Science.gov

Sample records for active layer based

  1. 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.

  2. Evidence for reduced charge recombination in carbon nanotube/perovskite-based active layers

    NASA Astrophysics Data System (ADS)

    Bag, Monojit; Renna, Lawrence A.; Jeong, Seung Pyo; Han, Xu; Cutting, Christie L.; Maroudas, Dimitrios; Venkataraman, D.

    2016-10-01

    Using impedance spectroscopy and computation, we show that incorporation of multi-walled carbon nanotubes (MWCNTs) in the bulk of the active layer of perovskite-based solar cells reduces charge recombination and increases the open circuit voltage. An ∼87% reduction in recombination was achieved when MWCNTs were introduced in the planar-heterostructure perovskite solar cell containing mixed counterions. The open circuit voltage (Voc) of perovskite/MWCNTs devices was increased by 70 mV, while the short circuit current density (Jsc) and fill factor (FF) remained unchanged.

  3. Layer-by-layer structured polysaccharides-based multilayers on cellulose acetate membrane: Towards better hemocompatibility, antibacterial and antioxidant activities

    NASA Astrophysics Data System (ADS)

    Peng, Lincai; Li, Hui; Meng, Yahong

    2017-04-01

    The development of multifunctional cellulose acetate (CA) membranes with enhanced hemocompatibility and antibacterial and antioxidant activities is extremely important for biomedical applications. In this work, significant improvements in hemocompatibility and antibacterial and antioxidant activities of cellulose acetate (CA) membranes were achieved via layer-by-layer (LBL) deposition of chitosan (CS) and water-soluble heparin-mimicking polysaccharides (i.e., sulfated Cantharellus cibarius polysaccharides, SCP) onto their surface. The surface chemical compositions, growth manner, surface morphologies, and wetting ability of CS/SCP multilayer-modified CA membranes were characterized, respectively. The systematical evaluation of hemocompatibility revealed that CS/SCP multilayer-modified CA membranes significantly improved blood compatibility including resistance to non-specific protein adsorption, suppression of platelet adhesion and activation, prolongation of coagulation times, inhibition of complement activation, as well as reduction in blood hemolysis. Meanwhile, CS/SCP multilayer-modified CA membranes exhibited strong growth inhibition against Escherichia coli and Staphylococcus aureus, as well as high scavenging abilities against superoxide and hydroxyl radicals. In summary, the CS/SCP multilayers could confer CA membranes with integrated hemocompatibility and antibacterial and antioxidant activities, which might have great potential application in the biomedical field.

  4. Ferroelectrics based absorbing layers

    NASA Astrophysics Data System (ADS)

    Hao, Jianping; Sadaune, Véronique; Burgnies, Ludovic; Lippens, Didier

    2014-07-01

    We show that ferroelectrics-based periodic structure made of BaSrTiO3 (BST) cubes, arrayed onto a metal plate with a thin dielectric spacer film exhibit a dramatic enhancement of absorbance with value close to unity. The enhancement is found around the Mie magnetic resonance of the Ferroelectrics cubes with the backside metal layer stopping any transmitted waves. It also involves quasi-perfect impedance matching resulting in reflection suppression via simultaneous magnetic and electrical activities. In addition, it was shown numerically the existence of a periodicity optimum, which is explained from surface waves analysis along with trade-off between the resonance damping and the intrinsic loss of ferroelectrics cubes. An experimental verification in a hollow waveguide configuration with a good comparison with full-wave numerical modelling is at last reported by measuring the scattering parameters of single and dual BST cubes schemes pointing out coupling effects for densely packed structures.

  5. A photovoltaic device based on a poly(phenyleneethynylene)/SWNT composite active layer.

    PubMed

    Liu, Qian; Mao, Jie; Liu, Zunfeng; Zhang, Nan; Wang, Yu; Yang, Liying; Yin, Shougen; Chen, Yongsheng

    2008-03-19

    Although research on the use of single walled carbon nanotubes (SWNTs) as the acceptor in polymer photovoltaic cells is currently making great progress, their poor dispersion in a polymer matrix has greatly hindered the overall performance of the devices. Here a novel bulk heterojunction structure based on a poly(phenyleneethynylene)/SWNT composite was designed to improve the dispersion of SWNTs in the composite based on their structural similarity and strong interaction. Better dispersion and higher performance are achieved compared with a common control device based on a poly(3-octylthiophene)/SWNT composite layer.

  6. Active vibration control of functionally graded beams with piezoelectric layers based on higher order shear deformation theory

    NASA Astrophysics Data System (ADS)

    Bendine, K.; Boukhoulda, F. B.; Nouari, M.; Satla, Z.

    2016-12-01

    This paper reports on a study of active vibration control of functionally graded beams with upper and lower surface-bonded piezoelectric layers. The model is based on higher-order shear deformation theory and implemented using the finite element method (FEM). The proprieties of the functionally graded beam (FGB) are graded along the thickness direction. The piezoelectric actuator provides a damping effect on the FGB by means of a velocity feedback control algorithm. A Matlab program has been developed for the FGB model and compared with ANSYS APDL. Using Newmark's method numerical solutions are obtained for the dynamic equations of FGB with piezoelectric layers. Numerical results show the effects of the constituent volume fraction and the influence the feedback control gain on the frequency and dynamic response of FGBs.

  7. GeSn-based p-i-n photodiodes with strained active layer on a Si wafer

    SciTech Connect

    Tseng, H. H.; Li, H.; Mashanov, V.; Yang, Y. J.; Cheng, H. H.; Chang, G. E.; Soref, R. A.; Sun, G.

    2013-12-02

    We report an investigation of GeSn-based p-i-n photodiodes with an active GeSn layer that is almost fully strained. The results show that (a) the response of the Ge/GeSn/Ge heterojunction photodiodes is stronger than that of the reference Ge-based photodiodes at photon energies above the 0.8 eV direct bandgap of bulk Ge (<1.55 μm), and (b) the optical response extends to lower energy regions (1.55–1.80 μm wavelengths) as characterized by the strained GeSn bandgap. A cusp-like spectral characteristic is observed for samples with high Sn contents, which is attributed to the significant strain-induced energy splitting of heavy and light hole bands. This work represents a step forward in developing GeSn-based infrared photodetectors.

  8. Global model of the F2 layer peak height for low solar activity based on GPS radio-occultation data

    NASA Astrophysics Data System (ADS)

    Shubin, V. N.; Karpachev, A. T.; Tsybulya, K. G.

    2013-11-01

    We propose a global median model SMF2 (Satellite Model of the F2 layer) of the ionospheric F2-layer height maximum (hmF2), based on GPS radio-occultation data for low solar activity periods (F10.7A<80). The model utilizes data provided by GPS receivers onboard satellites CHAMP (~100,000 hmF2 values), GRACE (~70,000) and COSMIC (~2,000,000). The data were preprocessed to remove cases where the absolute maximum of the electron density lies outside the F2 region. Ground-based ionospheric sounding data were used for comparison and validation. Spatial dependence of hmF2 is modeled by a Legendre-function expansion. Temporal dependence, as a function of Universal Time (UT), is described by a Fourier expansion. Inputs of the model are: geographical coordinates, month and F10.7A solar activity index. The model is designed for quiet geomagnetic conditions (Kр=1-2), typical for low solar activity. SMF2 agrees well with the International Reference Ionosphere model (IRI) in those regions, where the ground-based ionosonde network is dense. Maximal difference between the models is found in the equatorial belt, over the oceans and the polar caps. Standard deviations of the radio-occultation and Digisonde data from the predicted SMF2 median are 10-16 km for all seasons, against 13-29 km for IRI-2012. Average relative deviations are 3-4 times less than for IRI, 3-4% against 9-12%. Therefore, the proposed hmF2 model is more accurate than IRI-2012.

  9. 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.

  10. 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

  11. Simulation and Fabrication of SAW-Based Gas Sensor with Modified Surface State of Active Layer and Electrode Orientation for Enhanced H2 Gas Sensing

    NASA Astrophysics Data System (ADS)

    Hasan, Md. Nazibul; Maity, Santanu; Sarkar, Argha; Bhunia, Chandan Tilak; Acharjee, Debabrata; Joseph, Aneesh M.

    2017-02-01

    The design, analysis, optimization, and fabrication of layered and nanostructure-based surface acoustic wave (SAW) gas sensors are presented. A lithium niobate and zinc oxide (ZnO) nano multilayer structure is proposed to enhance the sensitivity of the SAW-based gas sensor. Different materials are considered for the intermediate layer in the design for optimization purposes. The sensitivity of the sensor could be improved due to increased active surface area obtained by varying the aspect ratio of the nanorods, the thickness of the intermediate layer, and the gap between the electrodes. The total displacement and frequency shift of the device were significantly improved. Overall, the mechanically engineered surface-based (nanorod) SAW gas sensor offered better sensing response than the layered SAW gas sensor in terms of sensitivity performance.

  12. Layered nickel based superconductors

    SciTech Connect

    Ronning, Filip; Bauer, Eric D; Park, Tuson; Kurita, Nobuyuki; Klimczuk, T; Movshovich, R; Thompson, J D; Sefat, A S; Mandrus, D

    2009-01-01

    We review the properties of Ni-based superconductors which contain Ni{sub 2}X{sub 2} (X=As, P, Bi, Si, Ge, B) planes, a common structural element to the recently discovered FeAs superconductors. We also compare the properties ofthe Ni-and Fe-based systems from a perspective ofelectronic structure as well as structure-property relations.

  13. Active-Layer Soil Moisture Content Regional Variations in Alaska and Russia by Ground-Based and Satellite-Based Methods, 2002 Through 2014

    NASA Astrophysics Data System (ADS)

    Muskett, Reginald; Romanovsky, Vladimir; Cable, William; Kholodov, Alexander

    2016-04-01

    Soil moisture is a vital physical parameter of the active-layer in permafrost environments, and associated biological and geophysical processes operative at the microscopic to hemispheric spatial scales and at hourly to multidecadal time scales. While in-situ measurements can give the highest quality of information on a site-specific basis, the vast permafrost terrains of North America and Eurasia require space-based techniques for assessments of cause and effect and long-term changes and impacts from the changes of permafrost and the active-layer. Satellite-based 6.925 and 10.65 GHz sensor algorithmic retrievals of soil moisture by Advanced Microwave Scanning Radiometer - Earth Observation System (AMSR-E) onboard NASA-Aqua and follow-on AMSR2 onboard JAXA-Global Change Observation Mission - Water-1 are ongoing since July 2002. Accurate land-surface temperature and vegetation parameters are critical to the success of passive microwave algorithmic retrieval schemes. Strategically located soil moisture measurements are needed for spatial and temporal co-location evaluation and validation of the space-based algorithmic estimates. We compare on a daily basis ground-based (subsurface-probe) 50- and 70-MHz radio-frequency soil moisture measurements with NASA- and JAXA-algorithmic retrieval passive microwave retrievals. We find improvements in performance of the JAXA-algorithm (AMSR-E reprocessed and AMSR2 ongoing) relative to the earlier NASA-algorithm version. In the boreal forest regions accurate land-surface temperatures and vegetation parameters are still needed for algorithmic retrieval success. Over the period of AMSR-E retrievals we find evidence of at the high northern latitudes of growing terrestrial radio-frequency interference in the 10.65 GHz channel soil moisture content. This is an important error source for satellite-based active and passive microwave remote sensing soil moisture retrievals in Arctic regions that must be addressed. Ref: Muskett, R

  14. Electric double-layer capacitors with tea waste derived activated carbon electrodes and plastic crystal based flexible gel polymer electrolytes

    NASA Astrophysics Data System (ADS)

    Suleman, M.; Deraman, M.; Othman, M. A. R.; Omar, R.; Hashim, M. A.; Basri, N. H.; Nor, N. S. M.; Dolah, B. N. M.; Hanappi, M. F. Y. M.; Hamdan, E.; Sazali, N. E. S.; Tajuddin, N. S. M.; Jasni, M. R. M.

    2016-08-01

    We report a novel configuration of symmetrical electric double-layer capacitors (EDLCs) comprising a plastic crystalline succinonitrile (SN) based flexible polymer gel electrolyte, incorporated with sodium trifluoromethane sulfonate (NaTf) immobilised in a host polymer poly (vinylidine fluoride-co-hexafluoropropylene) (PVdF-HFP). The cost-effective activated carbon powder possessing a specific surface area (SSA) of ~ 1700 m2g-1 containing a large proportion of meso-porosity has been derived from tea waste to use as supercapacitor electrodes. The high ionic conductivity (~3.6×10-3 S cm-1 at room temperature) and good electrochemical stability render the gel polymer electrolyte film a suitable candidate for the fabrication of EDLCs. The performance of the EDLCs has been tested by electrochemical impedance spectroscopy (EIS), cyclic voltammetry (CV), and galvanostatic charge-discharge studies. The performance of the EDLC cell is found to be promising in terms of high values of specific capacitance (~270 F g-1), specific energy (~ 36 Wh kg-1), and power density (~ 33 kW kg-1).

  15. Active-Layer Soil Moisture Content Regional Variations in Alaska and Russia by Ground-Based and Satellite-Based Methods, 2002 Through 2014

    NASA Astrophysics Data System (ADS)

    Muskett, Reginald; Romanovsky, Vladimir; Cable, William; Kholodov, Alexander

    2015-04-01

    Soil moisture is a vital physical parameter of the active-layer in permafrost environments, and associated biological and geophysical processes operative at the microscopic to hemispheric spatial scales and at hourly to multidecadal time scales. While in-situ measurements can give the highest quality of information on a site-specific basis, the vast permafrost terrains of North America and Eurasia require space-based techniques for assessments of cause and effect and long-term changes and impacts from the changes of permafrost and the active-layer. Satellite-based 6.925 and 10.65 GHz sensor algorithmic retrievals of soil moisture by Advanced Microwave Scanning Radiometer - Earth Observation System (AMSR-E) onboard NASA-Aqua and follow-on AMSR2 onboard JAXA-Global Change Observation Mission - Water-1 are ongoing since July 2002. Accurate land-surface temperature and vegetation parameters are critical to the success of passive microwave algorithmic retrieval schemes. Strategically located soil moisture measurements are needed for spatial and temporal co-location evaluation and validation of the space-based algorithmic estimates. We compare on a daily basis ground-based (subsurface-probe) 50- and 70-MHz radio-frequency soil moisture measurements with NASA- and JAXA-algorithmic retrieval passive microwave retrievals. We find improvements in performance of the JAXA-algorithm (AMSR-E reprocessed and AMSR2 ongoing) relative to the earlier NASA-algorithm version. In the boreal forest regions accurate land-surface temperatures and vegetation parameters are still needed for algorithmic retrieval success. Over the period of AMSR-E retrievals we find evidence of at the high northern latitudes of growing terrestrial radio-frequency interference in the 10.65 GHz channel soil moisture content. This is an important error source for satellite-based active and passive microwave remote sensing soil moisture retrievals in Arctic regions that must be addressed. Ref: International

  16. Active-Layer Soil Moisture Content Regional Variations in Alaska and Russia by Ground-Based and Satellite-Based Methods, 2002 Through 2014

    NASA Astrophysics Data System (ADS)

    Muskett, R. R.; Romanovsky, V. E.; Cable, W.; Kholodov, A. L.

    2015-12-01

    Soil moisture is a vital physical parameter of the active-layer in permafrost environments, and associated biological and geophysical processes operative at the microscopic to hemispheric spatial scales and at hourly to multidecadal time scales. While in-situ measurements can give the highest quality of information on a site-specific basis, the vast permafrost terrains of North America and Eurasia require space-based techniques for assessments of cause and effect and long-term changes and impacts from the changes of permafrost and the active-layer. Satellite-based 6.925 and 10.65 GHz sensor algorithmic retrievals of soil moisture by Advanced Microwave Scanning Radiometer - Earth Observation System (AMSR-E) onboard NASA-Aqua and follow-on AMSR2 onboard JAXA-Global Change Observation Mission - Water-1 are ongoing since July 2002. Accurate land-surface temperature and vegetation parameters are critical to the success of passive microwave algorithmic retrieval schemes. Strategically located soil moisture measurements are needed for spatial and temporal co-location evaluation and validation of the space-based algorithmic estimates. We compare on a daily basis ground-based (subsurface-probe) 50- and 70-MHz radio-frequency soil moisture measurements with NASA- and JAXA-algorithmic retrieval passive microwave retrievals. We find improvements in performance of the JAXA-algorithm (AMSR-E reprocessed and AMSR2 ongoing) relative to the earlier NASA-algorithm version. In the boreal forest regions accurate land-surface temperatures and vegetation parameters are still needed for algorithmic retrieval success. Over the period of AMSR-E retrievals we find evidence of at the high northern latitudes of growing terrestrial radio-frequency interference in the 10.65 GHz channel soil moisture content. This is an important error source for satellite-based active and passive microwave remote sensing soil moisture retrievals in Arctic regions that must be addressed. Ref: Muskett, R

  17. Development of White-Light Emitting Active Layers in Nitride Based Heterostructures for Phosphorless Solid State Lighting

    SciTech Connect

    Jan Talbot; Kailash Mishra

    2007-12-31

    This report provides a summary of research activities carried out at the University of California, San Diego and Central Research of OSRAM SYLVANIA in Beverly, MA partially supported by a research contract from US Department of Energy, DE-FC26-04NT422274. The main objective of this project was to develop III-V nitrides activated by rare earth ions, RE{sup 3+}, which could eliminate the need for phosphors in nitride-based solid state light sources. The main idea was to convert electron-hole pairs injected into the active layer in a LED die to white light directly through transitions within the energy levels of the 4f{sup n}-manifold of RE{sup 3+}. We focused on the following materials: Eu{sup 3+}(red), Tb{sup 3+}(green), Er{sup 3+}(green), Dy{sup 3+}(yellow) and Tm{sup 3+}(blue) in AlN, GaN and alloys of AlN and GaN. Our strategy was to explore candidate materials in powder form first, and then study their behavior in thin films. Thin films of these materials were to be deposited on sapphire substrates using pulsed laser deposition (PLD) and metal organic vapor phase epitaxy (MOVPE). The photo- and cathode-luminescence measurements of these materials were used to investigate their suitability for white light generation. The project proceeded along this route with minor modifications needed to produce better materials and to expedite our progress towards the final goal. The project made the following accomplishments: (1) red emission from Eu{sup 3+}, green from Tb{sup 3+}, yellow from Dy{sup 3+} and blue from Tm{sup 3+} in AlN powders; (2) red emission from Eu{sup 3+} and green emission from Tb{sup 3+} in GaN powder; (3) red emission from Eu{sup 3+} in alloys of GaN and AlN; (4) green emission from Tb{sup 3+} in GaN thin films by PLD; (5) red emission from Eu{sup 3+} and Tb{sup 3+} in GaN thin films deposited by MOVPE; (6) energy transfer from host to RE{sup 3+}; (7) energy transfer from Tb{sup 3+} to Eu{sup 3+} in AlN powders; (8) emission from AlN powder samples

  18. A label-free ultrasensitive electrochemical DNA sensor based on thin-layer MoS2 nanosheets with high electrochemical activity.

    PubMed

    Wang, Xinxing; Nan, Fuxin; Zhao, Jinlong; Yang, Tao; Ge, Tong; Jiao, Kui

    2015-02-15

    A label-free and ultrasensitive electrochemical DNA biosensor, based on thin-layer molybdenum disulfide (MoS2) nanosheets sensing platform and differential pulse voltammetry detection, is constructed in this paper. The thin-layer MoS2 nanosheets were prepared via a simple ultrasound exfoliation method from bulk MoS2, which is simpler and no distortion compared with mechanical cleavage and lithium intercalation. Most importantly, this procedure allows the formation of MoS2 with enhanced electrochemical activity. Based on the high electrochemical activity and different affinity toward ssDNA versus dsDNA of the thin-layer MoS2 nanosheets sensing platform, the tlh gene sequence assay can be performed label-freely from 1.0 × 10(-16)M to 1.0 × 10(-10)M with a detection limit of 1.9 × 10(-17)M. Without labeling and the use of amplifiers, the detection method described here not only expands the application of MoS2, but also offers a viable alternative for DNA analysis, which has the priority in sensitivity, simplicity, and costs. Moreover, the proposed sensing platform has good electrocatalytic activity, and can be extended to detect more targets, such as guanine and adenine, which further expands the application of MoS2.

  19. Analysis of low active-pharmaceutical-ingredient signal drugs based on thin layer chromatography and surface-enhanced Raman spectroscopy.

    PubMed

    Li, Xiao; Chen, Hui; Zhu, Qingxia; Liu, Yan; Lu, Feng

    2016-11-30

    Active pharmaceutical ingredients (API) embedded in the excipients of the formula can usually be unravelled by normal Raman spectroscopy (NRS). However, more and more drugs with low API content and/or low Raman scattering coefficient were insensitive to NRS analysis, which was for the first time defined as Low API-Signal Drugs (LASIDs) in this paper. The NRS spectra of these LASIDs were similar to their dominant excipients' profiles, such as lactose, starch, microcrystalline cellulose (MCC), etc., and were classified into three types as such. 21 out of 100 kinds of drugs were screened as LASIDs and characterized further by Raman microscopic mapping. Accordingly, we proposed a tailored solution to the qualitation and quantitation problem of these LASIDs, using surface-enhanced Raman spectroscopic (SERS) detection on the thin layer chromatographic (TLC) plate both in situ and after-separation. Experimental conditions and parameters including TLC support matrix, SERS substrate, detection mode, similarity threshold, internal standard, etc., were optimized. All LASIDs were satisfactorily identified and the quantitation results agreed well with those of high performance liquid chromatography (HPLC). For some structural analogues of LASIDs, although they presented highly similar SERS spectra and were tough to distinguish even with Raman microscopic mapping, they could be successfully discriminated from each other by coupling SERS (with portable Raman spectrometer) with TLC. These results demonstrated that the proposed solution could be employed to detect the LASIDs with high accuracy and cost-effectiveness.

  20. Distinct summer and winter bacterial communities in the active layer of Svalbard permafrost revealed by DNA- and RNA-based analyses

    SciTech Connect

    Schostag, Morten; Stibal, Marek; Jacobsen, Carsten S.; Bælum, Jacob; Taş, Neslihan; Elberling, Bo; Jansson, Janet K.; Semenchuk, Philipp; Priemé, Anders

    2015-04-30

    The active layer of soil overlaying permafrost in the Arctic is subjected to dramatic annual changes in temperature and soil chemistry, which likely affect bacterial activity and community structure. We studied seasonal variations in the bacterial community of active layer soil from Svalbard (78°N) by co-extracting DNA and RNA from 12 soil cores collected monthly over a year. PCR amplicons of 16S rRNA genes (DNA) and reverse transcribed transcripts (cDNA) were quantified and sequenced to test for the effect of low winter temperature and seasonal variation in concentration of easily degradable organic matter on the bacterial communities. The copy number of 16S rRNA genes and transcripts revealed no distinct seasonal changes indicating potential bacterial activity during winter despite soil temperatures well below -10°C. Multivariate statistical analysis of the bacterial diversity data (DNA and cDNA libraries) revealed a season-based clustering of the samples, and, e.g., the relative abundance of potentially active Cyanobacteria peaked in June and Alphaproteobacteria increased over the summer and then declined from October to November. The structure of the bulk (DNA-based) community was significantly correlated with pH and dissolved organic carbon, while the potentially active (RNA-based) community structure was not significantly correlated with any of the measured soil parameters. A large fraction of the 16S rRNA transcripts was assigned to nitrogen-fixing bacteria (up to 24% in June) and phototrophic organisms (up to 48% in June) illustrating the potential importance of nitrogen fixation in otherwise nitrogen poor Arctic ecosystems and of phototrophic bacterial activity on the soil surface.

  1. Distinct summer and winter bacterial communities in the active layer of Svalbard permafrost revealed by DNA- and RNA-based analyses

    DOE PAGES

    Schostag, Morten; Stibal, Marek; Jacobsen, Carsten S.; ...

    2015-04-30

    The active layer of soil overlaying permafrost in the Arctic is subjected to dramatic annual changes in temperature and soil chemistry, which likely affect bacterial activity and community structure. We studied seasonal variations in the bacterial community of active layer soil from Svalbard (78°N) by co-extracting DNA and RNA from 12 soil cores collected monthly over a year. PCR amplicons of 16S rRNA genes (DNA) and reverse transcribed transcripts (cDNA) were quantified and sequenced to test for the effect of low winter temperature and seasonal variation in concentration of easily degradable organic matter on the bacterial communities. The copy numbermore » of 16S rRNA genes and transcripts revealed no distinct seasonal changes indicating potential bacterial activity during winter despite soil temperatures well below -10°C. Multivariate statistical analysis of the bacterial diversity data (DNA and cDNA libraries) revealed a season-based clustering of the samples, and, e.g., the relative abundance of potentially active Cyanobacteria peaked in June and Alphaproteobacteria increased over the summer and then declined from October to November. The structure of the bulk (DNA-based) community was significantly correlated with pH and dissolved organic carbon, while the potentially active (RNA-based) community structure was not significantly correlated with any of the measured soil parameters. A large fraction of the 16S rRNA transcripts was assigned to nitrogen-fixing bacteria (up to 24% in June) and phototrophic organisms (up to 48% in June) illustrating the potential importance of nitrogen fixation in otherwise nitrogen poor Arctic ecosystems and of phototrophic bacterial activity on the soil surface.« less

  2. Distinct summer and winter bacterial communities in the active layer of Svalbard permafrost revealed by DNA- and RNA-based analyses

    PubMed Central

    Schostag, Morten; Stibal, Marek; Jacobsen, Carsten S.; Bælum, Jacob; Taş, Neslihan; Elberling, Bo; Jansson, Janet K.; Semenchuk, Philipp; Priemé, Anders

    2015-01-01

    The active layer of soil overlaying permafrost in the Arctic is subjected to dramatic annual changes in temperature and soil chemistry, which likely affect bacterial activity and community structure. We studied seasonal variations in the bacterial community of active layer soil from Svalbard (78°N) by co-extracting DNA and RNA from 12 soil cores collected monthly over a year. PCR amplicons of 16S rRNA genes (DNA) and reverse transcribed transcripts (cDNA) were quantified and sequenced to test for the effect of low winter temperature and seasonal variation in concentration of easily degradable organic matter on the bacterial communities. The copy number of 16S rRNA genes and transcripts revealed no distinct seasonal changes indicating potential bacterial activity during winter despite soil temperatures well below −10°C. Multivariate statistical analysis of the bacterial diversity data (DNA and cDNA libraries) revealed a season-based clustering of the samples, and, e.g., the relative abundance of potentially active Cyanobacteria peaked in June and Alphaproteobacteria increased over the summer and then declined from October to November. The structure of the bulk (DNA-based) community was significantly correlated with pH and dissolved organic carbon, while the potentially active (RNA-based) community structure was not significantly correlated with any of the measured soil parameters. A large fraction of the 16S rRNA transcripts was assigned to nitrogen-fixing bacteria (up to 24% in June) and phototrophic organisms (up to 48% in June) illustrating the potential importance of nitrogen fixation in otherwise nitrogen poor Arctic ecosystems and of phototrophic bacterial activity on the soil surface. PMID:25983731

  3. Hydrothermal regimes of the dry active layer

    NASA Astrophysics Data System (ADS)

    Ishikawa, Mamoru; Zhang, Yinsheng; Kadota, Tsutomu; Ohata, Tetsuo

    2006-04-01

    Evaporation and condensation in the soil column clearly influence year-round nonconductive heat transfer dynamics in the dry active layer underlying semiarid permafrost regions. We deduced this from heat flux components quantified using state-of-the-art micrometeorological data sets obtained in dry and moist summers and in winters with various snow cover depths. Vapor moves easily through large pores, some of which connect to the atmosphere, allowing (1) considerable active layer warming driven by pipe-like snowmelt infiltration, and (2) direct vapor linkage between atmosphere and deeper soils. Because of strong adhesive forces, water in the dry active layer evaporates with great difficulty. The fraction of latent heat to total soil heat storage ranged from 26 to 45% in dry and moist summers, respectively. These values are not negligible, despite being smaller than those of arctic wet active layer, in which only freezing and thawing were considered.

  4. An insolation activated dust layer on Mars

    NASA Astrophysics Data System (ADS)

    de Beule, Caroline; Wurm, Gerhard; Kelling, Thorben; Koester, Marc; Kocifaj, Miroslav

    2015-11-01

    The illuminated dusty surface of Mars acts like a gas pump. It is driven by thermal creep at low pressure within the soil. In the top soil layer this gas flow has to be sustained by a pressure gradient. This is equivalent to a lifting force on the dust grains. The top layer is therefore under tension which reduces the threshold wind speed for saltation. We carried out laboratory experiments to quantify the thickness of this activated layer. We use basalt with an average particle size of 67 μm. We find a depth of the active layer of 100-200 μm. Scaled to Mars the activation will reduce threshold wind speeds for saltation by about 10%.

  5. [Two-layer adhesive film Diplen-denta C--a new compound containing polymer base and active component Solcoseryl].

    PubMed

    Abakarova, D S

    2007-01-01

    Characteristics of the main components of a new effective long-lasting dosage form--biopolymer two-layer adhesive solcoseryl containing film Diplen-denta C--are presented. It has a potent wound-healing action on oral mucosa, retains therapeutic properties during long time, is self dissolving and can be easily fixed on oral mucous membrane.

  6. Antibacterial activity of graphene layers

    NASA Astrophysics Data System (ADS)

    Dybowska-Sarapuk, Ł.; Kotela, A.; Krzemiński, J.; Janczak, D.; Wróblewska, M.; Marchel, H.; Łegorz, P.; Jakubowska, M.

    2016-09-01

    The bacterial biofilm is a direct cause of complications in management of various medical conditions. There is an ongoing search for a feasible method to prevent its growth, as an alternative to antibiotics, which are ineffective. The aim of the study was to prepare and evaluate a detailed algorithm for production of graphene coatings, using economically efficient methods of printed electronics (such as ink-jet printing or spray coating), and assess their antibacterial properties. Based on the preliminary results of our work we suggest that graphene coating may inhibit the formation of microbial biofilms. Further research is needed to verify antibacterial properties of graphene coatings and its future applications in prevention of biofilm-related infections, e.g. by coating surgical instruments, catheters or tracheostomy tubes. In addition, we propose a series of hypotheses to be evaluated in further work.

  7. InSAR analysis of surface deformation over permafrost to estimate active layer thickness based on one-dimensional heat transfer model of soils

    PubMed Central

    Li, Zhiwei; Zhao, Rong; Hu, Jun; Wen, Lianxing; Feng, Guangcai; Zhang, Zeyu; Wang, Qijie

    2015-01-01

    This paper presents a novel method to estimate active layer thickness (ALT) over permafrost based on InSAR (Interferometric Synthetic Aperture Radar) observation and the heat transfer model of soils. The time lags between the periodic feature of InSAR-observed surface deformation over permafrost and the meteorologically recorded temperatures are assumed to be the time intervals that the temperature maximum to diffuse from the ground surface downward to the bottom of the active layer. By exploiting the time lags and the one-dimensional heat transfer model of soils, we estimate the ALTs. Using the frozen soil region in southern Qinghai-Tibet Plateau (QTP) as examples, we provided a conceptual demonstration of the estimation of the InSAR pixel-wise ALTs. In the case study, the ALTs are ranging from 1.02 to 3.14 m and with an average of 1.95 m. The results are compatible with those sparse ALT observations/estimations by traditional methods, while with extraordinary high spatial resolution at pixel level (~40 meter). The presented method is simple, and can potentially be used for deriving high-resolution ALTs in other remote areas similar to QTP, where only sparse observations are available now. PMID:26480892

  8. Mesoporous layer-by-layer ordered nanohybrids of layered double hydroxide and layered metal oxide: highly active visible light photocatalysts with improved chemical stability.

    PubMed

    Gunjakar, Jayavant L; Kim, Tae Woo; Kim, Hyo Na; Kim, In Young; Hwang, Seong-Ju

    2011-09-28

    Mesoporous layer-by-layer ordered nanohybrids highly active for visible light-induced O(2) generation are synthesized by self-assembly between oppositely charged 2D nanosheets of Zn-Cr-layered double hydroxide (Zn-Cr-LDH) and layered titanium oxide. The layer-by-layer ordering of two kinds of 2D nanosheets is evidenced by powder X-ray diffraction and cross-sectional high resolution-transmission electron microscopy. Upon the interstratification process, the original in-plane atomic arrangements and electronic structures of the component nanosheets remain intact. The obtained heterolayered nanohybrids show a strong absorption of visible light and a remarkably depressed photoluminescence signal, indicating an effective electronic coupling between the two component nanosheets. The self-assembly between 2D inorganic nanosheets leads to the formation of highly porous stacking structure, whose porosity is controllable by changing the ratio of layered titanate/Zn-Cr-LDH. The resultant heterolayered nanohybrids are fairly active for visible light-induced O(2) generation with a rate of ∼1.18 mmol h(-1) g(-1), which is higher than the O(2) production rate (∼0.67 mmol h(-1) g(-1)) by the pristine Zn-Cr-LDH material, that is, one of the most effective visible light photocatalysts for O(2) production, under the same experimental condition. This result highlights an excellent functionality of the Zn-Cr-LDH-layered titanate nanohybrids as efficient visible light active photocatalysts. Of prime interest is that the chemical stability of the Zn-Cr-LDH is significantly improved upon the hybridization, a result of the protection of the LDH lattice by highly stable titanate layer. The present findings clearly demonstrate that the layer-by-layer-ordered assembly between inorganic 2D nanosheets is quite effective not only in improving the photocatalytic activity of the component semiconductors but also in synthesizing novel porous LDH-based hybrid materials with improved chemical

  9. 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.

  10. Low-Temperature Electrical Characteristics of Si-Based Device with New Tetrakis NiPc-SNS Active Layer

    NASA Astrophysics Data System (ADS)

    Yavuz, Arzu Büyükyağci; Carbas, Buket Bezgın; Sönmezoğlu, Savaş; Soylu, Murat

    2016-01-01

    A new tetrakis 4-(2,5-di-2-thiophen-2-yl-pyrrol-1-yl)-substituted nickel phthalocyanine (NiPc-SNS) has been synthesized. This synthesized NiPc-SNS thin film was deposited on p-type Si substrate using the spin coating method (SCM) to fabricate a NiPc-SNS/ p-Si heterojunction diode. The temperature-dependent electrical characteristics of the NiPc-SNS/ p-Si heterojunction with good rectifying behavior were investigated by current-voltage ( I- V) measurements between 50 K and 300 K. The results indicate that the ideality factor decreases while the barrier height increases with increasing temperature. The barrier inhomogeneity across the NiPc-SNS/ p-Si heterojunction reveals a Gaussian distribution at low temperatures. These results provide further evidence of the more complicated mechanisms occurring in this heterojunction. Based on these findings, NiPc-SNS/ p-Si junction diodes are feasible for use in low-temperature applications.

  11. Magmatic and phreatomagmatic volcanic activity at Mt. Takahe, West Antarctica, based on tephra layers in the Byrd ice core and field observations at Mt. Takahe

    NASA Astrophysics Data System (ADS)

    Palais, Julie M.; Kyle, Philip R.; McIntosh, William C.; Seward, Diane

    1988-12-01

    The morphology, grain size characteristics and composition of ash particles in 30 ka to 150 ka tephra layers from the Byrd ice core were examined to characterize the eruptions which produced them and to test the suggestion that they were erupted from Mt. Takahe, a shield volcano in Marie Byrd Land, West Antarctica. Volcanic deposits at Mt. Takahe were examined for evidence of recent activity which could correlate with the tephra layers in the ice core. Coarse- and fine-ash layers have been recognized in the Byrd ice core. The coarse-ash layers have a higher mass concentration than the fine-ash layers and are characterized by fresh glass shards > 50 μm diameter, many containing elongate pipe vesicles. The fine-ash layers have a lower mass concentration and contain a greater variety of particles, typically < 20 μm diameter. Many of these particles are aggregate grains composed of glass and crystal fragments showing S and Cl surface alteration. The grain-size distributions of the coarse and fine-ash layers overlap, in part because of the aggregate nature of grains in the fine-ash layers. The coarse-ash layers are interpreted as having formed by magmatic eruption whereas the fine-ash layers are believed to be hydrovolcanic in origin. Mt. Takahe is the favored source for the tephra because: (a) chemical analyses of samples from the volcano are distinctive, being peralkaline trachyte, and similar in composition to the analyzed tephra; (b) Mt. Takahe is a young volcano (< 0.3 Ma); (c) pyroclastic deposits on Mt. Takahe indicate styles of eruption similar to that inferred for the ice core tephra; and (d) Mt. Takahe is only about 350 km from the calculated site of tephra deposition. A speculative eruptive history for Mt. Takahe is established by combining observations from Mt. Takahe and the Byrd ice core tephra. Initial eruptions at Mt. Takahe were subglacial and then graded into alternating subaerial and subglacial activity. The tephra suggest alternating subaerial

  12. Photovoltaic cells based on ternary P3HT:PCBM:polymethine dye active layer transparent in the visible range of light

    NASA Astrophysics Data System (ADS)

    Bliznyuk, Valery N.; Gasiorowski, Jacek; Ishchenko, Alexander A.; Bulavko, Gennadiy V.; Rahaman, Mahfujur; Hingerl, Kurt; Zahn, Dietrich R. T.; Sariciftci, Niyazi S.

    2016-12-01

    Optical and photovoltaic properties were studied for ternary photovoltaic cells containing a traditional donor-acceptor bulk-heterojunction (BHJ) active layer modified with polymethine dye molecules in a broad range of compositions and wavelengths. An effect of composition induced optical transparency, due to the strong modification of the density of states, was observed for symmetrical compositions with approximately equal amount of components. Based on our spectroscopic ellipsometry and atomic force microscopy (AFM) studies we can suggest that the variation of the refractive index, which is significantly reduced in the visible range for ternary systems, is involved in the physical mechanism of the phenomenon. Despite of an addition of the IR absorbing component (which allows broadening of the absorption band to up to 800 nm) no improvement in the power conversion efficiency (PCE) is observed in comparison to the binary BHJ system (P3HT:PCBM). Nevertheless, we believe that further advance of the efficiency will be possible if the energy levels will be chemically designed to avoid formation of charge traps at the BHJ interface during light excitation. Such fine adjustment of the system should become possible with a proper choice of polymer:dye composition due to a high versatility of the polymethine dyes demonstrated in previous studies.

  13. Activation of the Solid Silica Layer of Aerosol-Based C/SiO₂ Particles for Preparation of Various Functional Multishelled Hollow Microspheres.

    PubMed

    Li, Xiangcun; Luo, Fan; He, Gaohong

    2015-05-12

    Double-shelled C/SiO2 hollow microspheres with an outer nanosheet-like silica shell and an inner carbon shell were reported. C/SiO2 aerosol particles were synthesized first by a one-step rapid aerosol process. Then the solid silica layer of the aerosol particles was dissolved and regrown on the carbon surface to obtain novel C/SiO2 double-shelled hollow microspheres. The new microspheres prepared by the facile approach possess high surface area and pore volume (226.3 m(2) g(-1), 0.51 cm(3) g(-1)) compared with the original aerosol particles (64.3 m(2) g(-1), 0.176 cm(3) g(-1)), providing its enhanced enzyme loading capacity. The nanosheet-like silica shell of the hollow microspheres favors the fixation of Au NPs (C/SiO2/Au) and prevents them from growing and migrating at 500 °C. Novel C/C and C/Au/C (C/Pt/C) hollow microspheres were also prepared based on the hollow nanostructure. C/C microspheres (482.0 m(2) g(-1), 0.92 cm(3) g(-1)) were ideal electrode materials. In particular, the Au NPs embedded into the two carbon layers (C/Au/C, 431.2 m(2) g(-1), 0.774 cm(3) g(-1)) show a high catalytic activity and extremely chemical stability even at 850 °C. Moreover, C/SiO2/Au, C/Au/C microspheres can be easily recycled and reused by an external magnetic field because of the presence of Fe3O4 species in the inner carbon shell. The synthetic route reported here is expected to simplify the fabrication process of double-shelled or yolk-shell microspheres, which usually entails multiple steps and a previously synthesized hard template. Such a capability can facilitate the preparation of various functional hollow microspheres by interfacial design.

  14. 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.

  15. 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.

  16. A novel layered bismuth-based photocatalytic material LiBi3O4Cl2 with rad OH and h+ as the active species for efficient photodegradation applications

    NASA Astrophysics Data System (ADS)

    Wang, Shuobo; Huang, Hongwei; Zhang, Yihe

    2016-12-01

    Developing new photocatalysts is of significant importance for their potential environmental and energetic applications. Herein, a novel layered bismuth-based photocatalytic material LiBi3O4Cl2 was developed by a simple solid-state reaction. The morphology, microstructures and optical properties were investigated by XRD, SEM, TEM and DRS. The band gap of LiBi3O4Cl2 has been determined to be 3.35 eV, and its ECB and EVB were also estimated. The photocatalytic property of LiBi3O4Cl2 is surveyed by oxidative decomposition of rhodamine B (RhB), methyl orange (MO), methylene blue (MB) and phenol in aqueous solution. The results demonstrated that LiBi3O4Cl2 is an efficient UV light active photocatalyst, which can destroy the contaminants with irradiation. It is also more effective in degrading pollutants than the related layered bismuth-based photocatalyst Bi4NbO8Br. The photocatalysis mechanism is detailedly investigated by active species trapping measurement and terephthalic acid photoluminescence probing technique (TA-PL). It revealed that powerful hydroxyl radicals (rad OH) and photogenerated holes (h+) are the two main active species and are responsible for the efficient degradation process. This study provides a new layered bismuth-based photocatalytic material for environmental and energetic applications.

  17. Characterization and organic electric-double-layer-capacitor application of KOH activated coal-tar-pitch-based carbons: Effect of carbonization temperature

    NASA Astrophysics Data System (ADS)

    Choi, Poo Reum; Lee, Eunji; Kwon, Soon Hyung; Jung, Ji Chul; Kim, Myung-Soo

    2015-12-01

    The present study reports the influence of pre-carbonization on the properties of KOH-activated coal tar pitch (CTP). The change of crystallinity and pore structure of pre-carbonized CTPs as well as their activated carbons (ACs) as function of pre-carbonization temperature are investigated. The crystallinity of pre-carbonized CTPs increases with increasing the carbonization temperature up to 600 °C, but a disorder occurs during the carbonization around 700 °C and an order happens gradually with increasing the carbonization temperatures in range of 800-1000 °C. The CTPs pre-carbonized at high temperatures are more difficult to be activated with KOH than those pre-carbonized at low temperatures due to the increase of micro-crystalline size and the decrease of surface functional groups. The micro-pores and meso-pores are well developed at around 1.0 nm and 2.4 nm, respectively, as the ACs are pre-carbonized at temperatures of 500-600 °C, exhibiting high specific capacitances as electrode materials for electric double layer capacitor (EDLC). Although the specific surface area (SSA) and pore volume of ACs pre-carbonized at temperatures of 900-1000 °C are extraordinary low (non-porous) as compared to those of AC pre-carbonized at 600 °C, their specific capacitances are comparable to each other. The large specific capacitances with low SSA ACs can be attributed to the structural change resulting from the electrochemical activation during the 1st charge above 2.0 V.

  18. Synthesis and characterization of novel forward osmosis membranes based on layer-by-layer assembly.

    PubMed

    Saren, Qi; Qiu, Chang Quan; Tang, Chuyang Y

    2011-06-15

    Forward osmosis (FO) has received considerable interest for water- and energy-related applications in recent years. FO does not require an applied pressure and is believed to have a low fouling tendency. However, a major challenge in FO is the lack of high performance FO membranes. In the current work, novel nanofiltration (NF)-like FO membranes with good magnesium chloride retention were synthesized using layer-by-layer (LbL) assembly. The membrane substrate was tailored (high porosity, finger-like pores, thin cross-section, and high hydrophilicity) to achieve a small structural parameter of 0.5 mm. Increasing the number of polyelectrolyte layers improved the selectivity of the LbL membranes while reducing their water permeability. The more selective membrane 6#LbL (with 6 polyelectrolyte layers) had much lower reverse solute transport compared to 3#LbL and 1#LbL. Meanwhile, the FO water flux was found to be strongly affected by both membrane water permeability and solute reverse transport. Severe solute reverse transport was observed for the active-layer-facing-draw-solution membrane orientation, likely due to the suppression of Donnan exclusion as a result of the high ionic strength of the draw solution. In contrast, the active-layer-facing-feed-solution orientation showed remarkable FO performance (15, 20, and 28 L/m².h at 0.1, 0.5, and 1.0 M MgCl₂, respectively, for membrane 3#LbL using distilled water as feed solution), superior to other NF-like FO membranes reported in the literature. To the best of the knowledge of the authors, this is the first work on the synthesis and characterization of LbL based FO membranes.

  19. Catalytically active single-atom niobium in graphitic layers

    NASA Astrophysics Data System (ADS)

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

    2013-05-01

    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.

  20. Effects of geometrical confinement in membrane pores on enzyme-based layer-by-layer assemblies

    NASA Astrophysics Data System (ADS)

    Ramírez-Wong, Diana G.; Coelho-Diogo, Cristina; Aimé, Carole; Bonhomme, Christian; Jonas, Alain M.; Demoustier-Champagne, Sophie

    2015-05-01

    Micro- and nanoporous systems incorporating bioactive molecules, such as enzymes, are very promising supports for biocatalysis. Here, we investigate the influence of geometrical confinement on the layer-by-layer (LbL) assembly of enzyme-based thin films, using the polyionic couple (chitosan/β-lactamase)n. Thin films with different number of layers were prepared on flat silicon wafers and within cylindrical submicron pores of polycarbonate membranes to determine the impact of the confinement of macromolecules on: (i) the LbL film growth, (ii) the enzyme loading, and (iii) the biocatalytic efficiency. Solid-state NMR is employed to estimate the amount of enzyme loaded in the different types of LbL films, and the enzyme activity is determined by the study of the kinetics of nitrocefin hydrolysis. Film growth and loading of enzyme occur faster in the confined medium, until pores reach saturation. Moreover, when LbL films are grown within nanopores, the weight fraction of enzyme is very high and remains constant along the build-up. Conversely, the relative amount of enzyme in flat films significantly decreases with the number of layers due to the partial exchange during the growth. Finally, our study emphasizes that the immobilization of enzymes through LbL assembly in confined media can lead to very active surfaces with a restricted number of LbL cycles.

  1. Multielectrocatalysis by layer-by-layer films based on pararosaniline and vanadium-substituted phosphomolybdate.

    PubMed

    Fernandes, Diana M; Teixeira, Alexandra; Freire, Cristina

    2015-02-10

    Hybrid multilayer films based on the two molecular species pararosaniline (PR) and Keggin-type polyoxometalate K5[PMo11VO40)] (PMo11V) were prepared on different substrates using the electrostatic layer-by-layer (LbL) self-assembly method. The film buildup, monitored by electronic spectroscopy, showed a regular stepwise growth, and X-ray photoelectron spectroscopy data confirmed the presence of both molecular components within the LbL films. Scanning electron microscopy images revealed a completely covered surface with a nonuniform distribution of film components, and atomic force microscopy images confirmed a rough surface. The film electrochemical responses and permeability were studied by cyclic voltammetry. Films revealed three Mo-based redox processes (Mo(VI) → Mo(V)) and one V-based redox process (V(V) → V(IV)) in the potential range between 0.8 and -0.4 V vs Ag/AgCl. Studies with the redox probes [Fe(CN)6](3-/4-) and [Ru(NH3)6](3+/2+) showed that the films maintain the permeability even after six bilayers. Furthermore, the {PR/PMo11V}n multilayer films exhibit excellent Mo-based electrocatalytic activity toward reduction of iodate and V-based electrocatalytic activity toward ascorbic acid oxidation, thus acting as a versatile multielectrocatalyst.

  2. 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.

  3. Optical activity of transparent polymer layers characterized by spectral means

    NASA Astrophysics Data System (ADS)

    Cosutchi, Andreea Irina; Dimitriu, Dan Gheorghe; Zelinschi, Carmen Beatrice; Breaban, Iuliana; Dorohoi, Dana Ortansa

    2015-06-01

    The method based on the channeled spectrum, validated for inorganic optical active layers, is used now to determine the optical activity of some transparent polymer solutions in different solvents. The circular birefringence, the dispersion parameter and the specific rotation were estimated in the visible range by using the measurements of wavelengths in the channeled spectra of Hydroxypropyl cellulose in water, methanol and acetic acid. The experiments showed the specific rotation dependence on the polymer concentration and also on the solvent nature. The decrease of the specific rotation in the visible range with the increase in wavelength was evidenced. The method has some advantages as the rapidity of the experiments and the large spectral range in which it can be applied. One disadvantage is the fact that the channeled spectrum does not allow to establish the rotation sense of the electric field intensity.

  4. Optimalization activity of ZnO NR/TiO2 NR-P3HT as an active layer based on hybrid bulk heterojunction on dye sensitized solar cell (DSSC)

    NASA Astrophysics Data System (ADS)

    Saputri, Liya Nikmatul Maula Zulfa; Ramelan, Ari Handono; Hanif, Qonita Awliya; Hasanah, Yesi Ihdina Fityatal; Prajanira, Lau Bekti; Wahyuningsih, Sayekti

    2016-04-01

    Dye sensitized solar cell (DSSC) with metal inorganic and conjugated organic polymer mixture, ZnO NR/TiO2 NR-P3HT as an active layer based on hybrid bulk heterojunction has been studied. The hybrid material was used to optimize DSSC performs for better efficiency than only TiO2 as an electrode. Synthesis of TiO2 nanorods (NR) was conducted by ball milling 1000 rpm for 4 hours and strong base reaction by hydrothermal process at 120 °C overnight. And the ZnO NR was synthesized from Zn(NO3)2.4H2O precusor by hydrotermal process at 90 °C for 5 hours and calcined on various temperature s of 400, 600, and 800 °C. ZnO NR was coated into an Tndium Tin Oxide (TTO) glass to collecting electron s effectively, where TiO2 NR were incorporated with poly(3 -hexylthiophene) (P3HT) on various concentration s of 5, 10, 15 mg/mL to obtain a larger surface area. Material characterization were performed by X -Ray Diffraction (XRD) and Uv-Vis spectrophotometer. For an application of DSSC were measured by T-V Keithley Multimeter and the efficiency of DSSC at various P3HT's concentrations of 5, 10, 15 mg/mL were 7.44 × 10-3, 0.0114, 0.0104, respectively. The maximum efficiency of DSSC was showed when TiO2 NR-P3HT's concentration was 10 mg/mL.

  5. Active Boundary Layer Trip for Supersonic Flows

    NASA Astrophysics Data System (ADS)

    Schloegel, F.; Panigua, G.; Tirtey, S.

    2009-01-01

    The last decade has been full of excitement and success for the hypersonic community thanks to various Scramjet ground tests and launches. These studies have shown promising potentials but the viability to perform commercial flights at Mach 8 is still to be demonstrated. An ideal Scramjet is one which is capable of self- starting over a wide range of angles of attack and Mach number. The Scramjet designer has to ensure that the boundary layer over the inlet ramp is fully turbulent where shocks impact, hence reducing the risks of chocked flow conditions. Most studies have issued the efficiency of roughness trip to trigger the boundary layer transition. At hypersonic speed, heat transfer and drag dramatically increase resulting in skin friction averaging at 40% of the overall drag. This study investigates the possibility of triggering transition using perpendicular air jets on a flat plate place in a hypersonic cross-flow. Experiments were conducted in the von Karman Institute hypersonic blow down wind tunnel H3. This facility is mounted with a Mach 6 contoured nozzles and provides flows with Reynolds number in the range of 10x106/m to 30x106/m. The model consist of a flat plate manufactured with a built -in settling chamber, equipped with a pressure tap and a thermocouple to monitor the jet conditions. A first flat plate was manufactured with a black-coated Plexiglas top, for surface heat transfer measurement using an infrared camera. On the second model, a Upilex sheet equipped with 32 thin film gages was glued, time dependent heat transfer measurements up to 60kHz. The jet injection conditions have been varied and a Mach number of 5.5 kept constant. The flow topology was investigated using fast schlieren techniques and oil flow, in order to gain a better understanding.

  6. S-Layer Based Bio-Imprinting - Synthetic S-Layer Polymers

    DTIC Science & Technology

    2015-07-09

    AFRL-OSR-VA-TR-2015-0161 S-Layer Based Bio-Imprinting - Synthetic S-Layer Polymers Dietmar Pum ZENTRUM FUER NANOBIOTECHNOLOGIE Final Report 07/09...COVERED (From - To)      01-06-2012 to 31-05-2015 4.  TITLE AND SUBTITLE S-Layer Based Bio-Imprinting - Synthetic S-Layer Polymers 5a.  CONTRACT...the reassembled S-layer protein lattice. The start of the project focused on the selection, composition and chemical modification of suitable polymers

  7. Vibration control through passive constrained layer damping and active control

    NASA Astrophysics Data System (ADS)

    Lam, Margaretha J.; Inman, Daniel J.; Saunders, William R.

    1997-05-01

    To add damping to systems, viscoelastic materials (VEM) are added to structures. In order to enhance the damping effects of the VEM, a constraining layer is attached. When this constraining layer is an active element, the treatment is called active constrained layer damping (ACLD). Recently, the investigation of ACLD treatments has shown it to be an effective method of vibration suppression. In this paper, the treatment of a beam with a separate active element and passive constrained layer (PCLD) element is investigated. A Ritz- Galerkin approach is used to obtain discretized equations of motion. The damping is modeled using the GHM method and the system is analyzed in the time domain. By optimizing on the performance and control effort for both the active and passive case, it is shown that this treatment is capable of lower control effort with more inherent damping, and is therefore a better approach to damp vibration.

  8. Kinetic-based layer response to RMPs

    NASA Astrophysics Data System (ADS)

    Callen, J. D.; Hegna, C. C.; Cole, A. J.

    2012-10-01

    Plasma toroidal rotation can prevent reconnection of resonant magnetic perturbation (RMP) fields near rational surfaces. A low collisionality kinetic toroidal model of RMP-flutter-induced electron density and thermal transport in toroidally flowing plasmas has been developed [1]. Since this electron transport is non-ambipolar, it produces a co-current toroidal torque on the plasma. This low collisionality torque differs from fluid-based cylindrical results [2] in three key ways: the effective electron collision frequency is increased because only untrapped electrons carry parallel currents, this effect increases the singular layer width, and electron temperature gradient effects are included. A Te gradient torque is caused by the parallel electron thermal force which is usually neglected in Ohm's law. It changes the perpendicular electron flow where the torque at the rational surface vanishes to where (e/Te)(dφ/dr)=dpe/dr+cTdTe/dr in which cT is 0.71 for Z=1. The cT!=0 effect moves the radial location for RMP field penetration and hence reconnection to smaller radii relative to theories [2] that neglect the thermal force.[4pt] [1] J.D. Callen, A.J. Cole and C.C. Hegna, UW-CPTC 11-15R (2012).[0pt] [2] F.L. Waelbroeck et al., Nucl. Fusion 52, 074004 (2012).

  9. Structural complexities in the active layers of organic electronics.

    PubMed

    Lee, Stephanie S; Loo, Yueh-Lin

    2010-01-01

    The field of organic electronics has progressed rapidly in recent years. However, understanding the direct structure-function relationships between the morphology in electrically active layers and the performance of devices composed of these materials has proven difficult. The morphology of active layers in organic electronics is inherently complex, with heterogeneities existing across multiple length scales, from subnanometer to micron and millimeter range. A major challenge still facing the organic electronics community is understanding how the morphology across all of the length scales in active layers collectively determines the device performance of organic electronics. In this review we highlight experiments that have contributed to the elucidation of structure-function relationships in organic electronics and also point to areas in which knowledge of such relationships is still lacking. Such knowledge will lead to the ability to select active materials on the basis of their inherent properties for the fabrication of devices with prespecified characteristics.

  10. Annual dynamics within the active layer

    SciTech Connect

    Not Available

    1991-01-01

    We have continued our meteorological and hydrologic data collection in support of our process-oriented research. The six years of data collected to date is unique in its scope and continuity in a North Hemisphere Arctic setting. This valuable data base has allowed us to further our understanding of the interconnections and interactions between the atmosphere/hydrosphere/biosphere/lithosphere. The increased understanding of the heat and mass transfer processes has allowed us to increase our model-oriented research efforts. Examples of applications are the following. (1) Spring snowmelt on the North Slope of Alaska is the dominant hydrologic event of the year. This event provides most of the moisture for use by vegetation in the spring and early summer period. The mechanisms and timing of snowmelt are important factors in predicting runoff, the migrations of birds and large mammals and the diversity of plant communities. It is important globally due to the radical and abrupt change in the surface energy balance over vast areas. (2) We were able to explore the trends and differences in the snowmelt process along a transect from the Brooks Range to the Arctic Coastal plain. Snowpack ablation was monitored at three sites. These data were analyzed along with meteorologic data at each site. The initiation of ablation was site specific being largely controlled by the complementary addition of energy from radiation and sensible heat flux.

  11. 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.

  12. pH triggered superior selective adsorption and separation of both cationic and anionic dyes and photocatalytic activity on a fully exfoliated titanate layer-natural polymer based nanocomposite.

    PubMed

    Sarkar, Amit Kumar; Saha, Arka; Panda, Asit Baran; Pal, Sagar

    2015-11-18

    A fully exfoliated titanate layer-natural polymer amylopectin based nanocomposite, with pH responsive superior selective adsorption, separation of both cationic (MB: 599 mg g(-1) at pH 9) and anionic (MO: 558 mg g(-1) at pH 3) dyes and photodegradation properties, has been realized through simultaneous in situ layered titanate formation, exfoliation and polymerization.

  13. Sensitive monitoring of photocarrier densities in the active layer of a photovoltaic device with time-resolved terahertz reflection spectroscopy

    NASA Astrophysics Data System (ADS)

    Yamashita, Genki; Matsubara, Eiichi; Nagai, Masaya; Kim, Changsu; Akiyama, Hidefumi; Kanemitsu, Yoshihiko; Ashida, Masaaki

    2017-02-01

    We demonstrate the sensitive measurement of photocarriers in an active layer of a GaAs-based photovoltaic device using time-resolved terahertz reflection spectroscopy. We found that the reflection dip caused by Fabry-Pérot interference is strongly affected by the carrier profile in the active layer of the p-i-n structure. The experimental results show that this method is suitable for quantitative evaluation of carrier dynamics in active layers of solar cells under operating conditions.

  14. A rapid, micro-scale preliminary screening method for active components in Galangal with protective effect against hydrogen peroxide induced cell apoptosis through "thin layer chromatography" and "tetrazolium-based colorimetric assay" array correspondence.

    PubMed

    Cheng, Yuan; Li, Yuanting; Li, Jin; Deng, Yifeng

    2015-05-22

    A new method has been established for rapid preliminary screening active ingredients in natural products through thin layer chromatography (TLC) array responding with tetrazolium-based colorimetric assay (MTT assay) along with post LC-MS in micro-scale. The extract of the natural product was first separated by TLC. The separated spots obtained from TLC were visualized in situ with vanillin-ethanolic sulfuric acid agent to define the array correspondence between TLC spots and 384-cell culture plate for MTT cell viability assay. The TLC spots from the replicate TLC plates were then eluted and transferred into the wells of 384-cell culture plates according to the array respondence. The TLC spots with significant antioxidant activities were further screened by MTT assay, and subsequently traced and identified by LC-MS based on the TLC-MTT assay array correspondence. This new method was successfully applied to screen active ingredients in a Chinese medicine known as Galangal. Two major inhibitors for the decline of PC12 cell survival (Galangin, m/z 269.1, and 5-hydroxy-7-(4'-hydroxy-3'-methoxyphenyl)-1-phenyl-3-heptanone, m/z 327.2) were effectively screened and identified by this method.

  15. Engineering Seismic Base Layer for Defining Design Earthquake Motion

    SciTech Connect

    Yoshida, Nozomu

    2008-07-08

    Engineer's common sense that incident wave is common in a widespread area at the engineering seismic base layer is shown not to be correct. An exhibiting example is first shown, which indicates that earthquake motion at the ground surface evaluated by the analysis considering the ground from a seismic bedrock to a ground surface simultaneously (continuous analysis) is different from the one by the analysis in which the ground is separated at the engineering seismic base layer and analyzed separately (separate analysis). The reason is investigated by several approaches. Investigation based on eigen value problem indicates that the first predominant period in the continuous analysis cannot be found in the separate analysis, and predominant period at higher order does not match in the upper and lower ground in the separate analysis. The earthquake response analysis indicates that reflected wave at the engineering seismic base layer is not zero, which indicates that conventional engineering seismic base layer does not work as expected by the term 'base'. All these results indicate that wave that goes down to the deep depths after reflecting in the surface layer and again reflects at the seismic bedrock cannot be neglected in evaluating the response at the ground surface. In other words, interaction between the surface layer and/or layers between seismic bedrock and engineering seismic base layer cannot be neglected in evaluating the earthquake motion at the ground surface.

  16. Charge storage in polymer acid-doped polyaniline-based layer-by-layer electrodes.

    PubMed

    Jeon, Ju-Won; O'Neal, Josh; Shao, Lin; Lutkenhaus, Jodie L

    2013-10-23

    Polymeric electrodes that can achieve high doping levels and store charge reversibly are desired for electrochemical energy storage because they can potentially achieve high specific capacities and energies. One such candidate is the polyaniline:poly(2-acrylamido-2-methyl-1-propanesulfonic acid) (PANI:PAAMPSA) complex, a water-processable complex obtained via template polymerization that is known to reversibly achieve high doping levels at potentials of up to 4.5 V versus Li/Li+. Here, for the first time, PANI:PAAMPSA is successfully incorporated into layer-by-layer (LbL) electrodes. This processing technique is chosen for its ability to blend species on a molecular level and its ability to conformally coat a substrate. Three different polyaniline-based LbL electrodes comprised of PANI/PAAMPSA, PANI/PANI:PAAMPSA, and linear poly(ethylenimine)/PANI:PAAMPSA are compared in terms of film growth, charge storage, and reversibility. We found that the reversibility of PANI:PAAMPSA is retained within the LbL electrodes and that the PANI/PANI:PAAMPSA electrode exhibits the best performance in terms of capacity and cycle life. These results provide general guidelines for the assembly of PANI:PAAMPSA in LbL films and also demonstrate their potential as electrochemically active components in electrodes.

  17. Low-frequency absorption using a two-layer system with active control of input impedance.

    PubMed

    Cobo, Pedro; Fernández, Alejandro; Doutres, Olivier

    2003-12-01

    Broadband noise absorption, including low frequencies, may be obtained by a hybrid passive-active two-layer system. A porous layer in front of an air layer provides passive absorption, at medium and high frequencies. Active control of the input impedance of the two-layer system yields absorption at low frequencies. The active control system can implement either pressure-release or impedance-matching conditions. A simple analytical model based upon plane waves propagating in a tube permits the comparison of both control strategies. The results of this simple model show that the pressure-release condition affords higher absorption than the impedance-matching condition for some combinations of geometrical and material parameters. Experimental results corroborate the good performance of the pressure-release condition under the prescribed geometrical setup.

  18. S-Layer-Based Nanocomposites for Industrial Applications.

    PubMed

    Raff, Johannes; Matys, Sabine; Suhr, Matthias; Vogel, Manja; Günther, Tobias; Pollmann, Katrin

    This chapter covers the fundamental aspects of bacterial S-layers: what are S-layers, what is known about them, and what are their main features that makes them so interesting for the production of nanostructures. After a detailed introduction of the paracrystalline protein lattices formed by S-layer systems in nature the chapter explores the engineering of S-layer-based materials. How can S-layers be used to produce "industry-ready" nanoscale bio-composite materials, and which kinds of nanomaterials are possible (e.g., nanoparticle synthesis, nanoparticle immobilization, and multifunctional coatings)? What are the advantages and disadvantages of S-layer-based composite materials? Finally, the chapter highlights the potential of these innovative bacterial biomolecules for future technologies in the fields of metal filtration, catalysis, and bio-functionalization.

  19. 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.

  20. 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.

  1. Spatio-temporal modeling of Active Layer Thickness

    NASA Astrophysics Data System (ADS)

    Touyz, J.; Apanasovich, T. V.; Streletskiy, D. A.; Shiklomanov, N. I.

    2015-12-01

    Arctic Regions are 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 climate and environmental changes and plays an important role in the functioning of Arctic ecosystems, planning, and economic activities. Knowledge about spatio-temporal variability of ALT is crucial for environmental and engineering applications. The objective of this study is to provide the methodology to model and estimate spatio-temporal variation in the active layer thickness (ALT) at several sites located in the Circumpolar region spanning the Alaska North Slope, and to demonstrate its use in spatio-temporal interpolation as well as time-forward prediction. In our data analysis we estimate a parametric trend and examine residuals for the presence of spatial and temporal dependence. We propose models that provide a description of residual space-time variability in ALT. Formulations that take into account interaction among spatial and temporal components are also developed. Moreover, we compare our models to naive models in which residual spatio-temporal and temporal correlations are not considered. The predicted root mean squared and absolute errors are significantly reduced when our approach is employed. While the methodology is developed in the context of ALT, it can also be applied to model and predict other environmental variables which use similar spatio-temporal sampling designs.

  2. 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.

  3. Typology of nonlinear activity waves in a layered neural continuum.

    PubMed

    Koch, Paul; Leisman, Gerry

    2006-04-01

    Neural tissue, a medium containing electro-chemical energy, can amplify small increments in cellular activity. The growing disturbance, measured as the fraction of active cells, manifests as propagating waves. In a layered geometry with a time delay in synaptic signals between the layers, the delay is instrumental in determining the amplified wavelengths. The growth of the waves is limited by the finite number of neural cells in a given region of the continuum. As wave growth saturates, the resulting activity patterns in space and time show a variety of forms, ranging from regular monochromatic waves to highly irregular mixtures of different spatial frequencies. The type of wave configuration is determined by a number of parameters, including alertness and synaptic conditioning as well as delay. For all cases studied, using numerical solution of the nonlinear Wilson-Cowan (1973) equations, there is an interval in delay in which the wave mixing occurs. As delay increases through this interval, during a series of consecutive waves propagating through a continuum region, the activity within that region changes from a single-frequency to a multiple-frequency pattern and back again. The diverse spatio-temporal patterns give a more concrete form to several metaphors advanced over the years to attempt an explanation of cognitive phenomena: Activity waves embody the "holographic memory" (Pribram, 1991); wave mixing provides a plausible cause of the competition called "neural Darwinism" (Edelman, 1988); finally the consecutive generation of growing neural waves can explain the discontinuousness of "psychological time" (Stroud, 1955).

  4. Prediction of silicon-based layered structures for optoelectronic applications.

    PubMed

    Luo, Wei; Ma, Yanming; Gong, Xingao; Xiang, Hongjun

    2014-11-12

    A method based on the particle swarm optimization algorithm is presented to design quasi-two-dimensional materials. With this development, various single-layer and bilayer materials of C, Si, Ge, Sn, and Pb were predicted. A new Si bilayer structure is found to have a more favored energy than the previously widely accepted configuration. Both single-layer and bilayer Si materials have small band gaps, limiting their usages in optoelectronic applications. Hydrogenation has therefore been used to tune the electronic and optical properties of Si layers. We discover two hydrogenated materials of layered Si8H2 and Si6H2 possessing quasidirect band gaps of 0.75 and 1.59 eV, respectively. Their potential applications for light-emitting diode and photovoltaics are proposed and discussed. Our study opened up the possibility of hydrogenated Si layered materials as next-generation optoelectronic devices.

  5. 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.

  6. Generation of a Fibrin Based Three-Layered Skin Substitute.

    PubMed

    Kober, Johanna; Gugerell, Alfred; Schmid, Melanie; Kamolz, Lars-Peter; Keck, Maike

    2015-01-01

    A variety of skin substitutes that restore epidermal and dermal structures are currently available on the market. However, the main focus in research and clinical application lies on dermal and epidermal substitutes whereas the development of a subcutaneous replacement (hypodermis) is often disregarded. In this study we used fibrin sealant as hydrogel scaffold to generate a three-layered skin substitute. For the hypodermal layer adipose-derived stem cells (ASCs) and mature adipocytes were embedded in the fibrin hydrogel and were combined with another fibrin clot with fibroblasts for the construction of the dermal layer. Keratinocytes were added on top of the two-layered construct to form the epidermal layer. The three-layered construct was cultivated for up to 3 weeks. Our results show that ASCs and fibroblasts were viable, proliferated normally, and showed physiological morphology in the skin substitute. ASCs were able to differentiate into mature adipocytes during the course of four weeks and showed morphological resemblance to native adipose tissue. On the surface keratinocytes formed an epithelial-like layer. For the first time we were able to generate a three-layered skin substitute based on a fibrin hydrogel not only serving as a dermal and epidermal substitute but also including the hypodermis.

  7. Prediction of Silicon-Based Layered Structures for Optoelectronic Applications

    NASA Astrophysics Data System (ADS)

    Luo, Wei; Ma, Yanming; Gong, Xingao; Xiang, Hongjun; CCMG Team

    2015-03-01

    A method based on the particle swarm optimization (PSO) algorithm is presented to design quasi-two-dimensional (Q2D) materials. With this development, various single-layer and bi-layer materials in C, Si, Ge, Sn, and Pb were predicted. A new Si bi-layer structure is found to have a much-favored energy than the previously widely accepted configuration. Both single-layer and bi-layer Si materials have small band gaps, limiting their usages in optoelectronic applications. Hydrogenation has therefore been used to tune the electronic and optical properties of Si layers. We discover two hydrogenated materials of layered Si8H2andSi6H2 possessing quasi-direct band gaps of 0.75 eV and 1.59 eV, respectively. Their potential applications for light emitting diode and photovoltaics are proposed and discussed. Our study opened up the possibility of hydrogenated Si layered materials as next-generation optoelectronic devices.

  8. Multilabel Image Annotation Based on Double-Layer PLSA Model

    PubMed Central

    Zhang, Jing; Li, Da; Hu, Weiwei; Chen, Zhihua; Yuan, Yubo

    2014-01-01

    Due to the semantic gap between visual features and semantic concepts, automatic image annotation has become a difficult issue in computer vision recently. We propose a new image multilabel annotation method based on double-layer probabilistic latent semantic analysis (PLSA) in this paper. The new double-layer PLSA model is constructed to bridge the low-level visual features and high-level semantic concepts of images for effective image understanding. The low-level features of images are represented as visual words by Bag-of-Words model; latent semantic topics are obtained by the first layer PLSA from two aspects of visual and texture, respectively. Furthermore, we adopt the second layer PLSA to fuse the visual and texture latent semantic topics and achieve a top-layer latent semantic topic. By the double-layer PLSA, the relationships between visual features and semantic concepts of images are established, and we can predict the labels of new images by their low-level features. Experimental results demonstrate that our automatic image annotation model based on double-layer PLSA can achieve promising performance for labeling and outperform previous methods on standard Corel dataset. PMID:24999490

  9. Capacitance of carbon-based electrical double-layer capacitors.

    PubMed

    Ji, Hengxing; Zhao, Xin; Qiao, Zhenhua; Jung, Jeil; Zhu, Yanwu; Lu, Yalin; Zhang, Li Li; MacDonald, Allan H; Ruoff, Rodney S

    2014-01-01

    Experimental electrical double-layer capacitances of porous carbon electrodes fall below ideal values, thus limiting the practical energy densities of carbon-based electrical double-layer capacitors. Here we investigate the origin of this behaviour by measuring the electrical double-layer capacitance in one to five-layer graphene. We find that the capacitances are suppressed near neutrality, and are anomalously enhanced for thicknesses below a few layers. We attribute the first effect to quantum capacitance effects near the point of zero charge, and the second to correlations between electrons in the graphene sheet and ions in the electrolyte. The large capacitance values imply gravimetric energy storage densities in the single-layer graphene limit that are comparable to those of batteries. We anticipate that these results shed light on developing new theoretical models in understanding the electrical double-layer capacitance of carbon electrodes, and on opening up new strategies for improving the energy density of carbon-based capacitors.

  10. Capacitance of carbon-based electrical double-layer capacitors

    NASA Astrophysics Data System (ADS)

    Ji, Hengxing; Zhao, Xin; Qiao, Zhenhua; Jung, Jeil; Zhu, Yanwu; Lu, Yalin; Zhang, Li Li; MacDonald, Allan H.; Ruoff, Rodney S.

    2014-02-01

    Experimental electrical double-layer capacitances of porous carbon electrodes fall below ideal values, thus limiting the practical energy densities of carbon-based electrical double-layer capacitors. Here we investigate the origin of this behaviour by measuring the electrical double-layer capacitance in one to five-layer graphene. We find that the capacitances are suppressed near neutrality, and are anomalously enhanced for thicknesses below a few layers. We attribute the first effect to quantum capacitance effects near the point of zero charge, and the second to correlations between electrons in the graphene sheet and ions in the electrolyte. The large capacitance values imply gravimetric energy storage densities in the single-layer graphene limit that are comparable to those of batteries. We anticipate that these results shed light on developing new theoretical models in understanding the electrical double-layer capacitance of carbon electrodes, and on opening up new strategies for improving the energy density of carbon-based capacitors.

  11. 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

  12. Filtered Rayleigh scattering based measurements in compressible mixing layers

    NASA Technical Reports Server (NTRS)

    Elliott, G. S.; Samimy, M.; Arnette, S. A.

    1992-01-01

    Results are presented of experiments in which a Rayleigh-scattering-based technique was used to make quantitative planar measurements in the compressible free shear layers. To this end, the absorption characteristics of the iodine molecular filter were investigated, and initial planar density measurements in M(c) = 0.51 shear layer were performed. The preliminary results presented here demonstrate the validity of the measurement technique.

  13. Graphene-based multilayers constructed from layer-by-layer self-assembly techniques.

    PubMed

    Yu, Bing; Liu, Xiaomian; Cong, Hailin; Yuan, Hua; Wang, Dong; Li, Zejing

    2014-02-01

    This paper reviews the recent research and development of graphene-based multilayers fabricated from layer-by-layer (LBL) self-assembly technique. Graphene multilayer films, due to their excellent performances and specific applications, have attracted widespread attention during recent decades. In this paper, the preparation and property of self-assembled graphene multilayer films are introduced. The application of different graphene multilayer films in transparent conducting films (TCFs), field effect transistors (FETs), lithium ion batteries (LIBs), supercapacitors, and solar cells are summarized and discussed. The perspectives for the future developments of self-assembled graphene multilayer films are proposed.

  14. Active Constrained Layer Damping of Thin Cylindrical Shells

    NASA Astrophysics Data System (ADS)

    RAY, M. C.; OH, J.; BAZ, A.

    2001-03-01

    The effectiveness of the active constrained layer damping (ACLD) treatments in enhancing the damping characteristics of thin cylindrical shells is presented. A finite element model (FEM) is developed to describe the dynamic interaction between the shells and the ACLD treatments. Experiments are performed to verify the numerical predictions. 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.

  15. 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

  16. 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.

  17. A molecular photovoltaic system based on Dawson type polyoxometalate and porphyrin formed by layer-by-layer self assembly.

    PubMed

    Ahmed, Iftikhar; Farha, Rana; Goldmann, Michel; Ruhlmann, Laurent

    2013-01-18

    Films based on electrostatic interactions between tetracationic porphyrin and Dawson type polyoxometalate are formed by the so called layer-by-layer method. Their photovoltaic performances are investigated by photocurrent transient measurements which showed significant photocurrent response.

  18. A perovskite cell with a record-high-Voc of 1.61 V based on solvent annealed CH3NH3PbBr3/ICBA active layer

    NASA Astrophysics Data System (ADS)

    Wu, Chun-Guey; Chiang, Chien-Hung; Chang, Sheng Hsiung

    2016-02-01

    A high open-circuit voltage inverted perovskite solar cell based on a CH3NH3PbBr3 absorber and ICBA acceptor is reported. The CH3NH3PbBr3 film fabricated under ambient atmosphere at a moderate temperature (~100 °C) using a two-step spin-coating method is composed of aggregated nano-grains. Upon solvent annealing of the CH3NH3PbBr3/ICBA film, the efficiency of the resulting cell increases from 1.71% to 7.50% with a remarkably high open circuit voltage (Voc) of ca. 1.60 V. ICBA acts not only as a high LUMO acceptor to realize high Voc but also as a mending agent to increase the efficiency of the cell by penetrating into the defects/voids of the CH3NH3PbBr3 film via solvent annealing as evidenced by TRPL, XPS and SEM data. Solvent annealing of the active layer was proved to be simple and effective device engineering to improve the efficiency of the perovskite cell based on a low quality film and the Voc of the inverted perovskite cell can be tuned by the LUMO level of the acceptor were revealed. The CH3NH3PbBr3/ICBA film is semi-transparent with an average 50% transmittance under visible light. The moderatetemperature processed CH3NH3PbBr3 solar cell with high Voc and a semi-transparent absorber has great potential for application as the top cell in a tandem solar cell.A high open-circuit voltage inverted perovskite solar cell based on a CH3NH3PbBr3 absorber and ICBA acceptor is reported. The CH3NH3PbBr3 film fabricated under ambient atmosphere at a moderate temperature (~100 °C) using a two-step spin-coating method is composed of aggregated nano-grains. Upon solvent annealing of the CH3NH3PbBr3/ICBA film, the efficiency of the resulting cell increases from 1.71% to 7.50% with a remarkably high open circuit voltage (Voc) of ca. 1.60 V. ICBA acts not only as a high LUMO acceptor to realize high Voc but also as a mending agent to increase the efficiency of the cell by penetrating into the defects/voids of the CH3NH3PbBr3 film via solvent annealing as evidenced by TRPL

  19. Pipe flow of pumping wet shotcrete based on lubrication layer.

    PubMed

    Chen, Lianjun; Liu, Guoming; Cheng, Weimin; Pan, Gang

    2016-01-01

    Wet shotcrete can reduce dust and improve supporting strength, however, safe and efficient pipage is a key technical part of wet shotcrete process. The paper studied the pipe flow law of wet shotcrete based on lubrication layer by build the experimental pumping circuit of wet shotcrete that can carry out a number of full-scale pumping tests. The experimental results show there was a linear relationship between pressure loss and flow rate. Combined with the Buckingham rheological equation, the computing equations of the yield shear stress and plastic viscosity were deduced through linear regression. A simple analytical method allowing for a rough estimation of the pumping pressure was proposed and used when considering the lubrication layer of wet shotcrete in pipes. In addition, two kinds of particulate distributive models were established along the time axial to analyze the formation of lubrication layer which is related with particles migration. By computational fluid dynamics simulation, the lubrication layer thickness of different mix proportions was estimated. A new method for measuring the thickness of lubrication layer was proposed to verify it by binarization processing. Finally, according to the comparative analysis of experiments, simulation and computed value, it can be seen that the lubrication layer plays a key role in the process of wet shotcrete flow and with the increase of lubrication layer thickness pipe pressure declines gradually.

  20. 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.

  1. 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.

  2. GaInN-based tunnel junctions with graded layers

    NASA Astrophysics Data System (ADS)

    Takasuka, Daiki; Akatsuka, Yasuto; Ino, Masataka; Koide, Norikatsu; Takeuchi, Tetsuya; Iwaya, Motoaki; Kamiyama, Satoshi; Akasaki, Isamu

    2016-08-01

    We demonstrated low-resistivity GaInN-based tunnel junctions using graded GaInN layers. A systematic investigation of the samples grown by metalorganic vapor phase epitaxy revealed that a tunnel junction consisting of a 4 nm both-sides graded GaInN layer (Mg: 1 × 1020 cm-3) and a 2 nm GaN layer (Si: 7 × 1020 cm-3) showed the lowest specific series resistance of 2.3 × 10-4 Ω cm2 at 3 kA/cm2 in our experiment. The InN mole fraction in the 4 nm both-sides graded GaInN layer was changed from 0 through 0.4 to 0. The obtained resistance is comparable to those of standard p-contacts with Ni/Au and MBE-grown tunnel junctions.

  3. A layer reduction based community detection algorithm on multiplex networks

    NASA Astrophysics Data System (ADS)

    Wang, Xiaodong; Liu, Jing

    2017-04-01

    Detecting hidden communities is important for the analysis of complex networks. However, many algorithms have been designed for single layer networks (SLNs) while just a few approaches have been designed for multiplex networks (MNs). In this paper, we propose an algorithm based on layer reduction for detecting communities on MNs, which is termed as LRCD-MNs. First, we improve a layer reduction algorithm termed as neighaggre to combine similar layers and keep others separated. Then, we use neighaggre to find the community structure hidden in MNs. Experiments on real-life networks show that neighaggre can obtain higher relative entropy than the other algorithm. Moreover, we apply LRCD-MNs on some real-life and synthetic multiplex networks and the results demonstrate that, although LRCD-MNs does not have the advantage in terms of modularity, it can obtain higher values of surprise, which is used to evaluate the quality of partitions of a network.

  4. Thermally stable magnetic media based on antiferromagnetically coupled layers

    NASA Astrophysics Data System (ADS)

    Fullerton, Eric E.

    2001-03-01

    The combination of signal-to-noise requirements, write field limitations, and thermal activation of small particles is thought to limit the potential areal density of longitudinal media and is commonly referred to as the "superparamagnetic limit". Recording media composed of antiferromagnetically coupled (AFC) magnetic recording layers is a promising approach to extend areal densities of longitudinal media beyond these perceived limits [1,2]. The recording medium is made up of two ferromagnetic recording layer separated by a nonmagnetic layer whose thickness is tuned to couple the layers antiferromagnetically. For such a structure, the effective areal moment density (Mrt) of the composite structure is given by the difference between the ferromagnetic layers allowing the effective magnetic thickness to scale independently of the physical thickness of the media. The resulting media appears magnetically thin while being physically thick and, thus, allows AFC media to maintain thermal stability even for low Mrt values. Experimental realization of this concept using CoPtCrB alloy layers that demonstrates thermally stable low-Mrt media suitable for high-density recording will be discussed. This work is done in collaboration with D. T. Margulies, M. E. Schabes,M. Doerner, M. Carey, B. Gurney, A. Moser, M. Best, G. Zeltzer, K. Rubin, and H. Rosen. [1]. Fullerton et al., Appl. Phys. Lett. 77, 3806 (2000). [2]. Abarra et al., Appl. Phys. Lett. 77, 2581 (2000).

  5. Active-passive hybrid vibration control study in plates using enhanced smart constrained layer damping (ESCLD) treatment

    NASA Astrophysics Data System (ADS)

    Balamurugan, V.; Narayanan, S.

    2003-10-01

    In the present paper, the active-passive hybrid vibration control performance due to Enhanced Smart Constrained Layer Damping (ESCLD) treatment as proposed by Liao and Wang on plate like structures has been considered. This treatment consists of a viscoelastic layer constrained between a smart piezoelectric layer and the base structure being controlled. Also, the smart constraining layer is clamped to the base structure. This type of damping treatment has got both active and passive component of damping. The passive damping is through cyclic shearing of viscoelastic constrained layer which is further enhanced by activating the smart piezoelectric constraining layer and the active component of the damping is through the transfer of control moments from the piezoelectric layer to the base structure through the viscoelastic layer and also bypassed through the clamps. A plate finite element has been formulated using first order shear deformation theory, including the effect of transverse shear and rotary inertia. The effect of the viscoelastic shear layer and piezoelectric constraining layer on the mass and stiffness has been included in the model. The viscoelastic shear layer is modeled usig Golla-Hughes-McTavish (GHM) method, which is a time domain approach. The clamps (edge elements) are modeled as equivalent springs connecting the smart piezoelectric constraining layer with the structure to be controlled. LQR optimal control strategy is used to obtain optimal control gains. The effect of the viscoelastic material properties (shear modulus and loss factor) on the hybrid vibration control performance is studied for both SCLD (without edge elements) and ESCLD systems.

  6. 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.

  7. Silicon-Based Optical Modulator with Ferroelectric Layer

    NASA Technical Reports Server (NTRS)

    Sheldon, Douglas

    2006-01-01

    According to a proposal, a silicon dioxide layer in a high-speed, low-power, silicon- based electro-optical modulator would be replaced by a layer of lead zirconate titanate or other ferroelectric oxide material. The purpose of this modification is to enhance the power performance and functionality of the modulator. In its unmodified form, the particular silicon- based electro-optical modulator is of an advanced design that overcomes the speed limitation of prior silicon-based electro- optical modulators. Whereas modulation frequencies of such devices had been limited to about 20 MHz, this modulator can operate at modulation frequencies as high as 1 GHz. This modulator can be characterized as a silicon-waveguide-based metal oxide/semiconductor (MOS) capacitor phase shifter in which modulation of the index of refraction in silicon is obtained by exploiting the free-charge-carrier-plasma dispersion effect. As shown in the figure, the modulator includes an n-doped crystalline silicon slab (the silicon layer of a silicon- on-insulator wafer) and a p-doped polycrystalline silicon rib with a gate oxide layer (the aforementioned silicon dioxide layer) sandwiched between them. Under accumulation conditions, the majority charge carriers in the silicon waveguide modify the index of refraction so that a phase shift is induced in the optical mode propagating in the waveguide. The advantage of using an MOS capacitor phase shifter is that it is possible to achieve high modulation speed because there are no slow carrier-generation or -recombination processes involved in the accumulation operation. The main advantage of the proposed substitution of a ferroelectric oxide layer for the silicon dioxide layer would arise from the spontaneous polarization effect of the ferroelectric layer: This spontaneous polarization would maintain accumulation conditions in the absence of applied voltage. Consequently, once the device had been switched to a given optical state, it would remain in

  8. 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.

  9. Advanced optical interference filters based on metal and dielectric layers.

    PubMed

    Begou, Thomas; Lemarchand, Fabien; Lumeau, Julien

    2016-09-05

    In this paper, we investigate the design and the fabrication of an advanced optical interference filter based on metal and dielectric layers. This filter respects the specifications of the 2016 OIC manufacturing problem contest. We study and present all the challenges and solutions that allowed achieving a low deviation between the fabricated prototype and the target.

  10. 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.

  11. Terahertz modulators based on multiple non-Bernal graphene layers

    NASA Astrophysics Data System (ADS)

    Chatzakis, Ioannis; Li, Zhen; Benderskii, Alexander; Cronin, Stephen

    2015-03-01

    We investigate a THz modulator based on a stack of disoriented the non-Bernal stacks graphene layers (GLs) grown by chemical vapor deposition method (CVD) on SiO2 substrate. The non-Bernal stacking GLs results in the electron decoupling of the GLs, higher interband absorption and exhibit the same energy spectrum of the charge carriers to that in individual GLs. The detection efficiency in room temperature is high due low probability of the high energy of the optical phonons (~ 0.2 eV) absorption. Using terahertz time- domain spectroscopy, we show that the multi graphene layers exhibit fairly high responsivity due to high quantum efficiency.

  12. Lamb waves dispersion curves for diamond based piezoelectric layered structure

    NASA Astrophysics Data System (ADS)

    Sorokin, B. P.; Kvashnin, G. M.; Telichko, A. V.; Novoselov, A. S.; Burkov, S. I.

    2016-03-01

    The presence of spurious peaks in the amplitude-frequency response of diamond based piezoelectric layered structure was shown. Excitation of such peaks results in deterioration of an useful acoustical signal. It was shown that such spurious peaks should be associated with Lamb waves in a layered structure. By means of FEM analysis, the propagation of acoustic waves of different types in the piezoelectric layered structure "Al/AlN/Mo/(100) diamond" has been investigated in detail. By analyzing the elastic displacement patterns at frequencies from 0 up to 250 MHz, a set of all the possible acoustic waves, especially Lamb modes, have been studied, and dispersive curves of phase velocity have been plotted. A revised classification of Lamb modes has been introduced.

  13. Ultrathin platinum nanowires grown on single-layered nickel hydroxide with high hydrogen evolution activity

    NASA Astrophysics Data System (ADS)

    Yin, Huajie; Zhao, Shenlong; Zhao, Kun; Muqsit, Abdul; Tang, Hongjie; Chang, Lin; Zhao, Huijun; Gao, Yan; Tang, Zhiyong

    2015-03-01

    Design and synthesis of effective electrocatalysts for hydrogen evolution reaction in alkaline environments is critical to reduce energy losses in alkaline water electrolysis. Here we report a hybrid nanomaterial comprising of one-dimensional ultrathin platinum nanowires grown on two-dimensional single-layered nickel hydroxide. Judicious surface chemistry to generate the fully exfoliated nickel hydroxide single layers is explored to be the key for controllable growth of ultrathin platinum nanowires with diameters of about 1.8 nm. Impressively, this hybrid nanomaterial exhibits superior electrocatalytic activity for hydrogen evolution reaction in alkaline solution, which outperforms currently reported catalysts, and the obviously improved catalytic stability. We believe that this work may lead towards the development of single-layered metal hydroxide-based hybrid materials for applications in catalysis and energy conversion.

  14. Improved performance of diatomite-based dental nanocomposite ceramics using layer-by-layer assembly.

    PubMed

    Lu, Xiaoli; Xia, Yang; Liu, Mei; Qian, Yunzhu; Zhou, Xuefeng; Gu, Ning; Zhang, Feimin

    2012-01-01

    To fabricate high-strength diatomite-based ceramics for dental applications, the layer-by-layer technique was used to coat diatomite particles with cationic [poly(allylamine hydrochloride)] and anionic [poly(sodium 4-styrenesulfonate)] polymers to improve the dispersion and adsorption of positively charged nano-ZrO(2) (zirconia) as a reinforcing agent. The modified diatomite particles had reduced particle size, narrower size distribution, and were well dispersed, with good adsorption of nano-ZrO(2). To determine the optimum addition levels for nano-ZrO(2), ceramics containing 0, 20, 25, 30, and 35 wt% nano-ZrO(2) were sintered and characterized by the three-point bending test and microhardness test. In addition to scanning electron microscopy, propagation phase-contrast synchrotron X-ray microtomography was used to examine the internal structure of the ceramics. The addition of 30 wt% nano-ZrO(2) resulted in the highest flexural strength and fracture toughness with reduced porosity. Shear bond strength between the core and veneer of our diatomite ceramics and the most widely used dental ceramics were compared; the shear bond strength value for the diatomite-based ceramics was found to be significantly higher than for other groups (P < 0.05). Our results show that diatomite-based nanocomposite ceramics are good potential candidates for ceramic-based dental materials.

  15. Improved performance of diatomite-based dental nanocomposite ceramics using layer-by-layer assembly

    PubMed Central

    Lu, Xiaoli; Xia, Yang; Liu, Mei; Qian, Yunzhu; Zhou, Xuefeng; Gu, Ning; Zhang, Feimin

    2012-01-01

    To fabricate high-strength diatomite-based ceramics for dental applications, the layer-by-layer technique was used to coat diatomite particles with cationic [poly(allylamine hydrochloride)] and anionic [poly(sodium 4-styrenesulfonate)] polymers to improve the dispersion and adsorption of positively charged nano-ZrO2 (zirconia) as a reinforcing agent. The modified diatomite particles had reduced particle size, narrower size distribution, and were well dispersed, with good adsorption of nano-ZrO2. To determine the optimum addition levels for nano-ZrO2, ceramics containing 0, 20, 25, 30, and 35 wt% nano-ZrO2 were sintered and characterized by the three-point bending test and microhardness test. In addition to scanning electron microscopy, propagation phase-contrast synchrotron X-ray microtomography was used to examine the internal structure of the ceramics. The addition of 30 wt% nano-ZrO2 resulted in the highest flexural strength and fracture toughness with reduced porosity. Shear bond strength between the core and veneer of our diatomite ceramics and the most widely used dental ceramics were compared; the shear bond strength value for the diatomite-based ceramics was found to be significantly higher than for other groups (P < 0.05). Our results show that diatomite-based nanocomposite ceramics are good potential candidates for ceramic-based dental materials. PMID:22619551

  16. Layer-by-layer assembly of TiO2 nanowire/carbon nanotube films and characterization of their photocatalytic activity

    NASA Astrophysics Data System (ADS)

    Darányi, Mária; Csesznok, Tamás; Kukovecz, Ákos; Kónya, Zoltán; Kiricsi, Imre; Ajayan, Pulickel M.; Vajtai, Robert

    2011-05-01

    We report on the layer-by-layer (LbL) formation of TiO2-MWNT-TiO2 coatings on quartz with either trititanate derived TiO2 nanowires or Degussa P25 as the photocatalytically active material. The optimized deposition sequence is discussed in detail and the morphology of the prepared coatings is analyzed by SEM and XRD. The heterogeneous photocatalytic performance of the coatings was tested in the methyl orange oxidation reaction. The apparent first order rate constant fell in the 0.01-0.20 h - 1 range over a 2.5 × 2.5 cm2 film depending on the type and the thickness of the titanate coating. Building a multiwall carbon nanotube layer into the middle of the layer improved the photocatalytic activity for each material for all of the studied thicknesses. P25 based films performed 2-5 times better than TiO2 nanowire films; however, the pores in the P25 based films were largely blocked because the isotropic P25 nanoparticles form closely packed layers by themselves and even more so with the comparably sized multiwall carbon nanotubes. Therefore, films derived from titanate nanowires appear to be more suitable for use as multifunctional, photocatalytically active filtration media.

  17. Layer-by-layer assembly of TiO2 nanowire/carbon nanotube films and characterization of their photocatalytic activity.

    PubMed

    Darányi, Mária; Csesznok, Tamás; Kukovecz, Akos; Kónya, Zoltán; Kiricsi, Imre; Ajayan, Pulickel M; Vajtai, Robert

    2011-05-13

    We report on the layer-by-layer (LbL) formation of TiO(2)-MWNT-TiO(2) coatings on quartz with either trititanate derived TiO(2) nanowires or Degussa P25 as the photocatalytically active material. The optimized deposition sequence is discussed in detail and the morphology of the prepared coatings is analyzed by SEM and XRD. The heterogeneous photocatalytic performance of the coatings was tested in the methyl orange oxidation reaction. The apparent first order rate constant fell in the 0.01-0.20 h(-1) range over a 2.5 × 2.5 cm(2) film depending on the type and the thickness of the titanate coating. Building a multiwall carbon nanotube layer into the middle of the layer improved the photocatalytic activity for each material for all of the studied thicknesses. P25 based films performed 2-5 times better than TiO(2) nanowire films; however, the pores in the P25 based films were largely blocked because the isotropic P25 nanoparticles form closely packed layers by themselves and even more so with the comparably sized multiwall carbon nanotubes. Therefore, films derived from titanate nanowires appear to be more suitable for use as multifunctional, photocatalytically active filtration media.

  18. Active layer hydrology in an arctic tundra ecosystem: quantifying water sources and cycling using water stable isotopes

    SciTech Connect

    Throckmorton, Heather M.; Newman, Brent D.; Heikoop, Jeffrey M.; Perkins, George B.; Feng, Xiahong; Graham, David E.; O'Malley, Daniel; Vesselinov, Velimir V.; Young, Jessica; Wullschleger, Stan D.; Wilson, Cathy J.

    2016-04-16

    Climate change and thawing permafrost in the Arctic will significantly alter landscape hydro-geomorphology and the distribution of soil moisture, which will have cascading effects on climate feedbacks (CO2 and CH4) and plant and microbial communities. Fundamental processes critical to predicting active layer hydrology are not well understood. This study applied water stable isotope techniques (δ2H and δ18O) to infer sources and mixing of active layer waters in a polygonal tundra landscape in Barrow, Alaska (USA), in August and September of 2012. Results suggested that winter precipitation did not contribute substantially to surface waters or subsurface active layer pore waters measured in August and September. Summer rain was the main source of water to the active layer, with seasonal ice melt contributing to deeper pore waters later in the season. Surface water evaporation was evident in August from a characteristic isotopic fractionation slope (δ2H vs δ18O). Freeze-out isotopic fractionation effects in frozen active layer samples and textural permafrost were indistinguishable from evaporation fractionation, emphasizing the importance of considering the most likely processes in water isotope studies, in systems where both evaporation and freeze-out occur in close proximity. The fractionation observed in frozen active layer ice was not observed in liquid active layer pore waters. Such a discrepancy between frozen and liquid active layer samples suggests mixing of meltwater, likely due to slow melting of seasonal ice. In conclusion, this research provides insight into fundamental processes relating to sources and mixing of active layer waters, which should be considered in process-based fine-scale and intermediate-scale hydrologic models.

  19. Influence Of Clear-cutting On Thermal and hydrological Regime In The Active Layer Near Yakutsk, Eastern Siberia

    NASA Astrophysics Data System (ADS)

    Iwahana, G.; Kobayashi, Y.; Machimura, T.; Fedorov, A. N.; Fukuda, M.

    2004-12-01

    Thermal and hydrological conditions in the active layer were investigated simultaneously at a mature larch forest (control site) and a cutover, which experienced clear-cutting in November 2000 during the thawing periods from 2001 to 2003, near Yakutsk, Eastern Siberia. The two sites were located about 100m apart and the cutover was formerly a part of the control larch forest site. The aims were to clarify the characteristics of heat and water budget in the active layer, and to assess the influence of clear-cutting on permafrost and active layer conditions, based on field observations at both intact and clear-cut forest. Clear-cutting enhanced ground thawing and the difference in the active layer thickness between the forest and the cutover (1-year) was 14cm. The soil water content drastically decreased at the forest, while that at the cutover was retained in during the first thawing season after clear-cutting. Marked changes in the active layer conditions were limited only to the first thawing season. The difference in the maximum thaw depth did not expand significantly in the second thawing season despite the increased ground heat flux at the cutover site. Thermal and hydrological analyses of the active layer revealed that the storage of latent heat was a predominant component in the energy balance in the active layer. Thus, the soil moisture condition, especially spring ice content in the active layer, plays an important role in controlling the energy balance of the active layer. Further increases in the maximum thaw depth at the cutover site were inhibited by the thermal inertial effect of the larger amount of ice in the second spring after disturbance.

  20. Active layer hydrology in an arctic tundra ecosystem: quantifying water sources and cycling using water stable isotopes

    DOE PAGES

    Throckmorton, Heather M.; Newman, Brent D.; Heikoop, Jeffrey M.; ...

    2016-04-16

    Climate change and thawing permafrost in the Arctic will significantly alter landscape hydro-geomorphology and the distribution of soil moisture, which will have cascading effects on climate feedbacks (CO2 and CH4) and plant and microbial communities. Fundamental processes critical to predicting active layer hydrology are not well understood. This study applied water stable isotope techniques (δ2H and δ18O) to infer sources and mixing of active layer waters in a polygonal tundra landscape in Barrow, Alaska (USA), in August and September of 2012. Results suggested that winter precipitation did not contribute substantially to surface waters or subsurface active layer pore waters measuredmore » in August and September. Summer rain was the main source of water to the active layer, with seasonal ice melt contributing to deeper pore waters later in the season. Surface water evaporation was evident in August from a characteristic isotopic fractionation slope (δ2H vs δ18O). Freeze-out isotopic fractionation effects in frozen active layer samples and textural permafrost were indistinguishable from evaporation fractionation, emphasizing the importance of considering the most likely processes in water isotope studies, in systems where both evaporation and freeze-out occur in close proximity. The fractionation observed in frozen active layer ice was not observed in liquid active layer pore waters. Such a discrepancy between frozen and liquid active layer samples suggests mixing of meltwater, likely due to slow melting of seasonal ice. In conclusion, this research provides insight into fundamental processes relating to sources and mixing of active layer waters, which should be considered in process-based fine-scale and intermediate-scale hydrologic models.« less

  1. Electrochemical double-layer capacitors based on functionalized graphene

    NASA Astrophysics Data System (ADS)

    Pope, Michael Allan

    graphene monolayers can exhibit four-fold higher double-layer capacitance than pristine graphene. High temperature annealing lowered the capacitance until it approached that of pristine graphene. An optimal level of functionalization and lattice disorder is found necessary to retain high double-layer capacitance suggesting that graphene-based materials can be chemically tailored to engineer higher capacitance electrodes. The second half of this thesis focuses on understanding the factors that control the SSA of FGS aggregates when processed into dense electrodes and the development of a new electrode fabrications strategy to improve the ion-accessible surface area of FGS-based electrodes. Using various processing conditions, it was demonstrated that aggregates can exhibit a wide range of SSAs (1 m 2/g to 1750 m2/g) accessible to the adsorption of nitrogen or methylene blue. The effects of capillary forces, van der Waals interactions and aggregation kinetics on the SSA were explored and an aggregation model was proposed to account for these effects. In order to minimize aggregation, a new strategy for preparing graphene-based electrodes for EDLCs was developed. Colloidal gels of graphene oxide in a water-ethanol-ionic liquid solution were assembled into graphene-ionic liquid laminated structures. Our process involves evaporating the solvents water and ethanol yielding a graphene oxide/ionic liquid composite, followed by thermal reduction of the graphene oxide to electrically conducting functionalized graphene. This yields an electrode in which the ionic liquid serves not only as the working electrolyte but also as a spacer to separate the graphene sheets and to increase their electrolyte-accessible surface area. Using this approach, we achieve an outstanding energy density of 17.5 Wh/kg at a gravimetric capacitance of 156 F/g and 3 V operating voltage, due to a high effective density of the active electrode material of 0.46 g/cm2. By increasing the ionic liquid content and

  2. Activity and lifetime of urease immobilized using layer-by-layer nano self-assembly on silicon microchannels.

    PubMed

    Forrest, Scott R; Elmore, Bill B; Palmer, James D

    2005-01-01

    Urease has been immobilized and layered onto the walls of manufactured silicon microchannels. Enzyme immobilization was performed using layer-by-layer nano self-assembly. Alternating layers of oppositely charged polyelectrolytes, with enzyme layers "encased" between them, were deposited onto the walls of the silicon microchannels. The polycations used were polyethylenimine (PEI), polydiallyldimethylammonium (PDDA), and polyallylamine (PAH). The polyanions used were polystyrenesulfonate (PSS) and polyvinylsulfate (PVS). The activity of the immobilized enzyme was tested by pumping a 1 g/L urea solution through the microchannels at various flow rates. Effluent concentration was measured using an ultraviolet/visible spectrometer by monitoring the absorbance of a pH sensitive dye. The architecture of PEI/PSS/PEI/urease/PEI with single and multiple layers of enzyme demonstrated superior performance over the PDDA and PAH architectures. The precursor layer of PEI/PSS demonstrably improved the performance of the reactor. Conversion rates of 70% were achieved at a residence time of 26 s, on d 1 of operation, and >50% at 51 s, on d 15 with a six-layer PEI/urease architecture.

  3. Semiconducting properties of layered cadmium sulphide-based hybrid nanocomposites

    PubMed Central

    2011-01-01

    A series of hybrid cadmium salt/cationic surfactant layered nanocomposites containing different concentrations of cadmium sulphide was prepared by exchanging chloride by sulphide ions in the layered precursor CdXx(OH)y(CnTA)z in a solid phase/gas reaction, resulting in a series of layered species exhibiting stoichiometries corresponding to CdSvXx(OH)y(CnTA)z, constituted by two-dimensional CdCl2/CdS ultra-thin sheets sandwiched between two self-assembled surfactant layers. The electronic structure of CdS in the nanocomposite is similar to that of bulk, but showing the expected features of two-dimensional confinement of the semiconductor. The nanocomposite band gap is found to depend in a non-linear manner on both the length of the hydrocarbon chain of the surfactant and the concentration of the sulphide in the inorganic sheet. The products show photocatalytic activity at least similar and usually better than that of "bulk" CdS in a factor of two. PMID:21896162

  4. Semiconducting properties of layered cadmium sulphide-based hybrid nanocomposites

    NASA Astrophysics Data System (ADS)

    López-Cabaña, Zoraya; Marfa Sotomayor Torres, Clivia; González, Guillermo

    2011-09-01

    A series of hybrid cadmium salt/cationic surfactant layered nanocomposites containing different concentrations of cadmium sulphide was prepared by exchanging chloride by sulphide ions in the layered precursor CdX x (OH) y (CnTA) z in a solid phase/gas reaction, resulting in a series of layered species exhibiting stoichiometries corresponding to CdS v X x (OH) y (CnTA) z , constituted by two-dimensional CdCl2/CdS ultra-thin sheets sandwiched between two self-assembled surfactant layers. The electronic structure of CdS in the nanocomposite is similar to that of bulk, but showing the expected features of two-dimensional confinement of the semiconductor. The nanocomposite band gap is found to depend in a non-linear manner on both the length of the hydrocarbon chain of the surfactant and the concentration of the sulphide in the inorganic sheet. The products show photocatalytic activity at least similar and usually better than that of "bulk" CdS in a factor of two.

  5. 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.

  6. 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.

  7. 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.

  8. 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.

  9. 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.

  10. The low-mode approximation for modeling of stellar activity in single-layer and two-layer media

    NASA Astrophysics Data System (ADS)

    Yukhina, Nadezhda; Popova, Helen; Potemina, Ksenia

    The cycles of solar magnetic activity are connected with a solar dynamo that operates in the convective zone. Solar dynamo mechanism is based on the combined action of the differential rotation and the alpha-effect. Application of these concepts allows us to get an oscillating solution as a wave of the toroidal field propagating from middle latitudes to the equator. We investigated the dynamo model with the meridional circulation by the low-mode approach. This approach is based on an assumption that the solar magnetic field can be described by non-linear dynamical systems with a relatively small number of parameters. Such non-linear dynamical systems are based on the equations of dynamo models. With this method dynamical systems have been built for single and double layer media and contain the meridional flow and thickness of the convection zone of the star. It was shown the possibility of coexistence of quiasi-biennial and 22-year cycle and existence of the triple cycle (quasi-biennial, 22- and hundred-year cycles). We obtained the different regimes (oscillations, vacillations, dynamo-bursts) depending on the value of the dynamo-number, the meridional circulation, and thickness of the convection zone. We discuss the features of these regimes and compare them with the observed features of evolution of the solar and geo magnetic fields. We built batterfly-diagrams for the helicity, the toroidal and poloidal magnetic field for different regimes.

  11. Finite Element Formulation and Active Vibration Control Study on Beams Using Smart Constrained Layer Damping (scld) Treatment

    NASA Astrophysics Data System (ADS)

    BALAMURUGAN, V.; NARAYANAN, S.

    2002-01-01

    This work deals with the active vibration control of beams with smart constrained layer damping (SCLD) treatment. SCLD design consists of viscoelastic shear layer sandwiched between two layers of piezoelectric sensors and actuator. This composite SCLD when bonded to a vibrating structure acts as a smart treatment. The sensor piezoelectric layer measures the vibration response of the structure and a feedback controller is provided which regulates the axial deformation of the piezoelectric actuator (constraining layer), thereby providing adjustable and significant damping in the structure. The damping offered by SCLD treatment has two components, active action and passive action. The active action is transmitted from the piezoelectric actuator to the host structure through the viscoelastic layer. The passive action is through the shear deformation in the viscoelastic layer. The active action apart from providing direct active control also adjusts the passive action by regulating the shear deformation in the structure. The passive damping component of this design eliminates spillover, reduces power consumption, improves robustness and reliability of the system, and reduces vibration response at high-frequency ranges where active damping is difficult to implement. A beam finite element model has been developed based on Timoshenko's beam theory with partially covered SCLD. The Golla-Hughes-McTavish (GHM) method has been used to model the viscoelastic layer. The dissipation co-ordinates, defined using GHM approach, describe the frequency-dependent viscoelastic material properties. Models of PCLD and purely active systems could be obtained as a special case of SCLD. Using linear quadratic regulator (LQR) optimal control, the effects of the SCLD on vibration suppression performance and control effort requirements are investigated. The effects of the viscoelastic layer thickness and material properties on the vibration control performance are investigated.

  12. Methane transport from the active layer to lakes in the Arctic using Toolik Lake, Alaska, as a case study.

    PubMed

    Paytan, Adina; Lecher, Alanna L; Dimova, Natasha; Sparrow, Katy J; Kodovska, Fenix Garcia-Tigreros; Murray, Joseph; Tulaczyk, Slawomir; Kessler, John D

    2015-03-24

    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 × 10(4) nM, 61.6 dpm⋅m(-3), and 4.5 × 10(5) dpm⋅m(-3) compared with 1.3 × 10(2) nM, 5.7 dpm⋅m(-3), and 4.4 × 10(3) 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 (r(2) > 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.

  13. 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

  14. Breakpoint Tuning in DCT-Based Nonlinear Layered Video Codecs

    NASA Astrophysics Data System (ADS)

    Cuenca, Pedro; Orozco-Barbosa, Luis; Delicado, Francisco; Garrido, Antonio

    2004-12-01

    Many studies have been conducted to evaluate the benefits of using layered video coding schemes as a means to improve the robustness of video communications systems. In this paper, we study a frame-aware nonlinear layering scheme for the transport of a DCT-based video over packet-switched networks. This scheme takes into account the relevance of the different elements of the video sequence composing the encoded video sequence. Throughout a detailed study over a large set of video streams, we show that by properly tuning the encoding parameters, it is feasible to gracefully degrade or even maintain the video quality while reducing the amount of data representing the video sequence. We then provide the major guidelines to properly tune up the encoding parameters allowing us to set the basis towards the development of more robust video communications systems.

  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. Modeling active constrained-layer damping using Golla-Hughes-McTavish approach

    NASA Astrophysics Data System (ADS)

    Lam, Margaretha J.; Saunders, William R.; Inman, Daniel J.

    1995-05-01

    Viscoelastic material (VEM) adds damping to structures. In order to enhance the damping effects of the viscoelastic material, a constraining layer is attached. If this constraining layer is a piezoelectric patch, the system is said to have active constrained layer damping (ACLD). In this paper, the damping effects due to viscoelastic material which has an active constraining layer is modeled using the Golla-Hughes-McTavish (GHM) damping method. The piezoelectric patch and structure are modeled using a Galerkin approach in order to account for the effect of the constraining layer on the beam.

  17. 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

  18. Electrokinetic microactuator arrays for active sublayer control of turbulent boundary layers

    NASA Astrophysics Data System (ADS)

    Diez-Garias, Francisco J.

    2002-09-01

    The present study has been the first to examine the electrokinetic principle as the basis for a new class of microscale actuator arrays for active sublayer control on full scale aeronautical and hydronautical vehicles under realistic operating conditions. The Helmholtz-Smoluchowski scalings that govern such electrokinetic actuator arrays show significant performance advantages from their miniaturization to the microscale. The electrokinetic microactuator arrays that are the subject of this study seek to interrupt the bursting process associated with naturally-occurring streamwise sublayer vortices in the turbulent boundary layer. Specific performance requirements for microactuator spacing, flow rate, and frequency response for active sublayer control have been determined from fundamental scaling laws for the streamwise vortical structures in the sublayer of turbulent boundary layers. In view of the inherently local nature of the sublayer dynamics, a general system architecture for microactuator arrays appropriate for active sublayer control has been developed based on the concept of relatively small and independent "unit cells", each with their own sensing, processing, and actuation capability, that greatly simplifies the sensing and processing requirements needed to achieve practical sublayer control. A fundamental three-layer design has been developed for such electrokinetic microactuator arrays, in which electrokinetic flow is induced by an impulsively applied electric field across a center layer, with a bottom layer containing an electrolyte reservoir and a common electrode, and a top layer that containing individual electrodes and lead-outs for each microactuator in the unit cell. Microfabrication techniques have been developed that permit mass production of large numbers of individual electrokinetic microactuators in unit cells on comparatively large-area tiles. Several generations of such electrokinetic microactuator arrays have been built leading to the

  19. Strain relaxation of thick (11–22) semipolar InGaN layer for long wavelength nitride-based device

    SciTech Connect

    Kim, Jaehwan; Min, Daehong; Jang, Jongjin; Lee, Kyuseung; Chae, Sooryong; Nam, Okhyun

    2014-10-28

    In this study, the properties of thick stress-relaxed (11–22) semipolar InGaN layers were investigated. Owing to the inclination of growth orientation, misfit dislocations (MDs) occurred at the heterointerface when the strain state of the (11–22) semipolar InGaN layers reached the critical point. We found that unlike InGaN layers based on polar and nonpolar growth orientations, the surface morphologies of the stress-relaxed (11–22) semipolar InGaN layers did not differ from each other and were similar to the morphology of the underlying GaN layer. In addition, misfit strain across the whole InGaN layer was gradually relaxed by MD formation at the heterointerface. To minimize the effect of surface roughness and defects in GaN layers on the InGaN layer, we conducted further investigation on a thick (11–22) semipolar InGaN layer grown on an epitaxial lateral overgrown GaN template. We found that the lateral indium composition across the whole stress-relaxed InGaN layer was almost uniform. Therefore, thick stress-relaxed (11–22) semipolar InGaN layers are suitable candidates for use as underlying layers in long-wavelength devices, as they can be used to control strain accumulation in the heterostructure active region without additional influence of surface roughness.

  20. The layer boundary effect on multi-layer mesoporous TiO2 film based dye sensitized solar cells

    DOE PAGES

    Xu, Feng; Zhu, Kai; Zhao, Yixin

    2016-10-10

    Multi-layer mesoporous TiO2 prepared by screen printing is widely used for fabrication of high-efficiency dye-sensitized solar cells (DSSCs). Here, we compare the three types of ~10 um thick mesoporous TiO2 films, which were screen printed as 1-, 2- and 4-layers using the same TiO2 nanocrystal paste. The layer boundary of the multi-layer mesoporous TiO2 films was observed in the cross-section SEM. The existence of a layer boundary could reduce the photoelectron diffusion length with the increase of layer number. However, the photoelectron diffusion lengths of the Z907 dye sensitized solar cells based on these different layered mesoporous TiO2 films aremore » all longer than the film thickness. Consequently, the photovoltaic performance seems to have little dependence on the layer number of the multi-layer TiO2 based DSSCs.« less

  1. Nanocontact based spin torque oscillators with two free layers

    NASA Astrophysics Data System (ADS)

    Soucaille, R.; Kim, J.-V.; Devolder, T.; Petit-Watelot, S.; Manfrini, M.; Van Roy, W.; Lagae, L.

    2017-03-01

    We study a spin torque oscillator based on magnetic vortices hosted by a pseudo spin valve, and generated and confined by a nanocontact configuration. In addition to the standard functioning modes of such spin torque oscillators, we present evidence for field and current conditions leading to a novel extinction regime, where the oscillator response is transiently quenched. We model the dynamics analytically for two non-interacting vortices, one in each magnetic layer. The similarity of their trajectories makes them prone to interact. We argue that they can synchronize and then follow identical orbits, which leads to the extinction of the RF voltage emission.

  2. Superconductivity in layered BiS2-based compounds

    DOE PAGES

    Yazici, D.; Jeon, I.; White, B. D.; ...

    2015-02-25

    Here, a novel family of superconductors based on BiS2-based superconducting layers were discovered in 2012. In short order, other BiS2-based superconductors with the same or related crystal structures were discovered with superconducting critical temperatures Tc of up to 10 K. Many experimental and theoretical studies have been carried out with the goal of establishing the basic properties of these new materials and understanding the underlying mechanism for superconductivity. In this selective review of the literature, we distill the central discoveries from this extensive body of work, and discuss the results from different types of experiments on these materials within themore » context of theoretical concepts and models.« less

  3. Improved color rendering of phosphor-converted white light-emitting diodes with dual-blue active layers and n-type AlGaN layer.

    PubMed

    Yan, Qi-Rong; Zhang, Yong; Li, Shu-Ti; Yan, Qi-Ang; Shi, Pei-Pei; Niu, Qiao-Li; He, Miao; Li, Guo-Ping; Li, Jun-Rui

    2012-05-01

    An InGaN/GaN blue light-emitting diode (LED) structure and an InGaN/GaN blue-violet LED structure were grown sequentially on the same sapphire substrate by metal-organic chemical vapor deposition. It was found that the insertion of an n-type AlGaN layer below the dual blue-emitting active layers showed better spectral stability at the different driving current relative to the traditional p-type AlGaN electron-blocking layer. In addition, color rendering index of a Y3Al5O12:Ce3+ phosphor-converted white LED based on a dual blue-emitting chip with n-type AlGaN reached 91 at 20 mA, and Commission Internationale de L'Eclairage coordinates almost remained at the same point from 5 to 60 mA.

  4. Model-based damage evaluation of layered CFRP structures

    NASA Astrophysics Data System (ADS)

    Munoz, Rafael; Bochud, Nicolas; Rus, Guillermo; Peralta, Laura; Melchor, Juan; Chiachío, Juan; Chiachío, Manuel; Bond, Leonard J.

    2015-03-01

    An ultrasonic evaluation technique for damage identification of layered CFRP structures is presented. This approach relies on a model-based estimation procedure that combines experimental data and simulation of ultrasonic damage-propagation interactions. The CFPR structure, a [0/90]4s lay-up, has been tested in an immersion through transmission experiment, where a scan has been performed on a damaged specimen. Most ultrasonic techniques in industrial practice consider only a few features of the received signals, namely, time of flight, amplitude, attenuation, frequency contents, and so forth. In this case, once signals are captured, an algorithm is used to reconstruct the complete signal waveform and extract the unknown damage parameters by means of modeling procedures. A linear version of the data processing has been performed, where only Young modulus has been monitored and, in a second nonlinear version, the first order nonlinear coefficient β was incorporated to test the possibility of detection of early damage. The aforementioned physical simulation models are solved by the Transfer Matrix formalism, which has been extended from linear to nonlinear harmonic generation technique. The damage parameter search strategy is based on minimizing the mismatch between the captured and simulated signals in the time domain in an automated way using Genetic Algorithms. Processing all scanned locations, a C-scan of the parameter of each layer can be reconstructed, obtaining the information describing the state of each layer and each interface. Damage can be located and quantified in terms of changes in the selected parameter with a measurable extension. In the case of the nonlinear coefficient of first order, evidence of higher sensitivity to damage than imaging the linearly estimated Young Modulus is provided.

  5. Polysaccharide-based polyelectrolytes hollow microcapsules constructed by layer-by-layer technique.

    PubMed

    Zhang, Yifeng; Chen, Cong; Wang, Jianguo; Zhang, Lina

    2013-07-25

    Two water-soluble polysaccharide derivatives, carboxymethylated and quarternized glucans (CMGP and QGP) were synthesized for the first time from water-insoluble polysaccharides (GP) extracted from Ganoderma lucidum. Hollow microspheres were constructed using electrostatic layer-by-layer (LbL) deposition of the CMGP and QGP polyelectrolytes onto colloidal ZnO particles followed by the core decomposition with an acid solution. The structures of the multilayered CMGP/QGP microspheres were investigated by transmission electron microscopy (TEM), zeta potential and dynamic light scattering (DLS). The results revealed that the multilayer thickness increased regularly from 48 to 145 nm as the number of deposited CMGP/QGP layers was increased from two to seven, and the mean increment of thickness was ∼25 nm per layer, reflecting the high regularity of the layer-by-layer assembly. This work provided an easy method to construct hollow microcapsules with biocompatibility and controlled dimensions.

  6. Boron-Based Layered Structures for Energy Storage

    SciTech Connect

    Zhao, Y.; Wei, S. H.

    2012-01-01

    Based on Density Functional Theory simulations, we have studied the boron-based graphite-like materials, i.e., LiBC and MgB2 for energy storage. First, when half of the Li-ions in the LiBC are removed, the BC layered structure is still preserved. The Li intercalation potential (equilibrium lithium-insertion voltage of 2.3-2.4 V relative to lithium metal) is significantly higher than that in graphite, allowing Li0.5BC to function as a cathode material. The reversible electrochemical reaction, LiBC = Li0.5BC + 0.5Li, enables a specific energy density of 1088 Wh/kg and a volumetric energy density of 2463 Wh/L. Second, 75% of the Mg ions in MgB2 can be removed and reversibly inserted with the layered boron structures being preserved through an in-plane topological transformation between the hexagonal lattice domains and triangular domains. The mechanism of such a charge-driven transformation originates from the versatile valence state of boron in its planar form.

  7. Imaging Layers Based on Surface-Initiated Polymers

    NASA Astrophysics Data System (ADS)

    Montague, Martha; Edwards, Erik; Nealey, Paul

    2002-03-01

    Photoresist structures at the 70 nm and 50 nm technology nodes are of molecular dimensions, and allowable tolerances and margins are of atomic dimensions. It is unclear whether current resist processing based on preferential solubility of protected or deprotected polymer molecules in aqueous base will afford the necessary process latitude at this scale. We are developing thin film imaging materials (100 to 200 nm thick) composed of polymer chains that are grafted (polymerized) directly on the surface of the substrate. These brushes have been grown from silicon wafers using "living" free radical initiators that are tethered to the surface of the wafer. We pattern this system by taking advantage of chemical amplification. An acid-labile linkage was incorporated into the tether of the polymer brush, and by using a photo acid generator we can create acid in exposed regions of our imaging layer. This strategy allows us to decouple the imaging process from the chemistry of the polymer. The resist then can be designed to optimize properties such as transparency and etch resistance. We will evaluate the imaging layers for process latitude and resolution.

  8. Layered Double Hydroxide-Based Nanocarriers for Drug Delivery

    PubMed Central

    Bi, Xue; Zhang, Hui; Dou, Liguang

    2014-01-01

    Biocompatible clay materials have attracted particular attention as the efficient drug delivery systems (DDS). In this article, we review developments in the use of layered double hydroxides (LDHs) for controlled drug release and delivery. We show how advances in the ability to synthesize intercalated structures have a significant influence on the development of new applications of these materials. We also show how modification and/or functionalization can lead to new biotechnological and biomedical applications. This review highlights the most recent progresses in research on LDH-based controlled drug delivery systems, focusing mainly on: (i) DDS with cardiovascular drugs as guests; (ii) DDS with anti-inflammatory drugs as guests; and (iii) DDS with anti-cancer drugs as guests. Finally, future prospects for LDH-based drug carriers are also discussed. PMID:24940733

  9. 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.

  10. Effects of hole-transporting layers of perovskite-based solar cells

    NASA Astrophysics Data System (ADS)

    Suzuki, Atsushi; Kida, Tomoyasu; Takagi, Tatsuru; Oku, Takeo

    2016-02-01

    Fabrication and characterization of the photovoltaic and optical properties, and microstructure of perovskite-based solar cells with lead phthalocyanine (PbPc), zinc phthalocyanine, poly[bis(4-phenyl)(2,4,6-trimethylphenyl)amine], and copper(I) thiocyanate as hole-transporting layers were investigated. X-ray diffraction analysis and energy-dispersive X-ray spectroscopy were used to identify surface morphologies of the crystal structure and the elemental composition. Introducing PbPc into perovskite solar cells extended the retaining period of photovoltaic activity and performance. The effects of the hole-transporting layer on incident photon-to-current efficiency were investigated. The energy diagram and photovoltaic mechanism of the perovskite solar cells with the hole-transporting layer are discussed.

  11. Multi-layer carbon-based coatings for field emission

    DOEpatents

    Sullivan, John P.; Friedmann, Thomas A.

    1998-01-01

    A multi-layer resistive carbon film field emitter device for cold cathode field emission applications. The multi-layered film of the present invention consists of at least two layers of a conductive carbon material, preferably amorphous-tetrahedrally coordinated carbon, where the resistivities of adjacent layers differ. For electron emission from the surface, the preferred structure can be a top layer having a lower resistivity than the bottom layer. For edge emitting structures, the preferred structure of the film can be a plurality of carbon layers, where adjacent layers have different resistivities. Through selection of deposition conditions, including the energy of the depositing carbon species, the presence or absence of certain elements such as H, N, inert gases or boron, carbon layers having desired resistivities can be produced.

  12. Multi-layer carbon-based coatings for field emission

    DOEpatents

    Sullivan, J.P.; Friedmann, T.A.

    1998-10-13

    A multi-layer resistive carbon film field emitter device for cold cathode field emission applications is disclosed. The multi-layered film of the present invention consists of at least two layers of a conductive carbon material, preferably amorphous-tetrahedrally coordinated carbon, where the resistivities of adjacent layers differ. For electron emission from the surface, the preferred structure can be a top layer having a lower resistivity than the bottom layer. For edge emitting structures, the preferred structure of the film can be a plurality of carbon layers, where adjacent layers have different resistivities. Through selection of deposition conditions, including the energy of the depositing carbon species, the presence or absence of certain elements such as H, N, inert gases or boron, carbon layers having desired resistivities can be produced. 8 figs.

  13. Hybrid pn-junction solar cells based on layers of inorganic nanocrystals and organic semiconductors: optimization of layer thickness by considering the width of the depletion region.

    PubMed

    Saha, Sudip K; Guchhait, Asim; Pal, Amlan J

    2014-03-07

    We report the formation and characterization of hybrid pn-junction solar cells based on a layer of copper diffused silver indium disulfide (AgInS2@Cu) nanoparticles and another layer of copper phthalocyanine (CuPc) molecules. With copper diffusion in the nanocrystals, their optical absorption and hence the activity of the hybrid pn-junction solar cells was extended towards the near-IR region. To decrease the particle-to-particle separation for improved carrier transport through the inorganic layer, we replaced the long-chain ligands of copper-diffused nanocrystals in each monolayer with short-ones. Under illumination, the hybrid pn-junctions yielded a higher short-circuit current as compared to the combined contribution of the Schottky junctions based on the components. A wider depletion region at the interface between the two active layers in the pn-junction device as compared to that of the Schottky junctions has been considered to analyze the results. Capacitance-voltage characteristics under a dark condition supported such a hypothesis. We also determined the width of the depletion region in the two layers separately so that a pn-junction could be formed with a tailored thickness of the two materials. Such a "fully-depleted" device resulted in an improved photovoltaic performance, primarily due to lessening of the internal resistance of the hybrid pn-junction solar cells.

  14. Ultrahigh Enzyme Activity Assembled in Layered Double Hydroxides via Mg(2+)-Allosteric Effector.

    PubMed

    Wang, Min; Huang, Shu-Wan; Xu, Dan; Bao, Wen-Jing; Xia, Xing-Hua

    2015-06-02

    It is well-known that some metal ions could be allosteric effectors of allosteric enzymes to activate/inhibit the catalytic activities of enzymes. In nanobiocatalytic systems constructed based on the positive metal ion-induced allosteric effect, the incorporated enzymes will be activated and thus exhibit excellent catalytic performance. Herein, we present an environmentally friendly strategy to construct a novel allosteric effect-based β-galactosidase/Mg-Al layered double hydroxide (β-gal/Mg-Al-LDH) nanobiocatalytic system via the delamination-reconstruction method. The intercalated β-gal in the LDH galleries changes its conformation significantly due to the Mg(2+)-induced allosteric interactions and other weak interactions, which causes the activation of enzymatic activity. The β-gal/Mg-Al-LDH nanobiocatalytic system shows much higher catalytic activity and affinity toward its substrate and about 30 times higher catalytic reaction velocity than the free β-gal, which suggests that Mg(2+)-induced allosteric effect plays a vital role in the improvement of enzymatic performance.

  15. 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.

  16. 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

  17. Photoelectrochemical, photophysical and morphological studies of electrostatic layer-by-layer thin films based on poly(p-phenylenevinylene) and single-walled carbon nanotubes.

    PubMed

    Almeida, L C P; Zucolotto, V; Domingues, R A; Atvars, T D Z; Nogueira, A F

    2011-11-01

    The preparation of multilayer films based on poly(p-phenylenevinylene) (PPV) and carboxylic-functionalized single-walled carbon nanotubes (SWNT-COOH) by electrostatic interaction using the layer-by-layer (LbL) deposition method is reported herein. The multilayer build-up, monitored by UV-Vis and photoluminescence (PL) spectroscopies, displayed a linear behavior with the number of PPV and SWNT-COOH layers deposited that undergo deviation and spectral changes for thicker films. Film morphology was evaluated by AFM and epifluorescence microscopies showing remarkable changes after incorporation of SWNT-COOH layers. Films without SWNT show roughness and present dispersed grains; films with SWNT-COOH layers are flatter and some carbon nanotube bundles can be visualized. The photoinduced charge transfer from the conducting polymer to SWNT-COOH was analyzed by PL quenching either by the decrease of the emission intensity or by the presence of dark domains in the epifluorescence micrographs. Photoelectrochemical characterization was performed under white light and the films containing SWNT-COOH displayed photocurrent values between 2.0 μA cm(-2) and 7.5 μA cm(-2), as the amount of these materials increases in the film. No photocurrent was observed for the film without carbon nanotubes. Photocurrent generation was enhanced and became more stable when an intermediate layer of PEDOT:PSS was interposed between the active layer and the ITO electrode, indicating an improvement in hole transfer to the contacts. Our results indicate that these multilayer films are promising candidates as active layers for organic photovoltaic cells.

  18. A modified soil water based Richards equation for layered soils

    NASA Astrophysics Data System (ADS)

    Kalinka, F.; Ahrens, B.

    2010-09-01

    Most Soil-Vegetation-Atmosphere-Transfer (SVAT) models like TERRA-ML (implemented e.g. in the CCLM model (www.clm-community.eu)) use the soil moisture based Richards equation to simulate vertical water fluxes in soils, assuming a homogeneous soil type. Recently, high-resolution soil type datasets (e.g. BüK 1000, only for Germany (Federal Institute for Geosciences and Natural Resources, BGR, www.bgr.bund.de) or Harmonized World Soil Database (HWSD, version 1.1, FAO/IIASA/ISRIC/ISSCAS/JRC, March 2009)) have been developed. Deficiencies in the numerical solution of the soil moisture based Richards equation may occur if inhomogeneous soil type data is implemented, because there are possibly discontinuities in soil moisture due to various soil type characteristics. One way to fix this problem is to use the potential based Richards equation, but this may lead to problems in conservation of mass. This presentation will suggest a possible numerical solution of the soil moisture based Richards equation for inhomogeneous soils. The basic idea is to subtract the equilibrium state of it from soil moisture fluxes. This should reduce discontinuities because each soil layer aspires the equilibrium state and therefore differences might be of the same order. First sensitivity studies have been done for the Main river basin, Germany.

  19. Morphology development of layered silicate epoxy based nanocomposites

    NASA Astrophysics Data System (ADS)

    Benson Tolle, Tia

    2005-07-01

    Nanotailoring of polymeric materials offers significant benefits in terms of new and improved properties or new property trade spaces. Significant improvements to thermoplastics have been demonstrated over the past decade stimulated by the pioneering work of Kojima, Usuki, and Okada. The ability to nanotailor epoxy-based composites could have significant payoffs to aerospace and non-aerospace applications. However the dynamic nature of a crosslinking system such as epoxies poses unique challenges to the development of controlled morphologies. Before ultimate control of morphology and material design towards property enhancements can occur, fundamental understanding of how morphologies of various scales develop with processing parameters must be developed. This dissertation summarizes the effects of various processing variables on the development of morphology within organically modified layered silicate-epoxy-amine materials. The effect of various morphologies on fracture behavior is also examined, and suggests that ordered morphologies on the nanoscale can provide for effective toughening of epoxies.

  20. Limiting factors for carbon based chemical double layer capacitors

    NASA Technical Reports Server (NTRS)

    Rose, M. Frank; Johnson, C.; Owens, T.; Stevens, B.

    1993-01-01

    The Chemical Double Layer (CDL) capacitor improves energy storage density dramatically when compared with conventional electrolytic capacitors. When compared to batteries, the CDL Capacitor is much less energy dense; however, the power density is orders of magnitude better. As a result, CDL-battery combinations present an interesting pulse power system with many potential applications. Due to the nature of the CDL it is inherently a low voltage device. The applications of the CDL can be tailored to auxiliary energy and burst mode storages which require fast charge/discharge cycles. Typical of the applications envisioned are power system backup, directed energy weapons concepts, electric automobiles, and electric actuators. In this paper, we will discuss some of the general characteristics of carbon-based CDL technology describing the structure, performance parameters, and methods of construction. Further, analytical and experimental results which define the state of the art are presented and described in terms of impact on applications.

  1. 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.

  2. Q-learning-based cross-layer Learning Engine design for cognitive radio network

    NASA Astrophysics Data System (ADS)

    Liu, Congbin; Jiang, Hong; Yang, Yanchao; Ma, Jinghui

    2013-03-01

    In cognitive radio (CR) networks, Learning Engine has considerable significance on dynamic spectrum access (DSA) and implementation of cognitive function. In this paper, a cross-layer learning engine design scheme is proposed by jointly considering physical-layer dynamic channel selection, modulation and coding scheme, data-link layer frame length in CR networks, with the purpose to maximize system throughput and simultaneously meet heterogeneous Quality of Service (QoS) requirements. The wireless fading channel is modeled as a continuous state space Markov decision process (MDP) and the licensed network activity is abstracted as a finite-state one. We introduce Q-learning algorithm to realize the function of learning from state space and adapt wireless environment. And meanwhile a large scale Qfunction approximator based on support vector machine (SVM) is employed to effectively reduce storage requirement and decrease the operation complexity. A cross-layer learning engine communication platform is realized by using Matlab simulator. the simulation results demonstrate that while lacking system prior knowledge, the learning engine can effectively achieve configuration function by system cross-layer learning approach, and furthermore, it can converge to the best—i.e., realize reconfiguration function in CR networks while meeting users' QoS.

  3. Gate-Induced Superconductivity in Layered-Material-Based Electric Double Layer Transistors

    NASA Astrophysics Data System (ADS)

    Ye, J. T.; Zhang, Y. J.; Matsuhashi, Y.; Craciun, M. F.; Russo, S.; Kasahara, Y.; Morpurgo, A. F.; Iwasa, Y.

    2012-12-01

    High carrier density part of many materials could be accessed by a variation of the field effect transistor technique: electric double layer transistor. Carrier density regime of n~1014 cm-2 can be easily accessed electrostatically realizing effective doping without chemical modification. In this study, we utilized micro-cleavage on a number of interesting layered materials. And realized high carrier density state and high performance transport on atomically flat surfaces.

  4. Ground-based lidar for atmospheric boundary layer ozone measurements.

    PubMed

    Kuang, Shi; Newchurch, Michael J; Burris, John; Liu, Xiong

    2013-05-20

    Ground-based lidars are suitable for long-term ozone monitoring as a complement to satellite and ozonesonde measurements. However, current ground-based lidars are unable to consistently measure ozone below 500 m above ground level (AGL) due to both engineering issues and high retrieval sensitivity to various measurement errors. In this paper, we present our instrument design, retrieval techniques, and preliminary results that focus on the high-temporal profiling of ozone within the atmospheric boundary layer (ABL) achieved by the addition of an inexpensive and compact mini-receiver to the previous system. For the first time, to the best of our knowledge, the lowest, consistently achievable observation height has been extended down to 125 m AGL for a ground-based ozone lidar system. Both the analysis and preliminary measurements demonstrate that this lidar measures ozone with a precision generally better than ±10% at a temporal resolution of 10 min and a vertical resolution from 150 m at the bottom of the ABL to 550 m at the top. A measurement example from summertime shows that inhomogeneous ozone aloft was affected by both surface emissions and the evolution of ABL structures.

  5. Ground-Based Lidar for Atmospheric Boundary Layer Ozone Measurements

    NASA Technical Reports Server (NTRS)

    Kuang, Shi; Newchurch, Michael J.; Burris, John; Liu, Xiong

    2013-01-01

    Ground-based lidars are suitable for long-term ozone monitoring as a complement to satellite and ozonesonde measurements. However, current ground-based lidars are unable to consistently measure ozone below 500 m above ground level (AGL) due to both engineering issues and high retrieval sensitivity to various measurement errors. In this paper, we present our instrument design, retrieval techniques, and preliminary results that focus on the high-temporal profiling of ozone within the atmospheric boundary layer (ABL) achieved by the addition of an inexpensive and compact mini-receiver to the previous system. For the first time, to the best of our knowledge, the lowest, consistently achievable observation height has been extended down to 125 m AGL for a ground-based ozone lidar system. Both the analysis and preliminary measurements demonstrate that this lidar measures ozone with a precision generally better than 10% at a temporal resolution of 10 min and a vertical resolution from 150 m at the bottom of the ABL to 550 m at the top. A measurement example from summertime shows that inhomogeneous ozone aloft was affected by both surface emissions and the evolution of ABL structures.

  6. Methods of Fabricating a Layer of Metallic Glass-Based Material Using Immersion and Pouring Techniques

    NASA Technical Reports Server (NTRS)

    Hofmann, Douglas (Inventor)

    2015-01-01

    Systems and methods in accordance with embodiments of the invention implement layers of metallic glass-based materials. In one embodiment, a method of fabricating a layer of metallic glass includes: applying a coating layer of liquid phase metallic glass to an object, the coating layer being applied in a sufficient quantity such that the surface tension of the liquid phase metallic glass causes the coating layer to have a smooth surface; where the metallic glass has a critical cooling rate less than 1000 K/s; and cooling the coating layer of liquid phase metallic glass to form a layer of solid phase metallic glass.

  7. 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.

  8. -Ti-Based Homogeneous and Bi-layered Composites

    NASA Astrophysics Data System (ADS)

    Gupta, Neha; Parameswaran, Venkitanarayanan; Basu, Bikramjit

    2014-09-01

    The growing threats due to increased use of small-caliber armor piercing projectiles demand the development of new light-weight body armor materials. In this context, TiB2 appears to be a promising ceramic material. However, poor sinterability and low fracture toughness remain two major issues for TiB2. In order to address these issues together, Ti as a sinter-aid is used to develop TiB2-( x wt pct Ti), ( x = 10, 20) homogeneous composites and a bi-layered composite (BLC) with each layer having Ti content of 10 and 20 wt pct. The present study uniquely demonstrates the efficacy of two-stage spark plasma sintering route to develop dense TiB2-Ti composites with an excellent combination of nanoscale hardness (~36 GPa) and indentation fracture toughness (~12 MPa m1/2). In case of BLC, these properties are not compromised w.r.t. homogeneous composites, suggesting the retention of baseline material properties even in the bi-layer design due to optimal relief of residual stresses. The better indentation toughness of TiB2-(10 wt pct Ti) and TiB2-(20 wt pct Ti) composites can be attributed to the observed crack deflection/arrest, indicating better damage tolerance. Transmission electron microscope investigation reveals the presence of dense dislocation networks and deformation twins in α-Ti at the grain boundaries and triple pockets, surrounded by TiB2 grains. The dynamic strength of around 4 GPa has been measured using Split Hopkinson Pressure Bar tests in a reproducible manner at strain rates of the order of 600 s-1. The damage progression under high strain rate has been investigated by acquiring real time images for the entire test duration using ultra-high speed imaging. An attempt has been made to establish microstructure-property correlation and a simple analysis based on Mohr-Coulomb theory is used to rationalize the measured strength properties.

  9. Orexin-dependent activation of layer VIb enhances cortical network activity and integration of non-specific thalamocortical inputs.

    PubMed

    Hay, Y Audrey; Andjelic, Sofija; Badr, Sammy; Lambolez, Bertrand

    2015-11-01

    Neocortical layer VI is critically involved in thalamocortical activity changes during the sleep/wake cycle. It receives dense projections from thalamic nuclei sensitive to the wake-promoting neuropeptides orexins, and its deepest part, layer VIb, is the only cortical lamina reactive to orexins. This convergence of wake-promoting inputs prompted us to investigate how layer VIb can modulate cortical arousal, using patch-clamp recordings and optogenetics in rat brain slices. We found that the majority of layer VIb neurons were excited by nicotinic agonists and orexin through the activation of nicotinic receptors containing α4-α5-β2 subunits and OX2 receptor, respectively. Specific effects of orexin on layer VIb neurons were potentiated by low nicotine concentrations and we used this paradigm to explore their intracortical projections. Co-application of nicotine and orexin increased the frequency of excitatory post-synaptic currents in the ipsilateral cortex, with maximal effect in infragranular layers and minimal effect in layer IV, as well as in the contralateral cortex. The ability of layer VIb to relay thalamocortical inputs was tested using photostimulation of channelrhodopsin-expressing fibers from the orexin-sensitive rhomboid nucleus in the parietal cortex. Photostimulation induced robust excitatory currents in layer VIa neurons that were not pre-synaptically modulated by orexin, but exhibited a delayed, orexin-dependent, component. Activation of layer VIb by orexin enhanced the reliability and spike-timing precision of layer VIa responses to rhomboid inputs. These results indicate that layer VIb acts as an orexin-gated excitatory feedforward loop that potentiates thalamocortical arousal.

  10. Diffusion-Based Design of Multi-Layered Ophthalmic Lenses for Controlled Drug Release.

    PubMed

    Pimenta, Andreia F R; Serro, Ana Paula; Paradiso, Patrizia; Saramago, Benilde; Colaço, Rogério

    2016-01-01

    The study of ocular drug delivery systems has been one of the most covered topics in drug delivery research. One potential drug carrier solution is the use of materials that are already commercially available in ophthalmic lenses for the correction of refractive errors. In this study, we present a diffusion-based mathematical model in which the parameters can be adjusted based on experimental results obtained under controlled conditions. The model allows for the design of multi-layered therapeutic ophthalmic lenses for controlled drug delivery. We show that the proper combination of materials with adequate drug diffusion coefficients, thicknesses and interfacial transport characteristics allows for the control of the delivery of drugs from multi-layered ophthalmic lenses, such that drug bursts can be minimized, and the release time can be maximized. As far as we know, this combination of a mathematical modelling approach with experimental validation of non-constant activity source lamellar structures, made of layers of different materials, accounting for the interface resistance to the drug diffusion, is a novel approach to the design of drug loaded multi-layered contact lenses.

  11. Diffusion-Based Design of Multi-Layered Ophthalmic Lenses for Controlled Drug Release

    PubMed Central

    Pimenta, Andreia F. R.; Serro, Ana Paula; Paradiso, Patrizia; Saramago, Benilde

    2016-01-01

    The study of ocular drug delivery systems has been one of the most covered topics in drug delivery research. One potential drug carrier solution is the use of materials that are already commercially available in ophthalmic lenses for the correction of refractive errors. In this study, we present a diffusion-based mathematical model in which the parameters can be adjusted based on experimental results obtained under controlled conditions. The model allows for the design of multi-layered therapeutic ophthalmic lenses for controlled drug delivery. We show that the proper combination of materials with adequate drug diffusion coefficients, thicknesses and interfacial transport characteristics allows for the control of the delivery of drugs from multi-layered ophthalmic lenses, such that drug bursts can be minimized, and the release time can be maximized. As far as we know, this combination of a mathematical modelling approach with experimental validation of non-constant activity source lamellar structures, made of layers of different materials, accounting for the interface resistance to the drug diffusion, is a novel approach to the design of drug loaded multi-layered contact lenses. PMID:27936138

  12. A two-layered classifier based on the radial basis function for the screening of thalassaemia.

    PubMed

    Masala, G L; Golosio, B; Cutzu, R; Pola, R

    2013-11-01

    The thalassaemias are blood disorders with hereditary transmission. Their distribution is global, with particular incidence in areas affected by malaria. Their diagnosis is mainly based on haematologic and genetic analyses. The aim of this study was to differentiate between persons with the thalassaemia trait and normal subjects by inspecting characteristics of haemochromocytometric data. The paper proposes an original method that is useful in screening activity for thalassaemia classification. A complete working system with a friendly graphical user interface is presented. A unique feature of the presented work is the adoption of a two-layered classification system based on Radial basis function, which improves the performance of the system.

  13. Enhancement of Exciton Emission in Lead Halide-Based Layered Perovskites by Cation Mixing.

    PubMed

    Era, Masanao; Komatsu, Yumeko; Sakamoto, Naotaka

    2016-04-01

    Spin-coated films of a lead halide, PbX: X = I and Br, layered perovskites having cyclohexenylethyl ammonium molecule as an organic layer, which were mixed with other metal halide-based layered perovskites consisting of various divalent metal halides (for example, Ca2, Cdl2, FeI2, SnBr2 and so on), were prepared. The results of X-ray diffraction measurements exhibited that solid solution formation between PbX-based layered perovskite and other divalent metal halide-based layered perovskites was observed up to very high molar concentration of 50 molar% in the mixed film samples when divalent cations having ionic radius close to that of Pb2+ were employed. In the solid solution films, the exciton emission was much enhanced at room temperature. Exciton emission intensity of Pbl-based layered perovskite mixed with Cal-based layered perovskite (20 molar%) is about 5 times large that of the pristine Pbl-based layered perovskite, and that of PbBr-based layered perovskite mixed with SnBr-based layered perovskite (20 molar%) was also about 5 times large that of the pristine PbBr-based layered perovskite at room temperature.

  14. 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.

  15. Quantitative Collection and Enzymatic Activity of Glucose Oxidase Nanotubes Fabricated by Templated Layer-by-Layer Assembly.

    PubMed

    Zhang, Shouwei; Demoustier-Champagne, Sophie; Jonas, Alain M

    2015-08-10

    We report on the fabrication of enzyme nanotubes in nanoporous polycarbonate membranes via the layer-by-layer (LbL) alternate assembly of polyethylenimine (PEI) and glucose oxidase (GOX), followed by dissolution of the sacrificial template in CH2Cl2, collection, and final dispersion in water. An adjuvant-assisted filtration methodology is exploited to extract quantitatively the nanotubes without loss of activity and morphology. Different water-soluble CH2Cl2-insoluble adjuvants are tested for maximal enzyme activity and nanotube stability; whereas NaCl disrupts the tubes by screening electrostatic interactions, the high osmotic pressure created by fructose also contributes to loosening the nanotubular structures. These issues are solved when using neutral, high molar mass dextran. The enzymatic activity of intact free nanotubes in water is then quantitatively compared to membrane-embedded nanotubes, showing that the liberated nanotubes have a higher catalytic activity in proportion to their larger exposed surface. Our study thus discloses a robust and general methodology for the fabrication and quantitative collection of enzymatic nanotubes and shows that LbL assembly provides access to efficient enzyme carriers for use as catalytic swarming agents.

  16. Methacrylate-based monolithic layers for planar chromatography of polymers.

    PubMed

    Maksimova, E F; Vlakh, E G; Tennikova, T B

    2011-04-29

    A series of macroporous monolithic methacrylate-based materials was synthesized by in situ free radical UV-initiated copolymerization of functional monomers, such as glycidyl methacrylate (GMA), butyl methacrylate (BuMA), 2-aminoethyl methacrylate (AEMA), 2-hydroxyethyl methacrylate (HEMA) and 2-cyanoethyl methacrylate (CEMA), with crosslinking agent, namely, ethylene glycol dimethacrylate (EDMA). The materials obtained were applied as the stationary phases in simple and robust technique - planar chromatography (PLC). The method of separation layer fabrication representing macroporous polymer monolith bound to the specially prepared glass surface was developed and optimized. The GMA-EDMA and BuMA-EDMA matrixes were successfully applied for the separation of low molecular weight compounds (the mixture of several dies), as well as poly(vinylpyrrolidone) and polystyrene homopolymers of different molecular weights using reversed-phase mechanism. The materials based on copolymers AEMA-HEMA-EDMA and CEMA-HEMA-EDMA were used for normal-phase PLC separation of 2,4-dinitrophenyl amino acids and polystyrene standards.

  17. Lipid Layer-based Corrosion Monitoring on Metal Substrates

    DTIC Science & Technology

    2013-04-01

    explore lipid layers as a potential biosensor for corrosion. It is hypothesized that applying a lipid layer to metals will allow for corrosion monitoring...Corrosion monitoring, lipid layers, biosensor 16. SECURITY CLASSIFICATION OF: 17. LIMITATION OF ABSTRACT UU 18. NUMBER OF PAGES 14 19a...occurs as the material’s surface is oxidized in an electrochemical reaction, commonly in the presence of oxygen and water, which initially causes

  18. Amperometric glucose biosensor based on layer-by-layer covalent attachment of AMWNTs and IO(4)(-)-oxidized GOx.

    PubMed

    Sun, Yingying; Wang, Haiying; Sun, Changqing

    2008-09-15

    Multi-wall carbon nanotubes (MWNTs) functionalized with amino groups were prepared via silane treatment using 3-aminopropyltrimethoxysilane (APS) as a silane-coupling agent. The resultant amino terminated MWNTs (AMWNTs) were applied to construct glucose biosensors with IO(4)(-)-oxidized glucose oxidase (IO(4)(-)-oxidized GOx) through the layer-by-layer (LBL) covalent self-assembly method without any cross-linker. Scanning electron microscopy (SEM) indicated that the assembled AMWNTs were almost in a form of small bundles or single nanotubes, and the surface density increased uniformly with the number of GOx/AMWNTs bilayers. From the analysis of voltammetric signals, a linear increment of the coverage of GOx per bilayer was estimated. The resulting biosensor showed excellent catalytic activity towards the electroreduction of dissolved oxygen at low overvoltage, based on which glucose concentration was monitored conveniently. The enzyme electrode exhibited good electrocatalytic response towards the glucose and that response increased with the number of GOx/AMWNTs bilayers, suggesting that the analytical performance such as sensitivity and detection limit of the glucose biosensors could be tuned to the desired level by adjusting the number of deposited GOx/AMWNTs bilayers. The biosensor constructed with four bilayers of GOx/AMWNTs showed high sensitivity of 7.46 microA mM(-1)cm(-2) and the detection limit of 8.0 microM, with a fast response less than 10s. Because of relative low applied potential, the interference from other electro-oxidizable compounds was minimized, which improved the selectivity of the biosensors. Furthermore, the obtained enzyme electrodes also showed remarkable stability due to the covalent interaction between the GOx and AMWNTs.

  19. A new generation of electrochemical supercapacitors based on layer-by-layer polymer films

    NASA Astrophysics Data System (ADS)

    Christinelli, Wania Ap.; Gonçalves, Roger; Pereira, Ernesto C.

    2016-01-01

    Here we report supercapacitors fabricated with the layer-by-layer (LBL) technique using two polymers, namely poly(o-methoxyaniline) (POMA) and poly(3-thiophene acetic acid) (PTAA). The electrochemical performances of POMA/PTAA supercapacitors were characterized by cyclic voltammetry and electrochemical impedance spectroscopy. The results were compared with POMA casting film. The specific capacitance of LBL films increases almost linearly with a number of bilayers which were not observed for POMA casting films. The results of this investigation demonstrate that the self-doping effect between POMA and PTAA can change the properties on films and can be successfully used as a supercapacitor technology.

  20. 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.

  1. Pervaporation dehydration of ethanol by hyaluronic acid/sodium alginate two-active-layer composite membranes.

    PubMed

    Gao, Chengyun; Zhang, Minhua; Ding, Jianwu; Pan, Fusheng; Jiang, Zhongyi; Li, Yifan; Zhao, Jing

    2014-01-01

    The composite membranes with two-active-layer (a capping layer and an inner layer) were prepared by sequential spin-coatings of hyaluronic acid (HA) and sodium alginate (NaAlg) on the polyacrylonitrile (PAN) support layer. The SEM showed a mutilayer structure and a distinct interface between the HA layer and the NaAlg layer. The coating sequence of two-active-layer had an obvious influence on the pervaporation dehydration performance of membranes. When the operation temperature was 80 °C and water concentration in feed was 10 wt.%, the permeate fluxes of HA/Alg/PAN membrane and Alg/HA/PAN membrane were similar, whereas the separation factor were 1130 and 527, respectively. It was found that the capping layer with higher hydrophilicity and water retention capacity, and the inner layer with higher permselectivity could increase the separation performance of the composite membranes. Meanwhile, effects of operation temperature and water concentration in feed on pervaporation performance as well as membrane properties were studied.

  2. Soil moisture redistribution and its effect on inter-annual active layer temperature and thickness variations in a dry loess terrace in Adventdalen, Svalbard

    NASA Astrophysics Data System (ADS)

    Schuh, Carina; Frampton, Andrew; Hvidtfeldt Christiansen, Hanne

    2017-02-01

    High-resolution field data for the period 2000-2014 consisting of active layer and permafrost temperature, active layer soil moisture, and thaw depth progression from the UNISCALM research site in Adventdalen, Svalbard, is combined with a physically based coupled cryotic and hydrogeological model to investigate active layer dynamics. The site is a loess-covered river terrace characterized by dry conditions with little to no summer infiltration and an unsaturated active layer. A range of soil moisture characteristic curves consistent with loess sediments is considered and their effects on ice and moisture redistribution, heat flux, energy storage through latent heat transfer, and active layer thickness is investigated and quantified based on hydro-climatic site conditions. Results show that soil moisture retention characteristics exhibit notable control on ice distribution and circulation within the active layer through cryosuction and are subject to seasonal variability and site-specific surface temperature variations. The retention characteristics also impact unfrozen water and ice content in the permafrost. Although these effects lead to differences in thaw progression rates, the resulting inter-annual variability in active layer thickness is not large. Field data analysis reveals that variations in summer degree days do not notably affect the active layer thaw depths; instead, a cumulative winter degree day index is found to more significantly control inter-annual active layer thickness variation at this site. A tendency of increasing winter temperatures is found to cause a general warming of the subsurface down to 10 m depth (0.05 to 0.26 °C yr-1, observed and modelled) including an increasing active layer thickness (0.8 cm yr-1, observed and 0.3 to 0.8 cm yr-1, modelled) during the 14-year study period.

  3. Folder: a MATLAB-based tool for modelling deformation in layered media subject to layer parallel shortening or extension

    NASA Astrophysics Data System (ADS)

    Adamuszek, Marta; Dabrowski, Marcin; Schmid, Daniel W.

    2016-04-01

    into account. The influence of the wall proximity on the fold shape evolution is presented based on an example of a single layer perturbed with a bell-shape function embedded in the matrix of various heights. We carry out simulations for both linear and non-linear viscous materials of layer and matrix. The numerical studies showed that the confinement effect is more pronounced for the case of the non-linear materials, where it significantly influences number of generated folds and their shape. The close proximity of the wall promotes development of larger number of folds with similar shapes.

  4. 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.

  5. 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.

  6. Depth heterogeneity of fully aromatic polyamide active layers in reverse osmosis and nanofiltration membranes.

    PubMed

    Coronell, Orlando; Mariñas, Benito J; Cahill, David G

    2011-05-15

    We studied the depth heterogeneity of fully aromatic polyamide (PA) active layers in commercial reverse osmosis (RO) and nanofiltration (NF) membranes by quantifying near-surface (i.e., top 6 nm) and volume-averaged properties of the active layers using X-ray photoelectron spectrometry (XPS) and Rutherford backscattering spectrometry (RBS), respectively. Some membranes (e.g., ESPA3 RO) had active layers that were depth homogeneous with respect to the concentration and pK(a) distribution of carboxylic groups, degree of polymer cross-linking, concentration of barium ion probe that associated with ionized carboxylic groups, and steric effects experienced by barium ion. Other membranes (e.g., NF90 NF) had active layers that were depth heterogeneous with respect to the same properties. Our results therefore support the existence of both depth-homogeneous and depth-heterogeneous active layers. It remains to be assessed whether the depth heterogeneity consists of gradually changing properties throughout the active layer depth or of distinct sublayers with different properties.

  7. PEMFC catalyst layers: the role of micropores and mesopores on water sorption and fuel cell activity.

    PubMed

    Soboleva, Tatyana; Malek, Kourosh; Xie, Zhong; Navessin, Titichai; Holdcroft, Steven

    2011-06-01

    The effects of carbon microstructure and ionomer loading on water vapor sorption and retention in catalyst layers (CLs) of PEM fuel cells are investigated using dynamic vapor sorption. Catalyst layers based on Ketjen Black and Vulcan XC-72 carbon blacks, which possess distinctly different surface areas, pore volumes, and microporosities, are studied. It is found that pores <20 nm diameter facilitate water uptake by capillary condensation in the intermediate range of relative humidities. A broad pore size distribution (PSD) is found to enhance water retention in Ketjen Black-based CLs whereas the narrower mesoporous PSD of Vulcan CLs is shown to have an enhanced water repelling action. Water vapor sorption and retention properties of CLs are correlated to electrochemical properties and fuel cell performance. Water sorption enhances electrochemical properties such as the electrochemically active surface area (ESA), double layer capacitance and proton conductivity, particularly when the ionomer content is very low. The hydrophilic properties of a CL on the anode and the cathode are adjusted by choosing the PSD of carbon and the ionomer content. It is shown that a reduction of ionomer content on either cathode or anode of an MEA does not necessarily have a significant detrimental effect on the MEA performance compared to the standard 30 wt % ionomer MEA. Under operation in air and high relative humidity, a cathode with a narrow pore size distribution and low ionomer content is shown to be beneficial due to its low water retention properties. In dry operating conditions, adequate ionomer content on the cathode is crucial, whereas it can be reduced on the anode without a significant impact on fuel cell performance.

  8. Motor Cortex Microcircuit Simulation Based on Brain Activity Mapping

    PubMed Central

    Chadderdon, George L.; Mohan, Ashutosh; Suter, Benjamin A.; Neymotin, Samuel A.; Kerr, Cliff C.; Francis, Joseph T.; Shepherd, Gordon M. G.; Lytton, William W.

    2016-01-01

    The deceptively simple laminar structure of neocortex belies the complexity of intra- and interlaminar connectivity. We developed a computational model based primarily on a unified set of brain activity mapping studies of mouse M1. The simulation consisted of 775 spiking neurons of 10 cell types with detailed population-to-population connectivity. Static analysis of connectivity with graph-theoretic tools revealed that the corticostriatal population showed strong centrality, suggesting that would provide a network hub. Subsequent dynamical analysis confirmed this observation, in addition to revealing network dynamics that cannot be readily predicted through analysis of the wiring diagram alone. Activation thresholds depended on the stimulated layer. Low stimulation produced transient activation, while stronger activation produced sustained oscillations where the threshold for sustained responses varied by layer: 13% in layer 2/3, 54% in layer 5A, 25% in layer 5B, and 17% in layer 6. The frequency and phase of the resulting oscillation also depended on stimulation layer. By demonstrating the effectiveness of combined static and dynamic analysis, our results show how static brain maps can be related to the results of brain activity mapping. PMID:24708371

  9. Perpendicular magnetic tunnel junctions based on thin CoFeB free layer and Co-based multilayer synthetic antiferromagnet pinned layers

    NASA Astrophysics Data System (ADS)

    Natarajarathinam, A.; Zhu, R.; Visscher, P. B.; Gupta, S.

    2012-04-01

    We have previously reported on fully perpendicular Co/Pd multilayer (ML)-based CoFeB/MgO/CoFeB magnetic tunnel junctions (MTJs). However, Co/Pd ML-based MTJs have rarely exhibited tunneling magnetoresistance (TMR) ratios greater than 10%. This has been attributed to the inability to pull a sufficiently thick CoFeB layer perpendicular on top of MgO, as well as the incomplete bcc templating of CoFeB from MgO owing to the adjacent fcc Co/Pd MLs. Other researchers have used amorphous thin Ta bridge layers to transition between the bcc and fcc layers. Thin CoFeB with various seed or capping layers have also shown fully perpendicular anisotropy, and thus have gained interest in use as a free layer. Here we report on fully perpendicular MTJs of this type, with a thin CoFeB free layer and a Co/Pd ML-based SAF pinned layer with a thin amorphous Ta bridge layer to transition from bcc CoFeB to the fcc multilayers. The experimentally measured M-H loops show excellent agreement with micromagnetic simulations. Current-in-plane tunneling measurements indicated TMR values of nearly 40% for fully perpendicular stacks annealed at 150 °C for 2 h. Annealing at higher temperatures degraded the magnetoresistance for these Co/Pd ML based SAF pinned MTJs.

  10. Activated Transport in the Separate Layers that Form the νT=1 Exciton Condensate

    NASA Astrophysics Data System (ADS)

    Wiersma, R. D.; Lok, J. G.; Kraus, S.; Dietsche, W.; von Klitzing, K.; Schuh, D.; Bichler, M.; Tranitz, H.-P.; Wegscheider, W.

    2004-12-01

    We observe the total filling factor νT=1 quantum Hall state in a bilayer two-dimensional electron system with virtually no tunneling. We find thermally activated transport in the balanced system with a monotonic increase of the activation energy with decreasing d/ℓB below 1.65. In the imbalanced system we find activated transport in each of the layers separately, yet the activation energies show a striking asymmetry around the balance point, implying a different excitation spectrum for the separate layers forming the condensed state.

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

    PubMed Central

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

    2016-01-01

    Abstract 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

  12. 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

  13. Exploring active layer thaw depth and water content dynamics with multi-channel GPR

    NASA Astrophysics Data System (ADS)

    Wollschlaeger, U.; Gerhards, H.; Westermann, S.; Pan, X.; Boike, J.; Schiwek, P.; Yu, Q.; Roth, K.

    2011-12-01

    In permafrost landscapes, the active layer is the highly dynamic uppermost section of the ground where many important hydrological, biological and geomorphological processes take place. Active layer hydrological processes are controlled by many different factors like thaw depth, soil textural properties, vegetation, and snow cover. These may lead to complex runoff patterns that are difficult to estimate from point measurements in boreholes. New multi-channel GPR systems provide the opportunity to non-invasively estimate reflector depth and average volumetric water content of distinct soil layers over distances ranging from some ten meters up to a few kilometers. Due to the abrupt change in dielectric permittivity between frozen and unfrozen ground, multi-channel GPR is a valuable technique for mapping the depth of the frost table along with the volumetric water content of the active layer without the need of laborious drillings or frost probe measurements. Knowing both values, the total amount of water stored in the active layer can be determined which may be used as an estimate of its latent heat content. Time series of measurements allow spatial monitoring of the progression of the thawing front. Multi-channel GPR thus offers new opportunities for monitoring active layer hydrological processes. This presentation will provide a brief introduction of the multi-channel GPR evaluation technique and will present different applications from several permafrost sites.

  14. LiNiFe-based layered structure oxide and composite for advanced single layer fuel cells

    NASA Astrophysics Data System (ADS)

    Zhu, Bin; Fan, Liangdong; Deng, Hui; He, Yunjune; Afzal, Muhammad; Dong, Wenjing; Yaqub, Azra; Janjua, Naveed K.

    2016-06-01

    A layered structure metal oxide, LiNi0.1Fe0.90O2-δ (LNF), is explored for the advanced single layer fuel cells (SLFCs). The temperature dependent impedance profiles and concentration cells (hydrogen concentration, oxygen concentration, and H2/air atmospheres) tests prove LNF to be an intrinsically electronic conductor in air while mixed electronic and proton conductor in H2/air environment. SLFCs constructed by pure LNF materials show significant short circuiting reflected by a low device OCV and power output (175 mW cm-2 at 500 °C) due to high intrinsic electronic conduction. The power output is improved up to 640 and 760 mW cm-2, respectively at 500 and 550 °C by compositing LNF with ion conducting material, e.g., samarium doped ceria (SDC), to balance the electronic and ionic conductivity; both reached at 0.1 S cm-1 level. Such an SLFC gives super-performance and simplicity over the conventional 3-layer (anode, electrolyte and cathode) FCs, suggesting strong scientific and commercial impacts.

  15. 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.

  16. Silicon based substrate with calcium aluminosilicate/thermal barrier layer

    NASA Technical Reports Server (NTRS)

    Eaton, Jr., Harry Edwin (Inventor); Allen, William Patrick (Inventor); Miller, Robert Alden (Inventor); Jacobson, Nathan S. (Inventor); Smialek, James L. (Inventor); Opila, Elizabeth J. (Inventor); Lee, Kang N. (Inventor); Nagaraj, Bangalore A. (Inventor); Wang, Hongyu (Inventor); Meschter, Peter Joel (Inventor)

    2001-01-01

    A barrier layer for a silicon containing substrate which inhibits the formation of gaseous species of silicon when exposed to a high temperature aqueous environment comprises a calcium alumino silicate.

  17. Silicon based substrate with environmental/ thermal barrier layer

    NASA Technical Reports Server (NTRS)

    Eaton, Jr., Harry Edwin (Inventor); Allen, William Patrick (Inventor); Jacobson, Nathan S. (Inventor); Bansal, Nanottam P. (Inventor); Opila, Elizabeth J. (Inventor); Smialek, James L. (Inventor); Lee, Kang N. (Inventor); Spitsberg, Irene T. (Inventor); Wang, Hongyu (Inventor); Meschter, Peter Joel (Inventor)

    2002-01-01

    A barrier layer for a silicon containing substrate which inhibits the formation of gaseous species of silicon when exposed to a high temperature aqueous environment comprises a barium-strontium alumino silicate.

  18. Aeromechanical stability augmentation of helicopters using enhanced active constrained layer damping treatment on rotor flex beams

    NASA Astrophysics Data System (ADS)

    Badre Alam, Askari

    This thesis presents a study conducted to explore the feasibility of employing Enhanced Active Constrained Layer (EACL) damping treatment in helicopter rotor systems to alleviate aeromechanical instability. The central idea is to apply the EACL treatment on the flexbeams of soft in-plane bearingless main rotors (BMRs) and increase the damping of the first lag mode. In this research, it is explored whether EACL damping treatment can provide sufficient damping in rotor system without exceeding the physical design limits of actuators. To study the feasibility of the EACL damping treatment, a finite element based mathematical model of a rotor with EACL damping treatment on flexbeam is developed. A bench top experiment is conducted to verify the mathematical model. It is shown that the experimental results correlate well with the analytical results. A derivative controller, with control voltage based on the flexbeam tip transverse velocity, is used in this investigation. A filter is developed to remove 1/rev component of the feedback signal. An optimization study is conducted to understand the influence of EACL design parameters on the performance of the damping treatment. A study is conducted to analyze delamination of EACL damping treatment. In this study, a new finite element model is developed that is capable of accurately predicting both, the performance and interlaminar stresses in EACL damping treatment. A new configuration of PCL damping treatment is developed by tapering the constraining layer at the free ends. As compared to a conventional PCL, this configuration has significantly lower interlaminar stresses and similar damping performance. A study is conducted to compare ACL with purely active configuration. It was shown that in ACL configuration, the interlaminar stresses are an-order-of-magnitude lower than the purely active configuration for similar damping levels. A new ACL configuration is designed by changing the poling direction of the PZT constraining

  19. Co/Pd Multilayer Based Recording Layers for Perpendicular Media

    DTIC Science & Technology

    2001-04-01

    composition material. EELS revealed that the intergranular material is a CoPd alloy with substantially lesser density than the material that makes the body...plain-view TEM images of Co/Pd multilayer films oil Ta and ITO buffer layers. performance of the media that utilizes such multilayers as recording layers...multilayer filn grown on a Ta buffer is demonstrated in Fig.3 where mostly collective magnetization reversal takes place at essentially the same external field

  20. Vibration and damping characteristics of cylindrical shells with active constrained layer damping treatments

    NASA Astrophysics Data System (ADS)

    Zheng, Ling; Zhang, Dongdong; Wang, Yi

    2011-02-01

    In this paper, the application of active constrained layer damping (ACLD) treatments is extended to the vibration control of cylindrical shells. The governing equation of motion of cylindrical shells partially treated with ACLD treatments is derived on the basis of the constitutive equations of elastic, piezoelectric and visco-elastic materials and an energy approach. The damping of a visco-elastic layer is modeled by the complex modulus formula. A finite element model is developed to describe and predict the vibration characteristics of cylindrical shells partially treated with ACLD treatments. A closed-loop control system based on proportional and derivative feedback of the sensor voltage generated by the piezo-sensor of the ACLD patches is established. The dynamic behaviors of cylindrical shells with ACLD treatments such as natural frequencies, loss factors and responses in the frequency domain are further investigated. The effects of several key parameters such as control gains, location and coverage of ACLD treatments on vibration suppression of cylindrical shells are also discussed. The numerical results indicate the validity of the finite element model and the control strategy approach. The potential of ACLD treatments in controlling vibration and sound radiation of cylindrical shells used as major critical structures such as cabins of aircraft, hulls of submarines and bodies of rockets and missiles is thus demonstrated.

  1. 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

  2. Single-hidden-layer feed-forward quantum neural network based on Grover learning.

    PubMed

    Liu, Cheng-Yi; Chen, Chein; Chang, Ching-Ter; Shih, Lun-Min

    2013-09-01

    In this paper, a novel single-hidden-layer feed-forward quantum neural network model is proposed based on some concepts and principles in the quantum theory. By combining the quantum mechanism with the feed-forward neural network, we defined quantum hidden neurons and connected quantum weights, and used them as the fundamental information processing unit in a single-hidden-layer feed-forward neural network. The quantum neurons make a wide range of nonlinear functions serve as the activation functions in the hidden layer of the network, and the Grover searching algorithm outstands the optimal parameter setting iteratively and thus makes very efficient neural network learning possible. The quantum neuron and weights, along with a Grover searching algorithm based learning, result in a novel and efficient neural network characteristic of reduced network, high efficient training and prospect application in future. Some simulations are taken to investigate the performance of the proposed quantum network and the result show that it can achieve accurate learning.

  3. Fine-scale wavelike structures in the surface-based turbulent layer at Dome C, Antarctica

    NASA Astrophysics Data System (ADS)

    Petenko, Igor; Argentini, Stefania; Kallistratova, Margarita; Mastrantonio, Giangiuseppe; Casasanta, Giampietro; Sozzi, Roberto; Conidi, Alessandro

    2016-04-01

    A long-term experiment to study the spatial and temporal structure of thermal turbulence in the extremely stable boundary layer was carried out at the Concordia station, Dome C in Antarctica during 2012. The atmospheric boundary layer at this site during the winter is strongly stably stratified with temperature inversions reaching a strength 35°C in 100-200 m. Despite high static stability, intense thermal turbulence occurs sometimes in the surface layer extending from the surface to heights of a few - a few tens of metres. The spatial and temporal structure of the turbulence was observed by an advanced high-resolution sodar in the height range from 2 m to 150 m with vertical resolution ≈ 2 m and time resolution of 2 s. The variation and statistics of the depth of the surface-based turbulent layer (STL) is determined for the entire winter period. The median value of the STL depth is found to be l6 m, while the depth of the inversion layer is of 125 m. The wind speed is a parameter that affects the formation and development of the STL. Typical patterns of turbulence structure as shown by the sodar echograms are analysed and classified. Wave activity within the STL is observed for a significant part of the time; the time scales that characterize these undulation processes are determined. Often regular trains of waves with periods of 30-60 s and a periodicity of 5-10 minutes are observed. Some characteristics of the wavelike structures (form, spatial and temporal scales) are determined and the correlation with meteorological parameters is analysed. The Richardson number estimated using the vertical profiles of temperature and wind velocity from the 45-m meteorological tower, indicates that in some cases significant turbulence may occurr even when Ri is larger than the critical value equal to 0.25.

  4. A new strategy for inhibition of the spoilage yeasts Saccharomyces cerevisiae and Zygosaccharomyces bailii based on combination of a membrane-active peptide with an oligosaccharide that leads to an impaired glycosylphosphatidylinositol (GPI)-dependent yeast wall protein layer.

    PubMed

    Bom, I J; Klis, F M; de Nobel, H; Brul, S

    2001-12-01

    Glycosylphosphatidylinositol (GPI)-dependent cell wall proteins in yeast are connected to the beta-1,3-glucan network via a beta-1,6-glucan moiety. Addition of gentiobiose or beta-1,6-glucan oligomers to growing cells affected the construction of a normal layer of GPI-dependent cell wall proteins at the outer rim of the Saccharomyces cerevisiae cell wall. Treated S. cerevisiae cells secreted significant amounts of cell wall protein 2, were much more sensitive to the lytic action of zymolyase 20T and displayed a marked increase in sensitivity to the small amphipathic antimicrobial peptide MB-21. Similar results in terms of sensitization of yeast cells to the antimicrobial peptide were obtained with the notorious food spoilage yeast Zygosaccharomyces bailii. Our results indicate that treating cells with a membrane-perturbing compound together with compounds that lead to an impaired construction of a normal GPI-dependent yeast wall protein layer represents an effective strategy to prevent the growth of major food spoilage yeasts.

  5. Boosting oxygen reduction/evolution reaction activities with layered perovskite catalysts.

    PubMed

    Chen, Dengjie; Wang, Jian; Zhang, Zhenbao; Shao, Zongping; Ciucci, Francesco

    2016-08-25

    Layered PrBaMn2O5+δ (H-PBM) was simply prepared by annealing pristine Pr0.5Ba0.5MnO3-δ in H2. The oxygen reduction/evolution reaction activities are remarkably enhanced by employing H-PBM. The improvement can be ascribed to the introduction of additional oxygen vacancies, an optimized eg filling of Mn ions, and the facile incorporation of oxygen into layered H-PBM.

  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. 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.

  8. Highly sensitive recognition element based on birefringent porous silicon layers

    NASA Astrophysics Data System (ADS)

    Gross, E.; Kovalev, D.; Künzner, N.; Timoshenko, V. Yu.; Diener, J.; Koch, F.

    2001-10-01

    Anisotropically nanostructured silicon layers exhibit a strong in-plane birefringence. Their optical anisotropy parameters are found to be extremely sensitive to the presence of dielectric substances inside of the pores. Polarization-resolved transmittance measurements provide an extremely sensitive tool to analyze the adsorption of various atoms and molecules in negligible quantities. A variation of the transmitted linearly polarized light intensity up to two orders of magnitude combined with a fast optical response in the range of seconds make these layers a good candidate for sensor applications.

  9. Optimization-based Approach to Cross-layer Resource Management in Wireless Networked Control Systems

    DTIC Science & Technology

    2013-05-01

    distribution is unlimited. Optimization-based approach to cross-layer resource management in Wireless networked control systems The views, opinions...Box 12211 Research Triangle Park, NC 27709-2211 cross-layer resource management , sampling rate adaptation, networked control system REPORT...7749 2 ABSTRACT Optimization-based approach to cross-layer resource management in Wireless networked control systems Report Title Wireless Networked

  10. Group-III nitride based high electron mobility transistor (HEMT) with barrier/spacer layer

    DOEpatents

    Chavarkar, Prashant; Smorchkova, Ioulia P.; Keller, Stacia; Mishra, Umesh; Walukiewicz, Wladyslaw; Wu, Yifeng

    2005-02-01

    A Group III nitride based high electron mobility transistors (HEMT) is disclosed that provides improved high frequency performance. One embodiment of the HEMT comprises a GaN buffer layer, with an Al.sub.y Ga.sub.1-y N (y=1 or y 1) layer on the GaN buffer layer. An Al.sub.x Ga.sub.1-x N (0.ltoreq.x.ltoreq.0.5) barrier layer on to the Al.sub.y Ga.sub.1-y N layer, opposite the GaN buffer layer, Al.sub.y Ga.sub.1-y N layer having a higher Al concentration than that of the Al.sub.x Ga.sub.1-x N barrier layer. A preferred Al.sub.y Ga.sub.1-y N layer has y=1 or y.about.1 and a preferred Al.sub.x Ga.sub.1-x N barrier layer has 0.ltoreq.x.ltoreq.0.5. A 2DEG forms at the interface between the GaN buffer layer and the Al.sub.y Ga.sub.1-y N layer. Respective source, drain and gate contacts are formed on the Al.sub.x Ga.sub.1-x N barrier layer. The HEMT can also comprising a substrate adjacent to the buffer layer, opposite the Al.sub.y Ga.sub.1-y N layer and a nucleation layer between the Al.sub.x Ga.sub.1-x N buffer layer and the substrate.

  11. 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

  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. Modelling ice layer formation using a preferential flow formulation in the physics based multi-layer SNOWPACK model

    NASA Astrophysics Data System (ADS)

    Wever, Nander; Würzer, Sebastian; Fierz, Charles; Lehning, Michael

    2016-04-01

    For physics based snow cover models, simulating the formation of dense ice layers inside the snowpack has been a long time challenge. In spite of their small vertical extend, the presence of ice lenses inside the snowpack can have a profound impact on vapor, heat and liquid water flow. These effects may ultimately influence processes on larger scales when, for example, looking at hydrological processes or wet snow avalanche formation. Also microwave emission signals from the snowpack are strongly influenced by the presence of ice layers. Recent laboratory experiments and modelling techniques of liquid water flow in snow have advanced the understanding of liquid water flow in snow, in particular the formation of preferential flow paths. We present a modelling approach in the one-dimensional, multi-layer snow cover model SNOWPACK for preferential flow that is based on a dual-domain approach (i.e., separation into a matrix flow and a preferential flow domain) and solving Richards equation for both. In recently published laboratory experiments, water ponding inside the snowpack has been identified to initiate preferential flow. Those studies also quantified the part of the snowpack involved in preferential flow as a function of grain size. By combining these concepts with an empirical function to determine refreezing of preferential flow water inside the snowpack, we are able to simulate preferential water flow in the model. We found that preferential flow paths arriving at a layer transition in the snowpack may lead to ponding conditions. Subsequent refreezing then may form dense ice layers (>700 kg/m3). We compare the simulations to 14 years of biweekly snow profiles made at the Weissfluhjoch study plot at 2540m altitude in the Eastern Swiss Alps. We show that we are able to reproduce several ice lenses that were observed in the field, whereas some profiles remain challenging to simulate.

  14. 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

  15. 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.

  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. New photocathode using ZnSe substrates with GaAs active layer

    NASA Astrophysics Data System (ADS)

    Jin, Xiuguang; Takeda, Yoshikazu; Fuchi, Shingo

    2017-03-01

    GaAs active layers were successfully fabricated on ZnSe substrates using a metalorganic vapor phase epitaxy system. As a photocathode, a GaAs active layer shows a high quantum efficiency (QE) of 9% at 532 nm laser light illumination, which is comparable to a QE of 11% from GaAs bulk. In addition, a photoemission current of 10 µA was obtained from this photocathode. One more important point is that this photocathode could realize back-side illumination of 532 nm laser light, and thus its widespread applications are expected in microscopy and accelerator fields.

  18. Electrochemical cell studies based on non-aqueous magnesium electrolyte for electric double layer capacitor applications

    NASA Astrophysics Data System (ADS)

    Chandrasekaran, Ramasamy; Koh, Meiten; Yamauchi, Akiyoshi; Ishikawa, Masashi

    Performances of electric double layer capacitors (EDLCs) based on an activated carbon electrode with acetonitrile (ACN), propylene carbonate (PC), or a ternary electrolyte, i.e., PC:ethylene carbonate (EC):diethyl carbonate (DEC), at 1 mol dm -3 of magnesium perchlorate [Mg(ClO 4) 2] salt have been investigated. The electrochemical responses were studied by impedance spectroscopy, cyclic voltammetry, and galvanostatic charge-discharge experiments at 25 °C in a three-electrode configuration. For a comparative evaluation, lithium perchlorate (LiClO 4) salt-based systems were also evaluated. All the observed results showed typical EDLC characteristics within the potential range between 0 and 1 V vs. an Ag/Ag + reference electrode. The Mg-based systems exhibited similar or rather better performances than the corresponding Li-based electrolytes; in particular, the rate capability of Mg-based ACN and PC electrolytes was much better than the corresponding Li-based electrolytes, indicating the high accessibility and utility of activated carbon pores by solvated Mg ions.

  19. Few layer graphene based superlattices as efficient thermal insulators

    NASA Astrophysics Data System (ADS)

    Ni, Yuxiang; Chalopin, Yann; Volz, Sebastian

    2013-09-01

    While graphene and few layer graphene (FLG) are considered as having the highest thermal conductivity in their in-plane directions, our molecular dynamics (MD) simulations however show that those systems are also characterized by a superior thermal contact resistance, which could be largely tuned with the layer number when in contact with a silica substrate. Taking advantages of such a resistive interface, MD simulations show that SiO2/FLG superlattices have a thermal conductivity as low as 0.30 W/m K, exhibiting a promising prospect in nano-scale thermal insulation. These findings pave the way for an improved thermal management of nanoscale systems such as thermal barrier coatings and phase change memory materials with atomic-scale super-insulators.

  20. Layered holographic stereogram based on inverse Fresnel diffraction.

    PubMed

    Zhang, Hao; Zhao, Yan; Cao, Liangcai; Jin, Guofan

    2016-01-20

    We propose an efficient algorithm using layered holographic stereogram for three-dimensional (3D) computer-generated holograms. The hologram is spatially partitioned into multiple holographic elements (hogels) to provide the occlusion effect and motion parallax by use of multiple viewpoint rendering. Each hogel is calculated with inverse Fresnel diffraction by slicing the viewing frustum according to the depth image. The sliced layers can provide accurate depth cues for reconstruction since the geometric information of the 3D scene is faithfully matched. The algorithm is compatible with computer graphics rendering techniques and robust for holograms with different parameters. When the hogel size equals 1 mm, the signal-to-noise ratio of the diffraction calculation is above 39 dB with a propagation distance longer than 10 mm. Numerical simulations and optical experiments have demonstrated that the proposed method can reconstruct quality 3D images with reduced computational load.

  1. Thin-film monocrystalline-silicon solar cells based on a seed layer approach with 11% efficiency

    NASA Astrophysics Data System (ADS)

    Gordon, I.; Qiu, Y.; Van Gestel, D.; Poortmans, J.

    2010-09-01

    Solar modules made from thin-film crystalline-silicon layers of high quality on glass substrates could lower the price of photovoltaic electricity substantially. Almost half of the price of wafer-based silicon solar modules is currently due to the cost of the silicon wafers themselves. Using crystalline-silicon thin-film as the active material would substantially reduce the silicon consumption while still ensuring a high cell-efficiency potential and a stable cell performance. One way to create a crystalline-silicon thin film on glass is by using a seed layer approach in which a thin crystalline-silicon layer is first created on a non-silicon substrate, followed by epitaxial thickening of this layer. In this paper, we present new solar cell results obtained on 10-micron thick monocrystalline-silicon layers, made by epitaxial thickening of thin seed layers on transparent glass-ceramic substrates. We used thin (001)-oriented silicon single-crystal seed layers on glass-ceramic substrates provided by Corning Inc. that are made by a process based on anodic bonding and implant-induced separation. Epitaxial thickening of these seed layers was realized in an atmospheric-pressure chemical vapor deposition system. Simple solar cell structures in substrate configuration were made from the epitaxial mono-silicon layers. The Si surface was plasma-textured to reduce the front-side reflection. No other light trapping features were incorporated. Efficiencies of up to 11% were reached with Voc values above 600 mV indicating the good electronic quality of the material. We believe that by further optimizing the material quality and by integrating an efficient light trapping scheme, the efficiency potential of these single-crystal silicon thin films on glass-ceramics should be higher than 15%.

  2. Transfer-printing of active layers to achieve high quality interfaces in sequentially deposited multilayer inverted polymer solar cells fabricated in air

    PubMed Central

    Vohra, Varun; Anzai, Takuya; Inaba, Shusei; Porzio, William; Barba, Luisa

    2016-01-01

    Abstract Polymer solar cells (PSCs) are greatly influenced by both the vertical concentration gradient in the active layer and the quality of the various interfaces. To achieve vertical concentration gradients in inverted PSCs, a sequential deposition approach is necessary. However, a direct approach to sequential deposition by spin-coating results in partial dissolution of the underlying layers which decreases the control over the process and results in not well-defined interfaces. Here, we demonstrate that by using a transfer-printing process based on polydimethylsiloxane (PDMS) stamps we can obtain increased control over the thickness of the various layers while at the same time increasing the quality of the interfaces and the overall concentration gradient within the active layer of PSCs prepared in air. To optimize the process and understand the influence of various interlayers, our approach is based on surface free energy, spreading parameters and work of adhesion calculations. The key parameter presented here is the insertion of high quality hole transporting and electron transporting layers, respectively above and underneath the active layer of the inverted structure PSC which not only facilitates the transfer process but also induces the adequate vertical concentration gradient in the device to facilitate charge extraction. The resulting non-encapsulated devices (active layer prepared in air) demonstrate over 40% increase in power conversion efficiency with respect to the reference spin-coated inverted PSCs. PMID:27877901

  3. Cross-layer active predictive congestion control protocol for wireless sensor networks.

    PubMed

    Wan, Jiangwen; Xu, Xiaofeng; Feng, Renjian; Wu, Yinfeng

    2009-01-01

    In wireless sensor networks (WSNs), there are numerous factors that may cause network congestion problems, such as the many-to-one communication modes, mutual interference of wireless links, dynamic changes of network topology and the memory-restrained characteristics of nodes. All these factors result in a network being more vulnerable to congestion. In this paper, a cross-layer active predictive congestion control scheme (CL-APCC) for improving the performance of networks is proposed. Queuing theory is applied in the CL-APCC to analyze data flows of a single-node according to its memory status, combined with the analysis of the average occupied memory size of local networks. It also analyzes the current data change trends of local networks to forecast and actively adjust the sending rate of the node in the next period. In order to ensure the fairness and timeliness of the network, the IEEE 802.11 protocol is revised based on waiting time, the number of the node's neighbors and the original priority of data packets, which dynamically adjusts the sending priority of the node. The performance of CL-APCC, which is evaluated by extensive simulation experiments. is more efficient in solving the congestion in WSNs. Furthermore, it is clear that the proposed scheme has an outstanding advantage in terms of improving the fairness and lifetime of networks.

  4. Dual-frequency plasmon lasing modes in active three-layered bimetallic Ag/Au nanoshells

    NASA Astrophysics Data System (ADS)

    Wu, DaJian; Wu, XueWei; Cheng, Ying; Jin, BiaoBing; Liu, XiaoJun

    2015-11-01

    The optical properties of three-layered silver-gold-silica (SGS) nanoshells with gain have been investigated theoretically by using Mie theory. Surface plasmon amplification by stimulated emission of radiation (spaser) phenomena can be observed at two plasmon modes of the active SGS nanoshell in the visible region. It is found with the decrease in the radius of the inner Ag core that the critical value of ɛg″(ωg ) for the super-resonance of the low-energy mode increases first and then decreases while that for the high-energy mode decreases. An interesting overlap between the two curves for the critical value of ɛg″(ωg ) can be found at a special core radius. At this point, two super-resonances can be achieved concurrently at the low- and high-energy modes of the active SGS nanoshell with the same gain coefficient. This dual-frequency spaser based on the bimetallic Ag/Au nanoshell may be an efficient candidate for designing the nanolaser.

  5. Electrically conductive PVC layers filled with active carbon containing H+-conducting porous structures of sulfuric acid complexes of cyclams on fabrics

    NASA Astrophysics Data System (ADS)

    Tsivadze, A. Yu.; Fridman, A. Ya.; Morozova, E. M.; Sokolova, N. P.; Voloshchuk, A. M.; Petukhova, G. A.; Bardyshev, I. I.; Gorbunov, A. M.; Novikov, A. K.; Polyakova, I. Ya.; Titova, V. N.; Yavich, A. A.; Petrova, N. V.; Krasil'nikova, O. K.

    2015-07-01

    Electrically conductive PVC layers are synthesized. The layers are filled with active carbons containing porous H+-conductive structures of hydroxyethylcyclam/sulfuric acid complexes crosslinked with cellulose fabric. They are interlaid with layers based on the same structures containing added benzene and hexane adsorbates and solvates. It is found that upon anode or cathode polarization of the layers as H+-conductive electrochemical bridges in air and in the vapor and liquid phases of benzene and hexane, either the electroreduction of H+ to H2 or the electrooxidation of H2O to O2 occurs in the areas of contact between active carbon particles and the complexes. The dependences of rates of H2 and O2 formation on the voltage are studied. The magnitudes of overvoltage and the constants of electrochemical reactions are found to depend on the composition of a layer.

  6. Enhanced Performance of Organic Thin Film Transistor Devices Using Hydroxyethyl-Terminated P3HT as the Active Layer.

    PubMed

    Yeh, Je-Yuan; Tsiang, Raymond Chien-Chao

    2015-05-01

    Hydroxyethyl-terminated poly(3-hexylthiophene) (P3HT-OH) have been synthesized via a catalyst-transfer polycondensation using Grignard metathesis mediated by a nickel-based catalyst. This hydrophilic P3HT-OH is compared against the hydrophobic P3HT when used as an active layer on silicon dioxide (SiO2) wafer for organic thin-film-transistor (OTFT) fabrication. Hydroxyl groups at a 7.5% weight content lead to more chain regularity when polymer is bonded to SiO2 wafer surface and thus enhance the performance of OTFT Device, such as an 114.2% increase in ON/OFF ratio, an 12.4% increase in mobility, a 23.3% decrease in threshold voltage and a 30.1% decrease in surface roughness. Analysis and measurements reported in this paper have illustrated for the first time the feasibility of imparting hydrophilicity to the active layer for improving the OTFT performance.

  7. Ambient Intelligence Context-Based Cross-Layer Design in Wireless Sensor Networks

    PubMed Central

    Liu, Yang; Seet, Boon-Chong; Al-Anbuky, Adnan

    2014-01-01

    By exchanging information directly between non-adjacent protocol layers, cross-layer (CL) interaction can significantly improve and optimize network performances such as energy efficiency and delay. This is particularly important for wireless sensor networks (WSNs) where sensor devices are energy-constrained and deployed for real-time monitoring applications. Existing CL schemes mainly exploit information exchange between physical, medium access control (MAC), and routing layers, with only a handful involving application layer. For the first time, we proposed a framework for CL optimization based on user context of ambient intelligence (AmI) application and an ontology-based context modeling and reasoning mechanism. We applied the proposed framework to jointly optimize MAC and network (NET) layer protocols for WSNs. Extensive evaluations show that the resulting optimization through context awareness and CL interaction for both MAC and NET layer protocols can yield substantial improvements in terms of throughput, packet delivery, delay, and energy performances. PMID:25317760

  8. Activation energy of thermal desorption of silicon oxide layers on silicon substrates

    NASA Astrophysics Data System (ADS)

    Enta, Yoshiharu; Osanai, Shodai; Ogasawara, Takahito

    2017-02-01

    Thermal desorption rates of silicon oxide layers, from 20 to 120 nm in thickness, on silicon substrates in vacuum have been accurately obtained from intervals between ring structures formed inside voids on the oxide layers. From the temperature dependence of the desorption rate, the activation energy and frequency factor of the desorption reaction have been derived as a function of the oxide thickness. The obtained values are compared with the previous studies, and as a result, the activation energy is found to be almost constant ( 4 eV) in a wide range of the oxide thickness. The frequency factor decreases as the inverse square of the oxide thickness. The decomposition kinetics of the oxide layer is also discussed from the obtained results.

  9. Electrochemical release testing of nickel-titanium orthodontic wires in artificial saliva using thin layer activation.

    PubMed

    Cioffi, M; Gilliland, D; Ceccone, G; Chiesa, R; Cigada, A

    2005-11-01

    Alloys based on Ni-Ti intermetallics generally exhibit special shape memory and pseudoelastic properties, which make them desirable for use in the dental field as orthodontic wires. The possibility of nickel release from these materials is of high concern, because the allergenicity of this element. The aim of this study was to test pseudoelastic Ni-Ti wires in simulated physiological conditions, investigating the combined effect of strain and fluoridated media: the wires were examined both under strained (5% tensile strain) and unstrained conditions, in fluoridated artificial saliva at 37 degrees C. Real time electrochemical nickel release testing was performed using a novel application of a radiotracer based method, thin layer activation (TLA). TLA was validated, in unstrained conditions, against adsorptive stripping voltammetry methodology. Control tests were also performed in non-fluoridated artificial saliva. From our research it transpired that the corrosion behaviour of Ni-Ti alloy is highly affected by the fluoride content, showing a release of 4.79+/-0.10 microg/cm2/day, but, differently from other biomaterials, it does not seem to be affected by elastic tensile strain. The application of the TLA method in the biomedical field appears a suitable technique to monitor in real time the corrosion behaviour of biomedical devices.

  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. Sustained, Controlled and Stimuli-Responsive Drug Release Systems Based on Nanoporous Anodic Alumina with Layer-by-Layer Polyelectrolyte

    NASA Astrophysics Data System (ADS)

    Porta-i-Batalla, Maria; Eckstein, Chris; Xifré-Pérez, Elisabet; Formentín, Pilar; Ferré-Borrull, J.; Marsal, Lluis F.

    2016-08-01

    Controlled drug delivery systems are an encouraging solution to some drug disadvantages such as reduced solubility, deprived biodistribution, tissue damage, fast breakdown of the drug, cytotoxicity, or side effects. Self-ordered nanoporous anodic alumina is an auspicious material for drug delivery due to its biocompatibility, stability, and controllable pore geometry. Its use in drug delivery applications has been explored in several fields, including therapeutic devices for bone and dental tissue engineering, coronary stent implants, and carriers for transplanted cells. In this work, we have created and analyzed a stimuli-responsive drug delivery system based on layer-by-layer pH-responsive polyelectrolyte and nanoporous anodic alumina. The results demonstrate that it is possible to control the drug release using a polyelectrolyte multilayer coating that will act as a gate.

  12. Sustained, Controlled and Stimuli-Responsive Drug Release Systems Based on Nanoporous Anodic Alumina with Layer-by-Layer Polyelectrolyte.

    PubMed

    Porta-I-Batalla, Maria; Eckstein, Chris; Xifré-Pérez, Elisabet; Formentín, Pilar; Ferré-Borrull, J; Marsal, Lluis F

    2016-12-01

    Controlled drug delivery systems are an encouraging solution to some drug disadvantages such as reduced solubility, deprived biodistribution, tissue damage, fast breakdown of the drug, cytotoxicity, or side effects. Self-ordered nanoporous anodic alumina is an auspicious material for drug delivery due to its biocompatibility, stability, and controllable pore geometry. Its use in drug delivery applications has been explored in several fields, including therapeutic devices for bone and dental tissue engineering, coronary stent implants, and carriers for transplanted cells. In this work, we have created and analyzed a stimuli-responsive drug delivery system based on layer-by-layer pH-responsive polyelectrolyte and nanoporous anodic alumina. The results demonstrate that it is possible to control the drug release using a polyelectrolyte multilayer coating that will act as a gate.

  13. Layer-based buffer aware rate adaptation design for SHVC video streaming

    NASA Astrophysics Data System (ADS)

    Gudumasu, Srinivas; Hamza, Ahmed; Asbun, Eduardo; He, Yong; Ye, Yan

    2016-09-01

    This paper proposes a layer based buffer aware rate adaptation design which is able to avoid abrupt video quality fluctuation, reduce re-buffering latency and improve bandwidth utilization when compared to a conventional simulcast based adaptive streaming system. The proposed adaptation design schedules DASH segment requests based on the estimated bandwidth, dependencies among video layers and layer buffer fullness. Scalable HEVC video coding is the latest state-of-art video coding technique that can alleviate various issues caused by simulcast based adaptive video streaming. With scalable coded video streams, the video is encoded once into a number of layers representing different qualities and/or resolutions: a base layer (BL) and one or more enhancement layers (EL), each incrementally enhancing the quality of the lower layers. Such layer based coding structure allows fine granularity rate adaptation for the video streaming applications. Two video streaming use cases are presented in this paper. The first use case is to stream HD SHVC video over a wireless network where available bandwidth varies, and the performance comparison between proposed layer-based streaming approach and conventional simulcast streaming approach is provided. The second use case is to stream 4K/UHD SHVC video over a hybrid access network that consists of a 5G millimeter wave high-speed wireless link and a conventional wired or WiFi network. The simulation results verify that the proposed layer based rate adaptation approach is able to utilize the bandwidth more efficiently. As a result, a more consistent viewing experience with higher quality video content and minimal video quality fluctuations can be presented to the user.

  14. 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

  15. Number of graphene layers exhibiting an influence on oxidation of DNA bases: analytical parameters.

    PubMed

    Goh, Madeline Shuhua; Pumera, Martin

    2012-01-20

    This article investigates the analytical performance of double-, few- and multi-layer graphene upon oxidation of adenine and guanine. We observed that the sensitivity of differential pulse voltammetric response of guanine and adenine is significantly higher at few-layer graphene surface than single-layer graphene. We use glassy carbon electrode as substrate coated with graphenes. Our findings shall have profound influence on construction of graphene based genosensors.

  16. Epigenetic Salt Accumulation and Water Movement in the Active Layer of Central Yakutia in Eastern Siberia

    NASA Astrophysics Data System (ADS)

    Lopez Caceres, M.; Brouchkov, A.; Nakayama, H.; Takakai, F.; Fedorov, A.; Fukuda, M.

    2005-12-01

    Observations of soil moisture and salt content were conducted from May to August at Neleger station in Eastern Siberia. Seasonal changes of salt and soil moisture distribution in the active layer of larch forest (undisturbed) and a thermokarst depression known as alas (disturbed) were studied. Electric conductivity (ECe) of the intact forest revealed higher concentrations that increased with depth from the soil surface into the active layer and the underlying permafrost, 1 mS cm-1 at 1.1m to 2.6 mS cm-1 at 160 cm depth in the permafrost. However, maximum value of 5.4 mS cm-1 at 0.6 m depth was found in the dry area of alas. The concentration of ions, especially Na+, Mg2+, Ca2+, SO42-as well as HCO3- in the upper layers of this long-term disturbed site indicates the upward movement of ions together with water. Higher concentration of solutes was found in profiles with deeper seasonal thawing. The accumulation of salts in alas occurs from spring through the growing season. The low concentration of salt in the surface soil layers appears to be linked to leaching of salts by rainfall. There are substantial differences between water content and electric conductivity of soil in forest and alas. Modern salinization of the active layer in alas is epigenetic, and it happens in summer as a result of spring water collection and high summer evaporation; the gradual salt accumulation in alas in comparison to forest is controlled by annual balance of water and salts in the active layer. Present climatic trends point to continuous permafrost degradation in eastern Siberia increasing the risk of surface salinization which has already contributed to change the landscape by hindering the growth of forests.

  17. Epigenetic salt accumulation and water movement in the active layer of central Yakutia in eastern Siberia

    NASA Astrophysics Data System (ADS)

    Lopez, C. M. Larry; Brouchkov, A.; Nakayama, H.; Takakai, F.; Fedorov, A. N.; Fukuda, M.

    2007-01-01

    Observations of soil moisture and salt content were conducted from May to August at Neleger station in eastern Siberia. Seasonal changes of salt and soil moisture distribution in the active layer of larch forest (undisturbed) and a thermokarst depression known as an alas (disturbed) were studied. Electric conductivity ECe of the intact forest revealed higher concentrations that increased with depth from the soil surface into the active layer and the underlying permafrost: 1 mS cm-1 at 1.1 m, to 2.6 mS cm-1 at 160 cm depth in the permafrost. However, a maximum value of 5.4 mS cm-1 at 0.6 m depth was found in the dry area of the alas. The concentration of ions, especially Na+, Mg2+, Ca2+, SO42- and HCO3- in the upper layers of this long-term disturbed site, indicates the upward movement of ions together with water. A higher concentration of solutes was found in profiles with deeper seasonal thawing. The accumulation of salts in the alas occurs from spring through into the growing season. The low concentration of salt in the surface soil layers appears to be linked to leaching of salts by rainfall. There are substantial differences between water content and electric conductivity of soil in the forest and alas. Modern salinization of the active layer in the alas is epigenetic, and it happens in summer as a result of spring water collection and high summer evaporation; the gradual salt accumulation in the alas in comparison with the forest is controlled by the annual balance of water and salts in the active layer. Present climatic trends point to continuous permafrost degradation in eastern Siberia increasing the risk of surface salinization, which has already contributed to changing the landscape by hindering the growth of forest. Copyright

  18. MOS structures based on epitaxial HgCdTe layers

    SciTech Connect

    Antonov, V.V.; Belashov, Y.G.; Kazak, E.P.; Mezentseva, M.P.; Voitsekhovskii, A.V.

    1985-08-01

    The authors present the results of a study of the dependence of the surface photoelectromotive force at wavelengths of 3.39 and 10.6 micrometers on the field electrode for MOS structures prepared from epitaxial Hg /SUB 1-x/ Cd /SUB x/ Te layers (x=0.20-0.25). They analyze the nature of the inhomogeneities in the region near the surface of semiconducting samples prepared under various heat treatment conditions and present their findings in a series of three charts.

  19. Modeling Active Layer Depth Over Permafrost for the Arctic Drainage Basin and the Comparison to Measurements at CALM Field Sites

    NASA Astrophysics Data System (ADS)

    Oelke, C.; Zhang, T.; Serreze, M.; Armstrong, R.

    2002-12-01

    A finite difference model for one-dimensional heat conduction with phase change is applied to investigate soil freezing and thawing processes over the Arctic drainage basin. Calculations are performed on the 25~km~x~25~km resolution NSIDC EASE-Grid. NCEP re-analyzed sigma-0.995 surface temperature with a topography correction, and SSM/I-derived weekly snow height are used as forcing parameters. The importance of using an annual cycle of snow density for different snow classes is emphasized. Soil bulk density and the percentages of silt/clay and sand/gravel are from the SoilData System of the International Geosphere Biosphere Programme. In addition, we parameterize a spatially and vertically variable peat layer and modify soil bulk density and thermal conductivity accordingly. Climatological soil moisture content is from the Permafrost/Water Balance Model (P/WBM) at the University of New Hampshire. The model domain is divided into 3~layers with distinct thermal properties of frozen and thawed soil, respectively. Calculations are performed on 54~model nodes ranging from a thickness of 10~cm near the surface to 1~m at 15~m depth. Initial temperatures are chosen according to the grid cell's IPA permafrost classification on EASE grid. Active layer depths, simulated for the summers of 1999 and 2000, compare well to maximal thaw depths measured at about 60 Circumarctic Active Layer Monitoring Network (CALM) field sites. A remaining RMS-error between modeled and measured values is attributed mainly to scale discrepancies (100~m~x~100~m vs. 25~km~x~25~km) based on differences in the fields of air temperature, snow height, and soil bulk density. For the whole pan-Arctic land mass and the time period 1980 through 2001, this study shows the regionally highly variable active layer depth, frozen ground depth, lengths of freezing and thawing periods, and the day of year when the maxima are reached.

  20. Active constrained layer damping of geometrically nonlinear vibrations of functionally graded plates using piezoelectric fiber-reinforced composites

    NASA Astrophysics Data System (ADS)

    Panda, Satyajit; Ray, M. C.

    2008-04-01

    In this paper, a geometrically nonlinear dynamic analysis has been presented for functionally graded (FG) plates integrated with a patch of active constrained layer damping (ACLD) treatment and subjected to a temperature field. The constraining layer of the ACLD treatment is considered to be made of the piezoelectric fiber-reinforced composite (PFRC) material. The temperature field is assumed to be spatially uniform over the substrate plate surfaces and varied through the thickness of the host FG plates. The temperature-dependent material properties of the FG substrate plates are assumed to be graded in the thickness direction of the plates according to a power-law distribution while the Poisson's ratio is assumed to be a constant over the domain of the plate. The constrained viscoelastic layer of the ACLD treatment is modeled using the Golla-Hughes-McTavish (GHM) method. Based on the first-order shear deformation theory, a three-dimensional finite element model has been developed to model the open-loop and closed-loop nonlinear dynamics of the overall FG substrate plates under the thermal environment. The analysis suggests the potential use of the ACLD treatment with its constraining layer made of the PFRC material for active control of geometrically nonlinear vibrations of FG plates in the absence or the presence of the temperature gradient across the thickness of the plates. It is found that the ACLD treatment is more effective in controlling the geometrically nonlinear vibrations of FG plates than in controlling their linear vibrations. The analysis also reveals that the ACLD patch is more effective for controlling the nonlinear vibrations of FG plates when it is attached to the softest surface of the FG plates than when it is bonded to the stiffest surface of the plates. The effect of piezoelectric fiber orientation in the active constraining PFRC layer on the damping characteristics of the overall FG plates is also discussed.

  1. 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.

  2. Groundwater hydrochemistry in the active layer of the proglacial zone, Finsterwalderbreen, Svalbard

    USGS Publications Warehouse

    Cooper, R.J.; Wadham, J.L.; Tranter, M.; Hodgkins, R.; Peters, N.E.

    2002-01-01

    Glacial bulk meltwaters and active-layer groundwaters were sampled from the proglacial zone of Finsterwalderbreen during a single melt season in 1999, in order to determine the geochemical processes that maintain high chemical weathering rates in the proglacial zone of this glacier. Results demonstrate that the principle means of solute acquisition is the weathering of highly reactive moraine and fluvial active-layer sediments by supra-permafrost groundwaters. Active-layer groundwater derives from the thaw of the proglacial snowpack, buried ice and glacial bulk meltwaters. Groundwater evolves by sulphide oxidation and carbonate dissolution. Evaporation- and freeze-concentration of groundwater in summer and winter, respectively produce Mg-Ca-sulphate salts on the proglacial surface. Re-dissolution of these salts in early summer produces groundwaters that are supersaturated with respect to calcite. There is a pronounced spatial pattern to the geochemical evolution of groundwater. Close to the main proglacial channel, active layer sediments are flushed diurnally by bulk meltwaters. Here, Mg-Ca-sulphate deposits become exhausted in the early season and geochemical evolution proceeds by a combination of sulphide oxidation and carbonate dissolution. At greater distances from the channel, the dissolution of Mg-Ca-sulphate salts is a major influence and dilution by the bulk meltwaters is relatively minor. The influence of sulphate salt dissolution decreases during the sampling season, as these salts are exhausted and waters become increasingly routed by subsurface flowpaths. ?? 2002 Elsevier Science B.V. All rights reserved.

  3. 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...

  4. New First Order Raman-active Modes in Few Layered Transition Metal Dichalcogenides

    PubMed Central

    Terrones, H.; Corro, E. Del; Feng, S.; Poumirol, J. M.; Rhodes, D.; Smirnov, D.; Pradhan, N. R.; Lin, Z.; Nguyen, M. A. T.; Elías, A. L.; Mallouk, T. E.; Balicas, L.; Pimenta, M. A.; Terrones, M.

    2014-01-01

    Although the main Raman features of semiconducting transition metal dichalcogenides are well known for the monolayer and bulk, there are important differences exhibited by few layered systems which have not been fully addressed. WSe2 samples were synthesized and ab-initio calculations carried out. We calculated phonon dispersions and Raman-active modes in layered systems: WSe2, MoSe2, WS2 and MoS2 ranging from monolayers to five-layers and the bulk. First, we confirmed that as the number of layers increase, the E′, E″ and E2g modes shift to lower frequencies, and the A′1 and A1g modes shift to higher frequencies. Second, new high frequency first order A′1 and A1g modes appear, explaining recently reported experimental data for WSe2, MoSe2 and MoS2. Third, splitting of modes around A′1 and A1g is found which explains those observed in MoSe2. Finally, exterior and interior layers possess different vibrational frequencies. Therefore, it is now possible to precisely identify few-layered STMD. PMID:24572993

  5. Layered CU-based electrode for high-dielectric constant oxide thin film-based devices

    DOEpatents

    Auciello, Orlando

    2010-05-11

    A layered device including a substrate; an adhering layer thereon. An electrical conducting layer such as copper is deposited on the adhering layer and then a barrier layer of an amorphous oxide of TiAl followed by a high dielectric layer are deposited to form one or more of an electrical device such as a capacitor or a transistor or MEMS and/or a magnetic device.

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

    NASA Astrophysics Data System (ADS)

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

    2016-08-01

    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.

  7. 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

  8. The North American Arctic Transect: Baseline Vegetation and Active Layer Maps for the IPY

    NASA Astrophysics Data System (ADS)

    Munger, C.; Walker, D.; Raynolds, M.; Kade, A.; Vonlanthen, C.; Kuss, P.; Daanen, R.

    2006-12-01

    Maps of vegetation and active layer were made at 21 10x10-m grids at 11 localities along an 1800-km bioclimate North American Arctic Transect (NAAT). Locations were chosen in each of the five Arctic bioclimate subzones (Subzones A (cold) to E (warm)) and the northern boreal forest. The primary purpose of the maps was to analyze the relationship of the patchy mosaics of plant communities to patterns of plant biomass, microhabitats, active-layer depth, and snow-accumulation along an arctic bioclimate gradient. Vegetation maps show small patterned-ground features (non-sorted circles, earth hummocks, turf hummocks, and small non-sorted circles). The scale of vegetation patterning decreases with latitude; in subzone A, landscape heterogeneity is best visible at small (decimeter) scales, with major differences in plant communities and biomass associated with the cracks vs. the centers of small non-sorted polygons. Toward the southern end of the gradient (Subzone E), the vegetation within the grids is homogenous tussock tundra with minor variations in plant communities mainly associated with earth hummocks and small non-sorted circles that occur between cottongrass tussocks. Patterns of plant communities in the grids are clearly reflected in maps of active-layer thickness and snow depth. In subzones C and D, well-developed non-sorted circles develop wherever there are peaty soils, creating significant micro-scale gradients in soil temperature and soil moisture, which contribute to large differences in active-layer thickness and to frost heave. Thaw depths, therefore, have the most micro-scale variability in the middle part of the climate gradient where there is maximum contrast in plant cover and biomass between circles and inter-circle areas. This contrast is greatest towards the beginning of summer and decreases as the season progresses. The local topography associated with differential winter heave in the patterned ground features was also reflected in the snow

  9. Tyrosinase and Layer-by-Layer supported tyrosinases in the synthesis of lipophilic catechols with antiinfluenza activity.

    PubMed

    Bozzini, Tiziana; Botta, Giorgia; Delfino, Michela; Onofri, Silvano; Saladino, Raffaele; Amatore, Donatella; Sgarbanti, Rossella; Nencioni, Lucia; Palamara, Anna Teresa

    2013-12-15

    Catechol derivatives with lipophilic properties have been selectively synthesized by tyrosinase in high yield avoiding long and tedious protection/deprotection steps usually required in traditional procedures. The synthesis was effective also with immobilized tyrosinase able to perform for more runs. The novel catechols were evaluated against influenza A virus, that continue to represent a severe threat worldwide. A significant antiviral activity was observed in derivatives characterized by antioxidant activity and long carbon alkyl side-chains, suggesting the possibility of a new inhibition mechanism based on both redox and lipophilic properties.

  10. New hard layer design of MRAM based on ring elements

    NASA Astrophysics Data System (ADS)

    Mani, Anand Subra

    Memories are characterized by their ability to store and retain data, by data access times and by their robustness under extreme operating conditions. Magnetic Random Access Memory devices are one of the emerging technologies, which promise a lot of scope for faster and denser memories. Non-volatility and insensitivity to radiation are two most important aspects of MRAM. Faster selective writing is obtained by controlling the formation of two stable data storing states and by simple switching between these states. We present three patterns- circular rings, square rings, and rectangular rings for the hard layer of the MRAM with controlled asymmetry. The patterns were studied with a focus on the uniformity and predictability of data switching, and stability of data storage. Magnetic Force Microscopy experiments and OOMMF (Object Oriented Micro Magnetic Framework) code were used for testing the magnetic behavior of these patterns under the influence of an applied magnetic field. The results revealed that the shape of the pattern used for the storage layer and the direction of applied field greatly influences the switching process in the patterns and the formation of stable data storing states.

  11. Diamond-based protective layer for optical biosensors

    NASA Astrophysics Data System (ADS)

    Majchrowicz, D.; Ficek, M.; Baran, T.; WÄ sowicz, M.; Struk, P.; Jedrzejewska-Szczerska, M.

    2016-09-01

    Optical biosensors have become a powerful alternative to the conventional ways of measurement owing to their great properties, such as high sensitivity, high dynamic range, cost effectiveness and small size. Choice of an optical biosensor's materials is an important factor and impacts the quality of the obtained spectra. Examined biological objects are placed on a cover layer which may react with samples in a chemical, biological and mechanical way, therefore having a negative impact on the measurement reliability. Diamond, a metastable allotrope of carbon with sp3 hybridization, shows outstanding properties such as: great chemical stability, bio-compatibility, high thermal conductivity, wide bandgap and optical transparency. Additionally it possesses great mechanical durability, which makes it a long-lasting material. The protective diamond thin films were deposited on the substrate using Microwave Plasma Assisted Chemical Vapor Deposition (MW PA CVD) system. The surface morphology and roughness was assessed with atomic force microscopy and profilometry. We have performed a series of measurements to assess the biocompatibility of diamond thin films with whole blood. The results show that thin diamond protective layer does not affect the red blood cells, while retaining the sensors high resolution and dynamic range of measurement. Therefore, we conclude that diamond thin films are a viable protective coating for optical biosensors, which allows to examine many biological elements. We project that it can be particularly useful not only for biological objects but also under extreme conditions like radioactive or chemically aggressive environments and high temperatures.

  12. Novel Polymer Nanocomposites Resulted from Melt Processing of Polystyrene-Based Substrates Coated with Layer-by-Layer Assemblies

    NASA Astrophysics Data System (ADS)

    Soltani, Iman; Spontak, Richard J.

    The novel polymer nanocomposites (PNCs) prepared through two steps of coating polystyrene-based substrates with layer-by-layer (LBL) deposition of montmorillonite and alternative polyelectrolyte layers of polyethyleneimine and polyethylene terephthalate ionomer, followed by their cyclic melt pressing, demonstrated particular morphologies. Transmission electron microscopy images at high magnification scales showed the occurrence of swollen intercalation and flocculated exfoliations of clay platelets, down to a few nanometer thickness, inside and sometimes out of LBL assemblies crushed portions. In fact, intercalation and exfoliation of clay platelets, established in LBL assemblies, increased by shear applied through their repetitive melt pressing. Additionally, x-ray diffractometry traces confirmed the aforementioned increase in clay intercalation. These high aspect ratio LBL assemblies portions formed highly tortuous labyrinths, which may work as scavenging centers to promote barrier properties of the PNCs against transport of gases like oxygen and carbon dioxide. It is despite spontaneously low interaction between hydrophobic styrenic groups and almost hydrophilic natural clay and moderate efficiency of cyclic pressing for providing intensive shear stress on samples.

  13. Research on Fast Nitriding by Direct Current Field Base on the Deep-layer QPQ Technology

    NASA Astrophysics Data System (ADS)

    Wang, K.; Luo, D. F.; Zhang, L.

    In recent years the QPQ technical innovator is the development and application of deep-layer QPQ. But also brings a lot of problems need to solve. This article introduces a new technology use direct current field at low temperature and short time base on the deep-layer QPQ. Use 45# as material, we make a comparative between DC treatment and normal treatment at the same condition. The results show that the DC treatment was beneficial forms of the nitrided layer and the performance index was the same as normal treatment. The formation of the nitrided layer in the direct current field situation is analyzed.

  14. 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

  15. 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.

  16. Numerical investigation on active isolation of ground shock by soft porous layers

    NASA Astrophysics Data System (ADS)

    Wang, J. G.; Sun, W.; Anand, S.

    2009-04-01

    The mitigation and reduction of blast-induced ground shock in near field is an interesting topic worth considering for the protection of buried structures. Soft porous materials are usually used to form an isolation layer around the buried structures. However, the interaction of soft porous layer and surrounding geomedia as well as buried structures is not well understood. In this paper, the effects of soft porous layer barriers on the reduction of buried blast-induced ground shock are numerically studied. Based on the prototype dimensions of a centrifuge test, a numerical model is set up with two steel boxes symmetrically buried at two sides of the charge. One box is directly located in soil mass without protection (unprotected) and the other is located behind a soft porous layer barrier (protected). The soft porous layer barriers studied here include an open trench, an inundated water trench, three in-filled geofoam walls with different densities, and a concrete wall. The numerical responses of the two boxes are evaluated when subjected to the protection of different soft porous layer barriers. These numerical simulations show that both open trench and geofoam barriers can effectively reduce blast-induced stress waves. However, inundated water trench and concrete wall have almost no effect on the reduction of ground shock. Therefore, a geofoam barrier is more practicable in soil mass.

  17. Radiative transfer theory for active remote sensing of a layer of small ellipsoidal scatterers. [of vegetation

    NASA Technical Reports Server (NTRS)

    Tsang, L.; Kubacsi, M. C.; Kong, J. A.

    1981-01-01

    The radiative transfer theory is applied within the Rayleigh approximation to calculate the backscattering cross section of a layer of randomly positioned and oriented small ellipsoids. The orientation of the ellipsoids is characterized by a probability density function of the Eulerian angles of rotation. The radiative transfer equations are solved by an iterative approach to first order in albedo. In the half space limit the results are identical to those obtained via the approach of Foldy's and distorted Born approximation. Numerical results of the theory are illustrated using parameters encountered in active remote sensing of vegetation layers. A distinctive characteristic is the strong depolarization shown by vertically aligned leaves.

  18. Synthesis and Characterization of Layered Double Hydroxides Containing Optically Active Transition Metal Ion

    NASA Astrophysics Data System (ADS)

    Tyagi, S. B.; Kharkwal, Aneeta; Nitu; Kharkwal, Mamta; Sharma, Raghunandan

    2017-01-01

    The acetate intercalated layered double hydroxides of Zn and Mn, have been synthesized by chimie douce method. The materials were characterized by XRD, TGA, CHN, IR, XPS, SEM-EDX and UV-visible spectroscopy. The photoluminescence properties was also studied. The optical properties of layered hydroxides are active transition metal ion dependent, particularly d1-10 system plays an important role. Simultaneously the role of host - guest orientation has been considered the basis of photoluminescence. Acetate ion can be exchanged with iodide and sulphate ions. The decomposed product resulted the pure phase Mn doped zinc oxide are also reported.

  19. 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

  20. Flexible Capacitive Tactile Sensor Based on Micropatterned Dielectric Layer.

    PubMed

    Li, Tie; Luo, Hui; Qin, Lin; Wang, Xuewen; Xiong, Zuoping; Ding, Haiyan; Gu, Yang; Liu, Zheng; Zhang, Ting

    2016-09-01

    Flexible tactile sensors are considered as an effective way to realize the sense of touch, which can perform the synchronized interactions with surrounding environment. Here, the utilization of bionic microstructures on natural lotus leaves is demonstrated to design and fabricate new-type of high-performance flexible capacitive tactile sensors. Taking advantage of unique surface micropattern of lotus leave as the template for electrodes and using polystyrene microspheres as the dielectric layer, the proposed devices present stable and high sensing performance, such as high sensitivity (0.815 kPa(-1) ), wide dynamic response range (from 0 to 50 N), and fast response time (≈38 ms). In addition, the flexible capacitive sensor is not only applicable to pressure (touch of a single hair), but also to bending and stretching forces. The results indicate that the proposed capacitive tactile sensor is a promising candidate for the future applications in electronic skins, wearable robotics, and biomedical devices.

  1. Excellent c-Si surface passivation by thermal atomic layer deposited aluminum oxide after industrial firing activation

    NASA Astrophysics Data System (ADS)

    Liao, B.; Stangl, R.; Ma, F.; Mueller, T.; Lin, F.; Aberle, A. G.; Bhatia, C. S.; Hoex, B.

    2013-09-01

    We demonstrate that by using a water (H2O)-based thermal atomic layer deposited (ALD) aluminum oxide (Al2O3) film, excellent surface passivation can be attained on planar low-resistivity silicon wafers. Effective carrier lifetime values of up to 12 ms and surface recombination velocities as low as 0.33 cm s-1 are achieved on float-zone wafers after a post-deposition thermal activation of the Al2O3 passivation layer. This post-deposition activation is achieved using an industrial high-temperature firing process which is commonly used for contact formation of standard screen-printed silicon solar cells. Neither a low-temperature post-deposition anneal nor a silicon nitride capping layer is required in this case. Deposition temperatures in the 100-400 °C range and peak firing temperatures of about 800 °C (set temperature) are investigated. Photoluminescence imaging shows that the surface passivation is laterally uniform. Corona charging and capacitance-voltage measurements reveal that the negative fixed charge density near the AlOx/c-Si interface increases from 1.4 × 1012 to 3.3 × 1012 cm-2 due to firing, while the midgap interface defect density reduces from 3.3 × 1011 to 0.8 × 1011 cm-2 eV-1. This work demonstrates that direct firing activation of thermal ALD Al2O3 is feasible, which could be beneficial for solar cell manufacturing.

  2. Active layer solution-processed NIR-OLEDs based on ternary erbium(III) complexes with 1,1,1-trifluoro-2,4-pentanedione and different N,N-donors.

    PubMed

    Martín-Ramos, P; Coya, C; Lavín, V; Martín, I R; Silva, M Ramos; Silva, P S Pereira; García-Vélez, M; Alvarez, A L; Martín-Gil, J

    2014-12-28

    Using a fluorinated 1,1,1-trifluoro-2,4-pentanedione (Htfac) ligand and either 2,2'-bipyridine (bipy), bathophenanthroline (bath) or 5-nitro-1,10-phenanthroline (5NO2phen) as an ancillary ligand, three new ternary erbium(iii) octacoordinated complexes have been synthesized. The single crystal structures of the new complexes (namely [Er(tfac)3(bipy)], [Er(tfac)3(bath)] and [Er(tfac)3(5NO2phen)]) have been determined and their properties have been investigated by Fourier transform infrared (FTIR) spectroscopy, Raman spectroscopy and thermodynamic analysis. After ligand-mediated excitation of these complexes in the UV, they all show the characteristic near-infrared (NIR) luminescence of the corresponding Er(3+) ion at 1532 nm. The same emission in the C-band transmission window can also be obtained from the solution-processed organic light-emitting diodes (OLEDs) with structure: glass/ITO/PEDOT:PSS/[Er(tfac)3(N,N-donor)]/Ca/Al. In spite of the fact that the photoluminescence intensity of [Er(tfac)3(5NO2phen)] is stronger than those of [Er(tfac)3(bipy)] and [Er(tfac)3(bath)], the best electroluminescence results correspond to the OLED based on the [Er(tfac)3(bath)] complex, as a consequence of the superior electron transport capabilities of bathophenanthroline.

  3. Active layer temperature in two Cryosols from King George Island, Maritime Antarctica

    NASA Astrophysics Data System (ADS)

    Michel, Roberto F. M.; Schaefer, Carlos Ernesto G. R.; Poelking, Everton L.; Simas, Felipe N. B.; Fernandes Filho, Elpidio I.; Bockheim, James G.

    2012-06-01

    This study presents soil temperature and moisture regimes from March 2008 to January 2009 for two active layer monitoring (CALM-S) sites at King George Island, Maritime Antarctica. The monitoring sites were installed during the summer of 2008 and consist of thermistors (accuracy of ± 0.2 °C), arranged vertically with probes at different depths and one soil moisture probe placed at the bottommost layer at each site (accuracy of ± 2.5%), recording data at hourly intervals in a high capacity datalogger. The active layer thermal regime in the studied period for both soils was typical of periglacial environments, with extreme variation in surface temperature during summer resulting in frequent freeze and thaw cycles. The great majority of the soil temperature readings during the eleven month period was close to 0 °C, resulting in low values of freezing and thawing degree days. Both soils have poor thermal apparent diffusivity but values were higher for the soil from Fildes Peninsula. The different moisture regimes for the studied soils were attributed to soil texture, with the coarser soil presenting much lower water content during all seasons. Differences in water and ice contents may explain the contrasting patterns of freezing of the studied soils, being two-sided for the coarser soil and one-sided for the loamy soil. The temperature profile of the studied soils during the eleven month period indicates that the active layer reached a maximum depth of approximately 92 cm at Potter and 89 cm at Fildes. Longer data sets are needed for more conclusive analysis on active layer behaviour in this part of Antarctica.

  4. Active layer dynamics in three sites with contrasted topography in the Byers Peninsula (Livingston Island, Antarctica)

    NASA Astrophysics Data System (ADS)

    Oliva, Marc; Ruiz-Fernández, Jesús; Vieira, Gonçalo

    2015-04-01

    Topography exerts a key role on permafrost distribution in areas where mean annual temperatures are slightly negative. This is the case of low-altitude environments in Maritime Antarctica, namely in the South Shetland Islands, where permafrost is marginal to discontinuous until elevations of 20-40 m asl turning to continuous at higher areas. Consequently, the active layer dynamics is also strongly conditioned by the geomorphological setting. In January 2014 we installed three sites for monitoring the active layer dynamics across the Byers Peninsula (Livingston Island, South Shetland Islands) in different geomorphological environments at elevations between 60 and 100 m. The purpose was to examine the role of the topography and microclimatic conditions on the active layer dynamics. At each site a set of loggers was set up to monitor: air temperatures, snow thickness, ground temperatures until 80 cm together with the coupling atmosphere-ground temperatures. During the first year of monitoring the mean annual air temperatures show similar values in the three sites, in all cases slightly below freezing. The snowy conditions during this year in this archipelago have resulted in a late melting of snow, which has also conditioned the duration of frozen conditions in the uppermost soil layers. Topography has a strong influence on snow cover duration, which in turn affects frozen ground conditions. The Domo site is located in a higher position with respect to the central plateau of Byers; here, the wind is stronger and snow cover thinner, which has conditioned a longer thawing season than in the other two sites (Cerro Negro, Escondido). These two sites are located in topographically protected areas favouring snow accumulation. The longer persistence of snow conditions a longer duration of negative temperatures in the active layer of the permafrost. This research was financially supported by the HOLOANTAR project (Portuguese Science Foundation) and the AXA Research Fund.

  5. Layer-specific optogenetic activation of pyramidal neurons causes beta–gamma entrainment of neonatal networks

    PubMed Central

    Bitzenhofer, Sebastian H; Ahlbeck, Joachim; Wolff, Amy; Wiegert, J. Simon; Gee, Christine E.; Oertner, Thomas G.; Hanganu-Opatz, Ileana L.

    2017-01-01

    Coordinated activity patterns in the developing brain may contribute to the wiring of neuronal circuits underlying future behavioural requirements. However, causal evidence for this hypothesis has been difficult to obtain owing to the absence of tools for selective manipulation of oscillations during early development. We established a protocol that combines optogenetics with electrophysiological recordings from neonatal mice in vivo to elucidate the substrate of early network oscillations in the prefrontal cortex. We show that light-induced activation of layer II/III pyramidal neurons that are transfected by in utero electroporation with a high-efficiency channelrhodopsin drives frequency-specific spiking and boosts network oscillations within beta–gamma frequency range. By contrast, activation of layer V/VI pyramidal neurons causes nonspecific network activation. Thus, entrainment of neonatal prefrontal networks in fast rhythms relies on the activation of layer II/III pyramidal neurons. This approach used here may be useful for further interrogation of developing circuits, and their behavioural readout. PMID:28216627

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

    DOE PAGES

    Atchley, Adam L.; Coon, Ethan T.; Painter, Scott L.; ...

    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

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

    SciTech Connect

    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 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.

  8. Activation of Al2O3 passivation layers on silicon by microwave annealing

    NASA Astrophysics Data System (ADS)

    Ziegler, Johannes; Otto, Martin; Sprafke, Alexander N.; Wehrspohn, Ralf B.

    2013-11-01

    Thin aluminum oxide layers deposited on silicon by thermal atomic layer deposition can be used to reduce the electronic recombination losses by passivating the silicon surfaces. To activate the full passivation ability of such layers, a post-deposition annealing step at moderate temperatures (≈400 ∘C, duration≈30 min) is required. Such an annealing step is commonly done in an oven in air, nitrogen, or forming gas atmosphere. In this work, we investigate the ability to reduce the duration of the annealing step by heating the silicon wafer with a microwave source. The annealing time is significantly reduced to durations below 1 min while achieving effective minority carrier lifetimes similar or higher to that of conventionally oven-annealed samples.

  9. The Modelling and Vibration Control of Beams with Active Constrained Layer Damping

    NASA Astrophysics Data System (ADS)

    SHI, Y. M.; LI, Z. F.; HUA, H. X.; FU, Z. F.; LIU, T. X.

    2001-08-01

    The finite element method (FEM) is combined with the Golla-Hughes-McTavish (GHM) model of viscoelastic materials (VEM) to model a cantilever beam with active constrained layer damping treatments. This approach avoids time-consuming iteration in solving modal frequencies, modal damping ratios and responses. But the resultant finite element (FE) model has too many degrees of freedom (d.o.f.s) from the point of view of control, nor is it observable and controllable. A new model reduction procedure is proposed. An iterative dynamic condensation is performed in the physical space, and Guyan condensation is taken as an initial iteration approximation. A reduced order model (ROM) of suitable size emerges, but it is still not observable and controllable. Accordingly, a robust model reduction method is then employed in the state space. A numerical example proves that this procedure reduces the model and assures the stability, controllability and observability of the final reduced order model (FROM). Finally, a controller is designed by linear-quadratic Gaussian (LQG) method based on the FROM. The vibration attenuation is evident

  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. Photoluminescence-based quality control for thin film absorber layers of photovoltaic devices

    DOEpatents

    Repins, Ingrid L.; Kuciauskas, Darius

    2015-07-07

    A time-resolved photoluminescence-based system providing quality control during manufacture of thin film absorber layers for photovoltaic devices. The system includes a laser generating excitation beams and an optical fiber with an end used both for directing each excitation beam onto a thin film absorber layer and for collecting photoluminescence from the absorber layer. The system includes a processor determining a quality control parameter such as minority carrier lifetime of the thin film absorber layer based on the collected photoluminescence. In some implementations, the laser is a low power, pulsed diode laser having photon energy at least great enough to excite electron hole pairs in the thin film absorber layer. The scattered light may be filterable from the collected photoluminescence, and the system may include a dichroic beam splitter and a filter that transmit the photoluminescence and remove scattered laser light prior to delivery to a photodetector and a digital oscilloscope.

  12. Considerably improved photovoltaic performance of carbon nanotube-based solar cells using metal oxide layers.

    PubMed

    Wang, Feijiu; Kozawa, Daichi; Miyauchi, Yuhei; Hiraoka, Kazushi; Mouri, Shinichiro; Ohno, Yutaka; Matsuda, Kazunari

    2015-02-18

    Carbon nanotube-based solar cells have been extensively studied from the perspective of potential application. Here we demonstrated a significant improvement of the carbon nanotube solar cells by the use of metal oxide layers for efficient carrier transport. The metal oxides also serve as an antireflection layer and an efficient carrier dopant, leading to a reduction in the loss of the incident solar light and an increase in the photocurrent, respectively. As a consequence, the photovoltaic performance of both p-single-walled carbon nanotube (SWNT)/n-Si and n-SWNT/p-Si heterojunction solar cells using MoOx and ZnO layers is improved, resulting in very high photovoltaic conversion efficiencies of 17.0 and 4.0%, respectively. These findings regarding the use of metal oxides as multifunctional layers suggest that metal oxide layers could improve the performance of various electronic devices based on carbon nanotubes.

  13. Considerably improved photovoltaic performance of carbon nanotube-based solar cells using metal oxide layers

    NASA Astrophysics Data System (ADS)

    Wang, Feijiu; Kozawa, Daichi; Miyauchi, Yuhei; Hiraoka, Kazushi; Mouri, Shinichiro; Ohno, Yutaka; Matsuda, Kazunari

    2015-02-01

    Carbon nanotube-based solar cells have been extensively studied from the perspective of potential application. Here we demonstrated a significant improvement of the carbon nanotube solar cells by the use of metal oxide layers for efficient carrier transport. The metal oxides also serve as an antireflection layer and an efficient carrier dopant, leading to a reduction in the loss of the incident solar light and an increase in the photocurrent, respectively. As a consequence, the photovoltaic performance of both p-single-walled carbon nanotube (SWNT)/n-Si and n-SWNT/p-Si heterojunction solar cells using MoOx and ZnO layers is improved, resulting in very high photovoltaic conversion efficiencies of 17.0 and 4.0%, respectively. These findings regarding the use of metal oxides as multifunctional layers suggest that metal oxide layers could improve the performance of various electronic devices based on carbon nanotubes.

  14. MoS2 atomic layers with artificial active edge sites as transparent counter electrodes for improved performance of dye-sensitized solar cells.

    PubMed

    Zhang, Jing; Najmaei, Sina; Lin, Hong; Lou, Jun

    2014-05-21

    A novel MoS2 transparent counter electrode for dye-sensitized solar cells is reported. In order to enhance the catalytic activity of the electrode, active edge sites are created artificially by patterning holes on MoS2 atomic layers. Electrochemical analysis shows that the electrochemical activity is significantly improved after the patterning of holes. The photon-to-electron efficiency of the dye-sensitized solar cells based on MoS2 atomic layer counter electrodes is increased remarkably from 2% to 5.8% after the hole patterning.

  15. A Cross-Layer User Centric Vertical Handover Decision Approach Based on MIH Local Triggers

    NASA Astrophysics Data System (ADS)

    Rehan, Maaz; Yousaf, Muhammad; Qayyum, Amir; Malik, Shahzad

    Vertical handover decision algorithm that is based on user preferences and coupled with Media Independent Handover (MIH) local triggers have not been explored much in the literature. We have developed a comprehensive cross-layer solution, called Vertical Handover Decision (VHOD) approach, which consists of three parts viz. mechanism for collecting and storing user preferences, Vertical Handover Decision (VHOD) algorithm and the MIH Function (MIHF). MIHF triggers the VHOD algorithm which operates on user preferences to issue handover commands to mobility management protocol. VHOD algorithm is an MIH User and therefore needs to subscribe events and configure thresholds for receiving triggers from MIHF. In this regard, we have performed experiments in WLAN to suggest thresholds for Link Going Down trigger. We have also critically evaluated the handover decision process, proposed Just-in-time interface activation technique, compared our proposed approach with prominent user centric approaches and analyzed our approach from different aspects.

  16. Graphene-based carbon-layered electrode array technology for neural imaging and optogenetic applications.

    PubMed

    Park, Dong-Wook; Schendel, Amelia A; Mikael, Solomon; Brodnick, Sarah K; Richner, Thomas J; Ness, Jared P; Hayat, Mohammed R; Atry, Farid; Frye, Seth T; Pashaie, Ramin; Thongpang, Sanitta; Ma, Zhenqiang; Williams, Justin C

    2014-10-20

    Neural micro-electrode arrays that are transparent over a broad wavelength spectrum from ultraviolet to infrared could allow for simultaneous electrophysiology and optical imaging, as well as optogenetic modulation of the underlying brain tissue. The long-term biocompatibility and reliability of neural micro-electrodes also require their mechanical flexibility and compliance with soft tissues. Here we present a graphene-based, carbon-layered electrode array (CLEAR) device, which can be implanted on the brain surface in rodents for high-resolution neurophysiological recording. We characterize optical transparency of the device at >90% transmission over the ultraviolet to infrared spectrum and demonstrate its utility through optical interface experiments that use this broad spectrum transparency. These include optogenetic activation of focal cortical areas directly beneath electrodes, in vivo imaging of the cortical vasculature via fluorescence microscopy and 3D optical coherence tomography. This study demonstrates an array of interfacing abilities of the CLEAR device and its utility for neural applications.

  17. Establishment of a biomimetic device based on tri-layer polymer actuators--propulsion fins.

    PubMed

    Alici, Gursel; Spinks, Geoffrey; Huynh, Nam N; Sarmadi, Laleh; Minato, Rick

    2007-06-01

    We propose to use bending type tri-layer polymer actuators as propulsion fins for a biomimetic device consisting of a rigid body, like a box fish having a carapace, and paired fins running through the rigid body, like a fish having pectoral fins. The fins or polymer bending actuators can be considered as individually controlled flexible membranes. Each fin is activated with sinusoidal inputs such that there is a phase lag between the movements of successive fins to create enough thrust force for propulsion. Eight fins with 0.125 aspect ratio have been used along both sides of the rigid body to move the device in the direction perpendicular to the longitudinal axis of the body. The designed device with the paired fins was successfully tested, moving in an organic solution consisting of solvent, propylene carbonate (PC), and electrolyte. The design procedure outlined in this study is offered as a guide to making functional devices based on polymer actuators and sensors.

  18. Physics-based Enrichment of Planetary Boundary Layer LES

    NASA Astrophysics Data System (ADS)

    Ghate, Aditya; Lele, Sanjiva

    2016-11-01

    A new multiscale simulation methodology is introduced to facilitate efficient simulations of very high Reynolds number wall bounded flows such as the PBL. The two-simulation, one-way coupled, scale splitting methodology combining a) Non-linear wave space model using the Gabor Transform and spectral eddy-viscosity, b) Representation of the subfilter fields via a set of random modes, and c) Large Eddy Simulation using a robust subgrid scale model, is introduced. The viability of the methodology is investigated using 3 increasingly sophisticated idealizations for the PBL. In the first idealization, the surface layer is approximated using a uniform shear and a positive (stable) temperature gradient which makes the problem homogeneous. The second idealization models the PBL as a constant pressure gradient driven half channel thus introducing inhomogeneity in the vertical direction. The high latitude Stable PBL used in GABLS1 intercomparison study serves as the third idealization for the PBL and it further introduces Coriolis and Stratification effects. These idealizations help validate the two-simulation methodology, where comparisons are made in terms of statistics such as space-time correlations, k-omega spectra and profiles of second order correlations.

  19. Bionanocomposites based on layered double hydroxides as drug delivery systems

    NASA Astrophysics Data System (ADS)

    Aranda, Pilar; Alcântara, Ana C. S.; Ribeiro, Ligia N. M.; Darder, Margarita; Ruiz-Hitzky, Eduardo

    2012-10-01

    The present work introduces new biohybrid materials involving layered double hydroxides (LDH) and biopolymers to produce bionanocomposites, able to act as effective drug delivery systems (DDS). Ibuprofen (IBU) and 5-aminosalicylic acid (5-ASA) have been chosen as model drugs, being intercalated in a Mg-Al LDH matrix. On the one side, the LDHIBU intercalation compound prepared by ion-exchange reaction was blended with the biopolymers zein, a highly hydrophobic protein, and alginate, a polysaccharide widely applied for encapsulating drugs. On the other side, the LDH- 5-ASA intercalation compound prepared by co-precipitation was assembled to the polysaccharides chitosan and pectin, which show mucoadhesive properties and resistance to acid pH values, respectively. Characterization of the intercalation compounds and the resulting bionanocomposites was carried out by means of different experimental techniques: X-ray diffraction, infrared spectroscopy, chemical and thermal analysis, as well as optical and scanning electron microscopies. Data on the swelling behavior and drug release under different pH conditions are also reported.

  20. Bi-layered calcium phosphate cement-based composite scaffold mimicking natural bone structure

    PubMed Central

    He, Fupo; Ye, Jiandong

    2013-01-01

    In this study, a core/shell bi-layered calcium phosphate cement (CPC)-based composite scaffold with adjustable compressive strength, which mimicked the structure of natural cortical/cancellous bone, was fabricated. The dense tubular CPC shell was prepared by isostatic pressing CPC powder with a specially designed mould. A porous CPC core with unidirectional lamellar pore structure was fabricated inside the cavity of dense tubular CPC shell by unidirectional freeze casting, followed by infiltration of poly(lactic-co-glycolic acid) and immobilization of collagen. The compressive strength of bi-layered CPC-based composite scaffold can be controlled by varying thickness ratio of dense layer to porous layer. Compared to the scaffold without dense shell, the pore interconnection of bi-layered scaffold was not obviously compromised because of its high unidirectional interconnectivity but poor three dimensional interconnectivity. The in vitro results showed that the rat bone marrow stromal cells attached and proliferated well on the bi-layered CPC-based composite scaffold. This novel bi-layered CPC-based composite scaffold is promising for bone repair. PMID:27877603

  1. Correlation between active layer thickness and ambient gas stability in IGZO thin-film transistors

    NASA Astrophysics Data System (ADS)

    Gao, Xu; Lin, Meng-Fang; Mao, Bao-Hua; Shimizu, Maki; Mitoma, Nobuhiko; Kizu, Takio; Ou-Yang, Wei; Nabatame, Toshihide; Liu, Zhi; Tsukagoshi, Kazuhito; Wang, Sui-Dong

    2017-01-01

    Decreasing the active layer thickness has been recently reported as an alternative way to achieve fully depleted oxide thin-film transistors for the realization of low-voltage operations. However, the correlation between the active layer thickness and device resistivity to environmental changes is still unclear, which is important for the optimized design of oxide thin-film transistors. In this work, the ambient gas stability of IGZO thin-film transistors is found to be strongly correlated to the IGZO thickness. The TFT with the thinnest IGZO layer shows the highest intrinsic electron mobility in a vacuum, which is greatly reduced after exposure to O2/air. The device with a thick IGZO layer shows similar electron mobility in O2/air, whereas the mobility variation measured in the vacuum is absent. The thickness dependent ambient gas stability is attributed to a high-mobility region in the IGZO surface vicinity with less sputtering-induced damage, which will become electron depleted in O2/air due to the electron transfer to adsorbed gas molecules. The O2 adsorption and deduced IGZO surface band bending is demonstrated by the ambient-pressure x-ray photoemission spectroscopy results.

  2. Metal insulator semiconductor solar cell devices based on a Cu{sub 2}O substrate utilizing h-BN as an insulating and passivating layer

    SciTech Connect

    Ergen, Onur; Gibb, Ashley; Vazquez-Mena, Oscar; Zettl, Alex; Regan, William Raymond

    2015-03-09

    We demonstrate cuprous oxide (Cu{sub 2}O) based metal insulator semiconductor Schottky (MIS-Schottky) solar cells with efficiency exceeding 3%. A unique direct growth technique is employed in the fabrication, and hexagonal boron nitride (h-BN) serves simultaneously as a passivation and insulation layer on the active Cu{sub 2}O layer. The devices are the most efficient of any Cu{sub 2}O based MIS-Schottky solar cells reported to date.

  3. 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.

  4. Enlargement of Axo-Somatic Contacts Formed by GAD-Immunoreactive Axon Terminals onto Layer V Pyramidal Neurons in the Medial Prefrontal Cortex of Adolescent Female Mice Is Associated with Suppression of Food Restriction-Evoked Hyperactivity and Resilience to Activity-Based Anorexia.

    PubMed

    Chen, Yi-Wen; Wable, Gauri Satish; Chowdhury, Tara Gunkali; Aoki, Chiye

    2016-06-01

    Many, but not all, adolescent female mice that are exposed to a running wheel while food restricted (FR) become excessive wheel runners, choosing to run even during the hours of food availability, to the point of death. This phenomenon is called activity-based anorexia (ABA). We used electron microscopic immunocytochemistry to ask whether individual differences in ABA resilience may correlate with the lengths of axo-somatic contacts made by GABAergic axon terminals onto layer 5 pyramidal neurons (L5P) in the prefrontal cortex. Contact lengths were, on average, 40% greater for the ABA-induced mice, relative to controls. Correspondingly, the proportion of L5P perikaryal plasma membrane contacted by GABAergic terminals was 45% greater for the ABA mice. Contact lengths in the anterior cingulate cortex correlated negatively and strongly with the overall wheel activity after FR (R = -0.87, P < 0.01), whereas those in the prelimbic cortex correlated negatively with wheel running specifically during the hours of food availability of the FR days (R = -0.84, P < 0.05). These negative correlations support the idea that increases in the glutamic acid decarboxylase (GAD) terminal contact lengths onto L5P contribute toward ABA resilience through suppression of wheel running, a behavior that is intrinsically rewarding and helpful for foraging but maladaptive within a cage.

  5. 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

    2015-02-03

    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.

  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. Determinants of carbon release from the active layer and permafrost deposits on the Tibetan Plateau

    NASA Astrophysics Data System (ADS)

    Chen, Leiyi; Liang, Junyi; Qin, Shuqi; Liu, Li; Fang, Kai; Xu, Yunping; Ding, Jinzhi; Li, Fei; Luo, Yiqi; Yang, Yuanhe

    2016-10-01

    The sign and magnitude of permafrost carbon (C)-climate feedback are highly uncertain due to the limited understanding of the decomposability of thawing permafrost and relevant mechanistic controls over C release. Here, by combining aerobic incubation with biomarker analysis and a three-pool model, we reveal that C quality (represented by a higher amount of fast cycling C but a lower amount of recalcitrant C compounds) and normalized CO2-C release in permafrost deposits were similar or even higher than those in the active layer, demonstrating a high vulnerability of C in Tibetan upland permafrost. We also illustrate that C quality exerts the most control over CO2-C release from the active layer, whereas soil microbial abundance is more directly associated with CO2-C release after permafrost thaw. Taken together, our findings highlight the importance of incorporating microbial properties into Earth System Models when predicting permafrost C dynamics under a changing environment.

  8. Effect of a fluid layer on the sound radiation of a plate and its active control

    NASA Astrophysics Data System (ADS)

    Sun, Yao; Pan, Jie; Yang, Tiejun

    2015-11-01

    In this paper, a baffled plate facing a layer of fluid is used to investigate the effects of the radiating environment on the plate's sound radiation and its active control. By varying the thickness of the fluid layer, different radiation environments are presented to the plate, resulting in a variation in the efficiencies and shapes of the radiation modes of the plate. As the design of feed-forward control of the radiated sound power and of feedback control of the vibration velocity or volume velocity is limited by the properties of the secondary control path (an open-loop frequency response function), the performance of the control system may be deteriorated if a controller optimally designed for one radiation environment is used for a different environment. The effects of radiation environment on the properties of the secondary control path and performance of active control are investigated.

  9. Determinants of carbon release from the active layer and permafrost deposits on the Tibetan Plateau.

    PubMed

    Chen, Leiyi; Liang, Junyi; Qin, Shuqi; Liu, Li; Fang, Kai; Xu, Yunping; Ding, Jinzhi; Li, Fei; Luo, Yiqi; Yang, Yuanhe

    2016-10-05

    The sign and magnitude of permafrost carbon (C)-climate feedback are highly uncertain due to the limited understanding of the decomposability of thawing permafrost and relevant mechanistic controls over C release. Here, by combining aerobic incubation with biomarker analysis and a three-pool model, we reveal that C quality (represented by a higher amount of fast cycling C but a lower amount of recalcitrant C compounds) and normalized CO2-C release in permafrost deposits were similar or even higher than those in the active layer, demonstrating a high vulnerability of C in Tibetan upland permafrost. We also illustrate that C quality exerts the most control over CO2-C release from the active layer, whereas soil microbial abundance is more directly associated with CO2-C release after permafrost thaw. Taken together, our findings highlight the importance of incorporating microbial properties into Earth System Models when predicting permafrost C dynamics under a changing environment.

  10. Control of the boundary layer separation about an airfoil by active surface heating

    NASA Technical Reports Server (NTRS)

    Maestrello, Lucio; Badavi, Forooz F.; Noonan, Kevin W.

    1988-01-01

    Application of active control to separated flow on the RC(6)-08 airfoil at high angle of attack by localized surface heating is numerically simulated by integrating the compressible two-dimensional nonlinear Navier-Stokes equations solver. Active control is simulated by local modification of the temperature boundary condition over a narrow strip on the upper surface of the airfoil. Both mean and perturbed profiles are favorably altered when excited with the same natural frequency of the shear layer by moderate surface heating for both laminar and turbulent separation. The shear layer is found to be very sensitive to localized surface heating in the vicinity of the separation point. The excitation field at the surface sufficiently altered both the local as well as the global circulation to cause a significant increase in lift and reduction in drag.

  11. 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.

  12. The active layer morphology of organic solar cells probed with grazing incidence scattering techniques.

    PubMed

    Müller-Buschbaum, Peter

    2014-12-10

    Grazing incidence X-ray scattering (GIXS) provides unique insights into the morphology of active materials and thin film layers used in organic photovoltaic devices. With grazing incidence wide angle X-ray scattering (GIWAXS) the molecular arrangement of the material is probed. GIWAXS is sensitive to the crystalline parts and allows for the determination of the crystal structure and the orientation of the crystalline regions with respect to the electrodes. With grazing incidence small angle X-ray scattering (GISAXS) the nano-scale structure inside the films is probed. As GISAXS is sensitive to length scales from nanometers to several hundred nanometers, all relevant length scales of organic solar cells are detectable. After an introduction to GISAXS and GIWAXS, selected examples for application of both techniques to active layer materials are reviewed. The particular focus is on conjugated polymers, such as poly(3-hexylthiophene) (P3HT).

  13. MMP Activity in the Hybrid Layer Detected with in situ Zymography

    PubMed Central

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

    2012-01-01

    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

  14. Layered HEVC/H.265 video transmission scheme based on hierarchical QAM optimization

    NASA Astrophysics Data System (ADS)

    Feng, Weidong; Zhou, Cheng; Xiong, Chengyi; Chen, Shaobo; Wang, Junxi

    2015-12-01

    High Efficiency Video Coding (HEVC) is the state-of-art video compression standard which fully support scalability features and is able to generate layered video streams with unequal importance. Unfortunately, when the base layer (BL) which is more importance to the stream is lost during the transmission, the enhancement layer (EL) based on the base layer must be discarded by receiver. Obviously, using the same transmittal strategies for BL and EL is unreasonable. This paper proposed an unequal error protection (UEP) system using different hierarchical amplitude modulation (HQAM). The BL data with high priority are mapped into the most reliable HQAM mode and the EL data with low priority are mapped into HQAM mode with fast transmission efficiency. Simulations on scalable HEVC codec show that the proposed optimized video transmission system is more attractive than the traditional equal error protection (EEP) scheme because it effectively balances the transmission efficiency and reconstruction video quality.

  15. Development of the method of an electrohydrodynamic force effect on a boundary layer for active control of aerodynamic flows

    NASA Astrophysics Data System (ADS)

    Aleshin, B. S.; Khomich, V. Yu.; Chernyshev, S. L.

    2016-12-01

    The results of investigations on the possibility of an electrohydrodynamic force effect on a gas flow implemented with the help of a barrier discharge are presented. A new method of controlling the laminar flow around a base with suppression of instabilities of the incoming flow due to electrohydrodynamic force action on the boundary layer near the forward edge of a swept wing is proposed. An efficient multidischarge actuator system is developed and created for active control of aerodynamic flows with induced-air-flow characteristics exceeding the world analogues.

  16. 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.

  17. The activity of nanocrystalline Fe-based alloys as electrode materials for the hydrogen evolution reaction

    NASA Astrophysics Data System (ADS)

    Müller, Christian Immanuel; Sellschopp, Kai; Tegel, Marcus; Rauscher, Thomas; Kieback, Bernd; Röntzsch, Lars

    2016-02-01

    In view of alkaline water electrolysis, the activities for the hydrogen evolution reaction of nanocrystalline Fe-based electrode materials were investigated and compared with the activities of polycrystalline Fe and Ni. Electrochemical methods were used to elucidate the overpotential value, the charge transfer resistance and the double layer capacity. Structural properties of the electrode surface were determined with SEM, XRD and XPS analyses. Thus, a correlation between electrochemical and structural parameters was found. In this context, we report on a cyclic voltammetric activation procedure which causes a significant increase of the surface area of Fe-based electrodes leading to a boost in effective activity of the activated electrodes. It was found that the intrinsic activity of activated Fe-based electrodes is very high due to the formation of a nanocrystalline surface layer. In contrast, the activation procedure influences only the intrinsic activity of the Ni electrodes without the formation of a porous surface layer.

  18. High-precision structure fabrication based on an etching resistance layer

    NASA Astrophysics Data System (ADS)

    Zhang, Man; Deng, Qiling; Shi, Lifang; Cao, Axiu; Pang, Hui; Liu, Xin; Wang, Jiazhou; Hu, Song

    2016-10-01

    The high-precision fabrication of micro-/nano-structure is a challenge. In this paper, we proposed a new fabrication method of high-precision structure based on an etching resistance layer. The high-precision features were fabricated by photolithography technique, followed by the etching process to transfer the features to the substrate. During this process, the etching uniformity and error lead to the feature distortion. We introduced an etching resistance layer between feature layer and substrate. The etching process will stop when arriving at the resistance layer. Due to the high precision of the plating film, the high-precision structure depth was achieved. In our experiment, we introduced aluminum trioxide as the etching resistance layer. The structures with low depth error of less than 5% were fabricated.

  19. Layer-specificity in the effects of attention and working memory on activity in primary visual cortex

    PubMed Central

    van Kerkoerle, Timo; Self, Matthew W.; Roelfsema, Pieter R.

    2017-01-01

    Neuronal activity in early visual cortex depends on attention shifts but the contribution to working memory has remained unclear. Here, we examine neuronal activity in the different layers of the primary visual cortex (V1) in an attention-demanding and a working memory task. A current-source density analysis reveales top-down inputs in the superficial layers and layer 5, and an increase in neuronal firing rates most pronounced in the superficial and deep layers and weaker in input layer 4. This increased activity is strongest in the attention task but it is also highly reliable during working memory delays. A visual mask erases the V1 memory activity, but it reappeares at a later point in time. These results provide new insights in the laminar circuits involved in the top-down modulation of activity in early visual cortex in the presence and absence of visual stimuli. PMID:28054544

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

    PubMed Central

    Bock, Tobias

    2016-01-01

    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 on N-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

  1. Organic layer serves as a hotspot of microbial activity and abundance in Arctic tundra soils.

    PubMed

    Lee, Seung-Hoon; Jang, Inyoung; Chae, Namyi; Choi, Taejin; Kang, Hojeong

    2013-02-01

    Tundra ecosystem is of importance for its high accumulation of organic carbon and vulnerability to future climate change. Microorganisms play a key role in carbon dynamics of the tundra ecosystem by mineralizing organic carbon. We assessed both ecosystem process rates and community structure of Bacteria, Archaea, and Fungi in different soil layers (surface organic layer and subsurface mineral soil) in an Arctic soil ecosystem located at Spitsbergen, Svalbard during the summer of 2008 by using biochemical and molecular analyses, such as enzymatic assay, terminal restriction fragment length polymorphism (T-RFLP), quantitative polymerase chain reaction (qPCR), and pyrosequencing. Activity of hydrolytic enzymes showed difference according to soil type. For all three microbial communities, the average gene copy number did not significantly differ between soil types. However, archaeal diversities appeared to differ according to soil type, whereas bacterial and fungal diversity indices did not show any variation. Correlation analysis between biogeochemical and microbial parameters exhibited a discriminating pattern according to microbial or soil types. Analysis of the microbial community structure showed that bacterial and archaeal communities have different profiles with unique phylotypes in terms of soil types. Water content and hydrolytic enzymes were found to be related with the structure of bacterial and archaeal communities, whereas soil organic matter (SOM) and total organic carbon (TOC) were related with bacterial communities. The overall results of this study indicate that microbial enzyme activity were generally higher in the organic layer than in mineral soils and that bacterial and archaeal communities differed between the organic layer and mineral soils in the Arctic region. Compared to mineral soil, peat-covered organic layer may represent a hotspot for secondary productivity and nutrient cycling in this ecosystem.

  2. Performance of the active sidewall boundary-layer removal system for the Langley 0.3-meter Transonic Cryogenic Tunnel

    NASA Technical Reports Server (NTRS)

    Balakrishna, S.; Kilgore, W. Allen; Murthy, A. V.

    1989-01-01

    A performance evaluation of an active sidewall boundary-layer removal system for the Langley 0.3-m Transonic Cryogenic Tunnel (TCT) was evaluated in 1988. This system uses a compressor and two throttling digital valves to control the boundary-layer mass flow removal from the tunnel. The compressor operates near the maximum pressure ratio for all conditions. The system uses a surge prevention and flow recirculation scheme. A microprocessor based controller is used to provide the necessary mass flow and compressor pressure ratio control. Initial tests on the system indicated problems in realizing smooth mass flow control while running the compressor at high speed and high pressure ratios. An alternate method has been conceived to realize boundary-layer mass flow control which avoids the recirculation of the compressor mass flow and operation near the compressor surge point. This scheme is based on varying the speed of the compressor for a sufficient pressure ratio to provide needed mass flow removal. The system has a mass flow removal capability of about 10 percent of test section flow at M = 0.3 and 4 percent at M = 0.8. The system performance has been evaluated in the form of the compressor map, and compressor tunnel interface characteristics covering most of the 0.3-m TCT operational envelope.

  3. Study of multi-layer active magnetic regenerators using magnetocaloric materials with first and second order phase transition

    NASA Astrophysics Data System (ADS)

    Lei, T.; Engelbrecht, K.; Nielsen, K. K.; Neves Bez, H.; Bahl, C. R. H.

    2016-09-01

    Magnetocaloric materials (MCM) with a first order phase transition (FOPT) usually exhibit a large, although sharp, isothermal entropy change near their Curie temperature, compared to materials with a second order phase transition (SOPT). Experimental results of applying FOPT materials in recent magnetocaloric refrigerators (MCR) demonstrated the great potential for these materials, but a thorough study on the impact of the moderate adiabatic temperature change and strong temperature dependence of the magnetocaloric effect (MCE) is lacking. Besides, comparing active magnetic regenerators (AMR) using FOPT and SOPT materials is also of fundamental interest. We present modeling results of multi-layer AMRs using FOPT and SOPT materials based on a 1D numerical model. First the impact of isothermal entropy change, adiabatic temperature change and shape factor describing the temperature dependence of the MCE are quantified and analyzed by using artificially built magnetocaloric properties. Then, based on measured magnetocaloric properties of La(Fe,Mn,Si)13H y and Gd, an investigation on how to layer typical FOPT and SOPT materials with different temperature spans is carried out. Moreover, the sensitivity of variation in Curie temperature distribution for both groups of AMRs is investigated. Finally, a concept of mixing FOPT and SOPT materials is studied for improving the stability of layered AMRs with existing materials.

  4. Multiscale active layer morphologies for organic photovoltaics through self-assembly of nanospheres.

    PubMed

    Gehan, Timothy S; Bag, Monojit; Renna, Lawrence A; Shen, Xiaobo; Algaier, Dana D; Lahti, Paul M; Russell, Thomas P; Venkataraman, Dhandapani

    2014-09-10

    We address here the need for a general strategy to control molecular assembly over multiple length scales. Efficient organic photovoltaics require an active layer comprised of a mesoscale interconnected networks of nanoscale aggregates of semiconductors. We demonstrate a method, using principles of molecular self-assembly and geometric packing, for controlled assembly of semiconductors at the nanoscale and mesoscale. Nanoparticles of poly(3-hexylthiophene) (P3HT) or [6,6]-phenyl-C61-butyric acid methyl ester (PCBM) were fabricated with targeted sizes. Nanoparticles containing a blend of both P3HT and PCBM were also fabricated. The active layer morphology was tuned by the changing particle composition, particle radii, and the ratios of P3HT:PCBM particles. Photovoltaic devices were fabricated from these aqueous nanoparticle dispersions with comparable device performance to typical bulk-heterojunction devices. Our strategy opens a revolutionary pathway to study and tune the active layer morphology systematically while exercising control of the component assembly at multiple length scales.

  5. 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

    2015-11-07

    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.

  6. Reagentless biosensor based on layer-by-layer assembly of functional multiwall carbon nanotubes and enzyme-mediator biocomposite*

    PubMed Central

    Zhou, Xing-hua; Xi, Feng-na; Zhang, Yi-ming; Lin, Xian-fu

    2011-01-01

    A simple and controllable layer-by-layer (LBL) assembly method was proposed for the construction of reagentless biosensors based on electrostatic interaction between functional multiwall carbon nanotubes (MWNTs) and enzyme-mediator biocomposites. The carboxylated MWNTs were wrapped with polycations poly(allylamine hydrochloride) (PAH) and the resulting PAH-MWNTs were well dispersed and positively charged. As a water-soluble dye methylene blue (MB) could mix well with horseradish peroxidase (HRP) to form a biocompatible and negatively-charged HRP-MB biocomposite. A (PAH-MWNTs/HRP-MB)n bionanomultilayer was then prepared by electrostatic LBL assembly of PAH-MWNTs and HRP-MB on a polyelectrolyte precursor film-modified Au electrode. Due to the excellent biocompatibility of HRP-MB biocomposite and the uniform LBL assembly, the immobilized HRP could retain its natural bioactivity and MB could efficiently shuttle electrons between HRP and the electrode. The incorporation of MWNTs in the bionanomultilayer enhanced the surface coverage concentration of the electroactive enzyme and increased the catalytic current response of the electrode. The proposed biosensor displayed a fast response (2 s) to hydrogen peroxide with a low detection limit of 2.0×10−7 mol/L (S/N=3). This work provided a versatile platform in the further development of reagentless biosensors. PMID:21634040

  7. Bioavailable Carbon and the Relative Degradation State of Organic Matter in Active Layer and Permafrost Soils

    NASA Astrophysics Data System (ADS)

    Jastrow, J. D.; Burke, V. J.; Vugteveen, T. W.; Fan, Z.; Hofmann, S. M.; Lederhouse, J. S.; Matamala, R.; Michaelson, G. J.; Mishra, U.; Ping, C. L.

    2015-12-01

    The decomposability of soil organic carbon (SOC) in permafrost regions is a key uncertainty in efforts to predict carbon release from thawing permafrost and its impacts. The cold and often wet environment is the dominant factor limiting decomposer activity, and soil organic matter is often preserved in a relatively undecomposed and uncomplexed state. Thus, the impacts of soil warming and permafrost thaw are likely to depend at least initially on the genesis and past history of organic matter degradation before its stabilization in permafrost. We compared the bioavailability and relative degradation state of SOC in active layer and permafrost soils from Arctic tundra in Alaska. To assess readily bioavailable SOC, we quantified salt (0.5 M K2SO4) extractable organic matter (SEOM), which correlates well with carbon mineralization rates in short-term soil incubations. To assess the relative degradation state of SOC, we used particle size fractionation to isolate fibric (coarse) from more degraded (fine) particulate organic matter (POM) and separated mineral-associated organic matter into silt- and clay-sized fractions. On average, bulk SOC concentrations in permafrost were lower than in comparable active layer horizons. Although SEOM represented a very small proportion of the bulk SOC, this proportion was greater in permafrost than in comparable active layer soils. A large proportion of bulk SOC was found in POM for all horizons. Even for mineral soils, about 40% of bulk SOC was in POM pools, indicating that organic matter in both active layer and permafrost mineral soils was relatively undecomposed compared to typical temperate soils. Not surprisingly, organic soils had a greater proportion of POM and mineral soils had greater silt- and clay-sized carbon pools, while cryoturbated soils were intermediate. For organic horizons, permafrost organic matter was generally more degraded than in comparable active layer horizons. However, in mineral and cryoturbated horizons

  8. Starch Biocatalyst Based on α-Amylase-Mg/Al-Layered Double Hydroxide Nanohybrids.

    PubMed

    Bruna, Felipe; Pereira, Marita G; Polizeli, Maria de Lourdes T M; Valim, João B

    2015-08-26

    The design of new biocatalysts through the immobilization of enzymes, improving their stability and reuse, plays a major role in the development of sustainable methodologies toward the so-called green chemistry. In this work, α-amylase (AAM) biocatalyst based on Mg3Al-layered double-hydroxide (LDH) matrix was successfully developed with the adsorption method. The adsorption process was studied and optimized as a function of time and enzyme concentration. The biocatalyst was characterized, and the mechanism of interaction between AAM and LDH, as well as the immobilization effects on the catalytic activity, was elucidated. The adsorption process was fast and irreversible, thus yielding a stable biohybrid material. The immobilized AAM partially retained its enzymatic activity, and the biocatalyst rapidly hydrolyzed starch in an aqueous solution with enhanced efficiency at intermediate loading values of ca. 50 mg/g of AAM/LDH. Multiple attachments through electrostatic interactions affected the conformation of the immobilized enzyme on the LDH surface. The biocatalyst was successfully stored in its dry form, retaining 100% of its catalytic activity. The results reveal the potential usefulness of a LDH compound as a support of α-amylase for the hydrolysis of starch that may be applied in industrial and pharmaceutical processes as a simple, environmentally friendly, and low-cost biocatalyst.

  9. Photodetectors Based on Two-Dimensional Layer-Structured Hybrid Lead Iodide Perovskite Semiconductors.

    PubMed

    Zhou, Jiachen; Chu, Yingli; Huang, Jia

    2016-10-05

    Hybrid lead iodide perovskite semiconductors have attracted intense research interests recently because of their easy fabrication processes and high power conversion efficiencies in photovoltaic applications. Layer-structured materials have interesting properties such as quantum confinement effect and tunable band gap due to the unique two-dimensional crystalline structures. ⟨100⟩-oriented layer-structured perovskite materials are inherited from three-dimensional ABX3 perovskite materials with a generalized formula of (RNH3)2(CH3NH3)n-1MnX3n+1, and adopt the Ruddlesden-Popper type crystalline structure. Here we report the synthesis and investigation of three layer-structured perovskite materials with different layer numbers: (C4H9NH3)2PbI4 (n = 1, one-layered perovskite), (C4H9NH3)2(CH3NH3)Pb2I7 (n = 2, two-layered perovskite) and (C4H9NH3)2(CH3NH3)2Pb3I10 (n = 3, three-layered perovskite). Their photoelectronic properties were investigated in related to their molecular structures. Photodetectors based on these two-dimensional (2D) layer-structured perovskite materials showed tunable photoresponse with short response time in milliseconds. The photodetectors based on three-layered perovskite showed better performances than those of the other two devices, in terms of output current, responsivity, Ilight/Idark ratio, and response time, because of its smaller optical band gap and more condensed microstructure comparing the other two materials. These results revealed the relationship between the molecular structures, film microstructures and the photoresponse properties of 2D layer-structured hybrid perovskites, and demonstrated their potentials as flexible, functional, and tunable semiconductors in optoelectronic applications, by taking advantage of their tunable quantum well molecular structure.

  10. Properties of the F2-layer critical frequency median in the nocturnal subauroral ionosphere during low and moderate solar activity

    NASA Astrophysics Data System (ADS)

    Deminov, M. G.; Deminov, R. G.; Shubin, V. N.

    2016-11-01

    Based on an analysis of data from the European ionospheric stations at subauroral latitudes, it has been found that the main ionospheric trough (MIT) is not characteristic for the monthly median of the F2-layer critical frequency ( foF2), at least for low and moderate solar activity. In order to explain this effect, the properties of foF2 in the nocturnal subauroral ionosphere have been additionally studied for low geomagnetic activity, when the MIT localization is known quite reliably. It has been found that at low and moderate solar activity during night hours in winter, the foF2 data from ionospheric stations are often absent in the MIT area. For this reason, a model of the foF2 monthly median, which was constructed from the remaining data of these stations, contains no MIT or a very weakly pronounced MIT.

  11. A nanoporous AlN layer patterned by anodic aluminum oxide and its application as a buffer layer in a GaN-based light-emitting diode.

    PubMed

    Chen, Lung-Chien; Wang, Chih-Kai; Huang, Jenn-Bin; Hong, Lu-Sheng

    2009-02-25

    This work investigates a nanoporous aluminum nitride (AlN) layer prepared using an anodic aluminum oxide (AAO) process and its application as a buffer layer for a GaN-based light-emitting diode (LED) fabricated on sapphire substrate. Following this AAO process, the average pore spacing and pore diameter of the nanoporous AlN layer were in the ranges 180-200 nm and 100-150 nm, respectively. The light output power of the GaN-based LED with a nanoporous AlN layer was about 53% higher than that of a GaN-based LED without a nanoporous AlN layer at an injection current of 20 mA. At an injection current of 80 mA, the light output power was increased by about 34%.

  12. The robustness of multiplex networks under layer node-based attack

    PubMed Central

    Zhao, Da-wei; Wang, Lian-hai; Zhi, Yong-feng; Zhang, Jun; Wang, Zhen

    2016-01-01

    From transportation networks to complex infrastructures, and to social and economic networks, a large variety of systems can be described in terms of multiplex networks formed by a set of nodes interacting through different network layers. Network robustness, as one of the most successful application areas of complex networks, has attracted great interest in a myriad of research realms. In this regard, how multiplex networks respond to potential attack is still an open issue. Here we study the robustness of multiplex networks under layer node-based random or targeted attack, which means that nodes just suffer attacks in a given layer yet no additional influence to their connections beyond this layer. A theoretical analysis framework is proposed to calculate the critical threshold and the size of giant component of multiplex networks when nodes are removed randomly or intentionally. Via numerous simulations, it is unveiled that the theoretical method can accurately predict the threshold and the size of giant component, irrespective of attack strategies. Moreover, we also compare the robustness of multiplex networks under multiplex node-based attack and layer node-based attack, and find that layer node-based attack makes multiplex networks more vulnerable, regardless of average degree and underlying topology. PMID:27075870

  13. Entropy generation in a parallel-plate active magnetic regenerator with insulator layers

    NASA Astrophysics Data System (ADS)

    Mugica Guerrero, Ibai; Poncet, Sébastien; Bouchard, Jonathan

    2017-02-01

    This paper proposes a feasible solution to diminish conduction losses in active magnetic regenerators. Higher performances of these machines are linked to a lower thermal conductivity of the Magneto-Caloric Material (MCM) in the streamwise direction. The concept presented here involves the insertion of insulator layers along the length of a parallel-plate magnetic regenerator in order to reduce the heat conduction within the MCM. This idea is investigated by means of a 1D numerical model. This model solves not only the energy equations for the fluid and solid domains but also the magnetic circuit that conforms the experimental setup of reference. In conclusion, the addition of insulator layers within the MCM increases the temperature span, cooling load, and coefficient of performance by a combination of lower heat conduction losses and an increment of the global Magneto-Caloric Effect. The generated entropy by solid conduction, fluid convection, and conduction and viscous losses are calculated to help understand the implications of introducing insulator layers in magnetic regenerators. Finally, the optimal number of insulator layers is studied.

  14. Active flow control insight gained from a modified integral boundary layer equation

    NASA Astrophysics Data System (ADS)

    Seifert, Avraham

    2016-11-01

    Active Flow Control (AFC) can alter the development of boundary layers with applications (e.g., reducing drag by separation delay or separating the boundary layers and enhancing vortex shedding to increase drag). Historically, significant effects of steady AFC methods were observed. Unsteady actuation is significantly more efficient than steady. Full-scale AFC tests were conducted with varying levels of success. While clearly relevant to industry, AFC implementation relies on expert knowledge with proven intuition and or costly and lengthy computational efforts. This situation hinders the use of AFC while simple, quick and reliable design method is absent. An updated form of the unsteady integral boundary layer (UIBL) equations, that include AFC terms (unsteady wall transpiration and body forces) can be used to assist in AFC analysis and design. With these equations and given a family of suitable velocity profiles, the momentum thickness can be calculated and matched with an outer, potential flow solution in 2D and 3D manner to create an AFC design tool, parallel to proven tools for airfoil design. Limiting cases of the UIBL equation can be used to analyze candidate AFC concepts in terms of their capability to modify the boundary layers development and system performance.

  15. High gamma power in ECoG reflects cortical electrical stimulation effects on unit activity in layers V/VI

    NASA Astrophysics Data System (ADS)

    Yazdan-Shahmorad, Azadeh; Kipke, Daryl R.; Lehmkuhle, Mark J.

    2013-12-01

    Objective. Cortical electrical stimulation (CES) has been used extensively in experimental neuroscience to modulate neuronal or behavioral activity, which has led this technique to be considered in neurorehabilitation. Because the cortex and the surrounding anatomy have irregular geometries as well as inhomogeneous and anisotropic electrical properties, the mechanism by which CES has therapeutic effects is poorly understood. Therapeutic effects of CES can be improved by optimizing the stimulation parameters based on the effects of various stimulation parameters on target brain regions. Approach. In this study we have compared the effects of CES pulse polarity, frequency, and amplitude on unit activity recorded from rat primary motor cortex with the effects on the corresponding local field potentials (LFP), and electrocorticograms (ECoG). CES was applied at the surface of the cortex and the unit activity and LFPs were recorded using a penetrating electrode array, which was implanted below the stimulation site. ECoGs were recorded from the vicinity of the stimulation site. Main results. Time-frequency analysis of LFPs following CES showed correlation of gamma frequencies with unit activity response in all layers. More importantly, high gamma power of ECoG signals only correlated with the unit activity in lower layers (V-VI) following CES. Time-frequency correlations, which were found between LFPs, ECoGs and unit activity, were frequency- and amplitude-dependent. Significance. The signature of the neural activity observed in LFP and ECoG signals provides a better understanding of the effects of stimulation on network activity, representative of large numbers of neurons responding to stimulation. These results demonstrate that the neurorehabilitation and neuroprosthetic applications of CES targeting layered cortex can be further improved by using field potential recordings as surrogates to unit activity aimed at optimizing stimulation efficacy. Likewise, the signatures

  16. Fabricating Electrochromic Thin Films Based on Metallo-Polymers Using Layer-by-Layer Self-Assembly: An Attractive Laboratory Experiment

    ERIC Educational Resources Information Center

    Schott, Marco; Beck, Matthias; Winkler, Franziska; Lorrmann, Henning; Kurth, Dirk G.

    2015-01-01

    Metallo-supramolecular polyelectrolytes (MEPE) based on iron(II)-acetate and 1,4-bis(2,2':6',2?-terpyridin-4'-yl)benzene are assembled by layer-by-layer deposition on transparent electrode surfaces. When a potential is applied, the color of the film can be switched from blue to transparent. Due to the strong absorption and the fast switching…

  17. Superior Photostability and Photocatalytic Activity of ZnO Nanoparticles Coated with Ultrathin TiO2 Layers through Atomic-Layer Deposition.

    PubMed

    Sridharan, Kishore; Jang, Eunyong; Park, Young Min; Park, Tae Joo

    2015-12-21

    Atomic-layer deposition (ALD) is a thin-film growth technology that allows for conformal growth of thin films with atomic-level control over their thickness. Although ALD is successful in the semiconductor manufacturing industry, its feasibility for nanoparticle coating has been less explored. Herein, the ALD coating of TiO2 layers on ZnO nanoparticles by employing a specialized rotary reactor is demonstrated. The photocatalytic activity and photostability of ZnO nanoparticles coated with TiO2 layers by ALD and chemical methods were examined by the photodegradation of Rhodamine B dye under UV irradiation. Even though the photocatalytic activity of the presynthesized ZnO nanoparticles is higher than that of commercial P25 TiO2 nanoparticles, their activity tends to decline due to severe photocorrosion. The chemically synthesized TiO2 coating layer on ZnO resulted in severely declined photoactivity despite the improved photostability. However, ultrathin and conformal ALD TiO2 coatings (≈ 0.75-1.5 nm) on ZnO improved its photostability without degradation of photocatalytic activity. Surprisingly, the photostability is comparable to that of pure TiO2, and the photocatalytic activity to that of pure ZnO.

  18. Investigating the effects of capping layer on optical gain of nitride based semiconductor nanostructure lasers

    NASA Astrophysics Data System (ADS)

    Annabi Milani, E.; Mohadesi, V.; Asgari, A.

    2017-04-01

    In this study, the effects of GaN capping layer on the behaviour of AlGaN/GaN nanostructure based laser is considered. We have employed the self-consistent solution of Poisson and Schrodinger equations for calculation of the energy levels, wave functions and conduction and valance bands profile. The impact of different thicknesses of the capping layer has been studied for sheet carrier density, then on optical gain. The results indicate that, by increasing the thickness of the cap layer, the optical gain decreases.

  19. Rapid Fracture of Layered Shields Based on Al - Si3N4 Composite Material

    NASA Astrophysics Data System (ADS)

    Gilev, V. G.

    2003-05-01

    Structures of anti-bullet shields with an armor layer of an Al - Si3N4 composite material based on aluminum alloys AK5M2 and AL-23-1 reinforced by a porous Si3N4 ceramic formed from the components are considered. The effects of the amount of Si3N4 in the composite material, the thickness of the components in the ceramics, and the size proportions in the structure are studied. Shields of layered and layered-lattice types are shown to have high bullet resistance.

  20. Ni-base superalloy powder-processed porous layer for gas cooling in extreme environments

    DOE PAGES

    White, Emma M. H.; Heidloff, Andrew J.; Byrd, David J.; ...

    2016-05-26

    Extreme high temperature conditions demand novel solutions for hot gas filters and coolant access architectures, i.e., porous layers on exposed components. These high temperatures, for example in current turbine engines, are at or exceeding current material limits for high temperature oxidation/corrosion, creep resistance, and, even, melting temperature. Thus novel blade designs allowing greater heat removal are required to maintain airfoil temperatures below melting and/ or rapid creep deformation limits. Gas atomized Ni-base superalloy powders were partially sintered into porous layers to allow full-surface, transpirational cooling of the surface of airfoils. Furthermore, these powder-processed porous layers were fully characterized for surface,more » morphology, cross-sectional microstructure, and mechanical strength characteristics. A sintering model based on pure Ni surface diffusion correlated well with the experimental results and allowed reasonable control over the partial sintering process to obtain a specified level of porosity within the porous layer.« less

  1. Thermal stability of copper silicide passivation layers in copper-based multilevel interconnects

    NASA Astrophysics Data System (ADS)

    Hymes, S.; Kumar, K. S.; Murarka, S. P.; Ding, P. J.; Wang, W.; Lanford, W. A.

    1998-04-01

    Copper thin films were exposed to a dilute silane mixture at temperatures in the range of 190-363 °C. The resulting silicide surface layers were characterized by four-point probe, Rutherford backscattering spectrometry, and x-ray diffraction. A definitive stability regime is observed in which progressively higher copper content phases exist with increasing temperature. Cu3Si, formed in silane, on annealing converts to Cu5Si and eventually to no silicide layer by a silicon diffusion reaction that in an inert ambient drives silicon into underlying copper to form a solid solution. In oxidizing ambients, a similar phenomenon occurs but now silicon also diffuses to surfaces where it oxidizes to form a self-passivating SiO2 layer on surface. These results have important implications governing integration of copper silicide as a passivation layer and silicon hydride based dielectric deposition in copper-based multilevel interconnect in ultralarge scale integration.

  2. Ni-base superalloy powder-processed porous layer for gas cooling in extreme environments

    SciTech Connect

    White, Emma M. H.; Heidloff, Andrew J.; Byrd, David J.; Anderson, Ross D.; Anderson, Iver E.

    2016-05-26

    Extreme high temperature conditions demand novel solutions for hot gas filters and coolant access architectures, i.e., porous layers on exposed components. These high temperatures, for example in current turbine engines, are at or exceeding current material limits for high temperature oxidation/corrosion, creep resistance, and, even, melting temperature. Thus novel blade designs allowing greater heat removal are required to maintain airfoil temperatures below melting and/ or rapid creep deformation limits. Gas atomized Ni-base superalloy powders were partially sintered into porous layers to allow full-surface, transpirational cooling of the surface of airfoils. Furthermore, these powder-processed porous layers were fully characterized for surface, morphology, cross-sectional microstructure, and mechanical strength characteristics. A sintering model based on pure Ni surface diffusion correlated well with the experimental results and allowed reasonable control over the partial sintering process to obtain a specified level of porosity within the porous layer.

  3. Seasonal and solar activity variations of F3 layer and quadruple stratification (StF-4) near the equatorial region

    NASA Astrophysics Data System (ADS)

    Tardelli, A.; Fagundes, P. R.; Pezzopane, M.; Venkatesh, K.; Pillat, V. G.

    2016-12-01

    The study of multiple stratification of the F layer has the initial records in the midtwentieth century. Since then, many studies were focused on F3 layer. The diurnal, seasonal, and solar activity variations of the F3 layer characteristics have been investigated by several researchers. Recently, investigations on multiple stratifications of F layer received an important boost after the quadruple stratification (StF-4) was observed at Palmas (10.3°S, 48.3°W; dip latitude 6.6°S—near-equatorial region), Brazil. The present study reports the latest findings related with the seasonal and solar activity characteristics of the F3 layer and StF-4 near the equatorial region during the period from 2002 to 2006. A significant connection between StF-4 and F3 layer has been noticed, since the StF-4 is always preceded and followed by a F3 layer appearance. However, the F3 layer and the StF-4 present different seasonal and solar cycle variations. At a near-equatorial station Palmas, the F3 layer shows the maximum and minimum occurrences during summer and winter seasons, respectively. On the contrary, the StF-4 presents the maximum and minimum occurrences during winter and summer seasons, respectively. While the F3 layer occurrence is not affected by solar cycle, the StF-4 appearance is instead more frequent during high solar activity.

  4. Nanosecond laser-induced selective removal of the active layer of CuInGaSe2 solar cells by stress-assisted ablation

    NASA Astrophysics Data System (ADS)

    Buzás, András; Geretovszky, Zsolt

    2012-06-01

    We demonstrate that laser pulses of nanosecond duration (λ=1064 nm, τ=25 ns, PRR =5 kHz) are capable of the clean removal of the CuInGaSe2 (CIGS) and ZnO:Al layers in the layer structure of chalcogenide-based solar cells, leaving the underlying Mo layer undamaged and producing excellent crater morphology. Our results prove that the material removal process is governed by the thermomechanical stress developing in the CIGS layer due to rapid laser heating. In the mechanical ablation of the active layer, three phenomena play a crucial role, namely, delamination, buckling, and fracture. Morphological and compositional analysis of the laser-processed areas is used to identify the experimental parameters where clean mechanical ablation can be achieved. Numerical calculations, performed in the comsol software environment, are also presented to complement the experimental tendencies and verify the proposed model. Our calculation proves the development of a stress distribution that drives the delamination of the CIGS and Mo layers. As the delamination front proceeds radially outward, the separation of the layers ceases in the colder outer regions according to the Griffith's criterion and defines the size of the craters produced afterwards. The free-standing chalcogenide layer continues to deform, and buckling results in a growing tensile stress at the perimeter of the delaminated area, where ultimately fracture will finalize the removal process and facilitate the clean ablation of the laser-irradiated area.

  5. The layer boundary effect on multi-layer mesoporous TiO2 film based dye sensitized solar cells

    SciTech Connect

    Xu, Feng; Zhu, Kai; Zhao, Yixin

    2016-10-10

    Multi-layer mesoporous TiO2 prepared by screen printing is widely used for fabrication of high-efficiency dye-sensitized solar cells (DSSCs). Here, we compare the three types of ~10 um thick mesoporous TiO2 films, which were screen printed as 1-, 2- and 4-layers using the same TiO2 nanocrystal paste. The layer boundary of the multi-layer mesoporous TiO2 films was observed in the cross-section SEM. The existence of a layer boundary could reduce the photoelectron diffusion length with the increase of layer number. However, the photoelectron diffusion lengths of the Z907 dye sensitized solar cells based on these different layered mesoporous TiO2 films are all longer than the film thickness. Consequently, the photovoltaic performance seems to have little dependence on the layer number of the multi-layer TiO2 based DSSCs.

  6. Enhancing the performance of nanofiltration membranes by modifying the active layer with aramide dendrimers.

    PubMed

    de Jubera, Ana M Saenz; Gao, Yuan; Moore, Jeffrey S; Cahill, David G; Mariñas, Benito J

    2012-09-04

    The fully aromatic polyamide active layer of a commercial nanofiltration membrane was modified with three generations (G1, G2, and G3) of aramide dendrimers, all with oligoethylene glycol chains on their peripheries. Permeation experiments revealed that the rejection of Rhodamine WT, used as a surrogate for organic contaminants, improved 1-2 orders of magnitude for membranes modified with G2 and G3 dendrimers at loadings of 0.7-3.5 μg/cm(2) (dendrimer layer thicknesses of ~1-6 nm) compared to the performance of unmodified membranes. In contrast, the corresponding water permeability of dendrimer-modified membranes decreased by only ~30%. Although an enhancement in the rejection of H(3)AsO(3), NaCl, and BaCl(2) was also observed for dendritic membranes, the effect was less pronounced than that for rhodamine WT. Characterization of membranes modified with 3.5 μg/cm(2) dendrimers G2 and G3 by Rutherford backscattering spectrometry with the aid of heavy ion probes (Ag(+) and Ba(2+)) revealed that accessibility of the larger Ba(2+) probe to carboxylate groups on the active layer decreased for the membranes modified with dendrimers.

  7. Active control of acoustic radiation from laminated cylindrical shells integrated with a piezoelectric layer

    NASA Astrophysics Data System (ADS)

    Cao, Xiongtao; Shi, Lei; Zhang, Xusheng; Jiang, Guohe

    2013-06-01

    Active control of sound radiation from piezoelectric laminated cylindrical shells is theoretically investigated in the wavenumber domain. The governing equations of the smart cylindrical shells are derived by using first-order shear deformation theory. The smart layer is divided into lots of actuator patches, each of which is coated with two very thin electrodes at its inner and outer surfaces. Proportional derivative negative feedback control is applied to the actuator patches and the stiffness of the controlled layer is derived in the wavenumber domain. The equivalent driving forces and moments generated by the piezoelectric layer can produce distinct sound radiation. Large actuator patches cause strong wavenumber conversion and fluctuation of the far-field sound pressure, and do not make any contribution to sound reduction. Nevertheless, suitable small actuator patches induce weak wavenumber conversion and play an important role in the suppression of vibration and acoustic power. The derivative gain of the active control can effectively suppress sound radiation from smart cylindrical shells. The effects of small proportional gain on the sound field can be neglected, but large proportional gain has a great impact on the acoustic radiation of cylindrical shells. The influence of different piezoelectric materials on the acoustic power is described in the numerical results.

  8. Improving Performance via Blocking Layers in Dye-Sensitized Solar Cells Based on Nanowire Photoanodes.

    PubMed

    Li, Luping; Xu, Cheng; Zhao, Yang; Chen, Shikai; Ziegler, Kirk J

    2015-06-17

    Electron recombination in dye-sensitized solar cells (DSSCs) results in significant electron loss and performance degradation. However, the reduction of electron recombination via blocking layers in nanowire-based DSSCs has rarely been investigated. In this study, HfO2 or TiO2 blocking layers are deposited on nanowire surfaces via atomic layer deposition (ALD) to reduce electron recombination in nanowire-based DSSCs. The control cell consisting of ITO nanowires coated with a porous shell of TiO2 by TiCl4 treatment yields an efficiency of 2.82%. The efficiency increases dramatically to 5.38% upon the insertion of a 1.3 nm TiO2 compact layer between the nanowire surface and porous TiO2 shell. This efficiency enhancement implies that porous sol-gel coatings on nanowires (e.g., via TiCl4 treatment) result in significant electron recombination in nanowire-based DSSCs, while compact coatings formed by ALD are more advantageous because of their ability to act as a blocking layer. By comparing nanowire-based DSSCs with their nanoparticle-based counterparts, we find that the nanowire-based DSSCs suffer more severe electron recombination from ITO due to the much higher surface area exposed to the electrolyte. While the insertion of a high band gap compact layer of HfO2 between the interface of the conductive nanowire and TiO2 shell improves performance, a comparison of the cell performance between TiO2 and HfO2 compact layers indicates that charge collection is suppressed by the difference in energy states. Consequently, the use of high band gap materials at the interface of conductive nanowires and TiO2 is not recommended.

  9. Alginate/chitosan based bi-layer composite membrane as potential sustained-release wound dressing containing ciprofloxacin hydrochloride

    NASA Astrophysics Data System (ADS)

    Han, Fei; Dong, Yang; Song, Aihua; Yin, Ran; Li, Sanming

    2014-08-01

    The aims of this research were to develop and evaluate a novel ciprofloxacin hydrochloride loaded bi-layer composite membrane based on alginate and chitosan. In vitro antimicrobial activity, drug permeation study, morphology, cytotoxicity, primary skin irritation and in vivo pharmacodynamics were investigated. Results showed that the membranes could inhibit the growth of microorganisms for longer than 7 days. And there was no significant decrease in the metabolic activity of the Hacat fibroblasts cells were treated with the membranes. No edema and erythema were observed after administration of membranes on the rabbit skin after 14 days. Moreover, the results of pharmacodynamics showed that the membranes were more effective in improving the wound healing process. In conclusion, a novel bi-layer composite membrane was developed and results suggested that it could be exploited as sustained-release wound dressings.

  10. Nanoparticle layer deposition for highly controlled multilayer formation based on high- coverage monolayers of nanoparticles

    PubMed Central

    Liu, Yue; Williams, Mackenzie G.; Miller, Timothy J.; Teplyakov, Andrew V.

    2015-01-01

    This paper establishes a strategy for chemical deposition of functionalized nanoparticles onto solid substrates in a layer-by-layer process based on self-limiting surface chemical reactions leading to complete monolayer formation within the multilayer system without any additional intermediate layers – nanoparticle layer deposition (NPLD). This approach is fundamentally different from previously established traditional layer-by-layer deposition techniques and is conceptually more similar to well-known atomic and molecular – layer deposition processes. The NPLD approach uses efficient chemical functionalization of the solid substrate material and complementary functionalization of nanoparticles to produce a nearly 100% coverage of these nanoparticles with the use of “click chemistry”. Following this initial deposition, a second complete monolayer of nanoparticles is deposited using a copper-catalyzed “click reaction” with the azide-terminated silica nanoparticles of a different size. This layer-by-layer growth is demonstrated to produce stable covalently-bound multilayers of nearly perfect structure over macroscopic solid substrates. The formation of stable covalent bonds is confirmed spectroscopically and the stability of the multilayers produced is tested by sonication in a variety of common solvents. The 1-, 2- and 3-layer structures are interrogated by electron microscopy and atomic force microscopy and the thickness of the multilayers formed is fully consistent with that expected for highly efficient monolayer formation with each cycle of growth. This approach can be extended to include a variety of materials deposited in a predesigned sequence on different substrates with a highly conformal filling. PMID:26726273

  11. Layer V perirhinal cortical ensemble activity during object exploration: a comparison between young and aged rats.

    PubMed

    Burke, S N; Hartzell, A L; Lister, J P; Hoang, L T; Barnes, C A

    2012-10-01

    Object recognition memory requires the perirhinal cortex (PRC) and this cognitive function declines during normal aging. Recent electrophysiological recordings from young rats have shown that neurons in Layer V of the PRC are activated by three-dimensional objects. Thus, it is possible that age-related object recognition deficits result from alterations in PRC neuron activity in older animals. To examine this, the present study used cellular compartment analysis of temporal activity by fluorescence in situ hybridization (catFISH) with confocal microscopy to monitor cellular distributions of activity-induced Arc RNA in layer V of the PRC. Activity was monitored during two distinct epochs of object exploration. In one group of rats (6 young/6 aged) animals were placed in a familiar testing arena and allowed to explore five different three-dimensional objects for two 5-min sessions separated by a 20-min rest (AA). The second group of animals (6 young/6 aged) also explored the same objects for two 5-min sessions, but the environment was changed between the first and the second epoch (AB). Behavioral data showed that both age groups spent less time exploring objects during the second epoch, even when the environment changed, indicating successful recognition. Although the proportion of active neurons between epochs did not change in the AA group, in the AB group more neurons were active during epoch 2 of object exploration. This recruitment of neurons into the active neural ensemble could serve to signal that familiar stimuli are being encountered in a new context. When numbers of Arc positive neurons were compared between age groups, the old rats had significantly lower proportions of Arc-positive PRC neurons in both the AA and AB behavioral conditions. These data support the hypothesis that age-associated functional alterations in the PRC contribute to declines in stimulus recognition over the lifespan.

  12. Biomimetic sensing layer based on electrospun conductive polymer webs.

    PubMed

    Zampetti, E; Pantalei, S; Scalese, S; Bearzotti, A; De Cesare, F; Spinella, C; Macagnano, A

    2011-01-15

    The aim of the present study is to combine a bio-inspired nanofibrous artificial epithelium to the electronic nose (e-nose) principles. The sensing device set up was an electronic nose consisting of an array of 9 micro-chemoresistors (Cr-Au, 3×3) coated with electrospun nanofibrous structures. These were comprised of doped polyemeraldine base blended with 3 different polymers: polyethylene oxide, polyvinilpyrrolidone and polystyrene, which acted as carriers for the conducting polymer and were the major responsible of the features of each fibrous overlay (electrical parameters, selectivity and sensitivity ranges). The two sensing strategies here adopted and compared consisted in the use of 2 different textural coatings: a single- and a double-overlay, where the double-overlay resulting from overdeposition of 2 different polymer blends. Such e-nose included a plurality of nanofibres whose electrical parameters were at the same time depending on each polymer exposure to analytes (NO(2), NH(3)) and on the spatial distribution of the interlacing fibres. The morphology of the coating arrangements of this novel e-nose was investigated by scanning electron microscopy (SEM) and its sensor responses were processed by multicomponent data analyses (PCA and PLS) reporting encouraging results for detection and recognition of analytes at ppb levels.

  13. Using ground-penetrating radar, topography and classification of vegetation to model the sediment and active layer thickness in a periglacial lake catchment, western Greenland

    NASA Astrophysics Data System (ADS)

    Petrone, Johannes; Sohlenius, Gustav; Johansson, Emma; Lindborg, Tobias; Näslund, Jens-Ove; Strömgren, Mårten; Brydsten, Lars

    2016-11-01

    The geometries of a catchment constitute the basis for distributed physically based numerical modeling of different geoscientific disciplines. In this paper results from ground-penetrating radar (GPR) measurements, in terms of a 3-D model of total sediment thickness and active layer thickness in a periglacial catchment in western Greenland, are presented. Using the topography, the thickness and distribution of sediments are calculated. Vegetation classification and GPR measurements are used to scale active layer thickness from local measurements to catchment-scale models. Annual maximum active layer thickness varies from 0.3 m in wetlands to 2.0 m in barren areas and areas of exposed bedrock. Maximum sediment thickness is estimated to be 12.3 m in the major valleys of the catchment. A method to correlate surface vegetation with active layer thickness is also presented. By using relatively simple methods, such as probing and vegetation classification, it is possible to upscale local point measurements to catchment-scale models, in areas where the upper subsurface is relatively homogeneous. The resulting spatial model of active layer thickness can be used in combination with the sediment model as a geometrical input to further studies of subsurface mass transport and hydrological flow paths in the periglacial catchment through numerical modeling. The data set is available for all users via the PANGAEA database, doi:10.1594/PANGAEA.845258.

  14. Strained layer relaxation effect on current crowding and efficiency improvement of GaN based LED

    NASA Astrophysics Data System (ADS)

    Aurongzeb, Deeder

    2012-02-01

    Efficiency droop effect of GaN based LED at high power and high temperature is addressed by several groups based on career delocalization and photon recycling effect(radiative recombination). We extend the previous droop models to optical loss parameters. We correlate stained layer relaxation at high temperature and high current density to carrier delocalization. We propose a third order model and show that Shockley-Hall-Read and Auger recombination effect is not enough to account for the efficiency loss. Several strained layer modification scheme is proposed based on the model.

  15. 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

  16. Using activity-based costing in surgery.

    PubMed

    Grandlich, Cheryl

    2004-01-01

    ACTIVITY-BASED COSTING is an accounting technique that allows organizations to determine actual costs associated with their services based on the resources they consume. THIS TECHNIQUE can be used in a variety of ways, including targeting high-cost activities, forecasting financial baselines, and supporting resource allocation. FOUR STEPS should be followed when applying activity-based costing to surgical procedures. THIS ARTICLE explores how Froedtert Memorial Lutheran Hospital, Milwaukee, used activity-based costing.

  17. Effect of base layer materials on physiological and perceptual responses to exercise in personal protective equipment.

    PubMed

    Smith, Denise L; Arena, Logan; DeBlois, Jacob P; Haller, Jeannie M; Hultquist, Eric M; Lefferts, Wesley K; Russell, Tim; Wu, Annie; Fehling, Patricia C

    2014-05-01

    Ten men (non-firefighters) completed a 110 min walking/recovery protocol (three 20-min exercise bouts, with recovery periods of 10, 20, and 20 min following successive bouts) in a thermoneutral laboratory while wearing firefighting personal protective equipment over one of four base layers: cotton, modacrylic, wool, and phase change material. There were no significant differences in changes in heart rate, core temperature, rating of perceived exertion, thermal discomfort, and thermal strain among base layers. Sticking to skin, coolness/hotness, and clothing humidity sensation were more favorable (p < 0.05) for wool compared with cotton; no significant differences were identified for the other 7 clothing sensations assessed. Separate materials performance testing of the individual base layers and firefighting ensembles (base layer + turnout gear) indicated differences in thermal protective performance and total heat loss among the base layers and among ensembles; however, differences in heat dissipation did not correspond with physiological responses during exercise or recovery.

  18. Active plasmonic band-stop filters based on graphene metamaterial at THz wavelengths.

    PubMed

    Wei, Zhongchao; Li, Xianping; Yin, Jianjun; Huang, Rong; Liu, Yuebo; Wang, Wei; Liu, Hongzhan; Meng, Hongyun; Liang, Ruisheng

    2016-06-27

    Active plasmonic band-stop filters based on single- and double-layer doped graphene metamaterials at the THz wavelengths are proposed and investigated numerically by using the finite-difference time-domain (FDTD) method. The metamaterial unit cell structure is composed of two parallel graphene nanoscale ribbons. Simulated results exhibit that significant resonance wavelength shifts can be achieved with a slight variation of the doping concentration of the graphene ribbons. Besides, the asymmetry double-layer graphene metamaterial device has two apparent filter dips while the symmetry single-, double-layer and asymmetry single-layer graphene metamaterial devices just only one. The metamaterials with symmetry single-layer and asymmetry double-layer graphene can be used as a high-sensitivity refractive sensor with the sensitivity up to 5100 nm/RIU and a two-circuit switch, respectively. These prospects pave the way towards ultrafast active graphene-based plasmonic devices for THz applications.

  19. 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.

  20. Perpendicular magnetic tunnel junctions with synthetic antiferromagnetic pinned layers based on [Co/Pd] multilayers

    NASA Astrophysics Data System (ADS)

    Chang, Yao-Jen; Canizo-Cabrera, A.; Garcia-Vazquez, Valentin; Chang, Yang-Hua; Wu, Te-ho

    2013-05-01

    We fabricated MgO-based perpendicular magnetic tunnel junctions (p-MTJ) with Ta/CoFeB magnetic electrodes. Synthetic antiferromagnetic (SAF) pinned layers with perpendicular magnetic anisotropy (PMA) were included into the p-MTJs by using two Co/Pd multilayers (MLs) separated by a thin Ru spacer layer. The MTJs stack has the structure bottom contact/free layer CoFeB (1.0)/MgO (1)/pinned layer CoFeB (1.0)/Ta spacer layer/SAF/Ru cap layer/top contact (the units in parenthesis are in nanometers). The SAF was optimized by changing the repetition period n in one of the Co/Pd multilayers and the Ru thickness in order to obtain PMA with antiferromagnetic (AFM) coupling. The Ru spacer values were 0.7, 0.75, 0.8, 0.85, and 0.9 nm. The magnetic studies show that all magnetic films, including the Ta/CoFeB layers, are perpendicularly magnetized. The two Co/Pd MLs are AFM coupled for n > 2. Controlling the Ru thickness, the interlayer exchange coupling strength Jiec can be tailored. Jiec vs. Ru thickness exhibits a simple exponential decay. The electrical properties of the full p-MTJ with SAF show a low resistance-area (RA) product of 44.7 Ω μm2 and a tunnel magnetoresistance (TMR) ratio of 10.2%.

  1. Investigations of White Layer Formation During Machining of Powder Metallurgical Ni-Based ME 16 Superalloy

    NASA Astrophysics Data System (ADS)

    Veldhuis, S. C.; Dosbaeva, G. K.; Elfizy, A.; Fox-Rabinovich, G. S.; Wagg, T.

    2010-10-01

    Surface integrity of machined parts made from the advanced Ni-based superalloys is important for modern manufacturing in the aerospace industry. Metallographic observations of the ME 16 alloy microstructure were made using optical metallography and a high-resolution scanning electron microscope with energy dispersive x-ray spectrometer (HR SEM/EDS). Tool life of cemented carbide inserts with TiAlN coating during machining (finishing turning operation) of ME 16 superalloy has been studied and wear patterns of the cutting tools were identified. Surface integrity of the machined part after completion of the turning operation was investigated. The morphology of machined parts has been examined and cross-sections of the machined surfaces have been analyzed. The formation of white layer on the surface of the machined part was studied for varied machining conditions. It was found that a 2-4 µm thick white layer forms during turning of the ME 16 superalloy. This layer was investigated using EDS and XRD. The studies show that the white layer is an oxygen-containing layer with a high amount of aluminum, enriched by chromium and tungsten. Under specific cutting conditions, the structure of white layer transforms into a γ-alumina. Formation of this thermal barrier ceramic white layer on the surface of the machined part negatively affects its surface integrity and cutting tool life.

  2. Efficient low-temperature transparent electrocatalytic layers based on graphene oxide nanosheets for dye-sensitized solar cells.

    PubMed

    Seo, Seon Hee; Jeong, Eun Ji; Han, Joong Tark; Kang, Hyon Chol; Cha, Seung I; Lee, Dong Yoon; Lee, Geon-Woong

    2015-05-27

    Electrocatalytic materials with a porous structure have been fabricated on glass substrates, via high-temperature fabrication, for application as alternatives to platinum in dye-sensitized solar cells (DSCs). Efficient, nonporous, nanometer-thick electrocatalytic layers based on graphene oxide (GO) nanosheets were prepared on plastic substrates using electrochemical control at low temperatures of ≤100 °C. Single-layer, oxygen-rich GO nanosheets prepared on indium tin oxide (ITO) substrates were electrochemically deoxygenated in acidic medium within a narrow scan range in order to obtain marginally reduced GO at minimum expense of the oxygen groups. The resulting electrochemically reduced GO (E-RGO) had a high density of residual alcohol groups with high electrocatalytic activity toward the positively charged cobalt-complex redox mediators used in DSCs. The ultrathin, alcohol-rich E-RGO layer on ITO-coated poly(ethylene terephthalate) was successfully applied as a lightweight, low-temperature counter electrode with an extremely high optical transmittance of ∼97.7% at 550 nm. A cobalt(II/III)-mediated DSC employing the highly transparent, alcohol-rich E-RGO electrode exhibited a photovoltaic power conversion efficiency of 5.07%. This is superior to that obtained with conventionally reduced GO using hydrazine (3.94%) and even similar to that obtained with platinum (5.10%). This is the first report of a highly transparent planar electrocatalytic layer based on carbonaceous materials fabricated on ITO plastics for application in DSCs.

  3. 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

  4. Growth of monolithic full-color GaN-based LED with intermediate carrier blocking layers

    NASA Astrophysics Data System (ADS)

    El-Ghoroury, Hussein S.; Yeh, Milton; Chen, J. C.; Li, X.; Chuang, Chih-Li

    2016-07-01

    Specially designed intermediate carrier blocking layers (ICBLs) in multi-active regions of III-nitride LEDs were shown to be effective in controlling the carrier injection distribution across the active regions. In principle, the majority of carriers, both holes and electrons, can be guided into targeted quantum wells and recombine to generate light of specific wavelengths at controlled current-densities. Accordingly we proposed and demonstrated a novel monolithic InGaN-based LED to achieve three primary colors of light from one device at selected current densities. This LED structure, which has three different sets of quantum wells separated with ICBLs for three primary red-green-blue (RGB) colors, was grown by metal-organic chemical vapor deposition (MOCVD). Results show that this LED can emit light ranging from 460 to 650 nm to cover the entire visible spectrum. The emission wavelength starts at 650 nm and then decreases to 460 nm or lower as the injection current increases. In addition to three primary colors, many other colors can be obtained by color mixing techniques. To the best of our knowledge, this is the first demonstration of monolithic full-color LED grown by a simple growth technique without using re-growth process.

  5. Ultraviolet photodetectors based on ZnO nanorods-seed layer effect and metal oxide modifying layer effect.

    PubMed

    Zhou, Hai; Fang, Guojia; Liu, Nishuang; Zhao, Xingzhong

    2011-02-15

    Pt/ZnO nanorod (NR) and Pt/modified ZnO NR Schottky barrier ultraviolet (UV) photodetectors (PDs) were prepared with different seed layers and metal oxide modifying layer materials. In this paper, we discussed the effect of metal oxide modifying layer on the performance of UV PDs pre- and post-deposition annealing at 300°C, respectively. For Schottky barrier UV PDs with different seed layers, the MgZnO seed layer-PDs without metal oxide coating showed bigger responsivity and larger detectivity (Dλ*) than those of PDs with ZnO seed layer, and the reason was illustrated through energy band theory and the electron transport mechanism. Also the ratio of D254* to D546* was calculated above 8 × 102 for all PDs, which demonstrated that our PDs showed high selectivity for detecting UV light with less influence of light with long wavelength.

  6. Novel electrochemical sensors with electrodes based on multilayers fabricated by layer-by-layer synthesis and their analytical potential

    NASA Astrophysics Data System (ADS)

    Ermakov, S. S.; Nikolaev, K. G.; Tolstoy, V. P.

    2016-08-01

    The results of studies on layer-by-layer synthesis of multilayers on the electrode surface in order to design electrochemical sensors for the determination of concentrations of inorganic, organic and bioorganic compounds are summarized and analyzed. The principle of the method is discoursed and the key advantages of the approach are highlighted, such as the possibility of single layer synthesis with specified thickness and composition under mild conditions with further fabrication of multilayers. Charge transfer conditions in the layers on the electrode surface between the analyte molecules and electrode redox centres and the operating conditions for the optimal electrode are considered. The role of electrocatalysts and intermediates of these processes is noted. Particular attention is devoted to the methods for synthesis of gold nanoparticles with different diameters. Analytical characteristics for electrochemical sensors are presented and application prospects of the layer-by-layer synthesis to electrode fabrication are discussed. The bibliography includes 241 references.

  7. Auroral activity associated with Kelvin-Helmholtz instability at the inner edge of the low-latitude boundary layer

    NASA Technical Reports Server (NTRS)

    Farrugia, C. J.; Sandholt, P. E.; Burlaga, L. F.

    1994-01-01

    Auroral activity occurred in the late afternoon sector (approx. 16 MLT) in the northern hemisphere during the passage at Earth of an interplanetary magnetic cloud on January 14, 1988. The auroral activity consisted of a very dynamic display which was preceded and followed by quiet auroral displays. During the quiet displays, discrete rayed arcs aligned along the geomagnetic L shells were observed. In the active stage, rapidly evolving spiral forms centered on magnetic zenith were evident. The activity persisted for many minutes and was characterized by the absence of directed motion. They were strongly suggestive of intense filaments of upward field-aligned currents embedded in the large-scale region 1 current system. Distortions of the flux ropes as they connect from the equatorial magnetosphere to the ionosphere were witnessed. We assess as possible generating mechanisms three nonlocal sources known to be associated with field-aligned currents. Of these, partial compressions of the magnetosphere due to variations of solar wind dynamic pressure seem an unlikely source. The possibility that the auroral forms are due to reconnection is investigated but is excluded because the active aurora were observed on the closed field line region just equatorward of the convection reversal boundary. To support this conclusion further, we apply recent results on the mapping of ionospheric regions to the equatorial plane based on the Tsyganenko 1989 model (Kaufmann et al., 1993). We find that for comparable magnetic activity the aurora map to the equatorial plane at X(sub GSM) = approx. 3 R(sub E) and approx. 2 R(sub E) inward of the magnetopause, that is, the inner edge of the boundary layer close to dusk. Since the auroral forms are manifestly associated with magnetic field shear, a vortical motion at the equatorial end of the flux rope is indicated, making the Kelvin-Helmholtz instability acting at the inner edge of the low-latitude boundary layer the most probable generating

  8. MAPLE deposition of polypyrrole-based composite layers for bone regeneration

    NASA Astrophysics Data System (ADS)

    Paun, Irina Alexandra; Acasandrei, Adriana Maria; Luculescu, Catalin Romeo; Mustaciosu, Cosmin Catalin; Ion, Valentin; Mihailescu, Mona; Vasile, Eugenia; Dinescu, Maria

    2015-12-01

    We report on biocompatible, electrically conductive layers of polypyrrole (PPy)-based composites obtained by Matrix Assisted Pulsed Laser Evaporation (MAPLE) for envisioned bone regeneration. In order to preserve the conductivity of the PPy while overcoming its lack of biodegradability and low mechanical resilience, conductive PPy nanograins were embedded in two biocompatible, insulating polymeric matrices, i.e. poly(lactic-co-glycolic)acid (PLGA) and polyurethane (PU). PLGA offers the advantage of full biodegradability into non-toxic products, while PU provides toughness and elasticity. The PPy nanograins formed micro-domains and networks within the PLGA and PU matrices, in a compact spatial arrangement favorable for electrical percolation. The proposed approach allowed us to obtain PPy-based composite layers with biologically meaningful conductivities up to 10-2 S/cm for PPy loadings as low as 1:10 weight ratios. Fluorescent staining and viability assays showed that the MG63 osteoblast-like cells cultured on the PPy-based layers deposited by MAPLE were viable and retained their capacity to proliferate. The performance of the proposed method was demonstrated by quantitative evaluation of the calcium phosphate deposits from the cultured cells, as indicative for cell mineralization. Electrical stimulation using 200 μA currents passing through the PPy-based layers, during a time interval of 4 h, enhanced the osteogenesis in the cultured cells. Despite their lowest conductivity, the PPy/PU layers showed the best biocompatibility and the highest osteogenic potential.

  9. n +-Microcrystalline-Silicon Tunnel Layer in Tandem Si-Based Thin Film Solar Cells

    NASA Astrophysics Data System (ADS)

    Lee, Ching-Ting; Lee, Hsin-Ying; Chen, Kuan-Hao

    2016-10-01

    In this study, the p-SiC/ i-Si/ n-Si cell and the p-SiC/ i-SiGe/ n-Si cell deposited using plasma-enhanced chemical vapor deposition were cascaded for forming the tandem Si-based thin film solar cells to absorb the wide solar spectrum. To further improve the performances of the tandem Si-based thin film solar cells, a 5-nm-thick n +-microcrystalline-Si ( n +-μc-Si) tunnel layer deposited using the laser-assisted plasma-enhanced chemical vapor deposition was inserted between the p-SiC/ i-Si/ n-Si cell and the p-SiC/ i-SiGe/ n-Si cell. Since both the plasma and the CO2 laser were simultaneously utilized to efficiently decompose the reactant and doping gases, the carrier concentration and the carrier mobility of the n +-μc-Si tunnel layer were significantly improved. The ohmic contact formed between the p-SiC layer and the n +-μc-Si tunnel layer with low resistance was beneficial to the generated current transportation and the carrier recombination rate. Therefore, the conversion efficiency of the tandem solar cells was promoted from 8.57% and 8.82% to 9.91% compared to that without tunnel layer and with 5-nm-thick n +-amorphous-Si tunnel layer.

  10. Near-zero-residual layer nanoimprint based on hybrid nanoimprint soft lithography

    NASA Astrophysics Data System (ADS)

    Cui, Yushuang; Lu, Jingjun; Fu, XinXin; Bian, Jie; Yuan, Changsheng; Ge, Haixiong; Chen, Yanfeng

    2015-11-01

    A thin and uniform residual layer, especially zero-residual layer, is highly desired in the nanoimprint lithography, because it is critical to the succeeding pattern transfer process. In this study, a partial cavity filling method was applied on UV-curable resins instead of thermal plastic polymer to realize zero-residual layer based on a hybrid nanoimprint technique. The initial thickness of the UV-curable resin on the substrate was precisely quantified less than the cavity volume of the imprint mold by adjusting the resin concentration and spin coating speed. A near-zero-residual layer was successfully achieved under an extremely low imprint pressure by the control of the viscosity, surface tension and thickness of the UV-curable resist.

  11. MAPLE preparation and characterization of mixed arylenevinylene based oligomers:C60 layers

    NASA Astrophysics Data System (ADS)

    Stanculescu, A.; Socol, G.; Vacareanu, L.; Socol, M.; Rasoga, O.; Breazu, C.; Girtan, M.; Stanculescu, F.

    2016-06-01

    This paper presents some studies about the preparation by matrix-assisted pulsed laser evaporation (MAPLE) of mixed layers based on two arylenevinylene oligomers, 1,4-bis [4-(N,N‧-diphenylamino)phenylvinyl] benzene (L78) and 3,3‧-bis(N-hexylcarbazole)vinylbenzene (L13) as donor and buckminsterfullerene (C60) as acceptor, blended in three different weight ratios: 1:1, 1:2 and 1:3. The optical, morphological, structural and electrical properties of these mixed layers have been investigated emphasizing the effect of the layer composition and of the significant degree of disorder. I-V characteristics have revealed typically solar cell behaviour for the heterostructures prepared with mixed layers containing L78 (L13) and fullerene blended in a weight ratio of 1:2. The solar cell structure glass/ITO/L13:C60/Al has shown the best parameters.

  12. 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.

  13. First steps towards the realization of a double layer perceptron based on organic memristive devices

    NASA Astrophysics Data System (ADS)

    Emelyanov, A. V.; Lapkin, D. A.; Demin, V. A.; Erokhin, V. V.; Battistoni, S.; Baldi, G.; Dimonte, A.; Korovin, A. N.; Iannotta, S.; Kashkarov, P. K.; Kovalchuk, M. V.

    2016-11-01

    Memristors are widely considered as promising elements for the efficient implementation of synaptic weights in artificial neural networks (ANNs) since they are resistors that keep memory of their previous conductive state. Whereas demonstrations of simple neural networks (e.g., a single-layer perceptron) based on memristors already exist, the implementation of more complicated networks is more challenging and has yet to be reported. In this study, we demonstrate linearly nonseparable combinational logic classification (XOR logic task) using a network implemented with CMOS-based neurons and organic memrisitive devices that constitutes the first step toward the realization of a double layer perceptron. We also show numerically the ability of such network to solve a principally analogue task which cannot be realized by digital devices. The obtained results prove the possibility to create a multilayer ANN based on memristive devices that paves the way for designing a more complex network such as the double layer perceptron.

  14. Murein hydrolase activity of surface layer proteins from Lactobacillus acidophilus against Escherichia coli.

    PubMed

    Meng, Jun; Gao, Shu-Ming; Zhang, Qiu-Xiang; Lu, Rong-Rong

    2015-08-01

    The aim of this study was to investigate the murein hydrolase activities of the surface layer proteins (SLPs) from two strains of Lactobacillus acidophilus using zymography. The influence of these hydrolase activities on Escherichia coli ATCC 43893 was also evaluated by analysing their growth curve, cell morphology and physiological state. After the incubation of E. coli with SLPs, growth was inhibited, the number of viable cells was significantly reduced, examination by transmission electron microscopy showed that the cell wall was damaged and flow cytometry results indicated that the majority of the cells were sublethally injured. All of these results suggested that the SLPs of both L. acidophilus strains possessed murein hydrolase activities that were sublethal to E. coli cells.

  15. Powerful Amplification Cascades of FRET-Based Two-Layer Nonenzymatic Nucleic Acid Circuits.

    PubMed

    Quan, Ke; Huang, Jin; Yang, Xiaohai; Yang, Yanjing; Ying, Le; Wang, He; Xie, Nuli; Ou, Min; Wang, Kemin

    2016-06-07

    Nucleic acid circuits have played important roles in biological engineering and have increasingly attracted researchers' attention. They are primarily based on nucleic acid hybridizations and strand displacement reactions between nucleic acid probes of different lengths. Signal amplification schemes that do not rely on protein enzyme show great potential in analytical applications. While the single amplification circuit often achieves linear amplification that may not meet the need for detection of target in a very small amount, it is very necessary to construct cascade circuits that allow for larger amplification of inputs. Herein, we have successfully engineered powerful amplification cascades of FRET-based two-layer nonenzymatic nucleic acid circuits, in which the outputs of catalyzed hairpin assembly (CHA) activate hybridization chain reactions (HCR) circuits to induce repeated hybridization, allowing real-time monitoring of self-assembly process by FRET signal. The cascades can yield 50000-fold signal amplification with the help of the well-designed and high-quality nucleic acid circuit amplifiers. Subsequently, with coupling of structure-switching aptamer, as low as 200 pM adenosine is detected in buffer, as well as in human serum. To our knowledge, we have for the first time realized real-time monitoring adaptation of HCR to CHA circuits and achieved amplified detection of nucleic acids and small molecules with relatively high sensitivity.

  16. Ultrathin ultra-broadband electro-absorption modulator based on few-layer graphene based anisotropic metamaterial

    NASA Astrophysics Data System (ADS)

    Sayem, Ayed Al; Mahdy, M. R. C.; Jahangir, Ifat; Rahman, Md. Saifur

    2017-02-01

    In this article, a few-layered graphene-dielectric multilayer (metamaterial) electro-optic modulator has been proposed in the mid and far infrared range that works on electro-absorption mechanism. Graphene, both mono layer and few layer, is an actively tunable optical material that allows control of inter-band and intra-band transition by tuning its chemical potential. Utilizing this unique feature of graphene, we propose a multilayer graphene dielectric stack where few layer graphene is preferred over mono layer graphene. Although the total thickness of the stack still remains in the nanometer range, this device can exhibit superior performances in terms of (i) high modulation depth, (ii) ultra-broadband performance, (iii) ultra-low insertion loss due to inherent metamaterial properties, (iv)nano-scale footprint, (v) polarization independence and (vi) capability of being integrated to a silicon waveguide. Interestingly, these superior performances, achievable by using few layer graphene with carefully designed metamaterial, may not be possible with mono layer graphene. Our proposals have been validated by both the effective medium theory and general transfer matrix method.

  17. Different determinants of soil carbon decomposition between active and permafrost layers: evidence from alpine permafrost on the Tibetan Plateau

    NASA Astrophysics Data System (ADS)

    Yang, Y.; Chen, L.; Qin, S.; Ding, J.; Yang, G.; Li, F.

    2015-12-01

    The fate of permafrost carbon is of great concern among global change community due to its potential positive feedback to climate warming. However, the determinants of soil carbon decomposition between active layer and permafrost layers remain poorly understood. This incubation study was designed to test the following two hypotheses: 1) low carbon quantity and microbial abundances in permafrost soils limit decomposition rates compared with active layer soils; 2) carbon losses from active layer are more controlled by environmental factors, whereas those from permafrost depth are primarily determined by the microbial condition. We collected five active layer and permafrost soils from alpine grasslands on the Tibetan Plateau and compared the carbon dioxide (CO2) emissions at -5 and 5 °C in a 80-days aerobic incubation. The availability of organic carbon and microbial abundances (fungi, bacteria, and actinomycete) within permafrost soils were significantly lower than active layer soils, which, together with the environmental data supports the reduced cumulative CO2 emissions in permafrost depth. However, the decomposability of SOC from permafrost was similar or even higher than surface soils. The carbon loss not only depended on SOC quantity and microbial abundance, but also nitrogen availability and soil pH. Nevertheless, the controls on carbon emissions between active and permafrost layers were significantly different. Cumulative CO2 emission from active layers was best predicted by soil moisture, and carbon emission from permafrost depths was highly associated with fungal-PLFAs. Taken together, these results demonstrate that different controls on carbon emission between active layer and permafrost soils. These differences highlight the importance of distinguishing permafrost depth in Earth System Models when predicting the responses of deep soil carbon to environmental change.

  18. 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.

  19. Potassium channels control the interaction between active dendritic integration compartments in layer 5 cortical pyramidal neurons

    PubMed Central

    Harnett, Mark T.; Xu, Ning-Long; Magee, Jeffrey C.; Williams, Stephen R.

    2013-01-01

    Active dendritic synaptic integration enhances the computational power of neurons. Such nonlinear processing generates an object-localization signal in the apical dendritic tuft of layer 5B cortical pyramidal neurons during sensory-motor behaviour. Here we employ electrophysiological and optical approaches in brain-slices and behaving animals to investigate how excitatory synaptic input to this distal dendritic compartment influences neuronal output. We find that active dendritic integration throughout the apical dendritic tuft is highly compartmentalized by voltage-gated potassium (KV) channels. A high-density of both transient and sustained KV channels was observed in all apical dendritic compartments. These channels potently regulated the interaction between apical dendritic tuft, trunk, and axo-somatic integration zones to control neuronal output in vitro as well as the engagement of dendritic nonlinear processing in vivo during sensory-motor behaviour. Thus, KV channels dynamically tune the interaction between active dendritic integration compartments in layer 5B pyramidal neurons to shape behaviourally relevant neuronal computations. PMID:23931999

  20. Aminosilane layers on the plasma activated thermoplastics: influence of solvent on its structure and morphology.

    PubMed

    Sunkara, Vijaya; Cho, Yoon-Kyoung

    2013-12-01

    The chemistry and the structure of aminosilane layer on the plasma activated thermoplastic substrates, e.g., polycarbonate (PC), polystyrene (PS), poly(methyl methacrylate) (PMMA), and cyclic olefin co-polymer (COC) were investigated at the molecular level. The nature of the surface functional groups of the silane layers prepared by solution phase deposition in aqueous and anhydrous solvents were studied using various techniques including ellipsometry, goniometry, atomic force microscopy (AFM), X-ray photoelectron spectroscopy (XPS), and attenuated total reflectance infrared spectroscopy (ATR-IR). The XPS analyses revealed the presence of various oxygen functionalities on the plasma activated thermoplastics. Considerable differences were observed for the structure of aminosilane depending on the solvent used for the reaction. Deposition from aqueous solution resulted in relatively flat and smooth surfaces with consistent thickness compared to the anhydrous solution deposition. In the former case, 33% of the total nitrogen accounted for protonated amine and 16% for the free amino groups. In the latter, only 6% accounted for the protonated amine. The point of zero charge (pzc), on the aminosilane modified PC was found to be around 7, indicated that the surface is positively charged below pH 7 and negatively charged above pH 7. The surface analysis data suggested that various interactions are possible between the plasma activated thermoplastic surface and the aminosilane. In general, they are bound to the surface through covalent bond formation between the oxygen functionalities on the thermoplastic surface and the amino or the silanol groups of the aminosilane.

  1. Born energy, acid-base equilibrium, structure and interactions of end-grafted weak polyelectrolyte layers

    SciTech Connect

    Nap, R. J.; Tagliazucchi, M.; Szleifer, I.

    2014-01-14

    This work addresses the effect of the Born self-energy contribution in the modeling of the structural and thermodynamical properties of weak polyelectrolytes confined to planar and curved surfaces. The theoretical framework is based on a theory that explicitly includes the conformations, size, shape, and charge distribution of all molecular species and considers the acid-base equilibrium of the weak polyelectrolyte. Namely, the degree of charge in the polymers is not imposed but it is a local varying property that results from the minimization of the total free energy. Inclusion of the dielectric properties of the polyelectrolyte is important as the environment of a polymer layer is very different from that in the adjacent aqueous solution. The main effect of the Born energy contribution on the molecular organization of an end-grafted weak polyacid layer is uncharging the weak acid (or basic) groups and consequently decreasing the concentration of mobile ions within the layer. The magnitude of the effect increases with polymer density and, in the case of the average degree of charge, it is qualitatively equivalent to a small shift in the equilibrium constant for the acid-base equilibrium of the weak polyelectrolyte monomers. The degree of charge is established by the competition between electrostatic interactions, the polymer conformational entropy, the excluded volume interactions, the translational entropy of the counterions and the acid-base chemical equilibrium. Consideration of the Born energy introduces an additional energetic penalty to the presence of charged groups in the polyelectrolyte layer, whose effect is mitigated by down-regulating the amount of charge, i.e., by shifting the local-acid base equilibrium towards its uncharged state. Shifting of the local acid-base equilibrium and its effect on the properties of the polyelectrolyte layer, without considering the Born energy, have been theoretically predicted previously. Account of the Born energy leads

  2. Born energy, acid-base equilibrium, structure and interactions of end-grafted weak polyelectrolyte layers.

    PubMed

    Nap, R J; Tagliazucchi, M; Szleifer, I

    2014-01-14

    This work addresses the effect of the Born self-energy contribution in the modeling of the structural and thermodynamical properties of weak polyelectrolytes confined to planar and curved surfaces. The theoretical framework is based on a theory that explicitly includes the conformations, size, shape, and charge distribution of all molecular species and considers the acid-base equilibrium of the weak polyelectrolyte. Namely, the degree of charge in the polymers is not imposed but it is a local varying property that results from the minimization of the total free energy. Inclusion of the dielectric properties of the polyelectrolyte is important as the environment of a polymer layer is very different from that in the adjacent aqueous solution. The main effect of the Born energy contribution on the molecular organization of an end-grafted weak polyacid layer is uncharging the weak acid (or basic) groups and consequently decreasing the concentration of mobile ions within the layer. The magnitude of the effect increases with polymer density and, in the case of the average degree of charge, it is qualitatively equivalent to a small shift in the equilibrium constant for the acid-base equilibrium of the weak polyelectrolyte monomers. The degree of charge is established by the competition between electrostatic interactions, the polymer conformational entropy, the excluded volume interactions, the translational entropy of the counterions and the acid-base chemical equilibrium. Consideration of the Born energy introduces an additional energetic penalty to the presence of charged groups in the polyelectrolyte layer, whose effect is mitigated by down-regulating the amount of charge, i.e., by shifting the local-acid base equilibrium towards its uncharged state. Shifting of the local acid-base equilibrium and its effect on the properties of the polyelectrolyte layer, without considering the Born energy, have been theoretically predicted previously. Account of the Born energy leads

  3. 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.

  4. Single active-layer structured dual-function devices using hybrid polymer-quantum dots.

    PubMed

    Son, Dong-Ick; Park, Dong-Hee; Ie, Sang-Yub; Choi, Won-Kook; Choi, Ji-Won; Li, Fushan; Kim, Tae-Whan

    2008-10-01

    We demonstrate hybrid polymer-quantum dot dual-function devices with a single active-layer structure consisting of CdSe/ZnS semiconductor quantum dots dispersed with poly N-vinylcarbazole (PVK) and 1,3,5-tirs-(N-phenylbenzimidazol-2-yl) benzene (TPBi) fabricated on an indium-tin-oxide (ITO)/glass substrate by using a simple spin-coating technique. The dual-function devices are composed of light-emitting diodes (LED) on the top side and nonvolatile organic bistable memory devices (OBD) on the bottom side and can show electroluminescence (EL) along with electrical bistability concurrently. Both the functionality of LEDs and OBDs can be successfully achieved by adding an electron transport layer (ETL) TPBi to the OBD to attain an LED in which the lowest unoccupied molecular orbital (LUMO) level of TPBi is positioned at the energy level between the conduction band of CdSe/ZnS and the LiF/Al electrode. Through transmission electron microscopy (TEM) study, it is revealed that CdSe/ZnS QDs distributed on the interface of the hole transport layer (HTL) and ETL significantly take part in the electroluminescence process rather than those existing at the outer surface of the ETL.

  5. Improved Power Conversion Efficiency of Inverted Organic Solar Cells by Incorporating Au Nanorods into Active Layer.

    PubMed

    He, Yeyuan; Liu, Chunyu; Li, Jinfeng; Zhang, Xinyuan; Li, Zhiqi; Shen, Liang; Guo, Wenbin; Ruan, Shengping

    2015-07-29

    This Research Article describes a cooperative plasmonic effect on improving the performance of organic solar cells. When Au nanorods(NRs) are incorporated into the active layers, the designed project shows superior enhanced light absorption behavior comparing with control devices, which leads to the realization of organic solar cell with power conversion efficiency of 6.83%, accounting for 18.9% improvement. Further investigations unravel the influence of plasmonic nanostructures on light trapping, exciton generation, dissociation, and charge recombination and transport inside the thin films devices. Moreover, the introduction of high-conductivity Au NRs improves electrical conductivity of the whole device, which contributes to the enhanced fill factor.

  6. Surface and Active Layer Pore Water Chemistry from Ice Wedge Polygons, Barrow, Alaska, 2013-2014

    DOE Data Explorer

    David E. Graham; Baohua Gu; Elizabeth M. Herndon; Stan D. Wullschleger; Ziming Yang; Liyuan Liang

    2016-11-10

    This data set reports the results of spatial surveys of aqueous geochemistry conducted at Intensive Site 1 of the Barrow Environmental Observatory in 2013 and 2014 (Herndon et al., 2015). Surface water and soil pore water samples were collected from multiple depths within the tundra active layer of different microtopographic features (troughs, ridges, center) of a low-centered polygon (area A), high-centered polygon (area B), flat-centered polygon (area C), and transitional polygon (area D). Reported analytes include dissolved organic and inorganic carbon, dissolved carbon dioxide and methane, major inorganic anions, and major and minor cations.

  7. A proposed architecture for a satellite-based mobile communications network - The lowest three layers

    NASA Technical Reports Server (NTRS)

    Yan, T. Y.; Naderi, F. M.

    1986-01-01

    Architecture for a commercial mobile satellite network is proposed. The mobile satellite system (MSS) is composed of a network management center, mobile terminals, base stations, and gateways; the functions of each component are described. The satellite is a 'bent pipe' that performs frequency translations, and it has multiple UHF beams. The development of the MSS design based on the seven-layer open system interconnection model is examined. Consideration is given to the functions of the physical, data link, and network layers and the integrated adaptive mobile access protocol.

  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. Photocatalytic property and structural stability of CuAl-based layered double hydroxides

    SciTech Connect

    Lv, Ming; Liu, Haiqiang

    2015-07-15

    Three types of CuMAl layered double hydroxides (LDHs, M=Mg, Zn, Ni) were successfully synthesized by coprecipitation. Powder X-ray diffraction (XRD), inductively coupled plasma atomic emission spectrometry (ICP-AES) and UV–Vis diffuse reflectance spectrum (UV–vis) were used to confirm the formation of as-synthesized solids with good crystal structure. The photocatalytic activity of those LDH materials for CO{sub 2} reduction under visible light was investigated. The experimental results show that CuNiAl-LDHs with narrowest band gap and largest surface areas behave highest efficiency for methanol generation under visible light compared with CuMgAl-LDHs and CuZnAl-LDHs. The CuNiAL-LDH showed high yield for methanol production i.e. 0.210 mmol/g h, which was high efficient. In addition, the influence of the different M{sup 2+} on the structures and stability of the CuMAl-LDHs was also investigated by analyzing the geometric parameters, electronic arrangement, charge populations, hydrogen-bonding, and binding energies by density functional theory (DFT) analysis. The theoretical calculation results show that the chemical stability of LDH materials followed the order of CuMgAl-LDHs>CuZnAl-LDHs>CuNiAl-LDHs, which is just opposite with the photocatalytic activity and band gaps of three materials. - Graphical abstract: The host–guest calculation models and XRD patterns of CuMAl-LDHs: CuMgAl-LDHs (a), CuZnAl-LDHs (b) and CuNiAl-LDHs (c). - Highlights: • Three types of CuMAl layered double hydroxides (LDHs, M=Mg, Zn, Ni) has been synthesized. • CuMgNi shows narrower band gap and more excellent textural properties than other LDHs. • The band gap: CuMgAlbased on result from UV–vis analysis. • CuMgAl shows the highest stability and lowest photocatalytic activity, while CuNiAl just opposite.

  10. Polarized GaN-based LED with an integrated multi-layer subwavelength structure.

    PubMed

    Zhang, Guiju; Wang, Chinhua; Cao, Bing; Huang, Zengli; Wang, Jianfeng; Zhang, Baoshun; Xu, Ke

    2010-03-29

    A novel type of GaN-based LED with a highly polarized output using an integrated multi-layer subwavelength grating structure is proposed. Characteristics of both optical transmission and polarization extinction ratio of the polarized GaN-based LED with three different multi-layer subwavelength structures are investigated. It is found that both TM transmission (T(TM)) and the extinction ratio(ER) of the LED output can be effectively enhanced by incorporating a dielectric transition layer between the metal grating and GaN substrate with a lower refractive index than that of the GaN substrate. Flat sensitivity of the T(TM) on the period, duty cycle of the metallic grating, and the wide range of operating wavelength have been achieved in contrast to the conventional sensitive behavior in single-layer metallic grating. Up to 0.75 high duty cycle of the metallic grating can be employed to achieve >60dB ER while T(TM) maintains higher than ~90%, which breaks the conventional limit of T(TM) and ER being always a pair of trade-off parameters. Typical optimized multilayer structures in terms of material, thickness, grating periods and duty cycle using MgF(2) and ZnS, respectively, as the transition layers are obtained. The results provide guidance in designing, optimizing and fabricating the novel integrated GaN-based and polarized photonic devices.

  11. Chromatic Mechanical Response in 2-D Layered Transition Metal Dichalcogenide (TMDs) based Nanocomposites

    NASA Astrophysics Data System (ADS)

    Rahneshin, Vahid; Khosravi, Farhad; Ziolkowska, Dominika A.; Jasinski, Jacek B.; Panchapakesan, Balaji

    2016-10-01

    The ability to convert photons of different wavelengths directly into mechanical motion is of significant interest in many energy conversion and reconfigurable technologies. Here, using few layer 2H-MoS2 nanosheets, layer by layer process of nanocomposite fabrication, and strain engineering, we demonstrate a reversible and chromatic mechanical response in MoS2-nanocomposites between 405 nm to 808 nm with large stress release. The chromatic mechanical response originates from the d orbitals and is related to the strength of the direct exciton resonance A and B of the few layer 2H-MoS2 affecting optical absorption and subsequent mechanical response of the nanocomposite. Applying uniaxial tensile strains to the semiconducting few-layer 2H-MoS2 crystals in the nanocomposite resulted in spatially varying energy levels inside the nanocomposite that enhanced the broadband optical absorption up to 2.3 eV and subsequent mechanical response. The unique photomechanical response in 2H-MoS2 based nanocomposites is a result of the rich d electron physics not available to nanocomposites based on sp bonded graphene and carbon nanotubes, as well as nanocomposite based on metallic nanoparticles. The reversible strain dependent optical absorption suggest applications in broad range of energy conversion technologies that is not achievable using conventional thin film semiconductors.

  12. Chromatic Mechanical Response in 2-D Layered Transition Metal Dichalcogenide (TMDs) based Nanocomposites

    PubMed Central

    Rahneshin, Vahid; Khosravi, Farhad; Ziolkowska, Dominika A.; Jasinski, Jacek B.; Panchapakesan, Balaji

    2016-01-01

    The ability to convert photons of different wavelengths directly into mechanical motion is of significant interest in many energy conversion and reconfigurable technologies. Here, using few layer 2H-MoS2 nanosheets, layer by layer process of nanocomposite fabrication, and strain engineering, we demonstrate a reversible and chromatic mechanical response in MoS2-nanocomposites between 405 nm to 808 nm with large stress release. The chromatic mechanical response originates from the d orbitals and is related to the strength of the direct exciton resonance A and B of the few layer 2H-MoS2 affecting optical absorption and subsequent mechanical response of the nanocomposite. Applying uniaxial tensile strains to the semiconducting few-layer 2H-MoS2 crystals in the nanocomposite resulted in spatially varying energy levels inside the nanocomposite that enhanced the broadband optical absorption up to 2.3 eV and subsequent mechanical response. The unique photomechanical response in 2H-MoS2 based nanocomposites is a result of the rich d electron physics not available to nanocomposites based on sp bonded graphene and carbon nanotubes, as well as nanocomposite based on metallic nanoparticles. The reversible strain dependent optical absorption suggest applications in broad range of energy conversion technologies that is not achievable using conventional thin film semiconductors. PMID:27713550

  13. Chromatic Mechanical Response in 2-D Layered Transition Metal Dichalcogenide (TMDs) based Nanocomposites.

    PubMed

    Rahneshin, Vahid; Khosravi, Farhad; Ziolkowska, Dominika A; Jasinski, Jacek B; Panchapakesan, Balaji

    2016-10-07

    The ability to convert photons of different wavelengths directly into mechanical motion is of significant interest in many energy conversion and reconfigurable technologies. Here, using few layer 2H-MoS2 nanosheets, layer by layer process of nanocomposite fabrication, and strain engineering, we demonstrate a reversible and chromatic mechanical response in MoS2-nanocomposites between 405 nm to 808 nm with large stress release. The chromatic mechanical response originates from the d orbitals and is related to the strength of the direct exciton resonance A and B of the few layer 2H-MoS2 affecting optical absorption and subsequent mechanical response of the nanocomposite. Applying uniaxial tensile strains to the semiconducting few-layer 2H-MoS2 crystals in the nanocomposite resulted in spatially varying energy levels inside the nanocomposite that enhanced the broadband optical absorption up to 2.3 eV and subsequent mechanical response. The unique photomechanical response in 2H-MoS2 based nanocomposites is a result of the rich d electron physics not available to nanocomposites based on sp bonded graphene and carbon nanotubes, as well as nanocomposite based on metallic nanoparticles. The reversible strain dependent optical absorption suggest applications in broad range of energy conversion technologies that is not achievable using conventional thin film semiconductors.

  14. Validation of a radiosonde-based cloud layer detection method against a ground-based remote sensing method at multiple ARM sites

    NASA Astrophysics Data System (ADS)

    Zhang, Jinqiang; Li, Zhanqing; Chen, Hongbin; Cribb, Maureen

    2013-01-01

    Cloud vertical structure is a key quantity in meteorological and climate studies, but it is also among the most difficult quantities to observe. In this study, we develop a long-term (10 years) radiosonde-based cloud profile product for the U.S. Department of Energy's Atmospheric Radiation Measurement (ARM) program Southern Great Plains (SGP), Tropical Western Pacific (TWP), and North Slope of Alaska (NSA) sites and a shorter-term product for the ARM Mobile Facility (AMF) deployed in Shouxian, Anhui Province, China (AMF-China). The AMF-China site was in operation from 14 May to 28 December 2008; the ARM sites have been collecting data for over 15 years. The Active Remote Sensing of Cloud (ARSCL) value-added product (VAP), which combines data from the 95-GHz W-band ARM Cloud Radar (WACR) and/or the 35-GHz Millimeter Microwave Cloud Radar (MMCR), is used in this study to validate the radiosonde-based cloud layer retrieval method. The performance of the radiosonde-based cloud layer retrieval method applied to data from different climate regimes is evaluated. Overall, cloud layers derived from the ARSCL VAP and radiosonde data agree very well at the SGP and AMF-China sites. At the TWP and NSA sites, the radiosonde tends to detect more cloud layers in the upper troposphere.

  15. Multi-layered control of peroxisomal activity upon salt stress in Saccharomyces cerevisiae.

    PubMed

    Manzanares-Estreder, Sara; Espí-Bardisa, Joan; Alarcón, Benito; Pascual-Ahuir, Amparo; Proft, Markus

    2017-03-21

    Peroxisomes are dynamic organelles and the sole location for fatty acid β-oxidation in yeast cells. Here we report that peroxisomal function is crucial for the adaptation to salt stress, especially upon sugar limitation. Upon stress, multiple layers of control regulate the activity and the number of peroxisomes. Activated Hog1 MAP kinase triggers the induction of genes encoding enzymes for fatty acid activation, peroxisomal import and β-oxidation through the Adr1 transcriptional activator, which transiently associates with genes encoding fatty acid metabolic enzymes in a stress- and Hog1-dependent manner. Moreover, Na(+) and Li(+) stress increases the number of peroxisomes per cell in a Hog1-independent manner, which depends instead of the retrograde pathway and the dynamin related GTPases Dnm1 and Vps1. The strong activation of the Faa1 fatty acyl-CoA synthetase, which specifically localizes to lipid particles and peroxisomes, indicates that adaptation to salt stress requires the enhanced mobilization of fatty acids from internal lipid stores. Furthermore, the activation of mitochondrial respiration during stress depends on peroxisomes, mitochondrial acetyl-carnitine uptake is essential for salt resistance, and the number of peroxisomes attached to the mitochondrial network increases during salt adaptation, which altogether indicates that stress-induced peroxisomal β-oxidation triggers enhanced respiration upon salt shock. This article is protected by copyright. All rights reserved.

  16. Antifouling Surface Layers for Improved Signal-to-Noise of Particle-Based Immunoassays

    PubMed Central

    Chen, Annie; Kozak, Darby; Battersby, Bronwyn J.; Forrest, Robin M.; Scholler, Nathalie; Urban, Nicole; Trau, Matt

    2010-01-01

    A ten fold improvement in the signal-to-noise (S/N) ratio of an optically encoded silica particle-based immunoassay was achieved through incorporating a protein resistant poly(ethylene glycol) (PEG) surface layer and optimizing antibody immobilization conditions. PEG was activated using 2,2,2-trifluoroethanesulfonyl chloride (tresyl) and required a minimum reaction time of 1.5 hrs. The activated PEG had a reactive half life of approximately 5 hrs when stored in acidified dimethyl sulfoxide (DMSO). By increasing the protein incubation time and concentration, a maximum antibody loading on the particle surface of 1.6×10−2 molecules per nm2 was achieved. The assay S/N ratio was assessed using a multiplexed multicomponent optically encoded species-specific immunoassay. Encoded particles were covalently grafted or nonspecifically coated with either bovine or mouse IgG for the simultaneous detection of complimentary anti-IgG `target' or uncomplimentary anti-IgG `noise'. The versatility and potential as a serum-based assay platform was demonstrated by immobilizing either a polyclonal antibody or an engineered single-chain variable fragment (scFv) capture probe on particles for the detection of the ovarian cancer biomarker, mesothelin (MSLN). The MLSN antigen was spiked into PBS buffer or 50% human serum. Both capture probe orientations and media conditions showed similar low level detection limits of 5 ng/mL; however, a 40% decrease in maximum signal intensity was observed for assays run in 50% serum. PMID:19928944

  17. 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.

  18. An improved enhancement layer for octree based point cloud compression with plane projection approximation

    NASA Astrophysics Data System (ADS)

    Ainala, Khartik; Mekuria, Rufael N.; Khathariya, Birendra; Li, Zhu; Wang, Ye-Kui; Joshi, Rajan

    2016-09-01

    Recent advances in point cloud capture and applications in VR/AR sparked new interests in the point cloud data compression. Point Clouds are often organized and compressed with octree based structures. The octree subdivision sequence is often serialized in a sequence of bytes that are subsequently entropy encoded using range coding, arithmetic coding or other methods. Such octree based algorithms are efficient only up to a certain level of detail as they have an exponential run-time in the number of subdivision levels. In addition, the compression efficiency diminishes when the number of subdivision levels increases. Therefore, in this work we present an alternative enhancement layer to the coarse octree coded point cloud. In this case, the base layer of the point cloud is coded in known octree based fashion, but the higher level of details are coded in a different way in an enhancement layer bit-stream. The enhancement layer coding method takes the distribution of the points into account and projects points to geometric primitives, i.e. planes. It then stores residuals and applies entropy encoding with a learning based technique. The plane projection method is used for both geometry compression and color attribute compression. For color coding the method is used to enable efficient raster scanning of the color attributes on the plane to map them to an image grid. Results show that both improved compression performance and faster run-times are achieved for geometry and color attribute compression in point clouds.

  19. Comparative Metagenomic Analysis Of Microbial Communities From Active Layer And Permafrost After Short-Term Thaw

    NASA Astrophysics Data System (ADS)

    Vishnivetskaya, T. A.; Chauhan, A.; Saarunya, G.; Murphy, J.; Williams, D.; Layton, A. C.; Pfiffner, S. M.; Stackhouse, B. T.; Sanders, R.; Lau, C. M.; myneni, S.; Phelps, T. J.; Fountain, A. G.; Onstott, T. C.

    2012-12-01

    .Permafrost areas occupy 20-25% of the Earth and extend of 1 km depths. The total number of prokaryotes and their biomass in cold regions are estimated to be 1 x 1030 cells and 140 x1015 g of C, respectively. Thus these environments serve as a reservoir of microbial and biogeochemical activity, which is likely to increase upon thawing. We are currently performing long-term thawing experiments at 4o C on 18, geochemically well-characterized, 1 meter long, intact cores consisting of active-layer (0-70 cm depth) and permafrost, collected from a 7 meter diameter ice-wedge polygon located at the McGill Arctic Research Station on Axel Heiberg Island, Nunavut, Canada. The organic carbon content of these cores averages ~1% at depth but increases to 5.4% in the top 10 cm. The cores were subdivided into four treatment groups: saturated cores (thawed while receiving artificial rain), drained cores (being thawed under natural hydrological conditions), dark cores (thawed under natural hydrological conditions with no light input) and control cores (maintain permafrost table at 70 cm depth). Over the course of 10 weeks the cores were progressively thawed from -4oC to 4oC from the top down to simulate spring thaw conditions in the Arctic. The temperatures at 5 cm, 35 cm, 65 cm, and below the permafrost table in the core were recorded continuously. Pore water and gas samples from 4 depths in each core were collected every two weeks and analyzed for pH, anions, cations, H2, CH4, CO, O2, N2, CO2 and δ13C of CO2. Headspace gas samples were collected weekly and analyzed for the same gases as the pore gases. Sediment sub-samples from the 4 depths were collected and total community genomic DNA (gDNA) was isolated using FastDNA SPIN kit followed by Qiagen column purification. The average yield of gDNA was ~3.5 μg/g of soil for the upper 5 cm active layers and decreased to ~1.5 μg/g of soil in the permafrost. The bacterial 16S copy numbers estimated by real-time quantitative PCR

  20. Trapped charge densities in Al2O3-based silicon surface passivation layers

    NASA Astrophysics Data System (ADS)

    Jordan, Paul M.; Simon, Daniel K.; Mikolajick, Thomas; Dirnstorfer, Ingo

    2016-06-01

    In Al2O3-based passivation layers, the formation of fixed charges and trap sites can be strongly influenced by small modifications in the stack layout. Fixed and trapped charge densities are characterized with capacitance voltage profiling and trap spectroscopy by charge injection and sensing, respectively. Al2O3 layers are grown by atomic layer deposition with very thin (˜1 nm) SiO2 or HfO2 interlayers or interface layers. In SiO2/Al2O3 and HfO2/Al2O3 stacks, both fixed charges and trap sites are reduced by at least a factor of 5 compared with the value measured in pure Al2O3. In Al2O3/SiO2/Al2O3 or Al2O3/HfO2/Al2O3 stacks, very high total charge densities of up to 9 × 1012 cm-2 are achieved. These charge densities are described as functions of electrical stress voltage, time, and the Al2O3 layer thickness between silicon and the HfO2 or the SiO2 interlayer. Despite the strong variation of trap sites, all stacks reach very good effective carrier lifetimes of up to 8 and 20 ms on p- and n-type silicon substrates, respectively. Controlling the trap sites in Al2O3 layers opens the possibility to engineer the field-effect passivation in the solar cells.

  1. Intensity tunable infrared broadband absorbers based on VO2 phase transition using planar layered thin films

    PubMed Central

    Kocer, Hasan; Butun, Serkan; Palacios, Edgar; Liu, Zizhuo; Tongay, Sefaattin; Fu, Deyi; Wang, Kevin; Wu, Junqiao; Aydin, Koray

    2015-01-01

    Plasmonic and metamaterial based nano/micro-structured materials enable spectrally selective resonant absorption, where the resonant bandwidth and absorption intensity can be engineered by controlling the size and geometry of nanostructures. Here, we demonstrate a simple, lithography-free approach for obtaining a resonant and dynamically tunable broadband absorber based on vanadium dioxide (VO2) phase transition. Using planar layered thin film structures, where top layer is chosen to be an ultrathin (20 nm) VO2 film, we demonstrate broadband IR light absorption tuning (from ~90% to ~30% in measured absorption) over the entire mid-wavelength infrared spectrum. Our numerical and experimental results indicate that the bandwidth of the absorption bands can be controlled by changing the dielectric spacer layer thickness. Broadband tunable absorbers can find applications in absorption filters, thermal emitters, thermophotovoltaics and sensing. PMID:26294085

  2. Atomic Layering, Intermixing and Switching Mechanism in Ge-Sb-Te based Chalcogenide Superlattices

    PubMed Central

    Yu, Xiaoming; Robertson, John

    2016-01-01

    GeSbTe-based chalcogenide superlattice (CSLs) phase-change memories consist of GeSbTe layer blocks separated by van der Waals bonding gaps. Recent high resolution electron microscopy found two types of disorder in CSLs, a chemical disorder within individual layers, and SbTe bilayer stacking faults connecting one block to an adjacent block which allows individual block heights to vary. The disorder requires a generalization of the previous switching models developed for CSL systems. Density functional calculations are used to describe the stability of various types of intra-layer disorder, how the block heights can vary by means of SbTe-based stacking faults and using a vacancy-mediated kink motion, and also to understand the nature of the switching process in more chemically disordered CSLs. PMID:27853289

  3. Functional Exoenzymes as Indicators of Metabolically Active Bacteria in 124,000-Year-Old Sapropel Layers of the Eastern Mediterranean Sea

    PubMed Central

    Coolen, Marco J. L.; Overmann, Jörg

    2000-01-01

    Hydrolytic exoenzymes as indicators of metabolically active bacteria were investigated in four consecutive sapropel layers collected from bathyal sediments of the eastern Mediterranean Sea. For comparison, the organic carbon-poor layers between the sapropels, sediment from the anoxic Urania basin, and sediments of intertidal mud flats of the German Wadden Sea were also analyzed. The sapropel layers contained up to 1.5 · 108 bacterial cells cm−3, whereas cell numbers in the intermediate layers were lower by a factor of 10. In sapropels, the determination of exoenzyme activity with fluorescently labeled substrate analogues was impaired by the strong adsorption of up to 97% of the enzymatically liberated fluorophores (4-methylumbelliferone [MUF] and 7-amino-4-methylcoumarin [MCA]) to the sediment particles. Because all established methods for the extraction of adsorbed fluorophores proved to be inadequate for sapropel sediments, we introduce a correction method which is based on the measurement of equilibrium adsorption isotherms for both compounds. Using this new approach, high activities of aminopeptidase and alkaline phosphatase were detected even in a 124,000-year-old sapropel layer, whereas the activity of β-glucosidase was low in all layers. So far, it had been assumed that the organic matter which constitutes the sapropels is highly refractory. The high potential activities of bacterial exoenzymes indicate that bacteria in Mediterranean sapropels are metabolically active and utilize part of the subfossil kerogen. Since a high adsorption capacity was determined not only for the low-molecular-weight compounds MUF and MCA but also for DNA, the extraordinarily strong adsorption of structurally different substrates to the sapropel matrix appears to be the major reason for the long-term preservation of biodegradable carbon in this environment. PMID:10831442

  4. Organic light emitting field effect transistors based on an ambipolar p-i-n layered structure

    NASA Astrophysics Data System (ADS)

    Maiorano, V.; Bramanti, A.; Carallo, S.; Cingolani, R.; Gigli, G.

    2010-03-01

    A bottom contact/top gate ambipolar "p-i-n" layered light emitting field effect transistor with the active medium inserted between two doped transport layers, is reported. The doping profile results crucial to the capability of emitting light, as well as to the electrical characteristics of the device. In this sense, high output current at relative low applied gate/drain voltage and light emission along the whole large area transistor channel are observed, putting the basis to full integration of organic light emitting field effect transistors in planar complex devices.

  5. 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.

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

    DOE PAGES

    Newman, Brent D.; Throckmorton, Heather M.; Graham, David E.; ...

    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

  7. Photovoltaic performance of block copolymer devices is independent of the crystalline texture in the active layer

    DOE PAGES

    Guo, Changhe; Lee, Youngmin; Lin, Yen -Hao; ...

    2016-06-15

    The electronic properties of organic semiconductors are strongly influenced by intermolecular packing. When cast as thin films, crystalline π-conjugated molecules are strongly textured, potentially leading to anisotropic charge transport. Consequently, it is hypothesized that the orientation of crystallites in the active layer plays an important role in charge extraction and organic photovoltaic device performance. Here we demonstrate orientation control of molecular packing from mostly face-on to edge-on configurations in the active layer of P3HT-b-PFTBT block copolymer photovoltaics using 1-chloronaphthalene as a solvent additive. The effect of molecular orientations in P3HT crystals on charge transport and solar cell performance is examined.more » We find that optimized photovoltaic device performance is independent of the crystalline texture of P3HT. Our observations provide further insights into the molecular organization required for efficient charge transport and overall device efficiencies. That is, the dominant crystal orientation, whether face-on or edge-on, is not critical to organic solar cells. Furthermore, a broad distribution of crystallite orientations ensures pathways for charge transport in any direction and enables efficient charge extraction in photovoltaic devices.« less

  8. Photovoltaic performance of block copolymer devices is independent of the crystalline texture in the active layer

    SciTech Connect

    Guo, Changhe; Lee, Youngmin; Lin, Yen -Hao; Strzalka, Joseph; Wang, Cheng; Hexemer, Alexander; Jaye, Cherno; Fischer, Daniel A.; Verduzco, Rafael; Wang, Qing; Gomez, Enrique D.

    2016-06-15

    The electronic properties of organic semiconductors are strongly influenced by intermolecular packing. When cast as thin films, crystalline π-conjugated molecules are strongly textured, potentially leading to anisotropic charge transport. Consequently, it is hypothesized that the orientation of crystallites in the active layer plays an important role in charge extraction and organic photovoltaic device performance. Here we demonstrate orientation control of molecular packing from mostly face-on to edge-on configurations in the active layer of P3HT-b-PFTBT block copolymer photovoltaics using 1-chloronaphthalene as a solvent additive. The effect of molecular orientations in P3HT crystals on charge transport and solar cell performance is examined. We find that optimized photovoltaic device performance is independent of the crystalline texture of P3HT. Our observations provide further insights into the molecular organization required for efficient charge transport and overall device efficiencies. That is, the dominant crystal orientation, whether face-on or edge-on, is not critical to organic solar cells. Furthermore, a broad distribution of crystallite orientations ensures pathways for charge transport in any direction and enables efficient charge extraction in photovoltaic devices.

  9. Toward bulk heterojunction polymer solar cells with thermally stable active layer morphology

    NASA Astrophysics Data System (ADS)

    Cardinaletti, Ilaria; Kesters, Jurgen; Bertho, Sabine; Conings, Bert; Piersimoni, Fortunato; D'Haen, Jan; Lutsen, Laurence; Nesladek, Milos; Van Mele, Bruno; Van Assche, Guy; Vandewal, Koen; Salleo, Alberto; Vanderzande, Dirk; Maes, Wouter; Manca, Jean V.

    2014-01-01

    When state-of-the-art bulk heterojunction organic solar cells with ideal morphology are exposed to prolonged storage or operation at elevated temperatures, a thermally induced disruption of the active layer blend can occur, in the form of a separation of donor and acceptor domains, leading to diminished photovoltaic performance. Toward the long-term use of organic solar cells in real-life conditions, an important challenge is, therefore, the development of devices with a thermally stable active layer morphology. Several routes are being explored, ranging from the use of high glass transition temperature, cross-linkable and/or side-chain functionalized donor and acceptor materials, to light-induced dimerization of the fullerene acceptor. A better fundamental understanding of the nature and underlying mechanisms of the phase separation and stabilization effects has been obtained through a variety of analytical, thermal analysis, and electro-optical techniques. Accelerated aging systems have been used to study the degradation kinetics of bulk heterojunction solar cells in situ at various temperatures to obtain aging models predicting solar cell lifetime. The following contribution gives an overview of the current insights regarding the intrinsic thermally induced aging effects and the proposed solutions, illustrated by examples of our own research groups.

  10. 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.

  11. Determinants of carbon release from the active layer and permafrost deposits on the Tibetan Plateau

    PubMed Central

    Chen, Leiyi; Liang, Junyi; Qin, Shuqi; Liu, Li; Fang, Kai; Xu, Yunping; Ding, Jinzhi; Li, Fei; Luo, Yiqi; Yang, Yuanhe

    2016-01-01

    The sign and magnitude of permafrost carbon (C)-climate feedback are highly uncertain due to the limited understanding of the decomposability of thawing permafrost and relevant mechanistic controls over C release. Here, by combining aerobic incubation with biomarker analysis and a three-pool model, we reveal that C quality (represented by a higher amount of fast cycling C but a lower amount of recalcitrant C compounds) and normalized CO2–C release in permafrost deposits were similar or even higher than those in the active layer, demonstrating a high vulnerability of C in Tibetan upland permafrost. We also illustrate that C quality exerts the most control over CO2–C release from the active layer, whereas soil microbial abundance is more directly associated with CO2–C release after permafrost thaw. Taken together, our findings highlight the importance of incorporating microbial properties into Earth System Models when predicting permafrost C dynamics under a changing environment. PMID:27703168

  12. Admittance spectroscopy of solar cells based on GaPNAs layers

    SciTech Connect

    Baranov, A. I. Gudovskikh, A. S.; Zelentsov, K. S.; Nikitina, E. V.; Egorov, A. Yu.

    2015-04-15

    Admittance spectroscopy is used to study defect levels in the layers of a GaPNAs quaternary solid solution. Centers with an activation energy of 0.22 eV and a capture cross section of ∼2.4 × 10{sup −15} cm{sup 2} are found in doped n-GaPNAs layers grown on GaP substrates. These centers correspond to already known Si{sub Ga} + V{sub P} defects in n-GaP; annealing decreases their concentration by several times. A level with an activation energy of 0.23–0.24 eV and capture cross section of ∼9.0 × 10{sup −20} cm{sup 2} is found in undoped GaPNAs layers grown on Si and GaP substrates. The concentration of these centers substantially decreases upon annealing, and, at annealing temperatures exceeding 600°C, there is absolutely no response from these defects. For undoped GaPNAs layers grown on GaP substrates, a level with an activation energy of 0.18 eV and capture cross section of ∼1.1 × 10{sup −16} cm{sup 2} is also found. The concentration of these centers remains unchanged upon annealing.

  13. Development of advanced catalytic layer based on vertically aligned conductive polymer arrays for thin-film fuel cell electrodes

    NASA Astrophysics Data System (ADS)

    Jiang, Shangfeng; Yi, Baolian; Cao, Longsheng; Song, Wei; Zhao, Qing; Yu, Hongmei; Shao, Zhigang

    2016-10-01

    The degradation of carbon supports significantly influences the performance of proton exchange membrane fuel cells (PEMFCs), particularly in the cathode, which must be overcome for the wide application of fuel cells. In this study, advanced catalytic layer with electronic conductive polymer-polypyrrole (PPy) nanowire as ordered catalyst supports for PEMFCs is prepared. A platinum-palladium (PtPd) catalyst thin layer with whiskerette shapes forms along the long axis of the PPy nanowires. The resulting arrays are hot-pressed on both sides of a Nafion® membrane to construct a membrane electrode assembly (without additional ionomer). The ordered thin catalyst layer (approximately 1.1 μm) is applied in a single cell as the anode and the cathode without additional Nafion® ionomer. The single cell yields a maximum performance of 762.1 mW cm-2 with a low Pt loading (0.241 mg Pt cm-2, anode + cathode). The advanced catalyst layer indicates better mass transfer in high current density than that of commercial Pt/C-based electrode. The mass activity is 1.08-fold greater than that of DOE 2017 target. Thus, the as-prepared electrodes have the potential for application in fuel cells.

  14. 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.

  15. A representative volume element based micromechanical analysis of a Bi-layered Ganoid Fish scale.

    PubMed

    Nelms, Matthew; Hodo, Wayne; Rajendran, A M

    2017-02-07

    The Mississippi Alligator gar (Atractosteus spatula) possesses a flexible exoskeleton armor consisting of overlapping ganoid scales used for predatory protection. Each scale is a two-phase biomineralized composite containing bio-modified hydroxyapatite (hard) minerals and collagen (soft) fibers. The protective layer consists of a stiff outer ganoine layer, a characteristic "sawtooth" pattern at the interface with the compliant bone inner layer. The garfish scale exhibits a decreasing elastic modulus from the external to the internal layers. Scanning electron microscopy (SEM) images of the cross-section revealed a two-layered structure. Elastic moduli, measured from nanoindentation experiments, were correlated to structural changes across each layer. The "material" symmetry of this materially and geometrically nonlinear biomineralized composite is unknown. Therefore, to be able to determine the stiffness tensor requires the use of finite element analysis (FEA). The gar fish scale was computationally modeled using the representative volume element (RVE) based approach. As a result, the unknown symmetry induced by the architecture and material layering require the use of complex FEA boundary conditions. The simulation was conducted in the pure uniaxial strain regimes of tension and shear, which necessitated the mathematical determination so appropriate surface loading conditions could be applied. This paper provides the results from a highly-resolved mesoscale RVE model based on iso-strain boundary conditions (ISBC) to determine the elastic stiffness tensor for the composite system. By assuming isotropic behavior in individual elements, the results for the RVE reveal the fish scale has an "orthotropic symmetry" with slight local strain variations occurring at the sawtooth interface.

  16. Charge Transport in Field-Effect Transistors based on Layered Materials and their Heterostructures

    NASA Astrophysics Data System (ADS)

    Kumar, Jatinder

    In the quest for energy efficiency and device miniaturization, the research in using atomically thin materials for device applications is gaining momentum. The electronic network in layered materials is different from 3D counterparts. It is due to the interlayer couplings and density of states because of their 2D nature. Therefore, understanding the charge transport in layered materials is fundamental to explore the vast opportunities these ultra-thin materials offer. Hence, the challenges targeted in the thesis are: (1) understanding the charge transport in layered materials based on electronic network of quantum and oxide capacitances, (2) studying thickness dependence, ranging from monolayer to bulk, of full range-characteristics of field-effect transistor (FET) based on layered materials, (3) investigating the total interface trap charges to achieve the ultimate subthreshold slope (SS) theoretically possible in FETs, (4) understanding the effect of the channel length on the performance of layered materials, (5) understanding the effect of substrate on performance of the TMDC FETs and studying if the interface of transition metal dichalcogenides (TMDCs)/hexagonalboron nitride (h-BN) can have less enough trap charges to observe ambipolar behavior, (6) Exploring optoelectronic properties in 2D heterostructures that includes understanding graphene/WS2 heterostructure and its optoelectronic applications by creating a p-n junction at the interface. The quality of materials and the interface are the issues for observing and extracting clean physics out of these layered materials and heterostructures. In this dissertation, we realized the use of quantum capacitance in layered materials, substrate effects and carrier transport in heterostructure.

  17. A survey on multimedia-based cross-layer optimization in visual sensor networks.

    PubMed

    Costa, Daniel G; Guedes, Luiz Affonso

    2011-01-01

    Visual sensor networks (VSNs) comprised of battery-operated electronic devices endowed with low-resolution cameras have expanded the applicability of a series of monitoring applications. Those types of sensors are interconnected by ad hoc error-prone wireless links, imposing stringent restrictions on available bandwidth, end-to-end delay and packet error rates. In such context, multimedia coding is required for data compression and error-resilience, also ensuring energy preservation over the path(s) toward the sink and improving the end-to-end perceptual quality of the received media. Cross-layer optimization may enhance the expected efficiency of VSNs applications, disrupting the conventional information flow of the protocol layers. When the inner characteristics of the multimedia coding techniques are exploited by cross-layer protocols and architectures, higher efficiency may be obtained in visual sensor networks. This paper surveys recent research on multimedia-based cross-layer optimization, presenting the proposed strategies and mechanisms for transmission rate adjustment, congestion control, multipath selection, energy preservation and error recovery. We note that many multimedia-based cross-layer optimization solutions have been proposed in recent years, each one bringing a wealth of contributions to visual sensor networks.

  18. A Survey on Multimedia-Based Cross-Layer Optimization in Visual Sensor Networks

    PubMed Central

    Costa, Daniel G.; Guedes, Luiz Affonso

    2011-01-01

    Visual sensor networks (VSNs) comprised of battery-operated electronic devices endowed with low-resolution cameras have expanded the applicability of a series of monitoring applications. Those types of sensors are interconnected by ad hoc error-prone wireless links, imposing stringent restrictions on available bandwidth, end-to-end delay and packet error rates. In such context, multimedia coding is required for data compression and error-resilience, also ensuring energy preservation over the path(s) toward the sink and improving the end-to-end perceptual quality of the received media. Cross-layer optimization may enhance the expected efficiency of VSNs applications, disrupting the conventional information flow of the protocol layers. When the inner characteristics of the multimedia coding techniques are exploited by cross-layer protocols and architectures, higher efficiency may be obtained in visual sensor networks. This paper surveys recent research on multimedia-based cross-layer optimization, presenting the proposed strategies and mechanisms for transmission rate adjustment, congestion control, multipath selection, energy preservation and error recovery. We note that many multimedia-based cross-layer optimization solutions have been proposed in recent years, each one bringing a wealth of contributions to visual sensor networks. PMID:22163908

  19. Polyoxometalate-based layered structures for charge transport control in molecular devices.

    PubMed

    Douvas, Antonios M; Makarona, Eleni; Glezos, Nikos; Argitis, Panagiotis; Mielczarski, Jerzy A; Mielczarski, Ela

    2008-04-01

    Hybrid organic-inorganic films consisted of molecular layers of a Keggin-structure polyoxometalate (POM: 12-tungstophosphoric acid, H(3)PW(12)O(40)) and 1,12-diaminododecane (DD) on 3-aminopropyl triethoxysilane (APTES)-modified silicon surface, fabricated via the layer-by-layer (LBL) self-assembly method are evaluated as molecular materials for electronic devices. The effect of the fabrication process parameters, including primarily compositions of deposition solutions, on the structural characteristics of the POM-based multilayers was studied extensively with a combination of spectroscopic methods (UV, FTIR, and XPS). Well-characterized POM-based films (both single-layers and multilayers) in a controlled and reproducible way were obtained. The conduction mechanisms in single-layered and multilayered structures were elucidated by the electrical characterization of the produced films supported by the appropriate theoretical analysis. Fowler-Nordheim (FN) tunneling and percolation mechanisms were encountered in good correlation with the structural characteristics of the films encouraging further investigation on the use of these materials in electronic and, in particular, in memory devices.

  20. Performance limits of tunnel transistors based on mono-layer transition-metal dichalcogenides

    NASA Astrophysics Data System (ADS)

    Jiang, Xiang-Wei; Li, Shu-Shen

    2014-05-01

    Performance limits of tunnel field-effect transistors based on mono-layer transition metal dichalcogenides are investigated through numerical quantum mechanical simulations. The atomic mono-layer nature of the devices results in a much smaller natural length λ, leading to much larger electric field inside the tunneling diodes. As a result, the inter-band tunneling currents are found to be very high as long as ultra-thin high-k gate dielectric is possible. The highest on-state driving current is found to be close to 600 μA/μm at Vg = Vd = 0.5 V when 2 nm thin HfO2 layer is used for gate dielectric, outperforming most of the conventional semiconductor tunnel transistors. In the five simulated transition-metal dichalcogenides, mono-layer WSe2 based tunnel field-effect transistor shows the best potential. Deep analysis reveals that there is plenty room to further enhance the device performance by either geometry, alloy, or strain engineering on these mono-layer materials.

  1. Performance limits of tunnel transistors based on mono-layer transition-metal dichalcogenides

    SciTech Connect

    Jiang, Xiang-Wei Li, Shu-Shen

    2014-05-12

    Performance limits of tunnel field-effect transistors based on mono-layer transition metal dichalcogenides are investigated through numerical quantum mechanical simulations. The atomic mono-layer nature of the devices results in a much smaller natural length λ, leading to much larger electric field inside the tunneling diodes. As a result, the inter-band tunneling currents are found to be very high as long as ultra-thin high-k gate dielectric is possible. The highest on-state driving current is found to be close to 600 μA/μm at V{sub g} = V{sub d} = 0.5 V when 2 nm thin HfO{sub 2} layer is used for gate dielectric, outperforming most of the conventional semiconductor tunnel transistors. In the five simulated transition-metal dichalcogenides, mono-layer WSe{sub 2} based tunnel field-effect transistor shows the best potential. Deep analysis reveals that there is plenty room to further enhance the device performance by either geometry, alloy, or strain engineering on these mono-layer materials.

  2. Activity Based Curriculum for Elementary Education. Additional Activities, K-6.

    ERIC Educational Resources Information Center

    Wichita Public Schools, KS.

    This elementary curriculum is a vehicle to provide manipulative activities that reinforce academic skills through meaningful, relevant, activity-based awareness of modern society. The twenty-six activity plans included in the curriculum place a major emphasis upon realistic or concrete experiences that deal with the manipulation and exploration of…

  3. Unified Cloud and Mixing Parameterizations of the Marine Boundary Layer: EDMF and PDF-based Cloud Approaches

    DTIC Science & Technology

    2012-09-30

    600 m, topped by a non-precipitating shallow cumulus cloud layer. The boundary layer turbulence is forced mainly by buoyancy flux, the wind shear...STATEMENT A. Approved for public release; distribution is unlimited. Unified Cloud and...Mixing Parameterizations of the Marine Boundary Layer: EDMF and PDF-based cloud approaches Joao Teixeira Jet Propulsion Laboratory, California

  4. Contribution of Sp1 to Telomerase Expression and Activity in Skin Keratinocytes Cultured With a Feeder Layer.

    PubMed

    Bisson, Francis; Paquet, Claudie; Bourget, Jean-Michel; Zaniolo, Karine; Rochette, Patrick J; Landreville, Solange; Damour, Odile; Boudreau, François; Auger, François A; Guérin, Sylvain L; Germain, Lucie

    2015-02-01

    The growth of primary keratinocytes is improved by culturing them with a feeder layer. The aim of this study was to assess whether the feeder layer increases the lifespan of cultured epithelial cells by maintaining or improving telomerase activity and expression. The addition of an irradiated fibroblast feeder layer of either human or mouse origin (i3T3) helped maintain telomerase activity as well as expression of the transcription factor Sp1 in cultured keratinocytes. In contrast, senescence occurred earlier, together with a reduction of Sp1 expression and telomerase activity, in keratinocytes cultured without a feeder layer. Telomerase activity was consistently higher in keratinocytes grown on the three different feeder layers tested relative to cells grown without them. Suppression of Sp1 expression by RNA inhibition (RNAi) reduced both telomerase expression and activity in keratinocytes and also abolished their long-term growth capacity suggesting that Sp1 is a key regulator of both telomerase gene expression and cell cycle progression of primary cultured human skin keratinocytes. The results of the present study therefore suggest that the beneficial influence of the feeder layer relies on its ability to preserve telomerase activity in cultured human keratinocytes through the maintenance of stable levels of Sp1 expression.

  5. Ionization behavior, stoichiometry of association, and accessibility of functional groups in the active layers of reverse osmosis and nanofiltration membranes.

    PubMed

    Coronell, Orlando; González, Mari I; Mariñas, Benito J; Cahill, David G

    2010-09-01

    We characterized the fully aromatic polyamide (PA) active layers of six commercial reverse osmosis (RO) and nanofiltration (NF) membranes and found that in contrast to their similar elemental composition, total concentration of functional groups, and degree of polymerization, the ionization behavior and spatial distribution of carboxylic (R-COOH) groups within the active layers can be significantly different. We also studied the steric effects experienced by barium ion (Ba2+) in the active layers by determining the fraction of carboxylate (R-COO-) groups accessible to Ba2+; such fraction, referred to as the accessibility ratio (AR), was found to vary within the range AR=0.40-0.81, and to be generally independent of external solution pH. Additionally, we studied an NF membrane with a sulfonated polyethersulfone (SPES) active layer, and found that the concentration of sulfonate (R-SO3-) groups in the active layer was 1.67 M, independent of external solution pH and approximately three times higher than the maximum concentration (approximately 0.45+/-0.25 M) of R-COO- groups in PA active layers. The R-SO3- groups were found to be highly accessible to Ba2+ (AR=0.95+/-0.01).

  6. Layer-specific entrainment of γ-band neural activity by the α rhythm in monkey visual cortex.

    PubMed

    Spaak, Eelke; Bonnefond, Mathilde; Maier, Alexander; Leopold, David A; Jensen, Ole

    2012-12-18

    Although the mammalian neocortex has a clear laminar organization, layer-specific neuronal computations remain to be uncovered. Several studies suggest that gamma band activity in primary visual cortex (V1) is produced in granular and superficial layers and is associated with the processing of visual input. Oscillatory alpha band activity in deeper layers has been proposed to modulate neuronal excitability associated with changes in arousal and cognitive factors. To investigate the layer-specific interplay between these two phenomena, we characterized the coupling between alpha and gamma band activity of the local field potential in V1 of the awake macaque. Using multicontact laminar electrodes to measure spontaneous signals simultaneously from all layers of V1, we found a robust coupling between alpha phase in the deeper layers and gamma amplitude in granular and superficial layers. Moreover, the power in the two frequency bands was anticorrelated. Taken together, these findings demonstrate robust interlaminar cross-frequency coupling in the visual cortex, supporting the view that neuronal activity in the alpha frequency range phasically modulates processing in the cortical microcircuit in a top-down manner.

  7. Actomyosin dynamics drive local membrane component organization in an in vitro active composite layer

    PubMed Central

    Husain, Kabir; Iljazi, Elda; Bhat, Abrar; Bieling, Peter; Mullins, R. Dyche; Rao, Madan; Mayor, Satyajit

    2016-01-01

    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

  8. Dynamics of the Ligand Binding Domain Layer during AMPA Receptor Activation

    PubMed Central

    Baranovic, Jelena; Chebli, Miriam; Salazar, Hector; Carbone, Anna L.; Faelber, Katja; Lau, Albert Y.; Daumke, Oliver; Plested, Andrew J.R.

    2016-01-01

    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

  9. Analysis and Identification of Acid-Base Indicator Dyes by Thin-Layer Chromatography

    ERIC Educational Resources Information Center

    Clark, Daniel D.

    2007-01-01

    Thin-layer chromatography (TLC) is a very simple and effective technique that is used by chemists by different purposes, including the monitoring of the progress of a reaction. TLC can also be easily used for the analysis and identification of various acid-base indicator dyes.

  10. A fluorescent, photochromic and thermochromic trifunctional material based on a layered metal-viologen complex.

    PubMed

    Wan, Fang; Qiu, Li-Xia; Zhou, Liang-Liang; Sun, Yan-Qiong; You, Yi

    2015-11-14

    The azide anion as an energy acceptor and an electron donor has been introduced into a metal-viologen compound to form a 2D layered viologen-based trifunctional material, which exhibits the rare discolored function of reversible photochromism and thermochromism. Interestingly, its fluorescence can be switched by visible light irradiation and heating in air.

  11. Study of compressible mixing layers using filtered Rayleigh scattering based visualizations

    NASA Technical Reports Server (NTRS)

    Elliott, Gregory S.; Samimy, MO; Arnette, Stephen A.

    1992-01-01

    Filtered Rayleigh scattering-based flow visualizations of compressible mixing layers are reported. The lower compressibility case (Mc = 0.51) displays well-defined roller-type spanwise structures and streamwise streaks. The structures of the high compressibility case (Mc = 0.86) are more 3D and oblique.

  12. Phospholipids, Dietary Supplements, and Chicken Eggs: An Inquiry-Based Exercise Using Thin-Layer Chromatography

    ERIC Educational Resources Information Center

    Potteiger, Sara E.; Belanger, Julie M.

    2015-01-01

    This inquiry-based experiment is designed for organic or biochemistry undergraduate students to deduce the identity of phospholipids extracted from chicken eggs and dietary supplements. This is achieved using thin-layer chromatography (TLC) data, a series of guided questions of increasing complexity, and provided relative retention factor (Rf)…

  13. Tetrakis(1-imidazolyl) borate (BIM4) based zwitterionic and related molecules used as electron injection layers

    DOEpatents

    Li, Huaping; Xu, Yunhua; Bazan, Guillermo C

    2013-02-05

    Tetrakis(1-imidazolyl)borate (BIm4) based zwitterionic and/or related molecules for the fabrication of PLEDs is provided. Device performances with these materials approaches that of devices with Ba/Al cathodes for which the cathode contact is ohmic. Methods of producing such materials, and electron injection layers and devices containing these materials are also provided.

  14. Electric Double-Layer Capacitor Based on an Ionic Clathrate Hydrate

    SciTech Connect

    Lee, Wonhee; Kwon, Minchul; Park, Seongmin; Lim, Dongwook; Cha, Jong-Ho; Lee, Huen

    2013-05-13

    Herein, we suggest a new approach to an electric double-layer capacitor (EDLC) that is based on a proton-conducting ionic clathrate hydrate (ICH). The ice-like structures of clathrate hydrates, which are comprised of host water molecules and guest ions, make them suitable for applications in EDLC electrolytes, owing to their high proton conductivities and thermal stabilities. The carbon materials in the ICH Me{sub 4}NOH[DOT OPERATOR]5H{sub 2}O show a high specific capacitance, reversible charge–discharge behavior, and a long cycle life. The ionic-hydrate complex provides the following advantages in comparison with conventional aqueous and polymer electrolytes: 1)The ICH does not cause leakage problems under normal EDLC operating conditions. 2)The hydrate material can be utilized itself, without requiring any pre-treatments or activation for proton conduction, thus shortening the preparation procedure of the EDLC. 3)The crystallization of the ICH makes it possible to tailor practical EDLC dimensions because of its fluidity as a liquid hydrate. 4)The hydrate solid electrolyte exhibits more-favorable electrochemical stability than aqueous and polymer electrolytes. Therefore, ICH materials are expected to find practical applications in versatile energy devices that incorporate electrochemical systems.

  15. Edge effects in vertically-oriented graphene based electric double-layer capacitors

    NASA Astrophysics Data System (ADS)

    Yang, Huachao; Yang, Jinyuan; Bo, Zheng; Zhang, Shuo; Yan, Jianhua; Cen, Kefa

    2016-08-01

    Vertically-oriented graphenes (VGs) have been demonstrated as a promising active material for electric double-layer capacitors (EDLCs), partially due to their edge-enriched structure. In this work, the 'edge effects', i.e., edges as the promoters of high capacitance, in VG based EDLCs are investigated with experimental research and numerical simulations. VGs with diverse heights (i.e., edge-to-basal ratios) and edge densities are prepared with varying the plasma-enabled growth time and employing different plasma sources. Electrochemical measurements show that the edges play a predominant role on the charge storage behavior of VGs. A simulation is further conducted to unveil the roles of the edges on the separation and adsorption of ions within VG channels. The initial charge distribution of a VG plane is obtained with density functional theory (DFT) calculations, which is subsequently applied to a molecular dynamics (MD) simulation system to gain the insights into the microscope EDLC structures. Compared with the basal planes, the edges present higher initial charge density (by 4.2 times), higher ion packing density (by 2.6 times), closer ion packing location (by 0.8 Å), and larger ion separation degree (by 14%). The as-obtained findings will be instructive in designing the morphology and structure of VGs for enhanced capacitive performances.

  16. Facile Fabrication of 3D Layer-by-layer Graphene-gold Nanorod Hybrid Architecture for Hydrogen Peroxide Based Electrochemical Biosensor

    DTIC Science & Technology

    2015-01-01

    Facile fabrication of 3D layer-by-layer graphene-gold nanorod hybrid architecture for hydrogen peroxide based electrochemical biosensor Chenming Xue...the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/3.0/). 1. Introduction Electrochemical biosensors are highly effective in...measurement techniques such as radioisotope tracing, NMR spectroscopy, and microfluorometry assay [12,25,18]. In recent years, electrochemical biosensors

  17. In situ generated AgBr-enhanced ZnO nanorod-based photoelectrochemical aptasensing via layer-by-layer assembly.

    PubMed

    Li, Jing; Tu, Wenwen; Li, Hongbo; Bao, Jianchun; Dai, Zhihui

    2014-02-28

    A robust aptasensor for Ag(+) was proposed for the first time using an enhanced ZnO nanorod-based photoelectrochemistry by in situ generated AgBr via layer-by-layer assembly. This work opens up new avenues for application of one-dimensional ZnO nanorod arrays in photoelectrochemical sensing. Additionally, the strategy of employing in situ generated narrow-bandgap semiconductors paves a new way for photoelectrochemical sensing.

  18. Biomimetic interfaces based on S-layer proteins, lipid membranes and functional biomolecules

    PubMed Central

    Schuster, Bernhard; Sleytr, Uwe B.

    2014-01-01

    Designing and utilization of biomimetic membrane systems generated by bottom-up processes is a rapidly growing scientific and engineering field. Elucidation of the supramolecular construction principle of archaeal cell envelopes composed of S-layer stabilized lipid membranes led to new strategies for generating highly stable functional lipid membranes at meso- and macroscopic scale. In this review, we provide a state-of-the-art survey of how S-layer proteins, lipids and polymers may be used as basic building blocks for the assembly of S-layer-supported lipid membranes. These biomimetic membrane systems are distinguished by a nanopatterned fluidity, enhanced stability and longevity and, thus, provide a dedicated reconstitution matrix for membrane-active peptides and transmembrane proteins. Exciting areas in the (lab-on-a-) biochip technology are combining composite S-layer membrane systems involving specific membrane functions with the silicon world. Thus, it might become possible to create artificial noses or tongues, where many receptor proteins have to be exposed and read out simultaneously. Moreover, S-layer-coated liposomes and emulsomes copying virus envelopes constitute promising nanoformulations for the production of novel targeting, delivery, encapsulation and imaging systems. PMID:24812051

  19. Biomimetic interfaces based on S-layer proteins, lipid membranes and functional biomolecules.

    PubMed

    Schuster, Bernhard; Sleytr, Uwe B

    2014-07-06

    Designing and utilization of biomimetic membrane systems generated by bottom-up processes is a rapidly growing scientific and engineering field. Elucidation of the supramolecular construction principle of archaeal cell envelopes composed of S-layer stabilized lipid membranes led to new strategies for generating highly stable functional lipid membranes at meso- and macroscopic scale. In this review, we provide a state-of-the-art survey of how S-layer proteins, lipids and polymers may be used as basic building blocks for the assembly of S-layer-supported lipid membranes. These biomimetic membrane systems are distinguished by a nanopatterned fluidity, enhanced stability and longevity and, thus, provide a dedicated reconstitution matrix for membrane-active peptides and transmembrane proteins. Exciting areas in the (lab-on-a-) biochip technology are combining composite S-layer membrane systems involving specific membrane functions with the silicon world. Thus, it might become possible to create artificial noses or tongues, where many receptor proteins have to be exposed and read out simultaneously. Moreover, S-layer-coated liposomes and emulsomes copying virus envelopes constitute promising nanoformulations for the production of novel targeting, delivery, encapsulation and imaging systems.

  20. Modeling the effects of fire severity and climate warming on active layer and soil carbon dynamics of black spruce forests across the landscape in interior Alaska

    USGS Publications Warehouse

    Genet, H.; McGuire, Anthony David; Barrett, K.; Breen, A.; Euskirchen, E.S.; Johnstone, J.F.; Kasischke, E.S.; Melvin, A.M.; Bennett, A.; Mack, M.C.; Rupp, T.S.; Schuur, A.E.G.; Turetsky, M.R.; Yuan, F.

    2013-01-01

    There is a substantial amount of carbon stored in the permafrost soils of boreal forest ecosystems, where it is currently protected from decomposition. The surface organic horizons insulate the deeper soil from variations in atmospheric temperature. The removal of these insulating horizons through consumption by fire increases the vulnerability of permafrost to thaw, and the carbon stored in permafrost to decomposition. In this study we ask how warming and fire regime may influence spatial and temporal changes in active layer and carbon dynamics across a boreal forest landscape in interior Alaska. To address this question, we (1) developed and tested a predictive model of the effect of fire severity on soil organic horizons that depends on landscape-level conditions and (2) used this model to evaluate the long-term consequences of warming and changes in fire regime on active layer and soil carbon dynamics of black spruce forests across interior Alaska. The predictive model of fire severity, designed from the analysis of field observations, reproduces the effect of local topography (landform category, the slope angle and aspect and flow accumulation), weather conditions (drought index, soil moisture) and fire characteristics (day of year and size of the fire) on the reduction of the organic layer caused by fire. The integration of the fire severity model into an ecosystem process-based model allowed us to document the relative importance and interactions among local topography, fire regime and climate warming on active layer and soil carbon dynamics. Lowlands were more resistant to severe fires and climate warming, showing smaller increases in active layer thickness and soil carbon loss compared to drier flat uplands and slopes. In simulations that included the effects of both warming and fire at the regional scale, fire was primarily responsible for a reduction in organic layer thickness of 0.06 m on average by 2100 that led to an increase in active layer thickness

  1. Optoelectronic performance optimization for transparent conductive layers based on randomly arranged silver nanorods.

    PubMed

    Marus, Mikita; Hubarevich, Aliaksandr; Wang, Hong; Smirnov, Aliaksandr; Sun, Xiaowei; Fan, Weijun

    2015-03-09

    Optoelectronic performance of transparent conductive layers (TCLs) based on randomly arranged silver (Ag) nanorods (NRs) is simulated. Models for calculation of optical and electronic properties were proposed founded on finite-difference time-domain method and percolation theory respectively. Obtained simulation results are well conformed to experimental data. The influence of angle deviation of NR crossings on the transmittance and sheet resistance are demonstrated. The balance between transmittance and sheet resistance which can be easily set by varying the combinations of NR radius and NR number is shown. Our results demonstrate that randomly arranged Ag layers are promising candidates for flexible TCLs.

  2. An Integrated Observational and Model Synthesis Approach to Examine Dominant Environmental Controls on Active Layer Thickness

    NASA Astrophysics Data System (ADS)

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

    2015-12-01

    The active layer thickness (ALT) - the annual maximum depth of soil with above 0°C temperatures - in part determines the volume of carbon-rich stores available for decomposition and therefore potential greenhouse gas release into the atmosphere from Arctic tundra. However, understanding and predicting ALT in polygonal tundra landscapes is difficult due to the complex nature of hydrothermal atmospheric-surface-subsurface interactions in freezing/thawing soil. Simply deconvolving effects of single environmental controls on ALT is not possible with measurements alone as processes act in concert to drive thaw depth formation. Process-rich models of thermal hydrological dynamics, conversely, are a valuable tool for understanding the dominant controls and uncertainties in predicting permafrost conditions. By integrating observational data with known physical relationships to form process-rich models, synthetic experiments can then be used to explore a breadth of environmental conditions encountered and the effect of each environmental attribute may be assessed. Here a process rich thermal hydrology model, The Advanced Terrestrial Simulator, has been created and calibrated using observed data from Barrow, AK. An ensemble of 1D thermal hydrologic models were simulated that span a range of three environmental factors 1) thickness of organic rich soil, 2) snow depth, and 3) soil moisture content, to investigate the role of each factor on ALT. Results show that organic layer thickness acts as a strong insulator and is the dominant control of ALT, but the strength of the effect of organic layer thickness is also dependent on the saturation state. Using the ensemble results, the effect of peat thickness on ALT was then examined on a 2D domain. 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

  3. Laboratory-based observations of capillary barriers and preferential flow in layered snow

    NASA Astrophysics Data System (ADS)

    Avanzi, F.; Hirashima, H.; Yamaguchi, S.; Katsushima, T.; De Michele, C.

    2015-12-01

    Several evidences are nowadays available that show how the effects of capillary gradients and preferential flow on water transmission in snow may play a more important role than expected. To observe these processes and to contribute in their characterization, we performed observations on the development of capillary barriers and preferential flow patterns in layered snow during cold laboratory experiments. We considered three different layering (all characterized by a finer-over-coarser texture in grain size) and three different water input rates. Nine samples of layered snow were sieved in a cold laboratory, and subjected to a constant supply of dyed tracer. By means of visual inspection, horizontal sectioning and liquid water content measurements, the processes of ponding and preferential flow were characterized as a function of texture and water input rate. The dynamics of each sample were replicated using the multi-layer physically-based SNOWPACK model. Results show that capillary barriers and preferential flow are relevant processes ruling the speed of liquid water in stratified snow. Ponding is associated with peaks in LWC at the boundary between the two layers equal to ~ 33-36 vol. % when the upper layer is composed by fine snow (grain size smaller than 0.5 mm). The thickness of the ponding layer at the textural boundary is between 0 and 3 cm, depending on sample stratigraphy. Heterogeneity in water transmission increases with grain size, while we do not observe any clear dependency on water input rate. The extensive comparison between observed and simulated LWC profiles by SNOWPACK (using an approximation of Richards Equation) shows high performances by the model in estimating the LWC peak over the boundary, while water speed in snow is underestimated by the chosen water transport scheme.

  4. 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.

  5. 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.

  6. 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.

  7. 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.

  8. Determination of mixing-layer height by ground-based remote sensing

    NASA Astrophysics Data System (ADS)

    Emeis, S.; Schäfer, K.; Münkel, C.

    2009-09-01

    Different ground-based remote sensing methods are today available to profile the boundary-layer and to derive such information as vertical layering and mixing-layer height (MLH). A SODAR detects the vertical profile of temperature fluctuations and gradients. By an algorithm which uses the acoustic backscatter intensity and the variance of the vertical velocity component estimates of the MLH can be made. A ceilometer detects the vertical distribution of aerosol particles and water droplets. By an algorithm which uses the vertical gradient of the optical backscatter intensity estimates of the MLH can be made. A RASS directly detects the vertical temperature profile and therefore allows for a direct measurement of MLH by analysing the vertical temperature gradient. In this presentation MLH determination from all three instruments will be compared and a few applications in the fields of air quality and wind energy will be presented. Limitations and restrictions of the different methods will be discussed.

  9. A double-layer based model of ion confinement in electron cyclotron resonance ion source

    SciTech Connect

    Mascali, D. Neri, L.; Celona, L.; Castro, G.; Gammino, S.; Ciavola, G.; Torrisi, G.; Sorbello, G.

    2014-02-15

    The paper proposes a new model of ion confinement in ECRIS, which can be easily generalized to any magnetic configuration characterized by closed magnetic surfaces. Traditionally, ion confinement in B-min configurations is ascribed to a negative potential dip due to superhot electrons, adiabatically confined by the magneto-static field. However, kinetic simulations including RF heating affected by cavity modes structures indicate that high energy electrons populate just a thin slab overlapping the ECR layer, while their density drops down of more than one order of magnitude outside. Ions, instead, diffuse across the electron layer due to their high collisionality. This is the proper physical condition to establish a double-layer (DL) configuration which self-consistently originates a potential barrier; this “barrier” confines the ions inside the plasma core surrounded by the ECR surface. The paper will describe a simplified ion confinement model based on plasma density non-homogeneity and DL formation.

  10. Liquid-phase-deposited siloxane-based capping layers for silicon solar cells

    SciTech Connect

    Veith-Wolf, Boris; Wang, Jianhui; Hannu-Kuure, Milja; Chen, Ning; Hadzic, Admir; Williams, Paul; Leivo, Jarkko; Karkkainen, Ari; Schmidt, Jan

    2015-02-02

    We apply non-vacuum processing to deposit dielectric capping layers on top of ultrathin atomic-layer-deposited aluminum oxide (AlO{sub x}) films, used for the rear surface passivation of high-efficiency crystalline silicon solar cells. We examine various siloxane-based liquid-phase-deposited (LPD) materials. Our optimized AlO{sub x}/LPD stacks show an excellent thermal and chemical stability against aluminum metal paste, as demonstrated by measured surface recombination velocities below 10 cm/s on 1.3 Ωcm p-type silicon wafers after firing in a belt-line furnace with screen-printed aluminum paste on top. Implementation of the optimized LPD layers into an industrial-type screen-printing solar cell process results in energy conversion efficiencies of up to 19.8% on p-type Czochralski silicon.

  11. Liquid-phase-deposited siloxane-based capping layers for silicon solar cells

    NASA Astrophysics Data System (ADS)

    Veith-Wolf, Boris; Wang, Jianhui; Hannu-Kuure, Milja; Chen, Ning; Hadzic, Admir; Williams, Paul; Leivo, Jarkko; Karkkainen, Ari; Schmidt, Jan

    2015-02-01

    We apply non-vacuum processing to deposit dielectric capping layers on top of ultrathin atomic-layer-deposited aluminum oxide (AlOx) films, used for the rear surface passivation of high-efficiency crystalline silicon solar cells. We examine various siloxane-based liquid-phase-deposited (LPD) materials. Our optimized AlOx/LPD stacks show an excellent thermal and chemical stability against aluminum metal paste, as demonstrated by measured surface recombination velocities below 10 cm/s on 1.3 Ωcm p-type silicon wafers after firing in a belt-line furnace with screen-printed aluminum paste on top. Implementation of the optimized LPD layers into an industrial-type screen-printing solar cell process results in energy conversion efficiencies of up to 19.8% on p-type Czochralski silicon.

  12. Improved conversion efficiency of GaN-based solar cells with Mn-doped absorption layer

    NASA Astrophysics Data System (ADS)

    Sheu, Jinn-Kong; Huang, Feng-Wen; Lee, Chia-Hui; Lee, Ming-Lun; Yeh, Yu-Hsiang; Chen, Po-Cheng; Lai, Wei-Chih

    2013-08-01

    GaN-based solar cells with Mn-doped absorption layer grown by metal-organic vapor-phase epitaxy were investigated. The transmittance spectrum and the spectral response showed the presence of an Mn-related band absorption property. Power-dependent, dual-light excitation, and lock-in amplifier techniques were performed to confirm if the two-photon absorption process occurred in the solar cells with Mn-doped GaN absorption layer. Although a slight decrease in an open circuit voltage was observed, a prominent increase in the short circuit current density resulted in a significant enhancement of the overall conversion efficiency. Under one-sun air mass 1.5 G standard testing condition, the conversion efficiency of Mn-doped solar cells can be enhanced by a magnitude of 5 times compared with the cells without Mn-doped absorption layer.

  13. Low-Dimensional Nanomaterials as Active Layer Components in Thin-Film Photovoltaics

    NASA Astrophysics Data System (ADS)

    Shastry, Tejas Attreya

    Thin-film photovoltaics offer the promise of cost-effective and scalable solar energy conversion, particularly for applications of semi-transparent solar cells where the poor absorption of commercially-available silicon is inadequate. Applications ranging from roof coatings that capture solar energy to semi-transparent windows that harvest the immense amount of incident sunlight on buildings could be realized with efficient and stable thin-film solar cells. However, the lifetime and efficiency of thin-film solar cells continue to trail their inorganic silicon counterparts. Low-dimensional nanomaterials, such as carbon nanotubes and two-dimensional metal dichalcogenides, have recently been explored as materials in thin-film solar cells due to their exceptional optoelectronic properties, solution-processability, and chemical inertness. Thus far, issues with the processing of these materials has held back their implementation in efficient photovoltaics. This dissertation reports processing advances that enable demonstrations of low-dimensional nanomaterials in thin-film solar cells. These low-dimensional photovoltaics show enhanced photovoltaic efficiency and environmental stability in comparison to previous devices, with a focus on semiconducting single-walled carbon nanotubes as an active layer component. The introduction summarizes recent advances in the processing of carbon nanotubes and their implementation through the thin-film photovoltaic architecture, as well as the use of two-dimensional metal dichalcogenides in photovoltaic applications and potential future directions for all-nanomaterial solar cells. The following chapter reports a study of the interaction between carbon nanotubes and surfactants that enables them to be sorted by electronic type via density gradient ultracentrifugation. These insights are utilized to construct of a broad distribution of carbon nanotubes that absorb throughout the solar spectrum. This polychiral distribution is then shown

  14. New CVD-based method for the growth of high-quality crystalline zinc oxide layers

    NASA Astrophysics Data System (ADS)

    Huber, Florian; Madel, Manfred; Reiser, Anton; Bauer, Sebastian; Thonke, Klaus

    2016-07-01

    High-quality zinc oxide (ZnO) layers were grown using a new chemical vapour deposition (CVD)-based low-cost growth method. The process is characterized by total simplicity, high growth rates, and cheap, less hazardous precursors. To produce elementary zinc vapour, methane (CH4) is used to reduce a ZnO powder. By re-oxidizing the zinc with pure oxygen, highly crystalline ZnO layers were grown on gallium nitride (GaN) layers and on sapphire substrates with an aluminum nitride (AlN) nucleation layer. Using simple CH4 as precursor has the big advantage of good controllability and the avoidance of highly toxic gases like nitrogen oxides. In photoluminescence (PL) measurements the samples show a strong near-band-edge emission and a sharp line width at 5 K. The good crystal quality has been confirmed in high resolution X-ray diffraction (HRXRD) measurements. This new growth method has great potential for industrial large-scale production of high-quality single crystal ZnO layers.

  15. Ultrasound-based measurement of liquid-layer thickness: A novel time-domain approach

    NASA Astrophysics Data System (ADS)

    Praher, Bernhard; Steinbichler, Georg

    2017-01-01

    Measuring the thickness of a thin liquid layer between two solid materials is important when the adequate separation of metallic parts by a lubricant film (e.g., in bearings or mechanical seals) is to be assessed. The challenge in using ultrasound-based systems for such measurements is that the signal from the liquid layer is a superposition of multiple reflections. We have developed an algorithm for reconstructing this superimposed signal in the time domain. By comparing simulated and measured signals, the time-of-flight of the ultrasonic pulse in a layer can be estimated. With the longitudinal sound velocity known, the layer thickness can then be calculated. In laboratory measurements, we validate successfully (maximum relative error 4.9%) our algorithm for layer thicknesses ranging from 30 μm to 200 μm. Furthermore, we tested our method in the high-temperature environment of polymer processing by measuring the clearance between screw and barrel in the plasticisation unit of an injection moulding machine. The results of such measurements can indicate (i) the wear status of the tribo-mechanical screw-barrel system and (ii) unsuitable process conditions.

  16. Permafrost temperature and active-layer thickness of Yakutia with 0.5-degree spatial resolution for model evaluation

    NASA Astrophysics Data System (ADS)

    Beer, C.; Fedorov, A. N.; Torgovkin, Y.

    2013-09-01

    Based on the map of landscapes and permafrost conditions in Yakutia (Merzlotno-landshaftnaya karta Yakutskoi0 ASSR, Gosgeodeziya SSSR, 1991), rasterized maps of permafrost temperature and active-layer thickness of Yakutia, East Siberia were derived. The mean and standard deviation at 0.5-degree grid cell size are estimated by assigning a probability density function at 0.001-degree spatial resolution. The gridded datasets can be accessed at the PANGAEA repository (doi:10.1594/PANGAEA.808240). Spatial pattern of both variables are dominated by a climatic gradient from north to south, and by mountains and the soil type distribution. Uncertainties are highest in mountains and in the sporadic permafrost zone in the south. The maps are best suited as a benchmark for land surface models which include a permafrost module.

  17. In-flight active wave cancelation with delayed-x-LMS control algorithm in a laminar boundary layer

    NASA Astrophysics Data System (ADS)

    Simon, Bernhard; Fabbiane, Nicolò; Nemitz, Timotheus; Bagheri, Shervin; Henningson, Dan S.; Grundmann, Sven

    2016-10-01

    This manuscript demonstrates the first successful application of the delayed-x-LMS (dxLMS) control algorithm for TS-wave cancelation. Active wave cancelation of two-dimensional broadband Tollmien-Schlichting (TS) disturbances is performed with a single DBD plasma actuator. The experiments are conducted in flight on the pressure side of a laminar flow wing glove, mounted on a manned glider. The stability properties of the controller are investigated in detail with experimental flight data, DNS and stability analysis of the boundary layer. Finally, a model-free approach for dxLMS operation is introduced to operate the controller as a `black-box' system, which automatically adjusts the controller settings based on a group speed measurement of the disturbance wave packets. The modified dxLMS controller is operated without a model and is able to adapt to varying conditions that may occur during flight in atmosphere.

  18. In-Flight Active Wave Cancelation with Delayed-x-LMS Control Algorithm in a Laminar Boundary Layer

    NASA Astrophysics Data System (ADS)

    Simon, Bernhard; Fabbiane, Nicolo; Nemitz, Timotheus; Bagheri, Shervin; Henningson, Dan; Grundmann, Sven

    2016-11-01

    This manuscript demonstrates the first successful application of the delayed-x-LMS (dxLMS) control algorithm for TS-wave cancelation. Active wave cancelation of two-dimensional broad-band Tollmien-Schlichting (TS) disturbances is performed with a single DBD plasma actuator. The experiments are conducted in flight on the pressure side of a laminar flow wing glove, mounted on a manned glider. The stability properties of the controller are investigated in detail with experimental flight data, DNS and stability analysis of the boundary layer. Finally, a model-free approach for dxLMS operation is introduced to operate the controller as a "black box" system, which automatically adjusts the controller settings based on a group speed measurement of the disturbance wave packets. The modified dxLMS controller is operated without a model and is able to adapt to varying conditions that may occur during flight in atmosphere. DFG No.GR3524/4-1.

  19. Hierarchical layered and semantic-based image segmentation using ergodicity map

    NASA Astrophysics Data System (ADS)

    Yadegar, Jacob; Liu, Xiaoqing

    2010-04-01

    Image segmentation plays a foundational role in image understanding and computer vision. Although great strides have been made and progress achieved on automatic/semi-automatic image segmentation algorithms, designing a generic, robust, and efficient image segmentation algorithm is still challenging. Human vision is still far superior compared to computer vision, especially in interpreting semantic meanings/objects in images. We present a hierarchical/layered semantic image segmentation algorithm that can automatically and efficiently segment images into hierarchical layered/multi-scaled semantic regions/objects with contextual topological relationships. The proposed algorithm bridges the gap between high-level semantics and low-level visual features/cues (such as color, intensity, edge, etc.) through utilizing a layered/hierarchical ergodicity map, where ergodicity is computed based on a space filling fractal concept and used as a region dissimilarity measurement. The algorithm applies a highly scalable, efficient, and adaptive Peano- Cesaro triangulation/tiling technique to decompose the given image into a set of similar/homogenous regions based on low-level visual cues in a top-down manner. The layered/hierarchical ergodicity map is built through a bottom-up region dissimilarity analysis. The recursive fractal sweep associated with the Peano-Cesaro triangulation provides efficient local multi-resolution refinement to any level of detail. The generated binary decomposition tree also provides efficient neighbor retrieval mechanisms for contextual topological object/region relationship generation. Experiments have been conducted within the maritime image environment where the segmented layered semantic objects include the basic level objects (i.e. sky/land/water) and deeper level objects in the sky/land/water surfaces. Experimental results demonstrate the proposed algorithm has the capability to robustly and efficiently segment images into layered semantic objects

  20. 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

  1. Stabilization of starch-based microgel-lysozyme complexes using a layer-by-layer assembly technique.

    PubMed

    Zhang, Bao; Pan, Yi; Chen, Hanqing; Liu, Tengfei; Tao, Han; Tian, Yaoqi

    2017-01-01

    The layer-by-layer assembly of polyelectrolyte multilayers of chitosan (CS) and carboxymethyl starch (CMS) on soft and porous pH- and ionic strength-response microgels was determined by confocal laser scanning microscopy (CLSM) and zeta potential measurements. In vitro release of lysozyme from the stabilized microgels under simulated gastric and intestinal fluids was also investigated. The distribution of CS in the microgels was identified by CLSM, and the optimal molecular weight of CS was 100kDa, which could only be absorbed on the microgel surface. The CS was used as the first layer, while the CMS was used as the second layer, and the zeta potential revealed that the optimal weight ratios of CS and CMS to microgels in the complexes were 0.1 and 0.06, respectively. The in vitro release experiments suggested that the stabilized double-layer microgel complexes could potentially be applied as a carrier system to prevent early release in the stomach to target intestinal delivery.

  2. Strategies to optimize biosensors based on impedance spectroscopy to detect phytic acid using layer-by-layer films.

    PubMed

    Moraes, Marli L; Maki, Rafael M; Paulovich, Fernando V; Rodrigues Filho, Ubirajara P; de Oliveira, Maria Cristina F; Riul, Antonio; de Souza, Nara C; Ferreira, Marystela; Gomes, Henrique L; Oliveira, Osvaldo N

    2010-04-15

    Impedance spectroscopy has been proven a powerful tool for reaching high sensitivity in sensor arrays made with nanostructured films in the so-called electronic tongue systems, whose distinguishing ability may be enhanced with sensing units capable of molecular recognition. In this study we show that for optimized sensors and biosensors the dielectric relaxation processes involved in impedance measurements should also be considered, in addition to an adequate choice of sensing materials. We used sensing units made from layer-by-layer (LbL) films with alternating layers of the polyeletrolytes, poly(allylamine) hydrochloride (PAH) and poly(vinyl sulfonate) (PVS), or LbL films of PAH alternated with layers of the enzyme phytase, all adsorbed on gold interdigitate electrodes. Surprisingly, the detection of phytic acid was as effective in the PVS/PAH sensing system as with the PAH/phytase system, in spite of the specific interactions of the latter. This was attributed to the dependence of the relaxation processes on nonspecific interactions such as electrostatic cross-linking and possibly on the distinct film architecture as the phytase layers were found to grow as columns on the LbL film, in contrast to the molecularly thin PAH/PVS films. Using projection techniques, we were able to detect phytic acid at the micromolar level with either of the sensing units in a data analysis procedure that allows for further optimization.

  3. Single-layer graphene based SPR biochips for tuberculosis bacillus detection

    NASA Astrophysics Data System (ADS)

    Chiu, Nan-Fu; Huang, Teng-Yi; Kuo, Chun-Chuan; Lee, Wei-Che; Hsieh, Min-Hua; Lai, Hsin-Chih

    2012-06-01

    This paper is intended to demonstrate a facile and effective method to construct single layer graphene films onto the self-assembled monolayer (SAM) at Au electrodes based surface plasmon resonance (SPR) biochips integrated loop-mediated isothermal amplification (LAMP) for tuberculosis bacillus (TB) detection. It is a novel Au-SAM-graphene nanocomposites and taking advantages of the striking properties of both graphene and Au film, fundamental understanding in hybrid material manipulation and new electrochemical properties can be obtained. The sensitivity of TB detection in the LAMP-based assay for the amplification of the Insertion Sequence 6110 (IS6110) samples was determined by a single-layer graphene/Au thin film and compared with that of a conventional Au/Cr-based SPR chips. The results show that a graphene/Au SPR offers a potentially powerful assay, with a highly sensitive analysis, that may be applicable as an important tool for bio-marker detection.

  4. Spatiotemporal access model based on reputation for the sensing layer of the IoT.

    PubMed

    Guo, Yunchuan; Yin, Lihua; Li, Chao; Qian, Junyan

    2014-01-01

    Access control is a key technology in providing security in the Internet of Things (IoT). The mainstream security approach proposed for the sensing layer of the IoT concentrates only on authentication while ignoring the more general models. Unreliable communications and resource constraints make the traditional access control techniques barely meet the requirements of the sensing layer of the IoT. In this paper, we propose a model that combines space and time with reputation to control access to the information within the sensing layer of the IoT. This model is called spatiotemporal access control based on reputation (STRAC). STRAC uses a lattice-based approach to decrease the size of policy bases. To solve the problem caused by unreliable communications, we propose both nondeterministic authorizations and stochastic authorizations. To more precisely manage the reputation of nodes, we propose two new mechanisms to update the reputation of nodes. These new approaches are the authority-based update mechanism (AUM) and the election-based update mechanism (EUM). We show how the model checker UPPAAL can be used to analyze the spatiotemporal access control model of an application. Finally, we also implement a prototype system to demonstrate the efficiency of our model.

  5. Spatiotemporal Access Model Based on Reputation for the Sensing Layer of the IoT

    PubMed Central

    Guo, Yunchuan; Yin, Lihua; Li, Chao

    2014-01-01

    Access control is a key technology in providing security in the Internet of Things (IoT). The mainstream security approach proposed for the sensing layer of the IoT concentrates only on authentication while ignoring the more general models. Unreliable communications and resource constraints make the traditional access control techniques barely meet the requirements of the sensing layer of the IoT. In this paper, we propose a model that combines space and time with reputation to control access to the information within the sensing layer of the IoT. This model is called spatiotemporal access control based on reputation (STRAC). STRAC uses a lattice-based approach to decrease the size of policy bases. To solve the problem caused by unreliable communications, we propose both nondeterministic authorizations and stochastic authorizations. To more precisely manage the reputation of nodes, we propose two new mechanisms to update the reputation of nodes. These new approaches are the authority-based update mechanism (AUM) and the election-based update mechanism (EUM). We show how the model checker UPPAAL can be used to analyze the spatiotemporal access control model of an application. Finally, we also implement a prototype system to demonstrate the efficiency of our model. PMID:25177731

  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. 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

  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. 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.

  10. Giant Electron-Hole Interactions in Confined Layered Structures for Molecular Oxygen Activation.

    PubMed

    Wang, Hui; Chen, Shichuan; Yong, Dingyu; Zhang, Xiaodong; Li, Shuang; Shao, Wei; Sun, Xianshun; Pan, Bicai; Xie, Yi

    2017-04-05

    Numerous efforts have been devoted to understanding the excitation processes of photocatalysts, whereas the potential Coulomb interactions between photogenerated electrons and holes have been long ignored. Once these interactions are considered, excitonic effects will arise that undoubtedly influence the sunlight-driven catalytic processes. Herein, by taking bismuth oxyhalide as examples, we proposed that giant electron-hole interactions would be expected in confined layered structures, and excitons would be the dominating photoexcited species. Photocatalytic molecular oxygen activation tests were performed as a proof of concept, where singlet oxygen generation via energy transfer process was brightened. Further experiments verify that structural confinement is curial to the giant excitonic effects, where the involved catalytic process could be readily regulated via facet-engineering, thus enabling diverse reactive oxygen species generation. This study not only provides an excitonic prospective on photocatalytic processes, but also paves a new approach for pursuing systems with giant electron-hole interactions.

  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.

  12. Integrated structures/controls optimization of a smart composite plate with segmented active constrained layer damping

    NASA Astrophysics Data System (ADS)

    Beri, Rajan; Chattopadhyay, Aditi; Nam, Changho

    2000-06-01

    A rigorous multi-objective optimization procedure, is developed to address the integrated structures/control design of composite plates with surface bonded segmented active constrained layer (ACL) damping treatment. The Kresselmeier- Steinhauser function approach is used to formulate this multidisciplinary problem. The goal is to control vibration without incorporating a weight penalty. Objective functions and constraints include damping ratios, structural weight and natural frequencies. Design variables include the ply stacking sequence, dimensions and placement of segmented ACL. The optimal designs show improved plate vibratory characteristics and reduced structural weight. The results of the multi- objective optimization problem are compared to those of a single objective optimization with vibration control as the objective. Results establish the necessity for developing the integrated structures/controls optimization procedure.

  13. 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.

  14. Data base management systems activities

    NASA Technical Reports Server (NTRS)

    1983-01-01

    The Data Management System-1100 is designed to operate in conjunction with the UNIVAC 1100 Series Operating System on any 1100 Series computer. DMS-1100 is divided into the following four major software components: (1) Data Definition Languages (DDL); (2) Data Management Routine (DMR); (3) Data Manipulation Languages (DML); and (4) Data Base Utilities (DBU). These software components are described in detail.

  15. Active-layer thickness estimation from X-band SAR backscatter intensity

    NASA Astrophysics Data System (ADS)

    Widhalm, Barbara; Bartsch, Annett; Leibman, Marina; Khomutov, Artem

    2017-02-01

    The active layer above the permafrost, which seasonally thaws during summer, is an important parameter for monitoring the state of permafrost. Its thickness is typically measured locally, but a range of methods which utilize information from satellite data exist. Mostly, the normalized difference vegetation index (NDVI) obtained from optical satellite data is used as a proxy. The applicability has been demonstrated mostly for shallow depths of active-layer thickness (ALT) below approximately 70 cm. Some permafrost areas including central Yamal are, however, characterized by larger ALT. Surface properties including vegetation structure are also represented by microwave backscatter intensity. So far, the potential of such data for estimating ALT has not been explored. We therefore investigated the relationship between ALT and X-band synthetic aperture radar (SAR) backscatter of TerraSAR-X (averages for 10 × 10 m window) in order to examine the possibility of delineating ALT with continuous and larger spatial coverage in this area and compare it to the already-established method of using NDVI from Landsat (30 m). Our results show that the mutual dependency of ALT and TerraSAR-X backscatter on land cover types suggests a connection of both parameters. A range of 5 dB can be observed for an ALT range of 100 cm (40-140 cm), and an R2 of 0.66 has been determined over the calibration sites. An increase of ALT with increasing backscatter can be determined. The root mean square error (RMSE) over a comparably heterogeneous validation site with maximum ALT of > 150 cm is 20 cm. Deviations are larger for measurement locations with mixed vegetation types (especially partial coverage by cryptogam crust) with respect to the spatial resolution of the satellite data.

  16. Temperature and moisture effects on greenhouse gas emissions from deep active-layer boreal soils

    SciTech Connect

    Bond-Lamberty, Benjamin; Smith, Ashly P.; Bailey, Vanessa L.

    2016-12-21

    Rapid climatic changes, rising air temperatures, and increased fires are expected to drive permafrost degradation and alter soil carbon (C) cycling in many high-latitude ecosystems. How these soils will respond to changes in their temperature, moisture, and overlying vegetation is highly uncertain, but critical to understand given the large soil C stocks in these regions. We used a laboratory experiment to examine how temperature and moisture control CO2 and CH4 emissions from mineral soils sampled from the bottom of the annual active layer, i.e. directly above permafrost, in an Alaskan boreal forest. Gas emissions from thirty cores, subjected to two temperatures and either field moisture conditions or experimental drought, were tracked over a 100-day incubation; we also measured a variety of physical and chemical characteristics of the cores. Gravimetric water content was 0.31 ± 0.12 (unitless) at the beginning of the incubation; cores at field moisture were unchanged at the end, but drought cores had declined to 0.06 ± 0.04. Carbon dioxide fluxes were strongly influenced by incubation chamber temperature, core water content, and percent soil nitrogen, and had a temperature sensitivity (i.e. Q10) of 1.3 and 1.9 for the field moisture and drought treatments, respectively. Methane emissions were most strongly correlated with percent nitrogen, but neither temperature nor water content was a significant first-order predictor of CH4 fluxes. The cumulative production of C from CO2 was over six orders of magnitudes higher than that from CH4. These results suggest that deep active-layer soils may be much more sensitive to changes in moisture than to temperature, a critical factor as discontinuous permafrost melts in interior Alaska. Deep but unfrozen high-latitude soils have been shown to be strongly affected by long-term experimental warming, and these results provide insight into their future dynamics and feedback potential with future climate change.

  17. 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

  18. Influence of Plant Communities on Active Layer Depth in Boreal Forest

    NASA Astrophysics Data System (ADS)

    Phoenix, G. K.; Fisher, J. P.; Estop-Aragones, C.; Thierry, A.; Hartley, I. P.; Murton, J.; Charman, D.; Williams, M.

    2014-12-01

    Vegetation plays a crucial role in determining active layer depth (ALD) and hence also the extent that 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 multiple plots across 4 sites of contrasting vegetation and fire status, including 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

  19. Collection efficiency model based on boundary-layer characteristics for cyclones

    SciTech Connect

    Kim, W.S.; Lee, J.W.

    1997-10-01

    In cyclones, the boundary layer formed on the collecting-wall surface acts as a barrier for particle migration toward the wall due to a decreased centrifugal force on particles inside the boundary layer. A new theory for high-efficiency cyclones based on the boundary-layer characteristics is presented. The cyclone was divided into two regions: the turbulent-core region where the centrifugal force is large, and the near-wall region where the centrifugal force is small. Particle trajectories in the turbulent-core region are calculated from the mean fluid motion based on the quasi-steady drag assumption, and the collection probability of particles in the near-wall region is calculated by the deposition velocity that results from both turbulent diffusion and centrifugal force. The deposition velocity by centrifugal force was assumed equal to the equilibrium migration velocity at a certain point inside the boundary layer, and the distance to that point from the wall is assumed to be linearly proportional to the dimensionless-particle relaxation time. When the proportional constant was determined by fitting the theoretical results to experimental data, the theory showed an excellent enhancement in predicting the variation of collection efficiency with the inlet flow velocity and particle size.

  20. An effective structure prediction method for layered materials based on 2D particle swarm optimization algorithm.

    PubMed

    Wang, Yanchao; Miao, Maosheng; Lv, Jian; Zhu, Li; Yin, Ketao; Liu, Hanyu; Ma, Yanming

    2012-12-14

    A structure prediction method for layered materials based on two-dimensional (2D) particle swarm optimization algorithm is developed. The relaxation of atoms in the perpendicular direction within a given range is allowed. Additional techniques including structural similarity determination, symmetry constraint enforcement, and discretization of structure constructions based on space gridding are implemented and demonstrated to significantly improve the global structural search efficiency. Our method is successful in predicting the structures of known 2D materials, including single layer and multi-layer graphene, 2D boron nitride (BN) compounds, and some quasi-2D group 6 metals(VIB) chalcogenides. Furthermore, by use of this method, we predict a new family of mono-layered boron nitride structures with different chemical compositions. The first-principles electronic structure calculations reveal that the band gap of these N-rich BN systems can be tuned from 5.40 eV to 2.20 eV by adjusting the composition.

  1. Formation of an Intermediate Layer Between Grains in Nickel-Based Superalloy Turbine Blades

    NASA Astrophysics Data System (ADS)

    Kim, KeeHyun; Withey, Paul

    2017-03-01

    The boundary region formed on the surface of nickel-based single-crystal turbine blades was investigated by high-resolution microscopy observation. There was a distinguishable intermediate layer with the size of about 2 to 5 μm between the matrix and surface defect grains such as stray grains, multiple grains, freckle grains, and even low-angle grain boundaries which were formed during the solidification of turbine blades. The intermediate layer was composed of many elongated γ' as well as γ phases. In addition, only one side of the intermediate layer was coherent to the matrix grain or defect grain due to good orientation match. At the coherent interface, the γ' (as well as γ) phase started to extend from the parent grain and coincidently, rhenium-rich particles were detected. Furthermore, the particles existed within both elongated gamma prime and gamma phases, and even at their boundary. Based on experimental observations, the formation mechanism of this intermediate layer was discussed.

  2. Active control of the depletion boundary layers in microfluidic electrochemical reactors.

    PubMed

    Yoon, Seong Kee; Fichtl, Geoff W; Kenis, Paul J A

    2006-12-01

    In this paper, we describe three methods to improve the performance of pressure-driven laminar flow-based microreactors by manipulating reaction-depletion boundary layers to overcome mass transfer limitations at reactive surfaces on the walls, such as electrodes. The transport rate of the reactants to the reactive surfaces is enhanced by (i) removing the depleted zone through multiple periodically-placed outlets; (ii) adding fresh reactants through multiple periodically-placed inlets along the reactive surface; or (iii) producing a spiraling, transverse flow through the integration of herringbone ridges along the channel walls. For approaches (i) and (ii), the network of microfluidic channels needs to be designed such that under the operating conditions used the right amount of boundary layer at each outlet or inlet is removed or replenished, respectively. Here, we report a set of design rules, derived with the help of a fluidic resistance circuit model, to aid in the design of appropriate microfluidic networks. Also, the actual enhancement of the performance of the electrochemical microreactor, i.e. chemical conversion efficiency, using multiple inlets, multiple outlets, or herringbone ridges is reported.

  3. Modeling the effects of fire severity and climate warming on active layer thickness and soil carbon storage of black spruce forests across the landscape in interior Alaska

    SciTech Connect

    Genet, Helene; McGuire, A. David; Barrett, K.; Breen, Amy; Euskirchen, Eugenie S; Johnstone, J. F.; Kasischke, Eric S.; Melvin, A. M.; Bennett, A.; Mack, M. C.; Rupp, Scott T.; Schuur, Edward; Turetsky, M. R.; Yuan, Fengming

    2013-01-01

    There is a substantial amount of carbon stored in the permafrost soils of boreal forest ecosystems, where it is currently protected from decomposition. The surface organic horizons insulate the deeper soil from variations in atmospheric temperature. The removal of these insulating horizons through consumption by fire increases the vulnerability of permafrost to thaw, and the carbon stored in permafrost to decomposition. In this study we ask how warming and fire regime may influence spatial and temporal changes in active layer and carbon dynamics across a boreal forest landscape in interior Alaska. To address this question, we (1) developed and tested a predictive model of the effect of fire severity on soil organic horizons that depends on landscape-level conditions and (2) used this model to evaluate the long-term consequences of warming and changes in fire regime on active layer and soil carbon dynamics of black spruce forests across interior Alaska. The predictive model of fire severity, designed from the analysis of field observations, reproduces the effect of local topography (landform category, the slope angle and aspect and flow accumulation), weather conditions (drought index, soil moisture) and fire characteristics (day of year and size of the fire) on the reduction of the organic layercaused by fire. The integration of the fire severity model into an ecosystem process-based model allowed us to document the relative importance and interactions among local topography, fire regime and climate warming on active layer and soil carbon dynamics. Lowlands were more resistant to severe fires and climate warming, showing smaller increases in active layer thickness and soil carbon loss compared to drier flat uplands and slopes. In simulations that included the effects of both warming and fire at the regional scale, fire was primarily responsible for a reduction in organic layer thickness of 0.06 m on average by 2100 that led to an increase in active layer thickness

  4. The structure and tribological properties of gradient layers prepared by plasma-based ion implantation on 2024 Al alloy

    NASA Astrophysics Data System (ADS)

    Liao, J. X.; Xia, L. F.; Sun, M. R.; Liu, W. M.; Xu, T.; Xue, Q. J.

    2004-02-01

    Using plasma-based ion implantation, two types of gradient layers have been prepared on 2024 Al alloy. One is prepared by N-implantation then C-deposition, the other adds an interlayer composed of a Ti layer and a Ti-N layer between N-implantation and C-deposition. C-deposition is carried out at various implanting voltages or C2H2/H2 ratios. The composition depth profiles of these layers were characterized by x-ray photoelectron spectroscopy. The structure, morphologies and microstructure of the C layers were studied using Raman spectroscopy, atomic force microscope and transmission electron microscope, respectively. The surface hardness was measured with a Knoop tester and a mechanical property microprobe. The dry ball-on-disc wear tests were performed in ambient air. The gradient layer without interlayer is composed of an N-implanted layer rich in AlN and a diamond-like carbon (DLC) layer (film), and the two layers are connected with a C-Al transition layer containing Al4C3. The Ti layer rich in agr -Ti and the N-implanted layer are connected by a Ti-Al transition layer containing TiAl3, while the Ti-N layer rich in TiN and the DLC film are connected by a C-Ti transition layer containing TiC, TiCN, etc. Thus, the gradient layer with interlayers has optimized the gradient structure. DLC films are compact and amorphous, contain high sp3/sp2 ratios and depend on the implanting voltage and the C2H2/H2 ratio. Similarly, these gradient layers exhibit significant improvement in morphologies, surface hardness and tribological properties; the interlayer, the implanting voltage and the C2H2/H2 ratio all have prominent effects on these properties.

  5. 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.

  6. Small Molecule Thin Film Solar Cells With Active Layers Composed Of Copper Phthalocyanine (CuPc) And Fullerene (C70)

    NASA Astrophysics Data System (ADS)

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

    2011-07-01

    We have grown organic solar cells through bilayer structure using copper phthalocyanine (CuPc) as the donor material and fullerene (C70) as the acceptor. In this article, we demonstrate power conversion efficiency of 1.47% for the bilayered solar cells composed of CuPc and C70. Successful tuning of the thickness of the individual layers was carried out to obtain the optimum solar cell parameters. It has been found that efficiency of the bilayer devices depends primarily on the individual layer thickness and thermal annealing of the devices. Overall, bilayer structure is suitable when the active layers are insoluble in most of the commonly available solvents.

  7. Controlled assembly of layer-by-layer stacking continuous graphene oxide films and their application for actively modulated field electron emission cathodes.

    PubMed

    Huang, Yuan; She, Juncong; Yang, Wenjie; Deng, Shaozhi; Xu, Ningsheng

    2014-04-21

    A featured "vapor transportation" assembly technique was developed to attain layer-by-layer stacking continuous graphene oxide (GO) films on both flat and concavo-concave surfaces. Few-layer (layer number < 10) GO sheets were "evaporated" (carried by water vapor) from the water-dispersed GO suspension and smoothly/uniformly tiled on the substrate surface. We have found evidence of the influence of the deposition time and substrate-liquid separation on the film thickness. A model was proposed for interpreting the assembly process. It was found that a current conditioning would induce a reduction of the GO surface and form an Ohmic contact between the GO-metal interfaces. Accordingly, an actively modulated GO cold cathode was fabricated by locally depositing continuous GO sheets on the drain electrode of a metal-oxide-semiconductor field effect transistor (MOSFET). The field emission current of the GO cathode can be precisely controlled by the MOSFET gate voltage (VGS). A current modulation range from 1 × 10(-10) A to 6.9 × 10(-6) A (4 orders of magnitude) was achieved by tuning the VGS from 0.812 V to 1.728 V. Due to the self-acting positive feedback of the MOSFET, the emission current fluctuation was dramatically reduced from 57.4% (non-control) to 3.4% (controlled). Furthermore, the integrated GO cathode was employed for a lab-prototype display pixel application demonstrating the active modulation of the phosphor luminance, i.e. from 0.01 cd m(-2) to 34.18 cd m(-2).

  8. Controlled assembly of layer-by-layer stacking continuous graphene oxide films and their application for actively modulated field electron emission cathodes

    NASA Astrophysics Data System (ADS)

    Huang, Yuan; She, Juncong; Yang, Wenjie; Deng, Shaozhi; Xu, Ningsheng

    2014-03-01

    A featured ``vapor transportation'' assembly technique was developed to attain layer-by-layer stacking continuous graphene oxide (GO) films on both flat and concavo-concave surfaces. Few-layer (layer number < 10) GO sheets were ``evaporated'' (carried by water vapor) from the water-dispersed GO suspension and smoothly/uniformly tiled on the substrate surface. We have found evidence of the influence of the deposition time and substrate-liquid separation on the film thickness. A model was proposed for interpreting the assembly process. It was found that a current conditioning would induce a reduction of the GO surface and form an Ohmic contact between the GO-metal interfaces. Accordingly, an actively modulated GO cold cathode was fabricated by locally depositing continuous GO sheets on the drain electrode of a metal-oxide-semiconductor field effect transistor (MOSFET). The field emission current of the GO cathode can be precisely controlled by the MOSFET gate voltage (VGS). A current modulation range from 1 × 10-10 A to 6.9 × 10-6 A (4 orders of magnitude) was achieved by tuning the VGS from 0.812 V to 1.728 V. Due to the self-acting positive feedback of the MOSFET, the emission current fluctuation was dramatically reduced from 57.4% (non-control) to 3.4% (controlled). Furthermore, the integrated GO cathode was employed for a lab-prototype display pixel application demonstrating the active modulation of the phosphor luminance, i.e. from 0.01 cd m-2 to 34.18 cd m-2.

  9. 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.

  10. Atomic layer deposition-based functionalization of materials for medical and environmental health applications

    PubMed Central

    Narayan, Roger J.; Adiga, Shashishekar P.; Pellin, Michael J.; Curtiss, Larry A.; Hryn, Alexander J.; Stafslien, Shane; Chisholm, Bret; Shih, Chun-Che; Shih, Chun-Ming; Lin, Shing-Jong; Su, Yea-Yang; Jin, Chunming; Zhang, Junping; Monteiro-Riviere, Nancy A.; Elam, Jeffrey W.

    2010-01-01

    Nanoporous alumina membranes exhibit high pore densities, well-controlled and uniform pore sizes, as well as straight pores. Owing to these unusual properties, nanoporous alumina membranes are currently being considered for use in implantable sensor membranes and water purification membranes. Atomic layer deposition is a thin-film growth process that may be used to modify the pore size in a nanoporous alumina membrane while retaining a narrow pore distribution. In addition, films deposited by means of atomic layer deposition may impart improved biological functionality to nanoporous alumina membranes. In this study, zinc oxide coatings and platinum coatings were deposited on nanoporous alumina membranes by means of atomic layer deposition. PEGylated nanoporous alumina membranes were prepared by self-assembly of 1-mercaptoundec-11-yl hexa(ethylene glycol) on platinum-coated nanoporous alumina membranes. The pores of the PEGylated nanoporous alumina membranes remained free of fouling after exposure to human platelet-rich plasma; protein adsorption, fibrin networks and platelet aggregation were not observed on the coated membrane surface. Zinc oxide-coated nanoporous alumina membranes demonstrated activity against two waterborne pathogens, Escherichia coli and Staphylococcus aureus. The results of this work indicate that nanoporous alumina membranes may be modified using atomic layer deposition for use in a variety of medical and environmental health applications. PMID:20308114

  11. Optical design of ZnO-based antireflective layers for enhanced GaAs solar cell performance.

    PubMed

    Lee, Hye Jin; Lee, Jae Won; Kim, Hee Jun; Jung, Dae-Han; Lee, Ki-Suk; Kim, Sang Hyeon; Geum, Dae-myeong; Kim, Chang Zoo; Choi, Won Jun; Baik, Jeong Min

    2016-01-28

    A series of hierarchical ZnO-based antireflection coatings with different nanostructures (nanowires and nanosheets) is prepared hydrothermally, followed by means of RF sputtering of MgF2 layers for coaxial nanostructures. Structural analysis showed that both ZnO had a highly preferred orientation along the 〈0001〉 direction with a highly crystalline MgF2 shell coated uniformly. However, a small amount of Al was present in nanosheets, originating from Al diffusion from the Al seed layer, resulting in an increase of the optical bandgap. Compared with the nanosheet-based antireflection coatings, the nanowire-based ones exhibited a significantly lower reflectance (∼2%) in ultraviolet and visible light wavelength regions. In particular, they showed perfect light absorption at wavelength less than approximately 400 nm. However, a GaAs single junction solar cell with nanosheet-based antireflection coatings showed the largest enhancement (43.9%) in power conversion efficiency. These results show that the increase of the optical bandgap of the nanosheets by the incorporation of Al atoms allows more photons enter the active region of the solar cell, improving the performance.

  12. Partitioning of Alkali Metal Salts and Boric Acid from Aqueous Phase into the Polyamide Active Layers of Reverse Osmosis Membranes.

    PubMed

    Wang, Jingbo; Kingsbury, Ryan S; Perry, Lamar A; Coronell, Orlando

    2017-02-21

    The partition coefficient of solutes into the polyamide active layer of reverse osmosis (RO) membranes is one of the three membrane properties (together with solute diffusion coefficient and active layer thickness) that determine solute permeation. However, no well-established method exists to measure solute partition coefficients into polyamide active layers. Further, the few studies that measured partition coefficients for inorganic salts report values significantly higher than one (∼3-8), which is contrary to expectations from Donnan theory and the observed high rejection of salts. As such, we developed a benchtop method to determine solute partition coefficients into the polyamide active layers of RO membranes. The method uses a quartz crystal microbalance (QCM) to measure the change in the mass of the active layer caused by the uptake of the partitioned solutes. The method was evaluated using several inorganic salts (alkali metal salts of chloride) and a weak acid of common concern in water desalination (boric acid). All partition coefficients were found to be lower than 1, in general agreement with expectations from Donnan theory. Results reported in this study advance the fundamental understanding of contaminant transport through RO membranes, and can be used in future studies to decouple the contributions of contaminant partitioning and diffusion to contaminant permeation.

  13. 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.

  14. Activation patterns in superficial layers of neocortex change between experiences independent of behavior, environment, or the hippocampus.

    PubMed

    Takehara-Nishiuchi, Kaori; Insel, Nathan; Hoang, Lan T; Wagner, Zachary; Olson, Kathy; Chawla, Monica K; Burke, Sara N; Barnes, Carol A

    2013-09-01

    Previous work suggests that activation patterns of neurons in superficial layers of the neocortex are more sensitive to spatial context than activation patterns in deep cortical layers. A possible source of this laminar difference is the distribution of contextual information to the superficial cortical layers carried by hippocampal efferents that travel through the entorhinal cortex and subiculum. To evaluate the role that the hippocampus plays in determining context sensitivity in superficial cortical layers, behavior-induced expression of the immediate early gene Arc was examined in hippocampus-lesioned and control rats after exposing them to 2 distinct contexts. Contrary to expectations, hippocampal lesions had no observable effect on Arc expression in any neocortical layer relative to controls. Furthermore, another group of intact animals was exposed to the same environment twice, to determine the reliability of Arc-expression patterns across identical contextual and behavioral episodes. Although this condition included no difference in external input between 2 epochs, the significant layer differences in Arc expression still remained. Thus, laminar differences in activation or plasticity patterns are not likely to arise from hippocampal sources or differences in external inputs, but are more likely to be an intrinsic property of the neocortex.

  15. Synthesis and Electrochemical Behavior of Ceria Based Bi-Layer Films by Dip Coating Technique.

    PubMed

    Chinnu, M Karl; Anand, K Vijai; Kumar, R Mohan; Alagesan, T; Jayavel, R

    2015-01-01

    Ceria based bi-layer films of CeO2-CdS and CeO2-TiO2 were prepared by sol-gel based hydrothermal route combined with dip-coating. The synthesized samples were subjected to various characterizations such as X-ray diffraction, Field emission scanning electron microscopy, thermo-gravimetric analysis, UV-Vis absorption and photoluminescence studies. The prepared materials were dissolved in naffion solution and disposed as a thin film on glassy carbon electrode by dip coating technique. Electrochemical Li+ intercalation/deintercalation was performed by cyclic voltammetry and these results indicate that the CeO2/LiClO4 system is electrochemically reversible. The total intercalation/deintercalation of the CeO2 film, CeO2-CdS and CeO2-TiO2 bi-layer films was determined by cyclic voltammetry, which showed increased charge storage capacity.

  16. Ultrathin Polyaniline-based Buffer Layer for Highly Efficient Polymer Solar Cells with Wide Applicability

    NASA Astrophysics Data System (ADS)

    Zhao, Wenchao; Ye, Long; Zhang, Shaoqing; Fan, Bin; Sun, Mingliang; Hou, Jianhui

    2014-10-01

    Interfacial buffer layers often attribute the improved device performance in organic optoelectronic device. Herein, a water-soluble hydrochloric acid doped polyanilines (HAPAN) were utilized as p-type electrode buffer layer in highly efficient polymer solar cells (PSC) based on PBDTTT-EFT and several representative polymers. The PBDTTT-EFT-based conventional PSC featuring ultrathin HAPAN (1.3 nm) delivered high PCE approximately 9%, which is one of the highest values among conventional PSC devices. Moreover, ultrathin HAPAN also exhibited wide applicability in a variety of efficient photovoltaic polymers including PBDTTT-C-T, PTB7, PBDTBDD, PBTTDPP-T, PDPP3T and P3HT. The excellent performances were originated from the high transparency, small film roughness and suitable work function.

  17. Tunable surface electron spin splitting with electric double-layer transistors based on InN.

    PubMed

    Yin, Chunming; Yuan, Hongtao; Wang, Xinqiang; Liu, Shitao; Zhang, Shan; Tang, Ning; Xu, Fujun; Chen, Zhuoyu; Shimotani, Hidekazu; Iwasa, Yoshihiro; Chen, Yonghai; Ge, Weikun; Shen, Bo

    2013-05-08

    Electrically manipulating electron spins based on Rashba spin-orbit coupling (SOC) is a key pathway for applications of spintronics and spin-based quantum computation. Two-dimensional electron systems (2DESs) offer a particularly important SOC platform, where spin polarization can be tuned with an electric field perpendicular to the 2DES. Here, by measuring the tunable circular photogalvanic effect (CPGE), we present a room-temperature electric-field-modulated spin splitting of surface electrons on InN epitaxial thin films that is a good candidate to realize spin injection. The surface band bending and resulting CPGE current are successfully modulated by ionic liquid gating within an electric double-layer transistor configuration. The clear gate voltage dependence of CPGE current indicates that the spin splitting of the surface electron accumulation layer is effectively tuned, providing a way to modulate the injected spin polarization in potential spintronic devices.

  18. Estimating the absorption coefficient of the bottom layer in four-layered turbid mediums based on the time-domain depth sensitivity of near-infrared light reflectance.

    PubMed

    Sato, Chie; Shimada, Miho; Tanikawa, Yukari; Hoshi, Yoko

    2013-09-01

    Expanding our previously proposed "time segment analysis" for a two-layered turbid medium, this study attempted to selectively determine the absorption coefficient (μa) of the bottom layer in a four-layered human head model with time-domain near-infrared measurements. The difference curve in the temporal profiles of the light attenuation between an object and a reference medium, which are obtained from Monte Carlo simulations, is divided into segments along the time axis, and a slope for each segment is calculated to obtain the depth-dependent μa(μaseg). The reduced scattering coefficient (μs') of the reference is determined by curve fitting with the temporal point spread function derived from the analytical solution of the diffusion equation to the time-resolved reflectance of the object. The deviation of μaseg from the actual μa is expressed by a function of the ratio of μaseg in an earlier time segment to that in a later segment for mediums with different optical properties and thicknesses of the upper layers. Using this function, it is possible to determine the μa of the bottom layer in a four-layered epoxy resin-based phantom. These results suggest that the method reported here has potential for determining the μa of the cerebral tissue in humans.

  19. Development of Solution Buffer Layers for RABiTS Based YBCO Coated Conductors

    SciTech Connect

    Paranthaman, Mariappan Parans; Qiu, Xiaofeng; List III, Frederick Alyious; Zhang, Yifei; Li, Xiaoping; Sathyamurthy, Srivatsan; Thieme, C. L. H.; Rupich, M. W.

    2011-01-01

    Abstract The main objective of this research is to find a suitable alternate solution based seed layer for the standard RABiTS three-layer architecture of physical vapor deposited CeO cap/YSZ barrier/Y O seed on Ni-5%W metal tape. In the present work, we have identified CeO buffer layer as a potential replacement for Y O seeds. Using a metal-organic deposition (MOD) process, we have grown smooth, crack-free, epitaxial thin films of CeO (pure and Zr, Cu and Gd-doped) directly on biaxially textured Ni-5W substrates in short lengths. Detailed XRD studies indicate that a single epitaxial CeO phase with slightly improved out-of-plane texture compared to the texture of the underlying Ni-W substrates can be achieved in pure, undoped CeO samples. We have also demonstrated the growth of YSZ barrier layers on pure CeO seeds using sputtering. Both sputtered CeO cap layers and MOD-YBCO films were grown epitaxially on these YSZ-buffered MOD-CeO /Ni-5W substrates. High critical currents per unit width, of 264 A/cm (critical current density, of 3.3 MA/cm ) at 77 K and 0.01 T was achieved for 0.8 m thick MOD-YBCO films grown on MOD-CeO seeds. These results indicate that CeO films can be grown directly on Ni-5W substrates and still support high performance YBCO coated conductors. This work holds promise for a route for producing low-cost buffer architecture for RABiTS based YBCO coated conductors.

  20. Perfluorodecyltrichlorosilane-based seed-layer for improved chemical vapour deposition of ultrathin hafnium dioxide films on graphene

    PubMed Central

    Kitzmann, Julia; Göritz, Alexander; Fraschke, Mirko; Lukosius, Mindaugas; Wenger, Christian; Wolff, Andre; Lupina, Grzegorz

    2016-01-01

    We investigate the use of perfluorodecyltrichlorosilane-based self-assembled monolayer as seeding layer for chemical vapour deposition of HfO2 on large area CVD graphene. The deposition and evolution of the FDTS-based seed layer is investigated by X-ray photoelectron spectroscopy, Auger electron spectroscopy, and transmission electron microscopy. Crystalline quality of graphene transferred from Cu is monitored during formation of the seed layer as well as the HfO2 growth using Raman spectroscopy. We demonstrate that FDTS-based seed layer significantly improves nucleation of HfO2 layers so that graphene can be coated in a conformal way with HfO2 layers as thin as 10 nm. Proof-of-concept experiments on 200 mm wafers presented here validate applicability of the proposed approach to wafer scale graphene device fabrication. PMID:27381715

  1. Perfluorodecyltrichlorosilane-based seed-layer for improved chemical vapour deposition of ultrathin hafnium dioxide films on graphene

    NASA Astrophysics Data System (ADS)

    Kitzmann, Julia; Göritz, Alexander; Fraschke, Mirko; Lukosius, Mindaugas; Wenger, Christian; Wolff, Andre; Lupina, Grzegorz

    2016-07-01

    We investigate the use of perfluorodecyltrichlorosilane-based self-assembled monolayer as seeding layer for chemical vapour deposition of HfO2 on large area CVD graphene. The deposition and evolution of the FDTS-based seed layer is investigated by X-ray photoelectron spectroscopy, Auger electron spectroscopy, and transmission electron microscopy. Crystalline quality of graphene transferred from Cu is monitored during formation of the seed layer as well as the HfO2 growth using Raman spectroscopy. We demonstrate that FDTS-based seed layer significantly improves nucleation of HfO2 layers so that graphene can be coated in a conformal way with HfO2 layers as thin as 10 nm. Proof-of-concept experiments on 200 mm wafers presented here validate applicability of the proposed approach to wafer scale graphene device fabrication.

  2. Recent Advances in Layered Metal Chalcogenides as Superconductors and Thermoelectric Materials: Fe-Based and Bi-Based Chalcogenides.

    PubMed

    Mizuguchi, Yoshikazu

    2016-04-01

    Recent advances in layered (Fe-based and Bi-based) chalcogenides as superconductors or functional materials are reviewed. The Fe-chalcogenide (FeCh) family are the simplest Fe-based high-Tc superconductors. The superconductivity in the FeCh family is sensitive to external or chemical pressure, and high Tc is attained when the local structure (anion height) is optimized. The Bi-chalcogenide (BiCh2) family are a new group of layered superconductors with a wide variety of stacking structures. Their physical properties are also sensitive to external or chemical pressure. Recently, we revealed that the emergence of superconductivity and the Tc in this family correlate with the in-plane chemical pressure. Since the flexibility of crystal structure and electronic states are an advantage of the BiCh2 family for designing functionalities, I briefly review recent developments in this family as not only superconductors but also other functional materials.

  3. Layer-by-layer self-assembly of micro-capsules for the magnetic activation of semi-permeable nano-shells

    NASA Astrophysics Data System (ADS)

    Prouty, Malcolm D.

    2007-12-01

    Layer-by-layer (LbL) self-assembly has demonstrated broad perspectives for encapsulating, and the controllable delivery, of drugs. The nano-scale polymer layers have the capability of material protection. Magnetic nanoparticles have great potential to be applied with LbL technology to achieve both "focusing" of the encapsulated drugs to a specific location followed by "switching" them on to release the encapsulated drugs. In this work, Phor21-betaCG(ala), dextran, and dexamethasone were used as model drugs. Encapsulation of these drugs with layer-by-layer self-assembly formed biolnano robotic capsules for controlled delivery and drug release. Silica nanoparticles coated with polyelectrolyte layers of sodium carboxymethyl cellulose (CMC) or gelatin B, along with an oppositely charged peptide drug (Phor2l-betaCG(ala)), were prepared using LbL self-assembly and confirmed using QCM and zeta potential measurements. The peptide drug was assembled as a component of the multilayer walls. The release kinetics of the embedded peptide were determined. Up to 18% of the embedded Phor21-betaCG(ala) was released from the CMC multilayers over a period of 28 hours. The release was based on physiological conditions, and an external control mechanism using magnetic nanoparticles needed to be developed. Magnetic permeability control experiments were setup by applying LbL self-assembly on MnCO3 micro-cores to fabricate polyelectrolyte microcapsules embedded with superparamagnetic gold coated cobalt (Co Au) nanoparticles. An alternating magnetic field was applied to the microcapsules to check for changes in permeability. Permeability experiments were achieved by adding fluorescein isothiocyanate (FITC) labeled dextran to the microcapsule solution. Before an alternating magnetic field was applied, the capsules remained impermeable to the FITC-dextran; however, after an alternating magnetic field was applied for 30 minutes, approximately 99% of the capsules were filled with FITC

  4. Improvement in the electrical performance and bias-stress stability of dual-active-layered silicon zinc oxide/zinc oxide thin-film transistor

    NASA Astrophysics Data System (ADS)

    Liu, Yu-Rong; Zhao, Gao-Wei; Lai, Pai-To; Yao, Ruo-He

    2016-08-01

    Si-doped zinc oxide (SZO) thin films are deposited by using a co-sputtering method, and used as the channel active layers of ZnO-based TFTs with single and dual active layer structures. The effects of silicon content on the optical transmittance of the SZO thin film and electrical properties of the SZO TFT are investigated. Moreover, the electrical performances and bias-stress stabilities of the single- and dual-active-layer TFTs are investigated and compared to reveal the effects of the Si doping and dual-active-layer structure. The average transmittances of all the SZO films are about 90% in the visible light region of 400 nm-800 nm, and the optical band gap of the SZO film gradually increases with increasing Si content. The Si-doping can effectively suppress the grain growth of ZnO, revealed by atomic force microscope analysis. Compared with that of the undoped ZnO TFT, the off-state current of the SZO TFT is reduced by more than two orders of magnitude and it is 1.5 × 10-12 A, and thus the on/off current ratio is increased by more than two orders of magnitude. In summary, the SZO/ZnO TFT with dual-active-layer structure exhibits a high on/off current ratio of 4.0 × 106 and superior stability under gate-bias and drain-bias stress. Projected supported by the National Natural Science Foundation of China (Grant Nos. 61076113 and 61274085), the Natural Science Foundation of Guangdong Province (Grant No. 2016A030313474), and the University Development Fund (Nanotechnology Research Institute, Grant No. 00600009) of the University of Hong Kong, China.

  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. 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}.

  7. Active control of turbulent boundary layer sound transmission into a vehicle interior

    NASA Astrophysics Data System (ADS)

    Caiazzo, A.; Alujević, N.; Pluymers, B.; Desmet, W.

    2016-09-01

    In high speed automotive, aerospace, and railway transportation, the turbulent boundary layer (TBL) is one of the most important sources of interior noise. The stochastic pressure distribution associated with the turbulence is able to excite significantly structural vibration of vehicle exterior panels. They radiate sound into the vehicle through the interior panels. Therefore, the air flow noise becomes very influential when it comes to the noise vibration and harshness assessment of a vehicle, in particular at low frequencies. Normally, passive solutions, such as sound absorbing materials, are used for reducing the TBL-induced noise transmission into a vehicle interior, which generally improve the structure sound isolation performance. These can achieve excellent isolation performance at higher frequencies, but are unable to deal with the low-frequency interior noise components. In this paper, active control of TBL noise transmission through an acoustically coupled double panel system into a rectangular cavity is examined theoretically. The Corcos model of the TBL pressure distribution is used to model the disturbance. The disturbance is rejected by an active vibration isolation unit reacting between the exterior and the interior panels. Significant reductions of the low-frequency vibrations of the interior panel and the sound pressure in the cavity are observed.

  8. [Aluminum coordination and active sites on aluminas, Y-zeolites and pillared layered silicates]. Progress report

    SciTech Connect

    Fripiat, J.J.

    1994-02-01

    This report is organized in four sections. In the first the authors will outline structural features which are common to all fine grained alumina, as well as to non-framework alumina in zeolites. This section will be followed by a study of the surface vs. bulk coordination of aluminum. The third section will deal with measurement of the number of acid sites and the scaling of their strength. The fourth and last section will describe three model reactions: the isomerization of 1-butene and of 2 cis-butene; the isomerization and disproportionation of oxtho-xylene; and the transformation of trichloroethane into vinyl chloride followed by the polymerization of the vinyl chloride. The relationship between chemical activity and selectivity and what is known of the local structure of the active catalytic sites will be underlined. Other kinds of zeolites besides Y zeolite have been studied. Instead of the aluminum pillared silicates they found it more interesting to study the substitution of silicon by aluminum in a layered structure containing a permanent porosity (aluminated sepiolite).

  9. CdS-pillared CoAl-layered double hydroxide nanosheets with superior photocatalytic activity

    SciTech Connect

    Qiu, Yanqiang; Lin, Bizhou Jia, Fangcao; Chen, Yilin; Gao, Bifen; Liu, Peide

    2015-12-15

    Graphical abstract: - Highlights: • CdS nanocrystals were intercalated into CoAl-LDH interlayer. • The nanohybrid display superior visible-light photocatalytic activity. • A photoexcitation model for the pillared heterostructured system was proposed. - Abstract: A new nanohybrid was synthesized by mixing the positively charged 2D nanosheets of CoAl-layered double hydroxide (CoAl-LDH) and the negatively charged CdS nanosol suspensions. It was revealed that the CdS nanoparticles were intercalated into the interlayer region of CoAl-LDH with a spacing of 2.62 nm. The obtained nanohybrid exhibited a mesoporous texture with an expanded specific surface area of 62 m{sup 2} g{sup −1} and a superior photocatalytic activity in the degradation of acid red with a reaction constant of 1.26 × 10{sup −2} min{sup −1} under visible-light radiation, which is more than 2 times those of his parents CoAl-LDH and CdS.

  10. Mixed Layer Depth Seasonality within the Coral Sea Based on Argo Data

    PubMed Central

    Jaffrés, Jasmine B. D.

    2013-01-01

    The worldwide deployment of Argo floats has enabled much more detailed studies of global and regional seas over the last decade. Here, the seasonal variability of the mixed layer depth (MLD) within the Coral Sea was examined with CTD profiles from Argo floats. Multiple threshold values for both temperature and density have been employed to determine the most suitable threshold values for the Coral Sea. A threshold value of 0.04 kg/m3 for density and 0.2°C for temperature appear the most fitting for this region. Although MLD and isothermal layer depth (ILD) coincide quite well in most cases, the relatively common presence of temporary, non-seasonal barrier layers induces an ILD that is significantly deeper than the MLD. Consequently, an MLD estimation based on density is more appropriate. A distinct seasonality in the MLD is evident throughout the Coral Sea, but is generally more pronounced in higher southern latitudes (20–30°S). Salinity inversions are rare and mainly occur in the south-eastern Coral Sea, while barrier layers are more commonly associated with the north-eastern Coral Sea, a region characterised by high rainfall. The significance of regional currents is evident in the north-western Coral Sea, where temperature and ocean heat content is relatively low due to a northward moving boundary current. Shallow bathymetry, in turn, is linked to the absence of Argo data on the continental shelf and in the central Coral Sea. PMID:23593368

  11. Cross-layer restoration with software defined networking based on IP over optical transport networks

    NASA Astrophysics Data System (ADS)

    Yang, Hui; Cheng, Lei; Deng, Junni; Zhao, Yongli; Zhang, Jie; Lee, Young

    2015-10-01

    The IP over optical transport network is a very promising networking architecture applied to the interconnection of geographically distributed data centers due to the performance guarantee of low delay, huge bandwidth and high reliability at a low cost. It can enable efficient resource utilization and support heterogeneous bandwidth demands in highly-available, cost-effective and energy-effective manner. In case of cross-layer link failure, to ensure a high-level quality of service (QoS) for user request after the failure becomes a research focus. In this paper, we propose a novel cross-layer restoration scheme for data center services with software defined networking based on IP over optical network. The cross-layer restoration scheme can enable joint optimization of IP network and optical network resources, and enhance the data center service restoration responsiveness to the dynamic end-to-end service demands. We quantitatively evaluate the feasibility and performances through the simulation under heavy traffic load scenario in terms of path blocking probability and path restoration latency. Numeric results show that the cross-layer restoration scheme improves the recovery success rate and minimizes the overall recovery time.

  12. Transparent actuators and robots based on single-layer superaligned carbon nanotube sheet and polymer composites.

    PubMed

    Chen, Luzhuo; Weng, Mingcen; Zhang, Wei; Zhou, Zhiwei; Zhou, Yi; Xia, Dan; Li, Jiaxin; Huang, Zhigao; Liu, Changhong; Fan, Shoushan

    2016-03-28

    Transparent actuators have been attracting emerging interest recently, as they demonstrate potential applications in the fields of invisible robots, tactical displays, variable-focus lenses, and flexible cellular phones. However, previous technologies did not simultaneously realize macroscopic transparent actuators with advantages of large-shape deformation, low-voltage-driven actuation and fast fabrication. Here, we develop a fast approach to fabricate a high-performance transparent actuator based on single-layer superaligned carbon nanotube sheet and polymer composites. Various advantages of single-layer nanotube sheets including high transparency, considerable conductivity, and ultra-thin dimensions together with selected polymer materials completely realize all the above required advantages. Also, this is the first time that a single-layer nanotube sheet has been used to fabricate actuators with high transparency, avoiding the structural damage to the single-layer nanotube sheet. The transparent actuator shows a transmittance of 72% at the wavelength of 550 nm and bends remarkably with a curvature of 0.41 cm(-1) under a DC voltage for 5 s, demonstrating a significant advance in technological performances compared to previous conventional actuators. To illustrate their great potential usage, a transparent wiper and a humanoid robot "hand" were elaborately designed and fabricated, which initiate a new direction in the development of high-performance invisible robotics and other intelligent applications with transparency.

  13. Influence of Surface-Based Stable Layer Development on Asian Dust Behaviour Over Tokyo

    NASA Astrophysics Data System (ADS)

    Tsunematsu, Nobumitsu; Iwai, Hironori; Ishii, Shoken; Yasui, Motoaki; Murayama, Yasuhiro; Mizutani, Kohei

    2009-05-01

    The relationship between local meteorological fields and the behaviour of airborne Asian dust that arrived in the Tokyo metropolitan area on 1 April 2007 with the passage of a synoptic-scale cold front has been investigated through Doppler lidar observations, experiments using a regional atmospheric numerical model, and analyses of surface and upper-air meteorological observations. Results of the Doppler lidar observations showed that the Asian dust passed above the metropolitan area with strong south-westerly winds with speeds of 15-26 m s-1. Meteorological fields reproduced by the numerical experiments showed the development of a surface-based stable layer in the metropolitan area caused by nocturnal radiational cooling near the ground surface and south-westerly warm air advection at upper levels. The blocking effect of the mountainous region located to the west of the metropolitan area induced an area of stagnant air inside the metropolitan area and promoted the stable layer development. Although strong downdrafts prevailed in the upper air, the airborne Asian dust did not spread to the ground when the stable layer was formed. These results strongly indicate that the developed stable layer prevented strong downdrafts from spreading to the ground, acting as an obstacle to the transport of the Asian dust particles from the upper air towards the ground. This is considered to be one of the main causes of the low appearance frequency of Asian dust phenomena near the ground in the Tokyo metropolitan area and eastern Japan.

  14. Multi-layer beam with variable stiffness based on electroactive polymers

    NASA Astrophysics Data System (ADS)

    Henke, Markus; Sorber, Jörg; Gerlach, Gerald

    2012-04-01

    The contribution describes a new kind of multi-layer beam with a variable stiffness based on electroactive polymers (EAP). These structures are supposed to be components of new smart, self-sensing and -controlling composite materials for lightweight constructions. Dielectric Elastomer foils from Danfoss PolyPower are used to control the beam's stiffness. The basic idea is to change the area moment of inertia of bending beams. These beams are built up as multi-layer stacks of thin metal or PMMA plates. Its internal structure can be changed by the use of the electroactive polymers for controlling the area moment of inertia. So it is possible to strongly change the stiffness of bending beams up to two orders of magnitude. Thereby, the magnitude of varying the stiffness can be scaled by the number of layers and the number and type of electroactive polymer elements used within the bending beam. The mechanisms for controlling the area moment of inertia are described in detail. Modeling of the mechanical structure including the EAP uses a pseudo rigid-body model, a strain energy model as well as a finite element analysis. The theoretical calculations are verified by experiments. The prototype described here consists of two structural layers. First results show the feasibility of the proposed structure for mechanical components with stiffness control.

  15. 2-layer based microfluidic concentration generator by hybrid serial and volumetric dilutions.

    PubMed

    Lee, Kangsun; Kim, Choong; Kim, Youngeun; Jung, Keunhui; Ahn, Byungwook; Kang, Ji Yoon; Oh, Kwang W

    2010-04-01

    We present a 2-layer based microfluidic concentration generator by a hybrid of a serial and a volumetric dilution for dose-response experiments in drug screening. The hybrid dilution method using 2-layer based microfluidic network significantly reduces the total number of cascaded serial dilution stages. The proposed strategy is capable of generating a large number of universal stepwise monotonic concentrations with a wide range of logarithmic and linear scales. We have studied an equivalent electrical circuit to that of the 2-layer based microfluidic network, where the only variable parameter is channel length. We have designed a microfluidic dilution generator simultaneously covering 14 doses with a combination of 4-order logarithmic and 4-point linear concentrations. The design has been verified by a commercial circuit analysis software (e.g., P-Spice) for the electrical circuit analysis and a computational fluid dynamics software (e.g., CFD-ACE+) for the microfluidic circuit analysis. As a real-life application of the proposed dilution generator, we have successfully performed a dose-response experiment using MCF-7 human breast cancer cells. We expect that the proposed dilution method will be useful to study not only high throughput drug screening but also optimization in biology, chemistry, medicine, and material sciences.

  16. Anisotropic Thermal and Electrical Properties of Thin Thermal Interface Layers of Graphite Nanoplatelet-Based Composites

    PubMed Central

    Tian, Xiaojuan; Itkis, Mikhail E.; Bekyarova, Elena B.; Haddon, Robert C.

    2013-01-01

    Thermal interface materials (TIMs) are crucial components of high density electronics and the high thermal conductivity of graphite makes this material an attractive candidate for such applications. We report an investigation of the in-plane and through-plane electrical and thermal conductivities of thin thermal interface layers of graphite nanoplatelet (GNP) based composites. The in-plane electrical conductivity exceeds its through-plane counterpart by three orders of magnitude, whereas the ratio of the thermal conductivities is about 5. Scanning electron microscopy reveals that the anisotropy in the transport properties is due to the in-plane alignment of the GNPs which occurs during the formation of the thermal interface layer. Because the alignment in the thermal interface layer suppresses the through-plane component of the thermal conductivity, the anisotropy strongly degrades the performance of GNP-based composites in the geometry required for typical thermal management applications and must be taken into account in the development of GNP-based TIMs.

  17. An ellipsometric approach towards the description of inhomogeneous polymer-based Langmuir layers

    PubMed Central

    Rottke, Falko O; Schulz, Burkhard; Richau, Klaus; Kratz, Karl

    2016-01-01

    Summary The applicability of nulling-based ellipsometric mapping as a complementary method next to Brewster angle microscopy (BAM) and imaging ellipsometry (IE) is presented for the characterization of ultrathin films at the air–water interface. First, the methodology is demonstrated for a vertically nonmoving Langmuir layer of star-shaped, 4-arm poly(ω-pentadecalactone) (PPDL-D4). Using nulling-based ellipsometric mapping, PPDL-D4-based inhomogeneously structured morphologies with a vertical dimension in the lower nm range could be mapped. In addition to the identification of these structures, the differentiation between a monolayer and bare water was possible. Second, the potential and limitations of this method were verified by applying it to more versatile Langmuir layers of telechelic poly[(rac-lactide)-co-glycolide]-diol (PLGA). All ellipsometric maps were converted into thickness maps by introduction of the refractive index that was derived from independent ellipsometric experiments, and the result was additionally evaluated in terms of the root mean square roughness, R q. Thereby, a three-dimensional view into the layers was enabled and morphological inhomogeneity could be quantified. PMID:27826490

  18. Wrinkled substrate and Indium Tin Oxide-free transparent electrode making organic solar cells thinner in active layer

    NASA Astrophysics Data System (ADS)

    Liu, Kong; Lu, Shudi; Yue, Shizhong; Ren, Kuankuan; Azam, Muhammad; Tan, Furui; Wang, Zhijie; Qu, Shengchun; Wang, Zhanguo

    2016-11-01

    To enable organic solar cells with a competent charge transport efficiency, reducing the thickness of active layer without sacrificing light absorption efficiency turns out to be of high feasibility. Herein, organic solar cells on wrinkled metal surface are designed. The purposely wrinkled Al/Au film with a smooth surface provides a unique s