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

EPA Science Inventory

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

Secondary treatment of films of colloidal quantum dots for optoelectronics and devices produced thereby

DOEpatents

Semonin, Octavi Escala; Luther, Joseph M; Beard, Matthew C; Chen, Hsiang-Yu

2014-04-01

A method of forming an optoelectronic device. The method includes providing a deposition surface and contacting the deposition surface with a ligand exchange chemical and contacting the deposition surface with a quantum dot (QD) colloid. This initial process is repeated over one or more cycles to form an initial QD film on the deposition surface. The method further includes subsequently contacting the QD film with a secondary treatment chemical and optionally contacting the surface with additional QDs to form an enhanced QD layer exhibiting multiple exciton generation (MEG) upon absorption of high energy photons by the QD active layer. Devices having an enhanced QD active layer as described above are also disclosed.

Polymer-Based Surfaces Designed to Reduce Biofilm Formation: From Antimicrobial Polymers to Strategies for Long-Term Applications.

PubMed

Riga, Esther K; Vöhringer, Maria; Widyaya, Vania Tanda; Lienkamp, Karen

2017-10-01

Contact-active antimicrobial polymer surfaces bear cationic charges and kill or deactivate bacteria by interaction with the negatively charged parts of their cell envelope (lipopolysaccharides, peptidoglycan, and membrane lipids). The exact mechanism of this interaction is still under debate. While cationic antimicrobial polymer surfaces can be very useful for short-term applications, they lose their activity once they are contaminated by a sufficiently thick layer of adhering biomolecules or bacterial cell debris. This layer shields incoming bacteria from the antimicrobially active cationic surface moieties. Besides discussing antimicrobial surfaces, this feature article focuses on recent strategies that were developed to overcome the contamination problem. This includes bifunctional materials with simultaneously presented antimicrobial and protein-repellent moieties; polymer surfaces that can be switched from an antimicrobial, cell-attractive to a cell-repellent state; polymer surfaces that can be regenerated by enzyme action; degradable antimicrobial polymers; and antimicrobial polymer surfaces with removable top layers. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

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.

[Effects of intensive management on soil C and N pools and soil enzyme activities in Moso bamboo plantations.

PubMed

Yang, Meng; Li, Yong Fu; Li, Yong Chun; Xiao, Yong Heng; Yue, Tian; Jiang, Pei Kun; Zhou, Guo Mo; Liu, Juan

2016-11-18

In order to elucidate the effects of intensive management on soil carbon pool, nitrogen pool, enzyme activities in Moso bamboo (Phyllostachys pubescens) plantations, we collected soil samples from the soil surface (0-20 cm) and subsurface (20-40 cm) layers in the adjacent Moso bamboo plantations with extensive and intensive managements in Sankou Township, Lin'an City, Zhejiang Province. We determined different forms of C, N and soil invertase, urease, catalase and acid phosphatase activities. The results showed that long-term intensive management of Moso bamboo plantations significantly decreased the content and storage of soil organic carbon (SOC), with the SOC storage in the soil surface and subsurface layers decreased by 13.2% and 18.0%, respectively. After 15 years' intensive management of Masoo bamboo plantations, the contents of soil water soluble carbon (WSOC), hot water soluble carbon (HWSOC), microbial carbon (MBC) and readily oxidizable carbon (ROC) were significantly decreased in the soil surface and subsurface layers. The soil N storage in the soil surface and subsurface layers in intensively managed Moso bamboo plantations increased by 50.8% and 36.6%, respectively. Intensive management significantly increased the contents of nitrate-N (NO 3 - -N) and ammonium-N (NH 4 + -N), but decreased the contents of water-soluble nitrogen (WSON) and microbial biomass nitrogen (MBN). After 15 years' intensive management of Masoo bamboo plantations, the soil invertase, urease, catalase and acid phosphatase activities in the soil surface layer were significantly decreased, the soil acid phosphatase activity in the soil subsurface layer were significantly decreased, and other enzyme activities in the soil subsurface layer did not change. In conclusion, long-term intensive management led to a significant decline of soil organic carbon storage, soil labile carbon and microbial activity in Moso bamboo plantations. Therefore, we should consider the use of organic fertilizer in the intensive mana-gement process for the sustainable management of Moso bamboo plantations in the future.

Structural changes of anodic layer on titanium in sulfate solution as a function of anodization duration in constant current mode

NASA Astrophysics Data System (ADS)

Komiya, Shinji; Sakamoto, Kouta; Ohtsu, Naofumi

2014-03-01

The present study investigated the effect of anodization time, in constant current mode, on the anodic oxide layer formed on titanium (Ti). Anodization of the Ti substrate was　carried out in a 0.1 M (NH4)2SO4 aqueous solution with reaction times of various durations, after which the characteristics and photocatalytic activity were investigated in detail. The TiO2 layer fabricated in a short duration exhibited comparatively flat surface morphology and an anatase-type crystal structure. This layer acted as a photocatalyst only under ultraviolet light (UV) illumination. Upon prolonging the anodization, the layer structure changed drastically. The surface morphology became rough, and the crystal structure changed to rutile-type TiO2. Furthermore, the layer showed photocatalytic activity both under UV and visible light illumination. Further anodization increased the amount of methylene blue (MB) adsorbed on the surface, but did not cause additional change to the structure of the anodic layer. The surface morphology and crystal structure of the anodic layer were predominantly controlled by the anodization time; thus, the anodization time is an important parameter for controlling the characteristics of the anodic layer.

Surface Phenomena During Plasma-Assisted Atomic Layer Etching of SiO2.

PubMed

Gasvoda, Ryan J; van de Steeg, Alex W; Bhowmick, Ranadeep; Hudson, Eric A; Agarwal, Sumit

2017-09-13

Surface phenomena during atomic layer etching (ALE) of SiO 2 were studied during sequential half-cycles of plasma-assisted fluorocarbon (CF x ) film deposition and Ar plasma activation of the CF x film using in situ surface infrared spectroscopy and ellipsometry. Infrared spectra of the surface after the CF x deposition half-cycle from a C 4 F 8 /Ar plasma show that an atomically thin mixing layer is formed between the deposited CF x layer and the underlying SiO 2 film. Etching during the Ar plasma cycle is activated by Ar + bombardment of the CF x layer, which results in the simultaneous removal of surface CF x and the underlying SiO 2 film. The interfacial mixing layer in ALE is atomically thin due to the low ion energy during CF x deposition, which combined with an ultrathin CF x layer ensures an etch rate of a few monolayers per cycle. In situ ellipsometry shows that for a ∼4 Å thick CF x film, ∼3-4 Å of SiO 2 was etched per cycle. However, during the Ar plasma half-cycle, etching proceeds beyond complete removal of the surface CF x layer as F-containing radicals are slowly released into the plasma from the reactor walls. Buildup of CF x on reactor walls leads to a gradual increase in the etch per cycle.

Surface passivation investigation on ultra-thin atomic layer deposited aluminum oxide layers for their potential application to form tunnel layer passivated contacts

NASA Astrophysics Data System (ADS)

Xin, Zheng; Ling, Zhi Peng; Nandakumar, Naomi; Kaur, Gurleen; Ke, Cangming; Liao, Baochen; Aberle, Armin G.; Stangl, Rolf

2017-08-01

The surface passivation performance of atomic layer deposited ultra-thin aluminium oxide layers with different thickness in the tunnel layer regime, i.e., ranging from one atomic cycle (∼0.13 nm) to 11 atomic cycles (∼1.5 nm) on n-type silicon wafers is studied. The effect of thickness and thermal activation on passivation performance is investigated with corona-voltage metrology to measure the interface defect density D it(E) and the total interface charge Q tot. Furthermore, the bonding configuration variation of the AlO x films under various post-deposition thermal activation conditions is analyzed by Fourier transform infrared spectroscopy. Additionally, poly(3,4-ethylenedioxythiophene) poly(styrene sulfonate) is used as capping layer on ultra-thin AlO x tunneling layers to further reduce the surface recombination current density to values as low as 42 fA/cm2. This work is a useful reference for using ultra-thin ALD AlO x layers as tunnel layers in order to form hole selective passivated contacts for silicon solar cells.

Pressing effect in polymer solar cells with bulk heterojunction nanolayers.

PubMed

Park, Jiho; Nam, Sungho; Kim, Hwajeong; Kim, Youngkyoo

2011-01-01

We report the effect of pressing light-absorbing layers on the performance of polymer solar cells. The light-absorbing active layer was prepared on the transparent conducting oxide coated substrates from solutions that contain a mixture of regioregular poly(3-hexylthiophene) and soluble fullerene molecules. The active layers were pressed using a home-built micro-press system by controlling temperature and pressure, followed by the top electrode deposition. The surface of the active layers pressed was examined using atomic force microscope, while the photovoltaic characteristics of devices were measured under simulated solar light illumination (air mass 1.5 G, 100 mW/cm2). Results showed that the dark current of devices was noticeably increased by pressing the active layer without respect to the pressing temperature. The highest power conversion efficiency was achieved for the device with the active layer pressed under 10 kgf at 70 degrees C. The result was explained in terms of surface morphology and thermophysical effect.

Numerical evaluation of the laser-pulse modification modes of the metal surface layer in the presence of a surface-active component in the melt

NASA Astrophysics Data System (ADS)

Popov, V. N.; Cherepanov, A. N.

2017-09-01

Numerical evaluation of the laser-pulse modification of a metal layer with refractory nano-size particles was done. The modes of the laser-pulse action promoting creation of the flows for homogeneous distribution of modifying particles in the melt were determined for various amounts of the surface-active admixture in the metal.

Solid state radiative heat pump

DOEpatents

Berdahl, P.H.

1984-09-28

A solid state radiative heat pump operable at room temperature (300 K) utilizes a semiconductor having a gap energy in the range of 0.03-0.25 eV and operated reversibly to produce an excess or deficit of change carriers as compared equilibrium. In one form of the invention an infrared semiconductor photodiode is used, with forward or reverse bias, to emit an excess or deficit of infrared radiation. In another form of the invention, a homogenous semiconductor is subjected to orthogonal magnetic and electric fields to emit an excess or deficit of infrared radiation. Three methods of enhancing transmission of radiation the active surface of the semiconductor are disclosed. In one method, an anti-refection layer is coated into the active surface of the semiconductor, the anti-reflection layer having an index of refraction equal to the square root of that of the semiconductor. In the second method, a passive layer is speaced trom the active surface of the semiconductor by a submicron vacuum gap, the passive layer having an index of refractive equal to that of the semiconductor. In the third method, a coupler with a paraboloid reflecting surface surface is in contact with the active surface of the semiconductor, the coupler having an index of refraction about the same as that of the semiconductor.

Layer-by-layer evolution of structure, strain, and activity for the oxygen evolution reaction in graphene-templated Pt monolayers.

PubMed

Abdelhafiz, Ali; Vitale, Adam; Joiner, Corey; Vogel, Eric; Alamgir, Faisal M

2015-03-25

In this study, we explore the dimensional aspect of structure-driven surface properties of metal monolayers grown on a graphene/Au template. Here, surface limited redox replacement (SLRR) is used to provide precise layer-by-layer growth of Pt monolayers on graphene. We find that after a few iterations of SLRR, fully wetted 4-5 monolayer Pt films can be grown on graphene. Incorporating graphene at the Pt-Au interface modifies the growth mechanism, charge transfers, equilibrium interatomic distances, and associated strain of the synthesized Pt monolayers. We find that a single layer of sandwiched graphene is able to induce a 3.5% compressive strain on the Pt adlayer grown on it, and as a result, catalytic activity is increased due to a greater areal density of the Pt layers beyond face-centered-cubic close packing. At the same time, the sandwiched graphene does not obstruct vicinity effects of near-surface electron exchange between the substrate Au and adlayers Pt. X-ray photoelectron spectroscopy (XPS) and extended X-ray absorption fine structure (EXAFS) techniques are used to examine charge mediation across the Pt-graphene-Au junction and the local atomic arrangement as a function of the Pt adlayer dimension. Cyclic voltammetry (CV) and the oxygen reduction reaction (ORR) are used as probes to examine the electrochemically active area of Pt monolayers and catalyst activity, respectively. Results show that the inserted graphene monolayer results in increased activity for the Pt due to a graphene-induced compressive strain, as well as a higher resistance against loss of the catalytically active Pt surface.

A comparison between active and passive sensing of soil moisture from vegetated terrains

NASA Technical Reports Server (NTRS)

Fung, A. K.; Eom, H. J.

1985-01-01

A comparison between active and passive sensing of soil moisture over vegetated areas is studied via scattering models. In active sensing three contributing terms to radar backscattering can be identified: (1) the ground surface scatter term; (2) the volume scatter term representing scattering from the vegetation layer; and (3) the surface volume scatter term accounting for scattering from both surface and volume. In emission three sources of contribution can also be identified: (1) surface emission; (2) upward volume emission from the vegetation layer; and (3) downward volume emission scattered upward by the ground surface. As ground moisture increases, terms (1) and (3) increase due to increase in permittivity in the active case. However, in passive sensing, term (1) decreases but term (3) increases for the same reason. This self compensating effect produces a loss in sensitivity to change in ground moisture. Furthermore, emission from vegetation may be larger than that from the ground. Hence, the presence of vegetation layer causes a much greater loss of sensitivity to passive than active sensing of soil moisture.

A comparison between active and passive sensing of soil moisture from vegetated terrains

NASA Technical Reports Server (NTRS)

Fung, A. K.; Eom, H. J.

1984-01-01

A comparison between active and passive sensing of soil moisture over vegetated areas is studied via scattering models. In active sensing three contributing terms to radar backscattering can be identified: (1) the ground surface scatter term; (2) the volume scatter term representing scattering from the vegetation layer; and (3) the surface volume scatter term accounting for scattering from both surface and volume. In emission three sources of contribution can also be identified: (1) surface emission; (2) upward volume emission from the vegetation layer; and (3) downward volume emission scattered upward by the ground surface. As ground moisture increases, terms (1) and (3) increase due to increase in permittivity in the active case. However, in passive sensing, term (1) decreases but term (3) increases for the same reason. This self conpensating effect produces a loss in sensitivity to change in ground moisture. Furthermore, emission from vegetation may be larger than that from the ground. Hence, the presence of vegetation layer causes a much greater loss of sensitivity to passive than active sensing of soil moisture.

Wrinkled substrate and Indium Tin Oxide-free transparent electrode making organic solar cells thinner in active layer

NASA Astrophysics Data System (ADS)

Liu, Kong; Lu, Shudi; Yue, Shizhong; Ren, Kuankuan; Azam, Muhammad; Tan, Furui; Wang, Zhijie; Qu, Shengchun; Wang, Zhanguo

2016-11-01

To enable organic solar cells with a competent charge transport efficiency, reducing the thickness of active layer without sacrificing light absorption efficiency turns out to be of high feasibility. Herein, organic solar cells on wrinkled metal surface are designed. The purposely wrinkled Al/Au film with a smooth surface provides a unique scaffold for constructing thin organic photovoltaic devices by avoiding pinholes and defects around sharp edges in conventional nanostructures. The corresponding surface light trapping effect enables the thin active layer (PTB7-Th:PC71BM) with a high absorption efficiency. With the innovative MoO3/Ag/ZnS film as the top transparent electrode, the resulting Indium Tin Oxide-free wrinkled devices show a power conversion efficiency as 7.57% (50 nm active layer), higher than the planner counterparts. Thus, this paper provides a new methodology to improve the performance of organic solar cells by balancing the mutual restraint factors to a high level.

Interfacial Energy Alignment at the ITO/Ultra-Thin Electron Selective Dielectric Layer Interface and Its Effect on the Efficiency of Bulk-Heterojunction Organic Solar Cells.

PubMed

Itoh, Eiji; Goto, Yoshinori; Saka, Yusuke; Fukuda, Katsutoshi

2016-04-01

We have investigated the photovoltaic properties of an inverted bulk heterojunction (BHJ) cell in a device with an indium-tin-oxide (ITO)/electron selective layer (ESL)/P3HT:PCBM active layer/MoOx/Ag multilayered structure. The insertion of only single layer of poly(diallyl-dimethyl-ammonium chloride) (PDDA) cationic polymer film (or poly(ethyleneimine) (PEI) polymeric interfacial dipole layer) and titanium oxide nanosheet (TN) films as an ESL effectively improved cell performance. Abnormal S-shaped curves were observed in the inverted BHJ cells owing to the contact resistance across the ITO/active layer interface and the ITO/PDDA/TN/active layer interface. The series resistance across the ITO/ESL interface in the inverted BHJ cell was successfully reduced using an interfacial layer with a positively charged surface potential with respect to ITO base electrode. The positive dipole in PEI and the electronic charge phenomena at the electrophoretic deposited TN (ED-TN) films on ITO contributed to the reduction of the contact resistance at the electrode interface. The surface potential measurement revealed that the energy alignment by the transfer of electronic charges from the ED-TN to the base electrodes. The insertion of the ESL with a large positive surface potential reduced the potential barrier for the electron injection at ITO/TN interface and it improved the photovoltaic properties of the inverted cell with an ITO/TN/active layer/MoOx/Ag structure.

In silico, in vitro and antifungal activity of the surface layers formed on zinc during this biomaterial degradation

NASA Astrophysics Data System (ADS)

Alves, Marta M.; Marques, Luísa M.; Nogueira, Isabel; Santos, Catarina F.; Salazar, Sara B.; Eugénio, Sónia; Mira, Nuno P.; Montemor, M. F.

2018-07-01

Zinc (Zn) has been proposed as an alternative metallic biodegradable material to support transient wound-healing processes. Once a Zn piece is implanted inside the organism the degradation will depend upon the physiological surrounding environment. This, by modulating the composition of the surface layers formed on Zn devices, will govern the subsequent interactions with the surrounding living cells (e.g. biocompatibility and/or antifungal behaviour). In silico simulation of an implanted Zn piece at bone-muscle interface or inside the bone yielded the preferential precipitation of simonkolleite or zincite, respectively. To study the impact of these surface layers in the in vitro behaviour of Zn biomaterials, simonkolleite and zincite where synthesised. The successful production of simonkolleite or zincite was confirmed by an extensive physicochemical characterization. An in vitro layer formed on the top of these surface layers revealed that simonkolleite was rather inert, while zincite yielded a complex matrix containing hydroxyapatite, an important bone analogue. When analysing the "anti-biofilm" activity simonkolleite stood out for its activity against an important pathogenic fungi involved in implant-device infections, Candida albicans. The possible physiological implications of these findings are discussed.

[ACTIVITY OF ANTIMICROBIAL NANOSTRUCTURED BARRIER LAYERS BASED ON POLYETHYLENETEREPHTHALATE IN RELATION TO CLINICAL STRAINES OF MICROORGANISMS FOR SICK PERSONS OF GASTROENTEROLOGICAL PROFILE].

PubMed

Elinson, V M; Rusanova, E V; Vasilenko, I A; Lyamin, A N; Kostyuchenko, L N

2015-01-01

Homeostasis transgressions of enteral medium including disbiotic ones are often accompanying deseases of digestive tract. Espessially it touches upon sick persons connected with probe nourishing. One of the way for solving this problem is normalization of digestion microflore by means of wares with nanotechnological modifications of walls (probes, stomic tubes) which provide them antimicrobial properties and assist to normalization of digestive microbiotis and enteral homeostasis completely. The aim to study is research of antimicrobial activity of of nanostructured barrier layers based on polyethyleneterephthalate (PET) in relation to clinical straines of microorganisms. For barrier layer creation the approach on the base of methods of ion-plasma technology was used including ion-plasma treatment (nanostructuring) of the surface by ions noble and chemically active gases and following formation nanodimensional carbon films on the surface/ For the study of antimicrobial activity in relation to clinical straines of microorganisms we used the technique which allowed to establish the influence of parting degree of microorganisms suspension and time for samples exposing and microorganisms adsorbed on the surface. In experiment clinical straines obtained from different materials were used: Staphylococcus Hly+ and Calbicans--from pharyngeal mucosa, E. coli--from feces, K.pneumoniae--from urine. Sharing out and species identification of microorganisms were fulfilled according with legasy documents. In results of the study itwas obtained not only the presence of staticticaly confirmed antimicrobial activity of PET samples with nanostructured barrier layers in relation to different stimulators of nosocomical infections but also the influence of different factors connected with formation of nanostructured layers and consequently based with them physicochemical characteristics such as, in particular, surface energy, surface relief parameters, surface charg and others, as well as influence of microorganisms nature onto the interaction of between barrier layers and microorganisms.

Enhancing antimicrobial activity of TiO2/Ti by torularhodin bioinspired surface modification.

PubMed

Ungureanu, Camelia; Dumitriu, Cristina; Popescu, Simona; Enculescu, Monica; Tofan, Vlad; Popescu, Marian; Pirvu, Cristian

2016-02-01

Implant-associated infections are a major cause of morbidity and mortality. This study was performed using titanium samples coated by anodization with a titanium dioxide (TiO2) shielded nanotube layer. TiO2/Ti surface was modified by simple immersion in torularhodin solution and by using a mussel-inspired method based on polydopamine as bio adhesive for torularhodin immobilization. SEM analysis revealed tubular microstructures of torularhodin and the PDA ability to function as a catchy anchor between torularhodin and TiO2 surface. Corrosion resistance was associated with TiO2 barrier oxide layer and nano-organized oxide layer and the torularhodin surface modification does not bring significant changes in resistance of the oxide layer. Our results demonstrated that the torularhodin modified TiO2/Ti surface could effectively prevent adhesion and proliferation of Escherichia coli, Staphylococcus aureus, Enterococcus faecalis, Bacillus subtilis, and Pseudomonas aeruginosa. The new modified titanium surface showed good biocompatibility and well-behaved haemocompatibility. This biomaterial with enhanced antimicrobial activity holds great potential for future biomedical applications. Copyright © 2015 Elsevier B.V. All rights reserved.

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

NASA Astrophysics Data System (ADS)

Peng, Lincai; Li, Hui; Meng, Yahong

2017-04-01

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

Homogeneous near surface activity distribution by double energy activation for TLA

NASA Astrophysics Data System (ADS)

Takács, S.; Ditrói, F.; Tárkányi, F.

2007-10-01

Thin layer activation (TLA) is a versatile tool for activating thin surface layers in order to study real-time the surface loss by wear, corrosion or erosion processes of the activated parts, without disassembling or stopping running mechanical structures or equipment. The research problem is the determination of the irradiation parameters to produce point-like or large area optimal activity-depth distribution in the sample. Different activity-depth profiles can be produced depending on the type of the investigated material and the nuclear reaction used. To produce activity that is independent of the depth up to a certain depth is desirable when the material removed from the surface by wear, corrosion or erosion can be collected completely. By applying dual energy irradiation the thickness of this quasi-constant activity layer can be increased or the deviation of the activity distribution from a constant value can be minimized. In the main, parts made of metals and alloys are suitable for direct activation, but by using secondary particle implantation the wear of other materials can also be studied in a surface range a few micrometers thick. In most practical cases activation of a point-like spot (several mm2) is enough to monitor the wear, corrosion or erosion, but for special problems relatively large surfaces areas of complicated spatial geometry need to be activated uniformly. Two ways are available for fulfilling this task, (1) production of large area beam spot or scanning the beam over the surface in question from the accelerator side, or (2) a programmed 3D movement of the sample from the target side. Taking into account the large variability of tasks occurring in practice, the latter method was chosen as the routine solution in our cyclotron laboratory.

Osteoinductive activity of insulin-functionalized cell culture surfaces obtained using diazonium chemistry

NASA Astrophysics Data System (ADS)

Mikulska, Anna; Filipowska, Joanna; Osyczka, Anna; Nowakowska, Maria; Szczubiałka, Krzysztof

2014-12-01

Polymeric surfaces suitable for cell culture (DR/Pec) were constructed from diazoresin (DR) and pectin (Pec) in a form of ultrathin films using the layer-by-layer (LbL) technique. The surfaces were functionalized with insulin using diazonium chemistry. Such functionalized surfaces were used to culture human mesenchymal stem cells (hMSCs) to assess their suitability for bone tissue engineering and regeneration. The activity of insulin immobilized on the surfaces (DR/Pec/Ins) was compared to that of insulin dissolved in the culture medium. Human MSC grown on insulin-immobilized DR/Pec surfaces displayed increased proliferation and higher osteogenic activity. The latter was determined by means of alkaline phosphatase (ALP) activity, which increases at early stages of osteoblasts differentiation. Insulin dissolved in the culture medium did not stimulate cell proliferation and its osteogenic activity was significantly lower. Addition of recombinant human bone morphogenetic protein 2 (rhBMP-2) to the culture medium further increased ALP activity in hMSCs indicating additive osteogenic action of immobilized insulin and rhBMP-2

Similarity scaling of turbulence in small temperate lake: implication for gas flux: implication for gas flux

NASA Astrophysics Data System (ADS)

Tedford, E. W.; MacIntyre, S.; Miller, S. D.; Czikowsky, M. J.

2013-12-01

The actively mixing layer, or surface layer, is the region of the upper mixed layer of lakes, oceans and the atmosphere directly influenced by wind, heating and cooling. Turbulence within the surface mixing layer has a direct impact on important ecological processes. The Monin-Obukhov length scale (LMO) is a critical length scale used in predicting and understanding turbulence in the actively mixed layer. On the water side of the air-water interface, LMO is defined as: LMO=-u*^3/(0.4 JB0) where u*, the shear velocity, is defined as (τ/rho)^0.5 where τ is the shear stress and rho is the density of water and JBO is the buoyancy flux at the surface. Above the depth equal to the absolute value of the Monin-Obukhov length scale (zMO), wind shear is assumed to dominate the production of turbulent kinetic energy (TKE). Below zMO, the turbulence is assumed to be suppressed when JB0 is stabilizing (warming surface waters) and enhanced when the buoyancy flux is destabilizing (cooling surface waters). Our observed dissipations were well represented using the canonical similarity scaling equations. The Monin-Obukhov length scale was generally effective in separating the surface-mixing layer into two regions: an upper region, dominated by wind shear; and a lower region, dominated by buoyancy flux. During both heating and cooling and above a depth equal to |LMO|, turbulence was dominated by wind shear and dissipation followed law of the wall scaling although was slightly augmented by buoyancy flux during both heating and cooling. Below a depth equal to |LMO| during cooling, dissipation was nearly uniform with depth. Although distinguishing between an upper region of the actively mixing layer dominated by wind stress and a lower portion dominated by buoyancy flux is typically accurate the most accurate estimates of dissipation include the effects of both wind stress and buoyancy flux throughout the actively mixed layer. We demonstrate and discuss the impact of neglecting the non-dominant forcing (buoyancy flux above zMO and wind stress below zMO) above and below zMO.

THE ROLE OF WATER IN PROTOPLASMIC PERMEABILITY AND IN ANTAGONISM

PubMed Central

Osterhout, W. J. V.

1956-01-01

The behavior of the cell depends to a large extent on the permeability of the outer non-aqueous surface layer of the protoplasm. This layer is immiscible with water but may be quite permeable to it. It seems possible that a reversible increase or decrease in permeability may be due to a corresponding increase or decrease in the water content of the non-aqueous surface layer. Irreversible increase in permeability need not be due primarily to increase in the water content of the surface layer but may be caused chiefly by changes in the protoplasm on which the surface layer rests. It may include desiccation, precipitation, and other alterations. An artificial cell is described in which the outer protoplasmic surface layer is represented by a layer of guaiacol on one side of which is a solution of KOH + KCl representing the external medium and on the other side is a solution of CO2 representing the protoplasm. The K+ unites with guaiacol and diffuses across to the artificial protoplasm where its concentration becomes higher than in the external solution. The guaiacol molecule thus acts as a carrier molecule which transports K+ from the external medium across the protoplasmic surface. The outer part of the protoplasm may contain relatively few potassium ions so that the outwardly directed potential at the outer protoplasmic surface may be small but the inner part of the protoplasm may contain more potassium ions. This may happen when potassium enters in combination with carrier molecules which do not completely dissociate until they reach the vacuole. Injury and recovery from injury may be studied by measuring the movements of water into and out of the cell. Metabolism by producing CO2 and other acids may lower the pH and cause local shrinkage of the protoplasm which may lead to protoplasmic motion. Antagonism between Na+ and Ca++ appears to be due to the fact that in solutions of NaCl the surface layer takes up an excessive amount of water and this may be prevented by the addition of suitable amounts of CaCl2. In Nitella the outer non-aqueous surface layer may be rendered irreversibly permeable by sharply bending the cell without permanent damage to the inner non-aqueous surface layer surrounding the vacuole. The formation of contractile vacuoles may be imitated in non-living systems. An extract of the sperm of the marine worm Nereis which contains a highly surface-active substance can cause the egg to divide. It seems possible that this substance may affect the surface layer of the egg and cause it to take up water. A surface-active substance has been found in all the seminal fluids examined including those of trout, rooster, bull, and man. Duponol which is highly surface-active causes the protoplasm of Spirogyra to take up water and finally dissolve but it can be restored to the gel state by treatment with Lugol solution (KI + I). The transition from gel to sol and back again can be repeated many times in succession. The behavior of water in the surface layer of the protoplasm presents important problems which deserve careful examination. PMID:13346047

Enhancement of the surface methane hydrate-bearing layer based on the specific microorganisms form deep seabed sediment in Japan Sea.

NASA Astrophysics Data System (ADS)

Hata, T.; Yoneda, J.; Yamamoto, K.

2017-12-01

A methane hydrate-bearing layer located near the Japan Sea has been investigated as a new potential energy resource. In this study examined the feasibility of the seabed surface sediment strength located in the Japan Sea improvement technologies for enhancing microbial induced carbonate precipitation (MICP) process. First, the authors cultivated the specific urease production bacterium culture medium from this surface methane hydrate-bearing layer in the seabed (-600m depth) of Japan Sea. After that, two types of the laboratory test (consolidated-drained triaxial tests) were conducted using this specific culture medium from the seabed in the Japan Sea near the Toyama Prefecture and high urease activities bacterium named Bacillus pasteurii. The main outcomes of this research are as follows. 1) Specific culture medium focused on the urease production bacterium can enhancement of the urease activities from the methane hydrate-bearing layer near the Japan Sea side, 2) This specific culture medium can be enhancement of the surface layer strength, 3) The microbial induced carbonate precipitation process can increase the particle size compared to that of the original particles coating the calcite layer surface, 4) The mechanism for increasing the soil strength is based on the addition of cohesion like a cement stabilized soil.

Surface modification of a gold-coated microcantilever and application in biomarker detection

NASA Astrophysics Data System (ADS)

Binh Pham, Van; Nhat Khoa Phan, Thanh; Nguyen, Thanh Trung; Pham, Xuan Thanh Tung; Thanh Tuyen Le, Thi; Chien Dang, Mau

2015-12-01

Biosensors have been rapidly developed recently. Biological receptors, such as antibodies, must be immobilized on these sensors’ surfaces to make the sensor capable of capturing a target analyte. In this research we studied how to modify a gold-coated surface of a microcantilever, a sensor with high potential in biological and medical applications. Thiol chemistry was adapted to create a cysteamine layer on a gold surface, and subsequently glutaraldehyde was used as a cross-linking agent to react with amine groups in receptors. In order to evaluate the efficiency of immobilizing protein on an Au surface and also whether the protein retains its biological activity, horseradish peroxidase enzyme (HRP) with its activity to catalyze a reaction between 2,2‧-azino-bis [3-ethylbenzothiazoline-6-sulphonic acid] (ABTS) and {{{H}}}2{{{{O}}}2}- was used as a testing protein. The result showed that HRP was immobilized successfully on cysteamine and glutaraldehyde layers and retained its activity. The cantilever’s tip deflection was also measured, and results showed that each layer created surface stress and made the cantilever bend—in particular, the cysteamine layer induced bending as high as 6 μm. An antibody of alpha-fetoprotein (AFP) was immobilized on the cantilever surface, and the measurement deflection showed that the sensor responded to solution containing AFP with concentration from 100 to 500 ng ml-1.

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

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

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

Climate change and thawing permafrost in the Arctic will significantly alter landscape hydro-geomorphology and the distribution of soil moisture, which will have cascading effects on climate feedbacks (CO 2 and CH 4) and plant and microbial communities. Fundamental processes critical to predicting active layer hydrology are not well understood. This study applied water stable isotope techniques (δ 2H and δ 18O) to infer sources and mixing of active layer waters in a polygonal tundra landscape in Barrow, Alaska (USA), in August and September of 2012. Results suggested that winter precipitation did not contribute substantially to surface waters or subsurface activemore » layer pore waters measured in August and September. Summer rain was the main source of water to the active layer, with seasonal ice melt contributing to deeper pore waters later in the season. Surface water evaporation was evident in August from a characteristic isotopic fractionation slope (δ 2H vs δ 18O). Freeze-out isotopic fractionation effects in frozen active layer samples and textural permafrost were indistinguishable from evaporation fractionation, emphasizing the importance of considering the most likely processes in water isotope studies, in systems where both evaporation and freeze-out occur in close proximity. The fractionation observed in frozen active layer ice was not observed in liquid active layer pore waters. Such a discrepancy between frozen and liquid active layer samples suggests mixing of meltwater, likely due to slow melting of seasonal ice. In conclusion, this research provides insight into fundamental processes relating to sources and mixing of active layer waters, which should be considered in process-based fine-scale and intermediate-scale hydrologic models.« less

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

DOE PAGES

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

2016-04-16

Climate change and thawing permafrost in the Arctic will significantly alter landscape hydro-geomorphology and the distribution of soil moisture, which will have cascading effects on climate feedbacks (CO 2 and CH 4) and plant and microbial communities. Fundamental processes critical to predicting active layer hydrology are not well understood. This study applied water stable isotope techniques (δ 2H and δ 18O) to infer sources and mixing of active layer waters in a polygonal tundra landscape in Barrow, Alaska (USA), in August and September of 2012. Results suggested that winter precipitation did not contribute substantially to surface waters or subsurface activemore » layer pore waters measured in August and September. Summer rain was the main source of water to the active layer, with seasonal ice melt contributing to deeper pore waters later in the season. Surface water evaporation was evident in August from a characteristic isotopic fractionation slope (δ 2H vs δ 18O). Freeze-out isotopic fractionation effects in frozen active layer samples and textural permafrost were indistinguishable from evaporation fractionation, emphasizing the importance of considering the most likely processes in water isotope studies, in systems where both evaporation and freeze-out occur in close proximity. The fractionation observed in frozen active layer ice was not observed in liquid active layer pore waters. Such a discrepancy between frozen and liquid active layer samples suggests mixing of meltwater, likely due to slow melting of seasonal ice. In conclusion, this research provides insight into fundamental processes relating to sources and mixing of active layer waters, which should be considered in process-based fine-scale and intermediate-scale hydrologic models.« less

Membranes having aligned 1-D nanoparticles in a matrix layer for improved fluid separation

DOEpatents

Revanur, Ravindra; Lulevich, Valentin; Roh, Il Juhn; Klare, Jennifer E.; Kim, Sangil; Noy, Aleksandr; Bakajin, Olgica

2015-12-22

Membranes for fluid separation are disclosed. These membranes have a matrix layer sandwiched between an active layer and a porous support layer. The matrix layer includes 1-D nanoparticles that are vertically aligned in a porous polymer matrix, and which substantially extend through the matrix layer. The active layer provides species-specific transport, while the support layer provides mechanical support. A matrix layer of this type has favorable surface morphology for forming the active layer. Furthermore, the pores that form in the matrix layer tend to be smaller and more evenly distributed as a result of the presence of aligned 1-D nanoparticles. Improved performance of separation membranes of this type is attributed to these effects.

Surface morphology and structure of Ge layer on Si(111) after solid phase epitaxy

NASA Astrophysics Data System (ADS)

Yoshida, Ryoma; Tosaka, Aki; Shigeta, Yukichi

2018-05-01

The surface morphology change of a Ge layer on a Si(111) surface formed by solid phase epitaxy has been investigated with a scanning tunneling microscope (STM). The Ge film was deposited at room temperature and annealed at 400 °C or 600 °C. The STM images of the sample surface after annealing at 400 °C show a flat wetting layer (WL) with small three-dimensional islands on the WL. After annealing at 600 °C, the STM images show a surface roughening with large islands. From the relation between the average height of the roughness and the deposited layer thickness, it is confirmed that the diffusion of Ge atoms becomes very active at 600 °C. The Si crystal at the interface is reconstructed and the intermixing occurs over 600 °C. However, the intermixing is fairly restricted in the solid phase epitaxy growth at 400 °C. The surface morphology changes with the crystallization at 400 °C are discussed by the shape of the islands formed on the WL surface. It is shown that the diffusion of the Ge atoms in the amorphous phase is active even at 400 °C.

Effect of gold subsurface layer on the surface activity and segregation in Pt/Au/Pt3M (where M = 3d transition metals) alloy catalyst from first-principles.

PubMed

Kim, Chang-Eun; Lim, Dong-Hee; Jang, Jong Hyun; Kim, Hyoung Juhn; Yoon, Sung Pil; Han, Jonghee; Nam, Suk Woo; Hong, Seong-Ahn; Soon, Aloysius; Ham, Hyung Chul

2015-01-21

The effect of a subsurface hetero layer (thin gold) on the activity and stability of Pt skin surface in Pt3M system (M = 3d transition metals) is investigated using the spin-polarized density functional theory calculation. First, we find that the heterometallic interaction between the Pt skin surface and the gold subsurface in Pt/Au/Pt3M system can significantly modify the electronic structure of the Pt skin surface. In particular, the local density of states projected onto the d states of Pt skin surface near the Fermi level is drastically decreased compared to the Pt/Pt/Pt3M case, leading to the reduction of the oxygen binding strength of the Pt skin surface. This modification is related to the increase of surface charge polarization of outmost Pt skin atoms by the electron transfer from the gold subsurface atoms. Furthermore, a subsurface gold layer is found to cast the energetic barrier to the segregation loss of metal atoms from the bulk (inside) region, which can enhance the durability of Pt3M based catalytic system in oxygen reduction condition at fuel cell devices. This study highlights that a gold subsurface hetero layer can provide an additional mean to tune the surface activity toward oxygen species and in turn the oxygen reduction reaction, where the utilization of geometric strain already reaches its practical limit.

Measured Two-Dimensional Ice-Wedge Polygon Thermal and Active Layer Dynamics

NASA Astrophysics Data System (ADS)

Cable, W.; Romanovsky, V. E.; Busey, R.

2016-12-01

Ice-wedge polygons are perhaps the most dominant permafrost related features in the arctic landscape. The microtopography of these features, that includes rims, troughs, and high and low polygon centers, alters the local hydrology. During winter, wind redistribution of snow leads to an increased snowpack depth in the low areas, while the slightly higher areas often have very thin snow cover, leading to differences across the landscape in vegetation communities and soil moisture between higher and lower areas. To investigate the effect of microtopographic caused variation in surface conditions on the ground thermal regime, we established temperature transects, composed of five vertical array thermistor probes (VATP), across four different development stages of ice-wedge polygons near Barrow, Alaska. Each VATP had 16 thermistors from the surface to a depth of 1.5 m, for a total of 80 temperature measurements per polygon. We found snow cover, timing and depth, and active layer soil moisture to be major controlling factors in the observed thermal regimes. In troughs and in the centers of low-centered polygons, the combined effect of typically saturated soils and increased snow accumulation resulted in the highest mean annual ground temperatures (MAGT) and latest freezeback dates. While the centers of high-centered polygons, with thinner snow cover and a dryer active layer, had the lowest MAGT, earliest freezeback dates, and shallowest active layer. Refreezing of the active layer initiated at nearly the same time for all locations and polygons however, we found large differences in the proportion of downward versus upward freezing and the length of time required to complete the refreezing process between polygon types and locations. Using our four polygon stages as a space for time substitution, we conclude that ice-wedge degradation resulting in surface subsidence and trough deepening can lead to overall drying of the active layer and increased skewedness of snow distribution. Which in turn leads to shallower active layers, earlier freezeback dates, and lower MAGT. We also find that the large variation in active layer dynamics (active layer depth, downward vs upward freezing, and freezeback date) are important considerations to understanding and scaling biological processes occurring in these landscapes.

Application of a mixed metal oxide catalyst to a metallic substrate

NASA Technical Reports Server (NTRS)

Sevener, Kathleen M. (Inventor); Lohner, Kevin A. (Inventor); Mays, Jeffrey A. (Inventor); Wisner, Daniel L. (Inventor)

2009-01-01

A method for applying a mixed metal oxide catalyst to a metallic substrate for the creation of a robust, high temperature catalyst system for use in decomposing propellants, particularly hydrogen peroxide propellants, for use in propulsion systems. The method begins by forming a prepared substrate material consisting of a metallic inner substrate and a bound layer of a noble metal intermediate. Alternatively, a bound ceramic coating, or frit, may be introduced between the metallic inner substrate and noble metal intermediate when the metallic substrate is oxidation resistant. A high-activity catalyst slurry is applied to the surface of the prepared substrate and dried to remove the organic solvent. The catalyst layer is then heat treated to bind the catalyst layer to the surface. The bound catalyst layer is then activated using an activation treatment and calcinations to form the high-activity catalyst system.

Composite membrane with integral rim

DOEpatents

Routkevitch, Dmitri; Polyakov, Oleg G

2015-01-27

Composite membranes that are adapted for separation, purification, filtration, analysis, reaction and sensing. The composite membranes can include a porous support structure having elongate pore channels extending through the support structure. The composite membrane also includes an active layer comprising an active layer material, where the active layer material is completely disposed within the pore channels between the surfaces of the support structure. The active layer is intimately integrated within the support structure, thus enabling great robustness, reliability, resistance to mechanical stress and thermal cycling, and high selectivity. Methods for the fabrication of composite membranes are also provided.

Colloidal quantum dot active layers for light emitting diodes

NASA Astrophysics Data System (ADS)

Pagan, Jennifer G.; Stokes, Edward B.; Patel, Kinnari; Burkhart, Casey C.; Ahrens, Michael T.; Barletta, Philip T.; O'Steen, Mark

2006-07-01

In this paper the preliminary results of incorporating a novel active layer into a GaN light emitting diode (LED) are discussed. Integration of colloidal CdSe quantum dots into a GaN LED active layer is demonstrated. Properties of p-type Mg doped overgrowth GaN are examined via circular transmission line method (CTLM). Effects on surface roughness due to the active layer incorporation are examined using atomic force microscopy (AFM). Electroluminescence of LED test structures is reported, and an ideality factor of n = 1.6 is demonstrated.

Monolithic in-based III-V compound semiconductor focal plane array cell with single stage CCD output

NASA Technical Reports Server (NTRS)

Fossum, Eric R. (Inventor); Cunningham, Thomas J. (Inventor); Krabach, Timothy N. (Inventor); Staller, Craig O. (Inventor)

1994-01-01

A monolithic semiconductor imager includes an indium-based III-V compound semiconductor monolithic active layer of a first conductivity type, an array of plural focal plane cells on the active layer, each of the focal plane cells including a photogate over a top surface of the active layer, a readout circuit dedicated to the focal plane cell including plural transistors formed monolithically with the monolithic active layer and a single-stage charge coupled device formed monolithically with the active layer between the photogate and the readout circuit for transferring photo-generated charge accumulated beneath the photogate during an integration period to the readout circuit. The photogate includes thin epitaxial semiconductor layer of a second conductivity type overlying the active layer and an aperture electrode overlying a peripheral portion of the thin epitaxial semiconductor layer, the aperture electrode being connectable to a photogate bias voltage.

Surfactant-associated bacteria in the near-surface layer of the ocean.

PubMed

Kurata, Naoko; Vella, Kate; Hamilton, Bryan; Shivji, Mahmood; Soloviev, Alexander; Matt, Silvia; Tartar, Aurélien; Perrie, William

2016-01-12

Certain marine bacteria found in the near-surface layer of the ocean are expected to play important roles in the production and decay of surface active materials; however, the details of these processes are still unclear. Here we provide evidence supporting connection between the presence of surfactant-associated bacteria in the near-surface layer of the ocean, slicks on the sea surface, and a distinctive feature in the synthetic aperture radar (SAR) imagery of the sea surface. From DNA analyses of the in situ samples using pyrosequencing technology, we found the highest abundance of surfactant-associated bacterial taxa in the near-surface layer below the slick. Our study suggests that production of surfactants by marine bacteria takes place in the organic-rich areas of the water column. Produced surfactants can then be transported to the sea surface and form slicks when certain physical conditions are met. This finding has potential applications in monitoring organic materials in the water column using remote sensing techniques. Identifying a connection between marine bacteria and production of natural surfactants may provide a better understanding of the global picture of biophysical processes at the boundary between the ocean and atmosphere, air-sea exchange of greenhouse gases, and production of climate-active marine aerosols.

Surfactant-associated bacteria in the near-surface layer of the ocean

PubMed Central

Kurata, Naoko; Vella, Kate; Hamilton, Bryan; Shivji, Mahmood; Soloviev, Alexander; Matt, Silvia; Tartar, Aurélien; Perrie, William

2016-01-01

Certain marine bacteria found in the near-surface layer of the ocean are expected to play important roles in the production and decay of surface active materials; however, the details of these processes are still unclear. Here we provide evidence supporting connection between the presence of surfactant-associated bacteria in the near-surface layer of the ocean, slicks on the sea surface, and a distinctive feature in the synthetic aperture radar (SAR) imagery of the sea surface. From DNA analyses of the in situ samples using pyrosequencing technology, we found the highest abundance of surfactant-associated bacterial taxa in the near-surface layer below the slick. Our study suggests that production of surfactants by marine bacteria takes place in the organic-rich areas of the water column. Produced surfactants can then be transported to the sea surface and form slicks when certain physical conditions are met. This finding has potential applications in monitoring organic materials in the water column using remote sensing techniques. Identifying a connection between marine bacteria and production of natural surfactants may provide a better understanding of the global picture of biophysical processes at the boundary between the ocean and atmosphere, air-sea exchange of greenhouse gases, and production of climate-active marine aerosols. PMID:26753514

An organic surface modifier to produce a high work function transparent electrode for high performance polymer solar cells.

PubMed

Choi, Hyosung; Kim, Hak-Beom; Ko, Seo-Jin; Kim, Jin Young; Heeger, Alan J

2015-02-04

Modification of an ITO electrode with small-molecule organic surface modifier, 4-chloro-benzoic acid (CBA), via a simple spin-coating method produces a high-work-function electrode with high transparency and a hydrophobic surface. As an alternative to PEDOT:PSS, CBA modification achieves efficiency enhancement up to 8.5%, which is attributed to enhanced light absorption within the active layer and smooth hole transport from the active layer to the anode. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Endothelial glycocalyx: permeability barrier and mechanosensor.

PubMed

Curry, F E; Adamson, R H

2012-04-01

Endothelial cells are covered with a polysaccharide rich layer more than 400 nm thick, mechanical properties of which limit access of circulating plasma components to endothelial cell membranes. The barrier properties of this endothelial surface layer are deduced from the rate of tracer penetration into the layer and the mechanics of red and white cell movement through capillary microvessels. This review compares the mechanosensor and permeability properties of an inner layer (100-150 nm, close to the endothelial membrane) characterized as a quasi-periodic structure which accounts for key aspects of transvascular exchange and vascular permeability with those of the whole endothelial surface layers. We conclude that many of the barrier properties of the whole surface layer are not representative of the primary fiber matrix forming the molecular filter determining transvascular exchange. The differences between the properties of the whole layer and the inner glycocalyx structures likely reflect dynamic aspects of the endothelial surface layer including tracer binding to specific components, synthesis and degradation of key components, activation of signaling pathways in the endothelial cells when components of the surface layer are lost or degraded, and the spatial distribution of adhesion proteins in microdomains of the endothelial cell membrane.

Performance enhancement in organic photovoltaic solar cells using iridium (Ir) ultra-thin surface modifier (USM)

NASA Astrophysics Data System (ADS)

Pandey, Rina; Lim, Ju Won; Kim, Jung Hyuk; Angadi, Basavaraj; Choi, Ji Won; Choi, Won Kook

2018-06-01

In this study, Iridium (Ir) metallic layer as an ultra-thin surface modifier (USM) was deposited on ITO coated glass substrate using radio frequency magnetron sputtering for improving the photo-conversion efficiency of organic photovoltaic cells. Ultra-thin Ir acts as a surface modifier replacing the conventional hole transport layer (HTL) PEDOT:PSS in organic photovoltaic (OPV) cells with two different active layers P3HT:PC60BM and PTB7:PC70BM. The Ir USM (1.0 nm) coated on ITO glass substrate showed transmittance of 84.1% and work function of >5.0 eV, which is higher than that of ITO (4.5-4.7 eV). The OPV cells with Ir USM (1.0 nm) exhibits increased power conversion efficiency of 3.70% (for P3HT:PC60BM active layer) and 7.28% (for PTB7:PC70BM active layer) under 100 mW/cm2 illumination (AM 1.5G) which are higher than those of 3.26% and 6.95% for the same OPV cells but with PEDOT:PSS as HTL instead of Ir USM. The results reveal that the chemically stable Ir USM layer could be used as an alternative material for PEDOT:PSS in organic photovoltaic cells.

Flexible strategy for immobilizing redox-active compounds using in situ generation of diazonium salts. Investigations of the blocking and catalytic properties of the layers.

PubMed

Noël, Jean-Marc; Sjöberg, Béatrice; Marsac, Rémi; Zigah, Dodzi; Bergamini, Jean-François; Wang, Aifang; Rigaut, Stéphane; Hapiot, Philippe; Lagrost, Corinne

2009-11-03

A versatile two-step method is developed to covalently immobilize redox-active molecules onto carbon surfaces. First, a robust anchoring platform is grafted onto surfaces by electrochemical reduction of aryl diazonium salts in situ generated. Depending on the nature of the layer termini, -COOH or -NH(2), a further chemical coupling involving ferrocenemethylamine or ferrocene carboxylic acid derivatives leads to the covalent binding of ferrocene centers. The chemical strategy using acyl chloride activation is efficient and flexible, since it can be applied either to surface-reactive end groups or to reactive species in solution. Cyclic voltammetry analyses point to the covalent binding of ferrocene units restricted to the upper layers of the underlying aryl films, while AFM measurements show a lost of compactness of the layers after the chemical attachment of ferrocene centers. The preparation conditions of the anchoring layers were found to determine the interfacial properties of the resulted ferrocenyl-modified electrodes. The ferrocene units promoted effective redox mediation providing that the free redox probes are adequately chosen (i.e., vs size/formal potential) and the underlying layers exhibit strong blocking properties. For anchoring films with weaker blocking effect, the coexistence of two distinct phenomena, redox mediation and ET at pinholes could be evidenced.

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

DOE PAGES

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

2016-05-18

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

Relationships between structure and activity of carbon as a multifunctional support for electrocatalysts.

PubMed

Stevanović, Sanja I; Panić, Vladimir V; Dekanski, Aleksandar B; Tripković, Amalija V; Jovanović, Vladislava M

2012-07-14

We report on new insights into the relationships between structure and activity of glassy carbon (GC), as a model material for electrocatalyst support, during its anodization in acid solution. Our investigation strongly confirms the role of CFGs in promotion of Pt activity by the "spill-over" effect related to CO(ads) for methanol electrooxidation (MEO) on a carbon-supported Pt catalyst. Combined analysis of voltammetric and impedance behaviour as well as changes in GC surface morphology induced by intensification of anodizing conditions reveal an intrinsic influence of the carbon functionalization and the structure of a graphene oxide (GO) layer on the electrical and electrocatalytic properties of activated GC. Although GO continuously grows during anodization, it structurally changes from being a graphite inter-layer within graphite ribbons toward a continuous GO surface layer that deteriorates the native structure of GC. As a consequence of the increased distance between GO-spaced graphite layers, the GC conductivity decreases until the case of profound GO exfoliation under drastic anodizing conditions. This exposes the native, yet abundantly functionalized, GC texture. While GC capacitance continuously increases with intensification of anodizing conditions, the surface nano-roughness and GO resistance reach the highest values at modest anodizing conditions, and then decrease upon drastic anodization due to the onset of GO exfoliation. We found for the first time that the activity of a GC-supported Pt catalyst in MEO, as one of the promising half-reactions in polymer electrolyte fuel cells, strictly follows the changes in GC nano-roughness and GO-induced GC resistance. The highest GC/Pt MEO activity is reached when optimal distance between graphite layers and optimal degree of GC functionalization bring the highest amount of CFGs into intimate contact with the Pt surface. This confirms the promoting role of CFGs in MEO catalysis.

Photocatalytic activity and reusability of ZnO layer synthesised by electrolysis, hydrogen peroxide and heat treatment.

PubMed

Akhmal Saadon, Syaiful; Sathishkumar, Palanivel; Mohd Yusoff, Abdull Rahim; Hakim Wirzal, Mohd Dzul; Rahmalan, Muhammad Taufiq; Nur, Hadi

2016-08-01

In this study, the zinc oxide (ZnO) layer was synthesised on the surface of Zn plates by three different techniques, i.e. electrolysis, hydrogen peroxide and heat treatment. The synthesised ZnO layers were characterised using scanning electron microscopy, X-ray diffraction, UV-visible diffuse reflectance and photoluminescence spectroscopy. The photocatalytic activity of the ZnO layer was further assessed against methylene blue (MB) degradation under UV irradiation. The photocatalytic degradation of MB was achieved up to 84%, 79% and 65% within 1 h for ZnO layers synthesised by electrolysis, heat and hydrogen peroxide treatment, respectively. The reusability results show that electrolysis and heat-treated ZnO layers have considerable photocatalytic stability. Furthermore, the results confirmed that the photocatalytic efficiency of ZnO was directly associated with the thickness and enlarged surface area of the layer. Finally, this study proved that the ZnO layers synthesised by electrolysis and heat treatment had shown better operational stability and reusability.

Mitigating leaks in membranes

DOEpatents

Karnik, Rohit N.; Bose, Suman; Boutilier, Michael S.H.; Hadjiconstantinou, Nicolas G.; Jain, Tarun Kumar; O'Hern, Sean C.; Laoui, Tahar; Atieh, Muataz A.; Jang, Doojoon

2018-02-27

Two-dimensional material based filters, their method of manufacture, and their use are disclosed. In one embodiment, a membrane may include an active layer including a plurality of defects and a deposited material associated with the plurality of defects may reduce flow therethrough. Additionally, a majority of the active layer may be free from the material. In another embodiment, a membrane may include a porous substrate and an atomic layer deposited material disposed on a surface of the porous substrate. The atomic layer deposited material may be less hydrophilic than the porous substrate and an atomically thin active layer may be disposed on the atomic layer deposited material.

Osteoinductive activity of insulin-functionalized cell culture surfaces obtained using diazonium chemistry

PubMed Central

Mikulska, Anna; Filipowska, Joanna; Osyczka, Anna M.; Nowakowska, Maria; Szczubiałka, Krzysztof

2015-01-01

Polymeric surfaces suitable for cell culture (DR/Pec) were constructed from diazoresin (DR) and pectin (Pec) in a form of ultrathin films using the layer-by-layer (LbL) technique. The surfaces were functionalized with insulin using diazonium chemistry. Such functionalized surfaces were used to culture human mesenchymal stem cells (hMSCs) to assess their suitability for bone tissue engineering and regeneration. The activity of insulin immobilized on the surfaces (DR/Pec/Ins) was compared to that of insulin dissolved in the culture medium. Human MSC grown on insulin-immobilized DR/Pec surfaces displayed increased proliferation and higher osteogenic activity. The latter was determined by means of alkaline phosphatase (ALP) activity, which increases at early stages of osteoblasts differentiation. Insulin dissolved in the culture medium did not stimulate cell proliferation and its osteogenic activity was significantly lower. Addition of recombinant human bone morphogenetic protein 2 (rhBMP-2) to the culture medium further increased ALP activity in hMSCs indicating additive osteogenic action of immobilized insulin and rhBMP-2. PMID:25629028

Flow Pathways of Snow and Ground Ice Melt Water During Initial Seasonal Thawing of the Active Layer on Continuous Permafrost

NASA Astrophysics Data System (ADS)

Sjoberg, Y.; Johansson, E.; Rydberg, J.

2017-12-01

In most arctic environments, the snowmelt is the main hydrologic event of the year as a large fraction of annual precipitation rapidly moves through the catchment. Flow can occur on top of the frozen ground surface or through the developing active layer, and flow pathways are critical determinants for biogeochemical transport. We study the linkages between micro topography, active layer thaw, and water partitioning on a hillslope in Greenland during late snowmelt season to explore how seasonal subsurface flow pathways develop. During snowmelt, a parallel surface drainage pattern appears across the slope, consisting of small streams, and water also collects in puddles across the slope. Thaw rates in the active layer were significantly higher (T-test p<0.01) on wet parts of the slope (0.8 cm/day), compared to drier parts of the slope (0.6 cm/day). Analyses of stable water isotopic composition show that snow had the lightest isotopic signatures, but with a large spread of values, while seasonally frozen ground and standing surface water (puddles) were heavier. The stream water became heavier over the two-week sampling period, suggesting an increasing fraction of melted soil water input over time. In contrast, standing surface water (puddles) isotopic composition did not change over time. In boreal catchments, seasonal frost has previously been found to not significantly influence flow pathways during most snowmelt events, and pre-event groundwater make out most of the stream water during snowmelt. Our results from a continuous permafrost environment show that both surface (overland) and subsurface flow pathways in the active layer are active, and that a large fraction of the water moving on the hillslope comes from melted ground ice rather than snow in the late snowmelt season. This suggests a possibility that flow pathways during snowmelt could shift to deeper subsurface flow following degradation of continuous permafrost.

Carbon-Coated Current Collectors for High-Power Li-Ion Secondary Batteries

DTIC Science & Technology

2012-08-29

deposition condition. Surface analysis indicates that this thin C layer does not contain interfacial Al-carbide layer. LiFePO4 electrode using this C...layer does not contain an interfacial Al-carbide layer. LiFePO4 electrode using this C-coated Al current collector exhibits higher capacity under 10 C...cathode. LiFePO4 (LFPO) was used as active materials for test, and this cathode material was purchased from Aleees company. The LFPO active layer

Electrically injected visible vertical cavity surface emitting laser diodes

DOEpatents

Schneider, Richard P.; Lott, James A.

1994-01-01

Visible laser light output from an electrically injected vertical cavity surface emitting laser (VSCEL) diode is enabled by the addition of phase-matching spacer layers on either side of the active region to form the optical cavity. The spacer layers comprise InAlP which act as charge carrier confinement means. Distributed Bragg reflector layers are formed on either side of the optical cavity to act as mirrors.

Electrically injected visible vertical cavity surface emitting laser diodes

DOEpatents

Schneider, R.P.; Lott, J.A.

1994-09-27

Visible laser light output from an electrically injected vertical cavity surface emitting laser (VSCEL) diode is enabled by the addition of phase-matching spacer layers on either side of the active region to form the optical cavity. The spacer layers comprise InAlP which act as charge carrier confinement means. Distributed Bragg reflector layers are formed on either side of the optical cavity to act as mirrors. 5 figs.

Collective Surfing of Chemically Active Particles

NASA Astrophysics Data System (ADS)

Masoud, Hassan; Shelley, Michael J.

2014-03-01

We study theoretically the collective dynamics of immotile particles bound to a 2D surface atop a 3D fluid layer. These particles are chemically active and produce a chemical concentration field that creates surface-tension gradients along the surface. The resultant Marangoni stresses create flows that carry the particles, possibly concentrating them. For a 3D diffusion-dominated concentration field and Stokesian fluid we show that the surface dynamics of active particle density can be determined using nonlocal 2D surface operators. Remarkably, we also show that for both deep or shallow fluid layers this surface dynamics reduces to the 2D Keller-Segel model for the collective chemotactic aggregation of slime mold colonies. Mathematical analysis has established that the Keller-Segel model can yield finite-time, finite-mass concentration singularities. We show that such singular behavior occurs in our finite-depth system, and study the associated 3D flow structures.

Solid state radiative heat pump

DOEpatents

Berdahl, Paul H.

1986-01-01

A solid state radiative heat pump (10, 50, 70) operable at room temperature (300.degree. K.) utilizes a semiconductor having a gap energy in the range of 0.03-0.25 eV and operated reversibly to produce an excess or deficit of charge carriers as compared to thermal equilibrium. In one form of the invention (10, 70) an infrared semiconductor photodiode (21, 71) is used, with forward or reverse bias, to emit an excess or deficit of infrared radiation. In another form of the invention (50), a homogeneous semiconductor (51) is subjected to orthogonal magnetic and electric fields to emit an excess or deficit of infrared radiation. Three methods of enhancing transmission of radiation through the active surface of the semiconductor are disclosed. In one method, an anti-reflection layer (19) is coated into the active surface (13) of the semiconductor (11), the anti-reflection layer (19) having an index of refraction equal to the square root of that of the semiconductor (11). In the second method, a passive layer (75) is spaced from the active surface (73) of the semiconductor (71) by a submicron vacuum gap, the passive layer having an index of refractive equal to that of the semiconductor. In the third method, a coupler (91) with a paraboloid reflecting surface (92) is in contact with the active surface (13, 53) of the semiconductor (11, 51), the coupler having an index of refraction about the same as that of the semiconductor.

Ultrasound assisted deposition of silica coatings on titanium

NASA Astrophysics Data System (ADS)

Kaş, Recep; Ertaş, Fatma Sinem; Birer, Özgür

2012-10-01

We present a novel ultrasound assisted method for silica coating of titanium surfaces. The coatings are formed by “smashing” silica nanoparticles onto activated titanium surface in solution using intense ultrasonic field. Homogeneous silica coatings are formed by deposition of dense multiple layers of silica nanoparticles. Since the nanoparticles also grow during the reaction, the layers of the coatings have smaller particles on the substrate and larger particles towards the surface. The thickness of the coatings can be controlled with several experimental parameters. Silica layers with thickness over 200 nm are readily obtained.

Novel procedure to enhance PLA surface properties by chitosan irreversible immobilization

NASA Astrophysics Data System (ADS)

Stoleru, Elena; Dumitriu, Raluca Petronela; Munteanu, Bogdanel Silvestru; Zaharescu, Traian; Tănase, Elisabeta Elena; Mitelut, Amalia; Ailiesei, Gabriela-Liliana; Vasile, Cornelia

2016-03-01

A novel two step procedure was applied for poly(lactic acid) (PLA) functionalization consisting in the exposure to cold radiofrequency plasma in nitrogen atmosphere or to gamma irradiation followed by ;grafting to; of a chitosan layer using carbodiimide chemistry. The adhesion and stability of the deposited surface layer was assured by plasma/gamma irradiation treatment while the chitosan layer offers antifungal/antibacterial/antioxidant activities. Chitosan with different viscosities/deacetylation degree was deposited by electrospinning or immersion methods. Correlations between rheological behavior of chitosan solutions and chitosan layer deposition conditions are made. The PLA surface properties were investigated by water contact angle measurements, ATR-FTIR spectroscopy, AFM, chemiluminiscence, etc. It has been established that the surface roughness increases direct proportional with cold plasma duration and gamma irradiation dose and further increases by chitosan coating which at its turn depends on chitosan characteristics (viscosity and deacetylation degree) and method of deposition. Nano-fibers with relatively homogeneous and reproducible features are obtained by electrospinning of highly viscous chitosan while with the other two types of chitosan both microparticles and nano-fibers are formed. The chitosan coating obtained by immersion is more homogenous and compact and has a better antibacterial activity than the electrospun layer as fiber meshes.

Composite membranes and methods for making same

DOEpatents

Routkevitch, Dmitri; Polyakov, Oleg G

2012-07-03

Composite membranes that are adapted for separation, purification, filtration, analysis, reaction and sensing. The composite membranes can include a porous support structure having elongate pore channels extending through the support structure. The composite membrane also includes an active layer comprising an active layer material, where the active layer material is completely disposed within the pore channels between the surfaces of the support structure. The active layer is intimately integrated within the support structure, thus enabling great robustness, reliability, resistance to mechanical stress and thermal cycling, and high selectivity. Methods for the fabrication of composite membranes are also provided.

Long-term active-layer dynamics: results of 22 years of field observations in Northern Hemisphere permafrost regions.

NASA Astrophysics Data System (ADS)

Shiklomanov, N. I.; Nelson, F. E.; Streletskiy, D. A.; Klene, A. E.; Biskaborn, B. K.

2016-12-01

The uppermost layer of seasonal thawing above permafrost (the active layer) is an important regulator of energy and mass fluxes between the surface and the atmosphere in the polar regions. Active layer monitoring is an important component of efforts to assess the effects of global change in permafrost environments. The Circumpolar Active Layer Monitoring (CALM) program, established in the early 1990s, is designed to observe temporal and spatial variability of the active layer and its response to changes and variations in climatic conditions. The CALM network is an integral part of the Global Terrestrial Network for Permafrost (GTN-P), operating under the auspices of the Global Terrestrial Observing System (GTOS) /Global Climate Observing System (GCOS). Standardized thaw depth observations in the Northern Hemisphere are available for more than 200 GTN-P/CALM sites in the Northern Hemisphere. At each of the sites spatially distributed ALT measurements have been conducted annually by mechanical probing. The locations of sites represent generalized surface and subsurface conditions characteristic of broader regions. The data are assimilated and distributed though the CALM (www.gwu.edu/ calm) and GTN-P (gtnpdatabase.org) online databases. In this presentation we use data from approximately 20 years of continuous observations to examine temporal trends in active-layer thickness for several representative Arctic regions. Results indicate substantial interannual fluctuations in active-layer thickness, primarily in response to variations in air temperature. Decadal trends in ALT vary by region. A progressive increase in ALT has been observed in the Nordic countries, the Russian European North, West Siberia, East Siberia, the Russian Far East, and the Interior of Alaska. North American Arctic sites show no apparent thaw depth trend over 22-years of record. However, combined active layer, ground temperature and heave/subsidence observations conducted in northern Alaska demonstrate a complex, non-linear response of the active-layer/upper permafrost system to changes in climatic conditions.

Adsorption and activity of Thermomyces lanuginosus lipase on hydrophobic and hydrophilic surfaces measured with dual polarization interferometry (DPI) and confocal microscopy.

PubMed

Sonesson, Andreas W; Callisen, Thomas H; Brismar, Hjalmar; Elofsson, Ulla M

2008-02-15

The adsorption and activity of Thermomyces lanuginosus lipase (TLL) was measured with dual polarization interferometry (DPI) and confocal microscopy at a hydrophilic and hydrophobic surface. In the adsorption isotherms, it was evident that TLL both had higher affinity for the hydrophobic surface and adsorbed to a higher adsorbed amount (1.90 mg/m(2)) compared to the hydrophilic surface (1.40-1.50mg/m(2)). The thickness of the adsorbed layer was constant (approximately 3.5 nm) on both surfaces at an adsorbed amount >1.0mg/m(2), but decreased on the hydrophilic surface at lower surface coverage, which might be explained by partially unfolding of the TLL structure. However, a linear dependence of the refractive index of the adsorbed layer on adsorbed amount of TLL on C18 surfaces indicated that the structure of TLL was similar at low and high surface coverage. The activity of adsorbed TLL was measured towards carboxyfluorescein diacetate (CFDA) in solution, which upon lipase activity formed a fluorescent product. The surface fluorescence intensity increase was measured in a confocal microscope as a function of time after lipase adsorption. It was evident that TLL was more active on the hydrophilic surface, which suggested that a larger fraction of adsorbed TLL molecules were oriented with the active site facing the solution compared to the hydrophobic surface. Moreover, most of the activity remained when the TLL surface coverage decreased. Earlier reports on TLL surface mobility on the same surfaces have found that the lateral diffusion was highest on hydrophilic surfaces and at low surface coverage of TLL. Hence, a high lateral mobility might lead to a longer exposure time of the active site towards solution, thereby increasing the activity against a water-soluble substrate.

Passivation of phosphorus diffused silicon surfaces with Al2O3: Influence of surface doping concentration and thermal activation treatments

NASA Astrophysics Data System (ADS)

Richter, Armin; Benick, Jan; Kimmerle, Achim; Hermle, Martin; Glunz, Stefan W.

2014-12-01

Thin layers of Al2O3 are well known for the excellent passivation of p-type c-Si surfaces including highly doped p+ emitters, due to a high density of fixed negative charges. Recent results indicate that Al2O3 can also provide a good passivation of certain phosphorus-diffused n+ c-Si surfaces. In this work, we studied the recombination at Al2O3 passivated n+ surfaces theoretically with device simulations and experimentally for Al2O3 deposited with atomic layer deposition. The simulation results indicate that there is a certain surface doping concentration, where the recombination is maximal due to depletion or weak inversion of the charge carriers at the c-Si/Al2O3 interface. This pronounced maximum was also observed experimentally for n+ surfaces passivated either with Al2O3 single layers or stacks of Al2O3 capped by SiNx, when activated with a low temperature anneal (425 °C). In contrast, for Al2O3/SiNx stacks activated with a short high-temperature firing process (800 °C) a significant lower surface recombination was observed for most n+ diffusion profiles without such a pronounced maximum. Based on experimentally determined interface properties and simulation results, we attribute this superior passivation quality after firing to a better chemical surface passivation, quantified by a lower interface defect density, in combination with a lower density of negative fixed charges. These experimental results reveal that Al2O3/SiNx stacks can provide not only excellent passivation on p+ surfaces but also on n+ surfaces for a wide range of surface doping concentrations when activated with short high-temperature treatments.

Inversion by metalorganic chemical vapor deposition from N- to Ga-polar gallium nitride and its application to multiple quantum well light-emitting diodes

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

Hosalli, A. M.; Van Den Broeck, D. M.; Bedair, S. M.

2013-12-02

We demonstrate a metalorganic chemical vapor deposition growth approach for inverting N-polar to Ga-polar GaN by using a thin inversion layer grown with high Mg flux. The introduction of this inversion layer allowed us to grow p-GaN films on N-polar GaN thin film. We have studied the dependence of hole concentration, surface morphology, and degree of polarity inversion for the inverted Ga-polar surface on the thickness of the inversion layer. We then use this approach to grow a light emitting diode structure which has the MQW active region grown on the advantageous N-polar surface and the p-layer grown on themore » inverted Ga-polar surface.« less

The effects of spatial inhomogeneities on flow through the endothelial surface layer.

PubMed

Leiderman, Karin M; Miller, Laura A; Fogelson, Aaron L

2008-05-21

Flow through the endothelial surface layer (the glycocalyx and adsorbed plasma proteins) plays an important but poorly understood role in cell signaling through a process known as mechanotransduction. Characterizing the flow rates and shear stresses throughout this layer is critical for understanding how flow-induced ionic currents, deformations of transmembrane proteins, and the convection of extracellular molecules signal biochemical events within the cell, including cytoskeletal rearrangements, gene activation, and the release of vasodilators. Previous mathematical models of flow through the endothelial surface layer are based upon the assumptions that the layer is of constant hydraulic permeability and constant height. These models also assume that the layer is continuous across the endothelium and that the layer extends into only a small portion of the vessel lumen. Results of these models predict that fluid shear stress is dissipated through the surface layer and is thus negligible near endothelial cell membranes. In this paper, such assumptions are removed, and the resultant flow rates and shear stresses through the layer are described. The endothelial surface layer is modeled as clumps of a Brinkman medium immersed in a Newtonian fluid. The width and spacing of each clump, hydraulic permeability, and fraction of the vessel lumen occupied by the layer are varied. The two-dimensional Navier-Stokes equations with an additional Brinkman resistance term are solved using a projection method. Several fluid shear stress transitions in which the stress at the membrane shifts from low to high values are described. These transitions could be significant to cell signaling since the endothelial surface layer is likely dynamic in its composition, density, and height.

Nano-size defects in arsenic-implanted HgCdTe films: a HRTEM study

NASA Astrophysics Data System (ADS)

Bonchyk, O. Yu.; Savytskyy, H. V.; Swiatek, Z.; Morgiel, Y.; Izhnin, I. I.; Voitsekhovskii, A. V.; Korotaev, A. G.; Mynbaev, K. D.; Fitsych, O. I.; Varavin, V. S.; Dvoretsky, S. A.; Marin, D. V.; Yakushev, M. V.

2018-02-01

Radiation damage and its transformation under annealing were studied with bright-field and high-resolution transmission electron microscopy for arsenic-implanted HgCdTe films with graded-gap surface layers. In addition to typical highly defective layers in as-implanted material, a 50 nm-thick sub-surface layer with very low defect density was observed. The main defects in other layers after implantation were dislocation loops, yet after arsenic activation annealing, the dominating defects were single dislocations. Transport (from depth to surface), transformation and annihilation of radiation-induced defects were observed as a result of annealing, with the depth with the maximum defect density decreasing from 110 to 40 nm.

Well-aligned Vertically Oriented ZnO Nanorod Arrays and their Application in Inverted Small Molecule Solar Cells.

PubMed

Lin, Ming-Yi; Wu, Shang-Hsuan; Hsiao, Li-Jen; Budiawan, Widhya; Chen, Shih-Lun; Tu, Wei-Chen; Lee, Chia-Yen; Chang, Yia-Chung; Chu, Chih-Wei

2018-04-25

This manuscript describes how to design and fabricate efficient inverted solar cells, which are based on a two-dimensional conjugated small molecule (SMPV1) and [6,6]-phenyl-C71-butyric acid methyl ester (PC71BM), by utilizing ZnO nanorods (NRs) grown on a high quality Al-doped ZnO (AZO) seed layer. The inverted SMPV1:PC71BM solar cells with ZnO NRs that grew on both a sputtered and sol-gel processed AZO seed layer are fabricated. Compared with the AZO thin film prepared by the sol-gel method, the sputtered AZO thin film exhibits better crystallization and lower surface roughness, according to X-ray diffraction (XRD) and atomic force microscope (AFM) measurements. The orientation of the ZnO NRs grown on a sputtered AZO seed layer shows better vertical alignment, which is beneficial for the deposition of the subsequent active layer, forming better surface morphologies. Generally, the surface morphology of the active layer mainly dominates the fill factor (FF) of the devices. Consequently, the well-aligned ZnO NRs can be used to improve the carrier collection of the active layer and to increase the FF of the solar cells. Moreover, as an anti-reflection structure, it can also be utilized to enhance the light harvesting of the absorption layer, with the power conversion efficiency (PCE) of solar cells reaching 6.01%, higher than the sol-gel based solar cells with an efficiency of 4.74%.

Application of thin layer activation technique for surface wear studies in Zr based materials using charged particle induced nuclear reactions

NASA Astrophysics Data System (ADS)

Chowdhury, D. P.; Pal, Sujit; Parthasarathy, R.; Mathur, P. K.; Kohli, A. K.; Limaye, P. K.

1998-09-01

Thin layer activation (TLA) technique has been developed in Zr based alloy materials, e.g., zircaloy II, using 40 MeV α-particles from Variable Energy Cyclotron Centre at Calcutta. A brief description of the methodology of TLA technique is presented to determine the surface wear. The sensitivity of the measurement of surface wear in zircaloy material is found to be 0.22±0.05 μm. The surface wear is determined by TLA technique in zircaloy material which is used in pressurised heavy water reactor and the values have been compared with that obtained by conventional technique for the analytical validation of the TLA technique.

Closing the Seasonal Ocean Surface Temperature Balance in the Eastern Tropical Oceans from Remote Sensing and Model Reanalyses

NASA Technical Reports Server (NTRS)

Roberts, J. Brent; Clayson, C. A.

2012-01-01

Residual forcing necessary to close the MLTB on seasonal time scales are largest in regions of strongest surface heat flux forcing. Identifying the dominant source of error - surface heat flux error, mixed layer depth estimation, ocean dynamical forcing - remains a challenge in the eastern tropical oceans where ocean processes are very active. Improved sub-surface observations are necessary to better constrain errors. 1. Mixed layer depth evolution is critical to the seasonal evolution of mixed layer temperatures. It determines the inertia of the mixed layer, and scales the sensitivity of the MLTB to errors in surface heat flux and ocean dynamical forcing. This role produces timing impacts for errors in SST prediction. 2. Errors in the MLTB are larger than the historical 10Wm-2 target accuracy. In some regions, a larger accuracy can be tolerated if the goal is to resolve the seasonal SST cycle.

Microstructure and antibacterial property of in situ TiO(2) nanotube layers/titanium biocomposites.

PubMed

Cui, C X; Gao, X; Qi, Y M; Liu, S J; Sun, J B

2012-04-01

The TiO(2) nanotube layer was in situ synthesized on the surface of pure titanium by the electrochemical anodic oxidation. The diameter of nano- TiO(2) nanotubes was about 70~100 nm. The surface morphology and phase compositions of TiO(2) nanotube layers were observed and analyzed using the scanning electron microscope (SEM). The important processing parameters, including anodizing voltage, reaction time, concentration of electrolyte, were optimized in more detail. The photocatalytic activity of the nano- TiO(2) nanotube layers prepared with optimal conditions was evaluated via the photodegradation of methylthionine in aqueous solution. The antibacterial property of TiO(2) nanotube layers prepared with optimal conditions was evaluated by inoculating Streptococcus mutans on the TiO(2) nanotube layers in vitro. The results showed that TiO(2) nanotube layers/Ti biocomposites had very good antibacterial activity to resist Streptococcus mutans. As a dental implant biomaterial, in situ TiO(2) nanotube layer/Ti biocomposite has better and wider application prospects. Copyright © 2012 Elsevier Ltd. All rights reserved.

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

NASA Technical Reports Server (NTRS)

Zhang, Ting-Jun; Li, Shu-Sun

2003-01-01

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

Delayed ignition and propulsion of catalytic microrockets based on fuel-induced chemical dealloying of the inner alloy layer.

PubMed

Jodra, Adrián; Soto, Fernando; Lopez-Ramirez, Miguel Angel; Escarpa, Alberto; Wang, Joseph

2016-09-27

The delayed ignition and propulsion of catalytic tubular microrockets based on fuel-induced chemical dealloying of an inner alloy layer is demonstrated. Such timed delay motor activation process relies on the preferential gradual corrosion of Cu from the inner Pt-Cu alloy layer by the peroxide fuel. The dealloying process exposes the catalytically active Pt surface to the chemical fuel, thus igniting the microrockets propulsion autonomously without external stimuli. The delayed motor activation relies solely on the intrinsic material properties of the micromotor and the surrounding solution. The motor activation time can thus be tailored by controlling the composition of the Cu-Pt alloy layer and the surrounding media, including the fuel and NaCl concentrations and local pH. Speed acceleration in a given fuel solution is also demonstrated and reflects the continuous exposure of the Pt surface. The versatile "blastoff" control of these chemical microrockets holds considerable promise for designing self-regulated chemically-powered nanomachines with a "built-in" activation mechanism for diverse tasks.

Electrochemical cell having cylindrical electrode elements

DOEpatents

Nelson, Paul A.; Shimotake, Hiroshi

1982-01-01

A secondary, high temperature electrochemical cell especially adapted for lithium alloy negative electrodes, transition metal chalcogenide positive electrodes and alkali metal halide or alkaline earth metal halide electrolyte is disclosed. The cell is held within an elongated cylindrical container in which one of the active materials is filled around the outside surfaces of a plurality of perforate tubular current collectors along the length of the container. Each of the current collector tubes contain a concentric tubular layer of electrically insulative ceramic as an interelectrode separator. The active material of opposite polarity in elongated pin shape is positioned longitudinally within the separator layer. A second electrically conductive tube with perforate walls can be swagged or otherwise bonded to the outer surface of the pin as a current collector and the electrically insulative ceramic layer can be coated or otherwise layered onto the outer surface of this second current collector. Alternatively, the central pin electrode can include an axial core as a current collector.

Should precipitation influence dust emission in global dust models?

NASA Astrophysics Data System (ADS)

Okin, Gregory

2016-04-01

Soil moisture modulates the threshold shear stress required to initiate aeolian transport and dust emission. Most of the theoretical and laboratory work that has confirmed the impact of soil moisture has appropriately acknowledged that it is the soil moisture of a surface layer a few grain diameters thick that truly controls threshold shear velocity. Global and regional models of dust emission include the effect of soil moisture on transport threshold, but most ignore the fact that only the moisture of the very topmost "active layer" matters. The soil moisture in the active layer can differ greatly from that integrated through the top 2, 5, 10, or 100 cm (surface layers used by various global models) because the top 2 mm of heavy texture soils dries within ~1/2 day while sandy soils dry within less than 2 hours. Thus, in drylands where dust emission occurs, it is likely that this top layer is drier than the underlying soil in the days and weeks after rain. This paper explores, globally, the time between rain events in relation to the time for the active layer to dry and the timing of high wind events. This analysis is carried out using the same coarse reanalyses used in global dust models and is intended to inform the soil moisture controls in these models. The results of this analysis indicate that the timing between events is, in almost all dust-producing areas, significantly longer than the drying time of the active layer, even when considering soil texture differences. Further, the analysis shows that the probability of a high wind event during the period after a rain where the surface is wet is small. Therefore, in coarse global models, there is little reason to include rain-derived soil moisture in the modeling scheme.

Surface modification of silk fibroin fabric using layer-by-layer polyelectrolyte deposition and heparin immobilization for small-diameter vascular prostheses.

PubMed

Elahi, M Fazley; Guan, Guoping; Wang, Lu; Zhao, Xinzhe; Wang, Fujun; King, Martin W

2015-03-03

There is an urgent need to develop a biologically active implantable small-diameter vascular prosthesis with long-term patency. Silk-fibroin-based small-diameter vascular prosthesis is a promising candidate having higher patency rate; however, the surface modification is indeed required to improve its further hemocompatibility. In this study, silk fibroin fabric was modified by a two-stage process. First, the surface of silk fibroin fabric was coated using a layer-by-layer polyelectrolyte deposition technique by stepwise dipping the silk fibroin fabric into a solution of cationic poly(allylamine hydrochloride) (PAH) and anionic poly(acrylic acid) (PAA) solution. The dipping procedure was repeated to obtain the PAH/PAA multilayers deposited on the silk fibroin fabrics. Second, the polyelectrolyte-deposited silk fibroin fabrics were treated in EDC/NHS-activated low-molecular-weight heparin (LMWH) solution at 4 °C for 24 h, resulting in immobilization of LMWH on the silk fibroin fabrics surface. Scanning electron microscopy, atomic force microscopy, and energy-dispersive X-ray data revealed the accomplishment of LMWH immobilization on the polyelectrolyte-deposited silk fibroin fabric surface. The higher the number of PAH/PAA coating layers on the silk fibroin fabric, the more surface hydrophilicity could be obtained, resulting in a higher fetal bovine serum protein and platelets adhesion resistance properties when tested in vitro. In addition, compared with untreated sample, the surface-modified silk fibroin fabrics showed negligible loss of bursting strength and thus reveal the acceptability of polyelectrolytes deposition and heparin immobilization approach for silk-fibroin-based small-diameter vascular prostheses modification.

Room temperature bonding and debonding of polyimide film and glass substrate based on surface activate bonding method

NASA Astrophysics Data System (ADS)

Takeuchi, Kai; Fujino, Masahisa; Matsumoto, Yoshiie; Suga, Tadatomo

2018-02-01

The temporary bonding of polyimide (PI) films and glass substrates is a key technology for realizing flexible devices with thin-film transistors (TFTs). In this paper, we report the surface activated bonding (SAB) method using Si intermediate layers and its bonding and debonding mechanisms after heating. The bonding interface composed of Si and Fe shows a higher bond strength than the interface of only Si, while the bond strengths of both interfaces decrease with post bonding heating. It is also clarified by composition analysis on the debonded surfaces and cross-sectional observation of the bonding interface that the bond strength depends on the toughness of the intermediated layers and PI. The SAB method using Si intermediate layers is found to be applicable to the bonding and debonding of PI and glass.

SERDP Ecosystem Management Project (SEMP): 2005 Annual Report

DTIC Science & Technology

2007-03-01

The A-horizon forms at the soil surface by accumulation of humus , and is the layer of highest bio- diversity, biological activity, decomposition, and...by accumulation of humus , and is the layer of highest bio- logical activity, decomposition, and nutrient recycling.2 Two-thirds of the earth’s entire

Graphite carbon nitride/boron-doped graphene hybrid for efficient hydrogen generation reaction.

PubMed

Yang, Liang; Wang, Xin; Wang, Juan; Cui, Guomin; Liu, Daoping

2018-08-24

Metal-free carbon materials, with tuned surface chemical and electronic properties, hold great potential for the hydrogen evolution reaction (HER). We designed and synthesized a CN/BG hybrid electrocatalytic system with a porous and active graphite carbon nitride (CN) layer on boron-doped graphene (BG). A porous CN layer on graphene could provide exposed defects and edges that act as active sites for proton adsorption and reduction. The composition, structure, surface electronics, and chemical properties of this CN/BG hybrid system were tuned to obtain excellent HER activity and stability. Detailed surface chemical, morphological, and structural analyses demonstrated the synergetic effect arising from the electronic interaction between CN and BG, which contributed to the enhanced electrocatalytic performances.

Insight into the epitaxial encapsulation of Pd catalysts in an oriented metalloporphyrin network thin film for tandem catalysis.

PubMed

Vohra, M Ismail; Li, De-Jing; Gu, Zhi-Gang; Zhang, Jian

2017-06-14

A palladium catalyst (Pd-Cs) encapsulated metalloporphyrin network PIZA-1 thin film with bifunctional properties has been developed through a modified epitaxial layer-by-layer encapsulation approach. Combining the oxidation activity of Pd-Cs and the acetalization activity of the Lewis acidic sites in the PIZA-1 thin film, this bifunctional catalyst of the Pd-Cs@PIZA-1 thin film exhibits a good catalytic activity in a one-pot tandem oxidation-acetalization reaction. Furthermore, the surface components can be controlled by ending the top layer with different precursors in the thin film preparation procedures. The catalytic performances of these thin films with different surface composites were studied under the same conditions, which showed different reaction conversions. The result revealed that the surface component can influence the catalytic performance of the thin films. This epitaxial encapsulation offers a good understanding of the tandem catalysis for thin film materials and provides useful guidance to develop new thin film materials with catalytic properties.

Erosion-corrosion and cavitation-erosion measurements on copper alloys utilizing thin layer activation technique

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

Tsai, C.H.; Hsu, K.Y.; Kai, J.J.

1992-12-31

The surface layers of copper alloy specimens were made radioactive by bombarding with 5 MeV protons from a van de Graaff accelerator which converted Cu-65 into Zn-65 through (p,n) reaction. The amount of surface material loss could then be monitored by measuring the total remaining {gamma}-ray activity generated from Zn-65 decay. This technique, termed thin layer activation (TLA), has the advantage of in situ monitoring the rate of surface removal due to corrosion, erosion-corrosion, wearing, etc. In this work, the erosion-corrosion tests on aluminum brass and 90Cu-10Ni were conducted in circulating sea water and the erosion-corrosion rates measured using TLAmore » and conventional methods such as linear polarization resistance (LPR) method and weight loss coupons were compared. A vibrational cavitation-erosion test was also performed on aluminum bronze, in which the measurements by TLA were compared with those of weight loss measurements.« less

Wave phenomena in a high Reynolds number compressible boundary layer

NASA Technical Reports Server (NTRS)

Bayliss, A.; Maestrello, L.; Parikh, P.; Turkel, E.

1985-01-01

Growth of unstable disturbances in a high Reynolds number compressible boundary layer is numerically simulated. Localized periodic surface heating and cooling as a means of active control of these disturbances is studied. It is shown that compressibility in itself stabilizes the flow but at a lower Mach number, significant nonlinear distortions are produced. Phase cancellation is shown to be an effective mechanism for active boundary layer control.

Structure and hemocompatibility of nanocrystalline titanium nitride produced under glow-discharge conditions

NASA Astrophysics Data System (ADS)

Sowińska, Agnieszka; Czarnowska, Elżbieta; Tarnowski, Michał; Witkowska, Justyna; Wierzchoń, Tadeusz

2018-04-01

Significant efforts are being made towards developing novel antithrombotic materials. The purpose of the presented study was to characterize two variants of nitrided surface layers produced on alloy Ti-6Al-4V in different areas of low-temperature plasma - at the plasma potential (TiNp) or at the cathode potential (TiNc). The layers were characterized in terms of their microstructure, surface topography and wettability, and platelet response to the environment of different pH. The produced layers were of the TiN + Ti2N + αTiN-type, but the layer produced at the plasma potential was thinner, smoother and had lower surface free energy compared with that produced at the cathode potential. Biological evaluation demonstrated more fibrinogen buildup, less platelet adhesion and aggregation, and fewer strongly activated platelets on the TiNp surface compared with those parameters on the TiNc surface and on the titanium alloy in its initial state. Interestingly, both surface types were significantly resistant to fibrinogen adsorption and platelet adhesion in the environment of lower pH. In conclusion, the nitrided surface layer produced at the plasma potential is a promising material and this basic information is critical for further development of hemocompatible materials.

Effect of electrical discharging on formation of nanoporous biocompatible layer on Ti-6Al-4V alloys.

PubMed

Yang, Tzu-Sen; Huang, Mao-Suan; Wang, Mao-Sheng; Lin, Ming-Hong; Tsai, Meng-Yuan; Wang, Pei-Yi Wang

2013-08-01

In this study, the electrical discharge machining (EDM) was formed on the surface of the Ti-6Al-4V (Ti64) specimen. The properties of adhesion and proliferation of MG-63 cells were evaluated the interactions between the EDM-treated layer and cells. The incorporation of oxygen roughened the EDM-treated specimen surface on a microscale, where the nanoscale pores were superimposed. The EDM-treated layer, which can generate the thick anatase TiO2 on the Ti64 surface, afforded a cytocompatible environment. In cell culture, alkaline phosphatase activity and osteocalcin can be dramatically enhanced on the EDM-treated surfaces when compared with the untreated surface. In addition, the increase in peak currents to the EDM functionalization led to enhancement of multiple osteoblast functions. This study reveals that the chemistry and crystallinity of the EDM-treated layer played important roles in affecting osteoblastic responses to the specimens, which provided insight into the development of new biomedical implant surfaces.

Aluminum Coating Influence on Nitride Layer Performance Deposited by MO-CVD in Fluidized Bed on Austenitic Stainless Steel Substrate

NASA Astrophysics Data System (ADS)

Găluşcă, D. G.; Perju, M. C.; Nejneru, C.; Burduhos Nergiş, D. D.; Lăzărescu, I. E.

2018-06-01

The modification of surface properties by duplex treatments, involving the overlapping of two surface treatment techniques, has been established as an intelligent solution to create new applications for the substrate metallic material. There are driveline components operating under very tough wear and corrosion conditions, with high temperature and humidity variations. Such components are usually made of high Cr and Ni stainless steel and for the hardening of surfaces it is recommended a thermo chemical treatment. Since stainless steels, especially austenitic stainless steels, are difficult to nitride, experimental studies focus on increasing the depth of the nitride layer and surface hardness. Achieving the goal involves changing active layer chemical composition by introducing aluminum in the surface layer. In order to find a solution, a new surface treatment technique is produced by combining aluminum thin films by MO-CVD in a fluidized bed using a triisobutylaluminum precursor with a thermo chemical nitriding treatment.

Promoted Fixation of Molecular Nitrogen with Surface Oxygen Vacancies on Plasmon-Enhanced TiO2 Photoelectrodes.

PubMed

Li, Chengcheng; Wang, Tuo; Zhao, Zhi-Jian; Yang, Weimin; Li, Jian-Feng; Li, Ang; Yang, Zhilin; Ozin, Geoffrey A; Gong, Jinlong

2018-05-04

A hundred years on, the energy-intensive Haber-Bosch process continues to turn the N 2 in air into fertilizer, nourishing billions of people while causing pollution and greenhouse gas emissions. The urgency of mitigating climate change motivates society to progress toward a more sustainable method for fixing N 2 that is based on clean energy. Surface oxygen vacancies (surface O vac ) hold great potential for N 2 adsorption and activation, but introducing O vac on the very surface without affecting bulk properties remains a great challenge. Fine tuning of the surface O vac by atomic layer deposition is described, forming a thin amorphous TiO 2 layer on plasmon-enhanced rutile TiO 2 /Au nanorods. Surface O vac in the outer amorphous TiO 2 thin layer promote the adsorption and activation of N 2 , which facilitates N 2 reduction to ammonia by excited electrons from ultraviolet-light-driven TiO 2 and visible-light-driven Au surface plasmons. The findings offer a new approach to N 2 photofixation under ambient conditions (that is, room temperature and atmospheric pressure). © 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Layer-by-layer polyelectrolyte coating for surface-enhanced Raman scattering on gold nanostars inside hollow core photonic crystal fibers

NASA Astrophysics Data System (ADS)

Burmistrova, Natalia A.; Bondarenko, Sergei D.; Bratashov, Daniil N.; Shuvalov, Andrei A.; Chibrova, Anastasiya A.; Khlebtsov, Boris N.; Skibina, Julia S.; Goryacheva, Irina Y.

2018-04-01

Photonic crystal fibers with hollow core (HC PCFs) are a specific class of optical fibers characterized by microstructure with periodic holes oriented along fiber. The combination of HC PCF with Raman spectroscopy for biosensors creation is attractive in the terms of the low sample volume, the possibility to increase the integration time without sample degradation and maintaining constant focus during experiments. Here we propose layer-by-layer polyelectrolyte coating of HC PCF inner surface in order to obtain charge-selective absorption of analyte, stabilization of Surface-Enhanced Raman scattering (SERS)-active gold nanoparticles. Distance between SERS hotspots and glass reduces nonlinear signals from glass, and increases signal-to-noise ratio of SERS spectra.

Analysis of the pressure-induced potential arising through composite membranes with selective surface layers.

PubMed

Szymczyk, Anthony; Sbaï, Mohammed; Fievet, Patrick

2005-03-01

When a pressure gradient is applied through a charged selective membrane, the transmembrane electrical potential difference, called the filtration potential, results from both the applied pressure and induced concentration difference across the membrane. In this work we investigate the electrokinetic properties relative to both active and support layers of a composite ceramic membrane close to the nanofiltration range. First, the volume charge density of the active layer is obtained by fitting a transport model to experimental rejection rates (which are controlled by the active layer only). Next, the value of the volume charge density is used to compute the theoretical filtration potential through the active layer. For sufficiently high permeate volume fluxes, the concentration difference across the active layer becomes constant, which allows assessing the membrane potential of the active layer. Experimental measurements of the overall filtration potential arising through the whole membrane are performed. The contribution of the support layer to this overall filtration potential is put in evidence. That implies that the membrane potential of the active layer cannot be deduced directly from the overall filtration potential measurements. Finally, the contribution of the support layer is singled out by subtracting the theoretical filtration potential of the active layer from the experimental filtration potential measured across the whole membrane (i.e., support + active layers). The amphoteric behavior of both layers is put in evidence, which is confirmed by electrophoretic measurements carried out with the powdered support layer and by recently reported tangential streaming potential measurements.

The molecular mechanism of mediation of adsorbed serum proteins to endothelial cells adhesion and growth on biomaterials.

PubMed

Yang, Dayun; Lü, Xiaoying; Hong, Ying; Xi, Tingfei; Zhang, Deyuan

2013-07-01

To explore molecular mechanism of mediation of adsorbed proteins to cell adhesion and growth on biomaterials, this study examined endothelial cell adhesion, morphology and viability on bare and titanium nitride (TiN) coated nickel titanium (NiTi) alloys and chitosan film firstly, and then identified the type and amount of serum proteins adsorbed on the three surfaces by proteomic technology. Subsequently, the mediation role of the identified proteins to cell adhesion and growth was investigated with bioinformatics analyses, and further confirmed by a series of cellular and molecular biological experiments. Results showed that the type and amount of adsorbed serum proteins associated with cell adhesion and growth was obviously higher on the alloys than on the chitosan film, and these proteins mediated endothelial cell adhesion and growth on the alloys via four ways. First, proteins such as adiponectin in the adsorbed protein layer bound with cell surface receptors to generate signal transduction, which activated cell surface integrins through increasing intracellular calcium level. Another way, thrombospondin 1 in the adsorbed protein layer promoted TGF-β signaling pathway activation and enhanced integrins expression. The third, RGD sequence containing proteins such as fibronectin 1, vitronectin and thrombospondin 1 in the adsorbed protein layer bound with activated integrins to activate focal adhesion pathway, increased focal adhesion formation and actin cytoskeleton organization and mediated cell adhesion and spreading. In addition, the activated focal adhesion pathway promoted the expression of cell growth related genes and resulted in cell proliferation. The fourth route, coagulation factor II (F2) and fibronectin 1 in the adsorbed protein layer bound with cell surface F2 receptor and integrin, activated regulation of actin cytoskeleton pathway and regulated actin cytoskeleton organization. Copyright © 2013 Elsevier Ltd. All rights reserved.

Interrelation of the construction of the metamorphic InAlAs/InGaAs nanoheterostructures with the InAs content in the active layer of 76-100% with their surface morphology and electrical properties

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

Vasil'evskii, I. S., E-mail: ivasilevskii@mail.ru; Galiev, G. B.; Klimov, E. A.

The influence of the construction of a metamorphic buffer on the surface morphology and electrical properties of InAlAs/InGaAs/InAlAs nanoheterostructures with InAs content in the active layer from 76 to 100% with the use of the GaAs and InP substrates is studied. It is shown that such parameters as the electron mobility and the concentration, as well as the root-mean-square surface roughness, substantially depend on the construction of the metamorphic buffer. It is established experimentally that these parameters largely depend on the maximal local gradient of the lattice constant of the metamorphic buffer in the growth direction of the layers rathermore » than on its average value. It is shown that, with selection of the construction of the metamorphic buffer, it is possible to form nanostructured surfaces with a large-periodic profile.« less

Leveraging Subsidence in Permafrost with Remotely Sensed Active Layer Thickness (ReSALT) Products

NASA Astrophysics Data System (ADS)

Schaefer, K. M.; Chen, A.; Chen, J.; Chen, R. H.; Liu, L.; Michaelides, R. J.; Moghaddam, M.; Parsekian, A.; Tabatabaeenejad, A.; Thompson, J. A.; Zebker, H. A.; Meyer, F. J.

2017-12-01

The Remotely Sensed Active Layer Thickness (ReSALT) product uses the Interferometric Synthetic Aperture Radar (InSAR) technique to measure ground subsidence in permafrost regions. Seasonal subsidence results from the expansion of soil water into ice as the surface soil or active layer freezes and thaws each year. Subsidence trends result from large-scale thaw of permafrost and from the melting and subsequent drainage of excess ground ice in permafrost-affected soils. The attached figure shows the 2006-2010 average seasonal subsidence from ReSALT around Barrow, Alaska. The average active layer thickness (the maximum surface thaw depth during summer) is 30-40 cm, resulting in an average seasonal subsidence of 1-3 cm. Analysis of the seasonal subsidence and subsidence trends provides valuable insights into important permafrost processes, such as the freeze/thaw of the active layer, large-scale thawing due to climate change, the impact of fire, and infrastructure vulnerability. ReSALT supports the Arctic-Boreal Vulnerability Experiment (ABoVE) field campaign in Alaska and northwest Canada and is a precursor for a potential NASA-ISRO Synthetic Aperture Radar (NISAR) product. ReSALT includes uncertainties for all parameters and is validated against in situ measurements from the Circumpolar Active Layer Monitoring (CALM) network, Ground Penetrating Radar and mechanical probe measurements. Here we present examples of ReSALT products in Alaska to highlight the untapped potential of the InSAR technique to understand permafrost dynamics, with a strong emphasis on the underlying processes that drive the subsidence.

Adsorption-desorption mechanism of phosphate by immobilized nano-sized magnetite layer: interface and bulk interactions.

PubMed

Zach-Maor, Adva; Semiat, Raphael; Shemer, Hilla

2011-11-15

Phosphate adsorption mechanism by a homogenous porous layer of nano-sized magnetite particles immobilized onto granular activated carbon (nFe-GAC) was studied for both interface and bulk structures. X-ray Photoelectron Spectroscopy (XPS) analysis revealed phosphate bonding to the nFe-GAC predominantly through bidentate surface complexes. It was established that phosphate was adsorbed to the magnetite surface mainly via ligand exchange mechanism. Initially, phosphate was adsorbed by the active sites on the magnetite surface, after which it diffused into the interior of the nano-magnetite layer, as indicated by intraparticle diffusion model. This diffusion process continues regardless of interface interactions, revealing some of the outer magnetite binding sites for further phosphate uptake. Desorption, using NaOH solution, was found to be predominantly a surface reaction, at which hydroxyl ions replace the adsorbed phosphate ions only at the surface outer biding sites. Five successive fix-bed adsorption/regeneration cycles were successfully applied, without significant reduction in the nFe-GAC adsorption capacity and at high regeneration efficiency. Copyright © 2011 Elsevier Inc. All rights reserved.

Faster proton transfer dynamics of water on SnO2 compared to TiO2.

PubMed

Kumar, Nitin; Kent, Paul R C; Bandura, Andrei V; Kubicki, James D; Wesolowski, David J; Cole, David R; Sofo, Jorge O

2011-01-28

Proton jump processes in the hydration layer on the iso-structural TiO(2) rutile (110) and SnO(2) cassiterite (110) surfaces were studied with density functional theory molecular dynamics. We find that the proton jump rate is more than three times faster on cassiterite compared with rutile. A local analysis based on the correlation between the stretching band of the O-H vibrations and the strength of H-bonds indicates that the faster proton jump activity on cassiterite is produced by a stronger H-bond formation between the surface and the hydration layer above the surface. The origin of the increased H-bond strength on cassiterite is a combined effect of stronger covalent bonding and stronger electrostatic interactions due to differences of its electronic structure. The bridging oxygens form the strongest H-bonds between the surface and the hydration layer. This higher proton jump rate is likely to affect reactivity and catalytic activity on the surface. A better understanding of its origins will enable methods to control these rates.

Microfluidic Assisted Synthesis of Multipurpose Polymer Nanoassembly Particles for Fluorescence, LSPR, and SERS Activities.

PubMed

Visaveliya, Nikunjkumar; Köhler, J Michael

2015-12-22

Potential biomedical applications such as controlled delivery with sustained drug release profile demand for multifunctional polymeric particles of precise chemical composition and with welldefined physicochemical properties. The real challenge is to obtain the reproducible and homogeneous nanoparticles in a minimum number of preparation steps. Here, single-step nanoarchitectures of soft surface layered copolymer nanoparticles with a regular tuning in the size via micro flow-through assisted synthesis are reported. Interfacial copolymerization induces the controlled compartmentalization where a hydrophobic core adopts spherical shape in order to minimize the surface energy and simultaneously shelter in the hydrophilic shelllike surface layer. Surface layer can swell in the aqueous medium and allow controlled entrapping of functional hydrophobic nanoparticles in the hydrophilic interior via electrostatic interaction which can be particularly interesting for combined fluorescence activity. Furthermore, the nanoarchitecture of size and concentration controlled polymer-metal nanoassembly particles can be implemented as an ideal surface-enhanced Raman scattering substrate for detection of the trace amounts of various analytes. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Surface nanoporosity has a greater influence on osteogenic and bacterial cell adhesion than crystallinity and wettability

NASA Astrophysics Data System (ADS)

Rodriguez-Contreras, Alejandra; Guadarrama Bello, Dainelys; Nanci, Antonio

2018-07-01

There has been much emphasis on the influence of crystallinity and wettability for modulating cell activity, particularly for bone biomaterials. In this context, we have generated titanium oxide layers with similar mesoporous topography and surface roughness but with amorphous or crystalline oxide layers and differential wettability. We then investigated their influence on the behavior of MC3T3 osteoblastic and bacterial cells. There was no difference in cell adhesion, spreading and growth on amorphous and crystalline surfaces. The number of focal adhesions was similar, however, cells on the amorphous surface exhibited a higher frequency of mature adhesions. The crystallinity of the surface layers also had no bearing on bacterial adhesion. While it cannot be excluded that surface crystallinity, roughness and wettability contribute to some degree to determining cell behavior, our data suggest that physical characteristics of surfaces represent the major determinant.

Structure and functional properties of TiNiZr surface layers obtained by high-velocity oxygen fuel spraying

NASA Astrophysics Data System (ADS)

Rusinov, P. O.; Blednova, Zh M.; Borovets, O. I.

2017-05-01

The authors studied a complex method of surface modification of steels for materials with shape memory effect (SME) Ti-Ni-Zr with a high-velocity oxygen-fuel spraying (HVOF) of mechanically activated (MA) powder in a protective medium. We assessed the functional properties and X-ray diffraction studies, which showed that the formation of surface layers according to the developed technology ensures the manifestation of the shape memory effect.

Influence of Layer-by-Layer Polyelectrolyte Deposition and EDC/NHS Activated Heparin Immobilization onto Silk Fibroin Fabric

PubMed Central

Elahi, M. Fazley; Guan, Guoping; Wang, Lu; King, Martin W.

2014-01-01

To enhance the hemocompatibility of silk fibroin fabric as biomedical material, polyelectrolytes architectures have been assembled through the layer-by-layer (LbL) technique on silk fibroin fabric (SFF). In particular, 1.5 and 2.5 bilayer of oppositely charged polyelectrolytes were assembled onto SFF using poly(allylamine hydrochloride) (PAH) as polycationic polymer and poly(acrylic acid) (PAA) as polyanionic polymer with PAH topmost. Low molecular weight heparin (LMWH) activated with 1-ethyl-3-(dimethylaminopropyl) carbodiimide hydrochloride (EDC) and N-hydroxysuccinimide (NHS) was then immobilized on its surface. Alcian Blue staining, toluidine blue assay and X-ray photoelectron spectroscopy (XPS) confirmed the presence of heparin on modified SFF surfaces. The surface morphology of the modified silk fibroin fabric surfaces was characterized by scanning electron microscopy (SEM) and atomic force microscopy (AFM), and obtained increased roughness. Negligible hemolytic effect and a higher concentration of free hemoglobin by a kinetic clotting time test ensured the improved biological performance of the modified fibroin fabric. Overall, the deposition of 2.5 bilayer was found effective in terms of biological and surface properties of the modified fibroin fabric compared to 1.5 bilayer self-assembly technique. Therefore, this novel approach to surface modification may demonstrate long term patency in future in vivo animal trials of small diameter silk fibroin vascular grafts. PMID:28788601

Influence of the "surface effect" on the segregation parameters of S in Fe(100): A multi-scale modelling and Auger Electron Spectroscopy study

NASA Astrophysics Data System (ADS)

Barnard, P. E.; Terblans, J. J.; Swart, H. C.

2015-12-01

The article takes a new look at the process of atomic segregation by considering the influence of surface relaxation on the segregation parameters; the activation energy (Q), segregation energy (ΔG), interaction parameter (Ω) and the pre-exponential factor (D0). Computational modelling, namely Density Functional Theory (DFT) and the Modified Darken Model (MDM) in conjunction with Auger Electron Spectroscopy (AES) was utilized to study the variation of the segregation parameters for S in the surface region of Fe(100). Results indicate a variation in each of the segregation parameters as a function of the atomic layer under consideration. Values of the segregation parameters varied more dramatically as the surface layer is approached, with atomic layer 2 having the largest deviations in comparison to the bulk values. This atomic layer had the highest Q value and formed the rate limiting step for the segregation of S towards the Fe(100) surface. It was found that the segregation process is influenced by two sets of segregation parameters, those of the surface region formed by atomic layer 2, and those in the bulk material. This article is the first to conduct a full scale investigation on the influence of surface relaxation on segregation and labelled it the "surface effect".

On the Effect of Native SiO2 on Si over the SPR-mediated Photocatalytic Activities of Au and Ag Nanoparticles.

PubMed

Wang, Jiale; de Freitas, Isabel C; Alves, Tiago V; Ando, Romulo A; Fang, Zebo; Camargo, Pedro H C

2017-05-29

In hybrid materials containing plasmonic nanoparticles such as Au and Ag, charge-transfer processes from and to Au or Ag can affect both activities and selectivity in plasmonic catalysis. Inspired by the widespread utilization of commercial Si wafers in surface-enhanced Raman spectroscopy (SERS) studies, we investigated herein the effect of the native SiO 2 layer on Si wafers over the surface plasmon resonance (SPR)-mediated activities of the Au and Ag nanoparticles (NPs). We prepared SERS-active plasmonic comprised of Au and Ag NPs deposited onto a Si wafer. Here, two kinds of Si wafers were employed: Si with a native oxide surface layer (Si/SiO 2 ) and Si without a native oxide surface layer (Si). This led to Si/SiO 2 /Au, Si/SiO 2 /Ag, Si/Au, and Si/Ag NPs. The SPR-mediated oxidation of p-aminothiophenol (PATP) to p,p'-dimercaptoazobenzene (DMAB) was employed as a model transformation. By comparing the performances and band structures for the Si/Au and Si/Ag relative to Si/SiO 2 /Au and Si/SiO 2 /Ag NPs, it was found that the presence of a SiO 2 layer was crucial to enable higher SPR-mediated PATP to DMAB conversions. The SiO 2 layer acts to prevent the charge transfer of SPR-excited hot electrons from Au or Ag nanoparticles to the Si substrate. This enabled SPR-excited hot electrons to be transferred to adsorbed O 2 molecules, which then participate in the selective oxidation of PATP to DMAB. In the absence of a SiO 2 layer, SPR-excited hot electrons are preferentially transferred to Si instead of adsorbed O 2 molecules, leading to much lower PATP oxidation. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Side-polished fiber immunosensor based on surface plasmon resonance for detection of Legionella pneumophila

NASA Astrophysics Data System (ADS)

Tsao, Yu-Chia; Yang, Yi-Wen; Tsai, Woo-Hu; Yan, Tsong-Rong

2008-02-01

Side-polished fiber immunosensor based on surface plasmon resonance (SPR) onto self-assembled protein A layer was proposed for the detection of Legionella pneumophila. A self-assembled protein A layer on gold (Au) surface was fabricated by adsorbing a mixture of 11-mercaptoundecanoic acid (MUA) and activated by N-Ethyl-N'-(3-dimethylaminopropyl) carbodiimide/ N-Hydroxysuccinimide (EDC/NHS). The formation of self-assembled protein A and gold layer on side-polished surface and the binding of antibody and antigen in series were confirmed by SPR response on spectrum. The binding protein A layer can improve the sensitivity, which indirectly supports the configurations that antibody layer is immobilized on the binding protein A layer with a well-ordered orientation. The surface morphology analyses of self-assembled protein A layer on Au substrate and monoclonal antibody against L. pneumophila immobilized on protein A were demonstrated by SPR dip shifts on optical spectrum analyzer. The SPR fiber immunosensor for detection of L. pneumophila was developed and the detection limit was 10 CFU/ml with the SPR dip shift in wavelength from 1070 to 1105nm. The current fabrication technique of a SPR immunosensor using optical fiber for the detection of Legionella pneumophila could be applied to construct other biosensor.

Fabrication, characterization, and biological assessment of multilayer laminin γ2 DNA coatings on titanium surfaces.

PubMed

Yang, Guoli; Zhang, Jing; Dong, Wenjing; Liu, Li; Shi, Jue; Wang, Huiming

2016-03-21

The purpose of this work was to fabricate a multilayer laminin γ2 DNA coating on a titanium surface and evaluate its biological properties. A multilayer laminin γ2 DNA coating was fabricated on titanium using a layer-by-layer assembly technique. The rate of coating degradation was evaluated by detecting the amount of cDNA remaining. Surface analysis using X-ray photoelectron spectroscopy, atomic force microscopy, and surface contact angle measurements revealed the multilayer structure to consist of cationic lipid and confirmed that a laminin γ2 DNA layer could be fabricated on titanium via the layer-by-layer assembly process. The transfection efficiency was highest for five layers in the multilayer structure. HEK293 cells cultured on the multilayer films displayed significantly higher adhesion activity than the control group. The expression of laminin γ2 and the co-localization of integrin β4 and plectin were more obvious in HN4 cells cultured on the multilayer laminin γ2 DNA coating, while weak immunoreactivities were observed in the control group. We concluded that the DNA-loaded multilayer provided a surface with good biocompatibility and that the multilayer laminin γ2 DNA coating might be effective in improving cell adhesion and the formation of hemidesmosomes on titanium surfaces.

Fabrication, characterization, and biological assessment of multilayer laminin γ2 DNA coatings on titanium surfaces

PubMed Central

Yang, Guoli; Zhang, Jing; Dong, Wenjing; Liu, Li; Shi, Jue; Wang, Huiming

2016-01-01

The purpose of this work was to fabricate a multilayer laminin γ2 DNA coating on a titanium surface and evaluate its biological properties. A multilayer laminin γ2 DNA coating was fabricated on titanium using a layer-by-layer assembly technique. The rate of coating degradation was evaluated by detecting the amount of cDNA remaining. Surface analysis using X-ray photoelectron spectroscopy, atomic force microscopy, and surface contact angle measurements revealed the multilayer structure to consist of cationic lipid and confirmed that a laminin γ2 DNA layer could be fabricated on titanium via the layer-by-layer assembly process. The transfection efficiency was highest for five layers in the multilayer structure. HEK293 cells cultured on the multilayer films displayed significantly higher adhesion activity than the control group. The expression of laminin γ2 and the co-localization of integrin β4 and plectin were more obvious in HN4 cells cultured on the multilayer laminin γ2 DNA coating, while weak immunoreactivities were observed in the control group. We concluded that the DNA-loaded multilayer provided a surface with good biocompatibility and that the multilayer laminin γ2 DNA coating might be effective in improving cell adhesion and the formation of hemidesmosomes on titanium surfaces. PMID:26996815

Fabrication, characterization, and biological assessment of multilayer laminin γ2 DNA coatings on titanium surfaces

NASA Astrophysics Data System (ADS)

Yang, Guoli; Zhang, Jing; Dong, Wenjing; Liu, Li; Shi, Jue; Wang, Huiming

2016-03-01

The purpose of this work was to fabricate a multilayer laminin γ2 DNA coating on a titanium surface and evaluate its biological properties. A multilayer laminin γ2 DNA coating was fabricated on titanium using a layer-by-layer assembly technique. The rate of coating degradation was evaluated by detecting the amount of cDNA remaining. Surface analysis using X-ray photoelectron spectroscopy, atomic force microscopy, and surface contact angle measurements revealed the multilayer structure to consist of cationic lipid and confirmed that a laminin γ2 DNA layer could be fabricated on titanium via the layer-by-layer assembly process. The transfection efficiency was highest for five layers in the multilayer structure. HEK293 cells cultured on the multilayer films displayed significantly higher adhesion activity than the control group. The expression of laminin γ2 and the co-localization of integrin β4 and plectin were more obvious in HN4 cells cultured on the multilayer laminin γ2 DNA coating, while weak immunoreactivities were observed in the control group. We concluded that the DNA-loaded multilayer provided a surface with good biocompatibility and that the multilayer laminin γ2 DNA coating might be effective in improving cell adhesion and the formation of hemidesmosomes on titanium surfaces.

Partially Oxidized SnS2 Atomic Layers Achieving Efficient Visible-Light-Driven CO2 Reduction.

PubMed

Jiao, Xingchen; Li, Xiaodong; Jin, Xiuyu; Sun, Yongfu; Xu, Jiaqi; Liang, Liang; Ju, Huanxin; Zhu, Junfa; Pan, Yang; Yan, Wensheng; Lin, Yue; Xie, Yi

2017-12-13

Unraveling the role of surface oxide on affecting its native metal disulfide's CO 2 photoreduction remains a grand challenge. Herein, we initially construct metal disulfide atomic layers and hence deliberately create oxidized domains on their surfaces. As an example, SnS 2 atomic layers with different oxidation degrees are successfully synthesized. In situ Fourier transform infrared spectroscopy spectra disclose the COOH* radical is the main intermediate, whereas density-functional-theory calculations reveal the COOH* formation is the rate-limiting step. The locally oxidized domains could serve as the highly catalytically active sites, which not only benefit for charge-carrier separation kinetics, verified by surface photovoltage spectra, but also result in electron localization on Sn atoms near the O atoms, thus lowering the activation energy barrier through stabilizing the COOH* intermediates. As a result, the mildly oxidized SnS 2 atomic layers exhibit the carbon monoxide formation rate of 12.28 μmol g -1 h -1 , roughly 2.3 and 2.6 times higher than those of the poorly oxidized SnS 2 atomic layers and the SnS 2 atomic layers under visible-light illumination. This work uncovers atomic-level insights into the correlation between oxidized sulfides and CO 2 reduction property, paving a new way for obtaining high-efficiency CO 2 photoreduction performances.

Real-time x-ray studies of crystal growth modes during metal-organic vapor phase epitaxy of GaN on c- and m-plane single crystals

DOE PAGES

Perret, Edith; Highland, M. J.; Stephenson, G. B.; ...

2014-08-04

Non-polar orientations of III-nitride semiconductors have attracted significant interest due to their potential application in optoelectronic devices with enhanced efficiency. Using in-situ surface x-ray scattering during metal-organic vapor phase epitaxy (MOVPE) of GaN on non-polar (m-plane) and polar (c-plane) orientations of single crystal substrates, we have observed the homoepitaxial growth modes as a function of temperature and growth rate. On the m-plane surface we observe all three growth modes (step-flow, layer-by-layer, and three-dimensional) as conditions are varied. In contrast, the +c-plane surface exhibits a direct cross over between step-flow and 3-D growth, with no layer-by-layer regime. The apparent activation energymore » of 2.8 ± 0.2 eV observed for the growth rate at the layer-by-layer to step-flow boundary on the m-plane surface is consistent with those observed for MOVPE growth of other III-V compounds, indicating a large critical nucleus size for islands.« less

AlxGa1-xAs Single-Quantum-Well Surface-Emitting Lasers

NASA Technical Reports Server (NTRS)

Kim, Jae H.

1992-01-01

Surface-emitting solid-state laser contains edge-emitting Al0.08Ga0.92As single-quantum-well (SQW) active layer sandwiched between graded-index-of-refraction separate-confinement-heterostructure (GRINSCH) layers of AlxGa1-xAs, includes etched 90 degree mirrors and 45 degree facets to direct edge-emitted beam perpendicular to top surface. Laser resembles those described in "Pseudomorphic-InxGa1-xAs Surface-Emitting Lasers" (NPO-18243). Suitable for incorporation into optoelectronic integrated circuits for photonic computing; e.g., optoelectronic neural networks.

Suppression of surface segregation of the phosphorous δ-doping layer by insertion of an ultra-thin silicon layer for ultra-shallow Ohmic contacts on n-type germanium

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

Yamada, Michihiro; Uematsu, Masashi; Itoh, Kohei M., E-mail: kitoh@appi.keio.ac.jp

2015-09-28

We demonstrate the formation of abrupt phosphorus (P) δ-doping profiles in germanium (Ge) by the insertion of ultra-thin silicon (Si) layers. The Si layers at the δ-doping region significantly suppress the surface segregation of P during the molecular beam epitaxial growth of Ge and high-concentration active P donors are confined within a few nm of the initial doping position. The current-voltage characteristics of the P δ-doped layers with Si insertion show excellent Ohmic behaviors with low enough resistivity for ultra-shallow Ohmic contacts on n-type Ge.

Exchange of Groundwater and Surface-Water Mediated by Permafrost Response to Seasonal and Long Term Air Temperature Variation

USGS Publications Warehouse

Ge, Shemin; McKenzie, Jeffrey; Voss, Clifford; Wu, Qingbai

2011-01-01

Permafrost dynamics impact hydrologic cycle processes by promoting or impeding groundwater and surface water exchange. Under seasonal and decadal air temperature variations, permafrost temperature changes control the exchanges between groundwater and surface water. A coupled heat transport and groundwater flow model, SUTRA, was modified to simulate groundwater flow and heat transport in the subsurface containing permafrost. The northern central Tibet Plateau was used as an example of model application. Modeling results show that in a yearly cycle, groundwater flow occurs in the active layer from May to October. Maximum groundwater discharge to the surface lags the maximum subsurface temperature by two months. Under an increasing air temperature scenario of 3?C per 100 years, over the initial 40-year period, the active layer thickness can increase by three-fold. Annual groundwater discharge to the surface can experience a similar three-fold increase in the same period. An implication of these modeling results is that with increased warming there will be more groundwater flow in the active layer and therefore increased groundwater discharge to rivers. However, this finding only holds if sufficient upgradient water is available to replenish the increased discharge. Otherwise, there will be an overall lowering of the water table in the recharge portion of the catchment.

Theoretical investigation of the activity of cobalt oxides for the electrochemical oxidation of water.

PubMed

Bajdich, Michal; García-Mota, Mónica; Vojvodic, Aleksandra; Nørskov, Jens K; Bell, Alexis T

2013-09-11

The presence of layered cobalt oxides has been identified experimentally in Co-based anodes under oxygen-evolving conditions. In this work, we report the results of theoretical investigations of the relative stability of layered and spinel bulk phases of Co oxides, as well as the stability of selected surfaces as a function of applied potential and pH. We then study the oxygen evolution reaction (OER) on these surfaces and obtain activity trends at experimentally relevant electro-chemical conditions. Our calculated volume Pourbaix diagram shows that β-CoOOH is the active phase where the OER occurs in alkaline media. We calculate relative surface stabilities and adsorbate coverages of the most stable low-index surfaces of β-CoOOH: (0001), (0112), and (1014). We find that at low applied potentials, the (1014) surface is the most stable, while the (0112) surface is the more stable at higher potentials. Next, we compare the theoretical overpotentials for all three surfaces and find that the (1014) surface is the most active one as characterized by an overpotential of η = 0.48 V. The high activity of the (1014) surface can be attributed to the observation that the resting state of Co in the active site is Co(3+) during the OER, whereas Co is in the Co(4+) state in the less active surfaces. Lastly, we demonstrate that the overpotential of the (1014) surface can be lowered further by surface substitution of Co by Ni. This finding could explain the experimentally observed enhancement in the OER activity of Ni(y)Co(1-y)O(x) thin films with increasing Ni content. All energetics in this work were obtained from density functional theory using the Hubbard-U correction.

Influence of silicon doping of titanium nickelide near-surface layers on alloy cytocompatibility

NASA Astrophysics Data System (ADS)

Lotkov, A. I.; Matveev, A. L.; Artemyeva, L. V.; Meysner, S. N.; Matveeva, V. A.; Kudryashov, A. N.

2017-12-01

The cytocompatibility of titanium nickelide (TiNi) with near-surface layers doped with silicon ions was studied on mesenchymal stem cells of rat bone marrow cultivated in vitro. The cytotoxic effect of eluted components of material on the mesenchymal stem cells was determined using a RTCA iCELLigence cellular analyzer. The proliferative activity of mesenchymal stem cells cultivated in the presence or on the surfaces of titanium nickelide samples was estimated from the cell mitochondrial respiration rate in MTT tests using [2-(4-Iodophenyl)-3-(4-nitrophenyl)-5-(2, 4-disulfophenyl)-2H-tetrazolium] tetrazolium salt. It is shown that ion plasma modification of near-surface layers of titanium nickelide with silicon improves the cytocompatibility of the alloy.

Abrasion Testing of Candidate Outer Layer Fabrics for Lunar EVA Space Suits

NASA Technical Reports Server (NTRS)

Mitchell, Kathryn

2009-01-01

During the Apollo program, the space suit outer layer fabrics were severely abraded after just a few Extravehicular Activities (EVAs). For example, the Apollo 12 commander reported abrasive wear on the boots, which penetrated the outer layer fabric into the thermal protection layers after less than eight hours of surface operations. Current plans for the Constellation Space Suit Element require the space suits to support hundreds of hours of EVA on the Lunar surface, creating a challenge for space suit designers to utilize materials advances made over the last forty years and improve upon the space suit fabrics used in the Apollo program. A test methodology has been developed by the NASA Johnson Space Center Crew and Thermal Systems Division for establishing comparative abrasion wear characteristics between various candidate space suit outer layer fabrics. The abrasion test method incorporates a large rotary drum tumbler with rocks and loose lunar simulant material to induce abrasion in fabric test cylinder elements, representative of what might occur during long term planetary surface EVAs. Preliminary materials screening activities were conducted to determine the degree of wear on representative space suit outer layer materials and the corresponding dust permeation encountered between subsequent sub-layers of thermal protective materials when exposed to a simulated worst case eight hour EVA. The test method was used to provide a preliminary evaluation of four candidate outer layer fabrics for future planetary surface space suit applications. This paper provides a review of previous abrasion studies on space suit fabrics, details the methodologies used for abrasion testing in this particular study, shares the results of the testing, and provides recommendations for future work.

Abrasion Testing of Candidate Outer Layer Fabrics for Lunar EVA Space Suits

NASA Technical Reports Server (NTRS)

Mitchell, Kathryn C.

2010-01-01

During the Apollo program, the space suit outer layer fabrics were badly abraded after just a few Extravehicular Activities (EVAs). For example, the Apollo 12 commander reported abrasive wear on the boots, which penetrated the outer layer fabric into the thermal protection layers after less than eight hours of surface operations. Current plans for the Constellation Space Suit Element require the space suits to support hundreds of hours of EVA on the Lunar surface, creating a challenge for space suit designers to utilize materials advances made over the last forty years and improve upon the space suit fabrics used in the Apollo program. A test methodology has been developed by the NASA Johnson Space Center Crew and Thermal Systems Division for establishing comparative abrasion wear characteristics between various candidate space suit outer layer fabrics. The abrasion test method incorporates a large rotary drum tumbler with rocks and loose lunar simulant material to induce abrasion in fabric test cylinder elements, representative of what might occur during long term planetary surface EVAs. Preliminary materials screening activities were conducted to determine the degree of wear on representative space suit outer layer materials and the corresponding dust permeation encountered between subsequent sub -layers of thermal protective materials when exposed to a simulated worst case eight hour EVA. The test method was used to provide a preliminary evaluation of four candidate outer layer fabrics for future planetary surface space suit applications. This Paper provides a review of previous abrasion studies on space suit fabrics, details the methodologies used for abrasion testing in this particular study, and shares the results and conclusions of the testing.

Tensiometry and dilational rheology of mixed β-lactoglobulin/ionic surfactant adsorption layers at water/air and water/hexane interfaces.

PubMed

Dan, Abhijit; Gochev, Georgi; Miller, Reinhard

2015-07-01

Oscillating drop tensiometry was applied to study adsorbed interfacial layers at water/air and water/hexane interfaces formed from mixed solutions of β-lactoglobulin (BLG, 1 μM in 10 mM buffer, pH 7 - negative net charge) and the anionic surfactant SDS or the cationic DoTAB. The interfacial pressure Π and the dilational viscoelasticity modulus |E| of the mixed layers were measured for mixtures of varying surfactant concentrations. The double capillary technique was employed which enables exchange of the protein solution in the drop bulk by surfactant solution (sequential adsorption) or by pure buffer (washing out). The first protocol allows probing the influence of the surfactant on a pre-adsorbed protein layer thus studying the protein/surfactant interactions at the interface. The second protocol gives access to the residual values of Π and |E| measured after the washing out procedure thus bringing information about the process of protein desorption. The DoTAB/BLG complexes exhibit higher surface activity and higher resistance to desorption in comparison with those for the SDS/BLG complexes due to hydrophobization via electrostatic binding of surfactant molecules. The neutral DoTAB/BLG complexes achieve maximum elastic response of the mixed layer. Mixed BLG/surfactant layers at the water/oil interface are found to reach higher surface pressure and lower maximum dilational elasticity than those at the water/air surface. The sequential adsorption mode experiments and the desorption study reveal that binding of DoTAB to pre-adsorbed BLG globules is somehow restricted at the water/air surface in comparison with the case of complex formation in the solution bulk and subsequently adsorbed at the water/air surface. Maximum elasticity is achieved with washed out layers obtained after simultaneous adsorption, i.e. isolation of the most surface active DoTAB/BLG complex. These specific effects are much less pronounced at the W/H interface. Copyright © 2015 Elsevier Inc. All rights reserved.

New electrocatalysts for unitized regenerative fuel cell: Pt-Ir alloy deposited on the proton exchange membrane surface by impregnation-reduction method.

PubMed

Wan, Chieh-Hao; Wu, Chun-Lin; Lin, Meng-Tsun; Shih, Chihhsiong

2010-07-01

In this paper, a modified technique to prepare Pt-Ir catalyst layer on the proton exchange membrane (PEM) surface using the impregnation-reduction (IR) method is proposed to improve the electrocatalytic activity as well as the life cycle of the bifunctional oxygen electrode (BOE). The resulted electrocatalysts were characterized by the Scanning Electron Microscopy (SEM), X-ray Diffraction (XRD), Electron Probe Micro-Analysis (EPMA), and Transmission Electron Microscope (TEM). The electrocatalytic properties of the Pt-Ir layer on PEM surface for the oxygen reduction and water oxidation reactions as well as the life cycle of MEA were investigated. Experimental results showed that the Ir particles were dispersed densely in the platinum layer through the modified IR technique. The atomic ratio of Pt over Ir elements was 9:1, and the resulted thickness of the obtained Pt-Ir catalyst layer was about 1.0 microm. The Pt-Ir catalyst layer was composed of Pt layer doped with Ir nano-particles comprising nano Pt-Ir alloy phase. The large surface area of Ir core with Pt shell particles and the presence of nano Pt-Ir alloy phase led to a higher electrocatalytic activity of BOE. Due to the good binding between the Nafion membrane and the Pt-Ir alloy catalyst, as well as the composite structure of the resulted Pt-Ir, the life cycle of Unitized Regenerative Fuel Cell (URFC) is improved through this novel BOE.

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

NASA Astrophysics Data System (ADS)

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

2010-07-01

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

Innovative nanostructures for highly sensitive vibrational biosensing (Conference Presentation)

NASA Astrophysics Data System (ADS)

Popp, Juergen; Mayerhöfer, Thomas; Cialla-May, Dana; Weber, Karina; Huebner, Uwe

2016-03-01

Employing vibrational spectroscopy (IR-absorption and Raman spectroscopy) allows for the labelfree detection of molecular specific fingerprints of inorganic, organic and biological substances. The sensitivity of vibrational spectroscopy can be improved by several orders of magnitude via the application of plasmonic active surfaces. Within this contribution we will discuss two such approaches, namely surface enhanced Raman spectroscopy (SERS) as well as surface enhanced IR absorption (SEIRA). It will be shown that SERS using metal colloids as SERS active substrate in combination with a microfluidic lab-on-a-chip (LOC) device enables high throughput and reproducible measurements with highest sensitivity and specificity. The application of such a LOC-SERS approach for therapeutic drug monitoring (e.g. quantitative detection of antibiotics in a urine matrix) will be presented. Furthermore, we will introduce innovative bottom-up strategies to prepare SERS-active nanostructures coated with a lipophilic sensor layer as one-time use SERS substrates for specific food analysis (e.g. quantitative detection of toxic food colorants). The second part of this contribution presents a slit array metamaterial perfect absorber for IR sensing applications consisting of a dielectric layer sandwiched between two metallic layers of which the upper layer is perforated with a periodic array of slits. Light-matter interaction is greatly amplified in the slits, where also the analyte is concentrated, as the surface of the substrate is covered by a thin silica layer. Thus, already small concentrations of analytes down to a monolayer can be detected by refractive index sensing and identified by their spectral fingerprints with a standard mid-infrared lab spectrometer.

Corrosion resistance and biological activity of TiO2 implant coatings produced in oxygen-rich environments.

PubMed

Zhang, Rui; Wan, Yi; Ai, Xing; Liu, Zhanqiang; Zhang, Dong

2017-01-01

The physical and chemical properties of bio-titanium alloy implant surfaces play an important role in their corrosion resistance and biological activity. New turning and turning-rolling processes are presented, employing an oxygen-rich environment in order to obtain titanium dioxide layers that can both protect implants from corrosion and also promote cell adhesion. The surface topographies, surface roughnesses and chemical compositions of the sample surfaces were obtained using scanning electron microscopy, a white light interferometer, and the Auger electron spectroscopy, respectively. The corrosion resistance of the samples in a simulated body fluid was determined using electrochemical testing. Biological activity on the samples was also analyzed, using a vitro cell culture system. The results show that compared with titanium oxide layers formed using a turning process in air, the thickness of the titanium oxide layers formed using turning and turning-rolling processes in an oxygen-rich environment increased by 4.6 and 7.3 times, respectively. Using an oxygen-rich atmosphere in the rolling process greatly improves the corrosion resistance of the resulting samples in a simulated body fluid. On samples produced using the turning-rolling process, cells spread quickly and exhibited the best adhesion characteristics.

P-type surface effects for thickness variation of 2um and 4um of n-type layer in GaN LED

NASA Astrophysics Data System (ADS)

Halim, N. S. A. Abdul; Wahid, M. H. A.; Hambali, N. A. M. Ahmad; Rashid, S.; Ramli, M. M.; Shahimin, M. M.

2017-09-01

The internal quantum efficiency of III-Nitrides group, GaN light-emitting diode (LED) has been considerably limited due to the insufficient hole injection and this is caused by the lack of performance p-type doping and low hole mobility. The low hole mobility makes the hole less energetic, thus reduced the performance operation of GaN LED itself. The internal quantum efficiency of GaN-based LED with surface roughness (texture) can be changed by texture size, density, and thickness of GaN film or by the combined effects of surface shape and thickness of GaN film. Besides, due to lack of p-type GaN, attempts to look forward the potential of GaN LED relied on the thickness of n-type layer and surface shape of p-type GaN layer. This work investigates the characteristics of GaN LED with undoped n-GaN layer of different thickness and the surface shape of p-type layer. The LEDs performance is significantly altered by modifying the thickness and shape. Enhancement of n-GaN layer has led to the annihilation of electrical conductivity of the chip. Different surface geometry governs the emission rate extensively. Internal quantum efficiency is also predominantly affected by the geometry of n-GaN layer which subjected to the current spreading. It is recorded that the IQE droop can be minimized by varying the thickness of the active layer without amplifying the forward voltage. Optimum forward voltage (I-V), total emission rate relationship with the injected current and internal quantum efficiency (IQE) for 2,4 µm on four different surfaces of p-type layer are also reported in this paper.

Observations of the Evolution of Turbulent Dissipation within the Ocean Surface Boundary Layer: an OSMOSIS study

NASA Astrophysics Data System (ADS)

Lucas, N. S.; Allen, J.; Belcher, S. E.; Boyd, T.; Brannigan, L.; Inall, M.; Palmer, M.; Polton, J.; Rippeth, T. P.

2016-02-01

This study presents a new 9.5 day dataset showing the evolution of the Ocean Surface Boundary Layer (OSBL) and dissipation of turbulence kinetic energy (TKE), carried out as part of OSMOSIS[i], at a location in the North East Atlantic Ocean in September 2012. The TKE dissipation measurements were made using three methods; (i) repeated profiling between 100m and the surface by an Ocean Microstructure glider, (ii) three series of profiles made using a loosely tethered velocity microstructure glider and (iii) a moored pulse-pulse coherent high frequency ADCP. Supporting measurements show the evolution of the water column structure, including surface wave measurements from a TRIAXYS wave buoy. This data shows two distinct regimes; the first, spanning 4 days with relatively low winds, displays a distinct diurnal cycle with the deepening of the active mixing layer during the night which shoaled during the day. The second spanned a significant storm, (with maximum winds speeds reaching 20 m s-1 and significant wave heights reaching 6 m), during which, rather than a deepening of the mixed layer as predicted by classical theory, the primary effect was a broadening of the transition layer, similar to that found by Dohan and Davies (2011). During the storm, significant dissipation was observed throughout the surface mixed layer and into the transition layer, driving fluxes of heat downwards through the base of the surface mixed layer. [i] Ocean Surface Mixing and Submesoscale Interaction Study Dohan, K. & Davis, R.E., 2011. Mixing in the Transition Layer during Two Storm Events. Journal of Physical Oceanography. 41 (1). pp. 42-66.

Fabrication and characterization of iron oxide dextran composite layers

NASA Astrophysics Data System (ADS)

Iconaru, S. L.; Predoi, S. A.; Beuran, M.; Ciobanu, C. S.; Trusca, R.; Ghita, R.; Negoi, I.; Teleanu, G.; Turculet, S. C.; Matei, M.; Badea, Monica; Prodan, A. M.

2018-02-01

Super paramagnetic iron oxide nanoparticles such as maghemite have been shown to exhibit antimicrobial properties [1-5]. Moreover, the iron oxide nanoparticles have been proposed as a potential magnetically controllable antimicrobial agent which could be directed to a specific infection [3-5]. The present research has focused on studies of the surface and structure of iron oxide dextran (D-IO) composite layers surface and structure. These composite layers were deposited on Si substrates. The structure of iron oxide dextran composite layers was investigated by X-Ray Diffraction (XRD) and Fourier Transform Infrared Spectroscopy (FTIR) while the surface morphology was evaluated by Scanning Electron Microscopy (SEM). The structural characterizations of the iron oxide dextran composite layers revealed the basic constituents of both iron and dextran structure. Furthermore, the in vitro evaluation of the antifungal effect of the complex layers, which have been shown revealed to be active against C. albicans cells at distinct intervals of time, is exhibited. Our research came to confirm the fungicidal effect of iron oxide dextran composite layers. Also, our results suggest that iron oxide dextran surface may be used for medical treatment of biofilm associated Candida infections.

Preservation of Archaeal Surface Layer Structure During Mineralization

NASA Astrophysics Data System (ADS)

Kish, Adrienne; Miot, Jennyfer; Lombard, Carine; Guigner, Jean-Michel; Bernard, Sylvain; Zirah, Séverine; Guyot, François

2016-05-01

Proteinaceous surface layers (S-layers) are highly ordered, crystalline structures commonly found in prokaryotic cell envelopes that augment their structural stability and modify interactions with metals in the environment. While mineral formation associated with S-layers has previously been noted, the mechanisms were unconstrained. Using Sulfolobus acidocaldarius a hyperthermophilic archaeon native to metal-enriched environments and possessing a cell envelope composed only of a S-layer and a lipid cell membrane, we describe a passive process of iron phosphate nucleation and growth within the S-layer of cells and cell-free S-layer “ghosts” during incubation in a Fe-rich medium, independently of metabolic activity. This process followed five steps: (1) initial formation of mineral patches associated with S-layer; (2) patch expansion; (3) patch connection; (4) formation of a continuous mineral encrusted layer at the cell surface; (5) early stages of S-layer fossilization via growth of the extracellular mineralized layer and the mineralization of cytosolic face of the cell membrane. At more advanced stages of encrustation, encrusted outer membrane vesicles are formed, likely in an attempt to remove damaged S-layer proteins. The S-layer structure remains strikingly well preserved even upon the final step of encrustation, offering potential biosignatures to be looked for in the fossil record.

Zwitterionic sulfobetaine-grafted poly(vinylidene fluoride) membrane with highly effective blood compatibility via atmospheric plasma-induced surface copolymerization.

PubMed

Chang, Yung; Chang, Wan-Ju; Shih, Yu-Ju; Wei, Ta-Chin; Hsiue, Ging-Ho

2011-04-01

Development of nonfouling membranes to prevent nonspecific protein adsorption and platelet adhesion is critical for many biomedical applications. It is always a challenge to control the surface graft copolymerization of a highly polar monomer from the highly hydrophobic surface of a fluoropolymer membrane. In this work, the blood compatibility of poly(vinylidene fluoride) (PVDF) membranes with surface-grafted electrically neutral zwitterionic poly(sulfobetaine methacrylate) (PSBMA), from atmospheric plasma-induced surface copolymerization, was studied. The effect of surface composition and graft morphology, electrical neutrality, hydrophilicity and hydration capability on blood compatibility of the membranes were determined. Blood compatibility of the zwitterionic PVDF membranes was systematically evaluated by plasma protein adsorption, platelet adhesion, plasma-clotting time, and blood cell hemolysis. It was found that the nonfouling nature and hydration capability of grafted PSBMA polymers can be effectively controlled by regulating the grafting coverage and charge balance of the PSBMA layer on the PVDF membrane surface. Even a slight charge bias in the grafted zwitterionic PSBMA layer can induce electrostatic interactions between proteins and the membrane surfaces, leading to surface protein adsorption, platelet activation, plasma clotting and blood cell hemolysis. Thus, the optimized PSBMA surface graft layer in overall charge neutrality has a high hydration capability and the best antifouling, anticoagulant, and antihemolytic activities when comes into contact with human blood. © 2011 American Chemical Society

Slow-muon study of quaternary solar-cell materials: Single layers and p -n junctions

NASA Astrophysics Data System (ADS)

Alberto, H. V.; Vilão, R. C.; Vieira, R. B. L.; Gil, J. M.; Weidinger, A.; Sousa, M. G.; Teixeira, J. P.; da Cunha, A. F.; Leitão, J. P.; Salomé, P. M. P.; Fernandes, P. A.; Törndahl, T.; Prokscha, T.; Suter, A.; Salman, Z.

2018-02-01

Thin films and p -n junctions for solar cells based on the absorber materials Cu (In ,G a ) Se2 and Cu2ZnSnS4 were investigated as a function of depth using implanted low energy muons. The most significant result is a clear decrease of the formation probability of the Mu+ state at the heterojunction interface as well as at the surface of the Cu (In ,G a ) Se2 film. This reduction is attributed to a reduced bonding reaction of the muon in the absorber defect layer at its surface. In addition, the activation energies for the conversion from a muon in an atomiclike configuration to a anion-bound position are determined from temperature-dependence measurements. It is concluded that the muon probe provides a measurement of the effective surface defect layer width, both at the heterojunctions and at the films. The CIGS surface defect layer is crucial for solar-cell electrical performance and additional information can be used for further optimizations of the surface.

Passivation of phosphorus diffused silicon surfaces with Al{sub 2}O{sub 3}: Influence of surface doping concentration and thermal activation treatments

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

Richter, Armin, E-mail: armin.richter@ise.fraunhofer.de; Benick, Jan; Kimmerle, Achim

2014-12-28

Thin layers of Al{sub 2}O{sub 3} are well known for the excellent passivation of p-type c-Si surfaces including highly doped p{sup +} emitters, due to a high density of fixed negative charges. Recent results indicate that Al{sub 2}O{sub 3} can also provide a good passivation of certain phosphorus-diffused n{sup +} c-Si surfaces. In this work, we studied the recombination at Al{sub 2}O{sub 3} passivated n{sup +} surfaces theoretically with device simulations and experimentally for Al{sub 2}O{sub 3} deposited with atomic layer deposition. The simulation results indicate that there is a certain surface doping concentration, where the recombination is maximal duemore » to depletion or weak inversion of the charge carriers at the c-Si/Al{sub 2}O{sub 3} interface. This pronounced maximum was also observed experimentally for n{sup +} surfaces passivated either with Al{sub 2}O{sub 3} single layers or stacks of Al{sub 2}O{sub 3} capped by SiN{sub x}, when activated with a low temperature anneal (425 °C). In contrast, for Al{sub 2}O{sub 3}/SiN{sub x} stacks activated with a short high-temperature firing process (800 °C) a significant lower surface recombination was observed for most n{sup +} diffusion profiles without such a pronounced maximum. Based on experimentally determined interface properties and simulation results, we attribute this superior passivation quality after firing to a better chemical surface passivation, quantified by a lower interface defect density, in combination with a lower density of negative fixed charges. These experimental results reveal that Al{sub 2}O{sub 3}/SiN{sub x} stacks can provide not only excellent passivation on p{sup +} surfaces but also on n{sup +} surfaces for a wide range of surface doping concentrations when activated with short high-temperature treatments.« less

Mode-locking of an InAs Quantum Dot Based Vertical External Cavity Surface Emitting Laser Using Atomic Layer Graphene

DTIC Science & Technology

2015-07-16

SECURITY CLASSIFICATION OF: The InAs quantum dot (QD) grown on GaAs substrates represents a highly performance active region in the 1 - 1.3 µm...2015 Approved for Public Release; Distribution Unlimited Final Report: Mode-locking of an InAs Quantum Dot Based Vertical External Cavity Surface...ABSTRACT Final Report: Mode-locking of an InAs Quantum Dot Based Vertical External Cavity Surface Emitting Laser Using Atomic Layer Graphene Report

Cathodic Polarization Coats Titanium Based Implant Materials with Enamel Matrix Derivate (EMD)

PubMed Central

Frank, Matthias J.; Walter, Martin S.; Rubert, Marina; Thiede, Bernd; Monjo, Marta; Reseland, Janne E.; Haugen, Håvard J.; Lyngstadaas, Ståle Petter

2014-01-01

The idea of a bioactive surface coating that enhances bone healing and bone growth is a strong focus of on-going research for bone implant materials. Enamel matrix derivate (EMD) is well documented to support bone regeneration and activates growth of mesenchymal tissues. Thus, it is a prime candidate for coating of existing implant surfaces. The aim of this study was to show that cathodic polarization can be used for coating commercially available implant surfaces with an immobilized but functional and bio-available surface layer of EMD. After coating, XPS revealed EMD-related bindings on the surface while SIMS showed incorporation of EMD into the surface. The hydride layer of the original surface could be activated for coating in an integrated one-step process that did not require any pre-treatment of the surface. SEM images showed nano-spheres and nano-rods on coated surfaces that were EMD-related. Moreover, the surface roughness remained unchanged after coating, as it was shown by optical profilometry. The mass peaks observed in the matrix-assisted laser desorption/ionization time-of-flight mass spectroscopy (MALDI-TOF MS) analysis confirmed the integrity of EMD after coating. Assessment of the bioavailability suggested that the modified surfaces were active for osteoblast like MC3M3-E1 cells in showing enhanced Coll-1 gene expression and ALP activity. PMID:28788564

Selective UV–O3 treatment for indium zinc oxide thin film transistors with solution-based multiple active layer

NASA Astrophysics Data System (ADS)

Kim, Yu-Jung; Jeong, Jun-Kyo; Park, Jung-Hyun; Jeong, Byung-Jun; Lee, Hi-Deok; Lee, Ga-Won

2018-06-01

In this study, a method to control the electrical performance of solution-based indium zinc oxide (IZO) thin film transistors (TFTs) is proposed by ultraviolet–ozone (UV–O3) treatment on the selective layer during multiple IZO active layer depositions. The IZO film is composed of triple layers formed by spin coating and UV–O3 treatment only on the first layer or last layer. The IZO films are compared by X-ray photoelectron spectroscopy, and the results show that the atomic ratio of oxygen vacancy (VO) increases in the UV–O3 treatment on the first layer, while it decreases on last layer. The device characteristics of the bottom gated structure are also improved in the UV–O3 treatment on the first layer. This indicates that the selective UV–O3 treatment in a multi-stacking active layer is an effective method to optimize TFT properties by controlling the amount of VO in the IZO interface and surface independently.

Au-nanoparticles grafted on plasma treated PE

NASA Astrophysics Data System (ADS)

Švorčík, V.; Chaloupka, A.; Řezanka, P.; Slepička, P.; Kolská, Z.; Kasálková, N.; Hubáček, T.; Siegel, J.

2010-03-01

Polyethylene (PE) surface was treated with Ar plasma. Activated surface was grafted from methanol solution of 1,2-ethanedithiol. Then the sample was immersed into freshly prepared colloid solution of Au-nanoparticles. Finally Au layer was sputtered on the samples. Properties of the modified PE were studied using various methods: AFM, EPR, RBS and nanoindentation. It was shown that the plasma treatment results in degradation of polymer chain (AFM) and creation of free radicals by EPR. After grafting with dithiol, the concentration of free radicals declines. The presence of Au and S in the surface layer after the coating with Au-nanoparticles was proved by RBS. Plasma treatment changes PE surface morphology and increases surface roughness, too. Another significant change in surface morphology and roughness was observed after deposition of Au-nanoparticles. Nanoindentation measurements show that the grafting with Au-nanoparticles increases adhesion of subsequently sputtered Au layer.

Pulsed-Plasma Physical Vapor Deposition Approach Toward the Facile Synthesis of Multilayer and Monolayer Graphene for Anticoagulation Applications.

PubMed

Vijayaraghavan, Rajani K; Gaman, Cezar; Jose, Bincy; McCoy, Anthony P; Cafolla, Tony; McNally, Patrick J; Daniels, Stephen

2016-02-01

We demonstrate the growth of multilayer and single-layer graphene on copper foil using bipolar pulsed direct current (DC) magnetron sputtering of a graphite target in pure argon atmosphere. Single-layer graphene (SG) and few-layer graphene (FLG) films are deposited at temperatures ranging from 700 °C to 920 °C within <30 min. We find that the deposition and post-deposition annealing temperatures influence the layer thickness and quality of the graphene films formed. The films were characterized using atomic force microscopy (AFM), scanning electron microscopy (SEM), high-resolution transmission electron microscopy (HRTEM), Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), and optical transmission spectroscopy techniques. Based on the above studies, a diffusion-controlled mechanism was proposed for the graphene growth. A single-step whole blood assay was used to investigate the anticoagulant activity of graphene surfaces. Platelet adhesion, activation, and morphological changes on the graphene/glass surfaces, compared to bare glass, were analyzed using fluorescence microscopy and SEM techniques. We have found significant suppression of the platelet adhesion, activation, and aggregation on the graphene-covered surfaces, compared to the bare glass, indicating the anticoagulant activity of the deposited graphene films. Our production technique represents an industrially relevant method for the growth of SG and FLG for various applications including the biomedical field.

High power RF window deposition apparatus, method, and device

DOEpatents

Ives, Lawrence R.; Lucovsky, Gerald; Zeller, Daniel

2017-07-04

A process for forming a coating for an RF window which has improved secondary electron emission and reduced multipactor for high power RF waveguides is formed from a substrate with low loss tangent and desirable mechanical characteristics. The substrate has an RPAO deposition layer applied which oxygenates the surface of the substrate to remove carbon impurities, thereafter has an RPAN deposition layer applied to nitrogen activate the surface of the substrate, after which a TiN deposition layer is applied using Titanium tert-butoxide. The TiN deposition layer is capped with a final RPAN deposition layer of nitridation to reduce the bound oxygen in the TiN deposition layer. The resulting RF window has greatly improved titanium layer adhesion, reduced multipactor, and is able to withstand greater RF power levels than provided by the prior art.

Directionally Aligned Amorphous Polymer Chains via Electrohydrodynamic-Jet Printing: Analysis of Morphology and Polymer Field-Effect Transistor Characteristics.

PubMed

Kim, Yebyeol; Bae, Jaehyun; Song, Hyun Woo; An, Tae Kyu; Kim, Se Hyun; Kim, Yun-Hi; Park, Chan Eon

2017-11-15

Electrohydrodynamic-jet (EHD-jet) printing provides an opportunity to directly assembled amorphous polymer chains in the printed pattern. Herein, an EHD-jet printed amorphous polymer was employed as the active layer for fabrication of organic field-effect transistors (OFETs). Under optimized conditions, the field-effect mobility (μ FET ) of the EHD-jet printed OFETs was 5 times higher than the highest μ FET observed in the spin-coated OFETs, and this improvement was achieved without the use of complex surface templating or additional pre- or post-deposition processing. As the chain alignment can be affected by the surface energy of the dielectric layer in EHD-jet printed OFETs, dielectric layers with varying wettability were examined. Near-edge X-ray absorption fine structure measurements were performed to compare the amorphous chain alignment in OFET active layers prepared by EHD-jet printing and spin coating.

BslA(YuaB) forms a hydrophobic layer on the surface of Bacillus subtilis biofilms.

PubMed

Kobayashi, Kazuo; Iwano, Megumi

2012-07-01

Biofilms are surface-associated bacterial aggregates, in which bacteria are enveloped by polymeric substances known as the biofilm matrix. Bacillus subtilis biofilms display persistent resistance to liquid wetting and gas penetration, which probably explains the broad-spectrum resistance of the bacteria in these biofilms to antimicrobial agents. In this study, BslA (formerly YuaB) was identified as a major contributor to the surface repellency of B. subtilis biofilms. Disruption of bslA resulted in the loss of surface repellency and altered the biofilm surface microstructure. BslA localized to the biofilm matrix in an exopolysaccharide-dependent manner. Purified BslA exhibited amphiphilic properties and formed polymers in response to increases in the area of the air-water interface in vitro. Genetic and biochemical analyses showed that the self-polymerization activity of BslA was essential for its ability to localize to the biofilm matrix. Confocal laser scanning microscopy showed that BslA formed a layer on the biofilm surface. Taken together, we propose that BslA, standing for biofilm-surface layer protein, is responsible for the hydrophobic layer on the surface of biofilms. © 2012 Blackwell Publishing Ltd.

Microtopographic Evidence of Hillslope Susceptibility to Active Layer Detachments and Rapid Soil Erosion in Permafrost-dominated Watersheds

NASA Astrophysics Data System (ADS)

Rowland, J. C.; Shelef, E.; Sutfin, N. A.; Piliouras, A.; Andresen, C. G.; Wilson, C. J.

2017-12-01

Movement and storage rates of soil and carbon along permafrost-dominated hillslopes may vary dramatically from long-term steady creeping, at centimeters per year, to rapid gullying, land sliding, and active layer detachments of meter to decimeter sized portions of hillslopes. The rate and drivers of hillslope soil processes may have strong feedbacks on microtopography and hydrology that in turn strongly influence vegetation dynamics and biogeochemistry within watersheds. We observed evidence of both steady soil creep and more catastrophic soil erosion processes occurring across three small watersheds in the southern Seward Peninsula, AK. In these watersheds, we inferred active soil creep processes from the occurrence of solifluction lobes with partially buried shrubs and tilted survey benchmarks on slopes lacking lobes. More dramatic and rapid erosion of soils was evidenced by active layer detachments, extensional cracks in the tundra vegetation, gullying, and both small- and large-scale soil failure scarps. The margins and heads of valley hollows exhibited failure scars up to 4m in height. The spatial distribution of actively eroding areas suggests that some portions of hilllslopes may be more susceptible to rapid erosion. Coring of hillslope soils suggests a possible association between more actively eroding areas and the presence of an ice-rich layer (> 50%) at depths of approximately 90 cm down to the inferred top of bedrock at depths at 170 to 200 cm. We observed that the surface of these hillslope regions appears to have greater microtopographic roughness with a more chaotic and "lumpy" surface than portions of the hillslope were no massive ice layers were encountered. We hypothesize that the extensional cracking and chaotic surface roughness may arise from small-scale soil failures triggered when the seasonal thaw depth intersects the ice-rich layer. It may be possible to identify hillslope regions underlain by ice-rich layers with greater susceptibility for localized erosion and deformation based on a quantitative characterization of the hillslope microtopography. Using drone-based LiDAR topographic data to be acquired in late summer of 2017, we will quantitatively explore the relationship between microtopography and hillslope ice-content.

Stabilizing nanostructured solid oxide fuel cell cathode with atomic layer deposition.

PubMed

Gong, Yunhui; Palacio, Diego; Song, Xueyan; Patel, Rajankumar L; Liang, Xinhua; Zhao, Xuan; Goodenough, John B; Huang, Kevin

2013-09-11

We demonstrate that the highly active but unstable nanostructured intermediate-temperature solid oxide fuel cell cathode, La0.6Sr0.4CoO3-δ (LSCo), can retain its high oxygen reduction reaction (ORR) activity with exceptional stability for 4000 h at 700 °C by overcoating its surfaces with a conformal layer of nanoscale ZrO2 films through atomic layer deposition (ALD). The benefits from the presence of the nanoscale ALD-ZrO2 overcoats are remarkable: a factor of 19 and 18 reduction in polarization area-specific resistance and degradation rate over the pristine sample, respectively. The unique multifunctionality of the ALD-derived nanoscaled ZrO2 overcoats, that is, possessing porosity for O2 access to LSCo, conducting both electrons and oxide-ions, confining thermal growth of LSCo nanoparticles, and suppressing surface Sr-segregation is deemed the key enabler for the observed stable and active nanostructured cathode.

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

NASA Astrophysics Data System (ADS)

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

2017-01-01

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

Facile preparation of robust microcapsules by manipulating metal-coordination interaction between biomineral layer and bioadhesive layer.

PubMed

Zhang, Lei; Shi, Jiafu; Jiang, Zhongyi; Jiang, Yanjun; Meng, Ruijie; Zhu, Yuanyuan; Liang, Yanpeng; Zheng, Yang

2011-02-01

A novel approach combining biomimetic mineralization and bioadhesion is proposed to prepare robust and versatile organic-inorganic hybrid microcapsules. More specifically, these microcapsules are fabricated by sequential deposition of inorganic layer and organic layer on the surface of CaCO(3) microparticles, followed by the dissolution of CaCO(3) microparticles using EDTA. During the preparation process, protamine induces the hydrolysis and condensation of titania or silica precursor to form the inorganic layer or the biomineral layer. The organic layer or bioadhesive layer was formed through the rapid, spontaneous oxidative polymerization of dopamine into polydopamine (PDA) on the surface of the biomineral layer. There exist multiple interactions between the inorganic layer and the organic layer. Thus, the as-prepared organic-inorganic hybrid microcapsules acquire much higher mechanical stability and surface reactivity than pure titania or pure silica microcapsules. Furthermore, protamine/titania/polydopamine hybrid microcapsules display superior mechanical stability to protamine/silica/polydopamine hybrid microcapsules because of the formation of Ti(IV)-catechol coordination complex between the biomineral layer and the bioadhesive layer. As an example of application, three enzymes are respectively immobilized through physical encapsulation in the lumen, in situ entrapment within the wall and chemical attachment on the out surface of the hybrid microcapsules. The as-constructed multienzyme system displays higher catalytic activity and operational stability. Hopefully, the approach developed in this study will evolve as a generic platform for facile and controllable preparation of organic-inorganic hybrid materials with different compositions and shapes for a variety of applications in catalysis, sensor, drug/gene delivery.

Hemocompatible control of sulfobetaine-grafted polypropylene fibrous membranes in human whole blood via plasma-induced surface zwitterionization.

PubMed

Chen, Sheng-Han; Chang, Yung; Lee, Kueir-Rarn; Wei, Ta-Chin; Higuchi, Akon; Ho, Feng-Ming; Tsou, Chia-Chun; Ho, Hsin-Tsung; Lai, Juin-Yih

2012-12-21

In this work, the hemocompatibility of zwitterionic polypropylene (PP) fibrous membranes with varying grafting coverage of poly(sulfobetaine methacrylate) (PSBMA) via plasma-induced surface polymerization was studied. Charge neutrality of PSBMA-grafted layers on PP membrane surfaces was controlled by the low-pressure and atmospheric plasma treatment in this study. The effects of grafting composition, surface hydrophilicity, and hydration capability on blood compatibility of the membranes were determined. Protein adsorption onto the different PSBMA-grafted PP membranes from human fibrinogen solutions was measured by enzyme-linked immunosorbent assay (ELISA) with monoclonal antibodies. Blood platelet adhesion and plasma clotting time measurements from a recalcified platelet-rich plasma solution were used to determine if platelet activation depends on the charge bias of the grafted PSBMA layer. The charge bias of PSBMA layer deviated from the electrical balance of positively and negatively charged moieties can be well-controlled via atmospheric plasma-induced interfacial zwitterionization and was further tested with human whole blood. The optimized PSBMA surface graft layer in overall charge neutrality has a high hydration capability and keeps its original blood-inert property of antifouling, anticoagulant, and antithrmbogenic activities when it comes into contact with human blood. This work suggests that the hemocompatible nature of grafted PSBMA polymers by controlling grafting quality via atmospheric plasma treatment gives a great potential in the surface zwitterionization of hydrophobic membranes for use in human whole blood.

Denitrification potential in relation to lithology in five headwater riparian zones.

PubMed

Hill, Alan R; Vidon, Philippe G F; Langat, Jackson

2004-01-01

The influence of riparian zone lithology on nitrate dynamics is poorly understood. We investigated vertical variations in potential denitrification activity in relation to the lithology and stratigraphy of five headwater riparian zones on glacial till and outwash landscapes in southern Ontario, Canada. Conductive coarse sand and gravel layers occurred in four of the five riparian areas. These layers were thin and did not extend to the field-riparian perimeter in some riparian zones, which limited their role as conduits for ground water flow. We found widespread organic-rich layers at depths ranging from 40 to 300 cm that resulted from natural floodplain processes and the burial of surface soils by rapid valley-bottom sedimentation after European settlement. The organic matter content of these layers varied considerably from 2 to 5% (relic channel deposit) to 5 to 21% (buried soils) and 30 to 62% (buried peat). Denitrification potential (DNP) was measured by the acetylene block method in sediment slurries amended with nitrate. The highest DNP rates were usually found in the top 0- to 15-cm surface soil layer in all riparian zones. However, a steep decline in DNP with depth was often absent and high DNP activity occurred in the deep organic-rich layers. Water table variations in 2000-2002 indicated that ground water only interacted frequently with riparian surface soils between late March and May, whereas subsurface organic layers that sustain considerable DNP were below the water table for most of the year. These results suggest that riparian zones with organic deposits at depth may effectively remove nitrate from ground water even when the water table does not interact with organic-rich surface soil horizons.

Polymeric Coatings that Mimic the Endothelium: Combining Nitric Oxide Release with Surface-Bound Active Thrombomodulin and Heparin

PubMed Central

Wu, Biyun; Gerlitz, Bruce; Grinnell, Brian W.; Meyerhoff, Mark E.

2007-01-01

Multi-functional bilayer polymeric coatings are prepared with both controlled nitric oxide (NO) release and surface-bound active thrombomodulin (TM) alone or in combination with immobilized heparin. The outer-layer is made of CarboSil, a commercially available copolymer of silicone rubber (SR) and polyurethane (PU). The CarboSil is either carboxylated or aminated via an allophanate reaction with a diisocyanate compound followed by a urea-forming reaction between the generated isocyanate group of the polymer and the amine group of an amino acid (glycine), an oligopeptide (triglycine) or a diamine. The carboxylated CarboSil can then be used to immobilize TM through the formation of an amide bond between the surface carboxylic acid groups and the lysine residues of TM. Aminated CarboSil can also be employed to initially couple heparin to the surface, and then the carboxylic acid groups on heparin can be further used to anchor TM. Both surface-bound TM and heparin’s activity are evaluated by chromogenic assays and found to be at clinically significant levels. The underlying NO release layer is made with another commercial SR-PU copolymer (PurSil) mixed with a lipophilic NO donor (N-diazeniumdiolated dibutylhexanediamine (DBHD/N2O2)). The NO release rate can be tuned by changing the thickness of top coatings, and the duration of NO release at physiologically relevant levels can be as long as 2 weeks. The combination of controlled NO release as well as immobilized active TM and heparin from/on the same polymeric surface mimics the highly thromboresistant endothelium layer. Hence, such multifunctional polymer coatings should provide more blood-compatible surfaces for biomedical devices. PMID:17597201

Temperature-insensitive vertical-cavity surface-emitting lasers and method for fabrication thereof

DOEpatents

Chow, W.W.; Choquette, K.D.; Gourley, P.L.

1998-01-27

A temperature-insensitive vertical-cavity surface-emitting laser (VCSEL) and method for fabrication thereof are disclosed. The temperature-insensitive VCSEL comprises a quantum-well active region within a resonant cavity, the active region having a gain spectrum with a high-order subband (n {>=} 2) contribution thereto for broadening and flattening the gain spectrum, thereby substantially reducing any variation in operating characteristics of the VCSEL over a temperature range of interest. The method for forming the temperature-insensitive VCSEL comprises the steps of providing a substrate and forming a plurality of layers thereon for providing first and second distributed Bragg reflector (DBR) mirror stacks with an active region sandwiched therebetween, the active region including at least one quantum-well layer providing a gain spectrum having a high-order subband (n {>=} 2) gain contribution, and the DBR mirror stacks having predetermined layer compositions and thicknesses for providing a cavity resonance within a predetermined wavelength range substantially overlapping the gain spectrum. 12 figs.

Resilient Flexible Pressure-Activated Seal

NASA Technical Reports Server (NTRS)

Steinetz, Bruce M. (Inventor); Dunlap, Patrick H., Jr. (Inventor)

2009-01-01

A resilient, flexible, pressure-activated, high-temperature seal is adapted to be interposed between high and low pressure regions to provide sealing between opposing surfaces of adjacent relatively movable structures. The seal comprises at least one C-shaped sheet element. The C-shaped element design enables the seal to be pressure-activated to provide a radially outward biasing force, responsive to a seal-activating pressure differential acting across the seal thereby increasing resiliency. A centrally-located, resilient core structure provides load bearing and insulating properties. In an exemplary embodiment where at least two seal elements are used, each layer has a cutout slot pattern and the remaining strip material pattern. The slots provide flexibility to the seal, enabling the seal to be manually contoured to seal around corners and curves. The strip material of each layer covers the slots in each adjacent layer to minimize leakage through the slots. Attached barrier strips can block interface leakage between the seal and the opposing surfaces.

Temperature-insensitive vertical-cavity surface-emitting lasers and method for fabrication thereof

DOEpatents

Chow, Weng W.; Choquette, Kent D.; Gourley, Paul L.

1998-01-01

A temperature-insensitive vertical-cavity surface-emitting laser (VCSEL) and method for fabrication thereof. The temperature-insensitive VCSEL comprises a quantum-well active region within a resonant cavity, the active region having a gain spectrum with a high-order subband (n.gtoreq.2) contribution thereto for broadening and flattening the gain spectrum, thereby substantially reducing any variation in operating characteristics of the VCSEL over a temperature range of interest. The method for forming the temperature-insensitive VCSEL comprises the steps of providing a substrate and forming a plurality of layers thereon for providing first and second distributed Bragg reflector (DBR) mirror stacks with an active region sandwiched therebetween, the active region including at least one quantum-well layer providing a gain spectrum having a high-order subband (n.gtoreq.2) gain contribution, and the DBR mirror stacks having predetermined layer compositions and thicknesses for providing a cavity resonance within a predetermined wavelength range substantially overlapping the gain spectrum.

Improved performance by morphology control via fullerenes in PBDT-TBT-alkoBT based organic solar cells

DOE PAGES

Khatiwada, Devendra; Venkatesan, Swaminathan; Chen, QIliang; ...

2015-07-03

In this work, we report improved performance by controlling morphology using different fullerene derivatives in poly{2-octyldodecyloxy-benzo[1,2-b;3,4-b]dithiophene-alt-5,6-bis(dodecyloxy)-4,7- di(thieno[3,2-b]thiophen-2-yl)-benzo[c][1,2,5]thiadiazole} (PBDT-TBT-alkoBT) based organic solar cells. PC60BM and PC70BM fullerenes were used to investigate the characteristic change in morphology and device performance. Fullerene affects device efficiency by changing active layer morphology. PC70BM with broader absorption than PC 60BM resulted in reduced device performance which was elucidated by the intermixed granular morphology separating each larger grain in the PC70BM/polymer composite layer which created higher density of traps. However after adding additive 1,8-diiodooctane (DIO), the fibrous morphology was observed due to reduced solubility of polymer andmore » increased solubility of PC 70BM in chloroform. The fibrous morphology improved charge transport leading to increase in overall device performance. Atomic force microscopies (AFM), photo induced charge extraction by linearly increasing voltage (photo-CELIV), and Kelvin prove force microscope (KPFM) were used to investigate nanoscale morphology of active layer with different fullerene derivatives. For PC 60BM based active layer, AFM images revealed dense fibrous morphology and more distinct fibrous morphology was observed by adding DIO. The PC 70BM based active layer only exhibited intermixed granular morphology instead of fibrous morphology observed in PC60BM based active layer. However, addition of DIO in PC 70BM based active layer led to fibrous morphology. When additive DIO was not used, a wider distribution of surface potential was observed for PC 70BM than PC 60BM based active layer by KPFM measurements, indicating 2 polymer and fullerene domains are separated. When DIO was used, narrower distribution of surface potential for both PC 70BM and PC 60BM based active layers was observed. Photo-CELIV experiment showed larger extracted charge carrier density and mobility in PC 70BM/DIO film.« less

Improved performance by morphology control via fullerenes in PBDT-TBT-alkoBT based organic solar cells

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

Khatiwada, Devendra; Venkatesan, Swaminathan; Chen, QIliang

In this work, we report improved performance by controlling morphology using different fullerene derivatives in poly{2-octyldodecyloxy-benzo[1,2-b;3,4-b]dithiophene-alt-5,6-bis(dodecyloxy)-4,7- di(thieno[3,2-b]thiophen-2-yl)-benzo[c][1,2,5]thiadiazole} (PBDT-TBT-alkoBT) based organic solar cells. PC60BM and PC70BM fullerenes were used to investigate the characteristic change in morphology and device performance. Fullerene affects device efficiency by changing active layer morphology. PC70BM with broader absorption than PC 60BM resulted in reduced device performance which was elucidated by the intermixed granular morphology separating each larger grain in the PC70BM/polymer composite layer which created higher density of traps. However after adding additive 1,8-diiodooctane (DIO), the fibrous morphology was observed due to reduced solubility of polymer andmore » increased solubility of PC 70BM in chloroform. The fibrous morphology improved charge transport leading to increase in overall device performance. Atomic force microscopies (AFM), photo induced charge extraction by linearly increasing voltage (photo-CELIV), and Kelvin prove force microscope (KPFM) were used to investigate nanoscale morphology of active layer with different fullerene derivatives. For PC 60BM based active layer, AFM images revealed dense fibrous morphology and more distinct fibrous morphology was observed by adding DIO. The PC 70BM based active layer only exhibited intermixed granular morphology instead of fibrous morphology observed in PC60BM based active layer. However, addition of DIO in PC 70BM based active layer led to fibrous morphology. When additive DIO was not used, a wider distribution of surface potential was observed for PC 70BM than PC 60BM based active layer by KPFM measurements, indicating 2 polymer and fullerene domains are separated. When DIO was used, narrower distribution of surface potential for both PC 70BM and PC 60BM based active layers was observed. Photo-CELIV experiment showed larger extracted charge carrier density and mobility in PC 70BM/DIO film.« less

Charged particle detectors with active detector surface for partial energy deposition of the charged particles and related methods

DOEpatents

Gerts, David W; Bean, Robert S; Metcalf, Richard R

2013-02-19

A radiation detector is disclosed. The radiation detector comprises an active detector surface configured to generate charge carriers in response to charged particles associated with incident radiation. The active detector surface is further configured with a sufficient thickness for a partial energy deposition of the charged particles to occur and permit the charged particles to pass through the active detector surface. The radiation detector further comprises a plurality of voltage leads coupled to the active detector surface. The plurality of voltage leads is configured to couple to a voltage source to generate a voltage drop across the active detector surface and to separate the charge carriers into a plurality of electrons and holes for detection. The active detector surface may comprise one or more graphene layers. Timing data between active detector surfaces may be used to determine energy of the incident radiation. Other apparatuses and methods are disclosed herein.

Development of advanced micromirror arrays by flip-chip assembly

NASA Astrophysics Data System (ADS)

Michalicek, M. Adrian; Bright, Victor M.

2001-10-01

This paper presents the design, commercial prefabrication, modeling and testing of advanced micromirror arrays fabricated using a novel, simple and inexpensive flip-chip assembly technique. Several polar piston arrays and rectangular cantilever arrays were fabricated using flip-chip assembly by which the upper layers of the array are fabricated on a separate chip and then transferred to a receiving module containing the lower layers. Typical polar piston arrays boast 98.3% active surface area, highly planarized surfaces, low address potentials compatible with CMOS electronics, highly standardized actuation between devices, and complex segmentation of mirror surfaces which allows for custom aberration configurations. Typical cantilever arrays boast large angles of rotation as well as an average surface planarity of only 1.779 nm of RMS roughness across 100 +m mirrors. Continuous torsion devices offer stable operation through as much as six degrees of rotation while binary operation devices offer stable activated positions with as much as 20 degrees of rotation. All arrays have desirable features of costly fabrication services like five structural layers and planarized mirror surfaces, but are prefabricated in the less costly MUMPs process. Models are developed for all devices and used to compare empirical data.

Intercalated layered clay composites and their applications

NASA Astrophysics Data System (ADS)

Phukan, Anjali

Supported inorganic reagents are rapidly emerging as new and environmentally acceptable reagents and catalysts. The smectite group of layered clay minerals, such as, Montmorillonite, provides promising character for adsorption, catalytic activity, supports etc. for their large surface area, swelling behavior and ion exchange properties. Aromatic compounds intercalated in layered clays are useful in optical molecular devices. Clay is a unique material for adsorption of heavy metals and various toxic substances. Clay surfaces are known to be catalytically active due to their surface acidity. Acid activated clays possess much improved surface areas and acidities and have higher pore volumes so that can absorb large molecules in the pores. The exchangeable cations in clay minerals play a key role in controlling surface acidity and catalytic activity. Recently, optically active metal-complex-Montmorillonite composites are reported to be active in antiracemization purposes. In view of the above, a research work, relating to the preparation of different modified clay composites and their catalytic applications were carried out. The different aspects and results of the present work have been reported in four major chapters. Chapter I: This is an introductory chapter, which contains a review of the literature regarding clay-based materials. Clay minerals are phyllosilicates with layer structure. Montmorillonite, a member of smectite group of clay, is 2:1 phyllosilicate, where a layer is composed of an octahedral sheet sandwiched by two tetrahedral sheets. Such clay shows cation exchange capacity (CEC) and is expressed in milli-equivalents per 100 gm of dry clay. Clays can be modified by interaction with metal ion, metal complexes, metal cluster and organic cations for various applications. Clays are also modified by treating with acid followed by impregnation with metal salts or ions. Montmorillonite can intercalate suitable metal complexes in excess of CEC to form double or pseudo-trilayer composites. Metal ion and metal ion metal salts intercalated on Montmorillonite are efficient catalysts for Friedel-Crafts (FC) reactions, such as benzylation of benzene, synthesis of Raspberry ketone [4-(4'-hydroxyphenyl)butan-2-one] etc. Montmorillonite clay can be used as a good support for controlled release of pesticides and medicinal drugs, adsorbent for cationic dyes, toxic substances and heavy metals effective adsorbent for radioactive and toxic industrial wastes,...

Surface modifications of hydrogen storage alloy by heavy ion beams with keV to MeV irradiation energies

NASA Astrophysics Data System (ADS)

Abe, Hiroshi; Tokuhira, Shinnosuke; Uchida, Hirohisa; Ohshima, Takeshi

2015-12-01

This study deals with the effect of surface modifications induced from keV to MeV heavy ion beams on the initial reaction rate of a hydrogen storage alloy (AB5) in electrochemical process. The rare earth based alloys like this sample alloy are widely used as a negative electrode of Ni-MH (Nickel-Metal Hydride) battery. We aimed to improve the initial reaction rate of hydrogen absorption by effective induction of defects such as vacancies, dislocations, micro-cracks or by addition of atoms into the surface region of the metal alloys. Since defective layer near the surface can easily be oxidized, the conductive oxide layer is formed on the sample surface by O+ beams irradiation, and the conductive oxide layer might cause the improvement of initial reaction rate of hydriding. This paper demonstrates an effective surface treatment of heavy ion irradiation, which induces catalytic activities of rare earth oxides in the alloy surface.

Exchange of groundwater and surface-water mediated by permafrost response to seasonal and long term air temperature variation

USGS Publications Warehouse

Ge, S.; McKenzie, J.; Voss, C.; Wu, Q.

2011-01-01

Permafrost dynamics impact hydrologic cycle processes by promoting or impeding groundwater and surface water exchange. Under seasonal and decadal air temperature variations, permafrost temperature changes control the exchanges between groundwater and surface water. A coupled heat transport and groundwater flow model, SUTRA, was modified to simulate groundwater flow and heat transport in the subsurface containing permafrost. The northern central Tibet Plateau was used as an example of model application. Modeling results show that in a yearly cycle, groundwater flow occurs in the active layer from May to October. Maximum groundwater discharge to the surface lags the maximum subsurface temperature by two months. Under an increasing air temperature scenario of 3C per 100 years, over the initial 40-year period, the active layer thickness can increase by three-fold. Annual groundwater discharge to the surface can experience a similar three-fold increase in the same period. An implication of these modeling results is that with increased warming there will be more groundwater flow in the active layer and therefore increased groundwater discharge to rivers. However, this finding only holds if sufficient upgradient water is available to replenish the increased discharge. Otherwise, there will be an overall lowering of the water table in the recharge portion of the catchment. Copyright 2011 by the American Geophysical Union.

Self-optimizing, highly surface-active layered metal dichalcogenide catalysts for hydrogen evolution

NASA Astrophysics Data System (ADS)

Liu, Yuanyue; Wu, Jingjie; Hackenberg, Ken P.; Zhang, Jing; Wang, Y. Morris; Yang, Yingchao; Keyshar, Kunttal; Gu, Jing; Ogitsu, Tadashi; Vajtai, Robert; Lou, Jun; Ajayan, Pulickel M.; Wood, Brandon C.; Yakobson, Boris I.

2017-09-01

Low-cost, layered transition-metal dichalcogenides (MX2) based on molybdenum and tungsten have attracted substantial interest as alternative catalysts for the hydrogen evolution reaction (HER). These materials have high intrinsic per-site HER activity; however, a significant challenge is the limited density of active sites, which are concentrated at the layer edges. Here we unravel electronic factors underlying catalytic activity on MX2 surfaces, and leverage the understanding to report group-5 MX2 (H-TaS2 and H-NbS2) electrocatalysts whose performance instead mainly derives from highly active basal-plane sites, as suggested by our first-principles calculations and performance comparisons with edge-active counterparts. Beyond high catalytic activity, they are found to exhibit an unusual ability to optimize their morphology for enhanced charge transfer and accessibility of active sites as the HER proceeds, offering a practical advantage for scalable processing. The catalysts reach 10 mA cm-2 current density at an overpotential of ˜50-60 mV with a loading of 10-55 μg cm-2, surpassing other reported MX2 candidates without any performance-enhancing additives.

Incorporating microorganisms into polymer layers provides bioinspired functional living materials

PubMed Central

Gerber, Lukas C.; Koehler, Fabian M.; Grass, Robert N.; Stark, Wendelin J.

2012-01-01

Artificial two-dimensional biological habitats were prepared from porous polymer layers and inoculated with the fungus Penicillium roqueforti to provide a living material. Such composites of classical industrial ingredients and living microorganisms can provide a novel form of functional or smart materials with capability for evolutionary adaptation. This allows realization of most complex responses to environmental stimuli. As a conceptual design, we prepared a material surface with self-cleaning capability when subjected to standardized food spill. Fungal growth and reproduction were observed in between two specifically adapted polymer layers. Gas exchange for breathing and transport of nutrient through a nano-porous top layer allowed selective intake of food whilst limiting the microorganism to dwell exclusively in between a confined, well-enclosed area of the material. We demonstrated a design of such living materials and showed both active (eating) and waiting (dormant, hibernation) states with additional recovery for reinitiation of a new active state by observing the metabolic activity over two full nutrition cycles of the living material (active, hibernation, reactivation). This novel class of living materials can be expected to provide nonclassical solutions in consumer goods such as packaging, indoor surfaces, and in biotechnology. PMID:22198770

Defects in Arsenic Implanted p + -n- and n + -p- Structures Based on MBE Grown CdHgTe Films

NASA Astrophysics Data System (ADS)

Izhnin, I. I.; Fitsych, E. I.; Voitsekhovskii, A. V.; Korotaev, A. G.; Mynbaev, K. D.; Varavin, V. S.; Dvoretsky, S. A.; Mikhailov, N. N.; Yakushev, M. V.; Bonchyk, A. Yu.; Savytskyy, H. V.; Świątek, Z.

2018-02-01

Complex studies of the defect structure of arsenic-implanted (with the energy of 190 keV) Cd x Hg 1-x Te ( x = 0.22) films grown by molecular-beam epitaxy are carried out. The investigations were performed using secondary-ion mass spectroscopy, transmission electron microscopy, optical reflection in the visible region of the spectrum, and electrical measurements. Radiation donor defects were studied in n +- p- and n +- n-structures obtained by implantation and formed on the basis of p-type and n-type materials, respectively, without activation annealing. It is shown that in the layer of the distribution of implanted ions, a layer of large extended defects with low density is formed in the near-surface region followed by a layer of smaller extended defects with larger density. A different character of accumulation of electrically active donor defects in the films with and without a protective graded-gap surface layer has been revealed. It is demonstrated that p +- n- structures are formed on the basis of n-type material upon activation of arsenic in the process of postimplantation thermal annealing with 100% activation of impurity and complete annihilation of radiation donor defects.

The Relative Roles of Passive Surface Forces and Active Ion Transport in the Modulation of Airway Surface Liquid Volume and Composition

PubMed Central

Tarran, Robert; Grubb, Barbara R.; Gatzy, John T.; Davis, C. William; Boucher, Richard C.

2001-01-01

Two hypotheses have been proposed recently that offer different views on the role of airway surface liquid (ASL) in lung defense. The “compositional” hypothesis predicts that ASL [NaCl] is kept low (<50 mM) by passive forces to permit antimicrobial factors to act as a chemical defense. The “volume” hypothesis predicts that ASL volume (height) is regulated isotonically by active ion transport to maintain efficient mechanical mucus clearance as the primary form of lung defense. To compare these hypotheses, we searched for roles for: (1) passive forces (surface tension, ciliary tip capillarity, Donnan, and nonionic osmolytes) in the regulation of ASL composition; and (2) active ion transport in ASL volume regulation. In primary human tracheobronchial cultures, we found no evidence that a low [NaCl] ASL could be produced by passive forces, or that nonionic osmolytes contributed substantially to ASL osmolality. Instead, we found that active ion transport regulated ASL volume (height), and that feedback existed between the ASL and airway epithelia to govern the rate of ion transport and volume absorption. The mucus layer acted as a “reservoir” to buffer periciliary liquid layer height (7 μm) at a level optimal for mucus transport by donating or accepting liquid to or from the periciliary liquid layer, respectively. These data favor the active ion transport/volume model hypothesis to describe ASL physiology. PMID:11479349

Electrochemical characteristics of calcium-phosphatized AZ31 magnesium alloy in 0.9 % NaCl solution.

PubMed

Hadzima, Branislav; Mhaede, Mansour; Pastorek, Filip

2014-05-01

Magnesium alloys suffer from their high reactivity in common environments. Protective layers are widely created on the surface of magnesium alloys to improve their corrosion resistance. This article evaluates the influence of a calcium-phosphate layer on the electrochemical characteristics of AZ31 magnesium alloy in 0.9 % NaCl solution. The calcium phosphate (CaP) layer was electrochemically deposited in a solution containing 0.1 M Ca(NO3)2, 0.06 M NH4H2PO4 and 10 ml l(-1) of H2O2. The formed surface layer was composed mainly of brushite [(dicalcium phosphate dihidrate (DCPD)] as proved by energy-dispersive X-ray analysis. The surface morphology was observed by scanning electron microscopy. Immersion test was performed in order to observe degradation of the calcium phosphatized surfaces. The influence of the phosphate layer on the electrochemical characteristics of AZ31, in 0.9 % NaCl solution, was evaluated by potentiodynamic measurements and electrochemical impedance spectroscopy. The obtained results were analysed by the Tafel-extrapolation method and equivalent circuits method. The results showed that the polarization resistance of the DCPD-coated surface is about 25 times higher than that of non-coated surface. The CaP electro-deposition process increased the activation energy of corrosion process.

Study on photoemission surface of varied doping GaN photocathode

NASA Astrophysics Data System (ADS)

Qiao, Jianliang; Du, Ruijuan; Ding, Huan; Gao, Youtang; Chang, Benkang

2014-09-01

For varied doping GaN photocathode, from bulk to surface the doping concentrations are distributed from high to low. The varied doping GaN photocathode may produce directional inside electric field within the material, so the higher quantum efficiency can be obtained. The photoemission surface of varied doping GaN photocathode is very important to the high quantum efficiency, but the forming process of the surface state after Cs activation or Cs/O activation has been not known completely. Encircling the photoemission mechanism of varied GaN photocathode, considering the experiment phenomena during the activation and the successful activation results, the varied GaN photocathode surface model [GaN(Mg):Cs]:O-Cs after activation with cesium and oxygen was given. According to GaN photocathode activation process and the change of electronic affinity, the comparatively ideal NEA property can be achieved by Cs or Cs/O activation, and higher quantum efficiency can be obtained. The results show: The effective NEA characteristic of GaN can be gotten only by Cs. [GaN(Mg):Cs] dipoles form the first dipole layer, the positive end is toward the vacuum side. In the activation processing with Cs/O, the second dipole layer is formed by O-Cs dipoles, A O-Cs dipole includes one oxygen atom and two Cs atoms, and the positive end is also toward the vacuum side thus the escape of electrons can be promoted.

Semiconductor light-emitting devices having concave microstructures providing improved light extraction efficiency and method for producing same

DOEpatents

Tansu, Nelson; Gilchrist, James F; Ee, Yik-Khoon; Kumnorkaew, Pisist

2013-11-19

A conventional semiconductor LED is modified to include a microlens layer over its light-emitting surface. The LED may have an active layer including at least one quantum well layer of InGaN and GaN. The microlens layer includes a plurality of concave microstructures that cause light rays emanating from the LED to diffuse outwardly, leading to an increase in the light extraction efficiency of the LED. The concave microstructures may be arranged in a substantially uniform array, such as a close-packed hexagonal array. The microlens layer is preferably constructed of curable material, such as polydimethylsiloxane (PDMS), and is formed by soft-lithography imprinting by contacting fluid material of the microlens layer with a template bearing a monolayer of homogeneous microsphere crystals, to cause concave impressions, and then curing the material to fix the concave microstructures in the microlens layer and provide relatively uniform surface roughness.

Electrical activity of ferroelectric biomaterials and its effects on the adhesion, growth and enzymatic activity of human osteoblast-like cells

NASA Astrophysics Data System (ADS)

Vaněk, P.; Kolská, Z.; Luxbacher, T.; García, J. A. L.; Lehocký, M.; Vandrovcová, M.; Bačáková, L.; Petzelt, J.

2016-05-01

Ferroelectrics have been, among others, studied as electroactive implant materials. Previous investigations have indicated that such implants induce improved bone formation. If a ferroelectric is immersed in a liquid, an electric double layer and a diffusion layer are formed at the interface. This is decisive for protein adsorption and bioactive behaviour, particularly for the adhesion and growth of cells. The charge distribution can be characterized, in a simplified way, by the zeta potential. We measured the zeta potential in dependence on the surface polarity on poled ferroelectric single crystalline LiNbO3 plates. Both our results and recent results of colloidal probe microscopy indicate that the charge distribution at the surface can be influenced by the surface polarity of ferroelectrics under certain ‘ideal’ conditions (low ionic strength, non-contaminated surface, very low roughness). However, suggested ferroelectric coatings on the surface of implants are far from ideal: they are rough, polycrystalline, and the body fluid is complex and has high ionic strength. In real cases, it can therefore be expected that there is rather low influence of the sign of the surface polarity on the electric diffusion layer and thus on the specific adsorption of proteins. This is supported by our results from studies of the adhesion, growth and the activity of alkaline phosphatase of human osteoblast-like Saos-2 cells on ferroelectric LiNbO3 plates in vitro.

A DFT study on NEA GaN photocathode with an ultrathin n-type Si-doped GaN cap layer

NASA Astrophysics Data System (ADS)

Xia, Sihao; Liu, Lei; Kong, Yike; Diao, Yu

2016-10-01

Due to the drawbacks of conventional negative electron affinity (NEA) GaN photocathodes activated by Cs or Cs/O, a new-type NEA GaN photocathodes with heterojunction surface dispense with Cs activation are proposed. This structure can be obtained through the coverage of an ultrathin n-type Si-doped GaN cap layer on the p-type Mg-doped GaN emission layer. The influences of the cap layer on the photocathode are calculated using DFT. This study indicates that the n-type cap layer can promote the photoemission characteristics of GaN photocathode and demonstrates the probability of the preparation of a NEA GaN photocathode with an n-type cap layer.

Vortical ciliary flows actively enhance mass transport in reef corals.

PubMed

Shapiro, Orr H; Fernandez, Vicente I; Garren, Melissa; Guasto, Jeffrey S; Debaillon-Vesque, François P; Kramarsky-Winter, Esti; Vardi, Assaf; Stocker, Roman

2014-09-16

The exchange of nutrients and dissolved gasses between corals and their environment is a critical determinant of the growth of coral colonies and the productivity of coral reefs. To date, this exchange has been assumed to be limited by molecular diffusion through an unstirred boundary layer extending 1-2 mm from the coral surface, with corals relying solely on external flow to overcome this limitation. Here, we present direct microscopic evidence that, instead, corals can actively enhance mass transport through strong vortical flows driven by motile epidermal cilia covering their entire surface. Ciliary beating produces quasi-steady arrays of counterrotating vortices that vigorously stir a layer of water extending up to 2 mm from the coral surface. We show that, under low ambient flow velocities, these vortices, rather than molecular diffusion, control the exchange of nutrients and oxygen between the coral and its environment, enhancing mass transfer rates by up to 400%. This ability of corals to stir their boundary layer changes the way that we perceive the microenvironment of coral surfaces, revealing an active mechanism complementing the passive enhancement of transport by ambient flow. These findings extend our understanding of mass transport processes in reef corals and may shed new light on the evolutionary success of corals and coral reefs.

Solution-processable alumina: PVP nanocomposite dielectric layer for high-performance organic thin-film transistors

NASA Astrophysics Data System (ADS)

Lin, Hui; Kong, Xiao; Li, Yiran; Kuang, Peng; Tao, Silu

2018-03-01

In this article, we have investigated the effect of nanocomposite gate dielectric layer built by alumina (Al2O3) and poly(4-vinyphenol) (PVP) with solution method which could enhance the dielectric capability and decrease the surface polarity. Then, we used modify layer to optimize the surface morphology of dielectric layer to further improve the insulation capability, and finally we fabricated the high-performance and low-voltage organic thin-film transistors by using this nanocomposite dielectric layer. The result shows that the devices with Al2O3:10%PVP dielectric layer with a modified layer exhibited a mobility of 0.49 cm2/Vs, I on/Ioff ratio of 7.8 × 104, threshold voltage of - 1.2 V, sub-threshold swing of 0.3 V/dec, and operating voltage as low as - 4 V. The improvement of devices performance was owing to the good insulation capability, appropriate capacitance of dielectric layer, and preferable interface contact, smaller crystalline size of active layer.

Minnowbrook VI: 2009 Workshop on Flow Physics and Control for Internal and External Aerodynamics

NASA Technical Reports Server (NTRS)

LaGraff, John E.; Povinelli, Louis A.; Gostelow, J. Paul; Glauser, Mark

2010-01-01

Topics covered include: Flow Physics and control for Internal and External Aerodynamics (not in TOC...starts on pg13); Breaking CFD Bottlenecks in Gas-Turbine Flow-Path Design; Streamwise Vortices on the Convex Surfaces of Circular Cylinders and Turbomachinery Blading; DNS and Embedded DNS as Tools for Investigating Unsteady Heat Transfer Phenomena in Turbines; Cavitation, Flow Structure and Turbulence in the Tip Region of a Rotor Blade; Development and Application of Plasma Actuators for Active Control of High-Speed and High Reynolds Number Flows; Active Flow Control of Lifting Surface With Flap-Current Activities and Future Directions; Closed-Loop Control of Vortex Formation in Separated Flows; Global Instability on Laminar Separation Bubbles-Revisited; Very Large-Scale Motions in Smooth and Rough Wall Boundary Layers; Instability of a Supersonic Boundary-Layer With Localized Roughness; Active Control of Open Cavities; Amplitude Scaling of Active Separation Control; U.S. Air Force Research Laboratory's Need for Flow Physics and Control With Applications Involving Aero-Optics and Weapon Bay Cavities; Some Issues Related to Integrating Active Flow Control With Flight Control; Active Flow Control Strategies Using Surface Pressure Measurements; Reduction of Unsteady Forcing in a Vaned, Contra-Rotating Transonic Turbine Configuration; Active Flow Control Stator With Coanda Surface; Controlling Separation in Turbomachines; Flow Control on Low-Pressure Turbine Airfoils Using Vortex Generator Jets; Reduced Order Modeling Incompressible Flows; Study and Control of Flow Past Disk, and Circular and Rectangular Cylinders Aligned in the Flow; Periodic Forcing of a Turbulent Axisymmetric Wake; Control of Vortex Breakdown in Critical Swirl Regime Using Azimuthal Forcing; External and Turbomachinery Flow Control Working Group; Boundary Layers, Transitions and Separation; Efficiency Considerations in Low Pressure Turbines; Summary of Conference; and Final Plenary Session Transcript.

Phenomenological Transition of an Aluminum Surface in an Ionic Liquid and Its Beneficial Implementation in Batteries.

PubMed

Shvartsev, B; Gelman, D; Amram, D; Ein-Eli, Y

2015-12-29

Aluminum (Al) electrochemical dissolution in organic nonaqueous media and room temperature ionic liquids (RTILs) is partially hampered by the presence of a native oxide. In this work, Al activation in EMIm(HF)2.3F RTIL is reported. It was confirmed that as a result of the interaction of Al with the RTIL, a new film is formed instead of the pristine oxide layer. Aluminum surface modifications result in a transformation from a passive state to the active behavior of the metal. This was confirmed via the employment of electrochemical methods and characterization by XPS, AFM, and TEM. It was shown that the pristine oxide surface film dissolves in EMIm(HF)2.3F, allowing an Al-O-F layer to be formed instead. This newly built up layer dramatically restricts Al corrosion while enabling high rates of Al anodic dissolution. These beneficial features allow the implementation of Al as an anode in advanced portable power sources, such as aluminum-air batteries.

A method to generate the surface cell layer of the 3D virtual shoot apex from apical initials.

PubMed

Kucypera, Krzysztof; Lipowczan, Marcin; Piekarska-Stachowiak, Anna; Nakielski, Jerzy

2017-01-01

The development of cell pattern in the surface cell layer of the shoot apex can be investigated in vivo by use of a time-lapse confocal images, showing naked meristem in 3D in successive times. However, how this layer is originated from apical initials and develops as a result of growth and divisions of their descendants, remains unknown. This is an open area for computer modelling. A method to generate the surface cell layer is presented on the example of the 3D paraboloidal shoot apical dome. In the used model the layer originates from three apical initials that meet at the dome summit and develops through growth and cell divisions under the isotropic surface growth, defined by the growth tensor. The cells, which are described by polyhedrons, divide anticlinally with the smallest division plane that passes depending on the used mode through the cell center, or the point found randomly near this center. The formation of the surface cell pattern is described with the attention being paid to activity of the apical initials and fates of their descendants. The computer generated surface layer that included about 350 cells required about 1200 divisions of the apical initials and their derivatives. The derivatives were arranged into three more or less equal clonal sectors composed of cellular clones at different age. Each apical initial renewed itself 7-8 times to produce the sector. In the shape and location and the cellular clones the following divisions of the initial were manifested. The application of the random factor resulted in more realistic cell pattern in comparison to the pure mode. The cell divisions were analyzed statistically on the top view. When all of the division walls were considered, their angular distribution was uniform, whereas in the distribution that was limited to apical initials only, some preferences related to their arrangement at the dome summit were observed. The realistic surface cell pattern was obtained. The present method is a useful tool to generate surface cell layer, study activity of initial cells and their derivatives, and how cell expansion and division are coordinated during growth. We expect its further application to clarify the question of a number and permanence or impermanence of initial cells, and possible relationship between their shape and oriented divisions, both on the ground of the growth tensor approach.

Disruption of vertical motility by shear triggers formation of thin phytoplankton layers.

PubMed

Durham, William M; Kessler, John O; Stocker, Roman

2009-02-20

Thin layers of phytoplankton are important hotspots of ecological activity that are found in the coastal ocean, meters beneath the surface, and contain cell concentrations up to two orders of magnitude above ambient concentrations. Current interpretations of their formation favor abiotic processes, yet many phytoplankton species found in these layers are motile. We demonstrated that layers formed when the vertical migration of phytoplankton was disrupted by hydrodynamic shear. This mechanism, which we call gyrotactic trapping, can be responsible for the thin layers of phytoplankton commonly observed in the ocean. These results reveal that the coupling between active microorganism motility and ambient fluid motion can shape the macroscopic features of the marine ecological landscape.

Enzymatic activity in the surface microlayer and subsurface water in the harbour channel

NASA Astrophysics Data System (ADS)

Perliński, Piotr; Mudryk, Zbigniew J.; Antonowicz, Józef

2017-09-01

Hydrolytic activity of eight extracellular enzymes was determined spectrofluorimetric method in the surface microlayer and subsurface water in the harbour channel in Ustka. The ranking order of the potential enzyme activity rates in the studied water layers was as follows: lipase > phosphatase > aminopeptidase > β-glucosidase > α-glucosidase > xylanase > cellulase > chitinase. The level of activity of all studied hydrolases was higher in the surface microlayer than subsurface water. No clear gradients in the level of enzymatic activity were determined along the horizontal profile of the studied channel. Activity of extracellular enzymes was strongly influenced by the season.

Thermodynamics, interfacial pressure isotherms and dilational rheology of mixed protein-surfactant adsorption layers.

PubMed

Fainerman, V B; Aksenenko, E V; Krägel, J; Miller, R

2016-07-01

Proteins and their mixtures with surfactants are widely used in many applications. The knowledge of their solution bulk behavior and its impact on the properties of interfacial layers made great progress in the recent years. Different mechanisms apply to the formation process of protein/surfactant complexes for ionic and non-ionic surfactants, which are governed mainly by electrostatic and hydrophobic interactions. The surface activity of these complexes is often remarkably different from that of the individual protein and has to be considered in respective theoretical models. At very low protein concentration, small amounts of added surfactants can change the surface activity of proteins remarkably, even though no strongly interfacial active complexes are observed. Also small added amounts of non-ionic surfactants change the surface activity of proteins in the range of small bulk concentrations or surface coverages. The modeling of the equilibrium adsorption behavior of proteins and their mixtures with surfactants has reached a rather high level. These models are suitable also to describe the high frequency limits of the dilational viscoelasticity of the interfacial layers. Depending on the nature of the protein/surfactant interactions and the changes in the interfacial layer composition rather complex dilational viscoelasticities can be observed and described by the available models. The differences in the interfacial behavior, often observed in literature for studies using different experimental methods, are at least partially explained by a depletion of proteins, surfactants and their complexes in the range of low concentrations. A correction of these depletion effects typically provides good agreement between the data obtained with different methods, such as drop and bubble profile tensiometry. Copyright © 2015 Elsevier B.V. All rights reserved.

Construction of surface HA/TiO2 coating on porous titanium scaffolds and its preliminary biological evaluation.

PubMed

Chen, Hongjie; Wang, Chunli; Yang, Xiao; Xiao, Zhanwen; Zhu, Xiangdong; Zhang, Kai; Fan, Yujiang; Zhang, Xingdong

2017-01-01

A simple approach to fabricating hydroxyxapatite/titanium dioxide (HA/TiO 2 ) coating on porous titanium (Ti) scaffolds was developed in the present study. Surface TiO 2 layer was firstly formed on porous Ti scaffolds with multi-scale pores by acid-alkali (AA) treatment. The outer HA layer was then formed on the TiO 2 layer by subsequent pulse electrochemical deposition (ED) technique. All the three main process parameters, i.e. deposition times, current density and mass transfer mode affected the properties of the HA coating notably. Under the conditions of 90 deposition cycles, -10mA/cm 2 of pulse current density and stirring, a thin layer of homogeneous and nanorod-like HA sediments was formed on the substrate surface of porous Ti scaffolds. The results of protein adsorption and cellular experiments showed that compared to the single TiO 2 surface, the HA/TiO 2 surface allowed more adsorption of serum proteins and further enhanced the alkaline phosphatase (ALP) activity of MC3T3-E1 osteoblasts. Copyright © 2016 Elsevier B.V. All rights reserved.

Detection of Nisin and Fibrinogen Adsorption on Poly(ethylene Oxide) Coated Polyurethane Surfaces by Time-of-Flight Secondary Ion Mass Spectrometry (TOF-SIMS)

PubMed Central

Schilke, Karl F.; McGuire, Joseph

2011-01-01

Stable, pendant polyethylene oxide (PEO) layers were formed on medical-grade Pellethane® and Tygon® polyurethane surfaces, by adsorption and gamma-irradiation of PEO-polybutadiene-PEO triblock surfactants. Coated and uncoated polyurethanes were challenged individually or sequentially with nisin (a small polypeptide with antimicrobial activity) and/or fibrinogen, and then analyzed with time-of-flight secondary ion mass spectrometry (TOF-SIMS). Data reduction by robust principal components analysis (PCA) allowed detection of outliers, and distinguished adsorbed nisin and fibrinogen. Fibrinogen-contacted surfaces, with or without nisin, were very similar on uncoated polymer surfaces, consistent with nearly complete displacement or coverage of previously-adsorbed nisin by fibrinogen. In contrast, nisin-loaded PEO layers remained essentially unchanged upon challenge with fibrinogen, suggesting that the adsorbed nisin is stabilized within the pendant PEO layer, while the peptide-loaded PEO layer retains its ability to repel large proteins. Coatings of PEO loaded with therapeutic polypeptides on medical polymers have the potential to be used to produce anti-fouling and biofunctional surfaces for implantable or blood-contacting devices. PMID:21440897

Surface modification to improve fireside corrosion resistance of Fe-Cr ferritic steels

DOEpatents

Park, Jong-Hee; Natesan, Krishnamurti; Rink, David L.

2010-03-16

An article of manufacture and a method for providing an Fe--Cr ferritic steel article of manufacture having a surface layer modification for corrosion resistance. Fe--Cr ferritic steels can be modified to enhance their corrosion resistance to liquid coal ash and other chemical environments, which have chlorides or sulfates containing active species. The steel is modified to form an aluminide/silicide passivating layer to reduce such corrosion.

Fabricating solid carbon porous electrodes from powders

DOEpatents

Kaschmitter, James L.; Tran, Tri D.; Feikert, John H.; Mayer, Steven T.

1997-01-01

Fabrication of conductive solid porous carbon electrodes for use in batteries, double layer capacitors, fuel cells, capacitive dionization, and waste treatment. Electrodes fabricated from low surface area (<50 m.sup.2 /gm) graphite and cokes exhibit excellent reversible lithium intercalation characteristics, making them ideal for use as anodes in high voltage lithium insertion (lithium-ion) batteries. Electrodes having a higher surface area, fabricated from powdered carbon blacks, such as carbon aerogel powder, carbon aerogel microspheres, activated carbons, etc. yield high conductivity carbon compositives with excellent double layer capacity, and can be used in double layer capacitors, or for capacitive deionization and/or waste treatment of liquid streams. By adding metallic catalysts to be high surface area carbons, fuel cell electrodes can be produced.

Fabricating solid carbon porous electrodes from powders

DOEpatents

Kaschmitter, J.L.; Tran, T.D.; Feikert, J.H.; Mayer, S.T.

1997-06-10

Fabrication is described for conductive solid porous carbon electrodes for use in batteries, double layer capacitors, fuel cells, capacitive deionization, and waste treatment. Electrodes fabricated from low surface area (<50 m{sup 2}/gm) graphite and cokes exhibit excellent reversible lithium intercalation characteristics, making them ideal for use as anodes in high voltage lithium insertion (lithium-ion) batteries. Electrodes having a higher surface area, fabricated from powdered carbon blacks, such as carbon aerogel powder, carbon aerogel microspheres, activated carbons, etc. yield high conductivity carbon composites with excellent double layer capacity, and can be used in double layer capacitors, or for capacitive deionization and/or waste treatment of liquid streams. By adding metallic catalysts to high surface area carbons, fuel cell electrodes can be produced. 1 fig.

Origin of dislocation luminescence centers and their reorganization in p-type silicon crystal subjected to plastic deformation and high temperature annealing.

PubMed

Pavlyk, Bohdan; Kushlyk, Markiyan; Slobodzyan, Dmytro

2017-12-01

Changes of the defect structure of silicon p-type crystal surface layer under the influence of plastic deformation and high temperature annealing in oxygen atmosphere were investigated by deep-level capacitance-modulation spectroscopy (DLCMS) and IR spectroscopy of molecules and atom vibrational levels. Special role of dislocations in the surface layer of silicon during the formation of its energy spectrum and rebuilding the defective structure was established. It is shown that the concentration of linear defects (N ≥ 10 4  cm -2 ) enriches surface layer with electrically active complexes (dislocation-oxygen, dislocation-vacancy, and dislocation-interstitial atoms of silicon) which are an effective radiative recombination centers.

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.

Seismic sensitivity to sub-surface solar activity from 18 yr of GOLF/SoHO observations

NASA Astrophysics Data System (ADS)

Salabert, D.; García, R. A.; Turck-Chièze, S.

2015-06-01

Solar activity has significantly changed over the last two Schwabe cycles. After a long and deep minimum at the end of Cycle 23, the weaker activity of Cycle 24 contrasts with the previous cycles. In this work, the response of the solar acoustic oscillations to solar activity is used in order to provide insights into the structural and magnetic changes in the sub-surface layers of the Sun during this on-going unusual period of low activity. We analyze 18 yr of continuous observations of the solar acoustic oscillations collected by the Sun-as-a-star GOLF instrument on board the SoHO spacecraft. From the fitted mode frequencies, the temporal variability of the frequency shifts of the radial, dipolar, and quadrupolar modes are studied for different frequency ranges that are sensitive to different layers in the solar sub-surface interior. The low-frequency modes show nearly unchanged frequency shifts between Cycles 23 and 24, with a time evolving signature of the quasi-biennial oscillation, which is particularly visible for the quadrupole component revealing the presence of a complex magnetic structure. The modes at higher frequencies show frequency shifts that are 30% smaller during Cycle 24, which is in agreement with the decrease observed in the surface activity between Cycles 23 and 24. The analysis of 18 yr of GOLF oscillations indicates that the structural and magnetic changes responsible for the frequency shifts remained comparable between Cycle 23 and Cycle 24 in the deeper sub-surface layers below 1400 km as revealed by the low-frequency modes. The frequency shifts of the higher-frequency modes, sensitive to shallower regions, show that Cycle 24 is magnetically weaker in the upper layers of Sun. Appendices are available in electronic form at http://www.aanda.orgThe following 68 GOLF frequency tables are available and Table A.1 is also available at the CDS via anonymous ftp to http://cdsarc.u-strasbg.fr (ftp://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/578/A137

Near-Surface Profiles of Water Stable Isotope Components and Indicated Transitional History of Ice-Wedge Polygons Near Barrow

NASA Astrophysics Data System (ADS)

Iwahana, G.; Wilson, C.; Newman, B. D.; Heikoop, J. M.; Busey, R.

2017-12-01

Wetlands associated with ice-wedge polygons are commonly distributed across the Arctic Coastal Plain of northern Alaska, a region underlain by continuous permafrost. Micro-topography of the ice-wedge polygons controls local hydrology, and the micro-topography could be altered due to factors such like surface vegetation, wetness, freeze-thaw cycles, and permafrost degradation/aggradation under climate change. Understanding status of the wetlands in the near future is important because it determines biogeochemical cycle, which drives release of greenhouse gases from the ground. However, transitional regime of the ice-wedge polygons under the changing climate is not fully understood. In this study, we analyzed geochemistry of water extracted from frozen soil cores sampled down to about 1m depth in 2014 March at NGEE-Arctic sites in the Barrow Environmental Observatory. The cores were sampled from troughs/rims/centers of five different low-centered or flat-centered polygons. The frozen cores are divided into 5-10cm cores for each location, thawed in sealed plastic bags, and then extracted water was stored in vials. Comparison between the profiles of geochemistry indicated connection of soil water in the active layer at different location in a polygon, while it revealed that distinctly different water has been stored in permafrost layer at troughs/rims/centers of some polygons. Profiles of volumetric water content (VWC) showed clear signals of freeze-up desiccation in the middle of saturated active layers as low VWC anomalies at most sampling points. Water in the active layer and near-surface permafrost was classified into four categories: ice wedge / fresh meteoric / transitional / highly fractionated water. The overall results suggested prolonged separation of water in the active layer at the center of low-centered polygons without lateral connection in water path in the past.

Synthesis and Adsorption Properties of 4-Vinylpyridine and Styrene Copolymer In Situ Immobilized on Silica Surface

NASA Astrophysics Data System (ADS)

Yanovska, E. S.; Vretik, L. O.; Nikolaeva, O. A.; Polonska, Y.; Sternik, D.; Kichkiruk, O. Yu.

2017-03-01

Copolymer of 4-vinylpyridine with styrene was in situ immobilized on silica gel surface via the heterogeneous radical polymerization. Anchorage of the copolymer on the surface layer was confirmed by IR spectroscopy. The quantity of copolymer on the silica gel surface was evaluated as 25.73 wt.% by TG and DSC-MS analysis. "Islet" location of polymer layer on the silica surface was confirmed by the scanning electron microscopy. A high adsorption activity of silica gel with immobilized copolymer towards microquantitatives of Cu(II), Cd(II), Pb(II), Fe(III), and Ni(II) ions in steady state conditions as well as of Ni(II) ions in dynamic regime was found.

Synthesis and Adsorption Properties of 4-Vinylpyridine and Styrene Copolymer In Situ Immobilized on Silica Surface.

PubMed

Yanovska, E S; Vretik, L O; Nikolaeva, O A; Polonska, Y; Sternik, D; Kichkiruk, O Yu

2017-12-01

Copolymer of 4-vinylpyridine with styrene was in situ immobilized on silica gel surface via the heterogeneous radical polymerization. Anchorage of the copolymer on the surface layer was confirmed by IR spectroscopy. The quantity of copolymer on the silica gel surface was evaluated as 25.73 wt.% by TG and DSC-MS analysis. "Islet" location of polymer layer on the silica surface was confirmed by the scanning electron microscopy. A high adsorption activity of silica gel with immobilized copolymer towards microquantitatives of Cu(II), Cd(II), Pb(II), Fe(III), and Ni(II) ions in steady state conditions as well as of Ni(II) ions in dynamic regime was found.

Harmful Effects of Synthetic Surface-Active Detergents against Atopic Dermatitis.

PubMed

Deguchi, Hajime; Aoyama, Riho; Takahashi, Hideaki; Isobe, Yoshinari; Tsutsumi, Yutaka

2015-01-01

We report herein two cases of intractable atopic dermatitis successfully treated by simply avoiding the contact with surface-active detergents in the daily life and living. The detergents were closely related to the exacerbation and remission of the disease. Steroid ointment was no longer used. We discuss that the removal of horny layer lipids by surface-active detergents accelerates the transepidermal water loss and disturbs the barrier function of the epidermis and thus is intimately involved in the pathogenesis of atopic dermatitis.

Layer uniformity in glucose oxidase immobilization on SiO 2 surfaces

NASA Astrophysics Data System (ADS)

Libertino, Sebania; Scandurra, Antonino; Aiello, Venera; Giannazzo, Filippo; Sinatra, Fulvia; Renis, Marcella; Fichera, Manuela

2007-09-01

The goal of this work was the characterization, step by step, of the enzyme glucose oxidase (GOx) immobilization on silicon oxide surfaces, mainly by means of X-Ray photoelectron spectroscopy (XPS). The immobilization protocol consists of four steps: oxide activation, silanization, linker molecule deposition and GOx immobilization. The linker molecule, glutaraldehyde (GA) in this study, must be able to form a uniform layer on the sample surface in order to maximize the sites available for enzyme bonding and achieve the best enzyme deposition. Using a thin SiO 2 layer grown on Si wafers and following the XPS Si2p signal of the Si substrate during the immobilization steps, we demonstrated both the glutaraldehyde layer uniformity and the possibility to use XPS to monitor thin layer uniformity. In fact, the XPS substrate signal, not shielded by the oxide, is suppressed only when a uniform layer is deposited. The enzyme correct immobilization was monitored using the XPS C1s and N1s signals. Atomic force microscopy (AFM) measurements carried out on the same samples confirmed the results.

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

Thi, Trinh Cham, E-mail: s1240009@jaist.ac.jp; Koyama, Koichi; Ohdaira, Keisuke

We improve the passivation property of n-type crystalline silicon (c-Si) surface passivated with a catalytic chemical vapor deposited (Cat-CVD) Si nitride (SiN{sub x}) film by inserting a phosphorous (P)-doped layer formed by exposing c-Si surface to P radicals generated by the catalytic cracking of PH{sub 3} molecules (Cat-doping). An extremely low surface recombination velocity (SRV) of 2 cm/s can be achieved for 2.5 Ω cm n-type (100) floating-zone Si wafers passivated with SiN{sub x}/P Cat-doped layers, both prepared in Cat-CVD systems. Compared with the case of only SiN{sub x} passivated layers, SRV decreases from 5 cm/s to 2 cm/s. The decrease in SRVmore » is the result of field effect created by activated P atoms (donors) in a shallow P Cat-doped layer. Annealing process plays an important role in improving the passivation quality of SiN{sub x} films. The outstanding results obtained imply that SiN{sub x}/P Cat-doped layers can be used as promising passivation layers in high-efficiency n-type c-Si solar cells.« less

A facile fabrication of multifunctional knit polyester fabric based on chitosan and polyaniline polymer nanocomposite

NASA Astrophysics Data System (ADS)

Tang, Xiaoning; Tian, Mingwei; Qu, Lijun; Zhu, Shifeng; Guo, Xiaoqing; Han, Guangting; Sun, Kaikai; Hu, Xili; Wang, Yujiao; Xu, Xiaoqi

2014-10-01

Knit polyester fabric was successively modified and decorated with chitosan layer and polyaniline polymer nanocomposite layer in this paper. The fabric was firstly treated with chitosan to form a stable layer through the pad-dry-cure process, and then the polyaniline polymer nanocomposite layer was established on the outer layer by in situ chemical polymerization method using ammonium persulfate as oxidant and chlorhydric acid as dopant. The surface morphology of coated fabric was characterized by scanning electron microscopy (SEM), and the co-existence of chitosan layer and granular polyaniline polymer nanocomposite was confirmed and well dispersed on the fabric surface. The resultant fabric was endowed with remarkable electrical conductivity properties and efficient water-repellent capability, which also have been found stable after water laundering. In addition, the photocatalytic decomposition activity for reactive red dye was observed when the multifunctional knit polyester fabric was exposed to the illumination of ultraviolet lamp. These results indicated that chitosan and polyaniline polymer nanocomposite could form ideal multifunctional coatings on the surface of knit polyester fabric.

Measurement of the oxygen mass transfer through the air-water interface.

PubMed

Mölder, Erik; Mashirin, Alelxei; Tenno, Toomas

2005-01-01

Gas mass transfer through the liquid-gas interface has enormous importance in various natural and industrial processes. Surfactants or insoluble compounds adsorbed onto an interface will inhibit the gas mass transfer through the liquid-gas surface. This study presents a technique for measuring the oxygen mass transfer through the air-water interface. Experimental data obtained with the measuring device were incorporated into a novel mathematical model, which allowed one to calculate diffusion conduction of liquid surface layer and oxygen mass transfer coefficient in the liquid surface layer. A special measurement cell was constructed. The most important part of the measurement cell is a chamber containing the electrochemical oxygen sensor inside it. Gas exchange between the volume of the chamber and the external environment takes place only through the investigated surface layer. Investigated liquid was deoxygenated, which triggers the oxygen mass transfer from the chamber through the liquid-air interface into the liquid phase. The decrease of oxygen concentration in the cell during time was measured. By using this data it is possible to calculate diffusional parameters of the water surface layer. Diffusion conduction of oxygen through the air-water surface layer of selected wastewaters was measured. The diffusion conduction of different wastewaters was about 3 to 6 times less than in the unpolluted water surface. It was observed that the dilution of wastewater does not have a significant impact on the oxygen diffusion conduction through the wastewater surface layer. This fact can be explained with the presence of the compounds with high surface activity in the wastewater. Surfactants achieved a maximum adsorption and, accordingly, the maximum decrease of oxygen permeability already at a very low concentration of surfactants in the solution. Oxygen mass transfer coefficient of the surface layer of the water is found to be Ds/ls = 0.13 x 10(-3) x cm/s. A simple technique for measuring oxygen diffusion parameters through the air-water solution surface has been developed. Derived equations enable the calculation of diffusion parameters of the surface layer at current conditions. These values of the parameters permit one to compare the resistances of the gas-liquid interface to oxygen mass transfer in the case of adsorption of different substances on the surface layer. This simple technique may be used for a determination of oxygen permeability of different water-solution surface layers. It enables one to measure the resistance to the oxygen permeability of all inflowing wastewater surface layers in the wastewater treatment plant, and to initiate a preliminary cleaning of this wastewater if required. Similarly, we can measure oxygen permeability of natural waterbodies. Especially in the case of pollution, it is important to know to what extent the oxygen permeability of the water surface layer has been decreased. Based on the tehnique presented in this research, fieldwork equipment will be developed.

Polymer brush covalently attached to OH-functionalized mica surface via surface-initiated ATRP: control of grafting density and polymer chain length.

PubMed

Lego, Béatrice; François, Marion; Skene, W G; Giasson, Suzanne

2009-05-05

The controlled grafting density of poly(tert-butyl acrylate) was studied on OH-activated mica substrates via surface-initiated atom-transfer radical polymerization (ATRP). By properly adjusting parameters such as the immobilization reaction time and the concentration of an ATRP initiator, a wide range of initiator surface coverages and hence polymer densities on mica were possible. The covalently immobilized initiator successfully promoted the polymerization of tert-butyl acrylate on mica surfaces. The resulting polymer layer thickness was measured by AFM using a step-height method. Linear relationships of the polymer thickness with respect to the molecular weight of the free polymer and with respect to the monomer conversion were observed, suggesting that ATRP is well controlled and relatively densely end-grafted layers were obtained. The polymer grafting density controlled by adjusting the initiator surface coverage was confirmed by the polymer layer swelling capacity and film thickness measurements.

Formation of surface reaction products on bioactive glass and their effects on the expression of the osteoblastic phenotype and the deposition of mineralized extracellular matrix.

PubMed

el-Ghannam, A; Ducheyne, P; Shapiro, I M

1997-02-01

The objective of the study was to examine the effect of alkali ion release, pH control and buffer capacity on the expression of the osteoblastic phenotype. In addition we determined the importance of modifications of the surface of porous bioactive glass (BG) on the activity of rat calvaria osteoblasts in vitro. We found that at a low tissue culture medium (TCM) volume to BG surface area (Vol/SA) ratio, the products of glass corrosion elevated the pH of the TCM to a value that adversely affected cellular activity; thus, the matrix synthesized by the cells was non-mineralized. On the other hand, when the Vol/SA was high and the buffer capacity of the medium was not exceeded, the cells generated a mineralized extracellular matrix. Addressing the second issue, we observed that modification of the composition of the BG surface markedly influenced osteoblast activity. BG that was coated with either a calcium phosphate-rich layer only or a serum protein layer changed the phenotypic characteristics of the osteoblasts. The presence of either of these surfaces lowered the alkaline phosphatase activity of the attached cells; this finding indicated that the osteoblast phenotype was not conserved. However, when the BG was coated with a bilayer of calcium phosphate and serum proteins, the alkaline phosphatase (AP) activity was elevated and the extracellular matrix contained characteristic bone markers. Our findings indicate that the calcium phosphate-rich layer promotes adsorption and concentration of proteins from the TCM, and it is utilized by the osteoblasts to form the mineralized extracellular matrix.

Enhanced luminescence efficiency by surface plasmon coupling of Ag nanoparticles in a polymer light-emitting diode

NASA Astrophysics Data System (ADS)

Chen, Sy-Hann; Jhong, Jhen-Yu

2011-08-01

This study achieved a substantial enhancement in electroluminescence by coupling localized surface plasmons in a single layer of Ag nanoparticles. Thermal evaporation was used to fabricate 20-nm Ag particles sandwiched between a gallium-doped zinc oxide film and a glass substrate to form novel window materials for use in polymer light-emitting diodes (PLEDs). The PLEDs discussed herein are single-layer devices based on a poly(9,9-di-n-octyl-2,7-fluorene) (PFO) emissive layer. In addition to low cost, this novel fabrication method can effectively prevent interruption or degradation of the charge transport properties of the active layer to meet the high performance requirements of PLEDs. Due to the surface-plasmon-enhanced emission, the electroluminescence intensity was increased by nearly 1-fold, compared to that of the same PLED without the interlayer of Ag nanoparticles.

Thermal behavior and catalytic activity in naphthalene destruction of Ce-, Zr- and Mn-containing oxide layers on titanium

NASA Astrophysics Data System (ADS)

Vasilyeva, Marina S.; Rudnev, Vladimir S.; Wiedenmann, Florian; Wybornov, Svetlana; Yarovaya, Tatyana P.; Jiang, Xin

2011-11-01

The present paper is devoted to studies of the composition and surface structure, including those after annealing at high temperatures, and catalytic activity in the reaction of naphthalene destruction of Ce-, Zr- and Mn-containing oxide layers on titanium obtained by means of the plasma electrolytic oxidation (PEO) method. The composition and structure of the obtained systems were investigated using the methods of X-ray phase and energy dispersive analysis and scanning electron microscopy (SEM). It was demonstrated that Ce- and Zr- containing structures had relatively high thermal stability: their element and phase compositions and surface structure underwent virtually no changes after annealing in the temperature range 600-800 °C. Annealing of Ce- and Zr-containing coatings in the temperature range 850-900 °C resulted in substantial changes of their surface composition and structure: a relatively homogeneous and porous surface becomes coated by large pole-like crystals. The catalytic studies showed rather high activity of Ce- and Zr-containing coatings in the reaction of naphthalene destruction at temperatures up to 850 °C. Mn-containing structures of the type MnOx + SiO2 + TiO2/Ti have a well-developed surface coated by “nano-whiskers”. The phase composition and surface structure of manganese-containing layers changes dramatically in the course of thermal treatment. After annealing above 600 °C nano-whiskers vanish with formation of molten structures on the surface. The Mn-containing oxide systems demonstrated lower conversion degrees than the Ce- and Zr-containing coatings, which can be attributed to substantial surface modification and formation of molten manganese silicates at high temperatures.

Equilibrium of adsorption of mixed milk protein/surfactant solutions at the water/air interface.

PubMed

Kotsmar, C; Grigoriev, D O; Xu, F; Aksenenko, E V; Fainerman, V B; Leser, M E; Miller, R

2008-12-16

Ellipsometry and surface profile analysis tensiometry were used to study and compare the adsorption behavior of beta-lactoglobulin (BLG)/C10DMPO, beta-casein (BCS)/C10DMPO and BCS/C12DMPO mixtures at the air/solution interface. The adsorption from protein/surfactant mixed solutions is of competitive nature. The obtained adsorption isotherms suggest a gradual replacement of the protein molecules at the interface with increasing surfactant concentration for all studied mixed systems. The thickness, refractive index, and the adsorbed amount of the respective adsorption layers, determined by ellipsometry, decrease monotonically and reach values close to those for a surface covered only by surfactant molecules, indicating the absence of proteins from a certain surfactant concentration on. These results correlate with the surface tension data. A continuous increase of adsorption layer thickness was observed up to this concentration, caused by the desorption of segments of the protein and transforming the thin surface layer into a rather diffuse and thick one. Replacement and structural changes of the protein molecules are discussed in terms of protein structure and surface activity of surfactant molecules. Theoretical models derived recently were used for the quantitative description of the equilibrium state of the mixed surface layers.

Oxygen-implanted induced formation of oxide layer enhances blood compatibility on titanium for biomedical applications.

PubMed

Hung, Wei-Chiang; Chang, Fang-Mo; Yang, Tzu-Sen; Ou, Keng-Liang; Lin, Che-Tong; Peng, Pei-Wen

2016-11-01

Titanium dioxide (TiO2) layers were prepared on a Ti substrate by using oxygen plasma immersion ion implantation (oxygen PIII). The surface chemical states, structure, and morphology of the layers were studied using X-ray photoelectron spectroscopy, X-ray diffraction, Raman microscopy, atomic force microscopy and scanning electron microscope. The mechanical properties, such as the Young's modulus and hardness, of the layers were investigated using nanoindentation testing. The Ti(4+) chemical state was determined to be present on oxygen-PIII-treated surfaces, which consisted of nanocrystalline TiO2 with a rutile structure. Compared with Ti substrates, the oxygen-PIII-treated surfaces exhibited decreased Young's moduli and hardness. Parameters indicating the blood compatibility of the oxygen-PIII-treated surfaces, including the clotting time and platelet adhesion and activation, were studied in vitro. Clotting time assays indicated that the clotting time of oxygen-PIII-treated surfaces was longer than that of the Ti substrate, which was associated with decreased fibrinogen adsorption. In conclusion, the surface characteristics and the blood compatibility of Ti implants can be modified and improved using oxygen PIII. Copyright © 2016 Elsevier B.V. All rights reserved.

Rational Design of Bi Nanoparticles for Efficient Electrochemical CO 2 Reduction: The Elucidation of Size and Surface Condition Effects

DOE PAGES

Zhang, Zhiyong; Chi, Miaofang; Veith, Gabriel M.; ...

2016-08-08

Here we report an efficient electrochemical conversion of CO 2 to CO on surface-activated bismuth nanoparticles (NPs) in acetonitrile (MeCN) under ambient conditions, with the assistance of 1-butyl-3-methylimidazolium trifluoromethanesulfonate ([bmim][OTf]). Through the comparison between electrodeposited Bi films (Bi-ED) and different types of Bi NPs, we, for the first time, demonstrate the effects of catalyst’s size and surface condition on organic phase electrochemical CO 2 reduction. Our study reveals that the surface inhibiting layer (hydrophobic surfactants and Bi 3+ species) formed during the synthesis and purification process hinders the CO 2 reduction, leading to a 20% drop in Faradaic efficiency formore » CO evolution (FE CO). Bi particle size showed a significant effect on FE CO when the surface of Bi was air-oxidized, but this effect of size on FE CO became negligible on surface-activated Bi NPs. After the surface activation (hydrazine treatment) that effectively removed the native inhibiting layer, activated 36-nm Bi NPs exhibited an almost-quantitative conversion of CO 2 to CO (96.1% FE CO), and a mass activity for CO evolution (MA CO) of 15.6 mA mg –1, which is three-fold higher than the conventional Bi-ED, at ₋2.0 V (vs Ag/AgCl). Ultimately, this work elucidates the importance of the surface activation for an efficient electrochemical CO 2 conversion on metal NPs and paves the way for understanding the CO 2 electrochemical reduction mechanism in nonaqueous media.« less

Method of control position of laser focus during surfacing teeth of cutters

NASA Astrophysics Data System (ADS)

Zvezdin, V. V.; Hisamutdinov, R. M.; Rakhimov, R. R.; Israfilov, I. H.; Akhtiamov, R. F.

2017-09-01

Providing the quality laser of surfacing the edges of teeth requires control not only the energy of the radiation parameters, but also the position of the focal spot. The control channel of position of laser focus during surfacing, which determines the parameters of quality of the deposited layer, was calculated in the work. The parameters of the active opto-electronic system for the subsystem adjust the focus position relative to the deposited layer with a laser illumination of the cutting edges the teeth cutters were calculated, the model of a control channel based on thermal phenomena occurring in the zone of surfacing was proposed.

Solar Cell Polymer Based Active Ingredients PPV and PCBM

NASA Astrophysics Data System (ADS)

Hardeli, H.; Sanjaya, H.; Resikarnila, R.; Nitami H, R.

2018-04-01

A polymer solar cell is a solar cell based on a polymer bulk heterojunction structure using the method of thin film, which can convert solar energy into electrical energy. Absorption of light is carried by active material layer PPV: PCBM. This study aims to make solar cells tandem and know the value of converting solar energy into electrical energy and increase the value of efficiency generated through morphological control, ie annealing temperature and the ratio of active layer mixture. The active layer is positioned above the PEDOT:PSS layer on ITO glass substrate. The characterization results show the surface morphology of the PPV:PCBM active layer is quite evenly at annealing temperature of 165 ° C. The result of conversion of electrical energy with a UV light source in annealing samples with temperature 165 ° C is 0.03 mA and voltage of 4.085 V with an efficiency of 2.61% and mixed ratio variation was obtained in comparison of P3HT: PCBM is 1: 3

The structure of the cysteine protease and lectin-like domains of Cwp84, a surface layer-associated protein from Clostridium difficile

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

Bradshaw, William J.; Public Health England, Porton Down, Salisbury SP4 0JG; Kirby, Jonathan M.

2014-07-01

The crystal structure of Cwp84, an S-layer protein from Clostridium difficile is presented for the first time. The cathepsin L-like fold of cysteine protease domain, a newly observed ‘lectin-like’ domain and several other features are described. Clostridium difficile is a major problem as an aetiological agent for antibiotic-associated diarrhoea. The mechanism by which the bacterium colonizes the gut during infection is poorly understood, but undoubtedly involves a myriad of components present on the bacterial surface. The mechanism of C. difficile surface-layer (S-layer) biogenesis is also largely unknown but involves the post-translational cleavage of a single polypeptide (surface-layer protein A; SlpA)more » into low- and high-molecular-weight subunits by Cwp84, a surface-located cysteine protease. Here, the first crystal structure of the surface protein Cwp84 is described at 1.4 Å resolution and the key structural components are identified. The truncated Cwp84 active-site mutant (amino-acid residues 33–497; C116A) exhibits three regions: a cleavable propeptide and a cysteine protease domain which exhibits a cathepsin L-like fold followed by a newly identified putative carbohydrate-binding domain with a bound calcium ion, which is referred to here as a lectin-like domain. This study thus provides the first structural insights into Cwp84 and a strong base to elucidate its role in the C. difficile S-layer maturation mechanism.« less

Histochemical studies on protease formation in the cotyledons of germinating bean seeds.

PubMed

Yomo, H; Taylor, M P

1973-03-01

Protease formation in Phaseolus vulgaris L. cotyledons during seed germination was studied histochemically using a gelatin-film-substrate method. Protease activity can be detected by this method on the 5th day of germination, at approximately the same time that a rapid increase of activity was observed by a test-tube assay with casein as a substrate. At the early stage of germination, protease activity was observed throughout the cotyledon except in two or three cell layers below the cotyledon surface and in several cell layers around the vascular bundles. A highly active cell layer surrounding the protease-inactive cells near the vascular bundles is suggested to be a source of the protease.

Comparative Study of Surface Chemical Composition and Oxide Layer Modification upon Oxygen Plasma Cleaning and Piranha Etching on a Novel Low Elastic Modulus Ti25Nb21Hf Alloy

NASA Astrophysics Data System (ADS)

Paredes, Virginia; Salvagni, Emiliano; Rodríguez-Castellón, Enrique; Manero, José María

2017-08-01

Metals are widely employed for many biological artificial replacements, and it is known that the quality and the physical/chemical properties of the surface are crucial for the success of the implant. Therefore, control over surface implant materials and their elastic moduli may be crucial to avoid undesired effects. In this study, surface modification upon cleaning and activation of a low elastic modulus Ti alloy (Ti25Hf21Nb) was investigated. Two different methods, oxygen plasma (OP) cleaning and piranha (PI) solution, were studied and compared. Both surface treatments were effective for organic contaminant removal and to increase the Ti-oxide layer thickness rather than other metal-oxides present at the surface, which is beneficial for biocompatibility of the material. Furthermore, both techniques drastically increased hydrophilicity and introduced oxidation and hydroxylation (OH)-functional groups at the surface that may be beneficial for further chemical modifications. However, these treatments did not alter the surface roughness and bulk material properties. The surfaces were fully characterized in terms of surface roughness, wettability, oxide layer composition, and hydroxyl surface density through analytical techniques (interferometry, X-ray photoelectron spectroscopy (XPS), contact angle, and zinc complexation). These findings provide essential information when planning surface modifications for cleanliness, oxide layer thickness, and surface hydroxyl density, as control over these factors is essential for many applications, especially in biomaterials.

Viscous drag reduction in boundary layers

NASA Technical Reports Server (NTRS)

Bushnell, Dennis M. (Editor); Hefner, Jerry N. (Editor)

1990-01-01

The present volume discusses the development status of stability theory for laminar flow control design, applied aspects of laminar-flow technology, transition delays using compliant walls, the application of CFD to skin friction drag-reduction, active-wave control of boundary-layer transitions, and such passive turbulent-drag reduction methods as outer-layer manipulators and complex-curvature concepts. Also treated are such active turbulent drag-reduction technique applications as those pertinent to MHD flow drag reduction, as well as drag reduction in liquid boundary layers by gas injection, drag reduction by means of polymers and surfactants, drag reduction by particle addition, viscous drag reduction via surface mass injection, and interactive wall-turbulence control.

Galvanostatic interruption of lithium insertion into magnetite: Evidence of surface layer formation

DOE PAGES

Nicholas W. Brady; Takeuchi, Esther S.; Knehr, K. W.; ...

2016-04-24

Magnetite is a known lithium intercalation material, and the loss of active, nanocrystalline magnetite can be inferred from the open-circuit potential relaxation. Specifically, for current interruption after relatively small amounts of lithium insertion, the potential first increases and then decreases, and the decrease is hypothesized to be due to a formation of a surface layer, which increases the solid-state lithium concentration in the remaining active material. Comparisons of simulation to experiment suggest that the reactions with the electrolyte result in the formation of a thin layer of electrochemically inactive material, which is best described by a nucleation and growth mechanism.more » Simulations are consistent with experimental results observed for 6, 8 and 32-nm crystals. As a result, simulations capture the experimental differences in lithiation behavior between the first and second cycles.« less

Release properties of tannic acid from hydrogen bond driven antioxidative cellulose nanofibrous films.

PubMed

Zhou, Bin; Hu, Xiaoqian; Zhu, Jinjin; Wang, Zhenzhen; Wang, Xichang; Wang, Mingfu

2016-10-01

Layer-by-layer (LBL) assembled films have been exploited for surface-mediated bioactive compound delivery. Here, an antioxidative hydrogen-bonded multilayer electrospun nanofibrous film was fabricated from tannic acid (TA), acting as a polyphenolic antioxidant, and poly(ethylene glycol) (PEG) via layer-by-layer assembly. It overcame the burst release behavior of nanofibrous carrier, due to the reversible/dynamic nature of hydrogen bond, which was responded to external stimuli. The PEG/TA nanofibrous films disassembled gradually and released TA to the media, when soaked in aqueous solutions. The release rate of TA increased with increasing bilayer number, pH and temperature, but decreased with enhancing ionic strength. The surface morphology of the nanofibrous mats was observed by scanning electron microscopy (SEM). The following antioxidant activity assay revealed that it could scavenge DPPH free radicals and ABTS(+) cation radicals, a major biological activity of polyphenols. This technology can be used to fabricate other phenolic-containing slowly releasing antioxidative nanofibrous films. Copyright © 2016 Elsevier B.V. All rights reserved.

Poly(3,4-ethylenedioxythiophene)-Poly(styrenesulfonate) Interlayer Insertion Enables Organic Quaternary Memory.

PubMed

Cheng, Xue-Feng; Hou, Xiang; Qian, Wen-Hu; He, Jing-Hui; Xu, Qing-Feng; Li, Hua; Li, Na-Jun; Chen, Dong-Yun; Lu, Jian-Mei

2017-08-23

Herein, for the first time, quaternary resistive memory based on an organic molecule is achieved via surface engineering. A layer of poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonate) (PEDOT-PSS) was inserted between the indium tin oxide (ITO) electrode and the organic layer (squaraine, SA-Bu) to form an ITO/PEDOT-PSS/SA-Bu/Al architecture. The modified resistive random-access memory (RRAM) devices achieve quaternary memory switching with the highest yield (∼41%) to date. Surface morphology, crystallinity, and mosaicity of the deposited organic grains are greatly improved after insertion of a PEDOT-PSS interlayer, which provides better contacts at the grain boundaries as well as the electrode/active layer interface. The PEDOT-PSS interlayer also reduces the hole injection barrier from the electrode to the active layer. Thus, the threshold voltage of each switching is greatly reduced, allowing for more quaternary switching in a certain voltage window. Our results provide a simple yet powerful strategy as an alternative to molecular design to achieve organic quaternary resistive memory.

Numerical simulation of the control of the three-dimensional transition process in boundary layers

NASA Technical Reports Server (NTRS)

Kral, L. D.; Fasel, H. F.

1990-01-01

Surface heating techniques to control the three-dimensional laminar-turbulent transition process are numerically investigated for a water boundary layer. The Navier-Stokes and energy equations are solved using a fully implicit finite difference/spectral method. The spatially evolving boundary layer is simulated. Results of both passive and active methods of control are shown for small amplitude two-dimensional and three-dimensional disturbance waves. Control is also applied to the early stages of the secondary instability process using passive or active control techniques.

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

DOE Data Explorer

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

2016-11-10

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

Mono vs multilayer fibronectin coatings on polar/hydrophobic/ionic polyurethanes: Altering surface interactions with human monocytes.

PubMed

Gossart, Audrey; Battiston, Kyle G; Gand, Adeline; Pauthe, Emmanuel; Santerre, J Paul

2018-01-15

Monocyte interactions with materials that are biofunctionalized with fibronectin (Fn) are of interest because of the documented literature which associates this protein with white blood cell function at implant sites. A degradable-polar hydrophobic ionic polyurethane (D-PHI), has been reported to promote an anti-inflammatory response from human monocytes. The aim of the current work was to study the influence of intrinsic D-PHI material chemistry on Fn adsorption (mono and multi-layer structures), and to investigate the influence of such chemistry on the structural state of the Fn, as well as the latter's influence on the activity of human monocytes on the protein coated substrates. Significant differences in Fn adsorption, surface hydrophobicity and the availability of defined peptide sequences (N terminal, C terminal or Cell Binding Domain) for the Fn in mono vs multilayer structures were observed as a function of the changes in intrinsic material chemistry. A D-PHI-formulated polyurethane substrate with subtle changes in anionic and hydrophobic domain content relative to the polar non-ionic urethane/carbonate groups within the polymer matrix promoted the lowest activation of monocytes, in the presence of multi-layer Fn constructs. These results highlight the importance of chemical heterogeneity as a design parameter for biomaterial surfaces, and establishes a desired strategy for controlling human monocyte activity at the surface of devices, when these are coated with multi-layer Fn structures. The latter is an important step towards functionalizing the materials with multi-layer protein drug carriers as interventional therapeutic agents. The control of the behavior of monocytes, especially migration and activation, is of crucial interest to modulate the inflammatory response at the site of implanted biomaterial. Several studies report the influence of adsorbed serum proteins on the behavior of monocytes on biomaterials. However, few studies show the influence of surface chemical group distribution on the controlled adsorption and the subsequent induced conformation- of mono versus multi-layer assembled structures generated from specific proteins implicated in wound repair. The current research considered the role of Fn adsorption and conformation in thin films while interacting with the intrinsic chemistry of segmented block polyurethanes; and the influence of the former on modulation and activation of human monocytes. Copyright © 2017 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

A facile approach for reducing the working voltage of Au/TiO2/Au nanostructured memristors by enhancing the local electric field

NASA Astrophysics Data System (ADS)

Arab Bafrani, Hamidreza; Ebrahimi, Mahdi; Bagheri Shouraki, Saeed; Moshfegh, Alireza Z.

2018-01-01

Memristor devices have attracted tremendous interest due to different applications ranging from nonvolatile data storage to neuromorphic computing units. Exploring the role of surface roughness of the bottom electrode (BE)/active layer interface provides useful guidelines for the optimization of the memristor switching performance. This study focuses on the effect of surface roughness of the BE electrode on the switching characteristics of Au/TiO2/Au three-layer memristor devices. An optimized wet-etching treatment condition was found to modify the surface roughness of the Au BE where the measurement results indicate that the roughness of the Au BE is affected by both duration time and solution concentrations of the wet-etching process. Then we fabricated arrays of TiO2-based nanostructured memristors sandwiched between two sets of cross-bar Au electrode lines (junction area 900 μm2). The results revealed a reduction in the working voltages in current-voltage characteristic of the device performance when increasing the surface roughness at the Au(BE)/TiO2 active layer interface. The set voltage of the device (Vset) significantly decreased from 2.26-1.93 V when we increased the interface roughness from 4.2-13.1 nm. The present work provides information for better understanding the switching mechanism of titanium-dioxide-based devices, and it can be inferred that enhancing the roughness of the Au BE/TiO2 active layer interface leads to a localized non-uniform electric field distribution that plays a vital role in reducing the energy consumption of the device.

Atomic layer deposition of ruthenium on plasma-treated vertically aligned carbon nanotubes for high-performance ultracapacitors.

PubMed

Kim, Jun Woo; Kim, Byungwoo; Park, Suk Won; Kim, Woong; Shim, Joon Hyung

2014-10-31

It is challenging to realize a conformal metal coating by atomic layer deposition (ALD) because of the high surface energy of metals. In this study, ALD of ruthenium (Ru) on vertically aligned carbon nanotubes (CNTs) was carried out. To activate the surface of CNTs that lack surface functional groups essential for ALD, oxygen plasma was applied ex situ before ALD. X-ray photoelectron spectroscopy and Raman spectroscopy confirmed surface activation of CNTs by the plasma pretreatment. Transmission electron microscopy analysis with energy-dispersive x-ray spectroscopy composition mapping showed that ALD Ru grew conformally along CNTs walls. ALD Ru/CNTs were electrochemically oxidized to ruthenium oxide (RuOx) that can be a potentially useful candidate for use in the electrodes of ultracapacitors. Electrode performance of RuOx/CNTs was evaluated using cyclic voltammetry and galvanostatic charge-discharge measurements.

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

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

Kim, Jaehwan; Min, Daehong; Jang, Jongjin

2014-10-28

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

Iron layer-dependent surface-enhanced raman scattering of hierarchical nanocap arrays

NASA Astrophysics Data System (ADS)

Chen, Lei; Sun, Huanhuan; Zhao, Yue; Gao, Renxian; Wang, Yaxin; Liu, Yang; Zhang, Yongjun; Hua, Zhong; Yang, Jinghai

2017-11-01

In this report, we fabricated the multi-layer Ag/Fe/Ag sandwich cap-shaped films on monolayer non-closed packed (ncp) polystyrene colloidal particle (PSCP) templates through a layer-by-layer (LBL) depositing method. This research focused on the surface-enhanced Raman scattering (SERS) effect of the thickness of the deposited Fe film which was controlled by the sputtering time. The SERS intensities were increased firstly, and then decreased as the thickness of Fe layer grows gradually, which is attributed to the charge transition from the Fermi level of the Ag NPs to Fe layer. The use of multi-layer Ag/Fe/Ag sandwich cap-shaped films enables us to evaluate the contribution of surface plasmon resonance and charge distribution between Ag and Fe to SERS enhancement. Our work introduced a novel system (Ag/Fe/Ag) for high performance SERS and extended the SERS application of Fe. Furthermore, we have designed the Ag/Fe/Ag SERS-active substrate as the immunoassay chip for quantitative determination of AFP-L3 which is the biomarker of hepatocellular carcinoma (HCC). The proposed research demonstrates that the SERS substrates with Ag/Fe/Ag sandwich cap-shaped arrays have a high sensitivity for bioassay.

Satellite based assessment of recent permafrost extent and active layer trends over Alaska and Northwest Canada

NASA Astrophysics Data System (ADS)

Kim, Y.; Kimball, J. S.; PARK, H.; Yi, Y.

2017-12-01

Climate change in the Boreal-Arctic region has experienced greater surface air temperature (SAT) warming than the global average in recent decades, which is promoting permafrost thawing and active layer deepening. Permafrost extent (PE) and active layer thickness (ALT) are key environmental indicators of recent climate change, and strongly impact other eco-hydrological processes including land-atmosphere carbon exchange. We developed a new approach for regional estimation and monitoring of PE using daily landscape freeze-thaw (FT) records derived from satellite microwave (37 GHz) brightness temperature (Tb) observations. ALT was estimated within the PE domain using empirical modeling of land cover dependent edaphic factors and an annual thawing index derived from MODIS land surface temperature (LST) observations and reanalysis based surface air temperatures (SAT). The PE and ALT estimates were derived over the 1980-2016 satellite record and NASA ABoVE (Arctic Boreal Vulnerability Experiment) domain encompassing Alaska and Northwest Canada. The baseline model estimates were derived at 25-km resolution consistent with the satellite FT global record. Our results show recent widespread PE decline and deepening ALT trends, with larger spatial variability and model uncertainty along the southern PE boundary. Larger PE and ALT variability occurs over heterogeneous permafrost subzones characterized by dense vegetation, and variable snow cover and organic layer conditions. We also tested alternative PE and ALT estimates derived using finer (6-km) scale satellite Tb (36.5 GHz) and FT retrievals from a calibrated AMSR-E and AMSR2 sensor record. The PE and ALT results were compared against other independent observations, including process model simulations, in situ measurements, and permafrost inventory records. A model sensitivity analysis was conducted to evaluate snow cover, soil organic layer, and vegetation composition impacts to ALT. The finer delineation of permafrost and active layer conditions provides enhanced regional monitoring of PE and ALT changes over the ABoVE domain, including heterogeneous permafrost subzones.

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

NASA Astrophysics Data System (ADS)

Panda, Satyajit; Ray, M. C.

2008-04-01

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

Sulfate-reducing bacteria and their activities in cyanobacterial mats of Solar Lake (Sinai, Egypt)

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

Teske, A.; Ramsing, N.B.; Habicht, K.

1998-08-01

The sulfate-reducing bacteria within the surface layer of the hypersaline cyanobacterial mat of Solar Lake (Sinai, Egypt) were investigated with combined microbiological, molecular, and biogeochemical approaches. The diurnally oxic surface layer contained between 10{sup 6} and 10{sup 7} cultivable sulfate-reducing bacteria ml{sup {minus}1} day{sup {minus}1}, both in the same range as and sometimes higher than those in anaerobic deeper mat layers. In the oxic surface layer and in the mat layers below, filamentous sulfate-reducing Desulfonema bacteria were found in variable densities of 10{sup 4} and 10{sup 6} cells ml{sup {minus}1}. A Desulfonema-related, diurnally migrating bacterium was detected with PCR andmore » denaturing gradient gel electrophoresis within and below the oxic surface layer. Facultative aerobic respiration, filamentous morphology, motility, diurnal migration, and aggregate formation were the most conspicuous adaptations of Solar Lake sulfate-reducing bacteria to the mat matrix and to diurnal oxygen stress. A comparison of sulfate reduction rates within the mat and previously published photosynthesis rates showed that CO{sub 2} from sulfate reduction in the upper 5 mm accounted for 7 to 8% of the total photosynthetic CO{sub 2} demand of the mat.« less

Understanding and modeling volcanotectonic processes that generate surface deformation on active stratovolcanoes

NASA Astrophysics Data System (ADS)

Gudmundsson, A.

2005-05-01

Surface deformation on stratovolcanoes is the result of local stresses generated by various volcanotectonic processes. These processes include changes in fluid pressure in the associated geothermal fields and magma chambers, regional seismic or tectonic events, fault development, and dike injections. Here the focus is on magma-chamber pressure changes and dike injections. Surface deformation associated with magma-chamber pressure changes is normally referred to as inflation when the pressure increases, and as deflation when the pressure decreases. The processes that lead to inflation are primarily addition of new magma to the chamber and rapid exsolution of gas from the magma in the chamber. The processes that lead to deflation are primarily cooling (and contraction) of magma in the chamber, regional tectonic extension of the crust holding the chamber, and eruption and/or dike injection. Injection of dikes (including inclined sheets) is common in most active stratovolcanoes. However, no dike-fed eruptions can take place unless the local stress field within the volcano is favorable to feeder-dike formation. By contrast, if at any location - in any layer - in the stratovolcano the stress field is unfavorable to dike propagation, the dike becomes arrested and no eruption occurs. Detailed studies of dikes in stratovolcanoes worldwide indicate that most dikes become arrested and never reach the surface. However, arrested dikes may give rise to surface deformation, such as is commonly monitored during volcanic unrest periods. By definition, stratovolcanoes are composed of numerous alternating strata (layers) of pyroclastic material and lava flows. Commonly, these layers have widely different mechanical properties. In particular, some layers such as lava flows and welded pyroclastic flows may be stiff (with a high Young's modulus), whereas other layers, such as non-welded pyroclastic units, may be soft (with a low Young's modulus). Here I present new numerical models on the surface deformation on typical stratovolcanoes. The models show, first, that the surface deformation during magma-chamber inflation and deflation depends much on the chamber geometry, the loading conditions, and the mechanical properties of the rock units that constitute the volcano. Second, the models show that dike-induced stresses and surface deformation depend much on the mechanical properties of the layers between the dike tip and the surface. In particular, the models indicate that soft layers and weak contacts between layers may suppress the dike-induced tensile stresses and the associated surface deformation. Thus, many dikes may become injected and arrested with little or no surface deformation. Generally, the numerical models suggest that standard analytical surface-deformation models such as point sources (nuclei of strain) for magma-chamber pressure changes and dislocations for dikes should be used with great caution. These models normally assume the volcanoes and rift zones to behave as homogeneous, isotropic half spaces or semi-infinite plates. When applied to stratovolcanoes composed of layers of contrasting mechanical properties and, particularly at shallow depths, weak or open contacts, inversions using these analytical models may yield results that, at best, are unreliable.

Universal method for creating optically active nanostructures on layered materials

NASA Astrophysics Data System (ADS)

Kidd, Tim; He, Rui; Stollenwerk, Andrew; Oshea, Aaron; Beck, Ben; Spurgeon, Kyle; Gu, Genda

2014-03-01

We report a new method for the creating of nanostructures using a scanning electron microscope. Residual organic molecules on the surface of layered materials can be excited by electron beam radiation to burrow into the open spaces between the layers of these materials, and then are broken down further to form photoluminescent carbon nanoclusters. Surface characterization by atomic force microscopy shows the surface is nearly undamaged at the molecular level by this process, and a lack of nanostructure formation in non-layered materials confirms that the structures are created by sub-surface incorporation. The presence of carbon nanoclusters was determined by Raman Spectroscopy and photoluminescence in the visible light range. The nanostructures are react strongly to visible light, making them readily apparent using an optical microscope even for features measuring only a few nanometers tall. This technique can be used on apparently any layered material, with successful results on dichalcogenides, topological insulators, graphite, and high temperature copper oxide superconductors. This technique can create patterned nanostructures with vertical resolution at the nanometer scale and lateral resolution of tens of nanometers depending on beam spot size. This work is funded by University of Northern Iowa, NSF #DMR-1206530, and DOE #DE-AC02-98CH10886.

Subsurface flow pathway dynamics in the active layer of coupled permafrost-hydrogeological systems under seasonal and annual temperature variability.

NASA Astrophysics Data System (ADS)

Frampton, Andrew

2017-04-01

There is a need for improved understanding of the mechanisms controlling subsurface solute transport in the active layer in order to better understand permafrost-hydrological-carbon feedbacks, in particular with regards to how dissolved carbon is transported in coupled surface and subsurface terrestrial arctic water systems under climate change. Studying solute transport in arctic systems is also relevant in the context of anthropogenic pollution which may increase due to increased activity in cold region environments. In this contribution subsurface solute transport subject to ground surface warming causing permafrost thaw and active layer change is studied using a physically based model of coupled cryotic and hydrogeological flow processes combined with a particle tracking method. Changes in subsurface water flows and solute transport travel times are analysed for different modelled geological configurations during a 100-year warming period. Results show that for all simulated cases, the minimum and mean travel times increase non-linearly with warming irrespective of geological configuration and heterogeneity structure. The timing of the start of increase in travel time depends on heterogeneity structure, combined with the rate of permafrost degradation that also depends on material thermal and hydrogeological properties. These travel time changes are shown to depend on combined warming effects of increase in pathway length due to deepening of the active layer, reduced transport velocities due to a shift from horizontal saturated groundwater flow near the surface to vertical water percolation deeper into the subsurface, and pathway length increase and temporary immobilization caused by cryosuction-induced seasonal freeze cycles. The impact these change mechanisms have on solute and dissolved substance transport is further analysed by integrating pathway analysis with a Lagrangian approach, incorporating considerations for both dissolved organic and inorganic carbon releases. Further model development challenges are also highlighted and discussed, including coupling between subsurface and surface runoff, soil deformations, as well as site applications and larger system scales.

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

Zhang, Lehao

A nanocrystalline surface layer was produced on Mg-3 wt.% Li-6 wt.% Al alloy by means of surface mechanical attrition treatment (SMAT). Microstructure features of various sections were systematically characterized by transmission electron microscopy. The results indicate that grain refinement induced by SMAT is dominated mainly by dislocation slip. Twinning is active at the early stage of grain refinement process when the grain size is large. The dislocation-dominated deformation mechanism is attributed to the change of c/a ratio due to the alloying of Li in Mg matrix and the suppression of twinning due to grain refinement. Nanoindentation results show that themore » hardness of the surface is enhanced by SMAT. - Highlights: •Nanocrystalline surface layer was produced on Mg-3 wt.%Li-6 wt.%Al alloy by SMAT. •Grain refinement induced by SMAT is dominated mainly by dislocation slip. •Twinning is active at the early stage of grain refinement process. •The hardness of the surface was enhanced by SMAT.« less

Understanding the barriers to crystal growth: dynamical simulation of the dissolution and growth of urea from aqueous solution.

PubMed

Piana, Stefano; Gale, Julian D

2005-02-16

Both the dissolution and growth of a molecular crystalline material, urea, has been studied using dynamical atomistic simulation. The kinetic steps of dissolution and growth are clearly identified, and the activation energies for each possible step are calculated. Our molecular dynamics simulations indicate that crystal growth on the [001] face is characterized by a nucleation and growth mechanism. Nucleation on the [001] urea crystal face is predicted to occur at a very high rate, followed by rapid propagation of the steps. The rate-limiting step for crystallization is actually found to be the removal of surface defects, rather than the initial formation of the next surface layer. Through kinetic Monte Carlo modeling of the surface growth, it is found that this crystal face evolves via a rough surface topography, rather than a clean layer-by-layer mechanism.

Surface functionalization of magnetic nanoparticles formed by self-associating hydrophobized oxidized dextrans

NASA Astrophysics Data System (ADS)

Farber, Shimon; Ickowicz, Diana E.; Melnik, Kristie; Yudovin-Farber, Ira; Recko, Daniel; Rampersaud, Arfaan; Domb, Abraham J.

2014-06-01

Magnetic iron oxide nanoparticles surface covered with oleic acid layer followed by a second layer of hydrophobized oxidized dextran aldehyde were prepared and tested for physico-chemical properties and ligand- and cell-specific binding. It was demonstrated that oleic acid-iron oxide nanoparticles coated with an additional layer of hydrophobized oxidized dextran were dispersible in buffer solutions and possess surface aldehyde active groups available for further binding of ligands or markers via imine or amine bond formation. Hydrophobized dextrans were synthesized by periodate oxidation and conjugation of various alkanamines to oxidized dextran by imination. Physico-chemical properties, as separation using magnetic field, magnetite concentration, and particle diameter, of the prepared magnetic samples are reported. The biotin-binding protein, neutravidin, was coupled to the particle surface by a simple reductive amination procedure. The particles were used for specific cell separation with high specificity.

Synthesis and immobilization of Ag(0) nanoparticles on diazonium modified electrodes: SECM and cyclic voltammetry studies of the modified interfaces.

PubMed

Noël, Jean-Marc; Zigah, Dodzi; Simonet, Jacques; Hapiot, Philippe

2010-05-18

A versatile method was used to prepare modified surfaces on which metallic silver nanoparticles are immobilized on an organic layer. The preparation method takes advantage, on one hand, of the activated reactivity of some alkyl halides with Ag-Pd alloys to produce metallic silver nanoparticles and, on the other hand, of the facile production of an anchoring polyphenyl acetate layer by the electrografting of substituted diazonium salts on carbon surfaces. Transport properties inside such modified layers were investigated by cyclic voltammetry, scanning electrochemical microscopy (SECM) in feedback mode, and conducting AFM imaging for characterizing the presence and nature of the conducting pathways. The modification of the blocking properties of the surface (or its conductivity) was found to vary to a large extent on the solvents used for surface examination (H(2)O, CH(2)Cl(2), and DMF).

On the photon annealing of silicon-implanted gallium-nitride layers

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

Seleznev, B. I., E-mail: Boris.Seleznev@novsu.ru; Moskalev, G. Ya.; Fedorov, D. G.

2016-06-15

The conditions for the formation of ion-doped layers in gallium nitride upon the incorporation of silicon ions followed by photon annealing in the presence of silicon dioxide and nitride coatings are analyzed. The conditions of the formation of ion-doped layers with a high degree of impurity activation are established. The temperature dependences of the surface concentration and mobility of charge carriers in ion-doped GaN layers annealed at different temperatures are studied.

Active Layer and Water Geochemistry Dynamics throughout the Yukon River Basin

NASA Astrophysics Data System (ADS)

Mutter, E. A.; Toohey, R.; Herman-Mercer, N. M.; Schuster, P. F.

2017-12-01

The hydrology of the Yukon River Basin has changed over the last several decades as evidenced by a variety of discharge, gravimetric, and geochemical analyses. The Indigenous Observation Network (ION), a community-based project, was initiated by the Yukon River Inter-Tribal Watershed Council and USGS. Capitalizing on existing USGS monitoring and research infrastructure and supplementing USGS collected data, ION investigates changes in surface water geochemistry and active layer dynamics throughout the Yukon River Basin. Over 1600 samples of surface water geochemistry (i.e., major ions, dissolved organic carbon, and 18O and 2H) have been collected at 35 sites throughout the Yukon River and its major tributaries over the past 15 years. Active layer dynamics (maximum thaw depth, soil temperature and moisture) have been collected at 20 sites throughout the Yukon River Basin for the past eight years. Important regional differences in geochemistry and active layer parameters linked to permafrost continuity and tributaries will be highlighted. Additionally, annual trends and seasonal dynamics describing the spatial and temporal heterogeneity of the watershed will be presented in the context of observed hydrological changes. These data assist the global effort to characterize arctic river fluxes and their relationship to the carbon cycle, weathering and permafrost degradation.

Surface structure and chemistry of Pt/Cu/Pt(1 1 1) near surface alloy model catalyst in CO

NASA Astrophysics Data System (ADS)

Zeng, Shibi; Nguyen, Luan; Cheng, Fang; Liu, Lacheng; Yu, Ying; Tao, Franklin (Feng)

2014-11-01

Near surface alloy (NSA) model catalyst Pt/Cu/Pt(1 1 1) was prepared on Pt(1 1 1) through a controlled vapor deposition of Cu atoms. Different coordination environments of Pt atoms of the topmost Pt layer with the underneath Cu atoms in the subsurface result in different local electronic structures of surface Pt atoms. Surface structure and chemistry of the NAS model catalyst in Torr pressure of CO were studied with high pressure scanning tunneling microscopy (HP-STM) and ambient pressure X-ray photoelectron spectroscopy (AP-XPS). In Torr pressure of CO, the topmost Pt layer of Pt/Cu/Pt(1 1 1) is restructured to thin nanoclusters with size of about 1 nm. Photoemission feature of O 1s of CO on Pt/Cu/Pt(1 1 1) suggests CO adsorbed on both edge and surface of these formed nanoclusters. This surface is active for CO oxidation. Atomic layers of carbon are formed on Pt/Cu/Pt(1 1 1) at 573 K in 2 Torr of CO.

Functional Layer-by-Layer Thin Films of Inducible Nitric Oxide (NO) Synthase Oxygenase and Polyethylenimine: Modulation of Enzyme Loading and NO-Release Activity.

PubMed

Gunasekera, Bhagya; Abou Diwan, Charbel; Altawallbeh, Ghaith; Kalil, Haitham; Maher, Shaimaa; Xu, Song; Bayachou, Mekki

2018-03-07

Nitric oxide (NO) release counteracts platelet aggregation and prevents the thrombosis cascade in the inner walls of blood vessels. NO-release coatings also prevent thrombus formation on the surface of blood-contacting medical devices. Our previous work has shown that inducible nitric oxide synthase (iNOS) films release NO fluxes upon enzymatic conversion of the substrate l-arginine. In this work, we report on the modulation of enzyme loading in layer-by-layer (LbL) thin films of inducible nitric oxide synthase oxygenase (iNOSoxy) on polyethylenimine (PEI). The layer of iNOSoxy is electrostatically adsorbed onto the PEI layer. The pH of the iNOSoxy solution affects the amount of enzyme adsorbed. The overall negative surface charge of iNOSoxy in solution depends on the pH and hence determines the density of adsorbed protein on the positively charged PEI layer. We used buffered iNOSoxy solutions adjusted to pHs 8.6 and 7.0, while saline PEI solution was used at pH 7.0. Atomic force microscopy imaging of the outermost layer shows higher protein adsorption with iNOSoxy at pH 8.6 than with a solution of iNOSoxy at pH 7.0. Graphite electrodes with PEI/iNOSoxy films show higher catalytic currents for nitric oxide reduction mediated by iNOSoxy. The higher enzyme loading translates into higher NO flux when the enzyme-modified surface is exposed to a solution containing the substrate and a source of electrons. Spectrophotometric assays showed higher NO fluxes with iNOSoxy/PEI films built at pH 8.6 than with films built at pH 7.0. Fourier transform infrared analysis of iNOSoxy adsorbed on PEI at pH 8.6 and 7.0 shows structural differences of iNOSoxy in films, which explains the observed changes in enzymatic activity. Our findings show that pH provides a strategy to optimize the NOS loading and enzyme activity in NOS-based LbL thin films, which enables improved NO release with minimum layers of PEI/NOS.

Probing the energetics of organic–nanoparticle interactions of ethanol on calcite

PubMed Central

Wu, Di; Navrotsky, Alexandra

2015-01-01

Knowing the nature of interactions between small organic molecules and surfaces of nanoparticles (NP) is crucial for fundamental understanding of natural phenomena and engineering processes. Herein, we report direct adsorption enthalpy measurement of ethanol on a series of calcite nanocrystals, with the aim of mimicking organic–NP interactions in various environments. The energetics suggests a spectrum of adsorption events as a function of coverage: strongest initial chemisorption on active sites on fresh calcite surfaces, followed by major chemical binding to form an ethanol monolayer and, subsequently, very weak, near-zero energy, physisorption. These thermochemical observations directly support a structure where the ethanol monolayer is bonded to the calcite surface through its polar hydroxyl group, leaving the hydrophobic ends of the ethanol molecules to interact only weakly with the next layer of adsorbing ethanol and resulting in a spatial gap with low ethanol density between the monolayer and subsequent added ethanol molecules, as predicted by molecular dynamics and density functional calculations. Such an ordered assembly of ethanol on calcite NP is analogous to, although less strongly bonded than, a capping layer of organics intentionally introduced during NP synthesis, and suggests a continuous variation of surface structure depending on molecular chemistry, ranging from largely disordered surface layers to ordered layers that nevertheless are mobile and can rearrange or be displaced by other molecules to strongly bonded immobile organic capping layers. These differences in surface structure will affect chemical reactions, including the further nucleation and growth of nanocrystals on organic ligand-capped surfaces. PMID:25870281

Nanostructuring of Palladium with Low-Temperature Helium Plasma

PubMed Central

Fiflis, P.; Christenson, M.P.; Connolly, N.; Ruzic, D.N.

2015-01-01

Impingement of high fluxes of helium ions upon metals at elevated temperatures has given rise to the growth of nanostructured layers on the surface of several metals, such as tungsten and molybdenum. These nanostructured layers grow from the bulk material and have greatly increased surface area over that of a not nanostructured surface. They are also superior to deposited nanostructures due to a lack of worries over adhesion and differences in material properties. Several palladium samples of varying thickness were biased and exposed to a helium helicon plasma. The nanostructures were characterized as a function of the thickness of the palladium layer and of temperature. Bubbles of ~100 nm in diameter appear to be integral to the nanostructuring process. Nanostructured palladium is also shown to have better catalytic activity than not nanostructured palladium. PMID:28347109

Nanostructuring of Palladium with Low-Temperature Helium Plasma.

PubMed

Fiflis, P; Christenson, M P; Connolly, N; Ruzic, D N

2015-11-25

Impingement of high fluxes of helium ions upon metals at elevated temperatures has given rise to the growth of nanostructured layers on the surface of several metals, such as tungsten and molybdenum. These nanostructured layers grow from the bulk material and have greatly increased surface area over that of a not nanostructured surface. They are also superior to deposited nanostructures due to a lack of worries over adhesion and differences in material properties. Several palladium samples of varying thickness were biased and exposed to a helium helicon plasma. The nanostructures were characterized as a function of the thickness of the palladium layer and of temperature. Bubbles of ~100 nm in diameter appear to be integral to the nanostructuring process. Nanostructured palladium is also shown to have better catalytic activity than not nanostructured palladium.

Phase-separated, epitaxial composite cap layers for electronic device applications and method of making the same

DOEpatents

Aytug, Tolga [Knoxville, TN; Paranthaman, Mariappan Parans [Knoxville, TN; Polat, Ozgur [Knoxville, TN

2012-07-17

An electronic component that includes a substrate and a phase-separated layer supported on the substrate and a method of forming the same are disclosed. The phase-separated layer includes a first phase comprising lanthanum manganate (LMO) and a second phase selected from a metal oxide (MO), metal nitride (MN), a metal (Me), and combinations thereof. The phase-separated material can be an epitaxial layer and an upper surface of the phase-separated layer can include interfaces between the first phase and the second phase. The phase-separated layer can be supported on a buffer layer comprising a composition selected from the group consisting of IBAD MgO, LMO/IBAD-MgO, homoepi-IBAD MgO and LMO/homoepi-MgO. The electronic component can also include an electronically active layer supported on the phase-separated layer. The electronically active layer can be a superconducting material, a ferroelectric material, a multiferroic material, a magnetic material, a photovoltaic material, an electrical storage material, and a semiconductor material.

Las Vegas Basin Seismic Response Project: Measured Shallow Soil Velocities

NASA Astrophysics Data System (ADS)

Luke, B. A.; Louie, J.; Beeston, H. E.; Skidmore, V.; Concha, A.

2002-12-01

The Las Vegas valley in Nevada is a deep (up to 5 km) alluvial basin filled with interlayered gravels, sands, and clays. The climate is arid. The water table ranges from a few meters to many tens of meters deep. Laterally extensive thin carbonate-cemented lenses are commonly found across parts of the valley. Lenses range beyond 2 m in thickness, and occur at depths exceeding 200 m. Shallow seismic datasets have been collected at approximately ten sites around the Las Vegas valley, to characterize shear and compression wave velocities in the near surface. Purposes for the surveys include modeling of ground response to dynamic loads, both natural and manmade, quantification of soil stiffness to aid structural foundation design, and non-intrusive materials identification. Borehole-based measurement techniques used include downhole and crosshole, to depths exceeding 100 m. Surface-based techniques used include refraction and three different methods involving inversion of surface-wave dispersion datasets. This latter group includes two active-source techniques, the Spectral Analysis of Surface Waves (SASW) method and the Multi-Channel Analysis of Surface Waves (MASW) method; and a new passive-source technique, the Refraction Mictrotremor (ReMi) method. Depths to halfspace for the active-source measurements ranged beyond 50 m. The passive-source method constrains shear wave velocities to 100 m depths. As expected, the stiff cemented layers profoundly affect local velocity gradients. Scale effects are evident in comparisons of (1) very local measurements typified by borehole methods, to (2) the broader coverage of the SASW and MASW measurements, to (3) the still broader and deeper resolution made possible by the ReMi measurements. The cemented layers appear as sharp spikes in the downhole datasets and are problematic in crosshole measurements due to refraction. The refraction method is useful only to locate the depth to the uppermost cemented layer. The surface-wave methods, on the other hand, can process velocity inversions. With the broader coverage of the active-source surface wave measurements, through careful inversion that takes advantage of prior information to the greatest extent possible, multiple, shallow, stiff layers can be resolved. Data from such broader-coverage methods also provide confidence regarding continuity of the cemented layers. For the ReMi measurements, which provide the broadest coverage of all methods used, the more generalized shallow profile is sometimes characterized by a strong stiffness inversion at a depth of approximately 10 m. We anticipate that this impedance contrast represents the vertical extent of the multiple layered deposits of cemented media.

Atmospheric tides on Venus. III - The planetary boundary layer

NASA Technical Reports Server (NTRS)

Dobrovolskis, A. R.

1983-01-01

Diurnal solar heating of Venus' surface produces variable temperatures, winds, and pressure gradients within a shallow layer at the bottom of the atmosphere. The corresponding asymmetric mass distribution experiences a tidal torque tending to maintain Venus' slow retrograde rotation. It is shown that including viscosity in the boundary layer does not materially affect the balance of torques. On the other hand, friction between the air and ground can reduce the predicted wind speeds from about 5 to about 1 m/sec in the lower atmosphere, more consistent with the observations from Venus landers and descent probes. Implications for aeolian activity on Venus' surface and for future missions are discussed.

Directed Vertical Diffusion of Photovoltaic Active Layer Components into Porous ZnO-Based Cathode Buffer Layers.

PubMed

Kang, Jia-Jhen; Yang, Tsung-Yu; Lan, Yi-Kang; Wu, Wei-Ru; Su, Chun-Jen; Weng, Shih-Chang; Yamada, Norifumi L; Su, An-Chung; Jeng, U-Ser

2018-04-01

Cathode buffer layers (CBLs) can effectively further the efficiency of polymer solar cells (PSCs), after optimization of the active layer. Hidden between the active layer and cathode of the inverted PSC device configuration is the critical yet often unattended vertical diffusion of the active layer components across CBL. Here, a novel methodology of contrast variation with neutron and anomalous X-ray reflectivity to map the multicomponent depth compositions of inverted PSCs, covering from the active layer surface down to the bottom of the ZnO-based CBL, is developed. Uniquely revealed for a high-performance model PSC are the often overlooked porosity distributions of the ZnO-based CBL and the differential diffusions of the polymer PTB7-Th and fullerene derivative PC 71 BM of the active layer into the CBL. Interface modification of the ZnO-based CBL with fullerene derivative PCBEOH for size-selective nanochannels can selectively improve the diffusion of PC 71 BM more than that of the polymer. The deeper penetration of PC 71 BM establishes a gradient distribution of fullerene derivatives over the ZnO/PCBE-OH CBL, resulting in markedly improved electron mobility and device efficiency of the inverted PSC. The result suggests a new CBL design concept of progressive matching of the conduction bands. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Preliminary results on ocean dynamics from Skylab and their implications for future spacecraft

NASA Technical Reports Server (NTRS)

Hayes, J.; Pierson, W. J.; Cardone, V. J.

1975-01-01

The instrument aboard Skylab designated S193 - a combined passive and active microwave radar system acting as a radiometer, scatterometer, and altimeter - is used to measure the surface vector wind speeds in the planetary boundary layer over the oceans. Preliminary results corroborate the hypothesis that sea surface winds in the planetary boundary layer can be determined from satellite data. Future spacecraft plans for measuring a geoid with an accuracy up to 10 cm are discussed.

Deposition of gold nano-particles and nano-layers on polyethylene modified by plasma discharge and chemical treatment

NASA Astrophysics Data System (ADS)

Švorčík, V.; Chaloupka, A.; Záruba, K.; Král, V.; Bláhová, O.; Macková, A.; Hnatowicz, V.

2009-08-01

Polyethylene (PE) was treated in Ar plasma discharge and then grafted from methanol solution of 1,2-ethanedithiol to enhance adhesion of gold nano-particles or sputtered gold layers. The modified PE samples were either immersed into freshly prepared colloid solution of Au nano-particles or covered by sputtered, 50 nm thick gold nano-layer. Properties of the plasma modified, dithiol grafted and gold coated PE were studied using XPS, UV-VIS, AFM, EPR, RBS methods and nanoindentation. It was shown that the plasma treatment results in degradation of polymer chain, creation of excessive free radicals and conjugated double bonds. After grafting with 1,2-ethanedithiol the concentration of free radicals declined but the concentration of double bonds remained unchanged. Plasma treatment changes PE surface morphology and increases surface roughness too. Another significant change in the surface morphology and roughness was observed after deposition of Au nano-particles. The presence of Au on the sample surface after the coating with Au nano-particles was proved by XPS and RBS methods. Nanoindentation measurements shown that the grafting of plasma activated PE surface with dithiol increases significantly adhesion of sputtered Au nano-layer.

Optical polarimetry: Instrumentation and applications; Proceedings of the Seminar, San Diego, Calif., August 23, 24, 1977

NASA Technical Reports Server (NTRS)

Azzam, R. M. A. (Editor); Coffeen, D. L.

1977-01-01

Instrumentation used in optical polarimetry is discussed with reference to high-resolution spectropolarimetry, an orbiter cloud photopolarimeter, X-ray polarimeters, and the design of a self-nulling ellipsometer. Consideration is given to surface and thin-film ellipsometry noting studies of electrochemical surface layers, surface anisotropy, polish layers on infrared window materials, and anodic films. Papers on biological, chemical, and physical polarimetry are presented including birefringence in biological materials, vibrational optical activity, and the optical determination of the thermodynamic phase diagram of a metamagnet. Remote sensing is discussed in terms of polarization imagery, the optical polarimetry of particulate surfaces, and techniques and applications of elliptical polarimetry in astronomy and atmospheric studies.

Apparatus for externally controlled closed-loop feedback digital epitaxy

DOEpatents

Eres, D.; Sharp, J.W.

1996-07-30

A method and apparatus for digital epitaxy are disclosed. The apparatus includes a pulsed gas delivery assembly that supplies gaseous material to a substrate to form an adsorption layer of the gaseous material on the substrate. Structure is provided for measuring the isothermal desorption spectrum of the growth surface to monitor the active sites which are available for adsorption. The vacuum chamber housing the substrate facilitates evacuation of the gaseous material from the area adjacent the substrate following exposure. In use, digital epitaxy is achieved by exposing a substrate to a pulse of gaseous material to form an adsorption layer of the material on the substrate. The active sites on the substrate are monitored during the formation of the adsorption layer to determine if all the active sites have been filled. Once the active sites have been filled on the growth surface of the substrate, the pulse of gaseous material is terminated. The unreacted portion of the gas pulse is evacuated by continuous pumping. Subsequently, a second pulse is applied when availability of active sites is determined by studying the isothermal desorption spectrum. These steps are repeated until a thin film of sufficient thickness is produced. 5 figs.

Apparatus for externally controlled closed-loop feedback digital epitaxy

DOEpatents

Eres, Djula; Sharp, Jeffrey W.

1996-01-01

A method and apparatus for digital epitaxy. The apparatus includes a pulsed gas delivery assembly that supplies gaseous material to a substrate to form an adsorption layer of the gaseous material on the substrate. Structure is provided for measuring the isothermal desorption spectrum of the growth surface to monitor the active sites which are available for adsorption. The vacuum chamber housing the substrate facilitates evacuation of the gaseous material from the area adjacent the substrate following exposure. In use, digital epitaxy is achieved by exposing a substrate to a pulse of gaseous material to form an adsorption layer of the material on the substrate. The active sites on the substrate are monitored during the formation of the adsorption layer to determine if all the active sites have been filled. Once the active sites have been filled on the growth surface of the substrate, the pulse of gaseous material is terminated. The unreacted portion of the gas pulse is evacuated by continuous pumping. Subsequently, a second pulse is applied when availability of active sites is determined by studying the isothermal desorption spectrum. These steps are repeated until a thin film of sufficient thickness is produced.

Method of digital epitaxy by externally controlled closed-loop feedback

DOEpatents

Eres, D.; Sharp, J.W.

1994-07-19

A method and apparatus for digital epitaxy are disclosed. The apparatus includes a pulsed gas delivery assembly that supplies gaseous material to a substrate to form an adsorption layer of the gaseous material on the substrate. Structure is provided for measuring the isothermal desorption spectrum of the growth surface to monitor the active sites which are available for adsorption. The vacuum chamber housing the substrate facilitates evacuation of the gaseous material from the area adjacent the substrate following exposure. In use, digital epitaxy is achieved by exposing a substrate to a pulse of gaseous material to form an adsorption layer of the material on the substrate. The active sites on the substrate are monitored during the formation of the adsorption layer to determine if all the active sites have been filled. Once the active sites have been filled on the growth surface of the substrate, the pulse of gaseous material is terminated. The unreacted portion of the gas pulse is evacuated by continuous pumping. Subsequently, a second pulse is applied when availability of active sites is determined by studying the isothermal desorption spectrum. These steps are repeated until a thin film of sufficient thickness is produced. 4 figs.

Method of digital epilaxy by externally controlled closed-loop feedback

DOEpatents

Eres, Djula; Sharp, Jeffrey W.

1994-01-01

A method and apparatus for digital epitaxy. The apparatus includes a pulsed gas delivery assembly that supplies gaseous material to a substrate to form an adsorption layer of the gaseous material on the substrate. Structure is provided for measuring the isothermal desorption spectrum of the growth surface to monitor the active sites which are available for adsorption. The vacuum chamber housing the substrate facilitates evacuation of the gaseous material from the area adjacent the substrate following exposure. In use, digital epitaxy is achieved by exposing a substrate to a pulse of gaseous material to form an adsorption layer of the material on the substrate. The active sites on the substrate are monitored during the formation of the adsorption layer to determine if all the active sites have been filled. Once the active sites have been filled on the growth surface of the substrate, the pulse of gaseous material is terminated. The unreacted portion of the gas pulse is evacuated by continuous pumping. Subsequently, a second pulse is applied when availability of active sites is determined by studying the isothermal desorption spectrum. These steps are repeated until a thin film of sufficient thickness is produced.

Surface boundary layer turbulence in the Southern ocean

NASA Astrophysics Data System (ADS)

Merrifield, Sophia; St. Laurent, Louis; Owens, Breck; Naveira Garabato, Alberto

2015-04-01

Due to the remote location and harsh conditions, few direct measurements of turbulence have been collected in the Southern Ocean. This region experiences some of the strongest wind forcing of the global ocean, leading to large inertial energy input. While mixed layers are known to have a strong seasonality and reach 500m depth, the depth structure of near-surface turbulent dissipation and diffusivity have not been examined using direct measurements. We present data collected during the Diapycnal and Isopycnal Mixing Experiment in the Southern Ocean (DIMES) field program. In a range of wind conditions, the wave affected surface layer (WASL), where surface wave physics are actively forcing turbulence, is contained to the upper 15-20m. The lag-correlation between wind stress and turbulence shows a strong relationship up to 6 hours (˜1/2 inertial period), with the winds leading the oceanic turbulent response, in the depth range between 20-50m. We find the following characterize the data: i) Profiles that have a well-defined hydrographic mixed layer show that dissipation decays in the mixed layer inversely with depth, ii) WASLs are typically 15 meters deep and 30% of mixed layer depth, iii) Subject to strong winds, the value of dissipation as a function of depth is significantly lower than predicted by theory. Many dynamical processes are known to be missing from upper-ocean parameterizations of mixing in global models. These include surface-wave driven processes such as Langmuir turbulence, submesocale frontal processes, and nonlocal representations of mixing. Using velocity, hydrographic, and turbulence measurements, the existence of coherent structures in the boundary layer are investigated.

Atomic force microscopy studies of homoepitaxial GaN layers grown on GaN template by laser MBE

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

Choudhary, B. S.; Rajasthan Technical University, Rawatbhata Road, Kota 324010; Singh, A.

We have grown homoepitaxial GaN films on metal organic chemical vapor deposition (MOCVD) grown 3.5 µm thick GaN on sapphire (0001) substrate (GaN template) using an ultra-high vacuum (UHV) laser assisted molecular beam epitaxy (LMBE) system. The GaN films were grown by laser ablating a polycrystalline solid GaN target in the presence of active r.f. nitrogen plasma. The influence of laser repetition rates (10-30 Hz) on the surface morphology of homoepitaxial GaN layers have been studied using atomic force microscopy. It was found that GaN layer grown at 10 Hz shows a smooth surface with uniform grain size compared to the rough surfacemore » with irregular shape grains obtained at 30 Hz. The variation of surface roughness of the homoepitaxial GaN layer with and without wet chemical etching has been also studied and it was observed that the roughness of the film decreased after wet etching due to the curved structure/rough surface.« less

Surface engineering of nanoparticles in suspension for particle based bio-sensing

PubMed Central

Sen, Tapas; Bruce, Ian J.

2012-01-01

Surface activation of nanoparticles in suspension using amino organosilane has been carried out via strict control of a particle surface ad-layer of water using a simple but efficient protocol ‘Tri-phasic Reverse Emulsion’ (TPRE). This approach produced thin and ordered layers of particle surface functional groups which allowed the efficient conjugation of biomolecules. When used in bio-sensing applications, the resultant conjugates were highly efficient in the hybrid capture of complementary oligonucleotides and the detection of food borne microorganism. TPRE overcomes a number of fundamental problems associated with the surface modification of particles in aqueous suspension viz. particle aggregation, density and organization of resultant surface functional groups by controlling surface condensation of the aminosilane. The approach has potential for application in areas as diverse as nanomedicine, to food technology and industrial catalysis. PMID:22872809

Effects of surface chemical properties of activated carbon modified by amino-fluorination for electric double-layer capacitor.

PubMed

Jung, Min-Jung; Jeong, Euigyung; Cho, Seho; Yeo, Sang Young; Lee, Young-Seak

2012-09-01

The surface of phenol-based activated carbon (AC) was seriatim amino-fluorinated with solution of ammonium hydroxide and hydrofluoric acid in varying ratio to fabricate electrode materials for use in an electric double-layer capacitor (EDLC). The specific capacitance of the amino-fluorinated AC-based EDLC was measured in a 1 M H(2)SO(4) electrolyte, in which it was observed that the specific capacitances increased from 215 to 389 Fg(-1) and 119 and 250 Fg(-1) with the current densities of 0.1 and 1.0 Ag(-1), respectively, in comparison with those of an untreated AC-based EDLC when the amino-fluorination was optimized via seriatim mixed solution of 7.43 mol L(-1) ammonium hydroxide and 2.06 mol L(-1) hydrofluoric acid. This enhancement of capacitance was attributed to the synergistic effects of an increased electrochemical activity due to the formation of surface N- and F-functional groups and increased, specific surface area, and mesopore volumes, all of which resulted from the amino-fluorination of the electrode material. Copyright © 2012 Elsevier Inc. All rights reserved.

Novel fabrication method for 3D microstructures using surface-activated bonding and its application to micro-mechanical parts

NASA Astrophysics Data System (ADS)

Yamada, Takayuki; Takahashi, Mutsuya; Ozawa, Takashi; Tawara, Satoshi; Goto, Takayuki

2002-11-01

The purpose of this work is to demonstrate that a novel fabrication method for 3-D microstructures (FORMULA) is applicable to fabrication of micro mechanical parts with a large flexibility. This method is a kind of layer manufacturing method of thin films for metallic or dielectric microstructures using surface-activated bonding (SAB). The bonding interfaces of thin films are investigated by transmission electron microscope (TEM). Voids were observed at the interfaces of both pure aluminum films and Al-Cu alloy films. The ratio of void on the Al-Cu/Al-Cu interface is much larger than that of Al/Al interface, although the films have the same surface roughness of 3nm in Ra (average roughness). And approximately 10nm-thick amorphous intermediate layers were found at the interfaces. Furthermore, we have fabricated a micro gear of 900μm in diameter and 200μm in height, which is about ten times as large as our previous test pieces. Overhung structures such as a bridge structure and a cantilever were also fabricated without supporting layers beneath them.

Energetic basis of catalytic activity of layered nanophase calcium manganese oxides for water oxidation

PubMed Central

Birkner, Nancy; Nayeri, Sara; Pashaei, Babak; Najafpour, Mohammad Mahdi; Casey, William H.; Navrotsky, Alexandra

2013-01-01

Previous measurements show that calcium manganese oxide nanoparticles are better water oxidation catalysts than binary manganese oxides (Mn3O4, Mn2O3, and MnO2). The probable reasons for such enhancement involve a combination of factors: The calcium manganese oxide materials have a layered structure with considerable thermodynamic stability and a high surface area, their low surface energy suggests relatively loose binding of H2O on the internal and external surfaces, and they possess mixed-valent manganese with internal oxidation enthalpy independent of the Mn3+/Mn4+ ratio and much smaller in magnitude than the Mn2O3-MnO2 couple. These factors enhance catalytic ability by providing easy access for solutes and water to active sites and facile electron transfer between manganese in different oxidation states. PMID:23667149

Energetic basis of catalytic activity of layered nanophase calcium manganese oxides for water oxidation.

PubMed

Birkner, Nancy; Nayeri, Sara; Pashaei, Babak; Najafpour, Mohammad Mahdi; Casey, William H; Navrotsky, Alexandra

2013-05-28

Previous measurements show that calcium manganese oxide nanoparticles are better water oxidation catalysts than binary manganese oxides (Mn3O4, Mn2O3, and MnO2). The probable reasons for such enhancement involve a combination of factors: The calcium manganese oxide materials have a layered structure with considerable thermodynamic stability and a high surface area, their low surface energy suggests relatively loose binding of H2O on the internal and external surfaces, and they possess mixed-valent manganese with internal oxidation enthalpy independent of the Mn(3+)/Mn(4+) ratio and much smaller in magnitude than the Mn2O3-MnO2 couple. These factors enhance catalytic ability by providing easy access for solutes and water to active sites and facile electron transfer between manganese in different oxidation states.

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

Han, Yong; Axnanda, Stephanus; Crumlin, Ethan J.

Some rcent advances of ambient pressure X-ray photoelectron spectroscopy (AP-XPS) have enabled the chemical composition and the electrical potential profile at a liquid/electrode interface under electrochemical reaction conditions to be directly probed. In this work, we apply this operando technique to study the surface chemical composition evolution on a Co metal electrode in 0.1 M KOH aqueous solution under various electrical biases. It is found that an ~12.2 nm-thick layer of Co(OH) 2 forms at a potential of about -0.4 V Ag/AgCl, and upon increasing the anodic potential to about +0.4 V Ag/AgCl, this layer is partially oxidized into cobaltmore » oxyhydroxide (CoOOH). A CoOOH/Co(OH) 2 mixture layer is formed on the top of the electrode surface. Finally, the oxidized surface layer can be reduced to Co0 at a cathodic potential of -1.35 VAg/Cl. Our observations indicate that the ultrathin layer containing cobalt oxyhydroxide is the active phase for oxygen evolution reaction (OER) on a Co electrode in an alkaline electrolyte, consistent with previous studies.« less

Influence of patterning the TCO layer on the series resistance of thin film HIT solar cells

NASA Astrophysics Data System (ADS)

Champory, Romain; Mandorlo, Fabien; Seassal, Christian; Fave, Alain

2017-01-01

Thin HIT solar cells combine efficient surface passivation and high open circuit voltage leading to high conversion efficiencies. They require a TCO layer in order to ease carriers transfer to the top surface fingers. This Transparent Conductive Oxide layer induces parasitic absorption in the low wavelength range of the solar spectrum that limits the maximum short circuit current. In case of thin film HIT solar cells, the front surface is patterned in order to increase the effective life time of photons in the active material, and the TCO layer is often deposited with a conformal way leading to additional material on the sidewalls of the patterns. In this article, we propose an alternative scheme with a local etching of both the TCO and the front a-Si:H layers in order to reduce the parasitic absorption. We study how the local resistivity of the TCO evolves as a function of the patterns, and demonstrate how the increase of the series resistance can be compensated in order to increase the conversion efficiency.

Cwp84, a Clostridium difficile cysteine protease, exhibits conformational flexibility in the absence of its propeptide

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

Bradshaw, William J.; Public Health England, Porton Down, Salisbury SP4 0JG; Roberts, April K.

2015-02-19

Two structures of Cwp84, a cysteine protease from the S-layer of C. difficile, are presented after propeptide cleavage. They reveal the movement of three loops, two in the active-site groove and one on the surface of the lectin-like domain, exposing a hydrophobic pocket. In recent decades, the global healthcare problems caused by Clostridium difficile have increased at an alarming rate. A greater understanding of this antibiotic-resistant bacterium, particularly with respect to how it interacts with the host, is required for the development of novel strategies for fighting C. difficile infections. The surface layer (S-layer) of C. difficile is likely tomore » be of significant importance to host–pathogen interactions. The mature S-layer is formed by a proteinaceous array consisting of multiple copies of a high-molecular-weight and a low-molecular-weight S-layer protein. These components result from the cleavage of SlpA by Cwp84, a cysteine protease. The structure of a truncated Cwp84 active-site mutant has recently been reported and the key features have been identified, providing the first structural insights into the role of Cwp84 in the formation of the S-layer. Here, two structures of Cwp84 after propeptide cleavage are presented and the three conformational changes that are observed are discussed. These changes result in a reconfiguration of the active site and exposure of the hydrophobic pocket.« less

Stacked multilayers of alternating reduced graphene oxide and carbon nanotubes for planar supercapacitors

NASA Astrophysics Data System (ADS)

Moon, Geon Dae; Joo, Ji Bong; Yin, Yadong

2013-11-01

A simple layer-by-layer approach has been developed for constructing 2D planar supercapacitors of multi-stacked reduced graphene oxide and carbon nanotubes. This sandwiched 2D architecture enables the full utilization of the maximum active surface area of rGO nanosheets by using a CNT layer as a porous physical spacer to enhance the permeation of a gel electrolyte inside the structure and reduce the agglomeration of rGO nanosheets along the vertical direction. As a result, the stacked multilayers of rGO and CNTs are capable of offering higher output voltage and current production.A simple layer-by-layer approach has been developed for constructing 2D planar supercapacitors of multi-stacked reduced graphene oxide and carbon nanotubes. This sandwiched 2D architecture enables the full utilization of the maximum active surface area of rGO nanosheets by using a CNT layer as a porous physical spacer to enhance the permeation of a gel electrolyte inside the structure and reduce the agglomeration of rGO nanosheets along the vertical direction. As a result, the stacked multilayers of rGO and CNTs are capable of offering higher output voltage and current production. Electronic supplementary information (ESI) available: Experimental details, SEM and TEM images and additional electrochemical data. See DOI: 10.1039/c3nr04339h

Thermal stability and specular reflection behaviour of CoNbZr-based bottom spin valves with nano-oxide layer

NASA Astrophysics Data System (ADS)

Kim, Jong Soo; Lee, Seong-Rae

2004-06-01

The thermal stability and specularity aspects of a CoNbZr-based bottom spin valve (SV) employing a nano-oxide layer (NOL) were investigated. The magnetoresistance (MR) ratio of the as-deposited CoNbZr-based bottom SV increased by 62% (from 6.3 to 10.2%) with incorporation of the NOL. The enhancement of the MR ratio was considered to be due to the specular effect ( increased from 0.722 to 1.363 cm) of the NOL. The MR ratio of a Ta-based bottom SV decreased by about 45% (from 6.9 to 3.8%) when the samples were annealed at 300 °C for 240 min. By contrast, the MR ratio of the CoNbZr-based bottom SV with NOL increase d by 14 % (from 10.2 to 11.7%). The root mean square roughness value of the CoNbZr layer (0.07 nm) was superior to that of the Ta layer (0.43 nm). Although Mn in IrMn diffused out to the surface through the active layers resulting in the formation of Mn oxide at the surface in the CoNbZr-based bottom SV, no trace of Mn was found in the active layers and no significant degradation occurred.

Controlling the morphology and performance of FO membrane via adjusting the atmosphere humidity during casting procedure

NASA Astrophysics Data System (ADS)

Zuo, Hao-Ran; Cao, Gui-Ping; Wang, Meng; Zhang, Huan-Huan; Song, Chen-Chen; Fang, Xu; Wang, Tao

2018-03-01

Forward osmosis (FO) has received great interest for its considerable potential in a wide range of fields. In this work, the morphology and performance of FO membrane were regulated by adjusting the atmosphere humidity (HC) of casting procedure. The polysulfone support layer was casted under various atmosphere humidity levels ranging from 40% to 80%. By multi-techniques such as SEM, AFM, and XPS, it was proved that the atmosphere humidity had modified the surface morphology and thickness of the skin layer in support layer, which contributed up to 90% of the structure parameter, resulting in distinct morphology, thickness, and cross-linking degree of active layer. The active layer with sparse bead-like wrinkles on the smooth surface of support layer casted at HC = 65% showed the highest water permeability [26.9 (L/m2 h MPa)] and considerable low salt permeability [0.0390 (L/m2 h)]. It was found that the water flux of FO-65 was 27% and 46% higher than that of FO-80 in AL-DS and AL-FS mode, respectively, and the salt rejection was as high as 98%. Our work highlighted the importance of considering the effect of atmosphere humidity during casting when design an FO membrane for appropriate performance.

Solar cell modules with improved backskin and methods for forming same

DOEpatents

Hanoka, Jack I.

1998-04-21

A laminated solar cell module with a backskin layer that reduces the materials and labor required during the manufacturing process. The solar cell module includes a rigid front support layer formed of light transmitting material having first and second surfaces. A transparent encapsulant layer has a first surface disposed adjacent the second surface of the front support layer. A plurality of interconnected solar cells have a first surface disposed adjacent a second surface of the transparent encapsulant layer. The backskin layer is formed of a thermoplastic olefin, which includes first ionomer, a second ionomer, glass fiber, and carbon black. A first surface of the backskin layer is disposed adjacent a second surface of the interconnected solar cells. The transparent encapsulant layer and the backskin layer, in combination, encapsulate the interconnected solar cells. An end portion of the backskin layer can be wrapped around the edge of the module for contacting the first surface of the front support layer to form an edge seal. A laminated solar cell module with a backskin layer that reduces the materials and labor required during the manufacturing process. The solar cell module includes a rigid front support layer formed of light transmitting material having first and second surfaces. A transparent encapsulant layer has a first surface disposed adjacent the second surface of the front support layer. A plurality of interconnected solar cells have a first surface disposed adjacent a second surface of the transparent encapsulant layer. The backskin layer is formed of a thermoplastic olefin, which includes first ionomer, a second ionomer, glass fiber, and carbon black. A first surface of the backskin layer is disposed adjacent a second surface of the interconnected solar cells. The transparent encapsulant layer and the backskin layer, in combination, encapsulate the interconnected solar cells. An end portion of the backskin layer can be wrapped around the edge of the module for contacting the first surface of the front support layer to form an edge seal.

Sustained drag reduction in a turbulent flow using a low-temperature Leidenfrost surface

PubMed Central

Saranadhi, Dhananjai; Chen, Dayong; Kleingartner, Justin A.; Srinivasan, Siddarth; Cohen, Robert E.; McKinley, Gareth H.

2016-01-01

Skin friction drag contributes a major portion of the total drag for small and large water vehicles at high Reynolds number (Re). One emerging approach to reducing drag is to use superhydrophobic surfaces to promote slip boundary conditions. However, the air layer or “plastron” trapped on submerged superhydrophobic surfaces often diminishes quickly under hydrostatic pressure and/or turbulent pressure fluctuations. We use active heating on a superhydrophobic surface to establish a stable vapor layer or “Leidenfrost” state at a relatively low superheat temperature. The continuous film of water vapor lubricates the interface, and the resulting slip boundary condition leads to skin friction drag reduction on the inner rotor of a custom Taylor-Couette apparatus. We find that skin friction can be reduced by 80 to 90% relative to an unheated superhydrophobic surface for Re in the range 26,100 ≤ Re ≤ 52,000. We derive a boundary layer and slip theory to describe the hydrodynamics in the system and show that the plastron thickness is h = 44 ± 11 μm, in agreement with expectations for a Leidenfrost surface. PMID:27757417

Comparison of positive-pressure, passive ultrasonic, and laser-activated irrigations on smear-layer removal from the root canal surface.

PubMed

Sahar-Helft, Sharonit; Sarp, Ayşe Sena Kabaş; Stabholtz, Adam; Gutkin, Vitaly; Redenski, Idan; Steinberg, Doron

2015-03-01

The purpose of this study was to compare the efficacy of three irrigation techniques for smear-layer removal with 17% EDTA. Cleaning and shaping the root canal system during endodontic treatment produces a smear layer and hard tissue debris. Three irrigation techniques were tested for solution infiltration of this layer: positive-pressure irrigation, passive ultrasonic irrigation, and laser-activated irrigation. Sixty extracted teeth were divided into six equal groups; 17% EDTA was used for 60 sec irrigation of five of the groups. The groups were as follows: Group 1, treated only with ProTaper™ F3 Ni-Ti files; Group 2, positive-pressure irrigation, with a syringe; Group 3, passive ultrasonic irrigation, inserted 1 mm short of the working length; Group 4, passive ultrasonic irrigation, inserted in the upper coronal third of the root; Group 5, Er:YAG laser-activated irrigation, inserted 1 mm short of the working length; and Group 6, Er:YAG laser-activated irrigation, inserted in the upper coronal third of the root. Scanning electron microscopy showed that the smear layer is removed most efficiently using laser-activated irrigation at low energy with 17% EDTA, inserted either at the working length or only in the coronal upper third of the root. Amounts of Ca, P, and O were not significantly different on all treated dentin surfaces. Smear-layer removal was most effective when the root canals were irrigated using Er:YAG laser at low energy with 17% EDTA solution. Interestingly, removal of the smear layer along the entire canal was similar when the laser was inserted in the upper coronal third and at 1 mm short of the working length of the root canal. This effect was not observed with the ultrasonic and positive-pressure techniques.

Surface morphology and interdiffusion of LiF in Alq3-based organic light-emitting devices.

PubMed

Lee, Young Joo; Li, Xiaolong; Kang, Da-Yeon; Park, Seong-Sik; Kim, Jinwoo; Choi, Jeong-Woo; Kim, Hyunjung

2008-09-01

Highly efficient organic light-emitting devices (OLEDs) have been realized by insertion of a thin insulating lithium fluoride (LiF) layer between aluminum (Al) cathode and an electron transport layer, tris-(8-hydroxyquinoline) aluminum (Alq(3)). In this paper, we study the surface morphology of LiF on Alq(3) by synchrotron X-ray scattering and atomic force microscopy (AFM) as a function of thickness of LiF. We also study the interdiffusion of LiF into Al cathode as well as into Alq(3) layer as a function of temperature. Initially, LiF molecules are distributed randomly as clusters on the Alq(3) layer and then gradually form a layer as increasing LiF thickness. The interdiffusion of LiF into Al occurs more actively than into Alq(3) in annealing process. LiF on Alq(3) induces the ordering of Al to (111) direction strongly with increasing LiF thickness.

PLIF Visualization of Active Control of Hypersonic Boundary Layers Using Blowing

NASA Technical Reports Server (NTRS)

Bathel, Brett F.; Danehy, Paul M.; Inman, Jennifer A.; Alderfer, David W.; Berry, Scott A.

2008-01-01

Planar laser-induced fluorescence (PLIF) imaging was used to visualize the boundary layer flow on a 1/3-scale Hyper-X forebody model. The boundary layer was perturbed by blowing out of orifices normal to the model surface. Two blowing orifice configurations were used: a spanwise row of 17-holes spaced at 1/8 inch, with diameters of 0.020 inches and a single-hole orifice with a diameter of 0.010 inches. The purpose of the study was to visualize and identify laminar and turbulent structures in the boundary layer and to make comparisons with previous phosphor thermography measurements of surface heating. Jet penetration and its influence on the boundary layer development was also examined as was the effect of a compression corner on downstream boundary layer transition. Based upon the acquired PLIF images, it was determined that global surface heating measurements obtained using the phosphor thermography technique provide an incomplete indicator of transitional and turbulent behavior of the corresponding boundary layer flow. Additionally, the PLIF images show a significant contribution towards transition from instabilities originating from the underexpanded jets. For this experiment, a nitric oxide/nitrogen mixture was seeded through the orifices, with nitric oxide (NO) serving as the fluorescing gas. The experiment was performed in the 31-inch Mach 10 Air Tunnel at NASA Langley Research Center.

Composite oxygen transport membrane

DOEpatents

Lu, Zigui; Plonczak, Pawel J.; Lane, Jonathan A.

2016-11-08

A method is described 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. Preferred materials are (La.sub.0.8Sr.sub.0.2).sub.0.95Cr.sub.0.7Fe.sub.0.3O.sub.3-.delta. for the porous fuel oxidation layer, (La.sub.0.8Sr.sub.0.2).sub.0.95Cr.sub.0.5Fe.sub.0.5O.sub.3-.delta. for the dense separation layer, and (La.sub.0.8Sr.sub.0.2).sub.0.95Cr.sub.0.3Fe.sub.0.7O.sub.3-.delta. for the porous surface exchange layer. Firing the said fuel activation and separation layers in nitrogen atmosphere unexpectedly allows the separation layer to sinter into a fully densified mass.

S-layer proteins from Lactobacillus sp. inhibit bacterial infection by blockage of DC-SIGN cell receptor.

PubMed

Prado Acosta, Mariano; Ruzal, Sandra M; Cordo, Sandra M

2016-11-01

Many species of Lactobacillus sp. possess Surface(s) layer proteins in their envelope. Among other important characteristics S-layer from Lactobacillus acidophilus binds to the cellular receptor DC-SIGN (Dendritic Cell-Specific Intercellular adhesion molecule-3-Grabbing Non-integrin; CD209), which is involved in adhesion and infection of several families of bacteria. In this report we investigate the activity of new S-layer proteins from the Lactobacillus family (Lactobacillus acidophilus, Lactobacillus brevis, Lactobacillus helveticus and Lactobacillus kefiri) over the infection of representative microorganisms important to human health. After the treatment of DC-SIGN expressing cells with these proteins, we were able to diminish bacterial infection by up to 79% in both gram negative and mycobacterial models. We discovered that pre-treatment of the bacteria with S-layers from Lactobacillus acidophilus and Lactobacillus brevis reduced bacteria viability but also prevent infection by the pathogenic bacteria. We also proved the importance of the glycosylation of the S-layer from Lactobacillus kefiri in the binding to the receptor and thus inhibition of infection. This novel characteristic of the S-layers proteins may contribute to the already reported pathogen exclusion activity for these Lactobacillus probiotic strains; and might be also considered as a novel enzymatic antimicrobial agents to inhibit bacterial infection and entry to host cells. Copyright © 2016 Elsevier B.V. All rights reserved.

Broadband light-emitting diode

DOEpatents

Fritz, Ian J.; Klem, John F.; Hafich, Michael J.

1998-01-01

A broadband light-emitting diode. The broadband light-emitting diode (LED) comprises a plurality of III-V compound semiconductor layers grown on a semiconductor substrate, with the semiconductor layers including a pair of cladding layers sandwiched about a strained-quantum-well active region having a plurality of different energy bandgaps for generating light in a wavelength range of about 1.3-2 .mu.m. In one embodiment of the present invention, the active region may comprise a first-grown quantum-well layer and a last-grown quantum-well layer that are oppositely strained; whereas in another embodiment of the invention, the active region is formed from a short-period superlattice structure (i.e. a pseudo alloy) comprising alternating thin layers of InGaAs and InGaAlAs. The use a short-period superlattice structure for the active region allows different layers within the active region to be simply and accurately grown by repetitively opening and closing one or more shutters in an MBE growth apparatus to repetitively switch between different growth states therein. The broadband LED may be formed as either a surface-emitting LED or as an edge-emitting LED for use in applications such as chemical sensing, fiber optic gyroscopes, wavelength-division-multiplexed (WDM) fiber-optic data links, and WDM fiber-optic sensor networks for automobiles and aircraft.

Broadband light-emitting diode

DOEpatents

Fritz, I.J.; Klem, J.F.; Hafich, M.J.

1998-07-14

A broadband light-emitting diode is disclosed. The broadband light-emitting diode (LED) comprises a plurality of III-V compound semiconductor layers grown on a semiconductor substrate, with the semiconductor layers including a pair of cladding layers sandwiched about a strained-quantum-well active region having a plurality of different energy bandgaps for generating light in a wavelength range of about 1.3--2 {micro}m. In one embodiment of the present invention, the active region may comprise a first-grown quantum-well layer and a last-grown quantum-well layer that are oppositely strained; whereas in another embodiment of the invention, the active region is formed from a short-period superlattice structure (i.e. a pseudo alloy) comprising alternating thin layers of InGaAs and InGaAlAs. The use a short-period superlattice structure for the active region allows different layers within the active region to be simply and accurately grown by repetitively opening and closing one or more shutters in an MBE growth apparatus to repetitively switch between different growth states therein. The broadband LED may be formed as either a surface-emitting LED or as an edge-emitting LED for use in applications such as chemical sensing, fiber optic gyroscopes, wavelength-divisionmultiplexed (WDM) fiber-optic data links, and WDM fiber-optic sensor networks for automobiles and aircraft. 10 figs.

Automated assessment of the remineralization of artificial enamel lesions with polarization-sensitive optical coherence tomography

PubMed Central

Lee, Robert C.; Kang, Hobin; Darling, Cynthia L.; Fried, Daniel

2014-01-01

Accurate measurement of the highly mineralized transparent surface layer that forms on caries lesions is important for diagnosis of the lesion activity because chemical intervention can slow or reverse the caries process via remineralization. Previous in-vitro and in-vivo studies have demonstrated that polarization-sensitive optical coherence tomography (PS-OCT) can nondestructively image the subsurface lesion structure and the highly mineralized transparent surface zone of caries lesions. The purpose of this study was to develop an approach to automatically process 3-dimensional PS-OCT images and to accurately assess the remineralization process in simulated enamel lesions. Artificial enamel lesions were prepared on twenty bovine enamel blocks using two models to produce varying degree of demineralization and remineralization. The thickness of the transparent surface layer and the integrated reflectivity of the subsurface lesion were measured using PS-OCT. The automated transparent surface layer detection algorithm was able to successfully detect the transparent surface layers with high sensitivity ( = 0.92) and high specificity ( = 0.97). The estimated thickness of the transparent surface layer showed a strong correlation with polarized light microscopy (PLM) measurements of all regions (R2 = 0.90). The integrated reflectivity, ΔR, and the integrated mineral loss, ΔZ, showed a moderate correlation (R2 = 0.32). This study demonstrates that PS-OCT can automatically measure the changes in artificial enamel lesion structure and severity upon exposure to remineralization solutions. PMID:25401009

Zirconium oxide surface passivation of crystalline silicon

NASA Astrophysics Data System (ADS)

Wan, Yimao; Bullock, James; Hettick, Mark; Xu, Zhaoran; Yan, Di; Peng, Jun; Javey, Ali; Cuevas, Andres

2018-05-01

This letter reports effective passivation of crystalline silicon (c-Si) surfaces by thermal atomic layer deposited zirconium oxide (ZrOx). The optimum layer thickness and activation annealing conditions are determined to be 20 nm and 300 °C for 20 min. Cross-sectional transmission electron microscopy imaging shows an approximately 1.6 nm thick SiOx interfacial layer underneath an 18 nm ZrOx layer, consistent with ellipsometry measurements (˜20 nm). Capacitance-voltage measurements show that the annealed ZrOx film features a low interface defect density of 1.0 × 1011 cm-2 eV-1 and a low negative film charge density of -6 × 1010 cm-2. Effective lifetimes of 673 μs and 1.1 ms are achieved on p-type and n-type 1 Ω cm undiffused c-Si wafers, respectively, corresponding to an implied open circuit voltage above 720 mV in both cases. The results demonstrate that surface passivation quality provided by ALD ZrOx is consistent with the requirements of high efficiency silicon solar cells.

Durability of Anti-Infective Effect of Long-Term Silicone Sheath Catheters Impregnated with Antimicrobial Agents

PubMed Central

Tcholakian, Robert K.; Raad, Issam I.

2001-01-01

This study was performed to test the long-term antimicrobial efficacy of impregnated silicone catheters comprising an antimicrobial layer sandwiched between an external surface sheath and a luminal surface silicone sheath. The design of the catheter permits the introduction of various antimicrobials in addition to anticoagulants or antifibrins in the antimicrobial layer and allows their gradual release over a period of months after insertion. The in vitro data presented show that the catheter can provide antimicrobial activity for 90 days, after being replated for 15 7-day cycles of replating. When the catheters were immersed in human serum and incubated at 37°C, they demonstrated significant antimicrobial activity after more than 325 days of incubation. The significant long-term in vitro antimicrobial activity observed may imply effective in vivo activity for almost 1 year after insertion and could serve as a cost-effective alternative to surgically implantable silicone catheters. PMID:11408213

Tunnel barrier schottky

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

Chu, Rongming; Cao, Yu; Li, Zijian

2018-02-20

A diode includes: a semiconductor substrate; a cathode metal layer contacting a bottom of the substrate; a semiconductor drift layer on the substrate; a graded aluminum gallium nitride (AlGaN) semiconductor barrier layer on the drift layer and having a larger bandgap than the drift layer, the barrier layer having a top surface and a bottom surface between the drift layer and the top surface, the barrier layer having an increasing aluminum composition from the bottom surface to the top surface; and an anode metal layer directly contacting the top surface of the barrier layer.

Isolating the effect of pore size distribution on electrochemical double-layer capacitance using activated fluid coke

NASA Astrophysics Data System (ADS)

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

2015-12-01

Electrochemical double-layer capacitors (EDLCs) use physical ion adsorption in the capacitive electrical double layer of high specific surface area (SSA) materials to store electrical energy. Previous work shows that the SSA-normalized capacitance increases when pore diameters are less than 1 nm. However, there still remains uncertainty about the charge storage mechanism since the enhanced SSA-normalized capacitance is not observed in all microporous materials. In previous studies, the total specific surface area and the chemical composition of the electrode materials were not controlled. The current work is the first reported study that systematically compares the performance of activated carbon prepared from the same raw material, with similar chemical composition and specific surface area, but different pore size distributions. Preparing samples with similar SSAs, but different pores sizes is not straightforward since increasing pore diameters results in decreasing the SSA. This study observes that the microporous activated carbon has a higher SSA-normalized capacitance, 14.1 μF cm-2, compared to the mesoporous material, 12.4 μF cm-2. However, this enhanced SSA-normalized capacitance is only observed above a threshold operating voltage. Therefore, it can be concluded that a minimum applied voltage is required to induce ion adsorption in these sub-nanometer micropores, which increases the capacitance.

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

PubMed Central

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

2015-01-01

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

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

PubMed

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

2015-10-20

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

The role of S(II) and Pb(II) in xanthate flotation of smithsonite: Surface properties and mechanism

NASA Astrophysics Data System (ADS)

Jia, Kai; Feng, Qiming; Zhang, Guofan; Ji, Wanying; Zhang, Wukai; Yang, Bingqian

2018-06-01

Smithsonite is a readily dissolvable carbonate mineral that is naturally hydrophilic, making recovery of this ore by flotation difficult. The flotation results showed that conditioning with only sodium sulfide (Na2S) did not successfully allow the smithsonite samples to float, whereas treatment with a combination of S(II), Pb(II) and xanthate (with Na2S as the sulfurizing reagent, lead ions (Pb(II)) as the activator, and xanthate as the collector) improved the flotation of smithsonite, achieving a mass recovery of 95.8%. A combination of analytical techniques, including X-ray diffraction (XRD), atomic force microscopy (AFM) and X-ray photoelectron spectroscopy (XPS), in conjunction with depth profiling, was used to investigate the chemical nature of the sulfur and lead species on the smithsonite surface. For S(II)-conditioned smithsonite, a layer of ZnS formed on the smithsonite (ZnCO3) substrates; this newly formed ZnS coating was amorphous or poorly crystallized. For smithsonite samples conditioned with S(II) and Pb(II), the microstructures and the phase constituents, obtained by AFM and XRD analyses, confirmed the formation of the PbS species with a cubic galena structure on the surface. XPS depth profiling showed that the PbS layer was 18-nm thick, which corresponds to 30 PbS molecular layers. This study presents direct evidence that the coating of the activation product, PbS, on the smithsonite surface was similar to a relatively thick galena layer, which led to successful flotation.

Adhesion mapping of chemically modified and poly(ethylene oxide)-grafted glass surfaces.

PubMed

Jogikalmath, G; Stuart, J K; Pungor, A; Hlady, V

1999-08-01

Two-dimensional mapping of the adhesion pull-off forces was used to study the origin of surface heterogeneity in the grafted poly(ethylene oxide) (PEO) layer. The variance of the pull-off forces measured over the μm-sized regions after each chemical step of modifying glass surfaces was taken to be a measure of the surface chemical heterogeneity. The attachment of γ-glycidoxypropyltrimethoxy silane (GPS) to glass decreased the pull-off forces relative to the clean glass and made the surface more uniform. The subsequent hydrolysis of the terminal epoxide groups resulted in a larger surface heterogeneity which was modeled by two populations of the terminal hydroxyl groups, each with its own distribution of adhesion forces and force variance. The activation of the hydroxyls with carbonyldiimmidazole (CDI) healed the surface and lowered its adhesion, however, the force variance remained rather large. Finally, the grafting of the α,ω-diamino poly(ethyleneoxide) chains to the CDI-activated glass largely eliminated adhesion except at a few discrete regions. The adhesion on the PEO grafted layer followed the Poisson distribution of the pull-off forces. With the exception of the glass surface, a correlation between the water contact angles and the mean pull-off forces measured with the Si(3)N(4) tip surfaces was found for all modified glass surfaces.

AcmB Is an S-Layer-Associated β-N-Acetylglucosaminidase and Functional Autolysin in Lactobacillus acidophilus NCFM

PubMed Central

Johnson, Brant R.

2016-01-01

ABSTRACT Autolysins, also known as peptidoglycan hydrolases, are enzymes that hydrolyze specific bonds within bacterial cell wall peptidoglycan during cell division and daughter cell separation. Within the genome of Lactobacillus acidophilus NCFM, there are 11 genes encoding proteins with peptidoglycan hydrolase catalytic domains, 9 of which are predicted to be functional. Notably, 5 of the 9 putative autolysins in L. acidophilus NCFM are S-layer-associated proteins (SLAPs) noncovalently colocalized along with the surface (S)-layer at the cell surface. One of these SLAPs, AcmB, a β-N-acetylglucosaminidase encoded by the gene lba0176 (acmB), was selected for functional analysis. In silico analysis revealed that acmB orthologs are found exclusively in S-layer- forming species of Lactobacillus. Chromosomal deletion of acmB resulted in aberrant cell division, autolysis, and autoaggregation. Complementation of acmB in the ΔacmB mutant restored the wild-type phenotype, confirming the role of this SLAP in cell division. The absence of AcmB within the exoproteome had a pleiotropic effect on the extracellular proteins covalently and noncovalently bound to the peptidoglycan, which likely led to the observed decrease in the binding capacity of the ΔacmB strain for mucin and extracellular matrices fibronectin, laminin, and collagen in vitro. These data suggest a functional association between the S-layer and the multiple autolysins noncovalently colocalized at the cell surface of L. acidophilus NCFM and other S-layer-producing Lactobacillus species. IMPORTANCE Lactobacillus acidophilus is one of the most widely used probiotic microbes incorporated in many dairy foods and dietary supplements. This organism produces a surface (S)-layer, which is a self-assembling crystalline array found as the outermost layer of the cell wall. The S-layer, along with colocalized associated proteins, is an important mediator of probiotic activity through intestinal adhesion and modulation of the mucosal immune system. However, there is still a dearth of information regarding the basic cellular and evolutionary function of S-layers. Here, we demonstrate that multiple autolysins, responsible for breaking down the cell wall during cell division, are associated with the S-layer. Deletion of the gene encoding one of these S-layer-associated autolysins confirmed its autolytic role and resulted in reduced binding capacity to mucin and intestinal extracellular matrices. These data suggest a functional association between the S-layer and autolytic activity through the extracellular presentation of autolysins. PMID:27422832

AcmB Is an S-Layer-Associated β-N-Acetylglucosaminidase and Functional Autolysin in Lactobacillus acidophilus NCFM.

PubMed

Johnson, Brant R; Klaenhammer, Todd R

2016-09-15

Autolysins, also known as peptidoglycan hydrolases, are enzymes that hydrolyze specific bonds within bacterial cell wall peptidoglycan during cell division and daughter cell separation. Within the genome of Lactobacillus acidophilus NCFM, there are 11 genes encoding proteins with peptidoglycan hydrolase catalytic domains, 9 of which are predicted to be functional. Notably, 5 of the 9 putative autolysins in L. acidophilus NCFM are S-layer-associated proteins (SLAPs) noncovalently colocalized along with the surface (S)-layer at the cell surface. One of these SLAPs, AcmB, a β-N-acetylglucosaminidase encoded by the gene lba0176 (acmB), was selected for functional analysis. In silico analysis revealed that acmB orthologs are found exclusively in S-layer- forming species of Lactobacillus Chromosomal deletion of acmB resulted in aberrant cell division, autolysis, and autoaggregation. Complementation of acmB in the ΔacmB mutant restored the wild-type phenotype, confirming the role of this SLAP in cell division. The absence of AcmB within the exoproteome had a pleiotropic effect on the extracellular proteins covalently and noncovalently bound to the peptidoglycan, which likely led to the observed decrease in the binding capacity of the ΔacmB strain for mucin and extracellular matrices fibronectin, laminin, and collagen in vitro These data suggest a functional association between the S-layer and the multiple autolysins noncovalently colocalized at the cell surface of L. acidophilus NCFM and other S-layer-producing Lactobacillus species. Lactobacillus acidophilus is one of the most widely used probiotic microbes incorporated in many dairy foods and dietary supplements. This organism produces a surface (S)-layer, which is a self-assembling crystalline array found as the outermost layer of the cell wall. The S-layer, along with colocalized associated proteins, is an important mediator of probiotic activity through intestinal adhesion and modulation of the mucosal immune system. However, there is still a dearth of information regarding the basic cellular and evolutionary function of S-layers. Here, we demonstrate that multiple autolysins, responsible for breaking down the cell wall during cell division, are associated with the S-layer. Deletion of the gene encoding one of these S-layer-associated autolysins confirmed its autolytic role and resulted in reduced binding capacity to mucin and intestinal extracellular matrices. These data suggest a functional association between the S-layer and autolytic activity through the extracellular presentation of autolysins. Copyright © 2016 Johnson and Klaenhammer.

A highly active and stable IrO x/SrIrO 3 catalyst for the oxygen evolution reaction

DOE PAGES

Seitz, Linsey C.; Dickens, Colin F.; Nishio, Kazunori; ...

2016-09-02

Oxygen electrochemistry plays a key role in renewable energy technologies such as fuel cells and electrolyzers, but the slow kinetics of the oxygen evolution reaction (OER) limit the performance and commercialization of such devices. Here we report an iridium oxide/strontium iridium oxide (IrO x/SrIrO 3) catalyst formed during electrochemical testing by strontium leaching from surface layers of thin films of SrIrO 3. This catalyst has demonstrated specific activity at 10 milliamps per square centimeter of oxide catalyst (OER current normalized to catalyst surface area), with only 270 to 290 millivolts of overpotential for 30 hours of continuous testing in acidicmore » electrolyte. Here, density functional theory calculations suggest the formation of highly active surface layers during strontium leaching with IrO 3 or anatase IrO 2 motifs. The IrO x/SrIrO 3 catalyst outperforms known IrO x and ruthenium oxide (RuO x) systems, the only other OER catalysts that have reasonable activity in acidic electrolyte.« less

A highly active and stable IrOx/SrIrO3 catalyst for the oxygen evolution reaction.

PubMed

Seitz, Linsey C; Dickens, Colin F; Nishio, Kazunori; Hikita, Yasuyuki; Montoya, Joseph; Doyle, Andrew; Kirk, Charlotte; Vojvodic, Aleksandra; Hwang, Harold Y; Norskov, Jens K; Jaramillo, Thomas F

2016-09-02

Oxygen electrochemistry plays a key role in renewable energy technologies such as fuel cells and electrolyzers, but the slow kinetics of the oxygen evolution reaction (OER) limit the performance and commercialization of such devices. Here we report an iridium oxide/strontium iridium oxide (IrO x /SrIrO 3 ) catalyst formed during electrochemical testing by strontium leaching from surface layers of thin films of SrIrO 3 This catalyst has demonstrated specific activity at 10 milliamps per square centimeter of oxide catalyst (OER current normalized to catalyst surface area), with only 270 to 290 millivolts of overpotential for 30 hours of continuous testing in acidic electrolyte. Density functional theory calculations suggest the formation of highly active surface layers during strontium leaching with IrO 3 or anatase IrO 2 motifs. The IrO x /SrIrO 3 catalyst outperforms known IrO x and ruthenium oxide (RuO x ) systems, the only other OER catalysts that have reasonable activity in acidic electrolyte. Copyright © 2016, American Association for the Advancement of Science.

Titanium dioxide nanotubes functionalized with Cratylia mollis seed lectin, Cramoll, enhanced osteoblast-like cells adhesion and proliferation.

PubMed

Oliveira, Weslley F; Silva, Germana M M; Cabral Filho, Paulo E; Fontes, Adriana; Oliveira, Maria D L; Andrade, César A S; Silva, Márcia V; Coelho, Luana C B B; Machado, Giovanna; Correia, Maria T S

2018-09-01

An alternative to accelerate the osseointegration on titanium dioxide nanotubes (TNTs) used in osseointegrated implants is through the functionalization of these nanostructured surfaces with biomolecules. In this work, we immobilized a lectin with recognized mitogenic activity, the Cramoll lectin, extracted from Cratylia mollis seeds, on surfaces modified by TNTs. For the immobilization of Cramoll on TNTs surfaces, we used the Layer-by-Layer technique (LbL) by growing five alternate layers of poly(allylamine) hydrochloride (PAH) and poly(acrylic) acid (PAA); lastly we incubated the lectin, at different concentrations, with the TNTs-LbL. Before and after the immobilization procedures, the substrate surfaces were characterized by scanning electron microscopy (SEM), Fourier-transform infrared spectroscopy (FTIR), atomic force microscopy (AFM), and, electrochemical impedance spectroscopy (EIS). We also evaluated the Cramoll activity after immobilization on TNTs by using the lectin interaction with ovalbumin. The lectin did not lose its biological activity, even after immobilization onto nanotubular arrays. In addition, we observed an increase osteoblast-like cell adhesion on the TNTs-LbL-Cramoll system when compared to the bare TNTs surfaces. Moreover, a significative cell proliferation was identified on the substrates when Cramoll was immobilized at concentrations of 80, 160 and 320 μg/mL after 48 h of incubation by using the resazurin assay. Our results suggest that Cramoll was efficiently immobilized on a nanotubular array and this new platform presents a great potential to be tested in implantology. Copyright © 2018 Elsevier B.V. All rights reserved.

Mathematical Modelling of Arctic Polygonal Tundra with Ecosys: 1. Microtopography Determines How Active Layer Depths Respond to Changes in Temperature and Precipitation

NASA Astrophysics Data System (ADS)

Grant, R. F.; Mekonnen, Z. A.; Riley, W. J.; Wainwright, H. M.; Graham, D.; Torn, M. S.

2017-12-01

Microtopographic variation that develops among features (troughs, rims, and centers) within polygonal landforms of coastal arctic tundra strongly affects movement of surface water and snow and thereby affects soil water contents (θ) and active layer depth (ALD). Spatial variation in ALD among these features may exceed interannual variation in ALD caused by changes in climate and so needs to be represented in projections of changes in arctic ALD. In this study, increases in near-surface θ with decreasing surface elevation among polygon features at the Barrow Experimental Observatory (BEO) were modeled from topographic effects on redistribution of surface water and snow and from lateral water exchange with a subsurface water table during a model run from 1981 to 2015. These increases in θ caused increases in thermal conductivity that in turn caused increases in soil heat fluxes and hence in ALD of up to 15 cm with lower versus higher surface elevation which were consistent with increases measured at BEO. The modeled effects of θ caused interannual variation in maximum ALD that compared well with measurements from 1985 to 2015 at the Barrow Circumpolar Active Layer Monitoring (CALM) site (R2 = 0.61, RMSE = 0.03 m). For higher polygon features, interannual variation in ALD was more closely associated with annual precipitation than mean annual temperature, indicating that soil wetting from increases in precipitation may hasten permafrost degradation beyond that caused by soil warming from increases in air temperature. This degradation may be more rapid if increases in precipitation cause sustained wetting in higher features.

Lateral Hydrogen Diffusion at p-GaN Layers in Nitride-Based Light Emitting Diodes with Tunnel Junctions

NASA Astrophysics Data System (ADS)

Kuwano, Yuka; Kaga, Mitsuru; Morita, Takatoshi; Yamashita, Kouji; Yagi, Kouta; Iwaya, Motoaki; Takeuchi, Tetsuya; Kamiyama, Satoshi; Akasaki, Isamu

2013-08-01

We demonstrated lateral Mg activation along p-GaN layers underneath n-GaN surface layers in nitride-based light emitting diodes (LEDs) with GaInN tunnel junctions. A high temperature thermal annealing was effective for the lateral Mg activation when the p-GaN layers were partly exposed to an oxygen ambient as etched sidewalls. The activated regions gradually extended from the etched sidewalls to the centers with an increase of annealing time, observed as emission regions with current injection. These results suggest that hydrogen diffuses not vertically thorough the above n-GaN but laterally through the exposed portions of the p-GaN. The lowest voltage drop at the GaInN tunnel junction was estimated to be 0.9 V at 50 mA with the optimized annealing condition.

Device performance and lifetime of polymer:fullerene solar cells with UV-ozone-irradiated hole-collecting buffer layers.

PubMed

Lee, Seungsoo; Nam, Sungho; Lee, Hyena; Kim, Hwajeong; Kim, Youngkyoo

2011-11-18

We report the influence of UV-ozone irradiation of the hole-collecting buffer layers on the performance and lifetime of polymer:fullerene solar cells. UV-ozone irradiation was targeted at the surface of the poly(3,4-ethylenedioxythiophene): poly(styrenesulfonate) (PEDOT:PSS) layers by varying the irradiation time up to 600 s. The change of the surface characteristics in the PEDOT:PSS after UV-ozone irradiation was measured by employing optical absorption spectroscopy, photoelectron yield spectroscopy, and contact angle measurements, while Raman and X-ray photoelectron spectroscopy techniques were introduced for more microscopic analysis. Results showed that the UV-ozone irradiation changed the chemical structure/composition of the surface of the PEDOT:PSS layers leading to the gradual increase of ionization potential with irradiation time in the presence of up-and-down variations in the contact angle (polarity). This surface property change was attributed to the formation of oxidative components, as evidenced by XPS and Auger electron images, which affected the sheet resistance of the PEDOT:PSS layers. Interestingly, device performance was slightly improved by short irradiation (up to 10 s), whereas it was gradually decreased by further irradiation. The short-duration illumination test showed that the lifetime of solar cells with the UV-ozone irradiated PEDOT:PSS layer was improved due to the protective role of the oxidative components formed upon UV-ozone irradiation against the attack of sulfonic acid groups in the PEDOT:PSS layer to the active layer. Copyright © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Probing the energetics of organic–nanoparticle interactions of ethanol on calcite

DOE PAGES

Wu, Di; Navrotsky, Alexandra

2015-04-13

Knowing the nature of interactions between small organic molecules and surfaces of nanoparticles (NP) is crucial for fundamental understanding of natural phenomena and engineering processes. In this paper, we report direct adsorption enthalpy measurement of ethanol on a series of calcite nanocrystals, with the aim of mimicking organic–NP interactions in various environments. The energetics suggests a spectrum of adsorption events as a function of coverage: strongest initial chemisorption on active sites on fresh calcite surfaces, followed by major chemical binding to form an ethanol monolayer and, subsequently, very weak, near-zero energy, physisorption. Furthermore, these thermochemical observations directly support a structuremore » where the ethanol monolayer is bonded to the calcite surface through its polar hydroxyl group, leaving the hydrophobic ends of the ethanol molecules to interact only weakly with the next layer of adsorbing ethanol and resulting in a spatial gap with low ethanol density between the monolayer and subsequent added ethanol molecules, as predicted by molecular dynamics and density functional calculations. Such an ordered assembly of ethanol on calcite NP is analogous to, although less strongly bonded than, a capping layer of organics intentionally introduced during NP synthesis, and suggests a continuous variation of surface structure depending on molecular chemistry, ranging from largely disordered surface layers to ordered layers that nevertheless are mobile and can rearrange or be displaced by other molecules to strongly bonded immobile organic capping layers. Finally, these differences in surface structure will affect chemical reactions, including the further nucleation and growth of nanocrystals on organic ligand-capped surfaces.« less

Synthesis, performance, and modeling of immobilized nano-sized magnetite layer for phosphate removal.

PubMed

Zach-Maor, Adva; Semiat, Raphael; Shemer, Hilla

2011-05-15

A homogeneous layer of nano-sized magnetite particles (<4 nm) was synthesized by impregnation of modified granular activated carbon (GAC) with ferric chloride, for effective removal of phosphate. A proposed mechanism for the modification and formation of magnetite onto the GAC is specified. BET results showed a significant increase in the surface area of the matrix following iron loading, implying that a porous nanomagnetite layer was formed. Batch adsorption experiments revealed high efficiency of phosphate removal, by the newly developed adsorbent, attaining maximum adsorption capacity of 435 mg PO(4)/g Fe (corresponding to 1.1 mol PO(4)/mol Fe(3)O(4)). It was concluded that initially phosphate was adsorbed by the active sites on the magnetite surface, and then it diffused into the interior pores of the nanomagnetite layer. It was demonstrated that the latter is the rate-determining step for the process. Innovative correlation of the diffusion mechanism with the unique adsorption properties of the synthesized adsorbent is presented. Copyright © 2011 Elsevier Inc. All rights reserved.

A nuclear method to measure spallation by thermal cycling of protective surface layers

NASA Astrophysics Data System (ADS)

Stroosnijder, M. F.; Macchi, G.

1995-05-01

After a general introduction on spallation by thermal cycling, the principle of Thin Layer Activation (TLA) is outlined. A practical setup to measure spallation of protective surface layers by thermal cycling using TLA is discussed. Its use is illustrated with the study of the spallation behaviour of an advanced thermal barrier coating. It is shown that among the various benefits, TLA has a direct relation to material loss and shows a significant increase in sensitivity over other test methods. Due to its intrinsic properties, TLA can contribute to a greater scientific understanding of material degradation by thermal cycling and it can provide a more reliable assessment of the service lives of technical components.

Gas sensing in 2D materials

NASA Astrophysics Data System (ADS)

Yang, Shengxue; Jiang, Chengbao; Wei, Su-huai

2017-06-01

Two-dimensional (2D) layered inorganic nanomaterials have attracted huge attention due to their unique electronic structures, as well as extraordinary physical and chemical properties for use in electronics, optoelectronics, spintronics, catalysts, energy generation and storage, and chemical sensors. Graphene and related layered inorganic analogues have shown great potential for gas-sensing applications because of their large specific surface areas and strong surface activities. This review aims to discuss the latest advancements in the 2D layered inorganic materials for gas sensors. We first elaborate the gas-sensing mechanisms and introduce various types of gas-sensing devices. Then, we describe the basic parameters and influence factors of the gas sensors to further enhance their performance. Moreover, we systematically present the current gas-sensing applications based on graphene, graphene oxide (GO), reduced graphene oxide (rGO), functionalized GO or rGO, transition metal dichalcogenides, layered III-VI semiconductors, layered metal oxides, phosphorene, hexagonal boron nitride, etc. Finally, we conclude the future prospects of these layered inorganic materials in gas-sensing applications.

Surface soil moisture retrieval using the L-band synthetic aperture radar onboard the Soil Moisture Active Passive satellite and evaluation at core validation sites

USDA-ARS?s Scientific Manuscript database

This paper evaluates the retrieval of soil moisture in the top 5-cm layer at 3-km spatial resolution using L-band dual-copolarized Soil Moisture Active Passive (SMAP) synthetic aperture radar (SAR) data that mapped the globe every three days from mid-April to early July, 2015. Surface soil moisture ...

Planar fuel cell utilizing nail current collectors for increased active surface area

DOEpatents

George, Thomas J.; Meacham, G. B. Kirby

2002-03-26

A plurality of nail current collector members are useful in the gas flow passages of an electrochemical device to optimize the active surfaces of the device and to provide structural support. In addition, the thicknesses of cathode and anode layers within the electrochemical device are varied according to current flow through the device to reduce resistance and increase operating efficiency.

Planar fuel cell utilizing nail current collectors for increased active surface area

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

George, Thomas J.; Meacham, G.B. Kirby

1999-11-26

A plurality of nail current collector members are useful in the gas flow passages of an electrochemical device to optimize the active surfaces of the device and to provide structural support. In addition, the thicknesses of cathode and anode layers within the electrochemical device are varied according to current flow through the device to reduce resistance and increase operating efficiency.

Convection in a volatile nitrogen-ice-rich layer drives Pluto's geological vigour

NASA Astrophysics Data System (ADS)

McKinnon, William B.; Nimmo, Francis; Wong, Teresa; Schenk, Paul M.; White, Oliver L.; Roberts, J. H.; Moore, J. M.; Spencer, J. R.; Howard, A. D.; Umurhan, O. M.; Stern, S. A.; Weaver, H. A.; Olkin, C. B.; Young, L. A.; Smith, K. E.; Moore, J. M.; McKinnon, W. B.; Spencer, J. R.; Beyer, R.; Buie, M.; Buratti, B.; Cheng, A.; Cruikshank, D.; Dalle Ore, C.; Gladstone, R.; Grundy, W.; Howard, A.; Lauer, T.; Linscott, I.; Nimmo, F.; Olkin, C.; Parker, J.; Porter, S.; Reitsema, H.; Reuter, D.; Roberts, J. H.; Robbins, S.; Schenk, P. M.; Showalter, M.; Singer, K.; Strobel, D.; Summers, M.; Tyler, L.; Weaver, H.; White, O. L.; Umurhan, O. M.; Banks, M.; Barnouin, O.; Bray, V.; Carcich, B.; Chaikin, A.; Chavez, C.; Conrad, C.; Hamilton, D.; Howett, C.; Hofgartner, J.; Kammer, J.; Lisse, C.; Marcotte, A.; Parker, A.; Retherford, K.; Saina, M.; Runyon, K.; Schindhelm, E.; Stansberry, J.; Steffl, A.; Stryk, T.; Throop, H.; Tsang, C.; Verbiscer, A.; Winters, H.; Zangari, A.; New Horizons Geology, Geophysics and Imaging Theme Team

2016-06-01

The vast, deep, volatile-ice-filled basin informally named Sputnik Planum is central to Pluto's vigorous geological activity. Composed of molecular nitrogen, methane, and carbon monoxide ices, but dominated by nitrogen ice, this layer is organized into cells or polygons, typically about 10 to 40 kilometres across, that resemble the surface manifestation of solid-state convection. Here we report, on the basis of available rheological measurements, that solid layers of nitrogen ice with a thickness in excess of about one kilometre should undergo convection for estimated present-day heat-flow conditions on Pluto. More importantly, we show numerically that convective overturn in a several-kilometre-thick layer of solid nitrogen can explain the great lateral width of the cells. The temperature dependence of nitrogen-ice viscosity implies that the ice layer convects in the so-called sluggish lid regime, a unique convective mode not previously definitively observed in the Solar System. Average surface horizontal velocities of a few centimetres a year imply surface transport or renewal times of about 500,000 years, well under the ten-million-year upper-limit crater retention age for Sputnik Planum. Similar convective surface renewal may also occur on other dwarf planets in the Kuiper belt, which may help to explain the high albedos shown by some of these bodies.

Convection in a volatile nitrogen-ice-rich layer drives Pluto's geological vigour.

PubMed

McKinnon, William B; Nimmo, Francis; Wong, Teresa; Schenk, Paul M; White, Oliver L; Roberts, J H; Moore, J M; Spencer, J R; Howard, A D; Umurhan, O M; Stern, S A; Weaver, H A; Olkin, C B; Young, L A; Smith, K E

2016-06-02

The vast, deep, volatile-ice-filled basin informally named Sputnik Planum is central to Pluto's vigorous geological activity. Composed of molecular nitrogen, methane, and carbon monoxide ices, but dominated by nitrogen ice, this layer is organized into cells or polygons, typically about 10 to 40 kilometres across, that resemble the surface manifestation of solid-state convection. Here we report, on the basis of available rheological measurements, that solid layers of nitrogen ice with a thickness in excess of about one kilometre should undergo convection for estimated present-day heat-flow conditions on Pluto. More importantly, we show numerically that convective overturn in a several-kilometre-thick layer of solid nitrogen can explain the great lateral width of the cells. The temperature dependence of nitrogen-ice viscosity implies that the ice layer convects in the so-called sluggish lid regime, a unique convective mode not previously definitively observed in the Solar System. Average surface horizontal velocities of a few centimetres a year imply surface transport or renewal times of about 500,000 years, well under the ten-million-year upper-limit crater retention age for Sputnik Planum. Similar convective surface renewal may also occur on other dwarf planets in the Kuiper belt, which may help to explain the high albedos shown by some of these bodies.

Facile incorporation of hydroxyapatite onto an anodized Ti surface via a mussel inspired polydopamine coating

NASA Astrophysics Data System (ADS)

Zhe, Wang; Dong, Chaofang; Sefei, Yang; Dawei, Zhang; Kui, Xiao; Xiaogang, Li

2016-08-01

Inspired by the porous morphology of anodized Ti and the adhesive versatility of polydopamine (PDA), which can induce apatite mineralization, we fabricated a novel interface by coating a porous anodized TiO2 layer with PDA to rapidly immobilize HA on Ti-based substrates. It was found that the as-prepared PDA/anodized (HD) surface exhibited nanoscale roughness, which possessed an excellent ability to form apatite when immersed in 1.5× simulated body fluid (SBF), as observed by AFM and FE-SEM. The morphology and composition of each layer were further confirmed by XPS, XRD and FTIR. The corrosion resistance of the multilayer was investigated using potentiodynamic polarization curve and electrochemical impedance spectra (EIS) measurements in a 0.9 wt% NaCl solution, the results suggested that the HA/PDA/anodized (HDA) layer increased the corrosion resistance of pure Ti with higher corrosion potential and lower passive current, the surface wettability was also enhanced with the incorporation of HA. In vitro cellular assays showed that the HDA layer stimulated cell attachment and improved the alkaline phosphate (ALP) activity. Overall, the PDA/anodized treatment provided a viable method to quickly integrate HA, and the obtained HDA layer improved both corrosion resistance and biocompatibility of the Ti surface.

Ferromagnetic nanoparticles containing biologically active alkanolamines: preparation and properties

NASA Astrophysics Data System (ADS)

Segal, I.; Zablotskaya, A.; Lukevics, E.; Maiorov, M.; Zablotsky, D.

2005-12-01

The objective of the present study is to investigate the possibility of sorption on ultrafine magnetic particles of some model biologically active organosilicon alkanolamines, structural analogs of natural biologically active substances, choline and colamine, with increased lipophilicity. Double-coated ferromagnetic samples containing oleic acid, as a first layer, and organosilicon alcanolamines, as a second layer, were obtained and characterized by their physical/chemical (sorption and magnetisation) and biological (toxicity and cytotoxicity) properties. The present results clearly reveal the sorption of the biologically active alkanolamines on the surface of magnetic particles and a principal possibility to coat magnetite directly with biologically active alkanolamines, creating a mono-layer cover. The data presented in the study of cytotoxic properties of the newly obtained ferromagnetic nanoparticles show that it is reasonable to investigate such systems as potential cytotoxic agents. Tables 3, Figs 3, Refs 16.

Active and passive controls of Jeffrey nanofluid flow over a nonlinear stretching surface

NASA Astrophysics Data System (ADS)

Hayat, Tasawar; Aziz, Arsalan; Muhammad, Taseer; Alsaedi, Ahmed

This communication explores magnetohydrodynamic (MHD) boundary-layer flow of Jeffrey nanofluid over a nonlinear stretching surface with active and passive controls of nanoparticles. A nonlinear stretching surface generates the flow. Effects of thermophoresis and Brownian diffusion are considered. Jeffrey fluid is electrically conducted subject to non-uniform magnetic field. Low magnetic Reynolds number and boundary-layer approximations have been considered in mathematical modelling. The phenomena of impulsing the particles away from the surface in combination with non-zero mass flux condition is known as the condition of zero mass flux. Convergent series solutions for the nonlinear governing system are established through optimal homotopy analysis method (OHAM). Graphs have been sketched in order to analyze that how the temperature and concentration distributions are affected by distinct physical flow parameters. Skin friction coefficient and local Nusselt and Sherwood numbers are also computed and analyzed. Our findings show that the temperature and concentration distributions are increasing functions of Hartman number and thermophoresis parameter.

Process for producing methane from gas streams containing carbon monoxide and hydrogen

DOEpatents

Frost, Albert C.

1980-01-01

Carbon monoxide-containing gas streams are passed over a catalyst capable of catalyzing the disproportionation of carbon monoxide so as to deposit a surface layer of active surface carbon on the catalyst essentially without formation of inactive coke thereon. The surface layer is contacted with steam and is thus converted to methane and CO.sub.2, from which a relatively pure methane product may be obtained. While carbon monoxide-containing gas streams having hydrogen or water present therein can be used only the carbon monoxide available after reaction with said hydrogen or water is decomposed to form said active surface carbon. Although hydrogen or water will be converted, partially or completely, to methane that can be utilized in a combustion zone to generate heat for steam production or other energy recovery purposes, said hydrogen is selectively removed from a CO--H.sub.2 -containing feed stream by partial oxidation thereof prior to disproportionation of the CO content of said stream.

Phospholipid-sepiolite biomimetic interfaces for the immobilization of enzymes.

PubMed

Wicklein, Bernd; Darder, Margarita; Aranda, Pilar; Ruiz-Hitzky, Eduardo

2011-11-01

Biomimetic interfaces based on phosphatidylcholine (PC) assembled to the natural silicate sepiolite were prepared for the stable immobilization of the urease and cholesterol oxidase enzymes. This is an important issue in practical advanced applications such as biocatalysis or biosensing. The supported lipid bilayer (BL-PC), prepared from PC adsorption, was used for immobilization of enzymes and the resulting biomimetic systems were compared to several other supported layers including a lipid monolayer (ML-PC), a mixed phosphatidylcholine/octyl-galactoside layer (PC-OGal), a cetyltrimethylammonium monolayer (CTA), and also to the bare sepiolite surface. Interfacial characteristics of these layers were investigated with a focus on layer packing density, hydrophilicity/hydrophobicity, and surface charge, which are being considered as key points for enzyme immobilization and stabilization of their biological activity. Cytoplasmic urease and membrane-bound cholesterol oxidase, which served as model enzymes, were immobilized on the different PC-based hybrid materials to probe their biomimetic character. Enzymatic activity was assessed by cyclic voltammetry and UV-vis spectrophotometry. The resulting enzyme/bio-organoclay hybrids were applied as active phase of a voltammetric urea biosensor and cholesterol bioreactor, respectively. Urease supported on sepiolite/BL-PC proved to maintain its enzymatic activity over several months while immobilized cholesterol oxidase demonstrated high reusability as biocatalyst. The results emphasize the good preservation of bioactivity due to the accommodation of the enzymatic system within the biomimetic lipid interface on sepiolite.

Bulk chlorine uptake by polyamide active layers of thin-film composite membranes upon exposure to free chlorine-kinetics, mechanisms, and modeling.

PubMed

Powell, Joshua; Luh, Jeanne; Coronell, Orlando

2014-01-01

We studied the volume-averaged chlorine (Cl) uptake into the bulk region of the aromatic polyamide active layer of a reverse osmosis membrane upon exposure to free chlorine. Volume-averaged measurements were obtained using Rutherford backscattering spectrometry with samples prepared at a range of free chlorine concentrations, exposure times, and mixing, rinsing, and pH conditions. Our volume-averaged measurements complement previous studies that have quantified Cl uptake at the active layer surface (top ≈ 7 nm) and advance the mechanistic understanding of Cl uptake by aromatic polyamide active layers. Our results show that surface Cl uptake is representative of and underestimates volume-averaged Cl uptake under acidic conditions and alkaline conditions, respectively. Our results also support that (i) under acidic conditions, N-chlorination followed by Orton rearrangement is the dominant Cl uptake mechanism with N-chlorination as the rate-limiting step; (ii) under alkaline conditions, N-chlorination and dechlorination of N-chlorinated amide links by hydroxyl ion are the two dominant processes; and (iii) under neutral pH conditions, the rates of N-chlorination and Orton rearrangement are comparable. We propose a kinetic model that satisfactorily describes Cl uptake under acidic and alkaline conditions, with the largest discrepancies between model and experiment occurring under alkaline conditions at relatively high chlorine exposures.

Micro-arc oxidation as a tool to develop multifunctional calcium-rich surfaces for dental implant applications.

PubMed

Ribeiro, A R; Oliveira, F; Boldrini, L C; Leite, P E; Falagan-Lotsch, P; Linhares, A B R; Zambuzzi, W F; Fragneaud, B; Campos, A P C; Gouvêa, C P; Archanjo, B S; Achete, C A; Marcantonio, E; Rocha, L A; Granjeiro, J M

2015-09-01

Titanium (Ti) is commonly used in dental implant applications. Surface modification strategies are being followed in last years in order to build Ti oxide-based surfaces that can fulfill, simultaneously, the following requirements: induced cell attachment and adhesion, while providing a superior corrosion and tribocorrosion performance. In this work micro-arc oxidation (MAO) was used as a tool for the growth of a nanostructured bioactive titanium oxide layer aimed to enhance cell attachment and adhesion for dental implant applications. Characterization of the surfaces was performed, in terms of morphology, topography, chemical composition and crystalline structure. Primary human osteoblast adhesion on the developed surfaces was investigated in detail by electronic and atomic force microscopy as well as immunocytochemistry. Also an investigation on the early cytokine production was performed. Results show that a relatively thick hybrid and graded oxide layer was produced on the Ti surface, being constituted by a mixture of anatase, rutile and amorphous phases where calcium (Ca) and phosphorous (P) were incorporated. An outermost nanometric-thick amorphous oxide layer rich in Ca was present in the film. This amorphous layer, rich in Ca, improved fibroblast viability and metabolic activity as well as osteoblast adhesion. High-resolution techniques allowed to understand that osteoblasts adhered less in the crystalline-rich regions while they preferentially adhere and spread over in the Ca-rich amorphous oxide layer. Also, these surfaces induce higher amounts of IFN-γ cytokine secretion, which is known to regulate inflammatory responses, bone microarchitecture as well as cytoskeleton reorganization and cellular spreading. These surfaces are promising in the context of dental implants, since they might lead to faster osseointegration. Copyright © 2015 Elsevier B.V. All rights reserved.

The Otto Aufranc Award: enhanced biocompatibility of stainless steel implants by titanium coating and microarc oxidation.

PubMed

Lim, Young Wook; Kwon, Soon Yong; Sun, Doo Hoon; Kim, Yong Sik

2011-02-01

Stainless steel is one of the most widely used biomaterials for internal fixation devices, but is not used in cementless arthroplasty implants because a stable oxide layer essential for biocompatibility cannot be formed on the surface. We applied a Ti electron beam coating, to form oxide layer on the stainless steel surface. To form a thicker oxide layer, we used a microarc oxidation process on the surface of Ti coated stainless steel. Modification of the surface using Ti electron beam coating and microarc oxidation could improve the ability of stainless steel implants to osseointegrate. The ability of cells to adhere to grit-blasted, titanium-coated, microarc-oxidated stainless steel in vitro was compared with that of two different types of surface modifications, machined and titanium-coated, and microarc-oxidated. We performed energy-dispersive x-ray spectroscopy and scanning electron microscopy investigations to assess the chemical composition and structure of the stainless steel surfaces and cell morphology. The biologic responses of an osteoblastlike cell line (SaOS-2) were examined by measuring proliferation (cell proliferation assay), differentiation (alkaline phosphatase activity), and attraction ability (cell migration assay). Cell proliferation, alkaline phosphatase activity, migration, and adhesion were increased in the grit-blasted, titanium-coated, microarc-oxidated group compared to the two other groups. Osteoblastlike cells on the grit-blasted, titanium-coated, microarc-oxidated surface were strongly adhered, and proliferated well compared to those on the other surfaces. The surface modifications we used (grit blasting, titanium coating, microarc oxidation) enhanced the biocompatibility (proliferation and migration of osteoblastlike cells) of stainless steel. This process is not unique to stainless steel; it can be applied to many metals to improve their biocompatibility, thus allowing a broad range of materials to be used for cementless implants.

Orientation Control in Thin Films of a High-χ Block Copolymer with a Surface Active Embedded Neutral Layer.

PubMed

Zhang, Jieqian; Clark, Michael B; Wu, Chunyi; Li, Mingqi; Trefonas, Peter; Hustad, Phillip D

2016-01-13

Directed self-assembly (DSA) of block copolymers (BCPs) is an attractive advanced patterning technology being considered for future integrated circuit manufacturing. By controlling interfacial interactions, self-assembled microdomains in thin films of polystyrene-block-poly(methyl methacrylate), PS-b-PMMA, can be oriented perpendicular to surfaces to form line/space or hole patterns. However, its relatively weak Flory interaction parameter, χ, limits its capability to pattern sub-10 nm features. Many BCPs with higher interaction parameters are capable of forming smaller features, but these "high-χ" BCPs typically have an imbalance in surface energy between the respective blocks that make it difficult to achieve the required perpendicular orientation. To address this challenge, we devised a polymeric surface active additive mixed into the BCP solution, referred to as an embedded neutral layer (ENL), which segregates to the top of the BCP film during casting and annealing and balances the surface tensions at the top of the thin film. The additive comprises a second BCP with a "neutral block" designed to provide matched surface tensions with the respective polymers of the main BCP and a "surface anchoring block" with very low surface energy that drives the material to the air interface during spin-casting and annealing. The surface anchoring block allows the film to be annealed above the glass transition temperature of the two materials without intermixing of the two components. DSA was also demonstrated with this embedded neutral top layer formulation on a chemical patterned template using a single step coat and simple thermal annealing. This ENL technology holds promise to enable the use of high-χ BCPs in advanced patterning applications.

Combining surface enhanced Raman scattering (SERS) and high-performance thin-layer chromatography (HPTLC)

NASA Astrophysics Data System (ADS)

Koglin, E.

A new method for preparing SERS active surfaces using silver colloidal spheres deposited on HPTLC plates, used for thin-layer chromatography, is discussed in detail. The sensitivity of these activated HPTLC plates is so high that in-situ vibrational investigations of chromatogram spots are possible at the nanogram level. The HPTLC/SERS spectra of purine, benzoic acid and 1-nitro-pyrene adsorbed on silver colloidal activated silica gel plates are measured in the nanogram region. In addition we also report in this paper on the results of a feasibility study performed to evaluate the analytical potential of micro-Raman spectroscopy (triple monochromator, multichannel detection system) in SERS/HPTLC spot characterization. It permits the acquisition of Raman spectra from HPTLC spots down to 1 μm in size or other forms of microsamples approaching the picogram level in mass.

Study of the Effect of Nanoparticles and Surface Morphology on Reverse Osmosis and Nanofiltration Membrane Productivity

PubMed Central

Fang, Yuming; Duranceau, Steven J.

2013-01-01

To evaluate the significance of reverse osmosis (RO) and nanofiltration (NF) surface morphology on membrane performance, productivity experiments were conducted using flat-sheet membranes and three different nanoparticles, which included SiO2, TiO2 and CeO2. In this study, the productivity rate was markedly influenced by membrane surface morphology. Atomic force microscopy (AFM) analysis of membrane surfaces revealed that the higher productivity decline rates associated with polyamide RO membranes as compared to that of a cellulose acetate NF membrane was due to the inherent ridge-and-valley morphology of the active layer. The unique polyamide active layer morphology was directly related to the surface roughness, and was found to contribute to particle accumulation in the valleys causing a higher flux decline than in smoother membranes. Extended RO productivity experiments using laboratory grade water and diluted pretreated seawater were conducted to compare the effect that different nanoparticles had on membrane active layers. Membrane flux decline was not affected by particle type when the feed water was laboratory grade water. On the other hand, membrane productivity was affected by particle type when pretreated diluted seawater served as feed water. It was found that CeO2 addition resulted in the least observable flux decline, followed by SiO2 and TiO2. A productivity simulation was conducted by fitting the monitored flux data into a cake growth rate model, where the model was modified using a finite difference method to incorporate surface thickness variation into the analysis. The ratio of cake growth term (k1) and particle back diffusion term (k2) was compared in between different RO and NF membranes. Results indicated that k2 was less significant for surfaces that exhibited a higher roughness. It was concluded that the valley areas of thin-film membrane surfaces have the ability to capture particles, limiting particle back diffusion. PMID:24956946

Surface pre-treatment for barrier coatings on polyethylene terephthalate

NASA Astrophysics Data System (ADS)

Bahre, H.; Bahroun, K.; Behm, H.; Steves, S.; Awakowicz, P.; Böke, M.; Hopmann, Ch; Winter, J.

2013-02-01

Polymers have favourable properties such as light weight, flexibility and transparency. Consequently, this makes them suitable for food packaging, organic light-emitting diodes and flexible solar cells. Nonetheless, raw plastics do not possess sufficient barrier functionality against oxygen and water vapour, which is of paramount importance for most applications. A widespread solution is to deposit thin silicon oxide layers using plasma processes. However, silicon oxide layers do not always fulfil the requirements concerning adhesion and barrier performance when deposited on films. Thus, plasma pre-treatment is often necessary. To analyse the influence of a plasma-based pre-treatment on barrier performance, different plasma pre-treatments on three reactor setups were applied to a very smooth polyethylene terephthalate film before depositing a silicon oxide barrier layer. In this paper, the influence of oxygen and argon plasma pre-treatments towards the barrier performance is discussed examining the chemical and topological change of the film. It was observed that a short one-to-ten-second plasma treatment can reduce the oxygen transmission rate by a factor of five. The surface chemistry and the surface topography change significantly for these short treatment times, leading to an increased surface energy. The surface roughness rises slowly due to the development of small spots in the nanometre range. For very long treatment times, surface roughness of the order of the barrier layer's thickness results in a complete loss of barrier properties. During plasma pre-treatment, the trade-off between surface activation and roughening of the surface has to be carefully considered.

InSAR detects increase in surface subsidence caused by an Arctic tundra fire

USGS Publications Warehouse

Liu, Lin; Jafarov, Elchin E.; Schaefer, Kevin M.; Jones, Benjamin M.; Zebker, Howard A.; Williams, Christopher A.; Rogan, John; Zhang, Tingjun

2014-01-01

Wildfire is a major disturbance in the Arctic tundra and boreal forests, having a significant impact on soil hydrology, carbon cycling, and permafrost dynamics. This study explores the use of the microwave Interferometric Synthetic Aperture Radar (InSAR) technique to map and quantify ground surface subsidence caused by the Anaktuvuk River fire on the North Slope of Alaska. We detected an increase of up to 8 cm of thaw-season ground subsidence after the fire, which is due to a combination of thickened active layer and permafrost thaw subsidence. Our results illustrate the effectiveness and potential of using InSAR to quantify fire impacts on the Arctic tundra, especially in regions underlain by ice-rich permafrost. Our study also suggests that surface subsidence is a more comprehensive indicator of fire impacts on ice-rich permafrost terrain than changes in active layer thickness alone.

Investigation of nitrogen transport in active screen plasma nitriding processes - Uphill diffusion effect

NASA Astrophysics Data System (ADS)

Jasinski, J. J.; Fraczek, T.; Kurpaska, L.; Lubas, M.; Sitarz, M.

2018-07-01

The paper presents a structure of a nitrided layer formed with active screen plasma nitriding (ASPN) technique, which is a modification of plasma nitriding. The model investigated material was Fe Armco. The nitriding processes were carried out at 773 K for 6 h and 150 Pa. The main objective of this study was to confirm nitrogen migration effect and its influence on the nitride layer formation in different area of the layer interfaces (ε/ε+γ‧/γ‧). The results of the tests were evaluated using scanning electron microscopy (SEM, SEM/EBSD), transmission electron microscopy - electron energy loss spectroscopy (TEM-EFTEM), secondary ion mass spectroscopy (SIMS) and Wavelength Dispersive X-Ray Spectrometry (WDS). The analysis of the results suggests that the structures of the nitrided layers and nitrides morphology differ for various parameters and are dependent on the surface layer saturation mechanism for each of the temperatures and process parameters. New approaches in diffusion of nitrogen and carbon atoms and optimizing process were also analyzed. Nitrogen and also carbon transport in the sublayer was observed by several effects i.e. uphill diffusion effect which confirmed migration of the atoms in diffusive layer towards top surface (ε/ε+γ‧ interface) and stress change effect in the nitrogen saturation area of the (Fe(C,N)+γ‧) layer. Results showed in the paper might be used both for optimization of ASPN processes, modeling of nitrided layers formation mechanism and for controlling the nitrided layers morphology when nitriding different Fe based materials.

[Bone cement adhesion on ceramic surfaces - surface activation of retention surfaces of knee prostheses by atmospheric plasma versus thermal surface treatment].

PubMed

Marx, B; Marx, R; Reisgen, U; Wirtz, D

2015-04-01

CoCrMo alloys are contraindicated for allergy sufferers. For these patients, uncemented and cemented prostheses made of titanium alloy are indicated. Knee prostheses machined from that alloy, however, may have poor tribological behaviour, especially in relation to UHMWPE inlays. Therefore, for knee replacement cemented high-strength oxide ceramic prostheses are suitable for allergy sufferers and in cases of particle-induced aseptic loosening. For adhesion of bone cement, the ceramic surface, however, only exposes inefficient mechanical retention spots as compared with a textured metal surface. Undercuts generated by corundum blasting which in the short-term are highly efficient on a CoCrMo surface are not possible on a ceramic surface due to the brittleness of ceramics. Textures due to blasting may initiate cracks which will weaken the strength of a ceramic prosthesis. Due to the lack of textures mechanical retention is poor or even not existent. Micromotions are promoted and early aseptic loosening is predictable. Instead silicoating of the ceramic surface will allow specific adhesion and result in better hydrolytic stability of bonding thereby preventing early aseptic loosening. Silicoating, however, presupposes a clean and chemically active surface which can be achieved by atmospheric plasma or thermal surface treatment. In order to evaluate the effectiveness of silicoating the bond strengths of atmospheric plasma versus thermal surface treated and silicate layered ZPTA surfaces were compared with "as-fired" surfaces by utilising TiAlV probes (diameter 6 mm) for traction-adhesive strength tests. After preparing samples for traction-adhesive strength tests (sequence: ceramic substrate, silicate and silane, protective lacquer [PolyMA], bone cement, TiAlV probe) they were aged for up to 150 days at 37 °C in Ringer's solution. The bond strengths observed for all ageing intervals were well above 20 MPa and much higher and more hydrolytically stable for silicate layered compared with "as-fired" ZPTA samples. Silicoating may be effective for achieving high initial bond strength of bone cement on surfaces of oxide ceramics and also suitable to stabilise bond strength under hydrolytic conditions as present in the human body in the long-term. Activation by atmospheric plasma or thermal surface treatment seems to be effective for activation prior to silicoating. Due the proposed silicate layer migration, micromotions and debonding should be widely reduced or even eliminated. Georg Thieme Verlag KG Stuttgart · New York.

Atomic Layer-by-Layer Deposition of Pt on Pd Nanocubes for Catalysts with Enhanced Activity and Durability toward Oxygen Reduction

DOE PAGES

Xie, Shuifen; Choi, Sang -Il; Lu, Ning; ...

2014-05-05

Here, an effective strategy for reducing the Pt content while retaining the activity of a Pt-based catalyst is to deposit the Pt atoms as ultrathin skins of only a few atomic layers thick on nanoscale substrates made of another metal. During deposition, however, the Pt atoms often take an island growth mode because of a strong bonding between Pt atoms. Here we report a versatile route to the conformal deposition of Pt as uniform, ultrathin shells on Pd nanocubes in a solution phase. The introduction of the Pt precursor at a relatively slow rate and high temperature allowed the depositedmore » Pt atoms to spread across the entire surface of a Pd nanocube to generate a uniform shell. The thickness of the Pt shell could be controlled from one to six atomic layers by varying the amount of Pt precursor added into the system. Compared to a commercial Pt/C catalyst, the Pd@Pt nL (n = 1–6) core–shell nanocubes showed enhancements in specific activity and durability toward the oxygen reduction reaction (ORR). Density functional theory (DFT) calculations on model (100) surfaces suggest that the enhancement in specific activity can be attributed to the weakening of OH binding through ligand and strain effects, which, in turn, increases the rate of OH hydrogenation. A volcano-type relationship between the ORR specific activity and the number of Pt atomic layers was derived, in good agreement with the experimental results. Both theoretical and experimental studies indicate that the ORR specific activity was maximized for the catalysts based on Pd@Pt 2–3L nanocubes. Because of the reduction in Pt content used and the enhancement in specific activity, the Pd@Pt 1L nanocubes showed a Pt mass activity with almost three-fold enhancement relative to the Pt/C catalyst.« less

Predicting drought propagation within peat layers using a three dimensionally explicit voxel based model

NASA Astrophysics Data System (ADS)

Condro, A. A.; Pawitan, H.; Risdiyanto, I.

2018-05-01

Peatlands are very vulnerable to widespread fires during dry seasons, due to availability of aboveground fuel biomass on the surface and belowground fuel biomass on the sub-surface. Hence, understanding drought propagation occurring within peat layers is crucial with regards to disaster mitigation activities on peatlands. Using a three dimensionally explicit voxel-based model of peatland hydrology, this study predicted drought propagation time lags into sub-surface peat layers after drought events occurrence on the surface of about 1 month during La-Nina and 2.5 months during El-Nino. The study was carried out on a high-conservation-value area of oil palm plantation in West Kalimantan. Validity of the model was evaluated and its applicability for disaster mitigation was discussed. The animations of simulated voxels are available at: goo.gl/HDRMYN (El-Nino 2015 episode) and goo.gl/g1sXPl (La-Nina 2016 episode). The model is available at: goo.gl/RiuMQz.

Characterization and Modeling Of Microbial Carbon Metabolism In Thawing Permafrost

NASA Astrophysics Data System (ADS)

Graham, D. E.; Phelps, T. J.; Xu, X.; Carroll, S.; Jagadamma, S.; Shakya, M.; Thornton, P. E.; Elias, D. A.

2012-12-01

Increased annual temperatures in the Arctic are warming the surface and subsurface, resulting in thawing permafrost. Thawing exposes large pools of buried organic carbon to microbial degradation, increasing greenhouse gas generation and emission. Most global-scale land-surface models lack depth-dependent representations of carbon conversion and GHG transport; therefore they do not adequately describe permafrost thawing or microbial mineralization processes. The current work was performed to determine how permafrost thawing at moderately elevated temperatures and anoxic conditions would affect CO2 and CH4 generation, while parameterizing depth-dependent GHG production processes with respect to temperature and pH in biogeochemical models. These enhancements will improve the accuracy of GHG emission predictions and identify key biochemical and geochemical processes for further refinement. Three core samples were obtained from discontinuous permafrost terrain in Fairbanks, AK with a mean annual temperature of -3.3 °C. Each core was sectioned into surface/near surface (0-0.8 m), active layer (0.8-1.6 m), and permafrost (1.6-2.2 m) horizons, which were homogenized for physico-chemical characterization and microcosm construction. Surface samples had low pH values (6.0), low water content (18% by weight), low organic carbon (0.8%), and high C:N ratio (43). Active layer samples had higher pH values (6.4), higher water content (34%), more organic carbon (1.4%) and a lower C:N ratio (24). Permafrost samples had the highest pH (6.5), highest water content (46%), high organic carbon (2.5%) and the lowest C:N ratio (19). Most organic carbon was quantified as labile or intermediate pool versus stable pool in each sample, and all samples had low amounts of carbonate. Surface layer microcosms, containing 20 g sediment in septum-sealed vials, were incubated under oxic conditions, while similar active and permafrost layer samples were anoxic. These microcosms were incubated at -2, +3, or +5 °C for 6 months. The pH decreased in all samples (5.5 to 5.9). The proportions of carbon in labile and intermediate turnover pools from permafrost samples decreased during incubation, while microbial biomass carbon increased in all cases. Microcosm samples and original core material were analyzed by 16S rDNA pyrosequencing and showed increased populations of bacteria that ferment simple and complex carbohydrates, as well as acidophilic bacteria. Microbial diversity declined in permafrost samples. Concentrations of CO2 and CH4 were measured monthly by gas chromatography. CO2 production was highest in the surface/near surface incubations (4-14%) while CH4 was undetectable. Active layer sediments produced considerably less CO2 (0.2-0.7%) but CH4 was detected up to 0.25%. Concentrations of CO2 found in the deep permafrost incubations were comparable to those in the active layer, while CH4 was considerably higher ranging from 0.2-0.6%. Overall, the CO2 generation rate (0.02-0.12 μmol/g/month) was roughly 50 times that of methanogenesis (0.002-0.007 μmol/g/month). GHG levels peaked after 4 months, and the decreasing pH suggested that organic acid accumulation could control GHG biogenesis. Surprisingly, increasing temperature and water content did not necessarily increase GHG emission rates or proportions of CO2 and CH4.

Bonding thermoplastic polymers

DOEpatents

Wallow, Thomas I [Fremont, CA; Hunter, Marion C [Livermore, CA; Krafcik, Karen Lee [Livermore, CA; Morales, Alfredo M [Livermore, CA; Simmons, Blake A [San Francisco, CA; Domeier, Linda A [Danville, CA

2008-06-24

We demonstrate a new method for joining patterned thermoplastic parts into layered structures. The method takes advantage of case-II permeant diffusion to generate dimensionally controlled, activated bonding layers at the surfaces being joined. It is capable of producing bonds characterized by cohesive failure while preserving the fidelity of patterned features in the bonding surfaces. This approach is uniquely suited to production of microfluidic multilayer structures, as it allows the bond-forming interface between plastic parts to be precisely manipulated at micrometer length scales. The bond enhancing procedure is easily integrated in standard process flows and requires no specialized equipment.

The robust bio-immobilization based on pulsed plasma polymerization of cyclopropylamine and glutaraldehyde coupling chemistry

NASA Astrophysics Data System (ADS)

Manakhov, Anton; Makhneva, Ekaterina; Skládal, Petr; Nečas, David; Čechal, Jan; Kalina, Lukáš; Eliáš, Marek; Zajíčková, Lenka

2016-01-01

The performance of immunosensing devices crucially depends on the methodology of antibody or antigen immobilization on the sensor surface. Hence, the stable intermediate layers capable of specific and reproducible binding of antibodies are required. Herein, we introduce the amine rich (NHx concentration of 6 at.%) layers prepared by pulsed plasma polymerization of cyclopropylamine (CPA) for functionalization of the quartz crystal microbalance (QCM) surface by the antibody specific to human serum albumin. In these layers the amine groups serve as anchor for the antibody binding. The sensitivity of QCM sensors prepared in this way surpasses the one for the previously reported sensors functionalized by the thiol-based self-assembled monolayers by the factor of 2. Our results thus show that CPA plasma polymers have a significant potential for further development of the active layers for biosensing applications.

Layered Metal Nanoparticle Structures on Electrodes for Sensing, Switchable Controlled Uptake/Release, and Photo-electrochemical Applications.

PubMed

Tel-Vered, Ran; Kahn, Jason S; Willner, Itamar

2016-01-06

Layered metal nanoparticle (NP) assemblies provide highly porous and conductive composites of unique electrical and optical (plasmonic) properties. Two methods to construct layered metal NP matrices are described, and these include the layer-by-layer deposition of NPs, or the electropolymerization of monolayer-functionalized NPs, specifically thioaniline-modified metal NPs. The layered NP composites are used as sensing matrices through the use of electrochemistry or surface plasmon resonance (SPR) as transduction signals. The crosslinking of the metal NP composites with molecular receptors, or the imprinting of molecular recognition sites into the electropolymerized NP matrices lead to selective and chiroselective sensing interfaces. Furthermore, the electrosynthesis of redox-active, imprinted, bis-aniline bridged Au NP composites yields electrochemically triggered "sponges" for the switchable uptake and release of electron-acceptor substrates, and results in conductive surfaces of electrochemically controlled wettability. Also, photosensitizer-relay-crosslinked Au NP composites, or electrochemically polymerized layered semiconductor quantum dot/metal NP matrices on electrodes, are demonstrated as functional nanostructures for photoelectrochemical applications. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Elemental analyses of hypervelocity micro-particle impact sites on interplanetary dust experiment sensor surfaces

NASA Technical Reports Server (NTRS)

Simon, Charles G.; Hunter, J. L.; Griffis, D. P.; Misra, V.; Ricks, D. R.; Wortman, Jim J.

1992-01-01

The Interplanetary Dust Experiment (IDE) had over 450 electrically active ultra-high purity metal-oxide-silicon impact detectors located on the six primary sides of the Long Duration Exposure Facility (LDEF). Hypervelocity micro-particles that struck the active sensors with enough energy to breakdown the 0.4 to 1.0 micron thick SiO2 insulator layer separating the silicon base (the negative electrode), and the 1000 A thick surface layer of aluminum (the positive electrode) caused electrical discharges that were recorded for the first year of orbit. These discharge features, which include 50 micron diameter areas where the aluminum top layer has been vaporized, facilitate the location of the impacts. The high purity Al-SiO2-Si substrates allow detection of trace (ppm) amounts of hypervelocity impactor residues. After sputtering through a layer of surface contamination, secondary ion mass spectrometry (SIMS) is used to create two-dimensional elemental ion intensity maps of micro-particle impact sites on the IDE sensors. The element intensities in the central craters of the impacts are corrected for relative ion yields and instrumental conditions and then normalized to silicon. The results are used to classify the particles' origins as 'manmade', 'natural' or 'indeterminate'. The last classification results from the presence of too little impactor residue (a frequent occurrence on leading edge impacts), analytical interference from high background contamination, the lack of information on silicon residue, the limited usefulness of data on aluminum in the central craters, or a combination of these circumstances. Several analytical 'blank' discharges were induced on flight sensors by pressing down on the sensor surface with a pure silicon shard. Analyses of these blank discharges showed that the discharge energy blasts away the layer of surface contamination. Only Si and Al were detected inside the discharge zones, including the central craters, of these features. A total of 35 impacts on leading edge sensors and 22 impacts on trailing edge sensors were analyzed.

The vertical distribution of prokaryotes in the surface sediment of Jiaolong cold seep at the northern South China Sea.

PubMed

Wu, Yuzhi; Qiu, Jian-Wen; Qian, Pei-Yuan; Wang, Yong

2018-05-01

In deep-sea cold seeps, microbial communities are shaped by geochemical components in seepage solutions. In the present study, we report the composition of microbial communities and potential metabolic activities in the surface sediment of Jiaolong cold seep at the northern South China Sea. Pyrosequencing of 16S rRNA gene amplicons revealed that a majority of the microbial inhabitants of the surface layers (0-6 cm) were sulfur oxidizer bacteria Sulfurimonas and archaeal methane consumer ANME-1, while sulfate reducer bacteria SEEP-SRB1, ANME-1 and ANME-2 dominated the bottom layers (8-14 cm). The potential ecological roles of the microorganisms were further supported by the presence of functional genes for methane oxidation, sulfur oxidation, sulfur reduction and nitrate reduction in the metagenomes. Metagenomic analysis revealed a significant correlation between coverage of 16S rRNA gene of sulfur oxidizer bacteria, functional genes involved in sulfur oxidation and nitrate reduction in different layers, indicating that sulfur oxidizing may be coupled to nitrate reducing at the surface layers of Jiaolong seeping site. This is probably related to the sulfur oxidizers of Sulfurimonas and Sulfurovum, which may be the capacity of nitrate reduction or associated with unidentified syntrophic nitrate-reducing microbes in the surface of the cold seep.

Selective layer disordering in intersubband Al 0.028Ga 0.972 N/AlN superlattices with silicon nitride capping layer

DOE PAGES

Wierer, Jonathan J.; Allerman, Andrew A.; Skogen, Erik J.; ...

2015-06-01

We demonstrate the selective layer disordering in intersubband Al 0.028Ga 0.972 N/AlN superlattices using a silicon nitride (SiN x) capping layer. The (SiN x) capped superlattice exhibits suppressed layer disordering under high-temperature annealing. In addition, the rate of layer disordering is reduced with increased SiN x thickness. The layer disordering is caused by Si diffusion, and the SiN x layer inhibits vacancy formation at the crystal surface and ultimately, the movement of Al and Ga atoms across the heterointerfaces. In conclusion, patterning of the SiN x layer results in selective layer disordering, an attractive method to integrate active and passivemore » III–nitride-based intersubband devices.« less

The influence of SrO and CaO in silicate and phosphate bioactive glasses on human gingival fibroblasts.

PubMed

Massera, J; Kokkari, A; Närhi, T; Hupa, L

2015-06-01

In this paper, we investigate the effect of substituting SrO for CaO in silicate and phosphate bioactive glasses on the human gingival fibroblast activity. In both materials the presence of SrO led to the formation of a CaP layer with partial Sr substitution for Ca. The layer at the surface of the silicate glass consisted of HAP whereas at the phosphate glasses it was close to the DCPD composition. In silicate glasses, SrO gave a faster initial dissolution and a thinner reaction layer probably allowing for a continuous ion release into the solution. In phosphate glasses, SrO decreased the dissolution process and gave a more strongly bonded reaction layer. Overall, the SrO-containing silicate glass led to a slight enhancement in the activity of the gingival fibroblasts cells when compared to the SrO-free reference glass, S53P4. The cell activity decreased up to 3 days of culturing for all phosphate glasses containing SrO. Whereas culturing together with the SrO-free phosphate glass led to complete cell death at 7 days. The glasses containing SrO showed rapid cell proliferation and growth between 7 and 14 days, reaching similar activity than glass S53P4. The addition of SrO in both silicate and phosphate glasses was assumed beneficial for proliferation and growth of human gingival fibroblasts due to Sr incorporation in the reaction layer at the glass surface and released in the cell culture medium.

Surface Modification of Titanium Using Anodization to Enhance Antimicrobial Properties and Osseointegration

NASA Astrophysics Data System (ADS)

Jain, Sakshi

Titanium and its alloys are frequently used in dental and orthopedic implants because they have good mechanical strength, chemical stability and biocompatibility. These properties can be further improved by surface treatments such as anodization that are able to grow thicker and produce crystalline oxide layers with controlled morphological and physico-chemical properties. Both anatase (A) and rutile (R) crystalline phases of titanium oxide have been shown to promote bioactivity and antimicrobial effects. In a previous study in our laboratories, four electrolyte mixtures were optimized to produce anodized layers on commercially pure titanium consisting of specific anatase and rutile oxide ratios at an endpoint forming voltage of 180 V. In the present study, changes that occurred in the anodized layers with increasing forming voltage including crystallinity, thickness, surface morphology, surface roughness, surface chemistry, fractal dimension, shear strength, and corrosion resistance were determined for each of these electrolytes. The results showed the crystallinity, thickness, surface pore sizes, and surface roughness increased with increasing forming voltage. Incorporation of phosphorus into the anodized layers was shown in phosphoric acid containing electrolytes at higher forming voltages. Decreases in corrosion resistance were also shown at higher forming voltages in each electrolyte due to increased pore interconnectivity within the anodized layers. In addition, the apatite inducing ability of anodized layers in SBF was examined for selected forming voltages in each electrolyte. Anodization in phosphoric acid containing electrolytes was shown to be more favorable for apatite formation. The streptococcal and MRSA bacterial attachment before and after UV treatments was determined for selected forming voltages in each electrolyte. Additionally, the killing efficacy after 10-minute pre-irradiation with UVA or UVC treatments was determined. UVA treatments showed trends of at least a 20% reduction in bacterial attachment regardless of the crystallinity within the oxide for S. sanguinis. The anodized layer with an approximately equal distribution of anatase and rutile phases showed bacterial killing efficacy over 50% for S. sanguinis and over 80% for MRSA after UVA or UVC treatments. Finally, two forming voltage sample groups in two of the electrolytes were examined for MC3T3E-1 cell attachment, proliferation, and differentiation. Total intracellular protein content, alkaline phosphatase (ALP) activity, osteocalcin (OCN) activity, and cellular mineralization were investigated for different time periods up to 21 days. All sample groups showed suitable cellular proliferation, differentiation, and maturation but those anodized in the phosphoric acid containing electrolyte showed delayed proliferation and early differentiation and maturation. Also, anodized samples containing at least 50% anatase were shown to produce higher osteoblast mineralization compared to majority rutile phase anodized layers.

The atmospheric boundary layer — advances in knowledge and application

NASA Astrophysics Data System (ADS)

Garratt, J. R.; Hess, G. D.; Physick, W. L.; Bougeault, P.

1996-02-01

We summarise major activities and advances in boundary-layer knowledge in the 25 years since 1970, with emphasis on the application of this knowledge to surface and boundary-layer parametrisation schemes in numerical models of the atmosphere. Progress in three areas is discussed: (i) the mesoscale modelling of selected phenomena; (ii) numerical weather prediction; and (iii) climate simulations. Future trends are identified, including the incorporation into models of advanced cloud schemes and interactive canopy schemes, and the nesting of high resolution boundary-layer schemes in global climate models.

Colloidal lithography with electrochemical nickel deposition as a unique method for improved silver decorated nanocavities in SERS applications

NASA Astrophysics Data System (ADS)

Petruš, Ondrej; Oriňak, Andrej; Oriňaková, Renáta; Orságová Králová, Zuzana; Múdra, Erika; Kupková, Miriam; Kovaľ, Karol

2017-11-01

Two types of metallised nanocavities (single and hybrid) were fabricated by colloid lithography followed by electrochemical deposition of Ni and subsequently Ag layers. Introductory Ni deposition step iniciates more homogenous decoration of nanocavities with Ag nanoparticles. Silver nanocavity decoration has been so performed with lower nucleation rate and with Ag nanoparticles homogeinity increase. By this, two step Ni and Ag deposition trough polystyrene nanospheres (100, 300, 500, 700, 900 nm), the various Ag surfaces were obtained. Ni layer formation in the first step of deposition enabled more precise controlling of Ag film deposition and thus final Ag surface morphology. Prepared substrates were tested as active surfaces in SERS application. The best SERS signal enhancement was observed at 500 nm Ag nanocavities with normalised thickness Ni layer ∼0.5. Enhancement factor has been established at value 1.078 × 1010; time stability was determined within 13 weeks; charge distribution at nanocavity Ag surfaces as well as reflection spectra were calculated by FDTD method. Newly prepared nanocavity surface can be applied in SERS analysis, predominantly.

Tailored adhesion behavior of polyelectrolyte thin films deposited on plasma-treated poly(dimethylsiloxane) for functionalized membranes

NASA Astrophysics Data System (ADS)

Bassil, Joelle; Alem, Halima; Henrion, Gérard; Roizard, Denis

2016-04-01

Completely homogenous films formed via the layer-by-layer assembly of poly(diallyldimethylammonium chloride) (PDADMAC) and the poly(styrene sulfonate) were successfully obtained on plasma-treated poly(dimethylsiloxane) (PDMS) substrates. To modify the hydrophobicity of the PDMS surface, a cold plasma treatment was previously applied to the membrane, which led to the creation of hydrophilic groups on the surface of the membrane. PDMS wettability and surface morphology were successfully correlated with the plasma parameters. A combination of contact angle measurements, scanning electron microscopy (SEM) and atomic force microscopy (AFM) analysis was used to demonstrate that homogeneous and hydrophilic surfaces could be achieved on PDMS cold-plasma-treated membranes. The stability of the assembled PEL layer on the PDMS was evaluated using a combination of pull-off testing and X-ray photoelectron spectroscopy (XPS), which confirmed the relevance of a plasma pre-treatment as the adhesion of the polyelectrolyte multilayers was greatly enhanced when the deposition was completed on an activated PDMS surface at 80 W for 5 min.

Bifunctional catalytic electrode

NASA Technical Reports Server (NTRS)

Cisar, Alan (Inventor); Murphy, Oliver J. (Inventor); Clarke, Eric (Inventor)

2005-01-01

The present invention relates to an oxygen electrode for a unitized regenerative hydrogen-oxygen fuel cell and the unitized regenerative fuel cell having the oxygen electrode. The oxygen electrode contains components electrocatalytically active for the evolution of oxygen from water and the reduction of oxygen to water, and has a structure that supports the flow of both water and gases between the catalytically active surface and a flow field or electrode chamber for bulk flow of the fluids. The electrode has an electrocatalyst layer and a diffusion backing layer interspersed with hydrophilic and hydrophobic regions. The diffusion backing layer consists of a metal core having gas diffusion structures bonded to the metal core.

Systems and methods for advanced ultra-high-performance InP solar cells

DOEpatents

Wanlass, Mark

2017-03-07

Systems and Methods for Advanced Ultra-High-Performance InP Solar Cells are provided. In one embodiment, an InP photovoltaic device comprises: a p-n junction absorber layer comprising at least one InP layer; a front surface confinement layer; and a back surface confinement layer; wherein either the front surface confinement layer or the back surface confinement layer forms part of a High-Low (HL) doping architecture; and wherein either the front surface confinement layer or the back surface confinement layer forms part of a heterointerface system architecture.

Effect of different irrigation on smear layer removal after post space preparation.

PubMed

Gu, Xin-Hua; Mao, Cai-Yun; Kern, Matthias

2009-04-01

The purpose of this study was to evaluate the effect of different irrigating solutions on smear layer removal and dentinal tubule opening on root canal surfaces after post space preparation and to study whether additional ultrasonic irrigation has any effect on smear layer removal. Forty-eight anterior teeth were treated endodontically. After post space preparation, they were assigned to six groups: group 1, EDTA; group 2, EDTA with ultrasonic activation; group 3, sodium hypochlorite (NaOCl); group 4, NaOCl with ultrasonic activation; group 5, sodium chloride (NaCl); and group 6, NaCl with ultrasonic activation. Specimens were examined under a field-emission scanning electron microscope and scored for debris removal and dentinal tubule opening at the coronal, middle, and apical thirds of the root canal. The results showed that EDTA performed significantly better than NaCl and NaOCl in smear layer removal and dentinal tubule opening. Additional ultrasonic irrigation did not improve smear layer removal significantly.

Efficiency enhancement of solution-processed inverted organic solar cells with a carbon-nanotube-doped active layer

NASA Astrophysics Data System (ADS)

Lin, Wen-Kai; Su, Shui-Hsiang; Yeh, Meng-Cheng; Huang, Yang-Chan; Yokoyama, Meiso

2016-01-01

Solution-processed titanium-doped ZnO (TZO) is synthesized by the sol-gel method to be the electron-transporting layer (ETL) in an inverted organic solar cell (IOSC). Carbon nanotubes (CNTs) are doped into an active layer of poly(3-hexylthiophene):[6,6]-phenyl C 61 butyric acid methyl ester (P3HT:PCBM). The addition of CNTs in the P3HT:PCBM composite increases the conjugation length of P3HT:PCBM:CNTs, which simultaneously enhances the capacity of the composite to absorb solar energy radiation. Vanadium oxide (V2O5) was spin-coated onto the active layer to be a hole-transporting layer (HTL). The power conversion efficiency (PCE) results indicate that the V2O5 nanobelt structure possesses better phase separation and provides a more efficient surface area for the P3HT:PCBM:CNT active layer to increase photocurrent. The optimized IOSCs exhibited an open circuit voltage (Voc), a short-circuit current density (Jsc), a fill factor (FF), and a PCE of 0.55 V, 6.50 mA/cm2, 58.34%, and 2.20%, respectively, under simulated AM1.5G illumination of 100 mW/cm2.

Diffuse sorption modeling.

PubMed

Pivovarov, Sergey

2009-04-01

This work presents a simple solution for the diffuse double layer model, applicable to calculation of surface speciation as well as to simulation of ionic adsorption within the diffuse layer of solution in arbitrary salt media. Based on Poisson-Boltzmann equation, the Gaines-Thomas selectivity coefficient for uni-bivalent exchange on clay, K(GT)(Me(2+)/M(+))=(Q(Me)(0.5)/Q(M)){M(+)}/{Me(2+)}(0.5), (Q is the equivalent fraction of cation in the exchange capacity, and {M(+)} and {Me(2+)} are the ionic activities in solution) may be calculated as [surface charge, mueq/m(2)]/0.61. The obtained solution of the Poisson-Boltzmann equation was applied to calculation of ionic exchange on clays and to simulation of the surface charge of ferrihydrite in 0.01-6 M NaCl solutions. In addition, a new model of acid-base properties was developed. This model is based on assumption that the net proton charge is not located on the mathematical surface plane but diffusely distributed within the subsurface layer of the lattice. It is shown that the obtained solution of the Poisson-Boltzmann equation makes such calculations possible, and that this approach is more efficient than the original diffuse double layer model.

Reaction Heterogeneity in LiNi 0.8 Co 0.15 Al 0.05 O 2 Induced by Surface Layer

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

Grenier, Antonin; Liu, Hao; Wiaderek, Kamila M.

2017-08-15

Through operando synchrotron powder X-ray diffraction (XRD) analysis of layered transition metal oxide electrodes of composition LiNi0.8Co0.15Al0.05O2 (NCA), we decouple the intrinsic bulk reaction mechanism from surface-induced effects. For identically prepared and cycled electrodes stored in different environments, we demonstrate that the intrinsic bulk reaction for pristine NCA follows solid-solution mechanism, not a two-phase as suggested previously. By combining high resolution powder X-ray diffraction, diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) and surface sensitive X-ray photoelectron spectroscopy (XPS), we demonstrate that adventitious Li2CO3 forms on the electrode particle surface during exposure to air, through reaction with atmospheric CO2. This surfacemore » impedes ionic and electronic transport to the underlying electrode, with progressive erosion of this layer during cycling giving rise to different reaction states in particles with an intact vs an eroded Li2CO3 surface-coating. This reaction heterogeneity, with a bimodal distribution of reaction states, has previously been interpreted as a “two-phase” reaction mechanism for NCA, as an activation step that only occurs during the first cycle. Similar surface layers may impact the reaction mechanism observed in other electrode materials using bulk probes such as operando powder XRD.« less

Enhanced carbon monoxide utilization in methanation process

DOEpatents

Elek, Louis F.; Frost, Albert C.

1984-01-01

Carbon monoxide - containing gas streams are passed over a catalyst to deposit a surface layer of active surface carbon thereon essentially without the formation of inactive coke. The active carbon is subsequently reacted with steam or hydrogen to form methane. Surprisingly, hydrogen and water vapor present in the feed gas do not adversely affect CO utilization significantly, and such hydrogen actually results in a significant increase in CO utilization.

Bimetallic alloy electrocatalysts with multilayered platinum-skin surfaces

DOEpatents

Stamenkovic, Vojislav R.; Wang, Chao; Markovic, Nenad M.

2016-01-26

Compositions and methods of preparing a bimetallic alloy having enhanced electrocatalytic properties are provided. The composition comprises a PtNi substrate having a surface layer, a near-surface layer, and an inner layer, where the surface layer comprises a nickel-depleted composition, such that the surface layer comprises a platinum skin having at least one atomic layer of platinum.

Layered Model for Radiation-Induced Chemical Evolution of Icy Surface Composition on Kuiper Belt and Oort Cloud Bodies

NASA Technical Reports Server (NTRS)

Cooper, John F.; Hill, Matthew E.; Richardson, John D.; Sturner, Steven J.

2010-01-01

The diversity of albedos and surface colors on observed Kuiper Belt and Inner Oort Cloud objects remains to be explained in terms of competition between primordial intrinsic versus exogenic drivers of surface and near-surface evolution. Earlier models have attempted without success to attribute this diversity to the relations between surface radiolysis from cosmic ray irradiation and gardening by meteoritic impacts. A more flexible approach considers the different depth-dependent radiation profiles produced by low-energy plasma, suprathermal, and maximally penetrating charged particles of the heliospheric and local interstellar radiation environments. Generally red objects of the dynamically cold (low inclination, circular orbit) Classical Kuiper Belt might be accounted for from erosive effects of plasma ions and reddening effects of high energy cosmic ray ions, while suprathermal keV-MeV ions could alternatively produce more color neutral surfaces. The deepest layer of more pristine ice can be brought to the surface from meter to kilometer depths by larger impact events and potentially by cryovolcanic activity. The bright surfaces of some larger objects, e.g. Eris, suggest ongoing resurfacing activity. Interactions of surface irradiation, resultant chemical oxidation, and near-surface cryogenic fluid reservoirs have been proposed to account for Enceladus cryovolcanism and may have further applications to other icy irradiated bodies. The diversity of causative processes must be understood to account for observationally apparent diversities of the object surfaces.

Development and coupling analysis of active skin antenna

NASA Astrophysics Data System (ADS)

Zhou, Jinzhu; Huang, Jin; He, Qingqang; Tang, Baofu; Song, Liwei

2017-02-01

An active skin antenna is a multifunctional composite structure that can provide load-bearing structure and steerable beam pointing functions, and is usually installed in the structural surface of aircraft, warships, and armored vehicles. This paper presents an innovative design of the active skin antenna, which consists of a package layer, control and signal processing layer, and RF (radio frequency) layer. The RF layer is fabricated by low temperature co-fired ceramics, with 64 microstrip antenna elements, tile transmitting and receiving modules, microchannel heat sinks, and feeding networks integrated into a functional block 2.8 mm thick. In this paper, a full-sized prototype of an active skin antenna was designed, fabricated, and tested. Moreover, a coupling analysis method was presented to evaluate the mechanical and electromagnetic performance of the active skin antenna subjected to aerodynamic loads. A deformed experimental system was built to validate the effectiveness of the coupling analysis method, which was also implemented to evaluate the performance of the active skin antenna when subjected to aerodynamic pressure. The fabricated specimen demonstrated structural configuration feasibility, and superior environmental load resistance.

Improved Mobility and Bias Stability of Thin Film Transistors Using the Double-Layer a-InGaZnO/a-InGaZnO:N Channel.

PubMed

Yu, H; Zhang, L; Li, X H; Xu, H Y; Liu, Y C

2016-04-01

The amorphous indium-gallium-zinc oxide (a-IGZO) thin film transistors (TFTs) were demonstrated based on a double-layer channel structure, where the channel is composed of an ultrathin nitro-genated a-IGZO (a-IGZO:N) layer and an undoped a-IGZO layer. The double-layer channel device showed higher saturation mobility and lower threshold-voltage shift (5.74 cm2/Vs, 2.6 V) compared to its single-layer counterpart (0.17 cm2/Vs, 7.23 V). The improvement can be attributed to three aspects: (1) improved carrier transport properties of the channel by the a-IGZO:N layer with high carrier mobility and the a-IGZO layer with high carrier concentration, (2) reduced interfacial trap density between the active channel and the gate insulator, and (3) higher surface flatness of the double-layer channel. Our study reveals key insights into double-layer channel, involving selecting more suitable electrical property for back-channel layer and more suitable interface modification for active layer. Meanwhile, room temperature fabrication amorphous TFTs offer certain advantages on better flexibility and higher uniformity over a large area.

Single-unit-cell layer established Bi 2 WO 6 3D hierarchical architectures: Efficient adsorption, photocatalysis and dye-sensitized photoelectrochemical performance

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

Huang, Hongwei; Cao, Ranran; Yu, Shixin

Single-layer catalysis sparks huge interests and gains widespread attention owing to its high activity. Simultaneously, three-dimensional (3D) hierarchical structure can afford large surface area and abundant reactive sites, contributing to high efficiency. Herein, we report an absorbing single-unit-cell layer established Bi2WO6 3D hierarchical architecture fabricated by a sodium dodecyl benzene sulfonate (SDBS)-assisted assembled strategy. The DBS- long chains can adsorb on the (Bi2O2)2+ layers and hence impede stacking of the layers, resulting in the single-unit-cell layer. We also uncovered that SDS with a shorter chain is less effective than SDBS. Due to the sufficient exposure of surface O atoms, single-unit-cellmore » layer 3D Bi2WO6 shows strong selectivity for adsorption on multiform organic dyes with different charges. Remarkably, the single-unit-cell layer 3D Bi2WO6 casts profoundly enhanced photodegradation activity and especially a superior photocatalytic H2 evolution rate, which is 14-fold increase in contrast to the bulk Bi2WO6. Systematic photoelectrochemical characterizations disclose that the substantially elevated carrier density and charge separation efficiency take responsibility for the strengthened photocatalytic performance. Additionally, the possibility of single-unit-cell layer 3D Bi2WO6 as dye-sensitized solar cells (DSSC) has also been attempted and it was manifested to be a promising dye-sensitized photoanode for oxygen evolution reaction (ORR). Our work not only furnish an insight into designing single-layer assembled 3D hierarchical architecture, but also offer a multi-functional material for environmental and energy applications.« less

Heterojunction light emitting diodes fabricated with different n-layer oxide structures on p-GaN layers by magnetron sputtering

NASA Astrophysics Data System (ADS)

Kong, Bo Hyun; Han, Won Suk; Kim, Young Yi; Cho, Hyung Koun; Kim, Jae Hyun

2010-06-01

We grew heterojunction light emitting diode (LED) structures with various n-type semiconducting layers by magnetron sputtering on p-type GaN at high temperature. Because the undoped ZnO used as an active layer was grown under oxygen rich atmosphere, all LED devices showed the EL characteristics corresponding to orange-red wavelength due to high density of oxygen interstitial, which was coincident with the deep level photoluminescence emission of undoped ZnO. The use of the Ga doped layers as a top layer provided the sufficient electron carriers to active region and resulted in the intense EL emission. The LED sample with small quantity of Mg incorporated in MgZnO as an n-type top layer showed more intense emission than the LED with ZnO, in spite of the deteriorated electrical and structural properties of the MgZnO film. This might be due to the improvement of output extraction efficiency induced by rough surface.

Measurement of corner separation zone response on a compression ramp to plasma actuation within the hypersonic boundary layer

NASA Astrophysics Data System (ADS)

Hedlund, Brock E.; Houpt, Alec W.; Gordeyev, Stanislav V.; Leonov, Sergey B.

2017-10-01

This study was performed to characterize the dominant frequencies present in the boundary layer uptsream of and in the corner separation zone of a compression surface in Mach 4.5 flow and to determine a control effect of transient plasma actuation on the boundary layer. Schlieren imaging was used to distinguish the corner separation zone for 20°, 25°, and 30° compression ramps mounted on flat plates. Spectra of the natural disturbances present in the boundary layer and separation zone were gathered using a high-speed Shack-Hartmann wavefront sensor and surface mounted PCBTM pressure sensors while varying flow parameters by adjusting total pressure, temperature, and ramp angle. Shallow cavity discharge plasma actuators were used as a high-frequency localized thermal forcing mechanism of the boundary layer. The plasma effect was negligible for forcing frequencies (50 kHz) below the natural dominant frequency (~55-80 kHz). High frequency perturbations that can promote the transition to turbulence were amplified when the plasma forcing frequency (100 kHz) was higher than the natural dominant frequency (~55-80 kHz). This technique can potentially be used for active control of hypersonic boundary layer transition and the supersonic flow structure on the compression surface.

Modelling hazardous surface hoar layers in the mountain snowpack over space and time

NASA Astrophysics Data System (ADS)

Horton, Simon Earl

Surface hoar layers are a common failure layer in hazardous snow slab avalanches. Surface hoar crystals (frost) initially form on the surface of the snow, and once buried can remain a persistent weak layer for weeks or months. Avalanche forecasters have difficulty tracking the spatial distribution and mechanical properties of these layers in mountainous terrain. This thesis presents numerical models and remote sensing methods to track the distribution and properties of surface hoar layers over space and time. The formation of surface hoar was modelled with meteorological data by calculating the downward flux of water vapour from the atmospheric boundary layer. The timing of surface hoar formation and the modelled crystal size was verified at snow study sites throughout western Canada. The major surface hoar layers over several winters were predicted with fair success. Surface hoar formation was modelled over various spatial scales using meteorological data from weather forecast models. The largest surface hoar crystals formed in regions and elevation bands with clear skies, warm and humid air, cold snow surfaces, and light winds. Field surveys measured similar regional-scale patterns in surface hoar distribution. Surface hoar formation patterns on different slope aspects were observed, but were not modelled reliably. Mechanical field tests on buried surface hoar layers found layers increased in shear strength over time, but had persistent high propensity for fracture propagation. Layers with large crystals and layers overlying hard melt-freeze crusts showed greater signs of instability. Buried surface hoar layers were simulated with the snow cover model SNOWPACK and verified with avalanche observations, finding most hazardous surface hoar layers were identified with a structural stability index. Finally, the optical properties of surface hoar crystals were measured in the field with spectral instruments. Large plate-shaped crystals were less reflective at shortwave infrared wavelengths than other common surface snow grains. The methods presented in this thesis were developed into operational products that model hazardous surface hoar layers in western Canada. Further research and refinements could improve avalanche forecasts in regions prone to hazardous surface hoar layers.

Powder-in-tube and thick-film methods of fabricating high temperature superconductors having enhanced biaxial texture

DOEpatents

Goyal, Amit; Kroeger, Donald M.

2003-11-11

A method for forming an electronically active biaxially textured article includes the steps of providing a substrate having a single crystal metal or metal alloy surface, deforming the substrate to form an elongated substrate surface having biaxial texture and depositing an epitaxial electronically active layer on the biaxially textured surface. The method can include at least one annealing step after the deforming step to produce the biaxially textured substrate surface. The invention can be used to form improved biaxially textured articles, such as superconducting wire and tape articles having improved J.sub.c values.

Measuring water adsorption on mineral surfaces in air, CO2, and supercritical CO2 with a quartz-crystal microbalance

NASA Astrophysics Data System (ADS)

Bryan, C. R.; Wells, R. K.; Burton, P. D.; Heath, J. E.; Dewers, T. A.; Wang, Y.

2011-12-01

Carbon sequestration via underground storage in geologic formations is a proposed approach for reducing industrial CO2 emissions. However, current models for carbon injection and long-term storage of supercritical CO2 (scCO2) do not consider the development and stability of adsorbed water films at the scCO2-hydrophilic mineral interface. The thickness and properties of the water films control the surface tension and wettability of the mineral surface, and on the core scale, affect rock permeability, saturation, and capillary properties. The film thickness is strongly dependent upon the activity of water in the supercritical fluid, which will change as initially anhydrous scCO2 absorbs water from formation brine. As described in a companion paper by the coauthors, the thickness of the adsorbed water layer is controlled by the disjoining pressure; structural and van der Waals components dominate at low water activity, while electrostatic forces become more important with increasing film thickness (higher water activities). As scCO2 water activity and water layer thickness increase, concomitant changes in mineral surface properties and reservoir/caprock hydrologic properties will affect the mobility of the aqueous phase and of scCO2. Moreover, the development of a water layer may be critical to mineral dissolution reactions in scCO2. Here, we describe the use of a quartz-crystal microbalance (QCM) to monitor adsorption of water by mineral surfaces. QCMs utilize a piezoelectrically-stimulated quartz wafer to measure adsorbed or deposited mass via changes in vibrational frequency. When used to measure the mass of adsorbed liquid films, the frequency response of the crystal must be corrected for the viscoelastic, rather than elastic, response of the adsorbed layer. Results are presented for adsorption to silica in N2 and CO2 at one bar, and in scCO2. Additional data are presented for water uptake by clays deposited on a QCM wafer. In this case, water uptake occurs by the combined processes of interlayer cation hydration, surface adsorption, and capillary condensation. Sandia National Laboratories is a multi-program laboratory managed and operated by Sandia Corporation, a wholly owned subsidiary of Lockheed Martin Corporation, for the U.S. Department of Energy's National Nuclear Security Administration under contract DE-AC04-94AL85000. This work is supported by the DOE Sandia LDRD Program.

Infrared emitting device and method

DOEpatents

Kurtz, S.R.; Biefeld, R.M.; Dawson, L.R.; Howard, A.J.; Baucom, K.C.

1997-04-29

The infrared emitting device comprises a III-V compound semiconductor substrate upon which are grown a quantum-well active region having a plurality of quantum-well layers formed of a ternary alloy comprising InAsSb sandwiched between barrier layers formed of a ternary alloy having a smaller lattice constant and a larger energy bandgap than the quantum-well layers. The quantum-well layers are preferably compressively strained to increase the threshold energy for Auger recombination; and a method is provided for determining the preferred thickness for the quantum-well layers. Embodiments of the present invention are described having at least one cladding layer to increase the optical and carrier confinement in the active region, and to provide for waveguiding of the light generated within the active region. Examples have been set forth showing embodiments of the present invention as surface- and edge-emitting light emitting diodes (LEDs), an optically-pumped semiconductor laser, and an electrically-injected semiconductor diode laser. The light emission from each of the infrared emitting devices of the present invention is in the midwave infrared region of the spectrum from about 2 to 6 microns. 8 figs.

Display of fungal hydrophobin on the Pichia pastoris cell surface and its influence on Candida antarctica lipase B

PubMed Central

Wang, Pan; He, Jie; Sun, Yufei; Reynolds, Matthew; Zhang, Li; Han, Shuangyan; Liang, Shuli; Sui, Haixin; Lin, Ying

2016-01-01

To modify the Pichia pastoris cell surface, two classes of hydrophobins, SC3 from Schizophyllum commune and HFBI from Trichoderma reesei, were separately displayed on the cell wall. There was an observable increase in the hydrophobicity of recombinant strains. Candida antarctica lipase B (CALB) was then co-displayed on the modified cells, generating strains GS115/SC3-61/CALB-51 and GS115/HFBI-61/CALB-51. Interestingly, the hydrolytic and synthetic activities of strain GS115/HFBI-61/CALB-51 increased by 37% and 109%, respectively, but decreased by 26% and 43%, respectively, in strain GS115/SC3-61/CALB-51 compared with the hydrophobin-minus recombinant strain GS115/CALB-GCW51. The amount of glycerol by-product from the transesterification reaction adsorbed on the cell surface was significantly decreased following hydrophobin modification, removing the glycerol barrier and allowing substrates to access the active sites of lipases. Electron micrographs indicated that the cell wall structures of both recombinant strains appeared altered, including changes to the inner glucan layer and outer mannan layer. These results suggest that the display of hydrophobins can change the surface structure and hydrophobic properties of P. pastoris, and affect the catalytic activities of CALB displayed on the surface of P. pastoris cells. PMID:26969039

Application of sound and temperature to control boundary-layer transition

NASA Technical Reports Server (NTRS)

Maestrello, Lucio; Parikh, Paresh; Bayliss, A.; Huang, L. S.; Bryant, T. D.

1987-01-01

The growth and decay of a wave packet convecting in a boundary layer over a concave-convex surface and its active control by localized surface heating are studied numerically using direct computations of the Navier-Stokes equations. The resulting sound radiations are computed using linearized Euler equations with the pressure from the Navier-Stokes solution as a time-dependent boundary condition. It is shown that on the concave portion the amplitude of the wave packet increases and its bandwidth broadens while on the convex portion some of the components in the packet are stabilized. The pressure field decays exponentially away from the surface and then algebraically, exhibiting a decay characteristic of acoustic waves in two dimensions. The far-field acoustic behavior exhibits a super-directivity type of behavior with a beaming downstream. Active control by surface heating is shown to reduce the growth of the wave packet but have little effect on acoustic far field behavior for the cases considered. Active control by sound emanating from the surface of an airfoil in the vicinity of the leading edge is experimentally investigated. The purpose is to control the separated region at high angles of attack. The results show that injection of sound at shedding frequency of the flow is effective in an increase of lift and reduction of drag.

Biological and immunotoxicity evaluation of antimicrobial peptide-loaded coatings using a layer-by-layer process on titanium

PubMed Central

Shi, Jue; Liu, Yu; Wang, Ying; Zhang, Jing; Zhao, Shifang; Yang, Guoli

2015-01-01

The prevention and control of peri-implantitis is a challenge in dental implant surgery. Dental implants with sustained antimicrobial coating are an ideal way of preventing peri-implantitis. This study reports development of a non- immunotoxicity multilayered coating on a titanium surface that had sustained antimicrobial activity and limited early biofilm formation. In this study, the broad spectrum AMP, Tet213, was linked to collagen IV through sulfo-SMPB and has been renamed as AMPCol. The multilayer AMPCol coatings were assembled on smooth titanium surfaces using a LBL technique. Using XPS, AFM, contact angle analysis, and QCM, layer-by-layer accumulation of coating thickness was measured and increased surface wetting compared to controls was confirmed. Non-cytotoxicity to HaCaT and low erythrocyte hemolysis by the AMPCol coatings was observed. In vivo immunotoxicity assays showed IP administration of AMPCol did not effect serum immunoglobulin levels. This coating with controlled release of AMP decreased the growth of both a Gram-positive aerobe (Staphylococcus aureus) and a Gram-negative anaerobe (Porphyromonas gingivalis) up to one month. Early S. aureus biofilm formation was inhibited by the coating. The excellent long-term sustained antimicrobial activity of this multilayer coating is a potential method for preventing peri-implantitis through coated on the neck of implants before surgery. PMID:26548760

[MoS4]2- Cluster Bridges in Co-Fe Layered Double Hydroxides for Mercury Uptake from S-Hg Mixed Flue Gas.

PubMed

Xu, Haomiao; Yuan, Yong; Liao, Yong; Xie, Jiangkun; Qu, Zan; Shangguan, Wenfeng; Yan, Naiqiang

2017-09-05

[MoS 4 ] 2- clusters were bridged between CoFe layered double hydroxide (LDH) layers using the ion-exchange method. [MoS 4 ] 2- /CoFe-LDH showed excellent Hg 0 removal performance under low and high concentrations of SO 2 , highlighting the potential for such material in S-Hg mixed flue gas purification. The maximum mercury capacity was as high as 16.39 mg/g. The structure and physical-chemical properties of [MoS 4 ] 2- /CoFe-LDH composites were characterized with FT-IR, XRD, TEM&SEM, XPS, and H 2 -TPR. [MoS 4 ] 2- clusters intercalated into the CoFe-LDH layered sheets; then, we enlarged the layer-to-layer spacing (from 0.622 to 0.880 nm) and enlarged the surface area (from 41.4 m 2 /g to 112.1 m 2 /g) of the composite. During the adsorption process, the interlayer [MoS 4 ] 2- cluster was the primary active site for mercury uptake. The adsorbed mercury existed as HgS on the material surface. The absence of active oxygen results in a composite with high sulfur resistance. Due to its high efficiency and SO 2 resistance, [MoS 4 ] 2- /CoFe-LDH is a promising adsorbent for mercury uptake from S-Hg mixed flue gas.

Noble metal free photocatalytic H 2 generation on black TiO 2: On the influence of crystal facets vs. crystal damage

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

Liu, Ning; Steinrück, Hans-Georg; Osvet, Andres

In this study, we investigate noble metal free photocatalytic water splitting on natural anatase single crystal facets and on wafer slices of the [001] plane before and after these surfaces have been modified by high pressure hydrogenation and hydrogen ion-implantation. Here, we find that on the natural, intact low index planes, photocatalytic H 2 evolution (in the absence of a noble metal co-catalyst) can only be achieved when the hydrogenation treatment is accompanied by the introduction of crystal damage, such as simple scratching and miscut in the crystal, or by implantation damage. X-ray reflectivity, Raman, and optical reflection measurements showmore » that plain hydrogenation leads to a ≈ 1 nm thick black titania surface layer without activity, while a colorless, density modified, and ≈7 nm thick layer with broken crystal symmetry is present on the ion implanted surface. These results demonstrate that (i) the H-treatment of an intact anatase surface needs to be combined with defect formation for catalytic activation and (ii) activation does not necessarily coincide with the presence of black color.« less

A novel carbon electrode material for highly improved EDLC performance.

PubMed

Fang, Baizeng; Binder, Leo

2006-04-20

Porous materials, developed by grafting functional groups through chemical surface modification with a surfactant, represent an innovative concept in energy storage. This work reports, in detail, the first practical realization of a novel carbon electrode based on grafting of vinyltrimethoxysilane (vtmos) functional group for energy storage in electric double layer capacitor (EDLC). Surface modification with surfactant vtmos enhances the hydrophobisation of activated carbon and the affinity toward propylene carbonate (PC) solvent, which improves the wettability of activated carbon in the electrolyte solution based on PC solvent, resulting in not only a lower resistance to the transport of electrolyte ions within micropores of activated carbon but also more usable surface area for the formation of electric double layer, and accordingly, higher specific capacitance, energy density, and power capability available from the capacitor based on modified carbon. Especially, the effects from surface modification become superior at higher discharge rate, at which much better EDLC performance (i.e., much higher energy density and power capability) has been achieved by the modified carbon, suggesting that the modified carbon is a novel and very promising electrode material of EDLC for large current applications where both high energy density and power capability are required.

Growth cycle of Helicobacter pylori in gastric mucous layer.

PubMed

Nakazawa, Teruko

2002-12-01

Helicobacter pylori bacterium is characterized by its strong urease activity. Our studies on the role of H. pylori urease revealed; (i) it is essential for colonization, (ii) exogenous urea is required for acid resistance, (iii) the bacteria have the ability to move toward urea and sodium bicarbonate, (iv) urea hydrolysis accelerates chemotactic locomotion, and (v) decay of urease mRNA to accomplish the active center is pH-regulated; i.e., the mRNA is stabilized and destabilized under acidic and neutral conditions, respectively. Based on the above results, I propose the growth cycle of H. pylori in gastric mucous layer. H. pylori bacteria proliferate on the epithelial cell surface by utilizing nutrients derived from degraded cells. Proliferated bacteria leave the cell surface to pH-variable region where they encounter strong acid. Urease is activated with simultaneous opening of UreI channel so that urea is hydrolyzed to neutralize acid. Chemotaxis of H. pylori toward urea and sodium bicarbonate that are abundant on the cell surface is accelerated by urea hydrolysis so that the bacteria go back to the cell surface for the next round of proliferation. This growth cycle may allow the bacteria to infect persistently in the stomach.

Noble metal free photocatalytic H 2 generation on black TiO 2: On the influence of crystal facets vs. crystal damage

DOE PAGES

Liu, Ning; Steinrück, Hans-Georg; Osvet, Andres; ...

2017-02-13

In this study, we investigate noble metal free photocatalytic water splitting on natural anatase single crystal facets and on wafer slices of the [001] plane before and after these surfaces have been modified by high pressure hydrogenation and hydrogen ion-implantation. Here, we find that on the natural, intact low index planes, photocatalytic H 2 evolution (in the absence of a noble metal co-catalyst) can only be achieved when the hydrogenation treatment is accompanied by the introduction of crystal damage, such as simple scratching and miscut in the crystal, or by implantation damage. X-ray reflectivity, Raman, and optical reflection measurements showmore » that plain hydrogenation leads to a ≈ 1 nm thick black titania surface layer without activity, while a colorless, density modified, and ≈7 nm thick layer with broken crystal symmetry is present on the ion implanted surface. These results demonstrate that (i) the H-treatment of an intact anatase surface needs to be combined with defect formation for catalytic activation and (ii) activation does not necessarily coincide with the presence of black color.« less

Calcium-doped ceria/titanate tabular functional nanocomposite by layer-by-layer coating method

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

Liu, Xiang W., E-mail: lxwluck@gmail.co; Devaraju, M.K.; Yin, Shu

2010-07-15

Ca-doped ceria (CDC)/tabular titanate (K{sub 0.8}Li{sub 0.27}Ti{sub 1.73}O{sub 4}, TT) UV-shielding functional nanocomposite with fairly uniform CDC coating layers was prepared through a polyelectrolyte-associated layer-by-layer (LbL) coating method. TT with lepidocrocite-like layered structure was used as the substrate, poly (diallyldimethylammonium chloride) (PDDA) was used as a coupling agent, CDC nanoparticles were used as the main UV-shielding component. CDC/TT nanocomposites with various coating layers of CDC were obtained through a multistep coating process. The phases were studied by X-ray diffraction. The morphology and coating quality were studied by scanning electron microscopy and element mapping of energy dispersive X-ray analysis. The oxidationmore » catalytic activity, UV-shielding ability and using comfort were characterized by Rancimat test, UV-vis spectra and dynamic friction test, respectively. CDC/TT nanocomposites with low oxidation catalytic activity, high UV-shielding ability and good using comfort were finally obtained. - Graphical abstract: Through the control of surface charge of particles calcium-doped ceria/titanate composites with low oxidation catalytic activity, higher UV-shielding ability and excellent comfort was obtained by a facile layer-by-layer coating method.« less

Observing the Electrochemical Oxidation of Co Metal at the Solid/Liquid Interface Using Ambient Pressure X-ray Photoelectron Spectroscopy

DOE PAGES

Han, Yong; Axnanda, Stephanus; Crumlin, Ethan J.; ...

2017-08-28

Some rcent advances of ambient pressure X-ray photoelectron spectroscopy (AP-XPS) have enabled the chemical composition and the electrical potential profile at a liquid/electrode interface under electrochemical reaction conditions to be directly probed. In this work, we apply this operando technique to study the surface chemical composition evolution on a Co metal electrode in 0.1 M KOH aqueous solution under various electrical biases. It is found that an ~12.2 nm-thick layer of Co(OH) 2 forms at a potential of about -0.4 V Ag/AgCl, and upon increasing the anodic potential to about +0.4 V Ag/AgCl, this layer is partially oxidized into cobaltmore » oxyhydroxide (CoOOH). A CoOOH/Co(OH) 2 mixture layer is formed on the top of the electrode surface. Finally, the oxidized surface layer can be reduced to Co0 at a cathodic potential of -1.35 VAg/Cl. Our observations indicate that the ultrathin layer containing cobalt oxyhydroxide is the active phase for oxygen evolution reaction (OER) on a Co electrode in an alkaline electrolyte, consistent with previous studies.« less

Heparin-mimicking multilayer coating on polymeric membrane via LbL assembly of cyclodextrin-based supramolecules.

PubMed

Deng, Jie; Liu, Xinyue; Ma, Lang; Cheng, Chong; Shi, Wenbin; Nie, Chuanxiong; Zhao, Changsheng

2014-12-10

In this study, multifunctional and heparin-mimicking star-shaped supramolecules-deposited 3D porous multilayer films with improved biocompatibility were fabricated via a layer-by-layer (LbL) self-assembly method on polymeric membrane substrates. Star-shaped heparin-mimicking polyanions (including poly(styrenesulfonate-co-sodium acrylate; Star-PSS-AANa) and poly(styrenesulfonate-co-poly(ethylene glycol)methyl ether methacrylate; Star-PSS-EGMA)) and polycations (poly(methyl chloride-quaternized 2-(dimethylamino)ethyl methacrylate; Star-PMeDMA) were first synthesized by atom transfer radical polymerization (ATRP) from β-cyclodextrin (β-CD) based cores. Then assembly of 3D porous multilayers onto polymeric membrane surfaces was carried out by alternating deposition of the polyanions and polycations via electrostatic interaction. The surface morphology and composition, water contact angle, blood activation, and thrombotic potential as well as cell viability for the coated heparin-mimicking films were systematically investigated. The results of surface ATR-FTIR spectra and XPS spectra verified successful deposition of the star-shaped supramolecules onto the biomedical membrane surfaces; scanning electron microscopy (SEM) and atomic force microscopy (AFM) observations revealed that the modified substrate had 3D porous surface morphology, which might have a great biological influence on the biointerface. Furthermore, systematic in vitro investigation of protein adsorption, platelet adhesion, human platelet factor 4 (PF4, indicates platelet activation), activate partial thromboplastin time (APTT), thrombin time (TT), coagulation activation (thrombin-antithrombin III complex (TAT, indicates blood coagulant)), and blood-related complement activation (C3a and C5a, indicates inflammation potential) confirmed that the heparin-mimicking multilayer coated membranes exhibited ultralow blood component activations and excellent hemocompatibility. Meanwhile, after surface coating, endothelial cell viability was also promoted, which indicated that the heparin-mimicking multilayer coating might extend the application fields of polymeric membranes in biomedical fields.

The concurrent use of novel soil surface microclimate measurements to evaluate CO2 pulses in biocrusted interspaces in a cool desert ecosystem

USGS Publications Warehouse

Tucker, Colin; McHugh, Theresa A.; Howell, Armin; Gill, Richard; Weber, Bettina; Belnap, Jayne; Grote, Ed; Reed, Sasha C.

2017-01-01

Carbon cycling associated with biological soil crusts, which occupy interspaces between vascular plants in drylands globally, may be an important part of the coupled climate-carbon cycle of the Earth system. A major challenge to understanding CO2 fluxes in these systems is that much of the biotic and biogeochemical activity occurs in the upper few mm of the soil surface layer (i.e., the ‘mantle of fertility’), which exhibits highly dynamic and difficult to measure temperature and moisture fluctuations. Here, we report a multi-sensor approach to simultaneously measuring temperature and moisture of this biocrust surface layer (0–2 mm), and the deeper soil profile, concurrent with automated measurement of surface soil CO2effluxes. Our results illuminate robust relationships between biocrust water content and field CO2 pulses that have previously been difficult to detect and explain. All observed CO2 pulses over the measurement period corresponded to surface wetting events, including when the wetting events did not penetrate into the soil below the biocrust layer (0–2 mm). The variability of temperature and moisture of the biocrust surface layer was much greater than even in the 0–5 cm layer of the soil beneath the biocrust, or deeper in the soil profile. We therefore suggest that coupling surface measurements of biocrust moisture and temperature to automated CO2flux measurements may greatly improve our understanding of the climatic sensitivity of carbon cycling in biocrusted interspaces in our study region, and that this method may be globally relevant and applicable.

Electrical responses of artificial DNA nanostructures on solution-processed In-Ga-Zn-O thin-film transistors with multistacked active layers.

PubMed

Jung, Joohye; Kim, Si Joon; Yoon, Doo Hyun; Kim, Byeonghoon; Park, Sung Ha; Kim, Hyun Jae

2013-01-01

We propose solution-processed In-Ga-Zn-O (IGZO) thin-film transistors (TFTs) with multistacked active layers for detecting artificial deoxyribonucleic acid (DNA). Enhanced sensing ability and stable electrical performance of TFTs were achieved through use of multistacked active layers. Our IGZO TFT had a turn-on voltage (V(on)) of -0.8 V and a subthreshold swing (SS) value of 0.48 V/decade. A dry-wet method was adopted to immobilize double-crossover DNA on the IGZO surface, after which an anomalous hump effect accompanying a significant decrease in V(on) (-13.6 V) and degradation of SS (1.29 V/decade) was observed. This sensing behavior was attributed to the middle interfaces of the multistacked active layers and the negatively charged phosphate groups on the DNA backbone, which generated a parasitic path in the TFT device. These results compared favorably with those reported for conventional field-effect transistor-based DNA sensors with remarkable sensitivity and stability.

Orienting the Microstructure Evolution of Copper Phthalocyanine as an Anode Interlayer in Inverted Polymer Solar Cells for High Performance.

PubMed

Li, Zhiqi; Liu, Chunyu; Zhang, Xinyuan; Li, Shujun; Zhang, Xulin; Guo, Jiaxin; Guo, Wenbin; Zhang, Liu; Ruan, Shengping

2017-09-20

Recent advances in the interfacial modification of inverted-type polymer solar cells (PSCs) have resulted from controlling the surface energy of the cathode-modified layer (TiO 2 or ZnO) to enhance the short-circuit current (J sc ) or optimizing the contact morphology of the cathode (indium tin oxide or fluorine-doped tin oxide) and active layer to increase the fill factor. Herein, we report that the performance enhancement of PSCs is achieved by incorporating a donor macromolecule copper phthalocyanine (CuPc) as an anode modification layer. Using the approach based on orienting the microstructure evolution, uniformly dispersed island-shaped CuPc spot accumulations are built on the top of PTB7:PC 71 BM blend film, leading to an efficient spectral absorption and photogenerated exciton splitting. The best power conversion efficiency of PSCs is increased up to 9.726%. In addition to the enhanced light absorption, the tailored anode energy level alignment and optimized boundary morphology by incorporating the CuPc interlayer boost charge extraction efficiency and suppress the interfacial molecular recombination. These results demonstrate that surface morphology induction through molecular deposition is an effective method to improve the performance of PSCs, which reveals the potential implications of the interlayer between the organic active layer and the electrode buffer layer.

The electrodeposition of multilayers on a polymeric substrate in flexible organic photovoltaic solar cells

NASA Astrophysics Data System (ADS)

Guedes, Andre F. S.; Guedes, Vilmar P.; Souza, Monica L.; Tartari, Simone; Cunha, Idaulo J.

2015-09-01

Flexible organic photovoltaic solar cells have drawn intense attention due to their advantages over competing solar cell technologies. The method utilized to deposit as well as to integrate solutions and processed materials, manufacturing organic solar cells by the Electrodeposition System, has been presented in this research. In addition, we have demonstrated a successful integration of a process for manufacturing the flexible organic solar cell prototype and we have discussed on the factors that make this process possible. The maximum process temperature was 120°C, which corresponds to the baking of the active polymeric layer. Moreover, the new process of the Electrodeposition of complementary active layer is based on the application of voltage versus time in order to obtain a homogeneous layer with thin film. This thin film was not only obtained by the electrodeposition of PANI-X1 on P3HT/PCBM Blend, but also prepared in perchloric acid solution. Furthermore, these flexible organic photovoltaic solar cells presented power conversion efficiency of 12% and the inclusion of the PANI-X1 layer reduced the effects of degradation on these organic photovoltaic panels induced by solar irradiation. Thus, in the Scanning Electron Microscopy (SEM), these studies have revealed that the surface of PANI-X1 layers is strongly conditioned by the dielectric surface morphology.

Liquid eutectic GaIn as an alternative electrode for PTB7:PCBM organic solar cells

NASA Astrophysics Data System (ADS)

Thanh Hau Pham, Viet; Kieu Trinh, Thanh; Tam Nguyen Truong, Nguyen; Park, Chinho

2017-04-01

Conventional vacuum deposition process of aluminum (Al) is costly, time-consuming and difficult to apply to the large-scale production of organic photovoltaic devices (OPV). This paper reports a vacuum-free fabrication process of poly[[4,8-bis(2-ethylhexyl)oxy]benzo[1,2-b:4,5-b‧]dithiophene-2,6-diyl][3-fluoro-2-[(2-ethylhexyl)carbonyl]thienophenediyl]:[6,6]-phenyl C71 butyric acid methyl ester (PTB7:PCBM) bulk heterojunction organic solar cell with liquid eutectic gallium-indium (EGaIn) electrode as an alternative to the common Al electrode. The insertion of a thin poly(ethylene oxide) (PEO) layer after depositing organic photoactive layer could help prevent the diffusion of liquid EGaIn into the active layer and allow the deposition of the EGaIn electrode. The PEO interfacial layer was formed by spin-coating from a mixed solvent of alcohol and water. Among different alcohol+water (methanol, ethanol, ethylene glycol, n-propanol, isopropanol, and isobutanol) mixed solvent tested, the n-propanol+water mixed solvent showed the greatest enhancement to the performance of OPVs. The improved device performance was attributed to the reactivity of mixed solvent n-propanol+water toward the surface of PTB7:PCBM active layer, which could help optimize surface morphology.

Monolithically interconnected silicon-film™ module technology

NASA Astrophysics Data System (ADS)

DelleDonne, E. J.; Ford, D. H.; Hall, R. B.; Ingram, A. E.; Rand, J. A.; Barnett, A. M.

1999-03-01

AstroPower is developing an advanced thin-silicon-based, photovoltaic module product. A low-cost monolithic interconnected device is being integrated into a module that combines the design and process features of advanced light trapped, thin-silicon solar cells. This advanced product incorporates a low-cost substrate, a nominally 50-μm thick grown silicon layer with minority carrier diffusion lengths exceeding the active layer thickness, light trapping due to back-surface reflection, and back-surface passivation. The thin silicon layer enables high solar cell performance and can lead to a module conversion efficiency as high as 19%. These performance design features, combined with low-cost manufacturing using relatively low-cost capital equipment, continuous processing and a low-cost substrate, will lead to high-performance, low-cost photovoltaic panels.

Adsorption of virus-like particles on ion exchange surface: Conformational changes at different pH detected by dual polarization interferometry.

PubMed

Yang, Yanli; Mengran Yu; Zhang, Songping; Ma, Guanghui; Su, Zhiguo

2015-08-21

Disassembling of virus-like particles (VLPs) like hepatitis B virus surface antigen (HB-VLPs) during chromatographic process has been identified as a major cause of loss of antigen activity. In this study, dual polarization interferometry (DPI) measurement, together with chromatography experiments, were performed to study the adsorption and conformational change of HB-VLPs on ion exchange surface at three different pHs. Changes in pH values of buffer solution showed only minimal effect on the HB-VLPs assembly and antigen activity, while significantly different degree of HB-VLPs disassembling was observed after ion exchange chromatography (IEC) at different pHs, indicating the conformational change of HB-VLPs caused mainly by its interactions with the adsorbent surface. By creating an ion exchange surface on chip surface, the conformational changes of HB-VLPs during adsorption to the surface were monitored in real time by DPI for the first time. As pH increased from 7.0 to 9.0, strong electrostatic interactions between oppositely charged HB-VLPs and the ion exchange surface make the HB-VLPs spread thinly or even adsorbed in disassembled formation on the surface as revealed by significant decrease in thickness of the adsorbed layer measured by DPI. Such findings were consistent with the results of IEC experiments operated at different pHs, that more disassembled HB-VLPs were detected in the eluted proteins at pH 9.0. At low pH like pH 5.0, however, possible bi-layer adsorption was involved as evidenced by an adsorbed layer thickness higher than average diameter of the HB-VLPs. The "lateral" protein-protein interactions might be unfavorable and would make additional contribution to the disassembling of HB-VLPs besides the primary mechanism related to the protein-surface interactions; therefore, the lowest antigen activity was observed after IEC at pH 5.0. Such real-time information on conformational change of VLPs is helpful for better understanding the real mechanism for the disassembling of VLPs on the solid-liquid interface. Copyright © 2015 Elsevier B.V. All rights reserved.

Prediction of hydrocarbon surface seepage potential using infiltrometer data

NASA Astrophysics Data System (ADS)

Connors, J. J.; Jackson, J. L.; Engle, R. A.; Connors, J. L.

2017-12-01

Environmental regulations addressing above-ground storage tank (AST) spill control activities typically require owners/operators to demonstrate that local soil permeability values are low enough to adequately contain released liquids while emergency-response procedures are conducted. Frequently, geotechnical borings and soil samples/analyses, and/or monitoring well slug-test analyses, are used to provide hydraulic conductivity data for the required calculations. While these techniques are useful in assessing hydrological characteristics of the subsurface, they do not always assess the uppermost surface soil layer, where the bulk of the containment can occur. This layer may have been subject to long-term permeability-reduction by activities such as compaction by vehicular and foot traffic, micro-coatings by hydrophobic pollutants, etc. This presentation explores the usefulness of dual-ring infiltrometers, both in field and bench-scale tests, to rapidly acquire actual hydraulic conductivity values of surficial soil layers, which can be much lower than subsurface values determined using more traditional downhole geotechnical and hydrogeological approaches.

Aligned carbon nanotube, graphene and graphite oxide thin films via substrate-directed rapid interfacial deposition

NASA Astrophysics Data System (ADS)

D'Arcy, Julio M.; Tran, Henry D.; Stieg, Adam Z.; Gimzewski, James K.; Kaner, Richard B.

2012-05-01

A procedure for depositing thin films of carbon nanostructures is described that overcomes the limitations typically associated with solution based methods. Transparent and conductively continuous carbon coatings can be grown on virtually any type of substrate within seconds. Interfacial surface tension gradients result in directional fluid flow and film spreading at the water/oil interface. Transparent films of carbon nanostructures are produced including aligned ropes of single-walled carbon nanotubes and assemblies of single sheets of chemically converted graphene and graphite oxide. Process scale-up, layer-by-layer deposition, and a simple method for coating non-activated hydrophobic surfaces are demonstrated.A procedure for depositing thin films of carbon nanostructures is described that overcomes the limitations typically associated with solution based methods. Transparent and conductively continuous carbon coatings can be grown on virtually any type of substrate within seconds. Interfacial surface tension gradients result in directional fluid flow and film spreading at the water/oil interface. Transparent films of carbon nanostructures are produced including aligned ropes of single-walled carbon nanotubes and assemblies of single sheets of chemically converted graphene and graphite oxide. Process scale-up, layer-by-layer deposition, and a simple method for coating non-activated hydrophobic surfaces are demonstrated. Electronic supplementary information (ESI) available: Droplet coalescence, catenoid formation, mechanism of film growth, scanning electron micrographs showing carbon nanotube alignment, flexible transparent films of SWCNTs, AFM images of a chemically converted graphene film, and SEM images of SWCNT free-standing thin films. See DOI: 10.1039/c2nr00010e

Mathematical Modelling of Arctic Polygonal Tundra with Ecosys : 1. Microtopography Determines How Active Layer Depths Respond to Changes in Temperature and Precipitation

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

Grant, R. F.; Mekonnen, Z. A.; Riley, W. J.

Microtopographic variation that develops among features (troughs, rims, and centers) within polygonal landforms of coastal arctic tundra strongly affects movement of surface water and snow and thereby affects soil water contents (θ) and active layer depth (ALD). Spatial variation in ALD among these features may exceed interannual variation in ALD caused by changes in climate and so needs to be represented in projections of changes in arctic ALD. For this study, increases in near-surface θ with decreasing surface elevation among polygon features at the Barrow Experimental Observatory (BEO) were modeled from topographic effects on redistribution of surface water and snowmore » and from lateral water exchange with a subsurface water table during a model run from 1981 to 2015. These increases in θ caused increases in thermal conductivity that in turn caused increases in soil heat fluxes and hence in ALD of up to 15 cm with lower versus higher surface elevation which were consistent with increases measured at BEO. The modeled effects of θ caused interannual variation in maximum ALD that compared well with measurements from 1985 to 2015 at the Barrow Circumpolar Active Layer Monitoring (CALM) site (R 2 = 0.61, RMSE = 0.03 m). For higher polygon features, interannual variation in ALD was more closely associated with annual precipitation than mean annual temperature, indicating that soil wetting from increases in precipitation may hasten permafrost degradation beyond that caused by soil warming from increases in air temperature. This degradation may be more rapid if increases in precipitation cause sustained wetting in higher features.« less

Mathematical Modelling of Arctic Polygonal Tundra with Ecosys : 1. Microtopography Determines How Active Layer Depths Respond to Changes in Temperature and Precipitation

DOE PAGES

Grant, R. F.; Mekonnen, Z. A.; Riley, W. J.; ...

2017-11-17

Microtopographic variation that develops among features (troughs, rims, and centers) within polygonal landforms of coastal arctic tundra strongly affects movement of surface water and snow and thereby affects soil water contents (θ) and active layer depth (ALD). Spatial variation in ALD among these features may exceed interannual variation in ALD caused by changes in climate and so needs to be represented in projections of changes in arctic ALD. For this study, increases in near-surface θ with decreasing surface elevation among polygon features at the Barrow Experimental Observatory (BEO) were modeled from topographic effects on redistribution of surface water and snowmore » and from lateral water exchange with a subsurface water table during a model run from 1981 to 2015. These increases in θ caused increases in thermal conductivity that in turn caused increases in soil heat fluxes and hence in ALD of up to 15 cm with lower versus higher surface elevation which were consistent with increases measured at BEO. The modeled effects of θ caused interannual variation in maximum ALD that compared well with measurements from 1985 to 2015 at the Barrow Circumpolar Active Layer Monitoring (CALM) site (R 2 = 0.61, RMSE = 0.03 m). For higher polygon features, interannual variation in ALD was more closely associated with annual precipitation than mean annual temperature, indicating that soil wetting from increases in precipitation may hasten permafrost degradation beyond that caused by soil warming from increases in air temperature. This degradation may be more rapid if increases in precipitation cause sustained wetting in higher features.« less

Protecting the surface of a light absorber in a photoanode

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

Hu, Shu; Lewis, Nathan S.

A photoanode includes a passivation layer on a light absorber. The passivation layer is more resistant to corrosion than the light absorber. The photoanode includes a surface modifying layer that is location on the passivation layer such that the passivation layer is between the light absorber and the surface modifying layer. The surface modifying layer reduces a resistance of the passivation layer to conduction of holes out of the passivation layer.

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

PubMed Central

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

2016-01-01

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

A means to estimate thermal and kinetic parameters of coal dust layer from hot surface ignition tests.

PubMed

Park, Haejun; Rangwala, Ali S; Dembsey, Nicholas A

2009-08-30

A method to estimate thermal and kinetic parameters of Pittsburgh seam coal subject to thermal runaway is presented using the standard ASTM E 2021 hot surface ignition test apparatus. Parameters include thermal conductivity (k), activation energy (E), coupled term (QA) of heat of reaction (Q) and pre-exponential factor (A) which are required, but rarely known input values to determine the thermal runaway propensity of a dust material. Four different dust layer thicknesses: 6.4, 12.7, 19.1 and 25.4mm, are tested, and among them, a single steady state dust layer temperature profile of 12.7 mm thick dust layer is used to estimate k, E and QA. k is calculated by equating heat flux from the hot surface layer and heat loss rate on the boundary assuming negligible heat generation in the coal dust layer at a low hot surface temperature. E and QA are calculated by optimizing a numerically estimated steady state dust layer temperature distribution to the experimentally obtained temperature profile of a 12.7 mm thick dust layer. Two unknowns, E and QA, are reduced to one from the correlation of E and QA obtained at criticality of thermal runaway. The estimated k is 0.1 W/mK matching the previously reported value. E ranges from 61.7 to 83.1 kJ/mol, and the corresponding QA ranges from 1.7 x 10(9) to 4.8 x 10(11)J/kg s. The mean values of E (72.4 kJ/mol) and QA (2.8 x 10(10)J/kg s) are used to predict the critical hot surface temperatures for other thicknesses, and good agreement is observed between measured and experimental values. Also, the estimated E and QA ranges match the corresponding ranges calculated from the multiple tests method and values reported in previous research.

Layered Model for Radiation-Induced Chemical Evolution of Icy Surface Composition and Dynamics on Kuiper Belt and Oort Cloud Bodies

NASA Technical Reports Server (NTRS)

Cooper, John F.; Richardson, John D.

2010-01-01

The diversity of albedos and surface colors on observed Kuiper Belt and Inner Oort Cloud objects remains to be explained in terms of competition between primordial intrinsic versus exogenic drivers of surface and near-surface evolution. Earlier models have attempted without success to attribute this diversity to the relations between surface radiolysis from cosmic ray irradiation and gardening by meteoritic impacts. A more flexible approach considers the different depth-dependent radiation profiles produced by low-energy plasma, suprathermal, and maximally penetrating charged particles of the heliospheric and local interstellar radiation environment. Generally red objects of the dynamically cold (low inclination, circular orbit) Classical Kuiper Belt might be accounted for from erosive effects of plasma ions and reddening effects of high energy cosmic ray ions, while suprathermal keV-MeV ions could alternatively produce more color neutral surfaces. The deepest layer of more pristine ice can be brought to the surface from meter to kilometer depths by larger impact events and potentially by cryovolcanic activity. The bright surfaces of some larger objects, e.g. Eris, suggest ongoing resurfacing activity. Cycles of atmospheric formation and surface freezeout can further account for temporal variation as observed on Pluto. The diversity of causative processes must therefore be understood to account for observationally apparent diversities of the object surfaces.

Mechanism of the surface runoff generation processes of a permafrost watershed in the Qinghai-Tibet plateau

NASA Astrophysics Data System (ADS)

Genxu, W.

2017-12-01

There is a lack of knowledge about how to quantify runoff generation and the hydrological processes operating in permafrost catchments on permafrost-dominant catchments. To understand the mechanism of runoff generation processes in permafrost catchments, a typical headwater catchment with continuous permafrost on the Tibetan Plateau was measured. A new approach is presented in this study to account for runoff processes on the spring thawing period and autumn freezing period, when runoff generation clearly differs from that of non-permafrost catchments. This approach introduces a soil temperature-based water saturation function and modifies the soil water storage curve with a soil temperature threshold. The results show that surface soil thawing induced saturation excess runoff and subsurface interflow account for approximately 66-86% and 14-34% of total spring runoff, respectively, and the soil temperature significantly affects the runoff generation pattern, the runoff composition and the runoff coefficient with the enlargement of the active layer. The suprapermafrost groundwater discharge decreases exponentially with active layer frozen processes during autumn runoff recession, whereas the ratio of groundwater discharge to total runoff and the direct surface runoff coefficient simultaneously increase. The bidirectional freezing of the active layer controls and changes the autumn runoff processes and runoff composition. The new approach could be used to further develop hydrological models of cold regions dominated by permafrost.

Importance of lateral flux and its percolation depth on organic carbon export in Arctic tundra soil: Implications from a soil leaching experiment

NASA Astrophysics Data System (ADS)

Zhang, Xiaowen; Hutchings, Jack A.; Bianchi, Thomas S.; Liu, Yina; Arellano, Ana R.; Schuur, Edward A. G.

2017-04-01

Temperature rise in the Arctic is causing deepening of active layers and resulting in the mobilization of deep permafrost dissolved organic matter (DOM). However, the mechanisms of DOM mobilization from Arctic soils, especially upper soil horizons which are drained most frequently through a year, are poorly understood. Here we conducted a short-term leaching experiment on surface and deep organic active layer soils, from the Yukon River basin, to examine the effects of DOM transport on bulk and molecular characteristics. Our data showed a net release of DOM from surface soils equal to an average of 5% of soil carbon. Conversely, deep soils percolated with surface leachates retained up to 27% of bulk DOM while releasing fluorescent components (up to 107%), indicating selective release of aromatic components (e.g., lignin and tannin), while retaining nonchromophoric components, as supported by spectrofluorometric and ultrahigh-resolution mass spectroscopic techniques. Our findings highlight the importance of the lateral flux of DOM on ecosystem carbon balance as well as processing of DOM transport through organic active layer soils en route to rivers and streams. This work also suggests the potential role of leachate export as an important mechanism of C losses from Arctic soils, in comparison with the more traditional pathway from soil to atmosphere in a warming Arctic.

Response of phytoplankton and enhanced biogeochemical activity to an episodic typhoon event in the coastal waters of Japan

NASA Astrophysics Data System (ADS)

Tsuchiya, Kenji; Kuwahara, Victor S.; Yoshiki, Tomoko M.; Nakajima, Ryota; Shimode, Shinji; Kikuchi, Tomohiko; Toda, Tatsuki

2017-07-01

Daily field surveys were conducted at a coastal-shelf station in Sagami Bay, Japan after the passage of typhoon Malou in 2010 to evaluate the after-effect of a typhoon passage on the physical-chemical environment, phytoplankton bloom formation and microbial processes within and below the euphotic layer. The passage of Malou induced an abrupt decrease in salinity and increased loading of nutrients to the euphotic layer. Dinoflagellates dominated the phytoplankton community at the surface, whereas diatoms dominated below the surface just after the passage of Malou. Four days later, the dominant dinoflagellate taxa at the surface changed from Protoperidinium spp. to Prorocentrum spp. and Ceratium spp., indicating a dinoflagellate community succession from heterotrophic to autotrophic functional groups. Five days after passage, the dominant phytoplankton taxa shifted from dinoflagellates to diatom groups of Chaetoceros spp. and Cerataulina spp. throughout the water column. Below the euphotic layer, there were increases in diatom frustules, mainly composed of Chaetoceros spp. and Cerataulina spp., bacterial abundance and NH4+ concentrations. Diatom carbon biomass contributed to approximately half of particulate organic carbon (POC) below the euphotic layer, suggesting a significant contribution of diatoms to POC sinking flux after the passage of a typhoon. Bacterial abundance was positively correlated to both phaeopigment concentrations (p < 0.01) and NH4+ concentrations (p < 0.01), suggesting bacterial growth was associated with zooplankton grazing and remineralization of NH4+. The results suggest that the passage of a typhoon could significantly affect biogeochemical activities within and below the euphotic layer in temperate coastal waters.

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

PubMed

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

2015-03-02

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

[Characterization of Chromophoric dissolved organic matter (CDOM) in Zhoushan fishery using excitation-emission matrix spectroscopy (EEMs) and parallel factor analysis (PARAFAC)].

PubMed

Zhou, Qian-qian; Su, Rong-guo; Bai, Ying; Zhang, Chuan-song; Shi, Xiao-yong

2015-01-01

The composition, distribution characteristics and sources of chromophoric dissolved organic matter(CDOM) in Zhoushan Fishery in spring were evaluated by fluorescence excitation-emission matrix (EEM) combined with parallel factor analysis (EEMs-PARAFAC). Three humic-like components [C1 (330/420 nm)], C2 [(290) 365/440 nm] and C3 [(260) 370/490 nm)] and two protein-like components [C4(285/340 nm) and C5 (270/310 nm)] were identified by EEMs-PARAFAC. The horizontal distribution patterns of the five components were almost the same with only slight differences, showing decreasing trends with increasing distance from shore. In the surface and middle layers, the high value areas were located in the north of Hangzhou Bay estuary and the outlet of Xiazhimen channel, and the former's was higher in the surface layer while the latter's was higher in the middle layer. In the bottom layer, CDOM decreased gradiently from the inshore to offshore, with higher CDOM near Zhoushan Island. The distributions of fluorescence components showed an opposite trend with salinity, and no significant linear relationship with Chl-a concentration was found, which indicated that CDOM in the surface and middle layers were dominated by terrestrial input and human activities of Zhoushan Island and that of the bottom layer was attribute to human activities of Zhoushan Island. The vertical distribution of five fluorescent components along 30.5 degrees N transect showed a decreasing trend from the surface and middle layers to bottom layer with high values in inshore and offshore areas, which were correlated with the lower salinity and higher Chl-a concentration, respectively. On this transect, CDOM was mainly affected by Yangtze River input in coastal area but by bioactivities in offshore waters. Along the 30 degrees N transect, the vertical distribution patterns of CDOM were similar to those of 30.5 degrees N transect but there was a high value area in the bottom layer near the shore, attributing to the CDOM release from the marine sediment pore water to the water body because of physical force role like tidal, the underlying upwelling and so on. A strong correlation occurred between C1 and C3, C4, indicating that they had similar sources; a weak correlation was found between C1 and C2, C5, reflecting some differences among their sources. CDOM in Zhoushan Fishery in spring had low humification index (HIX) values, which reflected a low degree of humification, poor stability and a short resident time in the environment. For biological index (BIX), its higher values appeared in the offshore waters and the lower values occurred in the inshore area, reflecting a greater influence of human and biological activities, respectively.

The role of the hydrophobic phase in the unique rheological properties of saponin adsorption layers.

PubMed

Golemanov, Konstantin; Tcholakova, Slavka; Denkov, Nikolai; Pelan, Eddie; Stoyanov, Simeon D

2014-09-28

Saponins are a diverse class of natural, plant derived surfactants, with peculiar molecular structure consisting of a hydrophobic scaffold and one or several hydrophilic oligosaccharide chains. Saponins have strong surface activity and are used as natural emulsifiers and foaming agents in food and beverage, pharmaceutical, ore processing, and other industries. Many saponins form adsorption layers at the air-water interface with extremely high surface elasticity and viscosity. The molecular origin of the observed unique interfacial visco-elasticity of saponin adsorption layers is of great interest from both scientific and application viewpoints. In the current study we demonstrate that the hydrophobic phase in contact with water has a very strong effect on the interfacial properties of saponins and that the interfacial elasticity and viscosity of the saponin adsorption layers decrease in the order: air > hexadecane ≫ tricaprylin. The molecular mechanisms behind these trends are analyzed and discussed in the context of the general structure of the surfactant adsorption layers at various nonpolar phase-water interfaces.

Self-assembled three-dimensional and compressible interdigitated thin-film supercapacitors and batteries

PubMed Central

Nyström, Gustav; Marais, Andrew; Karabulut, Erdem; Wågberg, Lars; Cui, Yi; Hamedi, Mahiar M.

2015-01-01

Traditional thin-film energy-storage devices consist of stacked layers of active films on two-dimensional substrates and do not exploit the third dimension. Fully three-dimensional thin-film devices would allow energy storage in bulk materials with arbitrary form factors and with mechanical properties unique to bulk materials such as compressibility. Here we show three-dimensional energy-storage devices based on layer-by-layer self-assembly of interdigitated thin films on the surface of an open-cell aerogel substrate. We demonstrate a reversibly compressible three-dimensional supercapacitor with carbon nanotube electrodes and a three-dimensional hybrid battery with a copper hexacyanoferrate ion intercalating cathode and a carbon nanotube anode. The three-dimensional supercapacitor shows stable operation over 400 cycles with a capacitance of 25 F g−1 and is fully functional even at compressions up to 75%. Our results demonstrate that layer-by-layer self-assembly inside aerogels is a rapid, precise and scalable route for building high-surface-area 3D thin-film devices. PMID:26021485

Suppression of carbon desorption from 4H-SiC by irradiating a remote nitrogen plasma at a low temperature

NASA Astrophysics Data System (ADS)

Shimabayashi, Masaharu; Kurihara, Kazuaki; Sasaki, Koichi

2018-05-01

We remotely irradiated a nitrogen plasma onto the carbon-side surface of 4H-SiC at a low temperature, and examined the effect of sample cooling on the characteristics of the nitride layer. An improved nitride layer, which had higher concentrations of carbon and silicon and a lower concentration of oxygen, was formed in the region at depths of more than 0.6–0.9 nm from the top surface. The depth of the fragile nitride layer in the top region, where no improved characteristics of the nitride layer were observed, became smaller with sample cooling. In addition, on the basis of the experimental results, we discussed the difference in the activation energy of the nitriding reaction of 4H-SiC supported by atomic nitrogen and molecular nitrogen in the metastable \\text{A}3Σ \\text{u} + state.

Method for producing nanowire-polymer composite electrodes

DOEpatents

Pei, Qibing; Yu, Zhibin

2017-11-21

A method for producing flexible, nanoparticle-polymer composite electrodes is described. Conductive nanoparticles, preferably metal nanowires or nanotubes, are deposited on a smooth surface of a platform to produce a porous conductive layer. A second application of conductive nanoparticles or a mixture of nanoparticles can also be deposited to form a porous conductive layer. The conductive layer is then coated with at least one coating of monomers that is polymerized to form a conductive layer-polymer composite film. Optionally, a protective coating can be applied to the top of the composite film. In one embodiment, the monomer coating includes light transducing particles to reduce the total internal reflection of light through the composite film or pigments that absorb light at one wavelength and re-emit light at a longer wavelength. The resulting composite film has an active side that is smooth with surface height variations of 100 nm or less.

Multilayer coatings for flexible high-barrier materials

NASA Astrophysics Data System (ADS)

Vaško, Karol; Noller, Klaus; Mikula, Milan; Amberg-Schwab, Sabine; Weber, Ulrike

2009-06-01

A multilayer, flexible, and transparent high-barrier system based on flexible plastic foils, polyethyleneterephthalate (PET) and ethylene-tetrafluoroethylene-copolymer (ETFE), combined with vacuum-deposited, inorganic SiOx layers and hybrid ORMOCER® varnish layers were prepared in different orders on a semiproduction level. Barrier properties of prepared systems, as water vapour transmission (WVTR) and oxygen transmission (OTR), were measured and studied in connection with surface energy, surface topography, and water vapour adsorption properties. Correlations among layers sequence, barrier properties, and other parameters are presented, including some basic principles of permeation of substances through multilayer barrier systems. A combination of several inorganic and hybrid varnish layers is necessary to achieve the technological demands from a barrier standpoint. It is easier to suppress the oxygen transport than the water transport, due to the additional active penetration of water through hydrogen bonds and silanol creations at oxide interfaces, capillary condensation, and swelling with high internal pressure, leading to new defects.

Ion traps fabricated in a CMOS foundry

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

Mehta, K. K.; Ram, R. J.; Eltony, A. M.

2014-07-28

We demonstrate trapping in a surface-electrode ion trap fabricated in a 90-nm CMOS (complementary metal-oxide-semiconductor) foundry process utilizing the top metal layer of the process for the trap electrodes. The process includes doped active regions and metal interconnect layers, allowing for co-fabrication of standard CMOS circuitry as well as devices for optical control and measurement. With one of the interconnect layers defining a ground plane between the trap electrode layer and the p-type doped silicon substrate, ion loading is robust and trapping is stable. We measure a motional heating rate comparable to those seen in surface-electrode traps of similar size.more » This demonstration of scalable quantum computing hardware utilizing a commercial CMOS process opens the door to integration and co-fabrication of electronics and photonics for large-scale quantum processing in trapped-ion arrays.« less

Fine-tuning the Wall Thickness of Ordered Mesoporous Graphene by Exploiting Ligand Exchange of Colloidal Nanocrystals

NASA Astrophysics Data System (ADS)

Han, Dandan; Yan, Yancui; Wei, Jishi; Wang, Biwei; Li, Tongtao; Guo, Guannan; Yang, Dong; Xie, Songhai; Dong, Angang

2017-12-01

Because of their unique physical properties, three-dimensional (3D) graphene has attracted enormous attention over the past years. However, it is still a challenge to precisely control the layer thickness of 3D graphene. Here, we report a novel strategy to rationally adjust the wall thickness of ordered mesoporous graphene (OMG). By taking advantage of ligand exchange capability of colloidal Fe3O4 nanocrystals, we are able to fine-tune the wall thickness of OMG from 2 to 6 layers of graphene by tailoring the hydrocarbon ligands attached to the nanocrystal surface. When evaluated as electrocatalyst for oxygen reduction reaction upon S and N doping, the 4-layer OMG is found to show better catalytic performance compared with its 2- and 6-layer counterparts, which we attribute to the enhanced exposure of active sites resulting from its ultrathin wall thickness and high surface area.

Role of Surface Chemistry on Catalyst/Ionomer Interactions for Transition Metal–Nitrogen–Carbon Electrocatalysts

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

Artyushkova, Kateryna; Workman, Michael J.; Matanovic, Ivana

The role of the interaction between doped carbon-based materials and ionic conductors is essential in multiple technologies, from fuel cells and energy storage devices to conductive polymer composites. In this paper, we report how the surface chemistry of transition metal–nitrogen–carbon (MNC) electrocatalysts affects catalyst–ionomer interaction and the resulting structure of cathodes. The cathode structure resulting from these interactions is directly related to the performance in membrane electrode assembly (MEA) fuel cells. To advance the development of platinum group metal (PGM)-free electrodes for the oxygen reduction reaction it is necessary to understand the structure of the catalyst layers with focus onmore » chemistry and distribution of active sites and ionomer morphology. To assess catalyst interaction with an ionomer, X-ray photoelectron spectroscopy is applied to study the chemistry of catalyst layers while density functional theory (DFT) is used to calculate adsorption energies of the ionomer side chain on different nitrogen species. We report that a high surface concentration of hydrogenated nitrogen at the surface of MNC catalysts causes inefficient ionomer morphology, while an abundance of surface oxides promotes both an efficient distribution of active sites and an optimal ionomer–catalyst interface. The critical role of protonation of nitrogen within catalytic layers in inhibiting proton transport during fuel cell operation is also suggested. As a result, this is the first report of the effect the surface chemistry of MNC catalysts, in the presence of the ionomer, has on the structure and performance of MEA electrodes.« less

Role of Surface Chemistry on Catalyst/Ionomer Interactions for Transition Metal–Nitrogen–Carbon Electrocatalysts

DOE PAGES

Artyushkova, Kateryna; Workman, Michael J.; Matanovic, Ivana; ...

2017-12-18

The role of the interaction between doped carbon-based materials and ionic conductors is essential in multiple technologies, from fuel cells and energy storage devices to conductive polymer composites. In this paper, we report how the surface chemistry of transition metal–nitrogen–carbon (MNC) electrocatalysts affects catalyst–ionomer interaction and the resulting structure of cathodes. The cathode structure resulting from these interactions is directly related to the performance in membrane electrode assembly (MEA) fuel cells. To advance the development of platinum group metal (PGM)-free electrodes for the oxygen reduction reaction it is necessary to understand the structure of the catalyst layers with focus onmore » chemistry and distribution of active sites and ionomer morphology. To assess catalyst interaction with an ionomer, X-ray photoelectron spectroscopy is applied to study the chemistry of catalyst layers while density functional theory (DFT) is used to calculate adsorption energies of the ionomer side chain on different nitrogen species. We report that a high surface concentration of hydrogenated nitrogen at the surface of MNC catalysts causes inefficient ionomer morphology, while an abundance of surface oxides promotes both an efficient distribution of active sites and an optimal ionomer–catalyst interface. The critical role of protonation of nitrogen within catalytic layers in inhibiting proton transport during fuel cell operation is also suggested. As a result, this is the first report of the effect the surface chemistry of MNC catalysts, in the presence of the ionomer, has on the structure and performance of MEA electrodes.« less

Pure and Oxidized Copper Materials as Potential Antimicrobial Surfaces for Spaceflight Activities.

PubMed

Hahn, C; Hans, M; Hein, C; Mancinelli, R L; Mücklich, F; Wirth, R; Rettberg, P; Hellweg, C E; Moeller, R

2017-12-01

Microbial biofilms can lead to persistent infections and degrade a variety of materials, and they are notorious for their persistence and resistance to eradication. During long-duration space missions, microbial biofilms present a danger to crew health and spacecraft integrity. The use of antimicrobial surfaces provides an alternative strategy for inhibiting microbial growth and biofilm formation to conventional cleaning procedures and the use of disinfectants. Antimicrobial surfaces contain organic or inorganic compounds, such as antimicrobial peptides or copper and silver, that inhibit microbial growth. The efficacy of wetted oxidized copper layers and pure copper surfaces as antimicrobial agents was tested by applying cultures of Escherichia coli and Staphylococcus cohnii to these metallic surfaces. Stainless steel surfaces were used as non-inhibitory control surfaces. The production of reactive oxygen species and membrane damage increased rapidly within 1 h of exposure on pure copper surfaces, but the effect on cell survival was negligible even after 2 h of exposure. However, longer exposure times of up to 4 h led to a rapid decrease in cell survival, whereby the survival of cells was additionally dependent on the exposed cell density. Finally, the release of metal ions was determined to identify a possible correlation between copper ions in suspension and cell survival. These measurements indicated a steady increase of free copper ions, which were released indirectly by cells presumably through excreted complexing agents. These data indicate that the application of antimicrobial surfaces in spaceflight facilities could improve crew health and mitigate material damage caused by microbial contamination and biofilm formation. Furthermore, the results of this study indicate that cuprous oxide layers were superior to pure copper surfaces related to the antimicrobial effect and that cell density is a significant factor that influences the time dependence of antimicrobial activity. Key Words: Contact killing-E. coli-S. cohnii-Antimicrobial copper surfaces-Copper oxide layers-Human health-Planetary protection. Astrobiology 17, 1183-1191.

Enhanced catalyst stability for cyclic co methanation operations

DOEpatents

Risch, Alan P.; Rabo, Jule A.

1983-01-01

Carbon monoxide-containing gas streams are passed over a catalyst to deposit a surface layer of active surface carbon thereon essentially without the formation of inactive coke. The active carbon is thereafter reacted with steam or hydrogen to form methane. Enhanced catalyst stability for long term, cyclic operation is obtained by the incorporation of an alkali or alkaline earth dopant in a silica binding agent added to the catalyst-support additive composition.

Surface modification of titanium substrates with silver nanoparticles embedded sulfhydrylated chitosan/gelatin polyelectrolyte multilayer films for antibacterial application.

PubMed

Li, Wen; Xu, Dawei; Hu, Yan; Cai, Kaiyong; Lin, Yingcheng

2014-06-01

To develop Ti implants with potent antibacterial activity, a novel "sandwich-type" structure of sulfhydrylated chitosan (Chi-SH)/gelatin (Gel) polyelectrolyte multilayer films embedding silver (Ag) nanoparticles was coated onto titanium substrate using a spin-assisted layer-by-layer assembly technique. Ag ions would be enriched in the polyelectrolyte multilayer films via the specific interactions between Ag ions and -HS groups in Chi-HS, thus leading to the formation of Ag nanoparticles in situ by photo-catalytic reaction (ultraviolet irradiation). Contact angle measurement and field emission scanning electron microscopy equipped with energy dispersive X-ray spectroscopy were employed to monitor the construction of Ag-containing multilayer on titanium surface, respectively. The functional multilayered films on titanium substrate [Ti/PEI/(Gel/Chi-SH/Ag) n /Gel] could efficiently inhibit the growth and activity of Bacillus subtitles and Escherichia coli onto titanium surface. Moreover, studies in vitro confirmed that Ti substrates coating with functional multilayer films remained the biological functions of osteoblasts, which was reflected by cell morphology, cell viability and ALP activity measurements. This study provides a simple, versatile and generalized methodology to design functional titanium implants with good cyto-compatibility and antibacterial activity for potential clinical applications.

Layer-by-layer grown scalable redox-active ruthenium-based molecular multilayer thin films for electrochemical applications and beyond.

PubMed

Kaliginedi, Veerabhadrarao; Ozawa, Hiroaki; Kuzume, Akiyoshi; Maharajan, Sivarajakumar; Pobelov, Ilya V; Kwon, Nam Hee; Mohos, Miklos; Broekmann, Peter; Fromm, Katharina M; Haga, Masa-aki; Wandlowski, Thomas

2015-11-14

Here we report the first study on the electrochemical energy storage application of a surface-immobilized ruthenium complex multilayer thin film with anion storage capability. We employed a novel dinuclear ruthenium complex with tetrapodal anchoring groups to build well-ordered redox-active multilayer coatings on an indium tin oxide (ITO) surface using a layer-by-layer self-assembly process. Cyclic voltammetry (CV), UV-Visible (UV-Vis) and Raman spectroscopy showed a linear increase of peak current, absorbance and Raman intensities, respectively with the number of layers. These results indicate the formation of well-ordered multilayers of the ruthenium complex on ITO, which is further supported by the X-ray photoelectron spectroscopy analysis. The thickness of the layers can be controlled with nanometer precision. In particular, the thickest layer studied (65 molecular layers and approx. 120 nm thick) demonstrated fast electrochemical oxidation/reduction, indicating a very low attenuation of the charge transfer within the multilayer. In situ-UV-Vis and resonance Raman spectroscopy results demonstrated the reversible electrochromic/redox behavior of the ruthenium complex multilayered films on ITO with respect to the electrode potential, which is an ideal prerequisite for e.g. smart electrochemical energy storage applications. Galvanostatic charge-discharge experiments demonstrated a pseudocapacitor behavior of the multilayer film with a good specific capacitance of 92.2 F g(-1) at a current density of 10 μA cm(-2) and an excellent cycling stability. As demonstrated in our prototypical experiments, the fine control of physicochemical properties at nanometer scale, relatively good stability of layers under ambient conditions makes the multilayer coatings of this type an excellent material for e.g. electrochemical energy storage, as interlayers in inverted bulk heterojunction solar cell applications and as functional components in molecular electronics applications.

Influence of Smear Layer on the Antimicrobial Activity of a Sodium Hypochlorite/Etidronic Acid Irrigating Solution in Infected Dentin.

PubMed

Morago, Ana; Ordinola-Zapata, Ronald; Ferrer-Luque, Carmen María; Baca, Pilar; Ruiz-Linares, Matilde; Arias-Moliz, María Teresa

2016-11-01

The aim of this study was to evaluate the influence of the smear layer on the antimicrobial activity of a 2.5% sodium hypochlorite (NaOCl)/9% etidronic acid (HEBP) irrigating solution against bacteria growing inside dentin tubules. Dentin tubules were infected with Enterococcus faecalis by centrifugation. After 5 days of incubation, the smear layer had formed in half of the samples, which were then treated with 2.5% NaOCl either alone or combined with 9% HEBP for 3 minutes. The percentage of dead cells in infected dentinal tubules was measured using confocal laser scanning microscopy and the live/dead technique. The smear layer on the surface of the root canal wall was also observed by scanning electron microscopy. Results of the percentage of dead cells were compared using parametric tests after subjecting data to the normalized Anscombe transformation. The level of significance was P < .05. In the absence of the smear layer, 2.5% NaOCl alone and combined with 9% HEBP showed high antimicrobial activity without significant differences between the 2. The smear layer reduced the antimicrobial activity of 2.5% NaOCl significantly, whereas the solution with HEBP was not affected. No dentin tubules free of the smear layer were obtained in the 2.5% NaOCl group. In the case of 2.5% NaOCl/9% HEBP, 95.40% ± 3.63% of dentin tubules were cleaned. The presence of the smear layer reduced the antimicrobial activity of 2.5% NaOCl. The combination of 2.5% NaOCl/9% HEBP exerted antimicrobial activity that was not reduced by the smear layer. Copyright © 2016 American Association of Endodontists. Published by Elsevier Inc. All rights reserved.

Immobilization of enzymes by bioaffinity layering.

PubMed

Singh, Veena; Sardar, Meryam; Gupta, Munishwar Nath

2013-01-01

Bioaffinity immobilization exploits the affinity of the enzyme to a macro-(affinity ligand). Such a macro-(affinity ligand) could be a lectin, a water-soluble polymer, or a bioconjugate of a water-soluble polymer and the appropriate affinity ligand. Successive layering of the enzyme and the macro-(affinity ligand) on a matrix allows deposition of a large amount of enzyme activity on a small surface. Illustrative protocols show affinity layering of a pectinase and horseradish peroxidase on Concanavalin A-agarose and Concanavalin A-Sephadex matrices, respectively.

Reduction of microbial contamination on the surfaces of layer houses using slightly acidic electrolyzed water.

PubMed

Ni, L; Cao, W; Zheng, W C; Zhang, Q; Li, B M

2015-11-01

The objective of this study was to evaluate the effectiveness of slightly acidic electrolyzed water (SAEW) in reducing pathogens on pure cultures and on cotton fabric surfaces in the presence of organic matter and estimate its efficacy in comparison with povidone iodine solution for reducing pathogenic microorganisms on internal surfaces of layer houses. Pure cultures of E.coli, S.enteritidis, and S.aureus and cotton fabric surfaces inoculated with these strains were treated with SAEW in the presence of bovine serum albumin (BSA). In the absence of BSA, complete inactivation of all strains in pure cultures and on cotton fabric surfaces was observed after 2.5 and 5 min treatment with SAEW at 40 mg/L of available chlorine concentration (ACC), respectively. The bactericidal efficiency of SAEW increased with increasing ACC, but decreased with increasing BSA concentration. Then, the surfaces of the layer houses were sprayed with SAEW at 60, 80, and 100 mg/L of ACC and povidone iodine using the automated disinfection system at a rate of 110 mL/m(2), respectively. Samples from the floor, wall, feed trough, and egg conveyor belt surfaces were collected with sterile cotton swabs before and after spraying disinfection. Compared to tap water, SAEW and povidone iodine significantly reduced microbial populations on each surface of the layer houses. SAEW with 80 or 100 mg/L of ACC showed significantly higher efficacy than povidone iodine for total aerobic bacteria, staphylococci, coliforms, or yeasts and moulds on the floor and feed trough surfaces (P < 0.05). SAEW was more effective than povidone iodine at reducing total aerobic bacteria, coliforms, and yeasts and moulds on the wall surface. Additionally, SAEW had similar bactericidal activity with povidone iodine on the surface of the egg conveyor belt. Results suggest that SAEW exerts a higher or equivalent bactericidal efficiency for the surfaces compared to povidone iodine, and it may be used as an effective alternative for reducing microbial contamination on surfaces in layer houses. © 2015 Poultry Science Association Inc.

Session on coupled atmospheric/chemistry coupled models

NASA Technical Reports Server (NTRS)

Thompson, Anne

1993-01-01

The session on coupled atmospheric/chemistry coupled models is reviewed. Current model limitations, current issues and critical unknowns, and modeling activity are addressed. Specific recommendations and experimental strategies on the following are given: multiscale surface layer - planetary boundary layer - chemical flux measurements; Eulerian budget study; and Langrangian experiment. Nonprecipitating cloud studies, organized convective systems, and aerosols - heterogenous chemistry are also discussed.

Materials based on carbon-filled porous layers of PVC cyclam derivatives cross-linked with the surfaces of asbestos fabric fibers

NASA Astrophysics Data System (ADS)

Tzivadze, A. Yu.; Fridman, A. Ya.; Morozova, E. M.; Sokolova, N. P.; Voloshchuk, A. M.; Petukhova, G. A.; Bardishev, I. I.; Gorbunov, A. M.; Novikov, A. K.; Polyakova, I. Ya.; Titova, V. N.; Yavich, A. A.; Petrova, N. V.

2016-08-01

The synthesis of bilayer materials with porous upper layers composed of PVC hydroxyethylcyclam derivatives filled with carbon and a layer consisting of hydroxyethylcyclam, cross-linked via Si-O-C groups with the silica chains of a developed surface of asbestos fabric, is described. The aza-crown groups in these materials are bound with aqua complexes of H2SO4 or NaOH. The structure of the materials is examined, their adsorption characteristics are determined, and the rate of motion of H+ or OH- ions in electrochemical bridges is measured, while the formation of H2 and O2 in their cathodic and anodic polarization is determined as a function of voltage. It is shown that the upper layer of these materials is adsorption-active and electronand H+- or OH-- conductive, while the bottom layer is only H+- or OH-- conductive; through it, the upper layer is supplied with the H+ or OH- ions needed for the regeneration of the aqua complexes broken down to H2 and O2 on carbon particles.

Capillary Flow Layer-by-Layer: A Microfluidic Platform for the High-Throughput Assembly and Screening of Nanolayered Film Libraries

PubMed Central

2015-01-01

Layer-by-layer (LbL) assembly is a powerful tool with increasing real world applications in energy, biomaterials, active surfaces, and membranes; however, the current state of the art requires individual sample construction using large quantities of material. Here we describe a technique using capillary flow within a microfluidic device to drive high-throughput assembly of LbL film libraries. This capillary flow layer-by-layer (CF-LbL) method significantly reduces material waste, improves quality control, and expands the potential applications of LbL into new research spaces. The method can be operated as a simple lab benchtop apparatus or combined with liquid-handling robotics to extend the library size. Here we describe and demonstrate the technique and establish its ability to recreate and expand on the known literature for film growth and morphology. We use the same platform to assay biological properties such as cell adhesion and proliferation and ultimately provide an example of the use of this approach to identify LbL films for surface-based DNA transfection of commonly used cell types. PMID:24836460

Preparation of Copper and Chromium Alloyed Layers on Pure Titanium by Plasma Surface Alloying Technology

NASA Astrophysics Data System (ADS)

He, Xiaojing; Li, Meng; Wang, Huizhen; Zhang, Xiangyu; Tang, Bin

2015-05-01

Cu-Cr alloyed layers with different Cu and Cr contents on pure titanium were obtained by means of plasma surface alloying technology. The microstructure, chemical composition and phase composition of Cu-Cr alloyed layers were analyzed by scanning electron microscopy (SEM), energy dispersive spectrometer (EDS) and X-ray diffraction (XRD), respectively. The experimental results demonstrate that the alloyed layers are bonded strongly to pure titanium substrate and consist of unbound Ti, CuTi, Cu3Ti, CuTi3 and Cr2Ti. The thickness of Cu5Cr5 and Cu7Cr3 alloyed layer are about 18 μm and 28 μm, respectively. The antibacterial properties against gram-negative Escherichia coli (E.coli, ATCC10536) and gram-positive Staphylococcus aureus (S. aureus, ATCC6538) of untreated pure titanium and Cu-Cr alloyed specimen were investigated by live/dead fluorescence staining method. The study shows that Cu-Cr alloyed layers exhibit excellent antibacterial activities against both E.coli and S.aureus within 24 h, which may be attributed to the formation of Cu-containing phases.

Estrogenic activity, estrogens, and calcium in runoff post-layer litter application from rainfall simulated events

USDA-ARS?s Scientific Manuscript database

Estrogens in runoff from fields fertilized with animal wastes have been implicated as endocrine disruptors of fish in recipient surface waters. The goal of this study was to measure estrogenic activity in runoff post-application of animal waste with the greatest potential for estrogenic activity - ...

Impact of Conifer Forest Litter on Microwave Emission at L-Band

NASA Technical Reports Server (NTRS)

Kurum, Mehmet; O'Neill, Peggy E.; Lang, Roger H.; Cosh, Michael H.; Joseph, Alicia T.; Jackson, Thomas J.

2011-01-01

This study reports on the utilization of microwave modeling, together with ground truth, and L-band (1.4-GHz) brightness temperatures to investigate the passive microwave characteristics of a conifer forest floor. The microwave data were acquired over a natural Virginia Pine forest in Maryland by a ground-based microwave active/passive instrument system in 2008/2009. Ground measurements of the tree biophysical parameters and forest floor characteristics were obtained during the field campaign. The test site consisted of medium-sized evergreen conifers with an average height of 12 m and average diameters at breast height of 12.6 cm. The site is a typical pine forest site in that there is a surface layer of loose debris/needles and an organic transition layer above the mineral soil. In an effort to characterize and model the impact of the surface litter layer, an experiment was conducted on a day with wet soil conditions, which involved removal of the surface litter layer from one half of the test site while keeping the other half undisturbed. The observations showed detectable decrease in emissivity for both polarizations after the surface litter layer was removed. A first-order radiative transfer model of the forest stands including the multilayer nature of the forest floor in conjunction with the ground truth data are used to compute forest emission. The model calculations reproduced the major features of the experimental data over the entire duration, which included the effects of surface litter and ground moisture content on overall emission. Both theory and experimental results confirm that the litter layer increases the observed canopy brightness temperature and obscure the soil emission.

First-Principles Molecular Dynamics Study on the Electric-double layer Capacitance of Water-MXene interfaces

NASA Astrophysics Data System (ADS)

Ando, Yasunobu; Otani, Minoru

MXenes are a new, large family of layered materials synthesized from MAX phases by simple chemical treatments. Due to their enormous variations, MXenes have attracted great attention as promising candidates as anode materials for next-generation secondary batteries. Unfortunately, the specific capacitance of MXenes supercapacitors is lower than that of active-carbon ones. Theoretical investigation of the electric-double layer (EDL) at electrode interfaces is necessary to improve their capacitance. First-principles molecular dynamics (FPMD) simulation based on the density functional theory (DFT) is performed to estimate the EDL capacitance from a potential profile V(z) and a charge distribution q(z) induced by the ions at water-Ti2CTx (T =O, F) interfaces. Potential profiles V(z) of both Ti2CO2 and Ti2CF2 decrease about 1.0 eV steeply in a region of only 3 Å from a Ti layer, which is the same profile at the platinum interfaces. On the other hand, induced charge distribution q(z) depends on the species of surface termination. Induced electrons are introduced at Ti layers in the case of O surface termination. However, Ti2CF2 is not capable to store electrons at Ti layers because it is mono-valence anions. It indicates that effective surface-position of MXenes depends on the surface terminations. Our results are revealed that small induced charge leads the low EDL capacitance at MXene interfaces. This is because interface polarization due to strong interaction between water and Ti2CTx induces net charge. The surface net charge hinders the introduction of ion-induced charges.

Surface modification of nanoporous alumina layers by deposition of Ag nanoparticles. Effect of alumina pore diameter on the morphology of silver deposit and its influence on SERS activity

NASA Astrophysics Data System (ADS)

Pisarek, Marcin; Nowakowski, Robert; Kudelski, Andrzej; Holdynski, Marcin; Roguska, Agata; Janik-Czachor, Maria; Kurowska-Tabor, Elżbieta; Sulka, Grzegorz D.

2015-12-01

Self-organized Al2O3 nanoporous/nanotubular (Al2O3-NP) oxide layers decorated with silver nanoparticles (Ag-NPs) exhibiting specific properties may serve as attractive SERS substrates for investigating the interactions between an adsorbate and adsorbent, or as stable platforms for detecting various organic compounds. This article presents the influence of the size of the alumina nanopores with a deposit of silver nanoparticles obtained by the magnetron sputtering technique on the morphology of silver film. Moreover, the effect of pore diameter on the intensity of SERS spectra in Ag-NPs/Al2O3-NP/Al composites has also been estimated. For such investigations we used pyridine as a probe molecule, since it has a large cross-section for Raman scattering. To characterize the morphology of the composite oxide layer Ag-NPs/Al2O3-NP/Al, before and after deposition of Ag-NPs by PVD methods (Physical Vapor Deposition), we used scanning electron microscopy (SEM) and atomic force microscopy (AFM). The surface analytical technique of surface-enhanced Raman spectroscopy (SERS) was used to investigate the surface activity of the composite. The results obtained show that, for a carefully controlled amount of Ag (0.020 mg/cm2 - deposited on the top of alumina nanopores whose average size varies from ∼86 nm up to ∼320 nm) in the composites investigated, pore size significantly affects SERS enhancement. We obtained distinctly higher intensities of SERS spectra for substrates with an Ag-NPs deposit having a larger diameter of the alumina nanopores. AFM results suggest that both the lateral and perpendicular distribution of Ag-NPs within and on the top of the largest pores is responsible for the highest SERS activity of the resulting Ag-NPs/Al2O3-NP/Al composite layer, since it produces a variety of cavities and slits which function as resonators for the adsorbed molecules. The Ag-NPs/MeOx-NP/Me composite layers obtained ensure a good reproducibility of the SERS measurements.

Impact of active layer thickness of nitrogen-doped In–Sn–Zn–O films on materials and thin film transistor performances

NASA Astrophysics Data System (ADS)

Li, Zhi-Yue; Yang, Hao-Zhi; Chen, Sheng-Chi; Lu, Ying-Bo; Xin, Yan-Qing; Yang, Tian-Lin; Sun, Hui

2018-05-01

Nitrogen-doped indium tin zinc oxide (ITZO:N) thin film transistors (TFTs) were deposited on SiO2 (200 nm)/p-Si〈1 0 0〉 substrates by RF magnetron sputtering at room temperature. The structural, chemical compositions, surface morphology, optical and electrical properties as a function of the active layer thickness were investigated. As the active layer thickness increases, Zn content decreases and In content increases gradually. Meanwhile, Sn content is almost unchanged. When the thickness of the active layer is more than 45 nm, the ITZO:N films become crystallized and present a crystal orientation along InN(0 0 2) plan. No matter what the thickness is, ITZO:N films always display a high transmittance above 80% in the visible region. Their optical band gaps fluctuate between 3.4 eV and 3.62 eV. Due to the dominance of low interface trap density and high carrier concentration, ITZO:N TFT shows enhanced electrical properties as the active layer thickness is 35 nm. Its field-effect mobility, on/off radio and sub-threshold swing are 17.53 cm2 V‑1 · s‑1, 106 and 0.36 V/dec, respectively. These results indicate that the suitable thickness of the active layer can enhance the quality of ITZO:N films and decrease the defects density of ITZO:N TFT. Thus, the properties of ITZO:N TFT can be optimized by adjusting the thickness of the active layer.

Vancomycin incorporated chitosan/gelatin coatings coupled with TiO2-SrHAP surface modified cp-titanium for osteomyelitis treatment.

PubMed

D, Nancy; N, Rajendran

2018-04-15

Commercially pure Titanium (Cp-Ti) was electrophoretically modified using double layer coatings consisting of TiO 2 -SrHAP as the first layer (TH) followed by vancomycin incorporated Chitosan/Gelatin as the second layer (THV). The nano crystalline phase of coated Strontium incorporated hydroxyapatite (Sr-HAP) confirmed through X-ray diffraction studies (XRD). The polyelectrolyte complex formation between chitosan and gelatin, the stability of the drug, the bonding between chitosan and Sr-HAP were confirmed through infra-red spectroscopic studies (IR). The average roughness (R a ) value calculated from atomic force microscopy (AFM) corroborates with the water contact angle data, which clearly confirms the tuning property of the surface in relation to the surface energy and roughness of the coated samples. The total amount of vancomycin encapsulated was calculated to be 11.5 μg. Antibacterial activity was found against both Staphylococcus aureus strains methicillin resistant Staphylococcus aureus (MRSA) and methicillin sensitive Staphylococcus aureus (MRSA) for a drug concentration of 2.74 μg released after 12 h of immersion. The in-vitro cell culture studies showed enhanced cellular activity for THV samples. Thus, THV samples have a dual action at the surface, by resisting the bacterial adhesion and enhancing cellular interaction at the bio-interface, making it a promising candidate to treat osteomyelitis infection. Copyright © 2018. Published by Elsevier B.V.

Real-time monitoring of steady-state pulsed chemical beam epitaxy by p-polarized reflectance

NASA Astrophysics Data System (ADS)

Bachmann, K. J.; Sukidi, N.; Höpfner, C.; Harris, C.; Dietz, N.; Tran, H. T.; Beeler, S.; Ito, K.; Banks, H. T.

1998-01-01

The structure in the p-polarized reflectance (PR) intensity Rp4( t) - observed under conditions of pulsed chemical beam epitaxy (PCBE) - is modeled on the basis of the four-layer stack: ambient/surface reaction layer (SRL)/epilayer/substrate. Linearization of the PR intensity with regard to the phase factor associated with the SRL results in a good approximation that can be expressed as Rp4 = Rp3 + ΔRp. Rp3 is the reflectivity of the three-layer stack ambient-epilayer-substrate. ΔRp describes the properties of the SRL. An explicit relation is derived between ΔRp( t) and the time-dependent surface concentrations ch( t) ( h = 1, 2, …, N) of the constituents of the SRL, which holds for conditions of submonolayer coverage of the surface by source vapor molecules. Under conditions of low temperature PCBE at high flux, the SRL is expected to exhibit nonideal behavior, mandating replacement of the surface concentrations by activities. Also, in this case, the thickness of the SRL must be represented in terms of partial molar volumina Vh. Since the relation between ΔRp( t) and the activities of reactants, intermediates and products of the chemical reactions driving heteroepitaxial growth is non-linear, the extraction of kinetic parameters from the measured time dependence of the PR signal generally requires numerical modeling.

Novel Swelling-Resistant Sodium Alginate Membrane Branching Modified by Glycogen for Highly Aqueous Ethanol Solution Pervaporation.

PubMed

Ji, Chen-Hao; Xue, Shuang-Mei; Xu, Zhen-Liang

2016-10-12

A novel carbohydrate chain cross-linking method of sodium alginate (SA) is proposed in which glycogen with the branched-chain structure is utilized to cross-link with SA matrix by the bridging of glutaraldehyde (GA). The active layer of SA composite ceramic membrane modified by glycogen and GA for pervaporation (PV) demonstrates great advantages. The branched structure increases the chain density of the active layer, which compresses the free volume between the carbohydrate chains of SA. Large amounts of hydroxyl groups are consumed during the reaction with GA, which reduces the hydrogen bond formation between water molecules and the polysaccharide matrix. The two factors benefit the active layer with great improvement in swelling resistance, promoting the potential of the active layer for the dehydration of an ethanol-water solution containing high water content. Meanwhile, the modified active layer is loaded on the rigid α-Al 2 O 3 ceramic membrane by dip-coating method with the enhancement of anti-deformation and controllable thickness of the active layer. Characterization techniques such as SEM, AFM, XRD, FTIR, XPS, and water contact angle are utilized to observe the composite structure and surface morphology of the composite membrane, to probe the free volume variation, and to determine the chemical composition and hydrophilicity difference of the active layer caused by the different glycogen additive amounts. The membrane containing 3% glycogen in the selective layer demonstrates the flux at 1250 g m -2 h -1 coupled with the separation factor of 187 in the 25 wt % water content feed solution at the operating temperature of 75 °C, reflecting superior pervaporation processing capacity compared with the general organic PV membranes in the same condition.

Excitation functions of heavy ion induced nuclear reactions between 16O ion beam and natural copper: Measurements, analysis and its applicability in TLA study

NASA Astrophysics Data System (ADS)

Chowdhury, D. P.; Guin, R.; Saha, S. K.; Sudersanan, M.

2003-11-01

Experimental cross sections of a number of reaction channels of 16O ion induced reactions on natural copper target have been determined at different energies in the range of 50-110 MeV of 16O projectile by stacked foil activation technique. The cross sections have been compared with theoretical calculations using the computer code ALICE-91. The experimental values compared reasonably well with the corresponding theoretical estimates. The results indicate no significant role of incomplete fusion process in the 16O induced reactions on natural copper in the energy range of ⩽7 MeV/nucleon. As heavy ion beam produces an extremely narrow layer of activities in the surface of a material, these reactions could be useful for thin layer activation (TLA) study. The purpose of this work is to apply heavy ion activation in TLA technique for the study of surface wear with increased sensitivity.

Effect of blocking tactile information from the fingertips on adaptation and execution of grip forces to friction at the grasping surface.

PubMed

Bilaloglu, Seda; Lu, Ying; Geller, Daniel; Rizzo, John Ross; Aluru, Viswanath; Gardner, Esther P; Raghavan, Preeti

2016-03-01

Adaptation of fingertip forces to friction at the grasping surface is necessary to prevent use of inadequate or excessive grip forces. In the current study we investigated the effect of blocking tactile information from the fingertips noninvasively on the adaptation and efficiency of grip forces to surface friction during precision grasp. Ten neurologically intact subjects grasped and lifted an instrumented grip device with 18 different frictional surfaces under three conditions: with bare hands or with a thin layer of plastic (Tegaderm) or an additional layer of foam affixed to the fingertips. The coefficient of friction at the finger-object interface of each surface was obtained for each subject with bare hands and Tegaderm by measuring the slip ratio (grip force/load force) at the moment of slip. We found that the foam layer reduced sensibility for two-point discrimination and pressure sensitivity at the fingertips, but Tegaderm did not. However, Tegaderm reduced static, but not dynamic, tactile discrimination. Adaptation of fingertip grip forces to surface friction measured by the rate of change of peak grip force, and grip force efficiency measured by the grip-load force ratio at lift, showed a proportional relationship with bare hands but were impaired with Tegaderm and foam. Activation of muscles engaged in precision grip also varied with the frictional surface with bare hands but not with Tegaderm and foam. The results suggest that sensitivity for static tactile discrimination is necessary for feedforward and feedback control of grip forces and for adaptive modulation of muscle activity during precision grasp. Copyright © 2016 the American Physiological Society.

Tuning plasmons layer-by-layer for quantitative colloidal sensing with surface-enhanced Raman spectroscopy.

PubMed

Anderson, William J; Nowinska, Kamila; Hutter, Tanya; Mahajan, Sumeet; Fischlechner, Martin

2018-04-19

Surface-enhanced Raman spectroscopy (SERS) is well known for its high sensitivity that emerges due to the plasmonic enhancement of electric fields typically on gold and silver nanostructures. However, difficulties associated with the preparation of nanostructured substrates with uniform and reproducible features limit reliability and quantitation using SERS measurements. In this work we use layer-by-layer (LbL) self-assembly to incorporate multiple functional building blocks of collaborative assemblies of nanoparticles on colloidal spheres to fabricate SERS sensors. Gold nanoparticles (AuNPs) are packaged in discrete layers, effectively 'freezing nano-gaps', on spherical colloidal cores to achieve multifunctionality and reproducible sensing. Coupling between layers tunes the plasmon resonance for optimum SERS signal generation to achieve a 10 nM limit of detection. Significantly, using the layer-by-layer construction, SERS-active AuNP layers are spaced out and thus optically isolated. This uniquely allows the creation of an internal standard within each colloidal sensor to enable highly reproducible self-calibrated sensing. By using 4-mercaptobenzoic acid (4-MBA) as the internal standard adenine concentrations are quantified to an accuracy of 92.6-99.5%. Our versatile approach paves the way for rationally designed yet quantitative colloidal SERS sensors and their use in a variety of sensing applications.

Numerical experiments with a wind- and buoyancy-driven two-and-a-half-layer upper ocean model

NASA Astrophysics Data System (ADS)

Cherniawsky, J. Y.; Yuen, C. W.; Lin, C. A.; Mysak, L. A.

1990-09-01

We describe numerical experiments with a limited domain (15°-67°N, 65° west to east) coarse-resolution two-and-a-half-layer upper ocean model. The model consists of two active variable density layers: a Niiler and Kraus (1977) type mixed layer and a pycnocline layer, which overlays a semipassive deep ocean. The mixed layer is forced with a cosine wind stress and Haney type heat and precipitation-evaporation fluxes, which were derived from zonally averaged climatological (Levitus, 1982) surface temperatures and salinities for the North Atlantic. The second layer is forced from below with (1) Newtonian cooling to climatological temperatures and salinities at the lower boundary, (2) convective adjustment, which occurs whenever the density of the second layer is unstable with respect to climatology, and (3) mass entrainment in areas of strong upwelling, when the deep ocean ventilates through the bottom surface. The sensitivity of this model to changes in its internal (mixed layer) and external (e.g., a Newtonian coupling coefficient) parameters is investigated and compared to the results from a control experiment. We find that the model is not overly sensitive to changes in most of the parameters that were tested, albeit these results may depend to some extent on the choice of the control experiment.

Zonally asymmetric response of the Southern Ocean mixed-layer depth to the Southern Annular Mode

NASA Astrophysics Data System (ADS)

Sallée, J. B.; Speer, K. G.; Rintoul, S. R.

2010-04-01

Interactions between the atmosphere and ocean are mediated by the mixed layer at the ocean surface. The depth of this layer is determined by wind forcing and heating from the atmosphere. Variations in mixed-layer depth affect the rate of exchange between the atmosphere and deeper ocean, the capacity of the ocean to store heat and carbon and the availability of light and nutrients to support the growth of phytoplankton. However, the response of the Southern Ocean mixed layer to changes in the atmosphere is not well known. Here we analyse temperature and salinity data from Argo profiling floats to show that the Southern Annular Mode (SAM), the dominant mode of atmospheric variability in the Southern Hemisphere, leads to large-scale anomalies in mixed-layer depth that are zonally asymmetric. From a simple heat budget of the mixed layer we conclude that meridional winds associated with departures of the SAM from zonal symmetry cause anomalies in heat flux that can, in turn, explain the observed changes of mixed-layer depth and sea surface temperature. Our results suggest that changes in the SAM, including recent and projected trends attributed to human activity, drive variations in Southern Ocean mixed-layer depth, with consequences for air-sea exchange, ocean sequestration of heat and carbon, and biological productivity.

Method for providing adhesion to a metal surface

DOEpatents

Harrah, L.A.; Allred, R.E.; Wilson, K.V. Jr.

1992-02-18

A process for treating metal surfaces to obtain improved susceptibility to bonding with adhesive compositions is disclosed. A metal surface is oxidized with a halogen to form a monolayer of halide ions on the surface. The halide ions are then exchanged with azide ions to form an azide monolayer on the metal surface. Upon contact of the treated surface with an adhesive composition, the azide layer may be thermally or photochemically decomposed to form active nitrene species, which react to bond the adhesive composition to the metal surface.

Method for providing adhesion to a metal surface

DOEpatents

Harrah, Larry A.; Allred, Ronald E.; Wilson, Jr., Kennard V.

1992-01-01

A process for treating metal surfaces to obtain improved susceptibility to bonding with adhesive compositions is disclosed. A metal surface is oxidized with a halogen to form a monolayer of halide ions on the surface. The halide ions are then exchanged with azide ions to form an azide monolayer on the metal surface. Upon contact of the treated surface with an adhesive composition, the azide layer may be thermally or photochemically decomposed to form active nitrene species, which react to bond the adhesive composition to the metal surface.

Visualization of soil structure and pore structure modifications by pioneering ground beetles (Cicindelidae) in surface sediments of an artificial catchment

NASA Astrophysics Data System (ADS)

Badorreck, Annika; Gerke, Horst H.; Weller, Ulrich; Vontobel, Peter

2010-05-01

An artificial catchment was constructed to study initial soil and ecosystem development. As a key process, the pore structure dynamics in the soil at the surface strongly influences erosion, infiltration, matter dynamics, and vegetation establishment. Little is known, however, about the first macropore formation in the very early stage. This presentation focuses on observations of soil pore geometry and its effect on water flow at the surface comparing samples from three sites in the catchment and in an adjacent "younger" site composed of comparable sediments. The surface soil was sampled in cylindrical plastic rings (10 cm³) down to 2 cm depth in three replicates each site and six where caves from pioneering ground-dwelling beetles Cicindelidae were found. The samples were scanned with micro-X-ray computed tomography (at UFZ-Halle, Germany) with a resolution of 0.084 mm. The infiltration dynamics were visualized with neutronradiography (at Paul-Scherer-Institute, Switzerland) on slab-type soil samples in 2D. The micro-tomographies exhibit formation of surface sealing whose thickness and intensity vary with silt and clay content. The CT images show several coarser- and finer-textured micro-layers at the sample surfaces that were formed as a consequence of repeated washing in of finer particles in underlying coarser sediment. In micro-depressions, the uppermost layers consist of sorted fine sand and silt due to wind erosion. Similar as for desert pavements, a vesicular pore structure developed in these sediments on top, but also scattered in fine sand- and silt-enriched micro-layers. The ground-dwelling activity of Cicindelidae beetles greatly modifies the soil structure through forming caves in the first centimetres of the soil. Older collapsed caves, which form isolated pores within mixed zones, were also found. The infiltration rates were severely affected both, by surface crusts and activity of ground-dwelling beetles. The observations demonstrate relatively high abiotic and biotic dynamics of soil pore structure in the soil surface even during the very early development stages. The structure formation has potentially great effects on changing runoff and infiltration by forming sealing layers or preferential flow paths.

Radiative transfer in multilayered random medium with laminar structure - Green's function approach

NASA Technical Reports Server (NTRS)

Karam, M. A.; Fung, A. K.

1986-01-01

For a multilayered random medium with a laminar structure a Green's function approach is introduced to obtain the emitted intensity due to an arbitrary point source. It is then shown that the approach is applicable to both active and passive remote sensing. In active remote sensing, the computed radar backscattering cross section for the multilayered medium includes the effects of both volume multiple scattering and surface multiple scattering at the layer boundaries. In passive remote sensing, the brightness temperature is obtained for arbitrary temperature profiles in the layers. As an illustration the brightness temperature and reflectivity are calculated for a bounded layer and compared with results in the literature.

Boundary Layer Control for Hypersonic Airbreathing Vehicles

NASA Technical Reports Server (NTRS)

Berry, Scott A.; Nowak, Robert J.; Horvath, Thomas J.

2004-01-01

Active and passive methods for tripping hypersonic boundary layers have been examined in NASA Langley Research Center wind tunnels using a Hyper-X model. This investigation assessed several concepts for forcing transition, including passive discrete roughness elements and active mass addition (or blowing), in the 20-Inch Mach 6 Air and the 31-Inch Mach 10 Air Tunnels. Heat transfer distributions obtained via phosphor thermography, shock system details, and surface streamline patterns were measured on a 0.333-scale model of the Hyper-X forebody. The comparisons between the active and passive methods for boundary layer control were conducted at test conditions that nearly match the Hyper-X nominal Mach 7 flight test-point of an angle-of-attack of 2-deg and length Reynolds number of 5.6 million. For passive roughness, the primary parametric variation was a range of trip heights within the calculated boundary layer thickness for several trip concepts. The passive roughness study resulted in a swept ramp configuration, scaled to be roughly 0.6 of the calculated boundary layer thickness, being selected for the Mach 7 flight vehicle. For the active blowing study, the manifold pressure was systematically varied (while monitoring the mass flow) for each configuration to determine the jet penetration height, with schlieren, and transition movement, with the phosphor system, for comparison to the passive results. All the blowing concepts tested, which included various rows of sonic orifices (holes), two- and three-dimensional slots, and random porosity, provided transition onset near the trip location with manifold stagnation pressures on the order of 40 times the model surface static pressure, which is adequate to ensure sonic jets. The present results indicate that the jet penetration height for blowing was roughly half the height required with passive roughness elements for an equivalent amount of transition movement.

Active Fault Topography and Fault Outcrops in the Central Part of the Nukumi fault, the 1891 Nobi Earthquake Fault System, Central Japan

NASA Astrophysics Data System (ADS)

Sasaki, T.; Ueta, K.; Inoue, D.; Aoyagi, Y.; Yanagida, M.; Ichikawa, K.; Goto, N.

2010-12-01

It is important to evaluate the magnitude of earthquake caused by multiple active faults, taking into account the simultaneous effects. The simultaneity of adjacent active faults are often decided on the basis of geometric distances except for known these paleoseismic records. We have been studied the step area between the Nukumi fault and the Neodani fault, which appeared as consecutive ruptures in the 1891 Nobi earthquake, since 2009. The purpose of this study is to establish innovation in valuation technique of the simultaneity of adjacent active faults in addition to the paleoseismic record and the geometric distance. Geomorphological, geological and reconnaissance microearthquake surveys are concluded. The present work is intended to clarify the distribution of tectonic geomorphology along the Nukumi fault and the Neodani fault by high-resolution interpretations of airborne LiDAR DEM and aerial photograph, and the field survey of outcrops and location survey. The study area of this work is the southeastern Nukumi fault and the northwestern Neodani fault. We interpret DEM using shaded relief map and stereoscopic bird's-eye view made from 2m mesh DEM data which is obtained by airborne laser scanner of Kokusai Kogyo Co., Ltd. Aerial photographic survey is for confirmation of DEM interpretation using 1/16,000 scale photo. As a result of topographic survey, we found consecutive tectonic topography which is left lateral displacement of ridge and valley lines and reverse scarplets along the Nukumi fault and the Neodani fault . From Ogotani 2km southeastern of Nukumi pass which is located at the southeastern end of surface rupture along the Nukumi fault by previous study to Neooppa 9km southeastern of Nukumi pass, we can interpret left lateral topographies and small uphill-facing fault scarps on the terrace surface by detail DEM investigation. These topographies are unrecognized by aerial photographic survey because of heavy vegetation. We have found several new outcrops in this area where the surface ruptures of the 1891 Nobi earthquake have not been known. These outcrops have active fault which cut the layer of terrace deposit and slope deposit to the bottom of present soil layer in common. At the locality of Ogotani outcrop, the humic layer which age is from14th century to 15th century by 14C age dating is deformed by the active fault. The vertical displacement of the humic layer is 0.8-0.9m and the terrace deposit layer below the humic layer is ca. 1.3m. For this reason and the existence of fain grain deposit including AT tephra (28ka) in the footwall of the fault, this fault movement occurred more than once since the last glacial age. We conclude that the surface rupture of Nukumi fault in the 1891 Nobi earthquake is continuous to 9km southeast of Nukumi pass. In other words, these findings indicate that there is 10km parallel overlap zone between the surface rupture of the southeastern end of Nukumi fault and the northwestern end of Neodani fault.

Superpixel guided active contour segmentation of retinal layers in OCT volumes

NASA Astrophysics Data System (ADS)

Bai, Fangliang; Gibson, Stuart J.; Marques, Manuel J.; Podoleanu, Adrian

2018-03-01

Retinal OCT image segmentation is a precursor to subsequent medical diagnosis by a clinician or machine learning algorithm. In the last decade, many algorithms have been proposed to detect retinal layer boundaries and simplify the image representation. Inspired by the recent success of superpixel methods for pre-processing natural images, we present a novel framework for segmentation of retinal layers in OCT volume data. In our framework, the region of interest (e.g. the fovea) is located using an adaptive-curve method. The cell layer boundaries are then robustly detected firstly using 1D superpixels, applied to A-scans, and then fitting active contours in B-scan images. Thereafter the 3D cell layer surfaces are efficiently segmented from the volume data. The framework was tested on healthy eye data and we show that it is capable of segmenting up to 12 layers. The experimental results imply the effectiveness of proposed method and indicate its robustness to low image resolution and intrinsic speckle noise.

Acoustical evaluation of carbonized and activated cotton nonwovens.

PubMed

Jiang, N; Chen, J Y; Parikh, D V

2009-12-01

An activated carbon fiber nonwoven (ACF) was manufactured from a cotton nonwoven fabric. For the ACF acoustic application, a nonwoven composite of ACF with cotton nonwoven as a base layer was developed. Also produced were the composites of the cotton nonwoven base layer with a layer of glassfiber nonwoven, and the cotton nonwoven base layer with a layer of cotton fiber nonwoven. Their noise absorption coefficients and sound transmission loss were measured using the Brüel and Kjaer impedance tube instrument. Statistical significance of the differences between the composites was tested using the method of Duncan's grouping. The study concluded that the ACF composite exhibited a greater ability to absorb normal incidence sound waves than the composites with either glassfiber or cotton fiber. The analysis of sound transmission loss revealed that the three composites still obeyed the mass law of transmission loss. The composite with the surface layer of cotton fiber nonwoven possessed a higher fabric density and therefore showed a better sound insulation than the composites with glassfiber and ACF.

Multiple scattering effects with cyclical terms in active remote sensing of vegetated surface using vector radiative transfer theory

USDA-ARS?s Scientific Manuscript database

The energy transport in a vegetated (corn) surface layer is examined by solving the vector radiative transfer equation using a numerical iterative approach. This approach allows a higher order that includes the multiple scattering effects. Multiple scattering effects are important when the optical t...

Laser peening for reducing hydrogen embrittlement

DOEpatents

Hackel, Lloyd A.; Zaleski, Tania M.; Chen, Hao-Lin; Hill, Michael R.; Liu, Kevin K.

2010-05-25

A laser peening process for the densification of metal surfaces and sub-layers and for changing surface chemical activities provides retardation of the up-take and penetration of atoms and molecules, particularly Hydrogen, which improves the lifetime of such laser peened metals. Penetration of hydrogen into metals initiates an embrittlement that leaves the material susceptible to cracking.

Study of sporadical properties of crosslinked polyelectrolyte multilayers

NASA Astrophysics Data System (ADS)

Balu, Deebika

Polyelectrolyte multilayers (PEM) have become a highly studied class of materials due to the range of their applicability in many areas of research, including biology, chemistry and materials science. Recent advances in surface coatings have enabled modification of PEM surfaces to provide desirable properties such as controlled release, super-hydrophobicity, biocompatibility, antifouling and antibacterial properties. In the past decade, antimicrobial PEM coatings have been investigated as a safer alternative to the traditional disinfection methods that usually involve application of hazardous chemicals onto the surface to be cleaned. These antimicrobial coatings could be applied to common surfaces prone to colonization of bacteria (such as bench tops, faucet handles, etc) to supplement routine sanitization protocols by providing sustained antimicrobial activity. Vegetative bacteria (such as Escherichia coli) are more susceptible to antimicrobial agents than bacterial species that form spores. Hence, the antimicrobial activity of PEM coatings fabricated using Layer by Layer (LbL) technique were assayed using Bacillus anthracis spores (Sterne strain). In this thesis, the sporicidal effect of various polyelectrolyte multilayer coatings containing cross-linked polymers immersed in bleach have been evaluated as potential augmentation to existing disinfection methods.

Kinetic modeling of microscopic processes during electron cyclotron resonance microwave plasma-assisted molecular beam epitaxial growth of GaN/GaAs-based heterostructures

NASA Astrophysics Data System (ADS)

Bandić, Z. Z.; Hauenstein, R. J.; O'Steen, M. L.; McGill, T. C.

1996-03-01

Microscopic growth processes associated with GaN/GaAs molecular beam epitaxy (MBE) are examined through the introduction of a first-order kinetic model. The model is applied to the electron cyclotron resonance microwave plasma-assisted MBE (ECR-MBE) growth of a set of δ-GaNyAs1-y/GaAs strained-layer superlattices that consist of nitrided GaAs monolayers separated by GaAs spacers, and that exhibit a strong decrease of y with increasing T over the range 540-580 °C. This y(T) dependence is quantitatively explained in terms of microscopic anion exchange, and thermally activated N surface-desorption and surface-segregation processes. N surface segregation is found to be significant during GaAs overgrowth of GaNyAs1-y layers at typical GaN ECR-MBE growth temperatures, with an estimated activation energy Es˜0.9 eV. The observed y(T) dependence is shown to result from a combination of N surface segregation/desorption processes.

MEMS based pyroelectric thermal energy harvester

DOEpatents

Hunter, Scott R; Datskos, Panagiotis G

2013-08-27

A pyroelectric thermal energy harvesting apparatus for generating an electric current includes a cantilevered layered pyroelectric capacitor extending between a first surface and a second surface, where the first surface includes a temperature difference from the second surface. The layered pyroelectric capacitor includes a conductive, bimetal top electrode layer, an intermediate pyroelectric dielectric layer and a conductive bottom electrode layer. In addition, a pair of proof masses is affixed at a distal end of the layered pyroelectric capacitor to face the first surface and the second surface, wherein the proof masses oscillate between the first surface and the second surface such that a pyroelectric current is generated in the pyroelectric capacitor due to temperature cycling when the proof masses alternately contact the first surface and the second surface.

Thermal and Photochemical Reactions of NO2 on a Chromium (III) Oxide Surface

NASA Astrophysics Data System (ADS)

Nishino, N.; Finlayson-Pitts, B. J.

2011-12-01

Chromium oxide (Cr2O3) is a major component of the oxide layer on stainless steel surfaces. It is also widely used as pigment in paints and roofs and as a protective coating on various surfaces. While many studies have focused on the catalytic activity of Cr2O3 surfaces for selective catalytic reduction (SCR), less attention has been paid to its surface chemistry involving atmospherically important species such as NO2 under atmospheric conditions. In this study, we have investigated thermal and photochemical reactions of NO2 in the presence and the absence of water vapor, using a thin layer of Cr2O3 as a model for the surface of stainless steel as well as other similarly coated surfaces in the boundary layer. A 30 nm thick Cr2O3 film was deposited on a germanium attenuated total reflectance (ATR) crystal, and the changes in the surface species were monitored by Fourier Transform Infrared (FTIR) spectroscopy. Upon NO2 adsorption, nitrate (NO3-) ions appeared likely coordinated to Cr3+ ion(s). The NO3- peaks reversibly shifted when water vapor was added, suggesting that NO3- become solvated. Irradiation at 311 nm led to a decrease in NO3- ions under both dry and humid conditions. The major gas-phase species formed by the irradiation was NO under dry conditions, while NO2 was mainly formed in the presence of H2O. Possible mechanisms and the implications for heterogeneous NO2 chemistry in the boundary layer will be discussed. The results will also be compared to similar chemistry on other surfaces.

Application of non-equilibrium plasmas in treatment of wool fibers and seeds

NASA Astrophysics Data System (ADS)

Petrović, Zoran

2003-10-01

While large effort is under way to achieve stable, large area, non-equilibrium plasma reactors operating at atmospheric pressure we should still consider application of low pressure reactors, which provide well defined, easily controlled reactive plasmas. Therefore, the application of low pressure rf plasmas for the treatment of wool and seed was investigated. The studies were aimed at establishing optimal procedure to achieve better wettability, dyeability and printability of wool. Plasma treatment led to a modification of wool fiber topography and formation of new polar functional groups inducing the increase of wool hydrophylicity. Plasma activation of fiber surface was also used to achieve better binding of biopolymer chitosan to wool in order to increase the content of favorable functional groups and thus improving sorption properties of recycled wool fibers for heavy metal ions and acid dyes. In another study, the increase of germination percentage of seeds induced by plasmas was investigated. We have selected dry (unimbibed) Empress tree seeds (Paulownia tomentosa Steud.). Empress tree seed has been studied extensively and its mechanism of germination is well documented. Germination of these seeds is triggered by light in a limited range of wavelengths. Interaction between activated plasma particles and seed, inside the plasma reactor, leads to changes in its surface topography, modifies the surface layer and increases the active surface area. Consequently, some bioactive nitrogeneous compounds could be bound to the activated surface layer causing the increment of germination percentage.

Thin-film chemical sensors based on electron tunneling

NASA Technical Reports Server (NTRS)

Khanna, S. K.; Lambe, J.; Leduc, H. G.; Thakoor, A. P.

1985-01-01

The physical mechanisms underlying a novel chemical sensor based on electron tunneling in metal-insulator-metal (MIM) tunnel junctions were studied. Chemical sensors based on electron tunneling were shown to be sensitive to a variety of substances that include iodine, mercury, bismuth, ethylenedibromide, and ethylenedichloride. A sensitivity of 13 parts per billion of iodine dissolved in hexane was demonstrated. The physical mechanisms involved in the chemical sensitivity of these devices were determined to be the chemical alteration of the surface electronic structure of the top metal electrode in the MIM structure. In addition, electroreflectance spectroscopy (ERS) was studied as a complementary surface-sensitive technique. ERS was shown to be sensitive to both iodine and mercury. Electrolyte electroreflectance and solid-state MIM electroreflectance revealed qualitatively the same chemical response. A modified thin-film structure was also studied in which a chemically active layer was introduced at the top Metal-Insulator interface of the MIM devices. Cobalt phthalocyanine was used for the chemically active layer in this study. Devices modified in this way were shown to be sensitive to iodine and nitrogen dioxide. The chemical sensitivity of the modified structure was due to conductance changes in the active layer.

Radiometric Measurements of the Thermal Conductivity of Complex Planetary-like Materials

NASA Astrophysics Data System (ADS)

Piqueux, S.; Christensen, P. R.

2012-12-01

Planetary surface temperatures and thermal inertias are controlled by the physical and compositional characteristics of the surface layer material, which result from current and past geological activity. For this reason, temperature measurements are often acquired because they provide fundamental constraints on the geological history and habitability. Examples of regolith properties affecting surface temperatures and inertias are: grain sizes and mixture ratios, solid composition in the case of ices, presence of cement between grains, regolith porosity, grain roughness, material layering etc.. Other important factors include volatile phase changes, and endogenic or exogenic heat sources (i.e. geothermal heat flow, impact-related heat, biological activity etc.). In the case of Mars, the multitude of instruments observing the surface temperature at different spatial and temporal resolutions (i.e. IRTM, Thermoskan, TES, MiniTES, THEMIS, MCS, REMS, etc.) in conjunction with other instruments allows us to probe and characterize the thermal properties of the surface layer with an unprecedented resolution. While the derivation of thermal inertia values from temperature measurements is routinely performed by well-established planetary regolith numerical models, constraining the physical properties of the surface layer from thermal inertia values requires the additional step of laboratory measurements. The density and specific heat are usually constant and sufficiently well known for common geological materials, but the bulk thermal conductivity is highly variable as a function of the physical characteristics of the regolith. Most laboratory designs do not allow an investigation of the thermal conductivity of complex regolith configurations similar to those observed on planetary surfaces (i.e. cemented material, large grains, layered material, and temperature effects) because the samples are too small and need to be soft to insert heating or measuring devices. For this reason, we have built a new type of apparatus to measure the thermal conductivity of sample significantly larger than previous apparatus under planetary conditions of atmosphere and gas composition. Samples' edges are cooled down from room to LN2 temperature and the surface material temperature is recorded by an infrared camera without inserting thermocouples or heat sources. Sample surface cooling trends are fit with finite element models of heat transfer to retrieve the material thermal conductivity. Preliminary results confirm independent numerical modeling results predicting the thermal conductivity of complex materials: the thermal inertia of particulate material under Mars conditions is temperature-dependent, small amounts of cements significantly increase the bulk conductivity and inertia of particulate material, and one-grain-thick armors similar to those observed by the Mars Exploration Rovers behave like a thin highly conductive layer that does not significantly influence apparent thermal inertias. These results are used to further our interpretation of Martian temperature observations. For example local amounts of subsurface water ice or the fraction of cementing phase in the global Martian duricrust can be constrained; the search for subtle changes in near-surface heat flow can be performed more accurately, and surface thermal inertias under various atmospheric conditions of pressure and gas composition can be predicted.

Characterization and cell behavior of titanium surfaces with PLL/DNA modification via a layer-by-layer technique.

PubMed

Gao, Wenli; Feng, Bo; Lu, Xiong; Wang, Jianxin; Qu, Shuxin; Weng, Jie

2012-08-01

This study describes the fabrication of two types of multilayered films onto titanium by layer-by-layer (LBL) self-assembly, using poly-L-lysine (PLL) as the cationic polyelectrolyte and deoxyribonucleic acid (DNA) as the anionic polyelectrolyte. The assembling process of each component was studied using atomic force microscopy (AFM) and quartz crystal balance (QCM). Zeta potential of the LBL-coated microparticles was measured by dynamic light scattering. Titanium substrates with or without multilayered films were used in osteoblast cell culture experiments to study cell proliferation, viability, differentiation, and morphology. Results of AFM and QCM indicated the progressive build-up of the multilayered coatings. The surface morphology of three types of multilayered films showed elevations in the nanoscale range. The data of zeta potential showed that the surface terminated with PLL displayed positive charge while the surface terminated with DNA displayed negative charge. The proliferation of osteoblasts on modified titanium films was found to be greater than that on control (p < 0.05) after 3 and 7 days culture, respectively. Alamar blue measurement showed that the PLL/DNA-modified films have higher cell viability (p < 0.05) than the control. Still, the alkaline phosphatase activity assay revealed a better differentiated phenotype on three types of multilayered surfaces compared to noncoated controls. Collectively our results suggest that PLL/DNA were successfully used to surface engineer titanium via LBL technique, and enhanced its cell biocompatibility. Copyright © 2012 Wiley Periodicals, Inc.

Super-hydrophobic multilayer coatings with layer number tuned swapping in surface wettability and redox catalytic anti-corrosion application.

PubMed

Syed, Junaid Ali; Tang, Shaochun; Meng, Xiangkang

2017-06-30

The wetting characteristic of a metal surface can be controlled by employing different coating materials and external stimuli, however, layer number (n) modulated surface swapping between hydrophobicity and hydrophilicity in a multilayer structure to achieve prolonged anti-corrosion ability was not taken into consideration. In this study, we proposed a layer-by-layer (LbL) spin assembled polyaniline-silica composite/tetramethylsilane functionalized silica nanoparticles (PSC/TMS-SiO 2 ) coating with the combined effect of super-hydrophobicity and enhanced anti-corrosion ability. Interestingly, the hierarchical integration of two coating materials with inherently different surface roughness and energy in a multilayer structure allows the wetting feature to swap from hydrophobic to hydrophilic state by modulating n with decreasing hydrophilicity. The samples with odd n (TMS-SiO 2 surface) are hydrophobic while the samples with even n (PSC surface) exhibits the hydrophilic character. The TMS-SiO 2 content was optimized to achieve super-hydrophobic coating with significantly high water contact angle (CA) 153° ± 2° and small sliding angle (SA) 6° ± 2°. Beside its self-cleaning behavior, the electro-active PSC/TMS-SiO 2 coating also exhibits remarkably enhanced corrosion resistance against aggressive media. The corrosion resistance of the coating was remained stable even after 240 h of exposure, this enhancement is attributed to super-hydrophobicity and anodic shift in corrosion potential.

Toward rational nanoparticle synthesis: predicting surface intermixing in bimetallic alloy nanocatalysts

DOE PAGES

Roling, Luke T.; Mavrikakis, Manos

2017-09-19

In this paper, we present a database of first-principles calculated activation energy barriers for two competitive processes involving bimetallic adatom-surface permutations of ten transition metals: (i) adatom “hopping” diffusion and (ii) adatom substitution into the surface. We consider the surface structure sensitivity of these events as well as coverage effects. We find that surface hopping mechanisms are facile and always preferred to substitution events on close-packed fcc(111) and hcp(0001) surfaces. However, surface atom substitution is more facile on the more open fcc(100) surfaces and is competitive with adatom surface hopping, which is more difficult than on the close-packed surfaces. Finally,more » by comparing the absolute and relative magnitudes of the energetics of hopping and substitution, our calculations can offer qualitative predictions of intermixing and other phenomena relevant to nanocrystal growth, such as the tendency to form intermixed alloys or core–shell structures during layer-by-layer nanoparticle synthesis involving a given bimetallic pair, and thereby inform the rational design and synthesis of novel bimetallic nanomaterials.« less

Dynamics of biochemical processes and redox conditions in geochemically linked landscapes of oligotrophic bogs

NASA Astrophysics Data System (ADS)

Inisheva, L. I.; Szajdak, L.; Sergeeva, M. A.

2016-04-01

The biological activity in oligotrophic peatlands at the margins of the Vasyugan Mire has been studied. It is shown found that differently directed biochemical processes manifest themselves in the entire peat profile down to the underlying mineral substrate. Their activity is highly variable. It is argued that the notion about active and inert layers in peat soils is only applicable for the description of their water regime. The degree of the biochemical activity is specified by the physical soil properties. As a result of the biochemical processes, a micromosaic aerobic-anaerobic medium is developed under the surface waterlogged layer of peat deposits. This layer contains the gas phase, including oxygen. It is concluded that the organic and mineral parts of peat bogs represent a single functional system of a genetic peat profile with a clear record of the history of its development.

Influence of culture media on the physical and chemical properties of Ag-TiCN coatings

NASA Astrophysics Data System (ADS)

Carvalho, I.; Escobar Galindo, R.; Henriques, M.; Palacio, C.; Carvalho, S.

2014-08-01

The aim of this study was to verify the possible physical and chemical changes that may occur on the surface of Ag-TiCN coatings after exposure to the culture media used in microbiological and cytotoxic assays, respectively tryptic soy broth (TSB) and Dulbecco's modified eagle's medium (DMEM). After sample immersion for 24 h in the media, analyses were performed by glow discharge optical emission spectroscopy discharge radiation (GDOES), Rutherford backscattering spectroscopy (RBS) and x-ray photoelectron spectroscopy (XPS). The results of GDOES profile, RBS and XPS spectra, of samples immersed in TSB, demonstrated the formation of a thin layer of carbon, oxygen and nitrogen that could be due to the presence of proteins in TSB. After 24 h of immersion in DMEM, the results showed the formation of a thin layer of calcium phosphates on the surface, since the coatings displayed a highly oxidized surface in which calcium and phosphorus were detected. All these results suggested that the formation of a layer on the coating surface prevented the release of silver ions in concentrations that allow antibacterial activity.

Geological evidence for solid-state convection in Europa's ice shell.

PubMed

Pappalardo, R T; Head, J W; Greeley, R; Sullivan, R J; Pilcher, C; Schubert, G; Moore, W B; Carr, M H; Moore, J M; Belton, M J; Goldsby, D L

1998-01-22

The ice-rich surface of the jovian satellite Europa is sparsely cratered, suggesting that this moon might be geologically active today. Moreover, models of the satellite's interior indicate that tidal interactions with Jupiter might produce enough heat to maintain a subsurface liquid water layer. But the mechanisms of interior heat loss and resurfacing are currently unclear, as is the question of whether Europa has (or had at one time) a liquid water ocean. Here we report on the morphology and geological interpretation of distinct surface features-pits, domes and spots-discovered in high-resolution images of Europa obtained by the Galileo spacecraft. The features are interpreted as the surface manifestation of diapirs, relatively warm localized ice masses that have risen buoyantly through the subsurface. We find that the formation of the features can be explained by thermally induced solid-state convection within an ice shell, possibly overlying a liquid water layer. Our results are consistent with the possibility that Europa has a liquid water ocean beneath a surface layer of ice, but further tests and observations are needed to demonstrate this conclusively.

Geological evidence for solid-state convection in Europa's ice shell

USGS Publications Warehouse

Pappalardo, R.T.; Head, J.W.; Greeley, R.; Sullivan, R.J.; Pilcher, C.; Schubert, G.; Moore, W.B.; Carr, M.H.; Moore, Johnnie N.; Belton, M.J.S.; Goldsby, D.L.

1998-01-01

The ice-rich surface of the jovian satellite Europa is sparsely cratered, suggesting that this moon might be geologically active today. Moreover, models of the satellite's interior indicate that tidal interactions with Jupiter might produce enough heat to maintain a subsurface liquid water layer. But the mechanisms of interior heat loss and resurfacing are currently unclear, as is the question of whether Europa has (or had at one time) a liquid water ocean. Here we report on the morphology and geological interpretation of distinct surface features-pits, domes and spots-discovered in high-resolution images of Europa obtained by the Galileo spacecraft. The features are interpreted as the surface manifestation of diapirs, relatively warm localized ice masses that have risen buoyantly through the subsurface. We find that the formation of the features can be explained by thermally induced solid-state convection within an ice shell, possibly overlying a liquid water layer. Our results are consistent with the possibility that Europa has a liquid water ocean beneath a surface layer of ice, but further tests and observations are needed to demonstrate this conclusively.

Sensitivity enhancement of a surface plasmon resonance sensor using porous metamaterial layers

NASA Astrophysics Data System (ADS)

Cherifi, Abdellatif; Bouhafs, Benamar

2017-12-01

In this work, the surface plasmon resonance (SPR) device with two porous left handed metamaterial (LHM) layers separated by an insulator gap, is investigated. The effect of the insulator gap thickness and its refractive index (RI) on the angular response of the device is analyzed. The results show that the sensitivity of the SPR sensor is enhanced compared to the standard SPR sensors. Here, the multilayer structure is probed with 738 nm-wavelength, and electromagnetic properties of active porous LHM layers are described from the effective medium theory (EMT). Furthermore, in the increase of the porosity from 0 to 0.6, the designed nanocavity exhibits a fundamental SPR mode long-range (LR) type and it can be of interest in high-performance SPR sensing.

Room-Temperature Atomic Layer Deposition of Al2 O3 : Impact on Efficiency, Stability and Surface Properties in Perovskite Solar Cells.

PubMed

Kot, Malgorzata; Das, Chittaranjan; Wang, Zhiping; Henkel, Karsten; Rouissi, Zied; Wojciechowski, Konrad; Snaith, Henry J; Schmeisser, Dieter

2016-12-20

In this work, solar cells with a freshly made CH 3 NH 3 PbI 3 perovskite film showed a power conversion efficiency (PCE) of 15.4 % whereas the one with 50 days aged perovskite film only 6.1 %. However, when the aged perovskite was covered with a layer of Al 2 O 3 deposited by atomic layer deposition (ALD) at room temperature (RT), the PCE value was clearly enhanced. X-ray photoelectron spectroscopy study showed that the ALD precursors are chemically active only at the perovskite surface and passivate it. Moreover, the RT-ALD-Al 2 O 3 -covered perovskite films showed enhanced ambient air stability. © 2016 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Multiple relaxations of the cluster surface diffusion in a homoepitaxial SrTiO3 layer

NASA Astrophysics Data System (ADS)

Woo, Chang-Su; Chu, Kanghyun; Song, Jong-Hyun; Yang, Chan-Ho

2018-03-01

We examine the surface diffusion process of adatomic clusters on a (001)-oriented SrTiO3 single crystal using reflection high energy electron diffraction (RHEED). We find that the recovery curve of the RHEED intensity acquired after a homoepitaxial half-layer growth can be accurately fit into a double exponential function, indicating the existence of two dominant relaxation mechanisms. The characteristic relaxation times at selected growth temperatures are investigated to determine the diffusion activation barriers of 0.67 eV and 0.91 eV, respectively. The Monte Carlo simulation of the cluster hopping model suggests that the decrease in the number of dimeric and trimeric clusters during surface diffusion is the origin of the observed relaxation phenomena.

Surface transformation by a “cocktail” solvent enables stable cathode materials for sodium ion batteries

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

Mu, Linqin; Rahman, Muhammad Mominur; Zhang, Yan

Coating the surfaces of active materials has become an effective and indispensable path towards the stable operation of practical rechargeable batteries. Improving the affordability of coating processes can bring enormous manufacturing advantages to battery applications. Here in this paper, we report a cheap, simple and efficient method to create conformal coating layers on the primary particles of sodium layered oxide materials for improving battery performance. Mimicking the cathode–electrolyte interfacial reaction in practical cells, we create conformal coating layers via the spontaneous reaction between the oxidative cathode surfaces and a cocktail of reductive organic solvents. The conformal coating layers consist ofmore » metal–organic compounds with reduced transition metal cations, i.e., artificial cathode–electrolyte interphases (CEIs). The cells containing these coated cathode materials deliver much improved cycle life while maintaining reasonably high reversible capacity and rate capability. Furthermore, the structural stability and water resistance are enhanced, which can practically help simplify the storage protocol of cathode powders prior to battery manufacturing. The surfaces of most oxide cathode materials (e.g., lithium cathodes and sodium cathodes) are highly oxidative, and thus we expect that the present method, with tailored experimental parameters, can be readily applied to most battery systems.« less

Surface transformation by a “cocktail” solvent enables stable cathode materials for sodium ion batteries

DOE PAGES

Mu, Linqin; Rahman, Muhammad Mominur; Zhang, Yan; ...

2018-01-09

Coating the surfaces of active materials has become an effective and indispensable path towards the stable operation of practical rechargeable batteries. Improving the affordability of coating processes can bring enormous manufacturing advantages to battery applications. Here in this paper, we report a cheap, simple and efficient method to create conformal coating layers on the primary particles of sodium layered oxide materials for improving battery performance. Mimicking the cathode–electrolyte interfacial reaction in practical cells, we create conformal coating layers via the spontaneous reaction between the oxidative cathode surfaces and a cocktail of reductive organic solvents. The conformal coating layers consist ofmore » metal–organic compounds with reduced transition metal cations, i.e., artificial cathode–electrolyte interphases (CEIs). The cells containing these coated cathode materials deliver much improved cycle life while maintaining reasonably high reversible capacity and rate capability. Furthermore, the structural stability and water resistance are enhanced, which can practically help simplify the storage protocol of cathode powders prior to battery manufacturing. The surfaces of most oxide cathode materials (e.g., lithium cathodes and sodium cathodes) are highly oxidative, and thus we expect that the present method, with tailored experimental parameters, can be readily applied to most battery systems.« less

Growth behavior and growth rate dependency in LEDs performance for Mg-doped a-plane GaN

NASA Astrophysics Data System (ADS)

Song, Keun-Man; Kim, Jong-Min; Lee, Dong-Hun; Shin, Chan-Soo; Ko, Chul-Gi; Kong, Bo-Hyun; Cho, Hyung-Koun; Yoon, Dae-Ho

2011-07-01

We investigated the influence of growth rate of Mg-doped a-plane GaN on the surface morphological and electrical properties, and the characteristics of InGaN-based nonpolar LEDs. Mg-doped a-plane GaN layers were grown on r-plane sapphire substrate by metalorganic chemical vapor deposition (MOCVD). Scanning electron microscopy (SEM), transmission electron microscopy (TEM) and cathode luminescence (CL) analysis exhibited that the surface morphology changed from stripe features with large triangular pits to rough and rugged surface with small asymmetric V-shape pits, as the growth rate increased. The Mg incorporation into a-plane GaN layers increased with increasing growth rate of Mg-doped a-plane GaN, while the activation efficiency of Mg dopants decreased in a-plane GaN. Additionally, it was found that operation voltage at 20 mA decreased in characteristics of LEDs, as the growth rate of Mg-doped a-plane GaN decreased. Meanwhile, the EL intensity of LEDs with p-GaN layers grown at higher growth rate was improved compared to that of LEDs with p-GaN layers grown at lower growth rate. Such an increase of EL intensity is attributed to the rougher surface morphology with increasing growth rate of Mg-doped a-plane GaN.

Enhanced characteristics of blue InGaN /GaN light-emitting diodes by using selective activation to modulate the lateral current spreading length

NASA Astrophysics Data System (ADS)

Lin, Ray-Ming; Lu, Yuan-Chieh; Chou, Yi-Lun; Chen, Guo-Hsing; Lin, Yung-Hsiang; Wu, Meng-Chyi

2008-06-01

We have studied the characteristics of blue InGaN /GaN multiquantum-well light-emitting diodes (LEDs) after reducing the length of the lateral current path through the transparent layer through formation of a peripheral high-resistance current-blocking region in the Mg-doped GaN layer. To study the mechanism of selective activation in the Mg-doped GaN layer, we deposited titanium (Ti), gold (Au), Ti /Au, silver, and copper individually onto the Mg-doped GaN layer and investigated their effects on the hole concentration in the p-GaN layer. The Mg-doped GaN layer capped with Ti effectively depressed the hole concentration in the p-GaN layer by over one order of magnitude relative to that of the as-grown layer. This may suggest that high resistive regions are formed by diffusion of Ti and depth of high resistive region from the p-GaN surface depends on the capped Ti film thickness. Selective activation of the Mg-doped GaN layer could be used to modulate the length of the lateral current path. Furthermore, the external quantum efficiency of the LEDs was improved significantly after reducing the lateral current spreading length. In our best result, the external quantum efficiency was 52.3% higher (at 100mA) than that of the as-grown blue LEDs.

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.

Nanoimprinted Hybrid Metal-Semiconductor Plasmonic Multilayers with Controlled Surface Nano Architecture for Applications in NIR Detectors

PubMed Central

Khosroabadi, Akram A.; Gangopadhyay, Palash; Hernandez, Steven; Kim, Kyungjo; Peyghambarian, Nasser; Norwood, Robert A.

2015-01-01

We present a proof of concept for tunable plasmon resonance frequencies in a core shell nano-architectured hybrid metal-semiconductor multilayer structure, with Ag as the active shell and ITO as the dielectric modulation media. Our method relies on the collective change in the dielectric function within the metal semiconductor interface to control the surface. Here we report fabrication and optical spectroscopy studies of large-area, nanostructured, hybrid silver and indium tin oxide (ITO) structures, with feature sizes below 100 nm and a controlled surface architecture. The optical and electrical properties of these core shell electrodes, including the surface plasmon frequency, can be tuned by suitably changing the order and thickness of the dielectric layers. By varying the dimensions of the nanopillars, the surface plasmon wavelength of the nanopillar Ag can be tuned from 650 to 690 nm. Adding layers of ITO to the structure further shifts the resonance wavelength toward the IR region and, depending on the sequence and thickness of the layers within the structure, we show that such structures can be applied in sensing devices including enhancing silicon as a photodetection material. PMID:28793489

Characterization of cathode keeper wear by surface layer activation

NASA Technical Reports Server (NTRS)

Polk, James E.

2003-01-01

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

Integration of micro nano and bio technologies with layer-by-layer self-assembly

NASA Astrophysics Data System (ADS)

Kommireddy, Dinesh Shankar

In the past decade, layer-by-layer (LbL) nanoassembly has been used as a tool for immobilization and surface modification of materials with applications in biology and physical sciences. Often, in such applications, LbL assembly is integrated with various techniques to form functional surface coatings and immobilized matrices. In this work, integration of LbL with microfabrication and microfluidics, and tissue engineering are explored. In an effort to integrate microfabrication with LbL nanoassembly, microchannels were fabricated using soft-lithography and the surface of these channels was used for the immobilization of materials using LbL and laminar flow patterning. Synthesis of poly(dimethyldiallyl ammonium chloride)/poly(styrene sulfonate) and poly(dimethyldiallyl ammonium chloride)/bovine serum albumin microstrips is demonstrated with the laminar flow microfluidic reactor. Resulting micropatterns are 8-10 mum wide, separated with few micron gaps. The width of these microstrips as well as their position in the microchannel is controlled by varying the flow rate, time of interaction and concentration of the individual components, which is verified by numerical simulation. Spatially resolved pH sensitivity was observed by modifying the surface of the channel with a pH sensitive dye. In order to investigate the integration of LbL assembly with tissue engineering, glass substrates were coated with nanoparticle/polyelectrolyte layers, and two different cell types were used to test the applicability of these coatings for the surface modification of medical implants. Titanium dioxide (TiO 2), silicon dioxide, halloysite and montmorillonite nanoparticles were assembled with oppositely charged polyelectrolytes. In-vitro cytotoxicity tests of the nanoparticle substrates on human dermal firbroblasts (HDFs) showed that the nanoparticle surfaces do not have toxic effects on the cells. HDFs retained their phenotype on the nanoparticle coatings, by synthesizing type-I collagen. These cells also showed active proliferation on the nanoparticle substrates. Cells attached on TiO2 substrates showed faster rate of spreading compared with the other types of nanoparticle coatings. Mesenchymal stem cells (MSCs) were used as a second cell type to support and elaborate on the results obtained with the HDFs. Increasing surface roughness was observed with increasing number of layers of TiO2. Tests with a higher number of layers of TiO2, showed an increased attachment, proliferation and faster spreading of the MSCs on a larger number of layers of TiO2.

[Spatial variation of soil phosphorus in flooded area of the Yellow River based on GIS and geo-statistical methods: A case study in Zhoukou City, Henan, China.

PubMed

Jia, Zhen Yu; Zhang, Jun Hua; Ding, Sheng Yan; Feng, Shu; Xiong, Xiao Bo; Liang, Guo Fu

2016-04-22

Soil phosphorus is an important indicator to measure the soil fertility, because the content of soil phosphorus has an important effect on physical and chemical properties of soil, plant growth, and microbial activity in soil. In this study, the soil samples collecting and indoor analysis were conducted in Zhoukou City located in the flooded area of the Yellow River. By using GIS combined with geo-statistics, we tried to analyze the spatial variability and content distribution of soil total phosphorus (TP) and soil available phosphorus (AP) in the study area. Results showed that TP and AP of both soil layers (0-20 cm and 20-40 cm) were rich, and the contents of TP and AP in surface layer (0-20 cm) were higher than in the second layer (20-40 cm). TP and AP of both soil layers exhibited variation at medium level, and AP had varied much higher than TP. TP of both layers showed medium degree of anisotropy which could be well modeled by the Gaussian model. TP in the surface layer showed strong spatial correlation, but that of the second layer had medium spatial correlation. AP of both layers had a weaker scope in anisotropy which could be simulated by linear model, and both soil layers showed weaker spatial correlations. TP of both soil layers showed a slowly rising change from southwest to northeast of the study area, while it gradually declined from northwest to southeast. AP in soil surface layer exhibited an increase tendency firstly and then decrease from southwest to the northeast, while it decreased firstly and then increased from southeast to the northwest. AP in the second soil layer had an opposite change in the southwest to the northeast, while it showed continuously increasing tendency from northwest to the southeast. The contents of TP and AP in the surface layer presented high grades and the second layer of TP belonged to medium grade, but the second layer of AP was in a lower grade. The artificial factors such as land use type, cropping system, irrigation and fertilization were the main factors influencing the distribution and spatial variation of soil phosphorus in this area.

Enhancement of vortex induced forces and motion through surface roughness control

DOEpatents

Bernitsas, Michael M [Saline, MI; Raghavan, Kamaldev [Houston, TX

2011-11-01

Roughness is added to the surface of a bluff body in a relative motion with respect to a fluid. The amount, size, and distribution of roughness on the body surface is controlled passively or actively to modify the flow around the body and subsequently the Vortex Induced Forces and Motion (VIFM). The added roughness, when designed and implemented appropriately, affects in a predetermined way the boundary layer, the separation of the boundary layer, the level of turbulence, the wake, the drag and lift forces, and consequently the Vortex Induced Motion (VIM), and the fluid-structure interaction. The goal of surface roughness control is to increase Vortex Induced Forces and Motion. Enhancement is needed in such applications as harnessing of clean and renewable energy from ocean/river currents using the ocean energy converter VIVACE (Vortex Induced Vibration for Aquatic Clean Energy).

Strata-based forest fuel classification for wild fire hazard assessment using terrestrial LiDAR

NASA Astrophysics Data System (ADS)

Chen, Yang; Zhu, Xuan; Yebra, Marta; Harris, Sarah; Tapper, Nigel

2016-10-01

Fuel structural characteristics affect fire behavior including fire intensity, spread rate, flame structure, and duration, therefore, quantifying forest fuel structure has significance in understanding fire behavior as well as providing information for fire management activities (e.g., planned burns, suppression, fuel hazard assessment, and fuel treatment). This paper presents a method of forest fuel strata classification with an integration between terrestrial light detection and ranging (LiDAR) data and geographic information system for automatically assessing forest fuel structural characteristics (e.g., fuel horizontal continuity and vertical arrangement). The accuracy of fuel description derived from terrestrial LiDAR scanning (TLS) data was assessed by field measured surface fuel depth and fuel percentage covers at distinct vertical layers. The comparison of TLS-derived depth and percentage cover at surface fuel layer with the field measurements produced root mean square error values of 1.1 cm and 5.4%, respectively. TLS-derived percentage cover explained 92% of the variation in percentage cover at all fuel layers of the entire dataset. The outcome indicated TLS-derived fuel characteristics are strongly consistent with field measured values. TLS can be used to efficiently and consistently classify forest vertical layers to provide more precise information for forest fuel hazard assessment and surface fuel load estimation in order to assist forest fuels management and fire-related operational activities. It can also be beneficial for mapping forest habitat, wildlife conservation, and ecosystem management.

Impact of Sulfuric Acid Treatment of Halloysite on Physico-Chemic Property Modification.

PubMed

Gaaz, Tayser Sumer; Sulong, Abu Bakar; Kadhum, Abdul Amir H; Nassir, Mohamed H; Al-Amiery, Ahmed A

2016-07-26

Halloysite (HNT) is treated with sulfuric acid and the physico-chemical properties of its morphology, surface activity, physical and chemical properties have been investigated when HNT is exposed to sulfuric acid with treatment periods of 1 h (H1), 3 h (H3), 8 h (H8), and 21 h (H21). The significance of this and similar work lies in the importance of using HNT as a functional material in nanocomposites. The chemical structure was characterized by Fourier transform infrared spectroscopy (FTIR). The spectrum demonstrates that the hydroxyl groups were active for grafting modification using sulfuric acid, promoting a promising potential use for halloysite in ceramic applications as filler for novel clay-polymer nanocomposites. From the X-ray diffraction (XRD) spectrum, it can be seen that the sulfuric acid breaks down the HNT crystal structure and alters it into amorphous silica. In addition, the FESEM images reveal that the sulfuric acid treatment dissolves the AlO₆ octahedral layers and induces the disintegration of SiO₄ tetrahedral layers, resulting in porous nanorods. The Bruncher-Emmett-Teller (BET) surface area and total pore volume of HNTs showed an increase. The reaction of the acid with both the outer and inner surfaces of the nanotubes causes the AlO₆ octahedral layers to dissolve, which leads to the breakdown and collapse of the tetrahedral layers of SiO₄. The multi-fold results presented in this paper serve as a guide for further HNT functional treatment for producing new and advanced nanocomposites.

Evaluation of urban surface parameterizations in the WRF model using measurements during the Texas Air Quality Study 2006 field campaign

NASA Astrophysics Data System (ADS)

Lee, S.-H.; Kim, S.-W.; Angevine, W. M.; Bianco, L.; McKeen, S. A.; Senff, C. J.; Trainer, M.; Tucker, S. C.; Zamora, R. J.

2010-10-01

The impact of urban surface parameterizations in the WRF (Weather Research and Forecasting) model on the simulation of local meteorological fields is investigated. The Noah land surface model (LSM), a modified LSM, and a single-layer urban canopy model (UCM) have been compared, focusing on urban patches. The model simulations were performed for 6 days from 12 August to 17 August during the Texas Air Quality Study 2006 field campaign. Analysis was focused on the Houston-Galveston metropolitan area. The model simulated temperature, wind, and atmospheric boundary layer (ABL) height were compared with observations from surface meteorological stations (Continuous Ambient Monitoring Stations, CAMS), wind profilers, the NOAA Twin Otter aircraft, and the NOAA Research Vessel Ronald H. Brown. The UCM simulation showed better results in the comparison of ABL height and surface temperature than the LSM simulations, whereas the original LSM overestimated both the surface temperature and ABL height significantly in urban areas. The modified LSM, which activates hydrological processes associated with urban vegetation mainly through transpiration, slightly reduced warm and high biases in surface temperature and ABL height. A comparison of surface energy balance fluxes in an urban area indicated the UCM reproduces a realistic partitioning of sensible heat and latent heat fluxes, consequently improving the simulation of urban boundary layer. However, the LSMs have a higher Bowen ratio than the observation due to significant suppression of latent heat flux. The comparison results suggest that the subgrid heterogeneity by urban vegetation and urban morphological characteristics should be taken into account along with the associated physical parameterizations for accurate simulation of urban boundary layer if the region of interest has a large fraction of vegetation within the urban patch. Model showed significant discrepancies in the specific meteorological conditions when nocturnal low-level jets exist and a thermal internal boundary layer over water forms.

Effect of N2 annealing on AlZrO oxide

NASA Astrophysics Data System (ADS)

Pétry, J.; Richard, O.; Vandervorst, W.; Conard, T.; Chen, J.; Cosnier, V.

2003-07-01

In the path to the introduction of high-k dielectric into integrated circuit components, a large number of challenges has to be solved. Subsequent to the film deposition, the high-k film is exposed to additional high-temperature anneals for polycrystalline Si activation but also to improve its own electrical properties. Hence, concerns can be raised regarding the thermal stability of these stacks upon annealing. In this study, we investigated the effect of N2 annealing (700 to 900 °C) of atomic layer chemical vapor deposition AlZrO layers using x-ray photoelectron spectroscopy (XPS), time-of-flight secondary ion mass spectrometry (TOFSIMS), transmission electron microscopy (TEM), and Fourier transform infrared (FTIR) spectroscopy. The effect of the Si surface preparation [H-Si, 0.5 nm rapid thermal oxide (RTO), Al2O3] on the modification of the high-k oxide and the interfacial layer upon annealing was also analyzed. Compositional changes can be observed for all temperature and surface preparations. In particular, we observe a segregation of Al(oxide) toward the surface of the mixed oxide. In addition, an increase of the Si concentration in the high-k film itself can be seen with a diffusion profile extending toward the surface of the film. On the other hand, the modification of the interfacial layer is strongly dependent on the system considered. In the case of mixed oxide grown on 0.5 nm RTO, no differences are observed between the as-deposited layer and the layer annealed at 700 °C. At 800 °C, a radical change occurs: The initial RTO layer seems to be converted into a mixed layer composed of the initial SiO2 and Al2O3 coming from the mixed oxide, however without forming an Al-silicate layer. A similar situation is found for anneals at 900 °C, as well. When grown on 1.5 nm Al2O3 on 0.5 nm RTO, the only difference with the previous system is the observation of an Al-silicate fraction in the interfacial layer for the as-deposited and 700 °C annealed samples, which disappears at higher temperatures. Finally, considering layers deposited on a H-Si surface, we observe a slight increase of the interfacial thickness after annealing at 700 °C and no further changes for a higher annealing temperature.

Inverted bulk-heterojunction organic solar cells with the transfer-printed anodes and low-temperature-processed ultrathin buffer layers

NASA Astrophysics Data System (ADS)

Itoh, Eiji; Sakai, Shota; Fukuda, Katsutoshi

2018-03-01

We studied the effects of a hole buffer layer [molybdenum oxide (MoO3) and natural copper oxide layer] and a low-temperature-processed electron buffer layer on the performance of inverted bulk-heterojunction organic solar cells in a device consisting of indium-tin oxide (ITO)/poly(ethylene imine) (PEI)/titanium oxide nanosheet (TiO-NS)/poly(3-hexylthiopnehe) (P3HT):phenyl-C61-butyric acid methylester (PCBM)/oxide/anode (Ag or Cu). The insertion of ultrathin TiO-NS (˜1 nm) and oxide hole buffer layers improved the open circuit voltage V OC, fill factor, and rectification properties owing to the effective hole blocking and electron transport properties of ultrathin TiO-NS, and to the enhanced work function difference between TiO-NS and the oxide hole buffer layer. The insertion of the TiO-NS contributed to the reduction in the potential barrier at the ITO/PEI/TiO-NS/active layer interface for electrons, and the insertion of the oxide hole buffer layer contributed to the reduction in the potential barrier for holes. The marked increase in the capacitance under positive biasing in the capacitance-voltage characteristics revealed that the combination of TiO-NS and MoO3 buffer layers contributes to the selective transport of electrons and holes, and blocks counter carriers at the active layer/oxide interface. The natural oxide layer of the copper electrode also acts as a hole buffer layer owing to the increase in the work function of the Cu surface in the inverted cells. The performance of the cell with evaporated MoO3 and Cu layers that were transfer-printed to the active layer was almost comparable to that of the cell with MoO3 and Ag layers directly evaporated onto the active layer. We also demonstrated comparable device performance in the cell with all-printed MoO3 and low-temperature-processed silver nanoparticles as an anode.

Infrared emitting device and method

DOEpatents

Kurtz, Steven R.; Biefeld, Robert M.; Dawson, L. Ralph; Howard, Arnold J.; Baucom, Kevin C.

1997-01-01

An infrared emitting device and method. The infrared emitting device comprises a III-V compound semiconductor substrate upon which are grown a quantum-well active region having a plurality of quantum-well layers formed of a ternary alloy comprising InAsSb sandwiched between barrier layers formed of a ternary alloy having a smaller lattice constant and a larger energy bandgap than the quantum-well layers. The quantum-well layers are preferably compressively strained to increase the threshold energy for Auger recombination; and a method is provided for determining the preferred thickness for the quantum-well layers. Embodiments of the present invention are described having at least one cladding layer to increase the optical and carrier confinement in the active region, and to provide for waveguiding of the light generated within the active region. Examples have been set forth showing embodiments of the present invention as surface- and edge-emitting light emitting diodes (LEDs), an optically-pumped semiconductor laser, and an electrically-injected semiconductor diode laser. The light emission from each of the infrared emitting devices of the present invention is in the midwave infrared region of the spectrum from about 2 to 6 microns.

Solare Cell Roof Tile And Method Of Forming Same

DOEpatents

Hanoka, Jack I.; Real, Markus

1999-11-16

A solar cell roof tile includes a front support layer, a transparent encapsulant layer, a plurality of interconnected solar cells and a backskin layer. The front support layer is formed of light transmitting material and has first and second surfaces. The transparent encapsulant layer is disposed adjacent the second surface of the front support layer. The interconnected solar cells has a first surface disposed adjacent the transparent encapsulant layer. The backskin layer has a first surface disposed adjacent a second surface of the interconnected solar cells, wherein a portion of the backskin layer wraps around and contacts the first surface of the front support layer to form the border region. A portion of the border region has an extended width. The solar cell roof tile may have stand-offs disposed on the extended width border region for providing vertical spacing with respect to an adjacent solar cell roof tile.

Respiratory function of the plastron in the aquatic bug Aphelocheirus aestivalis (Hemiptera, Aphelocheiridae).

PubMed

Seymour, Roger S; Jones, Karl K; Hetz, Stefan K

2015-09-01

The river bug Aphelocheirus aestivalis is a 40 mg aquatic insect that, as an adult, relies totally on an incompressible physical gill to exchange respiratory gases with the water. The gill (called a 'plastron') consists of a stationary layer of air held in place on the body surface by millions of tiny hairs that support a permanent air-water interface, so that the insect never has to renew the gas at the water's surface. The volume of air in the plastron is extremely small (0.14 mm(3)), under slightly negative pressure and connected to the gas-filled tracheal system through spiracles on the cuticle. Here, we measure PO2 of the water and within the plastron gas with O2-sensing fibre optics to understand the effectiveness and limitations of the gas exchanger. The difference in PO2 is highest in stagnant water and decreases with increasing convection over the surface. Respiration of bugs in water-filled vials varies between 33 and 296 pmol O2 s(-1), depending on swimming activity. The effective thickness of the boundary layer around the plastron was calculated from respiration rate, PO2 difference and plastron surface area, according to the Fick diffusion equation and verified by direct measurements with the fibre-optic probes. In stagnant water, the boundary layer is approximately 500 μm thick, which nevertheless can satisfy the demands of resting bugs, even if the PO2 of the free water decreases to half that of air saturation. Active bugs require thinner boundary layers (∼ 100 μm), which are achieved by living in moving water or by swimming. © 2015. Published by The Company of Biologists Ltd.

Experimental demonstration of single electron transistors featuring SiO{sub 2} plasma-enhanced atomic layer deposition in Ni-SiO{sub 2}-Ni tunnel junctions

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

Karbasian, Golnaz, E-mail: Golnaz.Karbasian.1@nd.edu; McConnell, Michael S.; Orlov, Alexei O.

The authors report the use of plasma-enhanced atomic layer deposition (PEALD) to fabricate single-electron transistors (SETs) featuring ultrathin (≈1 nm) tunnel-transparent SiO{sub 2} in Ni-SiO{sub 2}-Ni tunnel junctions. They show that, as a result of the O{sub 2} plasma steps in PEALD of SiO{sub 2}, the top surface of the underlying Ni electrode is oxidized. Additionally, the bottom surface of the upper Ni layer is also oxidized where it is in contact with the deposited SiO{sub 2}, most likely as a result of oxygen-containing species on the surface of the SiO{sub 2}. Due to the presence of these surface parasitic layersmore » of NiO, which exhibit features typical of thermally activated transport, the resistance of Ni-SiO{sub 2}-Ni tunnel junctions is drastically increased. Moreover, the transport mechanism is changed from quantum tunneling through the dielectric barrier to one consistent with thermally activated resistors in series with tunnel junctions. The reduction of NiO to Ni is therefore required to restore the metal-insulator-metal (MIM) structure of the junctions. Rapid thermal annealing in a forming gas ambient at elevated temperatures is presented as a technique to reduce both parasitic oxide layers. This method is of great interest for devices that rely on MIM tunnel junctions with ultrathin barriers. Using this technique, the authors successfully fabricated MIM SETs with minimal trace of parasitic NiO component. They demonstrate that the properties of the tunnel barrier in nanoscale tunnel junctions (with <10{sup −15} m{sup 2} in area) can be evaluated by electrical characterization of SETs.« less

Antibacterial and antifouling properties of a polyurethane surface modified with perfluoroalkyl and silver nanoparticles.

PubMed

Xu, Deqiu; Su, Yuling; Zhao, Lili; Meng, Fancui; Liu, Chang; Guan, Yayuan; Zhang, Jiya; Luo, Jianbin

2017-02-01

Inspired by mussel-adhesion phenomena in nature, a simple, mild surface modification process was elaborated to endow the polyurethane (PU) substrate with antibacterial/antifouling properties. In the present study, polydopamine was coated directly onto polyurethane surfaces. AgNO 3 was then added and absorbed onto the surface by the active catechol and amine groups of the polydopamine coating. Meanwhile, the adsorbed Ag + ions were reduced in situ into metallic silver nanoparticles by the "bridge" of the polydopamine coating which yielded a coating with good antimicrobial properties. Finally, 1H, 1H, 2H, 2H-perfluorodecanethiol (CF 3 (CF 2 ) 7 CH 2 CH 2 SH, F-SH) was attached on the PDA coating via the Michael addition reaction. The hydrophobic F-SH layer above the antibacterial layer yielded a surface with excellent antifouling properties. Preliminary antibacterial assays indicate that the coated surfaces show enhanced antibacterial activity against Escherichia coli (Gram-negative bacteria) and Staphylococcus aureus (Gram-positive bacteria). Platelet adhesion was significantly reduced for the F-SH-coated PU film. These results suggest that the modified PU could be used as an antibacterial material for future biomedical applications. © 2016 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 105A: 531-538, 2017. © 2016 Wiley Periodicals, Inc.

Atrazine degradation and enzyme activities in an agricultural soil under two tillage systems.

PubMed

Mahía, Jorge; Martín, Angela; Carballas, Tarsy; Díaz-Raviña, Montserrat

2007-05-25

The content of atrazine and its metabolites (hydroxyatrazine, deethylatrazine and deisopropylatrazine) as well as the activities of two soil enzymes (urease and beta-glucosidase) were evaluated in an acid agricultural soil, located in a temperate humid zone (Galicia, NW Spain), with an annual ryegrass-maize rotation under conventional tillage (CT) and no tillage (NT). Samples were collected during two consecutive years from the arable layer at two depths (0-5 cm and 5-20 cm) and different times after atrazine application. Hydroxyatrazine and deisopropylatrazine were the main metabolites resulting from atrazine degradation in the acid soil studied, the highest levels being detected in the surface layer of the NT treatment. A residual effect of atrazine was observed since hydroxyatrazine was detected in the arable layer (0-5 cm, 5-20 cm) even one year after the herbicide application. Soil enzyme activities in the upper 5 cm layer under NT were consistently higher than those in the same layer under CT. Urease and beta-glucosidase activities decreased with depth in the profile under NT but they did not show any differences between the two depths for the plots under CT. For both tillage systems enzyme activities also reflected temporal changes during the maize cultivation; however, no consistent effect of the herbicide application was observed.

Stability and activity of lactate dehydrogenase on biofunctional layers deposited by activated vapor silanization (AVS) and immersion silanization (IS)

NASA Astrophysics Data System (ADS)

Calvo, Jorge Nieto-Márquez; Elices, Manuel; Guinea, Gustavo V.; Pérez-Rigueiro, José; Arroyo-Hernández, María

2017-09-01

The interaction between surfaces and biological elements, in particular, proteins is critical for the performance of biomaterials and biosensors. This interaction can be controlled by modifying the surface in a process known as biofunctionalization. In this work, the enzyme lactate dehydrogenase (LDH) is used to study the stability of the interaction between a functional protein and amine-functionalized surfaces. Two different functionalization procedures were compared: Activated Vapor Silanization (AVS) and Immersion Silanization (IS). Adsorption kinetics is shown to follow the Langmuir model for AVS-functionalized samples, while IS-functionalized samples show a certain instability if immersed in an aqueous medium for several hours. In turn, the enzymatic activity of LDH is preserved for longer times by using glutaraldehyde as crosslinker between the AVS biofunctional surface and the enzyme.

Erosion measurement techniques for plasma-driven railgun barrels

NASA Astrophysics Data System (ADS)

Jamison, K. A.; Niiler, Andrus

1987-04-01

Plasma-driven railguns are now in operation at several locations throughout the world. All share common problems in barrel erosion arising from the fact that the bore surface must contain a high temperature plasma armature which transmits the acceleration force to a projectile. The plasma temperature at the core of the armature is estimated to be 30 000 K or higher. Such conditions are erosive to most materials even when the exposure time is 100 μs or less. We have adapted two accelerator based techniques to aid in the study of this erosion. The first technique involves the collection and analysis of material ablated and left behind by the plasma. This analysis is based on the unfolding of the Rutherford backscattered (RBS) spectra of 1 MeV deuterons incident on residue collected from a railgun bore. The second technique is an erosion measurement involving thin layer activation (TLA) of surfaces. In this process, the copper rail surface is activated by 2.4 MeV protons creating a relatively thin (3 m) layer sparsely seeded with a long lived zinc isotope. Monitoring the decay of the activated sample before and after a firing can detect surface wear of about 0. 1 m. Results from the RBS and TLA experiments on the BRL plasma driven railgun are described.

The Otto Aufranc Award: Enhanced Biocompatibility of Stainless Steel Implants by Titanium Coating and Microarc Oxidation

PubMed Central

Lim, Young Wook; Kwon, Soon Yong; Sun, Doo Hoon

2010-01-01

Background Stainless steel is one of the most widely used biomaterials for internal fixation devices, but is not used in cementless arthroplasty implants because a stable oxide layer essential for biocompatibility cannot be formed on the surface. We applied a Ti electron beam coating, to form oxide layer on the stainless steel surface. To form a thicker oxide layer, we used a microarc oxidation process on the surface of Ti coated stainless steel. Modification of the surface using Ti electron beam coating and microarc oxidation could improve the ability of stainless steel implants to osseointegrate. Questions/purposes The ability of cells to adhere to grit-blasted, titanium-coated, microarc-oxidated stainless steel in vitro was compared with that of two different types of surface modifications, machined and titanium-coated, and microarc-oxidated. Methods We performed energy-dispersive x-ray spectroscopy and scanning electron microscopy investigations to assess the chemical composition and structure of the stainless steel surfaces and cell morphology. The biologic responses of an osteoblastlike cell line (SaOS-2) were examined by measuring proliferation (cell proliferation assay), differentiation (alkaline phosphatase activity), and attraction ability (cell migration assay). Results Cell proliferation, alkaline phosphatase activity, migration, and adhesion were increased in the grit-blasted, titanium-coated, microarc-oxidated group compared to the two other groups. Osteoblastlike cells on the grit-blasted, titanium-coated, microarc-oxidated surface were strongly adhered, and proliferated well compared to those on the other surfaces. Conclusions The surface modifications we used (grit blasting, titanium coating, microarc oxidation) enhanced the biocompatibility (proliferation and migration of osteoblastlike cells) of stainless steel. Clinical Relevance This process is not unique to stainless steel; it can be applied to many metals to improve their biocompatibility, thus allowing a broad range of materials to be used for cementless implants. PMID:20936386

Study of wear between piston ring and cylinder housing of an internal combustion engine by thin layer activation technique

NASA Astrophysics Data System (ADS)

Chowdhury, D. P.; Chaudhuri, Jayanta; Raju, V. S.; Das, S. K.; Bhattacharjee, B. B.; Gangadharan, S.

1989-07-01

The wear analysis of a compression ring and cylinder housing of an Internal Combustion Engine by thin layer activation (TLA) with 40 MeV α-particles from the Variable Energy Cyclotron at Calcutta is reported. The calibration curves have been obtained for Fe and Ni using stacked foil activation technique for determining the absolute wear in these machine parts. It has been possible to determine the pattern of wear on the points along the surface of machine components. The minimum detectable depth in this wear study has been estimated at 0.11 ± 0.04 μm.

Study of the Northern Qinghai-Tibetan Plateau Permafrost Active Layer Depth Rate Using Satellite Geodetic Observations

NASA Astrophysics Data System (ADS)

Jia, Y.; Su, X.; Shum, C. K.; Kim, J. W.; Kuo, C. Y.

2015-12-01

The Tibetan Plateau is the world's largest and the highest plateau with distinct and competing surface and subsurface processes. It is the Third Pole and the World Water Tower, owing to its vast ice reservoir with the largest number of glaciers in the world, and covered by a large (1.3 to 1.6 million km2) layer of discontinuous and sporadic alpine permafrost. The thawing over Tibetan Plateau permafrost regions is thought to be more severe compared with other high latitude permafrost regions by the fact that the permafrost is warm. During the past few decades, 82% of Tibetan Plateau glaciers have retreated and 10% permafrost has degraded. The overall mean active layer depth (ALD) rate increase over the Plateau is 1.4 cm yr-1, 1980-2001, based on model studies and comparison with in situ borehole data. Here we report on the work in progress to quantify ALD rate increase in the northern Tibetan Plateau near the Tibetan national highway, using multi-band SAR/InSAR for improved the thermokarst surface classification, Envisat radar altimetry and ALOS-1 InSAR observed land subsidence, ALD modeling for the various thermokarst surface to relate to subsidence measurements, and the associated validations using available in situ borehole subsidence measurements.

Multi-modality nanoparticles having optically responsive shape

DOEpatents

Chen, Fanqing; Bouchard, Louis-Serge

2015-05-19

In certain embodiments novel nanoparticles (nanowontons) are provided that are suitable for multimodal imaging and/or therapy. In one embodiment, the nanoparticles include a first biocompatible (e.g., gold) layer, an inner core layer (e.g., a non-biocompatible material), and a biocompatible (e.g., gold) layer. The first gold layer includes a concave surface that forms a first outer surface of the layered nanoparticle. The second gold layer includes a convex surface that forms a second outer surface of the layered nanoparticle. The first and second gold layers encapsulate the inner core material layer. Methods of fabricating such nanoparticles are also provided.

[Effect of tillage system on soil animal, microorganism and enzyme activity in paddy field].

PubMed

Gao, Ming; Zhou, Baotong; Wei, Chaofu; Xie, Deti; Zhang, Lei

2004-07-01

A long-term experiment showed that under ridge-no-tillage, the amount of soil animal in 0 - 20 cm layer was 14700 ind. x m(-2), while under no-tillage and fallow in winter, paddy-upland rotation, and conventional tillage, it was 10450, 7950 and 6275 ind. x m(-2), respectively. Soil microbial biomass and microbial biomass N were more in spring and autumn, and less in summer. Soil enzyme activity was higher in surface soil layer and lower in bottom soil layer. The amount of soil animal, microbial biomass and microbial biomass N and soil enzyme activity was in order of ridge-no-tillage > paddy-upland rotation > no-tillage and fallow in winter > conventional tillage. The results also indicated that ridge-no-tillage was advantageous to improve soil ecological environment and soil fertility in paddy field.

Hybrid passive/active damping for robust multivariable acoustic control in composite plates

NASA Astrophysics Data System (ADS)

Veeramani, Sudha; Wereley, Norman M.

1996-05-01

Noise transmission through a flexible kevlar-epoxy composite trim panel into an acoustic cavity or box is studied with the intent of controlling the interior sound fields. A hybrid noise attenuation technique is proposed which uses viscoelastic damping layers in the composite plate for passive attenuation of high frequency noise transmission, and uses piezo-electric patch actuators for active control in the low frequency range. An adaptive feedforward noise control strategy is applied. The passive structural damping augmentation incorporated in the composite plates is also intended to increase stability robustness of the active noise control strategy. A condenser microphone in the interior of the enclosure functions as the error sensor. Three composite plates were experimentally evaluated: one with no damping layer, the second with a 10 mil damping layer, and the third with a 15 mil damping layer. The damping layer was cocured in the kevlar-epoxy trim panels. Damping in the plates was increased from 1.6% for the plate with no damping layer, to 5.9% for the plate with a 15 mil damping layer. In experimental studies, the improved stability robustness of the controller was demonstrated by improved adaptive feedforward control algorithm convergence. A preliminary analytical model is presented that describes the dynamic behavior of a composite panel actuated by piezoelectric actuators bonded to its surface.

Electrophysiological mapping of the accessory olfactory bulb of the rabbit (Oryctolagus cuniculus).

PubMed

van Groen, T; Ruardy, L; da Silva, F H

1986-07-01

Field potentials elicited by electrical stimulation of the vomeronasal nerve were measured in the accessory olfactory bulb of the rabbit. Maps were made of the distribution of surface field potentials and of the corresponding depth profiles. The surface maps followed closely the contours of the accessory olfactory bulb: at the frontal border the field potential tended to zero and at the center of the structure the field potential attained a maximum. Depth profiles of the field potentials through the accessory olfactory bulb presented a surface-negative wave and, in depth, a positive wave. The polarity reversal occurred at the deep part of the granule cell layer. The zero equipotential line followed closely the curvature of the granule cell layer. Current source density analysis of the depth profiles revealed a main sink at the external plexiform and granule cell layers. This indicates that the main activity in the accessory olfactory bulb is generated by the synapses between the mitral cells and the granule cells as is found in the main olfactory bulb.

Flux canceling in three-dimensional radiative magnetohydrodynamic simulations

NASA Astrophysics Data System (ADS)

Thaler, Irina; Spruit, H. C.

2017-05-01

We aim to study the processes involved in the disappearance of magnetic flux between regions of opposite polarity on the solar surface using realistic three-dimensional (3D) magnetohydrodynamic (MHD) simulations. "Retraction" below the surface driven by magnetic forces is found to be a very effective mechanism of flux canceling of opposite polarities. The speed at which flux disappears increases strongly with initial mean flux density. In agreement with existing inferences from observations we suggest that this is a key process of flux disappearance within active complexes. Intrinsic kG strength concentrations connect the surface to deeper layers by magnetic forces, and therefore the influence of deeper layers on the flux canceling process is studied. We do this by comparing simulations extending to different depths. For average flux densities of 50 G, and on length scales on the order of 3 Mm in the horizontal and 10 Mm in depth, deeper layers appear to have only a mild influence on the effective rate of diffusion.

Indium-free organic thin-film solar cells using a plasmonic electrode

NASA Astrophysics Data System (ADS)

Takatori, Kentaro; Nishino, Takayuki; Okamoto, Takayuki; Takei, Hiroyuki; Ishibashi, Koji; Micheletto, Ruggero

2016-05-01

We propose a new kind of organic solar cell (OSC) that substitutes the standard indium tin oxide (ITO) electrode with a silver layer with randomly arranged circular nanoholes (plasmonic electrode). The quasi-random structure in the silver layer efficiently converts wideband incident light into surface plasmon polaritons propagating along the surface of the silver film. In this way, the converted surface plasmon polaritons enhance light absorption in the active layer. We describe in detail the fabrication process we used and we give a thorough report of the resulting optical characteristics and performances. Although the transmittance of the plasmonic electrode is approximately one-third of that of the ITO electrodes, the power conversion efficiency of the OSCs with our plasmonic electrode is comparable to that of conventional inverted solar cells using ITO electrodes. Moreover, the obtained incident photon to current efficiency was better than that of the inverted solar cells in the wavelength regions around 400 nm and over 620 nm.

Role of Arsenic During Aluminum Droplet Etching of Nanoholes in AlGaAs

NASA Astrophysics Data System (ADS)

Heyn, Christian; Zocher, Michel; Schnüll, Sandra; Hansen, Wolfgang

2016-09-01

Self-assembled nanoholes are drilled into (001) AlGaAs surfaces during molecular beam epitaxy (MBE) using local droplet etching (LDE) with Al droplets. It is known that this process requires a small amount of background arsenic for droplet material removal. The present work demonstrates that the As background can be supplied by both a small As flux to the surface as well as by the topmost As layer in an As-terminated surface reconstruction acting as a reservoir. We study the temperature-dependent evaporation of the As topmost layer with in situ electron diffraction and determine an activation energy of 2.49 eV. After thermal removal of the As topmost layer droplet etching is studied under well-defined As supply. We observe with decreasing As flux four regimes: planar growth, uniform nanoholes, non-uniform holes, and droplet conservation. The influence of the As supply is discussed quantitatively on the basis of a kinetic rate model.

Enzyme Armoring by an Organosilica Layer: Synthesis and Characterization of Hybrid Organic/Inorganic Nanobiocatalysts.

PubMed

Correro, M Rita; Sykora, Sabine; Corvini, Philippe F-X; Shahgaldian, Patrick

2017-01-01

The availability of highly stable and reusable enzymes is one of the main challenges in bio-based industrial processes. Enzyme immobilization and encapsulation represent promising strategies to reach this goal. In this chapter, the synthetic strategy to produce hybrid organic/inorganic nanobiocatalysts (NBC) is reported. This strategy is based on the sequential immobilization of an enzyme on the surface of silica nanoparticles followed by the growth, at the surface of the nanoparticles, of a shielding layer which serves as an armor to protect the enzyme against denaturation/degradation. This armor is produced through a thickness-controlled organosilane poly-condensation onto the nanoparticle surface around the enzyme to form a protective organosilica layer. The armored nanobiocatalysts present enhanced catalytic activity and improved stability against heat, pH, chaotropic agents, proteases, and ultrasound. The method is versatile in that it can be successfully adapted to a number of different enzymes. © 2017 Elsevier Inc. All rights reserved.

Chitosan-based ultrathin films as antifouling, anticoagulant and antibacterial protective coatings.

PubMed

Bulwan, Maria; Wójcik, Kinga; Zapotoczny, Szczepan; Nowakowska, Maria

2012-01-01

Ultrathin antifouling and antibacterial protective nanocoatings were prepared from ionic derivatives of chitosan using layer-by-layer deposition methodology. The surfaces of silicon, and glass protected by these nanocoatings were resistant to non-specific adsorption of proteins disregarding their net charges at physiological conditions (positively charged TGF-β1 growth factor and negatively charged bovine serum albumin) as well as human plasma components. The coatings also preserved surfaces from the formation of bacterial (Staphylococcus aureus) biofilm as shown using microscopic studies (SEM, AFM) and the MTT viability test. Moreover, the chitosan-based films adsorbed onto glass surface demonstrated the anticoagulant activity towards the human blood. The antifouling and antibacterial actions of the coatings were correlated with their physicochemical properties. The studied biologically relevant properties were also found to be dependent on the thickness of those nanocoatings. These materials are promising for biomedical applications, e.g., as protective coatings for medical devices, anticoagulant coatings and protective layers in membranes.

On a chaotic potential at the surface of a compensated semiconductor under conditions of the self-assembly of electrically active defects

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

Bondarenko, V. B., E-mail: enter@spbstu.ru; Filimonov, A. V.

2015-09-15

Natural irregularities of the electric potential on the surface of a semiconductor under conditions of the partial self-assembly of electrically active defects, i.e., on the formation of donor–acceptor pairs in depletion layers, are studied. The amplitude and character of the spatial distribution of the chaotic potential on the surface of a semiconductor in the cases of localized and delocalized states are determined. The dependence of the amplitude of the chaotic potential on the degree of compensation of the semiconductor is obtained.

Method of depositing an electrically conductive oxide buffer layer on a textured substrate and articles formed therefrom

DOEpatents

Paranthaman, M. Parans; Aytug, Tolga; Christen, David K.

2005-10-18

An article with an improved buffer layer architecture includes a substrate having a textured metal surface, and an electrically conductive lanthanum metal oxide epitaxial buffer layer on the surface of the substrate. The article can also include an epitaxial superconducting layer deposited on the epitaxial buffer layer. An epitaxial capping layer can be placed between the epitaxial buffer layer and the superconducting layer. A method for preparing an epitaxial article includes providing a substrate with a metal surface and depositing on the metal surface a lanthanum metal oxide epitaxial buffer layer. The method can further include depositing a superconducting layer on the epitaxial buffer layer, and depositing an epitaxial capping layer between the epitaxial buffer layer and the superconducting layer.

Method of depositing an electrically conductive oxide buffer layer on a textured substrate and articles formed therefrom

DOEpatents

Paranthaman, M. Parans; Aytug, Tolga; Christen, David K.

2003-09-09

An article with an improved buffer layer architecture includes a substrate having a textured metal surface, and an electrically conductive lanthanum metal oxide epitaxial buffer layer on the surface of the substrate. The article can also include an epitaxial superconducting layer deposited on the epitaxial buffer layer. An epitaxial capping layer can be placed between the epitaxial buffer layer and the superconducting layer. A method for preparing an epitaxial article includes providing a substrate with a metal surface and depositing on the metal surface a lanthanum metal oxide epitaxial buffer layer. The method can further include depositing a superconducting layer on the epitaxial buffer layer, and depositing an epitaxial capping layer between the epitaxial buffer layer and the superconducting layer.

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

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

Mashooq, Kishwar; Talukder, Muhammad Anisuzzaman, E-mail: anis@eee.buet.ac.bd

2016-05-21

Although ultra-thin-film solar cells can be attractive in reducing the cost, they suffer from low absorption as the thickness of the active layer is usually much smaller than the wavelength of incident light. Different nano-photonic techniques, including plasmonic structures, are being explored to increase the light absorption in ultra-thin-film solar cells. More than one layer of active materials with different energy bandgaps can be used in tandem to increase the light absorption as well. However, due to different amount of light absorption in different active layers, photo-generated currents in different active layers will not be the same. The current mismatchmore » between the tandem layers makes them ineffective in increasing the efficiency. In this work, we investigate the light absorption properties of tandem solar cells with two ultra-thin active layers working as two subcells and a metal layer with periodically perforated holes in-between the two subcells. While the metal layer helps to overcome the current mismatch, the periodic holes increase the absorption of incident light by helping extraordinary optical transmission of the incident light from the top to the bottom subcell, and by coupling the incident light to plasmonic and photonic modes within ultra-thin active layers. We extensively study the effects of the geometry of holes in the intermediate metal layer on the light absorption properties of tandem solar cells with ultra-thin active layers. We also study how different metals in the intermediate layer affect the light absorption; how the geometry of holes in the intermediate layer affects the absorption when the active layer materials are changed; and how the intermediate metal layer affects the collection of photo-generated electron-hole pairs at the terminals. We find that in a solar cell with 6,6-phenyl C61-butyric acid methyl ester top subcell and copper indium gallium selenide bottom subcell, if the periodic holes in the metal layer are square or polygon, total absorption remains approximately the same. However, the total absorption suffers significantly if the holes are triangle. The transmission spectra of incident light into the bottom subcell, and hence the absorption, change significantly for square and circle holes if the active materials change to cadmium selenide (CdSe) and cadmium telluride (CdTe) in the top and bottom subcells, respectively. Although the intermediate metal layer may induce electron-hole pair recombination due to surface defects, the short-circuit current density of an ultra-thin plasmonic solar cell with an intermediate metal layer with two-dimensional hole array is >9% of that of a structure without the intermediate metal layer.« less

Using GNSS-R techniques to investigate the near sub-surface of Mars with the Deep Space Network

NASA Astrophysics Data System (ADS)

Elliott, H. M.; Bell, D. J.; Jin, C.; Decrossas, E.; Asmar, S.; Lazio, J.; Preston, R. A.; Ruf, C. S.; Renno, N. O.

2017-12-01

Global Navigation Satellite Systems Reflectometry (GNSS-R) has shown that passive measurements using separate active sources can infer the soil moisture, snow pack depth and other quantities of scientific interest. Here, we expand upon this method and propose that a passive measurement of the sub-surface dielectric profile of Mars can be made by using multipath interference between reflections off the surface and subsurface dielectric discontinuities. This measurement has the ability to reveal changes in the soil water content, the depth of a layer of sand, thickness of a layer of ice, and even identify centimeter-scale layering which may indicate the presence of a sedimentary bed. We have created a numerical ray tracing model to understand the potential of using multipath interference techniques to investigate the sub-surface dielectric properties and structure of Mars. We have further verified this model using layered beds of sand and concrete in laboratory experiments and then used the model to extrapolate how this technique may be applied to future Mars missions. We will present new results demonstrating how to characterize a multipath interference patterns as a function of frequency and/or incidence angle to measure the thickness of a dielectric layer of sand or ice. Our results demonstrate that dielectric discontinuities in the subsurface can be measured using this passive sensing technique and it could be used to effectively measure the thickness of a dielectric layer in the proximity of a landed spacecraft. In the case of an orbiter, we believe this technique would be effective at measuring the seasonal thickness of CO2 ice in the Polar Regions. This is exciting because our method can produce similar results to traditional ground penetrating radars without the need to have an active radar transmitter in-situ. Therefore, it is possible that future telecommunications systems can serve as both a radio and a scientific instrument when used in conjunction with the Deep Space Network, a huge potential cost-savings for interplanetary missions.

In situ transmission electron microscopy observation of pulverization of aluminum nanowires and evolution of the thin surface Al2O3 layers during lithiation-delithiation cycles.

PubMed

Liu, Yang; Hudak, Nicholas S; Huber, Dale L; Limmer, Steven J; Sullivan, John P; Huang, Jian Yu

2011-10-12

Lithiation-delithiation cycles of individual aluminum nanowires (NWs) with naturally oxidized Al(2)O(3) surface layers (thickness 4-5 nm) were conducted in situ in a transmission electron microscope. Surprisingly, the lithiation was always initiated from the surface Al(2)O(3) layer, forming a stable Li-Al-O glass tube with a thickness of about 6-10 nm wrapping around the NW core. After lithiation of the surface Al(2)O(3) layer, lithiation of the inner Al core took place, which converted the single crystal Al to a polycrystalline LiAl alloy, with a volume expansion of about 100%. The Li-Al-O glass tube survived the 100% volume expansion, by enlarging through elastic and plastic deformation, acting as a solid electrolyte with exceptional mechanical robustness and ion conduction. Voids were formed in the Al NWs during the initial delithiation step and grew continuously with each subsequent delithiation, leading to pulverization of the Al NWs to isolated nanoparticles confined inside the Li-Al-O tube. There was a corresponding loss of capacity with each delithiation step when arrays of NWs were galvonostatically cycled. The results provide important insight into the degradation mechanism of lithium-alloy electrodes and into recent reports about the performance improvement of lithium ion batteries by atomic layer deposition of Al(2)O(3) onto the active materials or electrodes.

A new approach to define surface/sub-surface transition in gravel beds

NASA Astrophysics Data System (ADS)

Haynes, Heather; Ockelford, Anne-Marie; Vignaga, Elisa; Holmes, William

2012-12-01

The vertical structure of river beds varies temporally and spatially in response to hydraulic regime, sediment mobility, grain size distribution and faunal interaction. Implicit are changes to the active layer depth and bed porosity, both critical in describing processes such as armour layer development, surface-subsurface exchange processes and siltation/ sealing. Whilst measurements of the bed surface are increasingly informed by quantitative and spatial measurement techniques (e.g., laser displacement scanning), material opacity has precluded the full 3D bed structure analysis required to accurately define the surface-subsurface transition. To overcome this problem, this paper provides magnetic resonance imaging (MRI) data of vertical bed porosity profiles. Uniform and bimodal (σ g = 2.1) sand-gravel beds are considered following restructuring under sub-threshold flow durations of 60 and 960 minutes. MRI data are compared to traditional 2.5D laser displacement scans and six robust definitions of the surface-subsurface transition are provided; these form the focus of discussion.

Enrichment and association of lead and bacteria at particulate surfaces in a salt-marsh surface layer

USGS Publications Warehouse

Harvey, R.W.; Lion, Leonard W.; Young, L.Y.; Leckie, J.O.

1982-01-01

The particle-laden surface layer (approx 150-370 mu m) and subsurface waters of a South San Francisco Bay salt marsh were sampled over 2 tidal cycles and analyzed for particle numbers and particulate-associated and total concentrations of Pb and bacteria. Laboratory studies examined the ability of a bacterial isolate from the surface layer and a bacterial 'film-former' to sorb Pb at environmentally significant concentrations in seawater. Degrees by which Pb concentrated in the surface layer relative to the subsurface strongly correlated with enrichments of surface layer bacteria (bacterioneuston). A significant fraction of the bacterioneuston and surface layer Pb were associated with particles. Particle-bound bacterioneuston may interact with Pb at particulate surfaces in this microenvironment.

Influences and interactions of inundation, peat, and snow on active layer thickness: Modeling Archive

DOE Data Explorer

Scott Painter; Ethan Coon; Cathy Wilson; Dylan Harp; Adam Atchley

2016-04-21

This Modeling Archive is in support of an NGEE Arctic publication currently in review [4/2016]. The Advanced Terrestrial Simulator (ATS) was used to simulate thermal hydrological conditions across varied environmental conditions for an ensemble of 1D models of Arctic permafrost. The thickness of organic soil is varied from 2 to 40cm, snow depth is varied from approximately 0 to 1.2 meters, water table depth was varied from -51cm below the soil surface to 31 cm above the soil surface. A total of 15,960 ensemble members are included. Data produced includes the third and fourth simulation year: active layer thickness, time of deepest thaw depth, temperature of the unfrozen soil, and unfrozen liquid saturation, for each ensemble member. Input files used to run the ensemble are also included.

Pseudohalide-Exchanged Quantum Dot Solids Achieve Record Quantum Efficiency in Infrared Photovoltaics.

PubMed

Sun, Bin; Voznyy, Oleksandr; Tan, Hairen; Stadler, Philipp; Liu, Mengxia; Walters, Grant; Proppe, Andrew H; Liu, Min; Fan, James; Zhuang, Taotao; Li, Jie; Wei, Mingyang; Xu, Jixian; Kim, Younghoon; Hoogland, Sjoerd; Sargent, Edward H

2017-07-01

Application of pseudohalogens in colloidal quantum dot (CQD) solar-cell active layers increases the solar-cell performance by reducing the trap densities and implementing thick CQD films. Pseudohalogens are polyatomic analogs of halogens, whose chemistry allows them to substitute halogen atoms by strong chemical interactions with the CQD surfaces. The pseudohalide thiocyanate anion is used to achieve a hybrid surface passivation. A fourfold reduced trap state density than in a control is observed by using a suite of field-effect transistor studies. This translates directly into the thickest CQD active layer ever reported, enabled by enhanced transport lengths in this new class of materials, and leads to the highest external quantum efficiency, 80% at the excitonic peak, compared with previous reports of CQD solar cells. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Extracellular esterases of phylloplane yeast Pseudozyma antarctica induce defect on cuticle layer structure and water-holding ability of plant leaves.

PubMed

Ueda, Hirokazu; Mitsuhara, Ichiro; Tabata, Jun; Kugimiya, Soichi; Watanabe, Takashi; Suzuki, Ken; Yoshida, Shigenobu; Kitamoto, Hiroko

2015-08-01

Aerial plant surface (phylloplane) is a primary key habitat for many microorganisms but is generally recognized as limited in nutrient resources. Pseudozyma antarctica, a nonpathogenic yeast, is commonly isolated from plant surfaces and characterized as an esterase producer with fatty acid assimilation ability. In order to elucidate the biological functions of these esterases, culture filtrate with high esterase activity (crude enzyme) of P. antarctica was applied onto leaves of tomato and Arabidopsis. These leaves showed a wilty phenotype, which is typically associated with water deficiency. Furthermore, we confirmed that crude enzyme-treated detached leaves clearly lost their water-holding ability. In treated leaves of both plants, genes associated to abscisic acid (ABA; a plant stress hormone responding osmotic stress) were activated and accumulation of ABA was confirmed in tomato plants. Microscopic observation of treated leaf surfaces revealed that cuticle layer covering the aerial epidermis of leaves became thinner. A gas chromatography-mass spectrometry (GC-MS) analysis exhibited that fatty acids with 16 and 18 carbon chains were released in larger amounts from treated leaf surfaces, indicating that the crude enzyme has ability to degrade lipid components of cuticle layer. Among the three esterases detected in the crude enzyme, lipase A, lipase B, and P. antarctica esterase (PaE), an in vitro enzyme assay using para-nitrophenyl palmitate as substrate demonstrated that PaE was the most responsible for the degradation. These results suggest that PaE has a potential role in the extraction of fatty acids from plant surfaces, making them available for the growth of phylloplane yeasts.

Importance of lateral flux and its percolation depth on organic carbon export in Arctic tundra soil: Implications from a soil leaching experiment: Changes of OC in Arctic Soil Leachate

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

Zhang, Xiaowen; Hutchings, Jack A.; Bianchi, Thomas S.

Temperature rise in the Arctic is causing deepening of active layers and resulting in the mobilization of deep permafrost dissolved organic matter (DOM). However, the mechanisms of DOM mobilization from Arctic soils, especially upper soil horizons which are drained most frequently through a year, are poorly understood. Here, we conducted a short-term leaching experiment on surface and deep organic active layer soils, from the Yukon River basin, to examine the effects of DOM transport on bulk and molecular characteristics. Our data showed a net release of DOM from surface soils equal to an average of 5% of soil carbon. Conversely,more » deep soils percolated with surface leachates retained up to 27% of bulk DOM-while releasing fluorescent components (up to 107%), indicating selective release of aromatic components (e.g. lignin, tannin), while retaining non-chromophoric components, as supported by spectrofluorometric and ultra high resolution mass spectroscopic techniques. Our findings highlight the importance of the lateral flux of DOM on ecosystem carbon balance as well as processing of DOM transport through organic active layer soils en route to rivers and streams. This work also suggests the potential role of leachate export as an important mechanism of C losses from Arctic soils, in comparison with the more traditional pathway from soil to atmosphere in a warming Arctic.« less

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

NASA Astrophysics Data System (ADS)

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

2014-07-01

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

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

NASA Astrophysics Data System (ADS)

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

2014-12-01

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

Dissolved organic carbon and nitrogen release from boreal Holocene permafrost and seasonally frozen soils of Alaska

NASA Astrophysics Data System (ADS)

Wickland, Kimberly P.; Waldrop, Mark P.; Aiken, George R.; Koch, Joshua C.; Torre Jorgenson, M.; Striegl, Robert G.

2018-06-01

Permafrost (perennially frozen) soils store vast amounts of organic carbon (C) and nitrogen (N) that are vulnerable to mobilization as dissolved organic carbon (DOC) and dissolved organic and inorganic nitrogen (DON, DIN) upon thaw. Such releases will affect the biogeochemistry of permafrost regions, yet little is known about the chemical composition and source variability of active-layer (seasonally frozen) and permafrost soil DOC, DON and DIN. We quantified DOC, total dissolved N (TDN), DON, and DIN leachate yields from deep active-layer and near-surface boreal Holocene permafrost soils in interior Alaska varying in soil C and N content and radiocarbon age to determine potential release upon thaw. Soil cores were collected at three sites distributed across the Alaska boreal region in late winter, cut in 15 cm thick sections, and deep active-layer and shallow permafrost sections were thawed and leached. Leachates were analyzed for DOC, TDN, nitrate (NO3 ‑), and ammonium (NH4 +) concentrations, dissolved organic matter optical properties, and DOC biodegradability. Soils were analyzed for C, N, and radiocarbon (14C) content. Soil DOC, TDN, DON, and DIN yields increased linearly with soil C and N content, and decreased with increasing radiocarbon age. These relationships were significantly different for active-layer and permafrost soils such that for a given soil C or N content, or radiocarbon age, permafrost soils released more DOC and TDN (mostly as DON) per gram soil than active-layer soils. Permafrost soil DOC biodegradability was significantly correlated with soil Δ14C and DOM optical properties. Our results demonstrate that near-surface Holocene permafrost soils preserve greater relative potential DOC and TDN yields than overlying seasonally frozen soils that are exposed to annual leaching and decomposition. While many factors control the fate of DOC and TDN, the greater relative yields from newly thawed Holocene permafrost soils will have the largest potential impact in areas dominated by organic-rich soils.

Nanoscale observation of organic thin film by atomic force microscopy

NASA Astrophysics Data System (ADS)

Mochizuki, Shota; Uruma, Takeshi; Satoh, Nobuo; Saravanan, Shanmugam; Soga, Tetsuo

2017-08-01

Organic photovoltaics (OPVs) fabricated using organic semiconductors and hybrid solar cells (HSCs) based on organic semiconductors/quantum dots (QDs) have been attracting significant attention owing to their potential use in low-cost solar energy-harvesting applications and flexible, light-weight, colorful, large-area devices. In this study, we observed and evaluated the surface of a photoelectric conversion layer (active layer) of the OPVs and HSCs based on phenyl-C61-butyric acid methyl ester (PCBM), poly(3-hexylthiophene) (P3HT), and zinc oxide (ZnO) nanoparticles. The experiment was performed using atomic force microscopy (AFM) combined with a frequency modulation detector (FM detector) and a contact potential difference (CPD) detection circuit. We experimentally confirmed the changes in film thickness and surface potential, as affected by the ZnO nanoparticle concentration. From the experimental results, we confirmed that ZnO nanoparticles possibly affect the structures of PCBM and P3HT. Also, we prepared an energy band diagram on the basis of the observation results, and analyzed the energy distribution inside the active layer.

Mechanical Properties of Degraded PMR-15 Resin

NASA Technical Reports Server (NTRS)

Tsuji, Luis C.; McManus, Hugh L.; Bowles, Kenneth J.

1998-01-01

Thermo-oxidative aging produces a non-uniform degradation state in PMR-15 resin. A surface layer, usually attributed to oxidative degradation, forms. This surface layer has different properties from the inner material. A set of material tests was designed to separate the properties of the oxidized surface layer from the properties of interior material. Test specimens were aged at 316 C in either air or nitrogen, for durations of up to 800 hours. The thickness of the oxidized surface layer in air aged specimens, and the shrinkage and Coefficient of Thermal Expansion (CTE) of nitrogen aged specimens were measured directly. Four-point-bend tests were performed to determine modulus of both the oxidized surface layer and the interior material. Bimaterial strip specimens consisting of oxidized surface material and unoxidized interior material were constructed and used to determine surface layer shrinkage and CTE. Results confirm that the surface layer and core materials have substantially different properties.

Kinetics of the sorption of triterpene saponin by hypercrosslinked polystyrene

NASA Astrophysics Data System (ADS)

Mironenko, N. V.; Brezhneva, T. A.; Selemenev, V. F.

2013-03-01

The kinetics of sorption of triterpene saponin by the polymer sorbent NM-200 is considered. The influence of the surface activity of glycoside on the rate of formation and structure of the adsorption layer on the sorbent's surface is established. The rate-determining step of sorption is found to be diffusion into the sorbent grain. The value of the activation energy demonstrates the determining role of dispersion forces in the interaction between triterpene saponin and the polymer sorbent MN-200.

Controllable Broadband Optical Transparency and Wettability Switching of Temperature-Activated Solid/Liquid-Infused Nanofibrous Membranes.

PubMed

Manabe, Kengo; Matsubayashi, Takeshi; Tenjimbayashi, Mizuki; Moriya, Takeo; Tsuge, Yosuke; Kyung, Kyu-Hong; Shiratori, Seimei

2016-09-29

Inspired by biointerfaces, such as the surfaces of lotus leaves and pitcher plants, researchers have developed innovative strategies for controlling surface wettability and transparency. In particular, great success has been achieved in obtaining low adhesion and high transmittance via the introduction of a liquid layer to form liquid-infused surfaces. Furthermore, smart surfaces that can change their surface properties according to external stimuli have recently attracted substantial interest. As some of the best-performing smart surface materials, slippery liquid-infused porous surfaces (SLIPSs), which are super-repellent, demonstrate the successful achievement of switchable adhesion and tunable transparency that can be controlled by a graded mechanical stimulus. However, despite considerable efforts, producing temperature-responsive, super-repellent surfaces at ambient temperature and pressure remains difficult because of the use of nonreactive lubricant oil as a building block in previously investigated repellent surfaces. Therefore, the present study focused on developing multifunctional materials that dynamically adapt to temperature changes. Here, we demonstrate temperature-activated solidifiable/liquid paraffin-infused porous surfaces (TA-SLIPSs) whose transparency and control of water droplet movement at room temperature can be simultaneously controlled. The solidification of the paraffin changes the surface morphology and the size of the light-transmission inhibitor in the lubricant layer; as a result, the control over the droplet movement and the light transmittance at different temperatures is dependent on the solidifiable/liquid paraffin mixing ratio. Further study of such temperature-responsive, multifunctional systems would be valuable for antifouling applications and the development of surfaces with tunable optical transparency for innovative medical applications, intelligent windows, and other devices.

Unitary plate electrode

NASA Technical Reports Server (NTRS)

Rowlette, John J. (Inventor); Clough, Thomas J. (Inventor); Josefowicz, Jack Y. (Inventor); Sibert, John W. (Inventor)

1985-01-01

The unitary electrode (10) comprises a porous sheet (12) of fiberglass the strands (14) of which contain a coating (16) of conductive tin oxide. The lower portion of the sheet contains a layer (18) of resin and the upper layer (20) contains lead dioxide forming a positive active electrode on an electrolyte-impervious layer. The strands (14) form a continuous conduction path through both layers (16, 18). Tin oxide is prevented from reduction by coating the surface of the plate facing the negative electrode with a conductive, impervious layer resistant to reduction such as a thin film (130) of lead or graphite filled resin adhered to the plate with a layer (31) of conductive adhesive. The plate (10) can be formed by casting a molten resin from kettle (60) onto a sheet of glass wool (56) overlying a sheet of lead foil and then applying positive active paste from hopper (64) into the upper layer (68). The plate can also be formed by passing an assembly of a sheet ( 80) of resin, a sheet (86) of sintered glass and a sheet (90) of lead between the nip (92) of heated rollers (93, 95) and then filling lead oxide into the pores (116) of the upper layer (118).

SERS substrate based on silver nanoparticles and graphene: Dependence on the layer number of graphene

NASA Astrophysics Data System (ADS)

Garg, Preeti; Soni, R. K.; Raman, R.

2018-05-01

In this report, we describe a low-cost fabrication process for highly sensitive SERS substrate by using thermal evaporation technique. The SERS substrate structure consists of silver nanoparticles deposited on monolayer, bilayer and few layer graphene. The fabricated SERS substrates are investigated by field emission scanning electron microscope (FE-SEM), atomic force microscope (AFM), and confocal Raman spectroscope. From the surface morphology we have verified that the fabricated SERS substrate consist of high-density of silver nanoparticles with their size distribution varies from 10 to 150 nm. The surface-enhanced Raman scattering activities of these nanostructures is highest for monolayer graphene.

In situ Silver Spot Preparation and on-Plate Surface-Enhanced Raman Scattering Detection in Thin Layer Chromatography Separation

NASA Astrophysics Data System (ADS)

Herman, K.; Mircescu, N. E.; Szabo, L.; Leopold, L. F.; Chiş, V.; Leopold, N.

2013-05-01

An improved approach for surface-enhanced Raman scattering (SERS) detection of mixture constituents after thin layer chromatography (TLC) separation is presented. A SERS active silver substrate was prepared under open air conditions, directly on the thin silica film by photo-reduction of silver nitrate, allowing the detection of binary mixtures of cresyl violet, bixine, crystal violet, and Cu(II) complex of 4-(2-pyridylazo)resorcinol. The recorded SERS spectrum provides a unique spectral fingerprint for each molecule; therefore the use of analyte standards is avoided, thus rendering the presented procedure advantageous compared to the conventional detection methodology in TLC.

Selected wheat seed defense proteins exhibit competitive binding to model microbial lipid interfaces.

PubMed

Sanders, Michael R; Clifton, Luke A; Neylon, Cameron; Frazier, Richard A; Green, Rebecca J

2013-07-17

Puroindolines (Pins) and purothionins (Pths) are basic, amphiphilic, cysteine-rich wheat proteins that play a role in plant defense against microbial pathogens. This study examined the co-adsorption and sequential addition of Pins (Pin-a, Pin-b, and a mutant form of Pin-b with Trp-44 to Arg-44 substitution) and β-purothionin (β-Pth) model anionic lipid layers using a combination of surface pressure measurements, external reflection FTIR spectroscopy, and neutron reflectometry. Results highlighted differences in the protein binding mechanisms and in the competitive binding and penetration of lipid layers between respective Pins and β-Pth. Pin-a formed a blanket-like layer of protein below the lipid surface that resulted in the reduction or inhibition of β-Pth penetration of the lipid layer. Wild-type Pin-b participated in co-operative binding with β-Pth, whereas the mutant Pin-b did not bind to the lipid layer in the presence of β-Pth. The results provide further insight into the role of hydrophobic and cationic amino acid residues in antimicrobial activity.

Comparative research on activation technique for GaAs photocathodes

NASA Astrophysics Data System (ADS)

Chen, Liang; Qian, Yunsheng; Chang, Benkang; Chen, Xinlong; Yang, Rui

2012-03-01

The properties of GaAs photocathodes mainly depend on the material design and activation technique. In early researches, high-low temperature two-step activation has been proved to get more quantum efficiency than high-temperature single-step activation. But the variations of surface barriers for two activation techniques have not been well studied, thus the best activation temperature, best Cs-O ratio and best activation time for two-step activation technique have not been well found. Because the surface photovoltage spectroscopy (SPS) before activation is only in connection with the body parameters for GaAs photocathode such as electron diffusion length and the spectral response current (SRC) after activation is in connection with not only body parameters but also surface barriers, thus the surface escape probability (SEP) can be well fitted through the comparative research between SPS before activation and SEP after activation. Through deduction for the tunneling process of surface barriers by Schrödinger equation, the width and height for surface barrier I and II can be well fitted through the curves of SEP. The fitting results were well proved and analyzed by quantitative analysis of angle-dependent X-ray photoelectron spectroscopy (ADXPS) which can also study the surface chemical compositions, atomic concentration percentage and layer thickness for GaAs photocathodes. This comparative research method for fitting parameters of surface barriers through SPS before activation and SRC after activation shows a better real-time in system method for the researches of activation techniques.

Hot gas path component cooling system

DOEpatents

Lacy, Benjamin Paul; Bunker, Ronald Scott; Itzel, Gary Michael

2014-02-18

A cooling system for a hot gas path component is disclosed. The cooling system may include a component layer and a cover layer. The component layer may include a first inner surface and a second outer surface. The second outer surface may define a plurality of channels. The component layer may further define a plurality of passages extending generally between the first inner surface and the second outer surface. Each of the plurality of channels may be fluidly connected to at least one of the plurality of passages. The cover layer may be situated adjacent the second outer surface of the component layer. The plurality of passages may be configured to flow a cooling medium to the plurality of channels and provide impingement cooling to the cover layer. The plurality of channels may be configured to flow cooling medium therethrough, cooling the cover layer.

Protein folding on Biosensor tips: Folding of Maltodextrin glucosidase monitored by its interactions with GroEL

PubMed Central

Pastor, Ashutosh; Singh, Amit K.; Fisher, Mark T.; Chaudhuri, Tapan K.

2016-01-01

Protein folding has been extensively studied for past four decades by employing solution based experiments such as solubility, enzymatic activity, secondary structure analysis, and analytical methods like FRET, NMR and HD exchange. However, for rapid analysis of the folding process, solution based approaches are often plagued with aggregation side reactions resulting in poor yields. In this work we demonstrate that a Bio-Layer Interferometry (BLI) chaperonin detection system can be potentially applied to identify superior refolding conditions for denatured proteins. The degree of immobilized protein folding as a function of time can be detected by monitoring the binding of the high-affinity nucleotide-free form of the chaperonin GroEL. GroEL preferentially interacts with proteins that have hydrophobic surfaces exposed in their unfolded or partially folded form so a decrease in GroEL binding can be correlated with burial of hydrophobic surfaces as folding progresses. The magnitude of GroEL binding to the protein immobilized on Bio-layer interferometry biosensor inversely reflects the extent of protein folding and hydrophobic residue burial. We demonstrate conditions where accelerated folding can be observed for the aggregation prone protein Maltodextrin glucosidase (MalZ). Superior immobilized folding conditions identified on the Bio-layer interferometry biosensor surface were reproduced on Ni-NTA sepharose bead surfaces and resulted in significant improvement in folding yields of released MalZ (measured by enzymatic activity) compared to bulk refolding conditions in solution. PMID:27367928

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

PubMed

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

2015-08-10

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

Fabrication of ordered bulk heterojunction organic photovoltaic cells using nanopatterning and electrohydrodynamic spray deposition methods.

PubMed

Park, Sung-Eun; Kim, Sehwan; Kim, Kangmin; Joe, Hang-Eun; Jung, Buyoung; Kim, Eunkyoung; Kim, Woochul; Min, Byung-Kwon; Hwang, Jungho

2012-12-21

Organic photovoltaic cells with an ordered heterojunction (OHJ) active layer are expected to show increased performance. In the study described here, OHJ cells were fabricated using a combination of nanoimprinting and electrohydrodynamic (EHD) spray deposition methods. After an electron donor material was nanoimprinted with a PDMS stamp (valley width: 230 nm, period: 590 nm) duplicated from a Si nanomold, an electron acceptor material was deposited onto the nanoimprinted donor layer using an EHD spray deposition method. The donor-acceptor interface layer was observed by obtaining cross-sectional images with a focused ion beam (FIB) microscope. The photocurrent generation performance of the OHJ cells was evaluated with the current density-voltage curve under air mass (AM) 1.5 conditions. It was found that the surface morphology of the electron acceptor layer affected the current and voltage outputs of the photovoltaic cells. When an electron acceptor layer with a smooth thin (250 nm above the valley of the electron donor layer) surface morphology was obtained, power conversion efficiency was as high as 0.55%. The electrohydrodynamic spray deposition method used to produce OHJ photovoltaic cells provides a means for the adoption of large area, high throughput processes.

Formation of Au nano-patterns on various substrates using simplified nano-transfer printing method

NASA Astrophysics Data System (ADS)

Kim, Jong-Woo; Yang, Ki-Yeon; Hong, Sung-Hoon; Lee, Heon

2008-06-01

For future device applications, fabrication of the metal nano-patterns on various substrates, such as Si wafer, non-planar glass lens and flexible plastic films become important. Among various nano-patterning technologies, nano-transfer print method is one of the simplest techniques to fabricate metal nano-patterns. In nano-transfer printing process, thin Au layer is deposited on flexible PDMS mold, containing surface protrusion patterns, and the Au layer is transferred from PDMS mold to various substrates due to the difference of bonding strength of Au layer to PDMS mold and to the substrate. For effective transfer of Au layer, self-assembled monolayer, which has strong bonding to Au, is deposited on the substrate as a glue layer. In this study, complicated SAM layer coating process was replaced to simple UV/ozone treatment, which can activates the surface and form the -OH radicals. Using simple UV/ozone treatments on both Au and substrate, Au nano-pattern can be successfully transferred to as large as 6 in. diameter Si wafer, without SAM coating process. High fidelity transfer of Au nano-patterns to non-planar glass lens and flexible PET film was also demonstrated.

Antisoiling technology: Theories of surface soiling and performance of antisoiling surface coatings

NASA Technical Reports Server (NTRS)

Cuddihy, E. F.; Willis, P. B.

1984-01-01

Physical examination of surfaces undergoing natural outdoor soiling suggests that soil matter accumulates in up to three distinct layers. The first layer involves strong chemical attachment or strong chemisorption of soil matter on the primary surface. The second layer is physical, consisting of a highly organized arrangement of soil creating a gradation in surface energy from a high associated with the energetic first layer to the lowest possible state on the outer surfce of the second layer. The lowest possible energy state is dictated by the physical nature of the regional atmospheric soiling materials. These first two layers are resistant to removal by rain. The third layer constitutes a settling of loose soil matter, accumulating in dry periods and being removed during rainy periods. Theories and evidence suggest that surfaces that should be naturally resistant to the formation of the first two-resistant layers should be hard, smooth, hydrophobic, free of first-period elements, and have the lowest possible surface energy. These characteristics, evolving as requirements for low-soiling surfaces, suggest that surfaces or surface coatings should be of fluorocarbon chemistry. Evidence for the three-soil-layer concept, and data on the positive performance of candidate fluorocarbon coatings on glass and transparent plastic films after 28 months of outdoor exposure, are presented.

Organic light emitting diode with surface modification layer

DOEpatents

Basil, John D.; Bhandari, Abhinav; Buhay, Harry; Arbab, Mehran; Marietti, Gary J.

2017-09-12

An organic light emitting diode (10) includes a substrate (12) having a first surface (14) and a second surface (16), a first electrode (32), and a second electrode (38). An emissive layer (36) is located between the first electrode (32) and the second electrode (38). The organic light emitting diode (10) further includes a surface modification layer (18). The surface modification layer (18) includes a non-planar surface (30, 52).