Progress in the Analysis of Complex Atmospheric Particles

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

Laskin, Alexander; Gilles, Mary K.; Knopf, Daniel A.

2016-06-16

This manuscript presents an overview on recent advances in field and laboratory studies of atmospheric particles formed in processes of environmental air-surfaces interactions. The overarching goal of these studies is to advance predictive understanding of atmospheric particle composition, particle chemistry during aging, and their environmental impacts. The diversity between chemical constituents and lateral heterogeneity within individual particles adds to the chemical complexity of particles and their surfaces. Once emitted, particles undergo transformation via atmospheric aging processes that further modify their complex composition. We highlight a range of modern analytical approaches that enable multi-modal chemical characterization of particles with both molecularmore » and lateral specificity. When combined, they provide a comprehensive arsenal of tools for understanding the nature of particles at air-surface interactions and their reactivity and transformations with atmospheric aging. We discuss applications of these novel approaches in recent studies and highlight additional research areas to explore environmental effects of air-surface interactions.« less

Progress in the analysis of complex atmospheric particles

DOE PAGES

Laskin, Alexander; Gilles, Mary K.; Knopf, Daniel A.; ...

2016-06-01

This study presents an overview of recent advances in field and laboratory studies of atmospheric particles formed in processes of environmental air-surface interactions. The overarching goal of these studies is to advance predictive understanding of atmospheric particle composition, particle chemistry during aging, and their environmental impacts. The diversity between chemical constituents and lateral heterogeneity within individual particles adds to the chemical complexity of particles and their surfaces. Once emitted, particles undergo transformation via atmospheric aging processes that further modify their complex composition. We highlight a range of modern analytical approaches that enable multimodal chemical characterization of particles with both molecularmore » and lateral specificity. When combined, these approaches provide a comprehensive arsenal of tools for understanding the nature of particles at air-surface interactions and their reactivity and transformations with atmospheric aging. We discuss applications of these novel approaches in recent studies and highlight additional research areas to explore the environmental effects of air-surface interactions.« less

Evaluation of two dual-functional primers and a tribochemical surface modification system applied to the bonding of an indirect composite resin to metals.

PubMed

Yanagida, Hiroaki; Tanoue, Naomi; Ide, Takako; Matsumura, Hideo

2009-07-01

We evaluated the effects of two dual-functional primers and a tribochemical surface modification system on the bond strength between an indirect composite resin and gold alloy or titanium. Disk specimens (diameter, 10 mm; thickness, 2.5 mm) were cast from type 4 gold alloy and commercially pure titanium. The specimens were wetground to a final surface finish using 600-grit silicone carbide paper. The specimens were then air-dried and treated using the following four bonding systems: (1) air-abrasion with 50-70 mum alumina, (2) system 1 + alloy primer, (3) system 1 + metal link primer, and (4) tribochemical silica/silane coating (Rocatec). A light-polymerizing indirect composite resin (Ceramage) was applied to each metal specimen and polymerized according to the manufacturer's specifications. Shear bond strengths (MPa) were determined both before and after thermocycling (4 degrees C and 60 degrees C for 1 min each for 20 000 cycles). The values were compared using analysis of variance, post hoc Scheffe tests, and Mann-Whitney U tests (alpha = 0.05). The strengths decreased after thermocycling for all combinations. For both gold alloy and titanium, the bond strength with air-abrasion only was statistically lower than that with the other three modification methods after thermocycling. Titanium exhibited a significantly higher value (13.4 MPa) than gold alloy (10.5 MPa) with the air. abrasion and alloy primer system. Treatment with the tribochemical system or air abrasion followed by treatment with dual-functional priming agents was found to be effective for enhancement of the bonding between the indirect composite and gold alloy or titanium.

Characteristics of hierarchical micro/nano surface structure formation generated by picosecond laser processing in water and air

NASA Astrophysics Data System (ADS)

Rajab, Fatema H.; Whitehead, David; Liu, Zhu; Li, Lin

2017-12-01

Laser surface texturing or micro/nano surface structuring in the air has been extensively studied. However, until now, there are very few studies on the characteristics of laser-textured surfaces in water, and there was no reported work on picosecond laser surface micro/nano-structuring in water. In this work, the surface properties of picosecond laser surface texturing in water and air were analysed and compared. 316L stainless steel substrates were textured using a picosecond laser. The surface morphology and the chemical composition were characterised using Philips XL30 FEG-SEM, EDX and confocal laser microscopy. The wettability of the textured surfaces was determined using a contact angle analyser FTA 188. Results showed that a variety of hierarchical micro/nano surface patterns could be controlled by a suitable adjustment of laser parameters. Not only surface morphology but also remarkable differences in wettability, optical reflectivity and surface oxygen content were observed for different types of surface textures produced by laser surface texture in water and air. The possible mechanisms of the changes in the behaviour of laser-textured surfaces are discussed.

Tensile bond strength of resin composite repair in vitro using different surface preparation conditionings to an aged CAD/CAM resin nanoceramic.

PubMed

Stawarczyk, Bogna; Krawczuk, Andreas; Ilie, Nicoleta

2015-03-01

This study was conducted in order to assess the pretreatment method (air abrasion, both wet and dry, and Al2O3 grinder), the conditioning method (comprised of different adhesive systems), the repair resin composite (low and high modulus of elasticity), the contamination of CoJet air-abraded surfaces with water, and the effect phosphoric acid on the macrotensile bond strength (TBS) to aged CAD/CAM resin nanoceramic (RNC). Aged RNC substrates (LAVA Ultimate, 3M ESPE; N = 900; 10,000 cycles, 5 °C/55 °C) were air-abraded (CoJet 3M ESPE) with and without water contamination or treated with an Al2O3 grinder (Cimara, Voco). Immediately after pretreatment, half of the specimens were additionally cleaned with phosphoric acid, while the rest were only rinsed with water. Four intermediate agents (Futurabond U/VOCO, Scotchbond Universal/3M ESPE, One Coat Bond/Coltène Whaledent, visio.link/bredent) were selected for conditioning the surface, while no conditioned specimens acted as control groups. Specimens were thereafter repaired using two direct resin composites (Arabesk Top and GrandioSo, VOCO), stored for 24 h at 37 °C in H2O, and thermally aged for 10,000 cycles (5 °C/55 °C; n = 15/subgroup). TBS and failure types were determined and evaluated with four- and one-way ANOVA and χ (2) test (p < 0.05). The highest influence on TBS was exerted by the conditioning method (partial eta-squared (η P (2)) = 0.273, p < 0.05), followed by the resin composite repair (η P (2) = 0.07, p < 0.05) and the surface pretreatment method (η P (2) = 0.032, p < 0.05), while an acid contamination after surface pretreatment was insignificant (p = 0.154). Air abrasion produced superior TBS compared to grinding of the surface with Al2O3 prior to repair. The tested universal adhesives proved to be effective intermediate agents for repairing aged CAD/CAM RNC, while visio.link and Scotchbond Universal performed slightly better than Futurabond U. Phosphoric acid or water contamination of the air-abraded surface does not affect the repair bond strength.

Studies of Cosmic Ray Composition and Air Shower Structure with the Pierre Auger Observatory

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

Abraham, : J.; Abreu, P.; Aglietta, M.

2009-06-01

These are presentations to be presented at the 31st International Cosmic Ray Conference, in Lodz, Poland during July 2009. It consists of the following presentations: (1) Measurement of the average depth of shower maximum and its fluctuations with the Pierre Auger Observatory; (2) Study of the nuclear mass composition of UHECR with the surface detectors of the Pierre Auger Observatory; (3) Comparison of data from the Pierre Auger Observatory with predictions from air shower simulations: testing models of hadronic interactions; (4) A Monte Carlo exploration of methods to determine the UHECR composition with the Pierre Auger Observatory; (5) The delaymore » of the start-time measured with the Pierre Auger Observatory for inclined showers and a comparison of its variance with models; (6) UHE neutrino signatures in the surface detector of the Pierre Auger Observatory; and (7) The electromagnetic component of inclined air showers at the Pierre Auger Observatory.« less

Ultraviolet Light Surface Treatment as an Environmentally Benign Process for Production, Maintenance and Repair of Military Composite Structures

NASA Astrophysics Data System (ADS)

Drzal, Lawrence T.

2002-02-01

The principal objective of this work is to develop a low-cost, high-speed, environmentally benign, dry surface treatment method for production, and repair of military composite structures using ultraviolet (UV) light in ambient air. The potential advantage of this method is that it would eliminate volatile organic wastes (VOCs), reduce or eliminate the use of solutions and detergents, and provide a robust surface that would enhance or eliminate the use of solutions and detergents, and provide a robust surface that would enhance the wetting and spreading of paints, coatings and adhesives on polymeric and inorganic surfaces treated by this method. A manufacturing base for UV production equipment is in place although not for this application. There is a need for development of an environmentally friendly, cost effective as well as a robust surface treatment method that can clean a surface as well as create a beneficial chemistry for painting and produce optimum adhesive bonding of polymers, polymer composites and metal surfaces. With this in mind, three main technical objectives were sought in the work. The first objective was to determine the usefulness of UV and UV/O(3) to surface treatments to clean and chemically modify the surface of typical PMCs used in DOD systems. The second objective was to determine the effectiveness of this surface preparation for production and/or repair of adhesively bonded, painted and/or coated polymer matrix composite structures. Finally, a determination of the environmental and performance benefits of this method as a new environmentally benign processing method for the production and/or re air of adhesively SERDP, SERDP collection, robust surface, polymeric surface, inorganic surface, volatile organic compounds (VOC) emissions.

Biological and Chemical Significance of Surface Microlayers in Aquatic Ecosystems

ERIC Educational Resources Information Center

Parker, B.; Barsom, G.

1970-01-01

Reviews methods of study, chemical composition, physical properties and ecology of surface microlayers in marine and fresh water habitats. Relates to problems of air and water pollution. Suggests areas for further research. (EB)

Influence of stripping and cooling atmospheres on surface properties and corrosion of zinc galvanizing coatings

NASA Astrophysics Data System (ADS)

Yasakau, K. A.; Giner, I.; Vree, C.; Ozcan, O.; Grothe, R.; Oliveira, A.; Grundmeier, G.; Ferreira, M. G. S.; Zheludkevich, M. L.

2016-12-01

In this work the influence of stripping/cooling atmospheres used after withdrawal of steel sheet from Zn or Zn-alloy melt on surface properties of Zn (Z) and Zn-Al-Mg (ZM) hot-dip galvanizing coatings has been studied. The aim was to understand how the atmosphere (composed by nitrogen (N2) or air) affects adhesion strength to model adhesive and corrosive behaviour of the galvanized substrates. It was shown that the surface chemical composition and Volta potential of the galvanizing coatings prepared under the air or nitrogen atmosphere are strongly influenced by the atmosphere. The surface chemistry Z and ZM surfaces prepared under N2 contained a higher content of metal atoms and a richer hydroxide density than the specimens prepared under air atmosphere as assessed by X-ray photoelectron spectroscopy (XPS). The induced differences on the microstructure of the galvanized coatings played a key role on the local corrosion induced defects as observed by means of in situ Atomic force microscopy (AFM). Peel force tests performed on the substrates coated by model adhesive films indicate a higher adhesive strength to the surfaces prepared under nitrogen atmosphere. The obtained results have been discussed in terms of the microstructure and surface chemical composition of the galvanizing coatings.

Effect of Air-Polishing on Titanium Surfaces, Biofilm Removal, and Biocompatibility: A Pilot Study

PubMed Central

Bennani, Vincent; Hwang, Linda; Tawse-Smith, Andrew; Dias, George J.; Cannon, Richard D.

2015-01-01

Purpose. The aims of this in vitro study were to evaluate morphological changes induced by glycine powder air-polishing on titanium surfaces, biofilm removal, and biocompatibility. Material and Methods. Titanium grade IV discs were allocated into two groups: (1) discs without biofilm and (2) discs for Streptococcus mutans biofilm formation. Discs in each group were further subdivided into (a) no treatment and (b) air-polishing treatment with glycine powder. Discs were characterized by scanning electron microscopy (SEM), electron-dispersive spectroscopy (EDS), and confocal microscopy. Bacterial biofilms were quantified using a crystal violet dye-binding assay. Biocompatibility was evaluated by measuring the coverage and viability of L929 fibroblast cells cultured on the discs. Results. Air-polishing increased the roughness of treated discs (P < 0.05). EDS analysis did not show significant differences in the chemical composition of treated and nontreated discs. The amount of residual biofilm on treated discs was 8.6-fold lower than untreated controls (P < 0.05). Coverage of treated discs by fibroblasts was half that of untreated discs (P < 0.05) although both groups had the same cell viability. Conclusions. Air-polishing removed a significant amount of biofilm from titanium surfaces. The “polishing” was accompanied by increased surface roughness, but there were no changes in chemical and elemental compositions, nor the biocompatibility. PMID:26881198

A study of atmospheric mixing of trace gases by aerial sampling with a multi-rotor drone

NASA Astrophysics Data System (ADS)

Chang, Chih-Chung; Chang, Chih-Yuan; Wang, Jia-Lin; Lin, Ming-Ren; Ou-Yang, Chang-Feng; Pan, Hsiang-Hsu; Chen, Yen-Chen

2018-07-01

We exploited a novel sampling vehicle, a multi-rotor drone carrying a remote-controlled whole air sampling device, to collect aerial samples with high sample integrity and preservation conditions. An array of 106 volatile organic compounds (VOCs), CO, CH4, and CO2 were analyzed and compared between the aerial samples (300-m height) and the ground-level samples in pairs to inspect for vertical mixing of the trace gases at a coastal site under three different meteorological conditions of local circulation, frontal passage, and high-pressure peripheral circulation. A rather homogeneous composition was observed for the sample pairs immediately after the frontal passage, indicating a well-mixed condition below 300 m. In contrast, inhomogeneous mixing was observed for the sample pairs under the other two conditions (local circulation and high-pressure peripheral circulation), suggesting different layers of air masses. Furthermore, information of unique source markers, composition profiles, and lifetimes of compounds were used to differentiate the origins of the air masses aloft and at the surface to substantiate the observed inhomogeneity. The study demonstrates that, with the availability of the near-surface aerial sampling coupling with in-laboratory analysis, detailed compositions of trace gases can now be readily obtained with superior data quality. Based on the distinctive chemical compositions, the sources, transport, and atmospheric mixing of the airborne pollutants in the near-surface atmosphere can be better studied and understood.

Shear Moduli of Orthotropic Composites.

DTIC Science & Technology

1980-03-01

COMPOSITES N. J. Pagano Mechanics & Surface Interactions Branch Nonmetallic Materials Division March 1980 DT1C> Technical Report AFML-TR-79-4164 ELE(I JUN...Surface Interactions Br. Nonmetallic Materials Division Nonmetallic Materials Division FOR THE COMMANDER M.KLLChief metallic Materials Division "If your...SrtaceT’ Ileation ranch 10. PROGRAM ELEMENT. PROJECT, TASK Materials Laboratory 219 u,\\i’- Air Force Wright Aeronautical Laboratories 21310, WD Wright

Air Quality Forecasts Using the NASA GEOS Model

NASA Technical Reports Server (NTRS)

Keller, Christoph A.; Knowland, K. Emma; Nielsen, Jon E.; Orbe, Clara; Ott, Lesley; Pawson, Steven; Saunders, Emily; Duncan, Bryan; Follette-Cook, Melanie; Liu, Junhua;

The Diversity and Distribution of Fungi on Residential Surfaces

PubMed Central

Adams, Rachel I.; Miletto, Marzia; Taylor, John W.; Bruns, Thomas D.

2013-01-01

The predominant hypothesis regarding the composition of microbial assemblages in indoor environments is that fungal assemblages are structured by outdoor air with a moderate contribution by surface growth, whereas indoor bacterial assemblages represent a mixture of bacteria entered from outdoor air, shed by building inhabitants, and grown on surfaces. To test the fungal aspect of this hypothesis, we sampled fungi from three surface types likely to support growth and therefore possible contributors of fungi to indoor air: drains in kitchens and bathrooms, sills beneath condensation-prone windows, and skin of human inhabitants. Sampling was done in replicated units of a university-housing complex without reported mold problems, and sequences were analyzed using both QIIME and the new UPARSE approach to OTU-binning, to the same result. Surfaces demonstrated a mycological profile similar to that of outdoor air from the same locality, and assemblages clustered by surface type. “Weedy” genera typical of indoor air, such as Cladosporium and Cryptococcus, were abundant on sills, as were a diverse set of fungi of likely outdoor origin. Drains supported more depauperate assemblages than the other surfaces and contained thermotolerant genera such as Exophiala, Candida, and Fusarium. Most surprising was the composition detected on residents’ foreheads. In addition to harboring Malassezia, a known human commensal, skin also possessed a surprising richness of non-resident fungi, including plant pathogens such as ergot (Claviceps purperea). Overall, fungal richness across indoor surfaces was high, but based on known autecologies, most of these fungi were unlikely to be growing on surfaces. We conclude that while some endogenous fungal growth on typical household surfaces does occur, particularly on drains and skin, all residential surfaces appear – to varying degrees – to be passive collectors of airborne fungi of putative outdoor origin, a view of the origins of the indoor microbiome quite different from bacteria. PMID:24223861

Bioinspired super-antiwetting interfaces with special liquid-solid adhesion.

PubMed

Liu, Mingjie; Zheng, Yongmei; Zhai, Jin; Jiang, Lei

2010-03-16

Super-antiwetting interfaces, such as superhydrophobic and superamphiphobic surfaces in air and superoleophobic interfaces in water, with special liquid-solid adhesion have recently attracted worldwide attention. Through tuning surface microstructures and compositions to achieve certain solid/liquid contact modes, we can effectively control the liquid-solid adhesion in a super-antiwetting state. In this Account, we review our recent progress in the design and fabrication of these bioinspired super-antiwetting interfaces with special liquid-solid adhesion. Low-adhesion superhydrophobic surfaces are biologically inspired, typically by the lotus leaf. Wettability investigated at micro- and nanoscale reveals that the low adhesion of the lotus surface originates from the composite contact mode, a microdroplet bridging several contacts, within the hierarchical structures. Recently high-adhesion superhydrophobic surfaces have also attracted research attention. These surfaces are inspired by the surfaces of gecko feet and rose petals. Accordingly, we propose two biomimetic approaches for the fabrication of high-adhesion superhydrophobic surfaces. First, to mimic a sticky gecko's foot, we designed structures with nanoscale pores that could trap air isolated from the atmosphere. In this case, the negative pressure induced by the volume change of sealed air as the droplet is pulled away from surface can produce a normal adhesive force. Second, we constructed microstructures with size and topography similar to that of a rose petal. The resulting materials hold air gaps in their nanoscale folds, controlling the superhydrophobicity in a Wenzel state on the microscale. Furthermore, we can tune the liquid-solid adhesion on the same superhydrophobic surface by dynamically controlling the orientations of microstructures without altering the surface composition. The superhydrophobic wings of the butterfly (Morpho aega) show directional adhesion: a droplet easily rolls off the surface of wings along one direction but is pinned tightly against rolling in the opposite direction. Through coordinating the stimuli-responsive materials and appropriate surface-geometry structures, we developed materials with reversible transitions between a low-adhesive rolling state and a high-adhesive pinning state for water droplets on the superhydrophobic surfaces, which were controlled by temperature and magnetic and electric fields. In addition to the experiments done in air, we also demonstrated bioinspired superoleophobic water/solid interfaces with special adhesion to underwater oil droplets and platelets. In these experiments, the high content of water trapped in the micro- and nanostructures played a key role in reducing the adhesion of the oil droplets and platelets. These findings will offer innovative insights into the design of novel antibioadhesion materials.

Prediction of moisture and temperature changes in composites during atmospheric exposure

NASA Technical Reports Server (NTRS)

Tompkins, S. S.; Tenney, D. R.; Unnan, J.

1978-01-01

The effects of variations in diffusion coefficients, surface properties of the composite, panel tilt, ground reflection, and geographical location on the moisture concentration profiles and average moisture content of composite laminates were studied analytically. A heat balance which included heat input due to direct and sky diffuse solar radiation, ground reflection, and heat loss due to reradiation and convection was used to determine the temperature of composites during atmospheric exposure. The equilibrium moisture content was assumed proportional to the relative humidity of the air in the boundary layer of the composite. Condensation on the surface was neglected. Histograms of composite temperatures were determined and compared with those for the ambient environment.

Surface modification of polyester fabrics by atmospheric-pressure air/He plasma for color strength and adhesion enhancement

NASA Astrophysics Data System (ADS)

Zhang, Chunming; Zhao, Meihua; Wang, Libing; Qu, Lijun; Men, Yajing

2017-04-01

Surface properties of water-based pigmented inks for ink-jet printed polyester fabrics were modified with atmospheric-pressure air/He plasma to improve the color strength and pigment adhesion of the treated surfaces. The influence of various parameters, including the surface morphology, chemical compositions, surface energy and dynamic contact angles of the control and plasma treated samples was studied. Color strength and edge definition were used to evaluate the ink-jet printing performance of fabrics. The change in pigment adhesion to polyester fibers was analyzed by SEM (scanning electron microscopy). AFM (Atomic force microscope) and XPS (X-ray photoelectron spectroscopy) analyses indicated the increase in surface roughness and the oxygen-containing polar groups(Cdbnd O, Csbnd OH and COOH) reinforced the fixation of pigments on the fiber surface. The result from this study suggested that the improved pigment color yield was clearly affected by alteration of pigment adhesion enhanced by plasma surface modification. Polyester fabrics exhibited better surface property and ink-jet printing performance after the air/He mixture plasma treatment comparing with those after air plasma treatment.

Shear-bond-strength of orthodontic brackets to aged nano-hybrid composite-resin surfaces using different surface preparation.

PubMed

Demirtas, Hatice Kubra; Akin, Mehmet; Ileri, Zehra; Basciftci, Faruk Ayhan

2015-01-01

The aim of this study was to evaluate the effects of different surface preparation methods on the shear bond strength (SBS) of orthodontic metal brackets to aged nano-hybrid resin composite surfaces in vitro. A total of 100 restorative composite resin discs, 6 mm in diameter and 3 mm thick, were obtained and treated with an ageing procedure. After ageing, the samples were randomly divided as follows according to surface preparation methods: (1)Control, (2)37% phosphoric acid gel, (3)Sandblasting, (4)Diamond bur, (5)Air-flow and 20 central incisor teeth were used for the control etched group. SBS test were applied on bonded metal brackets to all samples. SBS values and residual adhesives were evaluated. Analysis of variance showed a significant difference (p<0.001) between the groups. Sandblasted group had the highest SBS value (12.85 MPa) in experimental groups. The sandblasting surface treatment is recommended as an effective method of bonding orthodontic metal brackets to nano-hybrid composite resin surfaces.

PEDOT:PSS as multi-functional composite material for enhanced Li-air-battery air electrodes.

PubMed

Yoon, Dae Ho; Yoon, Seon Hye; Ryu, Kwang-Sun; Park, Yong Joon

2016-01-27

We propose PSS as a multi-functional composite material for an enhanced Li-air-battery air electrode. The PSS layer was coated on the surface of carbon (graphene) using simple method. A electrode containing PSS-coated graphene (PEDOT electrode) could be prepared without binder (such as PVDF) because of high adhesion of PSS. PEDOT electrode presented considerable discharge and charge capacity at all current densities. These results shows that PSS acts as a redox reaction matrix and conducting binder in the air electrode. Moreover, after cycling, the accumulation of reaction products due to side reaction in the electrode was significantly reduced through the use of PSS. This implies that PSS coating layer can suppress the undesirable side reactions between the carbon and electrolyte (and/or Li2O2), which causes enhanced Li-air cell cyclic performance.

Graphene supported heterogeneous catalysts for Li-O2 batteries

NASA Astrophysics Data System (ADS)

Alaf, M.; Tocoglu, U.; Kartal, M.; Akbulut, H.

2016-09-01

In this study production and characterization of free-standing and flexible (i) graphene, (ii) α-MnO2/graphene, (iii) Pt/graphene (iv) α-MnO2/Pt/graphene composite cathodes for Li-air batteries were reported. Graphene supported heterogeneous catalysts were produced by a facile method. In order to prevent aggregation of graphene sheets and increase not only interlayer distance but also surface area, a trace amount multi-wall carbon nano tube (MWCNT) was introduced to the composite structure. The obtained composite catalysts were characterized by SEM, X-ray diffraction, N2 adsorption-desorption analyze and Raman spectroscopy. The electrochemical characterization tests including galvanostatic charge/discharge and electrochemical impedance spectroscopy (EIS) measurement of catalyst were carried out by using an ECC-Air test cell. These highly active graphene supported heterogeneous composite catalysts provide competitive properties relative to other catalyst materials for Li-air batteries.

Air Quality Forecasts Using the NASA GEOS Model: A Unified Tool from Local to Global Scales

NASA Technical Reports Server (NTRS)

Knowland, E. Emma; Keller, Christoph; Nielsen, J. Eric; Orbe, Clara; Ott, Lesley; Pawson, Steven; Saunders, Emily; Duncan, Bryan; Cook, Melanie; Liu, Junhua;

Analyzer for measurement of nitrogen oxide concentration by ozone content reduction in gas using solid state chemiluminescent sensor

NASA Astrophysics Data System (ADS)

Chelibanov, V. P.; Ishanin, G. G.; Isaev, L. N.

2014-05-01

Role of nitrogen oxide in ambient air is described and analyzed. New method of nitrogen oxide concentration measurement in gas phase is suggested based on ozone concentration measurement with titration by nitrogen oxide. Research of chemiluminescent sensor composition is carried out on experimental stand. The sensor produced on the base of solid state non-activated chemiluminescent composition is applied as ozone sensor. Composition is put on the surface of polymer matrix with developed surface. Sensor compositions includes gallic acid with addition of rodamine-6G. Model of interaction process between sensor composition and ozone has been developed, main products appeared during reaction are identified. The product determining the speed of luminescense appearance is found. This product belongs to quinone class. Then new structure of chemiluminescent composition was suggested, with absence of activation period and with high stability of operation. Experimental model of gas analyzer was constructed and operation algorithm was developed. It was demonstrated that developed NO measuring instrument would be applied for monitoring purposes of ambient air. This work was partially financially supported by Government of Russian Federation, Grant 074-U01

Bonding to new CAD/CAM resin composites: influence of air abrasion and conditioning agents as pretreatment strategy.

PubMed

Reymus, Marcel; Roos, Malgorzata; Eichberger, Marlis; Edelhoff, Daniel; Hickel, Reinhard; Stawarczyk, Bogna

2018-04-27

Because of their industrially standardized process of manufacturing, CAD/CAM resin composites show a high degree of conversion, making a reliable bond difficult to achieve. The purpose of this experiment was to investigate the tensile bond strength (TBS) of luting composite to CAD/CAM resin composite materials as influenced by air abrasion and pretreatment strategies. The treatment factors of the present study were (1) brand of the CAD/CAM resin composite (Brilliant Crios [Coltene/Whaledent], Cerasmart [GC Europe], Shofu Block HC [Shofu], and Lava Ultimate [3M]); (2) air abrasion vs. no air abrasion; and (3) pretreatment using a silane primer (Clearfil Ceramic Primer, Kuraray) vs. a resin primer (One Coat 7 Universal, Coltene/Whaledent). Subsequently, luting composite (DuoCem, Coltene/Whaledent) was polymerized onto the substrate surface using a mold. For each combination of the levels of the three treatment factors (4 (materials) × 2 (air abrasion vs. no air abrasion; resin) × 2 (primer vs. silane primer)), n = 15, specimens were prepared. After 24 h of water storage at 37 °C and 5000 thermo-cycles (5/55 °C), TBS was measured and failure types were examined. The resulting data was analyzed using Kaplan-Meier estimates of the cumulative failure distribution function with Breslow-Gehan tests and non-parametric ANOVA (Kruskal-Wallis test) followed by the multiple pairwise Mann-Whitney U test with α-error adjustment using the Benjamini-Hochberg procedure and chi-square test (p < 0.05). The additional air abrasion step increased TBS values and lowered failure rates. Specimens pretreated using a resin primer showed significantly higher TBS and lower failure rates than those pretreated using a silane primer. The highest failure rates were observed for groups pretreated with a silane primer. Within the Shofu Block HC group, all specimens without air abrasion and pretreatment with a silane primer debonded during the aging procedure. Before fixation of CAD/CAM resin composites, the restorations should be air abraded and pretreated using a resin primer containing methyl-methacrylate to successfully bond to the luting composite. The pretreatment of the CAD/CAM resin composite using merely a silane primer results in deficient adhesion. For a reliable bond of CAD/CAM resin composites to the luting composite, air abrasion and a special pretreatment strategy are necessary in order to achieve promising long-term results.

Effects of air abrasion with alumina or glass beads on surface characteristics of CAD/CAM composite materials and the bond strength of resin cements

PubMed Central

Nobuaki, ARAO; Keiichi, YOSHIDA; Takashi, SAWASE

2015-01-01

ABSTRACT Objective The study aimed to evaluate effects of air abrasion with alumina or glass beads on bond strengths of resin cements to CAD/CAM composite materials. Material and Methods CAD/CAM composite block materials [Cerasmart (CS) and Block HC (BHC)] were pretreated as follows: (a) no treatment (None), (b) application of a ceramic primer (CP), (c) alumina-blasting at 0.2 MPa (AB), (d) AB followed by CP (AB+CP), and (e) glass-beads blasting at 0.4 MPa (GBB) followed by CP (GBB+CP). The composite specimens were bonded to resin composite disks using resin cements [G-CEM Cerasmart (GCCS) and ResiCem (RC)]. The bond strengths after 24 h (TC 0) and after thermal cycling (TC 10,000 at 4–60°C) were measured by shear tests. Three-way ANOVA and the Tukey compromise post hoc tests were used to analyze statistically significant differences between groups (α=0.05). Results For both CAD/CAM composite materials, the None group exhibited a significant decrease in bond strength after TC 10,000 (p<0.05). AB showed significantly higher bond strength after TC 10,000 than the None group, while CP did not (p<0.05). GBB exhibited smaller surface defects than did AB; however, their surface roughnesses were not significantly different (p>0.05). The AB+CP group showed a significantly higher bond strength after TC 10,000 than did the AB group for RC (p<0.05), but not for GCCS. The GBB+CP group showed the highest bond strength for both thermal cyclings (p<0.05). Conclusions Air abrasion with glass beads was more effective in increasing bond durability between the resin cements and CAD/CAM composite materials than was using an alumina powder and a CP. PMID:26814465

Phase transition of LB films of mixed diblock copolymer at the air/water interface

NASA Astrophysics Data System (ADS)

Seo, Y. S.; Kim, K. S.; Samuilov, V.; Rafailovich, M. H.; Sokolov, J.; Lammertink, Rob G. H.; Vancso, G. J.

2000-03-01

We have studied the morphology of Langmuir blodgett films at the air/water interface of mixed diblock copolymer films. Solutions of poly(styrene-b-ferrocenyldimethylsilane) and PS-b-P2VP mixed in a ratio of 20/80 in chloroform were spread at the air/water interface. The morphology of the films was studied with AFM as a function of the surface pressure and the diblock copolymer molecular weight. The results show that the two diblock copolymers can be induced to mix at the air/water interface with increasing surface pressure. A reversible transition from spherical to cylindrical morphologies is induced in the mixture which can not be observed in films formed of the two components separately. The effective surface phase diagram as a function of block copolymer composition and pressure will be presented.

PEDOT:PSS as multi-functional composite material for enhanced Li-air-battery air electrodes

PubMed Central

Yoon, Dae Ho; Yoon, Seon Hye; Ryu, Kwang-Sun; Park, Yong Joon

2016-01-01

We propose PEDOT:PSS as a multi-functional composite material for an enhanced Li-air-battery air electrode. The PEDOT:PSS layer was coated on the surface of carbon (graphene) using simple method. A electrode containing PEDOT:PSS-coated graphene (PEDOT electrode) could be prepared without binder (such as PVDF) because of high adhesion of PEDOT:PSS. PEDOT electrode presented considerable discharge and charge capacity at all current densities. These results shows that PEDOT:PSS acts as a redox reaction matrix and conducting binder in the air electrode. Moreover, after cycling, the accumulation of reaction products due to side reaction in the electrode was significantly reduced through the use of PEDOT:PSS. This implies that PEDOT:PSS coating layer can suppress the undesirable side reactions between the carbon and electrolyte (and/or Li2O2), which causes enhanced Li-air cell cyclic performance. PMID:26813852

Performance evaluations of oxidation-resistant carbon-carbon composites in simulated hypersonic vehicle environments

NASA Technical Reports Server (NTRS)

Barrett, D. M.; Maahs, H. G.; Ohlhorst, C. W.; Vaughn, W. L.; Martin, R. H.

1989-01-01

An evaluation is made of the oxidation-protection requirements of carbon-carbon composite (CCC) structural components in a hypersonic vehicle aerothermodynamic environment, where maximum test temperatures in air are of the order of 2800 F, and pressures range from 0.03 to 1.0 atm. The specimens were exposed to high humidity between tests. Attention was given to the effects of coating composition and thickness, and of substrate architecture and surface preparation, on the oxidation resistance of CCCs. Both surface preparation and coating chemistry have a profound effect on coating adherence and longevity.

Properties of PMR Polyimide composites made with improved high strength graphite fibers

NASA Technical Reports Server (NTRS)

Vannucci, R. D.

1980-01-01

High strength, intermediate modulus graphite fibers were obtained from various commercial suppliers, and were used to fabricate PMR-15 and PMR-2 polyimide composites. The effects of the improved high strength graphite fibers on composite properties after exposure in air at 600 F were investigated. Two of the improved fibers were found to have an adverse effect on the long term performance of PMR composites. The influence of various factors such as fiber physical properties, surface morphology and chemical composition were also examined.

A Review of Communications Satellites and Related Spacecraft for Factors Influencing Mission Success. Volume 2

DTIC Science & Technology

1975-11-17

and control (subsystem) COMM., comm AEC Atomic Energy Commission comsat AFB Air Force Base COMSTAR ACE A-hr aerospace ground equipment ampere...array TDA Satellite Assembly Building TDAL Space and Missile Systems Organization (U.S. Air Force) TDM THIR satellite communications system TI...Satellite Control Facility (U.S. Air Force) TIROS selective chopper radiometer TLM, T/M surface composition mapping radiometer TOS TRUST

Development of technology for the fabrication of reliable laminar flow control panels on subsonic transports

NASA Technical Reports Server (NTRS)

1976-01-01

The feasibility of using porous composite materials (Kevlar, Doweave, and Leno Weave) as lightweight, efficient laminar flow control (LFC) surface materials is compared to the metallic 319L stainless Dynapore surfaces and electron beam drilled composite surfaces. Areas investigated include: (1) selection of the LFC-suitable surface materials, structural materials, and fabrication techniques for the LFC aircraft skins; (2) aerodynamic static air flow test results in terms of pressure drop through the LFC panel and the corresponding effective porosity; (3) structural design definition and analyses of the panels, and (4) contamination effects on static drop and effective porosity. Conclusions are presented and discussed.

Effect of atmosphere on the surface tension and viscosity of molten LiNbO 3 measured using the surface laser-light scattering method

NASA Astrophysics Data System (ADS)

Nagasaka, Yuji; Kobayashi, Yusuke

2007-09-01

The surface tension and the viscosity of molten LiNbO 3 (LN) having the congruent composition have been measured simultaneously in a temperature range from 1537 to 1756 K under argon gas and dry-air atmospheres. The present measurement technique involves surface laser-light scattering (SLLS) that detects nanometer-order-amplitude surface waves usually regarded as ripplons excited by thermal fluctuations. This technique's non-invasive nature allows it to avoid the experimental difficulties of conventional techniques resulting from the insertion of an actuator in the melt. The results of surface tension measurement obtained under a dry-air atmosphere are about 5% smaller than those obtained under an argon atmosphere near the melting temperature, and the temperature dependence of the surface tension under a dry-air atmosphere is twice that under an argon atmosphere. The uncertainty of surface tension measurement is estimated to be ±2.6% under argon and ±1.9% under dry air. The temperature dependence of viscosity can be well correlated with the results of Arrhenius-type equations without any anomalous behavior near the melting point. The viscosities obtained under a dry-air atmosphere were slightly smaller than those obtained under an argon atmosphere. The uncertainty of viscosity measurement is estimated to be ±11.1% for argon and ±14.3% for dry air. Moreover, we observed the real-time dynamic behavior of the surface tension and the viscosity of molten LN in response to argon and dry-air atmospheres.

What measurements tell us about air composition and emissions in three US oil and gas fields

NASA Astrophysics Data System (ADS)

Petron, G.; Miller, B. R.; Montzka, S. A.; Dlugokencky, E. J.; Kofler, J.; Sweeney, C.; Karion, A.; Frost, G. J.; Helmig, D.; Hueber, J.; Schnell, R. C.; Conley, S. A.; Tans, P. P.

2013-12-01

In 2012 and 2013, the NOAA Global Monitoring Division and several collaborators conducted intensive airborne and ground campaigns in three US oil and gas plays to study emissions of methane and surface ozone precursors. In this presentation we will focus on the multiple species analysis in discrete air samples collected with the NOAA Mobile Laboratory (ML) and the light aircraft in the Uinta Basin (Utah), Denver Julesburg Basin (Colorado) and Barnett Shale (Texas). Hydrocarbon ratios in samples collected with the ML downwind of specific sources show significantly more variability than the aircraft samples. These surface samples provide some useful information about the composition of various sources in each region. Ratios of the non-methane hydrocarbons on the ground and higher in the boundary layer show some differences between the plays, which could be explained by the different composition of the raw gas being produced or by different mixes of sources contributions. Understanding the speciation of atmospheric emissions is critical to identify emission vectors and to assess their potential air quality and climate impacts. Our measurement results will be compared with data from other studies, including emission inventories.

Use of segmented constrained layer damping treatment for improved helicopter aeromechanical stability

NASA Astrophysics Data System (ADS)

Liu, Qiang; Chattopadhyay, Aditi; Gu, Haozhong; Liu, Qiang; Chattopadhyay, Aditi; Zhou, Xu

2000-08-01

The use of a special type of smart material, known as segmented constrained layer (SCL) damping, is investigated for improved rotor aeromechanical stability. The rotor blade load-carrying member is modeled using a composite box beam with arbitrary wall thickness. The SCLs are bonded to the upper and lower surfaces of the box beam to provide passive damping. A finite-element model based on a hybrid displacement theory is used to accurately capture the transverse shear effects in the composite primary structure and the viscoelastic and the piezoelectric layers within the SCL. Detailed numerical studies are presented to assess the influence of the number of actuators and their locations for improved aeromechanical stability. Ground and air resonance analysis models are implemented in the rotor blade built around the composite box beam with segmented SCLs. A classic ground resonance model and an air resonance model are used in the rotor-body coupled stability analysis. The Pitt dynamic inflow model is used in the air resonance analysis under hover condition. Results indicate that the surface bonded SCLs significantly increase rotor lead-lag regressive modal damping in the coupled rotor-body system.

Effect of different surface treatments on shear bond strength of zirconia to three resin cements

NASA Astrophysics Data System (ADS)

Dadjoo, Nisa

Statement of problem: There are no standard guidelines for material selection to obtain acceptable bonding to high-strength zirconium oxide ceramic. Studies suggest resin cements in combination with MDP-containing primer is a reasonable choice, however, the other cements cannot be rejected and need further investigation. Objective: The purpose of this in vitro study was the evaluation of the shear bond strength of three composite resin cements to zirconia ceramic after using different surface conditioning methods. Materials and methods: One hundred and twenty sintered Y-TZP ceramic (IPS e.max ZirCAD) squares (8 x 8 x 4 mm) were embedded in acrylic molds, then divided into three groups (n=40) based on the type of cement used. Within each group, the specimens were divided into four subgroups (n=10) and treated as follows: (1) Air abrasion with 50microm aluminum oxide (Al2O 3) particles (ALO); (2) Air abrasion + Scotchbond Universal adhesive (SBU); (3) Air abrasion + Monobond Plus (MBP); (4) Air abrasion + Z-Prime Plus (ZPP). Composite cylinders were used as carriers to bond to conditioned ceramic using (1) RelyX Ultimate adhesive resin cement (RX); (2) Panavia SA self-adhesive resin cement (PSA); (3) Calibra esthetic cement (CAL). The bonded specimens were submerged in distilled water and subjected to 24-hour incubation period at 37°C. All specimens were stressed in shear at a constant crosshead speed of 0.5 mm/min until failure. Statistical analysis was performed by ANOVA. The bond strength values (MPa), means and standard deviations were calculated and data were analyzed using analysis of variance with Fisher's PLSD multiple comparison test at the 0.05 level of significance. The nature of failure was recorded. Results: The two-way ANOVA showed Panavia SA to have the highest strength at 44.3 +/- 16.9 MPa (p<0.05). The combination of Scotchbond Universal surface treatment with Panavia SA cement showed statistically higher bond strength (p=0.0054). The highest bond strengths for all three cements were observed with Scotchbond Universal surface treatment (p=0.0041). Calibra in combination with aluminum oxide air abrasion resulted in statistically lowest bond strength at 12.0 +/- 3.9 MPa. The predominant mode of failure was cohesive with cement remaining principally on the zirconium oxide samples in 57.5% of the specimens, followed by cement found on both the zirconium oxide samples and composite rods (mixed) in 32.5% of the samples. Only 10% of the specimens were found with cement on the composite rods (adhesive failure). Conclusions: Within the limitations of this in vitro study, the MDP-containing resin cement, Panavia SA, yielded the strongest bond to Y-TZP ceramic when compared to adhesive (RelyX Ultimate) or esthetic (Calibra) resin cements. Air abrasion particle + Scotchbond Universal surface treatment demonstrated the highest bond strength regardless of the cement. Significance: The variation of surface conditioning methods yielded different results in accordance with the cement types. Overall, Scotchbond Universal adhesive + air abrasion yielded the highest bond strengths among all three surface treatments. The phosphate monomer-containing luting system, Panavia SA, is acceptable for bonding to zirconia ceramics.

Oxidation characteristics of MgF2 in air at high temperature

NASA Astrophysics Data System (ADS)

Chen, H. K.; Jie, Y. Y.; Chang, L.

2017-02-01

High temperature oxidation properties of MgF2 in air were studied. The changes of phase composition, macro surface morphology, weight and elemental composition of MgF2 samples with temperature were investigated by using XRD, EDS and gravimetric analyses. The results show that the oxidation reaction of MgF2 converted to MgO occurred at high temperature, and the reaction was accelerated by the increase of temperature and the presence of impurities. This result clarifies the understanding of the high temperature oxidation behavior of MgF2 in air, and provides a theoretical basis for the reasonable application of MgF2 in optical coating materials, electronic ceramic materials and magnesium melt protection.

Improved helicopter aeromechanical stability analysis using segmented constrained layer damping and hybrid optimization

NASA Astrophysics Data System (ADS)

Liu, Qiang; Chattopadhyay, Aditi

2000-06-01

Aeromechanical stability plays a critical role in helicopter design and lead-lag damping is crucial to this design. In this paper, the use of segmented constrained damping layer (SCL) treatment and composite tailoring is investigated for improved rotor aeromechanical stability using formal optimization technique. The principal load-carrying member in the rotor blade is represented by a composite box beam, of arbitrary thickness, with surface bonded SCLs. A comprehensive theory is used to model the smart box beam. A ground resonance analysis model and an air resonance analysis model are implemented in the rotor blade built around the composite box beam with SCLs. The Pitt-Peters dynamic inflow model is used in air resonance analysis under hover condition. A hybrid optimization technique is used to investigate the optimum design of the composite box beam with surface bonded SCLs for improved damping characteristics. Parameters such as stacking sequence of the composite laminates and placement of SCLs are used as design variables. Detailed numerical studies are presented for aeromechanical stability analysis. It is shown that optimum blade design yields significant increase in rotor lead-lag regressive modal damping compared to the initial system.

Effects of High-Temperature Annealing in Air on Hi-Nicalon Fiber-Reinforced Celsian Matrix Composites

NASA Technical Reports Server (NTRS)

Bansal, Narottam P.

2008-01-01

BN/SiC-coated Hi-Nicalon fiber-reinforced celsian matrix composites (CMC) were annealed for 100 h in air at various temperatures to 1200 C, followed by flexural strength measurements at room temperature. Values of yield stress and strain, ultimate strength, and composite modulus remain almost unchanged for samples annealed up to 1100 C. A thin porous layer formed on the surface of the 1100 C annealed sample and its density decreased from 3.09 to 2.90 g/cu cm. The specimen annealed at 1200 C gained 0.43 wt%, was severely deformed, and was covered with a porous layer of thick shiny glaze which could be easily peeled off. Some gas bubbles were also present on the surface. This surface layer consisted of elongated crystals of monoclinic celsian and some amorphous phase(s). The fibers in this surface ply of the CMC had broken into small pieces. The fiber-matrix interface strength was characterized through fiber push-in technique. Values of debond stress, alpha(sub d), and frictional sliding stress, tau(sub f), for the as-fabricated CMC were 0.31+/-0.14 GPa and 10.4+/-3.1 MPa, respectively. These values compared with 0.53+/-0.47 GPa and 8.33+/-1.72 MPa for the fibers in the interior of the 1200 C annealed sample, indicating hardly any change in fiber-matrix interface strength. The effects of thermal aging on microstructure were investigated using scanning electron microscopy. Only the surface ply of the 1200 C annealed specimens had degraded from oxidation whereas the bulk interior part of the CMC was unaffected. A mechanism is proposed explaining the various steps involved during the degradation of the CMC on annealing in air at 1200 C.

Resin cement to indirect composite resin bonding: effect of various surface treatments.

PubMed

Kirmali, Omer; Barutcugil, Cagatay; Harorli, Osman; Kapdan, Alper; Er, Kursat

2015-01-01

Debonding at the composite-adhesive interface is a major problem for indirect composite restorations. The aim of this study was to evaluate the bond strength (BS) of an indirect composite resin after various surface treatments (air-abrasion with Al2O3, phosphoric acid-etchig and different applications of NdYAG laser irradiations). Fifty composite disks were subjected to secondary curing to complete polymerization and randomly divided into five experimental groups (n = 10) including Group 1, untreated (control); Group 2, phosphoric acid-etched; Group 3, air-abrasion with Al2 O3 ; Group 4, Nd:YAG laser irradiated with non-contact and Group 5, Nd:YAG laser irradiated with contact. They were then bonded to resin cement and shear BS was determined in a universal testing device at a crosshead speed of 1 mm/min. One way analysis of variance (ANOVA) and Tukey post-hoc tests were used to analyze the BS values. The highest BS value was observed in Group 4 and followed by Group 3. Tukey test showed that there was no statistical difference between Group1, 2 and 5. Furthermore, differences in BSs between Group 4 and the other groups except Group 3 were significant (p < 0.05) and also there were significant differences in BSs between Group 3 to 1 and Group 3 to 2 (p < 0.05). This study reveals that air-abrasion with Al2 O3 and Nd:YAG laser irradiation with non-contact provided a significant increase in BS between indirect composite and resin cement. © Wiley Periodicals, Inc.

Chemical composition of natural waters of contaminated area: The case for the Imandra Lake catchment (the Kola Peninsula)

NASA Astrophysics Data System (ADS)

Evtyugina, Z. A.; Guseva, N. V.; Kopylova, J. G.; A, Vorobeva D.

2016-03-01

The study of the current chemical composition of natural waters in the eastern and western parts of the Imandra Lake catchment was performed using ion chromatography, potentiometry and inductively coupled plasma mass spectrometry. It was found that the content of trace elements in the surface water is considerably higher than that in the groundwater. The nickel and copper concentrations exceed the background levels over 19 and 2 times respectively in groundwater, and 175 and 61 times in the surface waters. These data show that the Severonikel influences negatively air and surface water.

Products of n-hexane oxidation with air oxygen on an activated carbon surface

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

Barkauskas, Yu.; Kareiva, A.

Products of n-hexane oxidation on an activated carbon surface have been investigated. Carbon samples have been prepared using the Plackett-Burman method of mathematical design. The influence of carbon preparation stages on the composition of products of n-hexane oxidation has been discussed.

A study of cavity preparation by Er:YAG laser. Effects on the marginal leakage of composite resin restoration.

PubMed

Shigetani, Yoshimi; Tate, Yasuaki; Okamoto, Akira; Iwaku, Masaaki; Abu-Bakr, Neamat

2002-09-01

The purpose of this study was to evaluate marginal leakage of composite resin restoration from cavities prepared by Er:YAG laser. The observation of the dentin surface after the application of laser irradiation was performed by LSM, the cutting surface showed a rough surface similar to scales, and exposed dentinal tubules were observed without striations or a smeared layer formation that were observed when using a rotary cutting device. Leakage tests revealed no significant differences in the marginal seal for both enamel and dentin between cavities prepared by Er:YAG laser irradiation and when using an air-turbine. In this study, the usefulness of cavity preparation by Er:YAG laser irradiation in composite resin restoration was suggested.

Biogeochemical linkage between atmosphere and ocean in the eastern equatorial Pacific Ocean: Results from the EqPOS research cruise

NASA Astrophysics Data System (ADS)

Furutani, H.; Inai, Y.; Aoki, S.; Honda, H.; Omori, Y.; Tanimoto, H.; Iwata, T.; Ueda, S.; Miura, K.; Uematsu, M.

2012-12-01

Eastern equatorial Pacific Ocean is a unique oceanic region from several biogeochemical points of view. It is a remote open ocean with relatively high marine biological activity, which would result in limited influence of human activity but enhanced effect of marine natural processes on atmospheric composition. It is also characterized as high nutrient low chlorophyll (HNLC) ocean, in which availability of trace metals such as iron and zinc limits marine primary production and thus atmospheric deposition of these trace elements to the ocean surface is expected to play an important role in regulating marine primary production and defining unique microbial community. High sea surface temperature in the region generates strong vertical air convection which efficiently brings tropospheric atmospheric composition into stratosphere. In this unique eastern equatorial Pacific Ocean, EqPOS (Equatorial Pacific Ocean and Stratospheric/Tropospheric Atmospheric Study) research cruise was organized as a part of SOLAS Japan activity to understand biogeochemical ocean-atmospheric interaction in the region. Coordinated atmospheric, oceanic, and marine biological observations including sampling/characterization of thin air-sea interfacial layer (sea surface microlayer: SML) and launching large stratospheric air sampling balloons were carried out on-board R/V Hakuho Maru starting from 29 January for 39 days. Biogeochemically important trace/long-lived gases such as CO2, dimethyl sulfide (DMS), and some volatile organic carbons (VOCs) both in the atmosphere and seawater were continuously monitored and their air-sea fluxes were also observed using gradient and eddy-covariance techniques. Atmospheric gas measurement of CO2, CH4, N2O, SF6, CO, H2, Ar and isotopic composition of selected gases were further extended to stratospheric air by balloon-born sampling in addition to a vertical profiling of O3, CO2, and H2O with sounding sondes. Physical and chemical properties of marine atmospheric aerosols such as size distribution, total and cloud condensation nuclei concentrations, particle morphology, bulk and single particle chemical composition were also continuously determined to find out potential link between biogenic VOCs emitted from the ocean and aerosol composition. Biological and biogeochemical characterizations of marine microorganisms, suspended particulate matter, dissolved nutrients in seawater and SML were also conducted. In the presentation, brief overview of the research activities during the EqPOS cruise and biogeochemical linkage atmosphere and ocean via atmospheric and oceanic gaseous and particulate matter from ocean surface to stratosphere observed during the cruise and unique importance of SML would be presented.

Primary spectrum and composition with IceCube/IceTop

NASA Astrophysics Data System (ADS)

Gaisser, Thomas K.; IceCube Collaboration

2016-10-01

IceCube, with its surface array IceTop, detects three different components of extensive air showers: the total signal at the surface, GeV muons in the periphery of the showers and TeV muons in the deep array of IceCube. The spectrum is measured with high resolution from the knee to the ankle with IceTop. Composition and spectrum are extracted from events seen in coincidence by the surface array and the deep array of IceCube. The muon lateral distribution at the surface is obtained from the data and used to provide a measurement of the muon density at 600 meters from the shower core up to 30 PeV. Results are compared to measurements from other experiments to obtain an overview of the spectrum and composition over an extended range of energy. Consistency of the surface muon measurements with hadronic interaction models and with measurements at higher energy is discussed.

Measurements of Erosion Wear Volume Loss on Bare and Coated Polymer Matrix Composites

NASA Technical Reports Server (NTRS)

Miyoshi, Kazuhisa; Sutter, James K.; Mondry, Richard J.; Bowman, Cheryl; Ma, Kong; Horan, Richard A.; Naik, Subhash K.; Cupp, Randall J.

2003-01-01

An investigation was conducted to examine the erosion behavior of uncoated and coated polymer matrix composite (PMC) specimens subjected to solid particle impingement using air jets. The PMCs were carbon-Kevlar (DuPont, Wilmington, DE) fiber-epoxy resin composites with a temperature capability up to 393 K (248 F). Tungsten carbide-cobalt (WC-Co) was the primary topcoat constituent. Bondcoats were applied to the PMC substrates to improve coating adhesion; then, erosion testing was performed at the University of Cincinnati. All erosion tests were conducted with Arizona road-dust (ARD), impinging at angles of 20 and 90 on both uncoated and two-layer coated PMCs at a velocity of 229 m/s and at a temperature of 366 K (200 F). ARD contains primarily 10-m aluminum oxide powders. Vertically scanning interference microscopy (noncontact, optical profilometry) was used to evaluate surface characteristics, such as erosion wear volume loss and depth, surface topography, and surface roughness. The results indicate that noncontact, optical interferometry can be used to make an accurate determination of the erosion wear volume loss of PMCs with multilayered structures while preserving the specimens. The two-layered (WC-Co topcoat and metal bondcoat) coatings on PMCs remarkably reduced the erosion volume loss by a factor of approximately 10. The tenfold increase in erosion resistance will contribute to longer PMC component lives, lower air friction, reduced related breakdowns, decreased maintenance costs, and increased PMC reliability. The decrease in the surface roughness of the coated vanes will lead to lower air friction and will subsequently reduce energy consumption. Eventually, the coatings could lead to overall economic savings.

Polycyclic aromatic hydrocarbons in ambient air, surface soil and wheat grain near a large steel-smelting manufacturer in northern China.

PubMed

Liu, Weijian; Wang, Yilong; Chen, Yuanchen; Tao, Shu; Liu, Wenxin

2017-07-01

The total concentrations and component profiles of polycyclic aromatic hydrocarbons (PAHs) in ambient air, surface soil and wheat grain collected from wheat fields near a large steel-smelting manufacturer in Northern China were determined. Based on the specific isomeric ratios of paired species in ambient air, principle component analysis and multivariate linear regression, the main emission source of local PAHs was identified as a mixture of industrial and domestic coal combustion, biomass burning and traffic exhaust. The total organic carbon (TOC) fraction was considerably correlated with the total and individual PAH concentrations in surface soil. The total concentrations of PAHs in wheat grain were relatively low, with dominant low molecular weight constituents, and the compositional profile was more similar to that in ambient air than in topsoil. Combined with more significant results from partial correlation and linear regression models, the contribution from air PAHs to grain PAHs may be greater than that from soil PAHs. Copyright © 2016. Published by Elsevier B.V.

Prediction of aerodynamic heating and pressures on Shuttle Entry Air Data System (SEADS) nose cap and comparison with STS-61C flight data

NASA Technical Reports Server (NTRS)

Ting, Paul C.; Rochelle, William C.; Curry, Donald M.

1988-01-01

Results are presented from predictions of aerothermodynamic heating rates, temperatures, and pressures on the surface of the Shuttle Entry Air Data System (SEADS) nosecap during Orbiter reentry. These results are compared with data obtained by the first actual flight of the SEADS system aboard STS-61C. The data also used to predict heating rates and surface temperatures for a hypothetical Transatlantic Abort Landing entry trajectory, whose analysis involved ascertaining the increases in heating rate as the airstream flowed across regions of the lower surface catalycity carbon/carbon composite to the higher surface catalycity columbium pressure ports.

Extraction of CO2 from air samples for isotopic analysis and limits to ultra high precision delta18O determination in CO2 gas.

PubMed

Werner, R A; Rothe, M; Brand, W A

2001-01-01

The determination of delta18O values in CO2 at a precision level of +/-0.02 per thousand (delta-notation) has always been a challenging, if not impossible, analytical task. Here, we demonstrate that beyond the usually assumed major cause of uncertainty - water contamination - there are other, hitherto underestimated sources of contamination and processes which can alter the oxygen isotope composition of CO2. Active surfaces in the preparation line with which CO2 comes into contact, as well as traces of air in the sample, can alter the apparent delta18O value both temporarily and permanently. We investigated the effects of different surface materials including electropolished stainless steel, Duran glass, gold and quartz, the latter both untreated and silanized. CO2 frozen with liquid nitrogen showed a transient alteration of the 18O/16O ratio on all surfaces tested. The time to recover from the alteration as well as the size of the alteration varied with surface type. Quartz that had been ultrasonically cleaned for several hours with high purity water (0.05 microS) exhibited the smallest effect on the measured oxygen isotopic composition of CO2 before and after freezing. However, quartz proved to be mechanically unstable with time when subjected to repeated large temperature changes during operation. After several days of operation the gas released from the freezing step contained progressively increasing trace amounts of O2 probably originating from inclusions within the quartz, which precludes the use of quartz for cryogenically trapping CO2. Stainless steel or gold proved to be suitable materials after proper pre-treatment. To ensure a high trapping efficiency of CO2 from a flow of gas, a cold trap design was chosen comprising a thin wall 1/4" outer tube and a 1/8" inner tube, made respectively from electropolished stainless steel and gold. Due to a considerable 18O specific isotope effect during the release of CO2 from the cold surface, the thawing time had to be as long as 20 min for high precision delta18O measurements. The presence of traces of air in almost all CO2 gases that we analyzed was another major source of error. Nitrogen and oxygen in the ion source of our mass spectrometer (MAT 252, Finnigan MAT, Bremen, Germany) give rise to the production of NO2 at the hot tungsten filament. NO2+ is isobaric with C16O18O+ (m/z 46) and interferes with the delta18O measurement. Trace amounts of air are present in CO2 extracted cryogenically from air at -196 degrees C. This air, trapped at the cold surface, cannot be pumped away quantitatively. The amount of air present depends on the surface structure and, hence, the alteration of the measured delta18O value varies with the surface conditions. For automated high precision measurement of the isotopic composition of CO2 of air samples stored in glass flasks an extraction interface ('BGC-AirTrap') was developed which allows 18 analyses (including standards) per day to be made. For our reference CO2-in-air, stored in high pressure cylinders, the long term (>9 months) single sample precision was 0.012 per thousand for delta13C and 0.019 per thousand for delta18O. Copyright 2001 John Wiley & Sons, Ltd.

INTEGRATED AND FIBER OPTICS: Unidirectional coupling of radiation out of a composite dielectric waveguide

NASA Astrophysics Data System (ADS)

Avrutskiĭ, I. A.; Sychugov, V. A.; Tishchenko, A. V.; Svakhin, A. S.

1989-02-01

An analysis is made of the emission of light from a composite system representing a thin film on the surface of a corrugated diffused waveguide. Expressions are obtained for the radiative light losses in this waveguide. There is no emission of light into the substrate for certain relationships between the amplitudes and phases of the corrugations at the interfaces between the film and the adjoining medium and between the film and the waveguide. Numerical estimates of the losses are obtained for a case of practical importance, which is a corrugated diffused waveguide in glass with a film of Nb2O5 on the surface. A report is given of an experiment in which a grating was formed for coupling radiation out of a composite Cs+-diffused waveguide coated by a film of Nb2O5, which was capable of preferential (80%) emission of radiation into air, and in the presence of an immersion liquid ensured practically unidirectional coupling out of radiation into air.

Study of variation in surface morphology, chemical composition, crystallinity and hardness of laser irradiated silver in dry and wet environments

NASA Astrophysics Data System (ADS)

Ali, Nisar; Bashir, Shazia; Umm-i-Kalsoom; Begum, Narjis; Hussain, Tousif

2017-07-01

Variation in surface morphology, chemical composition, crystallinity and hardness of laser irradiated silver in dry and wet ambient environments has been investigated. For this purpose, the silver targets were exposed for various number of laser pulses in ambient environment of air, ethanol and de-ionized water for various number of laser pulses i.e. 500, 1000, 1500 and 2000. Scanning Electron Microscope (SEM) was employed to investigate the surface morphology of irradiated silver. SEM analysis reveals significant surface variations for both dry and wet ambient environments. For lower number of pulses, in air environment significant mass removal is observed but in case of ethanol no significant change in surface morphology is observed. In case of de-ionized water small sized cavities are observed with formation of protrusions with spherical top ends. For higher number of laser pulses, refilling of cavities by shock liquefied material, globules and protrusions are observed in case of dry ablation. For ablation in ethanol porous and coarse periodic ripples are observed whereas, for de-ionized water increasing density of protrusions is observed for higher number of pulses. EDS analysis exhibits the variation in chemical composition along with an enhanced diffusion of oxygen under both ambient conditions. The crystal structure of the exposed targets were explored by X-ray Diffraction (XRD) technique. XRD results support the EDS results. Formation of Ag2O in case of air and ethanol whereas, Ag2O and Ag3O in case of de-ionized water confirms the diffusion of oxygen into the silver surface after irradiation. Vickers Hardness tester was employed to measure the hardness of laser treated targets. Enhanced hardness is observed after irradiation in both dry and wet ambient environments. Initial decrease and then increase in hardness is observed with increase in number of laser pulses in air environment. In case of ethanol, increase in number of laser pulses results in continuous decrease in hardness. Whereas, in case of de-ionized water hardness increases with increase in number of laser pulses.

Treatment of poly(ethylene terephthalate) foils by atmospheric pressure air dielectric barrier discharge and its influence on cell growth

NASA Astrophysics Data System (ADS)

Kuzminova, Anna; Vandrovcová, Marta; Shelemin, Artem; Kylián, Ondřej; Choukourov, Andrei; Hanuš, Jan; Bačáková, Lucie; Slavínská, Danka; Biederman, Hynek

2015-12-01

In this contribution an effect of dielectric barrier discharge (DBD) sustained in air at atmospheric pressure on surface properties of poly(ethylene terephthalate) (PET) foils is studied. It is found that exposure of PET to DBD plasma leads to rapid changes of surface chemical composition, wettability, surface morphology as well as mechanical properties of PET surface. In addition, based on biological tests that were performed using two cell types (Saos-2 human osteoblast-like cells and HUVEC human umbilical vein endothelial cells), it may be concluded that DBD plasma treatment positively influences cell growth on PET. This effect was found to be connected predominantly with increased surface energy and oxygen content of the surface of treated PET foils.

Surface interactions, thermodynamics and topography of binary monolayers of Insulin with dipalmitoylphosphatidylcholine and 1-palmitoyl-2-oleoylphosphatidylcholine at the air/water interface.

PubMed

Grasso, E J; Oliveira, R G; Maggio, B

2016-02-15

The molecular packing, thermodynamics and surface topography of binary Langmuir monolayers of Insulin and DPPC (dipalmitoylphosphatidylcholine) or POCP (1-palmitoyl-2-oleoylphosphatidylcholine) at the air/water interface on Zn(2+) containing solutions were studied. Miscibility and interactions were ascertained by the variation of surface pressure-mean molecular area isotherms, surface compressional modulus and surface (dipole) potential with the film composition. Brewster Angle Microscopy was used to visualize the surface topography of the monolayers. Below 20mN/m Insulin forms stable homogenous films with DPPC and POPC at all mole fractions studied (except for films with XINS=0.05 at 10mN/m where domain coexistence was observed). Above 20mN/m, a segregation process between mixed phases occurred in all monolayers without squeezing out of individual components. Under compression the films exhibit formation of a viscoelastic or kinetically trapped organization leading to considerable composition-dependent hysteresis under expansion that occurs with entropic-enthalpic compensation. The spontaneously unfavorable interactions of Insulin with DPPC are driven by favorable enthalpy that is overcome by unfavorable entropic ordering; in films with POPC both the enthalpic and entropic effects are unfavorable. The surface topography reveals domain coexistence at relatively high pressure showing a striped appearance. The interactions of Insulin with two major membrane phospholipids induces composition-dependent and long-range changes of the surface organization that ought to be considered in the context of the information-transducing capabilities of the hormone for cell functioning. Copyright © 2015 Elsevier Inc. All rights reserved.

Composite Membrane with Underwater-Oleophobic Surface for Anti-Oil-Fouling Membrane Distillation.

PubMed

Wang, Zhangxin; Hou, Deyin; Lin, Shihong

2016-04-05

In this study, we fabricated a composite membrane for membrane distillation (MD) by modifying a commercial hydrophobic polyvinylidene fluoride (PVDF) membrane with a nanocomposite coating comprising silica nanoparticles, chitosan hydrogel and fluoro-polymer. The composite membrane exhibits asymmetric wettability, with the modified surface being in-air hydrophilic and underwater oleophobic, and the unmodified surface remaining hydrophobic. By comparing the performance of the composite membrane and the pristine PVDF membrane in direct contact MD experiments using a saline emulsion with 1000 ppm crude oil (in water), we showed that the fabricated composite membrane was significantly more resistant to oil fouling compared to the pristine hydrophobic PVDF membrane. Force spectroscopy was conducted for the interaction between an oil droplet and the membrane surface using a force tensiometer. The difference between the composite membrane and the pristine PVDF membrane in their interaction with an oil droplet served to explain the difference in the fouling propensities between these two membranes observed in MD experiments. The results from this study suggest that underwater oleophobic coating can effectively mitigate oil fouling in MD operations, and that the fabricated composite membrane with asymmetric wettability can enable MD to desalinate hypersaline wastewater with high concentrations of hydrophobic contaminants.

Variations of the aerosol concentration and chemical composition over the arid steppe zone of Southern Russia in summer

NASA Astrophysics Data System (ADS)

Artamonova, M. S.; Gubanova, D. P.; Iordanskii, M. A.; Lebedev, V. A.; Maksimenkov, L. O.; Minashkin, V. M.; Obvintsev, Y. I.; Chketiani, O. G.

2016-12-01

Variations in the surface aerosol over the arid steppe zone of Southern Russia have been measured. The parameters of atmospheric aerosol (mass concentration, both dispersed and elemental compositions) and meteorological parameters were measured in Tsimlaynsk raion (Rostov oblast). The chemical composition of aerosol particles in the atmospheric surface layer has been determined, and the coefficients of enrichment of elements with respect to clarkes in the Earth's crust have been calculated. It is shown that, in summer, arid aerosols are transported from both alkaline and sandy soils of Kalmykia to the air basin over the observation zone. Aerosol particles in the surface air layer over this region have been found to contain the products of combustion of oil, coal, and ethylized fuel. These combustion products make a small contribution to the total mass concentration of atmospheric aerosol; however, they are most hazardous to the health of people because of their sizes and heavy-metal contents. A high concentration of submicron sulfur-containing aerosol particles of chemocondensation nature has been recorded. Sources of aerosol of both natural and anthropogenic origins in southern Russia are discussed.

Ultrasonic assessment of bonding integrity in foam-based hybrid composite materials

NASA Astrophysics Data System (ADS)

Chen, M. Y.; Ko, R. T.; Hoppe, W. C.; Blackshire, J. L.

2013-01-01

Ultrasonic assessment of the bonding integrity between a composite layer and a foam substrate in foam-based hybrid composite materials was explored. The challenges of this task are: (1) the foam has air-like acoustic impedance and (2) contact surface wave generation on polymer matrix composites (PMC) is not conventional. To meet these challenges, a novel wedge made of a low velocity material was developed. The results showed that the bonding condition in these composites can be identified by monitoring the amplitude of the ultrasonic signals received.

The Effect of Tow Shearing on Reinforcement Positional Fidelity in the Manufacture of a Continuous Fiber Reinforced Thermoplastic Matrix Composite via Pultrusion-Like Processing of Commingled Feedstock

NASA Astrophysics Data System (ADS)

Warlick, Kent M.

While the addition of short fiber to 3D printed articles has increased structural performance, ultimate gains will only be realized through the introduction of continuous reinforcement placed along pre-planned load paths. Most additive manufacturing research focusing on the addition of continuous reinforcement has revolved around utilization of a prefrabricated composite filament or a fiber and matrix mixed within a hot end prior to deposition on a printing surface such that conventional extrusion based FDM can be applied. Although stronger 3D printed parts can be made in this manner, high quality homogenous composites are not possible due to fiber dominated regions, matrix dominated regions, and voids present between adjacent filaments. Conventional composite manufacturing processes are much better at creating homogeneous composites; however, the layer by layer approach in which they are made is inhibiting the alignment of reinforcement with loads. Automated Fiber Placement techniques utilize in plane bending deformation of the tow to facilitate tow steering. Due to buckling fibers on the inner radius of curves, manufacturers recommend a minimum curvature for path placement with this technique. A method called continuous tow shearing has shown promise to enable the placement of tows in complex patterns without tow buckling, spreading, and separation inherent in conventional forms of automated reinforcement positioning. The current work employs fused deposition modeling hardware and the continuous tow shearing technique to manufacture high quality fiber reinforced composites with high positional fidelity, varying continuous reinforcement orientations within a layer, and plastic elements incorporated enabling the ultimate gains in structural performance possible. A mechanical system combining concepts of additive manufacturing with fiber placement via filament winding was developed. Paths with and without tension inherent in filament winding were analyzed through microscopy in order to examine best and worst case scenarios. High quality fiber reinforced composite materials, in terms of low void content, high fiber volume fractions and homogeneity in microstructure, were manufactured in both of these scenarios. In order to improve fidelity and quality in fiber path transition regions, a forced air cooling manifold was designed, printed, and implemented into the current system. To better understand the composite performance that results from varying pertinent manufacturing parameters, the effect of feed rate, hot end temperature, forced air cooling, and deposition surface (polypropylene and previously deposited glass polypropylene commingled tow) on interply performance, microstructure, and positional fidelity were analyzed. Interply performance, in terms of average maximum load and average peel strength, was quantified through a t-peel test of the bonding quality between two surfaces. With use of forced air cooling, minor decreases in average peel strength were present due to a reduction in tow deposition temperature which was found to be the variable most indicative of performance. Average maximum load was comparable between the forced air cooled and non-air cooled samples. Microstructure was evaluated through characterization of composite area, void content, and flash percentage. Low void contents mostly between five to seven percent were attained. Further reduction of this void content to two percent is possible through higher processing temperatures; however, reduced composite area, low average peel strength performance, and the presence of smoke during manufacturing implied thermal degradation of the polypropylene matrix occurred in these samples with higher processing temperatures. Positional fidelity was measured through calculations of shear angle, shift width, and error of a predefined path. While positional fidelity variation was low with a polypropylene deposition surface, forced air cooling is necessary to achieve fidelity on top of an already deposited tow surface as evident by the fifty-six percent reduction in error tolerance profile achieved. Lastly, proof of concept articles with unique fiber paths and neat plastic elements incorporated were produced to demonstrate fiber placement along pre-planned load paths and the ability to achieve greater structural efficiency through the use of less material. The results show that high positional fidelity and high quality composites can be produced through the use of the tow shearing technique implemented in the developed mechanical system. The implementation of forced air cooling was critical in achieving fidelity and quality in transition regions. Alignment of continuous reinforcement with pre-planned load paths was demonstrated in the proof of concept article with varying fiber orientations within a layer. Combining fused deposition modeling of plastic with the placement of continuous reinforcement enabled a honeycomb composite to be produced with higher specific properties than traditional composites. Thus, the current system demonstrated a greater capability of achieving ultimate gains in structural performance than previously possible.

Aerial Neutron Detection of Cosmic-Ray Interactions with the Earth's Surface

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

Richard Maurer

2008-09-18

We have demonstrated the ability to measure the neutron flux produced by the cosmic-ray interaction with nuclei in the ground surface using aerial neutron detection. High energy cosmic-rays (primarily muons with GeV energies) interact with the nuclei in the ground surface and produce energetic neutrons via spallation. At the air-surface interface, the neutrons produced by spallation will either scatter within the surface material, become thermalized and reabsorbed, or be emitted into the air. The mean free path of energetic neutrons in air can be hundreds of feet as opposed to a few feet in dense materials. As such, the fluxmore » of neutrons escaping into the air provides a measure of the surface nuclei composition. It has been demonstrated that this effect can be measured at long range using neutron detectors on low flying helicopters. Radiological survey measurements conducted at Government Wash in Las Vegas, Nevada, have shown that the neutron background from the cosmic-soil interactions is repeatable and directly correlated to the geological data. Government Wash has a very unique geology, spanning a wide variety of nuclide mixtures and formations. The results of the preliminary measurements are presented.« less

Surface measurements of upper tropospheric water vapor isotopic composition on the Chajnantor Plateau, Chile

NASA Astrophysics Data System (ADS)

Galewsky, Joseph; Rella, Christopher; Sharp, Zachary; Samuels, Kimberly; Ward, Dylan

2011-09-01

Simultaneous, real-time measurements of atmospheric water vapor mixing ratio and isotopic composition (δD and δ18O) were obtained using cavity ringdown spectroscopy on the arid Chajnantor Plateau in the subtropical Chilean Andes (elevation 5080 m or 550 hPa; latitude 23°S) during July and August 2010. The measurements show surface water vapor mixing ratio as low as 215 ppmv, δD values as low as -540‰, and δ18O values as low as -68‰, which are the lowest atmospheric water vapor δ values reported from Earth's surface. The results are consistent with previous measurements from the base of the tropical tropopause layer (TTL) and suggest large-scale subsidence of air masses from the upper troposphere to the Earth's surface. The range of measurements is consistent with condensation under conditions of ice supersaturation and mixing with moister air from the lower troposphere that has been processed through shallow convection. Diagnostics using reanalysis data show that the extreme aridity of the Chajnantor Plateau is controlled by condensation in the upper tropical troposphere.

ESCA studies of lunar surface chemistry. [Electron Spectroscopic Chemical Analysis

NASA Technical Reports Server (NTRS)

Housley, R. M.; Grant, R. W.

1975-01-01

We have used ESCA to compare the composition of the natural exterior surface in lunar fines samples with that of the interior surface exposed by crushing. Even though the exterior surfaces have been exposed to air a significant amount of Fe in them is reduced. In addition, Ca, Al, and Mg are strongly depleted in exterior surfaces relative to Si, Ti, and Fe. Preferential sputtering by the solar wind is a possible explanation for these changes.

Properties of the surface snow in Princess Elizabeth Land, East Antarctica - climate and non-climate dependent variability of the surface mass balance and stable water isotopic composition

NASA Astrophysics Data System (ADS)

Vladimirova, D.; Ekaykin, A.; Lipenkov, V.; Popov, S. V.; Petit, J. R.; Masson-Delmotte, V.

2017-12-01

Glaciological and meteorological observations conducted during the past four decades in Princess Elizabeth Land, East Antarctica, are compiled. The database is used to investigate spatial patterns of surface snow isotopic composition and surface mass balance, including detailed information near subglacial lake Vostok. We show diverse relationships between snow isotopic composition and surface temperature. In the most inland part (elevation 3200-3400 m a.s.l.), surface snow isotopic composition varies independently from surface temperature, and is closely related to the distance to the open water source (with a slope of 0.98±0.17 ‰ per 100 km). Surface mass balance values are higher along the ice sheet slope, and relatively evenly distributed inland. The minimum values of snow isotopic composition and surface mass balance are identified in an area XX km southwestward from Vostok station. The spatial distribution of deuterium excess delineates regions influenced by the Indian Ocean and Pacific Ocean air masses, with Vostok area being situated close to their boundary. Anomalously high deuterium excess values are observed near Dome A, suggesting high kinetic fractionation for its moisture source, or specifically high post-deposition artifacts. The dataset is available for further studies such as the assessment of skills of general circulation or regional atmospheric models, and the search for the oldest ice.

Oxygen inhibition layer of composite resins: effects of layer thickness and surface layer treatment on the interlayer bond strength.

PubMed

Bijelic-Donova, Jasmina; Garoushi, Sufyan; Lassila, Lippo V J; Vallittu, Pekka K

2015-02-01

An oxygen inhibition layer develops on surfaces exposed to air during polymerization of particulate filling composite. This study assessed the thickness of the oxygen inhibition layer of short-fiber-reinforced composite in comparison with conventional particulate filling composites. The effect of an oxygen inhibition layer on the shear bond strength of incrementally placed particulate filling composite layers was also evaluated. Four different restorative composites were selected: everX Posterior (a short-fiber-reinforced composite), Z250, SupremeXT, and Silorane. All composites were evaluated regarding the thickness of the oxygen inhibition layer and for shear bond strength. An equal amount of each composite was polymerized in air between two glass plates and the thickness of the oxygen inhibition layer was measured using a stereomicroscope. Cylindrical-shaped specimens were prepared for measurement of shear bond strength by placing incrementally two layers of the same composite material. Before applying the second composite layer, the first increment's bonding site was treated as follows: grinding with 1,000-grit silicon-carbide (SiC) abrasive paper, or treatment with ethanol or with water-spray. The inhibition depth was lowest (11.6 μm) for water-sprayed Silorane and greatest (22.9 μm) for the water-sprayed short-fiber-reinforced composite. The shear bond strength ranged from 5.8 MPa (ground Silorane) to 36.4 MPa (water-sprayed SupremeXT). The presence of an oxygen inhibition layer enhanced the interlayer shear bond strength of all investigated materials, but its absence resulted in cohesive and mixed failures only with the short-fiber-reinforced composite. Thus, more durable adhesion with short-fiber-reinforced composite is expected. © 2014 Eur J Oral Sci.

Durable superhydrophobic paper enabled by surface sizing of starch-based composite films

NASA Astrophysics Data System (ADS)

Chen, Gang; Zhu, Penghui; Kuang, Yudi; Liu, Yu; Lin, Donghan; Peng, Congxing; Wen, Zhicheng; Fang, Zhiqiang

2017-07-01

Superhydrophobic paper with remarkable durability is of considerable interest for its practical applications. In this study, a scalable, inexpensive, and universal surface sizing technique was implemented to prepare superhydrophobic paper with enhanced durability. A thin layer of starch-based composite, acting as a bio-binder, was first coated onto the paper surface by a sophisticated manufacturing technique called surface sizing, immediately followed by a spray coating of hexamethyl disilazane treated silica nanoparticles (HMDS-SiNPs) dispersed in ethanol on the surface of the wet starch-coated sheet, and the dual layers dried at the same time. Consequently, durable superhydrophobic paper with bi-layer structure was obtained after air drying. The as-prepared superhydrophobic paper not only exhibited a self-cleaning behavior, but also presented an enhanced durability against scratching, bending/deformation, as well as moisture. The universal surface sizing of starch-based composites may pave the way for the up-scaled and cost-effective production of durable superhydrophobic paper.

Effect of air-blowing variables on bond strength of all-in-one adhesives to bovine dentin.

PubMed

Shinkai, Koichi; Suzuki, Shiro; Katoh, Yoshiroh

2006-12-01

This study evaluated the effect of air-blowing variables on the microtensile bond strength (microTBS) of two all-in-one adhesives. A bonding agent was applied to the flat dentin surface of extracted bovine teeth, and the surface left undisturbed for 20 seconds. Gentle or intensive air-blowing was applied for five seconds, and the adhesive photopolymerized for 10 seconds. Resin composite paste was placed and cured after each bonding treatment. Specimens were subjected to microTBS test with a crosshead speed of 1.0 mm/min. Data were statistically analyzed using ANOVA, followed by Bonferroni post hoc test. When Clearfil tri-S Bond was bonded to dentin, the microTBS value of specimens applied with intensive air-blowing was significantly higher than that applied with gentle air-blowing (p<0.01). On the other hand, with Fluoro Bond Shake One, the microTBS value of specimens applied with intensive air-blowing was significantly lower than that applied with gentle air-blowing (p<0.01).

Modification of polycarbonate surface in oxidizing plasma

NASA Astrophysics Data System (ADS)

Ovtsyn, A. A.; Smirnov, S. A.; Shikova, T. G.; Kholodkov, I. V.

2017-11-01

The properties of the surface of the film polycarbonate Lexan 8010 were experimentally studied after treatment in a DC discharge plasma in oxygen and air at pressures of 50-300 Pa and a discharge current of 80 mA. The contact angles of wetting and surface energies are measured. The topography of the surface was investigated by atomic force microscopy. The chemical composition of the surface was determined from the FT-IR spectroscopy data in the variant of total internal reflection, as well as X-ray photoelectron spectroscopy. Treatment in the oxidizing plasma leads to a change in morphology (average roughness increases), an increase in the surface energy, and the concentration of oxygen-containing groups (hydroxyl groups, carbonyl groups in ketones or aldehydes and in oxyketones) on the surface of the polymer. Possible reasons for the difference in surface properties of polymer under the action of oxygen and air plasma on it are discussed.

Data from a Thick Unsaturated Zone Underlying Two Artificial Recharge Sites along Oro Grande Wash in the Western Part of the Mojave Desert, near Victorville, San Bernardino County, California, 2001-2006

USGS Publications Warehouse

Clark, Dennis A.; Izbicki, John A.; Johnson, Russell D.; Land, Michael

2009-01-01

This report presents data on the physical and hydraulic properties of unsaturated alluvial deposits and on the chemical and isotopic composition of water collected at two recharge sites in the western part of the Mojave Desert, near Victorville, California, from 2001 to 2006. Unsaturated-zone monitoring sites were installed adjacent to the two recharge ponds using the ODEX air-hammer and air rotary method to depths of about 460 feet and 269 feet below land surface. Each of the two unsaturated-zone monitoring sites included a water-table well, matric-potential sensors, and suction-cup lysimeters installed in a single bore hole. Drilling procedures, lithologic and geophysical data, and site construction and instrumentation are described. Core material was analyzed for water content, bulk density, water potential, particle size, and water retention. The chemical composition of leachate from almost 400 samples of cores and cuttings was determined. Water from suction-cup lysimeters also was analyzed for chemical and isotopic composition. In addition, data on the chemical and isotopic composition of groundwater from the two water-table wells are reported along with chemical and isotopic composition of the surface water in the recharge ponds.

Hybrid response surface methodology-artificial neural network optimization of drying process of banana slices in a forced convective dryer.

PubMed

Taheri-Garavand, Amin; Karimi, Fatemeh; Karimi, Mahmoud; Lotfi, Valiullah; Khoobbakht, Golmohammad

2018-06-01

The aim of the study is to fit models for predicting surfaces using the response surface methodology and the artificial neural network to optimize for obtaining the maximum acceptability using desirability functions methodology in a hot air drying process of banana slices. The drying air temperature, air velocity, and drying time were chosen as independent factors and moisture content, drying rate, energy efficiency, and exergy efficiency were dependent variables or responses in the mentioned drying process. A rotatable central composite design as an adequate method was used to develop models for the responses in the response surface methodology. Moreover, isoresponse contour plots were useful to predict the results by performing only a limited set of experiments. The optimum operating conditions obtained from the artificial neural network models were moisture content 0.14 g/g, drying rate 1.03 g water/g h, energy efficiency 0.61, and exergy efficiency 0.91, when the air temperature, air velocity, and drying time values were equal to -0.42 (74.2 ℃), 1.00 (1.50 m/s), and -0.17 (2.50 h) in the coded units, respectively.

Characterization of Conventional and High-Translucency Y-TZP Dental Ceramics Submitted to Air Abrasion.

PubMed

Tostes, Bhenya Ottoni; Guimarães, Renato Bastos; Noronha-Filho, Jaime Dutra; Botelho, Glauco Dos Santos; Guimarães, José Guilherme Antunes; Silva, Eduardo Moreira da

2017-01-01

This study evaluated the effect of air-abrasion on t®m phase transformation, roughness, topography and the elemental composition of three Y-TZP (Yttria-stabilized tetragonal zirconia polycrystal) dental ceramics: two conventional (Lava Frame and IPS ZirCad) and one with high-translucency (Lava Plus). Plates obtained from sintered blocks of each ceramic were divided into four groups: AS (as-sintered); 30 (air-abrasion with 30 mm Si-coated Al2O3 particles); 50 (air-abrasion with 50 mm Al2O3 particles) and 150 (air-abrasion with 150 mm Al2O3 particles). After the treatments, the plates were submitted to X-ray diffractometry; 3-D profilometry and SEM/EDS. The AS surfaces were composed of Zr and t phases. All treatments produced t®m phase transformation in the ceramics. The diameter of air-abrasion particles influenced the roughness (150>50>30>AS) and the topography. SEM analysis showed that the three treatments produced groove-shaped microretentions on the ceramic surfaces, which increased with the diameter of air-abrasion particles. EDS showed a decrease in Zr content along with the emergence of O and Al elements after air-abrasion. Presence of Si was also detected on the plates air-abraded with 30 mm Si-coated Al2O3 particles. It was concluded that irrespective of the type and diameter of the particles, air-abrasion produced t®m phase transformation, increased the roughness and changed the elemental composition of the three Y-TZP dental ceramics. Lava Plus also behaved similarly to the conventional Y-TZP ceramics, indicating that this high translucency ceramic could be more suitable to build monolithic ceramic restorations in the aesthetic restorative dentistry field.

Cosmic Ray Studies with IceCube

NASA Astrophysics Data System (ADS)

Gonzalez, Javier

In this contribution we will give an overview of the cosmic ray studies conducted within the IceCube collaboration. The IceCube detector in the geographical south pole can be used to measure various characteristics of the extensive air showers induced by high energy cosmic rays. With IceTop, the surface component of the detector, we detect the electromagnetic and muon components of the air showers, while with the deep detector we detect the high energy muons. We have measured the energy spectrum of cosmic ray primaries in the range between 1.58PeV and 1.26 EeV. A combined analysis of the high energy muon bundles in the ice and the air shower footprint in IceTop provides a measure of primary composition. We will also discuss how the sensitivity to low energy muons in the air showers has the potential to produce additional measures of primary composition.

Air plasma spray processing and electrochemical characterization of Cu-SDC coatings for use in solid oxide fuel cell anodes

NASA Astrophysics Data System (ADS)

Benoved, Nir; Kesler, O.

Air plasma spraying has been used to produce porous composite anodes based on Ce 0.8Sm 0.2O 1.9 (SDC) and Cu for use in solid oxide fuel cells (SOFCs). Preliminarily, a range of plasma conditions has been examined for the production of composite coatings from pre-mixed SDC and CuO powders. Plasma gas compositions were varied to obtain a range of plasma temperatures. After reduction in H 2, coatings were characterized for composition and microstructure using EDX and SEM. As a result of these tests, symmetrical sintered electrolyte-supported anode-anode cells were fabricated by air plasma spraying of the anodes, followed by in situ reduction of the CuO to Cu. Full cells deposited on SS430 porous substrates were then produced in one integrated process. Fine CuO and SDC powders have been used to produce homogeneously mixed anode coatings with higher surface area microstructures, resulting in area-specific polarization resistances of 4.8 Ω cm 2 in impedance tests in hydrogen at 712 °C.

Telescope Array UHECR composition measurement via stereoscopic fluorescence observation

NASA Astrophysics Data System (ADS)

Stroman, Thomas; Bergman, Douglas; Telescope Array Collaboration

2016-03-01

When entering Earth's atmosphere at ultra-high energies, cosmic rays (UHECRs) produce extensive air showers whose longitudinal development is influenced by the incident primary particle's mass. Each longitudinal shower profile reaches its maximum particle count at an atmospheric slant depth Xmax, and the distributions of observed Xmax values can be compared to those predicted by detailed simulations of the air-shower physics and the detector; accurately simulated compositions that most closely resemble that found in nature will produce the best agreement between predicted and observed Xmax distributions. This is the basis of composition measurement at the Telescope Array experiment, the largest and most sensitive UHECR detector in the northern hemisphere. At the perimeter of a large surface-detector array are three fluorescence telescope stations, whose overlapping apertures enable high-precision reconstruction of Xmax from stereoscopic observation of air-shower longitudinal profiles. We present the distribution of Xmax observed during eight years of operation, and from comparisons with several simulated combinations of composition and high-energy hadronic physics, we show that a low primary mass is favored at E >10 18 . 2 eV.

High-Temperature, Dual-Atmosphere Corrosion of Solid-Oxide Fuel Cell Interconnects

NASA Astrophysics Data System (ADS)

Gannon, Paul; Amendola, Roberta

2012-12-01

High-temperature corrosion of ferritic stainless steel (FSS) surfaces can be accelerated and anomalous when it is simultaneously subjected to different gaseous environments, e.g., when separating fuel (hydrogen) and oxidant (air) streams, in comparison with single-atmosphere exposures, e.g., air only. This so-called "dual-atmosphere" exposure is realized in many energy-conversion systems including turbines, boilers, gasifiers, heat exchangers, and particularly in intermediate temperature (600-800°C) planar solid-oxide fuel cell (SOFC) stacks. It is generally accepted that hydrogen transport through the FSS (plate or tube) and its subsequent integration into the growing air-side surface oxide layer can promote accelerated and anomalous corrosion—relative to single-atmosphere exposure—via defect chemistry changes, such as increased cation vacancy concentrations, decreased oxygen activity, and steam formation within the growing surface oxide layers. Establishment of a continuous and dense surface oxide layer on the fuel side of the FSS can inhibit hydrogen transport and the associated effects on the air side. Minor differences in FSS composition, microstructure, and surface conditions can all have dramatic influences on dual-atmosphere corrosion behaviors. This article reviews high-temperature, dual-atmosphere corrosion phenomena and discusses implications for SOFC stacks, related applications, and future research.

Thermal Shock Properties of a 2D-C/SiC Composite Prepared by Chemical Vapor Infiltration

NASA Astrophysics Data System (ADS)

Zhang, Chengyu; Wang, Xuanwei; Wang, Bo; Liu, Yongsheng; Han, Dong; Qiao, Shengru; Guo, Yong

2013-06-01

The thermal shock properties of a two-dimensional carbon fiber-reinforced silicon carbide composite with a multilayered self-healing coating (2D-C/SiC) were investigated in air. The composite was prepared by low-pressure chemical vapor infiltration. 2D-C/SiC specimens were thermally shocked for different cycles between 900 and 300 °C. The thermal shock resistance was characterized by residual tensile properties and mass variation. The change of the surface morphology and microstructural evolution of the composite were examined by a scanning electron microscope. In addition, the phase evolution on the surfaces was identified using an X-ray diffractometer. It is found that the composite retains its tensile strength within 20 thermal shock cycles. However, the modulus of 2D-C/SiC decreases gradually with increasing thermal shock cycles. Extensive pullout of fibers on the fractured surface and peeling off of the coating suggest that the damage caused by the thermal shock involves weakening of the bonding strength of coating/composite and fiber/matrix. In addition, the carbon fibers in the near-surface zone were oxidized through the matrix cracks, and the fiber/matrix interfaces delaminated when the composite was subjected to a larger number of thermal shock cycles.

Fabrication of self-organized conical microstructures by excimer laser irradiation of cyanoacrylate-carbon nanotube composites

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

Liu Yuming; Liu Liang; Fan Shoushan

2005-02-07

Self-organized conical microstructures are fabricated by 308 nm XeCl excimer laser irradiation of cyanoacrylate-carbon nanotube composites in air. The morphology of the surface on the composite films is studied, varying the total number and fluence of the applied laser pulses. A simple mechanism of the fabrication based on the evaporation of cyanoacrylate and the burning of carbon nanotubes is proposed. The conical peak structures of cyanoacrylate-carbon nanotube composite films show good field-emission properties. Similar structures are also observed on carbon nanotube arrays.

Strength improvement and purification of Yb 2Si 2O 7-SiC nanocomposites by surface oxidation treatment

DOE PAGES

Nguyen, Son T.; Nakayama, Tadachika; Suematsu, Hisayuki; ...

2017-04-03

A two-step processing was developed to prepare Yb 2Si 2O 7-SiC nanocomposites. Yb 2Si 2O 7-Yb 2SiO 5-SiC composites were first fabricated by a solid state reaction/hot-pressing method. The composites were then annealed at 1250°C in air for 2 h to activate the oxidation of SiC, which effectively transformed the Yb 2SiO 5 into Yb 2Si 2O 7. The surface cracks purposely induced can be fully healed during the oxidation treatment. The treated composites have improved flexural strength compared to their pristine composites. As a result, the mechanism for crack-healing and silicate transformation have been proposed and discussed in detail.

Geostationary Coastal and Air Pollution Events (GEO-CAPE) Sensitivity Analysis Experiment

NASA Technical Reports Server (NTRS)

Lee, Meemong; Bowman, Kevin

2014-01-01

Geostationary Coastal and Air pollution Events (GEO-CAPE) is a NASA decadal survey mission to be designed to provide surface reflectance at high spectral, spatial, and temporal resolutions from a geostationary orbit necessary for studying regional-scale air quality issues and their impact on global atmospheric composition processes. GEO-CAPE's Atmospheric Science Questions explore the influence of both gases and particles on air quality, atmospheric composition, and climate. The objective of the GEO-CAPE Observing System Simulation Experiment (OSSE) is to analyze the sensitivity of ozone to the global and regional NOx emissions and improve the science impact of GEO-CAPE with respect to the global air quality. The GEO-CAPE OSSE team at Jet propulsion Laboratory has developed a comprehensive OSSE framework that can perform adjoint-sensitivity analysis for a wide range of observation scenarios and measurement qualities. This report discusses the OSSE framework and presents the sensitivity analysis results obtained from the GEO-CAPE OSSE framework for seven observation scenarios and three instrument systems.

Ozone changes under solar geoengineering: implications for UV exposure and air quality

NASA Astrophysics Data System (ADS)

Nowack, P. J.; Abraham, N. L.; Braesicke, P.; Pyle, J. A.

2015-11-01

Various forms of geoengineering have been proposed to counter anthropogenic climate change. Methods which aim to modify the Earth's energy balance by reducing insolation are often subsumed under the term Solar Radiation Management (SRM). Here, we present results of a standard SRM modelling experiment in which the incoming solar irradiance is reduced to offset the global mean warming induced by a quadrupling of atmospheric carbon dioxide. For the first time in an atmosphere-ocean coupled climate model, we include atmospheric composition feedbacks such as ozone changes under this scenario. Including the composition changes, we find large reductions in surface UV-B irradiance, with implications for vitamin D production, and increases in surface ozone concentrations, both of which could be important for human health. We highlight that both tropospheric and stratospheric ozone changes should be considered in the assessment of any SRM scheme, due to their important roles in regulating UV exposure and air quality.

Volatile compounds and phenolic composition of virgin olive oil: optimization of temperature and time of exposure of olive pastes to air contact during the mechanical extraction process.

PubMed

Servili, Maurizio; Selvaggini, Roberto; Taticchi, Agnese; Esposto, Sonia; Montedoro, GianFrancesco

2003-12-31

The operative conditions of malaxation such as temperature and time of exposure of olive pastes to air contact (TEOPAC) affect volatile and phenolic composition of virgin olive oil (VOO) and, as a consequence, its sensory and healthy qualities. In this paper, optimal temperature and TEOPAC during malaxation were studied, in lab scale, in two Italian cultivars using phenolic compounds, volatile composition, and sensory analysis of VOO as markers. The optimal temperature and TEOPAC, selected by response surface modeling,were cultivar-dependent being 30 min of TEOPAC at the lowest temperature investigated (22 degrees C) and 0 min of TEOPAC at 26 degrees C for Frantoio and Moraiolo cultivars, respectively.

Uptake of PAHs by cabbage root and leaf in vegetable plots near a large coking manufacturer and associations with PAHs in cabbage core.

PubMed

Xiong, GuanNan; Zhang, YunHui; Duan, YongHong; Cai, ChuanYang; Wang, Xin; Li, JingYa; Tao, Shu; Liu, WenXin

2017-08-01

Samples of ambient air (including gaseous and particulate phases), dust fall, surface soil, rhizosphere soil, core (edible part), outer leaf, and root of cabbage from eight vegetable plots near a large coking manufacturer were collected during the harvest period. Concentrations, compositions, and distributions of parent PAHs in different samples were determined. Our results indicated that most of the parent PAHs in air occurred in the gaseous phase, dominated by low molecular weight (LMW) species with two to three rings. Specific isomeric ratios and principal component analysis were employed to preliminarily identify the local sources of parent PAHs emitted. The main emission sources of parent PAHs could be apportioned as a mixture of coal combustion, coking production, and traffic tailing gas. PAH components with two to four rings were prevailing in dust fall, surface soil, and rhizosphere soil. Concentrations of PAHs in surface soil exhibited a significant positive correlation with topsoil TOC fractions. Compositional profiles in outer leaf and core of cabbage, dominated by LMW species, were similar to those in the local air. Overall, the order of parent PAH concentration in cabbage was outer leaf > root > core. Partial correlation analysis and multivariate linear stepwise regression revealed that PAH concentrations in cabbage core were closely associated with PAHs present both in root and in outer leaf, namely, affected by adsorption, then absorption, and translocation of PAHs from rhizosphere soil and ambient air, respectively.

Trends in NDVI and tundra community composition in the Arctic of NE Alaska between 1984 and 2009

Treesearch

Robert R. Pattison; Janet C. Jorgenson; Martha K. Raynolds; Jeffery M. Welker

2015-01-01

As Arctic ecosystems experience increases in surface air temperatures, plot-level analyses of tundra vegetation composition suggest that there are important changes occurring in tundra communities that are typified by increases in shrubs and declines in non-vascular species. At the same time analyses of NDVI indicate that the Arctic tundra is greening. Few studies have...

Chemical activation of commercial CNTs with simultaneous surface deposition of manganese oxide nano flakes for the creation of CNTs-graphene supported oxygen reduction ternary composite catalysts applied in air fuel cell

NASA Astrophysics Data System (ADS)

Sun, Ling; Liu, Danxian

2018-07-01

To elevate power performance is crucial for commercally potential metal air fuel cells. Non-precious metal oxide-based oxygen reduction catalytic electrode is much desirable. Rational combination with low-dimension nanomaterials are greatly expected as the supports. Herein, carbon nanotubes (CNTs)-graphene supported manganese oxides composite catalysts (CMnCs) were obtained through activating commercial CNTs, namely, immersing them in acidic KMnO4 solution at room condition. It avoided conventional hydrothermal process and template surfactants. CMnCs-based air cathodes were made via pilot manufacture technology and equipped in fuel cells. Through characterizations, CNTs was found structurally defective and their outer walls suffered cracking into graphene nano pieces during processing, which further enhanced oxygen reduction reaction (ORR). Nano sized manganese oxide flakes were simulataneously grown on the CNTs-graphene surfaces, identified as the manganite. The areal distribution was found closely related to the additive amount of KMnO4 with regard to CNTs, somewhat influencing catalytic performance. The ORR activities of these CMnCs exceeded raw CNTs and referred manganese catalysts under identical conditions, and also the CMnCs air fuel cells were capable of outputting ∼15% more power at 100 mA/cm2. This reseach provided an inspiring pilot evidence for updating air fuel cell power from economical carbon as well as industrialization.

Surface chemistry of rare-earth oxide surfaces at ambient conditions: reactions with water and hydrocarbons

NASA Astrophysics Data System (ADS)

Külah, Elçin; Marot, Laurent; Steiner, Roland; Romanyuk, Andriy; Jung, Thomas A.; Wäckerlin, Aneliia; Meyer, Ernst

2017-03-01

Rare-earth (RE) oxide surfaces are of significant importance for catalysis and were recently reported to possess intrinsic hydrophobicity. The surface chemistry of these oxides in the low temperature regime, however, remains to a large extent unexplored. The reactions occurring at RE surfaces at room temperature (RT) in real air environment, in particular, in presence of polycyclic aromatic hydrocarbons (PAHs), were not addressed until now. Discovering these reactions would shed light onto intermediate steps occurring in automotive exhaust catalysts before reaching the final high operational temperature and full conversion of organics. Here we first address physical properties of the RE oxide, nitride and fluoride surfaces modified by exposure to ambient air and then we report a room temperature reaction between PAH and RE oxide surfaces, exemplified by tetracene (C18H12) on a Gd2O3. Our study evidences a novel effect - oxidation of higher hydrocarbons at significantly lower temperatures (~300 K) than previously reported (>500 K). The evolution of the surface chemical composition of RE compounds in ambient air is investigated and correlated with the surface wetting. Our surprising results reveal the complex behavior of RE surfaces and motivate follow-up studies of reactions between PAH and catalytic surfaces at the single molecule level.

Physical characterization of a new composition of oxidized zirconium-2.5 wt% niobium produced using a two step process for biomedical applications

NASA Astrophysics Data System (ADS)

Pawar, V.; Weaver, C.; Jani, S.

2011-05-01

Zirconium and particularly Zr-2.5 wt%Nb (Zr2.5Nb) alloy are useful for engineering bearing applications because they can be oxidized in air to form a hard surface ceramic. Oxidized zirconium (OxZr) due to its abrasion resistant ceramic surface and biocompatible substrate alloy has been used as a bearing surface in total joint arthroplasty for several years. OxZr is characterized by hard zirconium oxide (oxide) formed on Zr2.5Nb using one step thermal oxidation carried out in air. Because the oxide is only at the surface, the bulk material behaves like a metal, with high toughness. The oxide, furthermore, exhibits high adhesion to the substrate because of an oxygen-rich diffusion hardened zone (DHZ) interposing between the oxide and the substrate. In this study, we demonstrate a two step process that forms a thicker DHZ and thus increased depth of hardening than that can be obtained using a one step oxidation process. The first step is thermal oxidation in air and the second step is a heat treatment in vacuum. The second step drives oxygen from the oxide formed in the first step deeper into the substrate to form a thicker DHZ. During the process only a portion of the oxide is dissolved. This new composition (DHOxZr) has approximately 4-6 μm oxide similar to that of OxZr. The nano-hardness of the oxide is similar but the DHZ is approximately 10 times thicker. The stoichiometry of the oxide is similar and a secondary phase rich in oxygen is present through the entire thickness. Due to the increased depth of hardening, the critical load required for the onset of oxide cracking is approximately 1.6 times more than that of the oxide of OxZr. This new composition has a potential to be used as a bearing surface in applications where greater depth of hardening is required.

3-D Surface Depression Profiling Using High Frequency Focused Air-Coupled Ultrasonic Pulses

NASA Technical Reports Server (NTRS)

Roth, Don J.; Kautz, Harold E.; Abel, Phillip B.; Whalen, Mike F.; Hendricks, J. Lynne; Bodis, James R.

1999-01-01

Surface topography is an important variable in the performance of many industrial components and is normally measured with diamond-tip profilometry over a small area or using optical scattering methods for larger area measurement. This article shows quantitative surface topography profiles as obtained using only high-frequency focused air-coupled ultrasonic pulses. The profiles were obtained using a profiling system developed by NASA Glenn Research Center and Sonix, Inc (via a formal cooperative agreement). (The air transducers are available as off-the-shelf items from several companies.) The method is simple and reproducible because it relies mainly on knowledge and constancy of the sound velocity through the air. The air transducer is scanned across the surface and sends pulses to the sample surface where they are reflected back from the surface along the same path as the incident wave. Time-of-flight images of the sample surface are acquired and converted to depth/surface profile images using the simple relation (d = V*t/2) between distance (d), time-of-flight (t), and the velocity of sound in air (V). The system has the ability to resolve surface depression variations as small as 25 microns, is useable over a 1.4 mm vertical depth range, and can profile large areas only limited by the scan limits of the particular ultrasonic system. (Best-case depth resolution is 0.25 microns which may be achievable with improved isolation from vibration and air currents.) The method using an optimized configuration is reasonably rapid and has all quantitative analysis facilities on-line including 2-D and 3-D visualization capability, extreme value filtering (for faulty data), and leveling capability. Air-coupled surface profilometry is applicable to plate-like and curved samples. In this article, results are shown for several proof-of-concept samples, plastic samples burned in microgravity on the STS-54 space shuttle mission, and a partially-coated cylindrical ceramic composite sample. Impressive results were obtained for all samples when compared with diamond-tip profiles and measurements from micrometers. The method is completely nondestructive, noninvasive, non-contact and does not require light-reflective surfaces.

Repair bond strength in aged methacrylate- and silorane-based composites.

PubMed

Bacchi, Atais; Consani, Rafael Leonardo; Sinhoreti, Mario Alexandre; Feitosa, Victor Pinheiro; Cavalcante, Larissa Maria; Pfeifer, Carmem Silva; Schneider, Luis Felipe

2013-10-01

To evaluate the tensile bond strength at repaired interfaces of aged dental composites, either dimethacrylate- or silorane-based, when subjected to different surface treatments. The composites used were Filtek P60 (methacrylate-based, 3M ESPE) and Filtek P90 (silorane-based, 3M ESPE), of which 50 slabs were stored for 6 months at 37°C. The surface of adhesion was abraded with a 600-grit silicone paper and the slabs repaired with the respective composite, according to the following surface treatment protocols: G1: no treatment; G2: adhesive application; G3: silane + adhesive; G4: sandblasting (Al2O3) + adhesive; G5: sandblasting (Al2O3) + silane + adhesive. After 24-h storage in distilled water at 37°C, tensile bond strength (TBS) was determined in a universal testing machine (Instron 4411) at a crosshead speed of 0.5 mm/min. The original data were submitted to two-way ANOVA and Tukey's test (α = 5%). The methacrylate-based composite presented a statistically significantly higher repair potential than did the silorane-based resin (p = 0.0002). Of the surface treatments for the silorane-based composite, aluminum-oxide air abrasion and adhesive (18.5 ± 3.3MPa) provided higher bond strength than only adhesive application or the control group without surface treatment. For Filtek P60, the control without treatment presented lower repair strength than all other groups with surface treatments, which were statistically similar to each other. The interaction between the factors resin composite and surface treatment was significant (p = 0.002). For aged silorane-based materials, repairs were considered successful after sandblasting (Al2O3) and adhesive application. For methacrylate resin, repair was successful with all surface treatments tested.

The effect of air thinning on dentin adhesive bond strength.

PubMed

Hilton, T J; Schwartz, R S

1995-01-01

The purpose of this study was to determine if air thinning three dentin adhesives would affect bond strength to dentin. Ninety human molars were mounted in acrylic and the occlusal surfaces ground to expose a flat dentin surface. Thirty teeth were randomly assigned to one of the following dentin bonding agent/composite combinations: A) Universal Bond 3/TPH (Caulk), B) All-Bond 2/Bis-Fil-P (Bisco), and C) Scotchbond Multi-Purpose/Z-100 (3m). The primers were applied following the manufacturers' instructions. The adhesives were applied by two methods. A thin layer of adhesive was applied with a brush to 15 specimens in each group and light cured. Adhesive was brushed on to the remaining 15 teeth in the group, air thinned for 3 seconds, and then polymerized. The appropriate composite was applied in 2 mm increments and light cured utilizing a 5 mm-in-diameter split Teflon mold. Following 3 months of water storage, all groups were shear tested to failure on an Instron Universal Testing Machine. Bond strength was significantly higher in all groups when the dentin bonding agent was painted on without being air thinned. Scotchbond Multi-Purpose had significantly higher bond strength than All-Bond 2, which had significantly higher bond strength than Universal Bond 3.

Temperature-assisted photochemical construction of CdS-based ordered porous films with photocatalytic activities on solution surfaces.

PubMed

Huang, Zhenxun; Sun, Fengqiang; Zhang, Yu; Gu, Kaiyuan; Zou, Xueqiong; Huang, Yuying; Wu, Qingsong; Zhang, Zihe

2011-04-15

Taking a colloidal monolayer floating on the surface of a precursor solution as template, free-standing CdS/Cd composites and pure CdS (CdS-based) ordered porous films had been prepared by a temperature-assisted photochemical strategy. After irradiation with UV-light and heat treatment, the films formed hemi-spherical pores due to the preferable deposition of CdS and Cd onto the PS spheres during the photochemical and interfacial reactions. When the temperature increased from 15 to 60°C, the air/water interface gradually changed into a vapor/water interface on the surface of the solution, resulting in variations of the final compositions. The optical properties of the films were hence changed. Because of the free-standing characteristic, the ordered porous films were first transferred on surface of polluted solutions as photocatalysts, which was a new mode in application of photocatalysts. The photocatalytic activities of films showed regular variations with the compositions in photodegradation of Rhodamine B. This method provides a simple route for tuning the properties of porous films through control of its composition and a flexible application of films on any surface. Copyright © 2011 Elsevier Inc. All rights reserved.

Wettability and XPS analyses of nickel-phosphorus surfaces after plasma treatment: An efficient approach for surface qualification in mechatronic processes

NASA Astrophysics Data System (ADS)

Vivet, L.; Joudrier, A.-L.; Bouttemy, M.; Vigneron, J.; Tan, K. L.; Morelle, J. M.; Etcheberry, A.; Chalumeau, L.

2013-06-01

Electroless nickel-high-phosphorus Ni-P plating is known for its physical properties. In case of electronic and mechatronic assembly processes achieved under ambient conditions the wettability of the Ni-P layer under ambient temperature and ambient air stays a point of surface quality investigation. This contribution will be devoted to the study of the surface properties of Ni-P films for which we performed air plasma treatment. We focus our attention on the evolution of the surface wettability, using the classical sessile drop technique. Interpreting the results with the OWRK model we extract the polar and disperse surface tension components from which we deduced typical evolution of the surface properties with the different treatment settings. By controlling the variations of the parameters of the plasma exposure we are able to change the responses of our Ni-P sample from total hydrophobic to total hydrophilic behaviours. All the intermediate states can be reached by adapting the treatment parameters. So it is demonstrated that the apparent Ni-P surface properties can be fully adapted and the surface setting can be well characterized by wettability measurements. To deep our knowledge of the surface modifications induced by plasma we performed parallel SEM and XPS analyses which provide informations on the structure and the chemical composition of the surface for each set of treatment parameters. Using this double approach we were able to propose a correlation between the evolution of surface chemical composition and surface wettability which are completely governed by the plasma treatment conditions. Chemical parameters as the elimination of the carbon contamination, the progressive surface oxidation, and the slight incorporation of nitrogen due to the air plasma interaction are well associated with the evolution of the wettability properties. So a complete engineering for the Ni-P surface preparation has been established. The sessile drop method can be considered as a very efficient method to propose qualification of treatments onto Ni-P surfaces before performing electronic and mechatronic assembly processes that are achieved under ambient conditions.

Midlatitude atmosphere-ocean interaction during El Nino. Part II. The northern hemisphere atmosphere

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

Alexander, M.A.

The influence of midlatitude air-sea interaction on the atmospheric anomalies associated with El Nino is investigated by coupling the Community Climate Model to a mixed-layer ocean model in the North Pacific. Prescribed El Nino conditions, warm sea surface temperatures (SST) in the tropical Pacific, cause a southward displacement and strengthening of the Aleutian Low. This results in enhanced (reduced) advection of cold Asian air over the west-central (northwest) Pacific and northward advection of warm air over the eastern Pacific. Allowing air-sea feedback in the North Pacific slightly modified the El Nino-induced near-surface wind, air temperature, and precipitation anomalies. The anomalousmore » cyclonic circulation over the North Pacific is more concentric and shifted slightly to the east in the coupled simulations. Air-sea feedback also damped the air temperature anomalies over most of the North Pacific and reduced the precipitation rate above the cold SST anomaly that develops in the central Pacific. The simulated North Pacific SST anomalies and the resulting Northern Hemisphere atmospheric anomalies are roughly one-third as large as those related to the prescribed El Nino conditions in a composite of five cases. The composite geopotential height anomalies associated with changes in the North Pacific SSTs have an equivalent barotropic structure and range from -65 m to 50 m at the 200-mb level. Including air-sea feedback in the North Pacific tended to damp the atmospheric anomalies caused by the prescribed El Nino conditions in the tropical Pacific. As a result, the zonally elongated geopotential height anomalies over the West Pacific are reduced and shifted to the east. However, the atmospheric changes associated with the North Pacific SST anomalies vary widely among the five cases.« less

Investigation of composition dependence of the nanowire samples grown on brass on synthesis conditions

NASA Astrophysics Data System (ADS)

Srivastava, Himanshu; Khooha, Ajay; Singh, Ajit; Ganguli, Tapas

2018-04-01

The study of the growth of nanowires on α-brass (Cu 65%, Zn 35%) substrate was done by annealing the substrates at different temperatures in air and varying flow of moist nitrogen. It was found that the surface composition of oxidized brass depended on the synthesis condition. Angle Dependent X-ray Fluorescence (ADXRF) measurements of the oxidized brass samples were done to study the variation of composition with the synthesis conditions and depth. The results showed that the cause of the compositional dependence on synthesis parameters is due to a process, inherent to the oxidation of brass.

One - step nanosecond laser microstructuring, sulfur hyperdoping, and annealing of silicon surfaces in liquid carbondisulfide

NASA Astrophysics Data System (ADS)

Van Luong, Nguyen; Danilov, P. A.; Ionin, A. A.; Khmel'nitskii, P. A.; Kudryashov, S. I.; Mel'nik, N. N.; Saraeva, I. N.; Смirnov, H. A.; Rudenko, A. A.; Zayarny, D. A.

2017-09-01

We perform a single-shot IR nanosecond laser processing of commercial silicon wafers in ambient air and under a 2 mm thick carbon disulfide liquid layer. We characterize the surface spots modified in the liquid ambient and the spots ablated under the same conditions in air in terms of its surface topography, chemical composition, band-structure modification, and crystalline structure by means of SEM and EDX microscopy, as well as of FT-IR and Raman spectroscopy. These studies indicate that single-step microstructuring and deep (up to 2-3% on the surface) hyperdoping of the crystalline silicon in its submicron surface layer, preserving via pulsed laser annealing its crystallinity and providing high (103 - 104 cm-1) spectrally at near- and mid-IR absorption coefficients, can be obtained in this novel approach, which is very promising for thin - film silicon photovoltaic devices

A high-performance, flexible and robust metal nanotrough-embedded transparent conducting film for wearable touch screen panels

NASA Astrophysics Data System (ADS)

Im, Hyeon-Gyun; An, Byeong Wan; Jin, Jungho; Jang, Junho; Park, Young-Geun; Park, Jang-Ung; Bae, Byeong-Soo

2016-02-01

We report a high-performance, flexible and robust metal nanotrough-embedded transparent conducting hybrid film (metal nanotrough-GFRHybrimer). Using an electro-spun polymer nanofiber web as a template and vacuum-deposited gold as a conductor, a junction resistance-free continuous metal nanotrough network is formed. Subsequently, the metal nanotrough is embedded on the surface of a glass-fabric reinforced composite substrate (GFRHybrimer). The monolithic composite structure of our transparent conducting film allows simultaneously high thermal stability (24 h at 250 °C in air), a smooth surface topography (Rrms < 1 nm) and excellent opto-electrical properties. A flexible touch screen panel (TSP) is fabricated using the transparent conducting films. The flexible TSP device stably operates on the back of a human hand and on a wristband.We report a high-performance, flexible and robust metal nanotrough-embedded transparent conducting hybrid film (metal nanotrough-GFRHybrimer). Using an electro-spun polymer nanofiber web as a template and vacuum-deposited gold as a conductor, a junction resistance-free continuous metal nanotrough network is formed. Subsequently, the metal nanotrough is embedded on the surface of a glass-fabric reinforced composite substrate (GFRHybrimer). The monolithic composite structure of our transparent conducting film allows simultaneously high thermal stability (24 h at 250 °C in air), a smooth surface topography (Rrms < 1 nm) and excellent opto-electrical properties. A flexible touch screen panel (TSP) is fabricated using the transparent conducting films. The flexible TSP device stably operates on the back of a human hand and on a wristband. Electronic supplementary information (ESI) available. See DOI: 10.1039/c5nr07657a

Physicochemical signatures of natural surfactant sea films from coastal Middle Adriatic stations

NASA Astrophysics Data System (ADS)

Frka, Sanja; Pogorzelski, Stanislaw; Kozarac, Zlatica; Ćosović, Božena

2013-04-01

Boundary layers between different environmental compartments represent critical interfaces for biological, chemical and physical processes. The sea surface microlayer (SSM) as a top layer of the sea surface represents natural interface between the atmosphere and ocean. Although < 1 mm in thickness the SML plays a key role in the global biogeochemical cycling because all gaseous, liquid and particulate materials must pass through this interface when exchanging between the ocean and the atmosphere. The SSM thus represents a very important driver enhancing air-water exchange processes. A variety of natural and anthropogenic organic compounds, particularly those which are surface active (SA) are generally enriched in the SML. It is widely acknowledged that the SSM is complex matrix of SA organics as carbohydrates, proteins, lipids and humic substances. Although lipid material is much less abundant than carbohydrates and proteins in the SML, their contribution to surface activity may be disproportionately large. The surfactant films at the air-sea interface change its physicochemical properties reducing air-sea exchange possesses by impeding molecular diffusion across the interface and influencing the hydrodynamic characteristics of water motion at the interface. Various biological, chemical and physical processes lead to the alteration of the film chemical composition, surface physical properties, surface concentration and spatial distribution of film-forming components. Instead of analyzing its chemical composition, it should be possible to scale the SML surface pressure-area (π-A) isotherms in terms of structural parameters which appear to be a sensitive and quantitative measure of the film physicochemical composition, surface concentration and miscibility of its film-forming components. We will present a large data set obtained by electrochemical and monolayer techniques, accompanied with the novel scaling approach for physicochemical characterization of SA substances of the natural microlayers from coastal Middle Adriatic stations including saline Rogoznica Lake and Krka river estuarine station. Higher primary production during late spring-early autumn is reflected in the presence of microlayers of higher surfactant activity containing on average molecules of lower molecular masses (Mw=0.65±0.27 kDa) and higher miscibility (y=6.46±1.33) and elasticity (E=18.33±2.02 mN/m) modulus in comparison to structural parameters (average Mw=2.15±1.58 kDa; y=3.51±1.46; E=6.41±1.97 mN/m) obtained for microlayers from period of lower organic matter production. Higher inhibition effect on the reduction process of cadmium ions is observed for natural microlayers abundant with SA material from more productive period. This kind of distribution is explained as the consequence of competitive adsorption of hydrophobic lipid-like substances of lower Mw which highly influence the surface structural properties of natural air-water interface forming there segregated surface films during more productive period. This study will offer different perspective on contemporary SML concept taking into account the lipids that act as end-members highly influencing seasonal change of SA concentration and surface structural properties of natural films at the air-water interface.

Effect of different surface treatments on the shear bond strength of nanofilled composite repairs

PubMed Central

Ahmadizenouz, Ghazaleh; Esmaeili, Behnaz; Taghvaei, Arnica; Jamali, Zahra; Jafari, Toloo; Amiri Daneshvar, Farshid; Khafri, Soraya

2016-01-01

Background. Repairing aged composite resin is a challenging process. Many surface treatment options have been proposed to this end. This study evaluated the effect of different surface treatments on the shear bond strength (SBS) of nano-filled composite resin repairs. Methods. Seventy-five cylindrical specimens of a Filtek Z350XT composite resin were fabricated and stored in 37°C distilled water for 24 hours. After thermocycling, the specimens were divided into 5 groups according to the following surface treatments: no treatment (group 1); air abrasion with 50-μm aluminum oxide particles (group 2); irradiation with Er:YAG laser beams (group 3); roughening with coarse-grit diamond bur + 35% phosphoric acid (group 4); and etching with 9% hydrofluoric acid for 120 s (group 5). Another group of Filtek Z350XT composite resin samples (4×6 mm) was fabricated for the measurement of cohesive strength (group 6). A silane coupling agent and an adhesive system were applied after each surface treatment. The specimens were restored with the same composite resin and thermocycled again. A shearing force was applied to the interface in a universal testing machine. Data were analyzed using one-way ANOVA and post hoc Tukey tests (P < 0.05). Results. One-way ANOVA indicated significant differences between the groups (P < 0.05). SBS of controls was significantly lower than the other groups; differences between groups 2, 3, 4, 5 and 6 were not significant. Surface treatment with diamond bur + 35% phosphoric acid resulted in the highest bond strength. Conclusion. All the surface treatments used in this study improved the shear bond strength of nanofilled composite resin used. PMID:27092209

Elemental composition and size distribution of particulates in Cleveland, Ohio

NASA Technical Reports Server (NTRS)

King, R. B.; Fordyce, J. S.; Neustadter, H. E.; Leibecki, H. F.

1975-01-01

Measurements were made of the elemental particle size distribution at five contrasting urban environments with different source-type distributions in Cleveland, Ohio. Air quality conditions ranged from normal to air pollution alert levels. A parallel network of high-volume cascade impactors (5-state) were used for simultaneous sampling on glass fiber surfaces for mass determinations and on Whatman-41 surfaces for elemental analysis by neutron activation for 25 elements. The elemental data are assessed in terms of distribution functions and interrelationships and are compared between locations as a function of resultant wind direction in an attempt to relate the findings to sources.

Elemental composition and size distribution of particulates in Cleveland, Ohio

NASA Technical Reports Server (NTRS)

Leibecki, H. F.; King, R. B.; Fordyce, J. S.; Neustadter, H. E.

1975-01-01

Measurements have been made of the elemental particle size distribution at five contrasting urban environments with different source-type distributions in Cleveland, Ohio. Air quality conditions ranged from normal to air pollution alert levels. A parallel network of high-volume cascade impactors (5-stage) were used for simultaneous sampling on glass fiber surfaces for mass determinations and on Whatman-41 surfaces for elemental analysis by neutron activation for 25 elements. The elemental data are assessed in terms of distribution functions and interrelationships and are compared between locations as a function of resultant wind direction in an attempt to relate the findings to sources.

Intermediate Temperature Stress Rupture of a Woven Hi-Nicalon, BN-Interphase, SiC Matric Composite in Air

NASA Technical Reports Server (NTRS)

Morscher, Gregory N.; Hurst, Janet; Brewer, David

1999-01-01

Woven Hi-Nicalon (TM) reinforced melt-infiltrated SiC matrix composites were tested under tensile stress-rupture conditions in air at intermediate temperatures. A comprehensive examination of the damage state and the fiber properties at failure was performed. Modal acoustic emission analysis was used to monitor damage during the experiment. Extensive microscopy of the composite fracture surfaces and the individual fiber fracture surfaces was used to determine the mechanisms leading to ultimate failure. The rupture properties of these composites were significantly worse than expected compared to the fiber properties under similar conditions. This was due to the oxidation of the BN interphase. Oxidation occurred through the matrix cracks that intersected the surface or edge of a tensile bar. These oxidation reactions resulted in minor degradation to fiber strength and strong bonding of the fibers to one another at regions of near fiber-to-fiber contact. It was found that two regimes for rupture exist for this material: a high stress regime where rupture occurs at a fast rate and a low stress regime where rupture occurs at a slower rate. For the high stress regime, the matrix damage state consisted of through thickness cracks. The average fracture strength of fibers that were pulled-out (the final fibers to break before ultimate failure) was controlled by the slow-crack growth rupture criterion in the literature for individual Hi-Nicalon (TM) fibers. For the low stress regime, the matrix damage state consisted of microcracks which grew during the rupture test. The average fracture strength of fibers that were pulled-out in this regime was the same as the average fracture strength of individual fibers pulled out in as-produced composites tested at room temperature.

Pilot evaluation of four experimental conditioning treatments to improve the bond strength between resin cement and Y-TZP ceramic.

PubMed

Monaco, Carlo; Cardelli, Paolo; Scotti, Roberto; Valandro, Luiz Felipe

2011-02-01

This study evaluated the bond strength between resin cement and Y-TZP ceramic (Yttrium-stabilized Tetragonal Zirconia Polycrystalline) submitted to different surface conditionings. Fifty Y-TZP ceramic discs (Ø= 10 mm) were allocated into five groups: Gr1 (control)-no conditioning; Gr2-tribochemical silica coating (30-μm SiO(2)) before sintering; Gr3-air abrasion with 50-μm Al(2)O(3) before sintering; Gr4-air abrasion with 110-μ Al(2)O(3) before sintering; Gr5 - air abrasion with 50-μm Al(2)O(3) after sintering. After specimen preparation, cylinders of composite resin were prepared and immediately cemented onto the ceramic. A shear test was performed. One-way ANOVA indicated a statistically significant difference among the groups (p= 0.0019). The mean shear bond strengths (MPa) were: Gr1 = 4.7 ± 0.8,(b) Gr2 = 4.6 ± 0.9,(b) Gr3 = 6.4 ± 1.0,(a) Gr4 = 6.5 ± 1.8,(a) Gr5 = 6 ± 1.3(ab) (same superscript letter indicates statistical similarity). Adhesive fracture between the ceramic and resin cement was the most common failure. No complete cohesive fracture at the ceramic or composite cylinders was noted. Within the limitations of this study, additional surface treatment with air abrasion before and after sintering provided a significant increase in bond strength. Tribochemical silica coating before sintering was not effective as a surface treatment. © 2011 by The American College of Prosthodontists.

Quantification of Local Warming Trend: A Remote Sensing-Based Approach

PubMed Central

Rahaman, Khan Rubayet; Hassan, Quazi K.

2017-01-01

Understanding the warming trends at local level is critical; and, the development of relevant adaptation and mitigation policies at those levels are quite challenging. Here, our overall goal was to generate local warming trend map at 1 km spatial resolution by using: (i) Moderate Resolution Imaging Spectroradiometer (MODIS)-based 8-day composite surface temperature data; (ii) weather station-based yearly average air temperature data; and (iii) air temperature normal (i.e., 30 year average) data over the Canadian province of Alberta during the period 1961–2010. Thus, we analysed the station-based air temperature data in generating relationships between air temperature normal and yearly average air temperature in order to facilitate the selection of year-specific MODIS-based surface temperature data. These MODIS data in conjunction with weather station-based air temperature normal data were then used to model local warming trends. We observed that almost 88% areas of the province experienced warming trends (i.e., up to 1.5°C). The study concluded that remote sensing technology could be useful for delineating generic trends associated with local warming. PMID:28072857

USSR Report, Space Biology and Aerospace Medicine, Vol. 18, No. 2, March-April 1984.

DTIC Science & Technology

1984-05-16

changes in composition and quantity of autogenous microflora, micro- flora of cabin air and surfaces did not present an appreciable threat with respect...R., "Biological Chemistry ," Leningrad, 5th ed., 1972. 14. Bol’shakova, T. Z., in "Spravochnik prakticheskogo vracha" [Clinical Physician’s...physical factors. The gas composition was measured qualita- tively and quantitatively. This determination showed a higher content of acetone and

On the Nature of Aerosol Particles in the Atmosphere of Irkutsk

NASA Astrophysics Data System (ADS)

Yermakov, A. N.; Golobokova, L. P.; Netsvetaeva, O. G.; Aloyan, A. E.; Arutyunyan, V. O.; Khodzher, T. V.

2018-03-01

Monitoring data on the ion composition of precipitation and the water-soluble fraction of aerosol have been used to identify two types of aerosol particles in the surface atmosphere of Irkutsk ("metal" and "ammonia" groups). The aerosol acidity is basically governed by the acidity of ammonia particles, and the ion composition depends on air relative humidity (RH). Preliminary estimates are given for the distribution of major cations and anions by aerosol groups.

Features of Wear-Resistant Cast Iron Coating Formation During Plasma-Powder Surfacing

NASA Astrophysics Data System (ADS)

Vdovin, K. N.; Emelyushin, A. N.; Nefed'ev, S. P.

2017-09-01

The structure of coatings deposited on steel 45 by plasma-powder surfacing of white wear-resistant cast iron is studied. The effects of surfacing regime and additional production effects on the welding bath during surfacing produced by current modulation, accelerated cooling of the deposited beads by blowing with air, and accelerated cooling of the substrate with running water on the structure, are determined. A new composition is suggested for powder material for depositing wear-resistant and corrosion-resistant coatings on a carbon steel by the plasma-powder process.

Frozen O 2 layer revealed by neutron reflectometry

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

Steffen, A.; Glavic, A.; Holderer, O.

2016-05-27

We investigated a 63 thick film originating from frozen air on a solid substrate via neutron reflectometry. Furthermore, the experiment shows that neutron reflectometry allows performing chemical surface analysis by quantifying the composition of this frozen layer and identifies the film to be frozen oxygen.

Apparatus for rapid measurement of aerosol bulk chemical composition

DOEpatents

Lee, Yin-Nan E.; Weber, Rodney J.

2003-01-01

An apparatus and method for continuous on-line measurement of chemical composition of aerosol particles with a fast time resolution are provided. The apparatus includes a modified particle size magnifier for producing activated aerosol particles and a collection device which collects the activated aerosol particles into a liquid stream for quantitative analysis by analytical methods. The method provided for on-line measurement of chemical composition of aerosol particles includes exposing aerosol carrying sample air to hot saturated steam thereby forming activated aerosol particles; collecting the activated aerosol particles by a collection device for delivery as a jet stream onto an impaction surface; flushing off the activated aerosol particles from the impaction surface into a liquid stream for delivery of the collected liquid stream to an analytical instrument for quantitative measurement.

Apparatus for rapid measurement of aerosol bulk chemical composition

DOEpatents

Lee, Yin-Nan E.; Weber, Rodney J.; Orsini, Douglas

2006-04-18

An apparatus for continuous on-line measurement of chemical composition of aerosol particles with a fast time resolution is provided. The apparatus includes an enhanced particle size magnifier for producing activated aerosol particles and an enhanced collection device which collects the activated aerosol particles into a liquid stream for quantitative analysis by analytical means. Methods for on-line measurement of chemical composition of aerosol particles are also provided, the method including exposing aerosol carrying sample air to hot saturated steam thereby forming activated aerosol particles; collecting the activated aerosol particles by a collection device for delivery as a jet stream onto an impaction surface; and flushing off the activated aerosol particles from the impaction surface into a liquid stream for delivery of the collected liquid stream to an analytical instrument for quantitative measurement.

From The Pierre Auger Observatory to AugerPrime

NASA Astrophysics Data System (ADS)

Parra, Alejandra; Martínez Bravo, Oscar; Pierre Auger Collaboration

2017-06-01

In the present work we report the principal motivation and reasons for the new stage of the Pierre Auger Observatory, AugerPrime. This upgrade has as its principal goal to clarify the origin of the highest energy cosmic rays through improvement in studies of the mass composition. To accomplished this goal, AugerPrime will use air shower universality, which states that extensive air showers can be completely described by three parameters: the primary energy E 0, the atmospheric shower depth of maximum X max, and the number of muons, Nμ . The Auger Collaboration has planned to complement its surface array (SD), based on water-Cherenkov detectors (WCD) with scintillator detectors, calls SSD (Scintillator Surface Detector). These will be placed at the top of each WCD station. The SSD will allow a shower to shower analysis, instead of the statistical analysis that the Observatory has previously done, to determine the mass composition of the primary particle by the electromagnetic to muonic ratio.

Impact of plasma treatment under atmospheric pressure on surface chemistry and surface morphology of extruded and injection-molded wood-polymer composites (WPC)

NASA Astrophysics Data System (ADS)

Hünnekens, Benedikt; Avramidis, Georg; Ohms, Gisela; Krause, Andreas; Viöl, Wolfgang; Militz, Holger

2018-05-01

The influence of plasma treatment performed at atmospheric pressure and ambient air as process gas by a dielectric barrier discharge (DBD) on the morphological and chemical surface characteristics of wood-polymer composites (WPC) was investigated by applying several surface-sensitive analytical methods. The surface free energy showed a distinct increase after plasma treatment for all tested materials. The analyzing methods for surface topography-laser scanning microscopy (LSM) and atomic force microscopy (AFM)-revealed a roughening induced by the treatment which is likely due to a degradation of the polymeric surface. This was accompanied by the formation of low-molecular-weight oxidized materials (LMWOMs), appearing as small globular structures. With increasing discharge time, the nodules increase in size and the material degradation proceeds. The surface degradation seems to be more serious for injection-molded samples, whereas the formation of nodules became more apparent and were evenly distributed on extruded surfaces. These phenomena could also be confirmed by scanning electron microscopy (SEM). In addition, differences between extruded and injection-molded surfaces could be observed. Besides the morphological changes, the chemical composition of the substrates' surfaces was affected by the plasma discharge. Infrared spectroscopy (ATR-FTIR) and X-ray photoelectron spectroscopy (XPS) indicated the formation of new oxygen containing polar groups on the modified surfaces.

Stratospheric ozone changes under solar geoengineering: implications for UV exposure and air quality

NASA Astrophysics Data System (ADS)

Nowack, Peer Johannes; Abraham, Nathan Luke; Braesicke, Peter; Pyle, John Adrian

2016-03-01

Various forms of geoengineering have been proposed to counter anthropogenic climate change. Methods which aim to modify the Earth's energy balance by reducing insolation are often subsumed under the term solar radiation management (SRM). Here, we present results of a standard SRM modelling experiment in which the incoming solar irradiance is reduced to offset the global mean warming induced by a quadrupling of atmospheric carbon dioxide. For the first time in an atmosphere-ocean coupled climate model, we include atmospheric composition feedbacks for this experiment. While the SRM scheme considered here could offset greenhouse gas induced global mean surface warming, it leads to important changes in atmospheric composition. We find large stratospheric ozone increases that induce significant reductions in surface UV-B irradiance, which would have implications for vitamin D production. In addition, the higher stratospheric ozone levels lead to decreased ozone photolysis in the troposphere. In combination with lower atmospheric specific humidity under SRM, this results in overall surface ozone concentration increases in the idealized G1 experiment. Both UV-B and surface ozone changes are important for human health. We therefore highlight that both stratospheric and tropospheric ozone changes must be considered in the assessment of any SRM scheme, due to their important roles in regulating UV exposure and air quality.

Air-stable hydrogen generation materials and enhanced hydrolysis performance of MgH2-LiNH2 composites

NASA Astrophysics Data System (ADS)

Ma, Miaolian; Ouyang, Liuzhang; Liu, Jiangwen; Wang, Hui; Shao, Huaiyu; Zhu, Min

2017-08-01

Hydrolysis of materials in water can be a promising solution of onsite hydrogen generation for realization of hydrogen economy. In this work, it was the first time that the MgH2-LiNH2 composites were explored as air-stable hydrolysis system for hydrogen generation. The MgH2-LiNH2 composites with different composition ratios were synthesized by ball milling with various durations and the hydrogen generation performances of the composite samples were investigated and compared. X-ray diffraction, X-ray photoelectron spectroscopy and scanning electron microscopy techniques were adopted to elucidate the performance improvement mechanisms. The hydrolysis properties of MgH2 were found to be significantly enhanced by the introduction of LiNH2. The 4MgH2-LiNH2 composite ball milled for 5 h can generate 887.2 mL g-1 hydrogen in 1 min and 1016 mL g-1 in 50 min, one of the best results so far for Mg based hydrolysis materials. The LiOH·H2O and NH4OH phases of hydrolysis products from LiNH2 may prevent formation of Mg(OH)2 passivation layer on the surface and supply enough channels for hydrolysis of MgH2. The MgH2-LiNH2 composites appeared to be very stable in air and no obvious negative effect on kinetics and hydrogen generation yield was observed. These good performances demonstrate that the studied MgH2-LiNH2 composites can be a promising and practicable hydrogen generation system.

Preparation of hierarchical structured nano-sized/porous poly(lactic acid) composite fibrous membranes for air filtration

NASA Astrophysics Data System (ADS)

Wang, Zhe; Pan, Zhijuan

2015-11-01

Hierarchical structured nano-sized/porous poly(lactic acid) (PLA-N/PLA-P) composite fibrous membranes with excellent air filtration performance were prepared via an electrospinning technique. Firstly, PLA-P fibers with different morphology were fabricated by varying the relative humidity, and the nanopores on fiber surface played a key role in improving the specific surface area and filtration performance of the resultant membranes. Secondly, hierarchical structure of PLA-N/PLA-P interlaced structured membranes and PLA-N/PLA-P double-layer structured membranes with different mass ratios for further enhanced air filtration performance were also successfully prepared by combining PLA-N fibers with PLA-P fibers. Filtration tests by measuring the penetration of sodium chloride (NaCl) aerosol particles with a 260 nm mass median diameter revealed that a moderate mass ratio of PLA-P fibers and PLA-N fibers contributed to improving the filtration performance of the hierarchical structured PLA-N/PLA-P composite membrane, and the double-layer structured PLA-N/PLA-P membrane possessed a higher filtration efficiency and quality factor than that of an interlaced structured PLA-N/PLA-P membrane with the same mass ratio. The as-prepared PLA-N/PLA-P double-layer structured membrane with a mass ratio of 1/5 showed a high filtration efficiency (99.999%) and a relatively low pressure drop (93.3 Pa) at the face velocity of 5.3 cm/s.

[Hygienic assessment of atmospheric air in the areas with different degrees of the development of the road-traffic complex].

PubMed

Rakhmanin, Yu A; Levanchuk, A V

The paper presents the results of a study of the qualitative composition and quantity of pollutants in atmospheric air in the course of operational wear of the road surface, braking system and tire treads of automobiles. On the basis of field research in samples ofatmospheric air ofthe city of St. Petersburg there were identified compounds of heavy metals andpolycyclic aromatic hydrocarbons (PAHs). There was established the dependence of the level of air pollution on traffic flows in locations of the city. Pollutants were shown to enter the air environment mainly in the form offine dust particles. There was justified the need for the control ofproducts of wear the road traffic complex in the hygienic assessment of the quality of ambient air ofmegalopises.

Synthesis of a conducting SiO2-carbon composite from commercial silicone grease and its conversion to paramagnetic SiO2 particles.

PubMed

Pol, V G; Pol, S V; George, P P; Markovsky, B; Gedanken, A

2006-07-13

The thermal decomposition of commercial silicone grease was carried out in a closed reactor (Swagelok) that was heated at 800 degrees C for 3 h, yielding a SiO2-carbon composite with a BET surface area of 369 m2/g. The bulk conductivity (5.72 x 10(-6) S x cm(-2)) of the SiO2-carbon composite was determined by impedance measurements. The as-prepared SiO2-carbon composite was further annealed at 500 degrees C in air for 2 h, which led to the formation of white paramagnetic silica particles (confirmed by ESR), possessing a surface area of 111 m2/g. The present synthetic technique requires unsophisticated equipment and a low-cost commercial precursor, and the reaction is carried out without a solvent, surfactant, or catalyst. The mechanism for the formation of a porous SiO2-carbon composite from the silicone grease is also presented.

Gas chemistry and thermometry of the Cerro Prieto, Mexico, geothermal field

USGS Publications Warehouse

Nehring, N.L.; D'Amore, F.

1984-01-01

Gas compositions of Cerro Prieto wells in 1977 reflected strong boiling in the reservoir around wells M-20 and M-25. This boiling zone appeared to be collapsing in 1982 when a number of wells in this area of the field were shut-in. In 1977 and 1982, gas compositions also showed boiling zones corresponding to faults H and L postulated by Halfman et al. (1982). Four gas geothermometers were applied, based on reservoir equilibria and calculated fugacities. The Fisher - Tropsch reaction predicted high temperatures and appeared to re-equilibrate slowly, whereas the H2S reaction predicted low temperatures and appeared to re-equilibrate rapidly. Hydrogen and NH3 reactions were intermediate. Like gas compositions, the geothermometers reflected reservoir processes, such as boiling. Surface gas compositions are related to well compositions, but contain large concentrations of N2 originating from air dissolved in groundwater. The groundwater appears to originate in the east and flow over the production field before mixing with reservoir gases near the surface. ?? 1984.

Quantifying the Impact of Land Cover Composition on Intra-Urban Air Temperature Variations at a Mid-Latitude City

PubMed Central

Yan, Hai; Fan, Shuxin; Guo, Chenxiao; Hu, Jie; Dong, Li

2014-01-01

The effects of land cover on urban-rural and intra-urban temperature differences have been extensively documented. However, few studies have quantitatively related air temperature to land cover composition at a local scale which may be useful to guide landscape planning and design. In this study, the quantitative relationships between air temperature and land cover composition at a neighborhood scale in Beijing were investigated through a field measurement campaign and statistical analysis. The results showed that the air temperature had a significant positive correlation with the coverage of man-made surfaces, but the degree of correlation varied among different times and seasons. The different land cover types had different effects on air temperature, and also had very different spatial extent dependence: with increasing buffer zone size (from 20 to 300 m in radius), the correlation coefficient of different land cover types varied differently, and their relative impacts also varied among different times and seasons. At noon in summer, ∼37% of the variations in temperature were explained by the percentage tree cover, while ∼87% of the variations in temperature were explained by the percentage of building area and the percentage tree cover on summer night. The results emphasize the key role of tree cover in attenuating urban air temperature during daytime and nighttime in summer, further highlighting that increasing vegetation cover could be one effective way to ameliorate the urban thermal environment. PMID:25010134

Interaction of gases with lunar materials. [surface properties of lunar fines, especially on exposure to water vapor

NASA Technical Reports Server (NTRS)

Holmes, H. F.; Gammage, R. B.

1975-01-01

The surface properties of lunar fines were investigated. Results indicate that, for the most part, these properties are independent of the chemical composition and location of the samples on the lunar surface. The leaching of channels and pores by adsorbed water vapor is a distinguishing feature of their surface chemistry. The elements of air, if adsorbed in conjunction with water vapor or liquid water, severely impedes the leaching process. In the absence of air, liquid water is more effective than water vapor in attacking the grains. The characteristics of Apollo 17 orange fines were evaluated and compared with those of other samples. The interconnecting channels produced by water vapor adsorption were found to be wider than usual for other types of fines. Damage tracks caused by heavy cosmic ray nuclei and an unusually high halogen content might provide for stronger etching conditions upon exposure to water vapor.

The Synoptic Climatology of Severe Thunderstorms in Manitoba.

NASA Astrophysics Data System (ADS)

Ladochy, Stephen Eugene Gabriel

The thesis presents the climatologies for Manitoba thunderstorms, hailstorms and tornadoes as well as investigates the synoptic weather conditions conducive for their development. The study not only uses standard meteorological information, but also various kinds of proxy data, in the form of damage reports. These damage reports complement the meteorological data by providing a higher resolution of observations, particularly in the sparsely populated regions. The synoptic conditions are relatively similar for all forms of severe thunderstorms, though the upper level jet stream (ULJ) is stronger for tornadoes, in general. Composite charts, drawn for 50 larger, more damaging hail days and 48 tornado days in the 1970's, helped identify important surface and upper air weather parameters and their inter -relationships with each other and the location of the storm. Time sequence composite charts were used to also show the development process in severe weather occurrences. From the composites, a synoptic weather type classification was devised with 10 categories to identify each storm by type. The most common pattern for severe weather has a strong southwesterly ULJ, with the storm occurring ahead of an advancing cold front. The ULJ patterns were drawn for each synoptic type days, showing differences between categories. The average conditions during tornado touchdowns were also seen from composite maps of surface and upper air isobaric charts. While severe thunderstorms are seen to occur under the "ideal" conditions, often described for U.S. severe weather, they can also be produced under other weather patterns and combinations of atmospheric parameters thought less favorable. The ULJ and LLJ (low-level jet stream) models used in U.S. studies do not always fit Manitoba storms, however, less favorable jet positions, at specific levels, can be compensated for by low-level advection of warm, and moist air.

40 CFR 63.341 - Definitions and nomenclature.

Code of Federal Regulations, 2012 CFR

2012-07-01

... air pollution control device or a chemical fume suppressant, that is used to reduce chromium emissions... trivalent chromium plating baths. For trivalent chromium baths, the bath composition is proprietary in most... to the surface tension. Trivalent chromium means the form of chromium in a valence state of +3...

Demonstration of Military Composites With Low Hazardous Air Pollutant Content

DTIC Science & Technology

2007-07-01

84506 § Naval Surface Warfare Center Carderock, West Bethesda, MD 20817 **Red River Army Depot, U.S. Army TACOM, Texarkana , TX 75507-5000 14...Depot, US Army TACOM Texarkana , TX 75507-5000 * To whom all correspondence should be addressed ABSTRACT Liquid resins used for molding

Surface Acoustic Wave Vibration Sensors for Measuring Aircraft Flutter

NASA Technical Reports Server (NTRS)

Wilson, William C.; Moore, Jason P.; Juarez, Peter D.

2016-01-01

Under NASA's Advanced Air Vehicles Program the Advanced Air Transport Technology (AATT) Project is investigating flutter effects on aeroelastic wings. To support that work a new method for measuring vibrations due to flutter has been developed. The method employs low power Surface Acoustic Wave (SAW) sensors. To demonstrate the ability of the SAW sensor to detect flutter vibrations the sensors were attached to a Carbon fiber-reinforced polymer (CFRP) composite panel which was vibrated at six frequencies from 1Hz to 50Hz. The SAW data was compared to accelerometer data and was found to resemble sine waves and match each other closely. The SAW module design and results from the tests are presented here.

Surface polaritons in grating composed of left-handed materials

NASA Astrophysics Data System (ADS)

Tiwari, D. C.; Premlal, P. L.; Chaturvedi, Vandana

2018-01-01

In this work, we developed a unique mathematical model to solve dispersion relation for surface polaritons (SPs) in artificial composite materials grating. Here, we have taken two types of materials for analysis. In the first case, the grating composed of epsilon-negative (ENG) material and air interface. In second case, grating composed of left-handed materials (LHMs) and ENG medium interface is considered. The dispersion curves of both p and s polarized SPs modes are obtained analytically. In the case of ENG grating and air interface, polaritons dispersion curves exist for p-polarization only, whereas for LHM grating and ENG medium interface, the polaritons dispersion curves for both p and s polarization are observed.

Composites with improved fiber-resin interfacial adhesion

NASA Technical Reports Server (NTRS)

Cizmecioglu, Muzaffer (Inventor)

1989-01-01

The adhesion of fiber reinforcement such as high modulus graphite to a matrix resin such as polycarbonate is greatly enhanced by applying a very thin layer, suitably from 50 Angstroms to below 1000 Angstroms, to the surface of the fiber such as by immersing the fiber in a dilute solution of the matrix resin in a volatile solvent followed by draining to remove excess solution and air drying to remove the solvent. The thin layer wets the fiber surface. The very dilute solution of matrix resin is able to impregnate multifilament fibers and the solution evenly flows onto the surface of the fibers. A thin uniform layer is formed on the surface of the fiber after removal of the solvent. The matrix resin coated fiber is completely wetted by the matrix resin during formation of the composite. Increased adhesion of the resin to the fibers is observed at fracture. At least 65 percent of the surface of the graphite fiber is covered with polycarbonate resin at fracture whereas uncoated fibers have very little matrix resin adhering to their surfaces at fracture and epoxy sized graphite fibers exhibit only slightly higher coverage with matrix resin at fracture. Flexural modulus of the composite containing matrix resin coated fibers is increased by 50 percent and flexural strength by 37 percent as compared to composites made with unsized fibers.

Directional self-cleaning superoleophobic surface.

PubMed

Zhao, Hong; Law, Kock-Yee

2012-08-14

In this work, we report the creation of a grooved surface comprising 3 μm grooves (height ~4 μm) separated by 3 μm from each other on a silicon wafer by photolithography. The grooved surface was then modified chemically with a fluorosilane layer (FOTS). The surface property was studied by both static and dynamic contact angle measurements using water, hexadecane, and a polyethylene wax ink as the probing liquids. Results show that the grooved surface is both superhydrophobic and superoleophobic. Its observed contact angles agree well with the calculated Cassie-Baxter angles. More importantly, we are able to make a replica of the composite wax ink-air interface and study it by SEM. Microscopy results not only show that the droplet of the wax ink "sits" on air in the composite interface but also further reveal that the ink drop actually pins underneath the re-entrant structure in the side wall of the grooved structure. Contact angle measurement results indicate that wetting on the grooved surface is anisotropic. Although liquid drops are found to have lower static and advancing contact angles in the parallel direction, the drops are found to be more mobile, showing smaller hysteresis and lower sliding angles (as compared to the FOTS wafer surface and a comparable 3-μm-diameter pillar array FOTS surface). The enhanced mobility is attributable to the lowering of the resistance against an advancing liquid because 50% of the advancing area is made of a solid strip where the liquid likes to wet. This also implies that the contact line for advancing is no longer smooth but rather is ragged, having the solid strip area leading the wetting and the air strip area trailing behind. This interpretation is supported by imaging the geometry of the contact lines using molten ink drops recovered from the sliding angle experiments in both the parallel and orthogonal directions. Because the grooved surface is mechanically stronger against mechanical abrasion, the self-cleaning effect exhibited in the parallel direction suggests that groove texturing is a viable approach to create mechanically robust, self-cleaning, superoleophobic surfaces.

Enhanced Performance of non-PGM Catalysts in Air Operated PEM-Fuel Cells

DOE PAGES

Barkholtz, Heather M.; Chong, Lina; Kaiser, Zachary Brian; ...

2016-10-13

Here a non-platinum group metal (non-PGM) oxygen reduction catalyst was prepared from “support-free” zeolitic imidazolate framework (ZIF) precursor and tested in the proton exchange membrane fuel cell with air as the cathode feed. The iron nitrogen and carbon composite (FeeNeC) based catalyst has high specific surface area decorated uniformly with active sites, which redefines the triple phase boundary (TPB) and requires re-optimization of the cathodic membrane electrode fabrication to ensure efficient mass and charge transports to the catalyst surface. This study reports an effort in optimizing catalytic ink formulation for the membrane electrode preparation and its impact to the fuelmore » cell performance under air. Through optimization, the fuel cell areal current density as high as 115.2 mA/cm 2 at 0.8 V or 147.6 mA/cm 2 at 0.8 V iR-free has been achieved under one bar air. We also investigated impacts on fuel cell internal impedance and the water formation.« less

Controlling the surface termination of NdGaO3 (110): the role of the gas atmosphere.

PubMed

Cavallaro, Andrea; Harrington, George F; Skinner, Stephen J; Kilner, John A

2014-07-07

In this work the effect of gas atmosphere on the surface termination reconstruction of single crystal NdGaO3 (110) (NGO) during thermal annealing was analyzed. Using Low Energy Ion Scattering (LEIS) it has been possible to study the chemical composition of the first atomic layer of treated NGO single crystal samples. NGO has been analyzed both as-received and after a specific thermal treatment at 1000 °C under different gas fluxes (argon, nitrogen, static air, synthetic air, nitrogen plus 5% hydrogen and wet synthetic air respectively). Thermal annealing of perovskite single crystals, as already reported in the literature, is used to obtain a fully A-cation surface termination. Nevertheless the effect of the gas-atmosphere on this process has not been previously reported. By the use of sequential low energy Ar(+) sputtering combined with the primary ion LEIS analysis, the reconstruction of the outermost atomic layers has allowed the clarification of the mechanism of NGO neodymium surface enrichment. It is proposed that the gallium at the surface is submitted to a reduction/evaporation mechanism caused by low oxygen partial pressure and/or high water pressure in the vector gas. Below the first surface atomic layers of an as-received NGO single-crystal a gallium-rich phase has also been observed.

Measurement of horizontal air showers with the Auger Engineering Radio Array

NASA Astrophysics Data System (ADS)

Kambeitz, Olga

2017-03-01

The Auger Engineering Radio Array (AERA), at the Pierre Auger Observatory in Argentina, measures the radio emission of extensive air showers in the 30-80 MHz frequency range. AERA consists of more than 150 antenna stations distributed over 17 km2. Together with the Auger surface detector, the fluorescence detector and the underground muon detector (AMIGA), AERA is able to measure cosmic rays with energies above 1017 eV in a hybrid detection mode. AERA is optimized for the detection of air showers up to 60° zenith angle, however, using the reconstruction of horizontal air showers with the Auger surface array, very inclined showers can also be measured. In this contribution an analysis of the AERA data in the zenith angle range from 62° to 80° will be presented. CoREAS simulations predict radio emission footprints of several km2 for horizontal air showers, which are now confirmed by AERA measurements. This can lead to radio-based composition measurements and energy determination of horizontal showers in the future and the radio detection of neutrino induced showers is possible.

Rotor blade construction for circulation control aircraft

NASA Technical Reports Server (NTRS)

Carter, Sr., Donald R. (Inventor); Sedlak, Matthew (Inventor); Krauss, Timothy A. (Inventor)

1986-01-01

A circulation control aircraft rotor blade having a spanwise Coanda surface 16 and a plurality of spanwise extending flexible composite material panels 18 cooperating with the surface to define slots for the discharge of compressed air from within the blade with each panel having first flexure means 60 associated with screw adjustments 36 for establishing a slot opening preload and second flexure means 62 associated with screw adjustments 38 for establishing a slot maximum opening.

Sulfur dioxide reactions on ice surfaces: Implications for dry deposition to snow

Treesearch

Martha H. Conklin; Richard A. Sommerfeld; S. Kay Laird; John E. Villinski

1993-01-01

Controlled exposure of ice to a reactive gas, SO2, demonstrated the importance of the chemical composition of the ice surface on the accumulation of acidity in snow. In a series of bench-scale continuous-flow column experiments run at four temperatures (-1, -8, -30 and -60°C), SO2 was shown to dissolve and to react with other species in the ice-air interfacial region...

Structure and microhardness of the plasma sprayed composite coatings after combined treatment

NASA Astrophysics Data System (ADS)

Ivannikov, A. Yu; Kalita, V. I.; Komlev, D. I.; Radyuk, A. A.; Bagmutov, V. P.; Zakharov, I. N.; Parshev, S. N.; Denisevich, D. S.

2018-04-01

The principal aim of this study was to evaluate the effect of combination of electromechanical treatment (EMT) and ultrasonic treatment on structure and microhardness of air plasma sprayed composite coatings from Ni–20Cr alloy and R6M5 high speed steel (HSS). The results of the microstructural studies showed fundamental changes of the treated by the EMT plasma sprayed coating with the formation of nanostructured crystalline phases. As a consequence of the coating thus formed, the number of pores in the coating structure reduced from 10.0±1.5% to 2.0±0.5%, the surface microhardness increased from 3100±500 MPa to 7900±400 MPa. Additional ultrasonic treatment on the selected mode decreased surface waviness, which was formed on the surface of the plasma sprayed composite coatings after the EMT. The obtained results revealed the high potential of the combined treatment for post-treatment of the plasma sprayed coatings.

The cosmic ray primary composition between 1015 and 1016 eV from Extensive Air Showers electromagnetic and TeV muon data

NASA Astrophysics Data System (ADS)

Aglietta, M.; Alessandro, B.; Antonioli, P.; Arneodo, F.; Bergamasco, L.; Bertaina, M.; Castagnoli, C.; Castellina, A.; Chiavassa, A.; Cini, G.; D'Ettorre Piazzoli, B.; di Sciascio, G.; Fulgione, W.; Galeotti, P.; Ghia, P. L.; Iacovacci, M.; Mannocchi, G.; Morello, C.; Navarra, G.; Saavedra, O.; Stamerra, A.; Trinchero, G. C.; Valchierotti, S.; Vallania, P.; Vernetto, S.; Vigorito, C.; Ambrosio, M.; Antolini, R.; Baldini, A.; Barbarino, G. C.; Barish, B. C.; Battistoni, G.; Becherini, Y.; Bellotti, R.; Bemporad, C.; Bernardini, P.; Bilokon, H.; Bower, C.; Brigida, M.; Bussino, S.; Cafagna, F.; Calicchio, M.; Campana, D.; Carboni, M.; Caruso, R.; Cecchini, S.; Cei, F.; Chiarella, V.; Choudhary, B. C.; Coutu, S.; Cozzi, M.; de Cataldo, G.; Dekhissi, H.; de Marzo, C.; de Mitri, I.; Derkaoui, J.; de Vincenzi, M.; di Credico, A.; Erriquez, O.; Favuzzi, C.; Forti, C.; Fusco, P.; Giacomelli, G.; Giannini, G.; Giglietto, N.; Giorgini, M.; Grassi, M.; Grillo, A.; Guarino, F.; Gustavino, C.; Habig, A.; Hanson, K.; Heinz, R.; Iarocci, E.; Katsavounidis, E.; Katsavounidis, I.; Kearns, E.; Kim, H.; Kyriazopoulou, S.; Lamanna, E.; Lane, C.; Levin, D. S.; Lipari, P.; Longley, N. P.; Longo, M. J.; Loparco, F.; Maaroufi, F.; Mancarella, G.; Mandrioli, G.; Margiotta, A.; Marini, A.; Martello, D.; Marzari-Chiesa, A.; Mazziotta, M. N.; Michael, D. G.; Monacelli, P.; Montaruli, T.; Monteno, M.; Mufson, S.; Musser, J.; Nicolò, D.; Nolty, R.; Orth, C.; Osteria, G.; Palamara, O.; Patera, V.; Patrizii, L.; Pazzi, R.; Peck, C. W.; Perrone, L.; Petrera, S.; Popa, V.; Rainò, A.; Reynoldson, J.; Ronga, F.; Satriano, C.; Scapparone, E.; Scholberg, K.; Sciubba, A.; Serra, P.; Sioli, M.; Sirri, G.; Sitta, M.; Spinelli, P.; Spinetti, M.; Spurio, M.; Steinberg, R.; Stone, J. L.; Sulak, L. R.; Surdo, A.; Tarlè, G.; Togo, V.; Vakili, M.; Walter, C. W.; Webb, R.

2004-03-01

The cosmic ray primary composition in the energy range between 1015 and 1016 eV, i.e., around the ``knee'' of the primary spectrum, has been studied through the combined measurements of the EAS-TOP air shower array (2005 m a.s.l., 105 m2 collecting area) and the MACRO underground detector (963 m a.s.l., 3100 m w.e. of minimum rock overburden, 920 m2 effective area) at the National Gran Sasso Laboratories. The used observables are the air shower size (Ne) measured by EAS-TOP and the muon number (Nμ) recorded by MACRO. The two detectors are separated on average by 1200 m of rock, and located at a respective zenith angle of about 30°. The energy threshold at the surface for muons reaching the MACRO depth is approximately 1.3 TeV. Such muons are produced in the early stages of the shower development and in a kinematic region quite different from the one relevant for the usual Nμ-Ne studies. The measurement leads to a primary composition becoming heavier at the knee of the primary spectrum, the knee itself resulting from the steepening of the spectrum of a primary light component (p, He) of Δγ=0.7+/-0.4 at E0~4×1015 eV. The result confirms the ones reported from the observation of the low energy muons at the surface (typically in the GeV energy range), showing that the conclusions do not depend on the production region kinematics. Thus, the hadronic interaction model used (CORSIKA/QGSJET) provides consistent composition results from data related to secondaries produced in a rapidity region exceeding the central one. Such an evolution of the composition in the knee region supports the ``standard'' galactic acceleration/propagation models that imply rigidity dependent breaks of the different components, and therefore breaks occurring at lower energies in the spectra of the light nuclei.

Interrelationships among Grain Size, Surface Composition, Air Stability, and Interfacial Resistance of Al-Substituted Li7La3Zr2O12 Solid Electrolytes.

PubMed

Cheng, Lei; Wu, Cheng Hao; Jarry, Angelique; Chen, Wei; Ye, Yifan; Zhu, Junfa; Kostecki, Robert; Persson, Kristin; Guo, Jinghua; Salmeron, Miquel; Chen, Guoying; Doeff, Marca

2015-08-19

The interfacial resistances of symmetrical lithium cells containing Al-substituted Li7La3Zr2O12 (LLZO) solid electrolytes are sensitive to their microstructures and histories of exposure to air. Air exposure of LLZO samples with large grain sizes (∼150 μm) results in dramatically increased interfacial impedances in cells containing them, compared to those with pristine large-grained samples. In contrast, a much smaller difference is seen between cells with small-grained (∼20 μm) pristine and air-exposed LLZO samples. A combination of soft X-ray absorption (sXAS) and Raman spectroscopy, with probing depths ranging from nanometer to micrometer scales, revealed that the small-grained LLZO pellets are more air-stable than large-grained ones, forming far less surface Li2CO3 under both short- and long-term exposure conditions. Surface sensitive X-ray photoelectron spectroscopy (XPS) indicates that the better chemical stability of the small-grained LLZO is related to differences in the distribution of Al and Li at sample surfaces. Density functional theory calculations show that LLZO can react via two different pathways to form Li2CO3. The first, more rapid, pathway involves a reaction with moisture in air to form LiOH, which subsequently absorbs CO2 to form Li2CO3. The second, slower, pathway involves direct reaction with CO2 and is favored when surface lithium contents are lower, as with the small-grained samples. These observations have important implications for the operation of solid-state lithium batteries containing LLZO because the results suggest that the interfacial impedances of these devices is critically dependent upon specific characteristics of the solid electrolyte and how it is prepared.

Cyclic Fatigue Durability of Uncoated and EBC Coated 3D SiC/SiC Composites Under Thermal Gradient Conditions at 2700F in Air

NASA Technical Reports Server (NTRS)

Smith, Craig; Harder, Bryan; Zhu, Dongming; Bhatt, Ramakrishna; Kalluri, Sreeramesh

2017-01-01

Ceramic matrix composites (CMCs) such as SiC/SiC are currently being designed and implemented in high temperature sections of aerospace turbine engines. Such components will be subject to through-thickness thermal gradients, which may affect the durability. In this study, SiC/SiC CMCs with a hybrid chemical vapor infiltrated (CVI) and polymer infiltration and pyrolysis (PIP) matrix were loaded in tension while one surface was heated with a laser and the opposite surface was cooled. Issues associated with laser testing will be discussed, along with initial results for coated and uncoated samples.

Synergistic effects of carboxymethyl cellulose and ZnO as alkaline electrolyte additives for aluminium anodes with a view towards Al-air batteries

NASA Astrophysics Data System (ADS)

Liu, Jie; Wang, Dapeng; Zhang, Daquan; Gao, Lixin; Lin, Tong

2016-12-01

The synergistic effects of carboxymethyl cellulose (CMC) and zinc oxide (ZnO) have been investigated as alkaline electrolyte additives for the AA5052 aluminium alloy anode in aluminium-air battery by the hydrogen evolution test, the electrochemical measurements and the surface analysis method. The combination of CMC and ZnO effectively retards the self-corrosion of AA5052 alloy in 4 M NaOH solution. A complex film is formed via the interaction between CMC and Zn2+ ions on the alloy surface. The carboxyl groups adsorbed on the surface of aluminium make the protective film more stable. The cathodic reaction process is mainly suppressed significantly. AA5052 alloy electrode has a good discharge performance in the applied electrolyte containing the composite CMC/ZnO additives.

Catalytic combustion of hydrogen-air mixtures in stagnation flows

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

Ikeda, H.; Libby, P.A.; Williams, F.A.

1993-04-01

The interaction between heterogeneous and homogeneous reactions arising when a mixture of hydrogen and air impinges on a platinum plate at elevated temperature is studied. A reasonably complete description of the kinetic mechanism for homogeneous reactions is employed along with a simplified model for heterogeneous reactions. Four regimes are identified depending on the temperature of the plate, on the rate of strain imposed on the flow adjacent to the plate and on the composition and temperature of the reactant stream: (1) surface reaction alone; (2) surface reaction inhibiting homogeneous reaction; (3) homogeneous reaction inhibiting surface reaction; and (4) homogeneous reactionmore » alone. These regimes are related to those found earlier for other chemical systems and form the basis of future experimental investigation of the chemical system considered in the present study.« less

Effect of air pollution on the total bacteria and pathogenic bacteria in different sizes of particulate matter.

PubMed

Liu, Huan; Zhang, Xu; Zhang, Hao; Yao, Xiangwu; Zhou, Meng; Wang, Jiaqi; He, Zhanfei; Zhang, Huihui; Lou, Liping; Mao, Weihua; Zheng, Ping; Hu, Baolan

2018-02-01

In recent years, air pollution events have occurred frequently in China during the winter. Most studies have focused on the physical and chemical composition of polluted air. Some studies have examined the bacterial bioaerosols both indoors and outdoors. But few studies have focused on the relationship between air pollution and bacteria, especially pathogenic bacteria. Airborne PM samples with different diameters and different air quality index values were collected in Hangzhou, China from December 2014 to January 2015. High-throughput sequencing of 16S rRNA was used to categorize the airborne bacteria. Based on the NCBI database, the "Human Pathogen Database" was established, which is related to human health. Among all the PM samples, the diversity and concentration of total bacteria were lowest in the moderately or heavily polluted air. However, in the PM2.5 and PM10 samples, the relative abundances of pathogenic bacteria were highest in the heavily and moderately polluted air respectively. Considering the PM samples with different particle sizes, the diversities of total bacteria and the proportion of pathogenic bacteria in the PM10 samples were different from those in the PM2.5 and TSP samples. The composition of PM samples with different sizes range may be responsible for the variances. The relative humidity, carbon monoxide and ozone concentrations were the main factors, which affected the diversity of total bacteria and the proportion of pathogenic bacteria. Among the different environmental samples, the compositions of the total bacteria were very similar in all the airborne PM samples, but different from those in the water, surface soil, and ground dust samples. Which may be attributed to that the long-distance transport of the airflow may influence the composition of the airborne bacteria. This study of the pathogenic bacteria in airborne PM samples can provide a reference for environmental and public health researchers. Copyright © 2017 Elsevier Ltd. All rights reserved.

Significant Atmospheric Aerosol Pollution Caused by World Food Cultivation

NASA Technical Reports Server (NTRS)

Bauer, Susanne E.; Tsigaridis, Kostas; Miller, Ron

2016-01-01

Particulate matter is a major concern for public health, causing cancer and cardiopulmonary mortality. Therefore, governments in most industrialized countries monitor and set limits for particulate matter. To assist policy makers, it is important to connect the chemical composition and severity of particulate pollution to its sources. Here we show how agricultural practices, livestock production, and the use of nitrogen fertilizers impact near-surface air quality. In many densely populated areas, aerosols formed from gases that are released by fertilizer application and animal husbandry dominate over the combined contributions from all other anthropogenic pollution. Here we test reduction scenarios of combustion-based and agricultural emissions that could lower air pollution. For a future scenario, we find opposite trends, decreasing nitrate aerosol formation near the surface while total tropospheric loads increase. This suggests that food production could be increased to match the growing global population without sacrificing air quality if combustion emission is decreased.

Numerical and experimental study on a pulsed-dc plasma jet

NASA Astrophysics Data System (ADS)

Liu, X. Y.; Pei, X. K.; Lu, X. P.; Liu, D. W.

2014-06-01

A numerical and experimental study of plasma jet propagation in a low-temperature, atmospheric-pressure, helium jet in ambient air is presented. A self-consistent, multi-species, two-dimensional axially symmetric plasma model with detailed finite-rate chemistry of helium-air mixture composition is used to provide insights into the propagation of the plasma jet. The obtained simulation results suggest that the sheath forms near the dielectric tube inner surface and shields the plasma channel from the tube surface. The strong electric field at the edge of the dielectric field enhances the ionization in the air mixing layer; therefore, the streamer head becomes ring-shaped when the streamer runs out of the tube. The avalanche-to-streamer transition is the main mechanism of streamer advancement. Penning ionization dominates the ionization reactions and increases the electrical conductivity of the plasma channel. The simulation results are supported by experimental observations under similar discharge conditions.

Significant atmospheric aerosol pollution caused by world food cultivation

NASA Astrophysics Data System (ADS)

Bauer, Susanne E.; Tsigaridis, Kostas; Miller, Ron

2016-05-01

Particulate matter is a major concern for public health, causing cancer and cardiopulmonary mortality. Therefore, governments in most industrialized countries monitor and set limits for particulate matter. To assist policy makers, it is important to connect the chemical composition and severity of particulate pollution to its sources. Here we show how agricultural practices, livestock production, and the use of nitrogen fertilizers impact near-surface air quality. In many densely populated areas, aerosols formed from gases that are released by fertilizer application and animal husbandry dominate over the combined contributions from all other anthropogenic pollution. Here we test reduction scenarios of combustion-based and agricultural emissions that could lower air pollution. For a future scenario, we find opposite trends, decreasing nitrate aerosol formation near the surface while total tropospheric loads increase. This suggests that food production could be increased to match the growing global population without sacrificing air quality if combustion emission is decreased.

Significant atmospheric aerosol pollution caused by world food cultivation

NASA Astrophysics Data System (ADS)

Bauer, Susanne E.; Tsigaridis, Kostas; Miller, Ron

2017-04-01

Particulate matter is a major concern for public health, causing cancer and cardiopulmonary mortality. Therefore, governments in most industrialized countries monitor and set limits for particulate matter. To assist policy makers, it is important to connect the chemical composition and severity of particulate pollution to it s sources. Here we show how agricultural practices, livestock production, and the use of nitrogen fertilizers impact near-surface air quality. In many densely populated areas, aerosols formed from gases that are released by fertilizer application and animal husbandry dominate over the combined contributions from all other anthropogenic pollution. Here we test reduction scenarios of combustion-based and agricultural emissions that could lower air pollution. For a future scenario, we find opposite trends, decreasing nitrate aerosol formation near the surface while total tropospheric loads increase. This suggests that food production could be increased to match the growing global population without sacrificing air quality if combustion emission is decreased.

Observed formation of easterly waves over northeast Africa

NASA Astrophysics Data System (ADS)

Jury, Mark R.

2018-06-01

This study explores the thermodynamic and kinematic features of easterly waves over northeast Africa in July-September season 2005-2015. A daily African easterly wave (AEW) index is formulated from transient satellite rainfall and reanalysis vorticity, and the ten most intense cases are studied by composite analysis. Surface moisture is advected from central Africa towards the Red Sea during AEW formation. The anomalous 600 hPa wind circulation is comprized of a cyclonic-south anticyclonic-north rotor pair and accentuated easterly jet along 17N. Composite convection is initiated over Ethiopia and subsequently intensifies following interaction with a zonal circulation located downstream. Composite AEW temperature anomalies reveal a cool lower-warm upper layer heating profile. 2-8 day variance of satellite OLR reaches a maximum over the southern Arabian Peninsula, suggesting an upstream role for surface heating and the Somali Jet. The large scale environment is analyzed by regression of the AEW index onto daily fields of rainfall, surface air pressure and temperature in July-September season ( N = 1004). The rainfall regression reflects a westward propagating AEW wave-train of higher values on 13N and lower values on 7N with a longitude spacing of 25°. The air pressure and temperature regression features a N-S dipole indicating an anomalous northward ITCZ. A low pressure signal west of the Maritime Continent coupled with a warm zone across the South Indian Ocean coincides with AEW formation over the eastern Sahel.

Properties of PMR polyimide composites made with improved high strength graphite fibers

NASA Technical Reports Server (NTRS)

Vannucci, R. D.

1980-01-01

Recent graphite fiber developments have resulted in high strength, intermediate modulus graphite fibers having improved thermo-oxidative resistance. These improved fibers, obtained from various commercial suppliers, were used to fabricate PMR-15 and PMR-11 polyimide composites. Studies were performed to investigate the effects of the improved high strength graphite fibers on composite properties after exposure in air at 600 F. The use of the more oxidatively resistant fibers did not result in improved performance at 600 F. Two of the improved fibers were found to have an adverse effect on the long-term performance of PMR composites. The influence of various factors such as fiber physical properties, surface morphology and chemical composition are also discussed.

Influence of drying time and temperature on bond strength of contemporary adhesives to dentine.

PubMed

Garcia, Fernanda C P; Almeida, Júlio C F; Osorio, Raquel; Carvalho, Ricardo M; Toledano, Manuel

2009-04-01

To evaluate the bond strength (microTBS) of self-etching adhesives in different solvent evaporation conditions. Flat dentine surfaces from extracted human third molars were bonded with: (1) 2 two-steps self-etching adhesives (Clearfil SE Bond-CSEB); (Protect Bond-PB) and (2) 2 one-step self-etch systems (Adper Prompt L Pop-ADPLP); (Xeno III-XIII). Bonded dentine surfaces were air-dried for 5s, 20s, 30s or 40s at either 21 degrees C or 38 degrees C. Composite build-ups were constructed incrementally. After storage in water for 24h at 37 degrees C, the specimens were prepared for microtensile bond strength testing. Data were analyzed by two-way ANOVA and Student-Newman-Keuls at alpha=0.05. CSEB and PB performed better at warm temperature with only 20s of air-blowing. The bond strength increased when XIII was performed at warm temperature at 40s air-blowing. Extended air-blowing not affect the performance of ADPLP, except at 30s air-blowing time at warm temperature. The use of a warm air-dry stream seems to be a clinical tool to improve the bond strength to self-etching adhesives.

Metal matrix composite fabrication processes for high performance aerospace structures

NASA Astrophysics Data System (ADS)

Ponzi, C.

A survey is conducted of extant methods of metal matrix composite (MMC) production in order to serve as a basis for prospective MMC users' selection of a matrix/reinforcement combination, cost-effective primary fabrication methods, and secondary fabrication techniques for the achievement of desired performance levels. Attention is given to the illustrative cases of structural fittings, control-surface connecting rods, hypersonic aircraft air inlet ramps, helicopter swash plates, and turbine rotor disks. Methods for technical and cost analysis modeling useful in process optimization are noted.

The adsorption properties of short chain alcohols and Triton X-100 mixtures at the water-air interface.

PubMed

Zdziennicka, Anna

2009-07-15

The adsorption behaviour at the water-air interface of aqueous solutions of Triton X-100 and methanol (ethanol) mixtures at constant Triton X-100 (TX-100) concentration equal to 10(-7), 10(-6), 10(-5), 10(-4), 6x10(-4) and 10(-3)M, respectively, in a wide range of alcohol concentration was investigated by surface tension measurements of solutions. The obtained values of the surface tension of aqueous solutions of "pure" methanol and ethanol and their mixtures with TX-100, as well as the values of propanol solutions and their mixtures with TX-100 as a function of alcohol concentration taken from the literature were compared with those calculated from the Szyszkowski, Connors and Fainerman and Miller equations. On the basis of this comparison it was stated that these equations can be useful for description of the solution surface tension in the wide range of alcohol concentration, but only at the concentrations of Triton X-100 corresponding to its unsaturated layer in the absence of alcohol. It was also stated that the Connors equation is more adequate for concentrated aqueous organic solutions. The measured values of the surface tension were used in the Gibbs equation to determine the surface excess concentration of Triton X-100 and alcohol. Next, on the basis of Gibbs adsorption isotherms those of Guggenheim and Adam and real adsorption isotherms were established. From the obtained adsorption isotherms it results that alcohol influences the shape of TX-100 isotherms in the whole range of alcohol and TX-100 concentration, but TX-100 influences the alcohol isotherms only at TX-100 concentration at which the saturated monolayer at the solution-air interface is formed in the absence of alcohol. This conclusion was confirmed by analysis of the composition of the surface layer in comparison to the composition of the bulk phase in the equilibrium state.

Native oxides formation and surface wettability of epitaxial III-V materials: The case of InP and GaAs

NASA Astrophysics Data System (ADS)

Gocalinska, A.; Rubini, S.; Pelucchi, E.

2016-10-01

The time dependent transition from hydrophobic to hydrophilic states of the metalorganic vapour phase epitaxy (MOVPE) grown InP, GaAs and InAs is systematically documented by contact angle measurements. Natural oxides forming on the surfaces of air-exposed materials, as well as the results of some typical wet chemical process to remove those oxides, were studied by X-ray photoemission spectroscopy (XPS), revealing, surprisingly, a fundamental lack of strong correlations between the surface oxide composition and the reported systematic changes in hydrophobicity.

Synthesis of hectorite-TiO2 and kaolinite-TiO2 nanocomposites with photocatalytic activity for the degradation of model air pollutants

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

Destaillats, Hugo; Kibanova, D.; Trejo, M.

2008-03-01

We studied the synthesis and photocatalytic activity of small-sized TiO{sub 2} supported on hectorite and kaolinite. Deposition of TiO{sub 2} on the clay mineral surface was conducted by using a sol-gel method with titanium isopropoxide as precursor. Anatase TiO{sub 2} particles formation was achieved by hydrothermal treatment at 180 C. Material characterization was conducted using XRD, SEM, XPS, ICP-OES, BET and porosimetry analysis. Efficiency in synthesizing clay-TiO{sub 2} composites depended strongly on the clay mineral structure. Incorporation of anatase in hectorite, an expandable clay mineral, was found to be very significant (> 36 wt.% Ti) and to be followed bymore » important structural changes at the clay mineral surface. Instead, no major structural modifications of the clay were observed for kaolinite-TiO{sub 2}, as compared with the untreated material. Photocatalytic performance of clay-TiO{sub 2} composites was evaluated with ATR-FTIR following the oxidation of adsorbed toluene and d-limonene, two model air pollutants. In either case, the photocatalytic removal efficiency of these hydrophobic substrates by the synthesized clay-TiO{sub 2} composites was comparable to that observed using pure commercial TiO{sub 2} (Degussa P25).« less

Sum-Frequency Generation Spectroscopy for Studying Organic Layers at Water-Air Interfaces: Microlayer Monitoring and Surface Reactivity

NASA Astrophysics Data System (ADS)

Laß, Kristian; Kleber, Joscha; Bange, Hermann; Friedrichs, Gernot

2015-04-01

The sea surface microlayer, according to commonly accepted terminology, comprises the topmost millimetre of the oceanic water column. It is often enriched with organic matter and is directly influenced by sunlight exposure and gas exchange with the atmosphere, hence making it a place for active biochemistry and photochemistry as well as for heterogeneous reactions. In addition, surface active material either is formed or accumulates directly at the air-water interface and gives rise to very thin layers, sometimes down to monomolecular thickness. This "sea surface nanolayer" determines the viscoelastic properties of the seawater surface and thus may impact the turbulent air-sea gas exchange rates. To this effect, this small scale layer presumably plays an important role for large scale changes of atmospheric trace gas concentrations (e.g., by modulating the ocean carbon sink characteristics) with possible implications for coupled climate models. To date, detailed knowledge about the composition, structure, and reactivity of the sea surface nanolayer is still scarce. Due to its small vertical dimension and the small amount of material, this surfactant layer is very difficult to separate and analyse. A way out is the application of second-order nonlinear optical methods, which make a direct surface-specific and background-free detection of this interfacial layer possible. In recent years, we have introduced the use of vibrational sum frequency generation (VSFG) spectroscopy to gain insight into natural and artificial organic monolayers at the air-water interface. In this contribution, the application of VSFG spectroscopy for the analysis of the sea surface nanolayer will be illustrated. Resulting spectra are interpreted in terms of layer composition and surfactant classes, in particular with respect to carbohydrate-containing molecules such as glycolipids. The partitioning of the detected surfactants into soluble and non-soluble ("wet" and "dry") surfactants will be discussed. Furthermore, the application of a combined VSFG/Langmuir trough experiment to investigate the reaction kinetics of heterogeneous oxidation processes will be highlighted. The ozonolysis of monolayers of unsaturated fatty acids serves as model system for natural aging processes of surfactant layers at the sea surface. Finally, a VSFG time series study of the sea surface nanolayer at a western Baltic Sea near-shore sampling station will be presented. The observed seasonality reveals a significant temporal shift with respect to the spring algal bloom showing that high organic material content in the microlayer does not necessarily correlate with high nanolayer abundance. This interesting finding and implications for the formation of surfactant material by degradation of biological material will be discussed briefly.

Compositional transformations in ion implanted polymers

NASA Astrophysics Data System (ADS)

Abdul-Kader, A. M.; Turos, A.; Grambole, D.; Jagielski, J.; Piątkowska, A.; Madi, N. K.; Al-Maadeed, M.

2005-10-01

Changes of surface layer composition produced by ion bombardment of polyethylene and polypropylene samples were studied. These materials are under consideration for load bearing surfaces in biological and technical applications. To improve their tribological properties, surface layers are usually modified by ionizing radiation. Therefore, to study the mechanism of transformations induced by ion beam bombardment selected polymers were implanted with H, He and Ar ions to the fluences ranging from 1 × 1013 to 2 × 1016/cm2. RBS and NRA techniques were applied for sample analysis. Important hydrogen release was observed with increasing ion dose and was correlated with the ion stopping power. Another important effect observed was the rapid oxidation of samples, which apparently occurs after exposure of implanted samples to the air. Up to 10 at.% of oxygen can be incorporated in the implanted layer.

Surface adsorption of oppositely charged C14TAB-PAMPS mixtures at the air/water interface and the impact on foam film stability.

PubMed

Fauser, Heiko; von Klitzing, Regine; Campbell, Richard A

2015-01-08

We have studied the oppositely charged polyelectrolyte/surfactant mixture of poly(acrylamidomethylpropanesulfonate) sodium salt (PAMPS) and tetradecyl trimethylammonium bromide (C14TAB) using a combination of neutron reflectivity and ellipsometry measurements. The interfacial composition was determined using three different analysis methods involving the two techniques for the first time. The bulk surfactant concentration was fixed at a modest value while the bulk polyelectrolyte concentration was varied over a wide range. We reveal complex changes in the surface adsorption behavior. Mixtures with low bulk PAMPS concentrations result in the components interacting synergistically in charge neutral layers at the air/water interface. At the bulk composition where PAMPS and C14TAB are mixed in an equimolar charge ratio in the bulk, we observe a dramatic drop in the surfactant surface excess to leave a large excess of polyelectrolyte at the interface, which we infer to have loops in its interfacial structure. Further increase of the bulk PAMPS concentration leads to a more pronounced depletion of material from the surface. Mixtures containing a large excess of PAMPS in the bulk showed enhanced adsorption, which is attributed to the large increase in total ionic strength of the system and screening of the surfactant headgroup charges. The data are compared to our former results on PAMPS/C14TAB mixtures [Kristen et al. J. Phys. Chem. B, 2009, 23, 7986]. A peak in the surface tension is rationalized in terms of the changing surface adsorption and, unlike in more concentrated systems, is unrelated to bulk precipitation. Also, a comparison between the determined interfacial composition with zeta potential and foam film stability data shows that the highest film stability occurs when there is enhanced synergistic adsorption of both components at the interface due to charge screening when the total ionic strength of the system is highest. The additional contribution to the foam stability of the negatively charged polyelectrolyte within the film bulk is also discussed.

Structure and chemical composition of layers adsorbed at interfaces with champagne.

PubMed

Aguié-Béghin, V; Adriaensen, Y; Péron, N; Valade, M; Rouxhet, P; Douillard, R

2009-11-11

The structure and the chemical composition of the layer adsorbed at interfaces involving champagne have been investigated using native champagne, as well as ultrafiltrate (UFch) and ultraconcentrate (UCch) obtained by ultrafiltration with a 10(4) nominal molar mass cutoff. The layer adsorbed at the air/liquid interface was examined by surface tension and ellipsometry kinetic measurements. Brewster angle microscopy demonstrated that the layer formed on polystyrene by adsorption or drop evaporation was heterogeneous, with a domain structure presenting similarities with the layer adsorbed at the air/liquid interface. The surface chemical composition of polystyrene with the adlayer was determined by X-ray photoelectron spectroscopy (XPS). The contribution of champagne constituents varied according to the liquid (native, UFch, and UCch) and to the procedure of adlayer formation (evaporation, adsorption, and adsorption + rinsing). However, their chemical composition was not significantly influenced either by ultrafiltration or by the procedure of deposition on polystyrene. Modeling this composition in terms of classes of model compounds gave approximately 35% (w/w) of proteins and 65% (w/w) of polysaccharides. In the adlayer, the carboxyl groups or esters represent about 18% of carbon due to nonpolypeptidic compounds, indicating the presence of either uronic acids in the complex structure of pectic polysaccharides or of polyphenolic esters. This structural and chemical information and its relationship with the experimental procedures indicate that proteins alone cannot be used as a realistic model for the macromolecules forming the adsorption layer of champagne. Polysaccharides, the other major macromolecular components of champagne wine, are assembled with proteins at the interfaces, in agreement with the heterogeneous character of the adsorbed layer at interfaces.

Effect of different surface treatments on microtensile bond strength of two resin cements to aged simulated composite core materials.

PubMed

Esmaeili, Behnaz; Alaghehmand, Homayoon; Shakerian, Mohadese

2015-01-01

Roughening of the aged composite resin core (CRC) surface seems essential for durable adhesion. The aim of this study was to investigate the influence of various surface treatments and different resin cements on microtensile bond strength (µ TBS) between two aged core build-up composites (CBCs) and feldspathic ceramic. A total of 16 composite blocks made of two CBCs, Core.it and Build-it were randomly assigned to four surface treatment groups after water storage and thermocycling (2 weeks and 500 cycles). Experimental groups included surface roughening with air abrasion (AA), hydrofluoric acid, pumice, and laser and then were bonded to computer-aided design/computer-aided manufacturing feldspathic ceramic blocks using two resin cements, Panavia F2 (PF), and Duo-link (DL). The µ TBS was tested, and the fracture mode was assessed. The data were analyzed with multiple analysis of variance to estimate the contribution of different surface treatments, resin cements, and two aged CRCs on µ TBS. Statistical significance level was set at α < 0.05. Surface treatment and cement type significantly affected bond strength (P < 0.001) but the type of CRC did not (P = 0.468). Between roughening methods, the highest and the lowest values of µ TBS were sequentially obtained in AA and Er.YAG laser groups. The highest bond strength was in AA group cemented with PF (31.83 MPa). The most common failure mode was cohesive fracture in the cement. Different surface treatments had different effects on µ TBS of aged CRCs to feldspathic ceramics. PF was significantly better than DL.

Graphite pellicles, methods of formation and properties

NASA Astrophysics Data System (ADS)

Topala, P.; Marin, L.; Besliu, V.; Stoicev, P.; Ojegov, A.; Cosovschii, P.

2015-11-01

The paper presents the results of experimental investigations aimed at the establishing the composition and the functional properties of the graphite pellicles formed on the metal surfaces by the action of plasma in the air media at normal pressure applying electrical discharges in impulse (EDI). It shows that they have the same behavior characteristics as fullerene, avoiding the stick effect between metal surfaces and between metal and liquid glass at temperatures of the order of 400-1200 °C.

Assessment of microphysical and chemical factors of aerosols over seas of the Russian Artic Eastern Section

NASA Astrophysics Data System (ADS)

Golobokova, Liudmila; Polkin, Victor

2014-05-01

The newly observed kickoff of the Northern Route development drew serious attention to state of the Arctic Resource environment. Occurring climatic and environmental changes are more sensitively seen in polar areas in particular. Air environment control allows for making prognostic assessments which are required for planning hazardous environmental impacts preventive actions. In August - September 2013, RV «Professor Khlustin» Northern Sea Route expeditionary voyage took place. En-route aerosol sampling was done over the surface of the Beringov, Chukotka and Eastern-Siberia seas (till the town of Pevek). The purpose of sampling was to assess spatio-temporal variability of optic, microphysical and chemical characteristics of aerosol particles of the surface layer within different areas adjacent to the Northern Sea Route. Aerosol test made use of automated mobile unit consisting of photoelectric particles counter AZ-10, aetalometr MDA-02, aspirator on NBM-1.2 pump chassis, and the impactor. This set of equipment allows for doing measurements of number concentration, dispersed composition of aerosols within sizes d=0.3-10 mkm, mass concentration of submicron sized aerosol, and filter-conveyed aerosols sampling. Filter-conveyed aerosols sampling was done using method accepted by EMEP and EANET monitoring networks. The impactor channel was upgraded to separate particles bigger than 1 mkm in size, and the fine grain fraction settled down on it. Reverse 5-day and 10-day trajectories of air mass transfer executed at heights of 10, 1500 and 3500 m were analyzed. The heights were selected by considerations that 3000 m is the height which characterizes air mass trend in the lower troposphere. 1500 m is the upper border of the atmospheric boundary layer, and the sampling was done in the Earth's surface layer at less than 10 m. Minimum values of the bespoken microphysical characteristics are better characteristic of higher latitudes where there are no man induced sources of aerosols while the natural ones are of lower severity due to low temperatures endemic for the Arctic Ocean areas. For doing the assessment of the air mass components chemical formulation samples of water soluble fraction of the atmospheric aerosol underwent chemical analysis. Sum of main ions within the aerosol composition varied from 0.23 to 16.2 mkg/m3. Minimum ion concentrations are defined in the aerosol sampled over the Chukotka sea surface at still. Chemical composition of the Beringov and Chukotka sea aerosol was dominated by impurities of sea origin coming from the ocean with air mass. Ion sum increased concentrations were observed in the Pevek area (Eastern Siberia Sea). Aerosol chemical composition building was impacted by air mass coming from the shore. Maximum concentrations of the bespoken components are seen in the aerosol sampled during stormy weather. Increase of wind made it for raising into the air of the sea origin particles. Ingestion of sprays onto the filter was eliminated by covering the sample catcher with a special protective hood. This completed survey is indicative of favourable state of atmosphere in the arctic resource of the Russian Arctic Eastern Section during Summer-Autumn season of 2013. The job is done under financial support of project. 23 Programs of fundamental research of the RAS Presidium, Partnership Integration Project, SB RAS. 25.

Steady-state equation of water vapor sorption for CaCl2-based chemical sorbents and its application

PubMed Central

Zhang, Haiquan; Yuan, Yanping; Sun, Qingrong; Cao, Xiaoling; Sun, Liangliang

2016-01-01

Green CaCl2-based chemical sorbent has been widely used in sorption refrigeration, air purification and air desiccation. Methods to improve the sorption rate have been extensively investigated, but the corresponding theoretical formulations have not been reported. In this paper, a sorption system of solid-liquid coexistence is established based on the hypothesis of steady-state sorption. The combination of theoretical analysis and experimental results indicates that the system can be described by steady-state sorption process. The steady-state sorption equation, μ = (η − γT) , was obtained in consideration of humidity, temperature and the surface area. Based on engineering applications and this equation, two methods including an increase of specific surface area and adjustment of the critical relative humidity (γ) for chemical sorbents, have been proposed to increase the sorption rate. The results indicate that the CaCl2/CNTs composite with a large specific surface area can be obtained by coating CaCl2 powder on the surface of carbon nanotubes (CNTs). The composite reached sorption equilibrium within only 4 h, and the sorption capacity was improved by 75% compared with pure CaCl2 powder. Furthermore, the addition of NaCl powder to saturated CaCl2 solution could significantly lower the solution’s γ. The sorption rate was improved by 30% under the same environment. PMID:27682811

Steady-state equation of water vapor sorption for CaCl2-based chemical sorbents and its application

NASA Astrophysics Data System (ADS)

Zhang, Haiquan; Yuan, Yanping; Sun, Qingrong; Cao, Xiaoling; Sun, Liangliang

2016-09-01

Green CaCl2-based chemical sorbent has been widely used in sorption refrigeration, air purification and air desiccation. Methods to improve the sorption rate have been extensively investigated, but the corresponding theoretical formulations have not been reported. In this paper, a sorption system of solid-liquid coexistence is established based on the hypothesis of steady-state sorption. The combination of theoretical analysis and experimental results indicates that the system can be described by steady-state sorption process. The steady-state sorption equation, μ = (η - γT) , was obtained in consideration of humidity, temperature and the surface area. Based on engineering applications and this equation, two methods including an increase of specific surface area and adjustment of the critical relative humidity (γ) for chemical sorbents, have been proposed to increase the sorption rate. The results indicate that the CaCl2/CNTs composite with a large specific surface area can be obtained by coating CaCl2 powder on the surface of carbon nanotubes (CNTs). The composite reached sorption equilibrium within only 4 h, and the sorption capacity was improved by 75% compared with pure CaCl2 powder. Furthermore, the addition of NaCl powder to saturated CaCl2 solution could significantly lower the solution’s γ. The sorption rate was improved by 30% under the same environment.

Light changes the atmospheric reactivity of soot

PubMed Central

Monge, Maria Eugenia; D’Anna, Barbara; Mazri, Linda; Giroir-Fendler, Anne; Ammann, Markus; Donaldson, D. J.; George, Christian

2010-01-01

Soot particles produced by incomplete combustion processes are one of the major components of urban air pollution. Chemistry at their surfaces lead to the heterogeneous conversion of several key trace gases; for example NO2 interacts with soot and is converted into HONO, which rapidly photodissociates to form OH in the troposphere. In the dark, soot surfaces are rapidly deactivated under atmospheric conditions, leading to the current understanding that soot chemistry affects tropospheric chemical composition only in a minor way. We demonstrate here that the conversion of NO2 to HONO on soot particles is drastically enhanced in the presence of artificial solar radiation, and leads to persistent reactivity over long periods. Soot photochemistry may therefore be a key player in urban air pollution. PMID:20080580

Tribological composition optimization of chromium-carbide-based solid lubricant coatings for foil gas bearings at temperatures to 650 C

NASA Technical Reports Server (NTRS)

Dellacorte, Christopher

1988-01-01

The determination of the tribilogically optimum composition of chromium-carbide-based solid lubricant coatings using a foil gas bearing test apparatus is described. The coatings contain a wear resistant chromium carbide `base stock' with the lubricant additives silver and BaF2-CaF2 eutectic. The coating composition is optimized for air-lubricated foil gas bearings at temperatures ranging from 25 to 650 C. The various compositions were prepared by powder blending, then plasma sprayed onto Inconel 718 test journals and diamond ground to the desired coating thickness and surface finish. The journals were operated against preoxidized Ni-Cr alloy foils, and the test bearings were subjected to repeated start-stop cycles under a bearing unit of 14 kPa. Sliding contact between the coated journal and the smooth foil occurs during bearing start-up before lift-off or hydrodynamic lubrication by the air film and during bearing coast-down. The bearings were tested for 9000 start-stop cycles or until specimen reached a predetermined failure level.

Investigation of ammonia air-surface exchange processes in a deciduous montane forest in the southeastern U.S.

EPA Science Inventory

Recent assessments of atmospheric deposition in North America note the increasing importance of reduced (NHx = NH3 + NH4+) forms of nitrogen (N) relative to oxidized forms. This shift in in the composition of inorganic nitrogen deposition has both ecological and policy implicati...

Parameterization of N2O5 Reaction Probabilities on the Surface of Particles Containing Ammonium, Sulfate, and Nitrate

EPA Science Inventory

A comprehensive parameterization was developed for the heterogeneous reaction probability (γ) of N₂O₅ as a function of temperature, relative humidity, particle composition, and phase state, for use in advanced air quality models. The reaction probabilities o...

Hybrid Composite Material and Solid Particle Erosion Studies

NASA Astrophysics Data System (ADS)

Chellaganesh, D.; Khan, M. Adam; Ashif, A. Mohamed; Ragul Selvan, T.; Nachiappan, S.; Winowlin Jappes, J. T.

2018-04-01

Composite is one of the predominant material for most challenging engineering components. Most of the components are in the place of automobile structure, aircraft structures, and wind turbine blade and so on. At the same all the components are indulged to mechanical loading. Recent research on composite material are machinability, wear, tear and corrosion studies. One of the major issue on recent research was solid particle air jet erosion. In this paper hybrid composite material with and without filler. The fibre are in the combination of hemp – kevlar (60:40 wt.%) as reinforcement using epoxy as a matrix. The natural material palm and coconut shell are used as filler materials in the form of crushed powder. The process parameter involved are air jet velocity, volume of erodent and angle of impingement. Experiment performed are in eight different combinations followed from 2k (k = 3) factorial design. From the investigation surface morphology was studied using electron microscope. Mass change with respect to time are used to calculate wear rate and the influence of the process parameters. While solid particle erosion the hard particle impregnates in soft matrix material. Influence of filler material has reduced the wear and compared to plain natural composite material.

Changes in optical characteristics of surface microlayers in the Peruvian upwelling region hint to photochemically and microbially-mediated DOM turnover

NASA Astrophysics Data System (ADS)

Engel, A.; Galgani, L.

2016-02-01

The coastal upwelling system off Peru is characterized by high biological activity and associated subsurface oxygen minimum zone, leading to an enhanced emission of atmospheric trace gases. High biological productivity in the water column may promote the establishment of enriched organic surface films, key environments for processes regulating gas fluxes across the water-air interface. During M91 cruise to the Peruvian upwelling, we focused our attention on the composition of the sea-surface microlayer (SML), the oceanic uppermost boundary directly subject to high solar radiation, often enriched in specific organic compounds of biological origin like Chromophoric Dissolved Organic Matter (CDOM) and marine gels. In the SML, the continuous photochemical and microbial recycling of organic matter may strongly influence gas exchange between marine systems and the atmosphere. In order to understand organic matter cycling in surface films, we analyzed SML and underlying water samples in 38 stations determining DOC concentrations, amino acids composition, marine gels, CDOM and bacterial abundance as indicators of photochemical and microbial alteration processes. CDOM composition was characterized by spectral slopes (S) values and Excitation-Emission Matrix fluorescence (EEMs), which allow to track changes in molecular weight (MW) of DOM, and to determine potential DOM sources. Profound changes in spectral slope properties were observed suggesting smaller MW CDOM in the SML compared to underlying water. Microbial and photochemical degradation are likely the main drivers for organic matter cycling in the top layer of the ocean. Consequences on the formation of inorganic and organic species highly relevant for air-sea gas exchange and for climate dynamics will be discussed.

Architectural Effects on Impact Resistance of Uncoated MI SiC/SiC Composites

NASA Technical Reports Server (NTRS)

Bhatt, R. T.; Cosgriff, L. M.; Fox, D. S.

2009-01-01

Impact tests were conducted on uncoated 2D and 2.5D MI SiC/SiC composite specimens at room temperature and 1316 C in air. The specimens were analyzed before and after impact using optical microscopy, pulsed thermography (PT) and computed tomography (CT). Preliminary results indicate the following. Both 2-D and 2.5D composites show increase in surface and volumetric damages with increasing impact velocity. However, 2-D composites are prone to delamination cracks. In both 2D and 2.5D composites, the magnitude of impact damage at a fixed impact velocity is slightly greater at room temperature than at 1315 C. At a fixed projectile velocity and test temperature, the depth of penetration of the projectile into the substrate is significantly lower in 2.5D composites than in 2D composites. Fiber architecture plays a significant role controlling impact damage in MI SiC/SiC composites.

Evidence for a mixed mass composition at the 'ankle' in the cosmic-ray spectrum

NASA Astrophysics Data System (ADS)

Aab, A.; Abreu, P.; Aglietta, M.; Ahn, E. J.; Al Samarai, I.; Albuquerque, I. F. M.; Allekotte, I.; Allison, P.; Almela, A.; Alvarez Castillo, J.; Alvarez-Muñiz, J.; Ambrosio, M.; Anastasi, G. A.; Anchordoqui, L.; Andrada, B.; Andringa, S.; Aramo, C.; Arqueros, F.; Arsene, N.; Asorey, H.; Assis, P.; Aublin, J.; Avila, G.; Badescu, A. M.; Balaceanu, A.; Baus, C.; Beatty, J. J.; Becker, K. H.; Bellido, J. A.; Berat, C.; Bertaina, M. E.; Biermann, P. L.; Billoir, P.; Biteau, J.; Blaess, S. G.; Blanco, A.; Blazek, J.; Bleve, C.; Boháčová, M.; Boncioli, D.; Bonifazi, C.; Borodai, N.; Botti, A. M.; Brack, J.; Brancus, I.; Bretz, T.; Bridgeman, A.; Briechle, F. L.; Buchholz, P.; Bueno, A.; Buitink, S.; Buscemi, M.; Caballero-Mora, K. S.; Caccianiga, B.; Caccianiga, L.; Cancio, A.; Canfora, F.; Caramete, L.; Caruso, R.; Castellina, A.; Cataldi, G.; Cazon, L.; Cester, R.; Chavez, A. G.; Chiavassa, A.; Chinellato, J. A.; Chudoba, J.; Clay, R. W.; Colalillo, R.; Coleman, A.; Collica, L.; Coluccia, M. R.; Conceição, R.; Contreras, F.; Cooper, M. J.; Coutu, S.; Covault, C. E.; Cronin, J.; Dallier, R.; D'Amico, S.; Daniel, B.; Dasso, S.; Daumiller, K.; Dawson, B. R.; de Almeida, R. M.; de Jong, S. J.; De Mauro, G.; de Mello Neto, J. R. T.; De Mitri, I.; de Oliveira, J.; de Souza, V.; Debatin, J.; del Peral, L.; Deligny, O.; Di Giulio, C.; Di Matteo, A.; Díaz Castro, M. L.; Diogo, F.; Dobrigkeit, C.; D'Olivo, J. C.; Dorofeev, A.; dos Anjos, R. C.; Dova, M. T.; Dundovic, A.; Ebr, J.; Engel, R.; Erdmann, M.; Erfani, M.; Escobar, C. O.; Espadanal, J.; Etchegoyen, A.; Falcke, H.; Fang, K.; Farrar, G.; Fauth, A. C.; Fazzini, N.; Fick, B.; Figueira, J. M.; Filevich, A.; Filipčič, A.; Fratu, O.; Freire, M. M.; Fujii, T.; Fuster, A.; García, B.; Garcia-Pinto, D.; Gaté, F.; Gemmeke, H.; Gherghel-Lascu, A.; Ghia, P. L.; Giaccari, U.; Giammarchi, M.; Giller, M.; Głas, D.; Glaser, C.; Glass, H.; Golup, G.; Gómez Berisso, M.; Gómez Vitale, P. F.; González, N.; Gookin, B.; Gordon, J.; Gorgi, A.; Gorham, P.; Gouffon, P.; Grillo, A. F.; Grubb, T. D.; Guarino, F.; Guedes, G. P.; Hampel, M. R.; Hansen, P.; Harari, D.; Harrison, T. A.; Harton, J. L.; Hasankiadeh, Q.; Haungs, A.; Hebbeker, T.; Heck, D.; Heimann, P.; Herve, A. E.; Hill, G. C.; Hojvat, C.; Holt, E.; Homola, P.; Hörandel, J. R.; Horvath, P.; Hrabovský, M.; Huege, T.; Hulsman, J.; Insolia, A.; Isar, P. G.; Jandt, I.; Jansen, S.; Johnsen, J. A.; Josebachuili, M.; Kääpä, A.; Kambeitz, O.; Kampert, K. H.; Kasper, P.; Katkov, I.; Keilhauer, B.; Kemp, E.; Kieckhafer, R. M.; Klages, H. O.; Kleifges, M.; Kleinfeller, J.; Krause, R.; Krohm, N.; Kuempel, D.; Kukec Mezek, G.; Kunka, N.; Kuotb Awad, A.; LaHurd, D.; Latronico, L.; Lauscher, M.; Lautridou, P.; Lebrun, P.; Legumina, R.; Leigui de Oliveira, M. A.; Letessier-Selvon, A.; Lhenry-Yvon, I.; Link, K.; Lopes, L.; López, R.; López Casado, A.; Luce, Q.; Lucero, A.; Malacari, M.; Mallamaci, M.; Mandat, D.; Mantsch, P.; Mariazzi, A. G.; Mariş, I. C.; Marsella, G.; Martello, D.; Martinez, H.; Martínez Bravo, O.; Masías Meza, J. J.; Mathes, H. J.; Mathys, S.; Matthews, J.; Matthews, J. A. J.; Matthiae, G.; Mayotte, E.; Mazur, P. O.; Medina, C.; Medina-Tanco, G.; Melo, D.; Menshikov, A.; Messina, S.; Micheletti, M. I.; Middendorf, L.; Minaya, I. A.; Miramonti, L.; Mitrica, B.; Mockler, D.; Molina-Bueno, L.; Mollerach, S.; Montanet, F.; Morello, C.; Mostafá, M.; Müller, G.; Muller, M. A.; Müller, S.; Naranjo, I.; Navas, S.; Nellen, L.; Neuser, J.; Nguyen, P. H.; Niculescu-Oglinzanu, M.; Niechciol, M.; Niemietz, L.; Niggemann, T.; Nitz, D.; Nosek, D.; Novotny, V.; Nožka, H.; Núñez, L. A.; Ochilo, L.; Oikonomou, F.; Olinto, A.; Pakk Selmi-Dei, D.; Palatka, M.; Pallotta, J.; Papenbreer, P.; Parente, G.; Parra, A.; Paul, T.; Pech, M.; Pedreira, F.; Pȩkala, J.; Pelayo, R.; Peña-Rodriguez, J.; Pereira, L. A. S.; Perrone, L.; Peters, C.; Petrera, S.; Phuntsok, J.; Piegaia, R.; Pierog, T.; Pieroni, P.; Pimenta, M.; Pirronello, V.; Platino, M.; Plum, M.; Porowski, C.; Prado, R. R.; Privitera, P.; Prouza, M.; Quel, E. J.; Querchfeld, S.; Quinn, S.; Ramos-Pollant, R.; Rautenberg, J.; Ravel, O.; Ravignani, D.; Reinert, D.; Revenu, B.; Ridky, J.; Risse, M.; Ristori, P.; Rizi, V.; Rodrigues de Carvalho, W.; Rodriguez Fernandez, G.; Rodriguez Rojo, J.; Rodríguez-Frías, M. D.; Rogozin, D.; Rosado, J.; Roth, M.; Roulet, E.; Rovero, A. C.; Saffi, S. J.; Saftoiu, A.; Salazar, H.; Saleh, A.; Salesa Greus, F.; Salina, G.; Sanabria Gomez, J. D.; Sánchez, F.; Sanchez-Lucas, P.; Santos, E. M.; Santos, E.; Sarazin, F.; Sarkar, B.; Sarmento, R.; Sarmiento-Cano, C.; Sato, R.; Scarso, C.; Schauer, M.; Scherini, V.; Schieler, H.; Schmidt, D.; Scholten, O.; Schovánek, P.; Schröder, F. G.; Schulz, A.; Schulz, J.; Schumacher, J.; Sciutto, S. J.; Segreto, A.; Settimo, M.; Shadkam, A.; Shellard, R. C.; Sigl, G.; Silli, G.; Sima, O.; Śmiałkowski, A.; Šmída, R.; Snow, G. R.; Sommers, P.; Sonntag, S.; Sorokin, J.; Squartini, R.; Stanca, D.; Stanič, S.; Stasielak, J.; Strafella, F.; Suarez, F.; Suarez Durán, M.; Sudholz, T.; Suomijärvi, T.; Supanitsky, A. D.; Sutherland, M. S.; Swain, J.; Szadkowski, Z.; Taborda, O. A.; Tapia, A.; Tepe, A.; Theodoro, V. M.; Timmermans, C.; Todero Peixoto, C. J.; Tomankova, L.; Tomé, B.; Tonachini, A.; Torralba Elipe, G.; Torres Machado, D.; Torri, M.; Travnicek, P.; Trini, M.; Ulrich, R.; Unger, M.; Urban, M.; Valbuena-Delgado, A.; Valdés Galicia, J. F.; Valiño, I.; Valore, L.; van Aar, G.; van Bodegom, P.; van den Berg, A. M.; van Vliet, A.; Varela, E.; Vargas Cárdenas, B.; Varner, G.; Vázquez, J. R.; Vázquez, R. A.; Veberič, D.; Verzi, V.; Vicha, J.; Villaseñor, L.; Vorobiov, S.; Wahlberg, H.; Wainberg, O.; Walz, D.; Watson, A. A.; Weber, M.; Weindl, A.; Wiencke, L.; Wilczyński, H.; Winchen, T.; Wittkowski, D.; Wundheiler, B.; Wykes, S.; Yang, L.; Yelos, D.; Younk, P.; Yushkov, A.; Zas, E.; Zavrtanik, D.; Zavrtanik, M.; Zepeda, A.; Zimmermann, B.; Ziolkowski, M.; Zong, Z.; Zuccarello, F.; Pierre Auger Collaboration

2016-11-01

We report a first measurement for ultrahigh energy cosmic rays of the correlation between the depth of shower maximum and the signal in the water Cherenkov stations of air-showers registered simultaneously by the fluorescence and the surface detectors of the Pierre Auger Observatory. Such a correlation measurement is a unique feature of a hybrid air-shower observatory with sensitivity to both the electromagnetic and muonic components. It allows an accurate determination of the spread of primary masses in the cosmic-ray flux. Up till now, constraints on the spread of primary masses have been dominated by systematic uncertainties. The present correlation measurement is not affected by systematics in the measurement of the depth of shower maximum or the signal in the water Cherenkov stations. The analysis relies on general characteristics of air showers and is thus robust also with respect to uncertainties in hadronic event generators. The observed correlation in the energy range around the 'ankle' at lg ⁡ (E /eV) = 18.5- 19.0 differs significantly from expectations for pure primary cosmic-ray compositions. A light composition made up of proton and helium only is equally inconsistent with observations. The data are explained well by a mixed composition including nuclei with mass A > 4. Scenarios such as the proton dip model, with almost pure compositions, are thus disfavored as the sole explanation of the ultrahigh-energy cosmic-ray flux at Earth.

Evidence for a mixed mass composition at the ‘ankle’ in the cosmic-ray spectrum

DOE PAGES

Aab, Alexander

2016-09-28

Here, we report a first measurement for ultra-high energy cosmic rays of the correlation between the depth of shower maximum and the signal in the water Cherenkov stations of air-showers registered simultaneously by the fluorescence and the surface detectors of the Pierre Auger Observatory. Such a correlation measurement is a unique feature of a hybrid air-shower observatory with sensitivity to both the electromagnetic and muonic components. It allows an accurate determination of the spread of primary masses in the cosmic-ray flux. Up till now, constraints on the spread of primary masses have been dominated by systematic uncertainties. The present correlation measurement is not affected by systematics in the measurement of the depth of shower maximum or the signal in the water Cherenkov stations. The analysis relies on general characteristics of air showers and is thus robust also with respect to uncertainties in hadronic event generators. The observed correlation in the energy range around the `ankle' atmore » $$\\lg(E/{\\rm eV})=18.5-19.0$$ differs significantly from expectations for pure primary cosmic-ray compositions. A light composition made up of proton and helium only is equally inconsistent with observations. The data are explained well by a mixed composition including nuclei with mass $A > 4$. Scenarios such as the proton dip model, with almost pure compositions, are thus disfavoured as the sole explanation of the ultrahigh-energy cosmic-ray flux at Earth.« less

Kaolinite-catalyzed air oxidation of hydrazine: Consideration of several compositional, structural and energetic factors in surface activation

NASA Technical Reports Server (NTRS)

Coyne, L. M.; Mariner, R.; Rice, A.

1991-01-01

Clay minerals have been shown to have numerous, curious, energetic properties by virtue of ultra-violet light release which can be triggered by gentle environmental changes such as wetting and dewetting by a variety of liquids, unique among them water and hydrazine. Since both water and hydrazine play multiple key roles in the air-oxidation of hydrazine on kaolinite surfaces, this reaction would seem to have prime potential for studying interrelationships of energy storage, release and chemical reactivity of clay surfaces, capacities basic to either the Bernal or Cairns-Smith roles of minerals in the origin of life. Establishment of the capacity for stored electronic energy to significantly alter surface chemistry is important, regardless of the reaction chosen to demonstrate it. Hydrazine air oxidation is overawingly complex, given the possibilities for step-wise control and monitoring of parameters. In the light of recently extended characterization of the kaolinite and model sheet catalysts we used to study hydrazine oxidation and gamma-irradiated silica, previous studies of hydrazine air-oxidation on aluminosilicate surfaces have been reevaluated. Our former conclusion remains intact that, whereas trace structural and surface contaminants do play some role in the catalysis of oxidation, they are not the only, nor even the dominant, catalytic centers. Initial intermediates in the oxidation can now be proposed which are consistent with production via O(-)-centers as well as ferric iron centers. The greater than square dependence of the initial reaction rate on the weight of the clay is discussed in the light of these various mechanistic possibilities.

Damage imaging in a laminated composite plate using an air-coupled time reversal mirror

DOE PAGES

Le Bas, P. -Y.; Remillieux, M. C.; Pieczonka, L.; ...

2015-11-03

We demonstrate the possibility of selectively imaging the features of a barely visible impact damage in a laminated composite plate by using an air-coupled time reversal mirror. The mirror consists of a number of piezoelectric transducers affixed to wedges of power law profiles, which act as unconventional matching layers. The transducers are enclosed in a hollow reverberant cavity with an opening to allow progressive emission of the ultrasonic wave field towards the composite plate. The principle of time reversal is used to focus elastic waves at each point of a scanning grid spanning the surface of the plate, thus allowingmore » localized inspection at each of these points. The proposed device and signal processing removes the need to be in direct contact with the plate and reveals the same features as vibrothermography and more features than a C-scan. More importantly, this device can decouple the features of the defect according to their orientation, by selectively focusing vector components of motion into the object, through air. For instance, a delamination can be imaged in one experiment using out-of-plane focusing, whereas a crack can be imaged in a separate experiment using in-plane focusing. As a result, this capability, inherited from the principle of time reversal, cannot be found in conventional air-coupled transducers.« less

Influence of warm air-drying on enamel bond strength and surface free-energy of self-etch adhesives.

PubMed

Shiratsuchi, Koji; Tsujimoto, Akimasa; Takamizawa, Toshiki; Furuichi, Tetsuya; Tsubota, Keishi; Kurokawa, Hiroyasu; Miyazaki, Masashi

2013-08-01

We examined the effect of warm air-drying on the enamel bond strengths and the surface free-energy of three single-step self-etch adhesives. Bovine mandibular incisors were mounted in self-curing resin and then wet ground with #600 silicon carbide (SiC) paper. The adhesives were applied according to the instructions of the respective manufacturers and then dried in a stream of normal (23°C) or warm (37°C) air for 5, 10, and 20 s. After visible-light irradiation of the adhesives, resin composites were condensed into a mold and polymerized. Ten samples per test group were stored in distilled water at 37°C for 24 h and then the bond strengths were measured. The surface free-energies were determined by measuring the contact angles of three test liquids placed on the cured adhesives. The enamel bond strengths varied according to the air-drying time and ranged from 15.8 to 19.1 MPa. The trends for the bond strengths were different among the materials. The value of the γS⁺ component increased slightly when drying was performed with a stream of warm air, whereas that of the γS⁻ component decreased significantly. These data suggest that warm air-drying is essential to obtain adequate enamel bond strengths, although increasing the drying time did not significantly influence the bond strength. © 2013 Eur J Oral Sci.

Cyclic Fatigue Durability of Uncoated and EBC Coated 3D SiC/SiC Composites Under Thermal Gradient Conditions at 2700F in Air

NASA Technical Reports Server (NTRS)

Smith, Craig; Harder, Bryan; Zhu, Dongming; Bhatt, Ramakrishna; Kalluri, Sreeramesh

2017-01-01

Ceramic matrix composites (CMCs) such as SiCSiC are currently being designed and implemented in high temperature sections of aerospace turbine engines. Such components will be subject to through-thickness thermal gradients, which may affect the durability. In this study, SiCSiC CMCs with a hybrid chemical vapor infiltrated (CVI) and polymer infiltration and pyrolysis (PIP) matrix were loaded in tension while one surface was heated with a laser and the opposite surface was cooled. The samples were each coated with an environmental barrier coating (EBC), which was produced by electron beam physical deposition (EBPVD). Results for CMCs tested with and without the EBC be discussed.

Adsorption of Egg-PC to an Air/Water and Triolein/Water Bubble Interface: Use of the 2-Dimensional Phase Rule to Estimate the Surface Composition of a Phospholipid/Triolein/Water Surface as a Function of Surface Pressure

PubMed Central

Mitsche, Matthew A.; Wang, Libo; Small, Donald M.

2010-01-01

Phospholipid monolayers play a critical role in the structure and stabilization of biological interfaces including all membranes, the alveoli of the lung, fat droplets in adipose tissue, and lipoproteins. The behavior of phospholipids in bilayers and at an air-water interface is well understood. However, the study of phospholipids at oil-water interfaces is limited due to technical challenges. In this study, egg-phosphatidylcholine (EPC) was deposited from small unilamellar vesicles onto a bubble of either air or triolein (TO) formed in a low salt buffer. The surface tension (γ) was measured using a drop tensiometer. We observed that EPC binds irreversibly to both interfaces and at equilibrium exerts ~12 and 15 mN/m of pressure (Π) at an air and TO interface, respectively. After EPC was bound to the interface, the unbound EPC was washed out of the cuvette and the surface was compressed to study the Π/area relationship. To determine the surface concentration (Γ), which cannot be measured directly, compression isotherms from a Langmuir trough and drop tensiometer were compared. The air-water interfaces had identical characteristics using both techniques, thus Γ on the bubble can be determined by overlaying the two isotherms. TO and EPC are both surface active so in a mixed TO/EPC monolayer both molecules will be exposed to water. Since TO is less surface active than EPC, as Π increases the TO is progressively ejected. To understand the Π/area isotherm of EPC on a TO bubble, a variety of TO-EPC mixtures were spread at the air-water interface. The isotherms show an abrupt break in the curve caused by the ejection of TO from the monolayer into a new bulk phase. By overlaying the compression isotherm above the ejection point with a TO bubble compression isotherm, Γ can be estimated. This allows determination of Γ of EPC on a TO bubble as a function of Π. PMID:20151713

Adsorption of egg phosphatidylcholine to an air/water and triolein/water bubble interface: use of the 2-dimensional phase rule to estimate the surface composition of a phospholipid/triolein/water surface as a function of surface pressure.

PubMed

Mitsche, Matthew A; Wang, Libo; Small, Donald M

2010-03-11

Phospholipid monolayers play a critical role in the structure and stabilization of biological interfaces, including all membranes, the alveoli of the lungs, fat droplets in adipose tissue, and lipoproteins. The behavior of phospholipids in bilayers and at an air-water interface is well understood. However, the study of phospholipids at oil-water interfaces is limited due to technical challenges. In this study, egg phosphatidylcholine (EPC) was deposited from small unilamellar vesicles onto a bubble of either air or triolein (TO) formed in a low-salt buffer. The surface tension (gamma) was measured using a drop tensiometer. We observed that EPC binds irreversibly to both interfaces and at equilibrium exerts approximately 12 and 15 mN/m of pressure (Pi) at an air and TO interface, respectively. After EPC was bound to the interface, the unbound EPC was washed out of the cuvette, and the surface was compressed to study the Pi/area relationship. To determine the surface concentration (Gamma), which cannot be measured directly, compression isotherms from a Langmuir trough and drop tensiometer were compared. The air-water interfaces had identical characteristics using both techniques; thus, Gamma on the bubble can be determined by overlaying the two isotherms. Both TO and EPC are surface-active, so in a mixed TO/EPC monolayer, both molecules will be exposed to water. Since TO is less surface-active than EPC, as Pi increases, the TO is progressively ejected. To understand the Pi/area isotherm of EPC on a TO bubble, a variety of TO-EPC mixtures were spread at the air-water interface. The isotherms show an abrupt break in the curve caused by the ejection of TO from the monolayer into a new bulk phase. By overlaying the compression isotherm above the ejection point with a TO bubble compression isotherm, Gamma can be estimated. This allows determination of Gamma of EPC on a TO bubble as a function of Pi.

High-Temperature Hot Air/Silane Coupling Modification of Wood Fiber and Its Effect on Properties of Wood Fiber/HDPE Composites.

PubMed

Chen, Feng; Han, Guangping; Li, Qingde; Gao, Xun; Cheng, Wanli

2017-03-13

The surfaces of poplar wood fibers were modified using high-temperature hot air (HTHA) treatment and silane coupling agent. The single factor test was then used to investigate the performances (e.g., the change of functional groups, polarity, cellulose crystallinity, and thermal stability) of modified poplar wood fibers (mPWF) through Fourier transform infrared spectrometry, X-ray diffraction and thermo-gravimetric analysis for the subsequent preparation of wood-plastic composites (WPCs). The effect of HTHA treatment conditions-such as temperature, inlet air velocity, and feed rate-on the performances of WPCs was also investigated by scanning electron microscopy and dynamic mechanical analysis. The main findings indicated that HTHA treatment could promote the hydration of mPWF and improve the mechanical properties of WPCs. Treatment temperature strongly affected the mechanical properties and moisture adsorption characteristics of the prepared composites. With the increase of treated temperature and feed rate, the number of hydroxyl groups, holocellulose content, and the pH of mPWF decreased. The degree of crystallinity and thermal stability and the storage modulus of the prepared composites of mPWF increased. However, dimensional stability and water absorption of WPCs significantly reduced. The best mechanical properties enhancement was observed with treatment temperature at 220 °C. This study demonstrated the feasibility for the application of an HTHA treatment in the WPC production industry.

High-Temperature Hot Air/Silane Coupling Modification of Wood Fiber and Its Effect on Properties of Wood Fiber/HDPE Composites

PubMed Central

Chen, Feng; Han, Guangping; Li, Qingde; Gao, Xun; Cheng, Wanli

2017-01-01

The surfaces of poplar wood fibers were modified using high-temperature hot air (HTHA) treatment and silane coupling agent. The single factor test was then used to investigate the performances (e.g., the change of functional groups, polarity, cellulose crystallinity, and thermal stability) of modified poplar wood fibers (mPWF) through Fourier transform infrared spectrometry, X-ray diffraction and thermo-gravimetric analysis for the subsequent preparation of wood-plastic composites (WPCs). The effect of HTHA treatment conditions—such as temperature, inlet air velocity, and feed rate—on the performances of WPCs was also investigated by scanning electron microscopy and dynamic mechanical analysis. The main findings indicated that HTHA treatment could promote the hydration of mPWF and improve the mechanical properties of WPCs. Treatment temperature strongly affected the mechanical properties and moisture adsorption characteristics of the prepared composites. With the increase of treated temperature and feed rate, the number of hydroxyl groups, holocellulose content, and the pH of mPWF decreased. The degree of crystallinity and thermal stability and the storage modulus of the prepared composites of mPWF increased. However, dimensional stability and water absorption of WPCs significantly reduced. The best mechanical properties enhancement was observed with treatment temperature at 220 °C. This study demonstrated the feasibility for the application of an HTHA treatment in the WPC production industry. PMID:28772646

Surface adsorption behaviour of milk whey protein and pectin mixtures under conditions of air-water interface saturation.

PubMed

Perez, Adrián A; Sánchez, Cecilio Carrera; Patino, Juan M Rodríguez; Rubiolo, Amelia C; Santiago, Liliana G

2011-07-01

Milk whey proteins (MWP) and pectins (Ps) are biopolymer ingredients commonly used in the manufacture of colloidal food products. Therefore, knowledge of the interfacial characteristics of these biopolymers and their mixtures is very important for the design of food dispersion formulations (foams and/or emulsions). In this paper, we examine the adsorption and surface dilatational behaviour of MWP/Ps systems under conditions in which biopolymers can saturate the air-water interface on their own. Experiments were performed at constant temperature (20 °C), pH 7 and ionic strength 0.05 M. Two MWP samples, β-lactoglobulin (β-LG) and whey protein concentrate (WPC), and two Ps samples, low-methoxyl pectin (LMP) and high-methoxyl pectin (HMP) were evaluated. The contribution of biopolymers (MWP and Ps) to the interfacial properties of mixed systems was evaluated on the basis of their individual surface molecular characteristics. Biopolymer bulk concentration capable of saturating the air-water interface was estimated from surface pressure isotherms. Under conditions of interfacial saturation, dynamic adsorption behaviour (surface pressure and dilatational rheological characteristics) of MWP/Ps systems was discussed from a kinetic point of view, in terms of molecular diffusion, penetration and configurational rearrangement at the air-water interface. The main adsorption mechanism in MWP/LMP mixtures might be the MWP interfacial segregation due to the thermodynamic incompatibility between MWP and LMP (synergistic mechanism); while the interfacial adsorption in MWP/HMP mixtures could be characterized by a competitive mechanism between MWP and HMP at the air-water interface (antagonistic mechanism). The magnitude of these phenomena could be closely related to differences in molecular composition and/or aggregation state of MWP (β-LG and WPC). Copyright © 2011 Elsevier B.V. All rights reserved.

Facile fabrication and characterization of poly(tetrafluoroethylene)@polypyrrole/nano-silver composite membranes with conducting and antibacterial property

NASA Astrophysics Data System (ADS)

Shi, Zhiquan; Zhou, Hui; Qing, Xutang; Dai, Tingyang; Lu, Yun

2012-06-01

Porous poly(tetrafluoroethylene) (PTFE) membranes play an important role in air purification and separation engineering. To achieve the bi-functionality of conducting and antibacterial property, two kinds of poly(tetrafluoroethylene)@ polypyrrole/nano-silver composite membranes have been prepared. One involves hydrophobic polypyrrole/nano-silver composite with hollow capsule nanostructures immobilized on the surface of the PTFE membranes. The other is a type of composite membranes with polypyrrole/nano-silver composite wholly packed on the fibrils of the expand PTFE membrane to form core/shell coaxial cable structures. The structure and morphology of the two kinds of composite membranes have been characterized by FTIR, UV-vis, XRD, TGA and SEM measurements. Possible formation mechanisms of the hollow capsules and the core/shell nanocable structures have been discussed in detail. The antibacterial effects of composite membranes are also briefly investigated.

A Systems Approach to the Solid Lubrication of Foil Air Bearings for Oil-Free Turbomachinery

NASA Technical Reports Server (NTRS)

DellaCorte, Christopher; Zaldana, Antonio R.; Radil, Kevin C.

2002-01-01

Foil air bearings are self-acting hydrodynamic bearings which rely upon solid lubricants to reduce friction and minimize wear during sliding which occurs at start-up and shut-down when surface speeds are too low to allow the formation of a hydrodynamic air film. This solid lubrication is typically accomplished by coating the non-moving foil surface with a thin, soft polymeric film. The following paper introduces a systems approach in which the solid lubrication is provided by a combination of self lubricating shaft coatings coupled with various wear resistant and lubricating foil coatings. The use of multiple materials, each providing different functions is modeled after oil-lubricated hydrodynamic sleeve bearing technology which utilizes various coatings and surface treatments in conjunction with oil lubricants to achieve optimum performance. In this study, room temperature load capacity tests are performed on journal foil air bearings operating at 14,000 rpm. Different shaft and foil coating technologies such as plasma sprayed composites, ceramic, polymer and inorganic lubricant coatings are evaluated as foil bearing lubricants. The results indicate that bearing performance is improved through the individual use of the lubricants and treatments tested. Further, combining several solid lubricants together yielded synergistically better results than any material alone.

Air - water temperature relationships in the trout streams of southeastern Minnesota’s carbonate - sandstone landscape

USGS Publications Warehouse

Krider, Lori A.; Magner, Joseph A.; Perry, Jim; Vondracek, Bruce C.; Ferrington, Leonard C.

2013-01-01

Carbonate-sandstone geology in southeastern Minnesota creates a heterogeneous landscape of springs, seeps, and sinkholes that supply groundwater into streams. Air temperatures are effective predictors of water temperature in surface-water dominated streams. However, no published work investigates the relationship between air and water temperatures in groundwater-fed streams (GWFS) across watersheds. We used simple linear regressions to examine weekly air-water temperature relationships for 40 GWFS in southeastern Minnesota. A 40-stream, composite linear regression model has a slope of 0.38, an intercept of 6.63, and R2 of 0.83. The regression models for GWFS have lower slopes and higher intercepts in comparison to surface-water dominated streams. Regression models for streams with high R2 values offer promise for use as predictive tools for future climate conditions. Climate change is expected to alter the thermal regime of groundwater-fed systems, but will do so at a slower rate than surface-water dominated systems. A regression model of intercept vs. slope can be used to identify streams for which water temperatures are more meteorologically than groundwater controlled, and thus more vulnerable to climate change. Such relationships can be used to guide restoration vs. management strategies to protect trout streams.

Auger compositional depth profiling of the metal contact-TlBr interface

NASA Astrophysics Data System (ADS)

Nelson, A. J.; Swanberg, E. L.; Voss, L. F.; Graff, R. T.; Conway, A. M.; Nikolic, R. J.; Payne, S. A.; Kim, H.; Cirignano, L.; Shah, K.

2015-08-01

Degradation of room temperature operation of TlBr radiation detectors with time is thought to be due to electromigration of Tl and Br vacancies within the crystal as well as the metal contacts migrating into the TlBr crystal itself due to electrochemical reactions at the metal/TlBr interface. Scanning Auger electron spectroscopy (AES) in combination with sputter depth profiling was used to investigate the metal contact surface/interfacial structure on TlBr devices. Device-grade TlBr was polished and subjected to a 32% HCl etch to remove surface damage and create a TlBr1-xClx surface layer prior to metal contact deposition. Auger compositional depth profiling results reveal non-equilibrium interfacial diffusion after device operation in both air and N2 at ambient temperature. These results improve our understanding of contact/device degradation versus operating environment for further enhancing radiation detector performance.

Three-dimensional surface imaging system for assessing human obesity

NASA Astrophysics Data System (ADS)

Xu, Bugao; Yu, Wurong; Yao, Ming; Pepper, M. Reese; Freeland-Graves, Jeanne H.

2009-10-01

The increasing prevalence of obesity suggests a need to develop a convenient, reliable, and economical tool for assessment of this condition. Three-dimensional (3-D) body surface imaging has emerged as an exciting technology for the estimation of body composition. We present a new 3-D body imaging system, which is designed for enhanced portability, affordability, and functionality. In this system, stereo vision technology is used to satisfy the requirement for a simple hardware setup and fast image acquisition. The portability of the system is created via a two-stand configuration, and the accuracy of body volume measurements is improved by customizing stereo matching and surface reconstruction algorithms that target specific problems in 3-D body imaging. Body measurement functions dedicated to body composition assessment also are developed. The overall performance of the system is evaluated in human subjects by comparison to other conventional anthropometric methods, as well as air displacement plethysmography, for body fat assessment.

A 3D surface imaging system for assessing human obesity

NASA Astrophysics Data System (ADS)

Xu, B.; Yu, W.; Yao, M.; Yao, X.; Li, Q.; Pepper, M. R.; Freeland-Graves, J. H.

2009-08-01

The increasing prevalence of obesity suggests a need to develop a convenient, reliable and economical tool for assessment of this condition. Three-dimensional (3D) body surface imaging has emerged as an exciting technology for estimation of body composition. This paper presents a new 3D body imaging system, which was designed for enhanced portability, affordability, and functionality. In this system, stereo vision technology was used to satisfy the requirements for a simple hardware setup and fast image acquisitions. The portability of the system was created via a two-stand configuration, and the accuracy of body volume measurements was improved by customizing stereo matching and surface reconstruction algorithms that target specific problems in 3D body imaging. Body measurement functions dedicated to body composition assessment also were developed. The overall performance of the system was evaluated in human subjects by comparison to other conventional anthropometric methods, as well as air displacement plethysmography, for body fat assessment.

Monte Carlo simulation of EAS generated by 10(14) - 10(16) eV protons

NASA Technical Reports Server (NTRS)

Fenyves, E. J.; Yunn, B. C.; Stanev, T.

1985-01-01

Detailed Monte Carlo simulations of extensive air showers to be detected by the Homestake Surface Underground Telescope and other similar detectors located at sea level and mountain altitudes have been performed for 10 to the 14th power to 10 to the 16th power eV primary energies. The results of these Monte Carlo calculations will provide an opportunity to compare the experimental data with different models for the composition and spectra of primaries and for the development of air showers. The results obtained for extensive air showers generated by 10 to the 14th power to 10 to the 16th power eV primary protons are reported.

How to most effectively expand the global surface ozone observing network

NASA Astrophysics Data System (ADS)

Sofen, E. D.; Bowdalo, D.; Evans, M. J.

2016-02-01

Surface ozone observations with modern instrumentation have been made around the world for more than 40 years. Some of these observations have been made as one-off activities with short-term, specific science objectives and some have been made as part of wider networks which have provided a foundational infrastructure of data collection, calibration, quality control, and dissemination. These observations provide a fundamental underpinning to our understanding of tropospheric chemistry, air quality policy, atmosphere-biosphere interactions, etc. brought together eight of these networks to provide a single data set of surface ozone observations. We investigate how representative this combined data set is of global surface ozone using the output from a global atmospheric chemistry model. We estimate that on an area basis, 25 % of the globe is observed (34 % land, 21 % ocean). Whereas Europe and North America have almost complete coverage, other continents, Africa, South America, Australia, and Asia (12-17 %) show significant gaps. Antarctica is surprisingly well observed (78 %). Little monitoring occurs over the oceans, with the tropical and southern oceans particularly poorly represented. The surface ozone over key biomes such as tropical forests and savanna is almost completely unmonitored. A chemical cluster analysis suggests that a significant number of observations are made of polluted air masses, but cleaner air masses whether over the land or ocean (especially again in the tropics) are significantly under-observed. The current network is unlikely to see the impact of the El Niño-Southern Oscillation (ENSO) but may be capable of detecting other planetary-scale signals. Model assessment and validation activities are hampered by a lack of observations in regions where the models differ substantially, as is the ability to monitor likely changes in surface ozone over the next century. Using our methodology we are able to suggest new sites which would help to close the gap in our ability to measure global surface ozone. An additional 20 surface ozone monitoring sites (a 20 % increase in the World Meteorological Organization Global Atmosphere Watch (WMO GAW) ozone sites or a 1 % increase in the total background network) located on 10 islands and in 10 continental regions would almost double the area observed. The cost of this addition to the network is small compared to other expenditure on atmospheric composition research infrastructure and would provide a significant long-term benefit to our understanding of the composition of the atmosphere, information which will also be available for consideration by air quality control managers and policy makers.

Design and fabrication of composite wing panels containing a production splice

NASA Technical Reports Server (NTRS)

Reed, D. L.

1975-01-01

Bolted specimens representative of both upper and lower wing surface splices of a transport aircraft were designed and manufactured for static and random load tension and compression fatigue testing including ground-air-ground load reversals. The specimens were fabricated with graphite-epoxy composite material. Multiple tests were conducted at various load levels and the results were used as input to a statistical wearout model. The statically designed specimens performed very well under highly magnified fatigue loadings. Two large panels, one tension and compression, were fabricated for testing by NASA-LRC.

Clinical anthropometrics and body composition from 3D whole-body surface scans.

PubMed

Ng, B K; Hinton, B J; Fan, B; Kanaya, A M; Shepherd, J A

2016-11-01

Obesity is a significant worldwide epidemic that necessitates accessible tools for robust body composition analysis. We investigated whether widely available 3D body surface scanners can provide clinically relevant direct anthropometrics (circumferences, areas and volumes) and body composition estimates (regional fat/lean masses). Thirty-nine healthy adults stratified by age, sex and body mass index (BMI) underwent whole-body 3D scans, dual energy X-ray absorptiometry (DXA), air displacement plethysmography and tape measurements. Linear regressions were performed to assess agreement between 3D measurements and criterion methods. Linear models were derived to predict DXA body composition from 3D scan measurements. Thirty-seven external fitness center users underwent 3D scans and bioelectrical impedance analysis for model validation. 3D body scan measurements correlated strongly to criterion methods: waist circumference R 2 =0.95, hip circumference R 2 =0.92, surface area R 2 =0.97 and volume R 2 =0.99. However, systematic differences were observed for each measure due to discrepancies in landmark positioning. Predictive body composition equations showed strong agreement for whole body (fat mass R 2 =0.95, root mean square error (RMSE)=2.4 kg; fat-free mass R 2 =0.96, RMSE=2.2 kg) and arms, legs and trunk (R 2 =0.79-0.94, RMSE=0.5-1.7 kg). Visceral fat prediction showed moderate agreement (R 2 =0.75, RMSE=0.11 kg). 3D surface scanners offer precise and stable automated measurements of body shape and composition. Software updates may be needed to resolve measurement biases resulting from landmark positioning discrepancies. Further studies are justified to elucidate relationships between body shape, composition and metabolic health across sex, age, BMI and ethnicity groups, as well as in those with metabolic disorders.

The Atom and the Ocean, Understanding the Atom Series.

ERIC Educational Resources Information Center

Hull, E. W. Seabrook

Included is a brief description of the characteristics of the ocean, its role as a resource for food and minerals, its composition and its interactions with land and air. The role of atomic physics in oceanographic exploration is illustrated by the use of nuclear reactors to power surface and submarine research vessels and the design and use of…

Bond Strength of Silorane- and Methacrylate-Based Composites to Resin-Modified Glass Ionomers

DTIC Science & Technology

2012-01-13

genre was given the name of resin-modified glass ionomers (RMGI) (Antonucci et al., 1988). The addition of resin improved many of the drawbacks of...entire surface for 15 seconds then gentle air was used to create an even film over the sample. This layer was cured for 10 seconds using the Bluephase

Assessing the Association Between Asthma and Air Quality in the Presence of Wildfires

NASA Astrophysics Data System (ADS)

Young, L. J.; Al-Hamdan, M. Z.; Lopiano, K. K.; Crosson, W. L.; Gotway, C. A.; DuClos, C.; Jordan, M.; Estes, M. G.; Luvall, J. C.; Estes, S. M.; Xu, X.; Holt, N. M.; Leary, E.

2012-12-01

Asthma hospital/emergency room (patient) data are used as the foundation for creating a health outcome indicator of human response to environmental air quality. Daily U.S. Environmental Protection Agency (EPA) Air Quality System (AQS) fine particulates (PM2.5) ground data and the U.S. National Aeronautical Space Administration (NASA) MODIS aerosol optical depth (AOD) data were acquired and processed for years of 2007 and 2008. Figure 1 shows the PM2.5 annual mean composite of all the 2007 B-spline daily surfaces. Initial models for predicting the number of weekly asthma cases within a Florida county has focused on environmental variables. Weekly maximums of PM2.5, relative humidity, and the proportions of the county with smoke and fire were the environmental variables included in the model. Cosine and sine functions of time were used to account for seasonality in asthma cases. Counties were considered to be random effects, thereby adjusting for differences in socio-demographics and other factors. The 2007 predictions for Miami-Dade county when using B-splines PM2.5 are displayed in Figures 2.; PM2.5 annual mean composite of all the 2007 daily surfaces developed using Al-Hamdan et al (2009) B-spline fitting algorithm ; Predicted and observed weekly asthma cases presenting to hospitals or emergency rooms in Miami-Dade county in Florida during 2007

Anti-Icing Formulas Prevent Train Delays

NASA Technical Reports Server (NTRS)

2013-01-01

In the winter of 2009, Washington, DC, workers faced the prospect of a difficult commute due to record-setting snowfalls. But thousands of the city's Metrorail riders found the public transportation system fully functional, thanks in part to a NASA technology invented years before. Just like trains, an airplane must be snow- and ice-free to ensure safe travel. Traditionally, fluids containing a compound called ethylene glycol have been used to inhibit ice on planes. In 1992, however, the US Air Force banned its purchase of this ingredient due to toxicity concerns. According to the Centers for Disease Control, exposure to large amounts of ethylene glycol through air or water can damage the kidneys, nervous system, lungs, and heart. Urine samples from airport deicing workers have contained traces of the substance. At the time of the Air Force s ban, Robert Lockyer was working at NASA s Ames Research Center in the Advanced Composites Model Development Branch, where he says "we decided to pick up the gauntlet and began researching existing fluid compositions and the processes used in deicing aircraft." Along with Lockyer, in 1997 Ames researchers Leonard Haslim and John Zuk devised a nontoxic, biodegradable, and cost effective substitute for ethylene glycol. When applied to a dry surface before a snow or ice event, the solution prevented ice from forming a bond with the surface. This made it easy to wipe away any accumulation.

Controllable stearic acid crystal induced high hydrophobicity on cellulose film surface.

PubMed

He, Meng; Xu, Min; Zhang, Lina

2013-02-01

A novel, highly hydrophobic cellulose composite film (RCS) with biodegradability was fabricated via solvent-vaporized controllable crystallization of stearic acid in the porous structure of cellulose films (RC). The interface structure and properties of the composite films were investigated with wide-angle X-ray diffraction (WAXD), scanning electron microscopy (SEM), differential scanning calorimetry (DSC), FT-IR, solid-state (13)C NMR, water uptake, tensile testing, water contact angle, and biodegradation tests. The results indicated that the RCS films exhibited high hydrophobicity (water contact angle achieved to 145°), better mechanical properties in the humid state and lower water uptake ratio than RC. Interestingly, the stearic acid crystallization was induced by the pore wall of the cellulose matrix to form a micronano binary structure, resulting in a rough surface. The rough surface with a hierarchical structure containing micronanospace on the RCS film surface could trap abundant air, leading to the high hydrophobicity. Moreover, the RCS films were flexible, biodegradable, and low-cost, showing potential applications in biodegradable water-proof packaging.

A comparative study of shear bond strength between metal and ceramic brackets and artificially aged composite restorations using different surface treatments.

PubMed

Eslamian, Ladan; Borzabadi-Farahani, Ali; Mousavi, Nasim; Ghasemi, Amir

2012-10-01

This in vitro study evaluated the shear bond strength (SBS) between ceramic brackets (CBs) and resin composite restorations (RCRs) prepared using different surface treatments. The findings were also compared with a similar study that used stainless steel brackets (SSBs). Forty-five premolars were restored with a nano-hybrid composite resin (Tetric EvoCeram) and randomly assigned to three surface treatment groups: group 1, 5 per cent hydrofluoric acid (HF); group 2, air abrasion (50 μm alumina particles); and group 3, diamond bur. Specimens were bonded with CBs (Fascination) and exposed to thermo-cycling (500 cycles). The shear force at a crosshead speed of 1 mm/minute was transmitted to brackets. The adhesive remnant index (ARIs) scores were recorded after bracket failure. The analysis of SBS variance (P < 0.01) and chi-square test of ARIs scores (P < 0.01) revealed significant differences among three groups tested. The SBS in group 3 (mean: 26.34 ± 4.76 MPa) and group 2 (mean: 26.68 ± 5.93 MPa) was significantly higher than group 1 (mean: 16.25 ± 5.42 MPa). The SBS was significantly higher in CBs (mean: 23.09 ± 7.19 MPa) compared to SSBs (mean: 15.56 ± 5.13 MPa). High ARIs (100 per cent) occurred in SSBs treated with a diamond bur, whereas CBs primarily failed at the resin-adhesive interface (P < 0.01). In two-thirds of the specimens (SSBs or CBs), no adhesive was left on the restoration after HF conditioning. The ARIs profile of CBs and SSBs that received surface treatments with air abrasion were similar (P > 0.05) and bond failure occurred mainly in adhesive-bracket base and resin-adhesive interfaces. The diamond bur surface treatment is recommended as a safe and cost-effective method of bonding CBs to RCRs.

Muons in air showers at the Pierre Auger Observatory: Measurement of atmospheric production depth

NASA Astrophysics Data System (ADS)

Aab, A.; Abreu, P.; Aglietta, M.; Ahlers, M.; Ahn, E. J.; Al Samarai, I.; Albuquerque, I. F. M.; Allekotte, I.; Allen, J.; Allison, P.; Almela, A.; Alvarez Castillo, J.; Alvarez-Muñiz, J.; Alves Batista, R.; Ambrosio, M.; Aminaei, A.; Anchordoqui, L.; Andringa, S.; Aramo, C.; Arqueros, F.; Asorey, H.; Assis, P.; Aublin, J.; Ave, M.; Avenier, M.; Avila, G.; Badescu, A. M.; Barber, K. B.; Bäuml, J.; Baus, C.; Beatty, J. J.; Becker, K. H.; Bellido, J. A.; Berat, C.; Bertou, X.; Biermann, P. L.; Billoir, P.; Blanco, F.; Blanco, M.; Bleve, C.; Blümer, H.; Boháčová, M.; Boncioli, D.; Bonifazi, C.; Bonino, R.; Borodai, N.; Brack, J.; Brancus, I.; Brogueira, P.; Brown, W. C.; Buchholz, P.; Bueno, A.; Buscemi, M.; Caballero-Mora, K. S.; Caccianiga, B.; Caccianiga, L.; Candusso, M.; Caramete, L.; Caruso, R.; Castellina, A.; Cataldi, G.; Cazon, L.; Cester, R.; Chavez, A. G.; Cheng, S. H.; Chiavassa, A.; Chinellato, J. A.; Chudoba, J.; Cilmo, M.; Clay, R. W.; Cocciolo, G.; Colalillo, R.; Collica, L.; Coluccia, M. R.; Conceição, R.; Contreras, F.; Cooper, M. J.; Coutu, S.; Covault, C. E.; Criss, A.; Cronin, J.; Curutiu, A.; Dallier, R.; Daniel, B.; Dasso, S.; Daumiller, K.; Dawson, B. R.; de Almeida, R. M.; De Domenico, M.; de Jong, S. J.; de Mello Neto, J. R. T.; De Mitri, I.; de Oliveira, J.; de Souza, V.; del Peral, L.; Deligny, O.; Dembinski, H.; Dhital, N.; Di Giulio, C.; Di Matteo, A.; Diaz, J. C.; Díaz Castro, M. L.; Diep, P. N.; Diogo, F.; Dobrigkeit, C.; Docters, W.; D'Olivo, J. C.; Dong, P. N.; Dorofeev, A.; Dorosti Hasankiadeh, Q.; Dova, M. T.; Ebr, J.; Engel, R.; Erdmann, M.; Erfani, M.; Escobar, C. O.; Espadanal, J.; Etchegoyen, A.; Facal San Luis, P.; Falcke, H.; Fang, K.; Farrar, G.; Fauth, A. C.; Fazzini, N.; Ferguson, A. P.; Fernandes, M.; Fick, B.; Figueira, J. M.; Filevich, A.; Filipčič, A.; Fox, B. D.; Fratu, O.; Fröhlich, U.; Fuchs, B.; Fuji, T.; Gaior, R.; García, B.; Garcia Roca, S. T.; Garcia-Gamez, D.; Garcia-Pinto, D.; Garilli, G.; Gascon Bravo, A.; Gate, F.; Gemmeke, H.; Ghia, P. L.; Giaccari, U.; Giammarchi, M.; Giller, M.; Glaser, C.; Glass, H.; Gomez Albarracin, F.; Gómez Berisso, M.; Gómez Vitale, P. F.; Gonçalves, P.; Gonzalez, J. G.; Gookin, B.; Gorgi, A.; Gorham, P.; Gouffon, P.; Grebe, S.; Griffith, N.; Grillo, A. F.; Grubb, T. D.; Guardincerri, Y.; Guarino, F.; Guedes, G. P.; Hansen, P.; Harari, D.; Harrison, T. A.; Harton, J. L.; Haungs, A.; Hebbeker, T.; Heck, D.; Heimann, P.; Herve, A. E.; Hill, G. C.; Hojvat, C.; Hollon, N.; Holt, E.; Homola, P.; Hörandel, J. R.; Horvath, P.; Hrabovský, M.; Huber, D.; Huege, T.; Insolia, A.; Isar, P. G.; Islo, K.; Jandt, I.; Jansen, S.; Jarne, C.; Josebachuili, M.; Kääpä, A.; Kambeitz, O.; Kampert, K. H.; Kasper, P.; Katkov, I.; Kégl, B.; Keilhauer, B.; Keivani, A.; Kemp, E.; Kieckhafer, R. M.; Klages, H. O.; Kleifges, M.; Kleinfeller, J.; Krause, R.; Krohm, N.; Krömer, O.; Kruppke-Hansen, D.; Kuempel, D.; Kunka, N.; La Rosa, G.; LaHurd, D.; Latronico, L.; Lauer, R.; Lauscher, M.; Lautridou, P.; Le Coz, S.; Leão, M. S. A. B.; Lebrun, D.; Lebrun, P.; Leigui de Oliveira, M. A.; Letessier-Selvon, A.; Lhenry-Yvon, I.; Link, K.; López, R.; Lopez Agüera, A.; Louedec, K.; Lozano Bahilo, J.; Lu, L.; Lucero, A.; Ludwig, M.; Lyberis, H.; Maccarone, M. C.; Malacari, M.; Maldera, S.; Maller, J.; Mandat, D.; Mantsch, P.; Mariazzi, A. G.; Marin, V.; Mariş, I. C.; Marsella, G.; Martello, D.; Martin, L.; Martinez, H.; Martínez Bravo, O.; Martraire, D.; Masías Meza, J. J.; Mathes, H. J.; Mathys, S.; Matthews, A. J.; Matthews, J.; Matthiae, G.; Maurel, D.; Maurizio, D.; Mayotte, E.; Mazur, P. O.; Medina, C.; Medina-Tanco, G.; Melissas, M.; Melo, D.; Menichetti, E.; Menshikov, A.; Messina, S.; Meyhandan, R.; Mićanović, S.; Micheletti, M. I.; Middendorf, L.; Minaya, I. A.; Miramonti, L.; Mitrica, B.; Molina-Bueno, L.; Mollerach, S.; Monasor, M.; Monnier Ragaigne, D.; Montanet, F.; Morello, C.; Moreno, J. C.; Mostafá, M.; Moura, C. A.; Muller, M. A.; Müller, G.; Münchmeyer, M.; Mussa, R.; Navarra, G.; Navas, S.; Necesal, P.; Nellen, L.; Nelles, A.; Neuser, J.; Niechciol, M.; Niemietz, L.; Niggemann, T.; Nitz, D.; Nosek, D.; Novotny, V.; Nožka, L.; Ochilo, L.; Olinto, A.; Oliveira, M.; Ortiz, M.; Pacheco, N.; Pakk Selmi-Dei, D.; Palatka, M.; Pallotta, J.; Palmieri, N.; Papenbreer, P.; Parente, G.; Parra, A.; Pastor, S.; Paul, T.; Pech, M.; PÈ©kala, J.; Pelayo, R.; Pepe, I. M.; Perrone, L.; Pesce, R.; Petermann, E.; Peters, C.; Petrera, S.; Petrolini, A.; Petrov, Y.; Piegaia, R.; Pierog, T.; Pieroni, P.; Pimenta, M.; Pirronello, V.; Platino, M.; Plum, M.; Porcelli, A.; Porowski, C.; Prado, R. R.; Privitera, P.; Prouza, M.; Purrello, V.; Quel, E. J.; Querchfeld, S.; Quinn, S.; Rautenberg, J.; Ravel, O.; Ravignani, D.; Revenu, B.; Ridky, J.; Riggi, S.; Risse, M.; Ristori, P.; Rizi, V.; Roberts, J.; Rodrigues de Carvalho, W.; Rodriguez Cabo, I.; Rodriguez Fernandez, G.; Rodriguez Rojo, J.; Rodríguez-Frías, M. D.; Ros, G.; Rosado, J.; Rossler, T.; Roth, M.; Roulet, E.; Rovero, A. C.; Rühle, C.; Saffi, S. J.; Saftoiu, A.; Salamida, F.; Salazar, H.; Saleh, A.; Salesa Greus, F.; Salina, G.; Sánchez, F.; Sanchez-Lucas, P.; Santo, C. E.; Santos, E.; Santos, E. M.; Sarazin, F.; Sarkar, B.; Sarmento, R.; Sato, R.; Scharf, N.; Scherini, V.; Schieler, H.; Schiffer, P.; Schmidt, A.; Scholten, O.; Schoorlemmer, H.; Schovánek, P.; Schulz, A.; Schulz, J.; Sciutto, S. J.; Segreto, A.; Settimo, M.; Shadkam, A.; Shellard, R. C.; Sidelnik, I.; Sigl, G.; Sima, O.; Śmiałkowski, A.; Šmída, R.; Snow, G. R.; Sommers, P.; Sorokin, J.; Squartini, R.; Srivastava, Y. N.; Stanič, S.; Stapleton, J.; Stasielak, J.; Stephan, M.; Stutz, A.; Suarez, F.; Suomijärvi, T.; Supanitsky, A. D.; Sutherland, M. S.; Swain, J.; Szadkowski, Z.; Szuba, M.; Taborda, O. A.; Tapia, A.; Tartare, M.; Thao, N. T.; Theodoro, V. M.; Tiffenberg, J.; Timmermans, C.; Todero Peixoto, C. J.; Toma, G.; Tomankova, L.; Tomé, B.; Tonachini, A.; Torralba Elipe, G.; Torres Machado, D.; Travnicek, P.; Trovato, E.; Tueros, M.; Ulrich, R.; Unger, M.; Urban, M.; Valdés Galicia, J. F.; Valiño, I.; Valore, L.; van Aar, G.; van den Berg, A. M.; van Velzen, S.; van Vliet, A.; Varela, E.; Vargas Cárdenas, B.; Varner, G.; Vázquez, J. R.; Vázquez, R. A.; Veberič, D.; Verzi, V.; Vicha, J.; Videla, M.; Villaseñor, L.; Vlcek, B.; Vorobiov, S.; Wahlberg, H.; Wainberg, O.; Walz, D.; Watson, A. A.; Weber, M.; Weidenhaupt, K.; Weindl, A.; Werner, F.; Whelan, B. J.; Widom, A.; Wiencke, L.; Wilczyńska, B.; Wilczyński, H.; Will, M.; Williams, C.; Winchen, T.; Wittkowski, D.; Wundheiler, B.; Wykes, S.; Yamamoto, T.; Yapici, T.; Younk, P.; Yuan, G.; Yushkov, A.; Zamorano, B.; Zas, E.; Zavrtanik, D.; Zavrtanik, M.; Zaw, I.; Zepeda, A.; Zhou, J.; Zhu, Y.; Zimbres Silva, M.; Ziolkowski, M.; Pierre Auger Collaboration

2014-07-01

The surface detector array of the Pierre Auger Observatory provides information about the longitudinal development of the muonic component of extensive air showers. Using the timing information from the flash analog-to-digital converter traces of surface detectors far from the shower core, it is possible to reconstruct a muon production depth distribution. We characterize the goodness of this reconstruction for zenith angles around 60° and different energies of the primary particle. From these distributions, we define Xmaxμ as the depth along the shower axis where the production of muons reaches maximum. We explore the potentiality of Xmaxμ as a useful observable to infer the mass composition of ultrahigh-energy cosmic rays. Likewise, we assess its ability to constrain hadronic interaction models.

Development of Spray on Bag for manufacturing of large composites parts: Diffusivity analysis

NASA Astrophysics Data System (ADS)

Dempah, Maxime Joseph

Bagging materials are utilized in many composites manufacturing processes. The selection is mainly driven by cost, temperature requirements, chemical compatibility and tear properties of the bag. The air barrier properties of the bag are assumed to be adequate or in many cases are not considered at all. However, the gas barrier property of a bag is the most critical parameter, as it can negatively affect the quality of the final laminate. The barrier property is a function of the bag material, uniformity, thickness and temperature. Improved barrier properties are needed for large parts, high pressure consolidated components and structures where air stays entrapped on the part surface. The air resistance property of the film is defined as permeability and is investigated in this thesis. A model was developed to evaluate the gas transport through the film and an experimental cell was implemented to characterize various commercial films. Understanding and characterizing the transport phenomena through the film allows optimization of the bagging material for various manufacturing processes. Spray-on-Bag is a scalable alternative bagging method compared to standard films. The approach allows in-situ fabrication of the bag on large and complex geometry structures where optimization of the bag properties can be varied on a local level. An experimental setup was developed and implemented using a six axis robot and an automated spraying system. Experiments were performed on a flat surface and specimens were characterized and compared to conventional films. Air barrier properties were within range of standard film approaches showing the potential to fabricate net shape bagging structures in an automated process.

A composite study of the MJO influence on the surface air temperature and precipitation over the Continental United States

NASA Astrophysics Data System (ADS)

Zhou, Shuntai; L'Heureux, Michelle; Weaver, Scott; Kumar, Arun

2012-04-01

The influence of the MJO on the continental United States (CONUS) surface air temperature (SAT) and precipitation is examined based on 30 years of daily data from 1979-2008. Composites are constructed for each of the eight phases of the Wheeler-Hendon MJO index over 12 overlapping three-month seasons. To ensure that the MJO signal is distinguished from other patterns of climate variability, several steps are taken: (a) only days classified as "MJO events" are used in the composites, (b) statistical significance of associated composites is assessed using a Monte Carlo procedure, and (c) intraseasonal frequencies are matched to the unfiltered data. Composites of other fields are also shown in order to examine how the SAT and precipitation anomalies are associated with large-scale circulations providing a link between the tropics and extratropics. The strongest and most significant MJO effects on SAT are found during the northern winter seasons. When enhanced convection is located over the equatorial Indian Ocean, below-average SAT tends to occur in New England and the Great Lakes region. As enhanced tropical convection shifts over the Maritime continent, above-average SAT appears in the eastern states of the US from Maine to Florida. The MJO influence on precipitation is also significant during northern winter seasons. When enhanced convection is located over the Maritime continent, more precipitation is observed in the central plains of the US. Enhanced precipitation also occurs over the west coast of the US when convective activity is stronger over the Indian Ocean. During the northern summer and fall, the MJO impact on precipitation is mainly significant at lower latitudes, over Mexico and southeastern US.

Influence of multiple-passes on microstructure and mechanical properties of Al-Mg/SiC surface composites fabricated via underwater friction stir processing

NASA Astrophysics Data System (ADS)

Srivastava, Manu; Rathee, Sandeep; Maheshwari, Sachin; Siddiquee, Arshad Noor

2018-06-01

Friction stir processing (FSP) is a relatively newly developed solid-state process involving surface modifications for fabricating metal matrix surface composites. Obtaining metal matrix nano-composites with uniform dispersion of reinforcement particles via FSP route is an intricate task to accomplish. In this work, AA5059/SiC nano surface composites (SCs) were developed. Effect of multiple FSP passes and SiC addition on microstructure and mechanical properties of fabricated SCs during underwater condition was investigated. Results reflected that the average microhardness value of base metal (BM) increases from 85 Hv to 159 Hv in stir zone of four pass underwater friction stir processed (FSPed) SC. Highest ultimate tensile strength (UTS) achieved during four pass FSPed sample was 377 MPa that is higher than UTS of BM (321 MPa) and four pass FSPed sample developed at ambient air FSP conditions (347 MPa). An appreciably narrower heat affected zone is obtained owing to fast cooling and reduced heat conduction during underwater FSP, amounting to higher UTS as compared to BM and SC at ambient conditions. Thus, it can be concluded that surrounding medium and number of FSP passes have significant impact on mechanical properties of fabricated SCs. Analysis of microstructures and distribution of SiC particles in fabricated SCs were studied by optical microscope and FESEM respectively and found in good corroboration with the mechanical properties.

Nonstoichiometric Zn Ferrite and ZnFe2O4/Fe2O3 Composite Spheres: Preparation, Magnetic Properties, and Chromium Removal

NASA Astrophysics Data System (ADS)

Hang, Chun-Liang; Yang, Li-Xia; Sun, Chang-Mei; Liang, Ying

2018-03-01

Monodisperse and porous nonstoichiometric Zn ferrite can be prepared by a solvothermal method. Such non-Zn ferrite was used to be the precursor for synthesis of ZnFe2O4/Fe2O3 composite via calcination at 600°C for 3 h in air. X-ray powder diffractometer (XRD) and Energy Dispersive Spectrometer (EDS) proved the nonstoichiometry of Zn ferrite synthesized by solvothermal method and the formation of ZnFe2O4/Fe2O3 composite via calcination. TEM image showed that non-Zn ferrite spheres with wormlike nanopore structure were made of primary nanocrystals. BET surface area of non-Zn ferrite was much higher than that of ZnFe2O4/Fe2O3 composite. Saturation magnetization of non-Zn ferrites was significantly higher than that of ZnFe2O4/Fe2O3 composites. Calcination of non-Zn ferrite resulted in the formation of large amount of non-magnetic Fe2O3,which caused a low magnetization of composite. Because of higher BET surface area and higher saturation magnetization, non-Zn ferrite presented better Cr6+ adsorption property than ZnFe2O4/Fe2O3 composites.

Effects of different surface treatments and accelerated artificial aging on the bond strength of composite resin repairs.

PubMed

Melo, Marco Aurélio Veiga de; Moysés, Marcos Ribeiro; Santos, Saulo Galvão dos; Alcântara, Carlos Eduardo Pinto; Ribeiro, José Carlos Rabelo

2011-01-01

The purpose of the present study was to assess the bond strength of composite resin repairs subjected to different surface treatments and accelerated artificial aging. 192 cylindrical samples (CSs) were prepared and divided into 24 groups (n = 8). Half of the CSs were stored in water for 24 h, and the other half were subjected to C-UV accelerated aging for non-metallic specimens. The treatments were phosphoric acid + silane + adhesive (PSA); phosphoric acid + adhesive (PA); diamond bur + phosphoric acid + silane + adhesive (DPSA); diamond bur + phosphoric acid + adhesive (DPA); air abrasion + phosphoric acid + silane + adhesive (APSA); and air abrasion + phosphoric acid + adhesive (APA). The repair was performed and the specimens were again aged as described above. A control group (n = 8) was established and did not receive any type of aging or surface treatment. The specimens were loaded to failure in shear mode with a crosshead speed of 0.5 mm/min until fracture. Data were analyzed by one-way ANOVA/Tukey's test (p < 0.05). No statistically significant differences were found among DPSA, DPA, APSA, APA, and the control group. The aged PSA and PA achieved low bonding values and were statistically different from the control group, whereas the non-aged PSA and PA presented no statistically significant difference from the control group. Repairs with the proposed surface treatments were viable on both recent and aged restorations; however, phosphoric acid + adhesive alone were effective only on recent restorations.

Compressive strength after blast of sandwich composite materials

PubMed Central

Arora, H.; Kelly, M.; Worley, A.; Del Linz, P.; Fergusson, A.; Hooper, P. A.; Dear, J. P.

2014-01-01

Composite sandwich materials have yet to be widely adopted in the construction of naval vessels despite their excellent strength-to-weight ratio and low radar return. One barrier to their wider use is our limited understanding of their performance when subjected to air blast. This paper focuses on this problem and specifically the strength remaining after damage caused during an explosion. Carbon-fibre-reinforced polymer (CFRP) composite skins on a styrene–acrylonitrile (SAN) polymer closed-cell foam core are the primary composite system evaluated. Glass-fibre-reinforced polymer (GFRP) composite skins were also included for comparison in a comparable sandwich configuration. Full-scale blast experiments were conducted, where 1.6×1.3 m sized panels were subjected to blast of a Hopkinson–Cranz scaled distance of 3.02 m kg−1/3, 100 kg TNT equivalent at a stand-off distance of 14 m. This explosive blast represents a surface blast threat, where the shockwave propagates in air towards the naval vessel. Hopkinson was the first to investigate the characteristics of this explosive air-blast pulse (Hopkinson 1948 Proc. R. Soc. Lond. A 89, 411–413 (doi:10.1098/rspa.1914.0008)). Further analysis is provided on the performance of the CFRP sandwich panel relative to the GFRP sandwich panel when subjected to blast loading through use of high-speed speckle strain mapping. After the blast events, the residual compressive load-bearing capacity is investigated experimentally, using appropriate loading conditions that an in-service vessel may have to sustain. Residual strength testing is well established for post-impact ballistic assessment, but there has been less research performed on the residual strength of sandwich composites after blast. PMID:24711494

Space Shuttle Environmental Effects: The First 5 Flights

NASA Technical Reports Server (NTRS)

Potter, A. (Editor)

1983-01-01

Environmental effects associated with the first five Space Shuttle flights were monitored by the National Aeronautics and Space Administration (NASA) and the U.S. Air Force (USAF). Results and interpretations from this effort were reported at the December 1982 joint NASA-USAF conference. The conference proceedings are presented in this document. Most of the monitoring activity was focused on the launch cloud, emphasizing surface effects on the biota and air quality, model prediction of surface concentrations of HCl gas and Al2O3 dust, and airborne measurements of cloud composition. In general, assessments and predictions made in the April 1978 Final Environmental Impact Statement for the Space Shuttle Program were verified. Fallout of acidic mist and dust within 3 mi to 5 mi of the launch pad was the only unexpected effect of the launch. Atomization of deluge water in the Shuttle exhaust is considered to be the most probable cause of this effect. Sonic booms were monitored for several landings at Edwards Air Force Base, California; results agreed well with model predictions.

Modification of carbon fabrics by radio-frequency capacitive discharge at low pressure to regulate mechanical properties of carbon fiber reinforced plastics based on it

NASA Astrophysics Data System (ADS)

Garifullin, A. R.; Krasina, I. V.; Skidchenko, E. A.; Shaekhov, M. F.; Tikhonova, N. V.

2017-01-01

To increase the values of mechanical properties of carbon fiber (CF) composite materials used in sports equipment production the method of radio-frequency capacitive (RFC) low-pressure plasma treatment in air was proposed. Previously it was found that this type of modification allows to effectively regulate the surface properties of fibers of different nature. This treatment method differs from the traditional ones by efficiency and environmental friendliness as it does not require the use of aggressive, environmentally hazardous chemicals. In this paper it was established that RFC low-pressure air plasma treatment of carbon fabrics enhances the interlaminar shear strength (ILSS) of carbon fiber reinforced plastic (CFRP). As a result of experimental studies of CF by Fourier Transform Infrared (FTIR) spectroscopy method it was proved that after radio-frequency capacitive plasma treatment at low pressure in air the oxygen-containing functional groups is grafted on the surface. These groups improve adhesion at the interface “matrix-fiber”.

A comparative study of thermochemical and cold plasma treatment on lignin-based activated carbon for adsorbing Fe(III)

NASA Astrophysics Data System (ADS)

Shi, Shukai; Wang, Xin; Chen, Weimin; Chen, Minzhi; Zhou, Xiaoyan

2018-05-01

The as-prepared lignin-based activated carbon (LAC) was post-treated by urea and radio-frequency cold plasma separately. The obtained results demonstrated that the BET surface and total volumes of the LAC and plasma-treated LACs were greater than the urea-modified sample. The analysis of surface elemental composition showed that the nitrogen content of urea-modified LAC and nitrogen plasma-treated LAC are 3.79% and 2.62% higher than that of original LAC respectively, while the oxygen content of air plasma-treated LAC is 10.23% higher than that of original LAC. The Fe(III) ions adsorbed studies with pseudo-second order kinetic model revealed that urea-modified LAC had faster chemisorption rates while air plasma-treated LAC had larger adsorption capacity within 3 h. Moreover, the adsorption capacity and chemisorption rates of LAC post-treated by nitrogen plasma are inferior to the air plasma-treated LAC.

Air bells of water spiders are an extended phenotype modified in response to gas composition.

PubMed

Schütz, Dolores; Taborsky, Michael; Drapela, Thomas

2007-10-01

The water spider Argyroneta aquatica (Clerck) is the only spider that spends its whole life under water. Water spiders keep an air bubble around their body for breathing and build under-water air bells, which they use for shelter and raising offspring, digesting and consuming prey, moulting, depositing eggs and sperm, and copulating. It is unclear whether these bells are an important oxygen reservoir for breathing under water, or whether they serve mainly to create water-free space for feeding and reproduction. In this study, we manipulated the composition of the gas inside the bell of female water spiders to test whether they monitor the quality of this gas, and replenish oxygen if required. We exchanged the entire gas in the bell either with pure O2, pure CO2, or with ambient air as control, and monitored behavioural responses. The test spiders surfaced and replenished air more often in the CO2 treatment than in the O2 treatment, and they increased bell building behaviour. In addition to active oxygen regulation, they monitored and adjusted the bells by adding silk. These results show that water spiders use the air bell as an oxygen reservoir, and that it functions as an external lung, which renders it essential for living under water permanently. A. aquatica is the only animal that collects, transports, and stores air, and monitors its property for breathing, which is an adaptive response of a terrestrial animal to the colonization of an aquatic habitat.

Circumventing shallow air contamination in Mid Ocean Ridge Basalts

NASA Astrophysics Data System (ADS)

Mukhopadhyay, Sujoy; Parai, Rita; Tucker, Jonathan; Middleton, Jennifer; Langmuir, Charles

2016-04-01

Noble gases in mantle-derived basalts provide a rich portrait of mantle degassing and surface-interior volatile exchange. However, the ubiquity of shallow-level air contamination frequently obscures the mantle noble gas signal. In a majority of samples, shallow air contamination dominates the noble gas budget. As a result, reconstructing the variability in heavy noble gas mantle source compositions and inferring the history of deep recycling of atmospheric noble gases is difficult. For example, in the gas-rich popping rock 2ΠD43, 129Xe/130Xe ratios reach 7.7±0.23 in individual step-crushes, but the bulk composition of the sample is close to air (129Xe/130Xe of 6.7). Here, we present results from experiments designed to elucidate the source of shallow air contamination in MORBs. Step-crushes were carried out to measure He, Ne, Ar and Xe isotopic compositions on two aliquots of a depleted popping glass that was dredged from between the Kane and Atlantis Fracture Zones of the Mid-Atlantic Ridge in May 2012. One aliquot was sealed in ultrapure N2 after dredge retrieval, while the other aliquot was left exposed to air for 3.5 years. The bulk 20Ne/22Ne and 129Xe/130Xe ratios measured in the aliquot bottled in ultrapure N2 are 12.3 and 7.6, respectively, and are nearly identical to the estimated mantle source values. On the other hand, step crushes in the aliquot left exposed to air for several years show Ne isotopic compositions that are shifted towards air, with a bulk 20Ne/22Ne of 11.5; the bulk 129Xe/130Xe, however, was close to 7.6. These results indicate that lighter noble gases exchange more efficiently between the bubbles trapped in basalt glass and air, suggesting a diffusive or kinetic mechanism for the incorporation of the shallow air contamination. Importantly, in Ne-Ar or Ar-Xe space, step-crushes from the bottled aliquot display a trend that can be easily fit with a simple two-component hyperbolic mixing between mantle and atmosphere noble gases. Step-crushes in the aliquot left exposed to air display significantly more scatter, which makes it difficult to fit a two-component mixing hyperbola and obtain the mantle source value for this aliquot. In summary, our simple and inexpensive experiment demonstrates that at least in some samples, significant air contamination is added after dredge retrieval from the ocean floor. Bottling samples in ultrapure N2 upon dredge retrieval can largely eliminate this component of shallow-level air contamination. As a result, the number of step crushes required to characterize a sample decreases and estimating the mantle source compositions of the basalts becomes significantly easier, which in turn leads to more refined estimates of mantle degassing and regassing rates.

Investigating cosmic rays and air shower physics with IceCube/IceTop

NASA Astrophysics Data System (ADS)

Dembinski, Hans

2017-06-01

IceCube is a cubic-kilometer detector in the deep ice at South Pole. Its square-kilometer surface array, IceTop, is located at 2800 m altitude. IceTop is large and dense enough to cover the cosmic-ray energy spectrum from PeV to EeV energies with a remarkably small systematic uncertainty, thanks to being close to the shower maximum. The experiment offers new insights into hadronic physics of air showers by observing three components: the electromagnetic signal at the surface, GeV muons in the periphery of the showers, and TeV muons in the deep ice. The cosmic-ray flux is measured with the surface signal. The mass composition is extracted from the energy loss of TeV muons observed in the deep ice in coincidence with signals at the surface. The muon lateral distribution is obtained from GeV muons identified in surface signals in the periphery of the shower. The energy spectrum of the most energetic TeV muons is also under study, as well as special events with laterally separated TeV muon tracks which originate from high-pT TeV muons. A combination of all these measurements opens the possibility to perform powerful new tests of hadronic interaction models used to simulate air showers. The latest results will be reviewed from this perspective.

Friction and wear of plasma-sprayed coatings containing cobalt alloys from 25 deg to 650 deg in air

NASA Technical Reports Server (NTRS)

Sliney, H. E.; Jacobson, T. P.

1979-01-01

Four different compositions of self-lubricating, plasma-sprayed, composite coatings with calcium fluoride dispersed throughout cobalt alloy-silver matrices were evaluated on a friction and wear apparatus. In addition, coatings of the cobalt alloys alone and one coating with a nickel alloy-silver matrix were evaluated for comparison. The wear specimens consisted of two, diametrically opposed, flat rub shoes sliding on the coated, cylindrical surface of a rotating disk. Two of the cobalt composite coatings gave a friction coefficient of about 0.25 and low wear at room temperature, 400 and 650 C. Wear rates were lower than those of the cobalt alloys alone or the nickel alloy composite coating. However, oxidation limited the maximum useful temperature of the cobalt composite coating to about 650 C compared to about 900 C for the nickel composite coating.

Permeability studies on 3D Ni foam/graphene composites

NASA Astrophysics Data System (ADS)

Yang, Zhuxian; Chen, Hongmei; Wang, Nannan; Xia, Yongde; Zhu, Yanqiu

2017-09-01

This study investigates the permeability of new 3D Ni foam/graphene composites (Ni foam covered with graphene) using compressed air, Ar and N2 as the probe gases. The results show that the introduction of graphene on the surface of Ni foam via in situ chemical vapour deposition is not detrimental to the permeability of the composites; on the contrary, in some cases it improves permeability. A modified Ergun-type correlation has been proposed, which represents very well the permeability of the Ni foam/graphene composites, especially at flow rates higher than 0.3 m s-1. Further studies show that graphene also helps to improve the thermal conductivity of the composite. These results suggest that the graphene involvement will make the Ni foam/graphene composite a good candidate for potential applications such as filters or heat exchangers suitable for working under harsh conditions such as at high temperatures, in corrosive environments, etc.

A high-performance, flexible and robust metal nanotrough-embedded transparent conducting film for wearable touch screen panels.

PubMed

Im, Hyeon-Gyun; An, Byeong Wan; Jin, Jungho; Jang, Junho; Park, Young-Geun; Park, Jang-Ung; Bae, Byeong-Soo

2016-02-21

We report a high-performance, flexible and robust metal nanotrough-embedded transparent conducting hybrid film (metal nanotrough-GFRHybrimer). Using an electro-spun polymer nanofiber web as a template and vacuum-deposited gold as a conductor, a junction resistance-free continuous metal nanotrough network is formed. Subsequently, the metal nanotrough is embedded on the surface of a glass-fabric reinforced composite substrate (GFRHybrimer). The monolithic composite structure of our transparent conducting film allows simultaneously high thermal stability (24 h at 250 °C in air), a smooth surface topography (Rrms < 1 nm) and excellent opto-electrical properties. A flexible touch screen panel (TSP) is fabricated using the transparent conducting films. The flexible TSP device stably operates on the back of a human hand and on a wristband.

Impact of Nanometer Graphite Addition on the Anti-deliquescence and Tribological Properties of Ni/MoS2 Lubricating Coating

NASA Astrophysics Data System (ADS)

Zhang, S.; Li, G. L.; Wang, H. D.; Xu, B. S.; Ma, G. Z.

In order to improve the long-standing problem of MoS2 coating that lubrication performance drop dramatic after storage in humid air, using nano-composite electro brush plating technology and Ni/MoS2-C combination coating with thinness of 100 μm was succeed deposited on GCr15 substrate. Microstructure, surface morphology and elements of this composite coating were analyzed using SEM, XPS and TEM while phase structure was tested by XRD. The tribological properties of this composite coating were tested by MSTS-1; Test the preceding tribological properties of Ni/MoS2-C composite coatings to the pure Ni/MoS2 after different period storage at room temperature and 100% relative humidity atmosphere of 12 h, 24 h, and 48 h as well as the element of the chemical changes. Research shows that there is a small amount of MoS2 in pure MoS2 coatings behind a 12 hours storage in humid air became MoO3 and the tribological performance decreased significantly followed, in the same conditions composite coating with nanometer graphite addition get a preferably tribological properties while the hardness of this coating was improved by the nanometer graphite addition and combination plating showed a well duration tribological properties as a result.

Thermal oxidation behavior of an Al-Li-Cu-Mg-Zr alloy

NASA Astrophysics Data System (ADS)

Ahmad, Maqsood

1987-04-01

The chemical composition of oxide films formed during thermal treatments of an Al-Li-Cu-Mg-Zr alloy has been studied by means of Auger electron spectroscopy and X-ray photoelectron spectroscopy. The oxide layers formed after oxidation of 2.5 minutes to 30 minutes at 530 °C in lab air have been characterized. In the early stages of oxidation the surface is composed of both the lithium rich oxides and magnesium rich oxides. However, after longer oxidation times the oxidation of lithium becomes predominant and the air/oxide interface is completely covered by lithium compounds. Oxidation products formed on the alloy surface have been studied by X-ray diffraction analysis. The following three phases, namely, Li2CO3, α-Li5AlO4, and γ-LiAlO2, were identified. During heat treatment in lab air at 530 °C and at atmospheric pressure the dominating reaction product is Li2CO3. Due to the selective oxidation of lithium a soft surface layer is developed. The width of the soft layer formed during solution heat treatments carried out in lab air and in salt bath environments has been determined by microhardness measurements. The lithium concentration profiles were calculated from a diffusion equation. The depletion of alloying elements from the near surface region during heat treatments has been investigated using energy dispersive X-ray analysis. The oxide morphology was examined using scanning electron microscopy and optical microscopy.

Thermal oxidation behavior of an Al-Li-Cu-Mg-Zr alloy

NASA Astrophysics Data System (ADS)

Ahmad, Maqsood

1987-05-01

The chemical composition of oxide films formed during thermal treatments of an Al-Li-Cu-Mg-Zr alloy has been studied by means of Auger electron spectroscopy and X-ray photoelectron spectroscopy. The oxide layers formed after oxidation of 2.5 minutes to 30 minutes at 530 °C in lab air have been characterized. In the early stages of oxidation the surface is composed of both the lithium rich oxides and magnesium rich oxides. However, after longer oxidation times the oxidation of lithium becomes predominant and the air/oxide interface is completely covered by lithium compounds. Oxidation products formed on the alloy surface have been studied by X-ray diffraction analysis. The following three phases, namely, Li2CO3, α-Li5AlO4, and γ-LiAlO2, were identified. During heat treatment in lab air at 530 °C and at atmospheric pressure the dominating reaction product is Li2CO3. Due to the selective oxidation of lithium a soft surface layer is developed. The width of the soft layer formed during solution heat treatments carried out in lab air and in salt bath environments has been determined by microhardness measurements. The lithium concentration profiles were calculated from a diffusion equation. The depletion of alloying elements from the near surface region during heat treatments has been investigated using energy dispersive X-ray analysis. The oxide morphology was examined using scanning electron microscopy and optical microscopy.

Development of the technology for the fabrication of reliable laminar from control panels

NASA Technical Reports Server (NTRS)

Meade, L. E.; Kays, A. O.; Ferrill, R. S.; Young, H. R.

1977-01-01

Materials were assessed and fabrication techniques were developed for use in the manufacture of wing surface materials compatible with the application of both aluminum alloys and nonmetallic composites. The concepts investigated included perforations and slots in the metallic test panels and microporosity and perforations in the composite test panels. Perforations were produced in the metallic test panels by the electron beam process and slots were developed by controlled gaps between the metal sheets. Microporosity was produced in the composite test panels by the resin bleed process, and perforations were produced by the fugitive fiber technique. Each of these concepts was fabricated into test panels, and air flow tests were conducted on the panels.

Development and characterization of sugarcane bagasse fiber and nano-silica reinforced epoxy hybrid composites

NASA Astrophysics Data System (ADS)

Fong, A. L.; Khandoker, N. A. N.; Debnath, S.

2018-04-01

This paper presents an experimental study on the mechanical performance of sugarcane bagasse fiber reinforced epoxy composite. Tensile and flexural properties of the composites were investigated in this research. Different weightage of short fiber and fiber particulates were utilized to study their effects on the mechanical performance of the composites in terms of tensile and flexural properties. 1% of nano-silica was reinforced to investigate its effect on the mechanical performance of the composites. Hand lay-up composite molding process was used to fabricate the composite samples. During fabrication, ultrasonic mixing was carried out to study the effects on mechanical performance of the fiber particulate reinforced composites. In overall, ultrasonic mixing and addition of nano-silica particles has improved the mechanical performance of the fiber particulate composites. Morphology analysis on surface of composites has shown the removal of air bubbles and deagglomeration. 1wt% of short fiber reinforced composite exhibits the highest tensile and flexural properties among all the samples. Sugarcane bagasse particulates reinforced composites were shown to have better performance compared to short fiber reinforced composites when the wt% of the fiber increase.

Optimal Substrate Preheating Model for Thermal Spray Deposition of Thermosets onto Polymer Matrix Composites

NASA Technical Reports Server (NTRS)

Ivosevic, M.; Knight, R.; Kalidindi, S. R.; Palmese, G. R.; Tsurikov, A.; Sutter, J. K.

2003-01-01

High velocity oxy-fuel (HVOF) sprayed, functionally graded polyimide/WC-Co composite coatings on polymer matrix composites (PMC's) are being investigated for applications in turbine engine technologies. This requires that the polyimide, used as the matrix material, be fully crosslinked during deposition in order to maximize its engineering properties. The rapid heating and cooling nature of the HVOF spray process and the high heat flux through the coating into the substrate typically do not allow sufficient time at temperature for curing of the thermoset. It was hypothesized that external substrate preheating might enhance the deposition behavior and curing reaction during the thermal spraying of polyimide thermosets. A simple analytical process model for the deposition of thermosetting polyimide onto polymer matrix composites by HVOF thermal spray technology has been developed. The model incorporates various heat transfer mechanisms and enables surface temperature profiles of the coating to be simulated, primarily as a function of substrate preheating temperature. Four cases were modeled: (i) no substrate preheating; (ii) substrates electrically preheated from the rear; (iii) substrates preheated by hot air from the front face; and (iv) substrates electrically preheated from the rear and by hot air from the front.

Transverse flexural tests as a tool for assessing damage to PMR-15 composites from isothermal aging in air at elevated temperatures

NASA Technical Reports Server (NTRS)

Bowles, Kenneth J.

1992-01-01

To date, the effect of thermo-oxidative aging on unidirectional composite mechanical properties has been monitored by the measurement of interlaminar shear strength (ILSS) and either three or four point longitudinal flexural strength (LFS) of the composites being tested. Both results are affected by the fiber-to-matrix bonding, the former being dependent on the shear resistance of the interface and the latter on the degree of load sharing by the fibers through the fiber/matrix interface. Recently, fiber/matrix interfacial bond strengths have been monitored using a transverse flexural strength (TFS) test method. This test method was used to evaluate the effect of fiber surface treatment on the fiber/matrix bond. The interface bonding was varied in these tests using Hercules A-fibers with three-types of surfaces that produce bonds of poor, better, and good quality. The TFS was found not only to be sensitive to the bonding, but also to the aging time of unidirectional A-fiber/PMR-15 composites. This relationship reflects the mechanism by which the PMR-15 degrades during thermal aging.

Effect of thione primers on adhesive bonding between an indirect composite material and Ag-Pd-Cu-Au alloy.

PubMed

Imai, Hideyuki; Koizumi, Hiroyasu; Shimoe, Saiji; Hirata, Isao; Matsumura, Hideo; Nikawa, Hiroki

2014-01-01

The current study evaluated the effect of primers on the shear bond strength of an indirect composite material joined to a silverpalladium-copper-gold (Ag-Pd-Cu-Au) alloy (Castwell). Disk specimens were cast from the alloy and were air-abraded with alumina. Eight metal primers were applied to the alloy surface. A light-polymerized indirect composite material (Solidex) was bonded to the alloy. Shear bond strength was determined both before and after the application of thermocycling. Two groups primed with Metaltite (thione) and M. L. Primer (sulfide) showed the greatest post-thermocycling bond strength (8.8 and 6.5 MPa). The results of the X-ray photoelectron spectroscopic (XPS) analysis suggested that the thione monomer (MTU-6) in the Metaltite primer was strongly adsorbed onto the Ag-Pd-Cu-Au alloy surface even after repeated cleaning with acetone. The application of either the thione (MTU-6) or sulfide primer is effective for enhancing the bonding between a composite material and Ag-Pd-Cu-Au alloy.

Adsorption of sophorolipid biosurfactants on their own and mixed with sodium dodecyl benzene sulfonate, at the air/water interface.

PubMed

Chen, Minglei; Dong, Chuchuan; Penfold, Jeff; Thomas, Robert K; Smyth, Thomas J P; Perfumo, Amedea; Marchant, Roger; Banat, Ibrahim M; Stevenson, Paul; Parry, Alyn; Tucker, Ian; Campbell, Richard A

2011-07-19

The adsorption of the lactonic (LS) and acidic (AS) forms of sophorolipid and their mixtures with the anionic surfactant sodium dodecyl benzene sulfonate (LAS) has been measured at the air/water interface by neutron reflectivity, NR. The AS and LS sophorolipids adsorb with Langmuir-like adsorption isotherms. The more hydrophobic LS is more surface active than the AS, with a lower critical micellar concentration, CMC, and stronger surface adsorption, with an area/molecule ∼70 Å(2) compared with 85 Å(2) for the AS. The acidic sophorolipid shows a maximum in its adsorption at the CMC which appears to be associated with a mixture of different isomeric forms. The binary LS/AS and LS/LAS mixtures show a strong surface partitioning in favor of the more surface active and hydrophobic LS component but are nevertheless consistent with ideal mixing at the interface. In contrast, the surface composition of the AS/LAS mixture is much closer to the solution composition, but the surface mixing is nonideal and can be accounted for by regular solution theory, RST. In the AS/LS/LAS ternary mixtures, the surface adsorption is dominated by the sophorolipid, and especially the LS component, in a way that is not consistent with the observations for the binary mixtures. The extreme partitioning in favor of the sophorolipid for the LAS/LS/AS (1:2) mixtures is attributed to a reduction in the packing constraints at the surface due to the AS component. Measurements of the surface structure reveal a compact monolayer for LS and a narrow solvent region for LS, LS/AS, and LS/LAS mixtures, consistent with the more hydrophobic nature of the LS component. The results highlight the importance of the relative packing constraints on the adsorption of multicomponent mixtures, and the impact of the lactonic form of the sophorolipid on the adsorption of the sophorolipid/LAS mixtures.

Notch Sensitivity of Fatigue Behavior of a Hi-Nicalon/SiC Ceramic Composite with an Oxidation Inhibited Matrix at 1200 degree C in Air and in Steam

DTIC Science & Technology

2011-03-24

Stress Ratio and Frequency. AGARD - CP -569, NATO, AGARD , SMP, 7 Rue Ancelle, 92200 Neuilly sur Seine, France, March 1996. 5. Chawla, K.K. Ceramic Matrix...fatigue at 1.0 Hz in air at 1200°C. σmax = 120 MPa, Nf = 77,575, tf = 21.5 h ........................................................ 73 Figure 55: SEM...areas of oxidation. ............ 73 Figure 56: SEM micrographs of the fiber fracture surfaces of specimen 13 tested in fatigue at 1.0 Hz in steam at

The Damage Law of HTPB Propellant under Thermomechanical Loading

NASA Astrophysics Data System (ADS)

Liu, Cheng-wu; Yang, Jian-hong; Wang, Xian-meng; Ma, Yong-kang

2016-01-01

By way of measuring the acoustic emission (AE) signals of Hydroxyl-terminated polybutadiene (HTPB) propellant in condition of uniform speed, and combined with the scanning electron microscopy (SEM) fracture surface observation, the damage law of HTPB composite solid propellant under thermomechanical loading was studied. The results show that the effects of thermomechanical loading on HTPB propellant are related to the time and can be divided into three different stages. In the first stage, thermal air aging dominates; in the second stage, interface damage is dominant; and in the third stage, thermal air aging is once again dominant.

Development of electrically conductive-superoleophobic micropillars for reducing surface adhesion of oil at low temperatures

NASA Astrophysics Data System (ADS)

Pan, Zihe; Wang, Tianchang; Zhou, Yikang; Zhao, Boxin

2016-12-01

Electrically conductive and superoleophobic micropillars have been developed through the construction of biomimetic micropillars using Ag-filled epoxy composites and the incorporation of FDTS on the micropillar surface. These micropillars are found to be superoleophobic with an oil contact angle of 140°, demonstrating excellent self-cleaning properties. The conductivity of micropillars allows for the Joule-heating effect to actively reduce the adhesion and even unfreeze the frozen oil droplets by passing electrical current. Electrical resistance of the composite micropillars was modulated by two orders of magnitudes by varying the contents of Ag flakes from 45 wt% to 65 wt%. The effectiveness of conductive micropillars for surface un-freezing was investigated by applying DC current to decrease the adhesion strength of frozen oil droplets on surfaces. The results showed a pronounced reduction of frozen oil adhesion force by 60% when the resistance increased from 7.5 Ω to 877 Ω after applying DC current for 2 min. By continuously applying DC current for 3 min, the frozen oil adhesion decreased to 0.05 N, reaching zero when the surface was heated up to -10 °C after applying DC current for 5 min. In contrast, when the droplet was heated up to -5 °C by hot air, there is still a substantial force of adhesion. The research findings demonstrate the use of constructing conductive-superoleophobic composite micropillars at surface for eliminating the frozen oil from surfaces at low temperatures.

AN ION CORRELATION PROGRAM FOR DECONVOLUTING COMPOSITE MASS SPECTRA ACQUIRED USING A DIRECT SURFACE IONIZATION SOURCE INTERFACED TO A TIME-OF-FLIGHT MASS SPECTROMETER

EPA Science Inventory

The rapid sampling provided by the DART in ambient air will allow rapid delineation of areas of dispersed chemicals after natural or man-made disasters. Exact masses and RIAs of dimer, precursor, and product ions measured by the oa-TOFMS entered dinto the Ion Correlation Program...

Hybrid Micro-Electro-Mechanical Tunable Filter

DTIC Science & Technology

2007-09-01

Figure 2.10), one can see the developers have used surface micromachining techniques to build the micromirror structure over the CMOS addressing...DBRs, microcavity composition, initial air gap, contact layers, substrate Dispersion Data Curve -fit dispersion data or generate dispersion function...measurements • Curve -fit the dispersion data or generate a continuous, wavelength-dependent, representation of material dispersion • Manually design the

KENNEDY SPACE CENTER, FLA. - In the Orbiter Processing Facility, an orbital maneuvering system (OMS) pod is suspended in air as it is moved toward Atlantis for installation. Two OMS pods are attached to the upper aft fuselage left and right sides. Fabricated primarily of graphite epoxy composite and aluminum, each pod is 21.8 feet long and 11.37 feet wide at its aft end and 8.41 feet wide at its forward end, with a surface area of approximately 435 square feet. Each pod houses the Reaction Control System propulsion components used for inflight maneuvering and is attached to the aft fuselage with 11 bolts.

NASA Image and Video Library

2003-10-30

KENNEDY SPACE CENTER, FLA. - In the Orbiter Processing Facility, an orbital maneuvering system (OMS) pod is suspended in air as it is moved toward Atlantis for installation. Two OMS pods are attached to the upper aft fuselage left and right sides. Fabricated primarily of graphite epoxy composite and aluminum, each pod is 21.8 feet long and 11.37 feet wide at its aft end and 8.41 feet wide at its forward end, with a surface area of approximately 435 square feet. Each pod houses the Reaction Control System propulsion components used for inflight maneuvering and is attached to the aft fuselage with 11 bolts.

Composition of weathering crusts on sandstones from natural outcrops and architectonic elements in an urban environment.

PubMed

Marszałek, Mariola; Alexandrowicz, Zofia; Rzepa, Grzegorz

2014-12-01

This work presents mineralogical and chemical characteristics of weathering crusts developed on sandstones exposed to various air pollution conditions. The samples have been collected from sandstone tors in the Carpathian Foothill and from buildings in Kraków. It has been stated that these crusts differ in both fabric and composition. The sandstone black crust from tors is rich in organic matter and composed of amorphous silica. Sulphate incrustations accompanied by dust particles have been only sometimes observed. Beneath the black crust, a zone coloured by iron (oxyhydr)oxides occurs. The enrichment of the surface crust in silica and iron compounds protects the rock interior from atmospheric impact. The sandstones from architectonic details are also covered by a thin carbon-rich black crust, but they are visibly loosened. Numerous salts, mainly gypsum and halite, crystallise here, thus enhancing deterioration of the rock. Moreover, spherical particles originated from industrial emissions are much more common. Gypsum in natural outcrops, forms isolated and well-developed crystals, whilst these found on the architectonic details are finer and densely cover the surface. Such diversity reflects various concentrations of acid air pollutants in solutions.

The impact of local surface changes in Borneo on atmospheric composition at wider spatial scales: coastal processes, land-use change and air quality

PubMed Central

Pyle, J. A.; Warwick, N. J.; Harris, N. R. P.; Abas, Mohd Radzi; Archibald, A. T.; Ashfold, M. J.; Ashworth, K.; Barkley, Michael P.; Carver, G. D.; Chance, K.; Dorsey, J. R.; Fowler, D.; Gonzi, S.; Gostlow, B.; Hewitt, C. N.; Kurosu, T. P.; Lee, J. D.; Langford, S. B.; Mills, G.; Moller, S.; MacKenzie, A. R.; Manning, A. J.; Misztal, P.; Nadzir, Mohd Shahrul Mohd; Nemitz, E.; Newton, H. M.; O'Brien, L. M.; Ong, Simon; Oram, D.; Palmer, P. I.; Peng, Leong Kok; Phang, Siew Moi; Pike, R.; Pugh, T. A. M.; Rahman, Noorsaadah Abdul; Robinson, A. D.; Sentian, J.; Samah, Azizan Abu; Skiba, U.; Ung, Huan Eng; Yong, Sei Eng; Young, P. J.

2011-01-01

We present results from the OP3 campaign in Sabah during 2008 that allow us to study the impact of local emission changes over Borneo on atmospheric composition at the regional and wider scale. OP3 constituent data provide an important constraint on model performance. Treatment of boundary layer processes is highlighted as an important area of model uncertainty. Model studies of land-use change confirm earlier work, indicating that further changes to intensive oil palm agriculture in South East Asia, and the tropics in general, could have important impacts on air quality, with the biggest factor being the concomitant changes in NOx emissions. With the model scenarios used here, local increases in ozone of around 50 per cent could occur. We also report measurements of short-lived brominated compounds around Sabah suggesting that oceanic (and, especially, coastal) emission sources dominate locally. The concentration of bromine in short-lived halocarbons measured at the surface during OP3 amounted to about 7 ppt, setting an upper limit on the amount of these species that can reach the lower stratosphere. PMID:22006963

The impact of local surface changes in Borneo on atmospheric composition at wider spatial scales: coastal processes, land-use change and air quality.

PubMed

Pyle, J A; Warwick, N J; Harris, N R P; Abas, Mohd Radzi; Archibald, A T; Ashfold, M J; Ashworth, K; Barkley, Michael P; Carver, G D; Chance, K; Dorsey, J R; Fowler, D; Gonzi, S; Gostlow, B; Hewitt, C N; Kurosu, T P; Lee, J D; Langford, S B; Mills, G; Moller, S; MacKenzie, A R; Manning, A J; Misztal, P; Nadzir, Mohd Shahrul Mohd; Nemitz, E; Newton, H M; O'Brien, L M; Ong, Simon; Oram, D; Palmer, P I; Peng, Leong Kok; Phang, Siew Moi; Pike, R; Pugh, T A M; Rahman, Noorsaadah Abdul; Robinson, A D; Sentian, J; Samah, Azizan Abu; Skiba, U; Ung, Huan Eng; Yong, Sei Eng; Young, P J

2011-11-27

We present results from the OP3 campaign in Sabah during 2008 that allow us to study the impact of local emission changes over Borneo on atmospheric composition at the regional and wider scale. OP3 constituent data provide an important constraint on model performance. Treatment of boundary layer processes is highlighted as an important area of model uncertainty. Model studies of land-use change confirm earlier work, indicating that further changes to intensive oil palm agriculture in South East Asia, and the tropics in general, could have important impacts on air quality, with the biggest factor being the concomitant changes in NO(x) emissions. With the model scenarios used here, local increases in ozone of around 50 per cent could occur. We also report measurements of short-lived brominated compounds around Sabah suggesting that oceanic (and, especially, coastal) emission sources dominate locally. The concentration of bromine in short-lived halocarbons measured at the surface during OP3 amounted to about 7 ppt, setting an upper limit on the amount of these species that can reach the lower stratosphere.

Equivalent Aqueous Phase Modulation of Domain Segregation in Myelin Monolayers and Bilayer Vesicles

PubMed Central

Oliveira, Rafael G.; Schneck, Emanuel; Funari, Sergio S.; Tanaka, Motomu; Maggio, Bruno

2010-01-01

Purified myelin can be spread as monomolecular films at the air/aqueous interface. These films were visualized by fluorescence and Brewster angle microscopy, showing phase coexistence at low and medium surface pressures (<20–30 mN/m). Beyond this threshold, the film becomes homogeneous or not, depending on the aqueous subphase composition. Pure water as well as sucrose, glycerol, dimethylsulfoxide, and dimethylformamide solutions (20% in water) produced monolayers that become homogeneous at high surface pressures; on the other hand, the presence of salts (NaCl, CaCl2) in Ringer's and physiological solution leads to phase domain microheterogeneity over the whole compression isotherm. These results show that surface heterogeneity is favored by the ionic milieu. The modulation of the phase-mixing behavior in monolayers is paralleled by the behavior of multilamellar vesicles as determined by small-angle and wide-angle x-ray scattering. The correspondence of the behavior of monolayers and multilayers is achieved only at high surface pressures near the equilibrium adsorption surface pressure; at lower surface pressures, the correspondence breaks down. The equilibrium surface tension on all subphases corresponds to that of the air/alkane interface (27 mN/m), independently on the surface tension of the clean subphase. PMID:20816062

Laser-Marking Mechanism of Thermoplastic Polyurethane/Bi2O3 Composites.

PubMed

Zhong, Wei; Cao, Zheng; Qiu, Pengfei; Wu, Dun; Liu, Chunlin; Li, Huili; Zhu, He

2015-11-04

Using bismuth oxide (Bi2O3) as a laser-marking additive and thermoplastic polyurethane (TPU) as the matrix, TPU/Bi2O3 composite materials were prepared by melt blending in a torque rheometer. The sheet samples prepared from the TPU/Bi2O3 composites were treated in air by scanning with a neodymium-doped yttrium aluminum garnet (Nd: YAG) pulsed laser beam at a wavelength of 1064 nm. Compared with the pure TPU sample, the laser-marked composite samples exhibited differences in marking contrast as the Bi2O3 content increased from 0.1% to 1.0% based on stereomicroscope analysis. Scanning electron microscopy, X-ray photoelectron spectroscopy, Raman spectroscopy, thermogravimetry analysis, and X-ray diffraction were used to characterize the laser-marked surface material of the composite samples. Furthermore, a mechanism for the laser-effected darkening of the TPU/Bi2O3 composites was proposed. The results herein indicated that the addition of the Bi2O3 laser-sensitive additive to TPU resulted in laser darkening of the TPU/Bi2O3 composites. The marking contrast and visual appearance of the surface of the TPU/Bi2O3 composites after laser irradiation was due to a synergistic effect consisting of carbonization via TPU pyrolysis and reduction of Bi2O3 to black bismuth metal.

Past, Present and Future of UHECR Observations

NASA Astrophysics Data System (ADS)

Dawson, B. R.; Fukushima, M.; Sokolsky, P.

2017-12-01

Great advances have been made in the study of ultra-high energy cosmic rays (UHECR) in the past two decades. These include the discovery of the spectral cut-off near 5 x 10^19 eV and complex structure at lower energies, as well as increasingly precise information about the composition of cosmic rays as a function of energy. Important improvements in techniques, including extensive surface detector arrays and high resolution air fluorescence detectors, have been instrumental in facilitating this progress. We discuss the status of the field, including the open questions about the nature of spectral structure, systematic issues related to our understanding of composition, and emerging evidence for anisotropy at the highest energies. We review prospects for upgraded and future observatories including Telescope Array, Pierre Auger and JEM-EUSO and other space-based proposals, and discuss promising new technologies based on radio emission from extensive air showers produced by UHECR.

Interface-Limited Spherulitic Growth of Hydroxyapatite/Chondroitin Sulfate Composite Enamel-like Films

NASA Astrophysics Data System (ADS)

Ma, Guobin; Xu, Yifei; Wang, Xiyan; Wang, Mu

2012-02-01

Understanding and mimicking the growth of hard tissues such as tooth enamel may lead to innovative approaches toward engineering novel functional materials and providing new therapeutics. Up to now, in vitro growth of enamel-like materials is still a great challenge, and the microscopic formation mechanisms are far from well understood. Here we report synthesis of large-scale hydroxyapatite (HAP) and chondroitin sulfate (ChS) composite films by an efficient solution-air interface growth method. The products have the characteristic hierarchical prism structures of enamel and the mechanical properties comparable to dentin. We demonstrate that the films are assembled by spherulites nucleated at the solution surface. The growth of the spherulites is limited by the interfaces between them as well as between the solution and air, leading to the ordered prism structure. The results are beneficial for a clearer understanding of the fundamentals of tooth enamel formation.

Explore the influence of agglomeration on electrochemical performance of an amorphous MnO2/C composite by controlling drying process

NASA Astrophysics Data System (ADS)

Cui, Mangwei; Kang, Litao; Shi, Mingjie; Xie, Lingli; Wang, Xiaomin; Zhao, Zhe; Yun, Shan; Liang, Wei

2017-09-01

Amorphous MnO2/C composite is prepared by a facile redox reaction between potassium permanganate (KMnO4) and commercial black pen ink. Afterwards, two different drying processes, air drying or freeze drying, are employed to adjust the agglomeration state of particles in samples and explore its influence on capacitive performance. Experimental results indicate that the air-dried sample demonstrates much better cycling stability than the freeze-dried one (capacity retention at 5000 cycles: 70.9 vs. 60.7%), probably because of the relatively strong agglomeration between particles in this sample. Nevertheless, strong agglomeration seems to deteriorate the specific capacitance (from 492 down to 440.5 F/g at 1 A/g) due to the decrease of porosity and specific surface area. This study suggests that agglomeration of primary particles plays an important role to balance the specific capacitance and cycling stability for electrode materials.

The first stage of Lunar Prospector's LMLV is erected at Pad 46, CCAS

NASA Technical Reports Server (NTRS)

1997-01-01

Workers erect the first stage of a Lockheed Martin Launch Vehicle-2 (LMLV-2) at Launch Complex 46 at Cape Canaveral Air Station, Fla. The Lunar Prospector spacecraft is scheduled to launch aboard the LMLV-2 in October for an 18-month mission that will orbit the Earth's Moon to collect data from the lunar surface. Designed for a low polar orbit investigation of the Moon, the Lunar Prospector will map the Moon's surface composition and possible polar ice deposits, measure magnetic and gravity fields, and study lunar outgassing events.

A survey of major east coast snowstorms, 1960-1983. Part 2: Case studies of eighteen storms

NASA Technical Reports Server (NTRS)

Kocin, P. J.; Uccellini, L. W.

1985-01-01

Snowfall, surface and upper air charts, and available satellite images are presented for eighteen major East Coast snowstorms that occurred between 1960 and 1983. The charts and descriptions of key fields are provided so that students, weather forecasters, and researchers alike can visualize how a large sample of major winter cyclones form and intensify. Although there are noted similarities in certain aspects of the surface and upper tropospheric development of the storms, significant case-to-case variability precludes the ability to effectively composite these weather systems.

Composition and structure of pyrophoric nickel catalysts according to X-ray diffraction data

NASA Astrophysics Data System (ADS)

Osadchaya, T. Yu.; Afineevskii, A. V.; Prozorov, D. A.; Kochetkov, S. P.; Rumyantsev, R. N.; Lukin, M. V.

2017-01-01

The properties of a nickel catalyst obtained by treatment of nickel-aluminum alloy with sodium hydroxide in the presence of H2O2 and additionally stabilized with increased pressure were studied. Additional stabilization decreased the catalyst activity by 25%, but gave a more distinct picture for an XRD analysis of the active catalyst surface and decreased the time of deactivation of the dehydrated catalyst with air oxygen. The catalyst stabilization was explained by the displacement of water, decrease in the pore size, and surface inhomogeneity.

Urban decay of trachyte: correlating crust composition with air quality

NASA Astrophysics Data System (ADS)

Germinario, Luigi; Maritan, Lara; Mazzoli, Claudio; Siegesmund, Siegfried

2017-04-01

Decay of trachyte in the urban built environment was investigated on the Renaissance city walls of Padua, in northern Italy. They were raised by the Republic of Venice Serenissima in the 16th century for defending its most important mainland center, using trachyte of the Euganean Hills as building stone, a subvolcanic porphyritic rock quarried nearby. Weathering crusts and patinas were sampled on trachyte exposed surfaces and analyzed by optical microscopy, SEM, EDS mapping, XRD and LA-ICPMS, in order to determine their mineralogical and microstructural features, and major- and trace-element chemical composition. The results were placed in direct correlation with quantitative environmental parameters, in particular concerning air quality and anthropogenic emission of pollutants, either measured or modelled. Influence of the specific composition of trachyte and other neighboring materials was explored as well. The weathering layers on trachyte turned out to be mainly originated by exogenous processes. The enrichment in carbon and heavy metals (lead, arsenic, chromium, nickel, cadmium, antimony, bismuth etc.) is traced back to deposition of particulate matter from road traffic and domestic combustion of woody biomass; a secondary source is industrial processes in Padua and Venice-Porto Marghera, one of the biggest coastal industrial zones in Europe. The crystalline matrix of the crusts and patinas is typically formed by carbonates, especially calcite: since their concentration is negligible in the host rock, their near-surface abundance can be explained mostly by leaching of calcium from neighboring lime-mortar joints, and its mobilization and reprecipitation on trachyte according to local pH fluctuations. It is worth noting that the calcite layers may even promote growth of gypsum crusts, but their occurrence is seldom though. The sole significant intrinsic factor of trachyte alteration is related to dissolution of iron from biotite and other Fe-bearing phases, which then migrates to surface forming brown-reddish patinas. Generally, composition of the weathering crusts and patinas of Euganean trachyte proves to be an informative marker for the relevant environmental conditions and their evolution.

Plasma surface modification of polypropylene track-etched membrane to improve its performance properties

NASA Astrophysics Data System (ADS)

Kravets, L. I.; Elinson, V. M.; Ibragimov, R. G.; Mitu, B.; Dinescu, G.

2018-02-01

The surface and electrochemical properties of polypropylene track-etched membrane treated by plasma of nitrogen, air and oxygen are studied. The effect of the plasma-forming gas composition on the surface morphology is considered. It has been found that the micro-relief of the membrane surface formed under the gas-discharge etching, changes. Moreover, the effect of the non-polymerizing gas plasma leads to formation of oxygen-containing functional groups, mostly carbonyl and carboxyl. It is shown that due to the formation of polar groups on the surface and its higher roughness, the wettability of the plasma-modified membranes improves. In addition, the presence of polar groups on the membrane surface layer modifies its electrochemical properties so that conductivity of plasma-treated membranes increase.

Microstructure and growth mechanism of Al{sub 2}O{sub 3}/Al ceramic matrix composite made by directed oxidation of Al alloys

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

Qin, C.D.; Lai, M.O.; Cotterell, B.

Since the Lanxide process was advanced for forming of Al{sub 2}O{sub 3} ceramic composite by directed oxidation of Al alloys, much work has been done with various mechanisms being proposed. The mechanisms have claimed that only certain dopants are essential to the growth process. Nevertheless, no united consensus has yet been reached. In the present work, Al alloy containing 5% Mg was oxidized in air for 12 hours at 1,150 C with or without surface dopants of MgO or Pd. The resultant composites showed very different microstructures. Without any surface doping, the alloy did not develop any portion of compositemore » as the initial intimate oxide film stops further oxidation. This intimate oxide film can either be broken off by mechanical means or penetrated by reaction with surface dopants, so that the composite can grow and develop. The results show that the previously reported incubation time is not only related to reaction processes but also to the initial mechanical disturbances. Doping with Pd made the composite darker in color as the grains of the alumina ceramic matrix and inclusions of Al metal are finer. This shows that Pd may make the top oxide layer less intimate, and more nucleation sites are therefore available for oxidation. A new model is presented for oxide sustained growth based on the existence of oxygen active top surface layer and the capillary flow of molten metal around ceramic phase.« less

Catalytic activity and stability of oxides: The role of near-surface atomic structures and compositions

DOE PAGES

Feng, Zhenxing; Hong, Wesley T.; Fong, Dillon D.; ...

2016-05-05

Electrocatalysts play an important role in catalyzing the kinetics for oxygen reduction and oxygen evolution reactions for many air-based energy storage and conversion devices, such as metal$-$air batteries and fuel cells. Although noble metals have been extensively used as electrocatalysts, their limited natural abundance and high costs have motivated the search for more cost-effective catalysts. Oxides are suitable candidates since they are relatively inexpensive andhave shown reasonably high activity for various electrochemical reactions. However, a lack of fundamental understanding of the reaction mechanisms has been a major hurdle toward improving electrocatalytic activity. Here, detailed studies of the oxide surface atomicmore » structure and chemistry (e.g.,cation migration) can provide much needed insights for the design of highly efficient and stable oxide electrocatalysts.« less

Effect of Tunable Surface Potential on the Structure of Spin-Cast Polymeric Blend Films

NASA Astrophysics Data System (ADS)

Hawker, C.; Huang, E.; Russell, T. P.

1998-03-01

The demixing of binary polymeric mixtures has been studied with various surface potentials. This was performed by spin casting polystyrene/poly(methyl methacrylate) mixtures on to silicon substrates that had been modified with an end-grafted random copolymer brush layer. The composition of the random copolymer brush, containing the same monomeric components as the homopolymers can be varied in a precise manner over the entire concentration range. Atomic force and optical microscopy were used to study the morphology formed during spin casting and after annealing. Further insight into the structure was gained by rinsing these films with preferential solvents to remove one of the constituents and by performing the microscopy measurements. Finally, x-ray photoelectron spectroscopy, XPS, was used to elucidate the composition of the film near the air/polymer interface. Our data show that the resulting thin film structure depends strongly on the composition of the end grafted random copolymer film. Furthermore, the effect of thickness, solvent used in casting, and annealing conditions will be addressed.

Cosmic ray spectrum and composition from three years of IceTop and IceCube

NASA Astrophysics Data System (ADS)

Rawlins, K.; IceCube Collaboration

2016-05-01

IceTop is the surface component of the IceCube Observatory, composed of frozen water tanks at the top of IceCube’s strings. Data from this detector can be analyzed in different ways with the goal of measuring cosmic ray spectrum and composition. The shower size S125 from IceTop alone can be used as a proxy for primary energy, and unfolded into an all-particle spectrum. In addition, S125 from the surface can be combined with high-energy muon energy loss information from the deep IceCube detector for those air showers which pass through both. Using these coincident events in a complementary analysis, both the spectrum and mass composition of primary cosmic rays can be extracted in parallel using a neural network. Both of these analyses have been performed on three years of IceTop and IceCube data. Both all-particle spectra as well as individual spectra for elemental groups are presented.

Optimization of wall thickness and lay-up for the shell-like composite structure loaded by non-uniform pressure field

NASA Astrophysics Data System (ADS)

Shevtsov, S.; Zhilyaev, I.; Oganesyan, P.; Axenov, V.

2017-01-01

The glass/carbon fiber composites are widely used in the design of various aircraft and rotorcraft components such as fairings and cowlings, which have predominantly a shell-like geometry and are made of quasi-isotropic laminates. The main requirements to such the composite parts are the specified mechanical stiffness to withstand the non-uniform air pressure at the different flight conditions and reduce a level of noise caused by the airflow-induced vibrations at the constrained weight of the part. The main objective of present study is the optimization of wall thickness and lay-up of composite shell-like cowling. The present approach assumes conversion of the CAD model of the cowling surface to finite element (FE) representation, then its wind tunnel testing simulation at the different orientation of airflow to find the most stressed mode of flight. Numerical solutions of the Reynolds averaged Navier-Stokes (RANS) equations supplemented by k-w turbulence model provide the spatial distributions of air pressure applied to the shell surface. At the formulation of optimization problem the global strain energy calculated within the optimized shell was assumed as the objective. A wall thickness of the shell had to change over its surface to minimize the objective at the constrained weight. We used a parameterization of the problem that assumes an initiation of auxiliary sphere with varied radius and coordinates of the center, which were the design variables. Curve that formed by the intersection of the shell with sphere defined boundary of area, which should be reinforced by local thickening the shell wall. To eliminate a local stress concentration this increment was defined as the smooth function defined on the shell surface. As a result of structural optimization we obtained the thickness of shell's wall distribution, which then was used to design the draping and lay-up of composite prepreg layers. The global strain energy in the optimized cowling was reduced in2.5 times at the weight growth up to 15%, whereas the eigenfrequencies at the 6 first natural vibration modes have been increased by 5-15%. The present approach and developed programming tools that demonstrated a good efficiency and stability at the acceptable computational costs can be used to optimize a wide range of shell-like structures made of quasi-isotropic laminates.

Hierarchical Composite Membranes with Robust Omniphobic Surface Using Layer-By-Layer Assembly Technique.

PubMed

Woo, Yun Chul; Kim, Youngjin; Yao, Minwei; Tijing, Leonard D; Choi, June-Seok; Lee, Sangho; Kim, Seung-Hyun; Shon, Ho Kyong

2018-02-20

In this study, composite membranes were fabricated via layer-by-layer (LBL) assembly of negatively charged silica aerogel (SiA) and 1H,1H,2H,2H-perfluorodecyltriethoxysilane (FTCS) on a polyvinylidene fluoride phase inversion membrane and interconnecting them with positively charged poly(diallyldimethylammonium chloride) (PDDA) via electrostatic interaction. The results showed that the PDDA-SiA-FTCS coated membrane had significantly enhanced the membrane structure and properties. New trifluoromethyl and tetrafluoroethylene bonds appeared at the surface of the coated membrane, which led to lower surface free energy of the composite membrane. Additionally, the LBL membrane showed increased surface roughness. The improved structure and property gave the LBL membrane an omniphobic property, as indicated by its good wetting resistance. The membrane performed a stable air gap membrane distillation (AGMD) flux of 11.22 L/m 2 h with very high salt rejection using reverse osmosis brine from coal seam gas produced water as feed with the addition of up to 0.5 mM SDS solution. This performance was much better compared to those of the neat membrane. The present study suggests that the enhanced membrane properties with good omniphobicity via LBL assembly make the porous membranes suitable for long-term AGMD operation with stable permeation flux when treating challenging saline wastewater containing low surface tension organic contaminants.

Lower tropospheric ozone and aerosol measurements at a coastal mountain site in Northern California

NASA Astrophysics Data System (ADS)

Post, A.; Conley, S. A.; Zhao, Y.; Cliff, S. S.; Faloona, I. C.; Wexler, A. S.; Lighthall, D.

2012-12-01

Increasing concern over the impacts of exogenous air pollution in California's Central Valley have prompted the establishment of a coastal, high altitude monitoring site at the Chews Ridge Observatory (1550 m) approximately 30 km east of Point Sur in Monterey County. Six months of ozone and aerosol measurements are presented in the context of long-range transport and its potential impact on surface air quality in the southern San Joaquin Valley. Moreover, approximately monthly ozone surveys are conducted by aircraft upwind, over the Pacific Ocean, and downwind, over the Central Valley, to characterize horizontal and vertical transport across the coastal mountains. The measurements exhibit no systematic diurnal variations of ozone or water vapor, an indication that the site primarily samples lower free tropospheric air which has not been significantly influenced by either local emissions or convective coupling to the surface. Aerosol size is measured with a scanning mobility particle sizer and composition is analyzed with an 8-stage rotating drum impactor whose substrates are characterized by X-ray fluorescence. Various elemental ratios and back trajectory calculations are used to infer the temporal patterns of influence that long range transport has on California air quality.

Greenland coastal air temperatures linked to Baffin Bay and Greenland Sea ice conditions during autumn through regional blocking patterns

NASA Astrophysics Data System (ADS)

Ballinger, Thomas J.; Hanna, Edward; Hall, Richard J.; Miller, Jeffrey; Ribergaard, Mads H.; Høyer, Jacob L.

2018-01-01

Variations in sea ice freeze onset and regional sea surface temperatures (SSTs) in Baffin Bay and Greenland Sea are linked to autumn surface air temperatures (SATs) around coastal Greenland through 500 hPa blocking patterns, 1979-2014. We find strong, statistically significant correlations between Baffin Bay freeze onset and SSTs and SATs across the western and southernmost coastal areas, while weaker and fewer significant correlations are found between eastern SATs, SSTs, and freeze periods observed in the neighboring Greenland Sea. Autumn Greenland Blocking Index values and the incidence of meridional circulation patterns have increased over the modern sea ice monitoring era. Increased anticyclonic blocking patterns promote poleward transport of warm air from lower latitudes and local warm air advection onshore from ocean-atmosphere sensible heat exchange through ice-free or thin ice-covered seas bordering the coastal stations. Temperature composites by years of extreme late freeze conditions, occurring since 2006 in Baffin Bay, reveal positive monthly SAT departures that often exceed 1 standard deviation from the 1981-2010 climate normal over coastal areas that exhibit a similar spatial pattern as the peak correlations.

Modeling of multi-phase interactions of reactive nitrogen between snow and air in Antarctica

NASA Astrophysics Data System (ADS)

McCrystall, M.; Chan, H. G. V.; Frey, M. M.; King, M. D.

2016-12-01

In polar and snow-covered regions, the snowpack is an important link between atmospheric, terrestrial and oceanic systems. Trace gases, including nitrogen oxides, produced via photochemical reactions in snow are partially released to the lower atmosphere with considerable impact on its composition. However, the post-depositional processes that change the chemical composition and physical properties of the snowpack are still poorly understood. Most current snow chemistry models oversimplify as they assume air-liquid interactions and aqueous phase chemistry taking place at the interface between the snow grain and air. Here, we develop a novel temperature dependent multi-phase (gas-liquid-ice) physical exchange model for reactive nitrogen. The model is validated with existing year-round observations of nitrate in the top 0.5-2 cm of snow and the overlying atmosphere at two very different Antarctic locations: Dome C on the East Antarctic Plateau with very low annual mean temperature (-54ºC) and accumulation rate (<30 kg m-2 yr-1); and Halley, a coastal site with at times at or above freezing temperatures during summer, high accumulation rate and high background level of sea salt aerosol. We find that below the eutectic temperature of the H2O/dominant ion mixture the surface snow nitrate is controlled by kinetic adsorption onto the surface of snow grains followed by grain diffusion. Above the eutectic temperature, in addition to the former two processes, thermodynamic equilibrium of HNO3 between interstitial air and liquid water pockets, possibly present at triple junctions or grooves at grain boundaries, greatly enhances the nitrate uptake by snow in agreement with the concentration peak observed in summer.

Opportunities for Saving Energy and Improving Air Quality in Urban Heat Islands

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

Akbari, Hashem

2007-07-01

World energy use is the main contributor to atmospheric CO2. In 2002, about 7.0 giga metric tons of carbon (GtC) were emitted internationally by combustion of gas, liquid, and solid fuels (CDIAC, 2006), 2 to 5 times the amount contributed by deforestation (Brown et al., 1988). The share of atmospheric carbon emissions for the United States from fossil fuel combustion was 1.6 GtC. Increasing use of fossil fuel and deforestation together have raised atmospheric CO{sub 2} concentration some 25% over the last 150 years. According to global climate models and preliminary measurements, these changes in the composition of the atmospheremore » have already begun raising the Earth's average temperature. If current energy trends continue, these changes could drastically alter the Earth's temperature, with unknown but potentially catastrophic physical and political consequences. During the last three decades, increased energy awareness has led to conservation efforts and leveling of energy consumption in the industrialized countries. An important byproduct of this reduced energy use is the lowering of CO{sub 2} emissions. Of all electricity generated in the United States, about one-sixth is used to air-condition buildings. The air-conditioning use is about 400 tera-watt-hours (TWh), equivalent to about 80 million metric tons of carbon (MtC) emissions, and translating to about $40 billion (B) per year. Of this $40 B/year, about half is used in cities that have pronounced 'heat islands'. The contribution of the urban heat island to the air-conditioning demand has increased over the last 40 years and it is currently at about 10%. Metropolitan areas in the United States (e.g., Los Angeles, Phoenix, Houston, Atlanta, and New York City) have typically pronounced heat islands that warrant special attention by anyone concerned with broad-scale energy efficiency (HIG, 2006). The ambient air is primarily heated through three processes: direct absorption of solar radiation, convection of heat from hot surfaces, and man-made heat (exhaust from cars, buildings, etc.). Air is fairly transparent to light--the direct absorption of solar radiation in atmospheric air only raises the air temperature by a small amount. Typically about 90% of solar radiation reaches the Earth's surface and then is either absorbed or reflected. The absorbed radiation on the surface increases the surface temperature. And in turn the hot surfaces heat the air. This convective heating is responsible for the majority of the diurnal temperature range. The contribution of man-made heat (e.g., air conditioning, cars) is very small, compared to the heating of air by hot surfaces, except for the downtown high-rise areas.« less

Noncontact Determination of Antisymmetric Plate Wave Velocity in Ceramic Matrix Composites

NASA Technical Reports Server (NTRS)

Kautz, Harold E.

1998-01-01

High-temperature materials are of increasing importance in the development of more efficient engines and components for the aeronautics industry. In particular, ceramic matrix composite (CMC) and metal matrix composite (MMC) structures are under active development for these applications. The acousto-ultrasonic (AU) method has been shown to be useful for assessing mechanical properties in composite structures. In particular, plate wave analysis can characterize composites in terms of their stiffness moduli. It is desirable to monitor changes in mechanical properties that occur during thermomechanical testing and to monitor the health of components whose geometry or position make them hard to reach with conventional ultrasonic probes. In such applications, it would be useful to apply AU without coupling directly to the test surface. For a number of years, lasers have been under investigation as remote ultrasonic input sources and ultrasound detectors. The use of an ultrasonic transducer coupled through an air gap has also been under study. So far at the NASA Lewis Research Center, we have been more successful in using lasers as ultrasonic sources than as output devices. On the other hand, we have been more successful in using an air-coupled piezoelectric transducer as an output device than as an input device. For this reason, we studied the laser in/air-coupled-transducer out combination-using a pulsed NdYAG laser as the ultrasonic source and an air-coupled-transducer as the detector. The present work is focused on one of the AU parameters of interest, the ultrasonic velocity of the antisymmetric plate-wave mode. This easily identified antisymmetric pulse can be used to determine shear and flexure modulus. It was chosen for this initial work because the pulse arrival times are likely to be the most precise. The following schematic illustrates our experimental arrangement for using laser in/air-transducer out on SiC/SiC composite tensile specimens. The NdYAG pulse was directed downward by a 90 infrared prism to the top of the specimen, but at the edge of one end. An energy sensor measured a single pulse at 13 millijoules (mJ) before it passed through the prism, which attenuated 15 percent of its energy. It also provided an output trigger for the waveform time-delay synthesizer.

Advances in Satellite Remote Sensing of Particulate Air Pollution: From MISR to MAIA

NASA Astrophysics Data System (ADS)

Diner, D. J.; Burke, K.; Xu, F.; Garay, M. J.; Kalashnikova, O. V.; Liu, Y.; Meng, X.; Wang, J.; Martin, R.; Ostro, B.

2017-12-01

Airborne particulate matter (PM) is a well-known cause of cardiovascular and respiratory disease. To estimate human exposure to PM pollution, satellite instruments such as the Terra Multi-angle Imaging SpectroRadiometer (MISR) and the Moderate resolution Imaging Spectroradiometer (MODIS) have been used in conjunction with surface monitors to map near-surface PM concentrations. The relative toxicity of different size and compositional mixtures of PM is not well understood. To address this, we are developing the Multi-Angle Imager for Aerosols (MAIA) investigation. The satellite instrument extends MISR's multiangular visible and near-infrared (VNIR) spectral coverage to 14 bands in the ultraviolet, VNIR, and shortwave IR; three of the bands are polarimetric to enhance sensitivity to aerosol size and composition. To constrain the retrievals, the observations will be combined with data from surface monitors and the WRF-Chem and GEOS-Chem chemical transport models. Existing surface PM speciation monitors will be supplemented by adding new stations to the Surface PARTiculate mAtter Network (SPARTAN). Unlike MISR, MAIA is a targeting instrument. Primary areas of interest include metropolitan areas in North and South America, Europe, the Middle East, Africa, India, and East Asia. PM retrieval algorithms are being developed using data from MISR and the high-altitude Airborne Multiangle SpectroPolarimetric Imager (AirMSPI). Epidemiologists on the MAIA science team will use the derived PM data products and birth, death, and hospital records to investigate adverse health impacts of different types of airborne particulates. MAIA's earliest possible launch date is mid-2020, making it possible for the data to be complemented by global observations from Terra as well as high temporal resolution atmospheric chemistry measurements from TEMPO (Tropospheric Emissions: Monitoring Pollution), GEMS (Geostationary Environment Monitoring Spectrometer), and Sentinel-4.

Preliminary Investigation to Determine the Suitable Mixture Composition for Corn Starch Matrix

NASA Astrophysics Data System (ADS)

Huzaimi Zakaria, Nazri; Ngali, Zamani; Zulkefli Selamat, Mohd

2017-01-01

The use of natural fiber as reinforcement in polymeric composites has been seen a dramatically increase over the last decades. The surge in the interest of natural fiber composite or biodegradable composite is mainly due to the attractive cost of production, improved of hardness, better fatigue endurance and good thermal and mechanical resistivity. In this work, corn starch in the form of powder is utilized as the matrix of the composite. However, starch is brittle and has low strength make it inappropriate candidate for matrix binder. The main objective of this study is to modify the mechanical properties of pure corn starch by mixing it with water, glycerol and vinegar. The composition ratio of water is 60~80%, corn starch 10~35%, glycerol is 5~15% and vinegar is 0~5%, ten samples (A-J) have been manufactured and the best mixture composition is selected based on few selection criteria. The selection criteria are visual impaction, hardness and density. From the results, the samples without vinegar are not suitable to be used because of the fungus availability on the surface. Meanwhile the results from the samples with 5 ml vinegar have no fungus on their surface even has been exposed to the ambient air. While the sample C has shown the best sample based on the visual, hardness and density test.

Seeking Low Ice Adhesion

DTIC Science & Technology

1979-04-01

stress. D. Cylinder torsion shear test (0 cone), where the adhesive layer is formed between a hollow cylinder and central core , one of which is rotated...products deemed worth testing. These are listed with addresses and contacts. Besides simple resins and other release agents, they include composites ...is incomplete, pockets of air are thermodynamic considerations. left in hollows or adhering to the surface, reduc- ing bonding. Such pockets also can

Low-CCN concentration air masses over the eastern North Atlantic: Seasonality, meteorology, and drivers

NASA Astrophysics Data System (ADS)

Wood, Robert; Stemmler, Jayson D.; Rémillard, Jasmine; Jefferson, Anne

2017-01-01

A 20 month cloud condensation nucleus concentration (NCCN) data set from Graciosa Island (39°N, 28°W) in the remote North Atlantic is used to characterize air masses with low cloud condensation nuclei (CCN) concentrations. Low-CCN events are defined as 6 h periods with mean NCCN<20 cm-3 (0.1% supersaturation). A total of 47 low-CCN events are identified. Surface, satellite, and reanalysis data are used to explore the meteorological and cloud context for low-CCN air masses. Low-CCN events occur in all seasons, but their frequency was 3 times higher in December-May than during June-November. Composites show that many of the low-CCN events had a common meteorological basis that involves southerly low-level flow and rather low wind speeds at Graciosa. Anomalously low pressure is situated to the west of Graciosa during these events, but back trajectories and lagged SLP composites indicate that low-CCN air masses often originate as cold air outbreaks to the north and west of Graciosa. Low-CCN events were associated with low cloud droplet concentrations (Nd) at Graciosa, but liquid water path (LWP) during low-CCN events was not systematically different from that at other times. Satellite Nd and LWP estimates from MODIS collocated with Lagrangian back trajectories show systematically lower Nd and higher LWP several days prior to arrival at Graciosa, consistent with the hypothesis that observed low-CCN air masses are often formed by coalescence scavenging in thick warm clouds, often in cold air outbreaks.

Catalytic evaluation on liquid phase oxidation of vanillyl alcohol using air and H2O2 over mesoporous Cu-Ti composite oxide

NASA Astrophysics Data System (ADS)

Saha, Subrata; Hamid, Sharifah Bee Abd; Ali, Tammar Hussein

2017-02-01

A mesoporous, highly crystalline Cu-Ti composite oxide catalyst was prepared via facile, simple and modified solution method varying Cu and Ti ratio for selective liquid phase oxidation of vanillyl alcohol. Various spectroscopic procedures were employed to systematically characterize the catalyst structural and physicochemical properties. The defect chemistry of the catalyst was confirmed from the presence of surface defects revealed through HRTEM imagery between the TiO2 (101) and Cu3TiO4 (012) planes, complemented by the XRD profiling. Further, presence of oxygen vacancy evidenced by O 1s XPS spectra were observed on the catalyst surface. Moreover, the stoichiometry of Cu and Ti in the catalyst synthesis protocol was notably found to be the vital determinant to alter the redox properties of Cu-Ti composite oxide catalyst supported by H2-TPR. O2-TPD analysis. Moreover, a rational investigation was done using different oxidants such as air and H2O2 with variables reaction conditions. The catalyst was active for liquid phase oxidation of vanillyl alcohol to vanillin with performance of 66% conversion and 71% selectivity using H2O2 in base free condition. And also, catalytic activity was significantly improved by 94% conversion with 86% selectivity to vanillin in liquid phase aerobic oxidation at the optimum reaction conditions. To expand the superiority of the catalyst, three times reusability study was also examined with appreciable catalytic activity.

Characterization of Extracellular Polymeric Substances Produced by Pseudomonas fragi Under Air and Modified Atmosphere Packaging.

PubMed

Wang, Guang-Yu; Ma, Fang; Wang, Hu-Hu; Xu, Xing-Lian; Zhou, Guang-Hong

2017-09-01

Extracellular polymeric substances (EPS) play an important role in bacterial biochemical properties. The characteristics of EPS from 2 strains of Pseudomonas fragi cultured in meat aerobically (control) and in modified atmosphere packaging (MAP) were studied. The amount and components of EPS, the surface properties, and the effect on biofilm formation of several spoilage organisms were evaluated. The results showed that MAP inhibited the growth of the P. fragi strains. Compared with the control, more loose and less bound EPS (containing protein and carbohydrate) were produced by P. fragi in MAP samples. MAP also caused increased cell autoaggregation and surface hydrophobicity. After the removal of the EPS, the surface property changes were strain-dependent, suggesting that membrane compositions were also changed. In addition, the EPS displayed significant antibiofilm activity on Pseudomonas fluorescens and Serratia liquefaciens. In conclusion, P. fragi strains not only modified the amount, components, and surface properties of EPS but also changed the cell membrane compositions to adapt to MAP stress. Moreover, EPS may play an important role in microbial community competitions. © 2017 Institute of Food Technologists®.

Polyimide/metal composite films via in situ decomposition of inorganic additives - Soluble polyimide versus polyimide precursor

NASA Technical Reports Server (NTRS)

Rancourt, J. D.; Porta, G. M.; Moyer, E. S.; Madeleine, D. G.; Taylor, L. T.

1988-01-01

Polyimide-metal oxide (Co3O4 or CuO) composite films have been prepared via in situ thermal decomposition of cobalt (II) chloride or bis(trifluoroacetylacetonato)copper(II). A soluble polyimide (XU-218) and its corresponding prepolymer (polyamide acid) were individually employed as the reaction matrix. The resulting composites exhibited a greater metal oxide concentration at the air interface with polyamide acid as the reaction matrix. The water of imidization that is released during the concurrent polyamide acid cure and additive decomposition is believed to promote metal migration and oxide formation. In contrast, XU-218 doped with either HAuCl4.3H2O or AgNO3 yields surface gold or silver when thermolyzed (300 C).

Coadsorption of Human Milk Lactoferrin into the Dipalmitoylglycerolphosphatidylcholine Phospholipid Monolayer Spread at the Air/Water Interface

PubMed Central

Miano, Fausto; Zhao, Xiubo; Lu, Jian R.; Penfold, Jeff

2007-01-01

The coadsorption of human milk lactoferrin into a spread monolayer of dipalmitoylglycerol phosphatidylcholine (DPPC) at the air/water interface has been studied by neutron reflection. The system is a good model of the preocular tear film outer interface, which was the motivation for the study. The association of the protein with the surface was indicated by an increase of the surface pressure exerted by the DPPC monolayer. The extent of lactoferrin coadsorption was found to decrease with increasing surface pressure in the lipid monolayer, a trend consistent with the observation reported for other proteins, such as lysozyme and β-lactoglobulin. The neutron reflectivity measurements were subsequently carried out at the three surface pressures of 8, 15, and 35 mN/m to examine the structure and composition of lactoferrin coadsorbed at the interface. Whereas the DPPC monolayer effectively prevented lactoferrin insertion at the high surface pressure, a measurable amount of lactoferrin was found at the air/water interface at the two lower surface pressures. At 15 mN/m it was difficult to identify the distribution of lactoferrin with respect to the DPPC monolayer, due to its relatively low adsorbed amount and much broader distribution. At the lowest surface pressure of 8 mN/m, the lactoferrin coadsorption was found to increase with time over the first few hours. After 5 h the distribution of the lactoferrin layer became similar to, though quantitatively lower than, that adsorbed in the absence of the DPPC monolayer. It is characterized by a top dense sublayer of 15 Å with a bottom diffuse sublayer of 60 Å, indicating structural unfolding induced by surface adsorption under these conditions. PMID:17114223

Microwave-assisted synthesis of porous carbon-titania and highly crystalline titania nanostructures.

PubMed

Parker, Alison; Marszewski, Michal; Jaroniec, Mietek

2013-03-01

Porous carbon-titania and highly crystalline titania nanostructured materials were obtained through a microwave-assisted one-pot synthesis. Resorcinol and formaldehyde were used as carbon precursors, triblock copolymer Pluronic F127 as a stabilizing agent, and titanium isopropoxide as a titania precursor. This microwave-assisted one-pot synthesis involved formation of carbon spheres according to the recently modified Stöber method followed by hydrolysis and condensation of titania precursor. This method afforded carbon-titania composite materials containing anatase phase with specific surface areas as high as 390 m(2) g(-1). The pure nanostructured titania, obtained after removal of carbon through calcination of the composite material in air, was shown to be the anatase phase with considerably higher degree of crystallinity and the specific surface area as high as 130 m(2) g(-1). The resulting titania, because of its high surface area, well-developed porosity, and high crystallinity, is of great interest for catalysis, water treatment, lithium batteries, and other energy-related applications.

Analytical Methods to Distinguish the Positive and Negative Spectra of Mineral and Environmental Elements Using Deep Ablation Laser-Induced Breakdown Spectroscopy (LIBS).

PubMed

Kim, Dongyoung; Yang, Jun-Ho; Choi, Soojin; Yoh, Jack J

2018-01-01

Environments affect mineral surfaces, and the surface contamination or alteration can provide potential information to understanding their regional environments. However, when investigating mineral surfaces, mineral and environmental elements appear mixed in data. This makes it difficult to determine their atomic compositions independently. In this research, we developed four analytical methods to distinguish mineral and environmental elements into positive and negative spectra based on depth profiling data using laser-induced breakdown spectroscopy (LIBS). The principle of the methods is to utilize how intensity varied with depth for creating a new spectrum. The methods were applied to five mineral samples exposed to four environmental conditions including seawater, crude oil, sulfuric acid, and air as control. The proposed methods are then validated by applying the resultant spectra to principal component analysis and data were classified by the environmental conditions and atomic compositions of mineral. By applying the methods, the atomic information of minerals and environmental conditions were successfully inferred in the resultant spectrum.

The impact of synoptic weather on UK surface ozone and implications for premature mortality

NASA Astrophysics Data System (ADS)

Pope, R. J.; Butt, E. W.; Chipperfield, M. P.; Doherty, R. M.; Fenech, S.; Schmidt, A.; Arnold, S. R.; Savage, N. H.

2016-12-01

Air pollutants, such as ozone, have adverse impacts on human health and cause, for example, respiratory and cardiovascular problems. In the United Kingdom (UK), peak surface ozone concentrations typically occur in the spring and summer and are controlled by emission of precursor gases, tropospheric chemistry and local meteorology which can be influenced by large-scale synoptic weather regimes. In this study we composite surface and satellite observations of summer-time (April to September) ozone under different UK atmospheric circulation patterns, as defined by the Lamb weather types. Anticyclonic conditions and easterly flows are shown to significantly enhance ozone concentrations over the UK relative to summer-time average values. Anticyclonic stability and light winds aid the trapping of ozone and its precursor gases near the surface. Easterly flows (NE, E, SE) transport ozone and precursor gases from polluted regions in continental Europe (e.g. the Benelux region) to the UK. Cyclonic conditions and westerly flows, associated with unstable weather, transport ozone from the UK mainland, replacing it with clean maritime (North Atlantic) air masses. Increased cloud cover also likely decrease ozone production rates. We show that the UK Met Office regional air quality model successfully reproduces UK summer-time ozone concentrations and ozone enhancements under anticyclonic and south-easterly conditions for the summer of 2006. By using established ozone exposure-health burden metrics, anticyclonic and easterly condition enhanced surface ozone concentrations pose the greatest public health risk.

In vivo effect of a self-etching primer on dentin.

PubMed

Milia, E; Lallai, M R; García-Godoy, F

1999-08-01

To determine the ultrastructural aspects of the dentin collagen area in the cavity preparation floor produced in vivo after phosphoric acid acid-etching or after using Clearfil Liner Bond 2 self-etching primer (LB2 Primer). Twenty-four non-carious third molars scheduled for extraction from young adult patients (16-30 years old) were used. Conventional Class I cavities (+/- 2 mm deep) were prepared on the occlusal surfaces of all teeth using a cylindrical diamond bur on a high-speed handpiece with copious water spray. To avoid dehydration of the dentin, the smear layer-covered dentin was briefly air-dried for 2 seconds. Cavities were assigned at random to the following groups: Group A: Dentin etched for 15 seconds with 34% phosphoric acid, rinsed for 20 seconds and then briefly air-dried for 2 seconds with oil-free compressed air leaving the surfaces slightly moist. Group B: LB2 Primer was applied to the cavity surfaces for 30 seconds and then briefly air-dried to remove the solvent. Group C: The untreated dentin smear layer was used as a control. In all three groups, the cavities were filled incrementally with a resin-based composite (APX), light curing every increment for 40 seconds. After 30 minutes, the teeth were extracted atraumatically and the samples immediately prepared for evaluation with the transmission electron microscope. The use of a self-etching primer did not produce significant morphological changes in the moist dentin substrate. Adverse morphological conditions where observed when there was an excess water on the dentin surface. Phosphoric acid altered the collagen more severely than the self-etching primer.

Synthesis and characterization of thin-transparent nanostructured films for surface protection

NASA Astrophysics Data System (ADS)

Veltri, S.; Sokullu, E.; Barberio, M.; Gauthier, M. A.; Antici, P.

2017-01-01

This work demonstrates that very thin and optically transparent nanocomposite films can be conveniently applied on surface materials, displaying potent antibacterial properties without affecting the aesthetics of the underlying material. In our approach we propose new composite materials, which ensure the surface protection by inactivating the bacteria before a biofilm can be formed. The films contain very small loadings of TiO2, graphene, or fullerene, and can easily be applied on large surfaces using conventional brushes or air-brushes. These nanocomposite films are very promising candidates for the preservation of statues, mosaics, floors, buildings, and other objects that are exposed to challenging environmental conditions such as Architectonical Heritage or building materials (materials featuring stone, pigments, bronze, granite, marble, and glass).

A Study on Tribological Behavior of Glass-Epoxy Composite Filled with Granite Dust

NASA Astrophysics Data System (ADS)

Ray, Subhrajit; Rout, Arun Ku; KuSahoo, Ashok

2017-08-01

Granite powder is one of the solid wastes generated from stone processing industry used as organic filler replacing the conventional ceramic fillers in polymer matrix composite to increase the mechanical properties. The present work investigates the addition of granite powder on erosion wear properties of epoxy-glass fiber composite. The solid particle erosion wear rates of these hybrid composites are recorded considering various control parameters as impingement angles, erodent sizes and impact velocities following erosion resistance test in an air erosion test device at room temperatures. The test was conducted as per the Taguchi experimental design to minimize the erosion loss of material. The SEM views show the surface resistivity for the granite added specimens. The microscopic study also indicates various methods of material removal, crater wear and other subjective allocation during erosion experiment of the samples.

Tracking Transport and Transformation of Aerosols using C and O-triple Isotopic Composition of Carbonates: CSI La Jolla

NASA Astrophysics Data System (ADS)

Thiemens, M. H.; Shaheen, R.; Chong, K.; Hill, A.; Wong, J.; Zhang, Z.; Dominguez, G.

2012-12-01

Aerosols affect climate in numerous ways, including change in the earth's energy balance by absorbing and scattering solar radiations, alteration of the hydrological cycle by serving as cloud condensation nuclei, change in biogeochemical cycles by providing nutrients. Another significant process is the effect on the chemical composition of the atmosphere by providing surfaces for heterogeneous chemical reactions. Fine particles of aerodynamic diameter less than 2.5μm (PM2.5) also impinge upon human health by admission to the respiratory system causing a range of cardiopulmonary diseases. Both climate and public health aspects depend on their physical and chemical properties, therefore, understanding physico-chemical and photochemical transformations on aerosol surfaces is important for predicting their effects on climate change, atmospheric chemistry and human health. Here we present initial findings on the processes occurring on aerosol surfaces using isotopes to delineate day and night time chemistry, thus resolving photochemistry effects, and to identify their sources by way of the carbon isotopes. Aerosols were collected on filter papers for 12h during the day and at night time from June-Dec. 2011in La Jolla, CA., using high volume, multi stage cascade impactors. CO2 released after treating these filter papers with 100% phosphoric acid at 27oC was collected, purified chromatographically and analyzed for both C and O isotopes. Our data indicate that both C and O isotopes can be used to distinguish between heterogeneous and photochemical transformations. Aerosol carbonates collected during the day time were depleted in δ13Cday = -23 to -28‰ and δ18Oday = +3 to +10‰ and were isotopically distinct from the carbonates collected at night time δ13Cnight = 0 to -12‰, δ18Onightnight = +23 to +32‰. Higher chloride concentration in the samples collected at night time indicated the transport of marine air masses whereas higher nitrate and sulfate concentration indicated urban air pollution in the samples collected during the day time. To further constraint the origin of air masses being collected at La Jolla, Ca, NOAA Hysplit back trajectories were analyzed for 24 and 48h at three different altitudes (500m, 1000m, <1500m). Our analysis found dominance of urban air masses from Los Angeles and San Diego area during the day time whereas aerosols collected at night time had a significant component of marine air masses and some contribution from San Diego areas at our sampling site, as expected. To further understand the role of ozone in heterogeneous and photochemical transformation, oxygen triple isotopic composition of the carbonates will be measured. Scanning electron microscopy will also be used to characterize the physical and chemical features of the aerosols. The comprehensive approach will facilitate to define changes in surface chemistry of the aerosols occuring during their transport and aging.

Fabrication of efficient graphene-doped polymer/fullerene bilayer organic solar cells in air using spin coating followed by ultrasonic vibration post treatment

NASA Astrophysics Data System (ADS)

Zabihi, Fatemeh; Chen, Qianli; Xie, Yu; Eslamian, Morteza

2016-12-01

In this work, in an attempt to improve the performance and lifetime of organic solar cells, P3HT photon absorbing polymer was doped with graphene (G) nano-sheets, to make light harvesting G-P3HT composite thin film. The composite this film was then employed as the donor of a bilayer organic solar cell with the structure of glass/ITO/PEDOT:PSS/G-P3HT/C60/Al. The reference P3HT:PCBM bulk heterojunction solar cell was also fabricated for comparison. All solution-processed layers were made by spin coating in humid air (Shanghai, China); C60 and Al were deposited by thermal evaporation. An effective mechanical treatment approach developed by the authors, i.e. the application of forced ultrasonic vibration on the wet spun-on films, was used to improve the dispersion of graphene in G-P3HT composite films to obtain a uniform nanostructure. This mechanical method eliminates tedious and expensive chemical steps, currently performed to engineer the structure of organic solar cells. It is evidenced that the G-P3HT composite thin films, post treated by ultrasonic vibration at the optimum vibration duration, possess superior electrical conductivity, charge carrier mobility and density, uniform surface potential distribution, and lower surface roughness, compared to those of P3HT and G-P3HT thin films made without vibration. The results show significant improvement in the power conversion efficiency (PCE) of vibration-treated G-P3HT/C60 cell (PCE = 5.17%, the highest reported for this structure), substantiating the strong positive effect of using graphene and forced vibration for the fabrication of P3HT active layer in the bilayer cell structure.

Contrasting cloud composition between coupled and decoupled marine boundary layer clouds

NASA Astrophysics Data System (ADS)

Wang, Zhen; Mora Ramirez, Marco; Dadashazar, Hossein; MacDonald, Alex B.; Crosbie, Ewan; Bates, Kelvin H.; Coggon, Matthew M.; Craven, Jill S.; Lynch, Peng; Campbell, James R.; Azadi Aghdam, Mojtaba; Woods, Roy K.; Jonsson, Haflidi; Flagan, Richard C.; Seinfeld, John H.; Sorooshian, Armin

2016-10-01

Marine stratocumulus clouds often become decoupled from the vertical layer immediately above the ocean surface. This study contrasts cloud chemical composition between coupled and decoupled marine stratocumulus clouds for dissolved nonwater substances. Cloud water and droplet residual particle composition were measured in clouds off the California coast during three airborne experiments in July-August of separate years (Eastern Pacific Emitted Aerosol Cloud Experiment 2011, Nucleation in California Experiment 2013, and Biological and Oceanic Atmospheric Study 2015). Decoupled clouds exhibited significantly lower air-equivalent mass concentrations in both cloud water and droplet residual particles, consistent with reduced cloud droplet number concentration and subcloud aerosol (Dp > 100 nm) number concentration, owing to detachment from surface sources. Nonrefractory submicrometer aerosol measurements show that coupled clouds exhibit higher sulfate mass fractions in droplet residual particles, owing to more abundant precursor emissions from the ocean and ships. Consequently, decoupled clouds exhibited higher mass fractions of organics, nitrate, and ammonium in droplet residual particles, owing to effects of long-range transport from more distant sources. Sodium and chloride dominated in terms of air-equivalent concentration in cloud water for coupled clouds, and their mass fractions and concentrations exceeded those in decoupled clouds. Conversely, with the exception of sea-salt constituents (e.g., Cl, Na, Mg, and K), cloud water mass fractions of all species examined were higher in decoupled clouds relative to coupled clouds. Satellite and Navy Aerosol Analysis and Prediction System-based reanalysis data are compared with each other, and the airborne data to conclude that limitations in resolving boundary layer processes in a global model prevent it from accurately quantifying observed differences between coupled and decoupled cloud composition.

Micromachined ultrasonic transducers: 11.4 MHz transmission in air and more

NASA Astrophysics Data System (ADS)

Ladabaum, Igal; Khuri-Yakub, B. T.; Spoliansky, Dimitri

1996-01-01

The fabrication and modeling of novel, capacitive, ultrasonic air transducers is reported. Transmission experiments in air at 11.4, 9.2, and 3.1 MHz are shown to correspond with theory. The transducers are made using surface micromachining techniques, which enable the realization of center frequencies ranging from 1.8 to 11.6 MHz. The bandwidth of the transducers ranges from 5% to 20%, depending on processing parameters. Custom circuitry is able to detect 10 MHz capacitance fluctuations as small as 10-18 F, which correspond to displacements on the order of 10-3 Å, in a bandwidth of 2 MHz with a signal to noise ratio of 20 dB. Such detection sensitivity is shown to yield air transducer systems capable of withstanding over 100 dB of signal attenuation, a figure of merit that has significant implications for ultrasonic imaging, nondestructive evaluation, gas flow and composition measurements, and range sensing.

Air pollutants degrade floral scents and increase insect foraging times

NASA Astrophysics Data System (ADS)

Fuentes, Jose D.; Chamecki, Marcelo; Roulston, T.'ai; Chen, Bicheng; Pratt, Kenneth R.

2016-09-01

Flowers emit mixtures of scents that mediate plant-insect interactions such as attracting insect pollinators. Because of their volatile nature, however, floral scents readily react with ozone, nitrate radical, and hydroxyl radical. The result of such reactions is the degradation and the chemical modification of scent plumes downwind of floral sources. Large Eddy Simulations (LES) are developed to investigate dispersion and chemical degradation and modification of floral scents due to reactions with ozone, hydroxyl radical, and nitrate radical within the atmospheric surface layer. Impacts on foraging insects are investigated by utilizing a random walk model to simulate insect search behavior. Results indicate that even moderate air pollutant levels (e.g., ozone mixing ratios greater than 60 parts per billion on a per volume basis, ppbv) substantially degrade floral volatiles and alter the chemical composition of released floral scents. As a result, insect success rates of locating plumes of floral scents were reduced and foraging times increased in polluted air masses due to considerable degradation and changes in the composition of floral scents. Results also indicate that plant-pollinator interactions could be sensitive to changes in floral scent composition, especially if insects are unable to adapt to the modified scentscape. The increase in foraging time could have severe cascading and pernicious impacts on the fitness of foraging insects by reducing the time devoted to other necessary tasks.

Effect of various surface treatment methods on the bond strength of the heat-pressed ceramic samples.

PubMed

Saraçoğlu, A; Cura, C; Cötert, H S

2004-08-01

This in vitro study was conducted to evaluate the interaction between the shear bond strength and the surface treatment method for a commercial dental ceramic. Ninety bonded ceramic units were manufactured for this study. Each unit was made by luting two cylinder-shaped ceramic samples to each other with a resin-composite luting agent. The units were then divided into nine groups, containing 10 units in each group. Samples from each group were treated with one of the following: etching with 4.9% hydrofluoric acid for 10, 20 and 40 s, 9.5% hydrofluoric acid for 10, 20 and 40 s, 40% orthophosphoric acid for 40 s, air abrasion with alumina in 50-microm particles, and grinding with a high-speed diamond bur. The treated samples were then silanated and luted with a resin-composite luting agent. The luted units were then loaded to failure. Two samples from each group were neither silanated nor luted after the surface treatment procedure, and morphological changes obtained by various surface treatment regimens were investigated by scanning electron microscopy. A statistically significant difference was observed among the mean shear bond strengths of the groups prepared with different surface treatment techniques (P = 0.00). Hydrofluoric acid appeared to be the most suitable chemical medium to produce a reliable ceramic bond. Etching time and concentration of the acidic medium were also observed as important prognostic variates. Orthophosphoric acid treatment was observed to be the least effective surface treatment method on the heat-pressed ceramic samples. Physical applications such as bur grinding and air blasting maintained stronger bonds than the orthophosphoric acid, while producing weaker bonds than surfaces treated with hydrofluoric acid in all concentrations and etching periods. The effect of the silane priming agent was not considered in this study. Copyright 2004 Blackwell Publishing Ltd.

Superhydrophobic materials for drug delivery

NASA Astrophysics Data System (ADS)

Yohe, Stefan Thomas

Superhydrophobicity is a property of material surfaces reflecting the ability to maintain air at the solid-liquid interface when in contact with water. These surfaces have characteristically high apparent contact angles, by definition exceeding 150°, as a result of the composite material-air surface formed under an applied water droplet. Superhydrophobic surfaces were first discovered on naturally occurring substrates, and have subsequently been fabricated in the last several decades to harness these favorable surface properties for a number of emerging applications, including their use in biomedical settings. This work describes fabrication and characterization of superhydrophobic 3D materials, as well as their use as drug delivery devices. Superhydrophobic 3D materials are distinct from 2D superhydrophobic surfaces in that air is maintained not just at the surface of the material, but also within the bulk. When the superhydrophobic 3D materials are submerged in water, water infiltrates slowly and continuously as a new water-air-material interface is formed with controlled displacement of air. Electrospinning and electrospraying are used to fabricate superhydrophobic 3D materials utilizing blends of the biocompatible polymers poly(epsilon-caprolactone) and poly(caprolactone-co-glycerol monostearate) (PGC-C18). PGC-C18 is significantly more hydrophobic than PCL (contact angle of 116° versus 83° for flat materials), and further additions of PGC-C18 into electrospun meshes and electrosprayed coatings affords increased stability of the entrapped air layer. For example, PCL meshes alone (500 mum thick) take 10 days to fully wet, and with 10% or 30% PGC-C18 addition wetting rates are dramatically slowed to 60% wetted by 77 days and 4% by 75 days, respectively. Stability of the superhydrophobic materials can be further probed with a variety of physio-chemical techniques, including pressure, surfactant containing solutions, and solvents of varying surface tension. Superhydrophobicity is shown to be enhanced with further increases in PGC-C18 content and surface roughness (a decrease in fiber size). We demonstrate the utility of superhydrophobicity as a method for drug delivery. When the camptothecin derivatives SN-38 and CPT-11 are encapsulated within electrospun meshes, changes in air layer stability (due to changes in PGC-C18 content) dictate the rate of drug release by controlling the rate in which water can permeate into the porous 3D electrospun structure. Drug release can be tuned from 2 weeks to >10 weeks from 300 mum meshes, and meshes effectively kill a variety of cancer cell lines (lung, colon, breast) when utilized in a cytotoxicity assay. After determining that air could be used to control the rate of drug release, superhydrophobic 3D materials are explored for three applications. First, meshes are considered as a potential combination reinforcement-drug delivery device for use in resectable colorectal cancer. Second, removal of the air layer in superhydrophobic meshes is used as a method to trigger drug release. The pressure generated from high-intensity focused ultrasound (0.75-4.25 MPa) can remove the air layer spatially and temporally, allowing drug release to be controlled with application of a sufficient treatment. Third, "connective" electrosprayed coatings are deposited on chemically distinct material surfaces, which are both three-dimensional and mechanically robust. In summary, superhydrophobic 3D materials are fabricated and characterized, and are utilized as drug delivery devices. Controlled air removal from these materials offers an entirely new strategy for drug delivery, and is promising for the applications considered in this work as well as many others.

Variation in diffusion of gases through PDMS due to plasma surface treatment and storage conditions.

PubMed

Markov, Dmitry A; Lillie, Elizabeth M; Garbett, Shawn P; McCawley, Lisa J

2014-02-01

Polydimethylsiloxane (PDMS) is a commonly used polymer in the fabrication of microfluidic devices due to such features as transparency, gas permeability, and ease of patterning with soft lithography. The surface characteristics of PDMS can also be easily changed with oxygen or low pressure air plasma converting it from a hydrophobic to a hydrophilic state. As part of such a transformation, surface methyl groups are removed and replaced with hydroxyl groups making the exposed surface to resemble silica, a gas impermeable substance. We have utilized Platinum(II)-tetrakis(pentaflourophenyl)porphyrin immobilized within a thin (~1.5 um thick) polystyrene matrix as an oxygen sensor, Stern-Volmer relationship, and Fick's Law of simple diffusion to measure the effects of PDMS composition, treatment, and storage on oxygen diffusion through PDMS. Results indicate that freshly oxidized PDMS showed a significantly smaller diffusion coefficient, indicating that the SiO2 layer formed on the PDMS surface created an impeding barrier. This barrier disappeared after a 3-day storage in air, but remained significant for up to 3 weeks if PDMS was maintained in contact with water. Additionally, higher density PDMS formulation (5:1 ratio) showed similar diffusion characteristics as normal (10:1 ratio) formulation, but showed 60 % smaller diffusion coefficient after plasma treatment that never recovered to pre-treatment levels even after a 3-week storage in air. Understanding how plasma surface treatments contribute to oxygen diffusion will be useful in exploiting the gas permeability of PDMS to establish defined normoxic and hypoxic oxygen conditions within microfluidic bioreactor systems.

Variation in diffusion of gases through PDMS due to plasma surface treatment and storage conditions

PubMed Central

Markov, Dmitry A.; Lillie, Elizabeth M.; Garbett, Shawn P.; McCawley, Lisa J.

2013-01-01

Polydimethylsiloxane (PDMS) is a commonly used polymer in the fabrication of microfluidic devices due to such features as transparency, gas permeability, and ease of patterning with soft lithography. The surface characteristics of PDMS can also be easily changed with oxygen or low pressure air converting it from a hydrophobic to a hydrophilic state. As part of such a transformation, surface methyl groups are removed and replaced with hydroxyl groups making the exposed surface to resemble silica, a gas impermeable substance. We have utilized Platinum(II)-tetrakis(pentaflourophenyl)porphyrin immobilized within a thin (~1.5 um thick) polystyrene matrix as an oxygen sensor, Stern-Volmer relationship, and Fick's Law of simple diffusion to measure the effects of PDMS composition, treatment, and storage on oxygen diffusion through PDMS. Results show that freshly oxidized PDMS showed a significantly smaller diffusion coefficient, indicating that the SiO2 layer formed on the PDMS surface created an impeding barrier. This barrier disappeared after a three-day storage in air, but remained significant for up to three weeks if PDMS was maintained in contact with water. Additionally, higher density PDMS formulation (5:1 ratio) showed similar diffusion characteristics as normal (10:1 ratio) formulation, but showed 60% smaller diffusion coefficient after plasma treatment that never recovered to pre-treatment levels even after a three-week storage in air. Understanding how plasma surface treatments contribute to oxygen diffusion will be useful in exploiting the gas permeability of PDMS to establish defined normoxic and hypoxic oxygen conditions within microfluidic bioreactor systems. PMID:24065585

Clinical anthropometrics and body composition from 3D whole-body surface scans

PubMed Central

Ng, BK; Hinton, BJ; Fan, B; Kanaya, AM; Shepherd, JA

2017-01-01

BACKGROUND/OBJECTIVES Obesity is a significant worldwide epidemic that necessitates accessible tools for robust body composition analysis. We investigated whether widely available 3D body surface scanners can provide clinically relevant direct anthropometrics (circumferences, areas and volumes) and body composition estimates (regional fat/lean masses). SUBJECTS/METHODS Thirty-nine healthy adults stratified by age, sex and body mass index (BMI) underwent whole-body 3D scans, dual energy X-ray absorptiometry (DXA), air displacement plethysmography and tape measurements. Linear regressions were performed to assess agreement between 3D measurements and criterion methods. Linear models were derived to predict DXA body composition from 3D scan measurements. Thirty-seven external fitness center users underwent 3D scans and bioelectrical impedance analysis for model validation. RESULTS 3D body scan measurements correlated strongly to criterion methods: waist circumference R2 = 0.95, hip circumference R2 = 0.92, surface area R2 = 0.97 and volume R2 = 0.99. However, systematic differences were observed for each measure due to discrepancies in landmark positioning. Predictive body composition equations showed strong agreement for whole body (fat mass R2 = 0.95, root mean square error (RMSE) = 2.4 kg; fat-free mass R2 = 0.96, RMSE = 2.2 kg) and arms, legs and trunk (R2 = 0.79–0.94, RMSE = 0.5–1.7 kg). Visceral fat prediction showed moderate agreement (R2 = 0.75, RMSE = 0.11 kg). CONCLUSIONS 3D surface scanners offer precise and stable automated measurements of body shape and composition. Software updates may be needed to resolve measurement biases resulting from landmark positioning discrepancies. Further studies are justified to elucidate relationships between body shape, composition and metabolic health across sex, age, BMI and ethnicity groups, as well as in those with metabolic disorders. PMID:27329614

Tailoring the properties of a zero-valent iron-based composite by mechanochemistry for nitrophenols degradation in wastewaters.

PubMed

Cagnetta, Giovanni; Huang, Jun; Lomovskiy, Igor O; Yu, Gang

2017-11-01

Zero-valent iron (ZVI) is a valuable material for environmental remediation, because of its safeness, large availability, and inexpensiveness. Moreover, its reactivity can be improved by addition of (nano-) particles of other elements such as noble metals. However, common preparation methods for this kind of iron-based composites involve wet precipitation of noble metal salt precursors, so they are often expensive and not green. Mechanochemical procedures can provide a solvent-free alternative, even at a large scale. The present study demonstrates that it is possible to tailor functional properties of ZVI-based materials, utilizing high-energy ball milling. All main preparation parameters are investigated and discussed. Specifically, a copper-carbon-iron ternary composite was prepared for fast degradation of 4-nitrophenol (utilized as model pollutant) to 4-aminophenol and other phenolic compounds. Copper and carbon are purposely chosen to insert specific properties to the composite: Copper acts as efficient nano-cathode that enhances electron transfer from iron to 4-nitrophenol, while carbon protects the iron surface from fast oxidation in open air. In this way, the reactive material can rapidly reduce high concentration of nitrophenols in water, it does not require acid washing to be activated, and can be stored in open air for one week without any significant activity loss.

Effect of duty-cycles on the air plasma gas-phase of dielectric barrier discharges

NASA Astrophysics Data System (ADS)

Barni, R.; Biganzoli, I.; Dell'Orto, E. C.; Riccardi, C.

2015-10-01

An experimental investigation concerning the effects of a duty-cycle in the supply of a dielectric barrier discharge in atmospheric pressure air has been performed. Electrical characteristics of the discharge have been measured, focusing mainly on the statistical properties of the current filaments and on dielectric surface charging, both affected by the frequent repetition of breakdown imposed by the duty-cycle. Information on the gas-phase composition was gathered too. In particular, a strong enhancement in the ozone formation rate is observed when suitable long pauses separate the active discharge phases. A simulation of the chemical kinetics in the gas-phase, based on a simplified discharge modeling, is briefly described in order to shed light on the observed increase in ozone production. The effect of a duty-cycle on surface modification of polymeric films in order to increase their wettability has been investigated too.

Evidence of Lunar Phase Influence on Global Surface Air Temperatures

NASA Technical Reports Server (NTRS)

Anyamba, Ebby; Susskind, Joel

2000-01-01

Intraseasonal oscillations appearing in a newly available 20-year record of satellite-derived surface air temperature are composited with respect to the lunar phase. Polar regions exhibit strong lunar phase modulation with higher temperatures occurs near full moon and lower temperatures at new moon, in agreement with previous studies. The polar response to the apparent lunar forcing is shown to be most robust in the winter months when solar influence is minimum. In addition, the response appears to be influenced by ENSO events. The highest mean temperature range between full moon and new moon in the polar region between 60 deg and 90 deg latitude was recorded in 1983, 1986/87, and 1990/91. Although the largest lunar phase signal is in the polar regions, there is a tendency for meridional equatorward progression of anomalies in both hemispheres so that the warning in the tropics occurs at the time of the new moon.

Air-Coupled Ultrasonic Measurements in Composites

NASA Astrophysics Data System (ADS)

Kommareddy, V.; Peters, J. J.; Dayal, V.; Hsu, D. K.

2004-02-01

Air-coupled ultrasound is a non-contact technique and has clear advantages over water-coupled testing. Research of air-coupled ultrasonics, especially using capacitance and micromachined transducers, has been extensively reported in the literature. This paper reports our experience of applying piezoceramic air-coupled transducers for nondestructive evaluation of composites. The beam profiles of air-coupled piezoceramic transducers, with and without apodization, were mapped out. The transmission of air-coupled ultrasonic energy through composite plates of different thickness was measured experimentally; model calculation of the transmission coefficient, taking into account the frequency bandwidth of the transducer, agreed with the measurement results. The occurrence of diffraction phenomenon ("Poisson bright spot") while imaging flaws in composite laminates was investigated. The resolution of scanned images obtained with air-coupled transducers was investigated for different frequency, focusing, and apodization conditions.

Composition and apparatus for detecting gamma radiation

DOEpatents

Hofstetter, Kenneth J.

1994-01-01

A gamma radiation detector and a radioluminiscent composition for use therein. The detector includes a radioluminscent composition that emits light in a characteristic wavelength region when exposed to gamma radiation, and means for detecting said radiation. The composition contains a scintillant such as anglesite (PbSO.sub.4) or cerussite (PbCO.sub.3) incorporated into an inert, porous glass matrix via a sol-gel process. Particles of radiation-sensitive scintillant are added to, a sol solution. The mixture is polymerized to form a gel, then dried under conditions that preserve the structural integrity and radiation sensitivity of the scintillant. The final product is a composition containing the uniformly-dispersed scintillant in an inert, optically transparent and highly porous matrix. The composition is chemically inert and substantially impervious to environmental conditions including changes in temperature, air pressure, and so forth. It can be fabricated in cylinders, blocks with holes therethrough for flow of fluid, sheets, surface coatings, pellets or other convenient shapes.

Composition and apparatus for detecting gamma radiation

DOEpatents

Hofstetter, K.J.

1994-08-09

A gamma radiation detector and a radioluminescent composition for use therein. The detector includes a radioluminescent composition that emits light in a characteristic wavelength region when exposed to gamma radiation, and means for detecting said radiation. The composition contains a scintillant such as anglesite (PbSO[sub 4]) or cerussite (PbCO[sub 3]) incorporated into an inert, porous glass matrix via a sol-gel process. Particles of radiation-sensitive scintillant are added to, a sol solution. The mixture is polymerized to form a gel, then dried under conditions that preserve the structural integrity and radiation sensitivity of the scintillant. The final product is a composition containing the uniformly-dispersed scintillant in an inert, optically transparent and highly porous matrix. The composition is chemically inert and substantially impervious to environmental conditions including changes in temperature, air pressure, and so forth. It can be fabricated in cylinders, blocks with holes therethrough for flow of fluid, sheets, surface coatings, pellets or other convenient shapes. 3 figs.

Analysis of the Effect of Surface Modification on Polyimide Composites Coated with Erosion Resistant Materials

NASA Technical Reports Server (NTRS)

Ndalama, Tchinga; Hirschfeld, Deidre; Sutter, James K. (Technical Monitor)

2003-01-01

The aim of this research is to enhance performance of composite coatings through modification of graphite-reinforced polyimide composite surfaces prior to metal bond coat/ hard topcoat application for use in the erosive and/or oxidative environments of advanced engines. Graphite reinforced polyimide composites, PMR-15 and PMR-II-50, formed by sheet molding and pre-pregging will be surface treated, overlaid with a bond coat and then coated with WC-Co. The surface treatment will include cleaning, RF plasma or ultraviolet light- ozone etching, and deposition of SiO(x) groups. These surface treatments will be studied in order to investigate and improve adhesion and oxidation resistance. The following panels were provided by NASA-Glenn Research Center(NASA-GRC): Eight compression molded PMR-II-50; 6 x 6 x 0.125 in. Two vacuum-bagged PMR-II-50; 12 x 12 x 0.125 in. Eight compression molded PMR-15; 6 x 6 x 0.125 in. One vacuum-bagged PMR-15; 12 x 12 x 0.125 in. All panels were made using a 12 x 12 in. T650-35 8HS (3K-tow) graphite fabric. A diamond-wafering blade, with deionized water as a cutting fluid, was used to cut PMR-II-50 and PMR-15 panels into 1 x 1 in. pieces for surface tests. The panel edges exhibiting delamination were used for the preliminary surface preparation tests as these would be unsuitable for strength and erosion testing. PMR-15 neat resin samples were also provided by NASA GRC. Surface profiles of the as-received samples were determined using a Dektak III Surface profile measuring system. Two samples of compression molded PMR-II-50 and PMR-15, vacuum-bagged PMR-II-50 and PMR-15 were randomly chosen for surface profile measurement according to ANSI/ASME B46.1. Prior to each measurement, the samples were blasted with compressed air to remove any artifacts. Five 10 mm-long scans were made on each sample. The short and long wavelength cutoff filter values were set at 100 and 1000 m, diamond stylus radius was 12.5 microns. Table 1 is a summary of the arithmetic average roughness (Ra) and waviness (Wa) for the composite surfaces.

Atmospheric emissions from the Deepwater Horizon spill constrain air-water partitioning, hydrocarbon fate, and leak rate

NASA Astrophysics Data System (ADS)

Ryerson, T. B.; Aikin, K. C.; Angevine, W. M.; Atlas, E. L.; Blake, D. R.; Brock, C. A.; Fehsenfeld, F. C.; Gao, R.-S.; de Gouw, J. A.; Fahey, D. W.; Holloway, J. S.; Lack, D. A.; Lueb, R. A.; Meinardi, S.; Middlebrook, A. M.; Murphy, D. M.; Neuman, J. A.; Nowak, J. B.; Parrish, D. D.; Peischl, J.; Perring, A. E.; Pollack, I. B.; Ravishankara, A. R.; Roberts, J. M.; Schwarz, J. P.; Spackman, J. R.; Stark, H.; Warneke, C.; Watts, L. A.

2011-04-01

The fate of deepwater releases of gas and oil mixtures is initially determined by solubility and volatility of individual hydrocarbon species; these attributes determine partitioning between air and water. Quantifying this partitioning is necessary to constrain simulations of gas and oil transport, to predict marine bioavailability of different fractions of the gas-oil mixture, and to develop a comprehensive picture of the fate of leaked hydrocarbons in the marine environment. Analysis of airborne atmospheric data shows massive amounts (˜258,000 kg/day) of hydrocarbons evaporating promptly from the Deepwater Horizon spill; these data collected during two research flights constrain air-water partitioning, thus bioavailability and fate, of the leaked fluid. This analysis quantifies the fraction of surfacing hydrocarbons that dissolves in the water column (˜33% by mass), the fraction that does not dissolve, and the fraction that evaporates promptly after surfacing (˜14% by mass). We do not quantify the leaked fraction lacking a surface expression; therefore, calculation of atmospheric mass fluxes provides a lower limit to the total hydrocarbon leak rate of 32,600 to 47,700 barrels of fluid per day, depending on reservoir fluid composition information. This study demonstrates a new approach for rapid-response airborne assessment of future oil spills.

Biodegradable polyester films from renewable aleuritic acid: surface modifications induced by melt-polycondensation in air

NASA Astrophysics Data System (ADS)

Jesús Benítez, José; Alejandro Heredia-Guerrero, José; Inmaculada de Vargas-Parody, María; Cruz-Carrillo, Miguel Antonio; Morales-Flórez, Victor; de la Rosa-Fox, Nicolás; Heredia, Antonio

2016-05-01

Good water barrier properties and biocompatibility of long-chain biopolyesters like cutin and suberin have inspired the design of synthetic mimetic materials. Most of these biopolymers are made from esterified mid-chain functionalized ω-long chain hydroxyacids. Aleuritic (9,10,16-trihydroxypalmitic) acid is such a polyhydroxylated fatty acid and is also the major constituent of natural lac resin, a relatively abundant and renewable resource. Insoluble and thermostable films have been prepared from aleuritic acid by melt-condensation polymerization in air without catalysts, an easy and attractive procedure for large scale production. Intended to be used as a protective coating, the barrier's performance is expected to be conditioned by physical and chemical modifications induced by oxygen on the air-exposed side. Hence, the chemical composition, texture, mechanical behavior, hydrophobicity, chemical resistance and biodegradation of the film surface have been studied by attenuated total reflection-Fourier transform infrared spectroscopy (ATR-FTIR), atomic force microscopy (AFM), nanoindentation and water contact angle (WCA). It has been demonstrated that the occurrence of side oxidation reactions conditions the surface physical and chemical properties of these polyhydroxyester films. Additionally, the addition of palmitic acid to reduce the presence of hydrophilic free hydroxyl groups was found to have a strong influence on these parameters.

Mercury capture by native fly ash carbons in coal-fired power plants

PubMed Central

Hower, James C.; Senior, Constance L.; Suuberg, Eric M.; Hurt, Robert H.; Wilcox, Jennifer L.; Olson, Edwin S.

2013-01-01

The control of mercury in the air emissions from coal-fired power plants is an on-going challenge. The native unburned carbons in fly ash can capture varying amounts of Hg depending upon the temperature and composition of the flue gas at the air pollution control device, with Hg capture increasing with a decrease in temperature; the amount of carbon in the fly ash, with Hg capture increasing with an increase in carbon; and the form of the carbon and the consequent surface area of the carbon, with Hg capture increasing with an increase in surface area. The latter is influenced by the rank of the feed coal, with carbons derived from the combustion of low-rank coals having a greater surface area than carbons from bituminous- and anthracite-rank coals. The chemistry of the feed coal and the resulting composition of the flue gas enhances Hg capture by fly ash carbons. This is particularly evident in the correlation of feed coal Cl content to Hg oxidation to HgCl2, enhancing Hg capture. Acid gases, including HCl and H2SO4 and the combination of HCl and NO2, in the flue gas can enhance the oxidation of Hg. In this presentation, we discuss the transport of Hg through the boiler and pollution control systems, the mechanisms of Hg oxidation, and the parameters controlling Hg capture by coal-derived fly ash carbons. PMID:24223466

The first stage of Lunar Prospector's LMLV is erected at Pad 46, CCAS

NASA Technical Reports Server (NTRS)

1997-01-01

Workers hoist the first stage of a Lockheed Martin Launch Vehicle-2 (LMLV-2) for placement at Launch Complex 46 at Cape Canaveral Air Station (CCAS), Fla. The Lunar Prospector spacecraft is scheduled to launch aboard the LMLV-2 from CCAS in October for an 18-month mission that will orbit the Earth's Moon to collect data from the lunar surface. Information gathered during the mission will allow construction of a detailed map of the surface composition of the Moon and will improve our understanding of its origin, evolution, current state, and resources.

Process to Produce Iron Nanoparticle Lunar Dust Simulant Composite

NASA Technical Reports Server (NTRS)

Hung, Ching-cheh; McNatt, Jeremiah

2010-01-01

A document discusses a method for producing nanophase iron lunar dust composite simulant by heating a mixture of carbon black and current lunar simulant types (mixed oxide including iron oxide) at a high temperature to reduce ionic iron into elemental iron. The product is a chemically modified lunar simulant that can be attracted by a magnet, and has a surface layer with an iron concentration that is increased during the reaction. The iron was found to be -iron and Fe3O4 nanoparticles. The simulant produced with this method contains iron nanoparticles not available previously, and they are stable in ambient air. These nanoparticles can be mass-produced simply.

Solder extrusion pressure bonding process and bonded products produced thereby

DOEpatents

Beavis, Leonard C.; Karnowsky, Maurice M.; Yost, Frederick G.

1992-01-01

Production of soldered joints which are highly reliable and capable of surviving 10,000 thermal cycles between about -40.degree. C. and 110.degree. C. Process involves interposing a thin layer of a metal solder composition between the metal surfaces of members to be bonded and applying heat and up to about 1000 psi compression pressure to the superposed members, in the presence of a reducing atmosphere, to extrude the major amount of the solder composition, contaminants including fluxing gases and air, from between the members being bonded, to form a very thin, strong intermetallic bonding layer having a thermal expansion tolerant with that of the bonded members.

Solder extrusion pressure bonding process and bonded products produced thereby

NASA Astrophysics Data System (ADS)

Beavis, L. C.; Karnowsky, M. M.; Yost, F. G.

1990-04-01

The production of soldered joints are highly reliable and capable of surviving 10,000 thermal cycles between about -40 and 110 C. The process involves interposing a thin layer of a metal solder composition between the metal surfaces of members to be bonded and applying heat up to about 1000 psi compression pressure to the superposed members, in the presence of a reducing atmosphere, to extrude the major amount of the solder composition, contaminants including fluxing gases and air, from between the members being bonded, to form a very thin, strong intermetallic bonding layer having a thermal expansion tolerant with that of the bonded members.

Optimization and Analysis of Laser Beam Machining Parameters for Al7075-TiB2 In-situ Composite

NASA Astrophysics Data System (ADS)

Manjoth, S.; Keshavamurthy, R.; Pradeep Kumar, G. S.

2016-09-01

The paper focuses on laser beam machining (LBM) of In-situ synthesized Al7075-TiB2 metal matrix composite. Optimization and influence of laser machining process parameters on surface roughness, volumetric material removal rate (VMRR) and dimensional accuracy of composites were studied. Al7075-TiB2 metal matrix composite was synthesized by in-situ reaction technique using stir casting process. Taguchi's L9 orthogonal array was used to design experimental trials. Standoff distance (SOD) (0.3 - 0.5mm), Cutting Speed (1000 - 1200 m/hr) and Gas pressure (0.5 - 0.7 bar) were considered as variable input parameters at three different levels, while power and nozzle diameter were maintained constant with air as assisting gas. Optimized process parameters for surface roughness, volumetric material removal rate (VMRR) and dimensional accuracy were calculated by generating the main effects plot for signal noise ratio (S/N ratio) for surface roughness, VMRR and dimensional error using Minitab software (version 16). The Significant of standoff distance (SOD), cutting speed and gas pressure on surface roughness, volumetric material removal rate (VMRR) and dimensional error were calculated using analysis of variance (ANOVA) method. Results indicate that, for surface roughness, cutting speed (56.38%) is most significant parameter followed by standoff distance (41.03%) and gas pressure (2.6%). For volumetric material removal (VMRR), gas pressure (42.32%) is most significant parameter followed by cutting speed (33.60%) and standoff distance (24.06%). For dimensional error, Standoff distance (53.34%) is most significant parameter followed by cutting speed (34.12%) and gas pressure (12.53%). Further, verification experiments were carried out to confirm performance of optimized process parameters.

The Effect of Journal Roughness and Foil Coatings on the Performance of Heavily Loaded Foil Air Bearings

NASA Technical Reports Server (NTRS)

Radil, Kevin C.; DellaCorte, Christopher

2001-01-01

Foil air bearing load capacity tests were conducted to investigate if a solid lubricant coating applied to the surface of the bearing's top foil can function as a break-in coating. Two foil coating materials, a conventional soft polymer film (polyimide) and a hard ceramic (alumina), were independently evaluated against as-ground and worn (run-in) journals coated with NASA PS304, a high-temperature solid lubricant composite coating. The foil coatings were evaluated at journal rotational speeds of 30,000 rpm and at 25 C. Tests were also performed on a foil bearing with a bare (uncoated) nickel-based superalloy top foil to establish a baseline for comparison. The test results indicate that the presence of a top foil solid lubricant coating is effective at increasing the load capacity performance of the foil bearing. Compared to the uncoated baseline, the addition of the soft polymer coating on the top foil increased the bearing load coefficient by 120% when operating against an as-ground journal surface and 85 percent against a run-in journal surface. The alumina coating increased the load coefficient by 40% against the as-ground journal but did not have any affect when the bearing was operated with the run-in journal. The results suggest that the addition of solid lubricant films provide added lubrication when the air film is marginal indicating that as the load capacity is approached foil air bearings transition from hydrodynamic to mixed and boundary lubrication.

On the measurement of guided wavefields via air-coupled ultrasonic transducers

NASA Astrophysics Data System (ADS)

Michaels, Jennifer E.; Michaels, Thomas E.

2015-03-01

Guided wavefields are now routinely measured with scanning laser vibrometers for both characterization of guided wave propagation and damage assessment. However, these measurements are usually time-consuming, particularly for imaging of large areas, primarily because of the degree of signal averaging required to reduce incoherent noise. A scanned air-coupled transducer is an alternative wavefield acquisition method that is based upon recording the very small amplitude pressure waves that leak into air from the out-of-plane motion of the guided wavefield. Air-coupled methods are attractive because they are not sensitive to small variations in surface optical reflectivity and special surface preparations are thus not necessary. In addition, not as much averaging is needed, making the acquisition process much faster. Unlike laser vibrometry, the recorded signals are not a direct measure of the wave motion, but experiments have shown that the acquired wavefields resemble those obtained from laser-based systems. For the work presented here, wavefield data were recorded with both methods for the same aluminum plate and composite panel specimens. Data are qualitatively compared in several domains to assess differences in temporal characteristics and modal content. Although signals are not identical, it is shown that the air-coupled transducer data exhibits similar modal content to that of the laser vibrometry data and may provide a reasonable alternative for some applications.

Engineering of air-stable Fe/C/Pd composite nanoparticles for environmental remediation applications

NASA Astrophysics Data System (ADS)

Haham, Hai; Grinblat, Judith; Sougrati, Moulay-Tahar; Stievano, Lorenzo; Margel, Shlomo

2015-09-01

The present manuscript presents a convenient method for the synthesis of iron/carbon (Fe/C) nanoparticles (NPs) coated with much smaller Pd NPs for the removal of halogenated organic pollutants. For this purpose, iron oxide/polyvinylpyrrolidone (IO/PVP) NPs were first prepared by the thermal decomposition of ferrocene mixed with PVP at 350 °C under an inert atmosphere. IO,Fe/C and Fe/C NPs coated with graphitic and amorphous carbon layers were then produced by annealing the IO/PVP NPs at 500 and 600 °C, respectively, under an inert atmosphere. The effect of the annealing temperature on the chemical composition, shape, crystallinity, surface area and magnetic properties of the IO/PVP, IO,Fe/C and Fe/C NPs has been elucidated. Air-stable Fe/C/Pd NPs were produced by mixing the precursor palladium acetate with the air-stable Fe/C NPs in ethanol. The obtained Fe/C/Pd NPs demonstrated significantly higher environmental activity than the Fe/C NPs on eosin Y, a model halogenated organic pollutant. The environmental activity of the Fe/C/Pd NPs also increased with their increasing Pd content.

A Composite Diagnosis of Synoptic-Scale Extratropical Cyclone Development over the United States

NASA Technical Reports Server (NTRS)

Rolfson, Donald M.; Smith, Phillip J.

1996-01-01

This paper presents a composite diagnosis of synoptic-scale forcing mechanisms associated with extratropical cyclone evolution. Drawn from 12 cyclone cases that occurred over the continental United States during the cool season months, the diagnosis provides a 'climatology' of development mechanisms for difference categories of cyclone evolution ranging from cyclone weakening through three stages of cyclone intensification. Computational results were obtained using an 'extended' form of the Zwack-Okossi equation applied to routine upper-air and surface data analyzed on a 230 km x 230 km grid. Results show that cyclonic vorticity advection, which maximizes in the upper troposphere, was the primary contributor to cyclone development regardless of the stage of development. A second consistent contributor to development was latent heat release. Horizontal temperature advection, often acknowledged as a development mechanism, was found to contribute to development only during more intense stages. During weakening and weaker development stages, temperature advection opposed development, as the warm-air advection invariably found at upper levels was dominated by cold air advection in the lower half of the troposphere. In the more intense stages, development was moderated by dry-adiabatic cooling associated with the ascending vertical motions.

Significant OH production under surface cleaning and air cleaning conditions: Impact on indoor air quality.

PubMed

Carslaw, N; Fletcher, L; Heard, D; Ingham, T; Walker, H

2017-11-01

We report measurements of hydroxyl (OH) and hydroperoxy (HO 2 ) radicals made by laser-induced fluorescence spectroscopy in a computer classroom (i) in the absence of indoor activities (ii) during desk cleaning with a limonene-containing cleaner (iii) during operation of a commercially available "air cleaning" device. In the unmanipulated environment, the one-minute averaged OH concentration remained close to or below the limit of detection (6.5×10 5  molecule cm -3 ), whilst that of HO 2 was 1.3×10 7  molecule cm -3 . These concentrations increased to ~4×10 6 and 4×10 8  molecule cm -3 , respectively during desk cleaning. During operation of the air cleaning device, OH and HO 2 concentrations reached ~2×10 7 and ~6×10 8  molecule cm -3 respectively. The potential of these OH concentrations to initiate chemical processing is explored using a detailed chemical model for indoor air (the INDCM). The model can reproduce the measured OH and HO 2 concentrations to within 50% and often within a few % and demonstrates that the resulting secondary chemistry varies with the cleaning activity. Whilst terpene reaction products dominate the product composition following surface cleaning, those from aromatics and other VOCs are much more important during the use of the air cleaning device. © 2017 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.

Lamb wave dispersion and anisotropy profiling of composite plates via non-contact air-coupled and laser ultrasound

NASA Astrophysics Data System (ADS)

Harb, M. S.; Yuan, F. G.

2015-03-01

Conventional ultrasound inspection has been a standard non-destructive testing method for providing an in-service evaluation and noninvasive means of probing the interior of a structure. In particular, measurement of the propagation characteristics of Lamb waves allows inspection of plates that are typical components in aerospace industry. A rapid, complete non-contact hybrid approach for excitation and detection of Lamb waves is presented and applied for non-destructive evaluation of composites. An air-coupled transducer (ACT) excites ultrasonic waves on the surface of a composite plate, generating different propagating Lamb wave modes and a laser Doppler vibrometer (LDV) is used to measure the out-of-plane velocity of the plate. This technology, based on direct waveform imaging, focuses on measuring dispersive curves for A0 mode in a composite laminate and its anisotropy. A two-dimensional fast Fourier transform (2D-FFT) is applied to out-of-plane velocity data captured experimentally using LDV to go from the time-spatial domain to frequency-wavenumber domain. The result is a 2D array of amplitudes at discrete frequencies and wavenumbers for A0 mode in a given propagation direction along the composite. The peak values of the curve are then used to construct frequency wavenumber and phase velocity dispersion curves, which are also obtained directly using Snell's law and the incident angle of the excited ultrasonic waves. A high resolution and strong correlation between numerical and experimental results are observed for dispersive curves with Snell's law method in comparison to 2D-FFT method. Dispersion curves as well as velocity curves for the composite plate along different directions of wave propagation are measured. The visual read-out of the dispersion curves at different propagation directions as well as the phase velocity curves provide profiling and measurements of the composite anisotropy. The results proved a high sensitivity of the air-coupled and laser ultrasound technique in non-contact characterization of Lamb wave dispersion and material anisotropy of composite plates using simple Snell's law method.

Investigation of the H2S poisoning process for sensing composite material based on carbon nanotubes and metal oxides

PubMed Central

Duan, Yichen; Pirolli, Laurent; Teplyakov, Andrew V.

2016-01-01

The poisoning of H2S sensing material based on the mixture of acid-treated carbon nanotubes, CuO and SnO2 was investigated by exposing the material to high doses of H2S (1% in volume) and following the changes spectroscopically. The presence of metal sulfides (CuS and SnS2), sulfates and thiols was confirmed on the surface of this material as the result of H2S poisoning. Further study revealed that leaving this material in air for extended period of time led to reoxidation of metal sulfides back to metal oxides. The formation of thiols and sulfates directly on carbon nanotubes is not reversible under these conditions; however, the extent of the overall surface reaction in this case is substantially lower than that for the composite material. PMID:27812240

The dust cloud of the century

NASA Astrophysics Data System (ADS)

Robock, A.

1983-02-01

The structure and composition of the dust cloud from the 4 April 1982 eruption of the El Chichon volcano in Chiapas state, Mexico, is examined and the possible effects of the dust cloud on the world's weather patterns are discussed. Observations of the cloud using a variety of methods are evaluated, including data from the GOES and NOAA-7 weather satellites, vertically pointing lidar measurements, the SME satellite, and the Nimbus-7 satellite. Studies of the gaseous and particulate composition of the cloud reveal the presence of large amounts of sulfuric acid particles, which have a long mean residence time in the atmosphere and have a large effect on the amount of solar radiation received at the earth's surface by scattering several percent of the radiation back to space. Estimates of the effect of this cloud on surface air temperature changes are presented based on findings from climate models.

STS-46 plasma composition measurements using the EOIM-3 mass spectrometer

NASA Technical Reports Server (NTRS)

Hunton, Donald E.; Trzcinski, Edmund; Gosselin, Roger; Koontz, Steven; Leger, Lubert; Visentine, James T.

1995-01-01

One of the active instruments incorporated into the Evaluation of Oxygen Interactions with Materials - 3 experiment was a quadrupole mass spectrometer. The primary objectives for this instrument, which was built by the Air Force Phillips Laboratory and was a veteran of the STS-4 flight in 1982, were to quantify the flux of atomic oxygen striking the test surfaces in the EOIM-3 payload and to detect surface reaction products from the materials in the carousel. Other speakers in this session have covered the results of these experiments. Prior to the 40-hour-long dedicated EOIM-3 mission segment at the end of the STS-46 flight, the authors used the mass spectrometer to make measurements of ion and neutral gas composition in the shuttle environment. About 25 hours of data were collected during a variety of mission events, including Eureca deployment at high altitude and many tethered satellite system operations.

Investigation of the H2S poisoning process for sensing composite material based on carbon nanotubes and metal oxides.

PubMed

Duan, Yichen; Pirolli, Laurent; Teplyakov, Andrew V

2016-11-01

The poisoning of H 2 S sensing material based on the mixture of acid-treated carbon nanotubes, CuO and SnO 2 was investigated by exposing the material to high doses of H 2 S (1% in volume) and following the changes spectroscopically. The presence of metal sulfides (CuS and SnS 2 ), sulfates and thiols was confirmed on the surface of this material as the result of H 2 S poisoning. Further study revealed that leaving this material in air for extended period of time led to reoxidation of metal sulfides back to metal oxides. The formation of thiols and sulfates directly on carbon nanotubes is not reversible under these conditions; however, the extent of the overall surface reaction in this case is substantially lower than that for the composite material.

Lagrangian process attribution of isotopic variations in near-surface water vapour in a 30-year regional climate simulation over Europe

NASA Astrophysics Data System (ADS)

Dütsch, Marina; Pfahl, Stephan; Meyer, Miro; Wernli, Heini

2018-02-01

Stable water isotopes are naturally available tracers of moisture in the atmosphere. Due to isotopic fractionation, they record information about condensation and evaporation processes during the transport of air parcels, and therefore present a valuable means for studying the global water cycle. However, the meteorological processes driving isotopic variations are complex and not very well understood so far, in particular on short (hourly to daily) timescales. This study presents a Lagrangian method for attributing the isotopic composition of air parcels to meteorological processes, which provides new insight into the isotopic history of air parcels. It is based on the temporal evolution of the isotope ratios, the humidity, the temperature, and the location of the air parcels. Here these values are extracted along 7-day backward trajectories started every 6 hours from near the surface in a 30-year regional climate simulation over Europe with the isotope-enabled version of the model of the Consortium for Small-Scale Modelling (COSMOiso). The COSMOiso simulation has a horizontal resolution of 0.25° and is driven at the lateral boundaries by a T106 global climate simulation with the isotope-enabled version of the European Centre Hamburg model (ECHAMwiso). Both simulations are validated against measurements from the Global Network of Isotopes in Precipitation (GNIP), which shows that nesting COSMOiso within ECHAMwiso improves the representation of δ2H and deuterium excess in monthly accumulated precipitation. The method considers all isotopic changes that occur inside the COSMOiso model domain, which, on average, correspond to more than half of the mean and variability in both δ2H and deuterium excess at the air parcels' arrival points. Along every trajectory, the variations in the isotope values are quantitatively decomposed into eight process categories (evaporation from the ocean, evapotranspiration from land, mixing with moister air, mixing with drier air, liquid cloud formation, mixed phase cloud formation, ice cloud formation, and no process). The results show that for air parcels arriving over the ocean, evaporation from the ocean is the primary factor controlling δ2H and deuterium excess. Over land, evapotranspiration from land and mixing with moister air are similarly important. Liquid and mixed phase cloud formation contribute to the variability of δ2H and deuterium excess, especially over continental Europe. In summary, the presented method helps to better understand the linkage between the meteorological history of air parcels and their isotopic composition, and may support the interpretation of stable water isotope measurements in future.

The CHRONOS mission: capability for sub-hourly synoptic observations of carbon monoxide and methane to quantify emissions and transport of air pollution

NASA Astrophysics Data System (ADS)

Edwards, David P.; Worden, Helen M.; Neil, Doreen; Francis, Gene; Valle, Tim; Arellano, Avelino F., Jr.

2018-02-01

The CHRONOS space mission concept provides time-resolved abundance for emissions and transport studies of the highly variable and highly uncertain air pollutants carbon monoxide and methane, with sub-hourly revisit rate at fine (˜ 4 km) horizontal spatial resolution across a North American domain. CHRONOS can provide complete synoptic air pollution maps (snapshots) of the continental domain with less than 10 min of observations. This rapid mapping enables visualization of air pollution transport simultaneously across the entire continent and enables a sentinel-like capability for monitoring evolving, or unanticipated, air pollution sources in multiple locations at the same time with high temporal resolution. CHRONOS uses a compact imaging gas filter correlation radiometer for these observations, with heritage from more than 17 years of scientific data and algorithm advances by the science teams for the Measurements of Pollution in the Troposphere (MOPITT) instrument on NASA's Terra spacecraft in low Earth orbit. To achieve continental-scale sub-hourly sampling, the CHRONOS mission would be conducted from geostationary orbit, with the instrument hosted on a communications or meteorological platform. CHRONOS observations would contribute to an integrated observing system for atmospheric composition using surface, suborbital and satellite data with atmospheric chemistry models, as defined by the Committee on Earth Observing Satellites. Addressing the U.S. National Academy's 2007 decadal survey direction to characterize diurnal changes in tropospheric composition, CHRONOS observations would find direct societal applications for air quality management and forecasting to protect public health.

Fabricating Superhydrophobic and Superoleophobic Surfaces with Multiscale Roughness Using Airbrush and Electrospray

NASA Astrophysics Data System (ADS)

AL-Milaji, Karam N.

Examples of superhydrophobic surfaces found in nature such as self-cleaning property of lotus leaf and walking on water ability of water strider have led to an extensive investigation in this area over the past few decades. When a water droplet rests on a textured surface, it may either form a liquid-solid-vapor composite interface by which the liquid droplet partially sits on air pockets or it may wet the surface in which the water replaces the trapped air depending on the surface roughness and the surface chemistry. Super water repellent surfaces have numerous applications in our daily life such as drag reduction, anti-icing, anti-fogging, energy conservation, noise reduction, and self-cleaning. In fact, the same concept could be applied in designing and producing surfaces that repel organic contaminations (e.g. low surface tension liquids). However, superoleophobic surfaces are more challenging to fabricate than superhydrophobic surfaces since the combination of multiscale roughness with re-entrant or overhang structure and surface chemistry must be provided. In this study, simple, cost-effective and potentially scalable techniques, i.e., airbrush and electrospray, were employed for the sake of making superhydrophobic and superoleophobic coatings with random and patterned multiscale surface roughness. Different types of silicon dioxide were utilized in this work to in order to study and to characterize the effect of surface morphology and surface roughness on surface wettability. The experimental findings indicated that super liquid repellent surfaces with high apparent contact angles and extremely low sliding angles were successfully fabricated by combining re-entrant structure, multiscale surface roughness, and low surface energy obtained from chemically treating the fabricated surfaces. In addition to that, the experimental observations regarding producing textured surfaces in mask-assisted electrospray were further validated by simulating the actual working conditions and geometries using COMSOL Multiphysics.

Degradation of oxygen reduction reaction kinetics in porous La0.6Sr0.4Co0.2Fe0.8O3-δ cathodes due to aging-induced changes in surface chemistry

NASA Astrophysics Data System (ADS)

Baqué, Laura C.; Soldati, Analía L.; Teixeira-Neto, Erico; Troiani, Horacio E.; Schreiber, Anja; Serquis, Adriana C.

2017-01-01

The modification of surface composition after long-term operation is one of the most reported degradation mechanisms of (La,Sr)(Co,Fe)O3-δ (LSCFO) cathodes for Solid Oxide Fuel Cells (SOFCs). Nevertheless, its effect on the oxygen reduction reaction kinetics of porous LSCFO cathodes has not been yet reliably established. In this work, La- and Sr-enrichment at the LSCFO surface of porous cathodes has been induced after 50 h aging at 800 °C under air. Such cation redistribution can extend up to ∼400 nm depth under the LSCFO surface as detected by high resolution Scanning Transmission Electron Microscopy-Energy Dispersive Spectroscopy maps acquired inside the cathode pores. The observed surface chemical changes hamper the oxygen surface exchange reaction at the LSCFO/gas interface. Accordingly, a suitable Electrochemical Impedance Spectroscopy analysis revealed that the oxygen ion conductivity remains practically unaltered during the aging treatment while the oxygen surface exchange resistance increases up to 1.8 times. As a result, the cathode impedance response deteriorates within the 10-0.1 Hz frequency range during the aging treatment, resulting in a total cathode area specific resistance increase of 150%. The methodology adopted has demonstrated to be very valuable for studying the degradation of SOFC cathodes produced by the modification of surface composition.

Comparison study of biomimetic strontium-doped calcium phosphate coatings by electrochemical deposition and air plasma spray: morphology, composition and bioactive performance.

PubMed

Li, Ling; Lu, Xia; Meng, Yizhi; Weyant, Christopher M

2012-10-01

In this study, strontium-doped calcium phosphate coatings were deposited by electrochemical deposition and plasma spray under different process parameters to achieve various coating morphologies. The coating composition was investigated by energy dispersive X-ray spectroscopy and X-ray diffraction. The surface morphologies of the coatings were studied through scanning electron microscopy while the cytocompatibility and bioactivity of the strontium-doped calcium phosphate coatings were evaluated using bone cell culture using MC3T3-E1 osteoblast-like cells. The addition of strontium leads to enhanced proliferation suggesting the possible benefits of strontium incorporation in calcium phosphate coatings. The morphology and composition of deposited coatings showed a strong influence on the growth of cells.

Inspection of defects of composite materials in inner cylindrical surfaces using endoscopic shearography

NASA Astrophysics Data System (ADS)

Macedo, Fabiano Jorge; Benedet, Mauro Eduardo; Fantin, Analucia Vieira; Willemann, Daniel Pedro; da Silva, Fábio Aparecido Alves; Albertazzi, Armando

2018-05-01

This work presents the development of a special shearography system with radial sensitivity and explores its applicability for detecting adhesion flaws on internal surfaces of flanged joints of composite material pipes. The inspection is performed from the inner surface of the tube where the flange is adhered. The system uses two conical mirrors to achieve radial sensitivity. A primary 45° conical mirror is responsible for promoting the inspection of the internal tubular surface on its 360° A special Michelson interferometer is formed replacing one of the plane mirrors by a conical mirror. The image reflected by this conical mirror is shifted away from the image center in a radial way and a radial shear is produced on the images. The concept was developed and a prototype built and tested. First, two tubular steel specimens internally coated with composite material and having known artificial defects were analyzed to test the ability of the system to detect the flaws. After the principle validation, two flanged joints were then analyzed: (a) a reference one, without any artificial defects and (b) a test one with known artificial defects, simulating adhesion failures with different dimensions and locations. In all cases, thermal loading was applied through a hot air blower on the outer surface of the joint. The system presented very good results on all inspected specimens, being able to detect adhesion flaws present in the flanged joints. The experimental results obtained in this work are promising and open a new front for inspections of inner surfaces of pipes with shearography.

Biobriefcase aerosol collector

DOEpatents

Bell, Perry M [Tracy, CA; Christian, Allen T [Madison, WI; Bailey, Christopher G [Pleasanton, CA; Willis, Ladona [Manteca, CA; Masquelier, Donald A [Tracy, CA; Nasarabadi, Shanavaz L [Livermore, CA

2009-09-22

A system for sampling air and collecting particles entrained in the air that potentially include bioagents. The system comprises providing a receiving surface, directing a liquid to the receiving surface and producing a liquid surface. Collecting samples of the air and directing the samples of air so that the samples of air with particles entrained in the air impact the liquid surface. The particles potentially including bioagents become captured in the liquid. The air with particles entrained in the air impacts the liquid surface with sufficient velocity to entrain the particles into the liquid but cause minor turbulence. The liquid surface has a surface tension and the collector samples the air and directs the air to the liquid surface so that the air with particles entrained in the air impacts the liquid surface with sufficient velocity to entrain the particles into the liquid, but cause minor turbulence on the surface resulting in insignificant evaporation of the liquid.

Manufacturing Precise, Lightweight Paraboloidal Mirrors

NASA Technical Reports Server (NTRS)

Hermann, Frederick Thomas

2006-01-01

A process for fabricating a precise, diffraction- limited, ultra-lightweight, composite- material (matrix/fiber) paraboloidal telescope mirror has been devised. Unlike the traditional process of fabrication of heavier glass-based mirrors, this process involves a minimum of manual steps and subjective judgment. Instead, this process involves objectively controllable, repeatable steps; hence, this process is better suited for mass production. Other processes that have been investigated for fabrication of precise composite-material lightweight mirrors have resulted in print-through of fiber patterns onto reflecting surfaces, and have not provided adequate structural support for maintenance of stable, diffraction-limited surface figures. In contrast, this process does not result in print-through of the fiber pattern onto the reflecting surface and does provide a lightweight, rigid structure capable of maintaining a diffraction-limited surface figure in the face of changing temperature, humidity, and air pressure. The process consists mainly of the following steps: 1. A precise glass mandrel is fabricated by conventional optical grinding and polishing. 2. The mandrel is coated with a release agent and covered with layers of a carbon- fiber composite material. 3. The outer surface of the outer layer of the carbon-fiber composite material is coated with a surfactant chosen to provide for the proper flow of an epoxy resin to be applied subsequently. 4. The mandrel as thus covered is mounted on a temperature-controlled spin table. 5. The table is heated to a suitable temperature and spun at a suitable speed as the epoxy resin is poured onto the coated carbon-fiber composite material. 6. The surface figure of the optic is monitored and adjusted by use of traditional Ronchi, Focault, and interferometric optical measurement techniques while the speed of rotation and the temperature are adjusted to obtain the desired figure. The proper selection of surfactant, speed or rotation, viscosity of the epoxy, and temperature make it possible to obtain the desired diffraction-limited, smooth (1/50th wave) parabolic outer surface, suitable for reflective coating. 7. A reflective coat is applied by use of conventional coating techniques. 8. Once the final figure is set, a lightweight structural foam is applied to the rear of the optic to ensure stability of the figure.

Efficiency of clay--TiO2 nanocomposites on the photocatalytic elimination of a model hydrophobic air pollutant.

PubMed

Kibanova, Daria; Cervini-Silva, Javiera; Destaillats, Hugo

2009-03-01

Clay-supported TiO2 photocatalysts can potentially improve the performance of air treatment technologies via enhanced adsorption and reactivity of target volatile organic compounds (VOCs). In this study, a benchtop photocatalytic flow reactor was used to evaluate the efficiency of hectorite-TiO2 and kaolinite-TiO2, two novel composite materials synthesized in our laboratory. Toluene, a model hydrophobic VOC and a common indoor air pollutant, was introduced in the air stream at realistic concentrations, and reacted under UVA (lamda(max) = 365 nm) or UVC (lamda(max) = 254 nm) irradiation. The UVC lamp generated secondary emission at 185 nm, leading to the formation of ozone and other short-lived reactive species. Performance of clay-Ti02 composites was compared with that of pure TiO2 (Degussa P25), and with UV irradiation in the absence of photocatalyst under identical conditions. Films of clay-TiO2 composites and of P25 were prepared by a dip-coating method on the surface of Raschig rings, which were placed inside the flow reactor. An upstream toluene concentration of approximately 170 ppbv was generated by diluting a constant flow of toluene vapor from a diffusion source with dry air, or with humid air at 10, 33, and 66% relative humidity (RH). Toluene concentrations were determined by collecting Tenax-TA sorbent tubes downstream of the reactor, with subsequent thermal desorption--GC/MS analysis. The fraction of toluene removed, %R, and the reaction rate, Tr, were calculated for each experimental condition from the concentrations measured with and without UV irradiation. Use of UVC light (UV/TiO2/O3) led to overall higher reactivity, which can be partially attributed to the contribution of gas phase reactions by short-lived radical species. When the reaction rate was normalized to the light irradiance, Tr/Ilamda,the UV/TiO2 reaction under UVA irradiation was more efficient for samples with a higher content of TiO2 (P25 and Hecto-TiO2), but notfor Kao-TiO2. In all cases, reaction rates peaked at 10% RH, with Tr values between 10 and 50% higherthan those measured under dry air. However, a net inhibition was observed as RH increased to 33% and 66%, indicating that water molecules competed effectively with toluene for reactive surface sites and limited the overall photocatalytic conversion. Compared to P25, inhibition by coadsorbed water was less significant for Kao-TiO2 samples, but was more dramatic for Hecto-TiO2 due to the high water uptake capacity of hectorite.

Efficiency of clay-TiO2 nanocomposites on the photocatalytic eliminationof a model hydrophobic air pollutant

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

Kibanova, Daria; Cervini-Silva, Javiera; Destaillats, Hugo

2009-01-01

Clay-supported TiO2 photocatalysts can potentially improve the performance of air treatment technologies via enhanced adsorption and reactivity of target volatile organic compounds (VOCs). In this study, a bench-top photocatalytic flow reactor was used to evaluate the efficiency of hectorite-TiO2 and kaolinite-TiO2, two novel composite materials synthesized in our laboratory. Toluene, a model hydrophobic VOC and a common indoor air pollutant, was introduced in the air stream at realistic concentrations, and reacted under UVA (gamma max = 365 nm) or UVC (gamma max = 254 nm) irradiation. The UVC lamp generated secondary emission at 185 nm, leading to the formation ofmore » ozone and other short-lived reactive species. Performance of clay-TiO2 composites was compared with that of pure TiO2 (Degussa P25), and with UV irradiation in the absence of photocatalyst under identical conditions. Films of clay-TiO2 composites and of P25 were prepared by a dip-coating method on the surface of Raschig rings, which were placed inside the flow reactor. An upstream toluene concentration of ~;;170 ppbv was generated by diluting a constant flow of toluene vapor from a diffusion source with dry air, or with humid air at 10, 33 and 66percent relative humidity (RH). Toluene concentrations were determined by collecting Tenax-TA (R) sorbent tubes downstream of the reactor, with subsequent thermal desorption -- GC/MS analysis. The fraction of toluene removed, percentR, and the reaction rate, Tr, were calculated for each experimental condition from the concentration changes measured with and without UV irradiation. Use of UVC light (UV/TiO2/O3) led to overall higher reactivity, which can be partially attributed to the contribution of gas phase reactions by short-lived radical species. When the reaction rate was normalized to the light irradiance, Tr/I gamma, the UV/TiO2 reaction under UVA irradiation was more efficient for samples with a higher content of TiO2 (P25 and Hecto-TiO2), but not for Kao-TiO2. In all cases, reaction rates peaked at 10percent RH, with Tr values between 10 and 50percent higher than those measured under dry air. However, a net inhibition was observed as RH increased to 33percent and 66percent, indicating that water molecules competed effectively with toluene for reactive surface sites and limited the overall photocatalytic conversion. Compared to P25, inhibition by co-adsorbed water was less significant for Kao-TiO2 samples, but was more dramatic for Hecto-TiO2 due to the high water uptake capacity of hectorite.« less

Impact of Convection and Long Range Transport on Short-Lived Trace Gases in the UT/LS

NASA Astrophysics Data System (ADS)

Atlas, E. L.; Schauffler, S.; Navarro, M. A.; Lueb, R.; Hendershot, R.; Ueyama, R.

2017-12-01

Chemical composition of the air in the upper troposphere/lower stratosphere is controlled by a balance of transport, photochemistry, and physical processes, such as interactions with clouds, ice, and aerosol. The chemistry of the air masses that reach the upper troposphere can potentially have profound impacts on the chemistry in the near tropopause region. For example, the transport of reactive organic halogens and their transformation to inorganic halogen species, e.g., Br, BrO, etc., can have a significant impact on ozone budgets in this region and even deeper the stratosphere. Trace gas measurements in the region near the tropopause can also indicate potential sources of surface emissions that are transported to high altitudes. Measurement of trace gases, including such compounds as non-methane hydrocarbons, hydrochlorofluorocarbons, halogenated solvents, methyl halides, etc., can be used to characterize source emissions from industrial, urban, biomass burning, or marine origins. Recent airborne research campaigns have been conducted to better characterize the chemical composition and variations in the UT/LS region. This presentation will discuss these measurements, with a special emphasis on the role of convection and transport in modifying the chemical composition of the UT/LS.

The detection of formaldehyde using microelectromechanical acoustic resonator with multiwalled carbon nanotubes-polyethyleneimine composite coating

NASA Astrophysics Data System (ADS)

Wang, Jingjing; Zhan, Da; Wang, Ke; Hang, Weiwei

2018-01-01

A micro-scale gas sensor based on mass-sensitive film bulk acoustic resonator is demonstrated for the detection of trace formaldehyde at room temperature. The composites mixed with multiwalled carbon nanotubes and polyethyleneimine (MWNTs-PEI) were coated on the resonator surface as the sensitive layer to specifically absorb formaldehyde molecules using a facile spray process. The influence of spraying processes on the formaldehyde sensing properties were investigated. Different response behaviors were determined by both the chemical absorption between formaldehyde molecules and the amine functional groups on PEI and the increase of absorption surface came from the nanostructure. The combination of high frequency of the film bulk acoustic resonator (~4.3 GHz) and the specific absorbability of MWNTs-PEI composites provided a high sensitivity in the detections of trace formaldehyde. The obtained ultra-low limit of detection was as low as 60 ppb with linear response, quick response/recovery time, good reproducibility and selectivity. The proposed sensor shows potential as a portable and convenient gas-sensing system for monitoring the low-level concentration of indoor air pollution.

Atomic force microscopy of adsorbed proteoglycan mimetic nanoparticles: Toward new glycocalyx-mimetic model surfaces.

PubMed

Hedayati, Mohammadhasan; Kipper, Matt J

2018-06-15

Blood vessels present a dense, non-uniform, polysaccharide-rich layer, called the endothelial glycocalyx. The polysaccharides in the glycocalyx include polyanionic glycosaminoglycans (GAGs). This polysaccharide-rich surface has excellent and unique blood compatibility. We report new methods for preparing and characterizing dense GAG surfaces that can serve as models of the vascular endothelial glycocalyx. The GAG-rich surfaces are prepared by adsorbing heparin or chondroitin sulfate-containing polyelectrolyte complex nanoparticles (PCNs) to chitosan-hyaluronan polyelectrolyte multilayers (PEMs). The surfaces are characterized by PeakForce tapping atomic force microscopy, both in air and in aqueous pH 7.4 buffer, and by PeakForce quantitative nanomechanics (PF-QNM) mode with high spatial resolution. These new surfaces provide access to heparin-rich or chondroitin sulfate-rich coatings that mimic both composition and nanoscale structural features of the vascular endothelial glycocalyx. Copyright © 2018. Published by Elsevier Ltd.

Lipid and Lipid-Polymer Mixtures at an Interface

NASA Astrophysics Data System (ADS)

Kim, Joon Heon; Kim, Mahn Won

2000-03-01

The surface pressure (Π) and surface area/molecule (A) isotherms of a mixture of DMPC (DL-α-phosphatidylcholine,Dimyristoyl) and PEG-DMPE (1,2-Diacyl-sn-Glycero-3-Phosphoethanolamine-N-[Poly(ethylene glycol)5000]) system were measured at various compositions by the Langmuir surface balance technique at an air/water interface. In the range where the surface pressure is less than about 8 dynes/cm, a PEG polymer chain of PEG-DMPE molecules remains on the surface and the isotherm can be explained by the 2-D power law behavior of chains in a good solvent. In the range above 8 dynes/cm, a part of the PEG polymer segment is dissolved into the water phase, and the surface pressure can be explained as the sum of the 2-D component and 3-D component. Furthermore, the mixing energy is negative, which indicates an attractive interaction between DMPC and PEG-DMPE.

Lipid and lipid-polymer mixtures at an interface

NASA Astrophysics Data System (ADS)

Kim, Joon Heon; Kim, Mahn Won

2000-06-01

The surface pressure (Π) and surface area/molecule (A) isotherms of a mixture of DMPC (DL-α-phosphatidylcholine, Dimyristoyl) and PEG-DMPE (1,2-Diacyl-sn-Glycero-3-Phosphoethanolamine-N-[Poly(ethylene glycol)5000]) system were measured at various compositions by the Langmuir surface balance technique at an air/water interface. In the range where the surface pressure is less than about 8 dynes/cm, a PEG polymer chain of PEG-DMPE molecules remains on the surface and the isotherm can be explained by the 2-D power law behavior of chains in a good solvent. In the range above 8 dynes/cm, a part of the PEG polymer segment is dissolved into the water phase, and the surface pressure can be explained as the sum of the 2-D component and 3-D component. Furthermore, the mixing energy is negative, which indicates an attractive interaction between DMPC and PEG-DMPE. .

A study on the relationships between corrosion properties and chemistry of thermally oxidised surface films formed on polished commercial magnesium alloys AZ31 and AZ61

NASA Astrophysics Data System (ADS)

Feliu, Sebastián; Samaniego, Alejandro; Barranco, Violeta; El-Hadad, A. A.; Llorente, Irene; Serra, Carmen; Galván, J. C.

2014-03-01

This paper studies the changes in chemical composition of the thin oxide surface films induced by heating in air at 200 °C for time intervals from 5 min to 60 min on the freshly polished commercial AZ31 and AZ61 alloys with a view to better understanding their protective properties. This thermal treatment resulted in the formation of layers enriched in metallic aluminium at the interface between the outer MgO surface films and the bulk material. A strong link was found between the degree of metallic Al enrichment in the subsurface layer (from 10 to 15 at.%) observed by XPS (X-ray photoelectron spectroscopy) in the AZ61 treated samples and the increase in protective properties observed by EIS (electrochemical impedance spectroscopy) in the immersion test in 0.6 M NaCl. Heating for 5-60 min in air at 200 °C seems to be an effective, easy to perform and inexpensive method for increasing the corrosion resistance of the AZ61 alloy by approximately two or three times.

Roles of additives and surface control in slurry atomization

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

Tsai, S.C.

1990-01-01

This report focuses on the effects of interparticle forces on the rheology and airblast atomization of micronized coal water slurry (CWS). We found that the CWS flow behavior index is determined by the relative importance of the interparticle van der Waals attraction and the interparticle electrostatic repulsion. The former intensifies as the Hamaker constant increases and the interparticle distance reduces while the latter increases as the particle surface charge density increases. The interparticle attraction causes particle aggregation, which breaks down at high shear rates, and thus leads to slurry pseudoplastic behavior. In contrast, the interparticle repulsion prevents particle aggregation andmore » thus leads to Newtonian behavior. Both atomized at low atomizing air pressures (less than 270 kPa) using twin-fluid jet atomizers of various distributor designs. We found that the atomized drop sizes of micronized coal water slurries substantially decrease as the atomizing air pressure exceeds a threshold value. The effects of coal volume fraction, coal particle surface charge, liquid composition and liquid viscosity on slurry atomization can be accounted for by their effects on slurry rheology. 26 refs.« less

Mid-latitude storm track variability and its influence on atmospheric composition

NASA Astrophysics Data System (ADS)

Knowland, K. E.; Doherty, R. M.; Hodges, K.

2013-12-01

Using the storm tracking algorithm, TRACK (Hodges, 1994, 1995, 1999), we have studied the behaviour of storm tracks in the North Atlantic basin, using 850-hPa relative vorticity from the ERA-Interim Re-analysis (Dee et al., 2011). We have correlated surface ozone measurements at rural coastal sites in Europe to the storm track data to explore the role mid-latitude cyclones and their transport of pollutants play in determining surface air quality in Western Europe. To further investigate this relationship, we have used the Monitoring Atmospheric Composition Climate (MACC) Re-analysis dataset (Inness et al., 2013) in TRACK. The MACC Re-analysis is a 10-year dataset which couples a chemistry transport model (Mozart-3; Stein 2009, 2012) to an extended version of the European Centre for Medium-Range Weather Forecasts' (ECMWF) Integrated Forecast System (IFS). Storm tracks in the MACC Re-analysis compare well to the storm tracks using the ERA-Interim Re-analysis for the same 10-year period, as both are based on ECMWF IFSs. We also compare surface ozone values from MACC to surface ozone measurements previously studied. Using TRACK, we follow ozone (O3) and carbon monoxide (CO) through the life cycle of storms from North America to Western Europe. Along the storm tracks, we examine the distribution of CO and O3 within 6 degrees of the center of each storm and vertically at different pressure levels in the troposphere. We hope to better understand the mechanisms with which pollution is vented from the boundary layer to the free troposphere, as well as transport of pollutants to rural areas. Our hope is to give policy makers more detailed information on how climate variability associated with storm tracks between 1979-2013 may affect air quality in Northeast USA and Western Europe.

Global Estimates of Average Ground-Level Fine Particulate Matter Concentrations from Satellite-Based Aerosol Optical Depth

NASA Technical Reports Server (NTRS)

Van Donkelaar, A.; Martin, R. V.; Brauer, M.; Kahn, R.; Levy, R.; Verduzco, C.; Villeneuve, P.

2010-01-01

Exposure to airborne particles can cause acute or chronic respiratory disease and can exacerbate heart disease, some cancers, and other conditions in susceptible populations. Ground stations that monitor fine particulate matter in the air (smaller than 2.5 microns, called PM2.5) are positioned primarily to observe severe pollution events in areas of high population density; coverage is very limited, even in developed countries, and is not well designed to capture long-term, lower-level exposure that is increasingly linked to chronic health effects. In many parts of the developing world, air quality observation is absent entirely. Instruments aboard NASA Earth Observing System satellites, such as the MODerate resolution Imaging Spectroradiometer (MODIS) and the Multi-angle Imaging SpectroRadiometer (MISR), monitor aerosols from space, providing once daily and about once-weekly coverage, respectively. However, these data are only rarely used for health applications, in part because the can retrieve the amount of aerosols only summed over the entire atmospheric column, rather than focusing just on the near-surface component, in the airspace humans actually breathe. In addition, air quality monitoring often includes detailed analysis of particle chemical composition, impossible from space. In this paper, near-surface aerosol concentrations are derived globally from the total-column aerosol amounts retrieved by MODIS and MISR. Here a computer aerosol simulation is used to determine how much of the satellite-retrieved total column aerosol amount is near the surface. The five-year average (2001-2006) global near-surface aerosol concentration shows that World Health Organization Air Quality standards are exceeded over parts of central and eastern Asia for nearly half the year.

The OceanFlux Greenhouse Gases methodology for deriving a sea surface climatology of CO2 fugacity in support of air-sea gas flux studies

NASA Astrophysics Data System (ADS)

Goddijn-Murphy, L. M.; Woolf, D. K.; Land, P. E.; Shutler, J. D.; Donlon, C.

2015-07-01

Climatologies, or long-term averages, of essential climate variables are useful for evaluating models and providing a baseline for studying anomalies. The Surface Ocean CO2 Atlas (SOCAT) has made millions of global underway sea surface measurements of CO2 publicly available, all in a uniform format and presented as fugacity, fCO2. As fCO2 is highly sensitive to temperature, the measurements are only valid for the instantaneous sea surface temperature (SST) that is measured concurrently with the in-water CO2 measurement. To create a climatology of fCO2 data suitable for calculating air-sea CO2 fluxes, it is therefore desirable to calculate fCO2 valid for a more consistent and averaged SST. This paper presents the OceanFlux Greenhouse Gases methodology for creating such a climatology. We recomputed SOCAT's fCO2 values for their respective measurement month and year using monthly composite SST data on a 1° × 1° grid from satellite Earth observation and then extrapolated the resulting fCO2 values to reference year 2010. The data were then spatially interpolated onto a 1° × 1° grid of the global oceans to produce 12 monthly fCO2 distributions for 2010, including the prediction errors of fCO2 produced by the spatial interpolation technique. The partial pressure of CO2 (pCO2) is also provided for those who prefer to use pCO2. The CO2 concentration difference between ocean and atmosphere is the thermodynamic driving force of the air-sea CO2 flux, and hence the presented fCO2 distributions can be used in air-sea gas flux calculations together with climatologies of other climate variables.

Kinetics of adsorption of whey proteins and hydroxypropyl-methyl-cellulose mixtures at the air-water interface.

PubMed

Pérez, Oscar E; Carrera Sánchez, Cecilio; Pilosof, Ana M R; Rodríguez Patino, Juan M

2009-08-15

The aim of this research is to quantify the competitive adsorption of a whey protein concentrate (WPC) and hydroxypropyl-methyl-cellulose (HPMC so called E4M, E50LV and F4M) at the air-water interface by means of dynamic surface tensiometry and Brewster angle microscopy (BAM). These biopolymers are often used together in many food applications. The concentration of both protein and HPMC, and the WPC/HPMC ratio in the aqueous bulk phase were variables, while pH (7), the ionic strength (0.05 M) and temperature (20 degrees C) were kept constant. The differences observed between mixed systems were in accordance with the relative bulk concentration of these biopolymers (C(HPMC) and C(WPC)) and the molecular structure of HPMC. At short adsorption times, the results show that under conditions where both WPC and HPMC could saturate the air-water interface on their own or when C(HPMC) > or = C(WPC), the polysaccharide dominates the surface. At concentrations where none of the biopolymers was able to saturate the interface, a synergistic behavior was observed for HPMC with lower surface activity (E50LV and F4M), while a competitive adsorption was observed for E4M (the HPMC with the highest surface activity). At long-term adsorption the rate of penetration controls the adsorption of mixed components. The results reflect complex competitive/synergistic phenomena under conditions of thermodynamic compatibility or in the presence of a "depletion mechanism". Finally, the order in which the different components reach the interface will influence the surface composition and the film properties.

Predictions and Verification of an Isotope Marine Boundary Layer Model

NASA Astrophysics Data System (ADS)

Feng, X.; Posmentier, E. S.; Sonder, L. J.; Fan, N.

2017-12-01

A one-dimensional (1D), steady state isotope marine boundary layer (IMBL) model is constructed. The model includes meteorologically important features absent in Craig and Gordon type models, namely height-dependent diffusion/mixing and convergence of subsiding external air. Kinetic isotopic fractionation results from this height-dependent diffusion which starts as pure molecular diffusion at the air-water interface and increases linearly with height due to turbulent mixing. The convergence permits dry, isotopically depleted air subsiding adjacent to the model column to mix into ambient air. In δD-δ18O space, the model results fill a quadrilateral, of which three sides represent 1) vapor in equilibrium with various sea surface temperatures (SSTs) (high d18O boundary of quadrilateral); 2) mixture of vapor in equilibrium with seawater and vapor in the subsiding air (lower boundary depleted in both D and 18O); and 3) vapor that has experienced the maximum possible kinetic fractionation (high δD upper boundary). The results can be plotted in d-excess vs. δ18O space, indicating that these processes all cause variations in d-excess of MBL vapor. In particular, due to relatively high d-excess in the descending air, mixing of this air into the MBL causes an increase in d-excess, even without kinetic isotope fractionation. The model is tested by comparison with seven datasets of marine vapor isotopic ratios, with excellent correspondence; >95% of observational data fall within the quadrilateral area predicted by the model. The distribution of observations also highlights the significant influence of vapor from the nearby converging descending air on isotopic variations in the MBL. At least three factors may explain the <5% of observations that fall slightly outside of the predicted region in both δD-δ18O and d-excess - δ18O space: 1) variations in seawater isotopic ratios, 2) variations in isotopic composition of subsiding air, and 3) influence of sea spray. The model can be used for understanding the effects of boundary layer processes and meteorological conditions on isotopic composition of vapor within, and vapor fluxes through the MBL, and how changes in moisture source regions affect the isotopic composition of precipitation. The model can be applied to modern as well as paleo- climate conditions.

Effect of Dentin Wetness on the Bond Strength of Universal Adhesives.

PubMed

Choi, An-Na; Lee, Ji-Hye; Son, Sung-Ae; Jung, Kyoung-Hwa; Kwon, Yong Hoon; Park, Jeong-Kil

2017-10-25

The effects of dentin wetness on the bond strength and adhesive interface morphology of universal adhesives have been investigated using micro-tensile bond strength (μTBS) testing and confocal laser scanning microscopy (CLSM). Seventy-two human third molars were wet ground to expose flat dentin surfaces. They were divided into three groups according to the air-drying time of the dentin surfaces: 0 (without air drying), 5, and 10 s. The dentin surfaces were then treated with three universal adhesives: G-Premio Bond, Single Bond Universal, and All-Bond Universal in self-etch or etch-and-rinse mode. After composite build up, a μTBS test was performed. One additional tooth was prepared for each group by staining the adhesives with 0.01 wt % of Rhodamine B fluorescent dye for CLSM analysis. The data were analyzed statistically using ANOVA and Tukey's post hoc tests (α = 0.05). Two-way ANOVA showed significant differences among the adhesive systems and dentin moisture conditions. An interaction effect was also observed ( p < 0.05). One-way ANOVA showed that All-Bond Universal was the only material influenced by the wetness of the dentin surfaces. Wetness of the dentin surface is a factor influencing the micro-tensile bond strength of universal adhesives.

Effect of Dentin Wetness on the Bond Strength of Universal Adhesives

PubMed Central

Lee, Ji-Hye; Son, Sung-Ae; Jung, Kyoung-Hwa; Kwon, Yong Hoon

2017-01-01

The effects of dentin wetness on the bond strength and adhesive interface morphology of universal adhesives have been investigated using micro-tensile bond strength (μTBS) testing and confocal laser scanning microscopy (CLSM). Seventy-two human third molars were wet ground to expose flat dentin surfaces. They were divided into three groups according to the air-drying time of the dentin surfaces: 0 (without air drying), 5, and 10 s. The dentin surfaces were then treated with three universal adhesives: G-Premio Bond, Single Bond Universal, and All-Bond Universal in self-etch or etch-and-rinse mode. After composite build up, a μTBS test was performed. One additional tooth was prepared for each group by staining the adhesives with 0.01 wt % of Rhodamine B fluorescent dye for CLSM analysis. The data were analyzed statistically using ANOVA and Tukey’s post hoc tests (α = 0.05). Two-way ANOVA showed significant differences among the adhesive systems and dentin moisture conditions. An interaction effect was also observed (p < 0.05). One-way ANOVA showed that All-Bond Universal was the only material influenced by the wetness of the dentin surfaces. Wetness of the dentin surface is a factor influencing the micro-tensile bond strength of universal adhesives. PMID:29068404

Nanoporous Silicon Combustion: Observation of Shock Wave and Flame Synthesis of Nanoparticle Silica.

PubMed

Becker, Collin R; Gillen, Greg J; Staymates, Matthew E; Stoldt, Conrad R

2015-11-18

The persistent hydrogen termination present in nanoporous silicon (nPS) is unique compared to other forms of nanoscale silicon (Si) which typically readily form a silicon dioxide passivation layer. The hydrogen terminated surface combined with the extremely high surface area of nPS yields a material capable of powerful exothermic reactions when combined with strong oxidizers. Here, a galvanic etching mechanism is used to produce nPS both in bulk Si wafers as well as in patterned regions of Si wafers with microfabricated ignition wires. An explosive composite is generated by filling the pores with sodium perchlorate (NaClO4). Using high-speed video including Schlieren photography, a shock wave is observed to propagate through air at 1127 ± 116 m/s. Additionally, a fireball is observed above the region of nPS combustion which persists for nearly 3× as long when reacted in air compared to N2, indicating that highly reactive species are generated that can further combust with excess oxygen. Finally, reaction products from either nPS-NaClO4 composites or nPS alone combusted with only high pressure O2 (400 psig) gas as an oxidizer are captured in a calorimeter bomb. The products in both cases are similar and verified by transmission electron microscopy (TEM) to include nano- to micrometer scale SiOx particles. This work highlights the complex oxidation mechanism of nPS composites and demonstrates the ability to use a solid state reaction to create a secondary gas phase combustion.

Assessment of resin-dentin interfacial morphology of two ethanol-based universal adhesives: A scanning electron microscopy study

PubMed Central

Awad, Mohamed Moustafa

2017-01-01

Objective: The objective of this study was to assess the resin-dentin interfacial morphology created by two universal adhesives using scanning electron microscopy (SEM). Materials and Methods: The occlusal surfaces of ten (n = 5) molars were reduced to expose a flat surface of dentin. Two universal adhesives, Scotchbond Universal Adhesive and Tetric N-Bond Universal, were independently applied to air-dried dentin. Light-cured resin-based composite restorative materials were used to incrementally build a composite “buildup.” The specimen was sectioned mesiodistally to expose the resin-dentin interface. The inner surfaces of the specimens were polished. Samples were immersed in hydrochloric acid and then rinsed using distilled water. This was followed by immersion of the samples in 1% sodium hypochlorite solution. Then, samples were thoroughly rinsing with distilled water. Dehydration of samples was performed using ascending concentration of ethyl alcohol. Prepared samples were observed SEM at magnifications ×1500 and x4000. Results: Both universal adhesives could penetrate dentin-forming well-defined resin tags, lateral branches as well as a uniform hybrid layer. Conclusions: Two tested universal adhesives applied in self-etch mode can infiltrate into dentin-producing high-quality interfacial morphology. Similar interfacial morphology may be due to the similarity in composition and application mode. PMID:28729794

Composite oxygen transport membrane

DOEpatents

Christie, Gervase Maxwell; Lane, Jonathan A.

2014-08-05

A method of producing a composite oxygen ion membrane and a composite oxygen ion membrane in which a porous fuel oxidation layer and a dense separation layer and optionally, a porous surface exchange layer are formed on a porous support from mixtures of (Ln.sub.1-xA.sub.x).sub.wCr.sub.1-yB.sub.yO.sub.3-.delta. and a doped zirconia. In the porous fuel oxidation layer and the optional porous surface exchange layer, A is Calcium and in the dense separation layer A is not Calcium and, preferably is Strontium. Preferred materials are (La.sub.0.8Ca.sub.0.2).sub.0.95Cr.sub.0.5Mn.sub.0.5O.sub.3-.delta. for the porous fuel oxidation and optional porous surface exchange layers and (La.sub.0.8Sr.sub.0.2).sub.0.95Cr.sub.0.5Fe.sub.0.5O.sub.3-.delta. for the dense separation layer. The use of such materials allows the membrane to sintered in air and without the use of pore formers to reduce membrane manufacturing costs. The use of materials, as described herein, for forming the porous layers have application for forming any type of porous structure, such as a catalyst support.

Furnishing spaceship environment: evaluation of bacterial biofilms on different materials used inside International Space Station.

PubMed

Perrin, Elena; Bacci, Giovanni; Garrelly, Laurent; Canganella, Francesco; Bianconi, Giovanna; Fani, Renato; Mengoni, Alessio

2018-05-08

Performed inside International Space Station (ISS) from 2011 to 2016, VIABLE (eValuatIon And monitoring of microBiofiLms insidE International Space Station) ISS was a long-lasting experiment aimed at evaluating the bacterial contamination on different surface space materials subjected to different pre-treatment, to provide useful information for future space missions. In this work, surfaces samples of the VIABLE ISS experiment were analyzed to determine both the total bacterial load (ATP-metry, qPCR) and the composition of the microbial communities (16S rRNA genes amplicon sequencing). Data obtained showed a low bacterial contamination of all the surfaces, with values in agreement with those allowed inside ISS, and with a taxonomic composition similar to those found in previous studies (Enterobacteriales, Bacillales, Lactobacillales and Actinomycetales). No pre-treatment or material effect were observed on both the bacterial load and the composition of the communities, but for both a slight effect of the position (expose/not expose to air) was observed. In conclusion, under the conditions used for VIABLE ISS, no material or pre-treatment seems to be better than others in terms of quantity and type of bacterial contamination. Copyright © 2018 Institut Pasteur. Published by Elsevier Masson SAS. All rights reserved.

Composite oxygen transport membrane

DOEpatents

Christie, Gervase Maxwell; Lane, Jonathan A.

2016-11-15

A method of producing a composite oxygen ion membrane and a composite oxygen ion membrane in which a porous fuel oxidation layer and a dense separation layer and optionally, a porous surface exchange layer are formed on a porous support from mixtures of (Ln.sub.1-xA.sub.x).sub.wCr.sub.1-yB.sub.yO.sub.3-.delta. and a doped zirconia. In the porous fuel oxidation layer and the optional porous surface exchange layer, A is Calcium and in the dense separation layer A is not Calcium and, preferably is Strontium. Preferred materials are (La.sub.0.8Ca.sub.0.2).sub.0.95Cr.sub.0.5Mn.sub.0.5O.sub.3-.delta. for the porous fuel oxidation and optional porous surface exchange layers and (La.sub.0.8Sr.sub.0.2).sub.0.95Cr.sub.0.5Fe.sub.0.5O.sub.3-.delta. for the dense separation layer. The use of such materials allows the membrane to sintered in air and without the use of pore formers to reduce membrane manufacturing costs. The use of materials, as described herein, for forming the porous layers have application for forming any type of porous structure, such as a catalyst support.

High-Frequency Focused Water-Coupled Ultrasound Used for Three-Dimensional Surface Depression Profiling

NASA Technical Reports Server (NTRS)

Roth, Don J.; Whalen, Mike F.; Hendricks, J. Lynne; Bodis, James R.

2001-01-01

To interface with other solids, many surfaces are engineered via methods such as plating, coating, and machining to produce a functional surface ensuring successful end products. In addition, subsurface properties such as hardness, residual stress, deformation, chemical composition, and microstructure are often linked to surface characteristics. Surface topography, therefore, contains the signatures of the surface and possibly links to volumetric properties, and as a result serves as a vital link between surface design, manufacturing, and performance. Hence, surface topography can be used to diagnose, monitor, and control fabrication methods. At the NASA Glenn Research Center, the measurement of surface topography is important in developing high-temperature structural materials and for profiling the surface changes of materials during microgravity combustion experiments. A prior study demonstrated that focused air-coupled ultrasound at 1 MHz could profile surfaces with a 25-m depth resolution and a 400-m lateral resolution over a 1.4-mm depth range. In this work, we address the question of whether higher frequency focused water-coupled ultrasound can improve on these specifications. To this end, we employed 10- and 25-MHz focused ultrasonic transducers in the water-coupled mode. The surface profile results seen in this investigation for 25-MHz water-coupled ultrasound, in comparison to those for 1-MHz air-coupled ultrasound, represent an 8 times improvement in depth resolution (3 vs. 25 m seen in practice), an improvement of at least 2 times in lateral resolution (180 vs. 400 m calculated and observed in practice), and an improvement in vertical depth range of 4 times (calculated).

Robust biomimetic-structural superhydrophobic surface on aluminum alloy.

PubMed

Li, Lingjie; Huang, Tao; Lei, Jinglei; He, Jianxin; Qu, Linfeng; Huang, Peiling; Zhou, Wei; Li, Nianbing; Pan, Fusheng

2015-01-28

The following facile approach has been developed to prepare a biomimetic-structural superhydrophobic surface with high stabilities and strong resistances on 2024 Al alloy that are robust to harsh environments. First, a simple hydrothermal treatment in a La(NO3)3 aqueous solution was used to fabricate ginkgo-leaf like nanostructures, resulting in a superhydrophilic surface on 2024 Al. Then a low-surface-energy compound, dodecafluoroheptyl-propyl-trimethoxylsilane (Actyflon-G502), was used to modify the superhydrophilic 2024 Al, changing the surface character from superhydrophilicity to superhydrophobicity. The water contact angle (WCA) of such a superhydrophobic surface reaches up to 160°, demonstrating excellent superhydrophobicity. Moreover, the as-prepared superhydrophobic surface shows high stabilities in air-storage, chemical and thermal environments, and has strong resistances to UV irradiation, corrosion, and abrasion. The WCAs of such a surface almost remain unchanged (160°) after storage in air for 80 days, exposure in 250 °C atmosphere for 24 h, and being exposed under UV irradiation for 24 h, are more than 144° whether in acidic or alkali medium, and are more than 150° after 48 h corrosion and after abrasion under 0.98 kPa for 1000 mm length. The remarkable durability of the as-prepared superhydrophobic surface can be attributed to its stable structure and composition, which are due to the existence of lanthanum (hydr)oxides in surface layer. The robustness of the as-prepared superhydrophobic surface to harsh environments will open their much wider applications. The fabricating approach for such robust superhydrophobic surface can be easily extended to other metals and alloys.

2010-2011 Performance of the AirNow Satellite Data Processor

NASA Astrophysics Data System (ADS)

Pasch, A. N.; DeWinter, J. L.; Haderman, M. D.; van Donkelaar, A.; Martin, R. V.; Szykman, J.; White, J. E.; Dickerson, P.; Zahn, P. H.; Dye, T. S.

2012-12-01

The U.S. Environmental Protection Agency's (EPA) AirNow program provides maps of real time hourly Air Quality Index (AQI) conditions and daily AQI forecasts nationwide (http://www.airnow.gov). The public uses these maps to make health-based decisions. The usefulness of the AirNow air quality maps depends on the accuracy and spatial coverage of air quality measurements. Currently, the maps use only ground-based measurements, which have significant gaps in coverage in some parts of the United States. As a result, contoured AQI levels have high uncertainty in regions far from monitors. To improve the usefulness of air quality maps, scientists at EPA, Dalhousie University, and Sonoma Technology, Inc. have been working in collaboration with the National Aeronautics and Space Administration (NASA) and the National Oceanic and Atmospheric Administration (NOAA) to incorporate satellite-estimated surface PM2.5 concentrations into the maps via the AirNow Satellite Data Processor (ASDP). These satellite estimates are derived using NASA/NOAA satellite aerosol optical depth (AOD) retrievals and GEOS-Chem modeled ratios of surface PM2.5 concentrations to AOD. GEOS-Chem is a three-dimensional chemical transport model for atmospheric composition driven by meteorological input from the Goddard Earth Observing System (GOES). The ASDP can fuse multiple PM2.5 concentration data sets to generate AQI maps with improved spatial coverage. The goal of ASDP is to provide more detailed AQI information in monitor-sparse locations and augment monitor-dense locations with more information. We will present a statistical analysis for 2010-2011 of the ASDP predictions of PM2.5 focusing on performance at validation sites. In addition, we will present several case studies evaluating the ASDP's performance for multiple regions and seasons, focusing specifically on days when large spatial gradients in AQI and wildfire smoke impact were observed.

Mineralogical, chemical and toxicological characterization of urban air particles.

PubMed

Čupr, Pavel; Flegrová, Zuzana; Franců, Juraj; Landlová, Linda; Klánová, Jana

2013-04-01

Systematic characterization of morphological, mineralogical, chemical and toxicological properties of various size fractions of the atmospheric particulate matter was a main focus of this study together with an assessment of the human health risks they pose. Even though near-ground atmospheric aerosols have been a subject of intensive research in recent years, data integrating chemical composition of particles and health risks are still scarce and the particle size aspect has not been properly addressed yet. Filling this gap, however, is necessary for reliable risk assessment. A high volume ambient air sampler equipped with a multi-stage cascade impactor was used for size specific particle collection, and all 6 fractions were a subject of detailed characterization of chemical (PAHs) and mineralogical composition of the particles, their mass size distribution and genotoxic potential of organic extracts. Finally, the risk level for inhalation exposure associated to the carcinogenic character of the studied PAHs has been assessed. The finest fraction (<0.45 μm) exhibited the highest mass, highest active surface, highest amount of associated PAHs and also highest direct and indirect genotoxic potentials in our model air sample. Risk assessment of inhalation scenario indicates the significant cancer risk values in PM 1.5 size fraction. This presented new approach proved to be a useful tool for human health risk assessment in the areas with significant levels of air dust concentration. Copyright © 2013 Elsevier Ltd. All rights reserved.

High-Throughput Screening Across Quaternary Alloy Composition Space: Oxidation of (AlxFeyNi1-x-y)∼0.8Cr∼0.2.

PubMed

Payne, Matthew A; Miller, James B; Gellman, Andrew J

2016-09-12

Composition spread alloy films (CSAFs) are commonly used as libraries for high-throughput screening of composition-property relationships in multicomponent materials science. Because lateral gradients afford two degrees of freedom, an n-component CSAF can, in principle, contain any composition range falling on a continuous two-dimensional surface through an (n - 1)-dimensional composition space. However, depending on the complexity of the CSAF gradients, characterizing and graphically representing this composition range may not be straightforward when n ≥ 4. The standard approach for combinatorial studies performed using quaternary or higher-order CSAFs has been to use fixed stoichiometric ratios of one or more components to force the composition range to fall on some well-defined plane in the composition space. In this work, we explore the synthesis of quaternary Al-Fe-Ni-Cr CSAFs with a rotatable shadow mask CSAF deposition tool, in which none of the component ratios are fixed. On the basis of the unique gradient geometry produced by the tool, we show that the continuous quaternary composition range of the CSAF can be rigorously represented using a set of two-dimensional "pseudoternary" composition diagrams. We then perform a case study of (AlxFeyNi1-x-y)∼0.8Cr∼0.2 oxidation in dry air at 427 °C to demonstrate how such CSAFs can be used to screen an alloy property across a continuous two-dimensional subspace of a quaternary composition space. We identify a continuous boundary through the (AlxFeyNi1-x-y)∼0.8Cr∼0.2 subspace at which the oxygen uptake into the CSAF between 1 and 16 h oxidation time increases abruptly with decreasing Al content. The results are compared to a previous study of the oxidation of AlxFeyNi1-x-y CSAFs in dry air at 427 °C.

Cosmic ray composition and energy spectrum from 1-30 PeV using the 40-string configuration of IceTop and IceCube

NASA Astrophysics Data System (ADS)

IceCube Collaboration; Abbasi, R.; Abdou, Y.; Ackermann, M.; Adams, J.; Aguilar, J. A.; Ahlers, M.; Altmann, D.; Andeen, K.; Auffenberg, J.; Bai, X.; Baker, M.; Barwick, S. W.; Baum, V.; Bay, R.; Beattie, K.; Beatty, J. J.; Bechet, S.; Becker, J. K.; Becker, K.-H.; Bell, M.; Benabderrahmane, M. L.; BenZvi, S.; Berdermann, J.; Berghaus, P.; Berley, D.; Bernardini, E.; Bertrand, D.; Besson, D. Z.; Bindig, D.; Bissok, M.; Blaufuss, E.; Blumenthal, J.; Boersma, D. J.; Bohm, C.; Bose, D.; Böser, S.; Botner, O.; Brayeur, L.; Brown, A. M.; Bruijn, R.; Brunner, J.; Buitink, S.; Caballero-Mora, K. S.; Carson, M.; Casey, J.; Casier, M.; Chirkin, D.; Christy, B.; Clevermann, F.; Cohen, S.; Cowen, D. F.; Silva, A. H. Cruz; Danninger, M.; Daughhetee, J.; Davis, J. C.; De Clercq, C.; Descamps, F.; Desiati, P.; de Vries-Uiterweerd, G.; DeYoung, T.; Díaz-Vélez, J. C.; Dreyer, J.; Dumm, J. P.; Dunkman, M.; Eagan, R.; Eisch, J.; Ellsworth, R. W.; Engdegård, O.; Euler, S.; Evenson, P. A.; Fadiran, O.; Fazely, A. R.; Fedynitch, A.; Feintzeig, J.; Feusels, T.; Filimonov, K.; Finley, C.; Fischer-Wasels, T.; Flis, S.; Franckowiak, A.; Franke, R.; Frantzen, K.; Fuchs, T.; Gaisser, T. K.; Gallagher, J.; Gerhardt, L.; Gladstone, L.; Glüsenkamp, T.; Goldschmidt, A.; Goodman, J. A.; Góra, D.; Grant, D.; Groß, A.; Grullon, S.; Gurtner, M.; Ha, C.; Ismail, A. Haj; Hallgren, A.; Halzen, F.; Hanson, K.; Heereman, D.; Heimann, P.; Heinen, D.; Helbing, K.; Hellauer, R.; Hickford, S.; Hill, G. C.; Hoffman, K. D.; Hoffmann, R.; Homeier, A.; Hoshina, K.; Huelsnitz, W.; Hulth, P. O.; Hultqvist, K.; Hussain, S.; Ishihara, A.; Jacobi, E.; Jacobsen, J.; Japaridze, G. S.; Jlelati, O.; Johansson, H.; Kappes, A.; Karg, T.; Karle, A.; Kiryluk, J.; Kislat, F.; Kläs, J.; Klein, S. R.; Köhne, J.-H.; Kohnen, G.; Kolanoski, H.; Köpke, L.; Kopper, C.; Kopper, S.; Koskinen, D. J.; Kowalski, M.; Krasberg, M.; Kroll, G.; Kunnen, J.; Kurahashi, N.; Kuwabara, T.; Labare, M.; Laihem, K.; Landsman, H.; Larson, M. J.; Lauer, R.; Lesiak-Bzdak, M.; Lünemann, J.; Madsen, J.; Maruyama, R.; Mase, K.; Matis, H. S.; McNally, F.; Meagher, K.; Merck, M.; Mészáros, P.; Meures, T.; Miarecki, S.; Middell, E.; Milke, N.; Miller, J.; Mohrmann, L.; Montaruli, T.; Morse, R.; Movit, S. M.; Nahnhauer, R.; Naumann, U.; Nowicki, S. C.; Nygren, D. R.; Obertacke, A.; Odrowski, S.; Olivas, A.; Olivo, M.; O'Murchadha, A.; Panknin, S.; Paul, L.; Pepper, J. A.; de los Heros, C. Pérez; Pieloth, D.; Pirk, N.; Posselt, J.; Price, P. B.; Przybylski, G. T.; Rädel, L.; Rawlins, K.; Redl, P.; Resconi, E.; Rhode, W.; Ribordy, M.; Richman, M.; Riedel, B.; Rodrigues, J. P.; Rothmaier, F.; Rott, C.; Ruhe, T.; Rutledge, D.; Ruzybayev, B.; Ryckbosch, D.; Salameh, T.; Sander, H.-G.; Santander, M.; Sarkar, S.; Saba, S. M.; Schatto, K.; Scheel, M.; Scheriau, F.; Schmidt, T.; Schmitz, M.; Schoenen, S.; Schöneberg, S.; Schönherr, L.; Schönwald, A.; Schukraft, A.; Schulte, L.; Schulz, O.; Seckel, D.; Seo, S. H.; Sestayo, Y.; Seunarine, S.; Smith, M. W. E.; Soiron, M.; Soldin, D.; Spiczak, G. M.; Spiering, C.; Stamatikos, M.; Stanev, T.; Stasik, A.; Stezelberger, T.; Stokstad, R. G.; Stößl, A.; Strahler, E. A.; Ström, R.; Sullivan, G. W.; Taavola, H.; Taboada, I.; Tamburro, A.; Ter-Antonyan, S.; Tilav, S.; Toale, P. A.; Toscano, S.; Usner, M.; van Eijndhoven, N.; van der Drift, D.; Van Overloop, A.; van Santen, J.; Vehring, M.; Voge, M.; Walck, C.; Waldenmaier, T.; Wallraff, M.; Walter, M.; Wasserman, R.; Weaver, Ch.; Wendt, C.; Westerhoff, S.; Whitehorn, N.; Wiebe, K.; Wiebusch, C. H.; Williams, D. R.; Wissing, H.; Wolf, M.; Wood, T. R.; Woschnagg, K.; Xu, C.; Xu, D. L.; Xu, X. W.; Yanez, J. P.; Yodh, G.; Yoshida, S.; Zarzhitsky, P.; Ziemann, J.; Zilles, A.; Zoll, M.

2013-02-01

The mass composition of high energy cosmic rays depends on their production, acceleration, and propagation. The study of cosmic ray composition can therefore reveal hints of the origin of these particles. At the South Pole, the IceCube Neutrino Observatory is capable of measuring two components of cosmic ray air showers in coincidence: the electromagnetic component at high altitude (2835 m) using the IceTop surface array, and the muonic component above ˜1 TeV using the IceCube array. This unique detector arrangement provides an opportunity for precision measurements of the cosmic ray energy spectrum and composition in the region of the knee and beyond. We present the results of a neural network analysis technique to study the cosmic ray composition and the energy spectrum from 1 PeV to 30 PeV using data recorded using the 40-string/40-station configuration of the IceCube Neutrino Observatory.

A comparative study of gelatin and starch-based nano-composite films modified by nano-cellulose and chitosan for food packaging applications.

PubMed

Noorbakhsh-Soltani, S M; Zerafat, M M; Sabbaghi, S

2018-06-01

Environmental concerns have led to extensive research for replacing polymer-based food packaging with bio-nano-composites. In this study, incorporation of nano-cellulose into gelatin and starch matrices is investigated for this purpose. Chitosan is used to improve mechanical, anti-fungal and waterproof properties. Experiments are designed and analyzed using response surface methodology. Nano-Cellulose is synthesized via acid hydrolysis and incorporated in base matrices through wet processing. Also, tensile strength test, food preservation, transparency in visible and UV and water contact angle are performed on the nano-composite films. DSC/TGA and air permeability tests are also performed on the optimal films. The results show that increasing nano-cellulose composition to 10% leads to increase the tensile strength at break to 8121 MN/m 2 and decrease the elongation at break. Also, increasing chitosan composition from 5% to 30% can enhance food preservation up to 15 days. Copyright © 2018 Elsevier Ltd. All rights reserved.

Electrocatalytic performances of g-C3N4-LaNiO3 composite as bi-functional catalysts for lithium-oxygen batteries

PubMed Central

Wu, Yixin; Wang, Taohuan; Zhang, Yidie; Xin, Sen; He, Xiaojun; Zhang, Dawei; Shui, Jianglan

2016-01-01

A low cost and non-precious metal composite material g-C3N4-LaNiO3 (CNL) was synthesized as a bifunctional electrocatalyst for the air electrode of lithium-oxygen (Li-O2) batteries. The composition strategy changed the electron structure of LaNiO3 and g-C3N4, ensures high Ni3+/Ni2+ ratio and more absorbed hydroxyl on the surface of CNL that can promote the oxygen reduction reaction (ORR) and oxygen evolution reaction (OER). The composite catalyst presents higher activities than the individual components g-C3N4 and LaNiO3 for both ORR and OER. In non-aqueous Li-O2 batteries, CNL shows higher capacity, lower overpotentials and better cycling stability than XC-72 carbon and LaNiO3 catalysts. Our results suggest that CNL composite is a promising cathode catalyst for Li-O2 batteries. PMID:27074882

KSC-97PC1801

NASA Image and Video Library

1997-12-16

The access tower around the Athena II rocket for the Lunar Prospector spacecraft, to be launched for NASA by Lockheed Martin, was rolled back today at Launch Complex 46 at Cape Canaveral Air Station for final prelaunch preparations. The small robotic spacecraft is designed to provide the first global maps of the Moon's surface compositional elements and its gravitational and magnetic fields. The launch of Lunar Prospector is currently scheduled for Jan. 5, 1998 at 8:31 p.m

KSC-97PC1800

NASA Image and Video Library

1997-12-16

The access tower around the Athena II rocket for the Lunar Prospector spacecraft, to be launched for NASA by Lockheed Martin, was rolled back today at Launch Complex 46 at Cape Canaveral Air Station for final prelaunch preparations. The small robotic spacecraft is designed to provide the first global maps of the Moon's surface compositional elements and its gravitational and magnetic fields. The launch of Lunar Prospector is currently scheduled for Jan. 5, 1998 at 8:31 p.m

Trace gas measurements from tethered balloon platforms

NASA Technical Reports Server (NTRS)

Bandy, Alan R.; Bandy, Terese L.; Youngbluth, Otto; Owens, Thomas L.

1987-01-01

Instrumentation and chemical sampling and analysis procedures are described for making measurements of atmospheric carbon disulfide in the concentration range 1-1000 pptv from tethered balloon platforms. Results of a study on the CS2 composition of air downward of a saltwater marsh are reported. A method for obtaining the necessary data for solving the budget equations for surface fluxes, chemical formation rates and chemical destruction rates using data acquired from tethered balloon platforms is presented.

Evaluation of anti-freeze viscosity modifier for potential external tank applications

NASA Technical Reports Server (NTRS)

Lynn, R. O. L.

1981-01-01

Viscosity modifiers and gelling agents were evaluated in combination with ethylene glycol and dimethyl sulfoxide water eutectics. Pectin and agarose are found to gel these eutectics effectively in low concentration, but the anti-freeze protection afforded by these compositions is found to be marginal in simulations of the intended applications. Oxygen vent shutters and vertical metallic surfaces were simulated, with water supplied as a spray, dropwise, and by condensation from the air.

The effect of water storage, elapsed time and contaminants on the bond strength and interfacial polymerization of a nanohybrid composite.

PubMed

Perriard, Jean; Lorente, Maria Cattani; Scherrer, Susanne; Belser, Urs C; Wiskott, H W Anselm

2009-12-01

To systematically characterize the effect of time lapse, water storage, and selected contaminants on the bond strength of a nanofilled dental composite. Half-dumbbell-shaped samples were fabricated out of light-polymerizing composite resin. To function as substrates they were aged for 30 days in water. Prior to bonding, the substrates' surfaces were subjected to the following treatments: 1) Removing a 0.2- to 0.4-mm layer using a fluted carbide bur; 2) grit blasting with 50 microm alumina particles; 3) etching with phosphoric acid gel; 4) grit blasting followed by etching; 5) blasting with tribochemical particles followed by silane application; 6) sanding with 400-grit paper, air aging of the adherent half-sample before bonding; 7) surface contamination with saliva; 8) surface contamination with blood. In each group (n = 30), freshly polymerized (except in group 6) adherent half-samples were bonded to the substrate half-samples by a layer of unfilled adhesive resin. Fifteen full dumbbell-shaped specimens were subjected to tensile testing after 1 h and 15 after 7 days water storage. In a positive control group, freshly cured half-samples were bonded shortly after fabrication. The tensile strength was analyzed using Weibull statistics and presented in terms of the material's characteristic strength and shape parameter. Fractographs of the two weakest and strongest samples of each group were produced. The surfaces were searched to locate hackle, wake hackle and the origin of the fracture. Surface roughness and time lapse increased the bond strength of the repaired specimens. All groups in which surface roughness was produced before bonding increased in repair strength. Post-bonding aging improved strength. Fractographs yielded interpretable data whenever larger surfaces of single phase bonding resin were present. 1) Roughening and etching an aged composite's surface prior to applying a coat of unfilled resin and the filled material increases repair bond strength by up to 100%. 2) The repair bond strength of a roughened aged composite is 25% to 30% inferior to the tensile strength of solid specimens. 3) After 7 days' storage in water, no detrimental effect could be seen from saliva or blood contamination if the surfaces were properly rinsed.

A Multi-Variate Fit to the Chemical Composition of the Cosmic-Ray Spectrum

NASA Astrophysics Data System (ADS)

Eisch, Jonathan

Since the discovery of cosmic rays over a century ago, evidence of their origins has remained elusive. Deflected by galactic magnetic fields, the only direct evidence of their origin and propagation remain encoded in their energy distribution and chemical composition. Current models of galactic cosmic rays predict variations of the energy distribution of individual elements in an energy region around 3x1015 eV known as the knee. This work presents a method to measure the energy distribution of individual elemental groups in the knee region and its application to a year of data from the IceCube detector. The method uses cosmic rays detected by both IceTop, the surface-array component, and the deep-ice component of IceCube during the 2009-2010 operation of the IC-59 detector. IceTop is used to measure the energy and the relative likelihood of the mass composition using the signal from the cosmic-ray induced extensive air shower reaching the surface. IceCube, 1.5 km below the surface, measures the energy of the high-energy bundle of muons created in the very first interactions after the cosmic ray enters the atmosphere. These event distributions are fit by a constrained model derived from detailed simulations of cosmic rays representing five chemical elements. The results of this analysis are evaluated in terms of the theoretical uncertainties in cosmic-ray interactions and seasonal variations in the atmosphere. The improvements in high-energy cosmic ray hadronic-interaction models informed by this analysis, combined with increased data from subsequent operation of the IceCube detector, could provide crucial limits on the origin of cosmic rays and their propagation through the galaxy. In the course of developing this method, a number of analysis and statistical techniques were developed to deal with the difficulties inherent in this type of measurement. These include a composition-sensitive air shower reconstruction technique, a method to model simulated event distributions with limited statistics, and a method to optimize and estimate the error on a regularized fit.

Biofilm-like properties of the sea surface and predicted effects on air-sea CO2 exchange

NASA Astrophysics Data System (ADS)

Wurl, Oliver; Stolle, Christian; Van Thuoc, Chu; The Thu, Pham; Mari, Xavier

2016-05-01

Because the sea surface controls various interactions between the ocean and the atmosphere, it has a profound function for marine biogeochemistry and climate regulation. The sea surface is the gateway for the exchange of climate-relevant gases, heat and particles. Thus, in order to determine how the ocean and the atmosphere interact and respond to environmental changes on a global scale, the characterization and understanding of the sea surface are essential. The uppermost part of the water column is defined as the sea-surface microlayer and experiences strong spatial and temporal dynamics, mainly due to meteorological forcing. Wave-damped areas at the sea surface are caused by the accumulation of surface-active organic material and are defined as slicks. Natural slicks are observed frequently but their biogeochemical properties are poorly understood. In the present study, we found up to 40 times more transparent exopolymer particles (TEP), the foundation of any biofilm, in slicks compared to the underlying bulk water at multiple stations in the North Pacific, South China Sea, and Baltic Sea. We found a significant lower enrichment of TEP (up to 6) in non-slick sea surfaces compared to its underlying bulk water. Moreover, slicks were characterized by a large microbial biomass, another shared feature with conventional biofilms on solid surfaces. Compared to non-slick samples (avg. pairwise similarity of 70%), the community composition of bacteria in slicks was increasingly (avg. pairwise similarity of 45%) different from bulk water communities, indicating that the TEP-matrix creates specific environments for its inhabitants. We, therefore, conclude that slicks can feature biofilm-like properties with the excessive accumulation of particles and microbes. We also assessed the potential distribution and frequency of slick-formation in coastal and oceanic regions, and their effect on air-sea CO2 exchange based on literature data. We estimate that slicks can reduce CO2 fluxes by up to 15%, and, therefore, play important local and regional roles in regulating air-sea interactions.

Combustion aerosols: factors governing their size and composition and implications to human health.

PubMed

Lighty, J S; Veranth, J M; Sarofim, A F

2000-09-01

Particulate matter (PM) emissions from stationary combustion sources burning coal, fuel oil, biomass, and waste, and PM from internal combustion (IC) engines burning gasoline and diesel, are a significant source of primary particles smaller than 2.5 microns (PM2.5) in urban areas. Combustion-generated particles are generally smaller than geologically produced dust and have unique chemical composition and morphology. The fundamental processes affecting formation of combustion PM and the emission characteristics of important applications are reviewed. Particles containing transition metals, ultrafine particles, and soot are emphasized because these types of particles have been studied extensively, and their emissions are controlled by the fuel composition and the oxidant-temperature-mixing history from the flame to the stack. There is a need for better integration of the combustion, air pollution control, atmospheric chemistry, and inhalation health research communities. Epidemiology has demonstrated that susceptible individuals are being harmed by ambient PM. Particle surface area, number of ultrafine particles, bioavailable transition metals, polycyclic aromatic hydrocarbons (PAH), and other particle-bound organic compounds are suspected to be more important than particle mass in determining the effects of air pollution. Time- and size-resolved PM measurements are needed for testing mechanistic toxicological hypotheses, for characterizing the relationship between combustion operating conditions and transient emissions, and for source apportionment studies to develop air quality plans. Citations are provided to more specialized reviews, and the concluding comments make suggestions for further research.

Room temperature synthesis and highly enhanced visible light photocatalytic activity of porous BiOI/BiOCl composites nanoplates microflowers.

PubMed

Dong, Fan; Sun, Yanjuan; Fu, Min; Wu, Zhongbiao; Lee, S C

2012-06-15

This research represents a highly enhanced visible light photocatalytic removal of 450 ppb level of nitric oxide (NO) in air by utilizing flower-like hierarchical porous BiOI/BiOCl composites synthesized by a room temperature template free method for the first time. The facile synthesis method avoids high temperature treatment, use of organic precursors and production of undesirable organic byproducts during synthesis process. The result indicated that the as-prepared BiOI/BiOCl composites samples were solid solution and were self-assembled hierarchically with single-crystal nanoplates. The aggregation of the self-assembled nanoplates resulted in the formation of 3D hierarchical porous architecture containing tri-model mesopores. The coupling to BiOI with BiOCl led to down-lowered valence band (VB) and up-lifted conduction band (CB) in contrast to BiOI, making the composites suitable for visible light excitation. The BiOI/BiOCl composites samples exhibited highly enhanced visible light photocatalytic activity for removal of NO in air due to the large surface areas and pore volume, hierarchical structure and modified band structure, exceeding that of P25, BiOI, C-doped TiO(2) and Bi(2)WO(6). This research results could provide a cost-effective approach for the synthesis of porous hierarchical materials and enhancement of photocatalyst performance for environmental and energetic applications owing to its low cost and easy scaling up. Copyright © 2012 Elsevier B.V. All rights reserved.

Tribological Properties of Ti(Al,O)/Al2O3 Composite Coating by Thermal Spraying

NASA Astrophysics Data System (ADS)

Salman, Asma; Gabbitas, Brian; Cao, Peng; Zhang, Deliang

The use of thermal spray coatings provides protection to the surfaces operating in severe environments. The main goal of the current work is to investigate the possibility of using a high velocity air fuel (HVAF) thermally sprayed wear resistant Ti(Al,O)/Al2O3 coating on tool steel (H13) which is used for making dies for aluminium high pressure die casting and dummy blocks aluminium extrusion. A feedstock of Ti(Al,O)/Al2O3 composite powder was produced from a mixture of Al and TiO2 powders by high energy mechanical milling, followed by a thermal reaction process. The feedstock was then thermally sprayed using a high velocity air-fuel (HVAF) technique onto H13 steel substrates to produce a composite coating. The present study describes and compares the tribological properties such as friction and sliding wear rate of the coating both at room and high temperature (700°C). The wear resistance of the coating was investigated by a tribometer using a spherical ended alumina pin as a counter body under dry and lubricating conditions. The results showed that composite coating has lower wear rate at high temperature than at room temperature without using lubricant. The composite coating was characterized using scanning electron microscopy (SEM), optical microscopy and X-ray diffractometry (XRD). This paper reports the experimental observations and discusses the wear resistance performance of the coatings at room and high temperatures.

Feasibility of Plasma Treated Clay in Clay/Polymer Nanocomposites Powders for use Laser Sintering (LS)

NASA Astrophysics Data System (ADS)

Almansoori, Alaa; Seabright, Ryan; Majewski, C.; Rodenburg, C.

2017-05-01

The addition of small quantities of nano-clay to nylon is known to improve mechanical properties of the resulting nano-composite. However, achieving a uniform dispersion and distribution of the clay within the base polymer can prove difficult. A demonstration of the fabrication and characterization of plasma-treated organoclay/Nylon12 nanocomposite was carried out with the aim of achieving better dispersion of clay platelets on the Nylon12 particle surface. Air-plasma etching was used to enhance the compatibility between clays and polymers to ensure a uniform clay dispersion in composite powders. Downward heat sintering (DHS) in a hot press is used to process neat and composite powders into tensile and XRD specimens. Morphological studies using Low Voltage Scanning Electron Microscopy (LV-SEM) were undertaken to characterize the fracture surfaces and clay dispersion in powders and final composite specimens. Thermogravimetric analysis (TGA) testing performed that the etched clay (EC) is more stable than the nonetched clay (NEC), even at higher temperatures. The influence of the clay ratio and the clay plasma treatment process on the mechanical properties of the nanocomposites was studied by tensile testing. The composite fabricated from (3% EC/N12) powder showed ~19 % improvement in elastic modulus while the composite made from (3% NEC/N12) powder was improved by only 14%). Most notably however is that the variation between tests is strongly reduced when etch clay is used in the composite. We attribute this to a more uniform distribution and better dispersion of the plasma treated clay within polymer powders and ultimately the composite.

SEM Imaging and Chemical Analysis of Aerosol Particles from Surface and Hi-altitudes in New Jersey.

NASA Astrophysics Data System (ADS)

Bandamede, M.; Boaggio, K.; Bancroft, L.; Hurler, K.; Magee, N. B.

2016-12-01

We report on Scanning Electron Microscopy analysis of aerosol particle morphology and chemistry. The work includes the first comparative SEM analysis of aerosol particles captured by balloon at high altitude. The particles were acquired in an urban/suburban environment in central New-Jersey. Particles were sampled from near the surface using ambient air filtration and at high-altitudes using a novel balloon-borne instrument (ICE-Ball, see abstract by K. Boaggio). Particle images and 3D geometry are acquired by a Hitachi SU-5000 SEM, with resolution to approximately 3 nm. Elemental analysis on particles is provided by Energy Dispersive X-Ray Spectroscopy (EDS, EDAX, Inc.). Uncoated imaging is conducted in low vacuum within the variable-pressure SEM, which provides improved detection and analysis of light-element compositions including Carbon. Preliminary results suggest that some similar particle types and chemical species are sampled at both surface and high-altitude. However, as expected, particle morphologies, concentrations, chemistry, and apparent origin vary significantly at different altitudes and under different atmospheric flow regimes. Improved characterization of high-altitude aerosol particles, and differences from surface particulate composition, may advance inputs for atmospheric cloud and radiation models.

Air electrode composition for solid oxide fuel cell

DOEpatents

Kuo, Lewis; Ruka, Roswell J.; Singhal, Subhash C.

1999-01-01

An air electrode composition for a solid oxide fuel cell is disclosed. The air electrode material is based on lanthanum manganite having a perovskite-like crystal structure ABO.sub.3. The A-site of the air electrode composition comprises a mixed lanthanide in combination with rare earth and alkaline earth dopants. The B-site of the composition comprises Mn in combination with dopants such as Mg, Al, Cr and Ni. The mixed lanthanide comprises La, Ce, Pr and, optionally, Nd. The rare earth A-site dopants preferably comprise La, Nd or a combination thereof, while the alkaline earth A-site dopant preferably comprises Ca. The use of a mixed lanthanide substantially reduces raw material costs in comparison with compositions made from high purity lanthanum starting materials. The amount of the A-site and B-site dopants is controlled in order to provide an air electrode composition having a coefficient of thermal expansion which closely matches that of the other components of the solid oxide fuel cell.

Air electrode composition for solid oxide fuel cell

DOEpatents

Kuo, L.; Ruka, R.J.; Singhal, S.C.

1999-08-03

An air electrode composition for a solid oxide fuel cell is disclosed. The air electrode material is based on lanthanum manganite having a perovskite-like crystal structure ABO{sub 3}. The A-site of the air electrode composition comprises a mixed lanthanide in combination with rare earth and alkaline earth dopants. The B-site of the composition comprises Mn in combination with dopants such as Mg, Al, Cr and Ni. The mixed lanthanide comprises La, Ce, Pr and, optionally, Nd. The rare earth A-site dopants preferably comprise La, Nd or a combination thereof, while the alkaline earth A-site dopant preferably comprises Ca. The use of a mixed lanthanide substantially reduces raw material costs in comparison with compositions made from high purity lanthanum starting materials. The amount of the A-site and B-site dopants is controlled in order to provide an air electrode composition having a coefficient of thermal expansion which closely matches that of the other components of the solid oxide fuel cell. 3 figs.

In-air microfluidics enables rapid fabrication of emulsions, suspensions, and 3D modular (bio)materials

PubMed Central

Visser, Claas Willem; Kamperman, Tom; Karbaat, Lisanne P.; Lohse, Detlef; Karperien, Marcel

2018-01-01

Microfluidic chips provide unparalleled control over droplets and jets, which have advanced all natural sciences. However, microfluidic applications could be vastly expanded by increasing the per-channel throughput and directly exploiting the output of chips for rapid additive manufacturing. We unlock these features with in-air microfluidics, a new chip-free platform to manipulate microscale liquid streams in the air. By controlling the composition and in-air impact of liquid microjets by surface tension–driven encapsulation, we fabricate monodisperse emulsions, particles, and fibers with diameters of 20 to 300 μm at rates that are 10 to 100 times higher than chip-based droplet microfluidics. Furthermore, in-air microfluidics uniquely enables module-based production of three-dimensional (3D) multiscale (bio)materials in one step because droplets are partially solidified in-flight and can immediately be printed onto a substrate. In-air microfluidics is cytocompatible, as demonstrated by additive manufacturing of 3D modular constructs with tailored microenvironments for multiple cell types. Its in-line control, high throughput and resolution, and cytocompatibility make in-air microfluidics a versatile platform technology for science, industry, and health care. PMID:29399628

Evolution of aerosol loading in Santiago de Chile between 1997 and 2014

NASA Astrophysics Data System (ADS)

Pistone, Kristina; Gallardo, Laura

2015-04-01

While aerosols produced by major cities are a significant component of anthropogenic climate forcing as well as an important factor in public health, many South American cities have not been a major focus of aerosol studies due in part to relatively few long-term observations in the region. Here we present a synthesis of the available data for the emerging megacity of Santiago, Chile. We report new results from a recent NASA AERONET (AErosol RObotic NETwork) site in the Santiago basin, combining these with previous AERONET observations in Santiago as well as with a new assessment of the 11-station air quality monitoring network currently administered by the Chilean Environment Ministry (MMA, Ministerio del Medio Ambiente) to assess changes in aerosol composition since 1997. While the average surface concentration of pollution components (specifically PM2.5 and PM10) has decreased, no significant change in total aerosol optical depth was observed. However, changes in aerosol size and composition are suggested by the proxy measurements. Previous studies have revealed limitations in purely satellite-based studies over Santiago due to biases from high surface reflection in the region, particularly in summer months (e.g. Escribano et al 2014). To overcome this difficulty and certain limitations in the air quality data, we next incorporate analysis of aerosol products from the Multi-angle Imaging SpectroRadiometer (MISR) instrument along with those from the Moderate Resolution Imaging Spectroradiometer (MODIS) instrument, both on NASA's Terra satellite, to better quantify the high bias of MODIS. Thus incorporating these complementary datasets, we characterize the aerosol over Santiago over the period 1997 to 2014, including the evolution of aerosol properties over time and seasonal dependencies in the observed trends. References: Escribano et al (2014), "Satellite Retrievals of Aerosol Optical Depth over a Subtropical Urban Area: The Role of Stratification and Surface Reflectance," Aerosol and Air Quality Research, doi:10.4209/aaqr.2013.03.0082.

CentNet—A deployable 100-station network for surface exchange research

NASA Astrophysics Data System (ADS)

Oncley, S.; Horst, T. W.; Semmer, S.; Militzer, J.; Maclean, G.; Knudson, K.

2014-12-01

Climate, air quality, atmospheric composition, surface hydrology, and ecological processes are directly affected by the Earth's surface. Complexity of this surface exists at multiple spatial scales, which complicates the understanding of these processes. NCAR/EOL currently provides a facility to the research community to make direct eddy-covariance flux observations to quantify surface-atmosphere interactions. However, just as model resolution has continued to increase, there is a need to increase the spatial density of flux measurements to capture the wide variety of scales that contribute to exchange processes close to the surface. NCAR/EOL now has developed the CentNet facility, that is envisioned to have on the order of 100 surface flux stations deployable for periods of months to years. Each station would measure standard meteorological variables, all components of the surface energy balance (including turbulence fluxes and radiation), atmospheric composition, and other quantities to characterize the surface. Thus, CentNet can support observational research in the biogeosciences, hydrology, urban meteorology, basic meteorology, and turbulence. CentNet has been designed to be adaptable to a wide variety of research problems while keeping operations manageable. Tower infrastructure has been designed to be lightweight, easily deployed, and with a minimal set-up footprint. CentNet uses sensor networks to increase spatial sampling at each station. The data system saves every sample on site to retain flexibility in data analysis. We welcome guidance on development and funding priorities as we build CentNet.

The Effect of Energy Densities on the Shear Bond Strength of Self-Adhering Flowable Composite to Er:YAG Pretreated Dentin.

PubMed

Nahas, Paul; Zeinoun, Toni; Majzoub, Zeina; Corbani, Karim; Nammour, Samir

2016-01-01

Objective . To investigate the shear bond strength of self-adhering flowable resin composite, to dentin, after exposing it to Er:YAG laser radiation, at different energy densities. Materials and Methods . Sixty freshly extracted human third molars were randomly divided into five groups ( n = 12). In the control group, dentin was left unirradiated, whereas, in the other four groups, dentin was irradiated with Er:YAG laser in noncontact mode (MSP mode = 100  µ s; 10 Hz; beam diameter: 1.3 mm; speed of 1 mm/second; air 6 mL/min; and water 4 mL/min), and respectively, with the following level of energy (50 mJ, 60 mJ, 80 mJ, and 100 mJ). Then, self-adhering flowable resin composite was bonded to all prepared dentin surfaces. Shear bond strength (SBS) was applied and fractured surfaces were examined using scanning electron microscopy. Results . SBS values showed significant differences in 60 mJ ( P < 0.05) compared to other groups. Morphological evaluation revealed tags or plugs in dentinal tubules, especially when 60 mJ and 80 mJ were used. All four groups tended to leave more residues on the dentin surface, than the control group. Conclusion . Er:YAG dentin irradiation may enhance SBS of the self-adhering flowable resin composite when it is used at the appropriate low level of energy density.

The Effect of Energy Densities on the Shear Bond Strength of Self-Adhering Flowable Composite to Er:YAG Pretreated Dentin

PubMed Central

Corbani, Karim

2016-01-01

Objective. To investigate the shear bond strength of self-adhering flowable resin composite, to dentin, after exposing it to Er:YAG laser radiation, at different energy densities. Materials and Methods. Sixty freshly extracted human third molars were randomly divided into five groups (n = 12). In the control group, dentin was left unirradiated, whereas, in the other four groups, dentin was irradiated with Er:YAG laser in noncontact mode (MSP mode = 100 µs; 10 Hz; beam diameter: 1.3 mm; speed of 1 mm/second; air 6 mL/min; and water 4 mL/min), and respectively, with the following level of energy (50 mJ, 60 mJ, 80 mJ, and 100 mJ). Then, self-adhering flowable resin composite was bonded to all prepared dentin surfaces. Shear bond strength (SBS) was applied and fractured surfaces were examined using scanning electron microscopy. Results. SBS values showed significant differences in 60 mJ (P < 0.05) compared to other groups. Morphological evaluation revealed tags or plugs in dentinal tubules, especially when 60 mJ and 80 mJ were used. All four groups tended to leave more residues on the dentin surface, than the control group. Conclusion. Er:YAG dentin irradiation may enhance SBS of the self-adhering flowable resin composite when it is used at the appropriate low level of energy density. PMID:27830151

Effect of surface treatment on retention of glass-fiber endodontic posts.

PubMed

Balbosh, Ali; Kern, Matthias

2006-03-01

The effects of surface treatment on the retention of prefabricated fiber-reinforced epoxy resin posts are not well understood because most studies measure retention shortly after cementation, without artificial aging. The purpose of this study was to evaluate the effect of surface treatment on the retention of glass-fiber endodontic posts luted with resin cement and subjected to artificial aging. Thirty-two single-rooted teeth were selected, the coronal aspect of each tooth was removed, and the remaining root received endodontic therapy. Specimens were then divided into 4 groups (n = 8). Post spaces were prepared to a depth of 10 mm by using ISO 90 rotary instruments. The tapered posts received 1 of 4 surface treatments: cleaning with alcohol (Alc), cleaning with alcohol and conditioning with ED-Primer material (Alc-ED), airborne-particle abrasion (Air), or airborne-particle abrasion and conditioning with ED-Primer material (Air-ED). All posts were luted with a composite resin luting agent (Panavia F) after conditioning the canal dentin with autopolymerizing dentin primer (ED-Primer) and without acid etching of the canal dentin. After cementation, the specimens were stored in water at 37 degrees C for 30 days and subjected to simulated aging conditions consisting of 7500 thermal cycles (5 degrees C/55 degrees C) and 300,000 mechanical loading cycles with 30 N. Retention (N) of the posts was measured with a universal testing machine with a crosshead speed of 2 mm/min. The data were analyzed using 1-way ANOVA and the Tukey HSD test (alpha = .05). The dislodged posts were also examined microscopically at x8 and x20 magnification to evaluate the mode of failure. The mean retentive values (N) and SDs of the test groups were as follows: Alc, 375.9 +/- 85.0; Alc-ED, 421.2 +/- 46.8; Air, 534.8 +/- 65.8; and Air-ED, 555.8 +/- 86.9. Airborne-particle-abraded posts had significantly higher retention compared with nonabraded posts (P < .001). Treating the post's surface with ED-Primer material prior to cementation had no significant effect on retention. The failure mode was purely adhesive at the resin cement-post interface for all nonabraded posts. A mixed failure mode, adhesive at the resin cement-dentin interface, at the resin cement-post interface, and cohesive in the resin cement, was observed for airborne-particle-abraded posts. Treating the surface of the posts with ED-Primer material before cementation with Panavia F cement produced no significant improvement in the retention of the posts. Airborne-particle abrasion of the surface of the post significantly improved the retention.

Bio-active glass air-abrasion has the potential to remove resin composite restorative material selectively

NASA Astrophysics Data System (ADS)

Milly, Hussam; Andiappan, Manoharan; Thompson, Ian; Banerjee, Avijit

2014-06-01

The aims of this study were to assess: (a) the chemistry, morphology and bioactivity of bio-active glass (BAG) air-abrasive powder, (b) the effect of three air-abrasion operating parameters: air pressure, powder flow rate (PFR) and the abrasive powder itself, on the selective removal of resin composite and (c) the required "time taken". BAG abrasive particles were characterised using scanning electron microscopy-energy dispersive X-ray spectrometry (SEM-EDX) and Fourier-transform infrared spectroscopy (FTIR). Standardised resin composite restorations created within an enamel analogue block (Macor™) in vitro, were removed using air-abrasion undersimulated clinical conditions. 90 standardised cavities were scanned before and after resin composite removal using laser profilometry and the volume of the resulting 3D images calculated. Multilevel linear model was used to identify the significant factors affecting Macor™ removal. BAG powder removed resin composite more selectively than conventional air-abrasion alumina powder using the same operating parameters (p < 0.001) and the effect of altering the unit's operating parameters was significant (p < 0.001). In conclusion, BAG powder is more efficient than alumina in the selective removal of resin composite particularly under specific operating parameters, and therefore may be recommended clinically as a method of preserving sound enamel structure when repairing and removing defective resin composite restorations.

Evaluation of the AirNow Satellite Data Processor for 2010-2012

NASA Astrophysics Data System (ADS)

Pasch, A. N.; DeWinter, J. L.; Dye, T.; Haderman, M.; Zahn, P. H.; Szykman, J.; White, J. E.; Dickerson, P.; van Donkelaar, A.; Martin, R.

2013-12-01

The U.S. Environmental Protection Agency's (EPA) AirNow program provides the public with real-time and forecasted air quality conditions. Millions of people each day use information from AirNow to protect their health. The AirNow program (http://www.airnow.gov) reports ground-level ozone (O3) and fine particulate matter (PM2.5) with a standardized index called the Air Quality Index (AQI). AirNow aggregates information from over 130 state, local, and federal air quality agencies and provides tools for over 2,000 agency staff responsible for monitoring, forecasting, and communicating local air quality. Each hour, AirNow systems generate thousands of maps and products. The usefulness of the AirNow air quality maps depends on the accuracy and spatial coverage of air quality measurements. Currently, the maps use only ground-based measurements, which have significant gaps in coverage in some parts of the United States. As a result, contoured AQI levels have high uncertainty in regions far from monitors. To improve the usefulness of air quality maps, scientists at EPA, Dalhousie University, and Sonoma Technology, Inc., in collaboration with the National Aeronautics and Space Administration (NASA) and the National Oceanic and Atmospheric Administration (NOAA), have completed a project to incorporate satellite-estimated surface PM2.5 concentrations into the maps via the AirNow Satellite Data Processor (ASDP). These satellite estimates are derived using NASA/NOAA satellite aerosol optical depth (AOD) retrievals and GEOS-Chem modeled ratios of surface PM2.5 concentrations to AOD. GEOS-Chem is a three-dimensional chemical transport model for atmospheric composition driven by meteorological input from the Goddard Earth Observing System (GEOS). The ASDP can fuse multiple PM2.5 concentration data sets to generate AQI maps with improved spatial coverage. The goals of ASDP are to provide more detailed AQI information in monitor-sparse locations and to augment monitor-dense locations with more information. The ASDP system uses a weighted-average approach using uncertainty information about each data set. Recent improvements in the estimation of the uncertainty of interpolated ground-based monitor data have allowed for a more complete characterization of the uncertainty of the surface measurements. We will present a statistical analysis for 2010-2012 of the ASDP predictions of PM2.5 focusing on performance at validation sites. In addition, we will present several case studies evaluating the ASDP's performance for multiple regions and seasons, focusing specifically on days when large spatial gradients in AQI and wildfire smoke impacts were observed.

A measurement of the cosmic ray spectrum and composition at the knee

NASA Astrophysics Data System (ADS)

Fowler, J. W.; Fortson, L. F.; Jui, C. C. H.; Kieda, D. B.; Ong, R. A.; Pryke, C. L.; Sommers, P.

2001-03-01

The energy spectrum and primary composition of cosmic rays with energy between 3×10 14 and 3×10 16 eV have been studied using the CASA-BLANCA detector. CASA consisted of 957 surface scintillation stations; BLANCA consisted of 144 angle-integrating Cherenkov light detectors located at the same site. CASA measured the charged particle distribution of air showers, while BLANCA measured the lateral distribution of Cherenkov light. The data are interpreted using the predictions of the CORSIKA air shower simulation coupled with four different hadronic interaction codes. The differential flux of cosmic rays measured by BLANCA exhibits a knee in the range of 2-3 PeV with a width of approximately 0.5 decades in primary energy. The power law indices of the differential flux below and above the knee are -2.72±0.02 and -2.95±0.02, respectively. We present our data both as a mean depth of shower maximum and as a mean nuclear mass. A multi-component fit using four elemental species suggests the same composition trends exhibited by the mean quantities, and also indicates that QGSJET and VENUS are the preferred hadronic interaction models. We find that an initially mixed composition turns lighter between 1 and 3 PeV, and then becomes heavier with increasing energies above 3 PeV.

Compositional changes in lipid microdomains of air-blood barrier plasma membranes in pulmonary interstitial edema.

PubMed

Palestini, Paola; Calvi, Chiara; Conforti, Elena; Daffara, Rossella; Botto, Laura; Miserocchi, Giuseppe

2003-10-01

We evaluated in anesthetized rabbits the compositional changes of plasmalemmal lipid microdomains from lung tissue samples after inducing pulmonary interstitial edema (0.5 ml/kg for 3 h, leading to approximately 5% increase in extravascular water). Lipid microdomains (lipid rafts and caveolae) were present in the detergent-resistant fraction (DRF) obtained after discontinuous sucrose density gradient. DRF was enriched in caveolin-1, flotillin, aquaporin-1, GM1, cholesterol, sphingomyelin, and phosphatidylserine, and their contents significantly increased in interstitial edema. The higher DRF content in caveolin, flotillin, and aquaporin-1 and of the ganglioside GM1 suggests an increase both in caveolar domains and in lipid rafts, respectively. Compositional changes could be ascribed to endothelial and epithelial cells that provide most of plasma membrane surface area in the air-blood barrier. Alterations in lipid components in the plasma membrane may reflect rearrangement of floating lipid platforms within the membrane and/or lipid translocation from intracellular stores. Lipid traffic could be stimulated by the marked increase in hydraulic interstitial pressure after initial water accumulation, from approximately -10 to 5 cmH2O, due to the low compliance of the pulmonary tissue, in particular in the basement membranes and in the interfibrillar substance. Compositional changes in lipid microdomains represent a sign of cellular activation and suggest the potential role of mechanotransduction in response to developing interstitial edema.

The effects of various surface treatments on the shear bond strengths of stainless steel brackets to artificially-aged composite restorations.

PubMed

Eslamian, Ladan; Borzabadi-Farahani, Ali; Mousavi, Nasim; Ghasemi, Amir

2011-05-01

To compare the shear bond strengths (SBS) of stainless steel brackets bonded to artificially-aged composite restorations after different surface treatments. Forty-five premolar teeth were restored with a nano-hybrid composite (Tetric EvoCeram), stored in deionised water for one week and randomly divided into three equal groups: Group I, he restorations were exposed to 5 per cent hydrofluoric acid for 60 seconds; Group II, the restorations were abraded with a micro-etcher (50 Iim alumina particles); Group III, the restorations were roughened with a coarse diamond bur. Similar premolar brackets were bonded to each restoration using the same resin adhesive and the specimens were then cycled in deionised water between 5 degrees C and 55 degrees C (500 cycles). The shear bond strengths were determined with a universal testing machine at a crosshead speed of 1 mm/min. The teeth and brackets were examined under a stereomicroscope and the adhesive remnants on the teeth scored with the adhesive remnant index (ARI). Specimens treated with the diamond bur had a significantly higher SBS (Mean: 18.45 +/- 3.82 MPa) than the group treated with hydrofluoric acid (Mean: 12.85 +/- 5.20 MPa). The mean SBS difference between the air-abrasion (Mean: 15.36 +/- 4.92 MPa) and hydrofluoric acid groups was not significant. High ARI scores occurred following abrasion with a diamond bur (100 per cent) and micro-etcher (80 per cent). In approximately two thirds of the teeth no adhesive was left on the restoration after surface treatment with hydofluoric acid. Surface treatment with a diamond bur resulted in a high bond strength between stainless steel brackets and artificially-aged composite restorations and was considered to be a safe and effective method of surface treatment. Most of the adhesive remained on the tooth following surface treatment with either the micro-etcher or the diamond bur.

The second stage of Lunar Prospector's LMLV is erected at Pad 46, CCAS

NASA Technical Reports Server (NTRS)

1997-01-01

The second stage of the Lockheed Martin Launch Vehicle-2 (LMLV-2) is hoisted into position at Launch Pad 46 at Cape Canaveral Air Station for mating to the rocket's first stage, which is out of camera view. The LMLV-2 will carry the Lunar Prospector spacecraft, scheduled to launch in October for an 18-month mission that will orbit the Earth's moon to collect data from the lunar surface. Designed for a low polar orbit investigation of the moon, the Lunar Prospector will map the moon's surface composition and possible polar ice deposits, measure magnetic and gravity fields, and study lunar outgassing events.

A geophysiologist's thoughts on geoengineering.

PubMed

Lovelock, James

2008-11-13

The Earth is now recognized as a self-regulating system that includes a reactive biosphere; the system maintains a long-term steady-state climate and surface chemical composition favourable for life. We are perturbing the steady state by changing the land surface from mainly forests to farm land and by adding greenhouse gases and aerosol pollutants to the air. We appear to have exceeded the natural capacity to counter our perturbation and consequently the system is changing to a new and as yet unknown but probably adverse state. I suggest here that we regard the Earth as a physiological system and consider amelioration techniques, geoengineering, as comparable to nineteenth century medicine.

Experimental studies of contact angle hysteresis phenomena on polymer surfaces – Toward the understanding and control of wettability for different applications.

PubMed

Grundke, K; Pöschel, K; Synytska, A; Frenzel, R; Drechsler, A; Nitschke, M; Cordeiro, A L; Uhlmann, P; Welzel, P B

2015-08-01

Contact angle hysteresis phenomena on polymer surfaces have been studied by contact angle measurements using sessile liquid droplets and captive air bubbles in conjunction with a drop shape method known as Axisymmetric Drop Shape Analysis - Profile (ADSA-P). In addition, commercially available sessile drop goniometer techniques were used. The polymer surfaces were characterized with respect to their surface structure (morphology, roughness, swelling) and surface chemistry (elemental surface composition, acid-base characteristics) by scanning electron microscopy (SEM), scanning force microscopy (SFM), ellipsometry, X-ray photoelectron spectroscopy (XPS) and streaming potential measurements. Heterogeneous polymer surfaces with controlled roughness and chemical composition were prepared by different routes using plasma etching and subsequent dip coating or grafting of polymer brushes, anodic oxidation of aluminium substrates coated with thin polymer films, deposition techniques to create regular patterned and rough fractal surfaces from core-shell particles, and block copolymers. To reveal the effects of swelling and reorientation at the solid/liquid interface contact angle hysteresis phenomena on polyimide surfaces, cellulose membranes, and thermo-responsive hydrogels have been studied. The effect of different solutes in the liquid (electrolytes, surfactants) and their impact on contact angle hysteresis were characterized for solid polymers without and with ionizable functional surface groups in aqueous electrolyte solutions of different ion concentrations and pH and for photoresist surfaces in cationic aqueous surfactant solutions. The work is an attempt toward the understanding of contact angle hysteresis phenomena on polymer surfaces aimed at the control of wettability for different applications. Copyright © 2014 Elsevier B.V. All rights reserved.

Surface Structure Formation in Direct Chill (DC) Casting of Al Alloys

NASA Astrophysics Data System (ADS)

Bayat, Nazlin; Carlberg, Torbjörn

2014-05-01

The aim of this study is to increase the understanding of the surface zone formation during direct chill (DC) casting of aluminum billets produced by the air slip technology. The depth of the shell zone, with compositions deviating from the bulk, is of large importance for the subsequent extrusion productivity and quality of final products. The surface microstructures of 6060 and 6005 aluminum alloys in three different surface appearances—defect free, wavy surface, and spot defects—were studied. The surface microstructures and outer appearance, segregation depth, and phase formation were investigated for the mentioned cases. The results were discussed and explained based on the exudation of liquid metal through the mushy zone and the fact that the exudated liquid is contained within a surface oxide skin. Outward solidification in the surface layer was quantitatively analyzed, and the oxide skin movements explained meniscus line formation. Phases forming at different positions in the segregation zone were analyzed and coupled to a cellular solidification in the exudated layer.

Effect of different emission inventories on modeled ozone and carbon monoxide in Southeast Asia

NASA Astrophysics Data System (ADS)

Amnuaylojaroen, T.; Barth, M. C.; Emmons, L. K.; Carmichael, G. R.; Kreasuwun, J.; Prasitwattanaseree, S.; Chantara, S.

2014-04-01

In order to improve our understanding of air quality in Southeast Asia, the anthropogenic emissions inventory must be well represented. In this work, we apply different anthropogenic emission inventories in the Weather Research and Forecasting Model with Chemistry (WRF-Chem) version 3.3 using MOZART gas-phase chemistry and GOCART aerosols to examine the differences in predicted carbon monoxide (CO) and ozone (O3) surface mixing ratios for Southeast Asia in March and December 2008. The anthropogenic emission inventories include the Reanalysis of the TROpospheric chemical composition (RETRO), the Intercontinental Chemical Transport Experiment-Phase B (INTEX-B), the MACCity emissions (adapted from the Monitoring Atmospheric Composition and Climate and megacity Zoom for the Environment projects), the Southeast Asia Composition, Cloud, Climate Coupling Regional Study (SEAC4RS) emissions, and a combination of MACCity and SEAC4RS emissions. Biomass burning emissions are from the Fire Inventory from NCAR (FINNv1) model. WRF-chem reasonably predicts the 2 m temperature, 10 m wind, and precipitation. In general, surface CO is underpredicted by WRF-Chem while surface O3 is overpredicted. The NO2 tropospheric column predicted by WRF-Chem has the same magnitude as observations, but tends to underpredict NO2 column over the equatorial ocean and near Indonesia. Simulations using different anthropogenic emissions produce only a slight variability of O3 and CO mixing ratios, while biomass burning emissions add more variability. The different anthropogenic emissions differ by up to 20% in CO emissions, but O3 and CO mixing ratios differ by ~4.5% and ~8%, respectively, among the simulations. Biomass burning emissions create a substantial increase for both O3 and CO by ~29% and ~16%, respectively, when comparing the March biomass burning period to December with low biomass burning emissions. The simulations show that none of the anthropogenic emission inventories are better than the others and any of the examined inventories can be used for air quality simulations in Southeast Asia.

Diatomite reinforced chitosan composite membrane as potential scaffold for guided bone regeneration.

PubMed

Tamburaci, Sedef; Tihminlioglu, Funda

2017-11-01

In this study, natural silica source, diatomite, incorporated novel chitosan based composite membranes were fabricated and characterized for bone tissue engineering applications as possible bone regeneration membrane. The effect of diatomite loading on the mechanical, morphological, chemical, thermal and surface properties, wettability and in vitro cytotoxicity and cell proliferation on of composite membranes were investigated and observed by tensile test, atomic force microscopy (AFM), Fourier transform infrared spectroscopy (FTIR), thermal gravimetric analysis (TGA), protein adsorption assay, air/water contact angle analysis and WST-1 respectively. Swelling studies were also performed by water absorption capacity determination. Results showed that incorporation of diatomite to the chitosan matrix increased the surface roughness, swelling capacity and tensile modulus of membranes. An increase of about 52% in Young's modulus was achieved for 10wt% diatomite composite membranes compared with chitosan membranes. High cell viability results were obtained with indirect extraction method. Besides, in vitro cell proliferation and ALP activity results showed that diatom incorporation significantly increased the ALP activity of Saos-2 cells cultured on chitosan membranes. The novel composite membranes prepared in the present study with tunable properties can be considered as a potential candidate as a scaffold in view of its enhanced physical & chemical properties as well as biological activities for bone tissue engineering applications. Copyright © 2017 Elsevier B.V. All rights reserved.

Solder extrusion pressure bonding process and bonded products produced thereby

DOEpatents

Beavis, L.C.; Karnowsky, M.M.; Yost, F.G.

1992-06-16

Disclosed is a process for production of soldered joints which are highly reliable and capable of surviving 10,000 thermal cycles between about [minus]40 C and 110 C. Process involves interposing a thin layer of a metal solder composition between the metal surfaces of members to be bonded and applying heat and up to about 1000 psi compression pressure to the superposed members, in the presence of a reducing atmosphere, to extrude the major amount of the solder composition, contaminants including fluxing gases and air, from between the members being bonded, to form a very thin, strong intermetallic bonding layer having a thermal expansion tolerant with that of the bonded members.

Simulation of seasonal US precipitation and temperature by the nested CWRF-ECHAM system

NASA Astrophysics Data System (ADS)

Chen, Ligang; Liang, Xin-Zhong; DeWitt, David; Samel, Arthur N.; Wang, Julian X. L.

2016-02-01

This study investigates the refined simulation skill that results when the regional Climate extension of the Weather Research and Forecasting (CWRF) model is nested in the ECMWF Hamburg version 4.5 (ECHAM) atmospheric general circulation model over the United States during 1980-2009, where observed sea surface temperatures are used in both models. Over the contiguous US, for each of the four seasons from winter to fall, CWRF reduces the root mean square error of the ECHAM seasonal mean surface air temperature simulation by 0.19, 0.82, 2.02 and 1.85 °C, and increases the equitable threat score of seasonal mean precipitation by 0.18, 0.11, 0.09 and 0.12. CWRF also simulates much more realistically daily precipitation frequency and heavy precipitation events, typically over the Central Great Plains, Cascade Mountains and Gulf Coast States. These CWRF skill enhancements are attributed to the increased spatial resolution and physics refinements in representing orographic, terrestrial hydrology, convection, and cloud-aerosol-radiation effects and their interactions. Empirical orthogonal function analysis of seasonal mean precipitation and surface air temperature interannual variability shows that, in general, CWRF substantially improves the spatial distribution of both quantities, while temporal evolution (i.e. interannual variability) of the first 3 primary patterns is highly correlated with that of the driving ECHAM (except for summer precipitation), and they both have low temporal correlations against observations. During winter, when large-scale forcing dominates, both models also have similar responses to strong ENSO signals where they successfully capture observed precipitation composite anomalies but substantially fail to reproduce surface air temperature anomalies. When driven by the ECMWF Reanalysis Interim, CWRF produces a very realistic interannual evolution of large-scale precipitation and surface air temperature patterns where the temporal correlations with observations are significant. These results indicate that CWRF can greatly improve mesoscale regional climate structures but it cannot change interannual variations of the large-scale patterns, which are determined by the driving lateral boundary conditions.

Investigation of ammonia air-surface exchange processes in a ...

EPA Pesticide Factsheets

Recent assessments of atmospheric deposition in North America note the increasing importance of reduced (NHx = NH3 + NH4+) forms of nitrogen (N) relative to oxidized forms. This shift in in the composition of inorganic nitrogen deposition has both ecological and policy implications. Deposition budgets developed from inferential models applied at the landscape scale, as well as regional and global chemical transport models, indicate that NH3 dry deposition contributes a significant portion of inorganic N deposition in many areas. However, the bidirectional NH3 flux algorithms employed in these models have not been extensively evaluated for North American conditions (e.g, atmospheric chemistry, meteorology, biogeochemistry). Further understanding of the processes controlling NH3 air-surface exchange in natural systems is critically needed. Based on preliminary results from the Southern Appalachian Nitrogen Deposition Study (SANDS), this presentation examines processes of NH3 air-surface exchange in a deciduous montane forest at the Coweeta Hydrologic Laboratory in western North Carolina. A combination of measurements and modeling are used to investigate net fluxes of NH3 above the forest and sources and sinks of NH3 within the canopy and forest floor. Measurements of biogeochemical NH4+ pools are used to characterize emission potential and NH3 compensation points of canopy foliage (i.e., green vegetation), leaf litter, and soil and their relation to NH3 fluxes

Heat transfer during condensation of steam from steam-gas mixtures in the passive safety systems of nuclear power plants

NASA Astrophysics Data System (ADS)

Portnova, N. M.; Smirnov, Yu B.

2017-11-01

A theoretical model for calculation of heat transfer during condensation of multicomponent vapor-gas mixtures on vertical surfaces, based on film theory and heat and mass transfer analogy is proposed. Calculations were performed for the conditions implemented in experimental studies of heat transfer during condensation of steam-gas mixtures in the passive safety systems of PWR-type reactors of different designs. Calculated values of heat transfer coefficients for condensation of steam-air, steam-air-helium and steam-air-hydrogen mixtures at pressures of 0.2 to 0.6 MPa and of steam-nitrogen mixture at the pressures of 0.4 to 2.6 MPa were obtained. The composition of mixtures and vapor-to-surface temperature difference were varied within wide limits. Tube length ranged from 0.65 to 9.79m. The condensation of all steam-gas mixtures took place in a laminar-wave flow mode of condensate film and turbulent free convection in the diffusion boundary layer. The heat transfer coefficients obtained by calculation using the proposed model are in good agreement with the considered experimental data for both the binary and ternary mixtures.

Synthesis of SiO2-Coated Core-Shell ZnO Composites for Preparing High-Voltage Varistors

NASA Astrophysics Data System (ADS)

Qu, Xiao; Yao, Da-Chuan; Liu, Jin-Ran; Wang, Mao-Hua; Zhang, Han-Ping

2018-01-01

Monodispersed ZnO composite microspheres were successfully prepared by a facile ultrasound irradiation method. Then, the uniform core-shell structured composites were synthesized through the hydrolysis of tetraethyl orthosilicate on the surface of the ZnO composite microspheres. Microstructural studies of the as-obtained powders were carried out using the techniques of the x-ray powder diffraction, field emission scanning electron microscopy and transmission electron microscopy with energy dispersive x-ray spectroscopy. The results show that the pink ZnO composite powders as the core were spherical structures with the size of approximately 100 nm, and the SiO2 shell was fully coated on the surface of the core. On the basis of these results, the effect of SiO2 content on the thickness of the synthesized composites and microstructure, as well as the electrical properties of the ZnO varistors sintered in air at 1150°C for 2 h, were fully studied. In particular, the ZnO varistor prepared with the appropriate amount of the SiO2 coating (˜40 nm) leads to a superior electrical performance with the high breakdown voltage of 418 V mm-1 and an excellent nonlinear coefficient of 70.7, compared with the varistors obtained without the SiO2 coating. The high performance is attributed to the smaller and more homogeneous ZnO grains obtained via the SiO2 coating.

Aluminum Matrix Composite (AlSi7Mg2Sr0.03/SiCp) Pistons Obtained by Mechanical Mixing Method

PubMed Central

2017-01-01

Metal matrix composites are undoubtedly a group of advanced engineering materials. Compared to unreinforced matrix material, they are characterized by increased strength, greater stiffness, increased wear resistance, better mechanical properties and dimensional stability at elevated temperatures as well as lower density. Due to its very favorable tribological properties for many years research has been conducted on the application of MMC in friction node. The article presents important technological aspects related to the production and properties of composite pistons. Under industrial conditions, a composite suspension (AlSi7Mg2Sr0.03/SiCp 10 vol %) was prepared to allow casting of the semi-finished pistons series. Machining parameters of the working surfaces of the piston were selected on the basis of the turning test made on PCD, PCNM and uncoated carbide tools. The tribological properties of the composite pistons were determined on the basis of the pin-on-disc and the abrasion wear. The scuffing tests carried out under real operating conditions have confirmed the possibility of using composite pistons in air compressors. PMID:29283419

Use of Slow Strain Rate Tensile Testing to Assess the Ability of Several Superalloys to Resist Environmentally-Assisted Intergranular Cracking

NASA Technical Reports Server (NTRS)

Gabb, Timothy P.; Telesman, Jack; Banik, Anthony; McDevitt, Erin

2014-01-01

Intergranular fatigue crack initiation and growth due to environmental degradation, especially at notched features, can often limit the fatigue life of disk superalloys at high temperatures. For clear comparisons, the effects of alloy composition on cracking in air needs to be understood and compared separately from variables associated with notches and cracks such as effective stress concentration, plastic flow, stress relaxation, and stress redistribution. The objective of this study was to attempt using simple tensile tests of specimens with uniform gage sections to compare the effects of varied alloy composition on environment-assisted cracking of several powder metal and cast and wrought superalloys including ME3, LSHR, Udimet 720(TradeMark) ATI 718Plus(Registered TradeMark) alloy, Haynes 282(Trademark), and Inconel 740(TradeMark) Slow and fast strain-rate tensile tests were found to be a useful tool to compare propensities for intergranular surface crack initiation and growth. The effects of composition and heat treatment on tensile fracture strain and associated failure modes were compared. Environment interactions were determined to often limit ductility, by promoting intergranular surface cracking. The response of various superalloys and heat treatments to slow strain rate tensile testing varied substantially, showing that composition and microstructure can significantly influence environmental resistance to cracking.

The bacterial community composition of the surface microlayer in a high mountain lake.

PubMed

Hörtnagl, Paul; Pérez, Maria Teresa; Zeder, Michael; Sommaruga, Ruben

2010-09-01

The existence of bacterioneuston in aquatic ecosystems is well established, but little is known about its composition and dynamics, particularly in lakes. The bacterioneuston underlies extreme conditions at the air-water boundary, which may influence its dynamics in a different way compared with the bacterioplankton. In this study, we assessed quantitative changes in major bacterial groups of the surface microlayer (SML) (upper 900 microm) and the underlying water (ULW) (0.2-0.5 m depth) of an alpine lake during two consecutive ice-free seasons. Analysis of the bacterial community composition was done using catalyzed reporter deposition FISH with oligonucleotide probes. In addition, several physicochemical parameters were measured to characterize these two water layers. Dissolved organic carbon was consistently enriched in the SML and the dissolved organic matter pool presented clear signals of photodegradation and photobleaching. The water temperature was generally colder in the SML than in the subsurface. The bacterial community of the SML and the ULW was dominated by Betaproteobacteria and Actinobacteria. The bacterial community composition was associated with different combinations of physicochemical factors in these two layers, but temporal changes showed similar trends in both layers over the two seasons. Our results identify the SML of alpine lakes as a microhabitat where specific bacterial members such as of Betaproteobacteria seem to be efficient colonizers.

Particulate matter concentration and chemical composition in the metro system of Rome, Italy.

PubMed

Perrino, C; Marcovecchio, F; Tofful, L; Canepari, S

2015-06-01

Air quality at the main station of the metro system of Rome (Termini hub) has been characterized by the point of view of particulate matter (PM) concentration and chemical composition. Indoor air in different environments (underground train platform and shopping center, metro carriages with and without air conditioning system) has been studied and compared with outdoor air at a nearby urban site. Air quality at the railway station, located outdoor at surface level, has been also considered for comparison. PM chemical characterization included ions, elemental carbon, organic carbon, macro-elements, and the bio-accessible and residual fractions of micro- and trace elements. Train platform and carriages without air conditioning resulted to be the most polluted environments, with indoor/outdoor ratio up to two orders of magnitude for many components. PM mass concentration was determined on filter membranes by the gravimetric procedure as well as from the optical particle counter (OPC) number concentration measurements. The OPC results, taken with the original calibration factor, were below 40 % of the value obtained by the gravimetric measurements. Only a chemical and morphological characterization of the collected dust could lead to a reconciliation of the results yielded by the two methods. Macro-components were used to estimate the strength of the main macro-sources. The most significant contribution is confirmed to derive from wheels, rails, and brakes abrasion; from soil re-suspension (over 50 % at the subway platform); and from organics (about 25 %). The increase in the concentration of elements was mostly due to the residual fraction, but also the bio-accessible fraction showed a remarkable enrichment, particularly in the case of Ba, Zn, Cd, and Ni.

Amphibious Airplane

NASA Technical Reports Server (NTRS)

1986-01-01

The airplane pictured is the new Air Shark I, a four-place amphibian that makes extensive use of composite materials and cruises at close to 200 miles per hour under power from a 200-horsepower engine. Air Shark I is a "homebuilt" airplane, assembled from a kit of parts and components furnished by Freedom Master Corporation, Satellite Beach, Florida. The airplane incorporates considerable NASA technology and its construction benefited from research assistance provided by Kennedy Space Center (KSC) In designing the Shark, company president Arthur M. Lueck was able to draw on NASA's aeronautical technology bank through KSC's computerized "recon" library. As a result of his work at KSC, the wing of the Air Shark I is a new airfoil developed by Langley Research Center for light aircraft. In addition, Lueck opted for NASA-developed "winglets," vertical extensions of the wing that reduce drag by smoothing air turbulence at the wingtips. The NASA technology bank also contributed to the hull design. Lueck is considering application of NASA laminar flow technology-means of smoothing the airflow over wing and fuselage-to later models for further improvement of the Shark's aerodynamic efficiency. A materials engineer, Lueck employed his own expertise in designing and selecting the materials for the composite segments, which include all structural members, exposed surfaces and many control components. The materials are fiber reinforced plastics, or FRP They offer a high strength-to-weight ratio, with a nominal strength rating about one and a half times that of structural steel. They provide other advantages: the materials can be easily molded into finished shapes without expensive tooling or machining, and they are highly corrosion resistant. The first homebuilt to be offered by Freedom Master, Air Shark I completed air and water testing in mid-1985 and the company launched production of kits.

Nineteenth century Parisian smoke variations inferred from Eiffel Tower atmospheric electrical observations

NASA Astrophysics Data System (ADS)

Harrison, R. G.; Aplin, K. L.

Atmospheric electrical measurements provide proxy data from which historic smoke pollution levels can be determined. This approach is applied to infer autumnal Parisian smoke levels in the 1890s, based on atmospheric electric potential measurements made at the surface and the summit of the Eiffel Tower (48.7°N, 2.4°E). A theoretical model of the development of the autumn convective boundary layer is used to determine when local pollution effects dominated the Eiffel Tower potential measurements. The diurnal variation of the Eiffel Tower potential showed a single oscillation, but it differs from the standard oceanic air potential gradient (PG) variations during the period 09-17 UT, when the model indicates that the Eiffel Tower summit should be within the boundary layer. Outside these hours, the potential changes closely follow the clean air PG variation: this finding is used to calibrate the Eiffel Tower measurements. The surface smoke pollution concentration found during the morning maximum was 60±30 μg m -3, substantially lower than the values previously inferred for Kew in 1863. A vertical smoke profile was also derived using a combination of the atmospheric electrical data and boundary layer meteorology theory. Midday smoke concentration decreased with height from 60 μg m -3 at the surface to 15 μg m -3 at the top of the Eiffel Tower. The 19th century PG measurements in both polluted and clean Parisian air present a unique resource for European air pollution and atmospheric composition studies, and early evidence of the global atmospheric electrical circuit.

Protein adsorption at the electrified air-water interface: implications on foam stability.

PubMed

Engelhardt, Kathrin; Rumpel, Armin; Walter, Johannes; Dombrowski, Jannika; Kulozik, Ulrich; Braunschweig, Björn; Peukert, Wolfgang

2012-05-22

The surface chemistry of ions, water molecules, and proteins as well as their ability to form stable networks in foams can influence and control macroscopic properties such as taste and texture of dairy products considerably. Despite the significant relevance of protein adsorption at liquid interfaces, a molecular level understanding on the arrangement of proteins at interfaces and their interactions has been elusive. Therefore, we have addressed the adsorption of the model protein bovine serum albumin (BSA) at the air-water interface with vibrational sum-frequency generation (SFG) and ellipsometry. SFG provides specific information on the composition and average orientation of molecules at interfaces, while complementary information on the thickness of the adsorbed layer can be obtained with ellipsometry. Adsorption of charged BSA proteins at the water surface leads to an electrified interface, pH dependent charging, and electric field-induced polar ordering of interfacial H(2)O and BSA. Varying the bulk pH of protein solutions changes the intensities of the protein related vibrational bands substantially, while dramatic changes in vibrational bands of interfacial H(2)O are simultaneously observed. These observations have allowed us to determine the isoelectric point of BSA directly at the electrolyte-air interface for the first time. BSA covered air-water interfaces with a pH near the isoelectric point form an amorphous network of possibly agglomerated BSA proteins. Finally, we provide a direct correlation of the molecular structure of BSA interfaces with foam stability and new information on the link between microscopic properties of BSA at water surfaces and macroscopic properties such as the stability of protein foams.

Preparation of Ag superhydrophobic surface on metal substrates

NASA Astrophysics Data System (ADS)

Li, J. Y.; Lu, S. X.; Xu, W. G.; Duan, Y. Q.; Yang, X. C.; Cheng, Y. Y.; He, G.; Cui, S.

2018-01-01

In this work, the facile approaches are developed for preparation the Ag superhydrophobic surfaces (SHSs) on zinc (Zn), copper (Cu) and aluminium (Al) substrates. The water contact angles (WCAs) of the Ag SHSs on Zn, Cu and Al substrates are 167°, 165° and 154°, respectively. Furthermore, the water sliding angle (WSA) of each surface is less than 1°. The morphology and chemical composition of the samples are characterized using scanning electron microscopy (SEM) and X-ray diffraction pattern (XRD). The as-prepared three kinds of SHSs possess the self-cleaning performance, which can quickly take the chalk away when the water droplets fall down the SHSs. In addition, the superhydrophobicity of the SHSs can well maintain after exposure to the air for 6 months, indicating that the surfaces can sustain good stability.

Effect of different adhesion strategies on bond strength of resin composite to composite-dentin complex.

PubMed

Özcan, M; Pekkan, G

2013-01-01

Service life of discolored and abraded resin composite restorations could be prolonged by repair or relayering actions. Composite-composite adhesion can be achieved successfully using some surface conditioning methods, but the most effective adhesion protocol for relayering is not known when the composite restorations are surrounded with dentin. This study evaluated the effect of three adhesion strategies on the bond strength of resin composite to the composite-dentin complex. Intact maxillary central incisors (N=72, n=8 per subgroup) were collected and the coronal parts of the teeth were embedded in autopolymerized poly(methyl tfr54methacrylate) surrounded by a polyvinyl chloride cylinder. Cylindrical cavities (diameter: 2.6 mm; depth: 2 mm) were opened in the middle of the labial surfaces of the teeth using a standard diamond bur, and the specimens were randomly divided into three groups. Two types of resin composite, namely microhybrid (Quadrant Anterior Shine; AS) and nanohybrid (Grandio; G), were photo-polymerized incrementally in the cavities according to each manufacturer's recommendations. The composite-enamel surfaces were ground finished to 1200-grit silicone carbide paper until the dentin was exposed. The surfaces of the substrate composites and the surrounding dentin were conditioned according to one of the following adhesion protocols: protocol 1: acid-etching (dentin) + silica coating (composite) + silanization (composite) + primer (dentin) + bonding agent (dentin + composite); protocol 2: silica coating (composite) + acid-etching (dentin) + silanization (composite) + primer (dentin) + bonding agent (dentin + composite); and protocol 3: acid-etching (dentin) + primer (dentin) + silanization (composite) + bonding agent (dentin + composite). Applied primer and bonding agents were the corresponding materials of the composite manufacturer. Silica coating (CoJet sand, 30 μm) was achieved using a chairside air-abrasion device (distance: 10 mm; duration: four seconds in circular motion). After conditioning protocols, the repair resin was adhered to the substrate surfaces using transparent polyethylene molds (diameter: 3.6 mm) incrementally and photo-polymerized. The substrate-adherend combinations were as follows: AS-AS, G-G, AS-G. Shear force was applied to the adhesive interface in a Universal Testing Machine (crosshead speed: 1 mm/min). The types of failures were further evaluated and categorized as follows: 1) cohesive in the composite substrate and 2) adhesive at the interface. Bond strength values (MPa) were statistically analyzed using two-way analysis of variance and least significant difference post hoc tests (α=0.05). Significant effects of the adhesion strategy (p=0.006) and the composite type (p=0.000) were found. Interaction terms were not significant (p=0.292). Regardless of the substrate-adherend combination, protocol 1 (17-22 MPa) showed significantly higher results than did protocols 2 (15-17 MPa) and 3 (11-17 MPa) (p=0.028, p=0.002, respectively). The highest results were obtained from the G-G combination after all three protocols (17-22 MPa). The incidence of cohesive failures was more common when the substrate and the adherend were the same composite type (AS-AS: 87.5%, 87.5%, 75%; G-G: 100%, 75%, 50% for protocols 1, 2, and 3, respectively). When substrate and adherend were used interchangeably, adhesive failures were more frequent (25%, 50%, and 100% for protocol 1, 2, and 3, respectively). When the substrate and the adherend are of the same type, greater repair strength could be expected. In the repair of composites next to the dentin, depending on the composite type, conditioning the composite with silica coating and silanization after etching the dentin adds to the repair strength compared to the results obtained with silane application only.

In vitro biofilm formation on resin-based composites after different finishing and polishing procedures.

PubMed

Cazzaniga, Gloria; Ottobelli, Marco; Ionescu, Andrei C; Paolone, Gaetano; Gherlone, Enrico; Ferracane, Jack L; Brambilla, Eugenio

2017-12-01

To evaluate the influence of surface treatments of different resin-based composites (RBCs) on S. mutans biofilm formation. 4 RBCs (microhybrid, nanohybrid, nanofilled, bulk-filled) and 6 finishing-polishing (F/P) procedures (open-air light-curing, light-curing against Mylar strip, aluminum oxide discs, one-step rubber point, diamond bur, multi-blade carbide bur) were evaluated. Surface roughness (SR) (n=5/group), gloss (n=5/group), scanning electron microscopy morphological analysis (SEM), energy-dispersive X-ray spectrometry (EDS) (n=3/group), and S. mutans biofilm formation (n=16/group) were assessed. EDS analysis was repeated after the biofilm assay. A morphological evaluation of S. mutans biofilm was also performed using confocal laser-scanning microscopy (CLSM) (n=2/group). The data were analyzed using Wilcoxon (SR, gloss) and two-way ANOVA with Tukey as post-hoc tests (EDS, biofilm formation). F/P procedures as well as RBCs significantly influenced SR and gloss. While F/P procedures did not significantly influence S. mutans biofilm formation, a significant influence of RBCs on the same parameter was found. Different RBCs showed different surface elemental composition. Both F/P procedures and S. mutans biofilm formation significantly modified this parameter. The tested F/P procedures significantly influenced RBCs surface properties but did not significantly affect S. mutans biofilm formation. The significant influence of the different RBCs tested on S. mutans biofilm formation suggests that material characteristics and composition play a greater role than SR. F/P procedures of RBCs may unexpectedly play a minor role compared to that of the restoration material itself in bacterial colonization. Copyright © 2017 Elsevier Ltd. All rights reserved.

Formation of high electrical-resistivity thin surface layer on carbonyl-iron powder (CIP) and thermal stability of nanocrystalline structure and vortex magnetic structure of CIP

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

Sugimura, K.; Miyajima, Y.; Sonehara, M.

2016-05-15

This study focuses on the carbonyl-iron powder (CIP) used in the metal composite bulk magnetic core for high-efficient/light-weight SiC/GaN power device MHz switching dc-dc converter, where the fine CIP with a mean diameter of 1.1 μm is used to suppress the MHz band eddy current inside the CIP body. When applying the CIP to composite core together with the resin matrix, high electrical resistivity layer must be formed on the CIP-surface in order to suppress the overlapped eddy current between adjacent CIPs. In this study, tens nm thick silica (SiO{sub 2}) was successfully deposited on the CIP-surface by using hydrolysismore » of TEOS (Si(OC{sub 2}H{sub 5}){sub 4}). Also tens nm thick oxidized layer of the CIP-surface was successfully formed by using CIP annealing in dry air. The SiC/GaN power device can operate at ambient temperature over 200 degree-C, and the composite magnetic core is required to operate at such ambient temperature. The as-made CIP had small coercivity below 800 A/m (10 Oe) due to its nanocrystalline-structure and had a single vortex magnetic structure. From the experimental results, both nanocrystalline and single vortex magnetic structure were maintained after heat-exposure of 250 degree-C, and the powder coercivity after same heat-exposure was nearly same as that of the as-made CIP. Therefore, the CIP with thermally stable nanocrystalline-structure and vortex magnetic state was considered to be heat-resistant magnetic powder used in the iron-based composite core for SiC/GaN power electronics.« less

Formation of high electrical-resistivity thin surface layer on carbonyl-iron powder (CIP) and thermal stability of nanocrystalline structure and vortex magnetic structure of CIP

NASA Astrophysics Data System (ADS)

Sugimura, K.; Miyajima, Y.; Sonehara, M.; Sato, T.; Hayashi, F.; Zettsu, N.; Teshima, K.; Mizusaki, H.

2016-05-01

This study focuses on the carbonyl-iron powder (CIP) used in the metal composite bulk magnetic core for high-efficient/light-weight SiC/GaN power device MHz switching dc-dc converter, where the fine CIP with a mean diameter of 1.1 μm is used to suppress the MHz band eddy current inside the CIP body. When applying the CIP to composite core together with the resin matrix, high electrical resistivity layer must be formed on the CIP-surface in order to suppress the overlapped eddy current between adjacent CIPs. In this study, tens nm thick silica (SiO2) was successfully deposited on the CIP-surface by using hydrolysis of TEOS (Si(OC2H5)4). Also tens nm thick oxidized layer of the CIP-surface was successfully formed by using CIP annealing in dry air. The SiC/GaN power device can operate at ambient temperature over 200 degree-C, and the composite magnetic core is required to operate at such ambient temperature. The as-made CIP had small coercivity below 800 A/m (10 Oe) due to its nanocrystalline-structure and had a single vortex magnetic structure. From the experimental results, both nanocrystalline and single vortex magnetic structure were maintained after heat-exposure of 250 degree-C, and the powder coercivity after same heat-exposure was nearly same as that of the as-made CIP. Therefore, the CIP with thermally stable nanocrystalline-structure and vortex magnetic state was considered to be heat-resistant magnetic powder used in the iron-based composite core for SiC/GaN power electronics.

Efficacy of ceramic repair material on the bond strength of composite resin to zirconia ceramic.

PubMed

Kirmali, Omer; Kapdan, Alper; Harorli, Osman Tolga; Barutcugil, Cagatay; Ozarslan, Mehmet Mustafa

2015-01-01

The aim of this study was to evaluate the shear bond strength of composite resin in five different repair systems. Sixty specimens (7 mm in diameter and 3 mm in height) of zirconia ceramic were fabricated. All specimen surfaces were prepared with a 30 µm fine diamond rotary cutting instrument with water irrigation for 10 s and dried with oil-free air. Specimens were then randomly divided into six groups for the following different intra-oral repair systems (n = 10): Group 1, control group; Group 2, Cojet system (3M ESPE, Seefeld, Germany); Group 3, Cimara® System (Voco, Cuxhaven, Germany); Group 4, Z-Prime Plus System (Bisco Inc., Schaumburg, IL); Group 5, Clearfil™ System (Kuraray, Osaka, Japan); and Group 6, Z-Bond System (Danville, CA). After surface conditioning, a composite resin Grandio (Voco, Cuxhaven, Germany) was applied to the zirconia surface using a cylindrical mold (5 mm in diameter and 3 mm in length) and incrementally filled up, according to the manufacturer's instructions of each intra-oral system. Each specimen was subjected to a shear load at a crosshead speed of 1 mm/min until fracture. One-way analysis of variance (ANOVA) and Tukey post-hoc tests were used to analyze the bond strength values. There were significant differences between Groups 2-6 and Group 1. The highest bond strength values were obtained with Group 2 (17.26 ± 3.22) and Group 3 (17.31 ± 3.62), while the lowest values were observed with Group 1 (8.96 ± 1.62) and Group 6 (12.85 ± 3.95). All repair systems tested increased the bond strength values between zirconia and composite resin that used surface grinding with a diamond bur.

Dynamic Bubble Surface Tension Measurements in Northwest Atlantic Seawater

NASA Astrophysics Data System (ADS)

Kieber, D. J.; Long, M. S.; Keene, W. C.; Kinsey, J. D.; Frossard, A. A.; Beaupre, S. R.; Duplessis, P.; Maben, J. R.; Lu, X.; Chang, R.; Zhu, Y.; Bisgrove, J.

2017-12-01

Numerous reports suggest that most organic matter (OM) associated with newly formed primary marine aerosol (PMA) originates from the sea-surface microlayer. However, surface-active OM rapidly adsorbs onto bubble surfaces in the water column and is ejected into the atmosphere when bubbles burst at the air-water interface. Here we present dynamic surface tension measurements of bubbles produced in near surface seawater from biologically productive and oligotrophic sites and in deep seawater collected from 2500 m in the northwest Atlantic. In all cases, the surface tension of bubble surfaces decreased within seconds after the bubbles were exposed to seawater. These observations demonstrate that bubble surfaces are rapidly saturated by surfactant material scavenged from seawater. Spatial and diel variability in bubble surface evolution indicate corresponding variability in surfactant concentrations and/or composition. Our results reveal that surface-active OM is found throughout the water column, and that at least some surfactants are not of recent biological origin. Our results also support the hypothesis that the surface microlayer is a minor to negligible source of OM associated with freshly produced PMA.

Foundation Design against Frost Action in Europe.

DTIC Science & Technology

1988-03-01

the inside of the foundation wall and consisted of 50mm of ’Rockwool’ (a mineral wool ). This insulation guides heat from the house down toward the...Separation of the floor slab from the inner part of the foundation wall by introducing mineral wool (Fig. 49c) gives a further slight reduction in...construction consisting, for example, of wood and mineral wool and including air spaces. Rt is the thermal resistance of the composite floor from surface to

Nanograin Ceramic Optical Composite Window

DTIC Science & Technology

2005-07-15

parts are sintered in air at 1100 C̊. Table 1: Carbon content of the calcined Alumina- Zirconia powders analyzed by LECO Calcination Temperature Carbon...estimated particle size of the Alumina and Zirconia powders Material name Surface area (m2/g) Estimated particle size (nm) Alumina 315.7 4.7 Zirconia...200 300 400 500 600 700 800 900 1000 2-Theta - Scale 20 30 40 50 60 70 80 Figure 3: XRD patterns of zirconia powder prepared by sonochemical method

Environmental Assessment: Zebra Mussel Eradication from the Base Lake at Offutt Air Force Base

DTIC Science & Technology

2008-09-11

water flow even in large diameter piping, increase sedimentation rates , and promote surface corrosion. Natural populations of 5,000 to 30,000...Body Weight (kg) Foraging Territory (ha) Food Ingestion Rate (kg dw/day) Food Ingestion Rate (kg ww/day) Water (L/day) Sediment / Soil Ingestion...Composition - based on diets for Missouri; Korschgen (1958) in USEPA (1993) Soil/ Sediment Ingestion Rate – Assumed 1% of dw ingestion rate ; USEPA (2000

Effect of ZrB2 addition on the oxidation behavior of Si-SiC-ZrB2 composites exposed at 1500°C in air.

PubMed

D'Amico, Claudio; Bianchi, Giovanni; Padovano, Elisa; Biamino, Sara; Aversa, Alberta; Badini, Claudio; Ortona, Alberto

2018-01-01

Silicon carbide ceramics obtained by reactive infiltration of silicon (SRI) have many industrial applications especially involving severe and high temperature conditions. In this study, the oxidation behavior in air of Si-SiC-ZrB 2 systems at a high temperature (1500°C) for dwelling times of up to 48 hours was examined. The oxidation process was analyzed on the basis of elemental maps and X-ray diffraction patterns taken, respectively, on the core and on the surface of the specimens, together with weight gains and the average thicknesses of the resulting scale. Further, flexural strength at room temperature was examined as a function of different oxidation times. The main chemical reactions and phase transformations involved in the oxidation process are reported. Several oxides were detected on the surface: zirconia, silica, zircon and 3-zirconium monoxide. All of the samples showed a parabolic oxidation kinetics, suggesting that the controlling mechanism was the diffusion; however, even after 48 hours, the oxidation process was not finished - indeed, all of the samples continued to gain weight. The oxidation of Si-SiC-ZrB 2 material produced via SRI was slower compared with previously investigated ZrB 2 -SiC composites processed with a different techniques and tested in similar conditions. The oxidation mechanism was found to be consistent with the convection cells model.

Facile way in fabricating a cotton fabric membrane for switchable oil/water separation and water purification

NASA Astrophysics Data System (ADS)

Li, Yubin; Feng, Ziliang; He, Yi; Fan, Yi; Ma, Jing; Yin, Xiangying

2018-05-01

With dopamine and NiFe2O4 particles, a novel modified cotton fabric (PDA-NiFe2O4@CF) was prepared by one-pot method. Surface morphology, composition of the PDA-NiFe2O4@CF were investigated with SEM, EDX, XRD and FT-IR, respectively. According to the results, the cotton fiber surface was well coated with NiFe2O4 particles. Subsequently, wetting behavior of the modified cotton fabric was determined. The PDA-NiFe2O4@CF is superamphiphilic in air, and a dual lyophobic behavior was indicated with an oil contact angle (OCA) of 153° under water and a water contact angle (WCA) of 145° under oil. The rough micro-nano scale surface structure and high-surface-energy compositions of the PDA-NiFe2O4@CF makes the surface to be easily covered by one medium and enables it to repel other unmixable medium simultaneously. Therefore, water-oil mixtures can be separated on demand. Besides, with the unusual dual lyophobic surface of PDA-NiFe2O4@CF, both two types of emulsions were separated by gravity driven. On the other hand, it was also found that the as-prepared PDA-NiFe2O4@CF had good adsorption performance for methylene blue.

Precise, contactless measurements of the surface tension of picolitre aerosol droplets† †Electronic supplementary information (ESI) available: Parametrizations used to infer concentration, density, viscosity, and surface tension from refractive index for sodium chloride and glutaric acid; description of the semi-analytical T-matrix calculations; Fig. S1 and S2. See DOI: 10.1039/c5sc03184b Click here for additional data file.

PubMed Central

Bzdek, Bryan R.; Power, Rory M.; Simpson, Stephen H.; Royall, C. Patrick

2016-01-01

The surface composition and surface tension of aqueous droplets can influence key aerosol characteristics and processes including the critical supersaturation required for activation to form cloud droplets in the atmosphere. Despite its fundamental importance, surface tension measurements on droplets represent a considerable challenge owing to their small volumes. In this work, we utilize holographic optical tweezers to study the damped surface oscillations of a suspended droplet (<10 μm radius) following the controlled coalescence of a pair of droplets and report the first contactless measurements of the surface tension and viscosity of droplets containing only 1–4 pL of material. An advantage of performing the measurement in aerosol is that supersaturated solute states (common in atmospheric aerosol) may be accessed. For pairs of droplets starting at their equilibrium surface composition, surface tensions and viscosities are consistent with bulk equilibrium values, indicating that droplet surfaces respond to changes in surface area on microsecond timescales and suggesting that equilibrium values can be assumed for growing atmospheric droplets. Furthermore, droplet surfaces are shown to be rapidly modified by trace species thereby altering their surface tension. This equilibration of droplet surface tension to the local environmental conditions is illustrated for unknown contaminants in laboratory air and also for droplets exposed to gas passing through a water–ethanol solution. This approach enables precise measurements of surface tension and viscosity over long time periods, properties that currently are poorly constrained. PMID:28758004

Measurement of the Muon Content of Air Showers with IceTop

NASA Astrophysics Data System (ADS)

Gonzalez, JG; IceCube Collaboration

2016-05-01

IceTop, the surface component of the IceCube detector, has measured the energy spectrum of cosmic ray primaries in the range between 1.6 PeV and 1.3 EeV. IceTop can also be used to measure the average density of GeV muons in the shower front at large radial distances (> 300 m) from the shower axis. Wei present the measurement of the muon lateral distribution function for primary cosmic rays with energies between 1.6 PeV and about 0.1 EeV, and compare it to proton and iron simulations. We also discuss how this information can be exploited in the reconstruction of single air shower events. By combining the information on the muon component with that of the electromagnetic component of the air shower, we expect to reduce systematic uncertainties in the inferred mass composition of cosmic rays arising from theoretical uncertainties in hadronic interaction models.

High-Thermal- and Air-Stability Cathode Material with Concentration-Gradient Buffer for Li-Ion Batteries.

PubMed

Shi, Ji-Lei; Qi, Ran; Zhang, Xu-Dong; Wang, Peng-Fei; Fu, Wei-Gui; Yin, Ya-Xia; Xu, Jian; Wan, Li-Jun; Guo, Yu-Guo

2017-12-13

Delivery of high capacity with high thermal and air stability is a great challenge in the development of Ni-rich layered cathodes for commercialized Li-ion batteries (LIBs). Herein we present a surface concentration-gradient spherical particle with varying elemental composition from the outer end LiNi 1/3 Co 1/3 Mn 1/3 O 2 (NCM) to the inner end LiNi 0.8 Co 0.15 Al 0.05 O 2 (NCA). This cathode material with the merit of NCM concentration-gradient protective buffer and the inner NCA core shows high capacity retention of 99.8% after 200 cycles at 0.5 C. Furthermore, this cathode material exhibits much improved thermal and air stability compared with bare NCA. These results provide new insights into the structural design of high-performance cathodes with high energy density, long life span, and storage stability materials for LIBs in the future.

Mixed Layer Temperature Budget for the Northward Propagating Summer Monsoon Intraseasonal Oscillation (MISO) in the Central Bay of Bengal

NASA Astrophysics Data System (ADS)

Girishkumar, M. S.; Joseph, J.; Thangaprakash, V. P.; Pottapinjara, V.; McPhaden, M. J.

2017-11-01

Composite analyses of mixed layer temperature (MLT) budget terms from near-surface meteorological and oceanic observations in the central Bay of Bengal are utilized to evaluate the modulation of air-sea interactions and MLT processes in response to the summer monsoon intraseasonal oscillation (MISO). For this purpose, we use moored buoy data at 15°N, 12°N, and 8°N along 90°E together with TropFlux meteorological parameters and the Ocean Surface Current Analyses Real-time (OSCAR) current product. Our analysis shows a strong cooling tendency in MLT with maximum amplitude in the central and northern BoB during the northward propagation of enhanced convective activity associated with the active phase of the MISO; conversely, warming occurs during the suppressed phase of the MISO. The surface mixed layer is generally heated during convectively inactive phases of the MISO primarily due to increased net surface heat flux into the ocean. During convectively active MISO phases, the surface mixed layer is cooled by the combined influence of net surface heat loss to the atmosphere and entrainment cooling at the base of mixed layer. The variability of net surface heat flux is primarily due to modulation of latent heat flux and shortwave radiation. Shortwave is mostly controlled by an enhancement or reduction of cloudiness during the active and inactive MISO phases and latent heat flux is mostly controlled by variations in air-sea humidity difference.

Enhancement in volatile organic compound sensitivity of aged Ag nanoparticle aggregates by plasma exposure

NASA Astrophysics Data System (ADS)

Hosomi, Kei; Ozaki, Koichi; Nishiyama, Fumitaka; Takahiro, Katsumi

2018-01-01

Silver nanoparticles (Ag NPs) tarnish easily upon exposure to ambient air, and eventually lose their ability as a plasmonic sensor via weakened localized surface plasmon resonance (LSPR). We have demonstrated the enhancement in plasmonic sensitivity of tarnished Ag NP aggregates to vapors of volatile organic compounds (VOCs) such as ethanol and butanol by Ar plasma exposure. The response of Ag NP aggregates to the VOC vapors was examined by measuring the change in optical extinction spectra before and after exposure to the vapors. The sensitivity of Ag NP aggregates decreased gradually when stored in ambient air. The performance of tarnished Ag NPs for ethanol sensing was recovered by exposure to argon (Ar) plasma for 15 s. The reduction from oxidized Ag to metallic one was recognized, while morphological change was hardly noticeable after the plasma exposure. We conclude, therefore, that a compositional change rather than a morphological change occurred on Ag NP surfaces enhances the sensing ability of tarnished Ag NP aggregates to the VOC vapors.

Inspecting Composites with Airborne Ultrasound: Through Thick and Thin

NASA Astrophysics Data System (ADS)

Hsu, David K.; Barnard, Daniel J.

2006-03-01

The inspection of composite materials and structures with air-coupled ultrasound has the obvious advantage that it is non-contact, non-contaminating, and free from couplants. However, the transmission efficiency from air to solid is extremely low due to the enormous difference in acoustic impedance. The development of more efficient airborne ultrasonic transducers over the years has made it possible, and even practical, to inspect composites with airborne ultrasound. It is now possible to drive newer, more efficient transducers with a portable ultrasonic flaw detector to inspect 2-inch thick solid CFRP in air. In this paper we describe our experience in applying air-coupled ultrasound to the inspection of a variety of composite structures, from honeycomb with thin composite facesheet to very thick solid laminates. General considerations for making airborne ultrasonic measurement in composite are given, and mechanism of transmission through honeycomb core, and resonance effects in transmitting through thick laminates will be described. NDE results of defects and damage in various composite structures will be presented.

A description and evaluation of an air quality model nested within global and regional composition-climate models using MetUM

NASA Astrophysics Data System (ADS)

Neal, Lucy S.; Dalvi, Mohit; Folberth, Gerd; McInnes, Rachel N.; Agnew, Paul; O'Connor, Fiona M.; Savage, Nicholas H.; Tilbee, Marie

2017-11-01

There is a clear need for the development of modelling frameworks for both climate change and air quality to help inform policies for addressing these issues simultaneously. This paper presents an initial attempt to develop a single modelling framework, by introducing a greater degree of consistency in the meteorological modelling framework by using a two-step, one-way nested configuration of models, from a global composition-climate model (GCCM) (140 km resolution) to a regional composition-climate model covering Europe (RCCM) (50 km resolution) and finally to a high (12 km) resolution model over the UK (AQUM). The latter model is used to produce routine air quality forecasts for the UK. All three models are based on the Met Office's Unified Model (MetUM). In order to better understand the impact of resolution on the downscaling of projections of future climate and air quality, we have used this nest of models to simulate a 5-year period using present-day emissions and under present-day climate conditions. We also consider the impact of running the higher-resolution model with higher spatial resolution emissions, rather than simply regridding emissions from the RCCM. We present an evaluation of the models compared to in situ air quality observations over the UK, plus a comparison against an independent 1 km resolution gridded dataset, derived from a combination of modelling and observations, effectively producing an analysis of annual mean surface pollutant concentrations. We show that using a high-resolution model over the UK has some benefits in improving air quality modelling, but that the use of higher spatial resolution emissions is important to capture local variations in concentrations, particularly for primary pollutants such as nitrogen dioxide and sulfur dioxide. For secondary pollutants such as ozone and the secondary component of PM10, the benefits of a higher-resolution nested model are more limited and reasons for this are discussed. This study highlights the point that the resolution of models is not the only factor in determining model performance - consistency between nested models is also important.

Microbial composition in bioaerosols of a high-throughput chicken-slaughtering facility.

PubMed

Lues, J F R; Theron, M M; Venter, P; Rasephei, M H R

2007-01-01

The microbial composition of the air in various areas of a high-throughput chicken-slaughtering facility was investigated. Over a 4-mo period, 6 processing areas were sampled, and the influence of environmental factors was monitored. The highest counts of microorganisms were recorded in the initial stages of processing, comprising the receiving-killing and defeathering areas, whereas counts decreased toward the evisceration, air-chilling, packaging, and dispatch areas. Maximum microbial counts were as follows: coliforms, 4.9 x 10(3) cfu/m(3); Escherichia coli 3.4 x 10(3) cfu/m(3); Bacillus cereus, 5.0 x 10(4) cfu/m(3); Staphylococcus aureus, 1.6 x 10(4) cfu/m(3); Pseudomonas aeruginosa, 7.0 x 10(4) cfu/m(3); presumptive Salmonella spp., 1.5 x 10(4) cfu/m(3); Listeria monocytogenes, 1.6 x 10(4) cfu/m(3); and fungi, 1.4 x 10(4) cfu/m(3). Higher counts of airborne microorganisms found in the receiving-killing and defeathering areas indicate the importance of controlling microbial levels before processing to prevent the spread of organisms downstream. This should limit the risk of carrying over contaminants from areas known to generate high counts to areas where the final food product is exposed to air and surface contamination.

High-temperature chemical stability of plasma-sprayed Ca{sub 0.5}Sr{sub 0.5}Zr{sub 4}P{sub 6}O{sub 24} coatings on Nicalon/SiC ceramic matrix composite and Ni-based superalloy substrates

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

Lee, W.Y.; Cooley, K.M.; Joslin, D.L.

The potential application of Ca{sub 0.5}Sr{sub 0.5}Zr{sub 4}P{sub 6}O{sub 24} (CS50) as a corrosion-resistant coating material for Si-based ceramics and as a thermal barrier coating material for Ni-based superalloys was explored. A {approximately}200 {micro}m thick CS50 coating was prepared by air plasma spray with commercially available powder. A Nicalon/SiC ceramic matrix composite and a Ni-based superalloy coated with a {approximately}200 {micro}m thick metallic bond coat layer were used as substrate materials. Both the powder and coating contained ZrP{sub 2}O{sub 7} as an impurity phase, and the coating was highly porous as-deposited. The coating deposited on the Nicalon/SiC substrate was chemicallymore » stable upon exposure to air and Na{sub 2}SO{sub 4}/O{sub 2} atmospheres at 1,000 C for 100 h. In contrast, the coating sprayed onto the superalloy substrate significantly reacted with the bond coat surface after similar oxidation in air.« less

Attachment of composite porous supra-particles to air-water and oil-water interfaces: theory and experiment.

PubMed

Paunov, Vesselin N; Al-Shehri, Hamza; Horozov, Tommy S

2016-09-29

We developed and tested a theoretical model for the attachment of fluid-infused porous supra-particles to a fluid-liquid interface. We considered the wetting behaviour of agglomerated clusters of particles, typical of powdered materials dispersed in a liquid, as well as of the adsorption of liquid-infused colloidosomes at the liquid-fluid interface. The free energy of attachment of a composite spherical porous supra-particle made from much smaller aggregated spherical particles to the oil-water interface was calculated. Two cases were considered: (i) a water-filled porous supra-particle adsorbed at the oil-water interface from the water phase, and, (ii) an oil-filled porous supra-particle adsorbed at the oil-water interface from the oil-phase. We derived equations relating the three-phase contact angle of the smaller "building block" particles and the contact angle of the liquid-infused porous supra-particles. The theory predicts that the porous supra-particle contact angle attached at the liquid interface strongly depends on the type of fluid infused in the particle pores and the fluid phase from which it approaches the liquid interface. We tested the theory by using millimetre-sized porous supra-particles fabricated by evaporation of droplets of polystyrene latex suspension on a pre-heated super-hydrophobic surface, followed by thermal annealing at the glass transition temperature. Such porous particles were initially infused with water or oil and approached to the oil-water interface from the infusing phase. The experiment showed that when attaching at the hexadecane-water interface, the porous supra-particles behaved as hydrophilic when they were pre-filled with water and hydrophobic when they were pre-filled with hexadecane. The results agree with the theoretically predicted contact angles for the porous composite supra-particles based on the values of the contact angles of their building block latex particles measured with the Gel Trapping Technique. The experimental data for the attachment of porous supra particles to the air-water interface from both air and water also agree with the theoretical model. This study gives important insights about how porous particles and particle aggregates attach to the oil-water interface in Pickering emulsions and the air-water surface in particle-stabilised aqueous foams relevant in ore flotation and a range of cosmetic, pharmaceutical, food, home and personal care formulations.

Effects of air-polishing powders on color stability of composite resins.

PubMed

Güler, Ahmet Umut; Duran, Ibrahim; Yücel, Ali Çağin; Ozkan, Pelin

2011-10-01

The purpose of this study was to investigate the effect of different air-polishing powders on the color stability of different types of composite resin restorative materials. Thirty cylindrical specimens (15×2 mm) were prepared for each of 7 composite resin restorative materials. All specimens were polished with a series of aluminum oxide polishing discs (Sof-Lex). The prepared specimens of each composite resin were randomly divided into 3 groups of 10 specimens each, for control (Group-C) and two air-powder applications (Group-CP: Cavitron Prophy-Jet; Group-PS: Sirona ProSmile prophylaxis powder). A standard air-polishing unit (ProSmile Handly) was used. All specimens were air-powdered for 10 s at 4-bar pressure. The distance of the spray nosel from the specimens was approximately 10 mm and angulation of the nosel was 90°. Specimens were stored in 100 mL of coffee (Nescafe Classic) for 24 h at 37°C. Color measurement of all specimens was recorded before and after exposure to staining agent with a colorimeter (Minolta CR-300). Color differences (∆E*) between the 2 color measurements (baseline and after 24 h storage) were calculated. The data were analyzed with a 2-way ANOVA test, and mean values were compared by the Tukey HSD test (p<0.05). According to the 2-way ANOVA results, composite resin restorative materials, air-polishing powders, and their interaction were statistically significant (p<0.05) For Aelite Aesthetic Enemal, Filtek Z250, Grandio, CeramX Mono, and Quixfil composite resin restorative materials, no significant difference was observed between Group-PS and Group-CP (p>.05) and these groups demonstrated the highest ∆E* values. For Filtek Silorane and IntenS, the highest ∆E* values were observed in Group-PS. The lowest ∆E* values for all composite resin groups were observed in Group-C. When comparing the 7 composite resin restorative materials, Aelite Aesthetic Enemal demonstrated significantly less ∆E* values than the other composite resins tested. The highest ∆E* values were observed in Quixfil. Except for Quixfil, all control groups of composite resins that were polished Sof-Lex exhibited clinically acceptable ∆E values (<3.7). Air-polishing applications increased the color change for all composite resin restorative materials tested. Composite restorations may require re-polishing after air-polishing.

Effects of air-polishing powders on color stability of composite resins

PubMed Central

GÜLER, Ahmet Umut; DURAN, Ibrahim; YÜCEL, Ali Çagin; ÖZKAN, Pelin

2011-01-01

Objectives The purpose of this study was to investigate the effect of different air-polishing powders on the color stability of different types of composite resin restorative materials. Material and methods Thirty cylindrical specimens (15×2 mm) were prepared for each of 7 composite resin restorative materials. All specimens were polished with a series of aluminum oxide polishing discs (Sof-Lex). The prepared specimens of each composite resin were randomly divided into 3 groups of 10 specimens each, for control (Group-C) and two air-powder applications (Group-CP: Cavitron Prophy-Jet; Group-PS: Sirona ProSmile prophylaxis powder). A standard air-polishing unit (ProSmile Handly) was used. All specimens were air-powdered for 10 s at 4-bar pressure. The distance of the spray nosel from the specimens was approximately 10 mm and angulation of the nosel was 90º. Specimens were stored in 100 mL of coffee (Nescafe Classic) for 24 h at 37ºC. Color measurement of all specimens was recorded before and after exposure to staining agent with a colorimeter (Minolta CR-300). Color differences (∆E*) between the 2 color measurements (baseline and after 24 h storage) were calculated. The data were analyzed with a 2-way ANOVA test, and mean values were compared by the Tukey HSD test (p≤0.05). Results According to the 2-way ANOVA results, composite resin restorative materials, air-polishing powders, and their interaction were statistically significant (p<0.05) For Aelite Aesthetic Enemal, Filtek Z250, Grandio, CeramX Mono, and Quixfil composite resin restorative materials, no significant difference was observed between Group-PS and Group-CP (p>.05) and these groups demonstrated the highest ∆E* values. For Filtek Silorane and IntenS, the highest ∆E* values were observed in Group-PS. The lowest ∆E* values for all composite resin groups were observed in Group-C. When comparing the 7 composite resin restorative materials, Aelite Aesthetic Enemal demonstrated significantly less ∆E* values than the other composite resins tested. The highest ∆E* values were observed in Quixfil. Conclusion Except for Quixfil, all control groups of composite resins that were polished Sof-Lex exhibited clinically acceptable ∆E values (<3.7). Air-polishing applications increased the color change for all composite resin restorative materials tested. Composite restorations may require re-polishing after air-polishing. PMID:21922122

Control of membrane permeability in air-stable droplet interface bilayers

DOE PAGES

Mruetusatorn, Prachya; Polizos, Georgios; Datskos, Panos G.; ...

2015-03-19

Air-stable droplet interface bilayers (airDIBs) on oil-infused surfaces are versatile model membranes for synthetic biology applications, including biosensing of airborne species. However, air-DIBs are subject to evaporation, which can, over time, destabilize them and reduce their useful lifetime compared to traditional DIBs that are fully submerged in oil. Here, we show that lifetimes of air-DIBs can be extended by as much as an order of magnitude by maintaining them at a temperature just above the dew point. We find that raising the temperature from near the dew point (7 C at 38.5 % relative humidity) to room temperature results inmore » loss of water molecules of hydration from the polar head groups of the lipid bilayer membrane due to evaporation in an irreversible process that increases the overall entropy of the system. This dehydration transition affects primarily the bilayer resistance, by increasing ion permeability through the increasingly disordered polar head group region of the bilayer. Temperature and/or relative humidity are conveniently tunable parameters for controlling the stability and composition of air-DIBs membranes, while still allowing for operation in ambient environments.« less

Thermotransduction and heat stress in dental structures during orthodontic debonding : Effectiveness of various cooling strategies.

PubMed

Kley, Philipp; Frentzen, Matthias; Küpper, Katharina; Braun, Andreas; Kecsmar, Susann; Jäger, Andreas; Wolf, Michael

2016-05-01

Recent studies have indicated possible thermal damage to pulpal tissue during orthodontic debonding. This study aimed to analyze the thermal loads acting upon dental structures and their transfer to the pulp during orthodontic debonding. Specific goals were to analyze temperature changes in local dental tissues, thermotransduction to the pulp cavity, and the effectiveness of common cooling strategies and of simulated intrapulpal circulation. Metal brackets were bonded to five extracted human molars and subsequently removed. While a carbide bur was applied to debond the residual composite from the tooth surface, various cooling strategies (no/air/water cooling) were employed with or without simulated intrapulpal circulation, accompanied by temperature measurements with a thermographic infrared camera on the enamel surface and with measuring probes in the pulp cavity. Appropriate evaluation software was used to calculate the enamel-to-pulp temperature gradients and for statistical analysis. Significant differences in temperature rise and heat development over time, both on the enamel surfaces and in the pulp cavities were found. The mean temperature rises associated with no/air/water cooling were 90.7/46.6/9.2 °C on the enamel surface versus 9/8/4.6 °C inside the pulp. However, thermotransduction from enamel to pulp remained below 10 % of the surface measurements in all groups. Simulated intrapulpal microcirculation was found to significantly reduce intrapulpal temperature levels. During debonding of residual bracket adhesives, provided that a carbide bur is properly used, our data indicate a low risk of reaching critical intrapulpal temperatures even in the absence of dedicated cooling and no risk if the instrumentation is accompanied by air or water cooling.

2014 Texas Military Value Task Force: Preparing for the Future

DTIC Science & Technology

2014-01-01

Mayor Bob Bruggeman, City of Texarkana 4. Naval Air Station Fort Worth Joint Reserve Base, City of Fort Worth 5. Dyess Air Force Base, Mayor Norm...Ellington Field): Composite – 98.2 Killeen (Fort Hood): Composite – 85.0 San Antonio (JBSA): Composite – 92.5 Texarkana (RRAD): Composite – 94.6 Wichita

Steady state fractionation of heavy noble gas isotopes in a deep unsaturated zone

USGS Publications Warehouse

Seltzer, Alan M.; Severinghaus, Jeffrey P.; Andraski, Brian J.; Stonestrom, David A.

2017-01-01

To explore steady state fractionation processes in the unsaturated zone (UZ), we measured argon, krypton, and xenon isotope ratios throughout a ∼110 m deep UZ at the United States Geological Survey (USGS) Amargosa Desert Research Site (ADRS) in Nevada, USA. Prior work has suggested that gravitational settling should create a nearly linear increase in heavy-to-light isotope ratios toward the bottom of stagnant air columns in porous media. Our high-precision measurements revealed a binary mixture between (1) expected steady state isotopic compositions and (2) unfractionated atmospheric air. We hypothesize that the presence of an unsealed pipe connecting the surface to the water table allowed for direct inflow of surface air in response to extensive UZ gas sampling prior to our first (2015) measurements. Observed isotopic resettling in deep UZ samples collected a year later, after sealing the pipe, supports this interpretation. Data and modeling each suggest that the strong influence of gravitational settling and weaker influences of thermal diffusion and fluxes of CO2 and water vapor accurately describe steady state isotopic fractionation of argon, krypton, and xenon within the UZ. The data confirm that heavy noble gas isotopes are sensitive indicators of UZ depth. Based on this finding, we outline a potential inverse approach to quantify past water table depths from noble gas isotope measurements in paleogroundwater, after accounting for fractionation during dissolution of UZ air and bubbles.

Impacts of aerosol-cloud interactions on past and future changes in tropospheric composition

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

Unger, N.; Menon, S.; Shindell, D. T.

2009-02-02

The development of effective emissions control policies that are beneficial to both climate and air quality requires a detailed understanding of all the feedbacks in the atmospheric composition and climate system. We perform sensitivity studies with a global atmospheric composition-climate model to assess the impact of aerosols on tropospheric chemistry through their modification on clouds, aerosol-cloud interactions (ACI). The model includes coupling between both tropospheric gas-phase and aerosol chemistry and aerosols and liquid-phase clouds. We investigate past impacts from preindustrial (PI) to present day (PD) and future impacts from PD to 2050 (for the moderate IPCC A1B scenario) that embracemore » a wide spectrum of precursor emission changes and consequential ACI. The aerosol indirect effect (AIE) is estimated to be -2.0 Wm{sup -2} for PD-PI and -0.6 Wm{sup -2} for 2050-PD, at the high end of current estimates. Inclusion of ACI substantially impacts changes in global mean methane lifetime across both time periods, enhancing the past and future increases by 10% and 30%, respectively. In regions where pollution emissions increase, inclusion of ACI leads to 20% enhancements in in-cloud sulfate production and {approx}10% enhancements in sulfate wet deposition that is displaced away from the immediate source regions. The enhanced in-cloud sulfate formation leads to larger increases in surface sulfate across polluted regions ({approx}10-30%). Nitric acid wet deposition is dampened by 15-20% across the industrialized regions due to ACI allowing additional re-release of reactive nitrogen that contributes to 1-2 ppbv increases in surface ozone in outflow regions. Our model findings indicate that ACI must be considered in studies of methane trends and projections of future changes to particulate matter air quality.« less

A gel probe equilibrium sampler for measuring arsenic porewater profiles and sorption gradients in sediments: II. Field application to Haiwee reservoir sediment

USGS Publications Warehouse

Campbell, K.M.; Root, R.; O'Day, P. A.; Hering, J.G.

2008-01-01

Arsenic (As) geochemistry and sorption behavior were measured in As- and iron (Fe)-rich sediments of Haiwee Reservoir by deploying undoped (clear) polyacrylamide gels and hydrous ferric oxide (HFO)-doped gels in a gel probe equilibrium sampler, which is a novel technique for directly measuring the effects of porewater composition on As adsorption to Fe oxides phases in situ. Arsenic is deposited at the sediment surface as As(V) and is reduced to As(III) in the upper layers of the sediment (0-8 cm), but the reduction of As(V) does not cause mobilization into the porewater. Dissolved As and Fe concentrations increased at depth in the sediment column driven by the reductive dissolution of amorphous Fe(III) oxyhydroxides and conversion to a mixed Fe(II, III) green rust-type phase. Adsorption of As and phosphorous (P) onto HFO-doped gels was inhibited at intermediate depths (10-20 cm), possibly due to dissolved organic or inorganic carbon, indicating that dissolved As concentrations were at least partially controlled by porewater composition rather than surface site availability. In sediments that had been recently exposed to air, the region of sorption inhibition was not observed, suggesting that prior exposure to air affected the extent of reductive dissolution, porewater chemistry, and As adsorption behavior. Arsenic adsorption onto the HFO-doped gels increased at depths >20 cm, and the extent of adsorption was most likely controlled by the competitive effects of dissolved phosphate. Sediment As adsorption capacity appeared to be controlled by changes in porewater composition and competitive effects at shallower depths, and by reductive dissolution and availability of sorption sites at greater burial depths. ?? 2008 American Chemical Society.

COMPOSITION CHANGES IN REFRIGERANT BLENDS FOR AUTOMOTIVE AIR CONDITIONING

EPA Science Inventory

Three refrigerant blends used to replace CFC-12 in automotive air conditioners were evaluated for composition changes due to typical servicing and leakage. When recommended service procedures were followed, changes in blend compositions were relatively small. Small changes in b...

Characterizing the PAHs in surface waters and snow in the Athabasca region: Implications for identifying hydrological pathways of atmospheric deposition.

PubMed

Birks, S J; Cho, S; Taylor, E; Yi, Y; Gibson, J J

2017-12-15

The composition of polycyclic aromatic hydrocarbons present in snow and surface waters in the Athabasca Oil Sands Region (AOSR) was characterized in order to identify major contributors to the organics detected in rivers and lakes in the region. PAH concentrations, measured by three monitoring programs in 2011, were used to compare the PAH compositions of snow and surface waters across the AOSR. The 2011 dataset includes total (dissolved+particulate) concentrations of thirty-four parent and alkylated PAH compounds in 105 snow, 272 river, and 3 lake samples. The concentration of PAHs in rivers varies seasonally, with the highest values observed in July. The timing of increases in PAH concentrations in rivers coincides with the high river discharge during the spring freshet, indicating that this major hydrological event may play an important role in delivering PAHs to rivers. However, the composition of PAHs present in rivers during this period differs from the composition of PAHs present in snow, suggesting that direct runoff and release of PAHs accumulated on snow may not be the major source of PAHs to the Athabasca River and its tributaries. Instead, snowmelt may contribute indirectly to increases in PAHs due to hydrological processes such as erosion of stream channels, remobilization of PAH-containing sediments, increased catchment runoff, and snowmelt-induced groundwater inputs during this dynamic hydrologic period. Better understanding of transformations of PAH profiles during transport along surface and subsurface flow paths in wetland-dominated boreal catchments would improve identification of potential sources and pathways in the region. The compositional differences highlight the challenges in identifying the origins of PAHs in a region with multiple potential natural and anthropogenic sources particularly when the potential transport pathways include air, soil and water. Copyright © 2017 Elsevier B.V. All rights reserved.

Normal-mode and free-Air gravity constraints on lateral variations in velocity and density of Earth's mantle

PubMed

Ishii; Tromp

1999-08-20

With the use of a large collection of free-oscillation data and additional constraints imposed by the free-air gravity anomaly, lateral variations in shear velocity, compressional velocity, and density within the mantle; dynamic topography on the free surface; and topography on the 660-km discontinuity and the core-mantle boundary were determined. The velocity models are consistent with existing models based on travel-time and waveform inversions. In the lowermost mantle, near the core-mantle boundary, denser than average material is found beneath regions of upwellings centered on the Pacific Ocean and Africa that are characterized by slow shear velocities. These anomalies suggest the existence of compositional heterogeneity near the core-mantle boundary.

Measurement of the Muon Production Depths at the Pierre Auger Observatory

DOE PAGES

Collica, Laura

2016-09-08

The muon content of extensive air showers is an observable sensitive to the primary composition and to the hadronic interaction properties. The Pierre Auger Observatory uses water-Cherenkov detectors to measure particle densities at the ground and therefore is sensitive to the muon content of air showers. We present here a method which allows us to estimate the muon production depths by exploiting the measurement of the muon arrival times at the ground recorded with the Surface Detector of the Pierre Auger Observatory. The analysis is performed in a large range of zenith angles, thanks to the capability of estimating and subtracting the electromagnetic component, and for energies betweenmore » $$10^{19.2}$$ and $$10^{20}$$ eV.« less

Numerical analysis of the in-well vapor-stripping system demonstration at Edwards Air Force Base

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

White, M.D.; Gilmore, T.J.

1996-10-01

Numerical simulations, with the Subsurface Transport Over Multiple Phases (STOMP) simulator, were applied to the field demonstration of an in-well vapor-stripping system at Edwards Air Force Base (AFB), near Mojave, California. The demonstration field site on the Edwards AFB was previously contaminated from traversing groundwater that was contained a varied composition of volatile organic compounds (VOCs), which primarily includes trichloroethylene (TCE). Contaminant TCE originated from surface basin that had been used to collect runoff during the cleaning of experimental rocket powered planes in the 1960s and 1970s. This report documents those simulations and associated numerical analyses. A companion report documentsmore » the in- well vapor-stripping demonstration from a field perspective.« less

Navy Fuel Composition and Screening Tool (FCAST) v2.8

DTIC Science & Technology

2016-05-10

allowed us to develop partial least squares (PLS) models based on gas chromatography–mass spectrometry (GC-MS) data that predict fuel properties. The...Chemometric property modeling Partial least squares PLS Compositional profiler Naval Air Systems Command Air-4.4.5 Patuxent River Naval Air Station Patuxent...Cumulative predicted residual error sum of squares DiEGME Diethylene glycol monomethyl ether FCAST Fuel Composition and Screening Tool FFP Fit for

Estimation of Surface Air Temperature from MODIS 1km Resolution Land Surface Temperature Over Northern China

NASA Technical Reports Server (NTRS)

Shen, Suhung; Leptoukh, Gregory G.; Gerasimov, Irina

2010-01-01

Surface air temperature is a critical variable to describe the energy and water cycle of the Earth-atmosphere system and is a key input element for hydrology and land surface models. It is a very important variable in agricultural applications and climate change studies. This is a preliminary study to examine statistical relationships between ground meteorological station measured surface daily maximum/minimum air temperature and satellite remotely sensed land surface temperature from MODIS over the dry and semiarid regions of northern China. Studies were conducted for both MODIS-Terra and MODIS-Aqua by using year 2009 data. Results indicate that the relationships between surface air temperature and remotely sensed land surface temperature are statistically significant. The relationships between the maximum air temperature and daytime land surface temperature depends significantly on land surface types and vegetation index, but the minimum air temperature and nighttime land surface temperature has little dependence on the surface conditions. Based on linear regression relationship between surface air temperature and MODIS land surface temperature, surface maximum and minimum air temperatures are estimated from 1km MODIS land surface temperature under clear sky conditions. The statistical errors (sigma) of the estimated daily maximum (minimum) air temperature is about 3.8 C(3.7 C).

Development of metal organic fromwork-199 immobilized zeolite foam for adsorption of common indoor VOCs.

PubMed

Saini, Vipin K; Pires, João

2017-05-01

Reticulated foam shaped adsorbents are more efficient for the removal of volatile organic compounds (VOCs), particularly from low VOC-concentration indoor air streams. In this study composite structure of zeolite and metal organic frameworks (MOFs), referred as ZMF, has been fabricated by immobilization of fine MOF-199 powder on foam shaped Zeolite Socony Mobil-5 (ZSM-5) Zeolitic structure, referred as ZF. The ZMF possess a uniform and well-dispersed coating of MOF-199 on the porous framework of ZF. It shows higher surface area, pore volume, and VOCs adsorption capacity, as compared to ZF-structure. Post-fabrication changes in selective adsorption properties of ZMF were studied with three common indoor VOCs (benzene, n-hexane, and cyclohexane), using gravimetric adsorption technique. The adsorption capacity of ZMF with different VOCs follow the order of benzene>n-hexane>cyclohexane. In comparison with MOF-199 and ZF, the composite structure ZMF shows improvement in selectivity for benzene from other two VOCs. Further, improvement in efficiency and stability of prepared ZMF was found to be associated with its high MOF loading capacity and unique morphological and structural properties. The developed composite structure with improved VOCs removal and recyclability could be a promising material for small to limited scale air pollution treatment units. Copyright © 2016. Published by Elsevier B.V.

Controllable synthesis of iron oxide nanoparticles in porous NaCl matrix

NASA Astrophysics Data System (ADS)

Kurapov, Yury A.; E Litvin, Stanislav; Romanenko, Sergey M.; Didikin, Gennadii G.; Oranskaya, Elena I.

2017-03-01

The paper gives the results of studying the structure of porous condensates of Fe + NaCl composition, chemical and phase compositions and dimensions of nanoparticles produced from the vapor phase by EB-PVD. Iron nanoparticles at fast removal from the vacuum oxidize in air and possess significant sorption capacity relative to oxygen and moisture. At heating in air, reduction of porous condensate weight occurs right to the temperature of 650 °C, primarily, due to desorption of physically sorbed moisture. Final oxidation of Fe3O4 to Fe2O3 proceeds in the range of 380 °C-650 °C, due to the remaining fraction of physically adsorbed oxygen. At iron concentrations of up to 10-15 at%, condensate sorption capacity is markedly increased with increase of iron concentration, i.e. of the quantity of fine particles. Increase of condensation temperature is accompanied by increase of nanoparticle size, resulting in a considerable reduction of the total area of nanoparticle surface, and, hence of their sorption capacity. In addition to condensation temperature, the size and phase composition of nanoparticles can also be controlled by heat treatment of initial condensate, produced at low condensation temperatures. Magnetite nanoparticles can be transferred into stable colloid systems.

First day of an oil spill on the open sea: early mass transfers of hydrocarbons to air and water.

PubMed

Gros, Jonas; Nabi, Deedar; Würz, Birgit; Wick, Lukas Y; Brussaard, Corina P D; Huisman, Johannes; van der Meer, Jan R; Reddy, Christopher M; Arey, J Samuel

2014-08-19

During the first hours after release of petroleum at sea, crude oil hydrocarbons partition rapidly into air and water. However, limited information is available about very early evaporation and dissolution processes. We report on the composition of the oil slick during the first day after a permitted, unrestrained 4.3 m(3) oil release conducted on the North Sea. Rapid mass transfers of volatile and soluble hydrocarbons were observed, with >50% of ≤C17 hydrocarbons disappearing within 25 h from this oil slick of <10 km(2) area and <10 μm thickness. For oil sheen, >50% losses of ≤C16 hydrocarbons were observed after 1 h. We developed a mass transfer model to describe the evolution of oil slick chemical composition and water column hydrocarbon concentrations. The model was parametrized based on environmental conditions and hydrocarbon partitioning properties estimated from comprehensive two-dimensional gas chromatography (GC×GC) retention data. The model correctly predicted the observed fractionation of petroleum hydrocarbons in the oil slick resulting from evaporation and dissolution. This is the first report on the broad-spectrum compositional changes in oil during the first day of a spill at the sea surface. Expected outcomes under other environmental conditions are discussed, as well as comparisons to other models.

Selective removal of composite sealants with near-UV laser pulses

NASA Astrophysics Data System (ADS)

Louie, Tiffany M.; Jones, Robert S.; Sarma, Anupama V.; Fried, Daniel

2004-05-01

It is often necessary to replace pit and fissure sealants and composite restorations. This task is complicated by the necessity for complete removal of the remaining composite to enable suitable adhesion of new composite. Previous studies have shown that lasers pulses from a frequency-tripled Nd:YAG laser (355-nm) can selectively remove residual composite after orthodontic bracket removal on enamel surfaces. UV laser light is preferentially absorbed by polymeric resins and the organic content of the tooth enamel. The objective of this study was to determine if such laser pulses are suitable for selective removal of the old composite from pit and fissure sealants and restorations without damaging surrounding sound tissues. Optical coherence tomography was used to acquire optical cross sections of the occlusal topography and peripheral tooth structure non-destructively before application of the sealants, after sealant application, and after sealant removal with 355-nm laser pulses with intensities ranging from 0-10 J/cm2. Thermocouples were used to monitor the temperature in the pulp chamber during composite removal under clinically relevant ablation rates, i.e., 30 Hz and 30 mJ per laser pulse. At an irradiation intensity of 1.3 J/cm2 pit and fissure sealants were completely removed without visible damage to the underlying enamel. At intensities above 1.5 J/cm2, the laser removes the resin layer while at the same time preferentially etching the surface of the enamel. Temperature excursions in the pulp chamber of extracted teeth was limited to less than 5°C if air-cooling was used during the rapid removal (1-2 min) of sealants, water-cooling was not needed. This is the first presentation of a method for the selective removal of composite restorative materials without damage to the underlying sound tooth structure.

30 CFR 57.5006 - Air Quality-Surface Only [Reserved

Code of Federal Regulations, 2014 CFR

2014-07-01

... 30 Mineral Resources 1 2014-07-01 2014-07-01 false Air Quality-Surface Only [Reserved] 57.5006... Quality, Radiation, Physical Agents, and Diesel Particulate Matter Air Quality-Surface and Underground...-Nitrosodimethylamine. Air Quality—Surface Only [Reserved] Air Quality—Underground Only ...

30 CFR 57.5006 - Air Quality-Surface Only [Reserved

Code of Federal Regulations, 2012 CFR

2012-07-01

... 30 Mineral Resources 1 2012-07-01 2012-07-01 false Air Quality-Surface Only [Reserved] 57.5006... Quality, Radiation, Physical Agents, and Diesel Particulate Matter Air Quality-Surface and Underground...-Nitrosodimethylamine. Air Quality—Surface Only [Reserved] Air Quality—Underground Only ...

30 CFR 57.5006 - Air Quality-Surface Only [Reserved

Code of Federal Regulations, 2013 CFR

2013-07-01

... 30 Mineral Resources 1 2013-07-01 2013-07-01 false Air Quality-Surface Only [Reserved] 57.5006... Quality, Radiation, Physical Agents, and Diesel Particulate Matter Air Quality-Surface and Underground...-Nitrosodimethylamine. Air Quality—Surface Only [Reserved] Air Quality—Underground Only ...

Preparation of Water-Repellent Glass by Sol-Gel Process Using Perfluoroalkylsilane and Tetraethoxysilane.

PubMed

Jeong, Hye-Jeong; Kim, Dong-Kwon; Lee, Soo-Bok; Kwon, Soo-Han; Kadono, Kohei

2001-03-01

Coating films on glass substrate were prepared by sol-gel process using alkoxide solutions containing perfluoroalkylsilane (PFAS) and tetraethoxysilane (TEOS). The physical properties of the coating films were characterized by SEM, FT-IR, and XRD. And their surface properties were investigated by measuring contact angles and atomic compositions. Transparent coating films with smooth surface and uniform thickness could be obtained. The contact angles of the coating films for water and methylene iodide are extremely high, at 118 degrees and 97 degrees, respectively, and their surface free energies are about 9.7 dyn/cm. It was found that the water-repellent glass prepared is very hydrophobic and exhibits excellent water-repellency. Hydrophobic perfluoroalkyl groups are preferentially enriched to the outermost layer at the coating film-air interface, and two layers probably exist in the coating film. The upper layer oriented toward the air is composed of mainly perfluoroalkyl groups originating from PFAS, and the lower layer is composed of mainly -OSiO- groups originating from TEOS. The heat treatment after drying step cannot influence the surface enrichment of the perfluoroalkyl group. The hydrolysis reaction should be more completely done before the dip coating step to obtain lower surface free energy. The burning temperature should be less than 300 degrees C because the perfluoroalkyl group begins to decompose from this temperature. Copyright 2001 Academic Press.

Development of wear resistant NFSS-HA novel biocomposites and study of their tribological properties for orthopaedic applications.

PubMed

Younesi, M; Bahrololoom, M E; Fooladfar, H

2010-02-01

Implants made of nickel free austenitic stainless steel can reduce the toxic effect of released nickel ion and compounds from the conventional stainless steels. On the other hand, hydroxyapatite is a ceramic which has been used in orthopaedic applications due to its good osteoconductivity, biocompatibility and bioactivity. However, there is no evidence in the literature up to now on producing composites based on nickel free stainless steel and hydroxyapatite and study of their tribology. The aim of this work was to produce novel biocomposites made up of nickel free stainless steel with hydroxyapatite (prepared by heat treating bone ash) and studying their tribology under various loads in air and in Ringer's physiological solution. Different amounts of hydroxyapatite powder (10, 20, 30 and 40% Vol.) were added to this nickel free stainless steel powder to get the biocomposites. Variation of their density, hardness, wear resistance and friction with the ceramic (hydroxyapatite) content and wear load were investigated in air and in Ringer's solution. The density of the composites was decreased by increasing the volume percentage of the hydroxyapatite, while wear resistance of the composites was increased. The wear mechanism of these composites was changed by increasing the wear load and consequently the volume loss was enhanced dramatically. Furthermore, by increasing the sliding distance, the rate of volume loss was decreased slightly. The friction coefficient of the composites was also decreased by increasing the weight percentage of hydroxyapatite. Effect of the physiological Ringer's solution on wear resistance and friction coefficient of the composites was nearly negligible. The wear mechanisms of the samples were identified by studying the SEM images of the worn surfaces of the tested samples in different wear loads and HA contents. Copyright 2009 Elsevier Ltd. All rights reserved.

Study of Surface Roughness and Cutting force in machining for 6068 Aluminium alloy

NASA Astrophysics Data System (ADS)

Purushothaman, D.; Kaushik Yanamundra, Krishna; Krishnan, Gokul; Perisamy, C.

2018-04-01

Metal matrix composites, in particular, Aluminium Hybrid Composites are gaining increasing attention for applications in air and land because of their superior strength to weight ratio, density and high temperature resistance. Aluminium alloys are being used for a wide range of applications in Aerospace and Automobile industries, to name a few. The Aluminium Alloy 6068 has been used as the specimen. It is mainly composed of Aluminium (93.22 - 97.6 %), Magnesium (0.60 - 1.2 %), Silicon (0.60 - 1.4 %) and Bismuth (0.60 - 1.1 %). Aluminium 6068 is widely used for manufacturing aircraft structures, fuselages and wings. It is also extensively used in fabricating automobile parts such as wheel spacers. In this study, tests for the measurement of surface roughness and cutting force has been carried out on the specimen, the results evaluated and conclusions are drawn. Also the simulation of the same is carried out in a commercial FE software – ABAQUS.

Fabrication of heterostructured BiOBr/Bi24O31Br10/TiO2 photocatalyst by pyrolysis of MOF composite for dye degradation

NASA Astrophysics Data System (ADS)

Zhu, Shuai-Ru; Wu, Meng-Ke; Zhao, Wen-Na; Yi, Fei-Yan; Tao, Kai; Han, Lei

2017-11-01

The pyrolysis of metal-organic frameworks has emerged as a promising route to synthesize metal oxides with diverse phase compositions, morphologies, sizes and surface areas. The BiOBr/Bi24O31Br10/TiO2 (BBT) heterostructures have been achieved for the first time by calcining BiOBr/MIL-125(Ti) composite at 500 °C in air. The BBT-2 composite exhibited the highest photocatalytic performance for degradation of RhB under visible light irradiation. The enhanced photocatalytic activity is attributed to narrower band-gaps and synergistic effect originating from the well-aligned straddling band-structures between BiOBr, Bi24O31Br10 and TiO2, also result in an faster interfacial charge transfer during the photocatalytic reaction. This work could be conductive to the design of heterostructured photocatalysts contained metal oxide by pyrolytic conversion of metal-organic frameworks for significantly improved photocatalytic performance.

76 FR 79270 - Aviation Proceedings, Agreements Filed the Week Ending December 3, 2011

Federal Register 2010, 2011, 2012, 2013, 2014

2011-12-21

...: Members of the International Air Transport Association. Subject: Composite Passenger Tariff Coordinating Conference Singapore, 14 October 2011. Composite Resolution 017i. (Memo PTC COMP 1652,). Intended Effective... of the International Air Transport Association. Subject :Composite Passenger Tariff Coordinating...

Experimental study of a passive thermal management system for high-powered lithium ion batteries using porous metal foam saturated with phase change materials

NASA Astrophysics Data System (ADS)

Li, W. Q.; Qu, Z. G.; He, Y. L.; Tao, Y. B.

2014-06-01

A highly efficient thermal strategy to manage a high-powered Li-ion battery package within the required safe temperature range is of great demand for electric vehicles (EVs) applications. A sandwiched cooling structure using copper metal foam saturated with phase change materials was designed. The thermal efficiency of the system was experimentally evaluated and compared with two control cases: a cooling mode with pure phase change materials and an air-cooling mode. The results showed that the thermal management with air natural convection cannot fulfill the safety demand of the Li-ion battery. The use of pure PCM can dramatically reduce the surface temperature and maintain the temperature within an allowable range due to the latent heat absorption and the natural convection of the melted PCM during the melting process. The foam-paraffin composite further reduced the battery's surface temperature and improved the uniformity of the temperature distribution caused by the improvement of the effective thermal conductivity. Additionally, the battery surface temperature increased with an increase in the porosity and the pore density of the metal foam.

Mars surface based factory. Phase 2, task 1C: Computer control of a water treatment system to support a space colony on Mars

NASA Technical Reports Server (NTRS)

Fuller, John; Ali, Warsame; Willis, Danette

1989-01-01

In a continued effort to design a surface based factory on Mars for the production of oxygen and water, a preliminary study was made of the surface and atmospheric composition on Mars and determined the mass densities of the various gases in the Martian atmosphere. Based on the initial studies, oxygen and water were determined to be the two products that could be produced economically under the Martian conditions. Studies were also made on present production techniques to obtain water and oxygen. Analyses were made to evaluate the current methods of production that were adaptable to the Martian conditions. Even though the initial effort was the production of oxygen and water, it was found necessary to produce some diluted gases that can be mixed with the oxygen produced to constitute 'breathable' air. The conceptual design of a breathable air manufacturing system, a means of drilling for underground water, and storage of water for future use were completed. The design objective was the conceptual design of an integrated system for the supply of quality water for biological consumption, farming, residential and industrial use.

Thermal Ignition

NASA Astrophysics Data System (ADS)

Boettcher, Philipp Andreas

Accidental ignition of flammable gases is a critical safety concern in many industrial applications. Particularly in the aviation industry, the main areas of concern on an aircraft are the fuel tank and adjoining regions, where spilled fuel has a high likelihood of creating a flammable mixture. To this end, a fundamental understanding of the ignition phenomenon is necessary in order to develop more accurate test methods and standards as a means of designing safer air vehicles. The focus of this work is thermal ignition, particularly auto-ignition with emphasis on the effect of heating rate, hot surface ignition and flame propagation, and puffing flames. Combustion of hydrocarbon fuels is traditionally separated into slow reaction, cool flame, and ignition regimes based on pressure and temperature. Standard tests, such as the ASTM E659, are used to determine the lowest temperature required to ignite a specific fuel mixed with air at atmospheric pressure. It is expected that the initial pressure and the rate at which the mixture is heated also influences the limiting temperature and the type of combustion. This study investigates the effect of heating rate, between 4 and 15 K/min, and initial pressure, in the range of 25 to 100 kPa, on ignition of n-hexane air mixtures. Mixtures with equivalence ratio ranging from 0.6 to 1.2 were investigated. The problem is also modeled computationally using an extension of Semenov's classical auto-ignition theory with a detailed chemical mechanism. Experiments and simulations both show that in the same reactor either a slow reaction or an ignition event can take place depending on the heating rate. Analysis of the detailed chemistry demonstrates that a mixture which approaches the ignition region slowly undergoes a significant modification of its composition. This change in composition induces a progressive shift of the explosion limit until the mixture is no longer flammable. A mixture that approaches the ignition region sufficiently rapidly undergoes only a moderate amount of thermal decomposition and explodes quite violently. This behavior can also be captured and analyzed using a one-step reaction model, where the heat release is in competition with the depletion of reactants. Hot surface ignition is examined using a glow plug or heated nickel element in a series of premixed n-hexane air mixtures. High-speed schlieren photography, a thermocouple, and a fast response pressure transducer are used to record flame characteristics such as ignition temperature, flame speed, pressure rises, and combustion mode. The ignition event is captured by considering the dominant balance of diffusion and chemical reaction that occurs near a hot surface. Experiments and models show a dependence of ignition temperature on mixture composition, initial pressure, and hot surface size. The mixtures exhibit the known lower flammability limit where the maximum temperature of the hot surface was insufficient at igniting the mixture. Away from the lower flammability limit, the ignition temperature drops to an almost constant value over a wide range of equivalence ratios (0.7 to 2.8) with large variations as the upper flammability limit is approached. Variations in the initial pressure and equivalence ratio also give rise to different modes of combustion: single flame, re-ignition, and puffing flames. These results are successfully compared to computational results obtained using a flamelet model and a detailed chemical mechanism for n-heptane. These different regimes can be delineated by considering the competition between inertia, i.e., flame propagation, and buoyancy, which can be expressed in the Richardson number. In experiments of hot surface ignition and subsequent flame propagation a 10 Hz puffing flame instability is visible in mixtures that are stagnant and premixed prior to the ignition sequence. By varying the size of the hot surface, power input, and combustion vessel volume, we determined that the instability is a function of the interaction of the flame with the fluid flow induced by the combustion products rather than the initial plume established by the hot surface. The phenomenon is accurately reproduced in numerical simulations and a detailed flow field analysis revealed a competition between the inflow velocity at the base of the flame and the flame propagation speed. The increasing inflow velocity, which exceeds the flame propagation speed, is ultimately responsible for creating a puff. The puff is then accelerated upward, allowing for the creation of the subsequent instabilities. The frequency of the puffing is proportional to the gravitational acceleration and inversely proportional to the flame speed. We propose a relation describing the dependence of the frequency on gravitational acceleration, hot surface diameter, and flame speed. This relation shows good agreement for lean and rich n-hexane-air as well as lean hydrogen-air flames.

Influence of handpiece maintenance sprays on resin bonding to dentin.

PubMed

Sugawara, Toyotarou; Kameyama, Atsushi; Haruyama, Akiko; Oishi, Takumi; Kukidome, Nobuyuki; Takase, Yasuaki; Tsunoda, Masatake

2010-01-01

To investigate the influence of maintenance spray on resin bonding to dentin. The crown of extracted, caries-free human molars was transversally sectioned with a model trimmer to prepare the dentin surfaces from mid-coronal sound dentin, and then uniformly abraded with #600 silicon carbide paper. The dentin surfaces were randomly divided into three groups: oil-free spray group where maintenance cleaner for air bearing handpieces was sprayed onto the dentin surface for 1 s and rinsed with water spray for 30 s; oil-containing spray group where maintenance cleaner for micro motor handpieces was sprayed onto the dentin surface for 1 s and rinsed with water spray for 30 s; and control group where the surface was rinsed with water spray for 30 s and then air-dried. These surfaces were then bonded with Clearfil SE Bond (Kuraray Medical), and resin composite (Clearfil AP-X, Kuraray Medical) build-up crowns were incrementally constructed on the bonded surfaces. After storage for 24 h in 37°C water, the bonded teeth were sectioned into hour-glass shaped slices (0.7-mm thick) perpendicular to the bonded surfaces. The specimens were then subjected to microtensile bond strength (μTBS) testing at a crosshead speed of 1.0 mm/min. Data were analyzed with one-way ANOVA and the Tukey-Kramer test. Maintenance spray-contaminated specimens (oil-free and oil-containing spray groups) showed significantly lower μTBS than control specimens (P < 0.05). However, there was no significant difference between the spray-contaminated groups (P > 0.05). Maintenance spray significantly reduces the bond strength of Clearfil SE Bond to dentin.

Aerosol Composition and Variability in Baltimore Measured during DISCOVER-AQ

NASA Astrophysics Data System (ADS)

Beyersdorf, A. J.; Ziemba, L. D.; Chen, G.; Thornhill, K. L.; Winstead, E. L.; Diskin, G. S.; Chatfield, R. B.; Natraj, V.; Anderson, B. E.

2012-12-01

In order to relate satellite-based measurements of aerosols to ground-level air quality, the correlation between aerosol optical properties (wavelength-dependent scattering and absorption measured by satellites) and mass measurements of aerosol loading (i.e. PM2.5 used for air quality monitoring) must be understood. This connection varies with many factors including those specific to the aerosol type (such as composition, size, hygroscopicity, and mass scattering and absorption efficiencies) and to the surrounding atmosphere (such as temperature, relative humidity and altitude). The DISCOVER-AQ (Deriving Information on Surface conditions from COlumn and VERtically resolved observations relevant to Air Quality) project was designed to provide a unique dataset for determining variability in and correlations between aerosol loading, composition, optical properties and meteorological conditions. Extensive in-situ profiling of the lower atmosphere in the Baltimore-Washington D.C. region was performed during fourteen flights during July 2011. Identical flight plans and profile locations throughout the campaign provide meaningful statistics for analysis. Measured aerosol mass was composed primarily of ammonium sulfate (campaign average of 36%) and water-soluble organics (58%). A distinct difference in composition was related to aerosol loading with high-loading days having a proportionally larger percentage of ammonium sulfate (up to 60%). This composition shift causes a change in the water-uptake potential (hygroscopicity) of the aerosols with higher relative organic composition decreasing water-uptake. On average, sulfate mass increased during the day due to increased photochemistry, while organics decreased. Analysis of the linkage between aerosol loading and optical properties was also performed. The absorption by black carbon was dependent on the amount of organic coating with an increase in mass absorption efficiency from 7.5 m2/g for bare soot to 16 m2/g at an organic mass fraction of 70%. The organic fraction was also found to correlate with the absorption Angstrom exponent which is a solely optical measurement. This relationship allows for a possible understanding of aerosol composition based on solely-optical methods (such as satellite-based sensors). Comparison of aerosol composition to scattering indicated significant scattering from non-hydrophilic particles. The origin seemed to be hydrophobic organic material, and the scattering effects were roughly the same magnitude as the water-soluble organics. Such aerosols are not simulated in many air pollution models, and require more field study. 246 profiles were performed at six locations throughout the region. Variability in aerosol scattering (as a proxy for aerosol optical depth) amongst the six sites is dependent on variability in aerosol loading, composition, and relative humidity (the amount of water available for water uptake onto the aerosols). Aerosol loading was found to be the predominant source accounting for 68% on average of the measured variability in scattering with minor contributions from relative humidity (24%) and aerosol composition (8%).

BOREAS TE-5 Surface Meteorological and Radiation Data

NASA Technical Reports Server (NTRS)

Hall, Forrest G. (Editor); Curd, Shelaine (Editor); Ehleriinger, Jim; Brooks, J. Renee; Flanagan, Larry

2000-01-01

The BOREAS TE-5 team collected measurements in the NSA and SSA on gas exchange, gas composition, and tree growth. Measurements of meteorological data, including air and soil temperature, RH, and PPFD, were 30-minute intervals during the 1994 IFCs at various sites in the BOREAS NSA and SSA. The data are provided in tabular ASCII files. The data files are available on a CD-ROM (see document number 20010000884), or from the Oak Ridge National Laboratory (ORNL) Distributed Active Archive Center (DAAC).

Results from the Telescope Array Experiment

NASA Astrophysics Data System (ADS)

Jui, Charles C. H.; Telescope Array Collaboration

2016-04-01

The Telescope Array (TA) is the largest ultrahigh energy cosmic ray detector in the northern hemisphere. The experiment consists of three fluorescence stations viewing the air space over a surface array of 507 scintillation counters deployed over 700 square kilometers. TA has been in operation since 2008. The most recent results from TA, including that of composition studies and search for arrival direction anisotropy, will be presented. We will also report on the progress of the new TA low energy extension (TALE).

Technical and economic assessment of swept-wing span-distributed load concepts for civil and military air cargo transports

NASA Technical Reports Server (NTRS)

1977-01-01

The feasibility of large freighter aircraft was assessed, including the impact of military requirements on the performance, economics, and fuel consumption characteristics. Only configurations having net payloads of 272,155 to 544,311 kilograms contained within swept wings of constant chord were studied. These configurations were of advanced composite construction with controllable winglets and full-span digitally-controlled trailing-edge surfaces. Civil, military, and joint civil/military production programs were considered.

Benefits and limitations of composites in carrier-based aircraft

NASA Technical Reports Server (NTRS)

Mcerlean, Donald P.

1992-01-01

There are many unique aspects of Navy air missions that lead to the differentiation between the design and performance of ship and shore-based aircraft. The major aspects are discussed from which essentially all Navy aircraft design requirements derive. (1) Navy aircraft operate from carriers at sea imposes a broad spectrum of physical conditions, constraints, and requirements ranging from the harsh sea environment, the space limitations of a carrier, takeoff and landing requirements as well as for endurance at long distances from the carrier. (2) Because the carrier and its airwing are intended to be capable of responding to a broad range of contingencies, mission flexibility is essential (maximum weapon carriage, rapid reconfiguration, multiple mission capability). (3) The embarked aircraft provides the long range defense of the battle group against air, surface and subsurface launched antiship missiles. (4) The carrier and its aircraft must operate independently and outside of normal supply lines. Taking into account these aspects, the use of composite materials in the design and performance of naval aircraft is outlined, also listing advantages and disadvantages.

The influence of concrete mixture’s rheological properties on the quality of formed concrete surfaces

NASA Astrophysics Data System (ADS)

Daukšys, M.; Klovas, A.; Venčkauskas, L.

2017-09-01

This study mainly lays emphasis on examining the influence of concrete mixture rheological properties on the quality of formed concrete surfaces. Mixture’s fine aggregate change was taken into the consideration. Over the course of concrete mixture preparation the inner ratio of fine aggregate (sand: fraction of 0/1 and 0/4) was changed. The idea was to increase the quantity of fine particles in the total aggregate’s volume therefore quantity of sand (fraction 0/1) was increased. Six different concrete mixture’s compositions were designed as well as three specimens (concrete piles of 1m2 surface area) were casted. Rheological properties of concrete mixtures were analytically obtained and the quality of formed concrete surfaces was evaluated using image analysis method “BetonGUY 2.0”. As can be obtained from the dependence between concrete mixture rheological properties and its formed surface quality, the increase of concrete mixture’s yield stress and plastic viscosity reduces the quantity of air pores on formed concrete surfaces.

Coalescence-induced jumping of micro-droplets on heterogeneous superhydrophobic surfaces

NASA Astrophysics Data System (ADS)

Attarzadeh, Reza; Dolatabadi, Ali

2017-01-01

The phenomenon of droplets coalescence-induced self-propelled jumping on homogeneous and heterogeneous superhydrophobic surfaces was numerically modeled using the volume of fluid method coupled with a dynamic contact angle model. The heterogeneity of the surface was directly modeled as a series of micro-patterned pillars. To resolve the influence of air around a droplet and between the pillars, extensive simulations were performed for different droplet sizes on a textured surface. Parallel computations with the OpenMP algorithm were used to accelerate computation speed to meet the convergence criteria. The composition of the air-solid surface underneath the droplet facilitated capturing the transition from a no-slip/no-penetration to a partial-slip with penetration as the contact line at triple point started moving to the air pockets. The wettability effect from the nanoscopic roughness and the coating was included in the model by using the intrinsic contact angle obtained from a previously published study. As the coalescence started, the radial velocity of the coalescing liquid bridge was partially reverted to the upward direction due to the counter-action of the surface. However, we found that the velocity varied with the size of the droplets. A part of the droplet kinetic energy was dissipated as the merged droplet started penetrating into the cavities. This was due to a different area in contact between the liquid and solid and, consequently, a higher viscous dissipation rate in the system. We showed that the effect of surface roughness is strongly significant when the size of the micro-droplet is comparable with the size of the roughness features. In addition, the relevance of droplet size to surface roughness (critical relative roughness) was numerically quantified. We also found that regardless of the viscous cutoff radius, as the relative roughness approached the value of 44, the direct inclusion of surface topography was crucial in the modeling of the droplet-surface interaction. Finally, we validated our model against existing experimental data in the literature, verifying the effect of relative roughness on the jumping velocity of a merged droplet.

Agile Thermal Management STT-RX. Towards High Energy Density, High Conductivity Thermal Energy Storage Composites (PREPRINT)

DTIC Science & Technology

2011-12-01

management system. This paper describes recent development of salt hydrate-based TES composites at the Air Force Research Laboratory. Salt hydrates are...composites. 15. SUBJECT TERMS thermal energy storage, composite, salt hydrate, graphic foam 16. SECURITY CLASSIFICATION OF: 17. LIMITATION OF...part of a thermal management system. This paper describes recent development of salt hydrate-based TES composites at the Air Force Research

Evaluation of indoor air composition time variation in air-tight occupied spaces during night periods

NASA Astrophysics Data System (ADS)

Markov, Detelin

2012-11-01

This paper presents an easy-to-understand procedure for prediction of indoor air composition time variation in air-tight occupied spaces during the night periods. The mathematical model is based on the assumptions for homogeneity and perfect mixing of the indoor air, the ideal gas model for non-reacting gas mixtures, mass conservation equations for the entire system and for each species, a model for prediction of basal metabolic rate of humans as well as a model for prediction of O2 consumption rate and both CO2 and H2O generation rates by breathing. Time variation of indoor air composition is predicted at constant indoor air temperature for three scenarios based on the analytical solution of the mathematical model. The results achieved reveal both the most probable scenario for indoor air time variation in air-tight occupied spaces as well as the cause for morning tiredness after having a sleep in a modern energy efficient space.

Evaluation of equivalent defect heat generation in carbon epoxy composite under powerful ultrasonic stimulation by using infrared thermography

NASA Astrophysics Data System (ADS)

Derusova, D. A.; Vavilov, V. P.; Pawar, S. S.

2015-04-01

Low velocity impact is a frequently observed event during the operation of an aircraft composite structure. This type of damage is aptly called as “blind-side impact damage” as it is barely visible as a dent on the impacted surface, but may produce extended delaminations closer to the rear surface. One-sided thermal nondestructive testing is considered as a promising technique for detecting impact damage but because of diffusive nature of optical thermal signals there is drop in detectability of deeper subsurface defects. Ultrasonic Infrared thermography is a potentially attractive nondestructive evaluation technique used to detect the defects through observation of vibration-induced heat generation. Evaluation of the energy released by such defects is a challenging task. In this study, the thin delaminations caused by impact damage in composites and which are subjected to ultrasonic excitation are considered as local heat sources. The actual impact damage in a carbon epoxy composite which was detected by applying a magnetostrictive ultrasonic device is then modeled as a pyramid-like defect with a set of delaminations acting as an air-filled heat sources. The temperature rise expected on the surface of the specimen was achieved by varying energy contribution from each delamination through trial and error. Finally, by comparing the experimental temperature elevations in defective area with the results of temperature simulations, we estimated the energy generated by each defect and defect power of impact damage as a whole. The results show good correlation between simulations and measurements, thus validating the simulation approach.

Preparation of a new adsorbent from activated carbon and carbon nanofiber (AC/CNF) for manufacturing organic-vacbpour respirator cartridge

PubMed Central

2013-01-01

In this study a composite of activated carbon and carbon nanofiber (AC/CNF) was prepared to improve the performance of activated carbon (AC) for adsorption of volatile organic compounds (VOCs) and its utilization for respirator cartridges. Activated carbon was impregnated with a nickel nitrate catalyst precursor and carbon nanofibers (CNF) were deposited directly on the AC surface using catalytic chemical vapor deposition. Deposited CNFs on catalyst particles in AC micropores, were activated by CO2 to recover the surface area and micropores. Surface and textural characterizations of the prepared composites were investigated using Brunauer, Emmett and Teller’s (BET) technique and electron microscopy respectively. Prepared composite adsorbent was tested for benzene, toluene and xylene (BTX) adsorption and then employed in an organic respirator cartridge in granular form. Adsorption studies were conducted by passing air samples through the adsorbents in a glass column at an adjustable flow rate. Finally, any adsorbed species not retained by the adsorbents in the column were trapped in a charcoal sorbent tube and analyzed by gas chromatography. CNFs with a very thin diameter of about 10-20 nm were formed uniformly on the AC/CNF. The breakthrough time for cartridges prepared with CO2 activated AC/CNF was 117 minutes which are significantly longer than for those cartridges prepared with walnut shell- based activated carbon with the same weight of adsorbents. This study showed that a granular form CO2 activated AC/CNF composite could be a very effective alternate adsorbent for respirator cartridges due to its larger adsorption capacities and lower weight. PMID:23369424

Calibration of diatom-pH-alkalinity methodology for the interpretation of the sedimentary record in Emerald Lake Integrated watershed study. Final report, 6 May 1985-10 October 1986

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

Holmes, R.W.

1986-10-10

The present study was designed to establish quantitative relationships between lake air-equilibrated pH, alkalinity, and diatoms occurring in the surface sediments in high-elevation Sierra Nevada Lakes. These relationships provided the necessary information to develop predictive equations relating lake pH to the composition of surface-sediment diatom assemblages in 27 study lakes. Using the Hustedt diatom pH classification system, Index B of Renberg and Hellberg, and multiple linear regression analysis, two equations were developed which predict lake pH from the relative abundance of sediment diatoms occurring in each of four diatom pH groupings.

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

NONE

Under contract with the US Department of Energy (DE-AC22-92PCO0367), Pittsburgh Energy Technology Center, Radian Corporation has conducted a test program to collect and analyze size-fractionated stack gas particulate samples for selected inorganic hazardous air pollutants (HAPS). Specific goals of the program are (1) the collection of one-gram quantities of size-fractionated stack gas particulate matter for bulk (total) and surface chemical charactization, and (2) the determination of the relationship between particle size, bulk and surface (leachable) composition, and unit load. The information obtained from this program identifies the effects of unit load, particle size, and wet FGD system operation on themore » relative toxicological effects of exposure to particulate emissions.« less

Cu-modified carbon spheres/reduced graphene oxide as a high sensitivity of gas sensor for NO2 detection at room temperature

NASA Astrophysics Data System (ADS)

Su, Zhibin; Tan, Li; Yang, Ruiqiang; Zhang, Yu; Tao, Jin; Zhang, Nan; Wen, Fusheng

2018-03-01

Nitrogen dioxide (NO2) as one of the most serious air pollution is harmful to people's health, therefore high-performance gas sensors is critically needed. Here, Cu-modified carbon spheres/reduced graphene oxide (Cu@CS/RGO) composite have been prepared as NO2 gas sensor material. Carbon sphere in the interlayer of RGO can increase the specific surface area of RGO. Copper nanoparticles decorated on the surface of CS can effectively enhance the adsorption activity of RGO as supplier of free electrons. The experimental results showed that its particular structure improved the gas sensitivity of RGO at different NO2 concentrations at room temperature.

Model polymer etching and surface modification by a time modulated RF plasma jet: role of atomic oxygen and water vapor

NASA Astrophysics Data System (ADS)

Luan, P.; Knoll, A. J.; Wang, H.; Kondeti, V. S. S. K.; Bruggeman, P. J.; Oehrlein, G. S.

2017-01-01

The surface interaction of a well-characterized time modulated radio frequency (RF) plasma jet with polystyrene, poly(methyl methacrylate) and poly(vinyl alcohol) as model polymers is investigated. The RF plasma jet shows fast polymer etching but mild chemical modification with a characteristic carbonate ester and NO formation on the etched surface. By varying the plasma treatment conditions including feed gas composition, environment gaseous composition, and treatment distance, we find that short lived species, especially atomic O for Ar/1% O2 and 1% air plasma and OH for Ar/1% H2O plasma, play an essential role for polymer etching. For O2 containing plasma, we find that atomic O initiates polymer etching and the etching depth mirrors the measured decay of O atoms in the gas phase as the nozzle-surface distance increases. The etching reaction probability of an O atom ranging from 10-4 to 10-3 is consistent with low pressure plasma research. We also find that adding O2 and H2O simultaneously into Ar feed gas quenches polymer etching compared to adding them separately which suggests the reduction of O and OH density in Ar/O2/H2O plasma.

Development and evaluation of a silver mordenite composite sorbent for the partitioning of xenon from krypton in gas compositions

DOE PAGES

Garn, Troy G.; Greenhalgh, Mitchell; Law, Jack D.

2015-12-22

A new engineered form composite sorbent for the selective separation of xenon from krypton in simulant composition off-gas streams resulting from the reprocessing of used nuclear fuel has been developed and evaluated. A sodium mordenite powder was incorporated into a macroporous polymer binder, formed into spherical beads and successfully converted to a 9 wt.% silver form composite sorbent. The final engineered form sorbent retained the characteristic surface area indicative of sodium mordenite powder. The sorbent was evaluated for xenon adsorption potential with capacities measured as high as 30 millimoles of xenon per kilogram of sorbent achieved at ambient temperature andmore » 460 millimoles of xenon per kilogram sorbent at 220 K. Xenon/krypton selectivity was calculated to be 22.4 with a 1020 µL/L xenon, 150 µL/L krypton in a balance of air feed gas at 220 K. Furthermore, adsorption/desorption thermal cycling effects were evaluated with results indicating sorbent performance was not significantly impacted while undergoing numerous adsorption/desorption thermal cycles.« less

Total etch technique and cavity isolation.

PubMed

Fusayama, T

1992-01-01

In the total etch technique for chemically adhesive composite restorations, the phosphoric acid penetrates only 10 microns or less into the vital dentin with the dentinal tubules being filled with the odontoblast processes. The acid is completely removed by subsequent air-water jet spray washing. The tubule apertures are perfectly sealed by the protective bonding agent layer with the resin tags adhering to the tubule walls and the resin-impregnated dentin surface. Isolation of the cavity from moisture contamination is required for only less than a few seconds after drying the etched cavity until the bonding agent coating and after this coating until the composite resin placement. Such a short time for isolation is quite easy even without a rubber dam when a trained assistant is cooperating.

Interface Engineering of Garnet Solid Electrolytes

NASA Astrophysics Data System (ADS)

Cheng, Lei

Solid lithium ion conductors represent a promising class of materials for next generation high energy density batteries, with the potential for enabling use of high capacity Li metal anodes and providing opportunities for novel lithium-free cathode materials. However, highly resistive interfaces stymie their practical use. This urgent scientific challenge requires mechanistic understanding of ion transport at interfaces, as well as development of novel processes to achieve low interfacial resistances. The goal of this PhD dissertation was to generate fundamental understandings of garnet-structured Al substituted Li7La3Zr2O 12 (LLZO) electrolyte surfaces and interfaces with lithium metal electrodes. Specifically in this research, the topmost surface microstructure, local chemical environment, and surface chemistry were carefully studied. The ceramic processing of garnet is discussed and ways to control the sintering behavior and microstructures were explored and successfully demonstrated. Factors contributing to high interfacial resistance were systematically studied. The source of the high interfacial impedance has been traced to the presence of Li2CO 3 on pellet surfaces resulting from air exposure after processing. In addition, it was discovered that surface grain boundaries are surprisingly fast ion transport pathways and surface microstructure is critically important to lithium ion transport at interfaces. Complex homo- and heterostructured LLZO solid electrolytes with controllable surface and bulk microstructures were successfully fabricated, which allowed the comparison and separation of the contribution from the surface and the bulk. Engineered pellet surfaces allowed us to achieve the lowest interfacial resistance ever reported for this composition, resulting in significantly improved cycling behavior. Lastly, it was found that LLZO surfaces can be effectively stabilized under air exposure conditions, preventing Li2CO3 formation and maintaining low interfacial resistances. This opens new opportunities for garnet solid electrolyte in practical applications.

Influence of material anisotropy on the hydroelastic response of composite plates in water

NASA Astrophysics Data System (ADS)

Akcabay, Deniz Tolga; Young, Yin Lu

2018-03-01

Flexible lightweight plate-like lifting surfaces in external flows have a diverse range of use from propelling and controlling marine and aerospace vehicles to converting wind and ocean energy to electrical energy. Design and analysis of such structures are complex for underwater applications where the water density is much higher than air. The hydrodynamic loads, which vary with the inflow speed, can significantly alter the dynamic response and stability. This paper focuses on the hydroelastic response of composite plates in water. The results show that the dynamics and stability of the structure can be significantly modified by taking advantage of the material anisotropic; on the contrary, careless composite material designs may lead to unwanted dynamic instability failures. The resonance frequencies, divergence speeds, and fluid loss coefficients change with material anisotropy and hydrodynamic loads. The resonance frequencies are much lower in water than in air. The critical divergence speed increases, if the principal fiber direction is oriented towards the inflow. Hydrodynamic damping is shown to be much higher than the material damping, and tend to increase with flow speed and to decrease with increasing modal frequency. The paper derives Response Amplitude Operators (RAOs) for sample composite plates in water and use them to predict the motion response when subject to stochastic flow excitations. We show how material anisotropy can be used to passively tailor the plate vibration response spectrum to limit or enhance flow-induced vibrations of the plate depending on the desired applications.

Canopies to Continents: What spatial scales are needed to represent landcover distributions in earth system models?

NASA Astrophysics Data System (ADS)

Guenther, A. B.; Duhl, T.

2011-12-01

Increasing computational resources have enabled a steady improvement in the spatial resolution used for earth system models. Land surface models and landcover distributions have kept ahead by providing higher spatial resolution than typically used in these models. Satellite observations have played a major role in providing high resolution landcover distributions over large regions or the entire earth surface but ground observations are needed to calibrate these data and provide accurate inputs for models. As our ability to resolve individual landscape components improves, it is important to consider what scale is sufficient for providing inputs to earth system models. The required spatial scale is dependent on the processes being represented and the scientific questions being addressed. This presentation will describe the development a contiguous U.S. landcover database using high resolution imagery (1 to 1000 meters) and surface observations of species composition and other landcover characteristics. The database includes plant functional types and species composition and is suitable for driving land surface models (CLM and MEGAN) that predict land surface exchange of carbon, water, energy and biogenic reactive gases (e.g., isoprene, sesquiterpenes, and NO). We investigate the sensitivity of model results to landcover distributions with spatial scales ranging over six orders of magnitude (1 meter to 1000000 meters). The implications for predictions of regional climate and air quality will be discussed along with recommendations for regional and global earth system modeling.

Out on a limb: Thermal microenvironments in the tropical forest canopy and their relevance to ants.

PubMed

Stark, Alyssa Y; Adams, Benjamin J; Fredley, Jennifer L; Yanoviak, Stephen P

2017-10-01

Small, cursorial ectotherms like ants often are immersed in the superheated air layers that develop millimeters above exposed, insolated surfaces (i.e., the thermal boundary layer). We quantified the thermal microenvironments around tree branches in the tropical rainforest canopy, and explored the effects of substrate color on the internal body temperature and species composition of arboreal ants. Branch temperatures during the day (09:00-16:00) were hottest (often > 50°C) and most variable on the upper surface, while the lowest and least variable temperatures occurred on the underside. Temperatures on black substrates declined with increasing distance above the surface in both the field and the laboratory. By contrast, a micro-scale temperature inversion occurred above white substrates. Wind events (ca. 2ms -1 ) eliminated these patterns. Internal temperatures of bodies of Cephalotes atratus workers experimentally heated in the laboratory were 6°C warmer on white vs. black substrates, and 6°C cooler than ambient in windy conditions. The composition of ant species foraging at baits differed between black-painted and unpainted tree branches, with a tendency for smaller ants to avoid the significantly hotter black surfaces. Collectively, these outcomes show that ants traversing canopy branches experience very heterogeneous thermal microenvironments that are partly influenced in predictable ways by branch surface coloration and breezy conditions. Copyright © 2017 Elsevier Ltd. All rights reserved.

Nature of catalytic activities of CoO nanocrystals in thermal decomposition of ammonium perchlorate.

PubMed

Li, Liping; Sun, Xuefei; Qiu, Xiaoqing; Xu, Jiaoxing; Li, Guangshe

2008-10-06

This work addresses the chemical nature of the catalytic activity of X-ray "pure" CoO nanocrystals. All samples were prepared by a solvothermal reaction route. X-ray diffraction indicates the formation of CoO in a cubic rock-salt structure, while infrared spectra and magnetic measurements demonstrate the coexistence of CoO and Co 3O 4. Therefore, X-ray "pure" CoO nanocrystals are a unique composite structure with a CoO core surrounded by an extremely thin Co 3O 4 surface layer, which is likely a consequence of the surface passivation of CoO nanocrystals from the air oxidation at room temperature. The CoO core shows a particle size of 22 or 280 nm, depending on the types of the precursors used. This composite nanostructure was initiated as a catalytic additive to promote the thermal decomposition of ammonium perchlorate (AP). Our preliminary investigations indicate that the maximum decomposition temperature of AP is significantly reduced in the presence of CoO/Co 3O 4 composite nanocrystals and that the maximum decomposition peak shifts toward lower temperatures as the loading amount of the composite nanocrystals increases. These findings are different from the literature reports when using many nanoscale oxide additives. Finally, the decomposition heat for the low-temperature decomposition stages of AP was calculated and correlated to the chemical nature of the CoO/Co 3O 4 composite nanostructures.

Highly potent silver-organoalkoxysilane antimicrobial porous nanomembrane

NASA Astrophysics Data System (ADS)

Umar, Sirajo; Liu, Yuanfeng; Wu, Yiguang; Li, Guangtao; Ding, Jiabo; Xiong, Runsong; Chen, Jinchun

2013-04-01

We used a simple electrospinning technique to fabricate a highly potent silver-organoalkoxysilane antimicrobial composite from AgNO3-polyvinylpyrrolidone (PVP)/3-aminopropyltrimethoxysilane (APTMS)/tetraethoxysilane (TEOS) solution. Spectroscopic and microscopic analyses of the composite showed that the fibers contain an organoalkoxysilane `skeleton,' 0.18 molecules/nm2 surface amino groups, and highly dispersed and uniformly distributed silver nanoparticles (5 nm in size). Incorporation of organoalkoxysilanes is highly beneficial to the antimicrobial mat as (1) amino groups of APTMS are adhesive and biocidal to microorganisms, (2) polycondensation of APTMS and TEOS increases the membrane's surface area by forming silicon bonds that stabilize fibers and form a composite mat with membranous structure and high porosity, and (3) the organoalkoxysilanes are also instrumental to the synthesis of the very small-sized and highly dispersed silver metal particles in the fiber mat. Antimicrobial property of the composite was evaluated by disk diffusion, minimum inhibition concentration (MIC), kinetic, and extended use assays on bacteria (Escherichia coli, Bacillus anthracis, Staphylococcus aureus, and Brucella suis), a fungus (Aspergillus niger), and the Newcastle disease virus. The membrane shows quick and sustained broad-spectrum antimicrobial activity. Only 0.3 mg of fibers is required to achieve MIC against all the test organisms. Bacteria are inhibited within 30 min of contact, and the fibers can be used repeatedly. The composite is silver efficient and environment friendly, and its membranous structure is suitable for many practical applications as in air filters, antimicrobial linen, coatings, bioadhesives, and biofilms.

Investigation of off-site airborne transport of lead from a superfund removal action site using lead isotope ratios and concentrations

USGS Publications Warehouse

Pribil, Michael J.; Maddaloni, Mark A.; Staiger, Kimberly; Wilson, Eric; Magriples, Nick; Ali, Mustafa; Santella, Dennis

2014-01-01

Lead (Pb) concentration and Pb isotopic composition of surface and subsurface soil samples were used to investigate the potential for off-site air transport of Pb from a former white Pb processing facility to neighboring residential homes in a six block area on Staten Island, NY. Surface and subsurface soil samples collected on the Jewett White Pb site were found to range from 1.122 to 1.138 for 206Pb/207Pb and 2.393 to 2.411 for 208Pb/207Pb. The off-site surface soil samples collected from residential backyards, train trestle, near site grass patches and background areas varied from 1.144 to 1.196 for 206Pb/207Pb and 2.427 to 2.464 for 208Pb/207Pb. Two soil samples collected along Richmond Terrace, where Jewett site soils accumulated after major rain events, varied from 1.136 to 1.147 for 206Pb/207Pb and 2.407 to 2.419 for 208Pb/207Pb. Lead concentration for on-site surface soil samples ranged from 450 to 8000 ug/g, on-site subsurface soil samples ranged from 90,000 to 240,000 ug/g and off-site samples varied from 380 to 3500 ug/g. Lead concentration and isotopic composition for the Staten Island off-site samples were similar to previously published data for other northeastern US cities and reflect re-suspension and re-mobilization of local accumulated Pb. The considerable differences in both the Pb isotopic composition and Pb concentration of on-site and off-site samples resulted in the ability to geochemically trace the transport of particulate Pb. Data in this study indicate minimal off-site surface transport of Pb from the Jewett site into the neighboring residential area.

76 FR 13444 - Aviation Proceedings, Agreements Filed the Week Ending February 26, 2011

Federal Register 2010, 2011, 2012, 2013, 2014

2011-03-11

...: Members of the International Air Transport Association. Subject: Composite Passenger Tariff Coordinating Conference, Geneva, 22 October 2010, Composite Resolutions 012, 026, 047a, 076xx, 076z, 087aa, Intended...: Members of the International Air Transport Association. Subject: Composite Passenger Tariff Coordinating...

Vertical characteristics of VOCs in the lower troposphere over the North China Plain during pollution periods.

PubMed

Sun, Jie; Wang, Yuesi; Wu, Fangkun; Tang, Guiqian; Wang, Lili; Wang, Yinghong; Yang, Yuan

2018-05-01

In recent years, photochemical smog and gray haze-fog have frequently appeared over northern China. To determine the spatial distribution of volatile organic compounds (VOC) during a pollution period, tethered balloon flights were conducted over a suburban site on the North China Plain. Statistical analysis showed that the VOCs concentrations peaked at the surface, and decreased with altitude. A rapid decrease appeared from the surface to 400 m, with concnetrations of alkanes, alkenes, aromatics and halocarbons decreasing by 48.0%, 53.3%, 43.3% and 51.1%, respectively. At heights in the range of 500-1000 m, alkenes concnetrations decline by 40.2%; alkanes and halocarbons concnetrations only decreased by 24.8% and 6.4%, respectively; and aromatics increased slightly by 5.5%. High concentrations VOCs covered a higher range of height (400 m) on heavy pollution days due to lacking of diffusion power. The VOCs concentrations decreased by 50% at 200 m on light pollution days. The transport of air mass affected the composition and concentration of high-altitude VOCs, especially on lightly polluted days. These air masses originated in areas with abundant traffic and combustion sources. Reactive aromatics (k OH >20,000 ppm -1  min -1 and k OH <20,000 ppm -1  min -1 ) were the main contributor to the ozone formation, accounting for 37%, on the surface on light pollution days. The contribution increased to 52% with pollution aggravated, and increased to 64% with height. The contributions of reactive aromatics were influenced by the degree of air mass aging. Under the umbrella of aging air mass, the contribution of reactive aromatics increased with height. Copyright © 2017. Published by Elsevier Ltd.

46 CFR 197.432 - Surface-supplied air diving.

Code of Federal Regulations, 2012 CFR

2012-10-01

... 46 Shipping 7 2012-10-01 2012-10-01 false Surface-supplied air diving. 197.432 Section 197.432...-supplied air diving. The diving supervisor shall insure that— (a) Surface-supplied air diving is conducted... space; and (f) The surface-supplied air diver has the equipment required by § 197.346 (b) or (d). ...

46 CFR 197.432 - Surface-supplied air diving.

Code of Federal Regulations, 2013 CFR

2013-10-01

... 46 Shipping 7 2013-10-01 2013-10-01 false Surface-supplied air diving. 197.432 Section 197.432...-supplied air diving. The diving supervisor shall insure that— (a) Surface-supplied air diving is conducted... space; and (f) The surface-supplied air diver has the equipment required by § 197.346 (b) or (d). ...

29 CFR 1910.425 - Surface-supplied air diving.

Code of Federal Regulations, 2013 CFR

2013-07-01

... 29 Labor 5 2013-07-01 2013-07-01 false Surface-supplied air diving. 1910.425 Section 1910.425... Procedures § 1910.425 Surface-supplied air diving. (a) General. Employers engaged in surface-supplied air...-supplied air diving shall not be conducted at depths deeper than 190 fsw, except that dives with bottom...

29 CFR 1910.425 - Surface-supplied air diving.

Code of Federal Regulations, 2012 CFR

2012-07-01

... 29 Labor 5 2012-07-01 2012-07-01 false Surface-supplied air diving. 1910.425 Section 1910.425... Procedures § 1910.425 Surface-supplied air diving. (a) General. Employers engaged in surface-supplied air...-supplied air diving shall not be conducted at depths deeper than 190 fsw, except that dives with bottom...

29 CFR 1910.425 - Surface-supplied air diving.

Code of Federal Regulations, 2010 CFR

2010-07-01

... 29 Labor 5 2010-07-01 2010-07-01 false Surface-supplied air diving. 1910.425 Section 1910.425... Procedures § 1910.425 Surface-supplied air diving. (a) General. Employers engaged in surface-supplied air...-supplied air diving shall not be conducted at depths deeper than 190 fsw, except that dives with bottom...

46 CFR 197.432 - Surface-supplied air diving.

Code of Federal Regulations, 2010 CFR

2010-10-01

... 46 Shipping 7 2010-10-01 2010-10-01 false Surface-supplied air diving. 197.432 Section 197.432...-supplied air diving. The diving supervisor shall insure that— (a) Surface-supplied air diving is conducted... space; and (f) The surface-supplied air diver has the equipment required by § 197.346 (b) or (d). ...

29 CFR 1910.425 - Surface-supplied air diving.

Code of Federal Regulations, 2011 CFR

2011-07-01

... 29 Labor 5 2011-07-01 2011-07-01 false Surface-supplied air diving. 1910.425 Section 1910.425... Procedures § 1910.425 Surface-supplied air diving. (a) General. Employers engaged in surface-supplied air...-supplied air diving shall not be conducted at depths deeper than 190 fsw, except that dives with bottom...

46 CFR 197.432 - Surface-supplied air diving.

Code of Federal Regulations, 2011 CFR

2011-10-01

... 46 Shipping 7 2011-10-01 2011-10-01 false Surface-supplied air diving. 197.432 Section 197.432...-supplied air diving. The diving supervisor shall insure that— (a) Surface-supplied air diving is conducted... space; and (f) The surface-supplied air diver has the equipment required by § 197.346 (b) or (d). ...

Sea surface microlayers: A unified physicochemical and biological perspective of the air-ocean interface

NASA Astrophysics Data System (ADS)

Cunliffe, Michael; Engel, Anja; Frka, Sanja; Gašparović, Blaženka; Guitart, Carlos; Murrell, J. Colin; Salter, Matthew; Stolle, Christian; Upstill-Goddard, Robert; Wurl, Oliver

2013-02-01

The sea surface microlayer (SML) covers more than 70% of the Earth's surface and is the boundary layer interface between the ocean and the atmosphere. This important biogeochemical and ecological system is critical to a diverse range of Earth system processes, including the synthesis, transformation and cycling of organic material, and the air-sea exchange of gases, particles and aerosols. In this review we discuss the SML paradigm, taking into account physicochemical and biological characteristics that define SML structure and function. These include enrichments in biogenic molecules such as carbohydrates, lipids and proteinaceous material that contribute to organic carbon cycling, distinct microbial assemblages that participate in air-sea gas exchange, the generation of climate-active aerosols and the accumulation of anthropogenic pollutants with potentially serious implications for the health of the ocean. Characteristically large physical, chemical and biological gradients thus separate the SML from the underlying water and the available evidence implies that the SML retains its integrity over wide ranging environmental conditions. In support of this we present previously unpublished time series data on bacterioneuston composition and SML surfactant activity immediately following physical SML disruption; these imply timescales of the order of minutes for the reestablishment of the SML following disruption. A progressive approach to understanding the SML and hence its role in global biogeochemistry can only be achieved by considering as an integrated whole, all the key components of this complex environment.

Influence of laser-target interaction regime on composition and properties of surface layers grown by laser treatment of Ti plates

NASA Astrophysics Data System (ADS)

Lavisse, L.; Berger, P.; Cirisan, M.; Jouvard, J. M.; Bourgeois, S.; de Lucas, M. C. Marco

2009-12-01

Surface laser treatment of commercially pure titanium plates was performed in air using two different Nd : YAG sources delivering pulses of 5 and 35 ns. The laser fluence conditions were set to obtain with each source either yellow or blue surface layers. Nuclear reaction analysis (NRA) was used to quantify the amount of light elements in the formed layers. Titanium oxinitrides, containing different amounts of oxygen and nitrogen, were mainly found, except in the case of long pulses and high laser fluence, which led to the growth of titanium dioxide. The structure of the layers was studied by x-ray diffraction and Raman spectroscopy. In addition, reflectance spectra showed the transition from a metal-like behaviour to an insulating TiO2-like behaviour as a function of the treatment conditions. Modelling of the laser-target interaction on the basis of the Semak model was performed to understand the different compositions and properties of the layers. Numerical calculations showed that vaporization dominates in the case of short pulses, whereas a liquid-ablation regime is achieved in the case of 35 ns long pulses.

Effect of air-abrasion on the retention of zirconia ceramic crowns luted with different cements before and after artificial aging.

PubMed

Shahin, Ramez; Kern, Matthias

2010-09-01

The purpose of this in vitro study was to evaluate the effect of intaglio surface air-abrasion on the retention of CAD/CAM produced zirconia ceramic crowns cemented with three different types of cement. In addition the influence of artificial aging in masticatory simulator and thermocycling was tested. Extracted human premolars were prepared for all-ceramic crowns (12 degrees taper, 3 mm axial length). CAD/CAM zirconia crowns were manufactured. Half of the crowns were air-abraded with 50 microm alumina particles at 0.25 MPa, the rest was left as machined. The crowns were luted with zinc phosphate cement (Hoffmann), glass ionomer cement (Ketac Cem), or composite resin (Panavia 21), subgroups were either stored for 3 days in 37 degrees water bath or stored for 150 days in 37 degrees water bath, with additional 37,500 thermal cycles (5-55 degrees) and 300,000 cycles dynamic loading with 5 kg in a masticatory simulator. Then crown retention was measured in tension at a crosshead speed of 2 mm/min using a universal testing machine. Statistical analysis was performed with three-way ANOVA. Mean retention values were ranged from 2.8 to 7.1 MPa after 3 days and from 1.6 to 6.1 MPa after artificial aging. Air-abrasion significantly increased crown retention (p<0.001), while artificial aging decreased retention (p=0.017). In addition, the luting material had a significant influence on retention (p<0.001) with the adhesive luting resin providing the highest retention. The use of phosphate monomer containing composite resin on air-abraded zirconia ceramic can be recommended as most retentive luting method. Copyright 2010 Academy of Dental Materials. Published by Elsevier Ltd. All rights reserved.

Integrating Measurement Based New Knowledge on Wildland Fire Emissions and Chemistry into the AIRPACT Air Quality Forecasting for the Pacific Northwest

NASA Astrophysics Data System (ADS)

Nergui, T.; Lee, Y.; Chung, S. H.; Lamb, B. K.; Yokelson, R. J.; Barsanti, K.

2017-12-01

A number of chamber and field measurements have shown that atmospheric organic aerosols and their precursors produced from wildfires are significantly underestimated in the emission inventories used for air quality models for various applications such as regulatory strategy development, impact assessments of air pollutants, and air quality forecasting for public health. The AIRPACT real-time air quality forecasting system consistently underestimates surface level fine particulate matter (PM2.5) concentrations in the summer at both urban and rural locations in the Pacific Northwest, primarily result of errors in organic particulate matter. In this work, we implement updated chemical speciation and emission factors based on FLAME-IV (Fourth Fire Lab at Missoula Experiment) and other measurements in the Blue-Sky fire emission model and the SMOKE emission preprocessor; and modified parameters for the secondary organic aerosol (SOA) module in CMAQ chemical transport model of the AIRPACT modeling system. Simulation results from CMAQ version 5.2 which has a better treatment for anthropogenic SOA formation (as a base case) and modified parameterization used for fire emissions and chemistry in the model (fire-soa case) are evaluated against airborne measurements downwind of the Big Windy Complex Fire and the Colockum Tarps Fire, both of which occurred in the Pacific Northwest in summer 2013. Using the observed aerosol chemical composition and mass loadings for organics, nitrate, sulfate, ammonium, and chloride from aircraft measurements during the Studies of Emissions and Atmospheric Composition, Clouds, and Climate Coupling by Regional Surveys (SEAC4RS) and the Biomass Burning Observation Project (BBOP), we assess how new knowledge gained from wildfire measurements improve model predictions for SOA and its contribution to the total mass of PM2.5 concentrations.

Controlled grafting of comb copolymer brushes on poly(tetrafluoroethylene) films by surface-initiated living radical polymerizations.

PubMed

Yu, W H; Kang, E T; Neoh, K G

2005-01-04

Surface modification of poly(tetrafluoroethylene) (PTFE) films by well-defined comb copolymer brushes was carried out. Peroxide initiators were generated directly on the PTFE film surface via radio frequency Ar plasma pretreatment, followed by air exposure. Poly(glycidyl methacrylate) (PGMA) brushes were first prepared by surface-initiated reversible addition-fragmentation chain transfer polymerization from the peroxide initiators on the PTFE surface in the presence of a chain transfer agent. Kinetics study revealed a linear increase in the graft concentration of PGMA with the reaction time, indicating that the chain growth from the surface was consistent with a "controlled" or "living" process. alpha-Bromoester moieties were attached to the grafted PGMA by reaction of the epoxide groups with 2-bromo-2-methylpropionic acid. The comb copolymer brushes were subsequently prepared via surface-initiated atom transfer radical polymerization of two hydrophilic vinyl monomers, including poly(ethylene glycol) methyl ether methacrylate and sodium salt of 4-styrenesulfonic acid. The chemical composition of the modified PTFE surfaces was characterized by X-ray photoelectron spectroscopy.

76 FR 41086 - Approval and Promulgation of Air Quality Implementation Plans; Ohio; Volatile Organic Compound...

Federal Register 2010, 2011, 2012, 2013, 2014

2011-07-13

... Promulgation of Air Quality Implementation Plans; Ohio; Volatile Organic Compound Reinforced Plastic Composites... compound (VOC) emissions from reinforced plastic composites production operations. This rule applies to any facility that has reinforced plastic composites production operations. This rule is approvable because it...

Data from a thick unsaturated zone underlying Oro Grande and Sheep Creek washes in the western part of the Mojave Desert, near Victorville, San Bernardino County, California

USGS Publications Warehouse

Izbicki, John A.; Clark, Dennis A.; Pimental, Maria I.; Land, Michael; Radyk, John C.; Michel, Robert L.

2000-01-01

This report presents data on the physical properties of unsaturated alluvial deposits and on the chemical and isotopic composition of soil water and soil gas collected at 12 monitoring sites in the western part of the Mojave Desert, near Victorville, California. Sites were installed using the ODEX air-hammer method. Seven sites were located in the active channels of Oro Grande and Sheep Creek Washes. The remaining five sites were located away from the active washes. Most sites were drilled to a depth of about 100 feet below land surface; two sites were drilled to the water table almost 650 feet below land surface. Drilling procedures, lithologic and geophysical data, and site construction and instrumentation are described. Core material was analyzed for water content, bulk density, water potential, particle size, and water retention. The chemical composition of leachate from almost 1,000 subsamples of cores and cuttings was determined. Water extracted from selected subsamples of cores was analyzed for tritium and the stable isotopes of oxygen and hydrogen. Water from suction-cup lysimeters and soil-gas samples also were analyzed for chemical and isotopic composition. In addition, data on the chemical and isotopic composition of bulk precipitation from five sites and on ground water from two water-table wells are reported.

Temporal variability of the chemical composition of surface aerosol in the Moscow region in 1999-2005 from the results of infrared spectroscopy of aerosol samples

NASA Astrophysics Data System (ADS)

Shukurova, L. M.; Gruzdev, A. N.

2010-06-01

The temporal variability of the chemical composition of surface aerosol with particle diameters of 0.7-2 μm is analyzed. This analysis is based on the results of measurements of infrared transmission spectra of aerosol samples collected with the use of a cascade impactor at the Zvenigorod Scientific Station of the Institute of Atmospheric Physics (IAP) in 1999-2005. Seasonal features of the aerosol chemical composition and its dependence on the particle size are revealed. The interdiurnal variability of the aerosol composition depends on the season, and it manifests itself more strongly in winter and spring. Air-mass changes lead to changes in the relation of sulfates and nitrates in the micron fraction of aerosol. The enrichment of samples in nitrates is especially characteristic of the winter and spring seasons. Compounds containing the NO2 group are often met in the samples of aerosol with particle sizes of 0.7-1.3 μm during the cold time of the year. The estimates of the optical thickness of micron aerosol in the sulfate absorption band are obtained, and optical-thickness variations of some scales are detected. The quantitative characteristics of statistical relations between different chemical components of aerosol inside individual fractions and between chemical components of the micron and submicron fractions are obtained and analyzed.

Novel Approach for Positioning Sensor Lead Wires on SiC-Based Monolithic Ceramic and FRCMC Components/Subcomponents Having Flat and Curved Surfaces

NASA Technical Reports Server (NTRS)

Kiser, J. Douglas; Singh, Mrityunjay; Lei, Jin-Fen; Martin, Lisa C.

1999-01-01

A novel attachment approach for positioning sensor lead wires on silicon carbide-based monolithic ceramic and fiber reinforced ceramic matrix composite (FRCMC) components has been developed. This approach is based on an affordable, robust ceramic joining technology, named ARCJoinT, which was developed for the joining of silicon carbide-based ceramic and fiber reinforced composites. The ARCJoinT technique has previously been shown to produce joints with tailorable thickness and good high temperature strength. In this study, silicon carbide-based ceramic and FRCMC attachments of different shapes and sizes were joined onto silicon carbide fiber reinforced silicon carbide matrix (SiC/ SiC) composites having flat and curved surfaces. Based on results obtained in previous joining studies. the joined attachments should maintain their mechanical strength and integrity at temperatures up to 1350 C in air. Therefore they can be used to position and secure sensor lead wires on SiC/SiC components that are being tested in programs that are focused on developing FRCMCs for a number of demanding high temperature applications in aerospace and ground-based systems. This approach, which is suitable for installing attachments on large and complex shaped monolithic ceramic and composite components, should enhance the durability of minimally intrusive high temperature sensor systems. The technology could also be used to reinstall attachments on ceramic components that were damaged in service.

The Role of Vegetation Response to Elevated CO2 in Modifying Land-Atmosphere Feedback Across the Central United States Agro-Ecosystem

NASA Astrophysics Data System (ADS)

Drewry, D.; Kumar, P.; Sivapalan, M.; Long, S.; Liang, X.

2009-05-01

Recent local-scale observational studies have demonstrated significant modifications to the partitioning of incident energy by two key mid-west agricultural species, soy and corn, as ambient atmospheric CO2 concentrations are experimentally augmented to projected future levels. The uptake of CO2 by soy, which utilizes the C3 photosynthetic pathway, has likewise been observed to significantly increase under elevated growth CO2 concentrations. Changes to the sensible and latent heat exchanges between the land surface and the atmospheric boundary layer (ABL) across large portions of the mid-western US has the potential to affect ABL growth and composition, and consequently feed-back to the near-surface environment (air temperature and vapor content) experienced by the vegetation. Here we present a simulation analysis that examines the changes in land-atmosphere feedbacks associated with projected increases in ambient CO2 concentrations over extended soy/corn agricultural areas characteristic of the US mid-west. The model canopies are partitioned into several layers, allowing for resolution of the shortwave and longwave radiation regimes that drive photosynthesis, stomatal conductance and leaf energy balance in each layer, along with the canopy microclimate. The canopy component of the model is coupled to a multi-layer soil-root model that computes soil moisture and heat transport and root water uptake. Model skill in capturing the sub-diurnal variability in canopy-atmosphere exchange is evaluated through multi-year records of canopy-top eddy covariance CO2, water vapor and heat fluxes collected at the Bondville (Illinois) FluxNet site. An evaluation of the ability of the model to simulate observed changes in energy balance components (canopy temperature, net radiation and soil heat flux) under elevated CO2 concentrations projected for 2050 (550 ppm) is made using observations collected at the SoyFACE Free Air Carbon Enrichment (FACE) experimental facilities located in central Illinois, by incorporating observed acclimations in leaf biochemsitry and canopy structure. The simulation control volume is then extended by coupling the canopy models to a simple model of daytime mixed-layer (ML) growth and composition, ie. air temperature and vapor content. Through this coupled canopy-ABL model we quantify the impact of elevated CO2 and vegetation acclimation on ML growth, temperature and vapor content and the consequent feedbacks to the land surface by way of the near-surface environment experienced by the vegetation. Particular focus is placed on the role of short-term drought, and possible changes in land cover composition between soy, a C3 crop, and corn, a more water-use efficient C4 crop, on modulating the strength of these CO2-induced feedbacks.

Cyclic Fiber Push-In Test Monitors Evolution of Interfacial Behavior in Ceramic Matrix Composites

NASA Technical Reports Server (NTRS)

Eldridge, Jeffrey I.

1998-01-01

SiC fiber-reinforced ceramic matrix composites are being developed for high-temperature advanced jet engine applications. Obtaining a strong, tough composite material depends critically on optimizing the mechanical coupling between the reinforcing fibers and the surrounding matrix material. This has usually been accomplished by applying a thin C or BN coating onto the surface of the reinforcing fibers. The performance of these fiber coatings, however, may degrade under cyclic loading conditions or exposure to different environments. Degradation of the coating-controlled interfacial behavior will strongly affect the useful service lifetime of the composite material. Cyclic fiber push-in testing was applied to monitor the evolution of fiber sliding behavior in both C- and BN-coated small-diameter (15-mm) SiC-fiber-reinforced ceramic matrix composites. The cyclic fiber push-in tests were performed using a desktop fiber push-out apparatus. At the beginning of each test, the fiber to be tested was aligned underneath a 10- mm-diameter diamond punch; then, the applied load was cycled between selected maximum and minimum loads. From the measured response, the fiber sliding distance and frictional sliding stresses were determined for each cycle. Tests were performed in both room air and nitrogen. Cyclic fiber push-in tests of C-coated, SiC-fiber-reinforced SiC showed progressive increases in fiber sliding distances along with decreases in frictional sliding stresses for continued cycling in room air. This rapid degradation in interfacial response was not observed for cycling in nitrogen, indicating that moisture exposure had a large effect in immediately lowering the frictional sliding stresses of C-coated fibers. These results indicate that matrix cracks bridged by C-coated fibers will not be stable, but will rapidly grow in moisture-containing environments. In contrast, cyclic fiber push-in tests of both BN-coated, SiC-fiber-reinforced SiC and BNcoated, SiC-fiber-reinforced barium strontium aluminosilicate showed no significant changes in fiber sliding behavior with continued short-term cycling in either room air or nitrogen. Although the composites with BN-coated fibers showed stable short-term cycling behavior in both environments, long-term (several-week) exposure of debonded fibers to room air resulted in dramatically increased fiber sliding distances and decreased frictional sliding stresses. These results indicate that although matrix cracks bridged by BNcoated fibers will show short-term stability, such cracks will show substantial growth with long-term exposure to moisture-containing environments. Newly formulated BN coatings, with higher moisture resistance, will be tested in the near future.

Leveraging Oceanic and Surface Intensive Field Campaign Data Sets for Validation and Improvement of Recent Hyperspectral IR Satellite Data Products

NASA Astrophysics Data System (ADS)

Joseph, E.; Nalli, N. R.; Oyola, M. I.; Morris, V. R.; Sakai, R.

2014-12-01

An overview is given of research to validate or improve the retrieval of environmental data records (EDRs) from recently deployed hyperspectral IR satellite sensors such as Suomi NPP Cross-track Infrared Microwave Sounder Suite (CrIMSS). The effort centers around several surface field intensive campaigns that are designed or leveraged for EDR validation. These data include ship-based observations of upper air ozone, pressure, temperature and relative humidity soundings; aerosol and cloud properties; and sea surface temperature. Similar intensive data from two land-based sites are also utilized as well. One site, the Howard University Beltsville site, is at a single point location but has a comprehensive array of observations for an extended period of time. The other land site, presently being deployed by the University at Albany, is under development with limited upper air soundings but will have regionally distributed surface based microwave profiling of temperature and relative humidity on the scale of 10 - 50 km and other standard meteorological observations. Combined these observations provide data that are unique in their wide range including, a variety of meteorological conditions and atmospheric compositions over the ocean and urban-suburban environments. With the distributed surface sites the variability of atmospheric conditions are captured concurrently across a regional spatial scale. Some specific examples are given of comparisons of moisture and temperature correlative EDRs from the satellite sensors and surface based observations. An additional example is given of the use of this data to correct sea surface temperature (SST) retrieval biases from the hyperspectral IR satellite observations due to aerosol contamination.

Characterization of Magnetic NiFe Nanoparticles with Controlled Bimetallic Composition

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

Liu, Yan; Chi, Yanxiu; Shan, Shiyao

2014-02-25

The exploration of the magnetic properties of bimetallic alloy nanoparticles for various technological applications requires the ability to control the morphology, composition, and surface properties. In this report, we describe new findings of an investigation of the morphology and composition of NiFe alloy nanoparticles synthesized under controlled conditions. The controllability over the bimetallic composition has been demonstrated by the observation of an approximate linear relationship between the composition in the nanoparticles and in the synthetic feeding. The morphology of the NiFe nanoparticles is consistent with an fcc-type alloy, with the lattice strain increasing linearly with the iron content in themore » nanoparticles. The alloy nanoparticles exhibit remarkable resistance to air oxidation in comparison with Ni or Fe particles. The thermal stability and the magnetic properties of the as-synthesized alloy nanoparticles are shown to depend on the composition. The alloy nanoparticles have also be sown to display low saturation magnetization and coercivity values in comparison with the Ni nanoparticles, in line with the superparamagnetic characteristic. These findings have important implications for the design of stable and controllable magnetic nanoparticles for various technological applications.« less

Polycyclic aromatic hydrocarbons (PAHs) in the water column and sediment core of Deep Bay, South China

NASA Astrophysics Data System (ADS)

Qiu, Yao-Wen; Zhang, Gan; Liu, Guo-Qing; Guo, Ling-Li; Li, Xiang-Dong; Wai, Onyx

2009-06-01

The levels of 15 polycyclic aromatic hydrocarbons (PAHs) were determined in seawater, suspended particulate matter (SPM), surface sediment and core sediment samples of Deep Bay, South China. The average concentrations Σ 15PAHs were 69.4 ± 24.7 ng l -1 in seawater, 429.1 ± 231.8 ng g -1 in SPM, and 353.8 ± 128.1 ng g -1 dry weight in surface sediment, respectively. Higher PAH concentrations were observed in SPM than in surface sediment. Temporal trend of PAH concentrations in core sediment generally increased from 1948 to 2004, with higher concentrations in top than in sub-surface, implying a stronger recent input of PAHs owing to the rapid economic development in Shenzhen. Compared with historical data, the PAH levels in surface sediment has increased, and this was further confirmed by the increasing trend of PAHs in the core sediment. Phenanthrene, fluoranthene and pyrene dominated in the PAH composition pattern profiles in the Bay. Compositional pattern analysis suggested that PAHs in the Deep Bay were derived from both pyrogenic and petrogenic sources, and diesel oil leakage, river runoff and air deposition may serve as important pathways for PAHs input to the Bay. Significant positive correlations between partition coefficient in surface sediment to that in water ( KOC) of PAH and their octanol/water partition coefficients ( KOW) were observed, suggesting that KOC of PAHs in sediment/water of Deep Bay may be predicted by the corresponding KOW.

Influence of Atmosphere on Electrochemical Performance of LiNi0.8Co0.1Mn0.1O2 Electrodes for Li-Ion Batteries

NASA Astrophysics Data System (ADS)

Wang, Ran; Wang, Jing; Chen, Shi; Gao, Ang; Su, Yuefeng; Wu, Feng

2018-01-01

Ni-rich layered materials have been regarded as competitive candidates for advanced lithium-ion batteries due to their high energy density, relatively low cost and environmentally-friendly nature. However, they suffer from serious degradation of cycling performance after exposing to air during their storage. Here we selected LiNi0.8Co0.1Mn0.1O2 as a typical Ni-rich positive material to study the influence upon exposure to ambient air on surface chemical composition and electrochemical performance. TEM confirms the existence of amorphous surface layer after contacting with atmosphere and the thickness is about 3-4 nm. The fresh LiNi0.8Co0.1Mn0.1O2 sample has capacity retention of 94.6% and 93.3% after 50 cycles at 0.2C and 1C, respectively, comparing to the 91.7% and 82.4% of the exposed sample. The charge-discharge curves and electrochemical impedance spectra indicate that exposure to air lead to increased impedance and polarization, which seriously affects LiNi0.8Co0.1Mn0.1O2 cycling properties. So, it is very important for Ni-rich cathode materials without contacting with atmosphere directly.

Coplanar surface barrier discharge ignited in water vapor—a selective source of OH radicals proved by (TA)LIF measurement

NASA Astrophysics Data System (ADS)

Procházka, V.; Tučeková, Z.; Dvořák, P.; Kováčik, D.; Slavíček, P.; Zahoranová, A.; Voráč, J.

2018-01-01

Coplanar dielectric barrier discharge (DBD) was ignited in pure water vapor at atmospheric pressure in order to generate highly oxidizing plasma with one specific type of reactive radicals. In order to prevent water condensation the used plasma reactor was heated to 120 {}\\circ C. The composition of the radical species in the discharge was studied by methods based on laser-induced fluorescence (LIF) and compared with analogous measurements realized in the same coplanar DBD ignited in air. Fast collisional processes and laser-surface interaction were taken into account during LIF data processing. It was found that coplanar DBD ignited in water vapor produces hydroxyl (OH) radicals with concentration in the order of 1020 m-3, which is 10× higher than the value measured in discharge in humid air (40% relative humidity at 21 {}\\circ C). The concentration of atomic hydrogen radicals in the DBD ignited in water vapor was below the detection limit, which proves that the generation of oxidizing plasma with dominance of one specific type of reactive radicals was achieved. The temporal evolution, spatial distribution, power dependence and rotational temperature of the OH radicals was determined in the DBD ignited in both water vapor and air.

Enhancement of oxidation resistance via a self-healing boron carbide coating on diamond particles

PubMed Central

Sun, Youhong; Meng, Qingnan; Qian, Ming; Liu, Baochang; Gao, Ke; Ma, Yinlong; Wen, Mao; Zheng, Weitao

2016-01-01

A boron carbide coating was applied to diamond particles by heating the particles in a powder mixture consisting of H3BO3, B and Mg. The composition, bond state and coverage fraction of the boron carbide coating on the diamond particles were investigated. The boron carbide coating prefers to grow on the diamond (100) surface than on the diamond (111) surface. A stoichiometric B4C coating completely covered the diamond particle after maintaining the raw mixture at 1200 °C for 2 h. The contribution of the boron carbide coating to the oxidation resistance enhancement of the diamond particles was investigated. During annealing of the coated diamond in air, the priory formed B2O3, which exhibits a self-healing property, as an oxygen barrier layer, which protected the diamond from oxidation. The formation temperature of B2O3 is dependent on the amorphous boron carbide content. The coating on the diamond provided effective protection of the diamond against oxidation by heating in air at 1000 °C for 1 h. Furthermore, the presence of the boron carbide coating also contributed to the maintenance of the static compressive strength during the annealing of diamond in air. PMID:26831205

Enhancement of oxidation resistance via a self-healing boron carbide coating on diamond particles.

PubMed

Sun, Youhong; Meng, Qingnan; Qian, Ming; Liu, Baochang; Gao, Ke; Ma, Yinlong; Wen, Mao; Zheng, Weitao

2016-02-02

A boron carbide coating was applied to diamond particles by heating the particles in a powder mixture consisting of H3BO3, B and Mg. The composition, bond state and coverage fraction of the boron carbide coating on the diamond particles were investigated. The boron carbide coating prefers to grow on the diamond (100) surface than on the diamond (111) surface. A stoichiometric B4C coating completely covered the diamond particle after maintaining the raw mixture at 1200 °C for 2 h. The contribution of the boron carbide coating to the oxidation resistance enhancement of the diamond particles was investigated. During annealing of the coated diamond in air, the priory formed B2O3, which exhibits a self-healing property, as an oxygen barrier layer, which protected the diamond from oxidation. The formation temperature of B2O3 is dependent on the amorphous boron carbide content. The coating on the diamond provided effective protection of the diamond against oxidation by heating in air at 1000 °C for 1 h. Furthermore, the presence of the boron carbide coating also contributed to the maintenance of the static compressive strength during the annealing of diamond in air.

Effects of sulfate ligand on uranyl carbonato surface species on ferrihydrite surfaces

USGS Publications Warehouse

Arai, Yuji; Fuller, C.C.

2012-01-01

Understanding uranium (U) sorption processes in permeable reactive barriers (PRB) are critical in modeling reactive transport for evaluating PRB performance at the Fry Canyon demonstration site in Utah, USA. To gain insight into the U sequestration mechanism in the amorphous ferric oxyhydroxide (AFO)-coated gravel PRB, U(VI) sorption processes on ferrihydrite surfaces were studied in 0.01 M Na2SO4 solutions to simulate the major chemical composition of U-contaminatedgroundwater (i.e., [SO42-]~13 mM L-1) at the site. Uranyl sorption was greater at pH 7.5 than that at pH 4 in both air- and 2% pCO2-equilibrated systems. While there were negligible effects of sulfate ligands on the pH-dependent U(VI) sorption (<24 h) in both systems, X-ray absorption spectroscopy (XAS) analysis showed sulfate ligand associated U(VI) surface species at the ferrihydrite–water interface. In air-equilibrated systems, binary and mono-sulfate U(VI) ternary surface species co-existed at pH 5.43. At pH 6.55–7.83, a mixture of mono-sulfate and bis-carbonato U(VI) ternary surface species became more important. At 2% pCO2, there was no contribution of sulfate ligands on the U(VI) ternary surface species. Instead, a mixture of bis-carbonato inner-sphere (38%) and tris-carbonato outer-sphere U(VI) ternary surface species (62%) was found at pH 7.62. The study suggests that the competitive ligand (bicarbonate and sulfate) coordination on U(VI) surface species might be important in evaluating the U solid-state speciation in the AFO PRB at the study site where pCO2 fluctuates between 1 and 2 pCO2%.

Effects of sulfate ligand on uranyl carbonato surface species on ferrihydrite surfaces.

PubMed

Arai, Yuji; Fuller, C C

2012-01-01

Understanding uranium (U) sorption processes in permeable reactive barriers (PRB) are critical in modeling reactive transport for evaluating PRB performance at the Fry Canyon demonstration site in Utah, USA. To gain insight into the U sequestration mechanism in the amorphous ferric oxyhydroxide (AFO)-coated gravel PRB, U(VI) sorption processes on ferrihydrite surfaces were studied in 0.01 M Na(2)SO(4) solutions to simulate the major chemical composition of U-contaminated groundwater (i.e., [SO(4)(2-)] ~13 mM L(-1)) at the site. Uranyl sorption was greater at pH 7.5 than that at pH 4 in both air- and 2% pCO(2)-equilibrated systems. While there were negligible effects of sulfate ligands on the pH-dependent U(VI) sorption (<24 h) in both systems, X-ray absorption spectroscopy (XAS) analysis showed sulfate ligand associated U(VI) surface species at the ferrihydrite-water interface. In air-equilibrated systems, binary and mono-sulfate U(VI) ternary surface species co-existed at pH 5.43. At pH 6.55-7.83, a mixture of mono-sulfate and bis-carbonato U(VI) ternary surface species became more important. At 2% pCO(2), there was no contribution of sulfate ligands on the U(VI) ternary surface species. Instead, a mixture of bis-carbonato inner-sphere (38%) and tris-carbonato outer-sphere U(VI) ternary surface species (62%) was found at pH 7.62. The study suggests that the competitive ligand (bicarbonate and sulfate) coordination on U(VI) surface species might be important in evaluating the U solid-state speciation in the AFO PRB at the study site where pCO(2) fluctuates between 1 and 2 pCO(2)%. Copyright © 2011 Elsevier Inc. All rights reserved.

Microbiota of the ground air layers in natural and industrial zones of the Kola Arctic.

PubMed

Korneykova, Maria V; Evdokimova, Galina A

2018-02-23

The fungi and bacteria number, as well as the species composition of the fungi in the ground air layer in the European Arctic region of Russia, primarily in the tundra (the Rybachy Peninsula), in the subzone of the northern taiga (the Pasvik State Nature Reserve) and in the industrial areas (the Copper-Nickel Plant "Pechenganickel," the Kandalaksha Aluminum Plant) have been studied. One hundred and ninety-two atmosphere air samples of various ecosystems have been analyzed. The sample collection took place in the summer-autumn period (June, July, September, in 2012-2015) with the aspirator, precipitating microorganisms on the surface of media. The number of microorganisms per 1 m 3 of air was calculated. The portion of the airborne fungi in the ground air layer both in the tundra and in the taiga was higher in comparison with the bacteria, and amounted to 60-77% of the total number colony forming units (CFU). The least number of microorganisms in the investigated period was registered in the Barents Sea coastal atmospheric air, only 11-15 microbial CFU per 1 m 3 . The airborne fungi diversity in the taiga zone was richer than in the tundra. The fungi of the g. Penicillium predominated in both zones air. Bacteria gram-positive (the division Fermicutes) predominated within the bacterial biota. The species Penicillium decumbens, P. raistrickii prevailed in the air of the background tundra zone regions. The representatives of the genus Torula and Sterilia mycelia, P. raistrickii predominated in the taiga zone. Close by the Copper-Nickel Plant (about 3 km), the air bacterial contamination (100-600 CFU per 1 m 3 ) was revealed, with prevailing bacteria gram-negative (the division Gracilicutes). The species Cladosporium oxysporum predominated in the air to the greatest possible extent of the contaminated region due to the emissions of the Kandalaksha Aluminum Plant. The species Gongronella butleri were uppermost due to the emissions of the Copper-Nickel Plant «Pechenganickel». The quantity of the dark-pigmented fungi in the air for both zones amounted to 25% of the total amount within the emphasized species. The composition of the air industrial emissions stimulated the development of specific airborne fungi which are essentially different from those of the background regions.

Logistics Implications of Composite Wings

DTIC Science & Technology

1993-12-01

Composite Wing and Air Logistics Center Locations 33 12 F-15E Strike Eagle Aircraft 34 la F-16C Fighting Falcon Aircraft 35 14 E-3 Sentry...Structure , 12 2 366th Wing Maintenance Concept 41 vOt Foreword The US Air Force has taken the initiative to reorganize into objective wings, at...the Air Force in 1967. He began his Air Force career as an F-102 radar weapon system specialist and worked on the flight line at Ramstein Air Base

40 CFR 63.5780 - What is the purpose of this subpart?

Code of Federal Regulations, 2010 CFR

2010-07-01

... Standards for Hazardous Air Pollutants: Reinforced Plastic Composites Production What This Subpart Covers... for hazardous air pollutants (NESHAP) for reinforced plastic composites production. This subpart also...