Te), were prepared in cyclohexyl pyrrolidinone by a liquid-phase exfoliation technique. The high quality of the two-dimensional nanostructures was verified by transmission electron microscopy and absorption spectroscopy. Open- and closed-aperture Z-scans were employed to study the nonlinear absorption and nonlinear refraction of the MoX₂ dispersions, respectively. All the three-layered nanostructures exhibit prominent ultrafast saturable absorption (SA) for both femtosecond (fs) and picosecond (ps) laser pulses over a broad wavelength range from the visible to the near infrared. While the dispersions treated with low-speed centrifugation (1500 rpm) have an SA response, and the MoS₂ and MoSe₂ dispersions after higher speed centrifugation (10,000 rpm) possess two-photon absorption for fs pulses at 1030 nm, which is due to the significant reduction of the average thickness of the nanosheets; hence, the broadening of band gap. In addition, all dispersions show obvious nonlinear self-defocusing for ps pulses at both 1064 nm and 532 nm, resulting from the thermally-induced nonlinear refractive index. The versatile ultrafast nonlinear properties imply a huge potential of the layered MoX2 semiconductors in the development of nanophotonic devices, such as mode-lockers, optical limiters, optical switches, etc. PMID:25097043

  13. On the absorption of solar radiation in a layer of oil beneath a layer of snow

    NASA Technical Reports Server (NTRS)

    Larsen, J. C.; Barkstrom, B. R.

    1976-01-01

    Solar energy deposition in oil layers covered by snow is calculated for three model snow types using radiative transfer theory. It is suggested that excess absorbed energy is unlikely to escape, so that some melting is likely to occur for snow depths less than about 4 cm.

  14. Semi-active control of piezoelectric coating's underwater sound absorption by combining design of the shunt impedances

    NASA Astrophysics Data System (ADS)

    Sun, Yang; Li, Zhaohui; Huang, Aigen; Li, Qihu

    2015-10-01

    Piezoelectric shunt damping technology has been applied in the field of underwater sound absorption in recent years. In order to achieve broadband echo reduction, semi-active control of sound absorption of multi-layered piezoelectric coating by shunt damping is significant. In this paper, a practical method is proposed to control the underwater sound absorption coefficients of piezoelectric coating layers by combining design of the shunt impedance that allows certain sound absorption coefficients at setting frequencies. A one-dimensional electro-acoustic model of the piezoelectric coating and the backing is established based on the Mason equivalent circuit theory. First, the shunt impedance of the coating is derived under the constraint of sound absorption coefficient at one frequency. Then, taking the 1-3 piezoelectric composite coating as an example, the sound absorption properties of the coating shunted to the designed shunt impedance are investigated. Next, on the basis of that, an iterative method for two constrained frequencies and an optimizing algorithm for multiple constrained frequencies are provided for combining design of the shunt impedances. At last, an experimental sample with four piezoelectric material layers is manufactured, of which the sound absorption coefficients are measured in an impedance tube. The experimental results show good agreement with the finite element simulation results. It is proved that a serial R-L circuit can control the peak frequency, maximum and bandwidth of the sound absorption coefficient and the combining R-L circuits shunted to multiple layers can control the sound absorption coefficients at multiple frequencies.

  15. Modeling of water absorption induced cracks in resin-based composite supported ceramic layer structures.

    PubMed

    Huang, Min; Thompson, V P; Rekow, E D; Soboyejo, W O

    2008-01-01

    Cracking patterns in the top ceramic layers of the modeled dental multilayers with polymer foundation are observed when they are immersed in water. This article developed a model to understand this cracking mechanism. When water diffuses into the polymer foundation of dental restorations, the foundation will expand; as a result, the stress will build up in the top ceramic layer because of the bending and stretching. A finite element model based on this mechanism is built to predict the stress build-up and the slow crack growth in the top ceramic layers during the water absorption. Our simulations show that the stress build-up by this mechanism is high enough to cause the cracking in the top ceramic layers and the cracking patterns predicted by our model are well consistent with those observed in experiments on glass/epoxy/polymer multilayers. The model is then used to discuss the life prediction of different dental ceramics. PMID:17497681

  16. Effect of pectin on jejunal glucose absorption and unstirred layer thickness in normal man.

    PubMed Central

    Flourie, B; Vidon, N; Florent, C H; Bernier, J J

    1984-01-01

    The effect of high methoxy apple pectin, a carbohydrate gelling agent, on the intestinal absorption of glucose, water, and sodium was studied in man. The effect of intraluminal fibre was evaluated in 22 healthy volunteers by the intestinal perfusion technique under an occlusive balloon. The test solutions (NaCl 130 mM, KCl 5 mM, glucose or mannitol 30 mM, PEG 4000 5 g/l) were perfused just beyond the ligament of Treitz at a rate of 10 ml/min. A 25 cm segment was studied. Three concentrations of pectin were tested: 6, 10, and 15 g/l. The effect of this pectin at two concentrations, 6 and 10 g/l, on the jejunal unstirred layer thickness was evaluated in nine other healthy subjects by an electrical technique. In mannitol solution, pectin reversed water and sodium absorption, whatever its concentration was, while in glucose solution it significantly reduced absorption of water and sodium at 10 and 15 g/l only (p less than 0.01). It significantly reduced glucose absorption at all concentrations (p less than 0.01). This reduction was found to be correlated with the solution viscosity (p less than 0.01). Pectin did not alter the glucose dependent sodium transport but increased significantly (p less than 0.001) the unstirred layer thickness. These results suggested that, in healthy man, pectin acutely given may impair intestinal absorption by means of an increased unstirred layer resistance. This effect could contribute to the diminished postprandial glycaemia observed in human subjects fed pectin. PMID:6432635

  17. Effect of pectin on jejunal glucose absorption and unstirred layer thickness in normal man.

    PubMed

    Flourie, B; Vidon, N; Florent, C H; Bernier, J J

    1984-09-01

    The effect of high methoxy apple pectin, a carbohydrate gelling agent, on the intestinal absorption of glucose, water, and sodium was studied in man. The effect of intraluminal fibre was evaluated in 22 healthy volunteers by the intestinal perfusion technique under an occlusive balloon. The test solutions (NaCl 130 mM, KCl 5 mM, glucose or mannitol 30 mM, PEG 4000 5 g/l) were perfused just beyond the ligament of Treitz at a rate of 10 ml/min. A 25 cm segment was studied. Three concentrations of pectin were tested: 6, 10, and 15 g/l. The effect of this pectin at two concentrations, 6 and 10 g/l, on the jejunal unstirred layer thickness was evaluated in nine other healthy subjects by an electrical technique. In mannitol solution, pectin reversed water and sodium absorption, whatever its concentration was, while in glucose solution it significantly reduced absorption of water and sodium at 10 and 15 g/l only (p less than 0.01). It significantly reduced glucose absorption at all concentrations (p less than 0.01). This reduction was found to be correlated with the solution viscosity (p less than 0.01). Pectin did not alter the glucose dependent sodium transport but increased significantly (p less than 0.001) the unstirred layer thickness. These results suggested that, in healthy man, pectin acutely given may impair intestinal absorption by means of an increased unstirred layer resistance. This effect could contribute to the diminished postprandial glycaemia observed in human subjects fed pectin. PMID:6432635

  18. Kinetics of Ion Transport in Perovskite Active Layers and Its Implications for Active Layer Stability.

    PubMed

    Bag, Monojit; Renna, Lawrence A; Adhikari, Ramesh Y; Karak, Supravat; Liu, Feng; Lahti, Paul M; Russell, Thomas P; Tuominen, Mark T; Venkataraman, D

    2015-10-14

    Solar cells fabricated using alkyl ammonium metal halides as light absorbers have the right combination of high power conversion efficiency and ease of fabrication to realize inexpensive but efficient thin film solar cells. However, they degrade under prolonged exposure to sunlight. Herein, we show that this degradation is quasi-reversible, and that it can be greatly lessened by simple modifications of the solar cell operating conditions. We studied perovskite devices using electrochemical impedance spectroscopy (EIS) with methylammonium (MA)-, formamidinium (FA)-, and MA(x)FA(1-x) lead triiodide as active layers. From variable temperature EIS studies, we found that the diffusion coefficient using MA ions was greater than when using FA ions. Structural studies using powder X-ray diffraction (PXRD) show that for MAPbI3 a structural change and lattice expansion occurs at device operating temperatures. On the basis of EIS and PXRD studies, we postulate that in MAPbI3 the predominant mechanism of accelerated device degradation under sunlight involves thermally activated fast ion transport coupled with a lattice-expanding phase transition, both of which are facilitated by absorption of the infrared component of the solar spectrum. Using these findings, we show that the devices show greatly improved operation lifetimes and stability under white-light emitting diodes, or under a solar simulator with an infrared cutoff filter or with cooling. PMID:26414066

  19. A sharp wet front analysis of capillary absorption into n-layer composite

    NASA Astrophysics Data System (ADS)

    Hall, Christopher; Green, Kim; Hoff, William D.; Wilson, Moira A.

    1996-12-01

    New analytical results are found for the capillary absorption of a liquid into a porous (sorptive) composite solid composed of n parallel layers of arbitrary thickness and material properties. The analysis is based on the `sharp wet front' model (also known as the the Green - Ampt model) and the results are exact for that model. A contact impedance acting at the interface between layers is included. The physical approximations of the model are discussed. The cumulative capillary absorption as a function of time is expressed in terms of the sorptivity, permeability and porosity of the materials of the individual layers. Experimental data obtained on composite bars of gypsum plaster and plaster/sand materials agree well with model predictions, although they test the model over only a limited range of parameter values. For these composite specimens, there is no evidence of a hydraulic contact impedance at the interface between layers. An asymptotic expression is given for the effective sorptivity of an alternating composite ABAB....

  20. Permafrost Active Layer Seismic Interferometry Experiment (PALSIE).

    SciTech Connect

    Abbott, Robert; Knox, Hunter Anne; James, Stephanie; Lee, Rebekah; Cole, Chris

    2016-01-01

    We present findings from a novel field experiment conducted at Poker Flat Research Range in Fairbanks, Alaska that was designed to monitor changes in active layer thickness in real time. Results are derived primarily from seismic data streaming from seven Nanometric Trillium Posthole seismometers directly buried in the upper section of the permafrost. The data were evaluated using two analysis methods: Horizontal to Vertical Spectral Ratio (HVSR) and ambient noise seismic interferometry. Results from the HVSR conclusively illustrated the method's effectiveness at determining the active layer's thickness with a single station. Investigations with the multi-station method (ambient noise seismic interferometry) are continuing at the University of Florida and have not yet conclusively determined active layer thickness changes. Further work continues with the Bureau of Land Management (BLM) to determine if the ground based measurements can constrain satellite imagery, which provide measurements on a much larger spatial scale.

  1. Layer-by-layer nanoencapsulation of camptothecin with improved activity

    PubMed Central

    Parekh, Gaurav; Pattekari, Pravin; Joshi, Chaitanya; Shutava, Tatsiana; DeCoster, Mark; Levchenko, Tatyana; Torchilin, Vladimir; Lvov, Yuri

    2014-01-01

    160 nm nanocapsules containing up to 60% of camptothecin in the core and 7–8 polyelectrolyte bilayers in the shell were produced by washless layer-by-layer assembly of heparin and block-copolymer of poly-L-lysine and polyethylene glycol. The outer surface of the nanocapsules was additionally modified with polyethylene glycol of 5 kDa or 20 kDa molecular weight to attain protein resistant properties, colloidal stability in serum and prolonged release of the drug from the capsules. An advantage of the LbL coated capsules is the preservation of camptothecin lactone form with the shell assembly starting at acidic pH and improved chemical stability of encapsulated drug at neutral and basic pH, especially in the presence of albumin that makes such formulation more active than free camptothecin. LbL nanocapsules preserve the camptothecin lactone form at pH 7.4 resulting in triple activity of the drug toward CRL2303 glioblastoma cell. PMID:24508806

  2. The effects of Kelvin-Helmholtz instability on resonance absorption layers in coronal loops

    NASA Technical Reports Server (NTRS)

    Karpen, Judith T.; Dahlburg, Russell B.; Davila, Joseph M.

    1994-01-01

    One of the long-standing uncertainties in the wave-resonance theory of coronal heating is the stability of the resonance layer. The wave motions in the resonance layer produce highly localized shear flows which vary sinusoidally in time with the resonance period. This configuration is potentially susceptible to the Kelvin-Helmholtz instability (KHI), which can enhance small-scale structure and turbulent broadening of shear layers on relatively rapid ideal timescales. We have investigated numerically the response of a characteristic velocity profile, derived from resonance absorption models, to finite fluid perturbations comparable to photospheric fluctuations. We find that the KHI primarily should affect long (approximately greater than 6 x 10(exp 4) km) loops where higher velocity flows (M approximately greater than 0.2) exist in resonance layers of order 100 km wide. There, the Kelvin-Helmholtz growth time is comparable to or less than the resonance quarter-period, and the potentially stabilizing magnetic effects are not felt until the instability is well past the linear growth stage. Not only is the resonance layer broadened by the KHI, but also the convective energy transport out of the resonance layer is increased, thus adding to the efficiency of the wave-resonance heating process. In shorter loops, e.g., those in bright points and compact flares, the stabilization due to the magnetic field and the high resonance frequency inhibit the growth of the Kelvin-Helmholtz instability beyond a minimal level.

  3. Experiments on hypersonic boundary layer transition on blunt cones with acoustic-absorption coating

    NASA Astrophysics Data System (ADS)

    Shiplyuk, A.; Lukashevich, S.; Bountin, D.; Maslov, A.; Knaus, H.

    2012-01-01

    The laminar-turbulent transition is studied experimentally on a cone with an acoustic-absorption coating and with different nose bluntness in a high-speed flow. The acoustic-absorption coating is a felt metal sheet with a random microstructure. Experiments were carried out on a 1-meter length 7 degree cone at free-stream Mach number M = 8 and zero angle of attack. Locations of the laminar-turbulent transition are detected using heat flux distributions registered by calorimeter sensors. In addition, boundary layer pulsations are measured by means of ultrafast heat flux sensors. It is shown that the laminar-turbulent transition is caused by the second-mode instability, and the laminar run extends as the bluntness is increased. The porous coating effectively suppresses this instability for all tested bluntness values and 1.3-1.85 times extends the laminar run.

  4. Coherent Control of the Optical Absorption in a Plasmonic Lattice Coupled to a Luminescent Layer

    NASA Astrophysics Data System (ADS)

    Pirruccio, Giuseppe; Ramezani, Mohammad; Rodriguez, Said Rahimzadeh-Kalaleh; Rivas, Jaime Gómez

    2016-03-01

    We experimentally demonstrate the coherent control, i.e., phase-dependent enhancement and suppression, of the optical absorption in an array of metallic nanoantennas covered by a thin luminescent layer. The coherent control is achieved by using two collinear, counterpropagating, and phase-controlled incident waves with wavelength matching the absorption spectrum of dye molecules coupled to the array. Symmetry arguments shed light on the relation between the relative phase of the incident waves and the excitation efficiency of the optical resonances of the system. This coherent control is associated with a phase-dependent distribution of the electromagnetic near fields in the structure which enables a significant reduction of the unwanted dissipation in the metallic structures.

  5. Coherent Control of the Optical Absorption in a Plasmonic Lattice Coupled to a Luminescent Layer.

    PubMed

    Pirruccio, Giuseppe; Ramezani, Mohammad; Rodriguez, Said Rahimzadeh-Kalaleh; Rivas, Jaime Gómez

    2016-03-11

    We experimentally demonstrate the coherent control, i.e., phase-dependent enhancement and suppression, of the optical absorption in an array of metallic nanoantennas covered by a thin luminescent layer. The coherent control is achieved by using two collinear, counterpropagating, and phase-controlled incident waves with wavelength matching the absorption spectrum of dye molecules coupled to the array. Symmetry arguments shed light on the relation between the relative phase of the incident waves and the excitation efficiency of the optical resonances of the system. This coherent control is associated with a phase-dependent distribution of the electromagnetic near fields in the structure which enables a significant reduction of the unwanted dissipation in the metallic structures. PMID:27015478

  6. Bicarbonate absorption stimulates active calcium absorption in the rat proximal tubule.

    PubMed Central

    Bomsztyk, K; Calalb, M B

    1988-01-01

    To evaluate the effect of luminal bicarbonate on calcium reabsorption, rat proximal tubules were perfused in vivo. Perfusion solution contained mannitol to reduce water flux to zero. Total Ca concentration was measured by atomic absorption spectrometry, Ca ion concentration in the tubule lumen (CaL2+) and the peritubular capillary (CaP2+), and luminal pH (pHL) with ion-selective microelectrodes and transepithelial voltage (VTE) with conventional microelectrodes. When tubules were perfused with buffer-free Cl-containing solution, net Ca absorption (JCa) averaged 3.33 pmol/min. Even though VTE was 1.64 mV lumen-positive, CaL2+, 1.05 mM, did not fall below the concentration in the capillary blood, 1.07 mM. When 27 mM of Cl was replaced with HCO3, there was luminal fluid acidification. Despite a decrease in VTE and CaL2+, JCa increased to 7.13 pmol/min, indicating that the enhanced JCa could not be accounted for by the reduced electrochemical gradient, delta CCa. When acetazolamide or an analogue of amiloride was added to the HCO3 solution, JCa was not different from the buffer-free solution, suggesting that HCO3-stimulated JCa may be linked to acidification. To further test this hypothesis, we used 27 mM Hepes as the luminal buffer. With Hepes there was luminal fluid acidification and JCa was not different from the buffer-free solution but delta CCa was significantly reduced, indicating enhanced active calcium transport. We conclude from the results of the present study that HCO3 stimulates active Ca absorption, a process that may be linked to acidification-mediated HCO3 absorption. PMID:3366902

  7. Computational and experimental study of a multi-layer absorptivity enhanced thin film silicon solar cell

    NASA Astrophysics Data System (ADS)

    Hajimirza, Shima; Howell, John R.

    2014-08-01

    We report on the computational design, fabrication and validation of a multi-layer silicon based thin film solar cell. The cell structure consists of a thin absorber layer of amorphous silicon deposited on a back-reflector aluminum layer and coated on top with ITO transparent conductive oxide. The structure is mounted on a glass substrate. We first use constrained optimization techniques along with numerical solvers of the electromagnetic equations (i.e. FDTD) to tune the geometry of the design. The resulting structure suggests that photon absorptivity in the thin film silicon can be enhanced by as much as 100% over the uncoated layer. The proposed design is then fabricated using thin film deposition techniques, along with a control sample of bare silicon absorber for comparison. AFM imaging and spectrophotometry experiments are applied to image and record the surface roughness and measure the reflectivity spectrum of the sample. Using the measured reflectivity spectrum, we then use inverse optimization to estimate the realized thin film dimensions, deposition error and unwanted oxidation volume. At the end, we use a statistical Monte Carlo analysis as a second method of verification to demonstrate that the measured spectra are in accordance with the expected curves from simulation, and to estimate the effects of fabrication error.

  8. Modeling the absorption behavior of solar thermal collector coatings utilizing graded alpha-C:H/TiC layers.

    PubMed

    Gruber, D P; Engel, G; Sormann, H; Schüler, A; Papousek, W

    2009-03-10

    Wavelength selective coatings are of common use in order to enhance the efficiency of devices heated by radiation such as solar thermal collectors. The use of suitable materials and the optimization of coating layer thicknesses are advisable ways to maximize the absorption. Further improvement is achievable by embedding particles in certain layers in order to modify material properties. We focus on optimizing the absorption behavior of a solar collector setup using copper as substrate, a layer of amorphous hydrogenated carbon with embedded titanium carbide particles (a-C:H/TiC), and an antireflection coating of amorphous silicon dioxide (aSiO(2)). For the setup utilizing homogeneous particle distribution, a relative absorption of 90.98% was found, while inhomogeneous particle embedding yielded 98.29%. These results are particularly interesting since until now, absorption of more than 95% was found only by using embedded Cr but not by using the more biocompatible Ti. PMID:19277084

  9. Preparation of Few-Layer Bismuth Selenide by Liquid-Phase-Exfoliation and Its Optical Absorption Properties

    PubMed Central

    Sun, Liping; Lin, Zhiqin; Peng, Jian; Weng, Jian; Huang, Yizhong; Luo, Zhengqian

    2014-01-01

    Bismuth selenide (Bi2Se3), a new topological insulator, has attracted much attention in recent years owing to its relatively simple band structure and large bulk band gap. Compared to bulk, few-layer Bi2Se3 is recently considered as a highly promising material. Here, we use a liquid-phase exfoliation method to prepare few-layer Bi2Se3 in N-methyl-2-pyrrolidone or chitosan acetic solution. The resulted few-layer Bi2Se3 dispersion demonstrates an interesting absorption in the visible light region, which is different from bulk Bi2Se3 without any absorption in this region. The absorption spectrum of few-layer Bi2Se3 depends on its size and layer number. At the same time, the nonlinear and saturable absorption of few-layer Bi2Se3 thin film in near infrared is also characterized well and further exploited to generate laser pulses by a passive Q-switching technique. Stable Q-switched operation is achieved with a lower pump threshold of 9.3 mW at 974 nm, pulse energy of 39.8 nJ and a wide range of pulse-repetition-rate from 6.2 to 40.1 kHz. Therefore, the few-layer Bi2Se3 may excite a potential applications in laser photonics and optoelectronic devices. PMID:24762534

  10. Bolometric detection of magnetoplasma resonances in microwave absorption by two-dimensional electron systems based on doping layer conductivity measurements in GaAs/AlGaAs heterostructures

    SciTech Connect

    Dorozhkin, S. I. Sychev, D. V.; Kapustin, A. A.

    2014-11-28

    We have implemented a new bolometric method to detect resonances in magneto-absorption of microwave radiation by two-dimensional electron systems (2DES) in selectively doped GaAs/AlGaAs heterostructures. Radiation is absorbed by the 2DES and the thermally activated conductivity of the doping layer supplying electrons to the 2DES serves as a thermometer. The resonant absorption brought about by excitation of the confined magnetoplasma modes appears as peaks in the magnetic field dependence of the low-frequency impedance measured between the Schottky gate and 2DES.

  11. Seasons on Saturn. II. Influence of solar activity on variation of methane absorption

    NASA Astrophysics Data System (ADS)

    Vidmachenko, A. P.

    2015-10-01

    Methane and ammonia in the atmosphere of Saturn are in the form of impurities at the level of less than tenths of a percentage. They take part in photochemical processes, the main products of which are hydrocarbons and ammonia NH3. Polyacetylenes absorb sunlight almost to 400 nm, and hydrocarbons <180 nm. Therefore, the solar activity cycle, the slope of the equator to the plane of the orbit, the orbital motion and the presence of the rings induce change in composition of the upper atmosphere. Radiation constants in the atmosphere depend on the physical and chemical conditions, decreasing from ~10 years at the visible clouds level, to months in tropopause, and days in stratosphere. The observed seasonal effects may be associated also with condensation and convection, and the dynamic time scale may be only tens of hours. The data analysis on the methane absorption distribution over the disk of Saturn for 1964-2012 showed a significant seasonal changes in the levels of visible clouds and above clouds haze. Changes of methane absorption along the meridian in the equinox 1966 and 1995, had the opposite course to the results in equinox 1980. But the expected differences in the change of methane absorption at the equinox 2009, similar to 1980, did not happen. Although all the physical and orbital characteristics of Saturn at equinoxes in these moments repeated, but the response to them were received various. A few years before the equinox in 1966, 1980 and 1995, the number of R, characterizing solar activity, varied from 40 to 180. Before equinox 2009 the Sun has minimal activity and the R value was practically zero. According to observations at the time of equinox 2009, convection in the Saturn's atmosphere stayed at a minimal level. After exiting of rings shadows in winter northern hemisphere deep cloud layer was "frozen" at the same low level at absence of active processes on the Sun. This allowed easily to register a thick layer of methane and ammonia gas. So how

  12. Changing the unstirred water layer in the intestine and its effect on absorption

    SciTech Connect

    Lu, L.

    1988-01-01

    The purpose of this research was to examine possible methods for reducing the thickness of the unstirred water layer (UWL) in the canine intestinal lumen in vivo, and to determine the effects of any reduction obtained upon intestinal absorption. The experimental approaches employed in attempting to improve stirring of the luminal fluid include: (1) addition of oleic acid plus Na-taurocholate (OA + TC) or other bile salts to the fluid used to lavage the intestinal loops since the lavage with OA + TC has been found to increase the motility of the villi; (2) increasing the lavage flow rate to 100 ml/min; (3) introduction of air bubbles into the lavage fluid. The effect of these procedures on the UWL was determined by isotopic analysis of the tissue of the experimental intestinal segment for non-absorbable {sup 14}C-labeled inulin which was included in the lavage solutions. The effects of these procedures on intestinal absorption of water and glucose are examined by measuring the difference in the volumes and the concentrations of {sup 3}H-labeled glucose in the inflowing and outflowing fluids to the experimental segment.

  13. Optimization of UV absorptivity of layered double hydroxide by intercalating organic UV-absorbent molecules.

    PubMed

    Mohsin, Sumaiyah Megat Nabil; Hussein, Mohd Zobir; Sarijo, Siti Halimah; Fakurazi, Sharida; Arulselvan, Palanisamy; Taufiq-Yap, Yun Hin

    2014-08-01

    Intercalation of Zn/Al layered double hydroxide (LDH) with benzophenone 9 (B9), a strong ultraviolet (UV) absorber, had been carried out by two different routes; co-precipitation and ion exchange method. Powder X-ray diffraction (PXRD) patterns of co-precipitated (ZB9C) and ion exchanged product (ZB91) showed basal spacing of 15.9 angstrom and 16.6 angstrom, respectively, as a result of the intercalation of B9 anions into the lamellae spaces of LDH. Intercalation was further confirmed by Fourier transform infrared spectra (FTIR), carbon, hydrogen, nitrogen and sulfur (CHNS) and thermogravimetric and differential thermogravimetric (TGA/DTG) studies. UV-vis absorption properties of the nanocomposite was investigated with diffuse reflectance UV-visible spectrometer and showed broader UV absorption range. Furthermore, stability of sunscreen molecules in LDH interlayer space was tested in deionized water, artificial sea water and skin pH condition to show slow deintercalation and high retention in host. Cytotoxicity study of the synthesized nanocomposites on human dermal fibroblast (HDF) cells shows no significant cytotoxicity after 24 h exposure for test concentrations up to 25 microg/mL. PMID:25016649

  14. Microwave absorption properties of double-layer composites using CoZn/NiZn/MnZn-ferrite and titanium dioxide

    NASA Astrophysics Data System (ADS)

    Das, Sukanta; Nayak, G. C.; Sahu, S. K.; Routray, P. C.; Roy, A. K.; Baskey, H.

    2015-03-01

    Zinc substituted ferrite powders Me0.5Zn0.5Fe2O4 (Me=Co, Mn and Ni) were prepared by the sol-gel auto-combustion method. The present study highlights development of Single layer and double layer composite microwave absorbing materials using Ferrites, Titanium dioxide and Epoxy matrix. Moreover microwave absorption property, i.e. reflection loss evaluated at X-band frequency. XRD analysis of the filler particles were carried out to evaluate crystal structure, average crystallite diameter. Morphology of the filler particles were studied with FESEM. Hysteresis behavior of the ferrites samples were studied with Vibrating Sample Magnetometer. The most important parameter governing the absorption properties of microwave absorbers i.e. permittivity and permeability studied in a vector network analyzer. Measured reflection loss value of single-layer NiZn-ferrite based microwave absorber reaches -11.2 dB at 12.05 GHz. Whereas, reflection loss value of double-layer CoZn-ferrite/ TiO2 based microwave absorber reaches -24.3 dB at 12.02 GHz. The result shows that microwave absorption property and bandwidth of absorption of double-layer microwave absorber was found to improve comparison to single layer.

  15. A multi-layered approach for absorptive glass-mat separators

    NASA Astrophysics Data System (ADS)

    Ferreira, A. L.

    The traditional method of manufacturing absorptive glass mats (AGMs) for valve-regulated lead-acid (VRLA) batteries is to blend two or more types of fibres together in an aqueous acidic solution and deposit this blend on to either a moving endless wire or a roto-former (another version of an endless wire). The sheet acquires consistency as the water is withdrawn; it is then pressed and dried against heated drums. The methods of fibre dispersion and deposition can be changed so that the different constituent fibre types of an AGM separator are processed separately in distinct and separate layers. This fibre segregation results in the enhancement of some key characteristics of the separator and thus brings some very definite advantages to the performance of VRLA batteries, e.g., the ability to deliver higher currents at higher discharge rates. Also, important AGM characteristics, such as wicking, porosity/pore-size and stratification, are radically modified by adoption of the multi-layered AGM design. As a consequence, the high-rate and cycling performances of VRLA batteries are equally affected.

  16. Near-infrared light absorption by polycrystalline SiSn alloys grown on insulating layers

    SciTech Connect

    Kurosawa, Masashi; Kato, Motohiro; Yamaha, Takashi; Taoka, Noriyuki; Nakatsuka, Osamu; Zaima, Shigeaki

    2015-04-27

    High-Sn-content SiSn alloys are strongly desired for the next-generation near-infrared optoelectronics. A polycrystalline growth study has been conducted on amorphous SiSn layers with a Sn-content of 2%–30% deposited on either a substrate of SiO{sub 2} or SiN. Incorporating 30% Sn into Si permits the crystallization of the amorphous layers at annealing temperatures below the melting point of Sn (231.9 °C). Composition analyses indicate that approximately 20% of the Sn atoms are substituted into the Si lattice after solid-phase crystallization at 150–220 °C for 5 h. Correspondingly, the optical absorption edge is red-shifted from 1.12 eV (Si) to 0.83 eV (Si{sub 1−x}Sn{sub x} (x ≈ 0.18 ± 0.04)), and the difference between the indirect and direct band gap is significantly reduced from 3.1 eV (Si) to 0.22 eV (Si{sub 1−x}Sn{sub x} (x ≈ 0.18 ± 0.04)). These results suggest that with higher substitutional Sn content the SiSn alloys could become a direct band-gap material, which would provide benefits for Si photonics.

  17. 3-D water vapor field in the atmospheric boundary layer observed with scanning differential absorption lidar

    NASA Astrophysics Data System (ADS)

    Späth, Florian; Behrendt, Andreas; Muppa, Shravan Kumar; Metzendorf, Simon; Riede, Andrea; Wulfmeyer, Volker

    2016-04-01

    High-resolution three-dimensional (3-D) water vapor data of the atmospheric boundary layer (ABL) are required to improve our understanding of land-atmosphere exchange processes. For this purpose, the scanning differential absorption lidar (DIAL) of the University of Hohenheim (UHOH) was developed as well as new analysis tools and visualization methods. The instrument determines 3-D fields of the atmospheric water vapor number density with a temporal resolution of a few seconds and a spatial resolution of up to a few tens of meters. We present three case studies from two field campaigns. In spring 2013, the UHOH DIAL was operated within the scope of the HD(CP)2 Observational Prototype Experiment (HOPE) in western Germany. HD(CP)2 stands for High Definition of Clouds and Precipitation for advancing Climate Prediction and is a German research initiative. Range-height indicator (RHI) scans of the UHOH DIAL show the water vapor heterogeneity within a range of a few kilometers up to an altitude of 2 km and its impact on the formation of clouds at the top of the ABL. The uncertainty of the measured data was assessed for the first time by extending a technique to scanning data, which was formerly applied to vertical time series. Typically, the accuracy of the DIAL measurements is between 0.5 and 0.8 g m-3 (or < 6 %) within the ABL even during daytime. This allows for performing a RHI scan from the surface to an elevation angle of 90° within 10 min. In summer 2014, the UHOH DIAL participated in the Surface Atmosphere Boundary Layer Exchange (SABLE) campaign in southwestern Germany. Conical volume scans were made which reveal multiple water vapor layers in three dimensions. Differences in their heights in different directions can be attributed to different surface elevation. With low-elevation scans in the surface layer, the humidity profiles and gradients can be related to different land cover such as maize, grassland, and forest as well as different surface layer

  18. Estimation of boundary layer humidity fluxes and statistics from airborne differential absorption lidar (DIAL)

    NASA Astrophysics Data System (ADS)

    Kiemle, Christoph; Ehret, Gerhard; Giez, Andreas; Davis, Kenneth J.; Lenschow, Donald H.; Oncley, Steven P.

    1997-12-01

    The water vapor differential absorption lidar (DIAL) of the German Aerospace Research Establishment (DLR) was flown aboard the National Center for Atmospheric Research (NCAR) Electra research aircraft during the Boreal Ecosystem-Atmosphere Study (BOREAS). The downward looking lidar system measured two-dimensional fields of aerosol backscatter and water vapor mixing ratio in the convective boundary layer (CBL) and across the CBL top (zt). We show a case study of DIAL observations of vertical profiles of mean water vapor, water vapor variance, skewness, and integral scale in the CBL. In the entrainment zone (EZ) and down to about 0.3 zi the DIAL observations agree with in situ observations and mixed-layer similarity theory. Below, the water vapor optical depth becomes large and the DIAL signal-to-noise ratio degrades. Knowing the water vapor surface flux and the convective velocity scale w* from in situ aircraft measurements, we derive entrainment fluxes by applying the mixed-layer gradient (MLG) and mixed-layer variance (MLV) methods to DIAL mixing ratio gradient and variance profiles. Entrainment flux estimates are sensitive to our estimate of zt. They are shown to be rather insensitive to the input surface flux and to the DIAL data spatial resolution within the investigated range. The estimates break down above about 0.9 zt as the flux-gradient and flux-variance relationships were developed to describe the large-scale mixing in the mid-CBL. The agreement with in situ entrainment flux estimations is within 30% for the MLV method. On a flight leg with significant mesoscale variability the entrainment flux turns out to be 70% higher than the in situ value. This is in good agreement with the fact that large-eddy simulations (LES) of mean water vapor profiles and variances, upon which the MLG and MLV methods are based, do not include mesoscale variability. The additional water vapor variance from mesoscales may then lead to the overestimate of the flux. Deviations from

  19. The effect of metal nano particle on optical absorption coefficient of multi-layer spherical quantum dot

    NASA Astrophysics Data System (ADS)

    Zamani, N.; Keshavarz, A.; Nadgaran, H.

    2016-06-01

    In this paper, we investigate the optical absorption coefficient of hybrid structure consisting of metal nano particle (MNP) coupled to multi-layer spherical quantum dot (MSQD). Energy eigenvalues and eigenfunctions of Schrödinger equation in this structure are obtained by using numerical solution (by the fourth-order Runge-Kutta method). The effect of MNP in the vicinity of MSQD is calculated by considering local field theory. Then the variation of optical absorption coefficient hybrid structure is calculated. The results show that the presence of MNP near MSQD enhances the optical absorption coefficient. Also, by changing the distance between MNP and MSQD and radius of MNP, variation of optical absorption coefficient and refractive index changes are introduced.

  20. Absorption enhancement in thin film a-Si solar cells with double-sided SiO2 particle layers

    NASA Astrophysics Data System (ADS)

    Chen, Le; Wang, Qing-Kang; Shen, Xiang-Qian; Chen, Wen; Huang, Kun; Liu, Dai-Ming

    2015-10-01

    Light absorption enhancement is very important for improving the power conversion efficiency of a thin film a-Si solar cell. In this paper, a thin-film a-Si solar cell model with double-sided SiO2 particle layers is designed, and then the underlying mechanism of absorption enhancement is investigated by finite difference time domain (FDTD) simulation; finally the feasible experimental scheme for preparing the SiO2 particle layer is discussed. It is found that the top and bottom SiO2 particle layers play an important role in anti-reflection and light trapping, respectively. The light absorption of the cell with double-sided SiO2 layers greatly increases in a wavelength range of 300 nm-800 nm, and the ultimate efficiency increases more than 22% compared with that of the flat device. The cell model with double-sided SiO2 particle layers reported here can be used in varieties of thin film solar cells to further improve their performances. Project supported by the National High-Tech Research and Development Program of China (Grant No. 2011AA050518), the University Research Program of Guangxi Education Department, China (Grant No. LX2014288), and the Natural Science Foundation of Guangxi Zhuang Autonomous Region, China (Grant No. 2013GXNSBA019014).

  1. Activation of rat intestinal mucosal mast cells by fat absorption.

    PubMed

    Ji, Yong; Sakata, Yasuhisa; Yang, Qing; Li, Xiaoming; Xu, Min; Yoder, Stephanie; Langhans, Wolfgang; Tso, Patrick

    2012-06-01

    Previous studies have linked certain types of gut mucosal immune cells with fat intake. We determined whether fat absorption activates intestinal mucosal mast cells (MMC), a key component of the gut mucosal immune system. Conscious intestinal lymph fistula rats were used. The mesenteric lymph ducts were cannulated, and the intraduodenal (i.d.) tubes were installed for the infusion of Liposyn II 20% (an intralipid emulsion). Lymphatic concentrations of histamine, rat MMC protease II (RMCPII), a specific marker of rat intestinal MMC degranulation, and prostaglandin D(2) (PGD(2)) were measured by ELISA. Intestinal MMC degranulation was visualized by immunofluorescent microscopy of jejunum sections taken at 1 h after Liposyn II gavage. Intraduodenal bolus infusion of Liposyn II 20% (4.4 kcal/3 ml) induced approximately a onefold increase in lymphatic histamine and PGD(2), ∼20-fold increase in lymphatic RMCPII, but only onefold increase in peripheral serum RMCPII concentrations. Release of RMCPII into lymph increased dose dependently with the amount of lipid fed. In addition, i.d. infusion of long-chain triacylglycerol trilinolein (C18:2 n-6, the major composite in Liposyn II) significantly increased the lymphatic RMCPII concentration, whereas medium-chain triacylglycerol tricaprylin (C8:0) did not alter lymph RMCPII secretion. Immunohistochemistry image revealed the degranulation of MMC into lamina propria after lipid feeding. These novel findings indicate that intestinal MMC are activated and degranulate to release MMC mediators to the circulation during fat absorption. This action of fatty acid is dose and chain length dependent. PMID:22461027

  2. Melanin as an active layer in biosensors

    SciTech Connect

    Piacenti da Silva, Marina Congiu, Mirko Oliveira Graeff, Carlos Frederico de; Fernandes, Jéssica Colnaghi Biziak de Figueiredo, Natália Mulato, Marcelo

    2014-03-15

    The development of pH sensors is of great interest due to its extensive application in several areas such as industrial processes, biochemistry and particularly medical diagnostics. In this study, the pH sensing properties of an extended gate field effect transistor (EGFET) based on melanin thin films as active layer are investigated and the physical mechanisms related to the device operation are discussed. Thin films were produced from different melanin precursors on indium tin oxide (ITO) and gold substrates and were investigated by Atomic Force Microscopy and Electrochemical Impedance Spectroscopy. Experiments were performed in the pH range from 2 to 12. EGFETs with melanin deposited on ITO and on gold substrates showed sensitivities ranging from 31.3 mV/pH to 48.9 mV/pH, depending on the melanin precursor and the substrate used. The pH detection is associated with specific binding sites in its structure, hydroxyl groups and quinone imine.

  3. Melanin as an active layer in biosensors

    NASA Astrophysics Data System (ADS)

    Piacenti da Silva, Marina; Fernandes, Jéssica Colnaghi; de Figueiredo, Natália Biziak; Congiu, Mirko; Mulato, Marcelo; de Oliveira Graeff, Carlos Frederico

    2014-03-01

    The development of pH sensors is of great interest due to its extensive application in several areas such as industrial processes, biochemistry and particularly medical diagnostics. In this study, the pH sensing properties of an extended gate field effect transistor (EGFET) based on melanin thin films as active layer are investigated and the physical mechanisms related to the device operation are discussed. Thin films were produced from different melanin precursors on indium tin oxide (ITO) and gold substrates and were investigated by Atomic Force Microscopy and Electrochemical Impedance Spectroscopy. Experiments were performed in the pH range from 2 to 12. EGFETs with melanin deposited on ITO and on gold substrates showed sensitivities ranging from 31.3 mV/pH to 48.9 mV/pH, depending on the melanin precursor and the substrate used. The pH detection is associated with specific binding sites in its structure, hydroxyl groups and quinone imine.

  4. Enhanced photocurrent density in graphene/Si based solar cell (GSSC) by optimizing active layer thickness

    SciTech Connect

    Rosikhin, Ahmad Hidayat, Aulia Fikri; Syuhada, Ibnu; Winata, Toto

    2015-12-29

    Thickness dependent photocurrent density in active layer of graphene/Si based solar cell has been investigated via analytical – simulation study. This report is a preliminary comparison of experimental and analytical investigation of graphene/Si based solar cell. Graphene sheet was interfaced with Si thin film forming heterojunction solar cell that was treated as a device model for photocurrent generator. Such current can be enhanced by optimizing active layer thickness and involving metal oxide as supporting layer to shift photons absorption. In this case there are two type of devices model with and without TiO{sub 2} in which the silicon thickness varied at 20 – 100 nm. All of them have examined and also compared with each other to obtain an optimum value. From this calculation it found that generated currents almost linear with thickness but there are saturated conditions that no more enhancements will be achieved. Furthermore TiO{sub 2} layer is effectively increases photon absorption but reducing device stability, maximum current is fluctuates enough. This may caused by the disturbance of excitons diffusion and resistivity inside each layer. Finally by controlling active layer thickness, it is quite useful to estimate optimization in order to develop the next solar cell devices.

  5. Facile fabrication of high-efficiency near-infrared absorption film with tungsten bronze nanoparticle dense layer

    NASA Astrophysics Data System (ADS)

    Lee, Seong Yun; Kim, Jae Young; Lee, Jun Young; Song, Ho Jun; Lee, Sangkug; Choi, Kyung Ho; Shin, Gyojic

    2014-06-01

    An excellent transparent film with effective absorption property in near-infrared (NIR) region based on cesium-doped tungsten oxide nanoparticles was fabricated using a facile double layer coating method via the theoretical considerations. The optical performance was evaluated; the double layer-coated film exhibited 10% transmittance at 1,000 nm in the NIR region and over 80% transmittance at 550 nm in the visible region. To optimize the selectivity, the optical spectrum of this film was correlated with a theoretical model by combining the contributions of the Mie-Gans absorption-based localized surface plasmon resonance and reflections by the interfaces of the heterogeneous layers and the nanoparticles in the film. Through comparison of the composite and double layer coating method, the difference of the nanoscale distances between nanoparticles in each layer was significantly revealed. It is worth noting that the nanodistance between the nanoparticles decreased in the double layer film, which enhanced the optical properties of the film, yielding a haze value of 1% or less without any additional process. These results are very attractive for the nanocomposite coating process, which would lead to industrial fields of NIR shielding and thermo-medical applications.

  6. Facile fabrication of high-efficiency near-infrared absorption film with tungsten bronze nanoparticle dense layer

    PubMed Central

    2014-01-01

    An excellent transparent film with effective absorption property in near-infrared (NIR) region based on cesium-doped tungsten oxide nanoparticles was fabricated using a facile double layer coating method via the theoretical considerations. The optical performance was evaluated; the double layer-coated film exhibited 10% transmittance at 1,000 nm in the NIR region and over 80% transmittance at 550 nm in the visible region. To optimize the selectivity, the optical spectrum of this film was correlated with a theoretical model by combining the contributions of the Mie-Gans absorption-based localized surface plasmon resonance and reflections by the interfaces of the heterogeneous layers and the nanoparticles in the film. Through comparison of the composite and double layer coating method, the difference of the nanoscale distances between nanoparticles in each layer was significantly revealed. It is worth noting that the nanodistance between the nanoparticles decreased in the double layer film, which enhanced the optical properties of the film, yielding a haze value of 1% or less without any additional process. These results are very attractive for the nanocomposite coating process, which would lead to industrial fields of NIR shielding and thermo-medical applications. PACS 78.67.Sc; 78.67.Bf; 81.15.-z PMID:24982605

  7. Determination of the orientation of OH bond axes in layer silicates by infrared absorption

    USGS Publications Warehouse

    Serratosa, J.M.; Bradley, W.F.

    1958-01-01

    It is observed that, among the micas and related crystallizations, trioctahedral compositions exhibit an OH bond axis normal to the cleavage flake, with an infrared absorption frequency near 3700 cm.-1, but that dioctahedral compositions exhibit OH bond axes near the plane of the cleavage flake and of lesser absorption frequencies.

  8. Absorption from a multi-layer circumnuclear medium and reflection from the accretion disc in NGC 1365

    NASA Astrophysics Data System (ADS)

    Risaliti, G.

    2016-05-01

    NGC 1365 hosts an X-ray obscured AGN known for both its variable absorption and its relativistic features in the reflection component. Recent simultaneous observations performed by XMM-Newton and NuSTAR caught the source in a rare, nearly unobscured state, revealing the presence of a warm absorber and a neutral, but low column density (∼ 1022 cm-2) absorber, usually not observable due to thicker layers along the line of sight. Here I propose a multi-layer structure of the circumnuclear medium which can explain all the observed absorption states of this source, and their variability properties. Remarkably, despite the spectral complexity due to this multi-component absorber, the relativistic reflection component (and hence the black hole spin) can be unambiguously measured through a time resolved spectroscopic analysis.

  9. Experiments on passive hypersonic boundary layer control using ultrasonically absorptive carbon-carbon material with random microstructure

    NASA Astrophysics Data System (ADS)

    Wagner, Alexander; Kuhn, Markus; Martinez Schramm, Jan; Hannemann, Klaus

    2013-10-01

    For the first time, the influence of ultrasonically absorptive carbon-carbon material on hypersonic laminar to turbulent boundary layer transition was investigated experimentally. A 7° half-angle blunted cone with a nose radius of 2.5 mm and a total length of 1,077 mm was tested at zero angle of attack in the High Enthalpy Shock Tunnel Göttingen of the German Aerospace Center (DLR) at Mach 7.5. One-third of the metallic model surface in circumferential direction was replaced by DLR in-house manufactured ultrasonically absorptive carbon-carbon material with random microstructure for passive transition control. The remaining model surface consisted of polished steel and served as reference surface. The model was equipped with coaxial thermocouples to determine the transition location by means of surface heat flux distribution. Flush-mounted piezoelectric fast-response pressure transducers were used to measure the pressure fluctuations in the boundary layer associated with second-mode instabilities. The free-stream unit Reynolds number was varied over a range of Re m = 1.5 × 106 m-1 to Re m = 6.4 × 106 m-1 at a stagnation enthalpy of h 0 ≈ 3.2 MJ/kg and a wall temperature ratio of T w/ T 0 ≈ 0.1. The present study revealed a clear damping of the second-mode instabilities and a delay of boundary layer transition along the ultrasonically absorptive carbon-carbon insert.

  10. Thin-Layer Chromatography: Four Simple Activities for Undergraduate Students.

    ERIC Educational Resources Information Center

    Anwar, Jamil; And Others

    1996-01-01

    Presents activities that can be used to introduce thin-layer chromatography at the undergraduate level in relatively less developed countries and that can be performed with very simple and commonly available apparati in high schools and colleges. Activities include thin-layer chromatography with a test-tube, capillary feeder, burette, and rotating…

  11. New Homogeneous Standards by Atomic Layer Deposition for Synchrotron X-ray Fluorescence and Absorption Spectroscopies.

    SciTech Connect

    Butterworth, A.L.; Becker, N.; Gainsforth, Z.; Lanzirotti, A.; Newville, M.; Proslier, T.; Stodolna, J.; Sutton, S.; Tyliszczak, T.; Westphal, A.J.; Zasadzinski, J.

    2012-03-13

    Quantification of synchrotron XRF analyses is typically done through comparisons with measurements on the NIST SRM 1832/1833 thin film standards. Unfortunately, these standards are inhomogeneous on small scales at the tens of percent level. We are synthesizing new homogeneous multilayer standards using the Atomic Layer Deposition technique and characterizing them using multiple analytical methods, including ellipsometry, Rutherford Back Scattering at Evans Analytical, Synchrotron X-ray Fluorescence (SXRF) at Advanced Photon Source (APS) Beamline 13-ID, Synchrotron X-ray Absorption Spectroscopy (XAS) at Advanced Light Source (ALS) Beamlines 11.0.2 and 5.3.2.1 and by electron microscopy techniques. Our motivation for developing much-needed cross-calibration of synchrotron techniques is borne from coordinated analyses of particles captured in the aerogel of the NASA Stardust Interstellar Dust Collector (SIDC). The Stardust Interstellar Dust Preliminary Examination (ISPE) team have characterized three sub-nanogram, {approx}1{micro}m-sized fragments considered as candidates to be the first contemporary interstellar dust ever collected, based on their chemistries and trajectories. The candidates were analyzed in small wedges of aerogel in which they were extracted from the larger collector, using high sensitivity, high spatial resolution >3 keV synchrotron x-ray fluorescence spectroscopy (SXRF) and <2 keV synchrotron x-ray transmission microscopy (STXM) during Stardust ISPE. The ISPE synchrotron techniques have complementary capabilities. Hard X-ray SXRF is sensitive to sub-fg mass of elements Z {ge} 20 (calcium) and has a spatial resolution as low as 90nm. X-ray Diffraction data were collected simultaneously with SXRF data. Soft X-ray STXM at ALS beamline 11.0.2 can detect fg-mass of most elements, including cosmochemically important oxygen, magnesium, aluminum and silicon, which are invisible to SXRF in this application. ALS beamline 11.0.2 has spatial resolution

  12. Sporadic E-Layers and Meteor Activity

    NASA Astrophysics Data System (ADS)

    Alimov, Obid

    2016-07-01

    In average width it is difficult to explain variety of particularities of the behavior sporadic layer Es ionospheres without attraction long-lived metallic ion of the meteoric origin. Mass spectrometric measurements of ion composition using rockets indicate the presence of metal ions Fe+, Mg+, Si+, Na+, Ca+, K+, Al+ and others in the E-region of the ionosphere. The most common are the ions Fe+, Mg+, Si+, which are primarily concentrated in the narrow sporadic layers of the ionosphere at altitudes of 90-130 km. The entry of meteoric matter into the Earth's atmosphere is a source of meteor atoms (M) and ions (M +) that later, together with wind shear, produce midlatitude sporadic Es layer of the ionosphere. To establish the link between sporadic Es layer and meteoroid streams, we proceeded from the dependence of the ionization coefficient of meteors b on the velocity of meteor particles in different meteoroid streams. We investigated the dependence of the critical frequency f0Es of sporadic E on the particle velocity V of meteor streams and associations. It was established that the average values of f0Es are directly proportional to the velocity V of meteor streams and associations, with the correlation coefficient of 0.53 < R < 0.74. Thus, the critical frequency of the sporadic layer Es increases with the increase of particle velocity V in meteor streams, which indicates the direct influence of meteor particles on ionization of the lower ionosphere and formation of long-lived metal atoms M and ions M+ of meteoric origin.

  13. Toward Efficient Thick Active PTB7 Photovoltaic Layers Using Diphenyl Ether as a Solvent Additive.

    PubMed

    Zheng, Yifan; Goh, Tenghooi; Fan, Pu; Shi, Wei; Yu, Junsheng; Taylor, André D

    2016-06-22

    The development of thick organic photovoltaics (OPV) could increase absorption in the active layer and ease manufacturing constraints in large-scale solar panel production. However, the efficiencies of most low-bandgap OPVs decrease substantially when the active layers exceed ∼100 nm in thickness (because of low crystallinity and a short exciton diffusion length). Herein, we report the use of solvent additive diphenyl ether (DPE) that facilitates the fabrication of thick (180 nm) active layers and triples the power conversion efficiency (PCE) of conventional thienothiophene-co-benzodithiophene polymer (PTB7)-based OPVs from 1.75 to 6.19%. These results demonstrate a PCE 20% higher than those of conventional (PTB7)-based OPV devices using 1,8-diiodooctane. Morphology studies reveal that DPE promotes the formation of nanofibrillar networks and ordered packing of PTB7 in the active layer that facilitate charge transport over longer distances. We further demonstrate that DPE improves the fill factor and photocurrent collection by enhancing the overall optical absorption, reducing the series resistance, and suppressing bimolecular recombination. PMID:27253271

  14. Local structure of Fe in Fe-doped misfit-layered calcium cobaltite: An X-ray absorption spectroscopy study

    SciTech Connect

    Prasoetsopha, Natkrita; Pinitsoontorn, Supree; Bootchanont, Atipong; Kidkhunthod, Pinit; Srepusharawoot, Pornjuk; Kamwanna, Teerasak; Amornkitbamrung, Vittaya; Kurosaki, Ken; Yamanaka, Shinsuke

    2013-08-15

    Polycrystalline Ca{sub 3}Co{sub 4−x}Fe{sub x}O{sub 9+δ} ceramics (x=0, 0.01, 0.03, 0.05) were fabricated using a simple thermal hydro-decomposition method and a spark plasma sintering technique. Thermoelectric property measurements showed that increasing Fe concentration resulted in a decrease in electrical resistivity, thermopower and thermal conductivity, leading to an improvement in the dimensionless figure-of-merit, >35% for x=0.05 at 1073 K. An X-ray absorption spectroscopy technique was used to investigate the local structure of Fe ions in the Ca{sub 3}Co{sub 4−x}Fe{sub x}O{sub 9+δ} structure for the first time. By fitting data from the extended X-ray absorption fine structure (EXAFS) spectra and analyzing the X-ray absorption near-edge structure (XANES) spectra incorporated with first principle simulation, it was shown that Fe was substituted for Co in the the Ca{sub 2}CoO{sub 3} (rocksalt, RS) layer rather than in the CoO{sub 2} layer. Variation in the thermoelectric properties as a function of Fe concentration was attributed to charge transfer between the CoO{sub 2} and the RS layers. The origin of the preferential Fe substitution site was investigated considering the ionic radii of Co and Fe and the total energy of the system. - Graphical abstract: The Fe K-edge XANES spectra of: (a) experimental result in comparison to the simulated spectra when Fe atoms were substituted in the RS layer; (b) with magnetic moment; (c) without magnetic moment, and in the CoO{sub 2} layer; (d) with magnetic moment and (e) without magnetic moment. Highlights: • Synthesis, structural studies, and thermoelectric properties of Ca{sub 3}Co{sub 4−x}Fe{sub x}O{sub 9+δ}. • Direct evidence for the local structure of the Fe ions in the Ca{sub 3}Co{sub 4−x}Fe{sub x}O{sub 9+δ} using XAS analysis. • EXAFS and XANES analysis showed that Fe was likely to be situated in the RS layer structure. • Changes in TE property with Fe content was due to charge transfer between

  15. SiN{sub x} layers on nanostructured Si solar cells: Effective for optical absorption and carrier collection

    SciTech Connect

    Cho, Yunae; Kim, Eunah; Gwon, Minji; Kim, Dong-Wook E-mail: dwkim@ewha.ac.kr; Park, Hyeong-Ho; Kim, Joondong E-mail: dwkim@ewha.ac.kr

    2015-10-12

    We compared nanopatterned Si solar cells with and without SiN{sub x} layers. The SiN{sub x} layer coating significantly improved the internal quantum efficiency of the nanopatterned cells at long wavelengths as well as short wavelengths, whereas the surface passivation helped carrier collection of flat cells mainly at short wavelengths. The surface nanostructured array enhanced the optical absorption and also concentrated incoming light near the surface in broad wavelength range. Resulting high density of the photo-excited carriers near the surface could lead to significant recombination loss and the SiN{sub x} layer played a crucial role in the improved carrier collection of the nanostructured solar cells.

  16. Active Galactic Nuclei Probed by QSO Absorption Lines

    NASA Astrophysics Data System (ADS)

    Misawa, Toru

    2007-07-01

    Quasars are the extremely bright nuclei found in about 10% of galaxies. A variety of absorption features (known collectively as quasar absorption lines) are detected in the rest-frame UV spectra of these objects. While absorption lines that have very broad widths originate in gas that is probably physocally related to the quasars, narrow absorption lines (NALs) were thought to arise in galaxies and/or in the intter-alacttic medium between the quasars and us. Using high-resolution spectra of quasars, it is found that a substantial fraction of NALs arise in gas in the immediate vicinity of the quasars. A dramatically variable, moderately-broad absorption line in the spectrum of the quasar HS 1603+3820l is also found. The variability of this line is monitored in a campaign with Subaru telescope. These observational results are compared to models for outflows from the quasars, specifically, models for accretion disk winds and evaporating obscuring tori. It is quite important to determine the mechanism of outflow because of its cosmological implications. The outflow could expel angular momentum from the accretion disk and enable quasars to accrete and shine. In addition, the outflow may also regulate star formation in the early stages of the assembly of the host galaxy and enrich the interstellar and intergalactic medium with metals.

  17. Defects forming the optical absorption edge in TlGaSe2 layered crystal

    NASA Astrophysics Data System (ADS)

    Seyidov, MirHasan Yu.; Suleymanov, Rauf A.; Şale, Yasin

    2016-09-01

    In this work, we present the results of optical experiments designed to investigate the changes in optical absorption spectra of TlGaSe2 ferroelectric-semiconductor with incommensurate (INC) phase in experimental conditions where crystal is kept several hours within the INC-phase (the regime of so called "memory" effect). The fundamental absorption of TlGaSe2, experimentally investigated by optical transmission measurements performed in the temperature range 15-300 K. An extraordinary modification of the optical absorption edge in the range of Urbach's tail is discovered as a result of the annealing within the INC-phase. The role of native defects forming the band edge in the observed phenomena in TlGaSe2 is discussed.

  18. Active unjamming of confluent cell layers

    NASA Astrophysics Data System (ADS)

    Marchetti, M. Cristina

    Cell motion inside dense tissues governs many biological processes, including embryonic development and cancer metastasis, and recent experiments suggest that these tissues exhibit collective glassy behavior. Motivated by these observations, we have studied a model of dense tissues that combines self-propelled particle models and vertex models of confluent cell layers. In this model, referred to as self-propelled Voronoi (SPV), cells are described as polygons in a Voronoi tessellation with directed noisy cell motility and interactions governed by a shape energy that incorporates the effects of cell volume incompressibility, contractility and cell-cell adhesion. Using this model, we have demonstrated a new density-independent solid-liquid transition in confluent tissues controlled by cell motility and a cell-shape parameter measuring the interplay of cortical tension and cell-cell adhesion. An important insight of this work is that the rigidity and dynamics of cell layers depends sensitively on cell shape. We have also used the SPV model to test a new method developed by our group to determine cellular forces and tissue stresses from experimentally accessible cell shapes and traction forces, hence providing the spatio-temporal distribution of stresses in motile dense tissues. This work was done with Dapeng Bi, Lisa Manning and Xingbo Yang. MCM was supported by NSF-DMR-1305184 and by the Simons Foundation.

  19. Temperature activated absorption during laser-induced damage: The evolution of laser-supported solid-state absorption fronts

    SciTech Connect

    Carr, C W; Bude, J D; Shen, N; Demange, P

    2010-10-26

    Previously we have shown that the size of laser induced damage sites in both KDP and SiO{sub 2} is largely governed by the duration of the laser pulse which creates them. Here we present a model based on experiment and simulation that accounts for this behavior. Specifically, we show that solid-state laser-supported absorption fronts are generated during a damage event and that these fronts propagate at constant velocities for laser intensities up to 4 GW/cm{sup 2}. It is the constant absorption front velocity that leads to the dependence of laser damage site size on pulse duration. We show that these absorption fronts are driven principally by the temperature-activated deep sub band-gap optical absorptivity, free electron transport, and thermal diffusion in defect-free silica for temperatures up to 15,000K and pressures < 15GPa. In addition to the practical application of selecting an optimal laser for pre-initiation of large aperture optics, this work serves as a platform for understanding general laser-matter interactions in dielectrics under a variety of conditions.

  20. CMOS color image sensor with overlaid organic photoconductive layers having narrow absorption band

    NASA Astrophysics Data System (ADS)

    Takada, Shunji; Ihama, Mikio; Inuiya, Masafumi; Komatsu, Takashi; Saito, Takahiro

    2007-02-01

    At EI2006, we proposed the CMOS image sensor, which was overlaid with organic photoconductive layers in order to incorporate in it large light-capturing ability of a color film owing to its multiple-layer structure, and demonstrated the pictures taken by the trial product of the proposed CMOS image sensor overlaid with an organic layer having green sensitivity. In this study, we have tried to get the optimized spectral sensitivity for the proposed CMOS image sensor by means of the simulation to minimize the color difference between the original Macbeth chart and its reproduction with the spectral sensitivity of the sensor as a parameter. As a result, it has been confirmed that the proposed CMOS image sensor with multiple-layer structure possesses high potential capability in terms of imagecapturing efficiency when it is provided with the optimized spectral sensitivity.

  1. Efficient solar photocatalytic activity of TiO2 coated nano-porous silicon by atomic layer deposition

    NASA Astrophysics Data System (ADS)

    Sampath, Sridhar; Maydannik, Philipp; Ivanova, Tatiana; Shestakova, Marina; Homola, Tomáš; Bryukvin, Anton; Sillanpää, Mika; Nagumothu, Rameshbabu; Alagan, Viswanathan

    2016-09-01

    In the present study, TiO2 coated nano-porous silicon (TiO2/PS) was prepared by atomic layer deposition (ALD) whereas porous silicon was prepared by stain etching method for efficient solar photocatalytic activity. TiO2/PS was characterized by FESEM, AFM, XRD, XPS and DRS UV-vis spectrophotometer. Absorbance spectrum revealed that TiO2/PS absorbs complete solar light with wave length range of 300 nm-800 nm and most importantly, it absorbs stronger visible light than UV light. The reason for efficient solar light absorption of TiO2/PS is that nanostructured TiO2 layer absorbs UV light and nano-porous silicon layer absorbs visible light which is transparent to TiO2 layer. The amount of visible light absorption of TiO2/PS directly increases with increase of silicon etching time. The effect of silicon etching time of TiO2/PS on solar photocatalytic activity was investigated towards methylene blue dye degradation. Layer by layer solar absorption mechanism was used to explain the enhanced photocatalytic activity of TiO2/PS solar absorber. According to this, the photo-generated electrons of porous silicon will be effectively injected into TiO2 via hetero junction interface which leads to efficient charge separation even though porous silicon is not participating in any redox reactions in direct.

  2. Sporadic Layer es and Siesmic Activity

    NASA Astrophysics Data System (ADS)

    Alimov, Obid; Blokhin, Alexandr; Kalashnikova, Tatyana

    2016-07-01

    To determine the influence of seismogenic disturbances on the calm state of the iono-sphere and assess the impact of turbulence development in sporadic-E during earthquake prepa-ration period we calculated the variation in the range of semitransparency ∆fES = f0ES - fbES. The study was based primarily on the ionograms obtained by vertical sounding of the ionosphere at Dushanbe at nighttime station from 15 to 29 August 1986. In this time period four successive earthquakes took place, which serves the purpose of this study of the impact of seis-mogenic processes on the intensity of the continuous generation of ionospheric turbulence. Analysis of the results obtained for seismic-ionospheric effects of 1986 earthquakes at station Dushanbe has shown that disturbance of ionospheric parameters during earthquake prepa-ration period displays a pronounced maximum with a duration of t = 1-6 hours. Ionospheric effects associated with the processes of earthquake preparation emerge quite predictably, which verifies seismogenic disturbances in the ionosphere. During the preparation of strong earthquakes, ionograms of vertical sounding produced at station Dushanbe - near the epicenter area - often shown the phenomenon of spreading traces of sporadic Es. It is assumed that the duration of manifestation of seismic ionospheric precursors in Du-shanbe τ = 1 - 6 hours may be associated with deformation processes in the Earth's crust and var-ious faults, as well as dissimilar properties of the environment of the epicentral area. It has been shown that for earthquakes with 4.5 ≤ M ≤ 5.5 1-2 days prior to the event iono-spheric perturbations in the parameters of the sporadic layer Es and an increase in the value of the range of semitransparency Es - ΔfEs were observed, which could lead to turbulence at altitudes of 100-130 km.

  3. Analysis of Charge Carrier Transport in Organic Photovoltaic Active Layers

    NASA Astrophysics Data System (ADS)

    Han, Xu; Maroudas, Dimitrios

    2015-03-01

    We present a systematic analysis of charge carrier transport in organic photovoltaic (OPV) devices based on phenomenological, deterministic charge carrier transport models. The models describe free electron and hole transport, trapping, and detrapping, as well as geminate charge-pair dissociation and geminate and bimolecular recombination, self-consistently with Poisson's equation for the electric field in the active layer. We predict photocurrent evolution in devices with active layers of P3HT, P3HT/PMMA, and P3HT/PS, as well as P3HT/PCBM blends, and photocurrent-voltage (I-V) relations in these devices at steady state. Charge generation propensity, zero-field charge mobilities, and trapping, detrapping, and recombination rate coefficients are determined by fitting the modeling predictions to experimental measurements. We have analyzed effects of the active layer morphology for layers consisting of both pristine drop-cast films and of nanoparticle (NP) assemblies, as well as effects on device performance of insulating NP doping in conducting polymers and of specially designed interlayers placed between an electrode and the active layer. The model predictions provide valuable input toward synthesis of active layers with prescribed morphology that optimize OPV device performance.

  4. Solar cells with (BGaIn)As and (InGa)(NAs) as absorption layers

    NASA Astrophysics Data System (ADS)

    Leibiger, G.; Krahmer, C.; Bauer, J.; Herrnberger, H.; Gottschalch, V.

    2004-12-01

    (BGaIn)As and (InGa)(NAs) have been tested for the application in solar cells. Single layers have been grown lattice matched on GaAs using MOVPE at low growth temperatures. Optical properties, i.e. band-gap energies and optical constants have been determined with photoluminescence and spectroscopic ellipsometry. n- and p-Type doping have been achieved with disilane and diethylzinc as doping precursors, respectively. Corresponding free carrier properties are discussed based on Hall measurements. Different solar cell structures with n- and p-doped (BGaIn)As and (InGa)(NAs) as base layer have been grown and successfully tested.

  5. A Ground-Based Profiling Differential Absorption LIDAR System for Measuring CO2 in the Planetary Boundary Layer

    NASA Technical Reports Server (NTRS)

    Andrews, Arlyn E.; Burris, John F.; Abshire, James B.; Krainak, Michael A.; Riris, Haris; Sun, Xiao-Li; Collatz, G. James

    2002-01-01

    Ground-based LIDAR observations can potentially provide continuous profiles of CO2 through the planetary boundary layer and into the free troposphere. We will present initial atmospheric measurements from a prototype system that is based on components developed by the telecommunications industry. Preliminary measurements and instrument performance calculations indicate that an optimized differential absorption LIDAR (DIAL) system will be capable of providing continuous hourly averaged profiles with 250m vertical resolution and better than 1 ppm precision at 1 km. Precision increases (decreases) at lower (higher) altitudes and is directly proportional to altitude resolution and acquisition time. Thus, precision can be improved if temporal or vertical resolution is sacrificed. Our approach measures absorption by CO2 of pulsed laser light at 1.6 microns backscattered from atmospheric aerosols. Aerosol concentrations in the planetary boundary layer are relatively high and are expected to provide adequate signal returns for the desired resolution. The long-term goal of the project is to develop a rugged, autonomous system using only commercially available components that can be replicated inexpensively for deployment in a monitoring network.

  6. The spatial distribution of p-mode absorption in active regions

    NASA Technical Reports Server (NTRS)

    Braun, D. C.; Labonte, B. J.; Duvall, T. L., Jr.

    1990-01-01

    The interaction of solar p-mode waves and active regions has been the subject of recent observational and theoretical investigations. Observations show that up to one-half of the power of incident high-degree acoustic may be absorbed in and around sunspots. In this paper the horizontal spatial distribution of high-degree p-mode absorption in solar active regions is explored. An appropriate Fourier-Hankel transform can be used to detect the mean absorption of waves passing through any given point on the solar surface. By repeating the analysis at multiple positions a map of the absorption can be constructed. A technique for optimal computation of absorption maps is developed and applied to observations of several active regions and an area of quiet sun near disk center. By comparing the distribution of p-mode absorption with magnetograms and line-wing intensity images, it is directly observed that the absorption is not limited to the location of the visible sunspots but is also associated with magnetic fields in the surrounding plage. It is estimated that the absorption efficiency scales roughly with the magnetic flux density, although the absorption appears to saturate inside the strongest fields.

  7. Absorption and Modification of Lower Hybrid Waves in the Scrape Off Layer

    NASA Astrophysics Data System (ADS)

    Parker, R.; Wallace, G.; Shiraiwa, S.; Baek, S.-G.; Faust, I.

    2015-11-01

    Loss of current drive efficiency of lower hybrid waves at high density in Alcator C-Mod current drive experiments has been attributed, at least in part, to interactions in the SOL. While ray-tracing calculations indicate that collisional absorption and modification of n|| during reflections in the SOL can be significant, their validity can be called into question owing to steep SOL gradients. In order to further quantify these losses, full-wave calculations using a plane-stratified SOL model have been carried out. The results show that the loss resulting from reflections in the SOL can be substantial, with collisional losses accounting for a loss of up to 50% per bounce of the incident wave power. The loss is sensitive to the SOL parameters with the strongest collisional absorption occurring in the case of steep temperature and weak density gradients. Modification of n|| can also be significant when the density gradient and normal to the flux surfaces are not aligned. These effects are less severe for the fast wave since its penetration into the SOL is significantly less than that of the slow wave. Work supported by USDoE awards DE-FC02-99ER54512 and DE-AC02-09CH11466.

  8. Variation in optical-absorption edge in SiN{sub x} layers with silicon clusters

    SciTech Connect

    Efremov, M. D. Volodin, V. A.; Marin, D. V.; Arzhannikova, S. A.; Kamaev, G. N.; Kochubei, S. A.; Popov, A. A.

    2008-02-15

    Using optical methods, data on optical constants are obtained for silicon nitride films synthesized by plasma-chemical vapor deposition (PCVD). Models for calculating the permittivity in the model of inhomogeneous phase mixture of silicon and silicon nitride are considered. It is found that the optical-absorption edge (E{sub g}) and the photoluminescence peak shift to longer wavelengths with increasing nitrogen atomic fraction x in sin{sub x} films. When x approaches the value 4/3 characteristic for stoichiometric silicon nitride Si{sub 3}N{sub 4}, a nonlinear sharp increase in E{sub g} is observed. Using Raman scattering, Si-Si bonds are revealed, which confirms the direct formation of silicon clusters during the film deposition. The relation between the composition of nonstoichiometric silicon nitride films, values of permittivity, and the optical-band width is established for light transmission.

  9. Three-layered absorptive glass mat separator with membrane for application in valve-regulated lead-acid batteries

    NASA Astrophysics Data System (ADS)

    Naidenov, V.; Pavlov, D.; Cherneva, M.

    During charge and discharge of the lead-acid cell equal amounts of H 2SO 4 participate in the reactions at the two types of plates (electrodes). However, the charge and discharge reactions at the positive plates involve also 2 mol of water per every mole of reacted PbO 2. Consequently, a concentration difference appears in the electrolyte between the two electrodes (horizontal stratification), which affects the reversibility of the processes at the two electrodes and thus the cycle life of the battery. The present paper proposes the use of a three-layered absorptive glass mat (AGM) separator, the middle layer playing the role of a membrane that divides (separates) the anodic and cathodic electrolyte spaces, and controls the exchange rates of H 2SO 4, H + ions, O 2 and H 2O flows between the two electrode spaces. To be able to perform this membrane function, the thinner middle AGM layer (0.2 mm) is processed with an appropriate polymeric emulsion to acquire balanced hydrophobic/hydrophilic properties, which sustain constant H 2SO 4 concentration in the two electrode spaces during cycling. Three types of polymeric emulsions have been used for treatment of the membrane: (a) polyvinylpyrollidonestyrene (MPVS), (b) polyvinylpyrrolidone "Luviskol" (MPVP), or (c) polytetrafluorethylene modified with Luviskol (MMAGM). It is established experimentally that the MMAGM membrane maintains equal acid concentration in the anodic and cathodic spaces (no horizontal stratification) during battery cycling and hence ensures longer cycle life performance.

  10. Optical reflection, transmission and absorption properties of single-layer black phosphorus from a model calculation

    NASA Astrophysics Data System (ADS)

    Margulis, Vl A.; Muryumin, E. E.; Gaiduk, E. A.

    2016-05-01

    An effective anisotropic tight-binding model is developed to analytically describe the low-energy electronic structure and optical response of phosphorene (a black phosphorus (BP) monolayer). Within the framework of the model, we derive explicit closed-form expressions, in terms of elementary functions, for the elements of the optical conductivity tensor of phosphorene. These relations provide a convenient parametrization of the highly anisotropic optical response of phosphorene, which allows the reflectance, transmittance, and absorbance of this material to be easily calculated as a function of the frequency of the incident radiation at arbitrary angles of incidence. The results of such a calculation are presented for both a free-standing phosphorene layer and the phosphorene layer deposited on a {{SiO}}2 substrate, and for the two principal cases of polarization of the incident radiation either parallel to or normal to the plane of incidence. Our findings (e.g., a ‘quasi-Brewster’ effect in the reflectance of the phosphorene/{{SiO}}2 overlayer system) pave the way for developing a new, purely optical method of distinguishing BP monolayers.

  11. Comparison of activated charcoal and ipecac syrup in prevention of drug absorption.

    PubMed

    Neuvonen, P J; Vartiainen, M; Tokola, O

    1983-01-01

    The efficacy of activated charcoal and ipecac syrup in the prevention of drug absorption was studied in 6 healthy adult volunteers, using a randomized, cross-over design. Paracetamol 1000 mg, tetracycline 500 mg and aminophylline 350 mg were ingested on an empty stomach with 100 ml water. Then, after 5 or 30 min, the subjects ingested, either activated charcoal suspension (50 g charcoal), syrup of ipecac, or, only after 5 min, water 300 ml. Activated charcoal, given either after 5 or 30 min, significantly (p less than 0.01 or less 0.05) reduced the absorption of these 3 drugs measured, for example as AUC0-24 h. Syrup of ipecac caused emesis on each occasion, with a mean delay of 15 min. When ipecac was given 5 min after the drugs, its effect on absorption was significant, but when it was given after 30 min only the absorption of tetracycline was reduced. Activated charcoal was significantly (p less than 0.05) more effective than ipecac in reducing drug absorption when given at the same time points. In cases of acute intoxication, depending on the quality and quantity of the drugs ingested, the relative efficacy of charcoal and ipecac may be somewhat different from that observed in the present study. Despite its emetic action, however, ipecac syrup is not very effective in preventing drug absorption and, in general, activated charcoal should also be given after induced emesis or gastric lavage. PMID:6134626

  12. Phase speed spectra of transient eddy fluxes and critical layer absorption

    NASA Technical Reports Server (NTRS)

    Randel, William J.; Held, Isaac M.

    1991-01-01

    Tropospheric zonal mean eddy fluxes of heat and momentum, and the divergence of the Eliassen-Palm flux, are decomposed into contributions from different zonal phase speeds. Data analyzed are the European Center for Medium Range Weather Forecasts operational global analyses covering 1980-1987. Eastward moving medium-scale waves (zonal waves 4-7) dominate the spectra of lower tropospheric heat fluxes in both hemispheres and all seasons. Upper tropospheric wave flux spectra are similar to the low level spectra in midlatitudes, but shift to slower zonal phase speeds as low latitudes are approached. The cause of this shift is the selective absorption of faster moving components in midlatitudes as the waves propagate meridionally. Latitude-phase speed distributions of eddy fluxes are constructed and compared to the zonal mean wind structure. These results demonstrate that upper tropospheric eddies break and decelerate the zonal mean flow approximately 10-20 deg in latitude away from their critical line (where phase speed equals zonal wind speed). Comparisons are also made with results from the middle stratosphere.

  13. Activation Layer Stabilization of High Polarization Photocathodes in Sub-Optimal RF Gun Environments

    SciTech Connect

    Gregory A. Mulhollan

    2010-11-16

    Specific activation recipes for bulk, 100 nm thick MBE grown and high polarization III-V photocathode material have been developed which mitigate the effects of exposure to background gasses. Lifetime data using four representative gasses were acquired for bulk GaAs, 100 nm unstrained GaAs and strained superlattice GaAs/GaAsP, all activated both with Cs and then Cs and Li (bi-alkali). Each photoemitter showed marked resilience improvement when activated using the bi-alkali recipe compared to the standard single alkali recipe. A dual alkali activation system at SLAC was constructed, baked and commissioned with the purpose of performing spin-polarization measurements on electrons emitted from the bi-alkali activated surfaces. An end station at SSRL was configured with the required sources for energy resolved photoemission measurements on the bi-alkali activated and CO2 dosed surfaces. The bi-alkali recipes were successfully implemented at SLAC/SSRL. Measurements at SLAC of the photoelectron spin-polarization from the modified activation surface showed no sign of a change in value compared to the standard activated material, i.e., no ill effects. Analysis of photoemission data indicates that the addition of Li to the activation layer results in a multi-layer structure. The presence of Li in the activation layer also acts as an inhibitor to CO2 absorption, hence better lifetimes in worse vacuum were achieved. The bi-alkali activation has been tested on O2 activated GaAs for comparison with NF3 activated surfaces. Comparable resilience to CO2 exposure was achieved for the O2 activated surface. An RF PECVD amorphous silicon growth system was modified to allow high temperature heat cleaning of GaAs substrates prior to film deposition. Growth versus thickness data were collected. Very thin amorphous silicon germanium layers were optimized to exhibit good behavior as an electron emitter. Growth of the amorphous silicon germanium films on the above substrates was fine tuned

  14. Improvement in the photocurrent collection due to enhanced absorption of light by synthesizing staggered layers of silver nanoclusters in silicon

    SciTech Connect

    Dhoubhadel, Mangal S.; Lakshantha, Wickramaarachchige J.; Rout, Bibhudutta; McDaniel, Floyd D.; Lightbourne, Sherard; D’Souza, Francis

    2015-07-23

    The quest for increased efficiency of solar cells has driven the research in synthesizing photovoltaic cells involving Si based materials. The efficiency of solar cells involving crystalline Si is stalled around 25% for the last decade. Recently Shi et al. had shown that light trapping can be enhanced by fabricating double layers of Ag nanoparticles in silicon based materials. The light trapping is critically important in a photo devices such as solar cells in order to increase light absorption and efficiency. In the present work, we report enhancement in the absorption of light in Ag ion implanted Si substrates. Multiple low energies Ag ions, ranging from ∼80 keV to ∼30 keV, with different fluences ranging from ∼1 × 10{sup 16} to ∼1 × 10{sup 17} atoms/cm{sup 2} were sequentially implanted into commercially available Si (100) substrates followed by post-thermal annealing to create different sizes of Ag nanoclusters (NC) at different depths in the top 100 nm of the Si. The absorbance of light is increased in Ag implanted Si with a significant increase in the current collection in I-V (current-voltage) photo switching measurements. The experimental photovoltaic cells fabricated with the Ag-implanted Si samples were optically characterized under AM (air mass) 1.5 solar radiation conditions (∼1.0 kW/m{sup 2}). An enhancement in the charge collection were measured in the annealed samples, where prominent Ag NCs were formed in the Si matrix compared to the as-implanted samples with amorphous layers. We believe the enhancement of the photo-current density from the samples with Ag NC is due to the improvement of efficiency of charge collection of e{sup −}-h{sup +} pairs produced by the incident light.

  15. Unpinning the Open-Circuit Voltage in Organic Solar Cells through Tuning Ternary Blend Active Layer Morphology

    NASA Astrophysics Data System (ADS)

    Khlyabich, Petr; Thompson, Barry; Loo, Yueh-Lin

    2015-03-01

    The use of ternary, as opposed to binary, blends having complementary absorption in active layers of organic bulk heterojunction solar cells is a simple approach to increase overall light absorption. While the open-circuit voltage (Voc) of such solar cells have generally been shown to be pinned by the smallest energy level difference between the donor and acceptor constituents, there have been materials systems, that when incorporated into active layers of solar cells, exhibit composition dependent and tunable Voc. Herein, we demonstrate that this Voc tunability in ternary blend solar cells is correlated with the morphology of the active layer. Chemical compatibility between the constituents in the blend, as probed by grazing-incidence X-ray diffraction (GIXD) measurements, affords Voc tuning. The constituents need not ``co-crystallize'' limited miscibility between the constituents in the active layers of solar cells affords Voc tunability. Poor physical interactions between the constituent domains within the active layers, on the other hand, result in devices that exhibit an invariant Voc that is pinned by the smallest energy level difference between the donor(s) and the acceptor(s). Our morphological studies thus support the proposed alloying model that was put forth originally.

  16. Sensitivity of thin cirrus clouds in the tropical tropopause layer to ice crystal shape and radiative absorption

    NASA Astrophysics Data System (ADS)

    Russotto, R. D.; Ackerman, T. P.; Durran, D. R.

    2016-03-01

    Subvisible cirrus clouds in the tropical tropopause layer (TTL) play potentially important roles in Earth's radiation budget and in the transport of water into the stratosphere. Previous work on these clouds with 2-D cloud-resolving models has assumed that all ice crystals were spherical, producing too few crystals greater than 60 μm in length compared with observations. In this study, the System for Atmospheric Modeling cloud-resolving model is modified in order to calculate the fall speeds, growth rates, and radiative absorption of nonspherical ice crystals. This extended model is used in simulations that aim to provide an upper bound on the effects of ice crystal shape on the time evolution of thin cirrus clouds and to identify the physical processes responsible for any such effects. Model runs assuming spheroidal crystals result in a higher center of cloud ice mass than in the control, spherical case, while the total mass of ice is little affected by the shape. Increasing the radiative heating results in less total cloud ice mass relative to the control case, an effect which is robust with more extreme perturbations to the absorption coefficients. This is due to higher temperatures reducing the relative humidity in the cloud and its environment, and greater entrainment of dry air due to dynamical changes. Comparisons of modeled ice crystal size distributions with recent airborne observations of TTL cirrus show that incorporating nonspherical shape has the potential to bring the model closer to observations.

  17. TESTING GUIDELINES FOR TECHNETIUM-99 ABSORPTION ON ACTIVATED CARBON

    SciTech Connect

    BYRNES ME

    2010-09-08

    CH2M HILL Plateau Remediation Company (CHPRC) is currently evaluating the potential use of activated carbon adsorption for removing technetium-99 from groundwater as a treatment method for the Hanford Site's 200 West Area groundwater pump-and-treat system. The current pump-and-treat system design will include an ion-exchange (IX) system for selective removal of technetium-99 from selected wells prior to subsequent treatment of the water in the central treatment system. The IX resin selected for technetium-99 removal is Purolite A530E. The resin service life is estimated to be approximately 66.85 days at the design technetium-99 loading rate, and the spent resin must be replaced because it cannot be regenerated. The resulting operating costs associated with resin replacement every 66.85 days are estimated at $0.98 million/year. Activated carbon pre-treatment is being evaluated as a potential cost-saving measure to offset the high operating costs associated with frequent IX resin replacement. This document is preceded by the Literature Survey of Technetium-99 Groundwater Pre-Treatment Option Using Granular Activated Carbon (SGW-43928), which identified and evaluated prior research related to technetium-99 adsorption on activated carbon. The survey also evaluated potential operating considerations for this treatment approach for the 200 West Area. The preliminary conclusions of the literature survey are as follows: (1) Activated carbon can be used to selectively remove technetium-99 from contaminated groundwater. (2) Technetium-99 adsorption onto activated carbon is expected to vary significantly based on carbon types and operating conditions. For the treatment approach to be viable at the Hanford Site, activated carbon must be capable of achieving a designated minimum technetium-99 uptake. (3) Certain radionuclides known to be present in 200 West Area groundwater are also likely to adsorb onto activated carbon. (4) Organic solvent contaminants of concern (COCs) will

  18. Lack of relationship between activity of intestinal alkaline phosphatase and calcium or phosphate absorption.

    PubMed

    Asteggiano, C; Tolosa, N; Pereira, R; Moreno, J; Cañas, F

    1981-01-01

    The effects of vitamin D3 and the aqueous extract of Solanum malacoxylon on intestinal alkaline phosphatase and tissue phosphate content were studied on rachitic chicks treated with large doses of ethane-1-hydroxy-1,1 diphosphonate (EHDP). The EHDP treatment blocks the increase of intestinal calcium or phosphate absorption induced by the vitamin D3, while it has no effects on the rise of intestinal alkaline phosphatase activity or the increment in tissue phosphate content. The lack of correlation between the increment of alkaline phosphatase and that of Ca or phosphate absorption in vitamin D3 plus EHDP treated chicks excludes a participation of the alkaline phosphatase in the mechanism of Ca or P intestinal absorption. The Ca or phosphorus absorption are elicited specifically by 1,25-(OH)2-D3, while alkaline phosphatase activity and phosphate tissue concentration respond to a broader spectrum of stimuli. PMID:6316731

  19. Stability of double-diffusive convection induced by selective absorption of radiation in a fluid layer

    NASA Astrophysics Data System (ADS)

    Wicks, Thomas J.; Hill, Antony A.

    2012-05-01

    Linear and nonlinear stability analyses were performed on a fluid layer with a concentration-based internal heat source. Clear bimodal behaviour in the neutral curve (with stationary and oscillatory modes) is observed in the region of the onset of oscillatory convection, which is a previously unobserved phenomenon in radiation-induced convection. The numerical results for the linear instability analysis suggest a critical value γ c of γ, a measure for the strength of the internal heat source, for which oscillatory convection is inhibited when γ > γ c . Linear instability analyses on the effect of varying the ratio of the salt concentrations at the upper and lower boundaries conclude that the ratio has a significant effect on the stability boundary. A nonlinear analysis using an energy approach confirms that the linear theory describes the stability boundary most accurately when γ is such that the linear theory predicts the onset of mostly stationary convection. Nevertheless, the agreement between the linear and nonlinear stability thresholds deteriorates for larger values of the solute Rayleigh number for any value of γ.

  20. Synthesis and selective IR absorption properties of iminodiacetic-acid intercalated MgAl-layered double hydroxide

    SciTech Connect

    Wang Lijing; Xu Xiangyu; Evans, David G.; Duan Xue; Li Dianqing

    2010-05-15

    An MgAl-NO{sub 3}-layered double hydroxide (LDH) precursor has been prepared by a method involving separate nucleation and aging steps (SNAS). Reaction with iminodiacetic acid (IDA) under weakly acidic conditions led to the replacement of the interlayer nitrate anions by iminodiacetic acid anions. The product was characterized by XRD, FT-IR, TG-DTA, ICP, elemental analysis and SEM. The results show that the original interlayer nitrate anions of LDHs precursor were replaced by iminodiacetic acid anions and that the resulting intercalation product MgAl-IDA-LDH has an ordered crystalline structure. MgAl-IDA-LDH was mixed with low density polyethylene (LDPE) using a masterbatch method. LDPE films filled with MgAl-IDA-LDH showed a higher mid to far infrared absorption than films filled with MgAl-CO{sub 3}-LDH in the 7-25 {mu}m range, particularly in the key 9-11 {mu}m range required for application in agricultural plastic films. - Graphical abstract: Intercalation of iminodiacetic acid (IDA) anions in a MgAl-NO{sub 3}-layered double hydroxide host leads to an enhancement of its infrared absorbing ability for application in agricultural plastic films.

  1. Elevated aerosol layers modify the O2-O2 absorption measured by ground-based MAX-DOAS

    NASA Astrophysics Data System (ADS)

    Ortega, Ivan; Berg, Larry K.; Ferrare, Richard A.; Hair, Johnathan W.; Hostetler, Chris A.; Volkamer, Rainer

    2016-06-01

    The oxygen collisional complex (O2-O2, or O4) is a greenhouse gas, and a calibration trace gas used to infer aerosol and cloud properties by Differential Optical Absorption Spectroscopy (DOAS). Recent reports suggest the need for an O4 correction factor (CFO4) when comparing simulated and measured O4 differential slant column densities (dSCD) by passive DOAS. We investigate the sensitivity of O4 dSCD simulations at ultraviolet (360 nm) and visible (477 nm) wavelengths towards separately measured aerosol extinction profiles. Measurements were conducted by the University of Colorado 2D-MAX-DOAS instrument and NASA's multispectral High Spectral Resolution Lidar (HSRL-2) during the Two Column Aerosol Project (TCAP) at Cape Cod, MA in July 2012. During two case study days with (1) high aerosol load (17 July, AOD~0.35 at 477 nm), and (2) near molecular scattering conditions (22 July, AOD<0.10 at 477 nm) the measured and calculated O4 dSCDs agreed within 6.4±0.4% (360 nm) and 4.7±0.6% (477 nm) if the HSRL-2 profiles were used as input to the calculations. However, if in the calculations the aerosol is confined to the surface layer (while keeping AOD constant) we find 0.53layers, unless accounted for, can cause negative bias in the simulated O4 dSCDs that can explain CFO4. The air density and aerosol profile aloft needs to be taken into account when interpreting the O4 from ground-based MAX-DOAS. Opportunities to identify and better characterize these elevated layers are also discussed.

  2. Contribution of sorbitol combined with activated charcoal in prevention of salicylate absorption.

    PubMed

    Keller, R E; Schwab, R A; Krenzelok, E P

    1990-06-01

    The use of cathartics and activated charcoal in treating toxic ingestions has become a standard treatment modality. Sorbitol has been shown to be the most rapidly acting cathartic, but its therapeutic significance has been debated. Using a previously described aspirin overdose model, ten healthy volunteers participated in a crossover design study that investigated the effect of activated charcoal alone versus that of activated charcoal and sorbitol in preventing salicylate absorption. In phase 1 of the study, subjects consumed 2.5 g aspirin followed by 25 g activated charcoal one hour later. Urine was collected for 48 hours and analyzed for quantitative salicylate metabolites. Phase 2 was identical except that 1.5 g/kg sorbitol was consumed with the activated charcoal. The mean amount of aspirin absorbed without the use of sorbitol was 1.26 +/- 0.15 g, whereas the mean absorption was 0.912 +/- 0.18 g with the addition of sorbitol. This is a 28% decrease in absorption of salicylates attributable to the use of sorbitol. The difference is significant at P less than .05 by the paired Student's t test. This study demonstrates that the addition of sorbitol significantly decreases drug absorption in a simulated drug overdose model. Effects on absorption in actual overdose situations and on patient outcome should be the subjects of further study. PMID:2188536

  3. GaAs/AlGaAs resonant tunneling diodes with a GaInNAs absorption layer for telecommunication light sensing

    NASA Astrophysics Data System (ADS)

    Hartmann, F.; Langer, F.; Bisping, D.; Musterer, A.; Höfling, S.; Kamp, M.; Forchel, A.; Worschech, L.

    2012-04-01

    Al0.6Ga0.4As/GaAs/Al0.6Ga0.4As double-barrier resonant-tunneling diodes (RTD) were grown by molecular beam epitaxy with a nearby, lattice-matched Ga0.89In0.11N0.04As0.96 absorption layer. RTD mesas with ring contacts and an aperture for optical excitation of charge carriers were fabricated on the epitaxial layers. Electrical and optical properties of the RTDs were investigated for different thicknesses of a thin GaAs spacer layer incorporated between the AlGaAs tunnel barrier adjacent to the GaInNAs absorption layer. Illumination of the RTDs with laser light of 1.3 μm wavelength leads to a pronounced photo-effect with a sensitivities of around 103 A/W.

  4. Direct Observation of Degenerate Two-Photon Absorption and Its Saturation in WS2 and MoS2 Monolayer and Few-Layer Films.

    PubMed

    Zhang, Saifeng; Dong, Ningning; McEvoy, Niall; O'Brien, Maria; Winters, Sinéad; Berner, Nina C; Yim, Chanyoung; Li, Yuanxin; Zhang, Xiaoyan; Chen, Zhanghai; Zhang, Long; Duesberg, Georg S; Wang, Jun

    2015-07-28

    The optical nonlinearity of WS2 and MoS2 monolayer and few-layer films was investigated using the Z-scan technique with femtosecond pulses from the visible to the near-infrared range. The nonlinear absorption of few- and multilayer WS2 and MoS2 films and their dependences on excitation wavelength were studied. WS2 films with 1-3 layers exhibited a giant two-photon absorption (TPA) coefficient as high as (1.0 ± 0.8) × 10(4) cm/GW. TPA saturation was observed for the WS2 film with 1-3 layers and for the MoS2 film with 25-27 layers. The giant nonlinearity of WS2 and MoS2 films is attributed to a two-dimensional confinement, a giant exciton effect, and the band edge resonance of TPA. PMID:26135798

  5. Low absorption loss p-AlGaN superlattice cladding layer for current-injection deep ultraviolet laser diodes

    NASA Astrophysics Data System (ADS)

    Martens, M.; Kuhn, C.; Ziffer, E.; Simoneit, T.; Kueller, V.; Knauer, A.; Rass, J.; Wernicke, T.; Einfeldt, S.; Weyers, M.; Kneissl, M.

    2016-04-01

    Current injection into AlGaN-based laser diode structures with high aluminum mole fractions for deep ultraviolet emission is investigated. The electrical characteristics of laser diode structures with different p-AlGaN short period superlattice (SPSL) cladding layers with various aluminum mole fractions are compared. The heterostructures contain all elements that are needed for a current-injection laser diode including cladding and waveguide layers as well as an AlGaN quantum well active region emitting near 270 nm. We found that with increasing aluminum content in the p-AlGaN cladding, the diode turn-on voltage increases, while the series resistance slightly decreases. By introducing an SPSL instead of bulk layers, the operating voltage is significantly reduced. A gain guided broad area laser diode structure with transparent p-Al0.70Ga0.30N waveguide layers and a transparent p-cladding with an average aluminum content of 81% was designed for strong confinement of the transverse optical mode and low optical losses. Using an optimized SPSL, this diode could sustain current densities of more than 4.5 kA/cm2.

  6. Local and Sustained Activity of Doxycycline Delivered with Layer-by-Layer Microcapsules.

    PubMed

    Luo, Dong; Gould, David J; Sukhorukov, Gleb B

    2016-04-11

    Achieving localized delivery of small molecule drugs has the potential to increase efficacy and reduce off target and side effects associated with systemic distribution. Herein, we explore the potential use of layer-by-layer (LbL) assembled microcapsules for the delivery of doxycycline. Absorbance of doxycycline onto core dextran sulfate of preassembled microcapsules provides an efficient method to load both synthetic and biodegradable microcapsules with the drug. Application of an outer layer lipid coat enhances the sustained in vitro release of doxycycline from both microcapsule types. To monitor doxycycline delivery in a biological system, C2C12 mouse myoblasts are engineered to express EGFP under the control of the optimized components of the tetracycline regulated gene expression system. Microcapsules are not toxic to these cells, and upon delivery to the cells, EGFP is more efficiently induced in those cells that contain engulfed microcapsules and monitored EGFP expression clearly demonstrates that synthetic microcapsules with a DPPC coat are the most efficient for sustain intracellular delivery. Doxycycline released from microcapsules also displayed sustained activity in an antimicrobial growth inhibition assay compared with doxycycline solution. This study reveals the potential for LbL microcapsules in small molecule drug delivery and their feasible use for achieving prolonged doxycycline activity. PMID:26967921

  7. Active layer hydrology for Imnavait Creek, Toolik, Alaska

    SciTech Connect

    Kane, D.L.

    1986-01-01

    In the annual hydrologic cycle, snowmelt is the most significant event at Imnavait Creek located near Toolik Lake, Alaska. Precipitation that has accumulated for more than 6 months on the surface melts in a relatively short period of 7 to 10 days once sustained melting occurs. During the ablation period, runoff dominates the hydrologic cycle. Some meltwater goes to rewetting the organic soils in the active layer. The remainder is lost primarily because of evaporation, since transpiration is not a very active process at this time. Following the snowmelt period, evapotranspiration becomes the dominate process, with base flow contributing the other watershed losses. It is important to note that the water initally lost by evapotranspiration entered the organic layer during melt. This water from the snowpack ensures that each year the various plant communities will have sufficient water to start a new summer of growth.

  8. Reconstruction of a 6-MeV bremsstrahlung spectrum by multi-layer absorption based on LiF:Mg, Cu, P

    NASA Astrophysics Data System (ADS)

    Huang, Jian-Wei; Wang, Nai-Yan

    2014-10-01

    In this paper, TLD (LiF: Mg, Cu, P) is used as detector. A multi-layer absorption (MLA) model is designed. Combined with Monte-Carlo processes, a bremsstrahlung X-ray spectrum is reconstructed by an iterative method; the reconstructed results agree with the results of simulations by the MCNP process essentially, especially in middle energy region.

  9. Layered shielding design for an active neutron interrogation system

    NASA Astrophysics Data System (ADS)

    Whetstone, Zachary D.; Kearfott, Kimberlee J.

    2016-08-01

    The use of source and detector shields in active neutron interrogation can improve detector signal. In simulations, a shielded detector with a source rotated π/3 rad relative to the opening decreased neutron flux roughly three orders of magnitude. Several realistic source and detector shield configurations were simulated. A layered design reduced neutron and secondary photon flux in the detector by approximately one order of magnitude for a deuterium-tritium source. The shield arrangement can be adapted for a portable, modular design.

  10. a Spatio-Temporal Framework for Modeling Active Layer Thickness

    NASA Astrophysics Data System (ADS)

    Touyz, J.; Streletskiy, D. A.; Nelson, F. E.; Apanasovich, T. V.

    2015-07-01

    The Arctic is experiencing an unprecedented rate of environmental and climate change. The active layer (the uppermost layer of soil between the atmosphere and permafrost that freezes in winter and thaws in summer) is sensitive to both climatic and environmental changes, and plays an important role in the functioning, planning, and economic activities of Arctic human and natural ecosystems. This study develops a methodology for modeling and estimating spatial-temporal variations in active layer thickness (ALT) using data from several sites of the Circumpolar Active Layer Monitoring network, and demonstrates its use in spatial-temporal interpolation. The simplest model's stochastic component exhibits no spatial or spatio-temporal dependency and is referred to as the naïve model, against which we evaluate the performance of the other models, which assume that the stochastic component exhibits either spatial or spatio-temporal dependency. The methods used to fit the models are then discussed, along with point forecasting. We compare the predicted fit of the various models at key study sites located in the North Slope of Alaska and demonstrate the advantages of space-time models through a series of error statistics such as mean squared error, mean absolute and percent deviance from observed data. We find the difference in performance between the spatio-temporal and remaining models is significant for all three error statistics. The best stochastic spatio-temporal model increases predictive accuracy, compared to the naïve model, of 33.3%, 36.2% and 32.5% on average across the three error metrics at the key sites for a one-year hold out period.

  11. Synthesis and selective IR absorption properties of iminodiacetic-acid intercalated MgAl-layered double hydroxide

    NASA Astrophysics Data System (ADS)

    Wang, Lijing; Xu, Xiangyu; Evans, David G.; Duan, Xue; Li, Dianqing

    2010-05-01

    An MgAl-NO 3-layered double hydroxide (LDH) precursor has been prepared by a method involving separate nucleation and aging steps (SNAS). Reaction with iminodiacetic acid (IDA) under weakly acidic conditions led to the replacement of the interlayer nitrate anions by iminodiacetic acid anions. The product was characterized by XRD, FT-IR, TG-DTA, ICP, elemental analysis and SEM. The results show that the original interlayer nitrate anions of LDHs precursor were replaced by iminodiacetic acid anions and that the resulting intercalation product MgAl-IDA-LDH has an ordered crystalline structure. MgAl-IDA-LDH was mixed with low density polyethylene (LDPE) using a masterbatch method. LDPE films filled with MgAl-IDA-LDH showed a higher mid to far infrared absorption than films filled with MgAl-CO 3-LDH in the 7-25 μm range, particularly in the key 9-11 μm range required for application in agricultural plastic films.

  12. Strong nonlinear saturation absorption-induced optical pinhole channel and super-resolution effects: a multi-layer system model.

    PubMed

    Wei, Jingsong; Yan, Hui

    2014-11-15

    This work focuses on the strong nonlinear saturation absorption (NSA)-induced optical super-resolution effect. A multi-layer system model is proposed to understand the strong NSA-induced formation of an optical pinhole channel and the generation of a super-resolution spot. Taking a Sb2Te3 thin film as an example, numerical simulations were conducted. The results illustrate that an optical pinhole channel is clearly formed by the NSA characteristics. This pinhole channel is similar to a near-field light probe. Light travels through the pinhole channel, and a super-resolution spot is generated at its apex. The near-field spot scanning experimental results show that the reduction ratio of the spot is approximately 44.8%, which is basically consistent with the numerical simulation result of 43%. This work is helpful for understanding optical nonlinear super-resolution effects and developing nanolithography, nanodata storage, high-resolution optical imaging technologies with nonlinear thin films. PMID:25490475

  13. Spatially resolved optical absorption spectroscopy of single- and few-layer MoS2 by hyperspectral imaging

    NASA Astrophysics Data System (ADS)

    Castellanos-Gomez, Andres; Quereda, Jorge; van der Meulen, Herko P.; Agraït, Nicolás; Rubio-Bollinger, Gabino

    2016-03-01

    The possibility of spatially resolving the optical properties of atomically thin materials is especially appealing as they can be modulated at the micro- and nanoscale by reducing their thickness, changing the doping level or applying a mechanical deformation. Therefore, optical spectroscopy techniques with high spatial resolution are necessary to get a deeper insight into the properties of two-dimensional (2D) materials. Here we study the optical absorption of single- and few-layer molybdenum disulfide (MoS2) in the spectral range from 1.24 eV to 3.22 eV (385 nm to 1000 nm) by developing a hyperspectral imaging technique that allows one to probe the optical properties with diffraction limited spatial resolution. We find hyperspectral imaging very suited to study indirect bandgap semiconductors, unlike photoluminescence which only provides high luminescence yield for direct gap semiconductors. Moreover, this work opens the door to study the spatial variation of the optical properties of other 2D systems, including non-semiconducting materials where scanning photoluminescence cannot be employed.

  14. Spatially resolved optical absorption spectroscopy of single- and few-layer MoS₂ by hyperspectral imaging.

    PubMed

    Castellanos-Gomez, Andres; Quereda, Jorge; van der Meulen, Herko P; Agraït, Nicolás; Rubio-Bollinger, Gabino

    2016-03-18

    The possibility of spatially resolving the optical properties of atomically thin materials is especially appealing as they can be modulated at the micro- and nanoscale by reducing their thickness, changing the doping level or applying a mechanical deformation. Therefore, optical spectroscopy techniques with high spatial resolution are necessary to get a deeper insight into the properties of two-dimensional (2D) materials. Here we study the optical absorption of single- and few-layer molybdenum disulfide (MoS2) in the spectral range from 1.24 eV to 3.22 eV (385 nm to 1000 nm) by developing a hyperspectral imaging technique that allows one to probe the optical properties with diffraction limited spatial resolution. We find hyperspectral imaging very suited to study indirect bandgap semiconductors, unlike photoluminescence which only provides high luminescence yield for direct gap semiconductors. Moreover, this work opens the door to study the spatial variation of the optical properties of other 2D systems, including non-semiconducting materials where scanning photoluminescence cannot be employed. PMID:26876671

  15. Vibration control of cylindrical shells using active constrained layer damping

    NASA Astrophysics Data System (ADS)

    Ray, Manas C.; Chen, Tung-Huei; Baz, Amr M.

    1997-05-01

    The fundamentals of controlling the structural vibration of cylindrical shells treated with active constrained layer damping (ACLD) treatments are presented. The effectiveness of the ACLD treatments in enhancing the damping characteristics of thin cylindrical shells is demonstrated theoretically and experimentally. A finite element model (FEM) is developed to describe the dynamic interaction between the shells and the ACLD treatments. The FEM is used to predict the natural frequencies and the modal loss factors of shells which are partially treated with patches of the ACLD treatments. The predictions of the FEM are validated experimentally using stainless steel cylinders which are 20.32 cm in diameter, 30.4 cm in length and 0.05 cm in thickness. The cylinders are treated with ACLD patches of different configurations in order to target single or multi-modes of lobar vibrations. The ACLD patches used are made of DYAD 606 visco-elastic layer which is sandwiched between two layers of PVDF piezo-electric films. Vibration attenuations of 85% are obtained with maximum control voltage of 40 volts. Such attenuations are attributed to the effectiveness of the ACLD treatment in increasing the modal damping ratios by about a factor of four over those of conventional passive constrained layer damping (PCLD) treatments. The obtained results suggest the potential of the ACLD treatments in controlling the vibration of cylindrical shells which constitute the major building block of many critical structures such as cabins of aircrafts, hulls of submarines and bodies of rockets and missiles.

  16. OH 1.563 micron Absorption from Starspots on Active Stars

    NASA Astrophysics Data System (ADS)

    O'Neal, Douglas; Neff, James E.

    1997-03-01

    We present results from a study of starspots on active stars using a pair of vibrational-rotational absorption lines of the OH molecule near 1.563mu m. We detect excess OH absorption due to dark, cool starspots on the RS CVn binaries II Pegasi, V1762 Cygni, and lambda Andromedae. This is the first detection of OH absorption from spots on stars other than the Sun. We have measured absorption equivalent widths of these OH lines (which are blended at the resolution of our observations) in inactive giant and dwarf stars of spectral types G, K, and M. We find that the total equivalent width of the line pair increases approximately linearly as effective temperature decreases from 5000 K to 3000 K. This greatly extends the temperature range over which starspots can be detected through molecular absorption features. We measure starspot filling factors by fitting the spectra of active stars with linear combinations of comparison star spectra representing the spot and non-spot regions of the star. Fitting only one spectral feature, we cannot derive independent constraints on starspot area and temperature. Assuming spot temperatures based on previous analyses, we find (for one epoch) spot filling factors between 35% and 48% for II Peg, 22% and 26% for lambda And, and 27% and 32% for V1762 Cyg.

  17. Involvement of active sodium transport in the rectal absorption of gentamicin sulfate in the presence and absence of absorption-promoting adjuvants.

    PubMed

    Fix, J A; Porter, P A; Leppert, P S

    1983-06-01

    The involvement of active sodium transport in the rectal absorption of gentamicin sulfate was examined in rats, employing aqueous microenemas of known total ionic strength (mu) in the presence or absence of absorption-promoting adjuvants. Rectal gentamicin bio-availability, which is negligible (1 +/- 1.2%) at an ionic strength of 0.15 without adjuvants, is significantly (p less than 0.01) increased by including adjuvants in the formulation (sodium salicylate, 12 +/- 4.0%; sodium-5-bromosalicylate, 59 +/- 15.1%; disodium ethylene (dinitrilo)tetraacetate, 24 +/- 9.3%). Pretreating the rectal mucosa cells with ouabain, a specific inhibitor of active sodium transport, significantly (p less than 0.01) reduced gentamicin absorption in response to all three adjuvants. In contrast to previous findings with sodium chloride, high ionic strength choline chloride (mu = 1.056) did not promote gentamicin absorption. The data indicate that active sodium transport is an integral component of rectal absorption of water-soluble compounds and may be involved in the mechanism of action of absorption-promoting adjuvants. PMID:6875833

  18. Surface activation of CNT Webs towards layer by layer assembly of biosensors.

    PubMed

    Musameh, Mustafa; Huynh, Chi P; Hickey, Mark; Kyratzis, Ilias Louis

    2016-04-25

    Several surface activation methods such as chemical, electrochemical and plasma have been used for enhancing the electrochemical performance of carbon based electrodes for various applications. However, some of these surface activation methods may not be useful depending on the chemical and physical properties of the activated surface. Herein we investigate the surface activation of carbon nanotube (CNT) webs by electrochemical and plasma techniques to enhance their electrochemical performance and enable the fabrication of a biosensor using the layer-by-layer (LBL) approach. The pretreated CNT webs were characterized by SEM, TEM, Raman, XPS and electrochemical methods. TEM images and Raman analysis showed an increase in the level of surface defects upon pretreatment with higher number of defects after electrochemical pretreatment. XPS analysis showed an increase in the level of oxygen functional groups after pretreatment (4 to 5 times increase) which resulted in enhanced water wettability especially for plasma pretreated CNT webs. The pretreated CNT web electrodes also showed an enhanced electrochemical activity towards the oxidation and reduction of different redox probes with higher sensitivity for the electrochemically pretreated CNT web electrode that was accompanied by a higher level of noise in amperometric measurements. A highly linear response was obtained for the untreated and the electrochemically pretreated CNT web electrodes towards the amperometric detection of NADH (R(2) of 0.9996 and 0.9986 respectively) while a non-linear response was observed for the plasma pretreated CNT web electrode (R(2) of 0.8538). The pretreated CNT web electrodes enabled the fabrication of a LBL biosensor for alcohol detection with highest operational stability obtained for the plasma pretreated CNT web surface. PMID:26818435

  19. Catalytically active single-atom niobium in graphitic layers.

    PubMed

    Zhang, Xuefeng; Guo, Junjie; Guan, Pengfei; Liu, Chunjing; Huang, Hao; Xue, Fanghong; Dong, Xinglong; Pennycook, Stephen J; Chisholm, Matthew F

    2013-01-01

    Carbides of groups IV through VI (Ti, V and Cr groups) have long been proposed as substitutes for noble metal-based electrocatalysts in polymer electrolyte fuel cells. However, their catalytic activity has been extremely limited because of the low density and stability of catalytically active sites. Here we report the excellent performance of a niobium-carbon structure for catalysing the cathodic oxygen reduction reaction. A large number of single niobium atoms and ultra small clusters trapped in graphitic layers are directly identified using state-of-the-art aberration-corrected scanning transmission electron microscopy. This structure not only enhances the overall conductivity for accelerating the exchange of ions and electrons, but it suppresses the chemical/thermal coarsening of the active particles. Experimental results coupled with theory calculations reveal that the single niobium atoms incorporated within the graphitic layers produce a redistribution of d-band electrons and become surprisingly active for O2 adsorption and dissociation, and also exhibit high stability. PMID:23715283

  20. Optically detected X-ray absorption spectroscopy measurements as a means of monitoring corrosion layers on copper.

    PubMed

    Dowsett, Mark G; Adriaens, Annemie; Jones, Gareth K C; Poolton, Nigel; Fiddy, Steven; Nikitenko, Sergé

    2008-11-15

    XANES and EXAFS information is conventionally measured in transmission through the energy-dependent absorption of X-rays or by observing X-ray fluorescence, but secondary fluorescence processes, such as the emission of electrons and optical photons (e.g., 200-1000 nm), can also be used as a carrier of the XAS signatures, providing complementary information such as improved surface specificity. Where the near-visible photons have a shorter range in a material, the data will be more surface specific. Moreover, optical radiation may escape more readily than X-rays through liquid in an environmental cell. Here, we describe a first test of optically detected X-ray absorption spectroscopy (ODXAS) for monitoring electrochemical treatments on copper-based alloys, for example, heritage metals. Artificially made corrosion products deposited on a copper substrate were analyzed in air and in a 1% (w/v) sodium sesquicarbonate solution to simulate typical conservation methods for copper-based objects recovered from marine environments. The measurements were made on stations 7.1 and 9.2 MF (SRS Daresbury, UK) using the mobile luminescence end station (MoLES), supplemented by XAS measurements taken on DUBBLE (BM26 A) at the ESRF. The ODXAS spectra usually contain fine structure similar to that of XAS spectra measured in X-ray fluorescence. Importantly, for the compounds examined, the ODXAS is significantly more surface specific, and >98% characteristic of thin surface layers of 0.5-1.5-microm thickness in cases where X-ray measurements are dominated by the substrate. However, EXAFS and XANES from broadband optical measurements are superimposed on a high background due to other optical emission modes. This produces statistical fluctuations up to double what would be expected from normal counting statistics because the data retain the absolute statistical fluctuation in the original raw count, while losing up to 70% of their magnitude when background is removed. The problem may be

  1. Quantitative Measurement of Protease-Activity with Correction of Probe Delivery and Tissue Absorption Effects

    PubMed Central

    Salthouse, Christopher D.; Reynolds, Fred; Tam, Jenny M.; Josephson, Lee; Mahmood, Umar

    2009-01-01

    Proteases play important roles in a variety of pathologies from heart disease to cancer. Quantitative measurement of protease activity is possible using a novel spectrally matched dual fluorophore probe and a small animal lifetime imager. The recorded fluorescence from an activatable fluorophore, one that changes its fluorescent amplitude after biological target interaction, is also influenced by other factors including imaging probe delivery and optical tissue absorption of excitation and emission light. Fluorescence from a second spectrally matched constant (non-activatable) fluorophore on each nanoparticle platform can be used to correct for both probe delivery and tissue absorption. The fluorescence from each fluorophore is separated using fluorescence lifetime methods. PMID:20161242

  2. Observation of halogen species in the Amundsen Gulf, Arctic, by active long-path differential optical absorption spectroscopy.

    PubMed

    Pöhler, Denis; Vogel, Leif; Friess, Udo; Platt, Ulrich

    2010-04-13

    In the polar tropospheric boundary layer, reactive halogen species (RHS) are responsible for ozone depletion as well as the oxidation of elemental mercury and dimethyl sulphide. After polar sunrise, air masses enriched in reactive bromine cover areas of several million square kilometers. Still, the source and release mechanisms of halogens are not completely understood. We report measurements of halogen oxides performed in the Amundsen Gulf, Arctic, during spring 2008. Active long-path differential optical absorption spectroscopy (LP-DOAS) measurements were set up offshore, several kilometers from the coast, directly on the sea ice, which was never done before. High bromine oxide concentrations were detected frequently during sunlight hours with a characteristic daily cycle showing morning and evening maxima and a minimum at noon. The, so far, highest observed average mixing ratio in the polar boundary layer of 41 pmol/mol (equal to pptv) was detected. Only short sea ice contact is required to release high amounts of bromine. An observed linear decrease of maximum bromine oxide levels with ambient temperature during sunlight, between -24 degrees C and -15 degrees C, provides indications on the conditions required for the emission of RHS. In addition, the data indicate the presence of reactive chlorine in the Arctic boundary layer. In contrast to Antarctica, iodine oxide was not detected above a detection limit of 0.3 pmol/mol. PMID:20160121

  3. Observation of halogen species in the Amundsen Gulf, Arctic, by active long-path differential optical absorption spectroscopy

    PubMed Central

    Pöhler, Denis; Vogel, Leif; Frieß, Udo; Platt, Ulrich

    2010-01-01

    In the polar tropospheric boundary layer, reactive halogen species (RHS) are responsible for ozone depletion as well as the oxidation of elemental mercury and dimethyl sulphide. After polar sunrise, air masses enriched in reactive bromine cover areas of several million square kilometers. Still, the source and release mechanisms of halogens are not completely understood. We report measurements of halogen oxides performed in the Amundsen Gulf, Arctic, during spring 2008. Active long-path differential optical absorption spectroscopy (LP-DOAS) measurements were set up offshore, several kilometers from the coast, directly on the sea ice, which was never done before. High bromine oxide concentrations were detected frequently during sunlight hours with a characteristic daily cycle showing morning and evening maxima and a minimum at noon. The, so far, highest observed average mixing ratio in the polar boundary layer of 41 pmol/mol (equal to pptv) was detected. Only short sea ice contact is required to release high amounts of bromine. An observed linear decrease of maximum bromine oxide levels with ambient temperature during sunlight, between -24 °C and -15 °C, provides indications on the conditions required for the emission of RHS. In addition, the data indicate the presence of reactive chlorine in the Arctic boundary layer. In contrast to Antarctica, iodine oxide was not detected above a detection limit of 0.3 pmol/mol. PMID:20160121

  4. Active Layer Thermal Response to Stream Water Temperatures

    NASA Astrophysics Data System (ADS)

    Cozzetto, K.; McKnight, D.

    2004-12-01

    The hyporheic zone is comprised of sediments below and adjacent to a stream through which stream water flows in and out. In polar regions, the shape, dimensions, physical and chemical characteristics of this zone are affected by the seasonal freezing and thawing of the active layer. One factor that may influence the active layer temperature regime is stream water temperature, both its absolute value and cyclic variations in its value. Many of the glacial meltwater streams in Taylor Valley in the McMurdo Dry Valleys of Antarctica, exhibit daily temperature patterns with lows of 0 or 1° C and highs of 10 or, on occasion, 15° C. Because the viscosity of water decreases significantly with increasing temperature, these daily maxima may increase infiltration and the exchange of water and heat between the stream and the hyporheic zone. To investigate the influence of stream water temperature and flow paths on the active layer temperature regime and vice versa, two conservative tracer injection experiments were conducted. Both took place in the same 200-meter reach, which was instrumented with temperature and conductivity probes. Both also took place at the same time of day during which the stream reaches its temperature maximum. However, in one experiment snow from a nearby patch was added to the stream to suppress the temperature maximum by 3° C from 10 to 7° C. The temperature data show that the snow addition slowed the rate of hyporheic zone warming and suppressed temperature increases in the hyporheic zone by 1-3° C when compared with the non-perturbation experiment. The electrical conductivity data indicate that during the snow addition experiment, the stream neither gained nor lost water while during the non-perturbation experiment, the stream lost water. These results suggest that the stream water cooling decreased infiltration and heat transfer into the hyporheic zone.

  5. Low temperature hydrogen plasma-assisted atomic layer deposition of copper studied using in situ infrared reflection absorption spectroscopy

    SciTech Connect

    Chaukulkar, Rohan P.; Rai, Vikrant R.; Agarwal, Sumit; Thissen, Nick F. W.

    2014-01-15

    Atomic layer deposition (ALD) is an ideal technique to deposit ultrathin, conformal, and continuous metal thin films. However, compared to the ALD of binary materials such as metal oxides and metal nitrides, the surface reaction mechanisms during metal ALD are not well understood. In this study, the authors have designed and implemented an in situ reflection-absorption infrared spectroscopy (IRAS) setup to study the surface reactions during the ALD of Cu on Al{sub 2}O{sub 3} using Cu hexafluoroacetylacetonate [Cu(hfac){sub 2}] and a remote H{sub 2} plasma. Our infrared data show that complete ligand-exchange reactions occur at a substrate temperature of 80 °C in the absence of surface hydroxyl groups. Based on infrared data and previous studies, the authors propose that Cu(hfac){sub 2} dissociatively chemisorbs on the Al{sub 2}O{sub 3} surface, where the Al-O-Al bridge acts as the surface reactive site, leading to surface O-Cu-hfac and O-Al-hfac species. Surface saturation during the Cu(hfac){sub 2} half-cycle occurs through blocking of the available chemisorption sites. In the next half-reaction cycle, H radicals from an H{sub 2} plasma completely remove these surface hfac ligands. Through this study, the authors have demonstrated the capability of in situ IRAS as a tool to study surface reactions during ALD of metals. While transmission and internal reflection infrared spectroscopy are limited to the first few ALD cycles, IRAS can be used to probe all stages of metal ALD starting from initial nucleation to the formation of a continuous film.

  6. Experiments on the active control of transitional boundary layers

    NASA Astrophysics Data System (ADS)

    Nelson, P. A.; Rioual, J.-L.; Fisher, M. J.

    Experimental results are presented which demonstrate that the streamwise position of the transition region of a flat plate boundary layer can be actively controlled. The means of control is through the application of suction through the surface of the plate, a progressive increase in suction rate being capable of producing transition at progressively larger distances downstream from the plate leading edge. A simple digital feedback regulator based on an integral control law is shown to be most effective in regulating the position of transition, an error signal being derived from measurements of pressure fluctuations on the surface of the plate.

  7. Tomographic multiaxis-differential optical absorption spectroscopy observations of Sun-illuminated targets: a technique providing well-defined absorption paths in the boundary layer.

    PubMed

    Frins, Erna; Bobrowski, Nicole; Platt, Ulrich; Wagner, Thomas

    2006-08-20

    A novel experimental procedure to measure the near-surface distribution of atmospheric trace gases by using passive multiaxis differential absorption optical spectroscopy (MAX-DOAS) is proposed. The procedure consists of pointing the receiving telescope of the spectrometer to nonreflecting surfaces or to bright targets placed at known distances from the measuring device, which are illuminated by sunlight. We show that the partial trace gas absorptions between the top of the atmosphere and the target can be easily removed from the measured total absorption. Thus it is possible to derive the average concentration of trace gases such as NO(2), HCHO, SO(2), H(2)O, Glyoxal, BrO, and others along the line of sight between the instrument and the target similar to the well-known long-path DOAS observations (but with much less expense). If tomographic arrangements are used, even two- or three-dimensional trace gas distributions can be retrieved. The basic assumptions of the proposed method are confirmed by test measurements taken across the city of Heidelberg. PMID:16892129

  8. An analysis of temperature-dependent absorption and photocurrent spectra in BaAl{sub 2}Se{sub 4} layers

    SciTech Connect

    Hong, K. J.; Jeong, T. S.; Youn, C. J.; Moon, J. D.

    2015-04-28

    The temperature-dependent photoresponse behavior of BaAl{sub 2}Se{sub 4} layers has been investigated through the analysis of optical absorption and photocurrent (PC) spectra. Based on these results, the optical band gap was well expressed by E{sub g}(T) = E{sub g}(0) − 4.39 × 10{sup −4}T{sup 2}/(T + 250), where E{sub g}(0) is estimated to be 3.4205, 3.6234, and 3.8388 eV for the transitions corresponding to the valence band states Γ{sub 3}(A), Γ{sub 4}(B), and Γ{sub 5}(C), respectively. From the PC measurement, three peaks A, B, and C corresponded with the intrinsic transitions from the valence band states of Γ{sub 3}(A), Γ{sub 4}(B), and Γ{sub 5}(C) to the conduction band state of Γ{sub 1}, respectively. According to the selection rule, the crystal field and spin orbit splitting were found to be 0.2029 and 0.2154 eV, respectively, through the direct use of PC spectroscopy. However, the PC intensities decreased with lowering temperature. In the log J{sub ph} versus 1/T plot, the dominant trap level at the high-temperature region was observed and its value was 12.7 meV. This level corresponds to the activation energy for the electronic transition from the shallow donor levels to the edge of the conduction band. It is estimated that the decrease in the PC intensity is caused by trapping centers related to native defects in the BaAl{sub 2}Se{sub 4} layers. Consequently, this trap level limited the PC intensity with decreasing temperature.

  9. Facile Fabrication of a Silver Nanoparticle Immersed, Surface-Enhanced Raman Scattering Imposed Paper Platform through Successive Ionic Layer Absorption and Reaction for On-Site Bioassays.

    PubMed

    Kim, Wansun; Kim, Yeon-Hee; Park, Hun-Kuk; Choi, Samjin

    2015-12-23

    We introduce a novel, facile, rapid, low-cost, highly reproducible, and power-free synthesizable fabrication method of paper-based silver nanoparticle (AgNP) immersed surface-enhanced Raman scattering (SERS) platform, known as the successive ionic layer absorption and reaction (SILAR) method. The rough and porous properties of the paper led to direct synthesis of AgNPs on the surface as well as in the paper due to capillary effects, resulting in improved plasmon coupling with interparticles and interlayers. The proposed SERS platform showed an enhancement factor of 1.1 × 10(9), high reproducibility (relative standard deviation of 4.2%), and 10(-12) M rhodamine B highly sensitive detection limit by optimizing the SILAR conditions including the concentration of the reactive solution (20/20 mM/mM AgNO3/NaBH4) and the number of SILAR cycles (six). The applicability of the SERS platform was evaluated using two samples including human cervical fluid for clinical diagnosis of human papillomavirus (HPV) infection, associated with cervical cancer, and a malachite green (MG) solution for fungicide and parasiticide in aquaculture, associated with human carcinogenesis. The AgNP-immersed SERS-functionalized platform using the SILAR technique allowed for high chemical structure sensitivity without additional tagging or chemical modification, making it a good alternative for early clinical diagnosis of HPV infection and detection of MG-activated human carcinogenesis. PMID:26619139

  10. Digital measurements of LF radio wave absorption in the lower ionosphere and inferred gravity wave activity

    NASA Astrophysics Data System (ADS)

    Lastovicka, J.; Boska, J.; Buresova, D.

    1993-10-01

    Low frequency (LF) radio wave absorption in the lower ionosphere has been measured at Pruhonice (approximately 50 deg N) since 1957. A new digital computer-controlled measuring-recording-processing system was introduced in 1988. The A3 method of radio wave absorption measurement, the measuring equipment used for the digital measurements at 270 kHz, is briefly described. The digital nighttime LF A3 measurements allow the use of absorption data for studying and monitoring the gravity wave activity in the upper middle atmosphere in the period range 10 min-3(2) hours. The resulting gravity wave spectra are as expected even though their shapes vary. Individual period bands sometimes exhibit a similar general pattern of variability in gravity wave activity (winter 1990), while in other intervals we observe a shift of gravity wave energy from one period band to another (winter 1991). No strong, pronounced and consistent response to strong geomagnetic storms and midwinter stratospheric warming is found. An apparent seasonal variation with winter minima observed in shorter-period gravity wave activity is an artefact of the changing length of the night. There is no significant seasonal variation of gravity wave activity in the analysed data. The method is very cheap -- the results are a by-product of measurements made for ionospheric purposes.

  11. Amorphous effect on the advancing of wide-range absorption and structural-phase transition in γ-In2Se3 polycrystalline layers

    NASA Astrophysics Data System (ADS)

    Ho, Ching-Hwa

    2014-04-01

    The exploitation of potential functions in material is crucial in materials research. In this study, we demonstrate a III-VI chalcogenide, polycrystalline γ-In2Se3, which simultaneously possesses the capabilities of thickness-dependent optical gaps and wide-energy-range absorption existed in the polycrystalline layers of γ-In2Se3. Transmission electron microscopy and Raman measurement show a lot of γ-phase nanocrystals contained in the disordered and polycrystalline state of the chalcogenide with medium-range order (MRO). The MRO effects on the γ-In2Se3 layers show thickness-dependent absorption-edge shift and thickness-dependent resistivities. The amorphous effect of MRO also renders a structural-phase transition of γ --> α occurred inside the γ-In2Se3 layer with a heat treatment of about 700°C. Photo-voltage-current (Photo V-I) measurements of different-thickness γ-In2Se3 layers propose a wide-energy-range photoelectric conversion unit ranging from visible to ultraviolet (UV) may be achieved by stacking γ-In2Se3 layers in a staircase form containing dissimilar optical gaps.

  12. Amorphous effect on the advancing of wide-range absorption and structural-phase transition in γ-In2Se3 polycrystalline layers.

    PubMed

    Ho, Ching-Hwa

    2014-01-01

    The exploitation of potential functions in material is crucial in materials research. In this study, we demonstrate a III-VI chalcogenide, polycrystalline γ-In2Se3, which simultaneously possesses the capabilities of thickness-dependent optical gaps and wide-energy-range absorption existed in the polycrystalline layers of γ-In2Se3. Transmission electron microscopy and Raman measurement show a lot of γ-phase nanocrystals contained in the disordered and polycrystalline state of the chalcogenide with medium-range order (MRO). The MRO effects on the γ-In2Se3 layers show thickness-dependent absorption-edge shift and thickness-dependent resistivities. The amorphous effect of MRO also renders a structural-phase transition of γ → α occurred inside the γ-In2Se3 layer with a heat treatment of about 700 °C. Photo-voltage-current (Photo V-I) measurements of different-thickness γ-In2Se3 layers propose a wide-energy-range photoelectric conversion unit ranging from visible to ultraviolet (UV) may be achieved by stacking γ-In2Se3 layers in a staircase form containing dissimilar optical gaps. PMID:24755902

  13. Amorphous effect on the advancing of wide-range absorption and structural-phase transition in γ-In2Se3 polycrystalline layers

    PubMed Central

    Ho, Ching-Hwa

    2014-01-01

    The exploitation of potential functions in material is crucial in materials research. In this study, we demonstrate a III-VI chalcogenide, polycrystalline γ-In2Se3, which simultaneously possesses the capabilities of thickness-dependent optical gaps and wide-energy-range absorption existed in the polycrystalline layers of γ-In2Se3. Transmission electron microscopy and Raman measurement show a lot of γ-phase nanocrystals contained in the disordered and polycrystalline state of the chalcogenide with medium-range order (MRO). The MRO effects on the γ-In2Se3 layers show thickness-dependent absorption-edge shift and thickness-dependent resistivities. The amorphous effect of MRO also renders a structural-phase transition of γ → α occurred inside the γ-In2Se3 layer with a heat treatment of about 700°C. Photo-voltage-current (Photo V-I) measurements of different-thickness γ-In2Se3 layers propose a wide-energy-range photoelectric conversion unit ranging from visible to ultraviolet (UV) may be achieved by stacking γ-In2Se3 layers in a staircase form containing dissimilar optical gaps. PMID:24755902

  14. Tunable Q-switched fiber laser based on saturable edge-state absorption in few-layer molybdenum disulfide (MoS₂).

    PubMed

    Woodward, R I; Kelleher, E J R; Howe, R C T; Hu, G; Torrisi, F; Hasan, T; Popov, S V; Taylor, J R

    2014-12-15

    We fabricate a few-layer molybdenum disulfide (MoS₂) polymer composite saturable absorber by liquid-phase exfoliation, and use this to passively Q-switch an ytterbium-doped fiber laser, tunable from 1030 to 1070 nm. Self-starting Q-switching generates 2.88 μs pulses at 74 kHz repetition rate, with over 100 nJ pulse energy. We propose a mechanism, based on edge states within the bandgap, responsible for the wideband nonlinear optical absorption exhibited by our few-layer MoS₂ sample, despite operating at photon energies lower than the material bandgap. PMID:25607060

  15. Microwave absorption properties of a double-layer absorber based on nanocomposite BaFe12O19/α-Fe and nanocrystalline α-Fe microfibers

    NASA Astrophysics Data System (ADS)

    Shen, Xiang-Qian; Liu, Hong-Bo; Wang, Zhou; Qian, Xin-Ye; Jing, Mao-Xiang; Yang, Xin-Chun

    2014-07-01

    The nanocomposite BaFe12O19/α-Fe and nanocrystalline α-Fe microfibers with diameters of 1-5 μm, high aspect ratios and large specific areas are prepared by the citrate gel transformation and reduction process. The nanocomposite BaFe12O19/α-Fe microfibers show some exchange—coupling interactions largely arising from the magnetization hard (BaFe12O19) and soft (α-Fe) nanoparticles. For the microwave absorptions, the double-layer structures consisting of the nanocomposite BaFe12O19/α-Fe and α-Fe microfibers each exhibit a wide band and strong absorption behavior. When the nanocomposite BaFe12O19/α-Fe microfibers are used as a matching layer of 2.3 mm in thickness and α-Fe microfibers as an absorbing layer of 1.2 mm in thickness, the optimal reflection loss (RL) achieves -47 dB at 15.6 GHz, the absorption bandwidth is about 12.7 GHz ranging from 5.3 to 18 GHz, exceeding -20 dB, which covers 72.5% C-band (4.2-8.2 GHz) and whole X-band (8.2-12.4 GHz) and Ku-band (12.4-18 GHz). The enhanced absorption properties of these double-layer absorbers are mainly ascribed to the improvement in impedance matching ability and microwave multi-reflection largely resulting from the dipolar polarization, interfacial polarization, exchange—coupling interaction, and small size effect.

  16. Cooled Transmission-Mode NEA-Photocathode with a Band-Graded Active Layer for High Brightness Electron Source

    NASA Astrophysics Data System (ADS)

    Jones, L. B.; Rozhkov, S. A.; Bakin, V. V.; Kosolobov, S. N.; Militsyn, B. L.; Scheibler, H. E.; Smith, S. L.; Terekhov, A. S.

    2009-08-01

    A Free-Electron Laser (FEL) places many exacting demands on a Negative Electron Affinity (NEA) photocathode, such as the need for an ultra-fast response time, low energy spread for emitted electrons, high quantum efficiency (Q.E.) and a high average photocurrent. However, these key requirements are conflicting, and cannot be fulfilled by conventional photocathode design. For example, to achieve ˜10 ps response time, the photocathode active layer should be thinned to ˜100-150 nm, but this thickness is insufficient to provide near-complete absorption of light with hv≈ɛg so high Q.E. cannot be achieved. Complete optical absorption and high Q.E. can be obtained using a thin active layer at higher photon energies, but this generates photoelectrons with excess kinetic energy within the semiconductor. These photoelectrons do not thermalise in a thin active layer, so yield a broad energy distribution in the emitted electrons. Moreover, cooling of the conventional semiconductor photocathode structure is ineffective due to its fragility, so it cannot be pressed firmly to a heat sink to attain good thermal contact. Consequently, the maximum CW photocurrent is limited to a few miiliamps. The goal of our work is to develop a new design of NEA-photocathode which is optimised for FEL applications.

  17. Active Flow Control on a Boundary-Layer-Ingesting Inlet

    NASA Technical Reports Server (NTRS)

    Gorton, Susan Althoff; Owens, Lewis R.; Jenkins, Luther N.; Allan, Brian G.; Schuster, Ernest P.

    2004-01-01

    Boundary layer ingestion (BLI) is explored as means to improve overall system performance for Blended Wing Body configuration. The benefits of BLI for vehicle system performance benefit are assessed with a process derived from first principles suitable for highly-integrated propulsion systems. This performance evaluation process provides framework within which to assess the benefits of an integrated BLI inlet and lays the groundwork for higher-fidelity systems studies. The results of the system study show that BLI provides a significant improvement in vehicle performance if the inlet distortion can be controlled, thus encouraging the pursuit of active flow control (AFC) as a BLI enabling technology. The effectiveness of active flow control in reducing engine inlet distortion was assessed using a 6% scale model of a 30% BLI offset, diffusing inlet. The experiment was conducted in the NASA Langley Basic Aerodynamics Research Tunnel with a model inlet designed specifically for this type of testing. High mass flow pulsing actuators provided the active flow control. Measurements were made of the onset boundary layer, the duct surface static pressures, and the mass flow through the duct and the actuators. The distortion was determined by 120 total pressure measurements located at the aerodynamic interface plane. The test matrix was limited to a maximum freestream Mach number of 0.15 with scaled mass flows through the inlet for that condition. The data show that the pulsed actuation can reduce distortion from 29% to 4.6% as measured by the circumferential distortion descriptor DC60 using less than 1% of inlet mass flow. Closed loop control of the actuation was also demonstrated using a sidewall surface static pressure as the response sensor.

  18. Novel gas sensor combined active fiber loop ring-down and dual wavelengths differential absorption method.

    PubMed

    Zhao, Yanjie; Chang, Jun; Ni, Jiasheng; Wang, Qingpu; Liu, Tongyu; Wang, Chang; Wang, Pengpeng; Lv, Guangping; Peng, Gangding

    2014-05-01

    A novel active fiber loop ring-down gas sensor combined with dual wavelengths differential absorption method is proposed. Two Distributed Feedback Laser Diodes (DFB LDs) with different wavelengths are employed. One LD whose wavelength covered with the absorption line of target gas is used for sensing. Another LD whose wavelength is centered outside the absorption line is used for reference. The gas absorption loss can be obtained by differencing the reference signal and sensing signal. Compared with traditional method of one wavelength employed, it can eliminate the influence of the cavity loss variety and photoelectric device drift in the system efficiently. An Erbium Doped Fiber Amplifier (EDFA) with Automatic Gain Control (AGC) is used to compensate the loss of the light in the ring-down cavity, which will increase the cavity round trips and improve the precision of gas detection. And two fiber Bragg gratings (FBGs) are employed to get rid of amplified spontaneous emission (ASE) spectrum noise as filters. The calibrating ethyne samples of different concentrations are measured with a 65 mm long gas cell in order to evaluate the effect of reference. The results show the relative deviation is found to be less than ± 0.4% of 0.1% ethyne when a certain additional loss from 0 to 1.2dB is introduced to the cavity and the relative deviation of measured concentration is less than ± 0.5% over 24 hours. PMID:24921822

  19. Hydroxyl 1.563 Micron Absorption from Starspots on Active Stars

    NASA Astrophysics Data System (ADS)

    O'Neal, Douglas; Neff, James E.; Saar, Steven H.; Mines, Jonathan K.

    2001-10-01

    We present results from a study of starspots on active stars using a pair of vibrational-rotational absorption lines of the OH molecule near 1.563 μm. We detect excess OH absorption due to dark, cool starspots on several active stars of the RS CVn and BY Dra classes. Our results for the single-lined spectroscopic binaries II Pegasi, V1762 Cygni, and λ Andromedae augment those from a previous study that used a less sensitive detector. In this study, we were able for the first time to use molecular absorption features to measure starspot properties on double-lined spectroscopic binaries. Measuring the equivalent widths of these OH lines in inactive giant and dwarf stars of spectral types G, K, and M, we find that the total equivalent width of the line pair increases approximately linearly as effective temperature decreases from 5000 to 3000 K. We measure starspot filling factors by fitting the spectra of active stars with linear combinations of comparison star spectra representing the spot and nonspot regions of the star.

  20. Boundary Layer Observations of Water Vapor and Aerosol Profiles with an Eye-Safe Micro-Pulse Differential Absorption Lidar (DIAL)

    NASA Astrophysics Data System (ADS)

    Nehrir, A. R.; Repasky, K. S.; Carlsten, J.; Ismail, S.

    2011-12-01

    Measurements of real-time high spatial and temporal resolution profiles of combined water vapor and aerosols in the boundary layer have been a long standing observational challenge to the meteorological, weather forecasting, and climate science communities. To overcome the high reoccurring costs associated with radiosondes as well as the lack of sufficient water vapor measurements over the continental united states, a compact and low cost eye-safe all semiconductor-based micro-pulse differential absorption lidar (DIAL) has been developed for water vapor and aerosol profiling in the lower troposphere. The laser transmitter utilizes two continuous wave external cavity diode lasers operating in the 830 nm absorption band as the online and offline seed laser sources. An optical switch is used to sequentially injection seed a tapered semiconductor optical amplifier (TSOA) with the two seed laser sources in a master oscillator power amplifier (MOPA) configuration. The TSOA is actively current pulsed to produce up to 7 μJ of output energy over a 1 μs pulse duration (150 m vertical resolution) at a 10 kHz pulse repetition frequency. The measured laser transmitter spectral linewidth is less than 500 kHz while the long term frequency stability of the stabilized on-line wavelength is ± 55 MHz. The laser transmitter spectral purity was measured to be greater than 0.9996, allowing for simultaneous measurements of water vapor in the lower and upper troposphere. The DIAL receiver utilizes a commercially available full sky-scanning capable 35 cm Schmidt-Cassegrain telescope to collect the scattered light from the laser transmitter. Light collected by the telescope is spectrally filtered to suppress background noise and is coupled into a fiber optic cable which acts as the system field stop and limits the full angle field of view to 140 μrad. The light is sampled by a fiber coupled APD operated in a Geiger mode. The DIAL instrument is operated autonomously where water vapor and

  1. Characterization of cathode keeper wear by surface layer activation

    NASA Technical Reports Server (NTRS)

    Polk, James E.

    2003-01-01

    In this study, the erosion rates of the discharge cathode keeper in a 30 cm NSTAR configuration ion thruster were measured using a technique known as Surface Layer Activation (SLA). This diagnostic technique involves producing a radioactive tracer in a given surface by bombardment with high energy ions. The decrease in activity of the tracer material may be monitored as the surface is subjected to wear processes and correlated to a depth calibration curve, yielding the eroded depth. Analysis of the activities was achieved through a gamma spectroscopy system. The primary objectives of this investigation were to reproduce erosion data observed in previous wear studies in order to validate the technique, and to determine the effect of different engine operating parameters on erosion rate. The erosion profile at the TH 15 (23 kw) setting observed during the 8200 hour Life Demonstration Test (LDT) was reproduced. The maximum keeper erosion rate at this setting was determined to be 0.085 pm/hr. Testing at the TH 8 (1.4 kw) setting demonstrated lower erosion rates than TH 15, along with a different wear profile. Varying the keeper voltage was shown to have a significant effect on the erosion, with a positive bias with respect to cathode potential decreasing the erosion rate significantly. Accurate measurements were achieved after operating times of only 40 to 70 hours, a significant improvement over other erosion diagnostic methods.

  2. Differences in spectral absorption properties between active neovascular macular degeneration and mild age related maculopathy.

    PubMed

    Balaskas, Konstantinos; Nourrit, Vincent; Dinsdale, Michelle; Henson, David B; Aslam, Tariq

    2013-05-01

    This study examines the differences in spectral absorption properties between the maculae of patients with active neovascular macular degeneration and those with early age related maculopathy (ARM). Patients attending for management of neovascular age related macular degeneration (AMD) underwent multispectral imaging with a system comprising of a modified digital fundus camera coupled with a 250-W tungsten-halogen lamp and a liquid crystal fast-tuneable filter. Images were obtained at 8 wavelengths between 496 and 700 nm. Aligned images were used to generate a DLA (differential light absorption, a measure of spectral absorption properties) map of the macular area. DLA maps were generated for both eyes of 10 sequential patients attending for anti-vascular endothelial growth factor injections. Each of these patients had active leaking neovascular AMD in one eye and early ARM or milder disease in the fellow eye. Eyes with neovascular AMD demonstrated lower average levels of DLA compared with their fellow eyes with early ARM (p=0.037, t test). The significant difference in DLA demonstrates the potential of multispectral imaging for differentiating the two pathologies non-invasively. PMID:23137662

  3. Light absorption and plasmon - exciton interaction in three-layer nanorods with a gold core and outer shell composed of molecular J- and H-aggregates of dyes

    NASA Astrophysics Data System (ADS)

    Shapiro, B. I.; Tyshkunova, E. S.; Kondorskiy, A. D.; Lebedev, V. S.

    2015-12-01

    Optical properties of hybrid rod-like nanoparticles, consisting of a gold core, an intermediate passive organic layer (spacer) and outer layer of ordered molecular cyanine dye aggregates, are experimentally and theoretically investigated. It is shown that these dyes can form not only ordered J-aggregates but also H-aggregates (differing by the packing angle of dye molecules in an aggregate and having other spectral characteristics) in the outer shell of the hybrid nanostructure. Absorption spectra of synthesised three-layer nanorods are recorded, and their sizes are determined. The optical properties of the composite nanostructures under study are found to differ significantly, depending on the type of the molecular aggregate formed in the outer shell. The experimental data are quantitatively explained based on computer simulation using the finite-difference time-domain (FDTD) method, and characteristic features of the plasmon - exciton interaction in the systems under study are revealed.

  4. Design of plasmonic photodetector with high absorptance and nano-scale active regions.

    PubMed

    Guo, Jingshu; Wu, Zhiwei; Li, Yuan; Zhao, Yanli

    2016-08-01

    We propose a novel plasmonic photodetector with high responsivity, utilizing nano-scale active regions. This design can be applied to diverse materials (group III-V or IV materials) and different operation wavelengths covering the O-U bands. The periodic structure utilizing Surface Plasmon Polariton Bloch Waves (SPP-BWs) has low optical power loss. FDTD simulation shows an absorptance of 74.4% which means a responsivity of about 0.74 A/W at 1550 nm. The low capacitance brings low noise, reduced power consumption, and a high electrical bandwidth which is estimated to be 140 GHz. Among the plasmonic PDs with inherent high speeds but low responsivities, our design makes the obvious progress on improving the absorptance. PMID:27505787

  5. A plant canopy light absorption model with application to wheat

    NASA Technical Reports Server (NTRS)

    Chance, J. E.; Lemaster, E. W.

    1977-01-01

    From the light absorption model the absorption of light in the photosynthetically active region of the spectrum was calculated for a Penjamo wheat crop for several situations including: (1) the percent absorption of the incident radiation by a canopy having a four layer structure; (2) the percent absorption of light by the individual layers within a four layer canopy and by the underlying soil; (3) the percent absorption of light by each vegetative canopy layer for variable sun angle; and (4) the cumulative solar energy absorbed by the developing wheat canopy as it progresses from a single layer through its growth stages to a three layer canopy. This calculation was also presented as a function of the leaf area index.

  6. Small fluorescence-activating and absorption-shifting tag for tunable protein imaging in vivo

    PubMed Central

    Plamont, Marie-Aude; Billon-Denis, Emmanuelle; Maurin, Sylvie; Gauron, Carole; Pimenta, Frederico M.; Specht, Christian G.; Shi, Jian; Quérard, Jérôme; Pan, Buyan; Rossignol, Julien; Moncoq, Karine; Morellet, Nelly; Volovitch, Michel; Lescop, Ewen; Chen, Yong; Triller, Antoine; Vriz, Sophie; Le Saux, Thomas; Jullien, Ludovic; Gautier, Arnaud

    2016-01-01

    This paper presents Yellow Fluorescence-Activating and absorption-Shifting Tag (Y-FAST), a small monomeric protein tag, half as large as the green fluorescent protein, enabling fluorescent labeling of proteins in a reversible and specific manner through the reversible binding and activation of a cell-permeant and nontoxic fluorogenic ligand (a so-called fluorogen). A unique fluorogen activation mechanism based on two spectroscopic changes, increase of fluorescence quantum yield and absorption red shift, provides high labeling selectivity. Y-FAST was engineered from the 14-kDa photoactive yellow protein by directed evolution using yeast display and fluorescence-activated cell sorting. Y-FAST is as bright as common fluorescent proteins, exhibits good photostability, and allows the efficient labeling of proteins in various organelles and hosts. Upon fluorogen binding, fluorescence appears instantaneously, allowing monitoring of rapid processes in near real time. Y-FAST distinguishes itself from other tagging systems because the fluorogen binding is highly dynamic and fully reversible, which enables rapid labeling and unlabeling of proteins by addition and withdrawal of the fluorogen, opening new exciting prospects for the development of multiplexing imaging protocols based on sequential labeling. PMID:26711992

  7. Small fluorescence-activating and absorption-shifting tag for tunable protein imaging in vivo.

    PubMed

    Plamont, Marie-Aude; Billon-Denis, Emmanuelle; Maurin, Sylvie; Gauron, Carole; Pimenta, Frederico M; Specht, Christian G; Shi, Jian; Quérard, Jérôme; Pan, Buyan; Rossignol, Julien; Moncoq, Karine; Morellet, Nelly; Volovitch, Michel; Lescop, Ewen; Chen, Yong; Triller, Antoine; Vriz, Sophie; Le Saux, Thomas; Jullien, Ludovic; Gautier, Arnaud

    2016-01-19

    This paper presents Yellow Fluorescence-Activating and absorption-Shifting Tag (Y-FAST), a small monomeric protein tag, half as large as the green fluorescent protein, enabling fluorescent labeling of proteins in a reversible and specific manner through the reversible binding and activation of a cell-permeant and nontoxic fluorogenic ligand (a so-called fluorogen). A unique fluorogen activation mechanism based on two spectroscopic changes, increase of fluorescence quantum yield and absorption red shift, provides high labeling selectivity. Y-FAST was engineered from the 14-kDa photoactive yellow protein by directed evolution using yeast display and fluorescence-activated cell sorting. Y-FAST is as bright as common fluorescent proteins, exhibits good photostability, and allows the efficient labeling of proteins in various organelles and hosts. Upon fluorogen binding, fluorescence appears instantaneously, allowing monitoring of rapid processes in near real time. Y-FAST distinguishes itself from other tagging systems because the fluorogen binding is highly dynamic and fully reversible, which enables rapid labeling and unlabeling of proteins by addition and withdrawal of the fluorogen, opening new exciting prospects for the development of multiplexing imaging protocols based on sequential labeling. PMID:26711992

  8. Uniform Fe3O4 coating on flower-like ZnO nanostructures by atomic layer deposition for electromagnetic wave absorption.

    PubMed

    Wan, Gengping; Wang, Guizhen; Huang, Xianqin; Zhao, Haonan; Li, Xinyue; Wang, Kan; Yu, Lei; Peng, Xiange; Qin, Yong

    2015-11-21

    An elegant atomic layer deposition (ALD) method has been employed for controllable preparation of a uniform Fe3O4-coated ZnO (ZnO@Fe3O4) core-shell flower-like nanostructure. The Fe3O4 coating thickness of the ZnO@Fe3O4 nanostructure can be tuned by varying the cycle number of ALD Fe2O3. When serving as additives for microwave absorption, the ZnO@Fe3O4-paraffin composites exhibit a higher absorption capacity than the ZnO-paraffin composites. For ZnO@500-Fe3O4, the effective absorption bandwidth below -10 dB can reach 5.2 GHz and the RL values below -20 dB also cover a wide frequency range of 11.6-14.2 GHz when the coating thickness is 2.3 mm, suggesting its potential application in the treatment of the electromagnetic pollution problem. On the basis of experimental observations, a mechanism has been proposed to understand the enhanced microwave absorption properties of the ZnO@Fe3O4 composites. PMID:26458422

  9. Inverse eigenvalue problems in vibration absorption: Passive modification and active control

    NASA Astrophysics Data System (ADS)

    Mottershead, John E.; Ram, Yitshak M.

    2006-01-01

    The abiding problem of vibration absorption has occupied engineering scientists for over a century and there remain abundant examples of the need for vibration suppression in many industries. For example, in the automotive industry the resolution of noise, vibration and harshness (NVH) problems is of extreme importance to customer satisfaction. In rotorcraft it is vital to avoid resonance close to the blade passing speed and its harmonics. An objective of the greatest importance, and extremely difficult to achieve, is the isolation of the pilot's seat in a helicopter. It is presently impossible to achieve the objectives of vibration absorption in these industries at the design stage because of limitations inherent in finite element models. Therefore, it is necessary to develop techniques whereby the dynamic of the system (possibly a car or a helicopter) can be adjusted after it has been built. There are two main approaches: structural modification by passive elements and active control. The state of art of the mathematical theory of vibration absorption is presented and illustrated for the benefit of the reader with numerous simple examples.

  10. Fabrication of multilayer mirrors consisting of oxide and nitride layers for continual use across the K-absorption edge of carbon.

    PubMed

    Ishino, Masahiko; Yoda, Osamu

    2004-03-20

    The development of multilayer mirrors for continual use around the K-absorption edge of carbon (4.4 nm) has been begun. Cobalt oxide (Co3O4), silicon oxide (SiO2), and boron nitride (BN) are found to be suitable for multilayer mirrors on the basis of theoretical calculations for wavelengths around the carbon K-absorption edge region. X-ray reflectivity curves with CuKalpha1 x rays of the fabricated Co3O4/SiO2 multilayers have sharp Bragg peaks, and the layer structures evaluated from transmission electron microscopy (TEM) observations are uniform. On the other hand, the Bragg peaks of Co3O4/BN multilayers split, and aggregated Co3O4 is observed. To improve the Co3O4 layer structure, chromium oxide (Cr2O3) was mixed into Co3O4. The mixed oxide layer structure in the Mix/BN multilayer (Mix = Co3O4 + Cr2O3) is relatively uniform, and the Bragg peaks do not split. PMID:15065714

  11. Basis and reversal of Na-bentazon antagonism on sethoxydim absorption and activity

    SciTech Connect

    Wanamarta, G.

    1987-01-01

    Various experimental adjuvants, including surfactants, paraffinic oil and soybean oil based crop oil concentrates (COC), were tested to maximize the herbicidal activity of sethoxydim /2(1-(ethoxyimino)butyl)-5-/2-(ethylthio)-3-hydroxy-2-cyclohexen-1-one// and bentazon (3-isopropyl-1H-2,1,3-benzothiadiazine-4(/sup 3/H)-one 2,2- dioxide). Identification of superior adjuvants was done by measuring the effects of these experimental adjuvants on herbicide spray droplet spreadability and /sup 14/C-herbicide absorption on target weed leaves.

  12. Active differential optical absorption spectroscopy for NO2 gas pollution using blue light emitting diodes

    NASA Astrophysics Data System (ADS)

    Aljalal, Abdulaziz; Gasmi, Khaled; Al-Basheer, Watheq

    2015-05-01

    Availability of high intensity light emitting diodes in the blue region offer excellent opportunity for using them in active Differential Optical Absorption Spectroscopy (DOAS) to detect air pollution. Their smooth and relatively broad spectral emissions as well as their long life make them almost ideal light sources for active DOAS. In this study, we report the usage of a blue light emitting diode in an active DOAS setup to measure traces of NO2 gas and achieving few parts per billion detection limit for a path length of 300 m. Details of the setup will be presented along with the effects on measurement accuracy due to shifts in the measured spectra calibration and due to using theoretical instrument Gaussian function instead of the measured instrument function.

  13. Effects of Soil Property Uncertainty on Projected Active Layer Thickness

    NASA Astrophysics Data System (ADS)

    Harp, D. R.; Atchley, A. L.; Coon, E.; Painter, S. L.; Wilson, C. J.; Romanovsky, V. E.; Liljedahl, A.

    2014-12-01

    Uncertainty in future climate is often assumed to contribute the largest uncertainty to active layer thickness (ALT) projections. However, the impact of soil property uncertainty on these projections may be significant. In this research, we evaluate the contribution of soil property uncertainty on ALT projections at the Barrow Environmental Observatory, Alaska. The effect of variations in porosity, thermal conductivity, saturation, and water retention properties of peat and mineral soil are evaluated. The micro-topography of ice wedge polygons present at the site is included in the analysis using three 1D column models to represent polygon center, rim and trough features. The Arctic Terrestrial Simulator (ATS) is used to model multiphase thermal and hydrological processes in the subsurface. We apply the Null-Space Monte Carlo (NSMC) algorithm to identify an ensemble of soil property combinations that produce simulated temperature profiles that are consistent with temperature measurements available from the site. ALT is simulated for the ensemble of soil property combinations for four climate scenarios. The uncertainty in ALT due to soil properties within and across climate scenarios is evaluated. This work was supported by LANL Laboratory Directed Research and Development Project LDRD201200068DR and by the The Next-Generation Ecosystem Experiments (NGEE Arctic) project. NGEE-Arctic is supported by the Office of Biological and Environmental Research in the DOE Office of Science.

  14. Active Layer Soil Carbon and Nutrient Mineralization, Barrow, Alaska, 2012

    DOE Data Explorer

    Stan D. Wullschleger; Holly M. Vander Stel; Colleen Iversen; Victoria L. Sloan; Richard J. Norby; Mallory P. Ladd; Jason K. Keller; Ariane Jong; Joanne Childs; Deanne J. Brice

    2015-10-29

    This data set consists of bulk soil characteristics as well as carbon and nutrient mineralization rates of active layer soils manually collected from the field in August, 2012, frozen, and then thawed and incubated across a range of temperatures in the laboratory for 28 day periods in 2013-2015. The soils were collected from four replicate polygons in each of the four Areas (A, B, C, and D) of Intensive Site 1 at the Next-Generation Ecosystem Experiments (NGEE) Arctic site near Barrow, Alaska. Soil samples were coincident with the established Vegetation Plots that are located in center, edge, and trough microtopography in each polygon. Data included are 1) bulk soil characteristics including carbon, nitrogen, gravimetric water content, bulk density, and pH in 5-cm depth increments and also by soil horizon, 2) carbon, nitrogen, and phosphorus mineralization rates for soil horizons incubated aerobically (and in one case both aerobically and anaerobically) for 28 days at temperatures that included 2, 4, 8, and 12 degrees C. Additional soil and incubation data are forthcoming. They will be available when published as part of another paper that includes additional replicate analyses.

  15. Active layer hydrology for Imnavait Creek, Toolik, Alaska

    SciTech Connect

    Hinzman, L.D.; Kane, D.L.

    1987-04-01

    The hydrology of the active layer of a watershed is described. In the annual hydrologic cycle, snowmelt is the most significant event at Imnavait Creek located near Toolik Lake, Alaska. Precipitation that has accumulated for more than 6 months on the surface melts in a relatively short period of 7 to 10 days once sustained melting occurs. Significant runoff events are few. Convective storms covering relatively small areas on the North Slope of Alaska can produce significant small-scale events in a small watershed scale,but these events are rapidly attenuated outside the basin. Data collection began in August 1984. We have continuously monitored the hydrologic, the meteorologic, and the soil's physical conditions. Information was collected through implementation of four snowmelt runoff plots and measurements of essential microclimate parameters. Soil moisture and temperature profiles were measured adjacent to each snowmelt runoff plot, and heat flux is collected adjacent to one of these plots. Meteorological parameters were measured locally. The water content of the snowpack prior to snowmelt was measured throughout the watershed and measured daily adjacent to each plot during snowmelt. The stream draining the basin was measured regularly during the spring melt event to provide information on watershed runoff rates and the volume of snowmelt.

  16. Active layer hydrology for Imnavait Creek, Toolik, Alaska

    SciTech Connect

    Hinzman, L.D.; Kane, D.L.

    1987-04-01

    The hydrology of the active layer of a watershed is described. In the annual hydrologic cycle, snowmelt is the most significant event at Imnavait Creek located near Toolik Lake, Alaska. Precipitation that has accumulated for more than 6 months on the surface melts in a relatively short period of 7 to 10 days once sustained melting occurs. Significant runoff events are few. Convective storms covering relatively small areas on the North Slope of Alaska can produce significant small-scale events in a small watershed scale,but these events are rapidly attenuated outside the basin. Data collection began in August 1984. We have continuously monitored the hydrologic, the meteorologic, and the soil`s physical conditions. Information was collected through implementation of four snowmelt runoff plots and measurements of essential microclimate parameters. Soil moisture and temperature profiles were measured adjacent to each snowmelt runoff plot, and heat flux is collected adjacent to one of these plots. Meteorological parameters were measured locally. The water content of the snowpack prior to snowmelt was measured throughout the watershed and measured daily adjacent to each plot during snowmelt. The stream draining the basin was measured regularly during the spring melt event to provide information on watershed runoff rates and the volume of snowmelt.

  17. Active millimeter wave detection of concealed layers of dielectric material

    NASA Astrophysics Data System (ADS)

    Bowring, N. J.; Baker, J. G.; Rezgui, N. D.; Southgate, M.; Alder, J. F.

    2007-04-01

    Extensive work has been published on millimetre wave active and passive detection and imaging of metallic objects concealed under clothing. We propose and demonstrate a technique for revealing the depth as well as the outline of partially transparent objects, which is especially suited to imaging layer materials such as explosives and drugs. The technique uses a focussed and scanned FMCW source, swept through many GHz to reveal this structure. The principle involved is that a parallel sided dielectric slab produces reflections at both its upper and lower surfaces, acting as a Fabry-Perot interferometer. This produces a pattern of alternating reflected peaks and troughs in frequency space. Fourier or Burg transforming this pattern into z-space generates a peak at the thickness of the irradiated sample. It could be argued that though such a technique may work for single uniform slabs of dielectric material, it will give results of little or no significance when the sample both scatters the incident radiation and gives erratic reflectivities due to its non-uniform thickness and permittivity . We show results for a variety of materials such as explosive simulants, powder and drugs, both alone and concealed under clothing or in a rucksack, which display strongly directional reflectivities at millimeter wavelengths, and whose location is well displayed by a varying thickness parameter as the millimetre beam is scanned across the target. With this system we find that samples can easily be detected at standoff distances of at least 4.6m.

  18. Microbial diversity in European alpine permafrost and active layers.

    PubMed

    Frey, Beat; Rime, Thomas; Phillips, Marcia; Stierli, Beat; Hajdas, Irka; Widmer, Franco; Hartmann, Martin

    2016-03-01

    Permafrost represents a largely understudied genetic resource. Thawing of permafrost with global warming will not only promote microbial carbon turnover with direct feedback on greenhouse gases, but also unlock an unknown microbial diversity. Pioneering metagenomic efforts have shed light on the permafrost microbiome in polar regions, but temperate mountain permafrost is largely understudied. We applied a unique experimental design coupled to high-throughput sequencing of ribosomal markers to characterize the microbiota at the long-term alpine permafrost study site 'Muot-da-Barba-Peider' in eastern Switzerland with an approximate radiocarbon age of 12 000 years. Compared to the active layers, the permafrost community was more diverse and enriched with members of the superphylum Patescibacteria (OD1, TM7, GN02 and OP11). These understudied phyla with no cultured representatives proposedly feature small streamlined genomes with reduced metabolic capabilities, adaptations to anaerobic fermentative metabolisms and potential ectosymbiotic lifestyles. The permafrost microbiota was also enriched with yeasts and lichenized fungi known to harbour various structural and functional adaptation mechanisms to survive under extreme sub-zero conditions. These data yield an unprecedented view on microbial life in temperate mountain permafrost, which is increasingly important for understanding the biological dynamics of permafrost in order to anticipate potential ecological trajectories in a warming world. PMID:26832204

  19. Towards NOAA Forecasts of Permafrost Active Layer Thickness

    NASA Astrophysics Data System (ADS)

    Livezey, M. M.; Jonassen, R. G.; Horsfall, F. M. C.; Jafarov, E. E.; Schaefer, K. M.

    2014-12-01

    NOAA's implementation of its 2014 Arctic Action Plan (AAP) lacks services related to permafrost change yet the Interagency Working Group on Coordination of Domestic Energy Development and Permitting in Alaska noted that warming permafrost challenges land-based development and calls for agencies to provide focused information needed by decision-makers. To address this we propose to link NOAA's existing seasonal forecasts of temperature and precipitation with a high-resolution model of the thermal state of permafrost (Jafarov et al., 2012) to provide near-term (one year ahead) forecasts of active layer thickness (ALT). Such forecasts would be an official NOAA statement of the expected thermal state of permafrost ALT in Alaska and would require: (1) long-term climate outlooks, (2) a permafrost model, (3) detailed specification of local spatial and vertical controls upon soil thermal state, (4) high-resolution vertical measurements of that thermal state, and (5) demonstration of forecast skill in pilot studies. Pilot efforts should focus on oil pipelines where the cost can be justified. With skillful forecasts, engineers could reduce costs of monitoring and repair as well as ecosystem damage by positioning equipment to more rapidly respond to predicted disruptions.

  20. Enzymatic digestive activity and absorption efficiency in Tagelus dombeii upon Alexandrium catenella exposure

    NASA Astrophysics Data System (ADS)

    Fernández-Reiriz, M. J.; Navarro, J. M.; Cisternas, B. A.; Babarro, J. M. F.; Labarta, U.

    2013-12-01

    We analyzed absorption efficiency (AE) and digestive enzyme activity (amylase, cellulase complex, and laminarinase) of the infaunal bivalve Tagelus dombeii originating from two geographic sites, Corral-Valdivia and Melinka-Aysén, which have different long-term paralytic shellfish poisoning (PSP) exposure rates. We report the effects of past feeding history (origin) on T. dombeii exposed to a mixed diet containing the toxic dinoflagellate Alexandrium catenella and another dinoflagellate-free control diet over a 12-day period in the laboratory. Absorption efficiency values of T. dombeii individuals that experienced PSP exposure in their habitat (Melinka-Aysén) remained unchanged during exposure to toxic food in the laboratory. In contrast, T. dombeii from a non-PSP exposure field site (Corral-Valdivia) showed a significant reduction in AE with toxic exposure time. This study established that the amylase and cellulase complexes were the most important enzymes in the digestive glands of Tagelus from both sites. The temporal evolution of enzymatic activity under toxic diet was fitted to exponential (amylase and cellulase) and to a logarithmic (laminarinase) models. In all fits, we found significant effect of origin in the model parameters. At the beginning of the experiment, higher enzymatic activity was observed for clams from Corral-Valdivia. The amylase activity decreased with time exposure for individuals from Corral and increased for individuals from Melinka. Cellulase activity did not vary over time for clams from Corral, but increased for individuals from Melinka and laminarinase activity decreased over time for individuals from Corral and remained unchanged over time for Melinka. A feeding history of exposure to the dinoflagellate A. catenella was reflected in the digestive responses of both T. dombeii populations.

  1. PbS Quantum Dots Sensitized TiO2 Solar Cells Prepared by Successive Ionic Layer Absorption and Reaction with Different Adsorption Layers.

    PubMed

    Yi, Jie; Duan, Yanfang; Liu, Chunxia; Gao, Shaohong; Han, Xueting; An, Limin

    2016-04-01

    Lead sulfide (PbS) quantum dots (QDs) have been synthesized via successive ionic layer adsorption and reaction (SILAR) on a titanium dioxide (TiO2) nanoporous film for the fabrication of quantum dot-sensitized solar cells (QDSCs). The reaction is environmental friendly and energy saving. The green synthesized PbS QDs match the maximum remittance region of the solar spectrum and are suitable as sensitizers for TiO2 electrodes for cell devices application. PbS QDs were adsorbed in different adsorption layers in order to improve the solar cell performance. The optical properties of PbS sensitized TiO2 films were studied by scanning electron microscopy and UV-Vis absorbance spectroscopy. The photovoltaic characteristics of the PbS QDSCs were analyzed by I-V characteristics and electrochemical impedance spectroscopy. As a result, the light harvesting was enhanced with increasing SILAR adsorption layers. The maximum photovoltaic conversion efficiency of the PbS QDSCs (3.14%) was obtained at the 12 adsorption layers with the highest short circuit current density and lowest charge transfer resistance. PMID:27451735

  2. Electroacoustic absorbers: bridging the gap between shunt loudspeakers and active sound absorption.

    PubMed

    Lissek, Hervé; Boulandet, Romain; Fleury, Romain

    2011-05-01

    The acoustic impedance at the diaphragm of an electroacoustic transducer can be varied using a range of basic electrical control strategies, amongst which are electrical shunt circuits. These passive shunt techniques are compared to active acoustic feedback techniques for controlling the acoustic impedance of an electroacoustic transducer. The formulation of feedback-based acoustic impedance control reveals formal analogies with shunt strategies, and highlights an original method for synthesizing electric networks ("shunts") with positive or negative components, bridging the gap between passive and active acoustic impedance control. This paper describes the theory unifying all these passive and active acoustic impedance control strategies, introducing the concept of electroacoustic absorbers. The equivalence between shunts and active control is first formalized through the introduction of a one-degree-of-freedom acoustic resonator accounting for both electric shunts and acoustic feedbacks. Conversely, electric networks mimicking the performances of active feedback techniques are introduced, identifying shunts with active impedance control. Simulated acoustic performances are presented, with an emphasis on formal analogies between the different control techniques. Examples of electric shunts are proposed for active sound absorption. Experimental assessments are then presented, and the paper concludes with a general discussion on the concept and potential improvements. PMID:21568400

  3. Determination of the geometric and electronic structure of activated bleomycin using X-ray absorption spectroscopy

    SciTech Connect

    Westre, T.E.; Loeb, K.E.; Zaleski, J.M.; Hedman, B.; Hodgson, K.O.; Solomon, E.I. )

    1995-02-01

    Activated Bleomycin (BLM) is the first mononuclear non-heme iron oxygen intermediate stable enough for detailed spectroscopic study. DNA degradation by activated BLM involves C-H bond cleavage at the C4[prime] position of deoxyribose moieties and results in the production of base propenals. It has been postulated that activated BLM is an oxo-ferryl intermediate on the basis of its reactivity and analogy with cytochrome P-450 chemistry. Alternatively, spectroscopic and model studies have indicated activated BLM to have an iron(III)-peroxide site. In this study, X-ray absorption spectroscopy (XAS) has been used to directly probe the oxidation and spin states of the iron in activated BLM and to determine if a short iron-oxo bond is present, which would be characteristic of the oxo-ferryl species of heme iron. Both the pre-edge and edge regions of the Fe K-edge spectra indicate that activated BLM is a low spin ferric complex. The pre-edge intensity of activated BLM is also similar to that of low spin ferric BLM and does not show the intensity enhancement which would be present if there were a short Fe-O bond. Furthermore, bond distances obtained from EXAFS are similar to those in low spin Fe[sup III]BLM and show no evidence for a short iron-oxo bond. 33 refs., 4 figs., 1 tab.

  4. Black Nb2O5 nanorods with improved solar absorption and enhanced photocatalytic activity.

    PubMed

    Zhao, Wenli; Zhao, Wei; Zhu, Guilian; Lin, Tianquan; Xu, Fangfang; Huang, Fuqiang

    2016-03-01

    Black titania, with greatly improved solar absorption, has demonstrated its effectiveness in photocatalysis and photoelectrochemical cells (PEC), inspiring us to explore the blackening of other wide band-gap oxide materials for enhanced performance. Herein, we report the fabrication of black, reduced Nb2O5 nanorods (r-Nb2O5), with active exposed (001) surfaces, and their enhanced photocatalytic and PEC properties. Black r-Nb2O5 nanorods were obtained via reduction of pristine Nb2O5 by molten aluminum in a two-zone furnace. Unlike the black titania, r-Nb2O5 nanorods are well-crystallized, without a core-shell structure, which makes them outstanding in photocatalytic stability. Substantial Nb(4+) cation and oxygen vacancies (VO) were introduced into r-Nb2O5, resulting in the enhanced absorption in both the visible and near-infrared regions and improved charge separation and transport capability. The advantage of the r-Nb2O5 was also proved by its more efficient photoelectrochemical performance (138 times at 1.23 VRHE) and higher photocatalytic hydrogen-generation activity (13 times) than pristine Nb2O5. These results indicate that black r-Nb2O5 is a promising material for PEC application and photocatalysis. PMID:26906245

  5. Wideband saturable absorption in few-layer molybdenum diselenide (MoSe₂) for Q-switching Yb-, Er- and Tm-doped fiber lasers.

    PubMed

    Woodward, R I; Howe, R C T; Runcorn, T H; Hu, G; Torrisi, F; Kelleher, E J R; Hasan, T

    2015-07-27

    We fabricate a free-standing molybdenum diselenide (MoSe2) saturable absorber by embedding liquid-phase exfoliated few-layer MoSe2 flakes into a polymer film. The MoSe2-polymer composite is used to Q-switch fiber lasers based on ytterbium (Yb), erbium (Er) and thulium (Tm) gain fiber, producing trains of microsecond-duration pulses with kilohertz repetition rates at 1060 nm, 1566 nm and 1924 nm, respectively. Such operating wavelengths correspond to sub-bandgap saturable absorption in MoSe2, which is explained in the context of edge-states, building upon studies of other semiconducting transition metal dichalcogenide (TMD)-based saturable absorbers. Our work adds few-layer MoSe2 to the growing catalog of TMDs with remarkable optical properties, which offer new opportunities for photonic devices. PMID:26367663

  6. Gastrointestinal absorption and biological activities of serine and cysteine proteases of animal and plant origin: review on absorption of serine and cysteine proteases

    PubMed Central

    Lorkowski, Gerhard

    2012-01-01

    Research has confirmed that peptides and larger protein molecules pass through the mucosal barrier of the gastrointestinal tract. Orally administered serine and cysteine proteases of plant and animal origin also reach blood and lymph as intact, high molecular weight and physiologically active protein molecules. Their absorption may be supported by a self-enhanced paracellular transport mechanism resulting in sub-nanomolar concentration of transiently free protease molecules or, in a complex with anti-proteases, at higher concentrations. Data from pharmacokinetic investigations reveals dose linearity for maximum plasma levels of free proteases not unusual for body proteases and a high inter-individual variability. There is no interference with each other after oral administration of protease combinations, and absorption follows an unusual invasion and elimination kinetic due to slow velocity of absorption and a fast 100% protein binding to anti-proteases. Oral application of proteases leads to increased proteolytic serum activity and increased plasma concentrations of the corresponding anti-proteases. Their biological activity is determined by their proteolytic activity as free proteases on soluble peptides/proteins or cell surface receptors (e.g. protease activated receptors) and their activity in the complex formed with their specific and/or unspecific anti-proteases. The anti-protease-complexes, during immune reaction and injuries often loaded with different cytokines, are cleared from body fluids and tissue by receptor mediated endocytosis on hepatocytes and/or blood cells. Oral administration of enteric coated tablets containing proteolytic enzymes of plant and animal origin may be a safe method to stabilize, positively influence or enhance physiological and immunological processes during disease processes and in healthy consumers. PMID:22461953

  7. The impact of active layer nanomorphology on the efficiency of organic solar cells based on a squaraine dye electron donor

    NASA Astrophysics Data System (ADS)

    Stoyanova, D.; Kitova, S.; Dikova, J.; Kandinska, M.; Vasilev, A.; Zhivkov, I.; Kovalenko, A.

    2016-03-01

    The possibilities were studied of improving the photovoltaic performance of solution processed BHJ solar cells by solvent vapor annealing (SVA) of the active layers, based on a squaraine dye Sq1 as a donor and the fullerene derivative PCBM as an acceptor. For this purpose, the optical properties were determined of as-deposited and of annealed with tetrahydrofuran (THF) vapors for different duration Sq1/PCMB layers, as well as the efficiency of cells built on their basis. A considerable change was established in the absorption spectra of treated for only a few seconds films and a twofold increase of the power conversion efficiency after 6 sec SVA. The results obtained are explained in terms of solvent vapor induced phase separation and formation of squaraine dye small aggregates in the blend nanostructure. The assumption made was confirmed by morphological investigation of as-deposited and of annealed Sq1/PCBM blended layers. On this basis, the impact of the active layer nanomorphology on the efficiency of solar cells based on squariane dye as electron donor is discussed.

  8. Short timescale inkjet ink component diffusion: an active part of the absorption mechanism into inkjet coatings.

    PubMed

    Lamminmäki, T T; Kettle, J P; Puukko, P J T; Ridgway, C J; Gane, P A C

    2012-01-01

    The structures of inkjet coatings commonly contain a high concentration of fine diameter pores together with a large pore volume capacity. To clarify the interactive role of the porous structure and the coincidentally occurring swelling of binder during inkjet ink vehicle imbibition, coating structures were studied in respect to their absorption behaviour for polar and non-polar liquid. The absorption measurement was performed using compressed pigment tablets, based on a range of pigment types and surface charge polarity, containing either polyvinyl alcohol (PVOH) or styrene acrylic latex (SA) as the binder, by recording the liquid uptake with a microbalance. The results indicate that, at the beginning of liquid uptake, at times less than 2 s, the small pores play the dominant role with respect to the inkjet ink vehicle imbibition. Simultaneously, water molecules diffuse into and within the hydrophilic PVOH binder causing binder swelling, which diminishes the number of active small pores and reduces the diameter of remaining pores, thus slowing the capillary flow as a function of time. The SA latex does not absorb the vehicle, and therefore the dominating phenomenon is then capillary absorption. However, the diffusion coefficient of the water vapour across separately prepared PVOH and SA latex films seems to be quite similar. In the PVOH, the polar liquid diffuses into the polymer network, whereas in the SA latex the hydrophobic nature prevents the diffusion into the polymer matrix and there exists surface diffusion. At longer timescale, permeation flow into the porous coating dominates as the resistive term controlling the capillary driven liquid imbibition rate. PMID:21981972

  9. Silica nanoparticles for the layer-by-layer assembly of fully electro-active cytochrome c multilayers

    PubMed Central

    2011-01-01

    Background For bioanalytical systems sensitivity and biomolecule activity are critical issues. The immobilization of proteins into multilayer systems by the layer-by-layer deposition has become one of the favorite methods with this respect. Moreover, the combination of nanoparticles with biomolecules on electrodes is a matter of particular interest since several examples with high activities and direct electron transfer have been found. Our study describes the investigation on silica nanoparticles and the redox protein cytochrome c for the construction of electro-active multilayer architectures, and the electron transfer within such systems. The novelty of this work is the construction of such artificial architectures with a non-conducting building block. Furthermore a detailed study of the size influence of silica nanoparticles is performed with regard to formation and electrochemical behavior of these systems. Results We report on interprotein electron transfer (IET) reaction cascades of cytochrome c (cyt c) immobilized by the use of modified silica nanoparticles (SiNPs) to act as an artificial matrix. The layer-by-layer deposition technique has been used for the formation of silica particles/cytochrome c multilayer assemblies on electrodes. The silica particles are characterized by dynamic light scattering (DLS), Fourier transformed infrared spectroscopy (FT-IR), Zeta-potential and transmission electron microscopy (TEM). The modified particles have been studied with respect to act as an artificial network for cytochrome c and to allow efficient interprotein electron transfer reactions. We demonstrate that it is possible to form electro-active assemblies with these non-conducting particles. The electrochemical response is increasing linearly with the number of layers deposited, reaching a cyt c surface concentration of about 80 pmol/cm2 with a 5 layer architecture. The interprotein electron transfer through the layer system and the influence of particle size are

  10. Correlations of Optical Absorption, Charge Trapping, and Surface Roughness of TiO2 Photoanode Layer Loaded with Neat Ag-NPs for Efficient Perovskite Solar Cells.

    PubMed

    Yang, Dongwook; Jang, Jae Gyu; Lim, Joohyun; Lee, Jin-Kyu; Kim, Sung Hyun; Hong, Jong-In

    2016-08-24

    We systematically investigated the effect of silver nanoparticles (Ag-NPs) on the power conversion efficiency (PCE) of perovskite solar cells (PSCs). Neat, spherical Ag-NPs at loading levels of 0.0, 0.5, 1.0, and 2.0 wt % were embedded into the titanium dioxide (TiO2) photoanode layer. The plasmonic effect of the Ag-NPs strongly enhanced the incident light absorption over a wide range of the visible wavelength region in addition to the inherent absorbance of the perovskite sensitizer. The low conduction energy level of the Ag-NPs compared to that of TiO2 provides trap sites for free charge carriers. Thus, the correlation between the enhancement of the optical absorption and the number of charge traps provided by the Ag-NPs is critical to determine the device performance, especially current density (Jsc) and PCE. This is confirmed by the quantitative comparison of the incident light absorption and the time-resolved photoluminescence decay according to the loading levels of the Ag-NPs in the TiO2 layer. The absorption enhancement from 380 to 750 nm in the UV-visible spectrum is proportional to the increase in the loading levels of the Ag-NPs. However, the Jsc increases with the device with 0.5 wt % Ag-NPs and gradually decreases with increases in the loading level above 0.5 wt % because of the different contributions to the absorbance and the charge trapping by different Ag-NP loading levels. In addition, the suppression of the surface roughness with dense packing by the Ag-NPs helps to improve the Jsc and the following PCE. Consequently, the PCE of the PSC with 0.5 wt % Ag-NPs is increased to 11.96%. These results are attributed to the balance between increased absorbance by the localized surface plasmon resonance and the decreased charge trapping as well as the decreased surface roughness of the TiO2 layer with the Ag-NPs. PMID:27471777

  11. 2D double-layer-tube-shaped structure Bi2S3/ZnS heterojunction with enhanced photocatalytic activities

    NASA Astrophysics Data System (ADS)

    Gao, Xiaoming; Wang, Zihang; Fu, Feng; Li, Xiang; Li, Wenhong

    2015-10-01

    Bi2S3/ZnS heterojunction with 2D double-layer-tube-shaped structures was prepared by the facile synthesis method. The corresponding relationship was obtained among loaded content to phase, morphology, and optical absorption property of Bi2S3/ZnS composite. The results shown that Bi2S3 loaded could evidently change the crystallinity of ZnS, enhance the optical absorption ability for visible light of ZnS, and improve the morphologies and microstructure of ZnS. The photocatalytic activities of the Bi2S3/ZnS sample were evaluated for the photodegradation of phenol and desulfurization of thiophene under visible light irradiation. The results showed that Bi2S3 loaded greatly improved the photocatalytic activity of ZnS, and the content of loaded Bi2S3 had an impact on the catalytic activity of ZnS. Moreover, the mechanism of enhanced photocatalytic activity was also investigated by analysis of relative band positions of Bi2S3 and ZnS, and photo-generated hole was main active radicals during photocatalytic oxidation process.

  12. Temperature distribution in a layer of an active thermal insulation system heated by a gas burner

    SciTech Connect

    Maruyama, Shigenao . Inst. of Fluid Science); Shimizu, Naotaka . Dept. of Mechanical Engineering)

    1993-12-01

    The temperature distribution in a layer of an active thermal insulation system was measured. A semitransparent porous layer was heated by a gas burner, and air was injected from the back face of the layer. The temperature in the layer was measured by thermocouples. The temperature distributions were compared with numerical solutions. The thermal penetration depth of the active thermal insulation layer with gas injection can be reduced to 3 mm. When the surface temperature of a conventional insulation layer without gas injection reached 1,500 K, the temperature at the back surface of a 10-mm-thick layer reached 600 K. The transient temperature of the active thermal insulation reached a steady state very quickly compared with that of the conventional insulation. These characteristics agreed qualitatively with the numerical solutions.

  13. [Intestinal absorption of different combinations of active compounds from Gegenqinlian decoction by rat single pass intestinal perfusion in situ].

    PubMed

    An, Rui; Zhang, Hua; Zhang, Yi-Zhu; Xu, Ran-Chi; Wang, Xin-Hong

    2012-12-01

    The aim is to study the intestinal absorption of different combinations of active compounds out of Gegenqinlian decoction. Rat single pass intestinal perfusion model with jugular vein cannulated was used. Samples were obtained continuously from the outlet perfusate and the mesenteric vein. The levels of puerarin, daidzin, liquilitin, baicalin, wogonoside, jatrorrhizine, berberine and palmatine were determined by LC-MS/MS and their permeability coefficients were calculated. The results showed that Glycyrrhiza could promote the absorption of the active ingredients in Pueraria which is the monarch herb; meanwhile, Pueraria also played a role in promoting the absorption of liquilitin. Based on the Gegenqinlian decoction and the different combinations experiments, the results concerning the absorption of baicalin and wogonoside were as follows. For baicalin, Pueraria and Glycyrrhiza could promote its absorption and the effect of Pueraria was more obvious. For wogonoside, Pueraria could also promote its absorption, while Glycyrrhiza played a opposite role. Pueraria and Glycyrrhiza both played a part in promoting the absorption of jateorhizine, berberine and palmatine, the effective compounds in Coptis. PMID:23460978

  14. H I 21 cm ABSORPTION AND UNIFIED SCHEMES OF ACTIVE GALACTIC NUCLEI

    SciTech Connect

    Curran, S. J.; Whiting, M. T.

    2010-03-20

    In a recent study of z >= 0.1 active galactic nuclei (AGNs), we found that 21 cm absorption has never been detected in objects in which the ultraviolet luminosity exceeds L{sub UV} {approx} 10{sup 23} W Hz{sup -1}. In this paper, we further explore the implications that this has for the currently popular consensus that it is the orientation of the circumnuclear obscuring torus, invoked by unified schemes of AGNs, which determines whether absorption is present along our sight line. The fact that at L{sub UV} {approx}< 10{sup 23} W Hz{sup -1}, both type-1 and type-2 objects exhibit a 50% probability of detection, suggests that this is not the case and that the bias against detection of H I absorption in type-1 objects is due purely to the inclusion of the L{sub UV} {approx}> 10{sup 23} W Hz{sup -1} sources. Similarly, the ultraviolet luminosities can also explain why the presence of 21 cm absorption shows a preference for radio galaxies over quasars and the higher detection rate in compact sources, such as compact steep spectrum or gigahertz peaked spectrum sources, may also be biased by the inclusion of high-luminosity sources. Being comprised of all 21 cm searched sources at z >= 0.1, this is a necessarily heterogeneous sample, the constituents of which have been observed by various instruments. By this same token, however, the dependence on the UV luminosity may be an all encompassing effect, superseding the unified schemes model, although there is the possibility that the exclusive 21 cm non-detections at high UV luminosities could be caused by a bias toward gas-poor ellipticals. Additionally, the high UV fluxes could be sufficiently exciting/ionizing the H I above 21 cm detection thresholds, although the extent to which this is related to the neutral gas deficit in ellipticals is currently unclear. Examining the moderate UV luminosity (L{sub UV} {approx}< 10{sup 23} W Hz{sup -1}) sample further, from the profile widths and offsets from the systemic velocities

  15. Grain sorting in the morphological active layer of a braided river physical model

    NASA Astrophysics Data System (ADS)

    Leduc, P.; Ashmore, P.; Gardner, J. T.

    2015-07-01

    A physical scale model of a gravel-bed braided river was used to measure vertical grain size sorting in the morphological active layer aggregated over the width of the river. This vertical sorting is important for analyzing braided river sedimentology, for numerical modeling of braided river morpho-dynamics and for measuring and predicting bed load transport rate. We define the morphological active layer as the bed material between the maximum and minimum bed elevations at a point over extended time periods sufficient for braiding processes to re-work the river bed. The vertical extent of the active layer was measured using 40 hourly high-resolution DEMs of the model river bed. An image texture algorithm was used to map bed material grain size of each DEM. Analysis of the 40 DEMs and texture maps provides data on the geometry of the morphological active layer and variation in grain size in three-dimensions. Normalizing active layer thickness and dividing into 10 sub-layers we show that all grain sizes occur with almost equal frequency in all sub-layers. Occurrence of patches and strings of coarser (or finer) material relates to preservation of particular morpho-textural features within the active layer. For numerical modeling and bed load prediction a morphological active layer that is fully mixed with respect to grain size is a reliable approximation.

  16. Layer dependence and gas molecule absorption property in MoS2 Schottky diode with asymmetric metal contacts

    PubMed Central

    Yoon, Hyong Seo; Joe, Hang-Eun; Jun Kim, Sun; Lee, Hee Sung; Im, Seongil; Min, Byung-Kwon; Jun, Seong Chan

    2015-01-01

    Surface potential measurement on atomically thin MoS2 flakes revealed the thickness dependence in Schottky barriers formed between high work function metal electrodes and MoS2 thin flakes. Schottky diode devices using mono- and multi- layer MoS2 channels were demonstrated by employing Ti and Pt contacts to form ohmic and Schottky junctions respectively. Characterization results indicated n-type behavior of the MoS2 thin flakes and the devices showed clear rectifying performance. We also observed the layer dependence in device characteristics and asymmetrically enhanced responses to NH3 and NO2 gases based on the metal work function and the Schottky barrier height change. PMID:25990304

  17. Photon-photon absorption and the uniqueness of the spectra of active galactic nuclei

    NASA Technical Reports Server (NTRS)

    Kazanas, D.

    1984-01-01

    The effects of the feedback of e(+)-e(-) pair reinjection in a plasma due to photon-photon absorption of its own radiation was examined. Under the assumption of continuous electron injection with a power law spectrum E to the minus gamma power and Compton losses only, it is shown that for gamma 2 the steady state electron distribution function has a unique form independent of the primary injection spectrum. This electron distribution function can, by synchrotron emission, reproduce the general characteristics of the observed radio to optical active galactic nuclei spectra. Inverse Compton scattering of the synchrotron photons by the same electron distribution can account for their X-ray spectra, and also implies gamma ray emission from these objects. This result is invoked to account for the similarity of these spectra, and it is consistent with observations of the diffuse gamma ray background.

  18. Thermally activated decomposition of (Ga,Mn)As thin layer at medium temperature post growth annealing

    NASA Astrophysics Data System (ADS)

    Melikhov, Y.; Konstantynov, P.; Domagala, J.; Sadowski, J.; Chernyshova, M.; Wojciechowski, T.; Syryanyy, Y.; Demchenko, I. N.

    2016-05-01

    The redistribution of Mn atoms in Ga1-xMnxAs layer during medium-temperature annealing, 250-450 oC, by Mn K-edge X-ray absorption fine structure (XAFS) recorded at ALBA facility, was studied. For this purpose Ga1-xMnxAs thin layer with x=0.01 was grown on AlAs buffer layer deposited on GaAs(100) substrate by molecular beam epitaxy (MBE) followed by annealing. The examined layer was detached from the substrate using a “lift-off” procedure in order to eliminate elastic scattering in XAFS spectra. Fourier transform analysis of experimentally obtained EXAFS spectra allowed to propose a model which describes a redistribution/diffusion of Mn atoms in the host matrix. Theoretical XANES spectra, simulated using multiple scattering formalism (FEFF code) with the support of density functional theory (WIEN2k code), qualitatively describe the features observed in the experimental fine structure.

  19. Management of light absorption in extraordinary optical transmission based ultra-thin-film tandem solar cells

    NASA Astrophysics Data System (ADS)

    Mashooq, Kishwar; Talukder, Muhammad Anisuzzaman

    2016-05-01

    Although ultra-thin-film solar cells can be attractive in reducing the cost, they suffer from low absorption as the thickness of the active layer is usually much smaller than the wavelength of incident light. Different nano-photonic techniques, including plasmonic structures, are being explored to increase the light absorption in ultra-thin-film solar cells. More than one layer of active materials with different energy bandgaps can be used in tandem to increase the light absorption as well. However, due to different amount of light absorption in different active layers, photo-generated currents in different active layers will not be the same. The current mismatch between the tandem layers makes them ineffective in increasing the efficiency. In this work, we investigate the light absorption properties of tandem solar cells with two ultra-thin active layers working as two subcells and a metal layer with periodically perforated holes in-between the two subcells. While the metal layer helps to overcome the current mismatch, the periodic holes increase the absorption of incident light by helping extraordinary optical transmission of the incident light from the top to the bottom subcell, and by coupling the incident light to plasmonic and photonic modes within ultra-thin active layers. We extensively study the effects of the geometry of holes in the intermediate metal layer on the light absorption properties of tandem solar cells with ultra-thin active layers. We also study how different metals in the intermediate layer affect the light absorption; how the geometry of holes in the intermediate layer affects the absorption when the active layer materials are changed; and how the intermediate metal layer affects the collection of photo-generated electron-hole pairs at the terminals. We find that in a solar cell with 6,6-phenyl C61-butyric acid methyl ester top subcell and copper indium gallium selenide bottom subcell, if the periodic holes in the metal layer are square or

  20. ZnO-Based Solar Blind Ultraviolet-B Photodetectors Using MgZnO Absorption Layer

    NASA Astrophysics Data System (ADS)

    Lee, Ching-Ting; Lin, Tzu-Shun; Chen, Chia-Hsun

    2015-12-01

    The heterostructured thin films of the solar blind p-ZnO:LiNO3/i-MgZnO/n-MgZnO:In ultraviolet-B photodetectors were deposited at a low temperature using the vapor cooling condensation system. The photodetectors exhibited an absorption cut-off wavelength of 310 nm and did not response in the visible wavelength range. A low dark current of 20 pA and a high rejection ratio of 3.60 × 103 were measured when a reverse bias voltage of -1 V was applied. The associated photoresponsivity of 0.2 A/W, the noise equivalent power of 9.50 × 10-12 W and the specific detectivity of 3.16 × 1012 cm Hz1/2 W-1 were obtained. Furthermore, the dominant noise originated from the flicker noise.

  1. Influence of liquid medium with different absorption and its layer thickness on bovine bone tibia ablation induced by CO2 laser

    NASA Astrophysics Data System (ADS)

    Li, Xuwei; Chen, Chuanguo; Zhang, Xianzeng; Zhan, Zhenlin; Xie, Shusen

    2014-11-01

    Liquid-assisted laser ablation has been investigated in laser surface cleaning, laser osteotomy, and dental tissue ablation. However, the actual mechanism of liquid-assisted ablation is not clear yet. The purpose of this study was to investigate the influence of liquid medium with different absorption and the liquid thickness on laser ablation efficiency. A pulsed CO2 laser was employed to ablate bovine bone tibia under liquid layer which varied from 0.6 mm to 2 mm. The applied pulse power level was set at 5 w and each crater was produced with six laser pulses. The results showed that the ablation cross-section area produced with various levels of pure water thickness (0.6, 0.8, 1 and 2 mm)were lower than under ink, and the ablation depth gradually decreased as the water layer becoming thicker. The biggest cross-section area in liquid thickness of ink was 0.8mm, but as the layer thicker than 0.8 mm the ablation depth decreased suddenly. There was thermal damage seen on samples in all of the groups, but less in pure water.

  2. X-rays absorption study on medieval corrosion layers for the understanding of very long-term indoor atmospheric iron corrosion

    NASA Astrophysics Data System (ADS)

    Monnier, J.; Réguer, S.; Vantelon, D.; Dillmann, P.; Neff, D.; Guillot, I.

    2010-05-01

    The study and prediction of very long-term atmospheric corrosion behaviour of ferrous alloys is of great importance in different fields. First the conservation of metallic artefacts in museum and the corrosion diagnosis on ferrous reinforcement used in ancient monuments since medieval times needs reliable data to understand the mechanisms. Second, in the frame of the interim storage of nuclear waste in France, it is necessary to model the long-term corrosion of low alloy steel overcontainer. The nature of phases and elements constituting the corrosion layers can greatly influence the corrosion mechanisms. On the one hand, it is crucial to precisely determine the nature of microscopic phases that can be highly reactive. On the other hand, some elements as P and S could modify this reactivity. To clarify this point and complementary to other studies using Raman micro spectroscopy technique, X-rays Absorption Spectroscopy (XAS) under synchrotron radiation plays a crucial role. It allows one to precisely identify the reactive phases in the corrosion layers. Micro-XAS was required in order to refine the spatial variation, at micrometer scale, of the predominant Fe oxidation state and to characterise the corresponding corrosion products. Moreover, the role of minor elements on phase’s stability and the chemical form of these elements in the rust layer, especially phosphorus and sulphur, was investigated.

  3. Effects of spatial variation of skull and cerebrospinal fluid layers on optical mapping of brain activities

    NASA Astrophysics Data System (ADS)

    Wang, Shuping; Shibahara, Nanae; Kuramashi, Daishi; Okawa, Shinpei; Kakuta, Naoto; Okada, Eiji; Maki, Atsushi; Yamada, Yukio

    2010-07-01

    In order to investigate the effects of anatomical variation in human heads on the optical mapping of brain activity, we perform simulations of optical mapping by solving the photon diffusion equation for layered-models simulating human heads using the finite element method (FEM). Particularly, the effects of the spatial variations in the thicknesses of the skull and cerebrospinal fluid (CSF) layers on mapping images are investigated. Mapping images of single active regions in the gray matter layer are affected by the spatial variations in the skull and CSF layer thicknesses, although the effects are smaller than those of the positions of the active region relative to the data points. The increase in the skull thickness decreases the sensitivity of the images to active regions, while the increase in the CSF layer thickness increases the sensitivity in general. The images of multiple active regions are also influenced by their positions relative to the data points and by their depths from the skin surface.

  4. Influence of Water Activated by Far infrared Porous Ceramics on Nitrogen Absorption in the Pig Feed.

    PubMed

    Meng, Junping; Liu, Jie; Liang, Jinsheng; Zhang, Hongchen; Ding, Yan

    2016-04-01

    Under modern and, intensive feeding livestock and poultry density has increased, and brought a deterioration of the farm environment. The livestock and their excrement generate harmful gases such as ammonia, etc. which restricted the sustainable development and improvement of production efficiency of animal husbandry. In this paper, a new kind of far infrared porous ceramics was prepared to activate, the animal drinking water. The activated water and common water were then supplied to pigs, and the fresh pig feces of experimental group and:control group were collected on a regular basis. The residual protein content in feces was tested by Kjeldahl nitrogen method to study the influence law of the porous ceramics on absorbing nitrogen element in animal feces. The results showed that compared with the control group, the protein content in the experimental group decreased on average by 39.2%. The activated drinking water was conducive to the absorption of nitrogen in pig feed. The clusters of water molecules became smaller under the action of the porous ceramics. Hence, they were easy to pass through the water protein channel on the cell membrane for speeding up the metabolism. PMID:27451750

  5. Layer-by-layer engineered nanocapsules of curcumin with improved cell activity.

    PubMed

    Kittitheeranun, Paveenuch; Sajomsang, Warayuth; Phanpee, Sarunya; Treetong, Alongkot; Wutikhun, Tuksadon; Suktham, Kunat; Puttipipatkhachorn, Satit; Ruktanonchai, Uracha Rungsardthong

    2015-08-15

    Nanocarriers based on electrostatic Layer-by-layer (LbL) assembly of CaCO3 nanoparticles (CaCO3 NPs) was investigated. These inorganic nanoparticles was used as templates to construct nanocapsules made from films based on two oppositely charged polyelectrolytes, poly(diallyldimethylammonium chloride), and poly (sodium 4-styrene-sulfonate sodium salt), followed by core dissolution. The naked CaCO3 NPs, CaCO3 NPs coated with the polyelectrolytes and hollow nanocapsules were found with hexagonal shape with average sizes of 350-400 nm. A reversal of the surface charge between positive to negative zeta potential values was found, confirming the adsorption of polyelectrolytes. The loading efficiency and release of curcumin were controlled by the hydrophobic interactions between the drug and the polyelectrolyte matrix of the hollow nanocapsules. The quantity of curcumin released from hollow nanocapsules was found to increase under acidic environments, which is a desirable for anti-cancer drug delivery. The hollow nanocapsules were found to localize in the cytoplasm and nucleus compartment of Hela cancer cells after 24 h of incubation. Hollow nanocapsules were non-toxic to human fibroblast cells. Furthermore, curcumin loaded hollow nanocapsules exhibited higher in vitro cell inhibition against Hela cells than that of free curcumin, suggesting that polyelectrolyte based-hollow nanocapsules can be utilized as new carriers for drug delivery. PMID:26143232

  6. AS-924, a novel, orally active, bifunctional prodrug of ceftizoxime: physicochemical properties, oral absorption in animals, and antibacterial activity.

    PubMed

    Mori, N; Kodama, T; Sakai, A; Suzuki, T; Sugihara, T; Yamaguchi, S; Nishijima, T; Aoki, A; Toriya, M; Kasai, M; Hatano, S; Kitagawa, M; Yoshimi, A; Nishimura, K

    2001-11-01

    AS-924 is an oral prodrug of the antibiotic ceftizoxime (CTIZ), a parenteral use cephalosporin. This novel prodrug, produced by esterifying CTIZ with a lipophilic pivaloyloxymethyl (POM) group and introducing a water soluble L-alanyl group, is expected to increase the bioavailability and thereby, augment the antibacterial activity of CTIZ in vivo compared with existing prodrugs. To study the effect of the L-alanyl group in AS-924 on its bioavailability, the plasma concentration profiles of CTIZ in dogs were examined following the dosing of AS-924 and CTIZ-POM, in powder form, after pretreatment with the antacid ranitidine, and following the dosing of AS-924 after pretreatment with a gastrointestinal motility stimulant metoclopramide or suppressant scopolamine butylbromide. The absorption rate of AS-924 was constant under these different conditions due to its unique balance of lipophilicity and water solubility. CTIZ is as antibacterially active as pre-existing oral cephalosporins against Gram-positive clinical isolates, while being more active against all Gram-negative isolates-particularly Enterobacteriaceae and Haemophilus influenzae. A simulation model for the eradication profile of bacteria in computer programmed pharmacokinetic (PK) system was carried out to study the antibacterial action of CTIZ in human. CTIZ was proven to eradicate Streptococcus pneumoniae and H. influenzae effectively, while cefpodoxime (CPOD), the active moiety of CPOD proxetil, eradicated S. pneumoniae, but not H. influenzae. These results confirm that, AS-924 is a potent oral antibiotic and would be expected to be clinically effective and efficient. PMID:11711261

  7. Heat Generation/Absorption Effects in a Boundary Layer Stretched Flow of Maxwell Nanofluid: Analytic and Numeric Solutions

    PubMed Central

    Awais, Muhammad; Hayat, Tasawar; Irum, Sania; Alsaedi, Ahmed

    2015-01-01

    Analysis has been done to investigate the heat generation/absorption effects in a steady flow of non-Newtonian nanofluid over a surface which is stretching linearly in its own plane. An upper convected Maxwell model (UCM) has been utilized as the non-Newtonian fluid model in view of the fact that it can predict relaxation time phenomenon which the Newtonian model cannot. Behavior of the relaxations phenomenon has been presented in terms of Deborah number. Transport phenomenon with convective cooling process has been analyzed. Brownian motion “Db” and thermophoresis effects “Dt” occur in the transport equations. The momentum, energy and nanoparticle concentration profiles are examined with respect to the involved rheological parameters namely the Deborah number, source/sink parameter, the Brownian motion parameters, thermophoresis parameter and Biot number. Both numerical and analytic solutions are presented and found in nice agreement. Comparison with the published data is also made to ensure the validity. Stream lines for Maxwell and Newtonian fluid models are presented in the analysis. PMID:26115101

  8. Heat Generation/Absorption Effects in a Boundary Layer Stretched Flow of Maxwell Nanofluid: Analytic and Numeric Solutions.

    PubMed

    Awais, Muhammad; Hayat, Tasawar; Irum, Sania; Alsaedi, Ahmed

    2015-01-01

    Analysis has been done to investigate the heat generation/absorption effects in a steady flow of non-Newtonian nanofluid over a surface which is stretching linearly in its own plane. An upper convected Maxwell model (UCM) has been utilized as the non-Newtonian fluid model in view of the fact that it can predict relaxation time phenomenon which the Newtonian model cannot. Behavior of the relaxations phenomenon has been presented in terms of Deborah number. Transport phenomenon with convective cooling process has been analyzed. Brownian motion "Db" and thermophoresis effects "Dt" occur in the transport equations. The momentum, energy and nanoparticle concentration profiles are examined with respect to the involved rheological parameters namely the Deborah number, source/sink parameter, the Brownian motion parameters, thermophoresis parameter and Biot number. Both numerical and analytic solutions are presented and found in nice agreement. Comparison with the published data is also made to ensure the validity. Stream lines for Maxwell and Newtonian fluid models are presented in the analysis. PMID:26115101

  9. Fine-Tunable Absorption of Uniformly Aligned Polyurea Thin Films for Optical Filters Using Sequentially Self-Limited Molecular Layer Deposition.

    PubMed

    Park, Yi-Seul; Choi, Sung-Eun; Kim, Hyein; Lee, Jin Seok

    2016-05-11

    Development of methods enabling the preparation of uniformly aligned polymer thin films at the molecular level is a prerequisite for realizing their optoelectronic characteristics as innovative materials; however, these methods often involve a compromise between scalability and accuracy. In this study, we have grown uniformly aligned polyurea thin films on a SiO2 substrate using molecular layer deposition (MLD) based on sequential and self-limiting surface reactions. By integrating plane-polarized Fourier-transform infrared, Raman spectroscopic tools, and density functional theory calculations, we demonstrated the uniform alignment of polyurea MLD films. Furthermore, the selective-wavelength absorption characteristics of thickness-controlled MLD films were investigated by integrating optical measurements and finite-difference time-domain simulations of reflection spectra, resulting from their thickness-dependent fine resonance with photons, which could be used as color filters in optoelectronics. PMID:27092573

  10. Composition analysis of a polymer electrolyte membrane fuel cell microporous layer using scanning transmission X-ray microscopy and near edge X-ray absorption fine structure analysis

    NASA Astrophysics Data System (ADS)

    George, Michael G.; Wang, Jian; Banerjee, Rupak; Bazylak, Aimy

    2016-03-01

    The novel application of scanning transmission X-ray microscopy (STXM) to the microporous layer (MPL) of a polymer electrolyte membrane fuel cell is investigated. A spatially resolved chemical component distribution map is obtained for the MPL of a commercially available SGL 25 BC sample. This is achieved with near edge X-ray absorption fine structure spectroscopic analysis. Prior to analysis the sample is embedded in non-reactive epoxy and ultra-microtomed to a thickness of 100 nm. Polytetrafluoroethylene (PTFE), carbon particle agglomerates, and supporting epoxy resin distributions are identified and reconstructed for a scanning area of 6 μm × 6 μm. It is observed that the spatial distribution of PTFE is strongly correlated to the carbon particle agglomerations. Additionally, agglomerate structures of PTFE are identified, possibly indicating the presence of a unique mesostructure in the MPL. STXM analysis is presented as a useful technique for the investigation of chemical species distributions in the MPL.

  11. Percutaneous absorption of herbicides derived from 2,4-dichlorophenoxyacid: structure-activity relationship.

    PubMed

    Beydon, Dominique; Payan, Jean-Paul; Ferrari, Elisabeth; Grandclaude, Marie-Christine

    2014-08-01

    Ethyl to octyl esters of 2,4-dichlorophenoxy-acetic acids (2,4DAA), 2,4-dichlorophenoxy-propionic acids (2,4DPA) or 2,4-dichlorophenoxy-butyric acids (2,4DBA) are present in the most commonly used herbicides. Their use involves a significant risk of skin exposure, but little is known about the percutaneous flux of these substances. Studies have shown that percutaneous transition of esters may be dependent on their hydrolysis by esterases present in the skin. In this study, we describe ex vivo percutaneous absorption of seven pure esters (methyl to decyl) with a 2,4DA structure for rats (n=6) and humans (n=7). Esters were applied at 50 μL cm(-2) to dermatomed skin (approximately 0.5 mm thick) for 24 h. The enzymatic constants for hydrolysis of each ester by skin esterases were determined in vitro using skin homogenates from both species. Structure-activity relationships linking the evolution of the ex vivo percutaneous flux of esters and the 2,4D structure with enzymatic (Vmax; Km) and/or physical parameters (molecular weight, molecular volume, size of the ester, log(kow)) were examined to develop a good flux estimation model. Although the percutaneous penetration of all of the esters of the 2,4D family are "esterase-dependent", the decreasing linear relationship between percutaneous penetration and hyrophobicity defined by the logarithm for the octanol-water partition coefficient (log(kow)) is the most pertinent model for estimating the percutaneous absorption of esters for both species. The mean flux of the free acid production by the esterases of the skin is not the limiting factor for percutaneous penetration. The rate of hydrolysis of the esters in the skin decreases linearly with log(kow), which would suggest that either the solubility of the esters in the zones of the skin that are rich in esterases or the accessibility to the active sites of the enzyme is the key factor. The structure-activity relationship resulting from this study makes it possible, in

  12. Airborne Measurements of Scattering and Absorption Coefficients in the Planetary Boundary Layer above the Po Valley, Italy, during the PEGASOS Campaigns

    NASA Astrophysics Data System (ADS)

    Rosati, B.; Weingartner, E.; Gysel, M.; Tillmann, R.; Mentel, T. F.; Decesari, S.; Marinoni, A.; Gobbi, G. P.; Fierli, F.; Cairo, F.; Bucci, S.; Zanatta, M.; Größ, J.; Baltensperger, U.

    2014-12-01

    Aerosol particles influence the Earth's radiation budget by interacting with the incoming sunlight. The chemical composition and size of aerosol particles determine their potential to scatter and absorb radiation as well as their capability to take up water (Zieger et al., 2011). If particles are hygroscopic their optical properties will be altered at enhanced relative humidities (RH) due to the increase in size and change in index of refraction. It is known that RH but also the chemical composition of aerosols change with altitude (Morgan et al., 2010) which makes it very important to investigate optical properties at different heights. Within the Pan-European Gas-Aerosols-climate interaction Study (PEGASOS) a set of instruments was installed on a Zeppelin to investigate changes of light scattering and absorption in the planetary boundary layer. In order to obtain the scattering properties, Mie calculations were performed for size distributions recorded with SMPS (scanning mobility particle sizer) and WELAS (optical size spectrometer). The index of refraction and the hygroscopicity of the aerosol particles were measured with the white-light humidified optical particle spectrometer (WHOPS). These measurements further allowed studying the RH-dependence of the optical properties. Moreover, a seven wavelength portable aethalometer was employed to determine the light absorption properties of the aerosol. In this work we will present vertical profiles of scattering and absorption coefficients measured during Zeppelin flights of the PEGASOS campaigns in Italy in 2012. Additionally comparisons with ground based measurements from nephelometers and aethalometers, as well as remote sensing results will be shown. W.T. Morgan et al., Enhancement of the aerosol direct radiative effect by semi-volatile aerosol components: Airborne measurements in North-Western Europe, Atmospheric Chemistry and Physics 10(2010), pp. 8151-8171.P. Zieger et al., Comparison of ambient aerosol

  13. Applicability of light-emitting diodes as light sources for active differential optical absorption spectroscopy measurements.

    PubMed

    Kern, Christoph; Trick, Sebastian; Rippel, Bernhard; Platt, Ulrich

    2006-03-20

    We present what is to our knowledge the first use of light-emitting diodes (LEDs) as light sources for long-path differential optical absorption spectroscopy (LP-DOAS) measurements of trace gases in the open atmosphere. Modern LEDs represent a potentially advantageous alternative to thermal light sources, in particular to xenon arc lamps, which are the most common active DOAS light sources. The radiative properties of a variety of LEDs were characterized, and parameters such as spectral shape, spectral range, spectral stability, and ways in which they can be influenced by environmental factors were analyzed. The spectra of several LEDs were found to contain Fabry-Perot etalon-induced spectral structures that interfered with the DOAS evaluation, in particular when a constant temperature was not maintained. It was shown that LEDs can be used successfully as light sources in active DOAS experiments that measure NO2 and NO3 near 450 and 630 nm, respectively. Average detection limits of 0.3 parts in 10(9) and 16 parts in 10(12) respectively, were obtained by use of a 6 km light path in the open atmosphere. PMID:16579579

  14. Determination of nickel in active pharmaceutical ingredients by electrothermal atomic absorption spectrometry.

    PubMed

    Bubnič, Zoran; Urleb, Uroš; Kreft, Katjuša; Veber, Marjan

    2010-03-01

    An electrothermal atomic absorption spectrometric procedure for the determination of nickel in active pharmaceutical ingredients was developed. Since the recoveries of nickel by the direct dissolution of samples in diluted nitric acid were low and caused errors in the determination of Ni in pharmaceutical samples, different approaches for sample pre-treatment were examined. It was found that the microwave digestion was the most suitable way for sample preparation. Various combinations of digestion agents and different microwave conditions were tested. The combination of nitric acid and hydrogen peroxide was found to be the most appropriate. The validity of the method was evaluated by recovery studies of spiked samples and by the comparison of the results obtained by inductively coupled plasma mass spectrometry (ICP-MS). The recovery ranged from 87.5 to 104.0% and a good agreement was achieved between both methods. The detection limit and the limit of quantification were 0.6 and 2.1 µg g-1 respectively. The precision of the method was confirmed by the determination of Ni in the spiked samples and was below 4%, expressed in terms of a relative standard deviation. The method was applied to the determination of nickel in production samples of active pharmaceutical ingredients and intermediates. PMID:24061653

  15. Grain sorting in the morphological active layer of a braided river physical model

    NASA Astrophysics Data System (ADS)

    Leduc, P.; Ashmore, P.; Gardner, J. T.

    2015-12-01

    A physical scale model of a gravel-bed braided river was used to measure vertical grain size sorting in the morphological active layer aggregated over the width of the river. This vertical sorting is important for analyzing braided river sedimentology, for numerical modeling of braided river morphodynamics, and for measuring and predicting bedload transport rate. We define the morphological active layer as the bed material between the maximum and minimum bed elevations at a point over extended time periods sufficient for braiding processes to rework the river bed. The vertical extent of the active layer was measured using 40 hourly high-resolution DEMs (digital elevation models) of the model river bed. An image texture algorithm was used to map bed material grain size of each DEM. Analysis of the 40 DEMs and texture maps provides data on the geometry of the morphological active layer and variation in grain size in three dimensions. By normalizing active layer thickness and dividing into 10 sublayers, we show that all grain sizes occur with almost equal frequency in all sublayers. Occurrence of patches and strings of coarser (or finer) material relates to preservation of particular morpho-textural features within the active layer. For numerical modeling and bedload prediction, a morphological active layer that is fully mixed with respect to grain size is a reliable approximation.

  16. Interstratified nanohybrid assembled by alternating cationic layered double hydroxide nanosheets and anionic layered titanate nanosheets with superior photocatalytic activity.

    PubMed

    Lin, Bizhou; Sun, Ping; Zhou, Yi; Jiang, Shaofeng; Gao, Bifen; Chen, Yilin

    2014-09-15

    Oppositely charged 2D inorganic nanosheets of ZnAl-layered double hydroxide and layered titanate were successfully assembled into an interstratified nanohybrid through simply mixing the corresponding nanosheet suspensions. Powder X-ray diffraction and high-resolution transmission electron microscope clearly revealed that the component nanosheets in the as-obtained nanohybrid ZnAl-Ti3O7 retain the 2D sheet skeletons of the pristine materials and that the two kinds of nanosheets are well arranged in a layer-by-layer alternating fashion with a basal spacing of about 1.3 nm, coincident with the thickness summation of the two component nanosheets. The effective interfacial heterojunction between them and the high specific surface area resulted in that the nanohybrid exhibits a superior photocatalytic activity in the degradation of methylene blue with a reaction constant k of 2.81 × 10(-2)min(-1), which is about 9 and 4 times higher than its precursors H2Ti3O7 and ZnAl-LDH, respectively. Based on UV-vis, XPS and photoelectrochemical measurements, a proposed photoexcitation model was provided to understand its photocatalytic behavior. PMID:25151238

  17. Application of Satellite SAR Imagery in Mapping the Active Layer of Arctic Permafrost

    NASA Technical Reports Server (NTRS)

    Zhang, Ting-Jun; Li, Shu-Sun

    2003-01-01

    The objective of this project is to map the spatial variation of the active layer over the arctic permafrost in terms of two parameters: (i) timing and duration of thaw period and (ii) differential frost heave and thaw settlement of the active layer. To achieve this goal, remote sensing, numerical modeling, and related field measurements are required. Tasks for the University of Colorado team are to: (i) determine the timing of snow disappearance in spring through changes in surface albedo (ii) simulate the freezing and thawing processes of the active layer and (iii) simulate the impact of snow cover on permafrost presence.

  18. X-ray absorption spectroscopy study of parent misfit-layered cobalt oxide [Sr₂O₂]q}CoO₂

    SciTech Connect

    Chou, Ta-Lei; Chan, Ting-Shan; Chen, Jin-Ming; Yamauchi, Hisao; Karppinen, Maarit

    2013-06-01

    Here we present a comprehensive X-ray absorption spectroscopy study carried out at Co-L₂,₃, Co-K, O-K and Sr-K edges for the parent misfit-layered cobalt oxide phase [Sr₂O₂]₀.₅₂CoO₂; comparison is made to another misfit-layered oxide [CoCa₂O₃]₀.₆₂CoO₂ and the perovskite oxide LaCoO₃. A high-quality sample of [Sr₂O₂]₀.₅₂CoO₂ was obtained through ultra-high-pressure synthesis using Sr₃Co₂O₆ and Sr(OH)₂∙8H₂O as starting materials. Different dosages of KClO₃ were mixed with the raw materials as an oxygen source and tested, but it was found that the window for the redox control of [Sr₂O₂]₀.₅₂CoO₂ is rather narrow. From Co-K and Co-L₂,₃ spectra a mixed III/IV valence state is revealed for cobalt in [Sr₂O₂]₀.₅₂}CoO₂, but the average valence value is a little lower than in [CoCa₂O₃]₀.₆₂CoO₂. Then, Sr-K spectrum indicates that the [Sr₂O₂] double-layer block in [Sr₂O₂]₀.₅₂CoO₂ clearly deviates from the cubic SrO rock-salt structure, suggesting a more complicated coordination environment for strontium. This together with a somewhat low Co-valence value and the fact that the phase formation of [Sr₂O₂]₀.₅₂CoO₂ required the presence of Sr(OH)₂∙8H₂O in the high-pressure synthesis suggest that the [Sr₂O₂] block contains ---OH groups, i.e. [Sr₂(O,OH)₂]₀.₅₂CoO₂. - Graphical abstract: [Sr₂O₂]₀.₅₂CoO₂ obtained through high-pressure synthesis is a parent of misfit-layered cobalt oxides, such as [CoCa₂O₃]₀.₆₂CoO₂ or [MmA₂O2+m]qCoO₂ in general. Our comprehensive X-ray absorption spectroscopy study shows that both [Sr₂O₂]₀.₅₂CoO₂ and [CoCa₂O₃]₀.₆₂CoO₂ possess mixed III/IV valence cobalt, but the average Co-valence is a little lower in the former. This is tentatively believed to be due to OH--- groups replacing part of O²⁻ ions in the [Sr

  19. Estimating organic micro-pollutant removal potential of activated carbons using UV absorption and carbon characteristics.

    PubMed

    Zietzschmann, Frederik; Altmann, Johannes; Ruhl, Aki Sebastian; Dünnbier, Uwe; Dommisch, Ingvild; Sperlich, Alexander; Meinel, Felix; Jekel, Martin

    2014-06-01

    Eight commercially available powdered activated carbons (PAC) were examined regarding organic micro-pollutant (OMP) removal efficiencies in wastewater treatment plant (WWTP) effluent. PAC characteristic numbers such as B.E.T. surface, iodine number and nitrobenzene number were checked for their potential to predict the OMP removal of the PAC products. Furthermore, the PAC-induced removal of UV254 nm absorption (UVA254) in WWTP effluent was determined and also correlated with OMP removal. None of the PAC characteristic numbers can satisfactorily describe OMP removal and accordingly, these characteristics have little informative value on the reduction of OMP concentrations in WWTP effluent. In contrast, UVA254 removal and OMP removal correlate well for carbamazepine, diclofenac, and several iodinated x-ray contrast media. Also, UVA254 removal can roughly describe the average OMP removal of all measured OMP, and can accordingly predict PAC performance in OMP removal. We therefore suggest UVA254 as a handy indicator for the approximation of OMP removal in practical applications where direct OMP concentration quantification is not always available. In continuous operation of large-scale plants, this approach allows for the efficient adjustment of PAC dosing to UVA254, in order to ensure reliable OMP removal whilst minimizing PAC consumption. PMID:24651017

  20. In-situ X-Ray Absorption Spectroscopy (XAS) Investigation of a Bifunctional Manganese Oxide Catalyst with High Activity for Electrochemical Water Oxidation and Oxygen Reduction

    PubMed Central

    Benck, Jesse D.; Gul, Sheraz; Webb, Samuel M.; Yachandra, Vittal K.; Yano, Junko; Jaramillo, Thomas F.

    2013-01-01

    In-situ x-ray absorption spectroscopy (XAS) is a powerful technique that can be applied to electrochemical systems, with the ability to elucidate the chemical nature of electrocatalysts under reaction conditions. In this study, we perform in-situ XAS measurements on a bifunctional manganese oxide (MnOx) catalyst with high electrochemical activity for the oxygen reduction reaction (ORR) and the oxygen evolution reaction (OER). Using x-ray absorption near edge structure (XANES) and extended x-ray absorption fine structure (EXAFS), we find that exposure to an ORR-relevant potential of 0.7 V vs. RHE produces a disordered Mn3II,III,IIIO4 phase with negligible contributions from other phases. After the potential is increased to a highly anodic value of 1.8 V vs. RHE, relevant to the OER, we observe an oxidation of approximately 80% of the catalytic thin film to form a mixed MnIII,IV oxide, while the remaining 20% of the film consists of a less oxidized phase, likely corresponding to unchanged Mn3II,III,IIIO4. XAS and electrochemical characterization of two thin film catalysts with different MnOx thicknesses reveals no significant influence of thickness on the measured oxidation states, at either ORR or OER potentials, but demonstrates that the OER activity scales with film thickness. This result suggests that the films have porous structure, which does not restrict electrocatalysis to the top geometric layer of the film. As the portion of the catalyst film that is most likely to be oxidized at the high potentials necessary for the OER is that which is closest to the electrolyte interface, we hypothesize that the MnIII,IV oxide, rather than Mn3II,III,IIIO4, is the phase pertinent to the observed OER activity. PMID:23758050

  1. Effects of xylitol on carbohydrate digesting enzymes activity, intestinal glucose absorption and muscle glucose uptake: a multi-mode study.

    PubMed

    Chukwuma, Chika Ifeanyi; Islam, Md Shahidul

    2015-03-01

    The present study investigated the possible mechanism(s) behind the effects of xylitol on carbohydrate digesting enzymes activity, muscle glucose uptake and intestinal glucose absorption using in vitro, ex vivo and in vivo experimental models. The effects of increasing concentrations of xylitol (2.5%-40% or 164.31 mM-2628.99 mM) on alpha amylase and alpha glucosidase activity in vitro and intestinal glucose absorption and muscle glucose uptake were investigated under ex vivo conditions. Additionally, the effects of an oral bolus dose of xylitol (1 g per kg BW) on gastric emptying and intestinal glucose absorption and digesta transit in the different segments of the intestinal tract were investigated in normal and type 2 diabetic rats at 1 hour after dose administration, when phenol red was used as a recovery marker. Xylitol exhibited concentration-dependent inhibition of alpha amylase (IC₅₀ = 1364.04 mM) and alpha glucosidase (IC₅₀ = 1127.52 mM) activity in vitro and small intestinal glucose absorption under ex vivo condition. Xylitol also increased dose dependent muscle glucose uptake with and without insulin, although the uptake was not significantly affected by the addition of insulin. Oral single bolus dose of xylitol significantly delayed gastric emptying, inhibited intestinal glucose absorption but increased the intestinal digesta transit rate in both normal and diabetic rats compared to their respective controls. The data of this study suggest that xylitol reduces intestinal glucose absorption via inhibiting major carbohydrate digesting enzymes, slowing gastric emptying and fastening the intestinal transit rate, but increases muscle glucose uptake in normal and type 2 diabetic rats. PMID:25656339

  2. The Role of Organic Capping Layers of Platinum Nanoparticles in Catalytic Activity of CO Oxidation

    SciTech Connect

    Park, Jeong Y.; Aliaga, Cesar; Renzas, J. Russell; Lee, Hyunjoo; Somorjai, Gabor A.

    2008-12-17

    We report the catalytic activity of colloid platinum nanoparticles synthesized with different organic capping layers. On the molecular scale, the porous organic layers have open spaces that permit the reactant and product molecules to reach the metal surface. We carried out CO oxidation on several platinum nanoparticle systems capped with various organic molecules to investigate the role of the capping agent on catalytic activity. Platinum colloid nanoparticles with four types of capping layer have been used: TTAB (Tetradecyltrimethylammonium Bromide), HDA (hexadecylamine), HDT (hexadecylthiol), and PVP (poly(vinylpyrrolidone)). The reactivity of the Pt nanoparticles varied by 30%, with higher activity on TTAB coated nanoparticles and lower activity on HDT, while the activation energy remained between 27-28 kcal/mol. In separate experiments, the organic capping layers were partially removed using ultraviolet light-ozone generation techniques, which resulted in increased catalytic activity due to the removal of some of the organic layers. These results indicate that the nature of chemical bonding between organic capping layers and nanoparticle surfaces plays a role in determining the catalytic activity of platinum colloid nanoparticles for carbon monoxide oxidation.

  3. Nanoemulsion strategy for olmesartan medoxomil improves oral absorption and extended antihypertensive activity in hypertensive rats.

    PubMed

    Gorain, Bapi; Choudhury, Hira; Kundu, Amit; Sarkar, Lipi; Karmakar, Sanmoy; Jaisankar, P; Pal, Tapan Kumar

    2014-03-01

    Olmesartan medoxomil (OM) is hydrolyzed to its active metabolite olmesartan by the action of aryl esterase to exert its antihypertensive actions by selectively blocking angiotensin II-AT1 receptor. Poor aqueous solubility and uncontrolled enzymatic conversion of OM to its poorly permeable olmesartan limits its oral bioavailability. The aim of the current study was to formulate a novel nanoemulsion of OM to improve its pharmacokinetics and therapeutic efficacy. The oil-in-water (o/w) nanoemulsion of OM was developed using lipoid purified soybean oil 700, sefsol 218 and solutol HS 15. We have characterized the nanoemulsions by considering their thermodynamic stability, morphology, droplet size, zeta potential and viscosity and in vitro drug release characteristics in fasting state simulated gastric fluid (pH 1.2) and intestinal fluid (pH 6.5). The thermodynamically stable nanoemulsions comprises of spherical nanometer sized droplets (<50 nm) with low polydispersity index showed enhanced permeability through the Caco-2 cell monolayer. The concentration of active olmesartan in rat plasma following oral absorption study was determined by our validated LC-MS/MS method. The result of the pharmacokinetic study showed 2.8-fold increased in area under the curve (AUC0-27) of olmesartan upon oral administration of OM nanoemulsion and sustained release profile. Subsequent, in vivo studies with nanoemulsion demonstrated better and prolonged control of experimentally induced hypertension with 3-fold reduction in conventional dose. By analysing the findings of the present investigations based on stability study, Caco-2 permeability, pharmacokinetic profile and pharmacodynamic evaluation indicated that the nanoemulsion of OM (OMF6) could significantly enhance the oral bioavailability of relatively insoluble OM contributing to improved clinical application. PMID:24388859

  4. Application of Satellite SAR Imagery in Mapping the Active Layer of Arctic Permafrost

    NASA Technical Reports Server (NTRS)

    Li, Shu-Sun; Romanovsky, V.; Lovick, Joe; Wang, Z.; Peterson, Rorik

    2003-01-01

    A method of mapping the active layer of Arctic permafrost using a combination of conventional synthetic aperture radar (SAR) backscatter and more sophisticated interferometric SAR (INSAR) techniques is proposed. The proposed research is based on the sensitivity of radar backscatter to the freeze and thaw status of the surface soil, and the sensitivity of INSAR techniques to centimeter- to sub-centimeter-level surface differential deformation. The former capability of SAR is investigated for deriving the timing and duration of the thaw period for surface soil of the active layer over permafrost. The latter is investigated for the feasibility of quantitative measurement of frost heaving and thaw settlement of the active layer during the freezing and thawing processes. The resulting knowledge contributes to remote sensing mapping of the active layer dynamics and Arctic land surface hydrology.

  5. Dynamics of the Thermal State of Active Layer at the Alaska North Slope and Northern Yakutia

    NASA Astrophysics Data System (ADS)

    Kholodov, A. L.; Romanovsky, V. E.; Marchenko, S.; Shiklomanov, N. I.; Fedorov-Davydov, D.

    2010-12-01

    Dynamics of the active layer is one of the most important indexes, reflecting permafrost response to the modern climate changes. Monitoring of active layer thickness dynamics is the main goal of CALM (Circumpolar Active Layer Monitoring) project. But, from different points of view, it is very important to know not only maximal depth of seasonal thawing but also dynamics of thermal field of active layer and duration of its staying in the unfrozen state. Current research was aimed on the analyzing data of temperature measurements have been done during the more then 10 years at the North Slope of Brooks Range (Alaska) and 2 years at the selected sites at the Northern Yakutia (Russia) and its comparison with the 17 to 10 years records of active layer thickness dynamics at the corresponding sites (http://www.udel.edu/Geography/calm/data/north.html). The area of investigation characterized by the typical tundra landscape and different kinds of micro topography. Reported observation sites located at the latitudinal range from 68.5 to 70.3N in Alaska and 70.5 to 71.75N in the Northern Yakutia. Observation have been done using the 1 meter long MRC probe with 11 sensors (every 10 cm) and single Campbell SCI A107 sensors in Alaska and 2-channel HOBO U23 data loggers with TMC-HD thermistors in the Northern Yakutia. Analyses of CALM data show what most observation sites in Alaska (except located near the Brooks Range and at the Arctic Ocean coast) do not subjected to the significant sustainable changes of active layer thickness over the last 10 years. At the same time active layer thickness at the Yakutian sites was increasing. Temperature observations show decreasing of the mean annual temperature at the average depth of active layer bottom at the Alaskan sites. But, because of general trend to increasing of period of thawing it does not lead to the decreasing of active layer thickness. Recent equipment deployment at the Tiksi and Allaikha sites (Northern Yakutia) does not

  6. Improving ice nucleation activity of zein film through layer-by-layer deposition of extracellular ice nucleators.

    PubMed

    Shi, Ke; Yu, Hailong; Lee, Tung-Ching; Huang, Qingrong

    2013-11-13

    Zein protein has been of scientific interest in the development of biodegradable functional food packaging. This study aimed at developing a novel zein-based biopolymer film with ice nucleation activity through layer-by-layer deposition of biogenic ice nucleators, that is, extracellular ice nucleators (ECINs) isolated from Erwinia herbicola , onto zein film surface. The adsorption behaviors and mechanisms were investigated using quartz crystal microbalance with dissipation monitoring (QCM-D). On unmodified zein surface, the highest ECINs adsorption occurred at pH 5.0; on UV/ozone treated zein surface followed by deposition of poly(diallyldimethylammonium chloride) (PDADMAC) layer, the optimum condition for ECINs adsorption occurred at pH 7.0 and I 0.05 M, where the amount of ECINs adsorbed was also higher than that on unmodified zein surface. QCM-D analyses further revealed a two-step adsorption process on unmodified zein surfaces, compared to a one-step adsorption process on PDADMAC-modified zein surface. Also, significantly, in order to quantify the ice nucleation activity of ECINs-coated zein films, an empirical method was developed to correlate the number of ice nucleators with the ice nucleation temperature measured by differential scanning calorimetry. Calculated using this empirical method, the highest ice nucleation activity of ECINs on ECINs-modified zein film reached 64.1 units/mm(2), which was able to elevate the ice nucleation temperature of distilled water from -15.5 °C to -7.3 °C. PMID:24106783

  7. Highly sensitive multi-layer pressure sensor with an active nanostructured layer of an organic molecular metal

    NASA Astrophysics Data System (ADS)

    Laukhin, V.; Lebedev, V.; Laukhina, E.; Rovira, C.; Veciana, J.

    2016-03-01

    This work addresses to the modern technologies that need to be instrumented with lightweight highly sensitive pressure sensors. The paper presents the development of a new plain flexible thin pressure sensor using a nanostructured layer of the highly sensitive organic piezoresistive metal β-(BEDT-TTF)2I3 as an active component; BEDT-TTF=bis (ethylenedithio)tetrathiafulvalene. The original construction approach permits one to operate the developed sensor on the principle of electrical resistance variations when its piezoresistive layer is elongated under a pressure increase. The pressure sensing element and a set of gold electrodes were integrated into one compact multi-layer design. The construction was optimized to enable one generic design for pressure ranges from 1 to 400 bar. The pressure tests showed that the sensor is able to control a small pressure change as a well definite electrical signal. So the developed type of the sensors is very attractive as a new generation of compact, lightweight, low-cost sensors that might monitor pressure with a good level of measurement accuracy.

  8. Crystallinity Modulation of Layered Carbon Nitride for Enhanced Photocatalytic Activities.

    PubMed

    Wang, Jianhai; Shen, Yanfei; Li, Ying; Liu, Songqin; Zhang, Yuanjian

    2016-08-22

    As an emerging metal-free semiconductor, covalently bonded carbon nitride (CN) has attracted much attention in photocatalysis. However, drawbacks such as a high recombination rate of excited electrons and holes hinder its potential applications. Tailoring the crystallinity of semiconductors is an important way to suppress unwanted charge recombination, but has rarely been applied to CN so far. Herein, a simple method to synthesize CN of high crystallinity by protonation of specific intermediate species during conventional polymerization is reported. Interestingly, the as-obtained CN exhibited improved photocatalytic activities of up to seven times those of the conventional bulk CN. This approach, with only a slight change to the conventional method, provides a facile way to effectively regulate the crystallinity of bulk CN to improve its photocatalytic activities and sheds light on large-scale industrial applications of CN with high efficiency for sustainable energy. PMID:27436164

  9. An active control system for the turbulent boundary layer

    NASA Astrophysics Data System (ADS)

    Lew, James

    This thesis presents the development process and the experimental results of a system constructed to apply real-time control to the structures of the turbulent boundary layer region in order to reduce surface shear stress. The system is composed of three main components: an array of MEMS surface shear stress, tauw sensors; a MEMS flap actuator; and a control logic which integrates the hardware components together into a closed system. The objective of this system is to reduce the stress contained in streak-like regions of high tauw. The sensor array, used to image the tauw distribution, is an extension of the thermal based tauw sensor developed by Jiang. Numerous studies have been performed using this device, the results of which have validated its performance. For this study, a new temperature compensation methodology, based on the surface temperature of the sensor chip, was employed in order to account for possible temperature variations at the wall surface. The actuator, a pneumatically driven flap, is developed as part of the present research. The device is, in essence, a 3 mm x 1 mm cantilever beam that sits on top of an inflatable diaphragm and is capable of actuation frequencies of over 200 Hz and amplitudes of over .11 mm. When it is oscillated in the open loop mode, the effect over one cycle of motion is an average reduction by as much as 2.5% in tauw in the region immediately downstream. A neural network is employed to identify the streak-like regions of interest. Results have shown that this network is successful in identifying the streak-like regions of interest. The control logic employs this network in a predictive, feed-forward scheme to determine the appropriate actuator response. Offline studies have shown that under optimal conditions, the signature of the streak-like regions can be eliminated. Online results conform well to the offline predictions. While unable to achieve the optimal conditions, online experiments show that the system is capable

  10. An investigation of catalytic active phase-support interactions by IR, NMR and x-ray absorption spectroscopies

    SciTech Connect

    Haller, G.L.

    1992-09-01

    Active catalytic phases (metal, mixed metals, oxide or mixed oxides) interacting with oxide support on which the active phase is dispersed can affect the percentage exposed, the morphology of supported particles, the degree of reducibility of cations, etc., in a variety of ways. Our objective is to characterize the physical chemistry of the active phase-oxide support interaction by spectroscopic methods and to correlate this structure with catalytic function. Two catalytic systems and their associated techniques (x-ray absorption and NMR) are discussed in this progress report. Firstly, the interaction of Pt-Ni supported on silica and L-zeolite are characterized and compared by x-ray absorption spectroscopy (EXAFS). Secondly, we present both experimental and calculational developments of NMR for the investigation of amorphous silica-alumina catalysts and/or supports.

  11. Contribution of S-Layer Proteins to the Mosquitocidal Activity of Lysinibacillus sphaericus

    PubMed Central

    Allievi, Mariana Claudia; Palomino, María Mercedes; Prado Acosta, Mariano; Lanati, Leonardo; Ruzal, Sandra Mónica; Sánchez-Rivas, Carmen

    2014-01-01

    Lysinibacillus sphaericus strains belonging the antigenic group H5a5b produce spores with larvicidal activity against larvae of Culex mosquitoes. C7, a new isolated strain, which presents similar biochemical characteristics and Bin toxins in their spores as the reference strain 2362, was, however, more active against larvae of Culex mosquitoes. The contribution of the surface layer protein (S-layer) to this behaviour was envisaged since this envelope protein has been implicated in the pathogenicity of several bacilli, and we had previously reported its association to spores. Microscopic observation by immunofluorescence detection with anti S-layer antibody in the spores confirms their attachment. S-layers and BinA and BinB toxins formed high molecular weight multimers in spores as shown by SDS-PAGE and western blot detection. Purified S-layer from both L. sphaericus C7 and 2362 strain cultures was by itself toxic against Culex sp larvae, however, that from C7 strain was also toxic against Aedes aegypti. Synergistic effect between purified S-layer and spore-crystal preparations was observed against Culex sp. and Aedes aegypti larvae. This effect was more evident with the C7 strain. In silico analyses of the S-layer sequence suggest the presence of chitin-binding and hemolytic domains. Both biochemical characteristics were detected for both S-layers strains that must justify their contribution to pathogenicity. PMID:25354162

  12. Evidence for Active Galactic Nucleus Feedback in the Broad Absorption Lines and Reddening of Mrk 231

    NASA Astrophysics Data System (ADS)

    Leighly, Karen M.; Terndrup, Donald M.; Baron, Eddie; Lucy, Adrian B.; Dietrich, Matthias; Gallagher, Sarah C.

    2014-06-01

    We present the first J-band spectrum of Mrk 231, which reveals a large He I* λ10830 broad absorption line with a profile similar to that of the well-known Na I broad absorption line. Combining this spectrum with optical and UV spectra from the literature, we show that the unusual reddening noted by Veilleux et al. is explained by a reddening curve like those previously used to explain low values of total-to-selective extinction in Type Ia supernovae. The nuclear starburst may be the origin and location of the dust. Spatially resolved emission in the broad absorption line trough suggests nearly full coverage of the continuum emission region. The broad absorption lines reveal higher velocities in the He I* lines (produced in the quasar-photoionized H II region) compared with the Na I and Ca II lines (produced in the corresponding partially ionized zone). Cloudy simulations show that a density increase is required between the H II and partially ionized zones to produce ionic column densities consistent with the optical and IR absorption line measurements and limits, and that the absorber lies ~100 pc from the central engine. These results suggest that the He I* lines are produced in an ordinary quasar BAL wind that impacts upon, compresses, and accelerates the nuclear starburst's dusty effluent (feedback in action), and the Ca II and Na I lines are produced in this dusty accelerated gas. This unusual circumstance explains the rarity of Na I absorption lines; without the compression along our line of sight, Mrk 231 would appear as an ordinary iron low-ionization, broad absorption line quasar.

  13. Photo-degradation in air of the active layer components in a thiophene-quinoxaline copolymer:fullerene solar cell.

    PubMed

    Hansson, Rickard; Lindqvist, Camilla; Ericsson, Leif K E; Opitz, Andreas; Wang, Ergang; Moons, Ellen

    2016-04-28

    We have studied the photo-degradation in air of a blend of [6,6]-phenyl-C61-butyric acid methyl ester (PCBM) and poly[2,3-bis-(3-octyloxyphenyl)quinoxaline-5,8-diyl-alt-thiophene-2,5-diyl] (TQ1), and how the photo-degradation affects the solar cell performance. Using near-edge X-ray absorption fine structure (NEXAFS) spectroscopy, changes to the electronic structure of TQ1 and PCBM caused by illumination in ambient air are investigated and compared between the pristine materials and the blend. The NEXAFS spectra show that the unoccupied molecular orbitals of TQ1 are not significantly changed by the exposure of pristine TQ1 to light in air, whereas those of PCBM are severely affected as a result of photo-induced degradation of PCBM. Furthermore, the photo-degradation of PCBM is accelerated by blending it with TQ1. While the NEXAFS spectrum of TQ1 remains unchanged upon illumination in air, its valence band spectrum shows that the occupied molecular orbitals are weakly affected. Yet, UV-Vis absorption spectra demonstrate photo-bleaching of TQ1, which is attenuated in the presence of PCBM in blend films. Illumination of the active layer of TQ1:PCBM solar cells prior to cathode deposition causes severe losses in electrical performance. PMID:27051887

  14. [THE EFFECT OF SATINS: ACTIVATION OF LIPOLYSIS AND ABSORPTION BY INSULIN-DEPENDED CELLS LIPOPROTEINS OF VERY LOW DENSITY, INCREASING OF BIO-AVAILABILITY OF POLYENOIC FATTY ACIDS AND DECREASING OF CHOLESTEROL OF LIPOPROTEINS OF LOW DENSITY].

    PubMed

    Titov, V N; Malyshev, P P; Amelyushkina, V A; Aripovsky, A V; Smirnov, G P; Polevaya, T Yu; Kabo, S I; Kukhartchuk, V V

    2015-10-01

    The Russian cardiologic R&D production complex of Minzdrav of Russia, 121552 Moscow, Russia The statins are synthetic xenobiotics alien to animal cells. They are unlikely capable to manifest pleiotropic effect. It is feasible to evaluate effect of statins by stages: a) initially a specific inhibition of synthesis of cholesterol alcohol; b) further indirect activation of hydrolysis of triglycerides in lipoproteins of very low density; c) nonspecific activation of cells' receptor absorption of palmitic and oleic lipoproteins of very low density and then d) linoleic and linolenic lipoproteins of low density with all polyenoic fatty acids. On balance, statins activate absorption ofpolyenoic fatty acids by cells. Just they manifest physiological, specific pleiotropic effect. The statins inhibit synthesis of pool of cholesterol alcohol-lipoproteins of very low density condensed between phosphatidylcholines in polar mono-layer phosphatidylcholines+cholesterol alcohol on surface oftriglycerides. The low permeability of mono-layer separates substrate-triglycerides in lipoproteins of very low density and post-heparin lipoprotein lipase in hydrophilic blood plasma. The higher is ratio cholesterol alcohol/phosphatidylcholines in mono-layer of lipoproteins of very low density the slower is lipolysis, formation of ligand lipoproteins of very low density and their absorption by cells under apoB-100-endocytosis. The statins normalize hyperlipemia by force of a) activation of absorption oflipoproteins of very low density by insulin-depended cells and b) activation of absorption of lipoproteins of low density by all cells, increasing of bio-availability of polyenoic fatty acids, activation of apoB-100-endocytosis. The limitation in food of content of palmitic saturated fatty acid and increasing of content of ω-3 polyenoic fatty acids improve "bio-availability" of polyenoic fatty acids and their absorption by cells and also decreases cholesterol alcohol/phosphatidylcholines and

  15. Photocatalytic activity of porous multiwalled carbon nanotube-TiO2 composite layers for pollutant degradation.

    PubMed

    Zouzelka, Radek; Kusumawati, Yuly; Remzova, Monika; Rathousky, Jiri; Pauporté, Thierry

    2016-11-01

    TiO2 nanoparticles are suitable building blocks nanostructures for the synthesis of porous functional thin films. Here we report the preparation of films using brookite, P25 titania and anatase pristine nanoparticles and of nanocomposite layers combining anatase nanoparticles and multi-walled carbon nanotube (MWCNT) at various concentrations. The structure and phase composition of the layers were characterized by X-ray diffraction and Raman spectroscopy. Their morphology and texture properties were determined by scanning electron microscopy and krypton adsorption experiments, respectively. Additionally to a strong absorption in the UV range, the composites exhibited light absorption in the visible range as well. The photocatalytic performance of the layers was tested in the degradation of aqueous solutions of 4-chlorophenol serving as a model of an eco-persistent pollutant. Besides the determination of the decrease in the concentration of 4-chlorophenol, also the formation of intermediate degradation products, namely hydroquinone and benzoquinone, was followed. The presence of MWCNTs had a beneficial effect on the photocatalytic performance, a marked increase in the photocatalytic degradation rate constant being observed even at very low concentrations of MWCNTs. Compared to a P25 reference layer, the first order rate reaction constant increased by about 100% for the composite films containing MWCNTs at concentrations above 0.6 wt%. The key parameters for the enhancement of the photocatalytic performance are discussed. The presence of carbon nanotubes influences beneficially the degradation of 4-chlorophenol by an attack of the primarily photoproduced hydroxyl radicals onto the 4-chlorophenol molecules. The degradation due to the direct charge transfer is practically not influenced at all. PMID:27262272

  16. Structure and infrared absorption of the first layer C2H2 on the NaCl(100) single-crystal surface.

    PubMed

    Cabello-Cartagena, A G; Vogt, J; Weiss, H

    2010-02-21

    The adsorbate structure of the first layer acetylene on the NaCl(100) single-crystal surface is investigated using polarization infrared spectroscopy in combination with low-energy electron diffraction (LEED) experiments, and potential calculations on the basis of pair potentials. In agreement with a previous study, a triplet of infrared absorptions in the region of the asymmetric stretch vibration of C(2)H(2) was observed and assigned to an adsorbate phase with (3 square root 2 x square root 2)R45 degrees translational symmetry determined in the LEED experiment. The polarization dependence of the infrared spectra is consistent with a parallel orientation of the molecules with respect to the surface. The number of molecules per unit cell is four to six as determined by photometric considerations. Total energy minimizations support a new structure model which contains five inequivalent molecules per unit cell in a herringbone arrangement. The application of a vibrational exciton approach demonstrates that this new structure model can reproduce the triplet spectrum observed in the infrared experiments. PMID:20170243

  17. Statistical effects in the absorption and optical activity of particulate suspensions.

    PubMed Central

    Bustamante, C; Maestre, M F

    1988-01-01

    The phenomenon of Duysens flattening of the absorption spectra resulting from the inhomogeneous distribution of the chromophores in the solution is analyzed. These inhomogeneities are treated as localized statistical fluctuations in the concentration of the absorbing species, by using the Gaussian distribution. A law of absorbance is obtained, and the effect of light scattering on the flattening is also characterized. The flattening in the circular dichroism spectra of particulate suspensions is then analyzed. It is shown that the degree of flattening of the circular dichroism of a suspension is, in general, different from the corresponding flattening of its absorption spectrum. A quantitative relationship between the two effects is established. PMID:3186738

  18. X-ray absorption spectroscopy study of parent misfit-layered cobalt oxide [Sr2O2]qCoO2

    NASA Astrophysics Data System (ADS)

    Chou, Ta-Lei; Chan, Ting-Shan; Chen, Jin-Ming; Yamauchi, Hisao; Karppinen, Maarit

    2013-06-01

    Here we present a comprehensive X-ray absorption spectroscopy study carried out at Co-L2,3, Co-K, O-K and Sr-K edges for the parent misfit-layered cobalt oxide phase [Sr2O2]0.52CoO2; comparison is made to another misfit-layered oxide [CoCa2O3]0.62CoO2 and the perovskite oxide LaCoO3. A high-quality sample of [Sr2O2]0.52CoO2 was obtained through ultra-high-pressure synthesis using Sr3Co2O6 and Sr(OH)2•8H2O as starting materials. Different dosages of KClO3 were mixed with the raw materials as an oxygen source and tested, but it was found that the window for the redox control of [Sr2O2]0.52CoO2 is rather narrow. From Co-K and Co-L2,3 spectra a mixed III/IV valence state is revealed for cobalt in [Sr2O2]0.52CoO2, but the average valence value is a little lower than in [CoCa2O3]0.62CoO2. Then, Sr-K spectrum indicates that the [Sr2O2] double-layer block in [Sr2O2]0.52CoO2 clearly deviates from the cubic SrO rock-salt structure, suggesting a more complicated coordination environment for strontium. This together with a somewhat low Co-valence value and the fact that the phase formation of [Sr2O2]0.52CoO2 required the presence of Sr(OH)2•8H2O in the high-pressure synthesis suggest that the [Sr2O2] block contains OH groups, i.e. [Sr2(O,OH)2]0.52CoO2.

  19. Multi-Molar Absorption of CO2 by the Activation of Carboxylate Groups in Amino Acid Ionic Liquids.

    PubMed

    Chen, Feng-Feng; Huang, Kuan; Zhou, Yan; Tian, Zi-Qi; Zhu, Xiang; Tao, Duan-Jian; Jiang, De-En; Dai, Sheng

    2016-06-13

    A new strategy for multi-molar absorption of CO2 is reported based on activating a carboxylate group in amino acid ionic liquids. It was illustrated that introducing an electron-withdrawing site to amino acid anions could reduce the negative inductive effect of the amino group while simultaneously activating the carboxylate group to interact with CO2 very efficiently. An extremely high absorption capacity of CO2 (up to 1.69 mol mol(-1) ) in aminopolycarboxylate-based amino acid ionic liquids was thus achieved. The evidence of spectroscopic investigations and quantum-chemical calculations confirmed the interactions between two kinds of sites in the anion and CO2 that resulted in superior CO2 capacities. PMID:27136274

  20. Interannual active layer thermal and dynamics evolution at the crater Lake CALM site, Deception Island (Antarctica).

    NASA Astrophysics Data System (ADS)

    Ramos, Miguel; Vieira, Gonzalo; Ángel De Pablo, Miguel; Molina, Antonio; Abramov, Andrey

    2015-04-01

    Deception Island, is an active strato-volcano on South Shetland Archipelago of Antarctica (62° 55' 0″ S, 60° 37' 0″ W), is a cold region with harsh remote and hostile environmental conditions. The permafrost and active layer existence, and the cold climate conditions together with volcanic material with height water content inside made this region of the Earth a perfect site to study the active layer and permafrost evolution involved in the Circumpolar Active Layer South (CALM-S) program. The active layer is measured in late January or firs february (during the end of the thaw period) at the "Crater Lake" CALM site (62°58'06.7''; 60°40'44.8'') on Deception Island, Antarctica, at the period 2006 to 2014 we obtained a mean annual value of 29,7±2 cm. In this paper, we describe the spatial active layer thickness distribution and report the reduction on the mean thickness between February 2006 and 2014. Below the active layer, permafrost could be also reported (with a mean thickness of 4.5± 0.5 m.) based on the temperature data acquired by sensors installed at different depth inside the soil; three different shallow boreholes was drilled (1.0 m., 1.6 m., 4.5 m. in depth) and we have been registered its temperature gradient at the 2010 to 2013 period. Here we use all those data 1) to describe the thermal behavior of the permafrost at the CALM site, and 2) to describe its evolution (aggradation/degradation) along fourteen years of continuous measurements. We develop this study, to known the thermal behavior of the permafrost and the active layer related with the air/soil interaction being one of the most important factors the snow layer that was measured by the installation of termo-snowmeters with the complement of an automatic digital camera during the 2008 to 2014 period. On the other hand, the pyroclastics soil materials has a very high values of water content then the latent heat in the freezing/thawing process controls the active layer evolution and the

  1. Efficient and Long-Lived Green Light-Emitting Diodes Based on ZnSSe:Te Active Layer

    NASA Astrophysics Data System (ADS)

    Lee, Hong Chan; Abe, Tomoki; Kaneko, Nobumasa; Adachi, Masahiro; Watanabe, Masashi; Fujita, Yusuke; Kasada, Hirofumi; Ando, Koshi

    2002-03-01

    Detailed optical characteristics of excitonic green emission/absorption in ZnSSe:Te epitaxial layers, grown by molecular beam epitaxy, were studied by photoluminescence (PL) and PL excitation measurements. Based on these optical properties, we have developed bright and long-lived green (˜500 nm) light-emitting diodes (LEDs) using ZnS0.11Se0.85:Te0.04 epilayers as active layers. The ZnSSe:Te-based LEDs exhibit a fairly long device lifetime (>2000 h) when operated at 3 A/cm2 under CW condition at room temperature. The green LEDs show only slow-mode degradation, and the degradation mode is quite different from that of II-VI-based laser diodes (LDs) and LEDs employing the ZnCdSe-ZnSe system. It is confirmed that the Te-doping-induced “alloy-hardening effect” plays an important role in both efficient emission and strong suppression of the device degradation.

  2. Poor permeability and absorption affect the activity of four alkaloids from Coptis.

    PubMed

    Cui, Han-Ming; Zhang, Qiu-Yan; Wang, Jia-Long; Chen, Jian-Long; Zhang, Yu-Ling; Tong, Xiao-Lin

    2015-11-01

    Coptidis rhizoma (Coptis) and its alkaloids exert various pharmacological functions in cells and tissues; however, the oral absorption of these alkaloids requires further elucidation. The present study aimed to examine the mechanism underlying the poor absorption of alkaloids, including berberine (BER), coptisine (COP), palmatine (PAL) and jatrorrhizine (JAT). An ultra‑performance liquid chromatography (UPLC) method was validated for the determination of BER, COP, PAL and JAT in the above experimental medium. In addition, the apparent oil‑water partition coefficient (Po/w); apparent permeability coefficient (Papp), determined using a parallel artificial membrane permeability assay (PAMPA) plate; membrane retention coefficient (R %); and effect of P‑glycoprotein (P‑gp) inhibitor on the Papp of the four alkaloids were investigated. The intestinal absorption rate constant (Ka) and absorption percentage (A %) of the four alkaloids were also determined. The results of the present study demonstrated that the Po/w of the four alkaloids in 0.1 mol·l‑1 HCl medium was significantly higher (P<0.01), compared with those of the alkaloids in phosphate buffer (pH 7.4). The Papp of BER was 1.0‑1.2x10‑6 cm·s‑1, determined using a PAMPA plate, and the Papp of BER, COP, PAL and JAT decreased sequentially. The concentrations of the four alkaloids on the apical‑to‑basolateral (AP‑BL) surface and the basolateral‑to‑apical (BL‑AP) surface increased in a linear manner, with increasing concentrations between 10 and 100 µmol. In addition, the transportation of BER on the BL‑AP surface was significantly faster (P<0.01), compared with that on the AP‑BL surface and, following the addition of verpamil (a P‑gp inhibitor), the Papp (AP‑BL) of the four alkaloids increased, whereas the Papp (BL‑AP) was significantly decreased (P<0.01). The rat intestinal perfusion experiment demonstrated that the four alkaloids were poorly absorbed; however, the Ka of BER

  3. Rapid electrostatics-assisted layer-by-layer assembly of near-infrared-active colloidal photonic crystals.

    PubMed

    Askar, Khalid; Leo, Sin-Yen; Xu, Can; Liu, Danielle; Jiang, Peng

    2016-11-15

    Here we report a rapid and scalable bottom-up technique for layer-by-layer (LBL) assembling near-infrared-active colloidal photonic crystals consisting of large (⩾1μm) silica microspheres. By combining a new electrostatics-assisted colloidal transferring approach with spontaneous colloidal crystallization at an air/water interface, we have demonstrated that the crystal transfer speed of traditional Langmuir-Blodgett-based colloidal assembly technologies can be enhanced by nearly 2 orders of magnitude. Importantly, the crystalline quality of the resultant photonic crystals is not compromised by this rapid colloidal assembly approach. They exhibit thickness-dependent near-infrared stop bands and well-defined Fabry-Perot fringes in the specular transmission and reflection spectra, which match well with the theoretical calculations using a scalar-wave approximation model and Fabry-Perot analysis. This simple yet scalable bottom-up technology can significantly improve the throughput in assembling large-area, multilayer colloidal crystals, which are of great technological importance in a variety of optical and non-optical applications ranging from all-optical integrated circuits to tissue engineering. PMID:27494632

  4. Layer-by-layer carbon nanotube bio-templates for in situ monitoring of the metabolic activity of nitrifying bacteria

    NASA Astrophysics Data System (ADS)

    Loh, Kenneth J.; Guest, Jeremy S.; Ho, Genevieve; Lynch, Jerome P.; Love, Nancy G.

    2009-03-01

    Despite the wide variety of effective disinfection and wastewater treatment techniques for removing organic and inorganic wastes, pollutants such as nitrogen remain in wastewater effluents. If left untreated, these nitrogenous wastes can adversely impact the environment by promoting the overgrowth of aquatic plants, depleting dissolved oxygen, and causing eutrophication. Although nitrification/denitrification processes are employed during advanced wastewater treatment, effective and efficient operation of these facilities require information of the pH, dissolved oxygen content, among many other parameters, of the wastewater effluent. In this preliminary study, a biocompatible CNT-based nanocomposite is proposed and validated for monitoring the biological metabolic activity of nitrifying bacteria in wastewater effluent environments (i.e., to monitor the nitrification process). Using carbon nanotubes and a pH-sensitive conductive polymer (i.e., poly(aniline) emeraldine base), a layer-by-layer fabrication technique is employed to fabricate a novel thin film pH sensor that changes its electrical properties in response to variations in ambient pH environments. Laboratory studies are conducted to evaluate the proposed nanocomposite's biocompatibility with wastewater effluent environments and its pH sensing performance.

  5. Dual active layer a-IGZO TFT via homogeneous conductive layer formation by photochemical H-doping

    PubMed Central

    2014-01-01

    In this study, InGaZnO (IGZO) thin film transistors (TFTs) with a dual active layer (DAL) structure are fabricated by inserting a homogeneous embedded conductive layer (HECL) in an amorphous IGZO (a-IGZO) channel with the aim of enhancing the electrical characteristics of conventional bottom-gate-structure TFTs. A highly conductive HECL (carrier concentration at 1.6 × 1013 cm-2, resistivity at 4.6 × 10-3 Ω∙cm, and Hall mobility at 14.6 cm2/Vs at room temperature) is fabricated using photochemical H-doping by irradiating UV light on an a-IGZO film. The electrical properties of the fabricated DAL TFTs are evaluated by varying the HECL length. The results reveal that carrier mobility increased proportionally with the HECL length. Further, a DAL TFT with a 60-μm-long HECL embedded in an 80-μm-long channel exhibits comprehensive and outstanding improvements in its electrical properties: a saturation mobility of 60.2 cm2/Vs, threshold voltage of 2.7 V, and subthreshold slope of 0.25 V/decade against the initial values of 19.9 cm2/Vs, 4.7 V, and 0.45 V/decade, respectively, for a TFT without HECL. This result confirms that the photochemically H-doped HECL significantly improves the electrical properties of DAL IGZO TFTs. PMID:25435832

  6. Carbon nanotubes supported cerium dioxide and platinum nanohybrids: Layer-by-layer synthesis and enhanced electrocatalytic activity for methanol oxidation

    NASA Astrophysics Data System (ADS)

    Lou, Xinyuan; Chen, Jiayi; Wang, Mengdi; Gu, Jialei; Wu, Ping; Sun, Dongmei; Tang, Yawen

    2015-08-01

    We successfully synthesize carbon nanotubes (CNTs) supported cerium dioxide and platinum (Pt/CeO2/CNTs) nanohybrids via layer-by-layer assembly. The composition, morphology and structure of the as-prepared Pt/CeO2/CNTs nanohybrids are characterized by transmission electron microscopy (TEM), energy-dispersive X-ray spectrometer (EDX), selected-area electron diffraction (SAED), X-ray diffraction (XRD), thermogravimetric analysis (TGA), and inductively coupled plasma atomic emission spectrometry (ICP-AES). By comparison of the electrocatalytic properties of the Pt/CeO2/CNTs with the Pt/CNTs, we systematically investigate the promotion effect of CeO2 on the Pt/CeO2/CNTs catalysts towards methanol oxidation. It is found that the introduction of CeO2 not only enhances the electrocatalytic activity and stability of the Pt/CeO2/CNTs catalyst for methanol oxidation but also minimizes the CO poisoning, probably accounting for the good oxygen carrying capacity of CeO2 and its high stability in acidic solution.

  7. Discrete-Layer Piezoelectric Plate and Shell Models for Active Tip-Clearance Control

    NASA Technical Reports Server (NTRS)

    Heyliger, P. R.; Ramirez, G.; Pei, K. C.

    1994-01-01

    The objectives of this work were to develop computational tools for the analysis of active-sensory composite structures with added or embedded piezoelectric layers. The targeted application for this class of smart composite laminates and the analytical development is the accomplishment of active tip-clearance control in turbomachinery components. Two distinct theories and analytical models were developed and explored under this contract: (1) a discrete-layer plate theory and corresponding computational models, and (2) a three dimensional general discrete-layer element generated in curvilinear coordinates for modeling laminated composite piezoelectric shells. Both models were developed from the complete electromechanical constitutive relations of piezoelectric materials, and incorporate both displacements and potentials as state variables. This report describes the development and results of these models. The discrete-layer theories imply that the displacement field and electrostatic potential through-the-thickness of the laminate are described over an individual layer rather than as a smeared function over the thickness of the entire plate or shell thickness. This is especially crucial for composites with embedded piezoelectric layers, as the actuating and sensing elements within these layers are poorly represented by effective or smeared properties. Linear Lagrange interpolation polynomials were used to describe the through-thickness laminate behavior. Both analytic and finite element approximations were used in the plane or surface of the structure. In this context, theoretical developments are presented for the discrete-layer plate theory, the discrete-layer shell theory, and the formulation of an exact solution for simply-supported piezoelectric plates. Finally, evaluations and results from a number of separate examples are presented for the static and dynamic analysis of the plate geometry. Comparisons between the different approaches are provided when

  8. Contrasting effects of strabismic amblyopia on metabolic activity in superficial and deep layers of striate cortex.

    PubMed

    Adams, Daniel L; Economides, John R; Horton, Jonathan C

    2015-05-01

    To probe the mechanism of visual suppression, we have raised macaques with strabismus by disinserting the medial rectus muscle in each eye at 1 mo of age. Typically, this operation produces a comitant, alternating exotropia with normal acuity in each eye. Here we describe an unusual occurrence: the development of severe amblyopia in one eye of a monkey after induction of exotropia. Shortly after surgery, the animal demonstrated a strong fixation preference for the left eye, with apparent suppression of the right eye. Later, behavioral testing showed inability to track or to saccade to targets with the right eye. With the left eye occluded, the animal demonstrated no visually guided behavior. Optokinetic nystagmus was absent in the right eye. Metabolic activity in striate cortex was assessed by processing the tissue for cytochrome oxidase (CO). Amblyopia caused loss of CO in one eye's rows of patches, presumably those serving the blind eye. Layers 4A and 4B showed columns of reduced CO, in register with pale rows of patches in layer 2/3. Layers 4C, 5, and 6 also showed columns of CO activity, but remarkably, comparison with more superficial layers showed a reversal in contrast. In other words, pale CO staining in layers 2/3, 4A, and 4B was aligned with dark CO staining in layers 4C, 5, and 6. No experimental intervention or deprivation paradigm has been reported previously to produce opposite effects on metabolic activity in layers 2/3, 4A, and 4B vs. layers 4C, 5, and 6 within a given eye's columns. PMID:25810480

  9. Contrasting effects of strabismic amblyopia on metabolic activity in superficial and deep layers of striate cortex

    PubMed Central

    Adams, Daniel L.; Economides, John R.

    2015-01-01

    To probe the mechanism of visual suppression, we have raised macaques with strabismus by disinserting the medial rectus muscle in each eye at 1 mo of age. Typically, this operation produces a comitant, alternating exotropia with normal acuity in each eye. Here we describe an unusual occurrence: the development of severe amblyopia in one eye of a monkey after induction of exotropia. Shortly after surgery, the animal demonstrated a strong fixation preference for the left eye, with apparent suppression of the right eye. Later, behavioral testing showed inability to track or to saccade to targets with the right eye. With the left eye occluded, the animal demonstrated no visually guided behavior. Optokinetic nystagmus was absent in the right eye. Metabolic activity in striate cortex was assessed by processing the tissue for cytochrome oxidase (CO). Amblyopia caused loss of CO in one eye's rows of patches, presumably those serving the blind eye. Layers 4A and 4B showed columns of reduced CO, in register with pale rows of patches in layer 2/3. Layers 4C, 5, and 6 also showed columns of CO activity, but remarkably, comparison with more superficial layers showed a reversal in contrast. In other words, pale CO staining in layers 2/3, 4A, and 4B was aligned with dark CO staining in layers 4C, 5, and 6. No experimental intervention or deprivation paradigm has been reported previously to produce opposite effects on metabolic activity in layers 2/3, 4A, and 4B vs. layers 4C, 5, and 6 within a given eye's columns. PMID:25810480

  10. Active/Passive Control of Sound Radiation from Panels using Constrained Layer Damping

    NASA Technical Reports Server (NTRS)

    Gibbs, Gary P.; Cabell, Randolph H.

    2003-01-01

    A hybrid passive/active noise control system utilizing constrained layer damping and model predictive feedback control is presented. This system is used to control the sound radiation of panels due to broadband disturbances. To facilitate the hybrid system design, a methodology for placement of constrained layer damping which targets selected modes based on their relative radiated sound power is developed. The placement methodology is utilized to determine two constrained layer damping configurations for experimental evaluation of a hybrid system. The first configuration targets the (4,1) panel mode which is not controllable by the piezoelectric control actuator, and the (2,3) and (5,2) panel modes. The second configuration targets the (1,1) and (3,1) modes. The experimental results demonstrate the improved reduction of radiated sound power using the hybrid passive/active control system as compared to the active control system alone.

  11. Polymer Solar Cell Device Characteristics Are Independent of Vertical Phase Separation in Active Layers

    NASA Astrophysics Data System (ADS)

    Loo, Yueh-Lin

    2013-03-01

    Preferential segregation of organic semiconductor constituents in multicomponent thin-film active layers has long been speculated to affect the characteristics of bulk-heterojunction polymer solar cells. Using soft-contact lamination and delamination schemes - with which we have been able to remove compositionally well characterized polymer thin films, flip them over so as to reverse their composition profiles, and then transfer them onto existing device platforms - we showed unambiguously that the device performance of P3HT:PCBM solar cells are independent of the interfacial segregation characteristics of the active layers. Temperature-dependent single-carrier diode measurements of the organic semiconductor constituents suggest that the origin of this invariance stems from the fact that P3HT comprises a high density of mid-gap states. Hole carriers in these mid-gap states can in turn recombine with electrons at the electron-collecting interface, effectively promoting electron transfer from the cathode to the active layer.

  12. Effect of layered composite meta-structures on the optical activity and ellipticity of structural biomolecules

    NASA Astrophysics Data System (ADS)

    Khoo, E. H.; Hor, Y. Li; Leong, Eunice S. P.; Liu, Y. J.

    2014-09-01

    In this paper, we design layered composite meta-structures to investigate its' effect on the optical activity and circular dichroism (CD). The layered composite meta-structures consist of thin gammadion nanostructure with thickness λ/10, where λ is the incident wavelength. The layered meta-structures are alternate between a dielectric and gold (AU) material. Each layered composite meta-gammadion is arranged together in an array of pitch 700 nm. In the first case, 3 layers of meta-gammadion, with metal-insulator-metal (MIM) and insulator-metal-insulator (IMI) configuration are simulated with material properties from optical hand book. There are 3 modes in the CD spectrum, which can be characterized into Bloch CD mode and hybrid CD modes. Compared with the CD spectrum of whole structure of gammadion in gold with same total height, the CD of the MIM layered composite are larger. When the number layer increase to 5, it is observed that the CD is reduced by 30% and there is a red shift in the Bloch CD mode and a slight blue shift in the hybrid CD modes. By further increasing the number of layers to 7, we observed further CD increment and larger wavelength shift in the CD modes. The layered composite meta-gammadion is fabricated using template stripping method. Experimental results also show excellent agreement with the simulation results for CD and wavelength shift. We submerge the layered meta-gammadion into a solution of chiral molecules. The CD spectrum of the meta-gammadion shows a larger wavelength shift compared to pure metal structures. This indicate a more sensitive and robust detection of chiral molecules.

  13. Active-layer thermal monitoring on the Fildes Peninsula, King George Island, maritime Antarctica

    NASA Astrophysics Data System (ADS)

    Michel, R. F. M.; Schaefer, C. E. G. R.; Simas, F. M. B.; Francelino, M. R.; Fernandes-Filho, E. I.; Lyra, G. B.; Bockheim, J. G.

    2014-12-01

    International attention to climate change phenomena has grown in the last decade; the active layer and permafrost are of great importance in understanding processes and future trends due to their role in energy flux regulation. The objective of this paper is to present active-layer temperature data for one Circumpolar Active Layer Monitoring South hemisphere (CALM-S) site located on the Fildes Peninsula, King George Island, maritime Antarctica over an 57-month period (2008-2012). The monitoring site was installed during the summer of 2008 and consists of thermistors (accuracy of ±0.2 °C), arranged vertically with probes at different depths, recording data at hourly intervals in a high-capacity data logger. A series of statistical analyses was performed to describe the soil temperature time series, including a linear fit in order to identify global trends, and a series of autoregressive integrated moving average (ARIMA) models was tested in order to define the best fit for the data. The affects of weather on the thermal regime of the active layer have been identified, providing insights into the influence of climate change on permafrost. The active-layer thermal regime in the studied period was typical of periglacial environments, with extreme variation in surface during the summer resulting in frequent freeze and thaw cycles. The active-layer thickness (ALT) over the studied period shows a degree of variability related to different annual weather conditions, reaching a maximum of 117.5 cm in 2009. The ARIMA model could describe the data adequately and is an important tool for more conclusive analysis and predictions when longer data sets are available. Despite the variability when comparing temperature readings and ACT over the studied period, no trend can be identified.

  14. Active layer thermal monitoring at Fildes Peninsula, King George Island, Maritime Antarctica

    NASA Astrophysics Data System (ADS)

    Michel, R. F. M.; Schaefer, C. E. G. R.; Simas, F. N. B.; Francelino M., R.; Fernandes-Filho, E. I.; Lyra, G. B.; Bockheim, J. G.

    2014-07-01

    International attention to the climate change phenomena has grown in the last decade; the active layer and permafrost are of great importance in understanding processes and future trends due to their role in energy flux regulation. The objective of the this paper is to present active layer temperature data for one CALM-S site located at Fildes Peninsula, King George Island, Maritime Antarctica over an fifth seven month period (2008-2012). The monitoring site was installed during the summer of 2008 and consists of thermistors (accuracy of ± 0.2 °C), arranged vertically with probes at different depths, recording data at hourly intervals in a~high capacity data logger. A series of statistical analysis were performed to describe the soil temperature time series, including a linear fit in order to identify global trend and a series of autoregressive integrated moving average (ARIMA) models were tested in order to define the best fit for the data. The controls of weather on the thermal regime of the active layer have been identified, providing insights about the influence of climate chance over the permafrost. The active layer thermal regime in the studied period was typical of periglacial environment, with extreme variation at the surface during summer resulting in frequent freeze and thaw cycles. The active layer thickness (ALT) over the studied period showed variability related to different annual weather conditions, reaching a maximum of 117.5 cm in 2009. The ARIMA model was considered appropriate to treat the dataset, enabling more conclusive analysis and predictions when longer data sets are available. Despite the variability when comparing temperature readings and active layer thickness over the studied period, no warming trend was detected.

  15. Invisible Active Galactic Nuclei. II. Radio Morphologies and Five New H i 21cm Absorption Line Detectors

    NASA Astrophysics Data System (ADS)

    Yan, Ting; Stocke, John T.; Darling, Jeremy; Momjian, Emmanuel; Sharma, Soniya; Kanekar, Nissim

    2016-03-01

    This is the second paper directed toward finding new highly redshifted atomic and molecular absorption lines at radio frequencies. To this end, we selected a sample of 80 candidates for obscured radio-loud active galactic nuclei (AGNs) and presented their basic optical/near-infrared (NIR) properties in Paper I. In this paper, we present both high-resolution radio continuum images for all of these sources and H i 21 cm absorption spectroscopy for a few selected sources in this sample. A-configuration 4.9 and 8.5 GHz Very Large Array continuum observations find that 52 sources are compact or have substantial compact components with size <0.″5 and flux densities >0.1 Jy at 4.9 GHz. The 36 most compact sources were then observed with the Very Long Baseline Array at 1.4 GHz. One definite and 10 candidate Compact Symmetric Objects (CSOs) are newly identified, which is a detection rate of CSOs ∼three times higher than the detection rate previously found in purely flux-limited samples. Based on possessing compact components with high flux densities, 60 of these sources are good candidates for absorption-line searches. Twenty-seven sources were observed for H i 21 cm absorption at their photometric or spectroscopic redshifts with only six detections (five definite and one tentative). However, five of these were from a small subset of six CSOs with pure galaxy optical/NIR spectra (i.e., any AGN emission is obscured) and for which accurate spectroscopic redshifts place the redshifted 21 cm line in a radio frequency intereference (RFI)-free spectral “window” (i.e., the percentage of H i 21 cm absorption-line detections could be as high as ∼90% in this sample). It is likely that the presence of ubiquitous RFI and the absence of accurate spectroscopic redshifts preclude H i detections in similar sources (only 1 detection out of the remaining 22 sources observed, 13 of which have only photometric redshifts); that is, H i absorption may well be present but is masked by

  16. Thermal conductivity tensors of the cladding and active layers of interband cascade lasers

    NASA Astrophysics Data System (ADS)

    Zhou, Chuanle; Cui, Boya; Vurgaftman, I.; Canedy, C. L.; Kim, C. S.; Kim, M.; Bewley, W. W.; Merritt, C. D.; Abell, J.; Meyer, J. R.; Grayson, M.

    2014-12-01

    The cross-plane and in-plane thermal conductivities of the W-active stages and InAs/AlSb superlattice optical cladding layer of an interband cascade laser (ICL) were characterized for temperatures ranging from 15 K to 324 K. The in-plane thermal conductivity of the active layer is somewhat larger than the cross-plane value at temperatures above about 30 K, while the thermal conductivity tensor becomes nearly isotropic at the lowest temperatures studied. These results will improve ICL performance simulations and guide the optimization of thermal management.

  17. MAPLE prepared heterostructures with arylene based polymer active layer for photovoltaic applications

    NASA Astrophysics Data System (ADS)

    Stanculescu, F.; Rasoga, O.; Catargiu, A. M.; Vacareanu, L.; Socol, M.; Breazu, C.; Preda, N.; Socol, G.; Stanculescu, A.

    2015-05-01

    This paper presents some studies about the preparation by matrix-assisted pulsed laser evaporation (MAPLE) technique of heterostructures with single layer of arylene based polymer, poly[N-(2-ethylhexyl)2.7-carbazolyl vinylene]/AMC16 and poly[N-(2-ethylhexyl)2.7-carbazolyl 1.4-phenylene ethynylene]/AMC22, and with layers of these polymers mixed with Buckminsterfullerene/C60 in the weight ratio of 1:2 (AMC16:C60) and 1:3 (AMC22:C60). The deposited layers have been characterized by spectroscopic (UV-Vis-NIR, PL, FTIR) and microscopic (SEM, AFM) methods. The effect of the polymer particularities on the optical and electrical properties of the structures based on polymer and polymer:C60 mixed layer has been analyzed. The study of the electrical properties has revealed typical solar cell behavior for the heterostructure prepared by MAPLE on glass/ITO/PEDOT-PSS with AMC16, AMC22 and AMC22:C60 layer, confirming that this method is adequate for the preparation of polymeric and mixed active layers for solar cells applications. The highest photovoltaic effect was shown by the solar cell structure realized with single layer of AMC16 polymer: glass/ITO/PEDOT-PSS/AMC16/Al.

  18. Material properties and field-effect transistor characteristics of hybrid organic/graphene active layers

    NASA Astrophysics Data System (ADS)

    Ha, Tae-Jun; Lee, Jongho; Chowdhury, Sk. Fahad; Akinwande, Deji; Dodabalapur, Ananth

    2012-10-01

    We report on the material properties and device characteristics of field-effect transistors (FETs) consisting of hybrid mono-layer graphene/organic semiconductor active layers. By capping with selected organic and polymeric layers, transformation of the electronic characteristics of mono-layer graphene FETs was observed. The off-state current is reduced while the on-state current and field-effect mobility are either unaffected or increased after depositing π-conjugated organic semiconductors. Significantly, capping mono-layer graphene FETs with fluoropolymer improved the on-off current ratio from 5 to 10 as well as increased the field-effect mobility by factor of two compared to plain graphene FETs. Removal of π-conjugated organic semiconductors or fluoropolymer from graphene FETs results in a return to the original electronic properties of mono-layer graphene FETs. This suggests that weak reversible electronic interactions between graphene and π-conjugated organic semiconductors/fluoropolymer favorably tune the material and electrical characteristics of mono-layer graphene.

  19. Antimicrobial Activity Evaluation on Silver Doped Hydroxyapatite/Polydimethylsiloxane Composite Layer.

    PubMed

    Ciobanu, C S; Groza, A; Iconaru, S L; Popa, C L; Chapon, P; Chifiriuc, M C; Hristu, R; Stanciu, G A; Negrila, C C; Ghita, R V; Ganciu, M; Predoi, D

    2015-01-01

    The goal of this study was the preparation, physicochemical characterization, and microbiological evaluation of novel hydroxyapatite doped with silver/polydimethylsiloxane (Ag:HAp-PDMS) composite layers. In the first stage, the deposition of polydimethylsiloxane (PDMS) polymer layer on commercially pure Si disks has been produced in atmospheric pressure corona discharges. Finally, the new silver doped hydroxyapatite/polydimethylsiloxane composite layer has been obtained by the thermal evaporation technique. The Ag:HAp-PDMS composite layers were characterized by various techniques, such as Scanning Electron Microscopy (SEM), Glow Discharge Optical Emission Spectroscopy (GDOES), and X-ray photoelectron spectroscopy (XPS). The antimicrobial activity of the Ag:HAp-PDMS composite layer was assessed against Candida albicans ATCC 10231 (ATCC-American Type Culture Collection) by culture based and confirmed by SEM and Confocal Laser Scanning Microscopy (CLSM) methods. This is the first study reporting the antimicrobial effect of the Ag:HAp-PDMS composite layer, which proved to be active against Candida albicans biofilm embedded cells. PMID:26504849

  20. Antimicrobial Activity Evaluation on Silver Doped Hydroxyapatite/Polydimethylsiloxane Composite Layer

    PubMed Central

    Ciobanu, C. S.; Groza, A.; Iconaru, S. L.; Popa, C. L.; Chapon, P.; Chifiriuc, M. C.; Hristu, R.; Stanciu, G. A.; Negrila, C. C.; Ghita, R. V.; Ganciu, M.; Predoi, D.

    2015-01-01

    The goal of this study was the preparation, physicochemical characterization, and microbiological evaluation of novel hydroxyapatite doped with silver/polydimethylsiloxane (Ag:HAp-PDMS) composite layers. In the first stage, the deposition of polydimethylsiloxane (PDMS) polymer layer on commercially pure Si disks has been produced in atmospheric pressure corona discharges. Finally, the new silver doped hydroxyapatite/polydimethylsiloxane composite layer has been obtained by the thermal evaporation technique. The Ag:HAp-PDMS composite layers were characterized by various techniques, such as Scanning Electron Microscopy (SEM), Glow Discharge Optical Emission Spectroscopy (GDOES), and X-ray photoelectron spectroscopy (XPS). The antimicrobial activity of the Ag:HAp-PDMS composite layer was assessed against Candida albicans ATCC 10231 (ATCC—American Type Culture Collection) by culture based and confirmed by SEM and Confocal Laser Scanning Microscopy (CLSM) methods. This is the first study reporting the antimicrobial effect of the Ag:HAp-PDMS composite layer, which proved to be active against Candida albicans biofilm embedded cells. PMID:26504849

  1. Effects of an enteric anaerobic bacterial culture supernatant and deoxycholate on intestinal calcium absorption and disaccharidase activity.

    PubMed Central

    Walshe, K; Healy, M J; Speekenbrink, A B; Keane, C T; Weir, D G; O'Moore, R R

    1990-01-01

    Fifty two strains of anaerobic bacteria isolated from the upper gut of patients with small intestinal bacterial overgrowth were screened for phospholipase activity. Bacteroides melaninogenicus spp intermedius had the greatest activity. The effects of culture supernatants of this organism and deoxycholate on intestinal calcium absorption and disaccharidase activity were studied using a rat closed loop model. The supernatant decreased the in vitro uptake of calcium by 15% (p less than 0.001). Deoxycholate reduced calcium uptake by 16% (p less than 0.001). Combined culture supernatant and deoxycholate reduced calcium uptake by 39% (p less than 0.001) suggesting a potentiation of supernatant activity by deoxycholate. Culture supernatant and deoxycholate, both alone and combined, significantly reduced lactase, sucrase, and maltase activity. Electron microscopic evidence showed degeneration of microvilli, disruption of mitochondrial structure, and swelling of the endoplasmic reticulum after exposure of the intestinal loops to the supernatant or deoxycholate. Images Figure 2 Figure 3 Figure 4 PMID:1973395

  2. X-ray absorption spectroscopic studies of the active sites of nickel- and copper-containing metalloproteins

    SciTech Connect

    Tan, G.O.

    1993-06-01

    X-ray absorption spectroscopy (XAS) is a useful tool for obtaining structural and chemical information about the active sites of metalloproteins and metalloenzymes. Information may be obtained from both the edge region and the extended X-ray absorption fine structure (EXAFS) or post-edge region of the K-edge X-ray absorption spectrum of a metal center in a compound. The edge contains information about the valence electronic structure of the atom that absorbs the X-rays. It is possible in some systems to infer the redox state of the metal atom in question, as well as the geometry and nature of ligands connected to it, from the features in the edge in a straightforward manner. The EXAFS modulations, being produced by the backscattering of the ejected photoelectron from the atoms surrounding the metal atom, provide, when analyzed, information about the number and type of neighbouring atoms, and the distances at which they occur. In this thesis, analysis of both the edge and EXAFS regions has been used to gain information about the active sites of various metalloproteins. The metalloproteins studied were plastocyanin (Pc), laccase and nickel carbon monoxide dehydrogenase (Ni CODH). Studies of Cu(I)-imidazole compounds, related to the protein hemocyanin, are also reported here.

  3. Microbial Activity in Active and Upper Permafrost Layers in Axel Heiberg Island

    NASA Astrophysics Data System (ADS)

    Vishnivetskaya, T. A.; Allan, J.; Cheng, K.; Chourey, K.; Hettich, R. L.; Layton, A.; Liu, X.; Murphy, J.; Mykytczuk, N. C.; Phelps, T. J.; Pfiffner, S. M.; Saarunya, G.; Stackhouse, B. T.; Whyte, L.; Onstott, T. C.

    2011-12-01

    Data on microbial communities and their metabolic activity in Arctic wetlands and underlying permafrost sediments is lacking. Samples were collected from different depths of a cryosol (D1, D2) and upper permafrost (D3) at the Axel Heiberg Island in July 2009. Upper cryosol has lower H2O but higher C and N content when compared to deeper horizons including upper permafrost layer. Deep cryosol and upper permafrost contained SO42- (155 and 132 ppm) and NO3- (0.12 and 0.10 ppm), respectively. The phylogenetic analyses of the environmental 16S rRNA genes showed the putative SRB were more abundant in permafrost (8%) than in cryosols, D1 (0.2%) and D2 (1.1%). Putative denitrifying bacteria varied along depth with near 0.1% in D1 and a significant increase in D2 (2.7%) and D3 (2.2%). Methanogens were not detected; methanotrophs were present at low levels in D3 (1%). Two sets of microcosms were set up. Firstly, anaerobic microcosms, amended with 10 mM glucose, sulfate or nitrate, were cultivated at varying temperatures (15o, 6o, and 0o C) for 10 months. Metabolic activity was monitored by measuring CO2 and CH4 every 3 months. A total of 89.5% of the D3-originated microcosms showed higher activity in comparison to cryosols in first 3 months. CH4 was not detected in these microcosms, whereas CO2 production was higher at 15o C or with glucose. Metaproteomics analyses of microcosms with higher levels of CO2 production indicated the presence of stress responsive proteins (e.g. DnaK, GroEL) and proteins essential for energy production and survival under carbon starvation (e.g. F0F1 ATP synthase, acyl-CoA dehydrogenase). These proteins have been previously shown to be up-regulated at low temperatures by permafrost bacteria. Metaproteomics data based on the draft sequences indicated the presence of proteins from the genera Bradyrhizobium, Sphingomonas, Lysinibacillus and Methylophilaceae and these bacteria were also detected by pyrosequencing. Secondly, a duplicate set of anaerobic

  4. Preparation of nanofiber polythiophene layered on Ba x Sr1- x Fe12O19/Fe3O4/polyacrylic acid core-shell structure and its microwave absorption investigation

    NASA Astrophysics Data System (ADS)

    Hosseini, Seyed Hossein; Moloudi, Maryam

    2015-09-01

    Ba x Sr1- x Fe12O19/Fe3O4/polyacrylic acid/polythiophene (Ba x Sr1- x Fe12O19/Fe3O4/PAA/PTh) nanocomposites with multi-core-shell structure were successfully synthesized by four steps. The samples were characterized by FTIR, X-ray diffraction (XRD), transmission electron microscope (TEM), vibrating sample magnetometer, and radar absorbing material reflectivity far-field radar cross-section method, respectively. XRD and TEM results indicated that the obtained nanoparticles have multi-core-shell morphology. The magnetic properties and microwave absorption analyses reveal that there are interphase interactions at the interface of Ba x Sr1- x Fe12O19, Fe3O4, PAA, and PTh, which can affect the magnetic properties and microwave absorption properties of the samples. The microwave-absorbing properties of nanocomposites were investigated at 8-14 GHz. A typical layer absorber exhibited an excellent microwave absorption with a -26 dB maximum absorption at 14 GHz. Compared with core material, the coercivity and saturation magnetization of multi-core-shell nanocomposites decrease obviously, but the microwave absorption properties of nanocomposites are improved greatly. The results show that these composite could be used as advancing absorption and shielding materials due to their favorable microwave-absorbing properties.

  5. Development of a low activation concrete shielding wall by multi-layered structure for a fusion reactor

    NASA Astrophysics Data System (ADS)

    Sato, Satoshi; Maegawa, Toshio; Yoshimatsu, Kenji; Sato, Koichi; Nonaka, Akira; Takakura, Kosuke; Ochiai, Kentaro; Konno, Chikara

    2011-10-01

    A multi-layered concrete structure has been developed to reduce induced activity in the shielding for neutron generating facilities such as a fusion reactor. The multi-layered concrete structure is composed of: (1) an inner low activation concrete, (2) a boron-doped low activation concrete as the second layer, and (3) ordinary concrete as the outer layer of the neutron shield. With the multi-layered concrete structure the volume of boron is drastically decreased compared to a monolithic boron-doped concrete. A 14 MeV neutron shielding experiment with multi-layered concrete structure mockups was performed at FNS and several reaction rates and induced activity in the mockups were measured. This demonstrated that the multi-layered concrete effectively reduced low energy neutrons and induced activity.

  6. NEAR-ULTRAVIOLET ABSORPTION, CHROMOSPHERIC ACTIVITY, AND STAR-PLANET INTERACTIONS IN THE WASP-12 SYSTEM

    SciTech Connect

    Haswell, C. A.; Fossati, L.; Holmes, S.; Kolb, U. C.; Busuttil, R.; Carter, A.; Ayres, T.; France, K.; Froning, C. S.; Street, R. A.; Hebb, L.; Cameron, A. Collier; Enoch, B.; Burwitz, V.; Rodriguez, J.; West, R. G.; Pollacco, D.; Wheatley, P. J. E-mail: l.fossati@open.ac.uk E-mail: leslie.hebb@vanderbilt.edu

    2012-11-20

    Extended gas clouds have been previously detected surrounding the brightest known close-in transiting hot Jupiter exoplanets, HD 209458 b and HD 189733 b; we observed the distant but more extreme close-in hot Jupiter system, WASP-12, with Hubble Space Telescope (HST). Near-UV (NUV) transits up to three times deeper than the optical transit of WASP-12 b reveal extensive diffuse gas, extending well beyond the Roche lobe. The distribution of absorbing gas varies between visits. The deepest NUV transits are at wavelength ranges with strong stellar photospheric absorption, implying that the absorbing gas may have temperature and composition similar to those of the stellar photosphere. Our spectra reveal significantly enhanced absorption (greater than 3{sigma} below the median) at {approx}200 individual wavelengths on each of two HST visits; 65 of these wavelengths are consistent between the two visits, using a strict criterion for velocity matching that excludes matches with velocity shifts exceeding {approx}20 km s{sup -1}. Excess transit depths are robustly detected throughout the inner wings of the Mg II resonance lines independently on both HST visits. We detected absorption in Fe II {lambda}2586, the heaviest species yet detected in an exoplanet transit. The Mg II line cores have zero flux, emission cores exhibited by every other observed star of similar age and spectral type are conspicuously absent. WASP-12 probably produces normal Mg II profiles, but the inner portions of these strong resonance lines are likely affected by extrinsic absorption. The required Mg{sup +} column is an order of magnitude greater than expected from the interstellar medium, though we cannot completely dismiss that possibility. A more plausible source of absorption is gas lost by WASP-12 b. We show that planetary mass loss can produce the required column. Our Visit 2 NUV light curves show evidence for a stellar flare. We show that some of the possible transit detections in resonance

  7. Activity induces traveling waves, vortices and spatiotemporal chaos in a model actomyosin layer

    NASA Astrophysics Data System (ADS)

    Ramaswamy, Rajesh; Jülicher, Frank

    2016-02-01

    Inspired by the actomyosin cortex in biological cells, we investigate the spatiotemporal dynamics of a model describing a contractile active polar fluid sandwiched between two external media. The external media impose frictional forces at the interface with the active fluid. The fluid is driven by a spatially-homogeneous activity measuring the strength of the active stress that is generated by processes consuming a chemical fuel. We observe that as the activity is increased over two orders of magnitude the active polar fluid first shows spontaneous flow transition followed by transition to oscillatory dynamics with traveling waves and traveling vortices in the flow field. In the flow-tumbling regime, the active polar fluid also shows transition to spatiotemporal chaos at sufficiently large activities. These results demonstrate that level of activity alone can be used to tune the operating point of actomyosin layers with qualitatively different spatiotemporal dynamics.

  8. Activity induces traveling waves, vortices and spatiotemporal chaos in a model actomyosin layer

    PubMed Central

    Ramaswamy, Rajesh; Jülicher, Frank

    2016-01-01

    Inspired by the actomyosin cortex in biological cells, we investigate the spatiotemporal dynamics of a model describing a contractile active polar fluid sandwiched between two external media. The external media impose frictional forces at the interface with the active fluid. The fluid is driven by a spatially-homogeneous activity measuring the strength of the active stress that is generated by processes consuming a chemical fuel. We observe that as the activity is increased over two orders of magnitude the active polar fluid first shows spontaneous flow transition followed by transition to oscillatory dynamics with traveling waves and traveling vortices in the flow field. In the flow-tumbling regime, the active polar fluid also shows transition to spatiotemporal chaos at sufficiently large activities. These results demonstrate that level of activity alone can be used to tune the operating point of actomyosin layers with qualitatively different spatiotemporal dynamics. PMID:26877263

  9. Studies on the effects of polyaspartate protease fertilizer enhancer in the absorptions of soil nutrition and the enzymatic activities of crops

    NASA Astrophysics Data System (ADS)

    Guoliang, Jiang; Dong, Yang; Yun, Liu; Guanghua, Zhang; Zhongjun, Li; Xinhua, Zhang

    2003-04-01

    The effects of polyaspartate protease fertilizer enhancer, made from oyster shell proteins, on the absorption of soil nutrition and the enzymatic activities of crops were studied. It has been found that the enhancer contributes 30%, 50% and 50% augmentation of nitrogen (N), phosphate (P) and potassium (K) absorption respectively and about 20% of nitrate reductase and peroxide enzyme activities of crops. These results show that polyaspartate protease fertilizer enhancer could improve significantly the absorption and utilization efficiencies of soil nutrition and the activities of nitrate reductase and peroxide enzyme of crops, thus elevating the utilization rates of chemical fertilizers to a certain extent.

  10. Photocatalytic activity of layered perovskite-like oxides in practically valuable chemical reactions

    NASA Astrophysics Data System (ADS)

    Rodionov, I. A.; Zvereva, I. A.

    2016-03-01

    The photocatalytic properties of layered perovskite-like oxides corresponding to the Ruddlesen–Popper, Dion–Jacobson and Aurivillius phases are considered. Of the photocatalytic reactions, the focus is on the reactions of water splitting, hydrogen evolution from aqueous solutions of organic substances and degradation of model organic pollutants. Possibilities to conduct these reactions under UV and visible light in the presence of layered perovskite-like oxides and composite photocatalysts based on them are shown. The specific surface area, band gap energy, particle morphology, cation and anion doping and surface modification are considered as factors that affect the photocatalytic activity. Special attention is paid to the possibilities to enhance the photocatalytic activity by intercalation, ion exchange and exfoliation, which are inherent in this class of compounds. Conclusions are made about the prospects for the use of layered perovskite-like oxides in photocatalysis. The bibliography includes 253 references.

  11. Monitoring of the active layer at Kapp Linne', SVALBARD 1972-2002

    NASA Astrophysics Data System (ADS)

    Akerman, J.

    2003-04-01

    The active layer has been monitored at ten sites in the vicinity of Kapp Linné, (78o03'42" 13o37'07") Svalbard during the period 1972 - 2002. The ten sites differ in elevation, distance from the sea, vegetation cover, substrate and active periglacial processes. From 1994 the International permafrost Association "CALM" standard grids, with measurement within 100x100m squares, has been applied. Microclimate and soil temperatures have been monitored by data logger covering levels form 2 m above to 7m below the ground. The macroclimate is covered by complete data series from the nearby weather station at Kapp Linne’, covering the period 1912 to 2002. A number of periglacial processes, especially slope processes, are monitored parallel with the active layer. The mean active layer for the sites varies between 1,13m and 0,43m. The deepest active layer is found in the exposed, well drained raised beach ridges and the shallowest in the bogs. The interannual variability during the observation period do not correlate well with the MAAT but better with the summer climate, June - August mean or DDT. The data clearly illustrate colder summers during the period 1972 to 1983 and after that steadily increasing summer temperatures. The active layer follows the same general pattern with good correlations. There are several surface indications as a response to the deepening active layer especially in the bogs. Thermokarst scars appear frequently and a majority of the palsa like mounds and pounus have disappeared. A drastic change in the vegetation on the bogs has also occurred, from dry heath to wet Carex vegetation. In summary the observations from Kapp Linne’ are; 1. A clear trend towards milder summers, 2. A clear trend towards deeper active layers, 3. All sites show a similar pattern, 4. The bogs are getting strikingly wetter, 5. Mounds in the bog sites are disappearing, 6. The slow slope processes are getting accelerated, 7. Thermokarst depressions and scars are appearing in

  12. Intercalation and controlled release of pharmaceutically active compounds from a layered double hydroxide.

    PubMed

    Khan, A I; Lei, L; Norquist, A J; O'Hare, D

    2001-11-21

    A series of pharmaceutically active compounds including diclofenac, gemfibrozil, ibuprofen, naproxen, 2-propylpentanoic acid, 4-biphenylacetic acid and tolfenamic acid can be reversibly intercalated into a layered double hydroxide, initial studies suggest that these materials may have application as the basis of a novel tuneable drug delivery system. PMID:12240066

  13. Extending the Diffuse Layer Model of Surface Acidity Behavior: III. Estimating Bound Site Activity Coefficients

    EPA Science Inventory

    Although detailed thermodynamic analyses of the 2-pK diffuse layer surface complexation model generally specify bound site activity coefficients for the purpose of accounting for those non-ideal excess free energies contributing to bound site electrochemical potentials, in applic...

  14. Active Layer and Moisture Measurements for Intensive Site 0 and 1, Barrow, Alaska

    DOE Data Explorer

    John Peterson

    2015-04-17

    These are measurements of Active Layer Thickness collected along several lines beginning in September, 2011 to the present. The data were collected at several time periods along the Site0 L2 Line, the Site1 AB Line, and an ERT Monitoring Line near Area A in Site1.

  15. The study of a light-activated albumin protein solder to bond layers of porcine small intestinal submucosa.

    PubMed

    Ware, Mark H; Buckley, Christine A

    2003-01-01

    This study investigated the feasibility of bonding layers of porcine small intestinal submucosa (SIS, Cook Biotech, Inc.) with a light-activated protein solder. SIS is an acellular, collagen-based extracellular matrix material that is approximately 100 microns thick. The solder consists of bovine serum albumin and indocyanine green dye (ICG) in deionized water. The solder is activated by an 808 nm diode laser, which denatures the albumin, causing the albumin to bond with the collagen of the tissue. The predictable absorption and thermal energy diffusion rates of ICG increase the chances of reproducible results. To determine the optimal condition for laser soldering SIS, the following parameters were varied: albumin concentration (from 30-45% (w/v) in increments of 5%), the concentration of ICG (from 0.5-2.0 mg/ml H2O) and the irradiance of the laser (10-64 W/cm2). While many of the solder compositions and laser irradiance combinations resulted in no bonding, a solder composition of 45% albumin, ICG concentration of 0.5 mg/ml H2O, and a laser irradiance of 21 W/cm2 did produce a bond between two pieces of SIS. The average shear strength of this bond was 29.5 +/- 17.1 kPa (n = 14). This compares favorably to our previous work using fibrin glue as an adhesive, in which the average shear strength was 27 +/- 15.8 kPa (n = 40). PMID:12724859

  16. Structural and optical study of core–shell InGaN layers of nanorod arrays with multiple stacks of InGaN/GaN superlattices for absorption of longer solar spectrum

    NASA Astrophysics Data System (ADS)

    Bae, Si-Young; Jung, Byung Oh; Lekhal, Kaddour; Lee, Dong-Seon; Deki, Manato; Honda, Yoshio; Amano, Hiroshi

    2016-05-01

    We report on the material and optical properties of core–shell InGaN layers grown on GaN nanorod arrays. The core–shell InGaN layers were well grown on polarization-reduced surfaces such as semipolar pyramids and nonpolar sidewalls. In addition, to compensate the biaxial strain between GaN and InGaN layers, we grew interlayers underneath a thick InGaN layer. Here, the interlayers were composed of multiple superlattice structures. We could observe that the indium composition of core–shell InGaN structures increased with the number of interlayers. This indicates that the absorption energy band of InGaN alloys can be better matched to the spectral irradiance of the solar spectrum in nature. We also implemented a simulation of Ga-polar and nonpolar InGaN-based solar cells based on the indium composition obtained from the experiments. The result showed that nonpolar InGaN solar cells had a much higher efficiency than Ga-polar InGaN solar cells with the same thickness of the absorption layer.

  17. Characterization of Yb:YAG active slab media based on a layered structure with different doping

    NASA Astrophysics Data System (ADS)

    Lapucci, A.; Ciofini, M.; Esposito, L.; Ferrara, P.; Gizzi, L. A.; Hostaša, J.; Labate, L.; Pirri, A.; Toci, G.; Vannini, M.

    2013-05-01

    Slabs with non-uniform doping distribution are studied with the aim of reducing thermal deformations in high-energy high-average-power Yb:YAG slab systems. We present a numerical analysis based on Finite Element Mesh (FEM) methods suitable to model non-uniform devices. The thermal variation of the refractive index, the end-faces deformations and the photo-elastic effect have been calculated in order to estimate the total thermal-lens effect. The stress distributions are also obtained. Some results of this numerical approach are compared to experimental thermal lens measurements in a simple geometry for both uniform and structured samples, in order to validate the numerical procedures. Finally we compare numerical simulations for different single- or double-sided pumping and cooling geometries. They show that structured slabs can reduce thermal gradients with respect to uniformly doped means with comparable absorption and geometry. This means a reduction of thermal lens effect and thus an increase of maximum allowed pump power loading. Previous literature reports some work made with structured slabs where higher doping was located in layers with lower pump radiation levels, in order to get a more uniform absorption. Interestingly our modeling indicates that reduced thermal effects are instead obtained when a higher doping is located close to the cooled surfaces.

  18. Thermal impacts of engineering activities and vegetation layer on permafrost in different alpine ecosystems of the Qinghai-Tibet Plateau, China

    NASA Astrophysics Data System (ADS)

    Wu, Qingbai; Zhang, Zhongqiong; Gao, Siru; Ma, Wei

    2016-08-01

    Climate warming and engineering activities have various impacts on the thermal regime of permafrost in alpine ecosystems of the Qinghai-Tibet Plateau. Using recent observations of permafrost thermal regimes along the Qinghai-Tibet highway and railway, the changes of such regimes beneath embankments constructed in alpine meadows and steppes are studied. The results show that alpine meadows on the Qinghai-Tibet Plateau can have a controlling role among engineering construction effects on permafrost beneath embankments. As before railway construction, the artificial permafrost table (APT) beneath embankments is not only affected by climate change and engineering activities but is also controlled by alpine ecosystems. However, the change rate of APT is not dependent on ecosystem type, which is predominantly affected by climate change and engineering activities. Instead, the rate is mainly related to cooling effects of railway ballast and heat absorption effects of asphalt pavement. No large difference between alpine and steppe can be identified regarding the variation of soil temperature beneath embankments, but this difference is readily identified in the variation of mean annual soil temperature with depth. The vegetation layer in alpine meadows has an insulation role among engineering activity effects on permafrost beneath embankments, but this insulation gradually disappears because the layer decays and compresses over time. On the whole, this layer is advantageous for alleviating permafrost temperature rise in the short term, but its effect gradually weakens in the long term.

  19. A Novel Surface Structure Consisting of Contact-active Antibacterial Upper-layer and Antifouling Sub-layer Derived from Gemini Quaternary Ammonium Salt Polyurethanes.

    PubMed

    He, Wei; Zhang, Yi; Li, Jiehua; Gao, Yunlong; Luo, Feng; Tan, Hong; Wang, Kunjie; Fu, Qiang

    2016-01-01

    Contact-active antibacterial surfaces play a vital role in preventing bacterial contamination of artificial surfaces. In the past, numerous researches have been focused on antibacterial surfaces comprising of antifouling upper-layer and antibacterial sub-layer. In this work, we demonstrate a reversed surface structure which integrate antibacterial upper-layer and antifouling sub-layer. These surfaces are prepared by simply casting gemini quaternary ammonium salt waterborne polyurethanes (GWPU) and their blends. Due to the high interfacial energy of gemini quaternary ammonium salt (GQAS), chain segments containing GQAS can accumulate at polymer/air interface to form an antibacterial upper-layer spontaneously during the film formation. Meanwhile, the soft segments composed of polyethylene glycol (PEG) formed the antifouling sub-layer. Our findings indicate that the combination of antibacterial upper-layer and antifouling sub-layer endow these surfaces strong, long-lasting antifouling and contact-active antibacterial properties, with a more than 99.99% killing efficiency against both gram-positive and gram-negative bacteria attached to them. PMID:27561546

  20. A Novel Surface Structure Consisting of Contact-active Antibacterial Upper-layer and Antifouling Sub-layer Derived from Gemini Quaternary Ammonium Salt Polyurethanes

    PubMed Central

    He, Wei; Zhang, Yi; Li, Jiehua; Gao, Yunlong; Luo, Feng; Tan, Hong; Wang, Kunjie; Fu, Qiang

    2016-01-01

    Contact-active antibacterial surfaces play a vital role in preventing bacterial contamination of artificial surfaces. In the past, numerous researches have been focused on antibacterial surfaces comprising of antifouling upper-layer and antibacterial sub-layer. In this work, we demonstrate a reversed surface structure which integrate antibacterial upper-layer and antifouling sub-layer. These surfaces are prepared by simply casting gemini quaternary ammonium salt waterborne polyurethanes (GWPU) and their blends. Due to the high interfacial energy of gemini quaternary ammonium salt (GQAS), chain segments containing GQAS can accumulate at polymer/air interface to form an antibacterial upper-layer spontaneously during the film formation. Meanwhile, the soft segments composed of polyethylene glycol (PEG) formed the antifouling sub-layer. Our findings indicate that the combination of antibacterial upper-layer and antifouling sub-layer endow these surfaces strong, long-lasting antifouling and contact-active antibacterial properties, with a more than 99.99% killing efficiency against both gram-positive and gram-negative bacteria attached to them. PMID:27561546

  1. Thermal regime of active layer at two lithologically contrasting sites on James Ross Island, Antarctic Peninsula.

    NASA Astrophysics Data System (ADS)

    Hrbáček, Filip; Nývlt, Daniel; Láska, Kamil

    2016-04-01

    Antarctic Peninsula region (AP) represents one of the most rapidly warming parts of our planet in the last 50 years. Despite increasing research activities along both western and eastern sides of AP in last decades, there is still a lot of gaps in our knowledge relating to permafrost, active layer and its thermal and physical properties. This study brings new results of active layer monitoring on James Ross Island, which is the largest island in northern AP. Its northern part, Ulu Peninsula, is the largest ice-free area (more than 200 km2) in the region. Due its large area, we focused this study on sites located in different lithologies, which would affect local thermal regime of active layer. Study site (1) at Abernethy Flats area (41 m a.s.l.) lies ~7 km from northern coast. Lithologically is formed by disintegrated Cretaceous calcareous sandstones and siltstones of the Santa Marta Formation. Study site (2) is located at the northern slopes of Berry Hill (56 m a.s.l.), about 0.4 km from northern coastline. Lithology is composed of muddy to intermediate diamictites, tuffaceous siltstones to fine grained sandstones of the Mendel Formation. Data of air temperature at 2 meters above ground and the active layer temperatures at 75 cm deep profiles were obtained from both sites in period 1 January 2012 to 31 December 2014. Small differences were found when comparing mean air temperatures and active temperatures at 5 and 75 cm depth in the period 2012-2014. While the mean air temperatures varied between -7.7 °C and -7.0 °C, the mean ground temperatures fluctuated between -6.6 °C and -6.1 °C at 5 cm and -6.9 °C and -6.0 °C at 75 cm at Abernethy Flats and Berry Hill slopes respectively. Even though ground temperature differences along the profiles weren't pronounced during thawing seasons, the maximum active layer thickness was significantly larger at Berry Hill slopes (80 to 82 cm) than at Abernethy Flats (52 to 64 cm). We assume this differences are affected by

  2. Evaluation of the Intestinal Absorption Mechanism of Casearin X in Caco-2 Cells with Modified Carboxylesterase Activity.

    PubMed

    Moreira da Silva, Rodrigo; Verjee, Sheela; de Gaitani, Cristiane Masetto; Moraes de Oliveira, Anderson Rodrigo; Pires Bueno, Paula Carolina; Cavalheiro, Alberto José; Peporine Lopes, Norberto; Butterweck, Veronika

    2016-04-22

    The clerodane diterpene casearin X (1), isolated from the leaves of Casearia sylvestris, is a potential new drug candidate due to its potent in vitro cytotoxic activity. In this work, the intestinal absorption mechanism of 1 was evaluated using Caco-2 cells with and without active carboxylesterases (CES). An LC-MS method was developed and validated for the quantification of 1. The estimation of permeability coefficients was possible only under CES-inhibited conditions in which 1 is able to cross the Caco-2 cell monolayer. The mechanism is probably by active transport, with no significant efflux, but with a high retention of the compound inside the cells. The enzymatic hydrolysis assay demonstrates the susceptibility of 1 to first-pass metabolism as substrate for specific CES expressed in human intestine. PMID:26990770

  3. Photocatalytic Activity of Bulk TiO{sub 2} Anatase and Rutile Single Crystals Using Infrared Absorption Spectroscopy

    SciTech Connect

    Xu Mingchun; Gao Youkun; Moreno, Elias Martinez; Kunst, Marinus; Muhler, Martin; Wang Yuemin; Idriss, Hicham; Woell, Christof

    2011-04-01

    A systematic study on the photocatalytic activity of well-defined, macroscopic bulk single-crystal TiO{sub 2} anatase and rutile samples has been carried out, which allows us to link photoreactions at surfaces of well-defined oxide semiconductors to an important bulk property with regard to photochemistry, the life time of e-h pairs generated in the bulk of the oxides by photon absorption. The anatase (101) surface shows a substantially higher activity, by an order of magnitude, for CO photo-oxidation to CO{sub 2} than the rutile (110) surface. This surprisingly large difference in activity tracks the bulk e-h pair lifetime difference for the two TiO{sub 2} modifications as determined by contactless transient photoconductance measurements on the corresponding bulk materials.

  4. Electrospun nanofibers of Er{sup 3+}-doped TiO{sub 2} with photocatalytic activity beyond the absorption edge

    SciTech Connect

    Zheng, Yali; Wang, Wenzhong

    2014-02-15

    Er{sup 3+}-doped TiO{sub 2} nanofibers with different Er{sup 3+} contents were prepared via electrospinning and characterized by X-ray diffraction, scanning electron microscopy, ultraviolet–visible diffuse reflectance spectroscopy and photocurrent measurement. Photocatalytic activities of the as-prepared samples were evaluated by the decolorization of methyl orange aqueous solution under simulated solar light irradiation. The results indicated that the photocatalytic activity of Er{sup 3+}-doped TiO{sub 2} nanofibers was much higher than that of the undoped one, and the optimal dosage of Er{sup 3+} at 1 mol% achieved the highest degradation rate. Moreover, the photocatalytic activity of Er{sup 3+}-doped TiO{sub 2} nanofibers under the irradiation of light with the wavelength beyond the absorption edge of TiO{sub 2} was explored by the decolorization of a dye, rhodamine B and the photodegradation of a typical colorless pollutant, phenol. The results further revealed the mechanism of the enhanced photocatalytic activity through Er{sup 3+} doping in TiO{sub 2} nanofibers. - Graphical abstract: Display Omitted - Highlights: ●Er{sup 3+}:TiO{sub 2} nanofibers with different Er{sup 3+} contents were prepared via electrospinning. ●The photocatalytic activity of Er{sup 3+}:TiO{sub 2} was much higher than that of undoped one. ●Er{sup 3+}:TiO{sub 2} could be activated by the light with wavelength beyond the absorption edge.

  5. Dispersion of nonlinear refractive index in layered WS2 and WSe2 semiconductor films induced by two-photon absorption.

    PubMed

    Dong, Ningning; Li, Yuanxin; Zhang, Saifeng; McEvoy, Niall; Zhang, Xiaoyan; Cui, Yun; Zhang, Long; Duesberg, Georg S; Wang, Jun

    2016-09-01

    Both the nonlinear absorption and nonlinear refraction properties of WS2 and WSe2 semiconductor films have been characterized by using Z-scan technique with femtosecond pulses at the wavelength of 1040 nm. It is found that these films have two-photon absorption response with the nonlinear absorption coefficient of ∼103  cm GW-1, and a dispersion of nonlinear refractive index in the WS2 films that translated from positive in the monolayer to negative in bulk materials. PMID:27607941

  6. Comparison of different irrigation activation techniques on smear layer removal: an in vitro study.

    PubMed

    Akyuz Ekim, Sefika Nur; Erdemir, Ali

    2015-03-01

    The purpose of this study was to evaluate the efficiency of different irrigation activation techniques on smear layer removal. About 80 single-rooted human maxillary central teeth were decoronated to a standardized length.The samples were prepared by using ProTaper system to size F4 and divided into eight equal groups (n = 10) according to the final irrigation activation technique; distilled water was used as an irrigant in Group 1. The other groups were treated with 2.5% NaOCl and 17% EDTA, respectively. Conventional syringe irrigation (CSI) was used in Group 2. Irrigation solutions were activated using passive ultrasonic irrigation (PUI, Group 3), EndoVac apical negative pressure (ANP, Group 4), diode laser (Group 5), Nd:YAG laser (Group 6), Er:YAG laser (Group 7), and Er:YAG laser using with photon-induced photoacoustic streaming (PIPS™, Group 8). Teeth were split longitudinally and subjected to scanning electron microscope (SEM). PIPS showed the best removal of smear layer when compared with PUI, ANP, Nd:YAG, and Er:YAG, but the difference was not statistically significant (P > 0.05). Smear layer scores obtained with PIPS technique were statistically significant different from those of obtained with control, CSI and diode laser groups (P < 0.05). All experimental irrigation techniques except ANP and diode laser removed smear layer more effectively at the coronal and middle levels compared to the apical level (P < 0.05). Irrigation activated/delivered techniques except diode laser have a positive effect on removing of smear layer. PMID:25582378

  7. Ultrathin and stable active layer of dense composite membrane enabled by poly(dopamine).

    PubMed

    Li, Ben; Liu, Wanpeng; Jiang, Zhongyi; Dong, Xiao; Wang, Baoyi; Zhong, Yurong

    2009-07-01

    We demonstrate that dopamine is able to self-polymerize and adhere firmly onto the substrate, which can create a hierarchical structure comprising an ultrathin active layer and a porous support layer. Such an approach opens a novel way to fabricating highly efficient and stable composite materials including composite membranes. More specifically, in this study the composite membranes are fabricated by simply dipping microporous substrate in aqueous dopamine solution under mild conditions. Nanoindentation measurement reveals the tight adhesion of dopamine onto microporous substrate, which is ascribed to numerous pi-pi and hydrogen-bonding interactions. The chemical composition of the active layer is analyzed by XPS, which demonstrates the self-polymerization of dopamine. The water contact angle of the dopamine coated membranes is reduced remarkably compared with that of the uncoated counterpart. Stylus profiler measurements display that the poly(dopamine) thickness increases as the coating time increases. FESEM images of the membranes' cross section show that an active layer (<100 nm) is deposited on the porous polysulfone (PS) substrate. Positron annihilation spectroscopy (PAS) is introduced to probe the fractional free volume properties throughout the cross section of the composite membranes and reveal that after dopamine double-coating the active layer becomes thicker and more compact. Moreover, pH and concentration of the dopamine solution exert notable influence on the fractional free volume of the composite membranes. The as-prepared membranes are tentatively employed for pervaporative desulfurization and exhibits satisfying separation performance as well as durability. This facile, versatile, and efficient approach enables a promising prospect for the wide applications of such novel kinds of ultrathin composite materials. PMID:19366196

  8. Absorption variability as a probe of the multiphase interstellar media surrounding active galaxies

    NASA Astrophysics Data System (ADS)

    Macquart, Jean-Pierre; Tingay, Steven

    2016-08-01

    We examine a model for the variable free-free and neutral hydrogen absorption inferred towards the cores of some compact radio galaxies in which a spatially fluctuating medium drifts in front of the source. We relate the absorption-induced intensity fluctuations to the statistics of the underlying opacity fluctuations. We investigate models in which the absorbing medium consists of either discrete clouds or a power-law spectrum of opacity fluctuations. We examine the variability characteristics of a medium comprised of Gaussian-shaped clouds in which the neutral and ionized matter are co-located, and in which the clouds comprise spherical constant-density neutral cores enveloped by ionized sheaths. The cross-power spectrum indicates the spatial relationship between neutral and ionized matter, and distinguishes the two models, with power in the Gaussian model declining as a featureless power-law, but that in the ionized sheath model oscillating between positive and negative values. We show how comparison of the HI and free-free power spectra reveals information on the ionization and neutral fractions of the medium. The background source acts as a low-pass filter of the underlying opacity power spectrum, which limits temporal fluctuations to frequencies $\\omega < \\dot{\\theta}_v / \\theta_{\\rm src}$, where $\\dot{\\theta}_v$ is the angular drift speed of the matter in front of the source, and it quenches the observability of opacity structures on scales smaller than the source size $\\theta_{\\rm src}$. For drift speeds of $\\sim 10^3\\,$km s$^{-1}$ and source brightness temperatures $\\sim 10^{12}\\,$K, this limitation confines temporal opacity fluctuations to timescales of order several months to decades.

  9. Absorption variability as a probe of the multiphase interstellar media surrounding active galaxies

    NASA Astrophysics Data System (ADS)

    Macquart, Jean-Pierre; Tingay, Steven

    2016-08-01

    We examine a model for the variable free-free and neutral hydrogen absorption inferred towards the cores of some compact radio galaxies in which a spatially fluctuating medium drifts in front of the source. We relate the absorption-induced intensity fluctuations to the statistics of the underlying opacity fluctuations. We investigate models in which the absorbing medium consists of either discrete clouds or a power-law spectrum of opacity fluctuations. We examine the variability characteristics of a medium comprised of Gaussian-shaped clouds in which the neutral and ionized matter are co-located, and in which the clouds comprise spherical constant-density neutral cores enveloped by ionized sheaths. The cross-power spectrum indicates the spatial relationship between neutral and ionized matter, and distinguishes the two models, with power in the Gaussian model declining as a featureless power-law, but that in the ionized sheath model oscillating between positive and negative values. We show how comparison of the H I and free-free power spectra reveals information on the ionization and neutral fractions of the medium. The background source acts as a low-pass filter of the underlying opacity power spectrum, which limits temporal fluctuations to frequencies ω ≲ dot{θ }_v/θ _src, where dot{θ }_v is the angular drift speed of the matter in front of the source, and it quenches the observability of opacity structures on scales smaller than the source size θsrc. For drift speeds of ˜103 km s-1 and source brightness temperatures ˜1012 K, this limitation confines temporal opacity fluctuations to time-scales of order several months to decades.

  10. Realizing the full potential of Remotely Sensed Active Layer Thickness (ReSALT) Products

    NASA Astrophysics Data System (ADS)

    Schaefer, K. M.; Chen, A.; Liu, L.; Parsekian, A.; Jafarov, E. E.; Panda, S. K.; Zebker, H. A.

    2015-12-01

    The Remotely Sensed Active Layer Thickness (ReSALT) product uses the Interferometric Synthetic Aperture Radar (InSAR) technique to measure ground subsidence, active layer thickness (ALT), and thermokarst activity in permafrost regions. ReSALT supports research for the Arctic-Boreal Vulnerability Experiment (ABoVE) field campaign in Alaska and northwest Canada and is a precursor for a potential Nasa-Isro Synthetic Aperture Radar (NISAR) product. ALT is a critical parameter for monitoring the status of permafrost and thermokarst activity is one of the key drivers of change in permafrost regions. The ReSALT product currently includes 1) long-term subsidence trends resulting from the melting and subsequent drainage of excess ground ice in permafrost-affected soils, 2) seasonal subsidence resulting from the expansion of soil water into ice as the active layer freezes and thaws, and 3) ALT estimated from the seasonal subsidence assuming a vertical profile of water within the soil column. ReSALT includes uncertainties for all parameters and is validated against in situ measurements from the Circumpolar Active Layer Monitoring (CALM) network, Ground Penetrating Radar and mechanical probe measurements. We present high resolution ReSALT products on the North Slope of Alaska: Prudhoe Bay, Barrow, Toolik Lake, Happy Valley, and the Anaktuvuk fire zone. We believe that the ReSALT product could be expanded to include maps of individual thermokarst features identified as spatial anomalies in the subsidence trends, with quantified expansion rates. We illustrate the technique with multiple examples of thermokarst features on the North Slope of Alaska. Knowing the locations and expansion rates for individual features allows us to evaluate risks to human infrastructure. Our results highlight the untapped potential of the InSAR technique to remotely sense ALT and thermokarst dynamics over large areas of the Arctic.

  11. Influences and interactions of inundation, peat, and snow on active layer thickness

    DOE PAGESBeta

    Atchley, Adam L.; Coon, Ethan T.; Painter, Scott L.; Harp, Dylan R.; Wilson, Cathy J.

    2016-05-18

    The effect of three environmental conditions: 1) thickness of organic soil, 2) snow depth, and 3) soil moisture content or water table height above and below the soil surface, on active layer thickness (ALT) are investigated using an ensemble of 1D thermal hydrology models. Sensitivity analyses of the ensemble exposed the isolated influence of each environmental condition on ALT and their multivariate interactions. The primary and interactive influences are illustrated in the form of color maps of ALT change. Results show that organic layer acts as a strong insulator, and its thickness is the dominant control of ALT, but themore » strength of the effect of organic layer thickness is dependent on the saturation state. Snow depth, subsurface saturation, and ponded water depth are strongly codependent and positively correlated to ALT.« less

  12. Influences of Peat, Surface and Subsurface Water, and Snow on Active Layer Thickness

    SciTech Connect

    Atchley, Adam; Coon, Ethan T.; Painter, Scott L; Harp, Dylan; Wilson, Cathy

    2016-01-01

    The effect of three environmental conditions: 1) thickness of organic soil, 2) snow depth, and 3) soil moisture content or water table height above and below the soil surface, on active layer thickness (ALT) are investigated using an ensemble of 1D thermal hydrology models. Sensitivity analyses of the ensemble exposed the isolated influence of each environmental condition on ALT and their multivariate interactions. The primary and interactive influences are illustrated in the form of color maps of ALT change. Results show that organic layer acts as a strong insulator, and its thickness is the dominant control of ALT, but the strength of the effect of organic layer thickness is dependent on the saturation state. Snow depth, subsurface saturation, and ponded water depth are strongly codependent and positively correlated to ALT.

  13. Influences of Peat, Surface and Subsurface Water, and Snow on Active Layer Thickness

    DOE PAGESBeta

    Atchley, Adam; Coon, Ethan T.; Painter, Scott L; Harp, Dylan; Wilson, Cathy

    2016-01-01

    The effect of three environmental conditions: 1) thickness of organic soil, 2) snow depth, and 3) soil moisture content or water table height above and below the soil surface, on active layer thickness (ALT) are investigated using an ensemble of 1D thermal hydrology models. Sensitivity analyses of the ensemble exposed the isolated influence of each environmental condition on ALT and their multivariate interactions. The primary and interactive influences are illustrated in the form of color maps of ALT change. Results show that organic layer acts as a strong insulator, and its thickness is the dominant control of ALT, but themore » strength of the effect of organic layer thickness is dependent on the saturation state. Snow depth, subsurface saturation, and ponded water depth are strongly codependent and positively correlated to ALT.« less

  14. Influences and interactions of inundation, peat, and snow on active layer thickness

    NASA Astrophysics Data System (ADS)

    Atchley, Adam L.; Coon, Ethan T.; Painter, Scott L.; Harp, Dylan R.; Wilson, Cathy J.

    2016-05-01

    Active layer thickness (ALT), the uppermost layer of soil that thaws on an annual basis, is a direct control on the amount of organic carbon potentially available for decomposition and release to the atmosphere as carbon-rich Arctic permafrost soils thaw in a warming climate. We investigate how key site characteristics affect ALT using an integrated surface/subsurface permafrost thermal hydrology model. ALT is most sensitive to organic layer thickness followed by snow depth but is relatively insensitive to the amount of water on the landscape with other conditions held fixed. The weak ALT sensitivity to subsurface saturation suggests that changes in Arctic landscape hydrology may only have a minor effect on future ALT. However, surface inundation amplifies the sensitivities to the other parameters and under large snowpacks can trigger the formation of near-surface taliks.

  15. DEEP SILICATE ABSORPTION FEATURES IN COMPTON-THICK ACTIVE GALACTIC NUCLEI PREDOMINANTLY ARISE DUE TO DUST IN THE HOST GALAXY

    SciTech Connect

    Goulding, A. D.; Forman, W. R.; Jones, C.; Trichas, M.; Alexander, D. M.; Mullaney, J. R.; Bauer, F. E.; Hickox, R. C.

    2012-08-10

    We explore the origin of mid-infrared (mid-IR) dust extinction in all 20 nearby (z < 0.05) bona fide Compton-thick (N{sub H} > 1.5 Multiplication-Sign 10{sup 24} cm{sup -2}) active galactic nuclei (AGNs) with hard energy (E > 10 keV) X-ray spectral measurements. We accurately measure the silicate absorption features at {lambda} {approx} 9.7 {mu}m in archival low-resolution (R {approx} 57-127) Spitzer Infrared Spectrograph spectroscopy, and show that only a minority ( Almost-Equal-To 45%) of nearby Compton-thick AGNs have strong Si-absorption features (S{sub 9.7} = ln (f{sub int}/f{sub obs}) {approx}> 0.5) which would indicate significant dust attenuation. The majority ( Almost-Equal-To 60%) are star formation dominated (AGN:SB < 0.5) at mid-IR wavelengths and lack the spectral signatures of AGN activity at optical wavelengths, most likely because the AGN emission lines are optically extinguished. Those Compton-thick AGNs hosted in low-inclination-angle galaxies exhibit a narrow range in Si-absorption (S{sub 9.7} {approx} 0-0.3), which is consistent with that predicted by clumpy-torus models. However, on the basis of the IR spectra and additional lines of evidence, we conclude that the dominant contribution to the observed mid-IR dust extinction is dust located in the host galaxy (i.e., due to disturbed morphologies, dust lanes, galaxy inclination angles) and not necessarily a compact obscuring torus surrounding the central engine.

  16. Layered Structure of Bacterial and Archaeal Communities and Their In Situ Activities in Anaerobic Granules▿ †

    PubMed Central

    Satoh, Hisashi; Miura, Yuki; Tsushima, Ikuo; Okabe, Satoshi

    2007-01-01

    The microbial community structure and spatial distribution of microorganisms and their in situ activities in anaerobic granules were investigated by 16S rRNA gene-based molecular techniques and microsensors for CH4, H2, pH, and the oxidation-reduction potential (ORP). The 16S rRNA gene-cloning analysis revealed that the clones related to the phyla Alphaproteobacteria (detection frequency, 51%), Firmicutes (20%), Chloroflexi (9%), and Betaproteobacteria (8%) dominated the bacterial clone library, and the predominant clones in the archaeal clone library were affiliated with Methanosaeta (73%). In situ hybridization with oligonucleotide probes at the phylum level revealed that these microorganisms were numerically abundant in the granule. A layered structure of microorganisms was found in the granule, where Chloroflexi and Betaproteobacteria were present in the outer shell of the granule, Firmicutes were found in the middle layer, and aceticlastic Archaea were restricted to the inner layer. Microsensor measurements for CH4, H2, pH, and ORP revealed that acid and H2 production occurred in the upper part of the granule, below which H2 consumption and CH4 production were detected. Direct comparison of the in situ activity distribution with the spatial distribution of the microorganisms implied that Chloroflexi contributed to the degradation of complex organic compounds in the outermost layer, H2 was produced mainly by Firmicutes in the middle layer, and Methanosaeta produced CH4 in the inner layer. We determined the effective diffusion coefficient for H2 in the anaerobic granules to be 2.66 × 10−5 cm2 s−1, which was 57% in water. PMID:17905889

  17. Vegetation-Soil-Active Layer Relationships Along a Low-Arctic Bioclimate Gradient, Alaska

    NASA Astrophysics Data System (ADS)

    Walker, D. A.; Jia, G. J.; Epstein, H. E.; Shiklomanov, N.; Nelson, F.; Hinzman, L. D.; Romanovsky, V. E.

    2002-12-01

    Northern Alaska has three of five Arctic bioclimate subzones, which are representative of the circumpolar Low Arctic. This portion of the Arctic has more or less continuous tundra plant cover and well-developed moss canopies. We examined the biomass and remotely sensed spectral properties of the vegetation canopy, active-layer thickness, and the soil properties at 21 sites on the Arctic Slope and Seward Peninsula of Alaska. The sites were grouped into three bioclimate subzones according the summer warmth at the sites. The summer warmth index (SWI) is the sum of the mean monthly temperatures greater than 0 degrees C. Subzone C, the coldest subzone, occurs in a narrow strip along the northern coast of the Alaska. Subzone D covers most of the Arctic Coastal Plain and the northwest portion of the Seward Peninsula, and Subzone E covers most of the Foothills and most of the unforested portion of the Seward Peninsula. The SWIs in Subzones C, D, and E are generally less than 10-15 degrees C, 15-25 degrees C, and 25-35 degrees C respectively. The average active layer depths were 44, 55, and 47 cm respectively The shallow active layer in Subzone E is to a large degree a response to the denser vegetation canopies in Subzone E. Total plant biomass in Subzone C, D, and E averaged 421 g m-2, 503 g m-2, and 1178 g m-2 respectively. The much higher biomass in Subzone E was due primarily to woody shrubs (40 g m-2 in Subzone C, 51 g m-2 in Subzone D, and 730 g m-2 in Subzone E). The normalized difference vegetation index (NDVI) is one measure of greenness. Highest NDVI values were obtained from acidic tundra regions in Subzone E, and the lowest NDVI values were obtained in the nonacidic areas of Subzone C. In summary, the insulative properties of the vegetation play a very important role controlling the thickness of the active layer, and the amount of vegetation biomass differs according to summer warmth and soil properties. Acidic soils in the warmest parts of the Arctic (Subzone E

  18. Activation Effect of Fullerene C60 on the Carbon Dioxide Absorption Performance of Amine-Rich Polypropylenimine Dendrimers.

    PubMed

    Andreoli, Enrico; Barron, Andrew R

    2015-08-24

    Converting amine-rich compounds into highly effective carbon dioxide (CO2 ) sorbents requires a better understanding and control of their properties. The reaction of fullerene C60 with polyethyleneimine converts the polymer into a high-performance CO2 sorbent. In this study, experimental evidence is reported for the activation effect of C60 on the amine moieties of the polymer. To do so, polypropylenimine (PPI) dendrimers that allowed for a systematic comparison of molecular composition and CO2 absorption were used. The addition of C60 to PPI to form PPI-C60 results in a reduction of the energy barrier of CO2 absorption, but also in a parallel decrease in the frequency of successful collisions between CO2 and PPI-C60 due to a possible disruption of the hydrogen-bonding network of amino groups and bound water in PPI. This finding supports the existence of a non-affinity "repulsive" effect between hydrophobic C60 and hydrophilic amines that forces them to be actively exposed to CO2. PMID:26223905

  19. Influence of the Halogen Activation on the Ozone Layer in XXIst Century

    NASA Astrophysics Data System (ADS)

    Larin, Igor; Aloyan, Artash; Yermakov, Alexandr

    2016-04-01

    The aim of the work is to evaluate a possible effect of heterophase chemical reactions (HCR) with participation of reservoir gases (ClONO2, HCl) and sulfate particles of the Junge layer on the ozone layer at mid-latitudes in the XXI century, which could be relevant for more accurate predicting a recovery of the ozone layer, taking into account that just these processes were the main cause of the ozone depletion at the end of XXth century. Required for calculating the dynamics of GHR data on the specific volume/surface of the sulfate aerosols in the lower stratosphere were taken from the data of field experiments. Their physico-chemical properties (chemical composition, density, water activity and free protons activity et al.) have been obtained with help of thermodynamic calculations (Atmospheric Inorganic Model, AIM). Altitude concentration profiles of individual gas components, as well as temperature and relative humidity (RH) at a given geographic location and season have been calculated using a two-dimensional model SOCRATES. The calculations have been made for the conditions of June 1995, 2040 and 2080 at 15 km altitude and 50° N latitude. It has been shown that the rate of ozone depletion as a result of processes involving halogen activation for the given conditions in 2040, 2080 is about 35% lower than a corresponding value in 1995 (a year of maximum effect of halogen activation). From this we can conclude that in the XXI century, despite the natural decline of ozone-depleting chlorofluorocarbons. processes of halogen activation of the ozone depletion with participation of sulfate aerosols should be taken into account in the calculations of the recovery of the ozone layer at mid-latitudes.

  20. Air-Coupled Piezoelectric Transducers with Active Polypropylene Foam Matching Layers

    PubMed Central

    Gómez Álvarez-Arenas, Tomás E.

    2013-01-01

    This work presents the design, construction and characterization of air-coupled piezoelectric transducers using 1–3 connectivity piezocomposite disks with a stack of matching layers being the outer one an active quarter wavelength layer made of polypropylene foam ferroelectret film. This kind of material has shown a stable piezoelectric response together with a very low acoustic impedance (<0.1 MRayl). These features make them a suitable candidate for the dual use or function proposed here: impedance matching layer and active material for air-coupled transduction. The transducer centre frequency is determined by the λ/4 resonance of the polypropylene foam ferroelectret film (0.35 MHz), then, the rest of the transducer components (piezocomposite disk and passive intermediate matching layers) are all tuned to this frequency. The transducer has been tested in several working modes including pulse-echo and pitch-catch as well as wide and narrow band excitation. The performance of the proposed novel transducer is compared with that of a conventional air-coupled transducers operating in a similar frequency range. PMID:23666129

  1. Activated oil sands fluid coke for electrical double-layer capacitors

    NASA Astrophysics Data System (ADS)

    Zuliani, Jocelyn E.; Kirk, Donald W.; Jia, Charles Q.; Tong, Shitang

    2014-12-01

    Electrochemical capacitors are important energy storage devices that have high power density, rapid charging cycles and are highly cyclable. In this study, activated fluid coke has demonstrated high surface area, improved capacitive properties, and high energy density. Fluid coke is a by-product generated from continuous high temperature bitumen upgrading, resulting in the formation of nearly spherical particles with concentric carbon layers. The residual sulphur impurities in fluid coke may enhance its energy storage performance. The activated coke samples have high specific surface areas, up to 1960 m2 g-1, and show promising capacitive performance, in 4 M KOH electrolyte, with high gravimetric and specific capacitances of 228-257 F g-1 and 13-14 μF cm-2, respectively. These results are comparable to other top performing activated carbon materials [1-3]. The activated fluid coke maintains high performance at fast charging rates, greater than 160 F g-1 at a current density of 7500 mA g-1. Activated fluid coke's high capacitance and promising rate performance are potentially associated with its unique layered, and the moderate sulphur content in the chemical structure. Activated fluid coke is a unique opportunity to use a limited use by-product to generate activated carbon that has a high surface area and promising energy storage properties.

  2. Long-term active layer and ground surface temperature trends: results of 12 years of observations at Alaskan CALM sites

    NASA Astrophysics Data System (ADS)

    Shiklomanov, N. I.; Nelson, F. E.; Streletskyi, D. A.; Klene, A. E.; Schimek, M.; Little, J.

    2006-12-01

    The uppermost layer of seasonal thawing above permafrost (the active layer) is an important regulator of energy and mass fluxes between the surface and the atmosphere in the polar regions. The Circumpolar Active Layer Monitoring (CALM) program is a network of sites at which data about active-layer thickness (ALT) and dynamics are collected. CALM was established in the 1990s to observe and detect the long-term response of the active layer and near-surface permafrost to changes in climate. Active layer monitoring is an important component of efforts to assess the effects of global change in permafrost environments. CALM strategies are evolving; this presentation showcases some additions to CALM observation procedures designed to monitor processes and detect changes not anticipated in the original CALM protocol of the early 1990s. In this study we used data from 12 (1995-2006) years of extensive, spatially oriented field observations at CALM sites in northern Alaska to examine landscape-specific spatial and temporal trends in active-layer thickness and air and ground surface temperature. Despite an observed increase in air temperature, active-layer thickness exhibited a decreasing trend over the study period. This result indicates that soil consolidation accompanying penetration of thaw into an ice-rich stratum at the base of the active layer has resulted in subsidence of the surface with little or no apparent thickening of the active layer, as traditionally defined. Differential Global Positioning Systems (DGPS) technology was used to detect frost heave and thaw settlement within representative landscapes. Preliminary results indicate that heave and settlement follow patterns of spatial variation similar to those of active-layer thickness. To evaluate the effect of vegetation on ground surface temperature, several heat-transfer coefficients were estimated, including land cover specific thermal diffusivity and empirical n-factors.

  3. MMP activity in the hybrid layer detected with in situ zymography.

    PubMed

    Mazzoni, A; Nascimento, F D; Carrilho, M; Tersariol, I; Papa, V; Tjäderhane, L; Di Lenarda, R; Tay, F R; Pashley, D H; Breschi, L

    2012-05-01

    Dentinal proteases are believed to play an important role in the degradation of hybrid layers (HL). This study investigated the HL gelatinolytic activity by in situ zymography and functional enzyme activity assay. The hypotheses were that HLs created by an etch-and-rinse adhesive exhibit active gelatinolytic activity, and MMP-2 and -9 activities in dentin increase during adhesive procedures. Etched-dentin specimens were bonded with Adper Scotchbond 1XT and restored with composite. Adhesive/dentin interface slices were placed on microscope slides, covered with fluorescein-conjugated gelatin, and observed with a multi-photon confocal microscope after 24 hrs. Human dentin powder aliquots were prepared and assigned to the following treatments: A, untreated; B, etched with 10% phosphoric acid; or C, etched with 10% phosphoric acid and mixed with Scotchbond 1XT. The MMP-2 and -9 activities of extracts of dentin powder were measured with functional enzyme assays. Intense and continuous enzyme activity was detected at the bottom of the HL, while that activity was more irregular in the upper HL. Both acid-etching and subsequent adhesive application significantly increased MMP-2 and -9 activities (p < 0.05). The results demonstrate, for the first time, intrinsic MMP activity in the HL, and intense activation of matrix-bound MMP activity with both etching and adhesive application. PMID:22354448

  4. Absorption properties of infrared active gases at high pressures. II - N2O and CO

    NASA Astrophysics Data System (ADS)

    Fukabori, M.; Nakazawa, T.; Tanaka, M.

    1986-10-01

    At high pressures, intensities of 0.153 + or - 0.002, 1.14 + or - 0.01, 1.67 + or - 0.01, 0.035 + or - 0.002, 3.25 + or 0.02, and 49.9 + or - 0.3/cm per (atm-cm)STP for the 2.0, 2.1, 2.3, 2.5, 2.6, and 2.9 micron N2O bands, respectively, and 2.07 + or - 0.02/cm per (atm-cm)STP for the first overtone CO band were found. Equivalent widths of selfbroadening spectra calculated from the Lorenzian line profile are found to gradually exceed measured values for both molecules as the absorber amount increases, due to excess absorption in the band wings of the calculated spectra, and it is suggested that the spectral lines of CO2, N2O and CO are sub-Lorenzian at high pressures.

  5. High Efficiency Alternating Current Driven Organic Light Emitting Devices Employing Active Semiconducting Gate Layers

    NASA Astrophysics Data System (ADS)

    Smith, Gregory; Xu, Junwei; Carroll, David

    2015-03-01

    In this work, we describe the role of semiconductor-polymer interfaces in alternating current (AC) driven organic electroluminescent (EL) devices. We implement inorganic semiconducting materials between the external contact and the active layers in organic light EL devices. Precise control of capacitance and charge injection is required to realize bright and efficient large area AC driven devices. We show how this architecture results in active gating to the polymer layers, resulting in the novel ability to control the capacitance and charge injection characteristics. We propose a model based on band bending at the semiconductor-polymer interface. Furthermore, we elucidate the influence of the semiconductor-polymer interface on the internally coupled magnetic field generated in an alternating current driven organic light emitting device configuration. Magnetic fields can alter the ratios of singlet and triplet populations, and we show that internal generation of a magnetic field can dramatically alter the efficiency of light emission in organic EL devices.

  6. Microtopographic and depth controls on active layer chemistry in Arctic polygonal ground

    SciTech Connect

    Newman, Brent D.; Throckmorton, Heather M.; Graham, David E.; Gu, Baohua; Hubbard, Susan S.; Liang, Liyuan; Wu, Yuxin; Heikoop, J. M.; Herndon, Elizabeth M.; Phelps, Tommy J.; Wilson, Cathy; Wullschleger, Stan D.

    2015-03-24

    Polygonal ground is a signature characteristic of Arctic lowlands, and carbon release from permafrost thaw can alter feedbacks to Arctic ecosystems and climate. This study describes the first comprehensive spatial examination of active layer biogeochemistry that extends across high- and low-centered, ice wedge polygons, their features, and with depth. Water chemistry measurements of 54 analytes were made on surface and active layer pore waters collected near Barrow, Alaska, USA. Significant differences were observed between high- and low-centered polygons suggesting that polygon types may be useful for landscape-scale geochemical classification. However, differences were found for polygon features (centers and troughs) for analytes that were not significant for polygon type, suggesting that finer-scale features affect biogeochemistry differently from polygon types. Depth variations were also significant, demonstrating important multidimensional aspects of polygonal ground biogeochemistry. These results have major implications for understanding how polygonal ground ecosystems function, and how they may respond to future change.

  7. Microtopographic and depth controls on active layer chemistry in Arctic polygonal ground

    NASA Astrophysics Data System (ADS)

    Newman, B. D.; Throckmorton, H. M.; Graham, D. E.; Gu, B.; Hubbard, S. S.; Liang, L.; Wu, Y.; Heikoop, J. M.; Herndon, E. M.; Phelps, T. J.; Wilson, C. J.; Wullschleger, S. D.

    2015-03-01

    Polygonal ground is a signature characteristic of Arctic lowlands, and carbon release from permafrost thaw can alter feedbacks to Arctic ecosystems and climate. This study describes the first comprehensive spatial examination of active layer biogeochemistry that extends across high- and low-centered, ice wedge polygons, their features, and with depth. Water chemistry measurements of 54 analytes were made on surface and active layer pore waters collected near Barrow, Alaska, USA. Significant differences were observed between high- and low-centered polygons suggesting that polygon types may be useful for landscape-scale geochemical classification. However, differences were found for polygon features (centers and troughs) for analytes that were not significant for polygon type, suggesting that finer-scale features affect biogeochemistry differently from polygon types. Depth variations were also significant, demonstrating important multidimensional aspects of polygonal ground biogeochemistry. These results have major implications for understanding how polygonal ground ecosystems function, and how they may respond to future change.

  8. Active layer hydrology for Imnavait Creek, Toolik, Alaska. Annual progress report, July 1984--January 1986

    SciTech Connect

    Kane, D.L.

    1986-12-31

    In the annual hydrologic cycle, snowmelt is the most significant event at Imnavait Creek located near Toolik Lake, Alaska. Precipitation that has accumulated for more than 6 months on the surface melts in a relatively short period of 7 to 10 days once sustained melting occurs. During the ablation period, runoff dominates the hydrologic cycle. Some meltwater goes to rewetting the organic soils in the active layer. The remainder is lost primarily because of evaporation, since transpiration is not a very active process at this time. Following the snowmelt period, evapotranspiration becomes the dominate process, with base flow contributing the other watershed losses. It is important to note that the water initally lost by evapotranspiration entered the organic layer during melt. This water from the snowpack ensures that each year the various plant communities will have sufficient water to start a new summer of growth.

  9. Dual Gate Thin Film Transistors Based on Indium Oxide Active Layers

    SciTech Connect

    Kekuda, Dhananjaya; Rao, K. Mohan; Tolpadi, Amita; Chu, C. W.

    2011-07-15

    Polycrystalline Indium Oxide (In{sub 2}O{sub 3}) thin films were employed as an active channel layer for the fabrication of bottom and top gate thin film transistors. While conventional SiO{sub 2} served as a bottom gate dielectric, cross-linked poly-4-vinylphenol (PVP) was used a top gate dielectric. These nano-crystalline TFTs exhibited n-channel behavior with their transport behavior highly dependent on the thickness of the channel. The correlation between the thickness of the active layer and TFT parameters such as on/off ratio, field-effect mobility, threshold voltage were carried out. The optical spectra revealed a high transmittance in the entire visible region, thus making them promising candidates for the display technology.

  10. Plant canopy light absorption model with application to wheat

    NASA Technical Reports Server (NTRS)

    Chance, J. E.; Lemaster, E. W.

    1978-01-01

    A light absorption model (LAM) for vegetative plant canopies has been derived from the Suits reflectance model. From the LAM the absorption of light in the photosynthetically active region of the spectrum (400-700 nm) has been calculated for a Penjamo wheat crop for several situations including (a) the percent absorption of the incident radiation by a canopy of LAI 3.1 having a four-layer structure, (b) the percent absorption of light by the individual layers within a four-layer canopy and by the underlying soil, (c) the percent absorption of light by each vegetative canopy layer for variable sun angle, and (d) the cumulative solar energy absorbed by the developing wheat canopy as it progresses from a single layer through its growth stages to a three-layer canopy. This calculation is also presented as a function of the leaf area index and is shown to be in agreement with experimental data reported by Kanemasu on Plainsman V wheat.

  11. A Comparison of Active and Passive Methods for Control of Hypersonic Boundary Layers on Airbreathing Configurations

    NASA Technical Reports Server (NTRS)

    Berry, Scott A.; Nowak, Robert J.

    2003-01-01

    Active and passive methods for control of hypersonic boundary layers have been experimentally examined in NASA Langley Research Center wind tunnels on a Hyper-X model. Several configurations for forcing transition using passive discrete roughness elements and active mass addition, or blowing, methods were compared in two hypersonic facilities, the 20-Inch Mach 6 Air and the 31-Inch Mach 10 Air tunnels. Heat transfer distributions, obtained via phosphor thermography, shock system details, and surface streamline patterns were measured on a 0.333-scale model of the Hyper-X forebody. The comparisons between the active and passive methods for boundary layer control were conducted at test conditions that nearly match the nominal Mach 7 flight trajectory of an angle-of-attack of 2-deg and length Reynolds number of 5.6 million. For the passive roughness examination, the primary parametric variation was a range of trip heights within the calculated boundary layer thickness for several trip concepts. The prior passive roughness study resulted in a swept ramp configuration being selected for the Mach 7 flight vehicle that was scaled to be roughly 0.6 of the calculated boundary layer thickness. For the active jet blowing study, the blowing manifold pressure was systematically varied for each configuration, while monitoring the mass flow, to determine the jet penetration height with schlieren and transition movement with the phosphor system for comparison to the passive results. All the blowing concepts tested were adequate for providing transition onset near the trip location with manifold stagnation pressures on the order of 40 times the model static pressure or higher.

  12. Influence of active layer and support layer surface structures on organic fouling propensity of thin-film composite forward osmosis membranes.

    PubMed

    Lu, Xinglin; Arias Chavez, Laura H; Romero-Vargas Castrillón, Santiago; Ma, Jun; Elimelech, Menachem

    2015-02-01

    In this study, we investigate the influence of surface structure on the fouling propensity of thin-film composite (TFC) forward osmosis (FO) membranes. Specifically, we compare membranes fabricated through identical procedures except for the use of different solvents (dimethylformamide, DMF and N-methyl-2-pyrrolidinone, NMP) during phase separation. FO fouling experiments were carried out with a feed solution containing a model organic foulant. The TFC membranes fabricated using NMP (NMP-TFC) had significantly less flux decline (7.47 ± 0.15%) when compared to the membranes fabricated using DMF (DMF-TFC, 12.70 ± 2.62% flux decline). Water flux was also more easily recovered through physical cleaning for the NMP-TFC membrane. To determine the fundamental cause of these differences in fouling propensity, the active and support layers of the membranes were extensively characterized for physical and chemical characteristics relevant to fouling behavior. Polyamide surface roughness was found to dominate all other investigated factors in determining the fouling propensities of our membranes relative to each other. The high roughness polyamide surface of the DMF-TFC membrane was also rich in larger leaf-like structures, whereas the lower roughness NMP-TFC membrane polyamide layer contained more nodular and smaller features. The support layers of the two membrane types were also characterized for their morphological properties, and the relation between support layer surface structure and polyamide active layer formation was discussed. Taken together, our findings indicate that support layer structure has a significant impact on the fouling propensity of the active layer, and this impact should be considered in the design of support layer structures for TFC membranes. PMID:25564877

  13. Impact of calcium-activated potassium channels on NMDA spikes in cortical layer 5 pyramidal neurons.

    PubMed

    Bock, Tobias; Stuart, Greg J

    2016-03-01

    Active electrical events play an important role in shaping signal processing in dendrites. As these events are usually associated with an increase in intracellular calcium, they are likely to be under the control of calcium-activated potassium channels. Here, we investigate the impact of calcium-activated potassium channels onN-methyl-d-aspartate (NMDA) receptor-dependent spikes, or NMDA spikes, evoked by glutamate iontophoresis onto basal dendrites of cortical layer 5 pyramidal neurons. We found that small-conductance calcium-activated potassium channels (SK channels) act to reduce NMDA spike amplitude but at the same time, also decrease the iontophoretic current required for their generation. This SK-mediated decrease in NMDA spike threshold was dependent on R-type voltage-gated calcium channels and indicates a counterintuitive, excitatory effect of SK channels on NMDA spike generation, whereas the capacity of SK channels to suppress NMDA spike amplitude is in line with the expected inhibitory action of potassium channels on dendritic excitability. Large-conductance calcium-activated potassium channels had no significant impact on NMDA spikes, indicating that these channels are either absent from basal dendrites or not activated by NMDA spikes. These experiments reveal complex and opposing interactions among NMDA receptors, SK channels, and voltage-gated calcium channels in basal dendrites of cortical layer 5 pyramidal neurons during NMDA spike generation, which are likely to play an important role in regulating the way these neurons integrate the thousands of synaptic inputs they receive. PMID:26936985

  14. Acoustic radiation from the submerged circular cylindrical shell treated with active constrained layer damping

    NASA Astrophysics Data System (ADS)

    Yuan, Li-Yun; Xiang, Yu; Lu, Jing; Jiang, Hong-Hua

    2015-12-01

    Based on the transfer matrix method of exploring the circular cylindrical shell treated with active constrained layer damping (i.e., ACLD), combined with the analytical solution of the Helmholtz equation for a point source, a multi-point multipole virtual source simulation method is for the first time proposed for solving the acoustic radiation problem of a submerged ACLD shell. This approach, wherein some virtual point sources are assumed to be evenly distributed on the axial line of the cylindrical shell, and the sound pressure could be written in the form of the sum of the wave functions series with the undetermined coefficients, is demonstrated to be accurate to achieve the radiation acoustic pressure of the pulsating and oscillating spheres respectively. Meanwhile, this approach is proved to be accurate to obtain the radiation acoustic pressure for a stiffened cylindrical shell. Then, the chosen number of the virtual distributed point sources and truncated number of the wave functions series are discussed to achieve the approximate radiation acoustic pressure of an ACLD cylindrical shell. Applying this method, different radiation acoustic pressures of a submerged ACLD cylindrical shell with different boundary conditions, different thickness values of viscoelastic and piezoelectric layer, different feedback gains for the piezoelectric layer and coverage of ACLD are discussed in detail. Results show that a thicker thickness and larger velocity gain for the piezoelectric layer and larger coverage of the ACLD layer can obtain a better damping effect for the whole structure in general. Whereas, laying a thicker viscoelastic layer is not always a better treatment to achieve a better acoustic characteristic. Project supported by the National Natural Science Foundation of China (Grant Nos. 11162001, 11502056, and 51105083), the Natural Science Foundation of Guangxi Zhuang Autonomous Region, China (Grant No. 2012GXNSFAA053207), the Doctor Foundation of Guangxi

  15. The cerebellar Golgi cell and spatiotemporal organization of granular layer activity

    PubMed Central

    D'Angelo, Egidio; Solinas, Sergio; Mapelli, Jonathan; Gandolfi, Daniela; Mapelli, Lisa; Prestori, Francesca

    2013-01-01

    The cerebellar granular layer has been suggested to perform a complex spatiotemporal reconfiguration of incoming mossy fiber signals. Central to this role is the inhibitory action exerted by Golgi cells over granule cells: Golgi cells inhibit granule cells through both feedforward and feedback inhibitory loops and generate a broad lateral inhibition that extends beyond the afferent synaptic field. This characteristic connectivity has recently been investigated in great detail and been correlated with specific functional properties of these neurons. These include theta-frequency pacemaking, network entrainment into coherent oscillations and phase resetting. Important advances have also been made in terms of determining the membrane and synaptic properties of the neuron, and clarifying the mechanisms of activation by input bursts. Moreover, voltage sensitive dye imaging and multi-electrode array (MEA) recordings, combined with mathematical simulations based on realistic computational models, have improved our understanding of the impact of Golgi cell activity on granular layer circuit computations. These investigations have highlighted the critical role of Golgi cells in: generating dense clusters of granule cell activity organized in center-surround structures, implementing combinatorial operations on multiple mossy fiber inputs, regulating transmission gain, and cut-off frequency, controlling spike timing and burst transmission, and determining the sign, intensity and duration of long-term synaptic plasticity at the mossy fiber-granule cell relay. This review considers recent advances in the field, highlighting the functional implications of Golgi cells for granular layer network computation and indicating new challenges for cerebellar research. PMID:23730271

  16. Enhancing the performance of BHJ solar cell via self-assembly templates in active layer

    NASA Astrophysics Data System (ADS)

    Liu, Ying; Li, Hongfei; Yang, Zhenhua; Nam, Chang-Yong; Satija, Sushil; Rafailovich, Miriam

    The bulk heterojunction (BHJ) solar cell is an important example of a polymer solar cell technology that has been proposed in recent years. However, due to the disordered inner structures in the active layer, control of the inner structure within the active layer is required to enhance the efficiency. In our approach, a self-assembly of tertiary polymer blend film is confined between the air and solid interfaces. The principal has been proved using a blend of PMMA: P3HT: PCBM where we showed that the PMMA phase formed a column structure in the P3HT, which template the PCBM phase between the electrodes. Neutron reflectometry was used to demonstrate the confinement of PCBM at the interface between P3HT and PMMA in the active layer. The columnar structured template is investigated under atomic force microscopy (AFM) and transmission electron microscopy (TEM). SCLC mobility measurement indicated an obvious improvement on both hole and electron mobility. The different morphological structures formed via phase segregation are correlated with the performance of the PEV cells fabricated at the BNL-CFN and significant enhancement for the efficiency is observed.

  17. Origin of photogenerated carrier recombination at the metal-active layer interface in polymer solar cells.

    PubMed

    Kumar, Mukesh; Dubey, Ashish; Reza, Khan Mamun; Adhikari, Nirmal; Qiao, Qiquan; Bommisetty, Venkat

    2015-11-01

    The role of the metal-active layer interface in photogenerated recombination has been investigated using nanoscale current sensing atomic force microscopy (CS-AFM) and intensity modulated photocurrent spectroscopy (IMPS) in as-deposited, pre-annealed and post-annealed bulk heterojunction (BHJ) solar cells. Aluminum (Al) confined post-annealed BHJ solar cells exhibited a significantly improved device efficiency compared to pre-annealed BHJ solar cells having similar photocarrier harvesting ability in the active layer. The nanoscale topography and CS-AFM results indicate a uniform PCBM rich phase at the metal-active layer interface in the post-annealed cells, but PCBM segregation in the pre-annealed cells. These two different annealing processes showed different carrier dynamics revealed using IMPS under various light intensities. The IMPS results suggest reduced photo generated carrier recombination in uniform PCBM rich post-annealed BHJ solar cells. This study reveals the importance of the metal-bend interface in BHJ solar cells in order to obtain efficient charge carrier extraction for high efficiency. PMID:26431263

  18. Self-assembly Columnar Structure in Active Layer of Bulk Heterojunction Solar Cell

    NASA Astrophysics Data System (ADS)

    Pan, Cheng; Segui, Jennifer; Yu, Yingjie; Li, Hongfei; Akgun, Bulent; Satijia, Sushil. K.; Gersappe, Dilip; Nam, Chang-Yong; Rafailovich, Miriam

    2012-02-01

    Bulk Heterojunction (BHJ) polymer solar cells are an area of intense interest due to their flexibility and relatively low cost. However, due to the disordered inner structure in active layer, the power conversion efficiency of BHJ solar cell is relatively low. Our research provides the method to produce ordered self-assembly columnar structure within active layer of bulk heterojunction (BHJ) solar cell by introducing polystyrene (PS) into the active layer. The blend thin film of polystyrene, poly (3-hexylthiophene-2,5-diyl) (P3HT) and [6,6]-phenyl C61 butyric acid methyl ester (PCBM) at different ratio are spin coated on substrate and annealed in vacuum oven for certain time. Atomic force microscopy (AFM) images show uniform phase segregation on the surface of polymer blend thin film and highly ordered columnar structure is then proven by etching the film with ion sputtering. TEM cross-section technology is also used to investigate the column structure. Neutron reflectometry was taken to establish the confinement of PCBM at the interface of PS and P3HT. The different morphological structures formed via phase segregation will be correlated with the performance of the PEV cells to be fabricated at the BNL-CFN.

  19. Solar selective absorption coatings

    DOEpatents

    Mahoney, Alan R.; Reed, Scott T.; Ashley, Carol S.; Martinez, F. Edward

    2004-08-31

    A new class of solar selective absorption coatings are disclosed. These coatings comprise a structured metallic overlayer such that the overlayer has a sub-micron structure designed to efficiently absorb solar radiation, while retaining low thermal emissivity for infrared thermal radiation. A sol-gel layer protects the structured metallic overlayer from mechanical, thermal, and environmental degradation. Processes for producing such solar selective absorption coatings are also disclosed.

  20. Solar selective absorption coatings

    DOEpatents

    Mahoney, Alan R.; Reed, Scott T.; Ashley, Carol S.; Martinez, F. Edward

    2003-10-14

    A new class of solar selective absorption coatings are disclosed. These coatings comprise a structured metallic overlayer such that the overlayer has a sub-micron structure designed to efficiently absorb solar radiation, while retaining low thermal emissivity for infrared thermal radiation. A sol-gel layer protects the structured metallic overlayer from mechanical, thermal, and environmental degradation. Processes for producing such solar selective absorption coatings are also disclosed.

  1. Architectural evolution of the Nojima fault and identification of the activated slip layer by Kobe earthquake

    NASA Astrophysics Data System (ADS)

    Tanaka, Hidemi; Omura, Kentaro; Matsuda, Tatsuo; Ikeda, Ryuji; Kobayashi, Kenta; Murakami, Masaki; Shimada, Koji

    2007-07-01

    Evolutionary history of Nojima Fault zone is clarified by comprehensive examinations of petrological, geophysical, and geochemical characterizations on a fault zone in deep-drilled core penetrating the Nojima Fault. On the basis of the results, we reconstruct a whole depth profile of the architecture of the Nojima Fault and identify the primal slip layer activated by 1995 Kobe earthquake. The deepest part (8- to 12-km depth) of the fault zone is composed of thin slip layers of pseudotachylite (5 to 10 mm thick each, 10 cm in total). Middle depth (4- to 8-km depth) of the fault zone is composed of fault core (6 to 10 m thick), surrounded by thick (100 m thick) damage zone, characterized by zeolite precipitation. The shallow part of the fault zone (1- to 4-km depth) is composed of distributed narrow shear zones, which are characterized by combination of thin (0.5 cm thick each, 10 cm in total) ultracataclasite layers at the core of shear zones, surrounded by thicker (1 to 3 m thick) damage zones associated with carbonate precipitation. An extremely thin ultracataclasite layer (7 mm thick), activated by the 1995 Kobe earthquake, is clearly identified from numerous past slip layers, overprinting one of the shear zones, as evidenced by conspicuous geological and geophysical anomalies. The Nojima Fault zone was 10 to 100 times thicker at middle depth than that of shallower and deeper depths. The thickening would be explained as a combination of physical and chemical effects as follows. (1) Thickening of "fault core" at middle depth would be attributed to normal stress dependence on thickness of the shear zone and (2) an extreme thickening of "damage zone" in middle depth of the crust would result from the weakening of the fault zone due to super hydrostatic fluid pressure at middle depths. The high fluid pressure would result from faster sealing with low-temperature carbonate at the shallower fault zone.

  2. X-ray Absorption and Emission Study of Dioxygen Activation by a Small-Molecule Manganese Complex

    PubMed Central

    Rees, Julian A.; Martin-Diaconescu, Vlad; Kovacs, Julie A.; DeBeer, Serena

    2015-01-01

    Manganese K-edge X-ray absorption (XAS) and Kβ emission (XES) spectroscopies were used to investigate the factors contributing to O–O bond activation in a small-molecule system. The recent structural characterization of a metastable peroxo-bridged dimeric Mn(III)2 complex derived from dioxygen has provided the first opportunity to obtain X-ray spectroscopic data on this type of species. Ground state and time-dependent density functional theory calculations have provided further insight into the nature of the transitions in XAS pre-edge and valence-to-core (VtC) XES spectral regions. An experimentally validated electronic structure description has also enabled the determination of structural and electronic factors that govern peroxo bond activation, and have allowed us to propose both a rationale for the metastability of this unique compound, as well as potential future ligand designs which may further promote or inhibit O–O bond scission. Finally, we have explored the potential of VtC XES as an element-selective probe of both the coordination mode and degree of activation of peroxomanganese adducts. The comparison of these results to a recent VtC XES study of iron-mediated dintrogen activation helps to illustrate the factors that may determine the success of this spectroscopic method for future studies of small-molecule activation at transition metal sites. PMID:26061165

  3. Absorption of enzymatically active sup 125 I-labeled bovine milk xanthine oxidase fed to rabbits

    SciTech Connect

    Rzucidlo, S.J. ); Zikakis, J.P. )

    1990-05-01

    Rabbits fed a regular laboratory diet supplemented with a high-fat milk containing xanthine oxidase (XO) were studied to determine the presence of active XO in the blood. A pilot feeding study, where rabbits consumed a high-fat diet containing xanthine oxidase, showed a correlation between dairy food consumption and XO activity in the blood. Antibody to dietary XO was also found. In a second study, rabbits were fed ad libitum the high-fat milk and blood serum samples were tested weekly for XO activity. No elevation in serum XO activity was found. A third study showed that serum XO activity was increased when rabbits were force fed the high-fat milk. The final study consisted of force feeding {sup 125}I-labeled XO to one rabbit to ascertain whether the observed increase in serum XO was due to dietary or endogenous XO. Isoelectric focusing of sera collected from the test rabbit strongly suggested that at least a portion of the serum XO contained the radioactive label. This is the first direct evidence showing the uptake of dietary active XO from the gut.

  4. Surface analytical characterization of chromium-stabilized protecting oxide layers on stainless steel referring to activity buildup

    NASA Astrophysics Data System (ADS)

    Thieme, M.; Scharnweber, D.; Drechsler, L.; Heiser, C.; Adolphi, B.; Weiss, A.

    1992-08-01

    Surface analytical methods were used to characterize both protecting oxide layers formed by hydrothermal chromate treatment (HTCT) on stabilized austenitic stainless steel and hydrothermally grown corrosion product layers (CPL) within the scope of lowering the activity buildup in the primary circuit of nuclear power plants. Morphology, thickness and chromium depth distribution of the layers proved to be considerably different from each other. According to Raman microspectrometry, there were also alterations in the chemical nature of the oxide species. Preceding electropolishing gave rise to particular properties of the respective layers. Prerequisites for an optimal corrosion behaviour of the protecting layers are discussed. Titanium-containing precipitations were oxidatively transformed by HTCT.

  5. Real-time monitoring of enzyme activity in a mesoporous silicon double layer

    NASA Astrophysics Data System (ADS)

    Orosco, Manuel M.; Pacholski, Claudia; Sailor, Michael J.

    2009-04-01

    The activity of certain proteolytic enzymes is often an indicator of disease states such as cancer, stroke and neurodegeneracy, so there is a need for rapid assays that can characterize the kinetics and substrate specificity of enzymatic reactions. Nanostructured membranes can efficiently separate biomolecules, but coupling a sensitive detection method to such a membrane remains difficult. Here, we demonstrate a single mesoporous nanoreactor that can isolate and quantify in real time the reaction products of proteases. The reactor consists of two layers of porous films electrochemically prepared from crystalline silicon. The upper layer, with large pore sizes (~100 nm in diameter), traps the protease and acts as the reactor. The lower layer, with smaller pore sizes (~6 nm), excludes the proteases and other large proteins and captures the reaction products. Infiltration of the digested fragments into the lower layer produces a measurable change in optical reflectivity, and this allows label-free quantification of enzyme kinetics in real time within a volume of ~5 nl.

  6. Active layer thermal regime at different vegetation covers at Lions Rump, King George Island, Maritime Antarctica

    NASA Astrophysics Data System (ADS)

    Almeida, Ivan C. C.; Schaefer, Carlos Ernesto G. R.; Fernandes, Raphael B. A.; Pereira, Thiago T. C.; Nieuwendam, Alexandre; Pereira, Antônio Batista

    2014-11-01

    Climate change impacts the biotic and abiotic components of polar ecosystems, affecting the stability of permafrost, active layer thickness, vegetation, and soil. This paper describes the active layer thermal regimes of two adjacent shallow boreholes, under the same soil but with two different vegetations. The study is location in Lions Rump, at King George Island, Maritime Antarctic, one of the most sensitive regions to climate change, located near the climatic limit of Antarctic permafrost. Both sites are a Turbic Cambic Cryosol formed on andesitic basalt, one under moss vegetation (Andreaea gainii, at 85 m a.s.l.) and another under lichen (Usnea sp., at 86 m a.s.l.), located 10 m apart. Ground temperature at same depths (10, 30 and 80 cm), water content at 80 cm depth and air temperature were recorded hourly between March 2009 and February 2011. The two sites showed significant differences in mean annual ground temperature for all depths. The lichen site showed a higher soil temperature amplitude compared to the moss site, with ground surface (10 cm) showing the highest daily temperature in January 2011 (7.3 °C) and the lowest daily temperature in August (- 16.5 °C). The soil temperature at the lichen site closely followed the air temperature trend. The moss site showed a higher water content at the bottommost layer, consistent with the water-saturated, low landscape position. The observed thermal buffering effect under mosses is primarily associated with higher moisture onsite, but a longer duration of the snowpack (not monitored) may also have influenced the results. Active layer thickness was approximately 150 cm at low-lying moss site, and 120 cm at well-drained lichen site. This allows to classify these soils as Cryosols (WRB) or Gelisols (Soil Taxonomy), with evident turbic features.

  7. Microbial activities at the benthic boundary layer in the Aegean Sea

    NASA Astrophysics Data System (ADS)

    Bianchi, A.; Tholosan, O.; Garcin, J.; Polychronaki, T.; Tselepides, A.; Buscail, R.; Duineveld, G.

    2003-05-01

    During the Aegean Sea component of the EU MTP-MATER project, benthic samples were acquired along a depth gradient from two continental margins in the Aegean Sea. Sampling was undertaken during spring and summer 1997 and the microbial metabolic activities measured (Vmax for aminopeptidase activity, 14C-glutamate respiration and assimilation) displayed seasonal variability even in deep-sea conditions. The metabolic rates encountered in the North Aegean (average depth 566±234 m), were approximately five-fold higher than in the deeper (1336±140 m) Southern part of the Aegean. The aminopeptidase rates, however, were the exception with higher values recorded in the more oligotrophic sediments of the Southern stations (1383±152 vs. 766±297 nmol MCA cm -2 h -1). A discrepancy in bacterial metabolism also appeared in the near bottom waters. In the Southern stations, 80% of the glutamate uptake was used for energy yielding processes and only 20% devoted to biomass production, while in the North Aegean, most of the used glutamate was incorporated into bacterial cells. During the early burial stages, bacterial mineralization rates estimated from 14C-glutamate respiration decreased drastically compared to the rates of biopolymer hydrolysis estimated by aminopeptidase assays. Thus, at the 2-cm depth layer, these rates were only 32 and up to 77% of the corresponding average values, respectively, in the superficial layer. Such a discrepancy between the evolution of these two metabolic activities is possibly due to the rapid removal of readily utilizable monomers in the surface deposits. The correlation between bacterial respiration and total organic carbon, or total organic nitrogen, is higher in the surficial sediment (0-2 and 2-4 cm) than in the underlying layer. Conversely, it is only at 4-cm depth layer that the hydrolysis rates appear correlated with organic carbon and nitrogen concentrations. This pattern confirms the drastic degradation of organic matter during the

  8. Polycarbonate activation for electroless plating by dimethylaminoborane absorption and subsequent nanoparticle deposition

    NASA Astrophysics Data System (ADS)

    Muench, Falk; Bohn, Sebastian; Rauber, Markus; Seidl, Tim; Radetinac, Aldin; Kunz, Ulrike; Lauterbach, Stefan; Kleebe, Hans-Joachim; Trautmann, Christina; Ensinger, Wolfgang

    2014-07-01

    Electroless plating of metal films on polymer substrates usually requires the presence of metal particles acting as catalytically active nuclei for the deposition reaction. Herein, we present a novel and versatile approach towards the activation of polycarbonate substrates with metal nanoparticles. It is based on the diffusion of dimethylaminoborane into the polymer matrix, followed by reaction of the sensitized substrates with metal salt solutions. The reducing agent uptake was controlled by changing the duration of the sensitization and the dimethylaminoborane concentration in the sensitization solution. Different seed types (Ag, Au, Pd, Pt and Rh) were deposited by variation of the activation solution. The proposed mechanism was confirmed with FTIR and TEM measurements. In addition, AFM revealed that apart from a slight roughening in the nanometer range, the surface morphology of the polymer remained unchanged, rendering the method viable for template-based nanomaterial fabrication. Due to its pronounced variability, the new technique allows to tailor the activity of polymer substrates for consecutive electroless plating. The feasibility and nanoscale homogeneity of the process were proven by the electroless fabrication of well-defined Au and Pt nanotubes in ion-track etched polycarbonate templates. The combination of features (use of simple and easily scalable wet-chemical processes, facile seed variation, high activation quality on complex surfaces) renders the outlined technique promising for the fabrication of intricate nanomaterials as well as for the metallization of macroscopic work pieces.

  9. Slowly digestible starch diets alter proximal glucosidase activity and glucose absorption

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Sucrase-isomaltase (Si) and maltase-glucoamylase (Mgam) are mucosal glucosidases required for digestion of starch to glucose. Ablation of maltase-Mgam reduces in vivo starch digestion. We tested whether slowly digestible starch diets induce changes in glucosidase activities. Rice starch was encaps...

  10. Study on Na layer response to geomagnetic activities based on Odin/OSIRIS Na density data

    NASA Astrophysics Data System (ADS)

    Tsuda, Takuo; Nakamura, Takuji; Hedin, Jonas; Gumbel, Jorg; Hosokawa, Keisuke; Ejiri, Mitsumu K.; Nishiyama, Takanori; Takahashi, Toru

    2016-07-01

    The Na layer is normally distributed from 80 to 110 km, and the height range is corresponding to the ionospheric D and E region. In the polar region, the energetic particles precipitating from the magnetosphere can often penetrate into the E region and even into the D region. Thus, the influence of the energetic particles to the Na layer is one of interests in the aspect of the atmospheric composition change accompanied with the auroral activity. There are several previous studies in this issue. For example, recently, we have reported an initial result on a clear relationship between the electron density increase (due to the energetic particles) and the Na density decrease from observational data sets obtained by Na lidar, EISCAT VHF radar, and optical instruments at Tromsoe, Norway on 24-25 January 2012. However, all of the previous studies had been carried out based on case studies by ground-based lidar observations. In this study, we have performed, for the first time, statistical analysis using Na density data from 2004 to 2009 obtained with the Optical Spectrograph and InfraRed Imager System (OSIRIS) onboard Odin satellite. In the presentation, we will show relationship between the Na density and geomagnetic activities, and its latitudinal variation. Based on these results, the Na layer response to the energetic particles will be discussed.

  11. Design method of the layered active magnetic regenerator (AMR) for hydrogen liquefaction by numerical simulation

    NASA Astrophysics Data System (ADS)

    Park, Inmyong; Kim, Youngkwon; Park, Jiho; Jeong, Sangkwon

    2015-09-01

    The design procedure of an active magnetic regenerator (AMR) operating between liquid nitrogen temperature and liquid hydrogen temperature is discussed with the selected magnetic refrigerants. Selected magnetic refrigerants (GdNi2, Dy0.85Er0.15Al2, Dy0.5Er0.5Al2, and Gd0.1Dy0.9Ni2) that have different transition temperatures are layered in an AMR to widen the temperature span. The optimum volume fraction of the layered refrigerants for the maximum COP with minimum volume is designed in a two-stage active magnetic regenerative refrigerator (AMRR) using one dimensional numerical simulation. The entropy generation in each stage of the AMR is calculated by the numerical simulation to optimize the proposed design. The main sources of the entropy generation in the AMR are pressure drop, convection and conduction heat transfers in the AMR. However, the entropy generation by the convective heat transfer is mostly dominant in the optimized cases. In this paper, the design parameters and the operating conditions such as the distribution of the selected refrigerants in the layered AMR, the intermediate temperature between two stages and the mass flow rate of heat transfer fluid are specifically determined to maximize the performance of the AMR. The proposed design method will facilitate the construction of AMR systems with various magnetic refrigerants and conditions such as AMR size, operating temperature range, and magnetic field variation.

  12. First insight into catalytic activity of anionic iron porphyrins immobilized on exfoliated layered double hydroxides.

    PubMed

    Nakagaki, Shirley; Halma, Matilte; Bail, Alesandro; Arízaga, Gregório Guadalupe Carbajal; Wypych, Fernando

    2005-01-15

    Mg-Al layered double hydroxide (LDH) intercalated with glycinate anions was synthesized through co-precipitation and exfoliated in formamide and the single-layer suspension was reacted with aqueous iron porphyrin solutions (Fe(TDFSPP) and Fe(TCFSPP)). The obtained materials were characterized by X-ray powder diffraction, UV-vis, and electron paramagnetic resonance and investigated in the oxidation reaction of cyclooctene and cyclohexane using iodosylbenzene as oxidant. The iron porphyrin seems to be immobilized at the surface of the glycinate intercalated LDH. The catalytic activities obtained in heterogeneous media for iron porphyrin, Fe(TDFSPP), was superior to the results obtained under homogeneous conditions, but the opposite effect was observed on the Fe(TCFSPP), indicating that, instead of the structural similarity of both iron porphyrins (second-generation porphyrins), the immobilization of each one produced different catalysts. The best catalytic activity of the Fe(TDFSPP)/Gly-LDH, compared to Fe(TCFSPP)/Gly-LDH, can be explained by the easy access of the oxidant and the substrate to the catalytic sites in the former, probably located at the surface of the layered double hydroxide pillared with glycinate anions. A model for the immobilization and a mechanism for the oxidation reaction will be discussed. PMID:15571697

  13. Imaging active layer and permafrost variability in the Arctic using electromagnetic induction data

    NASA Astrophysics Data System (ADS)

    Dafflon, B.; Hubbard, S. S.; Ulrich, C.; Peterson, J. E.; Wu, Y.; Chen, J.; Wullschleger, S. D.

    2012-12-01

    Characterizing the spatial variability of active layer and permafrost properties is critical for gaining an understanding of Arctic ecosystem functioning and for parameterizing process-rich models that simulate feedbacks to a changing climate. Due to the sensitivity of electrical conductivity measurements to moisture content, salinity and freeze state in the active layer and permafrost and the ease of collecting electromagnetic induction (EMI) data with portable tools over large regions, EMI holds great potential for characterization of permafrost systems. However, inversion of such EMI data to estimate the subsurface electrical conductivity distribution is challenging. The challenges are due to the insufficient amount of information (even when using multiple configurations that vary coil spacing, orientation and elevation and signal frequency) needed to find a unique solution. The non-uniqueness problem is typically approached by invoking prior information, such as inversion constraints and initial models. Unfortunately, such prior information can significantly influence the obtained inversion result. We describe the development and implementation of a new grid search based method for estimating electrical conductivity from EMI data that evaluates the influence of priors and the information contained in such data. The new method can be applied to investigate two or three layer 1-D models reproducing the recorded data within a specified range of uncertainty at each measurement location over a large surveyed site. Importantly, the method can quickly evaluate multiple priors and data from numerous measurement locations, since the time-consuming simulation of the EMI signals from the multi-dimension search grid needs to be performed only once. We applied the developed approach to EMI data acquired in Barrow, AK at the Next-Generation Ecosystem Experiments (NGEE Arctic) study site on the Barrow Environmental Observatory. Our specific focus was on a 475-meter linear

  14. Zinc cysteine active sites of metalloproteins: A density functional theory and x-ray absorption fine structure study

    NASA Astrophysics Data System (ADS)

    Dimakis, Nicholas; Farooqi, Mohammed Junaid; Garza, Emily Sofia; Bunker, Grant

    2008-03-01

    Density functional theory (DFT) and x-ray absorption fine structure (XAFS) spectroscopy are complementary tools for the biophysical study of active sites in metalloproteins. DFT is used to compute XAFS multiple scattering Debye Waller factors, which are then employed in genetic algorithm-based fitting process to obtain a global fit to the XAFS in the space of fitting parameters. Zn-Cys sites, which serve important functions as transcriptional switches in Zn finger proteins and matrix metalloproteinases, previously have proven intractable by this method; here these limitations are removed. In this work we evaluate optimal DFT nonlocal functionals and basis sets for determining optimal geometries and vibrational densities of states of mixed ligation Zn(His)4-n(Cys)n sites. Theoretical results are compared to experimental XAFS measurements and Raman spectra from the literature and tabulated for use.

  15. Advanced activity reporting in a multi-layered unattended ground sensor network

    NASA Astrophysics Data System (ADS)

    Joslin, Todd W.

    2007-04-01

    Sensor networks are emplaced throughout the world to remotely track activity. Typically, these sensors report data such as target direction or target classification. This information is reported to a personnel-based monitor or a command and control center. The ideal sensor system will have a long mission life capability and will report information-rich actionable intelligence with high data integrity at near real-time latency. This paper discusses a multi-layered approach that includes data fusion at the Sensor Node, Sensor Field, and Command and Control Center Layer to create cohesive reports that mitigate false alarms and multiple reports of the same target while providing accurate tracking data on a situational awareness level. This approach is influenced by low-power architecture, and designed to maximize information density and reduce flooding of sensor networks.

  16. Low-noise encoding of active touch by layer 4 in the somatosensory cortex.

    PubMed

    Hires, Samuel Andrew; Gutnisky, Diego A; Yu, Jianing; O'Connor, Daniel H; Svoboda, Karel

    2015-01-01

    Cortical spike trains often appear noisy, with the timing and number of spikes varying across repetitions of stimuli. Spiking variability can arise from internal (behavioral state, unreliable neurons, or chaotic dynamics in neural circuits) and external (uncontrolled behavior or sensory stimuli) sources. The amount of irreducible internal noise in spike trains, an important constraint on models of cortical networks, has been difficult to estimate, since behavior and brain state must be precisely controlled or tracked. We recorded from excitatory barrel cortex neurons in layer 4 during active behavior, where mice control tactile input through learned whisker movements. Touch was the dominant sensorimotor feature, with >70% spikes occurring in millisecond timescale epochs after touch onset. The variance of touch responses was smaller than expected from Poisson processes, often reaching the theoretical minimum. Layer 4 spike trains thus reflect the millisecond-timescale structure of tactile input with little noise. PMID:26245232

  17. On Active Layer Environments and Processes in Western Dronning Maud Land, Antarctica

    NASA Astrophysics Data System (ADS)

    Hansen, C. D.; Meiklejohn, I.; Nel, W.

    2012-12-01

    The current understanding of Antarctic permafrost is poor, particularly regarding its evolution, the current thermal characteristics, and relationships with pedogenesis, hydrology, geomorphic, dynamics, biotic activity and response to global changes. Results from borehole temperature measurements over a four-year period in Western Dronning Maud Land suggest that the active layer depth is dependent on the substrate, latitude, altitude and the volume of ground exposed; the latter alludes to the potential impact of surrounding ice on the ground thermal regime. The active layer depths at the monitoring sites, varied between 16 cm at Vesleskarvet, a small nunatak at 850 masl to 28 cm in granitic till at Jutulsessen (1 270 masl). The mean near surface (1.5 cm depth) ground temperatures from 2009 to 2012 in the region have a narrow range from -16.4°C at 850m to -17.5°C at 1270 masl. Permafrost temperatures for the same locations vary between -16.3°C and -18.3°C. While little variability exists between the mean temperatures at the study locations, each site is distinct and seasonal and shorter-term frost cycles have produced landforms that are characteristic of both permafrost and diurnal frost environments. One of the key aspects of investigation is the control that the active layer has on autochthonous blockfield development in the region. The, thus far, exploratory research is being used to understand controls on the landscape and the relationship between distribution and abundance of biota. Given the rapidly changing climates in the region, improving knowledge of what drives patterns of biodiversity at a local and regional scale is vital to assess consequences of environmental change.

  18. Sweet taste receptor expression in ruminant intestine and its activation by artificial sweeteners to regulate glucose absorption.

    PubMed

    Moran, A W; Al-Rammahi, M; Zhang, C; Bravo, D; Calsamiglia, S; Shirazi-Beechey, S P

    2014-01-01

    Absorption of glucose from the lumen of the intestine into enterocytes is accomplished by sodium-glucose co-transporter 1 (SGLT1). In the majority of mammalian species, expression (this includes activity) of SGLT1 is upregulated in response to increased dietary monosaccharides. This regulatory pathway is initiated by sensing of luminal sugar by the gut-expressed sweet taste receptor. The objectives of our studies were to determine (1) if the ruminant intestine expresses the sweet taste receptor, which consists of two subunits [taste 1 receptor 2 (T1R2) and 3 (T1R3)], and other key signaling molecules required for SGLT1 upregulation in nonruminant intestines, and (2) whether T1R2-T1R3 sensing of artificial sweeteners induces release of glucagon-like peptide-2 (GLP-2) and enhances SGLT1 expression. We found that the small intestine of sheep and cattle express T1R2, T1R3, G-protein gustducin, and GLP-2 in enteroendocrine L-cells. Maintaining 110-d-old ruminating calves for 60d on a diet containing a starter concentrate and the artificial sweetener Sucram (consisting of saccharin and neohesperidin dihydrochalcone; Pancosma SA, Geneva, Switzerland) enhances (1) Na(+)-dependent d-glucose uptake by over 3-fold, (2) villus height and crypt depth by 1.4- and 1.2-fold, and (3) maltase- and alkaline phosphatase-specific activity by 1.5-fold compared to calves maintained on the same diet without Sucram. No statistically significant differences were observed for rates of intestinal glucose uptake, villus height, crypt depth, or enzyme activities between 50-d-old milk-fed calves and calves maintained on the same diet containing Sucram. When adult cows were kept on a diet containing 80:20 ryegrass hay-to-concentrate supplemented with Sucram, more than a 7-fold increase in SGLT1 protein abundance was noted. Collectively, the data indicate that inclusion of this artificial sweetener enhances SGLT1 expression and mucosal growth in ruminant animals. Exposure of ruminant sheep

  19. Active layer thermal monitoring at Fildes Peninsula, King George Island, Maritime Antarctica

    NASA Astrophysics Data System (ADS)

    Michel, Roberto; Schaefer, Carlos; Simas, Felipe; Pregesbauer, Michael; Bockheim, James

    2013-04-01

    International attention on the climate change phenomena has grown in the last decade, intense modelling of climate scenarios were carried out by scientific investigations searching the sources and trends of these changes. The cryosphere and its energy flux became the focus of many investigations, being recognised as a key element for the understanding of future trends. The active layer and permafrost are key components of the terrestrial cryosphere due to their role in energy flux regulation and high sensitivity to climate change (Kane et al., 2001; Smith and Brown, 2009). Compared with other regions of the globe, our understanding of Antarctic permafrost is poor, especially in relation to its thermal state and evolution, its physical properties, links to pedogenesis, hydrology, geomorphic dynamics and response to global change (Bockheim, 1995, Bockheim et al., 2008). The active layer monitoring site was installed in the summer of 2008, and consist of thermistors (accuracy ± 0.2 °C) arranged in a vertical array (Turbic Eutric Cryosol 600 m asl, 10.5 cm, 32.5 cm, 67.5 cm and 83.5 cm). King George Island experiences a cold moist maritime climate characterized by mean annual air temperatures of -2°C and mean summer air temperatures above 0°C for up to four months (Rakusa-Suszczewski et al., 1993, Wen et al., 1994). Ferron et al., (2004) found great variability when analysing data from 1947 to1995 and identified cycles of 5.3 years of colder conditions followed by 9.6 years of warmer conditions. All probes were connected to a Campbell Scientific CR 1000 data logger recording data at hourly intervals from March 1st 2008 until November 30th 2012. Meteorological data for Fildes was obtained from the near by stations. We calculated the thawing days, freezing days; thawing degree days and freezing degree days; all according to Guglielmin et al. (2008). The active lawyer thickness was calculated as the 0 °C depth by extrapolating the thermal gradient from the two

  20. Absorption and Decomposition of CO2 by Active Ferrites Prepared by Atmospheric Plasma Spraying

    NASA Astrophysics Data System (ADS)

    Li, Shaowei; He, Zhida; Zheng, Yanjun; Chen, Changfeng

    2015-12-01

    Active ferrites, which play an important role in the catalytic decomposition of CO2, have been fabricated by atmospheric plasma spraying to incorporate FeO and anoxic iron oxide [Fe3O4-δ (0 < δ < 1)]. The complexity of phase composition, especially the presence of FeO, gives the resulting powder a greater ability to decompose CO2 when compared to hydrogen-reduced Fe3O4 or Fe2O3 particles. Spraying distance is found to play an important role in modulating the decomposition ability of the powders, while elevated temperatures can also enhance the catalytic decomposition of CO2.

  1. Role of interfacial friction for flow instabilities in a thin polar-ordered active fluid layer.

    PubMed

    Sarkar, Niladri; Basu, Abhik

    2015-11-01

    We construct a generic coarse-grained dynamics of a thin inflexible planar layer of polar-ordered suspension of active particles that is frictionally coupled to an embedding isotropic passive fluid medium with a friction coefficient Γ. Being controlled by Γ, our model provides a unified framework to describe the long-wavelength behavior of a variety of thin polar-ordered systems, ranging from wet to dry active matter and free-standing active films. Investigations of the linear instabilities around a chosen orientationally ordered uniform reference state reveal generic moving and static instabilities in the system that can depend sensitively on Γ. Based on our results, we discuss estimation of bounds on Γ in experimentally accessible systems. PMID:26651694

  2. Role of interfacial friction for flow instabilities in a thin polar-ordered active fluid layer

    NASA Astrophysics Data System (ADS)

    Sarkar, Niladri; Basu, Abhik

    2015-11-01

    We construct a generic coarse-grained dynamics of a thin inflexible planar layer of polar-ordered suspension of active particles that is frictionally coupled to an embedding isotropic passive fluid medium with a friction coefficient Γ . Being controlled by Γ , our model provides a unified framework to describe the long-wavelength behavior of a variety of thin polar-ordered systems, ranging from wet to dry active matter and free-standing active films. Investigations of the linear instabilities around a chosen orientationally ordered uniform reference state reveal generic moving and static instabilities in the system that can depend sensitively on Γ . Based on our results, we discuss estimation of bounds on Γ in experimentally accessible systems.

  3. The effect of particle vertical positioning on the absorption enhancement in plasmonic organic solar cells

    NASA Astrophysics Data System (ADS)

    Wang, Shu-Yi; Borca-Tasciuc, Diana-Andra; Kaminski, Deborah A.

    2012-06-01

    The light absorption enhancement of an organic solar cell with plasmonic nanoparticles (NP) embedded in the active layer is studied employing 3D finite element simulation. The effect of the vertical positioning of the particle monolayer inside the active layer is elucidated. The results indicate that the highest enhancement is obtained when the particles lay at the bottom of the active layer, an organization less difficult to control accurately in practice. The paper also discusses the difference in the absorption enhancement obtained for two existing definitions currently used in the literature. The results show that models assessing absorption by taking both host and nanoparticles into consideration may overpredict the enhancement even when integration is carried out only over the wavelength interval where the host absorption dominates.

  4. Low latitude F2- and F3- layer variabilities over India: Effects of solar activity and ExB drift

    NASA Astrophysics Data System (ADS)

    Peddapati, PavanChaitanya; Patra, Amit; Balan, Nanan; Vijaya Bhaskara Rao, S.

    In this paper we present and discuss the results on F2 and F3 layers based on ionosonde observations made from low latitude stations in India. We also use ExB drift using daytime 150 km echoes made with the Gadanki MST radar. We present two important aspects of the F2 and F3 layers: (1) The variability of F2 and F3 layer properties during low solar activity period of 2008-2009 and compare them with those observed during the high solar activity period of 2002-2003 (2) The variability of F2 and F3 layer properties with ExB drift values simultaneously observed during low solar activity period. The results show that ionospheric F2 and F3 layers have distinctly different features during high and low solar activities. The critical frequencies of the F2 and F3 layers are 5-6 MHz higher in the high solar activity than those of low solar activity. F2 layer shows stronger semi-annual and solar rotation associated variations during high solar activity than in low solar activity. Occurrence of the F3 layer, however, was quite similar in high and low solar activities except for winter solstice. Simultaneous observations of F2 and F3 layers, and ExB drift made during the low solar activity period clearly suggest that a threshold value of the ExB drift and its time integrated value are important for the formation of the F3 layer. The heights of the F2 and F3 layers linearly increase with ExB drift, indicating the dominant role of zonal electric field in determining the height of the F2 and F3 layers due to the close proximity of Gadanki to the magnetic equator. In order to gain further insight on the role of meridional neutral wind, we study this effect using Sheffield University Plasmasphere Ionosphere Model (SUPIM) by employing the observed ExB drift and F3 layer parameters and meridional neutral wind from Horizontal Wind Model 90 (HWM90).

  5. Metal nanoparticles enhanced optical absorption in thin film solar cells

    NASA Astrophysics Data System (ADS)

    Xie, Wanlu; Liu, Fang; Qu, Di; Xu, Qi; Huang, Yidong

    2011-12-01

    The plasmonic enhanced absorption for thin film solar cells with silver nanoparticles (NPs) deposited on top of the amorphous silicon film (a-Si:H) solar cells and embedded inside the active layer of organic solar cells (OSCs) has been simulated and analyzed. Obvious optical absorption enhancement is obtained not only at vertical incidence but also at oblique incidence. By properly adjusting the period and size of NPs, an increased absorption enhancement of about 120% and 140% is obtained for a-Si:H solar cells and OSCs, respectively.

  6. Vertical profiles of trapped greenhouse gases in Alaskan permafrost active layers before the spring thaw

    NASA Astrophysics Data System (ADS)

    Byun, Eunji; Yang, Ji-woong; Kim, Yongwon; Ahn, Jinho

    2015-04-01

    Seasonally frozen ground over permafrost is important in controlling annual greenhouse gas exchange between permafrost and atmosphere. Soil microbes decompose soil carbon and generate carbon dioxide and methane when they become activated. However, the actual greenhouse gas emission follows various efflux pathways. For example, seasonal freezing of the top soil layers can either restrain or press the gas emission from deeper layers. It has been reported that abrupt release of methane during spring is attributable to the emission of trapped gases that had failed to be released instantly after formation (1, 2). In order to examine the seasonally trapped greenhouse gases, we drilled five Alaskan permafrost cores before spring thaw; one from coastal tundra, two from typical boreal forests, one from area where fire occurred, and one from peat accumulated sites. Vertical profiles of carbon dioxide and methane concentrations were obtained with 5-10 cm depth intervals. We found methane peaks from two cores, indicating inhibition of methane efflux. We also analyzed organic carbon, nitrogen and water contents and compared them with the greenhouse gas profiles. We are continuing analysis for the soil temperature profiles of the sampling boreholes because the detailed temperature information might be related to microbial activity, and can be used as indirect indicators of soil water freezing and latent heat influences at some active layer depth (zero curtain effects). All the high-resolution analyses for subsurface environments may help to improve understanding greenhouse gas emission from permafrost regions. 1. Mastepanov M, et al. (2008) Large tundra methane burst during onset of freezing. Nature 456(7222):628-630. 2. Song C, et al. (2012) Large methane emission upon spring thaw from natural wetlands in the northern permafrost region. Environmental Research Letters 7(3):034009.

  7. Aluminum plasmonic nanostructures for improved absorption in organic photovoltaic devices

    NASA Astrophysics Data System (ADS)

    Kochergin, Vladimir; Neely, Lauren; Jao, Chih-Yu; Robinson, Hans D.

    2011-03-01

    We model the absorption enhancement in organic photovoltaic devices induced by incorporating Al, Ag, and Au nanoparticles in the active layer. We find that Al nanoparticles should yield significantly greater enhancement than Ag or Au. This is because the much higher plasma frequency of Al ensures a better overlap between plasmon resonance and absorption band of organic semiconductors. Our predictions are verified experimentally by demonstrating enhanced absorbance in a poly(3-hexylthiophene-2,5-diyl): [6,6]-phenyl C61 butyric acid methyl ester layer with embedded functionalized Al nanoparticles.

  8. Hot-Film and Hot-Wire Anemometry for a Boundary Layer Active Flow Control Test

    NASA Technical Reports Server (NTRS)

    Lenahan, Keven C.; Schatzman, David M.; Wilson, Jacob Samuel

    2013-01-01

    Unsteady active flow control (AFC) has been used experimentally for many years to minimize bluff-body drag. This technology could significantly improve performance of rotorcraft by cleaning up flow separation. It is important, then, that new actuator technologies be studied for application to future vehicles. A boundary layer wind tunnel was constructed with a 1ft-x-3ft test section and unsteady measurement instrumentation to study how AFC manipulates the boundary layer to overcome adverse pressure gradients and flow separation. This unsteady flow control research requires unsteady measurement methods. In order to measure the boundary layer characteristics, both hot-wire and hot-film Constant Temperature Anemometry is used. A hot-wire probe is mounted in the flow to measure velocity while a hot-film array lays on the test surface to measure skin friction. Hot-film sensors are connected to an anemometer, a Wheatstone bridge circuit with an output that corresponds to the dynamic flow response. From this output, the time varying flow field, turbulence, and flow reversal can be characterized. Tuning the anemometers requires a fan test on the hot-film sensors to adjust each output. This is a delicate process as several variables drastically affect the data, including control resistance, signal input, trim, and gain settings.

  9. Lidar observations of Ca and K metallic layers from Arecibo and comparison with micrometeor sporadic activity

    NASA Astrophysics Data System (ADS)

    Raizada, S.; Tepley, C. A.; Janches, D.; Friedman, J. S.; Zhou, Q.; Mathews, J. D.

    2004-04-01

    We report on the first simultaneous observations of Ca and K metallic layers using the low-latitude lidar systems located at the Arecibo Observatory in Puerto Rico (18.35°N, 66.75°W). We often observe sudden increases in both Ca and K densities during early morning hours on nights where meteor showers take place. During these periods, the Ca/K abundance ratio varied between 2 and 3. On occasion, differences were observed in Ca and K layers, which relate to differences in the chemistry of the two metals. It is known that metallic layers display distinct seasonal variations, but chemistry alone cannot explain the measured differences. Thus, we examined whether or not the seasonal distribution of micrometeoroids, derived from meteor observations using the Arecibo 430MHz radar, can account for the dissimilar metallic observations. We found that the deposition flux of micrometeoroids, with particle sizes ranging between 0.5 and 100μm, increased by a factor of two during the summer as compared with the winter, suggesting a seasonal variation of their sporadic activity. In addition, our data support the idea that differential ablation leads to a depletion of Ca atoms in the mesosphere.

  10. High levels of absorption in orientation-unbiased, radio-selected 3CR Active Galaxies

    NASA Astrophysics Data System (ADS)

    Wilkes, Belinda J.; Haas, Martin; Barthel, Peter; Leipski, Christian; Kuraszkiewicz, Joanna; Worrall, Diana; Birkinshaw, Mark; Willner, Steven P.

    2014-08-01

    A critical problem in understanding active galaxies (AGN) is the separation of intrinsic physical differences from observed differences that are due to orientation. Obscuration of the active nucleus is anisotropic and strongly frequency dependent leading to complex selection effects for observations in most wavebands. These can only be quantified using a sample that is sufficiently unbiased to test orientation effects. Low-frequency radio emission is one way to select a close-to orientation-unbiased sample, albeit limited to the minority of AGN with strong radio emission.Recent Chandra, Spitzer and Herschel observations combined with multi-wavelength data for a complete sample of high-redshift (1 24.2) = 2.5:1.4:1 in these high-luminosity (log L(0.3-8keV) ~ 44-46) sources. These ratios are consistent with current expectations based on modelingthe Cosmic X-ray Background. A strong correlation with radio orientation constrains the geometry of the obscuring disk/torus to have a ~60 degree opening angle and ~12 degree Compton-thick cross-section. The deduced ~50% obscured fraction of the population contrasts with typical estimates of ~20% obscured in optically- and X-ray-selected high-luminosity samples. Once the primary nuclear emission is obscured, AGN X-ray spectra are frequently dominated by unobscured non-nuclear or scattered nuclear emission which cannot be distinguished from direct nuclear emission with a lower obscuration level unless high quality data is available. As a result, both the level of obscuration and the estimated instrinsic luminosities of highly-obscured AGN are likely to be significantly (*10-1000) underestimated for 25-50% of the population. This may explain the lower obscured fractions reported for optical and X-ray samples which have no independent measure of the AGN

  11. A Melting Layer Model for Passive/Active Microwave Remote Sensing Applications. Part 1; Model Formulation and Comparison with Observations

    NASA Technical Reports Server (NTRS)

    Olson, William S.; Bauer, Peter; Viltard, Nicolas F.; Johnson, Daniel E.; Tao, Wei-Kuo

    2000-01-01

    In this study, a 1-D steady-state microphysical model which describes the vertical distribution of melting precipitation particles is developed. The model is driven by the ice-phase precipitation distributions just above the freezing level at applicable gridpoints of "parent" 3-D cloud-resolving model (CRM) simulations. It extends these simulations by providing the number density and meltwater fraction of each particle in finely separated size categories through the melting layer. The depth of the modeled melting layer is primarily determined by the initial material density of the ice-phase precipitation. The radiative properties of melting precipitation at microwave frequencies are calculated based upon different methods for describing the dielectric properties of mixed phase particles. Particle absorption and scattering efficiencies at the Tropical Rainfall Measuring Mission Microwave Imager frequencies (10.65 to 85.5 GHz) are enhanced greatly for relatively small (approx. 0.1) meltwater fractions. The relatively large number of partially-melted particles just below the freezing level in stratiform regions leads to significant microwave absorption, well-exceeding the absorption by rain at the base of the melting layer. Calculated precipitation backscatter efficiencies at the Precipitation Radar frequency (13.8 GHz) increase in proportion to the particle meltwater fraction, leading to a "bright-band" of enhanced radar reflectivities in agreement with previous studies. The radiative properties of the melting layer are determined by the choice of dielectric models and the initial water contents and material densities of the "seeding" ice-phase precipitation particles. Simulated melting layer profiles based upon snow described by the Fabry-Szyrmer core-shell dielectric model and graupel described by the Maxwell-Garnett water matrix dielectric model lead to reasonable agreement with radar-derived melting layer optical depth distributions. Moreover, control profiles

  12. Methane transport from the active layer to lakes in the Arctic using Toolik Lake, Alaska, as a case study

    PubMed Central

    Paytan, Adina; Lecher, Alanna L.; Dimova, Natasha; Sparrow, Katy J.; Kodovska, Fenix Garcia-Tigreros; Murray, Joseph; Tulaczyk, Slawomir; Kessler, John D.

    2015-01-01

    Methane emissions in the Arctic are important, and may be contributing to global warming. While methane emission rates from Arctic lakes are well documented, methods are needed to quantify the relative contribution of active layer groundwater to the overall lake methane budget. Here we report measurements of natural tracers of soil/groundwater, radon, and radium, along with methane concentration in Toolik Lake, Alaska, to evaluate the role active layer water plays as an exogenous source for lake methane. Average concentrations of methane, radium, and radon were all elevated in the active layer compared with lake water (1.6 × 104 nM, 61.6 dpm⋅m−3, and 4.5 × 105 dpm⋅m−3 compared with 1.3 × 102 nM, 5.7 dpm⋅m−3, and 4.4 × 103 dpm⋅m−3, respectively). Methane transport from the active layer to Toolik Lake based on the geochemical tracer radon (up to 2.9 g⋅m−2⋅y−1) can account for a large fraction of methane emissions from this lake. Strong but spatially and temporally variable correlations between radon activity and methane concentrations (r2 > 0.69) in lake water suggest that the parameters that control methane discharge from the active layer also vary. Warming in the Arctic may expand the active layer and increase the discharge, thereby increasing the methane flux to lakes and from lakes to the atmosphere, exacerbating global warming. More work is needed to quantify and elucidate the processes that control methane fluxes from the active layer to predict how this flux might change in the future and to evaluate the regional and global contribution of active layer water associated methane inputs. PMID:25775530

  13. Anti-androgenic activity of absorption-enhanced 3, 3’-diindolylmethane in prostatectomy patients

    PubMed Central

    Hwang, Clara; Sethi, Seema; Heilbrun, Lance K; Gupta, Nilesh S; Chitale, Dhananjay A; Sakr, Wael A; Menon, Mani; Peabody, James O; Smith, Daryn W; Sarkar, Fazlul H; Heath, Elisabeth I

    2016-01-01

    Consumption of cruciferous vegetables is associated with a decreased risk of developing prostate cancer. Antineoplastic effects of cruciferous vegetables are attributable to bioactive indoles, most prominently, 3, 3’-diindolylmethane (DIM). In addition to effects on proliferation and apoptosis, DIM acts as an antiandrogen in prostate cancer cell lines. This study characterized the effects of prostatic DIM on the androgen receptor (AR) in patients with prostate cancer. Men with localized prostate cancer were treated with a specially formulated DIM capsule designed for enhanced bioavailability (BR-DIM) at a dose of 225 mg orally twice daily for a minimum of 14 days. DIM levels and AR activity were assessed at the time of prostatectomy. Out of 28 evaluable patients, 26 (93%) had detectable prostatic DIM levels, with a mean concentration of 14.2 ng/gm. The mean DIM plasma level on BR-DIM therapy was 9.0 ng/mL; levels were undetectable at baseline and in follow-up samples. AR localization in the prostate was assessed with immunohistochemistry. After BR-DIM therapy, 96% of patients exhibited exclusion of the AR from the cell nucleus. In contrast, in prostate biopsy samples obtained prior to BR-DIM therapy, no patient exhibited AR nuclear exclusion. Declines in PSA were observed in a majority of patients (71%). Compliance was excellent and toxicity was minimal. In summary, BR-DIM treatment resulted in reliable prostatic DIM levels and anti-androgenic biologic effects at well tolerated doses. These results support further investigation of BR-DIM as a chemopreventive and therapeutic agent in prostate cancer. PMID:27069550

  14. Chitosan–cellulose composite for wound dressing material. Part 2. Antimicrobial activity, blood absorption ability, and biocompatibility

    PubMed Central

    Harkins, April L.; Duri, Simon; Kloth, Luther C.; Tran, Chieu D.

    2014-01-01

    Chitosan (CS), a polysaccharide derived from chitin, the second most abundant polysaccharide, is widely used in the medical world because of its natural and nontoxic properties and its innate ability for antibacterial and hemostasis effects. In this study, the novel composites containing CS and cellulose (CEL) (i.e., [CEL + CS]), which we have previously synthesized using a green and totally recyclable method, were investigated for their antimicrobial activity, absorption of anticoagulated whole blood, anti-inflammatory activity through the reduction of tumor necrosis factor-α (TNF-α) and interleukin-6 (IL-6), and the biocompatibility with human fibroblasts. The [CEL + CS] composites were found to inhibit the growth of both Gram positive and negative microorganisms. For examples, the regenerated 100% lyophilized chitosan material was found to reduce growth of Escherichia coli (ATCC 8739 and vancomycin resistant Enterococcus faecalis (ATCC 51299) by 78, 36, and 64%, respectively. The composites are nontoxic to fibroblasts; that is, fibroblasts, which are critical to the formation of connective tissue matrix were found to grow and proliferate in the presence of the composites. They effectively absorb blood, and at the same rate and volume as commercially available wound dressings. The composites, in both air-dried and lyophilized forms, significantly inhibit the production of TNF-α and IL-6 by stimulated macrophages. These results clearly indicate that the biodegradable, biocompatible and nontoxic [CEL + CS] composites, particularly those dried by lyophilizing, can be effectively used as a material in wound dressings. PMID:24407857

  15. Cost and sensitivity of restricted active-space calculations of metal L-edge X-ray absorption spectra.

    PubMed

    Pinjari, Rahul V; Delcey, Mickaël G; Guo, Meiyuan; Odelius, Michael; Lundberg, Marcus

    2016-02-15

    The restricted active-space (RAS) approach can accurately simulate metal L-edge X-ray absorption spectra of first-row transition metal complexes without the use of any fitting parameters. These characteristics provide a unique capability to identify unknown chemical species and to analyze their electronic structure. To find the best balance between cost and accuracy, the sensitivity of the simulated spectra with respect to the method variables has been tested for two models, [FeCl6 ](3-) and [Fe(CN)6 ](3-) . For these systems, the reference calculations give deviations, when compared with experiment, of ≤1 eV in peak positions, ≤30% for the relative intensity of major peaks, and ≤50% for minor peaks. When compared with these deviations, the simulated spectra are sensitive to the number of final states, the inclusion of dynamical correlation, and the ionization potential electron affinity shift, in addition to the selection of the active space. The spectra are less sensitive to the quality of the basis set and even a double-ζ basis gives reasonable results. The inclusion of dynamical correlation through second-order perturbation theory can be done efficiently using the state-specific formalism without correlating the core orbitals. Although these observations are not directly transferable to other systems, they can, together with a cost analysis, aid in the design of RAS models and help to extend the use of this powerful approach to a wider range of transition metal systems. PMID:26502979

  16. Electric field absorption and emission as an indicator of active electromagnetic nature of organisms--preliminary report.

    PubMed

    Skarja, Metod; Jerman, Igor; Ruzic, Romana; Leskovar, Robert T; Jejcic, Luka

    2009-01-01

    Measurements of the response of organisms to the near field exposure show that this response, i.e., its absorption, transmission, and emission (ATE) of the organism, markedly differs from the behavior expected if one treats the organism as a simple dissipative conductive body. The results point to the at least partial active response of the organism. This active electrical response can be attributed at least partially to the response of the endogenous electromagnetic field of organisms, first postulated by Frohlich, and to the material structures that form an inseparable whole with this field. The near electric field influence, both on the organism and of the organism on the sensors, can be established either through the vicinity or through a direct nonconductive contact. This response correlates with the physiological state of an organism. Measurements performed with mealworm beetles indicated that the normal living organisms absorb and use some energy of the near electric field and therefore the transmitted (re-emitted) signal is weaker. The inactivated or the dead organisms are more passive electrical absorbers. PMID:19337899

  17. Restricted active space calculations of L-edge X-ray absorption spectra: From molecular orbitals to multiplet states

    SciTech Connect

    Pinjari, Rahul V.; Delcey, Mickaël G.; Guo, Meiyuan; Lundberg, Marcus; Odelius, Michael

    2014-09-28

    The metal L-edge (2p → 3d) X-ray absorption spectra are affected by a number of different interactions: electron-electron repulsion, spin-orbit coupling, and charge transfer between metal and ligands, which makes the simulation of spectra challenging. The core restricted active space (RAS) method is an accurate and flexible approach that can be used to calculate X-ray spectra of a wide range of medium-sized systems without any symmetry constraints. Here, the applicability of the method is tested in detail by simulating three ferric (3d{sup 5}) model systems with well-known electronic structure, viz., atomic Fe{sup 3+}, high-spin [FeCl{sub 6}]{sup 3−} with ligand donor bonding, and low-spin [Fe(CN){sub 6}]{sup 3−} that also has metal backbonding. For these systems, the performance of the core RAS method, which does not require any system-dependent parameters, is comparable to that of the commonly used semi-empirical charge-transfer multiplet model. It handles orbitally degenerate ground states, accurately describes metal-ligand interactions, and includes both single and multiple excitations. The results are sensitive to the choice of orbitals in the active space and this sensitivity can be used to assign spectral features. A method has also been developed to analyze the calculated X-ray spectra using a chemically intuitive molecular orbital picture.

  18. Multifrequency VLBI Observations of the Broad Absorption Line Quasar J1020+4320: Recently Restarted Jet Activity?

    NASA Astrophysics Data System (ADS)

    Doi, Akihiro; Murata, Yasuhiro; Mochizuki, Nanako; Takeuchi, Hiroshi; Asada, Keiichi; Hayashi, Takayuki J.; Nagai, Hiroshi; Shibata, Katsunori M.; Oyama, Tomoaki; Jike, Takaaki; Fujisawa, Kenta; Sugiyama, Koichiro; Ogawa, Hideo; Kimura, Kimihiro; Honma, Mareki; Kobayashi, Hideyuki; Koyama, Shoko

    2013-06-01

    This paper reports on very-long-baseline interferometry observations of the radio-loud broad absorption line (BAL) quasar J1020+4320 at 1.7, 2.3, 6.7, and 8.4 GHz using the Japanese VLBI network (JVN) and European VLBI network (EVN). The radio morphology is compact with a size of ˜10 pc. The convex radio spectrum has been stable over the last decade; an observed peak frequency of 3.2 GHz is equivalent to 9.5 GHz in the rest frame, suggesting an age on the order of ˜100 years as a radio source, according to an observed correlation between the linear size and the peak frequency of compact steep spectrum (CSS) and giga-hertz peaked spectrum (GPS) radio sources. A low-frequency radio excess suggests a relic of past jet activity. J1020+4320 may be one of the quasars with recurrent and short-lived jet activity during a BAL-outflowing phase.

  19. Quick and Facile Preparation of Visible light-Driven TiO2 Photocatalyst with High Absorption and Photocatalytic Activity

    PubMed Central

    Yang, Yucheng; Zhang, Ting; Le, Ling; Ruan, Xuefeng; Fang, Pengfei; Pan, Chunxu; Xiong, Rui; Shi, Jing; Wei, Jianhong

    2014-01-01

    Self-doping TiO2 has recently attracted considerable attention for its high photocatalytic activity under visible-light irradiation. However, the literature reported synthetic methods until now were very time-consuming. In this study, we establish a quick and facile method for obtaining self-doping TiO2 with the use of directly treated commercial P25 at a desired temperature for only 5 min through spark plasma sintering technology. With the using of this method, the modified P25 samples exhibit significantly high photoelectric and photocatalytic performance. Furthermore, the sample prepared at 600°C exhibits the optimum catalytic activity. The photodegradation and H2 evolution rates of this samples are significantly higher than those of unmodified P25 sample under visible-light irradiation. The physical origin of the visible-light absorption for the modified P25 samples is investigated in detail according to their structural, optical, and electronic properties. This work will provide a quick and facile method for the large-scale synthesis of visible-light driven photocatalyst for practical applications. PMID:25391987

  20. Permafrost and active layer monitoring in the maritime Antarctic: Preliminary results from CALM sites on Livingston and Deception Islands

    USGS Publications Warehouse

    Ramos, M.; Vieira, G.; Blanco, J.J.; Hauck, C.; Hidalgo, M.A.; Tome, D.; Nevers, M.; Trindade, A.

    2007-01-01

    This paper describes results obtained from scientific work and experiments performed on Livingston and Deception Islands. Located in the South Shetland Archipelago, these islands have been some of the most sensitive regions over the last 50 years with respect to climate change with a Mean Annual Air Temperature (MAAT) close to -2 ºC. Three Circumpolar Active Layer Monitoring (CALM) sites were installed to record the thermal regime and the behaviour of the active layer in different places with similar climate, but with different soil composition, porosity, and water content. The study’s ultimate aim is to document the influence of climate change on permafrost degradation. Preliminary results, obtained in 2006, on maximum active-layer thickness (around 40 cm in the CALM of Deception Island), active layer temperature evolution, snow thickness, and air temperatures permit early characterization of energy exchange mechanisms between the ground and the atmosphere in the CALM-S sites.

  1. Layer-by-layer grown scalable redox-active ruthenium-based molecular multilayer thin films for electrochemical applications and beyond.

    PubMed

    Kaliginedi, Veerabhadrarao; Ozawa, Hiroaki; Kuzume, Akiyoshi; Maharajan, Sivarajakumar; Pobelov, Ilya V; Kwon, Nam Hee; Mohos, Miklos; Broekmann, Peter; Fromm, Katharina M; Haga, Masa-aki; Wandlowski, Thomas

    2015-11-14

    Here we report the first study on the electrochemical energy storage application of a surface-immobilized ruthenium complex multilayer thin film with anion storage capability. We employed a novel dinuclear ruthenium complex with tetrapodal anchoring groups to build well-ordered redox-active multilayer coatings on an indium tin oxide (ITO) surface using a layer-by-layer self-assembly process. Cyclic voltammetry (CV), UV-Visible (UV-Vis) and Raman spectroscopy showed a linear increase of peak current, absorbance and Raman intensities, respectively with the number of layers. These results indicate the formation of well-ordered multilayers of the ruthenium complex on ITO, which is further supported by the X-ray photoelectron spectroscopy analysis. The thickness of the layers can be controlled with nanometer precision. In particular, the thickest layer studied (65 molecular layers and approx. 120 nm thick) demonstrated fast electrochemical oxidation/reduction, indicating a very low attenuation of the charge transfer within the multilayer. In situ-UV-Vis and resonance Raman spectroscopy results demonstrated the reversible electrochromic/redox behavior of the ruthenium complex multilayered films on ITO with respect to the electrode potential, which is an ideal prerequisite for e.g. smart electrochemical energy storage applications. Galvanostatic charge-discharge experiments demonstrated a pseudocapacitor behavior of the multilayer film with a good specific capacitance of 92.2 F g(-1) at a current density of 10 μA cm(-2) and an excellent cycling stability. As demonstrated in our prototypical experiments, the fine control of physicochemical properties at nanometer scale, relatively good stability of layers under ambient conditions makes the multilayer coatings of this type an excellent material for e.g. electrochemical energy storage, as interlayers in inverted bulk heterojunction solar cell applications and as functional components in molecular electronics applications

  2. Transmission electron microscope observation of organic-inorganic hybrid thin active layers of light-emitting diodes

    NASA Astrophysics Data System (ADS)

    Jitsui, Yusuke; Ohtani, Naoki

    2012-10-01

    We performed transmission electron microscope (TEM) observation of organic-inorganic hybrid thin films fabricated by the sol-gel reaction and used as the active layers of organic light-emitting diodes. The cross-sectional TEM images show that the films consist of a triple-layer structure. To evaluate the composition of these layers, the distribution of atoms in them was measured by energy-dispersive X-ray fluorescence spectroscopy. As a result, most of the organic emissive material, poly(9,9-dioctyl-fluorene-co- N-4-butylphenyl-diphenylamine (TFB), was found to be distributed in the middle layer sandwiched by SiO and SiO2 layers. The surface SiO layer was fabricated due to the lack of oxygen. This means that the best sol-gel condition was changed due to the TFB doping; thus, the novel best condition should be found.

  3. Transmission electron microscope observation of organic-inorganic hybrid thin active layers of light-emitting diodes.

    PubMed

    Jitsui, Yusuke; Ohtani, Naoki

    2012-01-01

    We performed transmission electron microscope (TEM) observation of organic-inorganic hybrid thin films fabricated by the sol-gel reaction and used as the active layers of organic light-emitting diodes. The cross-sectional TEM images show that the films consist of a triple-layer structure. To evaluate the composition of these layers, the distribution of atoms in them was measured by energy-dispersive X-ray fluorescence spectroscopy. As a result, most of the organic emissive material, poly(9,9-dioctyl-fluorene-co-N-4-butylphenyl-diphenylamine (TFB), was found to be distributed in the middle layer sandwiched by SiO and SiO2 layers. The surface SiO layer was fabricated due to the lack of oxygen. This means that the best sol-gel condition was changed due to the TFB doping; thus, the novel best condition should be found. PMID:23095451

  4. Numerical Modeling of Active Flow Control in a Boundary Layer Ingesting Offset Inlet

    NASA Technical Reports Server (NTRS)

    Allan, Brian G.; Owens, Lewis R.; Berrier, Bobby L.

    2004-01-01

    This investigation evaluates the numerical prediction of flow distortion and pressure recovery for a boundary layer ingesting offset inlet with active flow control devices. The numerical simulations are computed using a Reynolds averaged Navier-Stokes code developed at NASA. The numerical results are validated by comparison to experimental wind tunnel tests conducted at NASA Langley Research Center at both low and high Mach numbers. Baseline comparisons showed good agreement between numerical and experimental results. Numerical simulations for the inlet with passive and active flow control also showed good agreement at low Mach numbers where experimental data has already been acquired. Numerical simulations of the inlet at high Mach numbers with flow control jets showed an improvement of the flow distortion. Studies on the location of the jet actuators, for the high Mach number case, were conducted to provide guidance for the design of a future experimental wind tunnel test.

  5. Enhancing photocatalytic activity of LaTiO2N by removal of surface reconstruction layer.

    PubMed

    Matsukawa, Michinori; Ishikawa, Ryo; Hisatomi, Takashi; Moriya, Yosuke; Shibata, Naoya; Kubota, Jun; Ikuhara, Yuichi; Domen, Kazunari

    2014-02-12

    LaTiO2N is an oxynitride photocatalyst that has ability to generate H2 and O2 from water under irradiation of light with wavelengths up to 600 nm. However, LaTiO2N necessitates sacrificial reagents that capture either photoexcited electrons or holes efficiently to be active in the photocatalytic reactions because of a considerable number of defects that cause trapping and recombination of photoexcited carriers. Therefore, identifying defect structures of LaTiO2N is important. In this study, using atomic-resolution scanning transmission electron microscopy, we evidence that eliminating defective surface reconstructed layers of LaTiO2N particles by the treatment with aqua regia can double the photocatalytic activity. PMID:24460145

  6. Topology optimization of magnetorheological fluid layers in sandwich plates for semi-active vibration control

    NASA Astrophysics Data System (ADS)

    Zhang, Xiaopeng; Kang, Zhan

    2015-08-01

    This paper investigates topology optimization of the magnetorheological (MR) fluid layer in a sandwich plate for improving the semi-active vibration control performance. Therein, a uniform magnetic field is applied across the MR fluid layer to provide a semi-active damping control effect. In the optimization model, the pseudo-densities describing the MR fluid material distribution are taken as design variables, and an artificial magneto-rheological fluid model (AMRF) with penalization is proposed to suppress intermediate density values. For reducing the vibration level under harmonic excitations, the dynamic compliance under a specific excitation frequency, or the frequency-aggregated dynamic compliance in a given frequency band, is taken as the objective function to be minimized. In this context, the adjoint-variable sensitivity analysis scheme is derived. The effectiveness and efficiency of the proposed method are demonstrated by numerical examples, in which the structural dynamic performance can be remarkably improved through optimization. The influences of several key factors on the optimal designs are also explored. It is shown that the AMRF model is effective in yielding clear boundaries in the final optimal solutions without use of additional regularization techniques.

  7. Dielectric elastomer based active layer for macro-scaled industrial application in roto-flexographic printing

    NASA Astrophysics Data System (ADS)

    Pinto, F.; D'Oriano, G.; Meo, M.

    2014-03-01

    The use of dielectric elastomer (DE) for the realisation of new generation actuators has attracted the interest of many researchers in the last ten years due to their high efficiency, a very good electromechanical coupling and large achievable strains [1-3]. Although these properties constitute a very important advantage, the industrial exploitation of such systems is hindered by the high voltages required for the actuation [4] that could potentially constitute also a risk for the operators. In this work we present a DE based active layer that can be used in different macro-scaled parts of industrial equipment for roto-flexographic printing substituting traditional mechanical devices, reducing manufacturing costs and enhancing its reliability. Moreover, the specific configuration of the system requires the driving voltage to be applied only in the mounting/dismounting step thus lowering further the operative costs without posing any threat for the workers. Starting from the industrial requirements, a complete thermo-mechanical characterisation using DSC and DMA was undertaken on acrylic elastomer films in order to investigate their behaviour under the operative frequencies and solicitations. Validation of the active layer was experimentally evaluated by manufacturing a DE actuator controlling both prestrain and nature of the complaint electrodes, and measuring the electrically induced Maxwell's strain using a laser vibrometer to evaluate the relative displacement along the z-axis.

  8. Microtopographic and depth controls on active layer chemistry in Arctic polygonal ground

    DOE PAGESBeta

    Newman, Brent D.; Throckmorton, Heather M.; Graham, David E.; Gu, Baohua; Hubbard, Susan S.; Liang, Liyuan; Wu, Yuxin; Heikoop, J. M.; Herndon, Elizabeth M.; Phelps, Tommy J.; et al

    2015-03-24

    Polygonal ground is a signature characteristic of Arctic lowlands, and carbon release from permafrost thaw can alter feedbacks to Arctic ecosystems and climate. This study describes the first comprehensive spatial examination of active layer biogeochemistry that extends across high- and low-centered, ice wedge polygons, their features, and with depth. Water chemistry measurements of 54 analytes were made on surface and active layer pore waters collected near Barrow, Alaska, USA. Significant differences were observed between high- and low-centered polygons suggesting that polygon types may be useful for landscape-scale geochemical classification. However, differences were found for polygon features (centers and troughs) formore » analytes that were not significant for polygon type, suggesting that finer-scale features affect biogeochemistry differently from polygon types. Depth variations were also significant, demonstrating important multidimensional aspects of polygonal ground biogeochemistry. These results have major implications for understanding how polygonal ground ecosystems function, and how they may respond to future change.« less

  9. Design of Bicontinuous Donor/Acceptor Morphologies for Use as Organic Solar Cell Active Layers

    NASA Astrophysics Data System (ADS)

    Kipp, Dylan; Mok, Jorge; Verduzco, Rafael; Ganesan, Venkat

    Two of the primary challenges limiting the marketability of organic solar cells are i) the smaller device efficiency of the organic solar cell relative to the conventional silicon-based solar cell and ii) the long term thermal instability of the device active layer. The achievement of equilibrium donor/acceptor morphologies with the characteristics believed to yield high device performance characteristics could address each of these two challenges. In this work, we present the results of a combined simulations and experiments-based approach to investigate if a conjugated BCP additive can be used to control the self-assembled morphologies taken on by conjugated polymer/PCBM mixtures. First, we use single chain in mean field Monte Carlo simulations to identify regions within the conjugated polymer/PCBM composition space in which addition of copolymers can lead to bicontinuous equilibrium morphologies with high interfacial areas and nanoscale dimensions. Second, we conduct experiments as directed by the simulations to achieve such morphologies in the PTB7 + PTB7- b-PNDI + PCBM model blend. We characterize the results of our experiments via a combination of transmission electron microscopy and X-ray scattering techniques and demonstrate that the morphologies from experiments agree with those predicted in simulations. Accordingly, these results indicate that the approach utilized represents a promising approach to intelligently design the morphologies taken on by organic solar cell active layers.

  10. Blended Wing Body Systems Studies: Boundary Layer Ingestion Inlets With Active Flow Control

    NASA Technical Reports Server (NTRS)

    Geiselhart, Karl A. (Technical Monitor); Daggett, David L.; Kawai, Ron; Friedman, Doug

    2003-01-01

    A CFD analysis was performed on a Blended Wing Body (BWB) aircraft with advanced, turbofan engines analyzing various inlet configurations atop the aft end of the aircraft. The results are presented showing that the optimal design for best aircraft fuel efficiency would be a configuration with a partially buried engine, short offset diffuser using active flow control, and a D-shaped inlet duct that partially ingests the boundary layer air in flight. The CFD models showed that if active flow control technology can be satisfactorily developed, it might be able to control the inlet flow distortion to the engine fan face and reduce the powerplant performance losses to an acceptable level. The weight and surface area drag benefits of a partially submerged engine shows that it might offset the penalties of ingesting the low energy boundary layer air. The combined airplane performance of such a design might deliver approximately 5.5% better aircraft fuel efficiency over a conventionally designed, pod-mounted engine.

  11. Cooperation between adsorbates accounts for the activation of atomic layer deposition reactions.

    PubMed

    Shirazi, Mahdi; Elliott, Simon D

    2015-04-14

    Atomic layer deposition (ALD) is a technique for producing conformal layers of nanometre-scale thickness, used commercially in non-planar electronics and increasingly in other high-tech industries. ALD depends on self-limiting surface chemistry but the mechanistic reasons for this are not understood in detail. Here we demonstrate, by first-principle calculations of growth of HfO2 from Hf(N(CH3)2)4-H2O and HfCl4-H2O and growth of Al2O3 from Al(CH3)3-H2O, that, for all these precursors, co-adsorption plays an important role in ALD. By this we mean that previously-inert adsorbed fragments can become reactive once sufficient numbers of molecules adsorb in their neighbourhood during either precursor pulse. Through the calculated activation energies, this 'cooperative' mechanism is shown to have a profound influence on proton transfer and ligand desorption, which are crucial steps in the ALD cycle. Depletion of reactive species and increasing coordination cause these reactions to self-limit during one precursor pulse, but to be re-activated via the cooperative effect in the next pulse. This explains the self-limiting nature of ALD. PMID:25786200

  12. Seismic Spatial Autocorrelation as a Technique to Track Changes in the Permafrost Active Layer

    NASA Astrophysics Data System (ADS)

    Abbott, R. E.

    2013-12-01

    We present preliminary results from an effort to continuously track freezing and thawing of the permafrost active layer using a small-aperture seismic array. The 7-element array of three-component posthole seismometers is installed on permafrost at Poker Flat Research Range, near Fairbanks, Alaska. The array is configured in two three-station circles with 75 and 25 meter radii that share a common center station. This configuration is designed to resolve omnidirectional, high-frequency seismic microtremor (i.e. ambient noise). Microtremor is continuously monitored and the data are processed using the spatial autocorrelation (SPAC) method. The resulting SPAC coefficients are then inverted for shear-wave velocity structure versus depth. Thawed active-layer soils have a much slower seismic velocity than frozen soils, allowing us to track the depth and intensity of thawing. Persistent monitoring on a permanent array would allow for a way to investigate year-to-year changes without costly site visits. Results from the seismic array will compared to, and correlated with, other measurement techniques, such as physical probing and remote sensing methods. Sandia National Laboratories is a multi-program laboratory managed and operated by Sandia Corporation, a wholly owned subsidiary of Lockheed Martin Corporation, for the U.S. Department of Energy's National Nuclear Security Administration under contract DE-AC04-94AL85000.

  13. Hydrogenated Amorphous Silicon Germanium Active Layer for Top Cell of a Multi Junction Cell Structure.

    PubMed

    Cho, Jaehyun; Iftiquar, S M; Kim, Minbum; Park, Jinjoo; Jung, Junhee; Kim, Jiwoong; Yi, Junsin

    2016-05-01

    Intrinsic hydrogenated amorphous silicon-germanium (a-SiGe:H) alloy is generally used in the bottom cell because of its low band gap. The a-SiGe:H has a higher photo conductivity in comparison to the a-Si:H; thus, it is expected that the a-SiGe:H can show better short circuit current density than that of the a-Si:H based solar cell. Therefore, we optimized a-SiGe:H active layer that can be a suitable choice for the front cell of a multi junction.solar cell. Furthermore, we carried out a comparative study of the solar cells that have a-SiGe:H and a-Si:H as respective active layers. The a-SiGe:H based solar cells show higher short circuit current density, while the a-Si:H based cells show higheropen circuit voltage. The current-voltage characteristics of these cells are as follows: (a) V(oc) = 770 mV, J(sc) = 15.0 mA/cm2, FF = 64.5%, and η = 7.47% for a-SiGe:H based cell; and (b) V(oc) = 826 mV, J(sc) = 13.63 mA/cm2, FF = 72.0%, and η = 8.1% for a-Si:H based cell. PMID:27483837

  14. Synthesis of few-layer MoS2 nanosheet-loaded Ag3PO4 for enhanced photocatalytic activity.

    PubMed

    Song, Yanhua; Lei, Yucheng; Xu, Hui; Wang, Cheng; Yan, Jia; Zhao, Haozhu; Xu, Yuanguo; Xia, Jiexiang; Yin, Sheng; Li, Huaming

    2015-02-21

    Novel few-layer MoS2/Ag3PO4 composites were fabricated. The results indicated that Ag3PO4 nanoparticles were directly formed on the surface of few-layer MoS2. The physical and chemical properties of the few-layer MoS2/Ag3PO4 composite photocatalysts were tested in order to investigate the effects of few-layer MoS2 on the photocatalytic activity of Ag3PO4. The photocatalytic activity of the few-layer MoS2/Ag3PO4 composites was evaluated by the photocatalytic degradation of Rhodamine B (RhB) and bisphenol A (BPA) under visible light irradiation. The photocatalytic activity of the few-layer MoS2/Ag3PO4 composites was higher than that of pure Ag3PO4. The optimal few-layer MoS2 content for the organic pollutant degradation of the heterojunction structures was determined. The synergic effect between few-layer MoS2 and Ag3PO4 was found to lead to an improved photogenerated carrier separation. The stability and the possible photocatalytic mechanism of the composites were also discussed. PMID:25567674

  15. Hypoxia Activates Calpains in the Nerve Fiber Layer of Monkey Retinal Explants

    PubMed Central

    Hirata, Masayuki; Shearer, Thomas R.; Azuma, Mitsuyoshi

    2015-01-01

    Purpose The vascular ischemic hypothesis attributes nerve damage in the retina to decreased blood flow in the ophthalmic artery, reduced oxygenation, and impaired axonal transport. Activation of calpain enzymes contributes to retinal cell death during hypoxia. However, we still do not know in which specific retinal layers calpains are activated. Thus, the purpose of the present study was to investigate where and when calpains are activated in an improved culture model of hypoxic monkey retina. Methods Monkey retinal explants were cultured on microporous membranes with the retinal ganglion cell (RGC) side facing up. Explants were incubated under hypoxic conditions, with or without additional reoxygenation. When it was used, the calpain inhibitor SNJ-1945 was maintained throughout the culture period. Immunohistochemistry and immunoblotting assays for α-spectrin, calpains 1 and 2, calpastatin, β-III tubulin, and γ-synuclein were performed with specific antibodies. Cell death was assessed by TUNEL staining. Results Under normoxic conditions, TUNEL-positive cells were minimal in our improved culture conditions. As early as 8 hours after hypoxia, the 150-kDa calpain-specific α-spectrin breakdown product appeared in the nerve fiber layer (NFL), where calpains 1 and 2 were localized. TUNEL-positive RGCs then increased at later time periods. The calpain inhibitor SNJ-1945 ameliorated changes induced by hypoxia or hypoxia/reoxygenation. Conclusions During hypoxia/reoxygenation in an improved, relevant monkey model, calpains were first activated in the NFL, followed by death of the parent RGCs. This observation suggest that calpain-induced degeneration of retinal nerve fibers may be an underlying mechanism for RGC death in hypoxic retinal neuropathies. PMID:26393472

  16. Activated macrophages as a feeder layer for growth of resident cardiac progenitor cells.

    PubMed

    Sepúlveda, Diana E; Cabeza Meckert, Patricia; Locatelli, Paola; Olea, Fernanda D; Pérez, Néstor G; Pinilla, Oscar A; Díaz, Romina G; Crottogini, Alberto; Laguens, Rubén P

    2016-08-01

    The adult heart contains a population of cardiac progenitor cells (CPCs). Growing and collecting an adequate number of CPCs demands complex culture media containing growth factors. Since activated macrophages secrete many growth factors, we investigated if activated isolated heart cells seeded on a feeder layer of activated peritoneal macrophages (PM) could result in CPCs and if these, in turn, could exert cardioprotection in rats with myocardial infarction (MI). Heart cells of inbred Wistar rats were isolated by collagenase digestion and cultured on PM obtained 72 h after intraperitoneal injection of 12 ml thioglycollate. Cells (1 × 10(6)) exhibiting CPC phenotype (immunohistochemistry) were injected in the periphery of rat MI 10 min after coronary artery occlusion. Control rats received vehicle. Three weeks later, left ventricular (LV) function (echocardiogram) was assessed, animals were euthanized and the hearts removed for histological studies. Five to six days after seeding heart cells on PM, spherical clusters composed of small bright and spherical cells expressing mostly c-Kit and Sca-1 antigens were apparent. After explant, those clusters developed cobblestone-like monolayers that expressed smooth muscle actin and sarcomeric actin and were successfully transferred for more than ten passages. When injected in the MI periphery, many of them survived at 21 days after coronary ligature, improved LV ejection fraction and decreased scar size as compared with control rats. CPC-derived cells with cardiocyte and smooth muscle phenotypes can be successfully grown on a feeder layer of activated syngeneic PM. These cells decreased scar size and improved heart function in rats with MI. PMID:25432330

  17. Dynamics of the Ligand Binding Domain Layer during AMPA Receptor Activation.

    PubMed

    Baranovic, Jelena; Chebli, Miriam; Salazar, Hector; Carbone, Anna L; Faelber, Katja; Lau, Albert Y; Daumke, Oliver; Plested, Andrew J R

    2016-02-23

    Ionotropic glutamate receptors are postsynaptic tetrameric ligand-gated channels whose activity mediates fast excitatory transmission. Glutamate binding to clamshell-shaped ligand binding domains (LBDs) triggers opening of the integral ion channel, but how the four LBDs orchestrate receptor activation is unknown. Here, we present a high-resolution x-ray crystal structure displaying two tetrameric LBD arrangements fully bound to glutamate. Using a series of engineered metal ion trapping mutants, we showed that the more compact of the two assemblies corresponds to an arrangement populated during activation of full-length receptors. State-dependent cross-linking of the mutants identified zinc bridges between the canonical active LBD dimers that formed when the tetramer was either fully or partially bound by glutamate. These bridges also stabilized the resting state, consistent with the recently published full-length apo structure. Our results provide insight into the activation mechanism of glutamate receptors and the complex conformational space that the LBD layer can sample. PMID:26910426

  18. Actomyosin dynamics drive local membrane component organization in an in vitro active composite layer.

    PubMed

    Köster, Darius Vasco; Husain, Kabir; Iljazi, Elda; Bhat, Abrar; Bieling, Peter; Mullins, R Dyche; Rao, Madan; Mayor, Satyajit

    2016-03-22

    The surface of a living cell provides a platform for receptor signaling, protein sorting, transport, and endocytosis, whose regulation requires the local control of membrane organization. Previous work has revealed a role for dynamic actomyosin in membrane protein and lipid organization, suggesting that the cell surface behaves as an active composite composed of a fluid bilayer and a thin film of active actomyosin. We reconstitute an analogous system in vitro that consists of a fluid lipid bilayer coupled via membrane-associated actin-binding proteins to dynamic actin filaments and myosin motors. Upon complete consumption of ATP, this system settles into distinct phases of actin organization, namely bundled filaments, linked apolar asters, and a lattice of polar asters. These depend on actin concentration, filament length, and actin/myosin ratio. During formation of the polar aster phase, advection of the self-organizing actomyosin network drives transient clustering of actin-associated membrane components. Regeneration of ATP supports a constitutively remodeling actomyosin state, which in turn drives active fluctuations of coupled membrane components, resembling those observed at the cell surface. In a multicomponent membrane bilayer, this remodeling actomyosin layer contributes to changes in the extent and dynamics of phase-segregating domains. These results show how local membrane composition can be driven by active processes arising from actomyosin, highlighting the fundamental basis of the active composite model of the cell surface, and indicate its relevance to the study of membrane organization. PMID:26929326

  19. Polyethylene/organically-modified layered-silicate nanocomposites with antimicrobial activity

    NASA Astrophysics Data System (ADS)

    Songtipya, P.; Jimenez-Gasco, M. M.; Manias, E.

    2009-03-01

    Despite the very intensive research on polymer nanocomposites, the opportunities for new functionalities possible by nanofillers still remain largely untapped. Here, we present polyethylene/inorganic nanocomposites that exhibit strongly enhanced mechanical performance and, at the same time, also an antimicrobial activity originating from the organo-filler nature. Specifically, PE/organically-modified layered-silicate nanocomposites were prepared via melt-processing, and antimicrobial activity was designed by proper choice of their organic modification. Their antimicrobial activity was measured against three micotoxinogen fungal strains (Penicillium roqueforti and claviforme, and Fusarium graminearum) as model soil-borne plant and food contaminants. Montmorillonite-based organofillers, which only differ in their organic modification, were used to exemplify how these surfactants can be designed to render antifungal activity to the nanocomposites. The comparative discussion of the growth of fungi on unfilled PE and nanocomposite PE films is used to demonstrate how the antimicrobial efficacy is dictated by the surfactant chemistry and, further, how the nanocomposites' inhibitory activity compares to that of the organo-fillers and the surfactants.

  20. Estimation of thermoelastic deformations in the near-surface layers of condensed media upon absorption of time-modulated laser radiation

    NASA Astrophysics Data System (ADS)

    Muratikov, K. L.

    2015-10-01

    Nonstationary thermoelastic deformation in the near-surface layers of condensed media are determined in the quasi-static approximation. The deformations are induced by the absorbed laser radiation. A 3D model is used to derive analytical expressions for normal and radial components of the deformation vector of the surface.

  1. Induction and modulation of persistent activity in a layer V PFC microcircuit model.

    PubMed

    Papoutsi, Athanasia; Sidiropoulou, Kyriaki; Cutsuridis, Vassilis; Poirazi, Panayiota

    2013-01-01

    Working memory refers to the temporary storage of information and is strongly associated with the prefrontal cortex (PFC). Persistent activity of cortical neurons, namely the activity that persists beyond the stimulus presentation, is considered the cellular correlate of working memory. Although past studies suggested that this type of activity is characteristic of large scale networks, recent experimental evidence imply that small, tightly interconnected clusters of neurons in the cortex may support similar functionalities. However, very little is known about the biophysical mechanisms giving rise to persistent activity in small-sized microcircuits in the PFC. Here, we present a detailed biophysically-yet morphologically simplified-microcircuit model of layer V PFC neurons that incorporates connectivity constraints and is validated against a multitude of experimental data. We show that (a) a small-sized network can exhibit persistent activity under realistic stimulus conditions. (b) Its emergence depends strongly on the interplay of dADP, NMDA, and GABAB currents. (c) Although increases in stimulus duration increase the probability of persistent activity induction, variability in the stimulus firing frequency does not consistently influence it. (d) Modulation of ionic conductances (I h , I D , I sAHP, I caL, I caN, I caR) differentially controls persistent activity properties in a location dependent manner. These findings suggest that modulation of the microcircuit's firing characteristics is achieved primarily through changes in its intrinsic mechanism makeup, supporting the hypothesis of multiple bi-stable units in the PFC. Overall, the model generates a number of experimentally testable predictions that may lead to a better understanding of the biophysical mechanisms of persistent activity induction and modulation in the PFC. PMID:24130519

  2. New paradigm for layered paleoproterozoic PGE intrusions of the Fennoscandian Shield: duration and multistage magmatic activity

    NASA Astrophysics Data System (ADS)

    Mitrofanov, Felix; Bayanova, Tamara; Serov, Pavel

    2014-05-01

    Layered mafic-ultramafic paleoproterozoic PGE intrusions are widespread in the N-E part of Fennoscandian Shield and belongs to two belt: North (Kola) and South (Finland and Karelia). Precise isotope-geochemical data using U-Pb (on zircon and baddeleyite) and Sm-Nd (rock-forming and sulfides minerals), systematic reflect long magmatic activity (with 2.53, 2.50, 2.45, 2.40 pulses) and duration of mantle event from 2.53 to 2.40 Ga. The Kola belt barren phases were dated in Fedorovo-Pansky massifs with 2.53 Ga for orthopyroxenites and olivine gabbro based on U-Pb (on zircon) and Sm-Nd (rock-forming minerals) data. Main PGE-bearing phases of gabbronorite (Mt. Generalskaya) norite (Monchepluton) and gabbronorite (Fedorovo-Pansky) massif have yielded 2.50 Ga on U-Pb and Sm-Nd dating. The second PGE-bearing phases with 2.45 Ga belong to anorthosite of Mt. Generalskaya, Fedorovo-Pansky and Monchetundra massifs. The same ages have layered PGE-bearing intrusions of Finland - Koitelainen, Penikat et. set. and Oulanga group in Karelia (Bayanova et al., 2009). The final mafic magmatic activity connected with dykes of Imandra lopolith with 2.40 Ga. Isotope geochemical ɛNd - ISr indicators for layered intrusions (more than 70 analyses) reflect enriched mantle EM-1 type reservoir with ISr values from 0.703-0.704. Isotope 3He/4He data for accessory minerals (ilmenite, magnetite et. set.) have significant lower and upper mantle contribution. The model Sm-Nd ages of protolith lies in 3.2-2.9 Ga and primary magma source as fertile according to (Arndt, 2010). The geological and isotope-geochemistry data for layered paleoproterozoic PGE-intrusions permit considered Fennoscandian Shield with Superior and Wyoming as a big magmatic LIP, which related with breakup of oldest Kenorland Sypercontitent. We thank to G. Wasserburg for 205 Pb artificial spike, J. Ludden for 91500 and Temora standards, F. Corfu, V. Todt and U. Poller for assistance in the establishing of the U-Pb method for single

  3. Atomic Layer-by-Layer Deposition of Pt on Pd Nanocubes for Catalysts with Enhanced Activity and Durability toward Oxygen Reduction

    SciTech Connect

    Xie, Shuifen; Choi, Sang; Lu, Ning; Roling, Luke T.; Herron, Jeffrey A.; Zhang, Lei; Park, Jinho; Wang, Jinguo; Kim, Moon J.; Xie, Zhaoxiong; Mavrikakis, Manos; Xia, Younan

    2014-06-11

    An effective strategy for reducing the Pt content while retaining the activity of a Pt-based catalyst is to deposit the Pt atoms as ultrathin skins of only a few atomic layers thick on nanoscale substrates made of another metal. During deposition, however, the Pt atoms often take an island growth mode because of a strong bonding between Pt atoms. Here we report a versatile route to the conformal deposition of Pt as uniform, ultrathin shells on Pd nanocubes in a solution phase. The introduction of the Pt precursor at a relatively slow rate and high temperature allowed the deposited Pt atoms to spread across the entire surface of a Pd nanocube to generate a uniform shell. The thickness of the Pt shell could be controlled from one to six atomic layers by varying the amount of Pt precursor added into the system. Compared to a commercial Pt/C catalyst, the Pd@PnL (n = 1-6) core-shell nanocubes showed enhancements in specific activity and durability toward the oxygen reduction reaction (ORR). Density functional theory (DFT) calculations on model (100) surfaces suggest that the enhancement in specific activity can be attributed to the weakening of OH binding through ligand and strain effects, which, in turn, increases the rate of OH hydrogenation. A volcano-type relationship between the ORR specific activity and the number of Pt atomic layers was derived, in good agreement with the experimental results. Both theoretical and experimental studies indicate that the ORR specific activity was maximized for the catalysts based on Pd@Pt2-3L nanocubes. Because of the reduction in Pt content used and the enhancement in specific activity, the Pd@Pt1L nanocubes showed a Pt mass activity with almost three-fold enhancement relative to the Pt/C catalyst.

  4. Multi-omics of permafrost, active layer and thermokarst bog soil microbiomes

    NASA Astrophysics Data System (ADS)

    Hultman, Jenni; Waldrop, Mark P.; Mackelprang, Rachel; David, Maude M.; McFarland, Jack; Blazewicz, Steven J.; Harden, Jennifer; Turetsky, Merritt R.; McGuire, A. David; Shah, Manesh B.; Verberkmoes, Nathan C.; Lee, Lang Ho; Mavrommatis, Kostas; Jansson, Janet K.

    2015-05-01

    Over 20% of Earth's terrestrial surface is underlain by permafrost with vast stores of carbon that, once thawed, may represent the largest future transfer of carbon from the biosphere to the atmosphere. This process is largely dependent on microbial responses, but we know little about microbial activity in intact, let alone in thawing, permafrost. Molecular approaches have recently revealed the identities and functional gene composition of microorganisms in some permafrost soils and a rapid shift in functional gene composition during short-term thaw experiments. However, the fate of permafrost carbon depends on climatic, hydrological and microbial responses to thaw at decadal scales. Here we use the combination of several molecular `omics' approaches to determine the phylogenetic composition of the microbial communities, including several draft genomes of novel species, their functional potential and activity in soils representing different states of thaw: intact permafrost, seasonally thawed active layer and thermokarst bog. The multi-omics strategy reveals a good correlation of process rates to omics data for dominant processes, such as methanogenesis in the bog, as well as novel survival strategies for potentially active microbes in permafrost.

  5. Multi-omics of permafrost, active layer and thermokarst bog soil microbiomes.

    PubMed

    Hultman, Jenni; Waldrop, Mark P; Mackelprang, Rachel; David, Maude M; McFarland, Jack; Blazewicz, Steven J; Harden, Jennifer; Turetsky, Merritt R; McGuire, A David; Shah, Manesh B; VerBerkmoes, Nathan C; Lee, Lang Ho; Mavrommatis, Kostas; Jansson, Janet K

    2015-05-14

    Over 20% of Earth's terrestrial surface is underlain by permafrost with vast stores of carbon that, once thawed, may represent the largest future transfer of carbon from the biosphere to the atmosphere. This process is largely dependent on microbial responses, but we know little about microbial activity in intact, let alone in thawing, permafrost. Molecular approaches have recently revealed the identities and functional gene composition of microorganisms in some permafrost soils and a rapid shift in functional gene composition during short-term thaw experiments. However, the fate of permafrost carbon depends on climatic, hydrological and microbial responses to thaw at decadal scales. Here we use the combination of several molecular 'omics' approaches to determine the phylogenetic composition of the microbial communities, including several draft genomes of novel species, their functional potential and activity in soils representing different states of thaw: intact permafrost, seasonally thawed active layer and thermokarst bog. The multi-omics strategy reveals a good correlation of process rates to omics data for dominant processes, such as methanogenesis in the bog, as well as novel survival strategies for potentially active microbes in permafrost. PMID:25739499

  6. Low-temperature photo-activated inorganic electron transport layers for flexible inverted polymer solar cells

    NASA Astrophysics Data System (ADS)

    Lee, Jung-Wook; Lee, Soo-Hyoung; Kim, Yong-Hoon; Park, Sung Kyu

    2014-09-01

    A simple and versatile route of forming sol-gel-derived metal oxide n-type electron transport layers (ETLs) for flexible inverted polymer solar cells (PSCs) is proposed using low-temperature photochemical activation process. The photochemical activation, which is induced by deep ultraviolet irradiation on sol-gel films, allows formation of metal oxide n-type ETLs such as zinc oxide (ZnO) and indium gallium zinc oxide films at a low temperature. Compared to poly(3-hexylthiophene)/phenyl-C61-butyric acid methyl ester inverted PSCs with thermally annealed ZnO ETLs (optimized efficiency of 3.26 ± 0.03 %), the inverted PSCs with photo-activated ZnO ETLs showed an improved efficiency of 3.60 ± 0.02 %. The enhanced photovoltaic property is attributed to efficient charge collection from low overall series resistance and high surface area-to-geometric area ratio by the photo-activated ZnO ETLs.

  7. Novel biohybrids of layered double hydroxide and lactate dehydrogenase enzyme: Synthesis, characterization and catalytic activity studies

    NASA Astrophysics Data System (ADS)

    Djebbi, Mohamed Amine; Braiek, Mohamed; Hidouri, Slah; Namour, Philippe; Jaffrezic-Renault, Nicole; Ben Haj Amara, Abdesslem

    2016-02-01

    The present work introduces new biohybrid materials involving layered double hydroxides (LDH) and biomolecule such as enzyme to produce bioinorganic system. Lactate dehydrogenase (Lac Deh) has been chosen as a model enzyme, being immobilized onto MgAl and ZnAl LDH materials via direct ion-exchange (adsorption) and co-precipitation methods. The immobilization efficiency was largely dependent upon the immobilization methods. A comparative study shows that the co-precipitation method favors the immobilization of great and tunable amount of enzyme. The structural behavior, chemical bonding composition and morphology of the resulting biohybrids were determined by X-ray diffraction (XRD) study, Fourier transform infrared (FTIR) spectroscopy and transmission electron microscopy (TEM), respectively. The free and immobilized enzyme activity and kinetic parameters were also reported using UV-Visible spectroscopy. However, the modified LDH materials showed a decrease in crystallinity as compared to the unmodified LDH. The change in activity of the immobilized lactate dehydrogenase was considered to be due, to the reduced accessibility of substrate molecules to the active sites of the enzyme and the partial conformational change of the Lac Deh molecules as a result of the immobilization way. Finally, it was proven that there is a correlation between structure/microstructure and enzyme activity dependent on the immobilization process.

  8. Multi-omics of Permafrost, Active Layer and Thermokarst Bog Soil Microbiomes

    SciTech Connect

    Hultman, Jenni; Waldrop, Mark P.; Mackelprang, Rachel; David, Maude; McFarland, Jack; Blazewicz, Steven J.; Harden, Jennifer W.; Turetsky, Merritt; McGuire, A. David; Shah, Manesh B.; VerBerkmoes, Nathan C.; Lee, Lang Ho; Mavrommatis, Konstantinos; Jansson, Janet K.

    2015-03-04

    Over 20% of Earth’s terrestrial surface is underlain by permafrost with vast stores of carbon that, if thawed may represent the largest future transfer of C from the biosphere to the atmosphere 1. This process is largely dependent on microbial responses, but we know little about microbial activity in intact, let alone in thawing permafrost. Molecular approaches have recently revealed the identities and functional gene composition of microorganisms in some permafrost soils 2-4 and a rapid shift in functional gene composition during short-term thaw experiments 3. However, the fate of permafrost C depends on climatic, hydrologic, and microbial responses to thaw at decadal scales 5, 6. Here the combination of several molecular “omics” approaches enabled us to determine the phylogenetic composition of the microbial community, including several draft genomes of novel species, their functional potential and activity in soils representing different states of thaw: intact permafrost, seasonally thawed active layer and thermokarst bog. The multi-omics strategy revealed a good correlation of process rates to omics data for dominant processes, such as methanogenesis in the bog, as well as novel survival strategies for potentially active microbes in permafrost.

  9. The application of atomic absorption spectrometry for the determination of residual active pharmaceutical ingredients in cleaning validation samples.

    PubMed

    Bubnič, Zoran; Urleb, Uroš; Kreft, Katjuša; Veber, Marjan

    2011-03-01

    The objective of this work was the development and validation of atomic absorption spectrometric (AAS) methods for the determination of residual active pharmaceutical ingredients (API) in rinse samples for cleaning validation. AAS as an indirect method for the determination of API in rinse samples can be applied when it is in the form of salt with metal ions or when the metal ion is a part of the API's structure. The electrothermal AAS methods (aqueous and ethanol medium) for the determination of magnesium in esomeprazole magnesium and the flame AAS method for the determination of lithium in lithium carbonate in rinse samples were developed. Various combinations of solvents were tested and a combination of 1% aqueous or ethanol solution of nitric acid for esomeprazole magnesium and 0.1% aqueous solution of nitric acid for lithium carbonate were found to be the most suitable. The atomization conditions in the graphite furnace and in the flame were carefully studied to avoid losses of analyte and to achieve suitable sensitivity. The cleaning verification methods were validated with respect to accuracy, precision, linearity, limit of detection, and quantification. In all the cases, the limits of detection were at the microgram level. The methods were successfully applied for the determination of esomeprazole magnesium and lithium carbonate in rinse samples from cleaning procedures. PMID:20923390

  10. Compartmentalization of trace elements in guinea pig tissues by INAA (instrumental neutron activation analysis) and AAS (atomic absorption spectroscopy)

    SciTech Connect

    Chatt, A.; Holzbecher, J.; Katz, S.A.

    1988-01-01

    Human scalp hair analysis has received considerable attention from a variety of disciplines over the last 20 yr or so. Trace element levels of hair have been used in environmental, epidemiological, forensic, nutritional, predictive, and preventive medicine studies. There still exist confusion, skepticism, and controversy, however, among the experts as well as lay persons in the interpretation of hair trace element data. Much of the criticism stems from the lack of quantitative and reliable data on the ability of hair to accurately reflect dose-response relationships. To better define the significance or hair trace element levels (under the auspices of the International Atomic Energy Agency), the authors have undertaken a controlled set of animal experiments in which trace element levels in hair and other tissues have been measured after a mild state of systemic intoxication by chronic, low-does exposure to cadmium and selenium. Instrumental neutron activation analysis (INAA) and atomic absorption spectroscopy (AAS) methods have been developed for the determination of several elements with a high degree of precision and accuracy.

  11. Monosaccharide absorption activity of Arabidopsis roots depends on expression profiles of transporter genes under high salinity conditions.

    PubMed

    Yamada, Kohji; Kanai, Motoki; Osakabe, Yuriko; Ohiraki, Haruka; Shinozaki, Kazuo; Yamaguchi-Shinozaki, Kazuko

    2011-12-16

    Plant roots are able to absorb sugars from the rhizosphere but also release sugars and other metabolites that are critical for growth and environmental signaling. Reabsorption of released sugar molecules could help reduce the loss of photosynthetically fixed carbon through the roots. Although biochemical analyses have revealed monosaccharide uptake mechanisms in roots, the transporters that are involved in this process have not yet been fully characterized. In the present study we demonstrate that Arabidopsis STP1 and STP13 play important roles in roots during the absorption of monosaccharides from the rhizosphere. Among 14 STP transporter genes, we found that STP1 had the highest transcript level and that STP1 was a major contributor for monosaccharide uptake under normal conditions. In contrast, STP13 was found to be induced by abiotic stress, with low expression under normal conditions. We analyzed the role of STP13 in roots under high salinity conditions where membranes of the epidermal cells were damaged, and we detected an increase in the amount of STP13-dependent glucose uptake. Furthermore, the amount of glucose efflux from stp13 mutants was higher than that from wild type plants under high salinity conditions. These results indicate that STP13 can reabsorb the monosaccharides that are released by damaged cells under high salinity conditions. Overall, our data indicate that sugar uptake capacity in Arabidopsis roots changes in response to environmental stresses and that this activity is dependent on the expression pattern of sugar transporters. PMID:22041897

  12. Estimation of elastic stress in the near-surface layers of solid objects caused by thermoelastic deformations under absorption of nonstationary laser radiation

    NASA Astrophysics Data System (ADS)

    Muratikov, K. L.

    2013-12-01

    Analytical expressions for the calculation of radial and tangential components of the elastic stress tensor that are generated by the nonstationary laser radiation in the near-surface layers of solid objects are derived in the framework of a 3D model and quasi-static approximation. The components of the stress tensor are analyzed in the systems with strong and weak focusing of laser radiation on the surface of the object.

  13. Geochemical drivers of organic matter decomposition in the active layer of Arctic tundra

    NASA Astrophysics Data System (ADS)

    Herndon, E.; Roy Chowdhury, T.; Mann, B.; Graham, D. E.; Wullschleger, S. D.; Gu, B.; Liang, L.

    2014-12-01

    Arctic tundra soils store large quantities of organic carbon that are susceptible to decomposition and release to the atmosphere as CO2 and CH4. Decomposition rates are limited by cold temperatures and widespread anoxia; however, ongoing changes in soil temperature, thaw depth, and water saturation are expected to influence rates and pathways of organic matter decomposition. In order to predict greenhouse gas releases from high-latitude ecosystems, it is necessary to identify how geochemical factors (e.g. terminal electron acceptors, carbon substrates) influence CO2 and CH4 production in tundra soils. This study evaluates spatial patterns of aqueous geochemistry in the active layer of low- to high-centered polygons located at the Barrow Environmental Observatory in northern Alaska. Pore waters from saturated soils were low in sulfate and nitrate but contained abundant Fe which may serve a major terminal electron acceptor for anaerobic microbial metabolism. Relatively high concentrations of soluble Fe accumulated in the middle of the active layer near the boundary between the organic and mineral horizon, and we infer that Fe-oxide reduction and dissolution in the mineral horizon produced soluble Fe that diffused upwards and was stabilized by complexation with dissolved organic matter. Fe concentrations in the bulk soil were higher in organic than mineral horizons due to the presence of these organic-Fe complexes and Fe-oxide precipitates. Dissolved CH4 increased with increasing proportions of dissolved Fe(III) in saturated soils from transitional and low-centered polygons. The opposite trend was observed in drier soils from flat- and high-centered polygons where deeper oxidation fronts may inhibit methanogenesis. Using multiple spectroscopic and molecular methods (e.g. UV-Vis, Fourier transform infrared, ultrahigh resolution mass spectrometry), we also observed that pore waters from the middle of the active layer contained more aromatic organics than in mineral

  14. Simulating cosmic radiation absorption and secondary particle production of solar panel layers of Low Earth Orbit (LEO) satellite with GEANT4

    NASA Astrophysics Data System (ADS)

    Yiǧitoǧlu, Merve; Veske, Doǧa; Nilüfer Öztürk, Zeynep; Bilge Demirköz, Melahat

    2016-07-01

    All devices which operate in space are exposed to cosmic rays during their operation. The resulting radiation may cause fatal damages in the solid structure of devices and the amount of absorbed radiation dose and secondary particle production for each component should be calculated carefully before the production. Solar panels are semiconductor solid state devices and are very sensitive to radiation. Even a short term power cut-off may yield a total failure of the satellite. Even little doses of radiation can change the characteristics of solar cells. This deviation can be caused by rarer high energetic particles as well as the total ionizing dose from the abundant low energy particles. In this study, solar panels planned for a specific LEO satellite, IMECE, are analyzed layer by layer. The Space Environment Information System (SPENVIS) database and GEANT4 simulation software are used to simulate the layers of the panels. The results obtained from the simulation will be taken in account to determine the amount of radiation protection and resistance needed for the panels or to revise the design of the panels.

  15. Exploring New Active Regions for Type 1 InasSb Strained-Layer Lasers

    SciTech Connect

    Biefeld, R.M.; Kurtz, S.R.; Phillips, J.D.

    1999-05-13

    We report on the metal-organic chemical vapor deposition (MOCVD) of mid- infrared InAsSb/InPSb optically pumped lasers grown using a high speed rotating disk reactor (RDR). The devices contain AlAsSb claddings and strained, type 1, InAsSb/InPSb active regions. By changing the layer thickness and composition of InAsSb/InPSb SLSs, we have prepared structures with low temperature (<20K) photoluminescence wavelengths ranging from 3.4 to 4.8 µm. We find a variation of bandgap from 0.272 to 0.324 eV for layer thicknesses of 9.0 to 18.2 nm. From these data we have estimated a valence band offset for the InAsSb/InPSb interface of about 400 meV. An InAsSb/InPSb SLS, optically pumped laser structure was grown on an InAs substrate with AlAs0.l6Sb0.84 claddings. A lasing threshold and spectrally narrowed laser emission was seen from 80 K through 200 K, the maximum temperature where Iasing occurred. The temperature dependence of the SLS laser threshold is described by a characteristic temperature, T0 = 72 K, from 80 to 200 K.

  16. Influence of quaternization of ammonium on antibacterial activity and cytocompatibility of thin copolymer layers on titanium.

    PubMed

    Waßmann, Marco; Winkel, Andreas; Haak, Katharina; Dempwolf, Wibke; Stiesch, Meike; Menzel, Henning

    2016-10-01

    Antimicrobial coatings are able to improve the osseointegration of dental implants. Copolymers are promising materials for such applications due to their combined properties of two different monomers. To investigate the influence of different monomer mixtures, we have been synthesized copolymers of dimethyl (methacryloxyethyl) phosphonate (DMMEP) and dipicolyl aminoethyl methacrylate in different compositions and have them characterized to obtain the r-parameters. Some of the copolymers with different compositions have also been alkylated with 1-bromohexane, resulting in quaternized ammonium groups. The copolymers have been deposited onto titanium surfaces resulting in ultrathin, covalently bound layers. These layers have been characterized by water contact angle measurements and ellipsometry. The influence of quaternary ammonium groups on antibacterial properties and cytocompatibility was studied: Activity against bacteria was tested with a gram positive Staphylococcus aureus strain. Cytocompatibility was tested with a modified LDH assay after 24 and 72 h to investigate adhesion and proliferation of human fibroblast cells on modified surfaces. The copolymer with the highest content of DMMEP showed a good reduction of S. aureus and in the alkylated version a very good reduction of about 95%. On the other hand, poor cytocompatibility is observed. However, our results show that this trend cannot be generalized for this copolymer system. PMID:27456132

  17. Morphology and geotechnique of active-layer detachment failures in discontinuous and continuous permafrost, northern Canada

    NASA Astrophysics Data System (ADS)

    Lewkowicz, Antoni G.; Harris, Charles

    2005-07-01

    Fifty active-layer detachment failures triggered after forest fire in the discontinuous permafrost zone (central Mackenzie Valley, 65° N.) are compared to several hundred others caused by summer meteorological triggers in continuous permafrost (Fosheim Peninsula, Ellesmere Island, 80°N). Most failures fall into compact or elongated morphological categories. The compact type occur next to stream channels and have little internal disturbance of the displaced block, whereas the elongated types can develop on any part of the slope and exhibit greater internal deformation. Frequency distributions of length-to-width and length-to-depth ratios are similar at all sites. Positive pore pressures, expected theoretically, were measured in the field at the base of the thawing layer. Effective stress analysis could predict the instability of slopes in both areas, providing cohesion across the thaw plane was set to zero and/or residual strength parameters were employed. The location of the shear planes or zones in relation to the permafrost table and the degree of post-failure secondary movements (including headwall recession and thermokarst development within the failure track) differed between the localities, reflecting dissimilarity in the environmental triggers and in the degree of ground thermal disturbance.

  18. Low-noise encoding of active touch by layer 4 in the somatosensory cortex

    PubMed Central

    Andrew Hires, Samuel; Gutnisky, Diego A; Yu, Jianing; O'Connor, Daniel H; Svoboda, Karel

    2015-01-01

    Cortical spike trains often appear noisy, with the timing and number of spikes varying across repetitions of stimuli. Spiking variability can arise from internal (behavioral state, unreliable neurons, or chaotic dynamics in neural circuits) and external (uncontrolled behavior or sensory stimuli) sources. The amount of irreducible internal noise in spike trains, an important constraint on models of cortical networks, has been difficult to estimate, since behavior and brain state must be precisely controlled or tracked. We recorded from excitatory barrel cortex neurons in layer 4 during active behavior, where mice control tactile input through learned whisker movements. Touch was the dominant sensorimotor feature, with >70% spikes occurring in millisecond timescale epochs after touch onset. The variance of touch responses was smaller than expected from Poisson processes, often reaching the theoretical minimum. Layer 4 spike trains thus reflect the millisecond-timescale structure of tactile input with little noise. DOI: http://dx.doi.org/10.7554/eLife.06619.001 PMID:26245232

  19. Comparison of EL emitted by LEDs on Si substrates containing Ge and Ge/GeSn MQW as active layers

    NASA Astrophysics Data System (ADS)

    Schwartz, B.; Arguirov, T.; Kittler, M.; Oehme, M.; Kostecki, K.; Kasper, E.; Schulze, J.

    2015-02-01

    We analyzed Ge- and GeSn/Ge multiple quantum well (MQW) light emitting diodes (LEDs). The structures were grown by molecular beam epitaxy (MBE) on Si. In the Ge LEDs the active layer was 300 nm thick. Sb doping was ranging from 1×1018 to 1×1020 cm-3. An unintentionally doped Ge-layer served as reference. The LEDs with the MQWs consist of ten alternating GeSn/Ge-layers. The Ge-layers were 10 nm thick and the GeSn-layers were grown with 6 % Sn and thicknesses between 6 and 12 nm. The top contact of all LEDs was identical. Accordingly, the light extraction is comparable. The electroluminescence (EL) analysis was performed under forward bias at different currents. Sample temperatures between <300 K and 80 K were studied. For the reference LED the direct transition at 0.8 eV dominates. With increasing current the peak is slightly redshifted due to Joule heating. Sb doping of the active Ge-layer affects the intensity and at 3×1019 cm-3 the strongest emission appears. It is ~4 times higher as compared to the reference. Moreover a redshift of the peak position is caused by bandgap narrowing. The LEDs with undoped GeSn/Ge-MQWs as active layer show a very broad luminescence band with a peak around 0.65 eV, pointing to a dominance of the GeSn-layers. The light emission intensity is at least 17 times stronger as compared to the reference Ge-LED. Due to incorporation of Sn in the MQWs the active layer should approach to a direct semiconductor. In indirect Si and Ge we observed an increase of intensity with increasing temperature, whereas the intensity of GeSn/Ge-MQWs was much less affected. But a deconvolution of the spectra revealed that the energy of indirect transition in the wells is still below the one of the direct transition.

  20. Chitosan-cellulose composite for wound dressing material. Part 2. Antimicrobial activity, blood absorption ability, and biocompatibility.

    PubMed

    Harkins, April L; Duri, Simon; Kloth, Luther C; Tran, Chieu D

    2014-08-01

    Chitosan (CS), a polysaccharide derived from chitin, the second most abundant polysaccharide, is widely used in the medical world because of its natural and nontoxic properties and its innate ability for antibacterial and hemostasis effects. In this study, the novel composites containing CS and cellulose (CEL) (i.e., [CEL + CS]), which we have previously synthesized using a green and totally recyclable method, were investigated for their antimicrobial activity, absorption of anticoagulated whole blood, anti-inflammatory activity through the reduction of tumor necrosis factor-α (TNF-α) and interleukin-6 (IL-6), and the biocompatibility with human fibroblasts. The [CEL + CS] composites were found to inhibit the growth of both Gram positive and negative micro-organisms. For examples, the regenerated 100% lyophilized chitosan material was found to reduce growth of Escherichia coli (ATCC 8739 and vancomycin resistant Enterococcus faecalis (ATCC 51299) by 78, 36, and 64%, respectively. The composites are nontoxic to fibroblasts; that is, fibroblasts, which are critical to the formation of connective tissue matrix were found to grow and proliferate in the presence of the composites. They effectively absorb blood, and at the same rate and volume as commercially available wound dressings. The composites, in both air-dried and lyophilized forms, significantly inhibit the production of TNF-α and IL-6 by stimulated macrophages. These results clearly indicate that the biodegradable, biocompatible and nontoxic [CEL + CS] composites, particularly those dried by lyophilizing, can be effectively used as a material in wound dressings. PMID:24407857

  1. Development of a portable active long-path differential optical absorption spectroscopy system for volcanic gas measurements

    USGS Publications Warehouse

    Vita, Fabio; Kern, Christoph; Inguaggiato, Salvatore

    2014-01-01

    Active long-path differential optical absorption spectroscopy (LP-DOAS) has been an effective tool for measuring atmospheric trace gases for several decades. However, instruments were large, heavy and power-inefficient, making their application to remote environments extremely challenging. Recent developments in fibre-coupling telescope technology and the availability of ultraviolet light emitting diodes (UV-LEDS) have now allowed us to design and construct a lightweight, portable, low-power LP-DOAS instrument for use at remote locations and specifically for measuring degassing from active volcanic systems. The LP-DOAS was used to measure sulfur dioxide (SO2) emissions from La Fossa crater, Vulcano, Italy, where column densities of up to 1.2 × 1018 molec cm−2 (~ 500 ppmm) were detected along open paths of up to 400 m in total length. The instrument's SO2 detection limit was determined to be 2 × 1016 molec cm−2 (~ 8 ppmm), thereby making quantitative detection of even trace amounts of SO2 possible. The instrument is capable of measuring other volcanic volatile species as well. Though the spectral evaluation of the recorded data showed that chlorine monoxide (ClO) and carbon disulfide (CS2) were both below the instrument's detection limits during the experiment, the upper limits for the X / SO2 ratio (X = ClO, CS2) could be derived, and yielded 2 × 10−3 and 0.1, respectively. The robust design and versatility of the instrument make it a promising tool for monitoring of volcanic degassing and understanding processes in a range of volcanic systems.

  2. Paenibacillus polymyxa BFKC01 enhances plant iron absorption via improved root systems and activated iron acquisition mechanisms.

    PubMed

    Zhou, Cheng; Guo, Jiansheng; Zhu, Lin; Xiao, Xin; Xie, Yue; Zhu, Jian; Ma, Zhongyou; Wang, Jianfei

    2016-08-01

    Despite the high abundance of iron (Fe) in most earth's soils, Fe is the major limiting factor for plant growth and development due to its low bioavailability. With an increasing recognition that soil microbes play important roles in plant growth, several strains of beneficial rhizobactria have been applied to improve plant nutrient absorption, biomass, and abiotic or biotic stress tolerance. In this study, we report the mechanisms of microbe-induced plant Fe assimilation, in which the plant growth promoting rhizobacteria (PGPR) Paenibacillus polymyxa BFKC01 stimulates plant's Fe acquisition machinery to enhance Fe uptake in Arabidopsis plants. Mechanistic studies show that BFKC01 transcriptionally activates the Fe-deficiency-induced transcription factor 1 (FIT1), thereby up-regulating the expression of IRT1 and FRO2. Furthermore, BFKC01 has been found to induce plant systemic responses with the increased transcription of MYB72, and the biosynthetic pathways of phenolic compounds are also activated. Our data reveal that abundant phenolic compounds are detected in root exudation of the BFKC01-inoculated plants, which efficiently facilitate Fe mobility under alkaline conditions. In addition, BFKC01 can secret auxin and further improved root systems, which enhances the ability of plants to acquire Fe from soils. As a result, BFKC01-inoculated plants have more endogenous Fe and increased photosynthetic capacity under alkaline conditions as compared to control plants. Our results demonstrate the potential roles of BFKC01 in promoting Fe acquisition in plants and underline the intricate integration of microbial signaling in controlling plant Fe acquisition. PMID:27105423

  3. Direct radiative forcing and atmospheric absorption by boundary layer aerosols in the southeastern US: model estimates on the basis of new observations

    NASA Astrophysics Data System (ADS)

    Yu, Shaocai; Zender, Charles S.; Saxena, V. K.

    In an effort to reduce uncertainties in the quantification of aerosol direct radiative forcing (ADRF) in the southeastern United States (US), a field column experiment was conducted to measure aerosol radiative properties and effects at Mt. Mitchell, North Carolina, and at an adjacent valley site. The experimental period was from June 1995 to mid-December 1995. The aerosol optical properties (single scattering albedo and asymmetry factor) needed to compute ADRF were obtained on the basis of a procedure involving a Mie code and a radiative transfer code in conjunction with the retrieved aerosol size distribution, aerosol optical depth, and diffuse-to-direct solar irradiance ratio. The regional values of ADRF at the surface and top of atmosphere (TOA), and atmospheric aerosol absorption are derived using the obtained aerosol optical properties as inputs to the column radiation model (CRM) of the community climate model (CCM3). The cloud-free instantaneous TOA ADRFs for highly polluted (HP), marine (M) and continental (C) air masses range from 20.3 to -24.8, 1.3 to -10.4, and 1.9 to -13.4 W m -2, respectively. The mean cloud-free 24-h ADRFs at the TOA (at the surface) for HP, M, and C air masses are estimated to be -8±4 (-33±16), -7±4 (-13±8), and -0.14±0.05 (-8±3) W m -2, respectively. On the assumption that the fractional coverage of clouds is 0.61, the annual mean ADRFs at the TOA and the surface are -2±1, and -7±2 W m -2, respectively. This also implies that aerosols currently heat the atmosphere over the southeastern US by 5±3 W m -2 on annual timescales due to the aerosol absorption in the troposphere.

  4. Nanocomposites of polymers with layered inorganic nanofillers: Antimicrobial activity, thermo-mechanical properties, morphology, and dispersion

    NASA Astrophysics Data System (ADS)

    Songtipya, Ponusa

    In the first part of the thesis, polyethylene/layered silicate nanocomposites that exhibit an antimicrobial activity were synthesized and studied. Their antimicrobial activity was designed to originate from non-leaching, novel cationic modifiers---amine-based surfactants---used as the organic-modification of the fillers. Specifically, PE/organically-modified montmorillonite ( mmt) nanocomposites were prepared via melt-processing, and simultaneous dispersion and antimicrobial activity was designed by proper choice of the fillers' organic modification. The antimicrobial activity was measured against three micotoxinogen fungal strains (Penicillium roqueforti and claviforme, and Fusarium graminearum ). Various mmt-based organofillers, which only differ in the type or amount of their organic modification, were used to exemplify how these surfactants can be designed to render antifungal activity to the fillers themselves and the respective nanocomposites. A comparative discussion of the growth of fungi on unfilled PE and nanocomposite PE films is used to demonstrate how the antimicrobial efficacy is dictated by the surfactant chemistry and, further, how the nanocomposites' inhibitory activity compares to that of the organo-fillers and the surfactants. An attempt to improve the thermomechanical reinforcement of PE/mmt nanocomposites while maintaining their antimicrobial activity, was also carried out by combining two different organically modified montmorillonites. However, a uniform microscopic dispersion could not be achieved through this approach. In the second part of this thesis, a number of fundamental studies relating to structure-property relations in nanocomposites were carried out, towards unveiling strategies that can concurrently optimize selected properties of polymers by the addition of nanofillers. Specifically, the dispersion-crystallinity-reinforcement relations in HDPE/mmt nanocomposites was investigated. The influence of a functional HDPE compatibilizer

  5. Cholesterol absorption.

    PubMed

    Ostlund, Richard E

    2002-03-01

    Cholesterol absorption is a key regulatory point in human lipid metabolism because it determines the amount of endogenous biliary as well as dietary cholesterol that is retained, thereby influencing whole body cholesterol balance. Plant sterols (phytosterols) and the drug ezetimibe reduce cholesterol absorption and low-density lipoprotein cholesterol in clinical trials, complementing the statin drugs, which inhibit cholesterol biosynthesis. The mechanism of cholesterol absorption is not completely known but involves the genes ABC1, ABCG5, and ABCG8, which are members of the ATP-binding cassette protein family and appear to remove unwanted cholesterol and phytosterols from the enterocyte. ABC1 is upregulated by the liver X (LXR) and retinoid X (RXR) nuclear receptors. Acylcholesterol acytransferase-2 is an intestinal enzyme that esterifies absorbed cholesterol and increases cholesterol absorption when dietary intake is high. New clinical treatments based on better understanding of absorption physiology are likely to substantially improve clinical cholesterol management in the future. PMID:17033296

  6. Comparison of Plasma Activation of Thin Water Layers by Direct and Remote Plasma Sources

    NASA Astrophysics Data System (ADS)

    Kushner, Mark

    2014-10-01

    Plasma activation of liquids is now being investigated for a variety of biomedical applications. The plasma sources used for this activation can be generally classified as direct (the plasma is in contact with the surface of the liquid) or remote (the plasma does not directly touch the liquid). The direct plasma source may be a dielectric barrier discharge (DBD) where the surface of the liquid is a floating electrode or a plasma jet in which the ionization wave forming the plasma plume reaches the liquid. The remote plasma source may be a DBD with electrodes electrically isolated from the liquid or a plasma jet in which the ionization wave in the plume does not reach the liquid. In this paper, a comparison of activation of thin water layers on top of tissue, as might be encountered in wound healing, will be discussed using results from numerical investigations. We used the modeling platform nonPDPSIM to simulate direct plasma activation of thin water layers using DBDs and remote activation using plasma jets using up to hundreds of pulses. The DBDs are sustained in humid air while the plasma jets consist of He/O2 mixtures flowed into humid air. For similar number of pulses and energy deposition, the direct DBD plasma sources produce more acidification and higher production of nitrates/nitrites in the liquid. This is due to the accumulation of NxOy plasma jets, the convective flow removes many of these species prior to their diffusing into the water or reacting to form higher nitrogen oxides. This latter effect is sensitive to the repetition rate which determines whether reactive species formed during prior pulses overlap with newly produced reactive species. in the gas phase. In the plasma jets, the convective flow removes many of these species prior to their diffusing into the water or reacting to form higher nitrogen oxides. This latter effect is sensitive to the repetition rate which determines whether reactive species formed during prior pulses overlap with

  7. Influences and interactions of inundation, peat, and snow on active layer thickness: Modeling Archive

    DOE Data Explorer

    Scott Painter; Ethan Coon; Cathy Wilson; Dylan Harp; Adam Atchley

    2016-04-21

    This Modeling Archive is in support of an NGEE Arctic publication currently in review [4/2016]. The Advanced Terrestrial Simulator (ATS) was used to simulate thermal hydrological conditions across varied environmental conditions for an ensemble of 1D models of Arctic permafrost. The thickness of organic soil is varied from 2 to 40cm, snow depth is varied from approximately 0 to 1.2 meters, water table depth was varied from -51cm below the soil surface to 31 cm above the soil surface. A total of 15,960 ensemble members are included. Data produced includes the third and fourth simulation year: active layer thickness, time of deepest thaw depth, temperature of the unfrozen soil, and unfrozen liquid saturation, for each ensemble member. Input files used to run the ensemble are also included.

  8. Reduction of Free Edge Peeling Stress of Laminated Composites Using Active Piezoelectric Layers

    PubMed Central

    Huang, Bin; Kim, Heung Soo

    2014-01-01

    An analytical approach is proposed in the reduction of free edge peeling stresses of laminated composites using active piezoelectric layers. The approach is the extended Kantorovich method which is an iterative method. Multiterms of trial function are employed and governing equations are derived by taking the principle of complementary virtual work. The solutions are obtained by solving a generalized eigenvalue problem. By this approach, the stresses automatically satisfy not only the traction-free boundary conditions, but also the free edge boundary conditions. Through the iteration processes, the free edge stresses converge very quickly. It is found that the peeling stresses generated by mechanical loadings are significantly reduced by applying a proper electric field to the piezoelectric actuators. PMID:25025088

  9. Some enzyme activities associated with the chlorophyll containing layers of the immature barley pericarp.

    PubMed

    Duffus, C M; Rosie, R

    1973-09-01

    Some photosynthetic and biochemical properties of the chlorophyl containing layers of the pericarp of developing barley have been investigated. The tissue changes from pale green to bright green early in development, chlorophyll disappearing only at the later stages of maturity. It contains chloroplasts and probably amyloplasts and starch bearing chloroplasts. It is capable of high rates of light dependent oxygen evolution. It has been shown that the enzyme phosphoenol pyruvate carboxylase (EC 4.1.1.31) is present in the pericarp and is 100 times as active in carbon dioxide fixation as ribulose diphosphate carboxylase (EC 4.1.1.39). Other enzymes present in the pericarp are phosphoenol pyruvate synthetase, pyrophosphatase (EC 3.6.1.1), malate NAD and NADP dehydrogenases (EC 1.1.1.37), malic enzyme (EC 1.1.1.40), and fructose 1,6 diphosphatase (EC 3.1.3.11). PMID:24458756

  10. Energetic basis of catalytic activity of layered nanophase calcium manganese oxides for water oxidation

    PubMed Central

    Birkner, Nancy; Nayeri, Sara; Pashaei, Babak; Najafpour, Mohammad Mahdi; Casey, William H.; Navrotsky, Alexandra

    2013-01-01

    Previous measurements show that calcium manganese oxide nanoparticles are better water oxidation catalysts than binary manganese oxides (Mn3O4, Mn2O3, and MnO2). The probable reasons for such enhancement involve a combination of factors: The calcium manganese oxide materials have a layered structure with considerable thermodynamic stability and a high surface area, their low surface energy suggests relatively loose binding of H2O on the internal and external surfaces, and they possess mixed-valent manganese with internal oxidation enthalpy independent of the Mn3+/Mn4+ ratio and much smaller in magnitude than the Mn2O3-MnO2 couple. These factors enhance catalytic ability by providing easy access for solutes and water to active sites and facile electron transfer between manganese in different oxidation states. PMID:23667149

  11. Layered Double Hydroxide Nanoclusters: Aqueous, Concentrated, Stable, and Catalytically Active Colloids toward Green Chemistry.

    PubMed

    Tokudome, Yasuaki; Morimoto, Tsuyoshi; Tarutani, Naoki; Vaz, Pedro D; Nunes, Carla D; Prevot, Vanessa; Stenning, Gavin B G; Takahashi, Masahide

    2016-05-24

    Increasing attention has been dedicated to the development of nanomaterials rendering green and sustainable processes, which occur in benign aqueous reaction media. Herein, we demonstrate the synthesis of another family of green nanomaterials, layered double hydroxide (LDH) nanoclusters, which are concentrated (98.7 g/L in aqueous solvent), stably dispersed (transparent sol for >2 weeks), and catalytically active colloids of nano LDHs (isotropic shape with the size of 7.8 nm as determined by small-angle X-ray scattering). LDH nanoclusters are available as colloidal building blocks to give access to meso- and macroporous LDH materials. Proof-of-concept applications revealed that the LDH nanocluster works as a solid basic catalyst and is separable from solvents of catalytic reactions, confirming the nature of nanocatalysts. The present work closely investigates the unique physical and chemical features of this colloid, the formation mechanism, and the ability to act as basic nanocatalysts in benign aqueous reaction systems. PMID:27124717

  12. Radiative transfer theory for active remote sensing of a layer of nonspherical particles

    NASA Technical Reports Server (NTRS)

    Tsang, L.; Kong, J. A.; Shin, R. T.

    1984-01-01

    The radiative transfer theory is applied to calculate the scattering by a layer of randomly positioned and oriented nonspherical particles. The scattering amplitude functions of each individual particle are calculated with Waterman's T matrix method, which utilizes vector spherical wave functions for expansion of incident, scattered, and surface fields. The orientation of the particles is described by a probability density function of the Eulerian angles of rotation. A rotation matrix is used to relate the T matrix of the principal frame to that of the natural frame of the particle. The extinction matrix and phase matrix of the radiative transfer equations are expressed in terms of the T matrix elements. The extinction matrix for nonspherical particles is generally nondiagonal. There are only two attenuation rates in a specified direction of propagation. The radiative transfer equations are solved by an iterative method to first order in albedo. Numerical results are illustrated as functions of incidence angle and frequency with applications to active remote sensing.

  13. Vertical structure and biological activity in the bottom nepheloid layer of the Gulf of Maine

    NASA Astrophysics Data System (ADS)

    Townsend, D. W.; Mayer, L. M.; Dortch, Q.; Spinrad, R. W.

    1992-02-01

    The bottom nepheloid layer (BNL) was investigated at a number of hydrographically different sites in the Gulf of Maine during August 1987. Observations were based on hydrographic measurements made from a surface ship and closely-spaced, near-bottom samples collected using a submersible. The BNL generally occurred as a turbid layer which extended 15-30 m above the bottom (m.a.b.), as indicated by in situ light transmission and increased concentrations of total suspended particulate matter (SPM). Phytoplankton pigments, electron transport activity (ETS), extracellular proteolytic enzyme activity (EPA), concentrations of particulate organic carbon and nitrogen (POC and PON), and protein were generally elevated in the BNL. They also displayed vertical distribution patterns in relation to near-bottom depth zones of increased abundances of zooplankton, bacteria and autotrophic and heterotrophic nanoplankton. We describe two zones of biological significance in the BNL. The first, at about 20 m.a.b. at most stations, was associated with greater zooplankton biomass (80 μm) and copepod abundances than those depth strata either above or below, and appeared to be related to a higher quality of food particles near the top of the BNL. A second zone was seen 1-3 m.a.b. at most stations in association with the greatest levels of SPM. This deeper zone was generally of a poorer food quality, as reflected by ratios of protein-N to total-N and showed increases in cell-specific EPA. We discuss the areal variability of the BNL in the Gulf of Maine as well as the biological enhancement and vertical structure as likely influenced by both physical and biological processes.

  14. Influence of Plant Communities on Active Layer Depth in Boreal Forest

    NASA Astrophysics Data System (ADS)

    Fisher, James; Estop Aragones, Cristian; Thierry, Aaron; Hartley, Iain; Murton, Julian; Charman, Dan; Williams, Mathew; Phoenix, Gareth

    2015-04-01

    Vegetation plays a crucial role in determining active layer depth (ALD) and hence the extent to which permafrost may thaw under climate change. Such influences are multifaceted and include, for example, promotion of shallow ALD by insulation from moss or shading by plant canopies in summer, or trapping of snow in evergreen tree canopies that reduces snow insulation of soil in winter. However, while the role of different vegetation components are understood at a conceptual level, quantitative understanding of the relative importance of different vegetation components and how they interact to determine active layer depth is lacking. In addition, major abiotic factors such as fire and soil hydrological properties will considerably influence the role of vegetation in mediating ALD, though again this is not well understood. To address this we surveyed 60 plots across 4 sites of contrasting vegetation and fire status, encompassing a range of soil moisture and organic matter thickness, in the discontinuous permafrost zone near Yellowknife, NT, Canada. In each plot we measured ALD and a range of vegetation and soil parameters to understand how key characteristics of the understory and canopy vegetation, and soil properties influence ALD. Measurements included moss depth, tree canopy LAI, understory LAI, understory height, vegetation composition, soil organic matter depth, slope and soil moisture. By undertaking these surveys in sites with contrasting hydrological conditions in both burned and unburned areas we have also been able to determine which characteristics of the vegetation and soil are important for protecting permafrost, which characteristics emerge as the most important factors across sites (i.e. irrespective of site conditions) and which factors have site (ecosystem) specific influences. This work provides a major insight into how ecosystem properties influence ALD and therefore also how changes in ecosystems properties arising from climate change may influence

  15. Microlens array induced light absorption enhancement in polymer solar cells.

    PubMed

    Chen, Yuqing; Elshobaki, Moneim; Ye, Zhuo; Park, Joong-Mok; Noack, Max A; Ho, Kai-Ming; Chaudhary, Sumit

    2013-03-28

    Over the last decade, polymer solar cells (PSCs) have attracted a lot of attention and highest power conversion efficiencies (PCE) are now close to 10%. Here we employ an optical structure - the microlens array (MLA) - to increase light absorption inside the active layer, and PCE of PSCs increased even for optimized devices. Normal incident light rays are refracted at the MLA and travel longer optical paths inside the active layers. Two PSC systems - poly(3-hexylthiophene-2,5-diyl):(6,6)-phenyl C61 butyric acid methyl ester (P3HT:PCBM) and poly[[9-(1-octylnonyl)-9H-carbazole-2,7-diyl]-2,5-thiophenediyl-2,1,3-benzothiadiazole-4,7-diyl-2,5-thiophenediyl]:(6,6)-phenyl C71 butyric acid methyl ester (PCDTBT:PC70BM) - were investigated. In the P3HT:PCBM system, MLA increased the absorption, absolute external quantum efficiency, and the PCE of an optimized device by ∼4.3%. In the PCDTBT:PC70BM system, MLA increased the absorption, absolute external quantum efficiency, and PCE by more than 10%. In addition, simulations incorporating optical parameters of all structural layers were performed and they support the enhancement of absorption in the active layer with the assistance of MLA. Our results show that utilizing MLA is an effective strategy to further increase light absorption in PSCs, in which optical losses account for ∼40% of total losses. MLA also does not pose materials processing challenges to the active layers since it is on the other side of the transparent substrate. PMID:23407762

  16. Many-body microhydrodynamics of colloidal particles with active boundary layers

    NASA Astrophysics Data System (ADS)

    Singh, Rajesh; Ghose, Somdeb; Adhikari, R.

    2015-06-01

    Colloidal particles with active boundary layers—regions surrounding the particles where non-equilibrium processes produce large velocity gradients—are common in many physical, chemical and biological contexts. The velocity or stress at the edge of the boundary layer determines the exterior fluid flow and, hence, the many-body interparticle hydrodynamic interaction. Here, we present a method to compute the many-body hydrodynamic interaction between N spherical active particles induced by their exterior microhydrodynamic flow. First, we use a boundary integral representation of the Stokes equation to eliminate bulk fluid degrees of freedom. Then, we expand the boundary velocities and tractions of the integral representation in an infinite-dimensional basis of tensorial spherical harmonics and, on enforcing boundary conditions in a weak sense on the surface of each particle, obtain a system of linear algebraic equations for the unknown expansion coefficients. The truncation of the infinite series, fixed by the degree of accuracy required, yields a finite linear system that can be solved accurately and efficiently by iterative methods. The solution linearly relates the unknown rigid body motion to the known values of the expansion coefficients, motivating the introduction of propulsion matrices. These matrices completely characterize hydrodynamic interactions in active suspensions just as mobility matrices completely characterize hydrodynamic interactions in passive suspensions. The reduction in the dimensionality of the problem, from a three-dimensional partial differential equation to a two-dimensional integral equation, allows for dynamic simulations of hundreds of thousands of active particles on multi-core computational architectures. In our simulation of 104 active colloidal particle in a harmonic trap, we find that the necessary and sufficient ingredients to obtain steady-state convective currents, the so-called ‘self-assembled pump’, are (a) one

  17. Layer-Specific fMRI Responses to Excitatory and Inhibitory Neuronal Activities in the Olfactory Bulb

    PubMed Central

    Poplawsky, Alexander John; Fukuda, Mitsuhiro; Murphy, Matthew

    2015-01-01

    High-resolution functional magnetic resonance imaging (fMRI) detects localized neuronal activity via the hemodynamic response, but it is unclear whether it accurately identifies neuronal activity specific to individual layers. To address this issue, we preferentially evoked neuronal activity in superficial, middle, and deep layers of the rat olfactory bulb: the glomerular layer by odor (5% amyl acetate), the external plexiform layer by electrical stimulation of the lateral olfactory tract (LOT), and the granule cell layer by electrical stimulation of the anterior commissure (AC), respectively. Electrophysiology, laser-Doppler flowmetry of cerebral blood flow (CBF), and blood oxygenation level-dependent (BOLD) and cerebral blood volume-weighted (CBV) fMRI at 9.4 T were performed independently. We found that excitation of inhibitory granule cells by stimulating LOT and AC decreased the spontaneous multi-unit activities of excitatory mitral cells and subsequently increased CBF, CBV, and BOLD signals. Odor stimulation also increased the hemodynamic responses. Furthermore, the greatest CBV fMRI responses were discretely separated into the same layers as the evoked neuronal activities for all three stimuli, whereas BOLD was poorly localized with some exception to the poststimulus undershoot. In addition, the temporal dynamics of the fMRI responses varied depending on the stimulation pathway, even within the same layer. These results indicate that the vasculature is regulated within individual layers and CBV fMRI has a higher fidelity to the evoked neuronal activity compared with BOLD. Our findings are significant for understanding the neuronal origin and spatial specificity of hemodynamic responses, especially for the interpretation of laminar-resolution fMRI. SIGNIFICANCE STATEMENT Functional magnetic resonance imaging (fMRI) is a noninvasive, in vivo technique widely used to map function of the entire brain, including deep structures, in animals and humans. However, it

  18. Kinetic Monte Carlo simulations of thermally activated magnetization reversal in dual-layer Exchange Coupled Composite recording media

    NASA Astrophysics Data System (ADS)

    Plumer, M. L.; Almudallal, A. M.; Mercer, J. I.; Whitehead, J. P.; Fal, T. J.

    The kinetic Monte Carlo (KMC) method developed for thermally activated magnetic reversal processes in single-layer recording media has been extended to study dual-layer Exchange Coupled Composition (ECC) media used in current and next generations of disc drives. The attempt frequency is derived from the Langer formalism with the saddle point determined using a variant of Bellman Ford algorithm. Complication (such as stagnation) arising from coupled grains having metastable states are addressed. MH-hysteresis loops are calculated over a wide range of anisotropy ratios, sweep rates and inter-layer coupling parameter. Results are compared with standard micromagnetics at fast sweep rates and experimental results at slow sweep rates.

  19. Estimations of moisture content in the active layer in an Arctic ecosystem by using ground-penetrating radar profiling

    NASA Astrophysics Data System (ADS)

    Gacitúa, Guisella; Tamstorf, Mikkel Peter; Kristiansen, Søren Munch; Uribe, José Andrés

    2012-04-01

    We applied high-frequency GPR at a study site in the high arctic ecosystem of Northeast Greenland to evaluate its usefulness in assessing depth of, and water content in, the active layer at Zackenberg Valley (74°N; 20°W) to evaluate its usefulness in the high arctic ecosystems. The study site includes different vegetation types, and it well represents of the entire valley, for which we aimed to determine the conditions and characteristics that influence the GPR performance in the active layer. The spatial distribution of moisture content along the transect studied was estimated using GPR data (400 MHz antenna), depth to permafrost, soil samples and vegetation observations. Vertical distribution of the water content in the unfrozen soil bulk was predicted for several points on the transect by combining data that influence the behavior of the radar waves with that of capacitive moisture probes. The statistical models resulted to be highly significant, thus assuming common conditions of the soil to the classified vegetation, we can obtain from the GPR data, truthful estimations of water content, and, moreover, we can predict the distribution to the bottom of the active layer. Hence, we conclude that GPR is a viable option for improving active layer spatial quantification of water contents that can be used to assess changes in the active layer in arctic regions.

  20. Surface modification of polypropylene non-woven fibers with TiO2 nanoparticles via layer-by-layer self assembly method: Preparation and photocatalytic activity.

    PubMed

    Pavasupree, Suttipan; Dubas, Stephan T; Rangkupan, Ratthapol

    2015-11-01

    Polypropylene (PP) meltblown fibers were coated with titanium dioxide (TiO2) nanoparticles using layer-by-layer (LbL) deposition technique. The fibers were first modified with 3 layers of poly(4-styrenesulfonic acid) (PSS) and poly(diallyl-dimethylammonium chloride) (PDADMAC) to improve the anchoring of the TiO2 nanoparticle clusters. PDADMAC, which is positively charged, was then used as counter polyelectrolyte in tandem with anionic TiO2 nanoparticles to construct TiO2/PDADMAC bilayer in the LbL fashion. The number of deposited TiO2/PDADMAC layers was varied from 1 to 7 bilayer, and could be used to adjust TiO2 loading. The LbL technique showed higher TiO2 loading efficiency than the impregnation approach. The modified fibers were tested for their photocatalytic activity against a model dye, Methylene Blue (MB). Results showed that the TiO2 modified fibers exhibited excellent photocatalytic activity efficiency similar to that of TiO2 powder dispersed in solution. The deposition of TiO2 3 bilayer on the PP substrate was sufficient to produce nanocomposite fibers that could bleach the MB solution in less than 4hr. TiO2-LbL constructions also preserved TiO2 adhesion on substrate surface after 1cycle of photocatalytic test. Successive photocatalytic test showed decline in MB reduction rate with loss of TiO2 particles from the substrate outer surface. However, even in the third cycle, the TiO2 modified fibers are still moderately effective as it could remove more than 95% of MB after 8hr of treatment. PMID:26574088

  1. Two-Dimensional Heterospectral Correlation Analysis of the Redox-Induced Conformational Transition in Cytochrome c Using Surface-Enhanced Raman and Infrared Absorption Spectroscopies on a Two-Layer Gold Surface

    PubMed Central

    2013-01-01

    The heme protein cytochrome c adsorbed to a two-layer gold surface modified with a self-assembled monolayer of 2-mercaptoethanol was analyzed using a two-dimensional (2D) heterospectral correlation analysis that combined surface-enhanced infrared absorption spectroscopy (SEIRAS) and surface-enhanced Raman spectroscopy (SERS). Stepwise increasing electric potentials were applied to alter the redox state of the protein and to induce conformational changes within the protein backbone. We demonstrate herein that 2D heterospectral correlation analysis is a particularly suitable and useful technique for the study of heme-containing proteins as the two spectroscopies address different portions of the protein. Thus, by correlating SERS and SEIRAS data in a 2D plot, we can obtain a deeper understanding of the conformational changes occurring at the redox center and in the supporting protein backbone during the electron transfer process. The correlation analyses are complemented by molecular dynamics calculations to explore the intramolecular interactions. PMID:23930980

  2. An investigation of catalytic active phase-support interactions by IR, NMR and x-ray absorption spectroscopies. Progress report, January 15, 1992--September 15, 1992

    SciTech Connect

    Haller, G.L.

    1992-09-01

    Active catalytic phases (metal, mixed metals, oxide or mixed oxides) interacting with oxide support on which the active phase is dispersed can affect the percentage exposed, the morphology of supported particles, the degree of reducibility of cations, etc., in a variety of ways. Our objective is to characterize the physical chemistry of the active phase-oxide support interaction by spectroscopic methods and to correlate this structure with catalytic function. Two catalytic systems and their associated techniques (x-ray absorption and NMR) are discussed in this progress report. Firstly, the interaction of Pt-Ni supported on silica and L-zeolite are characterized and compared by x-ray absorption spectroscopy (EXAFS). Secondly, we present both experimental and calculational developments of NMR for the investigation of amorphous silica-alumina catalysts and/or supports.

  3. Evidence for active galactic nucleus feedback in the broad absorption lines and reddening of MRK 231 {sup ,}

    SciTech Connect

    Leighly, Karen M.; Baron, Eddie; Lucy, Adrian B.; Terndrup, Donald M.; Dietrich, Matthias; Gallagher, Sarah C.

    2014-06-20

    We present the first J-band spectrum of Mrk 231, which reveals a large He I* λ10830 broad absorption line with a profile similar to that of the well-known Na I broad absorption line. Combining this spectrum with optical and UV spectra from the literature, we show that the unusual reddening noted by Veilleux et al. is explained by a reddening curve like those previously used to explain low values of total-to-selective extinction in Type Ia supernovae. The nuclear starburst may be the origin and location of the dust. Spatially resolved emission in the broad absorption line trough suggests nearly full coverage of the continuum emission region. The broad absorption lines reveal higher velocities in the He I* lines (produced in the quasar-photoionized H II region) compared with the Na I and Ca II lines (produced in the corresponding partially ionized zone). Cloudy simulations show that a density increase is required between the H II and partially ionized zones to produce ionic column densities consistent with the optical and IR absorption line measurements and limits, and that the absorber lies ∼100 pc from the central engine. These results suggest that the He I* lines are produced in an ordinary quasar BAL wind that impacts upon, compresses, and accelerates the nuclear starburst's dusty effluent (feedback in action), and the Ca II and Na I lines are produced in this dusty accelerated gas. This unusual circumstance explains the rarity of Na I absorption lines; without the compression along our line of sight, Mrk 231 would appear as an ordinary iron low-ionization, broad absorption line quasar.

  4. Synthesis of nanoporous activated iridium oxide films by anodized aluminum oxide templated atomic layer deposition.

    SciTech Connect

    Comstock, D. J.; Christensen, S. T.; Elam, J. W.; Pellin, M. J.; Hersam, M. C.

    2010-08-01

    Iridium oxide (IrOx) has been widely studied due to its applications in electrochromic devices, pH sensing, and neural stimulation. Previous work has demonstrated that both Ir and IrOx films with porous morphologies prepared by sputtering exhibit significantly enhanced charge storage capacities. However, sputtering provides only limited control over film porosity. In this work, we demonstrate an alternative scheme for synthesizing nanoporous Ir and activated IrOx films (AIROFs). This scheme utilizes atomic layer deposition to deposit a thin conformal Ir film within a nanoporous anodized aluminum oxide template. The Ir film is then activated by potential cycling in 0.1 M H{sub 2}SO{sub 4} to form a nanoporous AIROF. The morphologies and electrochemical properties of the films are characterized by scanning electron microscopy and cyclic voltammetry, respectively. The resulting nanoporous AIROFs exhibit a nanoporous morphology and enhanced cathodal charge storage capacities as large as 311 mC/cm{sup 2}.

  5. Active Control of Turbulent Boundary Layer Induced Sound Radiation from Multiple Aircraft Panels

    NASA Technical Reports Server (NTRS)

    Gibbs, Gary P.; Cabell, Randolph H.

    2002-01-01

    The objective of this work is to experimentally investigate active structural acoustic control of turbulent boundary layer (TBL) induced sound radiation from multiple panels on an aircraft sidewall. One possible approach for controlling sound radiation from multiple panels is a multi-input/multi-output scheme which considers dynamic coupling between the panels. Unfortunately, this is difficult for more than a few panels, and is impractical for a typical aircraft which contains several hundred such panels. An alternative is to implement a large number of independent control systems. Results from the current work demonstrate the feasibility of reducing broadband radiation from multiple panels utilizing a single-input/single-output (SISO) controller per bay, and is the first known demonstration of active control of TBL induced sound radiation on more than two bays simultaneously. The paper compares sound reduction for fully coupled control of six panels versus independent control on each panel. An online adaptive control scheme for independent control is also demonstrated. This scheme will adjust for slow time varying dynamic systems such as fuselage response changes due to aircraft pressurization, etc.

  6. An electrochemical double layer capacitor using an activated carbon electrode with gel electrolyte binder

    SciTech Connect

    Osaka, Tetsuya, Liu, X.; Nojima, Masashi; Momma, Toshiyuki

    1999-05-01

    An electric double layer capacitor (EDLC) was prepared with an activated carbon powder electrode with poly(vinylidene fluoride-hexafluoropropylene) (PVdF-HFP) based gel electrolyte. Ethylene carbonate (EC) and propylene carbonate (PC) were used as plasticizer and tetraethylammonium tetrafluoroborate (TEABF{sub 4}) was used as the supporting electrolyte. An optimized gel electrolyte of PVdF-HFP/PC/EC/TEABF{sub 4} - 23/31/35/11 mass ratio exhibited high ionic conductivity of 5 {times} 10{sup {minus}3} S/cm, high electrode capacitance, and good mechanical strength. An electrode consisting of activated carbon (AC) with the gel electrolyte as the binder (AC/PVdF-HFP based gel, 7/3 mass ratio) showed a higher specific capacitance and a lower ion diffusion resistance within the electrode than a carbon electrode, prepared with PVdF-HFP binder without plasticizer. This suggests that an electrode mixed with the gel electrolyte has a lower ion diffusion resistance inside the electrode. The highest specific capacitance of 123 F/g was achieved with an electrode containing AC with a specific surface area of 2500 m{sup 2}/g. A coin-type EDLC cell with optimized components showed excellent cycleability exceeding 10{sup 4} cycles with ca. 100% coulombic efficiency achieved when charging and discharging was repeated between 1.0 and 2.5 V at 1.66 mA/cm{sup 2}.

  7. Efficient methylammonium lead iodide perovskite solar cells with active layers from 300 to 900 nm

    SciTech Connect

    Momblona, C.; Malinkiewicz, O.; Soriano, A.; Gil-Escrig, L.; Bandiello, E.; Scheepers, M.; Bolink, H. J.; Edri, E.

    2014-08-01

    Efficient methylammonium lead iodide perovskite-based solar cells have been prepared in which the perovskite layer is sandwiched in between two organic charge transporting layers that block holes and electrons, respectively. This configuration leads to stable and reproducible devices that do not suffer from strong hysteresis effects and when optimized lead to efficiencies close to 15%. The perovskite layer is formed by using a dual-source thermal evaporation method, whereas the organic layers are processed from solution. The dual-source thermal evaporation method leads to smooth films and allows for high precision thickness variations. Devices were prepared with perovskite layer thicknesses ranging from 160 to 900 nm. The short-circuit current observed for these devices increased with increasing perovskite layer thickness. The main parameter that decreases with increasing perovskite layer thickness is the fill factor and as a result optimum device performance is obtained for perovskite layer thickness around 300 nm. However, here we demonstrate that with a slightly oxidized electron blocking layer the fill factor for the solar cells with a perovskite layer thickness of 900 nm increases to the same values as for the devices with thin perovskite layers. As a result the power conversion efficiencies for the cells with 300 and 900 nm are very similar, 12.7% and 12%, respectively.

  8. Percutaneous absorption from soil.

    PubMed

    Andersen, Rosa Marie; Coman, Garrett; Blickenstaff, Nicholas R; Maibach, Howard I

    2014-01-01

    Abstract Some natural sites, as a result of contaminants emitted into the air and subsequently deposited in soil or accidental industrial release, have high levels of organic and non-organic chemicals in soil. In occupational and recreation settings, these could be potential sources of percutaneous exposure to humans. When investigating percutaneous absorption from soil - in vitro or vivo - soil load, particle size, layering, soil "age" time, along with the methods of performing the experiment and analyzing the results must be taken into consideration. Skin absorption from soil is generally reduced compared with uptake from water/acetone. However, the absorption of some compounds, e.g., pentachlorophenol, chlorodane and PCB 1254, are similar. Lipophilic compounds like dichlorodiphenyltrichloroethane, benzo[A]pyrene, and metals have the tendency to form reservoirs in skin. Thus, one should take caution in interpreting results directly from in vitro studies for risk assessment; in vivo validations are often required for the most relevant risk assessment. PMID:25205703

  9. p-GaAs(Cs,O)-photocathodes: Demarcation of domains of validity for practical models of the activation layer

    SciTech Connect

    Bakin, V. V.; Toropetsky, K. V.; Scheibler, H. E.; Terekhov, A. S.; Jones, L. B.; Militsyn, B. L.; Noakes, T. C. Q.

    2015-05-04

    The (Cs,O)-activation procedure for p-GaAs(Cs,O)-photocathodes was studied with the aim of demarcating the domains of validity for the two practical models of the (Cs,O)-activation layer: The dipole layer (DL) model and the heterojunction (HJ) model. To do this, the photocathode was activated far beyond the normal maximum of quantum efficiency, and several photocathode parameters were measured periodically during this process. In doing so, the data obtained enabled us to determine the domains of validity for the DL- and HJ-models, to define more precisely the characteristic parameters of the photocathode within both of these domains and thus to reveal the peculiarities of the influence of the (Cs,O)-layer on the photoelectron escape probability.

  10. Photodetector with enhanced light absorption

    DOEpatents

    Kane, James

    1985-01-01

    A photodetector including a light transmissive electrically conducting layer having a textured surface with a semiconductor body thereon. This layer traps incident light thereby enhancing the absorption of light by the semiconductor body. A photodetector comprising a textured light transmissive electrically conducting layer of SnO.sub.2 and a body of hydrogenated amorphous silicon has a conversion efficiency about fifty percent greater than that of comparative cells. The invention also includes a method of fabricating the photodetector of the invention.

  11. Enhanced Electrocatalytic Performance for Oxygen Reduction via Active Interfaces of Layer-By-Layered Titanium Nitride/Titanium Carbonitride Structures

    PubMed Central

    Jin, Zhaoyu; Li, Panpan; Xiao, Dan

    2014-01-01

    Cathode materials always limit the performance of fuel cells while the commercial platinum-based catalysts hardly meet the requirements of low cost, durable and stable. Here a non-precious metal oxygen reduction reaction (ORR) electocatalyst based on titanium nitride/titanium carbonitride hierarchical structures (TNTCNHS) is demonstrated as high activity as Pt/C. In alkaline condition, tuning interface/mass ratio of TiN/TiCN, we observed the onset potential of ~0.93 V vs. RHE and a limit diffusion current density of ~5.1 mA cm−2 (at a rotating speed of 1600 rpm) on TNTCNHS with a relative low catalyst loading of ~0.1 mg cm−2. The kinetic current, durability and tolerance to crossover effect studies reveal even more efficient than carbon-supported platinum. The architecture fabrication for such electrocatalyst is easy to realize in industrial-scale facilities, for the use of chemical vapor deposition (CVD) technique could support a huge area production (more than 10000 cm2 for one pot) to satisfy the enormous market requirements in the future. PMID:25335930

  12. Salix polaris growth responses to active layer detachment and solifluction processes in High Arctic.

    NASA Astrophysics Data System (ADS)

    Siekacz, Liliana

    2015-04-01

    The work is dedicated to demonstrate the potential of Salix polaris grow properties in the dendrogemorphologic image, analyzing periglacially induced slope processes in the high Arctic.. Observed anatomical and morphological plants responses to solifluction and active layer detachment processes are presented qualitatively and quantitatively as a summary of presented features frequency. The results are discussed against the background of the other research results in this field. The investigations was performed in Ebba valley, in the vicinity of Petunia Bay, northernmost part of Billefjorden in central Spitsbergen (Svalbard). Environmental conditions are characterized by annual precipitation sum lower than 200 mm (Hagen et al.,1993) and average summer temperature of about 5°C, with maximum daily temperatures rarely exceeding 10°C (Rachlewicz, 2009). Collected shrub material was prepared according to the methods presented by Schweingruber and Poschlod (2005). Thin (approx. 15-20μm) sections of the whole cross-section were prepared with a sledge microtome, stained with Safranine and Astra blue and finally permanently fixed on microslides with Canada balsam and dried. Snapshots were taken partially for each cross-section with digital camera (ColorView III, Olympus) connected to a microscope (Olympus BX41) and merged into one, high resolution image. After all, ring widths were measured in 3-4 radii in every single cross-section using ImageJ software. Analyzed plants revealed extremely harsh environmental conditions of their growth. Buchwał et al. (2013) provided quantitative data concerning missing rings and partially missing rings in shrubs growing on Ebba valley floor. Mean ring width at the level of 79μm represents one of the smallest values of yearly growth ever noted. The share of missing rings and partially missing rings was 11,2% and 13,6% respectively. Plants growing on Ebba valley slope indicate almost twice smaller values of ring width (41μm), and higher

  13. Active Control of Panel Vibrations Induced by a Boundary Layer Flow

    NASA Technical Reports Server (NTRS)

    Chow, Pao-Liu

    1998-01-01

    In recent years, active and passive control of sound and vibration in aeroelastic structures have received a great deal of attention due to many potential applications to aerospace and other industries. There exists a great deal of research work done in this area. Recent advances in the control of sound and vibration can be found in the several conference proceedings. In this report we will summarize our research findings supported by the NASA grant NAG-1-1175. The problems of active and passive control of sound and vibration has been investigated by many researchers for a number of years. However, few of the articles are concerned with the sound and vibration with flow-structure interaction. Experimental and numerical studies on the coupling between panel vibration and acoustic radiation due to flow excitation have been done by Maestrello and his associates at NASA/Langley Research Center. Since the coupled system of nonlinear partial differential equations is formidable, an analytical solution to the full problem seems impossible. For this reason, we have to simplify the problem to that of the nonlinear panel vibration induced by a uniform flow or a boundary-layer flow with a given wall pressure distribution. Based on this simplified model, we have been able to study the control and stabilization of the nonlinear panel vibration, which have not been treated satisfactorily by other authors. The vibration suppression will clearly reduce the sound radiation power from the panel. The major research findings will be presented in the next three sections. In Section II we shall describe our results on the boundary control of nonlinear panel vibration, with or without flow excitation. Section III is concerned with active control of the vibration and sound radiation from a nonlinear elastic panel. A detailed description of our work on the parametric vibrational control of nonlinear elastic panel will be presented in Section IV. This paper will be submitted to the Journal

  14. Active diagenetic formation of metal-rich layers in N. E. Atlantic sediments

    NASA Astrophysics Data System (ADS)

    Wallace, H. E.; Thomson, J.; Wilson, T. R. S.; Weaver, P. P. E.; Higgs, N. C.; Hydes, D. J.

    1988-06-01

    Sediment cores from the Porcupine Abyssal Plain exhibit an indurated layer 0.5-3 cm thick at depths of approximately 50 cm. This is some 15-20 cm below the glacial/Holocene transition as interpreted by radiocarbon dating and the palaeontological criteria of RUDDIMAN and MCINTYRE (1981). The layer is forming currently at the oxic/post-oxic boundary in the sediments, as revealed by pore water data: O 2 and NO -3 are present in solution above the layer, while Fe 2+, Mn 2+, PO 3-4 and NH +4 are present in solution below, and all these species show concentration gradients indicating fluxes into the layer. These data are consistent with the hypothesis for the initiation and sustained formation of such layers proposed by WILSONet al. (1986a,b). The elements Mn, Ni, Co, Fe, P, V, Cu, Zn and U are all enriched to varying degrees in the vicinity of the layer. Some differential stratification of these elements in the vertical, consistent with a redox control, is observed at one site with a 0.5 cm layer, with Mn, Ni and Co above, Fe, P, V and Cu in the layer, and U below. At another site the metal-rich layer has higher Fe and P concentrations and is more indurated. Here all enrichments except Co are contained within a single layer sample, 3 cm thick.

  15. Layer-by-layer grown scalable redox-active ruthenium-based molecular multilayer thin films for electrochemical applications and beyond

    NASA Astrophysics Data System (ADS)

    Kaliginedi, Veerabhadrarao; Ozawa, Hiroaki; Kuzume, Akiyoshi; Maharajan, Sivarajakumar; Pobelov, Ilya V.; Kwon, Nam Hee; Mohos, Miklos; Broekmann, Peter; Fromm, Katharina M.; Haga, Masa-Aki; Wandlowski, Thomas

    2015-10-01

    Here we report the first study on the electrochemical energy storage application of a surface-immobilized ruthenium complex multilayer thin film with anion storage capability. We employed a novel dinuclear ruthenium complex with tetrapodal anchoring groups to build well-ordered redox-active multilayer coatings on an indium tin oxide (ITO) surface using a layer-by-layer self-assembly process. Cyclic voltammetry (CV), UV-Visible (UV-Vis) and Raman spectroscopy showed a linear increase of peak current, absorbance and Raman intensities, respectively with the number of layers. These results indicate the formation of well-ordered multilayers of the ruthenium complex on ITO, which is further supported by the X-ray photoelectron spectroscopy analysis. The thickness of the layers can be controlled with nanometer precision. In particular, the thickest layer studied (65 molecular layers and approx. 120 nm thick) demonstrated fast electrochemical oxidation/reduction, indicating a very low attenuation of the charge transfer within the multilayer. In situ-UV-Vis and resonance Raman spectroscopy results demonstrated the reversible electrochromic/redox behavior of the ruthenium complex multilayered films on ITO with respect to the electrode potential, which is an ideal prerequisite for e.g. smart electrochemical energy storage applications. Galvanostatic charge-discharge experiments demonstrated a pseudocapacitor behavior of the multilayer film with a good specific capacitance of 92.2 F g-1 at a current density of 10 μA cm-2 and an excellent cycling stability. As demonstrated in our prototypical experiments, the fine control of physicochemical properties at nanometer scale, relatively good stability of layers under ambient conditions makes the multilayer coatings of this type an excellent material for e.g. electrochemical energy storage, as interlayers in inverted bulk heterojunction solar cell applications and as functional components in molecular electronics applications

  16. High reliable and stable organic field-effect transistor nonvolatile memory with a poly(4-vinyl phenol) charge trapping layer based on a pn-heterojunction active layer

    NASA Astrophysics Data System (ADS)

    Xiang, Lanyi; Ying, Jun; Han, Jinhua; Zhang, Letian; Wang, Wei

    2016-04-01

    In this letter, we demonstrate a high reliable and stable organic field-effect transistor (OFET) based nonvolatile memory (NVM) with a polymer poly(4-vinyl phenol) (PVP) as the charge trapping layer. In the unipolar OFETs, the inreversible shifts of the turn-on voltage (Von) and severe degradation of the memory window (ΔVon) at programming (P) and erasing (E) voltages, respectively, block their application in NVMs. The obstacle is overcome by using a pn-heterojunction as the active layer in the OFET memory, which supplied a holes and electrons accumulating channel at the supplied P and E voltages, respectively. Both holes and electrons transferring from the channels to PVP layer and overwriting the trapped charges with an opposite polarity result in the reliable bidirectional shifts of Von at P and E voltages, respectively. The heterojunction OFET exhibits excellent nonvolatile memory characteristics, with a large ΔVon of 8.5 V, desired reading (R) voltage at 0 V, reliable P/R/E/R dynamic endurance over 100 cycles and a long retention time over 10 years.

  17. Monitoring of the permafrost surface active layer in Quebec and in the Arctic using remote sensing

    NASA Astrophysics Data System (ADS)

    Marchand, Nicolas; Royer, Alain; Krinner, Gerhard; Roy, Alexandre

    2014-05-01

    Projected future warming is particularly strong in the Northern high latitudes. Increases of temperatures are up to 2 to 6°C in the northern high latitudes, and up to 3 to 8°C in the North Pole area. Permafrosts (grounds with negative temperatures at least two years in a row) are present on 25 % of the northern hemisphere lands and contain high quantities of « frozen » carbon, estimated at 1400 Gt (40 % of the global terrestrial carbon). Recent studies have shown that a significant part (50%) of the first meters of the permafrost could melt within 2050, and 90 % within 2100. The aim of this study is to help understand the climate evolution in arctic areas, and more specifically of land areas covered by snow. We want to describe the ground temperature all year round even under snow cover. We hope to be able to deduce the active layer thickness evolution over the last ten years in northern Quebec. With the use of satellite data (fusion of Modis land surface temperature « LST » and AMSR-E brillance temperature « Tb », land cover …), and with the assimilation of these observations in the Canadian Landscape Surface Scheme (CLASS, CLASS-SSA) and in a simple radiative transfert model (HUT), we try to benefit from the advantages of each one of the sources in order to complete two objectives : 1- build a solid methodology in order to retrieve the land surface temperature, with and without snow cover, in taïga and toundra areas ; 2 - from those retrieved land surface temperatures, describe the ground temperature during summer as well as in winter (under snow) so that we can have a better look at the summer melt of the permafrost active layer. We have proposed a methodology that takes into account the evolution of two main input parameters of the CLASS model (air temperature and precipitations) in order to minimise the LST and Tb ouput. The proposed methodology seems to improve the results on the LST and Tb at 10 and 19 GHz in summer in a toundra environment

  18. Urban Geocryology: Mapping Urban-Rural Contrasts in Active-Layer Thickness, Barrow Penninsula, Northern Alaska

    NASA Astrophysics Data System (ADS)

    Klene, A. E.; Nelson, F. E.

    2014-12-01

    As development proceeds in the high latitudes, information about interactions between urban influences and the thickness of the active layer above permafrost becomes vital, particularly given the possibility of increasing temperatures accompanying climate change. Permafrost characteristics are often mapped at small geographical scales (i.e., over large areas), at low resolution, and without extensive field validation. Although maps of active-layer thickness (ALT) have been created for areas of relatively undisturbed terrain, this has rarely been done within urbanized areas, even though ALT is a critical factor in the design of roads, buildings, pipelines, and other elements of infrastructure. The need for detailed maps of ALT is emphasized in work on potential hazards in permafrost regions associated with global warming scenarios. Northern Alaska is a region considered to be at moderate to high risk for thaw-induced damage under climatic warming. The Native Village of Barrow (71°17'44"N; 156°45' 59"W), the economic, transportation, and administrative hub of the North Slope Borough, is the northernmost community in the USA, and the largest native settlement in the circum-Arctic. A winter urban heat island in Barrow, earlier snowmelt in the village, and dust deposition downwind of gravel pads and roads are all urban effects that could increase ALT. A recent empirical study documented a 17 to 41 cm difference in ALT between locations in the village of Barrow and surrounding undeveloped tundra, even in similar land-cover classes. We mapped ALT in the Barrow Peninsula, with particular attention to contrasts between the urbanized village and relatively undisturbed tundra in the nearby Barrow Environmental Observatory. The modified Berggren solution, an advanced analytic solution to the general Stefan problem of calculating frost and thaw depth, was used in a geographic context to map ALT over the 150 km² area investigated in the Barrow Urban Heat Island Study. The

  19. Isotopic Identification of Nitrate Sources and Cycling in Arctic Tundra Active Layer Soils and Permafrost

    NASA Astrophysics Data System (ADS)

    Heikoop, J. M.; Throckmorton, H.; Newman, B. D.; Perkins, G.; Gard, M.; Iversen, C. M.; Wilson, C. J.; Wullschleger, S. D.

    2014-12-01

    The effect of nitrogen cycling on release of carbon from tundra ecosystems is being studied as part of the US Department of Energy Next Generation Ecosystem Experiment - Arctic project. Sampling and analysis of active layer soil water at the Barrow Environmental Observatory (Alaska, USA) was performed in ancient drained thaw lake basins (DTLBs), drainages, and in polygonal terrain associated with inter-DTLB tundra. Within active layer soils, nitrate was most commonly found above analytical limits of detection in pore water from the unsaturated centers of high-centered polygons. Nitrate has also been detected, though less frequently, in soil water immediately above the frost table of an ancient (14C age of 2000 - 5500 BP) DTLB and in a small drainage adjacent to high-centered polygonal terrain. Nitrate from high-centered polygons had δ15N ranging from -9.2 to +8.5 ‰ and δ18O ranging from -8.4 to +1.4 ‰. The δ15N isotopic range is consistent with microbial mineralization and nitrification of reduced nitrogen sources including ammonium, dissolved organic nitrogen, and soil organic nitrogen. The range in δ18O of nitrate is also consistent with nitrification based on the δ18O of site waters. No evidence for an atmospheric nitrate signal, as defined by δ15N and δ18O of nitrate in snow and snowmelt, is seen. In contrast, nitrate in permafrost appears to be a mixture of pre-industrial atmospheric nitrate (with higher δ15N than modern atmospheric nitrate) and nitrate that is microbial in origin. Massive ice wedges appear to contain larger proportions of snowmelt (based on δ18O of ice) and atmospheric nitrate, whereas textural ice appears to contain a greater proportion of summer precipitation and microbially-derived nitrate. Nitrate from the ancient DTLB and drainage samples also has isotopic signatures that appear to represent a mixture of pre-industrial atmospheric nitrate and nitrate from microbial nitrification, and may, at least in part, be derived from

  20. Fate and Transport of Methane Formed in the Active Layer of Alaskan Permafrost

    NASA Astrophysics Data System (ADS)

    Conrad, M. E.; Curtis, J. B.; Smith, L. J.; Bill, M.; Torn, M. S.

    2015-12-01

    Over the past 2 years a series of tracer tests designed to estimate rates of methane formation via acetoclastic methanogenesis in the active layer of permafrost soils were conducted at the Barrow Environmental Observatory (BEO) in northernmost Alaska. The tracer tests consisted of extracting 0.5 to 1.0 liters of soil water in gas-tight bags from different features of polygons at the BEO, followed by addition of a tracer cocktail including acetate with a 13C-labeled methyl group and D2O (as a conservative tracer) into the soil water and injection of the mixture back into the original extraction site. Samples were then taken at depths of 30 cm (just above the bottom of the active layer), 20 cm, 10 cm and surface flux to determine the fate of the 13C-labeled acetate. During 2014 (2015 results are pending) water, soil gas, and flux gas were sampled for 60 days following injection of the tracer solution. Those samples were analyzed for concentrations and isotopic compositions of CH4, DIC/CO2 and water. At one site (the trough of a low-centered polygon) the 13C acetate was completely converted to 13CH4 within the first 2 days. The signal persisted for throughout the entire monitoring period at the injection depth with little evidence of transport or oxidation in any of the other sampling depths. In the saturated center of the same polygon, the acetate was also rapidly converted to 13CH4, but water turnover caused the signal to rapidly dissipate. High δ13C CO2 in flux samples from the polygon center indicate oxidation of the 13CH4 in near-surface waters. Conversely, CH4 production in the center of an unsaturated, flat-centered polygon was relatively small 13CH4 and dissipated rapidly without any evidence of either 13CH4 transport to shallower levels or oxidation. At another site in the edge of that polygon no 13CH4 was produced, but significant 13CO2/DIC was observed indicating direct aerobic oxidation of the acetate was occurring at this site. These results suggest that

  1. The physical understanding on dynamic readout/detection of super-resolution pits with nonlinear reverse saturation absorption thin films

    NASA Astrophysics Data System (ADS)

    Wei, Jingsong; Ding, Chenliang; Zhang, Xinghao

    2015-12-01

    The physical mechanism and understanding behind dynamic readout/detection of super-resolution pits with a nonlinear reverse-saturation absorption active layer, such as an InSb active layer, is presented on the basis of experimental results of open-aperture z-scan measurements and pump-probe transient time response analysis. The super-resolution of an InSb active layer is a result of the formation of a sub-wavelength scatterer region at the center of the focused spot. The frequency response function also verifies that the cutoff frequency with an InSb active layer is clearly extended compared to when an InSb active layer is not used. The findings are useful for understanding the physical process of the far-field super-resolution effect with nonlinear reverse-saturation absorption characteristics.

  2. Photocatalytic activity and reusability of ZnO layer synthesised by electrolysis, hydrogen peroxide and heat treatment.

    PubMed

    Akhmal Saadon, Syaiful; Sathishkumar, Palanivel; Mohd Yusoff, Abdull Rahim; Hakim Wirzal, Mohd Dzul; Rahmalan, Muhammad Taufiq; Nur, Hadi

    2016-08-01

    In this study, the zinc oxide (ZnO) layer was synthesised on the surface of Zn plates by three different techniques, i.e. electrolysis, hydrogen peroxide and heat treatment. The synthesised ZnO layers were characterised using scanning electron microscopy, X-ray diffraction, UV-visible diffuse reflectance and photoluminescence spectroscopy. The photocatalytic activity of the ZnO layer was further assessed against methylene blue (MB) degradation under UV irradiation. The photocatalytic degradation of MB was achieved up to 84%, 79% and 65% within 1 h for ZnO layers synthesised by electrolysis, heat and hydrogen peroxide treatment, respectively. The reusability results show that electrolysis and heat-treated ZnO layers have considerable photocatalytic stability. Furthermore, the results confirmed that the photocatalytic efficiency of ZnO was directly associated with the thickness and enlarged surface area of the layer. Finally, this study proved that the ZnO layers synthesised by electrolysis and heat treatment had shown better operational stability and reusability. PMID:26732538

  3. Interfacial diffusion behavior in Ni-BaTiO 3 MLCCs with ultra-thin active layers

    NASA Astrophysics Data System (ADS)

    Gong, Huiling; Wang, Xiaohui; Tian, Zhibin; Zhang, Hui; Li, Longtu

    2014-03-01

    The interfacial structure and diffusion behavior between the dielectric layers (BaTiO3) and internal electrode layers (Ni) in X5R-type multilayer ceramic capacitors (MLCCs, from -55°C to 85°C, at a temperature capacitance coefficient within ±15%) with ultra-thin active layers ( T = 1-3 µm) have been investigated by several microstructural techniques (SEM/TEM/HRTEM) with energy-dispersive x-ray spectroscopy (EDS). In the MLCC samples with different active layer thicknesses (1-3 µm), weak interfacial diffusion was observed between BaTiO3 and Ni. It was also found that the diffusion capability of Ni into the BaTiO3 layer was stronger than that of BaTiO3 to the Ni electrode, which indicated that the diffusion of Ni was the dominant factor for the interfacial diffusion behavior in the ultra-thin layered MLCCs. The mechanism of Ni diffusion is discussed in this study as well.

  4. Effects of Calcium Spikes in the Layer 5 Pyramidal Neuron on Coincidence Detection and Activity Propagation

    PubMed Central

    Chua, Yansong; Morrison, Abigail

    2016-01-01

    The role of dendritic spiking mechanisms in neural processing is so far poorly understood. To investigate the role of calcium spikes in the functional properties of the single neuron and recurrent networks, we investigated a three compartment neuron model of the layer 5 pyramidal neuron with calcium dynamics in the distal compartment. By performing single neuron simulations with noisy synaptic input and occasional large coincident input at either just the distal compartment or at both somatic and distal compartments, we show that the presence of calcium spikes confers a substantial advantage for coincidence detection in the former case and a lesser advantage in the latter. We further show that the experimentally observed critical frequency phenomenon, in which action potentials triggered by stimuli near the soma above a certain frequency trigger a calcium spike at distal dendrites, leading to further somatic depolarization, is not exhibited by a neuron receiving realistically noisy synaptic input, and so is unlikely to be a necessary component of coincidence detection. We next investigate the effect of calcium spikes in propagation of spiking activities in a feed-forward network (FFN) embedded in a balanced recurrent network. The excitatory neurons in the network are again connected to either just the distal, or both somatic and distal compartments. With purely distal connectivity, activity propagation is stable and distinguishable for a large range of recurrent synaptic strengths if the feed-forward connections are sufficiently strong, but propagation does not occur in the absence of calcium spikes. When connections are made to both the somatic and the distal compartments, activity propagation is achieved for neurons with active calcium dynamics at a much smaller number of neurons per pool, compared to a network of passive neurons, but quickly becomes unstable as the strength of recurrent synapses increases. Activity propagation at higher scaling factors can be

  5. Efficiency enhancement of solution-processed inverted organic solar cells with a carbon-nanotube-doped active layer

    NASA Astrophysics Data System (ADS)

    Lin, Wen-Kai; Su, Shui-Hsiang; Yeh, Meng-Cheng; Huang, Yang-Chan; Yokoyama, Meiso

    2016-01-01

    Solution-processed titanium-doped ZnO (TZO) is synthesized by the sol-gel method to be the electron-transporting layer (ETL) in an inverted organic solar cell (IOSC). Carbon nanotubes (CNTs) are doped into an active layer of poly(3-hexylthiophene):[6,6]-phenyl C 61 butyric acid methyl ester (P3HT:PCBM). The addition of CNTs in the P3HT:PCBM composite increases the conjugation length of P3HT:PCBM:CNTs, which simultaneously enhances the capacity of the composite to absorb solar energy radiation. Vanadium oxide (V2O5) was spin-coated onto the active layer to be a hole-transporting layer (HTL). The power conversion efficiency (PCE) results indicate that the V2O5 nanobelt structure possesses better phase separation and provides a more efficient surface area for the P3HT:PCBM:CNT active layer to increase photocurrent. The optimized IOSCs exhibited an open circuit voltage (Voc), a short-circuit current density (Jsc), a fill factor (FF), and a PCE of 0.55 V, 6.50 mA/cm2, 58.34%, and 2.20%, respectively, under simulated AM1.5G illumination of 100 mW/cm2.

  6. Diet effects on glucose absorption in the small intestine of neonatal calves: importance of intestinal mucosal growth, lactase activity, and glucose transporters.

    PubMed

    Steinhoff-Wagner, Julia; Zitnan, Rudolf; Schönhusen, Ulrike; Pfannkuche, Helga; Hudakova, Monika; Metges, Cornelia C; Hammon, Harald M

    2014-10-01

    Colostrum (C) feeding in neonatal calves improves glucose status and stimulates intestinal absorptive capacity, leading to greater glucose absorption when compared with milk-based formula feeding. In this study, diet effects on gut growth, lactase activity, and glucose transporters were investigated in several gut segments of the small intestine. Fourteen male German Holstein calves received either C of milkings 1, 3, and 5 (d 1, 2, and 3 in milk) or respective formulas (F) twice daily from d 1 to d 3 after birth. Nutrient content, and especially lactose content, of C and respective F were the same. On d 4, calves were fed C of milking 5 or respective F and calves were slaughtered 2h after feeding. Tissue samples from duodenum and proximal, mid-, and distal jejunum were taken to measure villus size and crypt depth, mucosa and brush border membrane vesicles (BBMV) were taken to determine protein content, and mRNA expression and activity of lactase and mRNA expression of sodium-dependent glucose co-transporter-1 (SGLT1) and facilitative glucose transporter (GLUT2) were determined from mucosal tissue. Additionally, protein expression of SGLT1 in BBMV and GLUT2 in crude mucosal membranes and BBMV were determined, as well as immunochemically localized GLUT2 in the intestinal mucosa. Villus circumference, area, and height were greater, whereas crypt depth was smaller in C than in F. Lactase activity tended to be greater in C than in F. Protein expression of SGLT1 was greater in F than in C. Parameters of villus size, lactase activity, SGLT1 protein expression, as well as apical and basolateral GLUT2 localization in the enterocytes differed among gut segments. In conclusion, C feeding, when compared with F feeding, enhances glucose absorption in neonatal calves primarily by stimulating mucosal growth and increasing absorptive capacity in the small intestine, but not by stimulating abundance of intestinal glucose transporters. PMID:25108868

  7. Active control of panel vibrations induced by boundary-layer flow

    NASA Technical Reports Server (NTRS)

    Chow, Pao-Liu

    1991-01-01

    Some problems in active control of panel vibration excited by a boundary layer flow over a flat plate are studied. In the first phase of the study, the optimal control problem of vibrating elastic panel induced by a fluid dynamical loading was studied. For a simply supported rectangular plate, the vibration control problem can be analyzed by a modal analysis. The control objective is to minimize the total cost functional, which is the sum of a vibrational energy and the control cost. By means of the modal expansion, the dynamical equation for the plate and the cost functional are reduced to a system of ordinary differential equations and the cost functions for the modes. For the linear elastic plate, the modes become uncoupled. The control of each modal amplitude reduces to the so-called linear regulator problem in control theory. Such problems can then be solved by the method of adjoint state. The optimality system of equations was solved numerically by a shooting method. The results are summarized.

  8. Ionophore-Based Voltammetric Ion Activity Sensing with Thin Layer Membranes.

    PubMed

    Cuartero, Maria; Crespo, Gaston A; Bakker, Eric

    2016-02-01

    As shown in recent work, thin layer ion-selective multi-ionophore membranes can be interrogated by cyclic voltammetry to detect the ion activity of multiple species simultaneously and selectively. Additional fundamental evidence is put forward on ion discrimination with thin multi-ionophore-based membranes with thicknesses of 200 ± 25 nm and backside contacted with poly-3-octylthiophene (POT). An anodic potential scan partially oxidizes the POT film (to POT(+)), thereby initiating the release of hydrophilic cations from the membrane phase to the sample solution at a characteristic potential. Varying concentration of added cation-exchanger demonstrates that it limits the ion transfer charge and not the deposited POT film. Voltammograms with multiple peaks are observed with each associated with the transfer of one type of ion (lithium, potassium, and sodium). Experimental conditions (thickness and composition of the membrane and concentration of the sample) are chosen that allow one to describe the system by a thermodynamic rather than kinetic model. As a consequence, apparent stability constants for sodium, potassium, and lithium (assuming 1:1 stoichiometry) with their respective ionophores are calculated and agree well with the values obtained by the potentiometric sandwich membrane technique. As an analytical application, a membrane containing three ionophores was used to determine lithium, sodium, and potassium in artificial samples at the same location and within a single voltammetric scan. Lithium and potassium were also determined in undiluted human plasma in the therapeutic concentration range. PMID:26712342

  9. Development of carbon free diffusion layer for activated carbon air cathode of microbial fuel cells.

    PubMed

    Yang, Wulin; Kim, Kyoung-Yeol; Logan, Bruce E

    2015-12-01

    The fabrication of activated carbon air cathodes for larger-scale microbial fuel cells requires a diffusion layer (DL) that is highly resistant to water leakage, oxygen permeable, and made using inexpensive materials. A hydrophobic polyvinylidene fluoride (PVDF) membrane synthesized using a simple phase inversion process was examined as a low cost ($0.9/m(2)), carbon-free DL that prevented water leakage at high pressure heads compared to a polytetrafluoroethylene/carbon black DL ($11/m(2)). The power density produced with a PVDF (20%, w/v) DL membrane of 1400±7mW/m(2) was similar to that obtained using a wipe DL [cloth coated with poly(dimethylsiloxane)]. Water head tolerance reached 1.9m (∼19kPa) with no mesh supporter, and 2.1m (∼21kPa, maximum testing pressure) with a mesh supporter, compared to 0.2±0.05m for the wipe DL. The elimination of carbon black from the DL greatly simplified the fabrication procedure and further reduced overall cathode costs. PMID:26342345

  10. Active control of panel vibrations induced by a boundary layer flow

    NASA Technical Reports Server (NTRS)

    Chow, Pao-Liu

    1995-01-01

    The problems of active and passive control of sound and vibration has been investigated by many researchers for a number of years. However, few of the articles are concerned with the sound and vibration with flow-structure interaction. Experimental and numerical studies on the coupling between panel vibration and acoustic radiation due to flow excitation have been done by Maestrello and his associates at NASA/Langley Research Center. Since the coupled system of nonlinear partial differential equations is formidable, an analytical solution to the full problem seems impossible. For this reason, we have to simplify the problem to that of the nonlinear panel vibration induced by a uniform flow or a boundary-layer flow with a given wall pressure distribution. Based on this simplified model, we have been able to consider the control and stabilization of the nonlinear panel vibration, which have not been treated satisfactorily by other authors. Although the sound radiation has not been included, the vibration suppression will clearly reduce the sound radiation power from the panel. The major research findings are presented in three sections. In section two we describe results on the boundary control of nonlinear panel vibration, with or without flow excitation. Sections three and four are concerned with some analytical and numerical results in the optimal control of the linear and nonlinear panel vibrations, respectively, excited by the flow pressure fluctuations. Finally, in section five, we draw some conclusions from research findings.

  11. Electrical activity of the Hartmann layers relative to surface viscous shearing in an annular magnetohydrodynamic flow

    NASA Astrophysics Data System (ADS)

    Delacroix, Jules; Davoust, Laurent

    2014-03-01

    As a first step towards two-phase magnetohydrodynamics (MHD), this paper addresses an original analytical coupling between surface rheology, e.g., a gradually oxidizing liquid metal surface, ruled by the Boussinesq number Bo, and a supporting annular MHD flow, ruled by the Hartmann number Ha, in the general layout of a classical annular deep-channel viscometer, as developed by Mannheimer and Schechter [J. Colloid Interface Sci. 32, 195-211 (1970)]. Using a matched asymptotic expansion based on the small parameter 1/Ha, we can express the surface velocity as a coupling variable in the jump momentum balance at the liquid surface. By solving the latter through the determination of the Green's function, the whole flow can be analytically calculated. A modified Boussinesq number, tilde{B_o}, is produced as a new non-dimensional parameter that provides the balance between surface viscous shearing and the Lorentz force. It is shown that the tilde{B_o} number drives the electrical activation of the Hartmann layers, heavily modifying the MHD flow topology and leading to the emergence of the Lorentz force, for which interaction with the flow is not classical. Finally, the evolution laws given in this study allow the determination of scaling laws for an original experimental protocol, which would make it possible to accurately determine the surface shear viscosity of a liquid metal with respect to the quality of the ambient atmosphere.

  12. Hydrology and geochemistry of small tundra drainage basins in response to active layer disturbance. Progress report

    SciTech Connect

    Rundle, A.S.

    1986-06-01

    Hydrology of far northern drainage basins in which the shallow organic-rich surface layer overlies a permanently frozen substrate, is poorly known, yet is of great importance in evaluating natural stability and in predicting response to disturbances effecting flow and the distribution of nutrient and sedimentary ions. First-year study of a 2.5 km/sup 2/ watershed supports the primacy of the short duration melt-off in the yearly hydrologic/geochemical cycle. At this time basin storage capacity is minimum and total runoff carries with it a seasonal maximum of nutrient ions, suspended and dissolved solids. Subsequent to melt-off, base flow is high but decreases as thaw releases seasonally frozen water, including some temporarily stored melt-off. Spring storm events produce rapid peak discharges because of the low storage capacity in the catchment. Rare, high intensity, short duration storms in early season can produce discharges that rival diurnal peaks at melt-off. With activation of vegetation following melt-off, some nutrient ions are no longer detectable and pH becomes acid. Summer drought periods are common and if sufficiently protracted, reduce stream flow to barely measurable quantities. At such times hydrographs may show small diurnal fluctuations in response to evapotranspiration cycles. Ion concentrations show an increase as senescence commences in mid-August.

  13. Patterned dual-layer achromatic micro-quarter-wave-retarder array for active polarization imaging.

    PubMed

    Zhao, Xiaojin; Pan, Xiaofang; Fan, Xiaolei; Xu, Ping; Bermak, Amine; Chigrinov, Vladimir G

    2014-04-01

    In this paper, we present a liquid-crystal-polymer (LCP)-based dual-layer micro-quarter-wave-retarder (MQWR) array for active polarization image sensors. The proposed MQWRs, for the first time, enable the extraction of the incident light's circularly polarized components in the whole visible regime, which correspond to the fourth parameter of Stokes vector. Compared with the previous implementations, our proposed MQWRs feature high achromaticity, making their applications no longer limited to monochromatic illumination. In addition, the presented thin structure exhibits an overall thickness of 2.43μm, leading to greatly alleviated optical cross-talk between adjacent photo-sensing pixels. Moreover, the reported superior optical performance (e.g. minor transmittance, extinction ratio) validates our optical design and optimization of the proposed MQWRs. Furthermore, the demonstrated simple fabrication recipe offers a cost-effective solution for the monolithic integration between the proposed MQWR array and the commercial solid-state image sensors, which makes the multi-spectral full Stokes polarization imaging system on a single chip feasible. PMID:24718177

  14. Occurrence of Sporadic -E layer during the Low Solar Activity over the Anomaly Crest Region Bhopal, India

    NASA Astrophysics Data System (ADS)

    Bhawre, Purushottam

    2016-07-01

    Ionospheric anomaly crest regions are most challenging for scientific community to understand its mechanism and investigation, for this purpose we are investigating some inospheric result for this region. The study is based on the ionogram data recorded by IPS-71 Digital Ionosonde installed over anomaly crust region Bhopal (Geo.Lat.23.2° N, Geo. Long77.4° E, Dip latitude18.4°) over a four year period from January 2007 to December 2010, covering the ending phase of 23rd Solar Cycle and starting phase of 24th solar cycle. This particular period is felt to be very suitable for examining the sunspot number and it encompasses periods of low solar activities. Quarterly ionograms are analyzed for 24 hours during these study years and have been carefully examined to note down the presence of sporadic- E. We also note down the space weather activities along with the study. The studies are divided in mainly four parts with space and geomagnetic activities during these periods. The occurrence probability of this layer is highest in summer solstice, moderate during equinox and low during winter solstice. Remarkable occurrence peaks appear from June to July in summer and from December to January in winter. The layer occurrence showed a double peak variation with distinct layer groups, in the morning (0200 LT) and the other during evening (1800 LT).The morning layer descent was associated with layer density increase indicating the strengthening of the layer while it decreased during the evening layer descent. The result indicates the presence of semi-diurnal tide over the location while the higher descent velocities could be due to the modulation of the ionization by gravity waves along with the tides. The irregularities associated with the gradient-drift instability disappear during the counter electrojet and the current flow is reversed in westward.

  15. Active control of Boundary Layer Separation & Flow Distortion in Adverse Pressure Gradient Flows via Supersonic Microjets

    NASA Technical Reports Server (NTRS)

    Alvi, Farrukh S.; Gorton, Susan (Technical Monitor)

    2005-01-01

    Inlets to aircraft propulsion systems must supply flow to the compressor with minimal pressure loss, flow distortion or unsteadiness. Flow separation in internal flows such as inlets and ducts in aircraft propulsion systems and external flows such as over aircraft wings, is undesirable as it reduces the overall system performance. The aim of this research has been to understand the nature of separation and more importantly, to explore techniques to actively control this flow separation. In particular, the use of supersonic microjets as a means of controlling boundary layer separation was explored. The geometry used for the early part of this study was a simple diverging Stratford ramp, equipped with arrays of supersonic microjets. Initial results, based on the mean surface pressure distribution, surface flow visualization and Planar Laser Scattering (PLS) indicated a reverse flow region. We implemented supersonic microjets to control this separation and flow visualization results appeared to suggest that microjets have a favorable effect, at least to a certain extent. However, the details of the separated flow field were difficult to determine based on surface pressure distribution, surface flow patterns and PLS alone. It was also difficult to clearly determine the exact influence of the supersonic microjets on this flow. In the latter part of this study, the properties of this flow-field and the effect of supersonic microjets on its behavior were investigated in further detail using 2-component (planar) Particle Image Velocimetry (PIV). The results clearly show that the activation of microjets eliminated flow separation and resulted in a significant increase in the momentum of the fluid near the ramp surface. Also notable is the fact that the gain in momentum due to the elimination of flow separation is at least an order of magnitude larger (two orders of magnitude larger in most cases) than the momentum injected by the microjets and is accomplished with very

  16. Effect of ethanolic extract of Cryptolepis sanguinolenta stem on in vivo and in vitro glucose absorption and transport: Mechanism of its antidiabetic activity

    PubMed Central

    Ajayi, A. F.; Akhigbe, R. E.; Adewumi, O. M.; Okeleji, L. O.; Mujaidu, K. B.; Olaleye, S. B.

    2012-01-01

    Objective: Extracts from various morphological parts of Cryptolepis sanguinolenta are widely used traditionally in folklore medicine in many parts of the world for the management, control, and/or treatment of a plethora of human ailments, including diabetes mellitus. In order to scientifically appraise some of the ethnomedical uses of Cryptolepis sanguinolenta, the present study was undertaken to investigate its influence at varying doses on intestinal glucose absorption and transport in relation to its hypoglycemic and hypolipidemic effects in rat experimental paradigms. Materials and Methods: The animals used were divided into four groups. Control animals received 2 ml of distilled water, while treated groups received 50, 150, and 250 mg/kg bw of Cryptolepis sanguinolenta extract per oral respectively daily for 21 days. Results: Cryptolepis sanguinolenta led to a significant decrease in glucose transport and absorption. It also caused significant reductions in plasma glucose, total cholesterol, triglyceride, and LDL cholesterol. Biochemical changes observed were suggestive of dose dependence. Histopathological studies also showed increased sizes of β cells of the pancreas. Conclusion: The findings in these normoglycemic laboratory animals suggest that Cryptolepis sanguinolenta has hypoglycemic and hypolipidemic activities, possibly by reducing glucose absorption and transport, and enhancing the structural and functional abilities of the β cells. This is the first study to report the effect of Cryptolepis sanguinolenta on intestinal glucose absorption. This effect could be attributed to its major bioactive principle, cryptolepine, an indoloquinoline alkaloid. This study thus lends credence to the use of Cryptolepis sanguinolenta in the management of diabetes mellitus. PMID:22701855

  17. Investigating the effect of solvent boiling temperature on the active layer morphology of diffusive bilayer solar cells

    NASA Astrophysics Data System (ADS)

    Vohra, Varun; Dörling, Bernhard; Higashimine, Koichi; Murata, Hideyuki

    2016-01-01

    Using chlorobenzene as a base solvent for the deposition of the poly(3-hexylthiophene-2,5-diyl) (P3HT) layer in P3HT:phenyl-C61-butyric acid methyl ester diffusive bilayer solar cells, we investigate the effect of adding of small amounts of high-boiling-point solvents with similar chemical structures on the resulting active layer morphologies. The results demonstrate that the crystallinity of the P3HT films as well as the vertical donor-acceptor gradient in the active layer can be tuned by this approach. The use of high-boiling-point solvents improved all photovoltaic parameters and resulted in a 32% increase in power conversion efficiency.

  18. Enzymatic and microbiological inhibitory activity in eggshell membranes as influenced by layer strains and age and storage variables.

    PubMed

    Ahlborn, G; Sheldon, B W

    2005-12-01

    Eggshell membranes (ESM) have been shown to exhibit antibacterial activity. The purpose of this study was to evaluate the enzymatic and biological [decimal reduction times (D-values)] activities of ESM as a function of bird breed, age, and ESM stabilization treatments. Younger White Leghorn (WL) hens produced ESM with 28% higher lysozyme activity than Rhode Island Red (RIR) layers. In contrast, older WL layers produced ESM with 17% less lysozyme activity than ESM from RIR layers. Similarly, beta-N-acetylglucosaminidase (beta-NAGase) ESM activities differed by hen age within breeds with younger hens yielding 14 to 16% more enzyme activity. D54 degrees C-values of Salmonella Typhimurium cells preexposed to WL ESM did not differ as a function of bird age (33, 50, and 81 wk). The ESM Lysozyme and beta-NAGase activities varied somewhat over a 6-mo storage study after treatment with 1 of 5 stabilization methods [i.e., storage at 4 degrees C, -20 degrees C, or ambient air storage after freeze drying, air drying (23 degrees C), or forced-air drying (50 degrees C)]. Both air and forced-air drying yielded significant reductions in beta-NAGase and lysozyme ESM activity (ca 12 to 30%) after the initial 24 h and then remained fairly stable during the extended storage. Freeze-dried samples retained the most enzymatic activity (95%) throughout the 6-mo trial, whereas refrigerated ESM lost 20 and 18% of the beta-NAGase and lysozyme activities, respectively. Frozen ESM lost 22% of the beta-NAGase activity, whereas lysozyme was nearly unaffected after 6 mo. The ESM biological activities against S. Typhimurium were not adversely impacted by layer breed or age. No significant loss in biological activity of ESM was detected 24 h after processing or after 6 mo of storage for refrigerated, frozen, and freeze-dried membranes, whereas significant reductions were observed for air- and heat-dried ESM. These findings demonstrate that ESM enzyme and biological activities are relatively

  19. Plasmon absorption modulator systems and methods

    DOEpatents

    Kekatpure, Rohan Deodatta; Davids, Paul

    2014-07-15

    Plasmon absorption modulator systems and methods are disclosed. A plasmon absorption modulator system includes a semiconductor substrate, a plurality of quantum well layers stacked on a top surface of the semiconductor substrate, and a metal layer formed on a top surface of the stack of quantum well layers. A method for modulating plasmonic current includes enabling propagation of the plasmonic current along a metal layer, and applying a voltage across the stack of quantum well layers to cause absorption of a portion of energy of the plasmonic current by the stack of quantum well layers. A metamaterial switching system includes a semiconductor substrate, a plurality of quantum well layers stacked on a top surface of the semiconductor substrate, and at least one metamaterial structure formed on a top surface of the stack of quantum well layers.

  20. 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. PMID:24104493

  1. Effects of stratified active layers on high-altitude permafrost warming: a case study on the Qinghai-Tibet Plateau

    NASA Astrophysics Data System (ADS)

    Pan, Xicai; Li, Yanping; Yu, Qihao; Shi, Xiaogang; Yang, Daqing; Roth, Kurt

    2016-07-01

    Seasonally variable thermal conductivity in active layers is one important factor that controls the thermal state of permafrost. The common assumption is that this conductivity is considerably lower in the thawed than in the frozen state, λt/λf < 1. Using a 9-year dataset from the Qinghai-Tibet Plateau (QTP) in conjunction with the GEOtop model, we demonstrate that the ratio λt/λf may approach or even exceed 1. This can happen in thick (> 1.5 m) active layers with strong seasonal total water content changes in the regions with summer-monsoon-dominated precipitation pattern. The conductivity ratio can be further increased by typical soil architectures that may lead to a dry interlayer. The unique pattern of soil hydraulic and thermal dynamics in the active layer can be one important contributor for the rapid permafrost warming at the study site. These findings suggest that, given the increase in air temperature and precipitation, soil hydraulic properties, particularly soil architecture in those thick active layers must be properly taken into account in permafrost models.

  2. Abscisic Acid Structure-Activity Relationships in Barley Aleurone Layers and Protoplasts (Biological Activity of Optically Active, Oxygenated Abscisic Acid Analogs).

    PubMed

    Hill, R. D.; Liu, J. H.; Durnin, D.; Lamb, N.; Shaw, A.; Abrams, S. R.

    1995-06-01

    Optically active forms of abscisic acid (ABA) and their oxygenated metabolites were tested for their biological activity by examining the effects of the compounds on the reversal of gibberellic acid-induced [alpha]-amylase activity in barley (Hordeum vulgare cv Himalaya) aleurone layers and the induction of gene expression in barley aleurone protoplasts transformed with a chimeric construct containing the promoter region of an albumin storage protein gene. Promotion of the albumin storage protein gene response had a more strict stereochemical requirement for elicitation of an ABA response than inhibition of [alpha]-amylase gene expression. The naturally occurring stereoisomer of ABA and its metabolites were more effective at eliciting an ABA-like response. ABA showed the highest activity, followed by 7[prime]-hydroxyABA, with phaseic acid being the least active. Racemic 8[prime]-hydroxy-2[prime],3[prime]-dihydroABA, an analog of 8[prime]-hydroxyABA, was inactive, whereas racemic 2[prime],3[prime]-dihydroABA was as effective as ABA. The differences in response of the same tissue to the ABA enantiomers lead us to conclude that there exists more than one type of ABA receptor and/or multiple signal transduction pathways in barley aleurone tissue. PMID:12228494

  3. Abscisic Acid Structure-Activity Relationships in Barley Aleurone Layers and Protoplasts (Biological Activity of Optically Active, Oxygenated Abscisic Acid Analogs).

    PubMed Central

    Hill, R. D.; Liu, J. H.; Durnin, D.; Lamb, N.; Shaw, A.; Abrams, S. R.

    1995-01-01

    Optically active forms of abscisic acid (ABA) and their oxygenated metabolites were tested for their biological activity by examining the effects of the compounds on the reversal of gibberellic acid-induced [alpha]-amylase activity in barley (Hordeum vulgare cv Himalaya) aleurone layers and the induction of gene expression in barley aleurone protoplasts transformed with a chimeric construct containing the promoter region of an albumin storage protein gene. Promotion of the albumin storage protein gene response had a more strict stereochemical requirement for elicitation of an ABA response than inhibition of [alpha]-amylase gene expression. The naturally occurring stereoisomer of ABA and its metabolites were more effective at eliciting an ABA-like response. ABA showed the highest activity, followed by 7[prime]-hydroxyABA, with phaseic acid being the least active. Racemic 8[prime]-hydroxy-2[prime],3[prime]-dihydroABA, an analog of 8[prime]-hydroxyABA, was inactive, whereas racemic 2[prime],3[prime]-dihydroABA was as effective as ABA. The differences in response of the same tissue to the ABA enantiomers lead us to conclude that there exists more than one type of ABA receptor and/or multiple signal transduction pathways in barley aleurone tissue. PMID:12228494

  4. Microglia in mouse retina contralateral to experimental glaucoma exhibit multiple signs of activation in all retinal layers

    PubMed Central

    2014-01-01

    Background Glaucomatous optic neuropathy, a leading cause of blindness, can progress despite control of intraocular pressure - currently the main risk factor and target for treatment. Glaucoma progression shares mechanisms with neurodegenerative disease, including microglia activation. In the present model of ocular hypertension (OHT), we have recently described morphological signs of retinal microglia activation and MHC-II upregulation in both the untreated contralateral eyes and OHT eyes. By using immunostaining, we sought to analyze and quantify additional signs of microglia activation and differences depending on the retinal layer. Methods Two groups of adult Swiss mice were used: age-matched control (naïve, n = 12), and lasered (n = 12). In the lasered animals, both OHT eyes and contralateral eyes were analyzed. Retinal whole-mounts were immunostained with antibodies against Iba-1, MHC-II, CD68, CD86, and Ym1. The Iba-1+ cell number in the plexiform layers (PL) and the photoreceptor outer segment (OS), Iba-1+ arbor area in the PL, and area of the retina occupied by Iba-1+ cells in the nerve fiber layer-ganglion cell layer (NFL-GCL) were quantified. Results The main findings in contralateral eyes and OHT eyes were: i) ameboid microglia in the NFL-GCL and OS; ii) the retraction of processes in all retinal layers; iii) a higher level of branching in PL and in the OS; iv) soma displacement to the nearest cell layers in the PL and OS; v) the reorientation of processes in the OS; vi) MHC-II upregulation in all retinal layers; vii) increased CD68 immunostaining; and viii) CD86 immunolabeling in ameboid cells. In comparison with the control group, a significant increase in the microglial number in the PL, OS, and in the area occupied by Iba-1+ cells in the NFL-GCL, and significant reduction of the arbor area in the PL. In addition, rounded Iba-1+ CD86+ cells in the NFL-GCL, OS and Ym1+ cells, and rod-like microglia in the NFL-GCL were restricted to OHT eyes

  5. Active intestinal absorption of fluoroquinolone antibacterial agent ciprofloxacin by organic anion transporting polypeptide, Oatp1a5.

    PubMed

    Arakawa, Hiroshi; Shirasaka, Yoshiyuki; Haga, Makoto; Nakanishi, Takeo; Tamai, Ikumi

    2012-09-01

    Fluoroquinolone antimicrobial drugs are absorbed efficiently after oral administration despite of their hydrophilic nature, implying an involvement of carrier-mediated transport in their membrane transport process. It has been that several fluoroquinolones are substrates of organic anion transporter polypeptides OATP1A2 expressed in human intestine derived Caco-2 cells. In the present study, to clarify the involvement of OATP in intestinal absorption of ciprofloxacin, the contribution of Oatp1a5, which is expressed at the apical membranes of rat enterocytes, to intestinal absorption of ciprofloxacin was investigated in rats. The intestinal membrane permeability of ciprofloxacin was measured by in situ and the vascular perfused closed loop methods. The disappeared and absorbed amount of ciprofloxacin from the intestinal lumen were increased markedly in the presence of 7,8-benzoflavone, a breast cancer resistance protein inhibitor, and ivermectin, a P-glycoprotein inhibitor, while it was decreased significantly in the presence of these inhibitors in combination with naringin, an Oatp1a5 inhibitor. Furthermore, the Oatp1a5-mediated uptake of ciprofloxacin was saturable with a K(m) value of 140 µm, and naringin inhibited the uptake with an IC(50) value of 18 µm by Xenopus oocytes expressing Oatp1a5. Naringin reduced the permeation of ciprofloxacin from the mucosal-to-serosal side, with an IC(50) value of 7.5 µm by the Ussing-type chamber method. The estimated IC(50) values were comparable to that of Oatp1a5. These data suggest that Oatp1a5 is partially responsible for the intestinal absorption of ciprofloxacin. In conclusion, the intestinal absorption of ciprofloxacin could be affected by influx transporters such as Oatp1a5 as well as the efflux transporters such as P-gp and Bcrp. PMID:22899169

  6. Bio-layer interferometry of a multivalent sulfated virus nanoparticle with heparin-like anticoagulant activity.

    PubMed

    Groner, Myles; Ng, Taryn; Wang, Weidong; Udit, Andrew K

    2015-07-01

    Heparin is a sulfated glycosaminoglycan that is routinely used as an anticoagulant. It is typically purified from bovine or porcine sources, leading to heterogeneity that poses several challenges when used clinically. We have found that the bacteriophage Qβ can be selectively sulfated to yield virus-like nanoparticles (sulf-VLP) that elicit anticoagulant activity similar to heparin. In an effort to explore the binding interactions that heparin-like VLPs make with cationic targets, described herein are bio-layer interferometry studies utilizing the BLItz platform that evaluate the interaction of sulf-VLP with the cationic peptide CDK5 (50% Lys). Streptavidin biosensors modified with biotin-CDK5 were found to bind strongly to sulf-VLP and not to the underivatized nanoparticle. Titration of sulf-VLP yielded concentration-dependent sensorgrams, permitting calculation of rate and equilibrium constants: k(on) = (8 ± 3) × 10(6) s(-1) for the association phase, k(off )= (5 ± 2) × 10(-3) M s(-1) for the dissociation phase, yielding an overall dissociation constant K(D)~ 1 nM. Fitting was best achieved using an equation possessing both exponential and linear terms, suggesting a mechanism more complex than 1:1 binding. To mitigate multivalency and rebinding effects, experiments were conducted with protamine (~70% Arg) added during the dissociation phase, leading to more pronounced dissociation curves and k off values that yielded a near-linear relationship with protamine concentration. PMID:25957844

  7. Feedbacks between tall shrubland development and active layer temperatures in northwest Siberian arctic tundra

    NASA Astrophysics Data System (ADS)

    Epstein, H. E.; Frost, G. V.; Walker, D. A.; Matyshak, G.

    2013-12-01

    Permafrost soils are a globally significant carbon store, but changes in permafrost thermal regime observed in recent decades across much of the Arctic suggest that permafrost carbon balance is likely to change with continued climate warming. Critical to changes in permafrost carbon balance in a warmer world, however, are feedbacks between changes in the composition and density of surface vegetation, and the thermal state of permafrost. Shrub expansion has been widely observed in the northwest Siberian Low Arctic, but the magnitude and direction of shrub-induced impacts to permafrost temperature and stability remain poorly understood. Here we evaluate changes to active layer properties and thermal regime that occur during tall shrubland development (shrubs > 1.5 m height) within a northwest Siberian landscape dominated by well-developed, small-scale patterned ground features (e.g., non-sorted circles). We measured the annual time-series of soil temperature at 5 cm and 20 cm depth, and the structural attributes of vegetation at patterned-ground microsites across four stages of tall shrubland development: low-growing tundra lacking erect shrubs, newly-developed shrublands, mature shrublands, and paludified shrublands. Mean summer soil temperatures declined with increasing shrub cover and moss thickness, but winter soil temperatures increased with shrub development. Shrubland development strongly attenuated cryoturbation, promoting the establishment of complete vegetation cover and the development of a continuous organic mat. Increased vegetation cover, in turn, led to further reduced cryoturbation and an aggrading permafrost table. These observations indicate that tall shrub expansion that is now occurring in patterned-ground landscapes of the northwest Siberian Arctic may buffer permafrost from atmospheric warming, and increase carbon storage in these systems at least in the short term.

  8. Active layer thermal monitoring of a Dry Valley of the Ellsworth Mountains, Continental Antarctica

    NASA Astrophysics Data System (ADS)

    Schaefer, Carlos Ernesto; Michel, Roberto; Souza, Karoline; Senra, Eduardo; Bremer, Ulisses

    2015-04-01

    The Ellsworth Mountains occur along the southern edge of the Ronne-Filchner Ice Shelf and are subdivided by the Minnesota Glacier into the Heritage Range to the east and the Sentinel Range to the West. The climate of the Ellsworth Mountains is strongly controlled by proximity to the Ronne-Filchner Ice Shelf and elevation. The mean annual air temperature at the 1,000 m level is estimated to be -25°C, and the average annual accumulation of water-equivalent precipitation likely ranges from 150 to 175 mm yr-1 (Weyant, 1966). The entire area is underlain by continuous permafrost of unknown thickness. Based on data collected from 22 pits, 41% of the sites contained dry permafrost below 70 cm, 27% had ice-cemented permafrost within 70 cm of the surface, 27% had bedrock within 70 cm, and 5% contained an ice-core (Bockheim, unpublished; Schaefer et al., 2015). Dry-frozen permafrost, which may be unique to Antarctica, appears to form from sublimation of moisture in ice-cemented permafrost over time. Active-layer depths in drift sheets of the Ellsworth Mountains range from 15 to 50 cm (Bockheim, unpublished); our understanding of Antarctic permafrost is poor, especially at the continent. The active layer monitoring sites were installed at Edson Hills, Ellsworth_Mountains, in the summer of 2012, and consist of thermistors (accuracy ± 0.2 °C) installed at 1 m above ground for air temperature measurements at two soil profiles on quartzite drift deposits, arranged in a vertical array (Lithic Haplorthel 886 m asl, 5 cm, 10 cm, 30 cm and Lithic Anyorthel 850 m asl, 5 cm, 10 cm, 30 cm). All probes were connected to a Campbell Scientific CR 1000 data logger recording data at hourly intervals from January 2nd 2012 until December 29th 2013. We calculated the thawing days (TD), freezing days (FD); isothermal days (ID), freeze thaw days (FTD), thawing degree days (TDD) and freezing degree days (FDD); all according to Guglielmin et al. (2008). Temperature at 5 cm reaches a maximum

  9. Activity and stability of immobilized carbonic anhydrase for promoting CO2 absorption into a carbonate solution for post-combustion CO2 capture

    USGS Publications Warehouse

    Zhang, S.; Zhang, Z.; Lu, Y.; Rostam-Abadi, M.; Jones, A.

    2011-01-01

    An Integrated Vacuum Carbonate Absorption Process (IVCAP) currently under development could significantly reduce the energy consumed when capturing CO2 from the flue gases of coal-fired power plants. The biocatalyst carbonic anhydrase (CA) has been found to effectively promote the absorption of CO2 into the potassium carbonate solution that would be used in the IVCAP. Two CA enzymes were immobilized onto three selected support materials having different pore structures. The thermal stability of the immobilized CA enzymes was significantly greater than their free counterparts. For example, the immobilized enzymes retained at least 60% of their initial activities after 90days at 50??C compared to about 30% for their free counterparts under the same conditions. The immobilized CA also had significantly improved resistance to concentrations of sulfate (0.4M), nitrate (0.05M) and chloride (0.3M) typically found in flue gas scrubbing liquids than their free counterparts. ?? 2011 Elsevier Ltd.

  10. Hole transporting material 5, 10, 15-tribenzyl-5H-diindolo[3, 2-a:3‧, 2‧-c]-carbazole for efficient optoelectronic applications as an active layer

    NASA Astrophysics Data System (ADS)

    Zheng, Yan-Qiong; J. Potscavage, William, Jr.; Zhang, Jian-Hua; Wei, Bin; Huang, Rong-Juan

    2015-02-01

    In order to explore the novel application of the transparent hole-transporting material 5,10,15-tribenzyl-5H-diindolo[3,2-a:3‧,2‧-c]-carbazole (TBDI), in this article TBDI is used as an active layer but not a buffer layer in a photodetector (PD), organic light-emitting diode (OLED), and organic photovoltaic cell (OPV) for the first time. Firstly, the absorption and emission spectra of a blend layer comprised of TBDI and electron-transporting material bis-(2-methyl-8-quinolinate) 4-phenylphenolate (BAlq) are investigated. Based on the absorption properties, an organic PD with a peak absorption at 320 nm is fabricated, and a relatively-high detectivity of 2.44 × 1011 cm·Hz1/2/W under 320-nm illumination is obtained. The TBDI/tris (8-hydroxyquinoline) aluminum (Alq3) OLED device exhibits a comparable external quantum efficiency and current efficiency to a traditional 4, 4-bis[N-(1-naphthyl)-N-phenyl-amino]biphenyl (α-NPD)/Alq3 OLED. A C70-based Schottky junction with 5 wt%-TBDI yields a power conversion efficiency of 5.0%, which is much higher than 1.7% for an α-NPD-based junction in the same configuration. These results suggest that TBDI has some promising properties which are in favor of the hole-transporting in Schottky junctions with a low-concentration donor. Project supported by the Funding Program for World-Leading Innovative R & D on Science and Technology (FIRST) from JSPS, the Fund from the Science and Technology Commission of Shanghai Municipality, China (Grant Nos. 14DZ2280900 and 14XD1401800), and the Natural Science Foundation of Shanghai (Grant No. 15ZR1416600).

  11. PLIF Visualization of Active Control of Hypersonic Boundary Layers Using Blowing

    NASA Technical Reports Server (NTRS)

    Bathel, Brett F.; Danehy, Paul M.; Inman, Jennifer A.; Alderfer, David W.; Berry, Scott A.

    2008-01-01

    Planar laser-induced fluorescence (PLIF) imaging was used to visualize the boundary layer flow on a 1/3-scale Hyper-X forebody model. The boundary layer was perturbed by blowing out of orifices normal to the model surface. Two blowing orifice configurations were used: a spanwise row of 17-holes spaced at 1/8 inch, with diameters of 0.020 inches and a single-hole orifice with a diameter of 0.010 inches. The purpose of the study was to visualize and identify laminar and turbulent structures in the boundary layer and to make comparisons with previous phosphor thermography measurements of surface heating. Jet penetration and its influence on the boundary layer development was also examined as was the effect of a compression corner on downstream boundary layer transition. Based upon the acquired PLIF images, it was determined that global surface heating measurements obtained using the phosphor thermography technique provide an incomplete indicator of transitional and turbulent behavior of the corresponding boundary layer flow. Additionally, the PLIF images show a significant contribution towards transition from instabilities originating from the underexpanded jets. For this experiment, a nitric oxide/nitrogen mixture was seeded through the orifices, with nitric oxide (NO) serving as the fluorescing gas. The experiment was performed in the 31-inch Mach 10 Air Tunnel at NASA Langley Research Center.

  12. A mechanism for weak double layers and coherent low-frequency electrostatic wave activity in the solar wind

    NASA Astrophysics Data System (ADS)

    Singh Lakhina, Gurbax; Singh, Satyavir

    2016-07-01

    A mechanism for the weak double layers and coherent low-frequency electrostatic wave activity observed by Wind spacecraft in the solar wind at 1 AU is proposed in terms of ion-acoustic solitons and double layers. The solar wind plasma is modelled by a three component plasma consisting of fluid hot protons, hot alpha particles streaming with respect to protons, and suprathermal electrons having κ- distribution. This system supports two types of, slow and fast, ion-acoustic solitary waves. The fast ion-acoustic mode is similar to the ion-acoustic mode of proton-electron plasma, and can support only positive potential solitons. The slow ion-acoustic mode is a new mode that occurs due to the presence of alpha particles. This mode can support both positive and negative solitons and double layers. An increase of the κ- index leads to an increase in the critical Mach number, maximum Mach number and the maximum amplitude of both slow and fast ion-acoustic solitons. The slow ion-acoustic double layer can explain the amplitudes and widths, but not shapes, of the weak double layers (WDLs) observed in the solar wind at 1 AU by Wind spacecraft. The Fourier transform of the slow ion-acoustic solitons/double layers would produce broadband low-frequency electrostatic waves having main peaks between 0.35 kHz to 1.6 kHz, with electric field in the range of E = (0.01 - 0.7 ) mV/m, in excellent agreement with the observed low-frequency electrostatic wave activity in the solar wind at 1 AU.

  13. Soil Active Layer Freeze/Thaw Detection Using Combined L- and P-Band Radar Remote Sensing

    NASA Astrophysics Data System (ADS)

    Du, J.; Kimball, J. S.; Moghaddam, M.

    2014-12-01

    Monitoring of soil active layer freeze-thaw (FT) dynamics is critical for studying high-latitude ecosystem and environmental changes. We evaluated the potential of inferring FT state dynamics within a tundra soil profile using combined L- and P-band radar remote sensing and forward radiative transfer modeling of backscatter characteristics. A first-order two-layer soil scattering model (FTSS) was developed in this study to analyze soil multi-layer scattering effects. The FTSS was evaluated against other sophisticated modeling approaches and showed comparable performance. The FTSS was then applied to analyzing L- and P-band microwave responses to layered soil. We find that soil volume scattering is rather weak for the two frequencies for frozen or dry soil with mean particle size below 10mm diameter. Dielectric contrast between adjacent soil layers can contribute to total backscatter at both L- and P-band with more significant impact on P-band than L-band signals depending on the depth of soil profile. Combined L- and P-band radar data are shown to have greater utility than single channel observations in detecting soil FT dynamics and dielectric profile inhomogeneity. Further analysis using available airborne synthetic aperture radar (SAR) data and in-situ measurements also confirm that soil profile heterogeneity can be effectively detected using combined L- and P-band radar backscatter data. This study demonstrates the potential of lower frequency SARs from airborne missions, including UAV-SAR and AirMOSS, for Arctic and alpine assessment of soil active layer properties.

  14. Intensity increases of actin layer-lines on activation of the Limulus muscle.

    PubMed Central

    Maéda, Y; Boulin, C; Gabriel, A; Sumner, I; Koch, M H

    1986-01-01

    Small angle x-ray diffraction patterns were recorded from isometrically contracting Limulus (horseshoe crab) telson levator muscle using a multiwire proportional-area detector on the storage ring DORIS. In the pattern a substantial increase in intensity is observed on the thin-filament-associated layer-line at 1/38 nm-1 (the first actin layer-line) with a maximum increase at a radial spacing of R = 0.07 nm-1 but there is a much smaller change in the intensity of the 5.9-nm layer-line, which also arises from the thin filament structure. The results suggest that during contraction the myosin heads, presumably being attached to the thin filaments, are arranged along the long-stranded helical tracks of the thin filaments but that the spatial relationship between the heads and the actin monomers varies. Intensity increases have also been observed (Maéda et al., manuscript in preparation) in the part of the patterns from frog muscle and barnacle muscle, which are attributable to the first actin layer-line. It is thus likely that the intensity increase of the first actin layer-line on the Limulus pattern is associated not with structural features which are special to Limulus muscle, but with the tension generating processes that are shared by muscles in general. Images FIGURE 1 FIGURE 2 PMID:3801566

  15. Effects of chemical reaction, heat and mass transfer on an unsteady mixed convection boundary layer flow over a wedge with heat generation/absorption in the presence of suction or injection

    NASA Astrophysics Data System (ADS)

    Ganapathirao, M.; Ravindran, R.; Momoniat, E.

    2015-02-01

    The purpose of this work is to study the effects of chemical reaction, heat and mass transfer on an unsteady mixed convection boundary layer flow over a vertical wedge with heat generation/absorption in the presence of uniform suction or injection. The fluid is assumed to be viscous and incompressible. The unsteadiness is caused by the time dependent free stream velocity varying arbitrarily with time. Both accelerating and decelerating free stream flows are considered. Non-similar solutions are obtained numerically by using an implicit finite difference scheme in combination with the quasi-linearization technique. Numerical computations are carried out for different values of dimensionless parameters on velocity, temperature and concentration profiles graphically reported in the present study. Also, numerical results are presented for the local skin friction coefficient, the local Nusselt number and the local Sherwood number. Results indicate that the time effect is crucial on velocity, temperature and concentration profiles, and on the local skin friction coefficient, the local Nusselt and Sherwood numbers. The buoyancy assisting force causes overshoot in the velocity profile for lower Prandtl number fluids. Results are compared with previously published work and are found to be in an excellent agreement.

  16. [Alleviated affect of exogenous CaCl2 on the growth, antioxidative enzyme activities and cadmium absorption efficiency of Wedelia trilobata hairy roots under cadmium stress].

    PubMed

    Shi, Heping; Wang, Yunling; Tsang, PoKeung Eric; Chan, LeeWah Andrew

    2012-06-01

    In order to study the physiological mechanism of exogenous calcium on the toxicity of heavy metal cadmium (Cd) to Wedelia trilobata hairy roots, the effects of Cd alone, and in combination with different concentrations of Ca on growth, contents of soluble protein and malondialdehyde (MDA), activities of superoxide dismutase (SOD) and peroxidase (POD), Cd2+ absorption in W. trilobata hairy roots were investigated. Cd concentrations lower than 50 micromol/L enhanced the growth of hairy roots, while concentrations higher than 100 micromol/L inhibited growth, making the branched roots short and small, and also turning the root tips brown, even black. In comparison with the control (0 micromol/L Cd), the soluble protein content in hairy roots was found to increase when cultured with 10-50 micromol/L Cd, and decrease when exposed to a cadmium concentration higher than 100 micromol/L Cd. In addition, the activities of POD and SOD activity and MDA content were significantly higher than the control. Compared to the control (hairy roots cultured without 10-30 mmol/L Ca), 100 micromol/L Cd or 300 micromol/L Cd in combination with 10-30 mmol/L Ca resulted in increased growth, causing the main root and secondary roots thicker and also an increase in soluble protein content. On the contrary, MDA content and POD and SOD activities decreased. Quantitative analysis by Atomic Absorption Spectrophotometry showed that W. trilobata hairy roots can absorb and adsorb heavy metal Cd in the ionic form of Cd2+. The maximum content of Cd2+ absorbed by the hairy roots was obtained with a concentration 100 micromol/L Cd2+ while that of Cd2+ adsorbed by hairy roots was achieved with a concentration of 300 micromol/L Cd2+. The exogenous addition of 10-30 mmol/L Ca2+ was found to reduce the absorption, adsorption of Cd2+ and the toxicity of Cd significantly. This reduction in toxicity was caused by the reduction in the absorption of Cd and decreasing the lipid peroxidation through regulating the

  17. The actuated performance of multi-layer piezoelectric actuator in active vibration control of honeycomb sandwich panel

    NASA Astrophysics Data System (ADS)

    Luo, Yajun; Xie, Shilin; Zhang, Xinong

    2008-11-01

    This paper discusses the use of the multi-layer piezoelectric actuator (MPA) in the active vibration control of the honeycomb sandwich panel (HSP). A literature overview of the available works is first presented. And the main motivation using the MPA in the AVC of HSP is discussed. Then, the honeycomb core is in advance treated as an orthotropic plate. The governing equations of the system are derived by the Hamilton principle on the basis of both displacement and transverse tress assumptions. The formulations of the actuation force/moment are obtained and indicate that the actuation force/moment are two four-order polynomial function of the piezoelectric layers number. Finally, active control experiments of a cantilever honeycomb sandwich panel (CHSP) are performed using the MPA. The control law of proportional velocity feedback is adopted in the experiments. These experiments include the resonant vibration control and the sinusoidal swept of the control system at the case of different piezoelectric layers number. The results show that the MPA can effectively control the vibration of the high damping HSP, and the control performance per voltage by the proposed actuator can be improved significantly through increasing the piezoelectric patch number. Consequently, the MPA exhibits better actuation capability than that with only single layer.

  18. The Hubble Space Telescope Quasar Absorption Line Key Project. 10: Galactic H I 21 centimeter emission toward 143 quasars and active Galactic nuclei

    NASA Technical Reports Server (NTRS)

    Lockman, Felix J.; Savage, Blair D.

    1995-01-01

    Sensitive H I 21 cm emission line spectra have been measured for the directions to 143 quasars and active galactic nuclei (AGNs) chosen from the observing lists for the Hubble Space Telescope (HST) Quasar Absorption Line Key Project. Narrow-band and wide-band data were obtained with the National Radio Astronomy Observatory (NRAO) 43 m radio telescope for each object. The narrow-band data have a velocity resolution of 1 km/s, extend from -220 to +170 km/s, and are corrected for stray 21 cm radiation. The wide-band data have a resolution of 4 km/s and extend from -1000 to +1000 km/s. The data are important for the interpretation of ultraviolet absorption lines near zero redshift in Key Project spectra. Twenty-two percent of the quasars lie behind Galactic high-velocity H I clouds with absolute value of V(sub LSR) greater than 100 km/s whose presence can increase the equivalent width of interstellar absorption lines significantly. This paper contains the emission spectra and measures of the H I velocities and column densities along the sight line to each quasar. We discuss how the measurements can be used to estimate the visual and ultraviolet extinction toward each quasar and to predict the approximate strength of the strong ultraviolet resonance lines of neutral gas species in the HST Key Project spectra.

  19. Active layer thickness and thaw subsidence in permafrost terrain: results from long-term observations near Barrow, Alaska

    NASA Astrophysics Data System (ADS)

    Shiklomanov, N. I.; Streletskiy, D. A.; Nelson, F. E.

    2012-12-01

    Patterns of active-layer thickness (ALT) on the North Slope of Alaska are highly variable, both spatially and temporally. Although geographic patterns of ALT repeat themselves from year to year, ALT is an integrated response to a large number of parameters. Thaw penetration into an ice-rich layer at the base of the active layer is accompanied by loss of volume (thaw consolidation) and results in subsidence at the ground surface. Differential thaw settlement occurs annually in permafrost environments as the layer of annual thaw (the active layer) develops. Significant ice segregation can occur at the bottom of the active layer during "cold" periods, due predominantly to freezing from below in the autumn and winter. This study examines trends in seasonal thawing of soils and vertical movements of the ground surface associated with formation and ablation of ice near the permafrost table in the Barrow region. The core thaw depth data set consists of ALT measurements conducted under the Circumpolar Active Layer Monitoring (CALM) program. The Barrow CALM site, represented by a regular 1 km2 grid, was established in the early 1990s. The reported ALT observations were initiated in 1992 and are measured annually in late August. Additional ALT measurements are available from a series of 10 x 10 meter plots established in 1962 as part of the Cold Regions Research and Engineering Laboratory (CRREL) research program at Barrow. Annual observations were made between 1962 and 1970. Measurements were reestablished in 1991 under the CALM program, following the original methodology. Field investigations to track interannual vertical movements associated with formation and ablation of ice near the permafrost table were initiated in 2003. Measurements continue annually at several CRREL plots representative of different elements of the tundra landscape. Observations were made at the end of the thawing season using Differential Global Positioning Systems (DGPS) technology. Results from

  20. High-Performance Fully Nanostructured Photodetector with Single-Crystalline CdS Nanotubes as Active Layer and Very Long Ag Nanowires as Transparent Electrodes.

    PubMed

    An, Qinwei; Meng, Xianquan; Sun, Pan

    2015-10-21

    Long and single-crystalline CdS nanotubes (NTs) have been prepared via a physical evaporation process. A metal-semiconductor-metal full-nanostructured photodetector with CdS NTs as active layer and Ag nanowires (NWs) of low resistivity and high transmissivity as electrodes has been fabricated and characterized. The CdS NTs-based photodetectors exhibit high performance, such as lowest dark currents (0.19 nA) and high photoresponse ratio (Ilight/Idark ≈ 4016) (among CdS nanostructure network photodetectors and NTs netwok photodetectors reported so far) and very low operation voltages (0.5 V). The photoconduction mechanism, including the formation of a Schottky barrier at the interface of Ag NW and CdS NTs and the effect of oxygen adsorption process on the Schottky barrier has also been provided in detail based on the studies of CdS NTs photodetector in air and vacuum. Furthermore, CdS NTs photodetector exhibits an enhanced photosensitivity as compared with CdS NWs photodetector. The enhancement in performance is dependent on the larger surface area of NTs adsorbing more oxygen in air and the microcavity structure of NTs with higher light absorption efficiency and external quantum efficiency. It is believed that CdS NTs can potentially be useful in the designs of 1D CdS-based optoelectronic devices and solar cells. PMID:26457660

  1. Method for making high resistance chromium-free semiconductor substrate body with low resistance active semiconductor layer by surface irradiation

    SciTech Connect

    Kniepkamp, H.

    1984-10-30

    A high resistance semiconductor substrate body with a thin low resistance active semiconductor layer thereon is generated by a method including the steps of subjecting the semiconductor substrate body to neutron bombardment to a degree which produces high resistance in the semiconductor body and whereby doping substances are generated in the substrate body by the thermal neutron bombardment. A thin low resistant active semiconductor layer is then generated on the substrate body by annealing, a surface of the semiconductor substrate body up to a selected depth by laser radiation or electron radiation such that the lattice deterioration which was caused by the neutron bombardment is eliminated but the doping which was generated by the transmutation of elements during neutron bombardment remains. The annealing can be undertaken only in selected regions on the surface of the semiconductor substrate body, thereby facilitating the construction of integrated circuit components thereon.

  2. Radiation tolerant GaAs MESFET with a highly-doped thin active layer grown by OMVPE

    SciTech Connect

    Nishiguchi, M.; Hashinaga, T.; Nishizawa, H.; Hayashi, H. ); Okazaki, N. ); Kitagawa, M.; Fujino, T. )

    1990-12-01

    A new structure of GaAs MESFET with high radiation tolerance is proposed. Changes in electrical parameters of a GaAs MESFET as a function of total {gamma}-ray dose have been found to be caused mainly by a decrease in the effective carrier concentration in an active layer. The authors have designed a new structure from a simulation based on an empirical relationship between the changes of the effective carrier concentration and the total {gamma}-ray dose. It has been successfully demonstrated by utilizing a highly-doped thin active layer (4 {times} 10{sup 18} cm{sup {minus}3}, 100 {Angstrom}) grown by OMVPE. This MESFET can withstand a dose ten times higher (1 {times} 10{sup 9} rads(GaAs)) than a conventional one can.

  3. Triple-Pulsed Two-Micron Integrated Path Differential Absorption Lidar: A New Active Remote Sensing Capability with Path to Space

    NASA Astrophysics Data System (ADS)

    Singh, Upendra N.; Refaat, Tamer F.; Petros, Mulugeta; Yu, Jirong

    2016-06-01

    The two-micron wavelength is suitable for monitoring atmospheric water vapor and carbon dioxide, the two most dominant greenhouse gases. Recent advances in 2-μm laser technology paved the way for constructing state-of-the-art lidar transmitters for active remote sensing applications. In this paper, a new triple-pulsed 2-μm integrated path differential absorption lidar is presented. This lidar is capable of measuring either two species or single specie with two different weighting functions, simultaneously and independently. Development of this instrument is conducted at NASA Langley Research Center. Instrument scaling for projected future space missions will be discussed.

  4. Triple-Pulsed Two-Micron Integrated Path Differential Absorption Lidar: A New Active Remote Sensing Capability with Path to Space

    NASA Technical Reports Server (NTRS)

    Singh, Upendra N.; Refaat, Tamer F.; Petros, Mulugeta; Yu, Jirong

    2015-01-01

    The two-micron wavelength is suitable for monitoring atmospheric water vapor and carbon dioxide, the two most dominant greenhouse gases. Recent advances in 2-micron laser technology paved the way for constructing state-of-the-art lidar transmitters for active remote sensing applications. In this paper, a new triple-pulsed 2-micron integrated path differential absorption lidar is presented. This lidar is capable of measuring either two species or single specie with two different weighting functions, simultaneously and independently. Development of this instrument is conducted at NASA Langley Research Center. Instrument scaling for projected future space missions will be discussed.

  5. Sequential Activation of Molecular Breathing and Bending during Spin-Crossover Photoswitching Revealed by Femtosecond Optical and X-Ray Absorption Spectroscopy.

    PubMed

    Cammarata, Marco; Bertoni, Roman; Lorenc, Maciej; Cailleau, Hervé; Di Matteo, Sergio; Mauriac, Cindy; Matar, Samir F; Lemke, Henrik; Chollet, Matthieu; Ravy, Sylvain; Laulhé, Claire; Létard, Jean-François; Collet, Eric

    2014-11-28

    We study the basic mechanisms allowing light to photoswitch at the molecular scale a spin-crossover material from a low- to a high-spin state. Combined femtosecond x-ray absorption performed at LCLS X-FEL and optical spectroscopy reveal that the structural stabilization of the photoinduced high-spin state results from a two step structural trapping. Molecular breathing vibrations are first activated and rapidly damped as part of the energy is sequentially transferred to molecular bending vibrations. During the photoswitching, the system follows a curved trajectory on the potential energy surface. PMID:25494090

  6. Sequential Activation of Molecular Breathing and Bending during Spin-Crossover Photoswitching Revealed by Femtosecond Optical and X-Ray Absorption Spectroscopy

    NASA Astrophysics Data System (ADS)

    Cammarata, Marco; Bertoni, Roman; Lorenc, Maciej; Cailleau, Hervé; Di Matteo, Sergio; Mauriac, Cindy; Matar, Samir F.; Lemke, Henrik; Chollet, Matthieu; Ravy, Sylvain; Laulhé, Claire; Létard, Jean-François; Collet, Eric

    2014-11-01

    We study the basic mechanisms allowing light to photoswitch at the molecular scale a spin-crossover material from a low- to a high-spin state. Combined femtosecond x-ray absorption performed at LCLS X-FEL and optical spectroscopy reveal that the structural stabilization of the photoinduced high-spin state results from a two step structural trapping. Molecular breathing vibrations are first activated and rapidly damped as part of the energy is sequentially transferred to molecular bending vibrations. During the photoswitching, the system follows a curved trajectory on the potential energy surface.

  7. Activation and deactivation of a robust immobilized Cp*Ir-transfer hydrogenation catalyst: a multielement in situ X-ray absorption spectroscopy study.

    PubMed

    Sherborne, Grant J; Chapman, Michael R; Blacker, A John; Bourne, Richard A; Chamberlain, Thomas W; Crossley, Benjamin D; Lucas, Stephanie J; McGowan, Patrick C; Newton, Mark A; Screen, Thomas E O; Thompson, Paul; Willans, Charlotte E; Nguyen, Bao N

    2015-04-01

    A highly robust immobilized [Cp*IrCl2]2 precatalyst on Wang resin for transfer hydrogenation, which can be recycled up to 30 times, was studied using a novel combination of X-ray absorption spectroscopy (XAS) at Ir L3-edge, Cl K-edge, and K K-edge. These culminate in in situ XAS experiments that link structural changes of the Ir complex with its catalytic activity and its deactivation. Mercury poisoning and "hot filtration" experiments ruled out leached Ir as the active catalyst. Spectroscopic evidence indicates the exchange of one chloride ligand with an alkoxide to generate the active precatalyst. The exchange of the second chloride ligand, however, leads to a potassium alkoxide-iridate species as the deactivated form of this immobilized catalyst. These findings could be widely applicable to the many homogeneous transfer hydrogenation catalysts with Cp*IrCl substructure. PMID:25768298

  8. Facile fabrication and enhanced visible light photocatalytic activity of few-layer MoS₂ coupled BiOBr microspheres.

    PubMed

    Di, Jun; Xia, Jiexiang; Ge, Yuping; Xu, Li; Xu, Hui; Chen, Jun; He, Minqiang; Li, Huaming

    2014-11-01

    Novel sphere-like MoS2/BiOBr composites were prepared by a facile ethylene glycol (EG)-assisted solvothermal process in the presence of the ionic liquid 1-hexadecyl-3-methylimidazolium bromide ([C16mim]Br). A nanostructured heterojunction, with few-layer MoS2 deposited on the surface of BiOBr microspheres, was constructed. During the synthetic process, the ionic liquid acted as a reactant, a template and a dispersing agent at the same time, leading to the formation of few-layer MoS2 dispersed on the surface of BiOBr microspheres. The MoS2/BiOBr composites exhibited much higher visible light photocatalytic activity towards rhodamine B (RhB) photodegradation than pure BiOBr. 3 wt% MoS2/BiOBr possessed the optimal photocatalytic activity, which was approximately 2.5 times as high as that of pure BiOBr. Through multiple characterization techniques, the relationship between the specific structure and the admirable photocatalytic activity of the MoS2/BiOBr microspheres was investigated. The critical role of the few-layer MoS2 in the MoS2/BiOBr microspheres was explored. A photocatalytic mechanism for the MoS2/BiOBr composites was also proposed. PMID:25190481

  9. Effectiveness of various irrigation activation protocols and the self-adjusting file system on smear layer and debris removal.

    PubMed

    Çapar, İsmail Davut; Aydinbelge, Hale Ari

    2014-01-01

    The purpose of the present study is to evaluate smear layer generation and residual debris after using self-adjusting file (SAF) or rotary instrumentation and to compare the debris and smear layer removal efficacy of the SAF cleaning/shaping irrigation system against final agitation techniques. One hundred and eight maxillary lateral incisor teeth were randomly divided into nine experimental groups (n = 12), and root canals were prepared using ProTaper Universal rotary files, with the exception of the SAF instrumentation group. During instrumentation, root canals were irrigated with a total of 16 mL of 5% NaOCl. For final irrigation, rotary-instrumented groups were irrigated with 10 mL of 17% EDTA and 10 mL of 5% NaOCl using different irrigation agitation regimens (syringe irrigation with needles, NaviTip FX, manual dynamic irrigation, CanalBrush, EndoActivator, EndoVac, passive ultrasonic irrigation (PUI), and SAF irrigation). In the SAF instrumentation group, root canals were instrumented for 4 min at a rate of 4 mL/min with 5% NaOCl and received a final flush with same as syringe irrigation with needles. The surface of the root dentin was observed using a scanning electron microscope. The SAF instrumentation group generated less smear layer and yielded cleaner canals compared to rotary instrumentation. The EndoActivator, EndoVac, PUI, and SAF irrigation groups increased the efficacy of irrigating solutions on the smear layer and debris removal. The SAF instrumentation yielded cleaner canal walls when compared to rotary instrumentation. None of the techniques completely removed the smear layer from the root canal walls. PMID:25285423

  10. Active optics for dynamical correction of fluctuations of atmospheric refraction on a differential optical absorption spectroscopy device.

    PubMed

    Fuentes-Inzunza, Rodrigo A; Gutiérrez, Javier; Saavedra, Carlos

    2012-10-20

    We have designed and developed a feedback mechanism for continuous monitoring in a long-pass differential optical absorption spectroscopy (LP-DOAS) setup. This allows one to correct photo-thermal deflection due to the local fluctuations refraction index of the air. For this purpose, using an unbalanced beam splitter, a small fraction of the collected DOAS signal is imaged onto a low-cost CCD camera using a biconvex lens, while the other portion of the signal is coupled into a fiber optic for trace gas detection. By monitoring the registered signal at the CCD camera, a feedback mechanism acting on the transversal position of the lens is able to compensate an arbitrary transversal displacement of the collected signal at the focal plane of the receiver telescope, allowing an optimal coupling into the optical fiber. PMID:23089775

  11. Performance evaluation of an active solar cooling system utilizing low cost plastic collectors and an evaporatively-cooled absorption chiller

    NASA Astrophysics Data System (ADS)

    Lof, G. O.; Westhoff, M. A.; Karaki, S.

    1984-02-01

    During the summer of 1982, air conditioning in Solar House 3 at Colorado State University was provided by an evaporatively-cooled absorption chiller. The single-effect lithium bromide chiller is an experimental three-ton unit from which heat is rejected by direct evaporative cooling of the condenser and absorber walls, thereby eliminating the need for a separate cooling tower. Domestic hot water was also provided by use of a double-walled heat exchanger and 80-gal hot water tank. A schematic of the system is given. Objectives of the project were: (1) evaluation of system performance over the course of one cooling season in Fort Collins, Colorado; (2) optimization of system operation and control; (3) development of a TRNSYS compatible model of the chiller; and (4) determination of cooling system performance in several U.S. climates by use of the model.

  12. Ketoconazole activates Cl- conductance and blocks Cl- and fluid absorption by cultured cystic fibrosis (CFPAC-1) cells.

    PubMed Central

    Kersting, U; Kersting, D; Spring, K R

    1993-01-01

    The role of arachidonic acid metabolites in the regulation of apical cell membrane Cl- conductance and transepithelial transport of fluid and Cl- by cultured pancreatic cells from cystic fibrosis (CFPAC-1) and corrected (PAC-1) cell lines was evaluated by the use of inhibitors. CFPAC-1 cells did not exhibit an apical membrane Cl- conductance, absorbed Cl- and fluid, and did not respond to stimulation or inhibition of cAMP action. PAC-1 cells exhibited a cAMP-responsive apical Cl- conductance, which was blocked by indomethacin, a cyclooxygenase inhibitor. Ketoconazole, an epoxygenase inhibitor, had virtually no effects on PAC-1 cell Cl- conductance but caused CFPAC-1 cells to develop a cAMP-insensitive Cl- conductance, blocked Cl- and fluid absorption, and reduced transepithelial electrical resistance. Ketoconazole treatment effectively reversed the cystic fibrosis defect in these cultured cells. PMID:7683418

  13. Thermal processes within the active layer of the rock glacier Murtèl-Corvatsch, Upper Engadin, Switzerland

    NASA Astrophysics Data System (ADS)

    Panz, Melanie; Hoelzle, Martin

    2010-05-01

    Coarse debris is a characteristic ground material in high alpine environments. The special thermal properties of this ground material favour the existence of permafrost. However, the most important processes explaining the common thermal anomaly found within these materials are still not yet fully understood. Many different approaches try to explain these processes. The most common explanation is the heat transfer between atmosphere and ground, driven by heat convection in autumn and winter and stable stratification of the interstitial air in summer. These processes could be shown at the investigated site in an earlier study (Hanson and Hoelzle 2005). On the contrary, Gruber and Hoelzle (2008) tried to explain the observed measurements independent of convective processes, only based on model calculations, which were based on the interaction between winter snow cover and the very low thermal conductivity of the coarse debris layer. In the present study, we took the ground surface temperature data from the uppermost 90 cm of the active layer of the rock glacier Murtèl-Corvatsch in combination with meteorological data, such as air temperature, snow depth and radiation to analyze the dominant heat transfer mechanisms during the different seasons. The main focus was to assess the contribution of convective processes. The potential for free convection was estimated using the Rayleigh number. In addition, the air circulation within the uppermost active layer measured by three wind sensors was taken into consideration. These data were compared with the other climate variables of the nearby meteorological station. After analyzing the data, it can be concluded that the potential for free convection in the cavities of the upper blocky layer is high as soon as the stable thermal stratification during the summer month gets instable due to a cooling of the surface. Especially in the autumn and early winter months a strong ground cooling could be observed caused by the low air

  14. Improved performance of polymer solar cells using PBDTT-F-TT:PC71BM blend film as active layer

    NASA Astrophysics Data System (ADS)

    Zang, Yue; Gao, Xiumin; Lu, Xinmiao; Xin, Qing; Lin, Jun; Zhao, Jufeng

    2016-07-01

    A detailed study of high-efficiency polymer solar cells (PSCs) based on a low bandgap polymer PBDTT-F-TT and PC71BM as the bulk heterojunction (BHJ) layer is carried out. By using 1,8-diiodooctane (DIO) as solvent additive to control the morphology of active layer and comparing different device architecture to optimize the optical field distribution, the power conversion efficiency (PCE) of the resulted devices can be reached as high as 9.34%. Comprehensive characterization and optical modeling of the resulting devices is performed to understand the effect of DIO and device geometry on photovoltaic performance. It was found that the addition of DIO can significantly improve the nanoscale morphology and increased electron mobility in the BHJ layer. The inverted device architecture was chosen because the results from optical modeling shows that it offers better optical field distribution and exciton generation profile. Based on these results, a low-temperature processed ZnO was finally introduced as an electron transport layer to facility the fabrication on flexible substrates and showed comparable performance with the device based on conventional ZnO interlayer prepared by sol-gel process.

  15. Complex Boron Redistribution in P+ Doped-polysilicon / Nitrogen Doped Silicon Bi-layers during Activation Annealing

    NASA Astrophysics Data System (ADS)

    Abadli, S.; Mansour, F.; Perrera, E. Bedel

    We have investigated and modeled the complex phenomenon of boron (B) redistribution process in strongly doped silicon bilayers structure. A one-dimensional two stream transfer model well adapted to the particular structure of bi- layers and to the effects of strong-concentrations has been developed. This model takes into account the instantaneous kinetics of B transfer, trapping, clustering and segregation during the thermal B activation annealing. The used silicon bi-layers have been obtained by low pressure chemical vapor deposition (LPCVD) method, using in-situ nitrogen- doped-silicon (NiDoS) layer and strongly B doped polycrystalline-silicon (P+) layer. To avoid long redistributions, thermal annealing was carried out at relatively lowtemperatures (600 °C and 700 °C) for various times ranging between 30 minutes and 2 hours. The good adjustment of the simulated profiles with the experimental secondary ion mass spectroscopy (SIMS) profiles allowed a fundamental understanding about the instantaneous physical phenomena giving and disturbing the complex B redistribution profiles-shoulders kinetics.

  16. Quantitative activity-induced manganese-dependent MRI for characterizing cortical layers in the primary somatosensory cortex of the rat.

    PubMed

    Auffret, Matthieu; Samim, Idrees; Lepore, Mario; Gruetter, Rolf; Just, Nathalie

    2016-03-01

    The ability of Mn(2+) to follow Ca(2+) pathways upon stimulation transform them into remarkable surrogate markers of neuronal activity using activity-induced manganese-dependent MRI (AIM-MRI). In the present study, a precise follow-up of physiological parameters during MnCl2 and mannitol infusions improved the reproducibility of AIM-MRI allowing in-depth evaluation of the technique. Pixel-by-pixel T1 data were investigated using histogram distributions in the barrel cortex (BC) and the thalamus before and after Mn(2+) infusion, after blood brain barrier opening and after BC activation. Mean BC T1 values dropped significantly upon trigeminal nerve (TGN) stimulation (-38 %, P = 0.02) in accordance with previous literature findings. T1 histogram distributions showed that 34 % of T1s in the range 600-1500 ms after Mn(2+ )+ mannitol infusions shifted to 50-350 ms after TGN stimulation corresponding to a twofold increase of the percentage of pixels with the lowest T1s in BC. Moreover, T1 changes in response to stimulation increased significantly from superficial cortical layers (I-III) to deeper layers (V-VI). Cortical cytoarchitecture detection during a functional paradigm was performed extending the potential of AIM-MRI. Quantitative AIM-MRI could thus offer a means to interpret local neural activity across cortical layers while identification of the role of calcium dynamics in vivo during brain activation could play a key role in resolving neurovascular coupling mechanisms. PMID:25366973

  17. A time-dependent density-functional theory and complete active space self-consistent field method study of vibronic absorption and emission spectra of coumarin

    NASA Astrophysics Data System (ADS)

    Li, Junfeng; Rinkevicius, Zilvinas; Cao, Zexing

    2014-07-01

    Time-dependent density-functional theory (TD-DFT) and complete active space multiconfiguration self-consistent field (CASSCF) calculations have been used to determine equilibrium structures and vibrational frequencies of the ground state and several singlet low-lying excited states of coumarin. Vertical and adiabatic transition energies of S1, S2, and S3 have been estimated by TD-B3LYP and CASSCF/PT2. Calculations predict that the dipole-allowed S1 and S3 states have a character of 1(ππ*), while the dipole-forbidden 1(nπ*) state is responsible for S2. The vibronic absorption and emission spectra of coumarin have been simulated by TD-B3LYP and CASSCF calculations within the Franck-Condon approximation, respectively. The simulated vibronic spectra show good agreement with the experimental observations available, which allow us to reasonably interpret vibronic features in the S0→S1 and S0→S3 absorption and the S0←S1 emission spectra. Based on the calculated results, activity, intensity, and density of the vibronic transitions and their contribution to the experimental spectrum profile have been discussed.

  18. A time-dependent density-functional theory and complete active space self-consistent field method study of vibronic absorption and emission spectra of coumarin.

    PubMed

    Li, Junfeng; Rinkevicius, Zilvinas; Cao, Zexing

    2014-07-01

    Time-dependent density-functional theory (TD-DFT) and complete active space multiconfiguration self-consistent field (CASSCF) calculations have been used to determine equilibrium structures and vibrational frequencies of the ground state and several singlet low-lying excited states of coumarin. Vertical and adiabatic transition energies of S1, S2, and S3 have been estimated by TD-B3LYP and CASSCF/PT2. Calculations predict that the dipole-allowed S1 and S3 states have a character of (1)(ππ*), while the dipole-forbidden (1)(nπ*) state is responsible for S2. The vibronic absorption and emission spectra of coumarin have been simulated by TD-B3LYP and CASSCF calculations within the Franck-Condon approximation, respectively. The simulated vibronic spectra show good agreement with the experimental observations available, which allow us to reasonably interpret vibronic features in the S0→S1 and S0→S3 absorption and the S0←S1 emission spectra. Based on the calculated results, activity, intensity, and density of the vibronic transitions and their contribution to the experimental spectrum profile have been discussed. PMID:25005288

  19. Influence of Shielding Gas and Mechanical Activation of Metal Powders on the Quality of Surface Sintered Layers

    NASA Astrophysics Data System (ADS)

    Saprykina, N. A.; Saprykin, A. A.; Arkhipova, D. A.

    2016-04-01

    The thesis analyses the influence of argon shielding gas and mechanical activation of PMS-1 copper powder and DSK-F75 cobalt chrome molybdenum powder on the surface sintered layer quality under various sintering conditions. Factors affecting the quality of the sintered surface and internal structure are studied. The obtained results prove positive impact of the shielding gas and mechanical activation. Sintering PMS-1 copper powder in argon shielding gas after mechanical activation leads to reduced internal stresses and roughness, as well as improved strength characteristics of the sintered surface. Analysis of sintered samples of mechanically activated DSK-F75 cobalt chrome molybdenum powder shows that the strength of the sintered surface grows porosity and coagulation changes.

  20. Optical Absorption in Liquid Semiconductors

    NASA Astrophysics Data System (ADS)

    Bell, Florian Gene

    An infrared absorption cell has been developed which is suitable for high temperature liquids which have absorptions in the range .1-10('3) cm('-1). The cell is constructed by clamping a gasket between two flat optical windows. This unique design allows the use of any optical windows chemically compatible with the liquid. The long -wavelength limit of the measurements is therefore limited only by the choice of the optical windows. The thickness of the cell can easily be set during assembly, and can be varied from 50 (mu)m to .5 cm. Measurements of the optical absorption edge were performed on the liquid alloy Se(,1-x)Tl(,x) for x = 0, .001, .002, .003, .005, .007, and .009, from the melting point up to 475(DEGREES)C. The absorption was found to be exponential in the photon energy over the experimental range from 0.3 eV to 1.2 eV. The absorption increased linearly with concentration according to the empirical relation (alpha)(,T)(h(nu)) = (alpha)(,1) + (alpha)(,2)x, and the absorption (alpha)(,1) was interpreted as the absorption in the absence of T1. (alpha)(,1) also agreed with the measured absorption in 100% Se at corresponding temperatures and energies. The excess absorption defined by (DELTA)(alpha) = (alpha)(,T)(h(nu))-(alpha)(,1) was interpreted as the absorption associated with Tl and was found to be thermally activated with an activation energy E(,t) = 0.5 eV. The exponential edge is explained as absorption on atoms immersed in strong electric fields surrounding ions. The strong fields give rise to an absorption tail similar to the Franz-Keldysh effect. A simple calculation is performed which is based on the Dow-Redfield theory of absorption in an electric field with excitonic